Inhibition of Histone Deacetylation Blocks Cardiac Hypertrophy Induced
http://www.100md.com
《循环学杂志》
the Departments of Pharmacology (H.J.K., Y.R.Q., J.-K.K., K.K.K., H.K.) and Anatomy (K.I.N.), Research Institute of Medical Sciences and Medical Research Center for Gene Regulation, Chonnam National University Medical School (H.J.K., K.I.N., N.K., K.K.K., H.K.), Gwangju, South Korea
The Heart Center (I.S.S., Y.A., M.H.J.) and Research Institute of Clinical Medicine (J.E.P.) of Chonnam National University Hospital, Gwangju, South Korea
National Research Laboratory for Cancer Epigenetics, Cancer Research Institute, Seoul National University College of Medicine, Seoul, South Korea (Y.-J.B.)
Cardiovascular Institute, University of Pennsylvania, Philadelphia (Z.Y., J.A.E.).
Abstract
Background— A number of distinct stress signaling pathways in myocardium cause cardiac hypertrophy and heart failure. Class II histone deacetylases (HDACs) antagonize several stress-induced pathways and hypertrophy. However, cardiac hypertrophy induced by transgenic overexpression of the homeodomain only protein, HOP, can be prevented by the nonspecific HDAC inhibitors trichostatin A and valproic acid, suggesting that alternate targets that oppose class II HDAC function might exist in myocardium. We tested the effects of several HDAC inhibitors, including a class I HDAC-selective inhibitor, SK-7041, on cardiac hypertrophy induced by angiotensin II (Ang II) treatment or aortic banding (AB).
Methods and Results— Cardiac hypertrophy was induced by chronic infusion of Ang II or by AB in mice or rats and evaluated by determining the ratio of heart weight to body weight or to tibia length, cross-sectional area, or echocardiogram. Cardiac hypertrophy induced by Ang II or AB for 2 weeks was significantly reduced by simultaneous administration of trichostatin A, valproic acid, or SK-7041. Echocardiogram revealed that exaggerated left ventricular systolic dimensions were relieved by HDAC inhibitors. HDAC inhibitors partially reversed preestablished cardiac hypertrophy and improved survival of AB mice. The expressions of atrial natriuretic factor, -tubulin, -myosin heavy chain, and interstitial fibrosis were reduced by HDAC inhibition.
Conclusions— These results suggest that the predominant effect of HDAC inhibition, mainly mediated by class I HDACs, is to prevent cardiac hypertrophy in response to a broad range of agonist and stretch stimuli.
Key Words: angiotensin aortic banding histone deacetylases hypertrophy
Introduction
In contrast to hyperplasia, which involves proliferation of cells, cardiac hypertrophy, an increase in the size of cardiac muscle cells, is often a primary adaptive response to exogenous physiological or pathological signals, such as myocardial infarction, hypertension, aortic stenosis, and valvular dysfunction. These stimuli in animal models and human diseases have generally been thought to induce prohypertrophic gene expression. Reactivation of fetal gene programs and repression of some adult cardiac genes are closely related to deterioration of heart function.1
Clinical Perspective p 59
Posttranslational modifications of histones play an important role in transcriptional regulation.2 In particular, acetylation of histone tails, mediated by histone acetyltransferases, is associated with activation of gene expression in myocardium.3 Conversely, repression of gene expression can be induced by histone deacetylation, which is mediated by a family of histone deacetylases (HDACs). HDACs are divided into 3 subfamilies on the basis of secondary structure.4 Class II HDACs, characterized by an amino-terminal domain that can interact with myocyte enhancer factor 2, have been strongly implicated as repressors of cardiac hypertrophic gene expression. HDAC5 and HDAC9, both class II HDACs, are highly expressed in myocardium, and inactivation of these genes promotes cardiac hypertrophy.5 These results might suggest that HDAC inhibition would promote hypertrophy. However, when isolated myocytes in primary culture are treated with chemical HDAC inhibitors, gene expression characteristic of hypertrophic signaling is paradoxically inhibited.6
Recently, we have shown that cardiac hypertrophy induced by transgenic overexpression of the homeodomain only protein, HOP, a transcriptional corepressor in the developing heart,7 can be prevented by treatment with the nonspecific HDAC inhibitors trichostatin A (TSA) and valproic acid (VAL). TSA also repressed hypertrophy induced by chronic infusion of isoproterenol, a -adrenergic agonist.8 In the present study we sought to determine whether HDAC inhibition would block hypertrophic responses induced by both receptor-mediated agonists and stretch. Our results suggest that nonspecific as well as class I–selective HDAC inhibitors may prove to be useful pharmacological agents for the prevention or treatment of cardiac hypertrophy and heart failure.
Methods
In Vivo Hypertrophy Models
Five- to 8-week-old adult male CD1 mice (n=225) and 6-week-old adult male Sprague-Dawley rats (n=40) were purchased from Daehan Biolink (Daejeon, Korea) and housed individually in plastic cages in a temperature-controlled room. The experimental protocol was approved by the Chonnam National University Medical School Research Institutional Animal Care and Use Committee. All surgical procedures and echocardiography were performed with the animals under anesthesia with ketamine (16.65 mg/kg IM) and xylazine (7.77 mg/kg IM).
Angiotensin II (Ang II) infusion was done at 1.3 mg/kg per day for 14 days. For preparation of aortic banding (AB), the left chest was opened at the second intercostal space with the animal under anesthesia. Partial aortic constriction was performed by ligating the ascending aorta with a 22-gauge needle with a 7-0 braided polyester suture. The increased blood flow velocity was confirmed by Doppler echocardiogram (Figure 1B and 1C). Sham-operated animals underwent the same surgical procedure without constricting the aorta. Establishment of hypertrophy was confirmed by echocardiography by measuring left ventricular (LV) wall thickness and dimensions, ratios of heart weight to body weight (HW/BW), and capacitance measurement in isolated cardiomyocytes after euthanasia.
Blood pressures of mice were evaluated by direct cannulation of the common carotid artery, connected to a polygraph (Grass 7E) through a pressure transducer. After the blood pressure was stabilized, the mean arterial pressure was recorded.
Implantation of osmotic minipumps and intraperitoneal administration of TSA (0.6 mg/kg/d) and VAL (0.71% in drinking water, ad libitum) were described previously.8 SK-7041 (SK) (In2Gen Co), dissolved in dimethyl sulfoxide, was administered 30 mg/kg per day IP 5 times a week for 2 weeks as described previously.9 The dose of HDAC inhibitors used has been reported to inhibit endogenous HDAC activity,9–13 and daily administration of TSA or VAL for a given period was well tolerated because it did not affect overall body weight or HW/BW ratio in control animals compared with those injected with vehicle alone (Figures 1A, 1D, 2A, 2 D). TSA, VAL, or SK did not affect cardiac contractility (Table 1).
Evaluation of Regression of Cardiac Hypertrophy
Regression of cardiac hypertrophy was evaluated by HW/BW or heart weight to tibia length (HW/TL) ratios and by echocardiogram. Cross-sectional areas of cardiomyocytes were also examined. For each experimental group, hearts from 4 to 6 animals were mounted after coronal section and stained with hematoxylin-eosin. Ten cardiomyocytes in LV free wall were randomly chosen, and cross-sectional areas were measured with Multi Gauge software (Fuji Photo Film Co) by a blinded investigator.
Echocardiographic studies were performed with a 15-MHz linear array transducer system (Acuson Sequoia c512, Siemens).8 Two-dimensionally guided M-mode of LV at the papillary level was obtained from the parasternal long-axis view. For each mouse, measurements were made from at least 4 beats. LV cavity dimension and wall thickness were measured, and percent change in LV dimension (fractional shortening [FS]) (LV%FS) was calculated as follows: LV%FS=[(LVDd–LVSd)/LVDd]x100, where LVDd is LV dimension at end-diastole and LVSd is LV dimension at end-systole. For the estimation of flow velocity, pulsed-wave Doppler sample volume was placed on the aorta just proximal and distal to the constriction (Figure 1B and 1C).
To determine whether preexisting cardiac hypertrophy could be affected by HDAC inhibition, 42 AB mice aged 8 weeks were randomly divided into 4 groups. The first group was euthanized at 2 weeks after operation, and hypertrophy was confirmed (AB2w group). TSA was administered daily to the second group from the next day of AB (AB+TSA2w group). The third group was maintained for 5 weeks without TSA (AB5w group). In the last group, 2 weeks after AB operation, daily injection of TSA was started and maintained for 3 additional weeks (AB2w+TSA3w group). For each experimental condition, age-matched mice with sham operation served as control. The long-term effect of HDAC inhibition was also evaluated by administration of VAL for 7 weeks, and survival rate as well as echocardiogram was examined.
Reverse Transcription–Polymerase Chain Reaction, Immunoblotting, and Histology
Reverse transcription–polymerase chain reaction (RT-PCR), immunoblotting, immunostaining, and Masson’s trichrome staining of tissues were described previously.8 Transcript levels of heart-specific genes were examined.7 Total RNA was isolated with TriZol reagent (Invitrogen Life Technologies), and 1 μg of RNA underwent reverse transcription reaction with Superscript first strand synthesis system for RT-PCR kit (Invitrogen Life Technologies). Quantification of the mRNA amounts was further confirmed with SYBR Green PCR kit (Applied Biosystems, Inc). Relative expression levels of genes were compared with those of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by the 2–C(t) method.14
For Western blot, anti–atrial natriuretic factor (ANF) (1:1000), anti–-tubulin antibody (1:1000, Zymed, South San Francisco, Calif), or anti-actin antibody (1:1000, Sigma, St Louis, Mo) was used. Nuclear fractions were extracted from isolated hearts with nuclear extraction kit (Panomics Inc), and the loaded protein amounts were checked by Ponceau S staining after separation on SDS-PAGE gel. The level of acetylation of histone H4 was assessed by immunoblotting with anti-acetyl histone H4 antibody (1:2000, Upstate Biotechnology Inc, Lake Placid, NY), following the manufacturer’s protocol.
For immunohistochemistry, primary antibody dilutions of ANF (Biodesign, Saco, Maine) and type I collagen (Abcam, Cambridge, UK) were 1:200 and 1:100, respectively. Cardiomyocyte apoptosis was evaluated by FragEL DNA fragmentation Detection kit with colorimetric TdT enzyme (Calbiochem), following the manufacturer’s protocol.
Results
Blockade of Cardiac Hypertrophy by Nonspecific HDAC Inhibitors
In previous work, we have shown that cardiac hypertrophy induced by constant infusion of isoproterenol can be significantly attenuated by TSA.8 We sought to determine whether nonspecific HDAC inhibition would also prevent the hypertrophy induced by an unrelated agonist or by pressure overload. Ang II is known to induce cardiac hypertrophy by activating receptor-mediated signaling cascades, including those involving mitogen-activated protein kinases, phosphatidylinositol 3-kinase, Akt, and janus-activating kinases.15 We treated CD1 mice with Ang II (1.3 mg/kg per day), which, as expected, induced cardiac hypertrophy, and HW/BW ratio was increased by 27% compared with the vehicle group. Concomitant treatment with VAL markedly reduced the hypertrophic response to Ang II (Figure 1A).
To determine whether cardiac hypertrophy induced by pressure overload in mice or rats could be prevented by HDAC inhibition, we treated AB mice or rats with TSA or VAL. AB induced a marked increase in flow velocity (Figure 1B and 1C) and LV wall thickness (Figure 3C and 3D) and a 46% increase in HW/BW ratio compared with sham-operated mice. VAL administration significantly attenuated this increase to 18% (Figure 1D), which was also evidenced by changes in HW/TL ratio (Figure 1E).
The Ang II–induced cardiac hypertrophy, as assessed by HW/BW ratio, was also significantly attenuated by TSA (Figure 2A), an unrelated agent with HDAC inhibitory activity.10 Blockade of cardiac hypertrophy by TSA in Ang II–treated animals raised the possibility that TSA might ameliorate the hypertension induced by Ang II, and thus the blockade of the hypertrophy might have been caused secondarily by reduction of afterload rather than by direct cardiac effects. To rule out this possibility, blood pressure was measured. As expected, Ang II markedly increased the blood pressure; however, TSA did not affect the increased or basal level of blood pressure (Figure 2B).
To determine whether regression of cardiac hypertrophy by HDAC inhibitors correlated with increases in histone acetylation in the cardiomyocytes, the effect of TSA treatment on histone H4 acetylation was determined by immunoblot analysis with an anti–acetyl histone H4 antibody. As shown in Figure 2C, TSA increased the acetylation of histone H4 of cardiomyocytes, whereas the total amount of histone was not changed.
Cardiac hypertrophy induced by AB, as shown by HW/BW ratio, was also significantly relieved by TSA (Figure 2D), which was further confirmed by changes in individual cardiomyocyte volume, measured by cross-sectional area (Figure 2E).
We performed similar experiments in rats and observed a comparable protective effect when AB rats were treated with TSA or VAL. AB significantly increased the HW/BW ratio by 47%, but this increase was significantly blunted to 25% by TSA administration (Figure I in the online-only Data Supplement; see http://circ.ahajournals.org/cgi/content/full/ 113/1/51/DC1).
Prevention of Cardiac Hypertrophy by SK-7041, a Class I HDAC-Selective Inhibitor
The present observations as well as the previous reports6,8 are somewhat unexpected and at odds with the previous findings that class II HDACs inhibit cardiac hypertrophy in response to various exogenous stimuli.4,5 However, the lack of specificity of HDAC inhibitors used led us to postulate that class I HDACs oppose class II HDACs in regulating cardiac hypertrophy and that the activity of class I HDACs predominates in the myocardium such that nonspecific HDAC inhibition results in blockade of hypertrophic pathways. Thus, we examined the effects of a selective class I HDAC inhibitor in our model.
Recently, novel hybrid HDAC inhibitors were synthesized by combining the hydroxamic acid of TSA and the pyridyl ring of MS-275, a synthetic benzamide derivative. One of these new HDAC inhibitors, 3-(4-substituted phenyl)-N-hydroxy-2-propenamide (SK-7041 [SK]),13 was found to have high selectivity to HDAC1 and HDAC2, both belonging to the class I HDAC family.9 To test whether cardiac hypertrophy induced by pressure overload could be prevented by class I–selective HDAC inhibition, we treated AB mice with SK. AB-induced cardiac enlargement was almost completely prevented by SK, as shown in Figure 3A, and the reduction of LV dimension was confirmed by M-mode echocardiogram (Figure 3C to 3F, Table 1). Histone acetylation status in SK-treated hearts is shown in Figure 3B. SK increased the histone H4 acetylation in both sham- and AB-operated groups (top panel).
AB increased HW/BW ratio by 46% in the vehicle-treated group; however, SK completely abolished the increase (to 2%) compared with the sham+SK group (Figure 3G). Because SK could induce mild weight loss in some mice, we measured tibia length and calculated HW/TL ratio. Similarly, the 51% increase in HW/TL ratio in the AB group was reduced to 3% by SK (Figure 3H). Table 1 shows the changes of LV dimensions as well as heart weight after administration of 3 HDAC inhibitors to AB mice. Although all 3 inhibitors significantly reduced the thickness of the interventricular septum and posterior wall, the reduction was greatest in the SK-treated group.
Regression of Preestablished Cardiac Hypertrophy and Long-Term Evaluation
We next examined whether HDAC inhibition can reverse preexisting cardiac hypertrophy, which might be of greater clinical significance. As expected, AB increased HW/BW ratio over a 2-week period, and this increase was significantly attenuated by simultaneous administration of TSA (Figure 4B). Maintenance of a cohort of AB mice with vehicle treatment for the subsequent 3 weeks resulted in a further increase in HW/BW ratio, suggesting that cardiac hypertrophy is progressive. Interestingly, however, TSA administration for a 3-week period after 2 weeks of AB relieved the preexisting cardiac hypertrophy and prevented further progression; HW/BW ratio was significantly reduced compared with AB2w as well as AB5w mice (Figure 4B). Reversal of preestablished cardiac hypertrophy was further confirmed by measuring HW/TL ratio, in which the level of regression appeared even more dramatic (Figure II in the online-only Data Supplement). The regression of the heart weight paralleled the reduction of LV wall thickness (Table 2).
The long-term effects of HDAC inhibition on cardiac hypertrophy and survival were evaluated in AB mice treated with or without VAL or TSA for 7 weeks. HW/TL in AB mice was increased by 41% over that in age-matched controls; however, this increase was blunted to 19% by VAL. Figure III in the online-only Data Supplement also shows similar changes in HW/BW. Some AB mice died suddenly and were found to have enlarged hearts with severe myocardial fibrosis. Kaplan-Meier analysis revealed that the survival rate was 54.7% at 40 days after surgery. However, administration with TSA or VAL improved the survival rate to 83.3% (Figure 2E).
Hypertrophic Markers
Cardiac hypertrophy reactivates the fetal gene program, characterized by a switch from -myosin heavy chain (-MHC) to -MHC gene expression in the adult murine heart.1,16 -MHC transcript levels as well as ANF transcripts were increased in Ang II and AB mice (Figure 5A and 5B). These increases were blunted by administration of TSA (Figure 5A) or SK (Figure 5B). The changes in ANF mRNA levels were confirmed by quantification, and both VAL and TSA significantly blunted the increase (Figure 5C).
In addition to ANF, -tubulin is another marker of cardiac hypertrophy and cardiac protein expression increases in response to diverse hypertrophic stimuli.17 As expected, AB increased the protein levels of ANF and -tubulin in mouse hearts. However, this increase was significantly blocked by treatment with TSA (Figure 5D) or SK (Figure 5E). Similar effects with regard to ANF and -tubulin expression were seen in rat heart samples after AB with and without TSA (Figure IV in the online-only Data Supplement).
We examined expression of ANF and deposition of type I collagen18 by immunohistochemistry after AB and Ang II, with and without TSA. Staining for both ANF and type I collagen was significantly enhanced in samples from AB rats (Figure 6B and 6E) compared with sham controls (Figure 6A and 6D). These changes in gene expression were normalized by TSA (Figure 6C and 6F). In AB mice, SK treatment also normalized the changes in ANF (Figure 6G to 6I).
AB for 2 and 7 weeks (Figure 6K and 6N) caused significant interstitial collagen deposition, as demonstrated by Masson’s trichrome staining. However, fibrosis was reduced in AB mice treated with SK for 2 weeks or VAL for 7 weeks (Figure 6L and 6O). Interestingly, in some mice with SK treatment, no evidence of interstitial fibrosis was seen (data not shown).
Previous reports that HDAC inhibitors, including SK, induce apoptosis of transformed cells9,19,20 and thereby can be used for cancer treatment9,21 raise the possibility that apoptosis in cardiomyocytes may occur in our animal models, leading to reduction of cardiac mass. However, terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling (TUNEL) staining showed no apparent increase in cardiomyocyte apoptosis in TSA- or SK-treated animals compared with the vehicle group (data not shown).
Discussion
Our results clarify that nonspecific HDAC inhibitors can function to attenuate cardiac hypertrophic changes induced by diverse stimuli including receptor-mediated agonists and pressure overload. In addition, we have shown that a class I HDAC-selective inhibitor prevents cardiac hypertrophy and that administration of HDAC inhibitors can induce regression of preestablished cardiac hypertrophy in at least some animal models.
Cardiac hypertrophy induced by transgenic overexpression of HOP or by chronic infusion of either isoproterenol or Ang II is prevented or significantly attenuated by concomitant treatment with TSA. Likewise, hypertrophy induced by AB, in which stretch-activated ion channels, integrins, and sarcomeric Z disks are involved in mediating hypertrophic signaling,22 is blocked by TSA or VAL. These results suggest that HDAC activation is a part of the final common pathway induced by diverse hypertrophic agonists and that inhibition of this step may serve as a therapeutic target for preventing or reversing cardiac hypertrophy and subsequent heart failure. Indeed, in this study, along with improved LV dimensions, as determined by echocardiogram, better survival in the TSA- or VAL-treated group in AB mice supports their beneficial effects on the transition of cardiac hypertrophy to heart failure. In addition, the regression of preestablished cardiac hypertrophy further raises the potential attractiveness for the therapeutic application of HDAC inhibitors.
It is unlikely that reduction in cardiac hypertrophy in the Ang II model was caused by relief of Ang II–induced hypertension, and we suggest that the primary target organ of HDAC inhibitors is heart rather than blood vessels. Likewise, cardiomyocyte apoptosis does not appear to be responsible for the reduction of heart mass. Previous reports6,23 have shown that TSA, VAL, or sodium butyrate, an alternate HDAC inhibitor, does not significantly affect the survival of primary cultured rat cardiomyocytes, and HDAC inhibitors in this study did not increase apoptosis in cardiomyocytes in vivo. Although HDAC inhibitors have significant proapoptotic effects in transformed cells,19 Park et al9 clearly showed that untransformed epithelial cells are much more resistant to SK-induced apoptosis than are cancer cells.
To date, at least 17 distinct HDACs have been reported in humans. Members of all 3 classes of HDACs are expressed in the heart, and, recently, class III HDACs were reported to be endogenous inhibitors of apoptosis in the heart.24 TSA or VAL inhibits both class I and class II HDACs. Given that class II HDACs function to antagonize cardiac hypertrophy,4,5 the antihypertrophic effect of nonspecific HDAC inhibitors is more likely to be mediated by class I HDACs. In this study we clearly demonstrate that class I HDACs in cardiomyocyte are prohypertrophic because SK, a class I HDAC-selective inhibitor, blocked the development of cardiac hypertrophy.
Given the proposed antagonistic actions of class I and class II HDACs, why do nonspecific HDAC inhibitors result in antihypertrophic effects The most plausible explanation is that class I HDAC activity predominates with regard to hypertrophic gene expression in the heart. Indeed, the enzymatic activity of class II HDACs is not required for the transcriptional repression of prohypertrophic genes in the heart, as a splice variant of HDAC9 that lacks a deacetylase domain is highly effective in repressing cardiac hypertrophy.5,25 These reports further support our conclusion that the net functional role of HDAC activity, probably mediated by class I HDACs, in cardiomyocytes is prohypertrophic.
Cell proliferation/growth arrest mechanisms are known to contribute to the regulation of cardiac hypertrophy.26 In cancer cells, for example, HDAC inhibitors relieve histone compaction to upregulate p21,27 which has been implicated as a repressor of hypertrophy.28 It is still unclear, however, whether HDACs may affect other prohypertrophic signal transduction cascades, because several nonhistone targets, such as tubulin and GATA transcription factor,23,29,30 which can affect cardiac remodeling, have been implicated. For example, in primarily cultured rat cardiomyocytes, TSA was shown to increase -MHC expression but to decrease cardiac tubulins. Although early growth response gene 1 (EGR-1) was elucidated as a primary mediator of the responses,23 direct evidence for the functional involvement of EGR-1 in in vivo hypertrophy remains to be demonstrated.
This work relies entirely on the use of pharmacological inhibitors of HDAC activity. Although we have attempted to use several different chemical inhibitors, it remains possible that the effects that we observed on cardiac hypertrophy are produced by effects of the drugs unrelated to their abilities to inhibit HDAC catalytic function. Indeed, alternative cellular functions for HDACs remain possibly unrelated to the regulation of chromatin structure as described above, and unappreciated functions of the pharmacological agents that we have used may exist. Nevertheless, the cardiac effects of these agents are of interest given the increasing likelihood of more widespread clinical use for noncardiac indications, including the treatment of neoplasia.21,31 Therefore, as well as development of novel HDAC inhibitors with selectivity and low toxicity, additional preclinical testing is indicated to validate the use of these inhibitors for prevention or reversal of cardiac hypertrophy and failure in humans.
Acknowledgments
This work was supported by the Korea Science and Engineering Foundation through the Medical Research Center for Gene Regulation (R13-2002-013-03002-0) at Chonnam National University. Dr Kee was supported by a Korea Research Foundation grant (KRF-2004-C00141). Dr Epstein was supported by grants from the National Institutes of Health. The authors are grateful to Do Su Kim and Jin Sung Park for their excellent assistance in surgical procedures, to Gwang Hyeon Eom for preparing pictures, and to Professor Emeritus Young Johng Kook, Chonnam National University Medical School, for reviewing the manuscript.
Disclosures
None.
References
Olson EN, Schneider MD. Sizing up the heart: development redux in disease. Genes Dev. 2003; 17: 1937–1956.
Schreiber SL, Bernstein BE. Signaling network model of chromatin. Cell. 2002; 111: 771–778.
Gusterson RJ, Jazrawi E, Adcock IM, Latchman DS. The transcriptional co-activators CREB binding protein (CBP) and p300 play a critical role in cardiac hypertrophy that is dependent on their histone acetyltransferase activity. J Biol Chem. 2003; 278: 6838–6847.
McKinsey TA, Zhang CL, Olson EN. Signaling chromatin to make muscle. Curr Opin Cell Biol. 2002; 14: 763–772.
Zhang CL, McKinsey TA, Chang S, Antos CL, Hill JA, Olson EN. Class II histone deacetylases act as signal-responsive repressors of cardiac hypertrophy. Cell. 2002; 110: 479–488.
Antos CL, McKinsey TA, Dreitz M, Hollingsworth LM, Zhang CL, Schreiber K, Rindt H, Gorczynski RJ, Olson EN. Dose-dependent blockade to cardiomyocyte hypertrophy by histone deacetylase inhibitors. J Biol Chem. 2003; 278: 28930–28937.
Chen F, Kook H, Milewski R, Gitler AD, Lu MM, Li J, Nazarian R, Schnepp R, Jen K, Biben C, Runke G, Mackay JP, Novotny J, Schwartz RJ, Harvey RP, Mullins MC, Epstein JA. HOP is an unusual homeobox gene that modulates cardiac development. Cell. 2002; 110: 713–723.
Kook H, Lepore JJ, Gitler AD, Lu MM, Wing-Man Yung W, Mackay J, Zhou R, Ferrari V, Gruber P, Epstein JA. Cardiac hypertrophy and histone deacetylase-dependent transcriptional repression mediated by the atypical homeodomain protein HOP. J Clin Invest. 2003; 112: 863–871.
Park JH, Jung Y, Kim TY, Kim SG, Jong HS, Lee JW, Kim DK, Lee JS, Kim NK, Kim TY, Bang YJ. Class I histone deacetylase-selective novel synthetic inhibitors potently inhibit human tumor proliferation. Clin Cancer Res. 2004; 10: 5271–5281.
Yoshida M, Kijima M, Akita M, Beppu T. Potent and specific inhibition of mammalian histone deacetylase both in vivo and in vitro by trichostatin A. J Biol Chem. 1990; 265: 17174–17179.
Nervi C, Borello U, Fazi F, Buffa V, Pelicci PG, Cossu G. Inhibition of histone deacetylase activity by trichostatin A modulates gene expression during mouse embryogenesis without apparent toxicity. Cancer Res. 2001; 61: 1247–1249.
Gottlicher M, Minucci S, Zhu P, Kramer OH, Schimpf A, Giavara S, Sleeman JP, Lo Coco F, Nervi C, Pelicci PG, Heinzel T. Valproic acid defines a novel class of HDAC inhibitors inducing differentiation of transformed cells. EMBO J. 2001; 20: 6969–6978.
Kim DK, Lee JY, Kim JS, Ryu JH, Choi JY, Lee JW, Im GJ, Kim TK, Seo JW, Park HJ, Yoo J, Park JH, Kim TY, Bang YJ. Synthesis and biological evaluation of 3-(4-substituted-phenyl)-N-hydroxy-2-propenamides, a new class of histone deacetylase inhibitors. J Med Chem. 2003; 46: 5745–5751.
Ismat FA, Zhang M, Kook H, Huang B, Zhou R, Ferrari VA, Epstein JA, Patel VV. Homeobox protein Hop functions in the adult cardiac conduction system. Circ Res. 2005; 96: 898–903.
Shah BH, Catt KJ. A centrol role of EGF receptor transactivation in angiotensin II–induced cardiac hypertrophy. Trends Pharmacol Sci. 2003; 24: 239–244.
Izumo S, Lompre AM, Matsuoka R, Koren G, Schwartz K, Nadal-Ginard B, Mahdavi V. Myosin heavy chain messenger RNA and protein isoform transitions during cardiac hypertrophy: interaction between hemodynamic and thyroid hormone-induced signals. J Clin Invest. 1987; 79: 970–977.
Belmadani S, Pous C, Ventura-Clapier R, Fischmeister R, Mery PF. Post-translational modifications of cardiac tubulin during chronic heart failure in the rat. Mol Cell Biochem. 2002; 237: 39–46.
Contard F, Koteliansky V, Marotte F, Dubus I, Rappaport L, Samuel JL. Specific alterations in the distribution of extracellular matrix components within rat myocardium during the development of pressure overload. Lab Invest. 1991; 64: 65–75.
Marks PA, Richon VM, Rifkind RA. Histone deacetylase inhibitors: inducers of differentiation or apoptosis of transformed cells. J Natl Cancer Inst. 2000; 92: 1210–1216.
Ryu JK, Lee WJ, Lee KH, Hwang JH, Kim YT, Yoon YB, Kim CY. SK-7041, a new histone deacetylase inhibitor, induces G(2)-M cell cycle arrest and apoptosis in pancreatic cancer cell lines. Cancer Lett. 2005; xx: 1–12.
Marks PA, Richon VM, Breslow R, Rifkind RA. Histone deacetylase inhibitors as new cancer drugs. Curr Opin Oncol. 2001; 13: 477–483.
Sadoshima J, Izumo S. The cellular and molecular response to cardiac myocytes to mechanical stress. Annu Rev Physiol. 1997; 59: 551–571.
Davis FJ, Pillai JB, Gupta M, Gupta MP. Concurrent opposite effects of trichostatin A, an inhibitor of histone deacetylases, on expression of alpha-MHC and cardiac tubulins: implication for gain in cardiac muscle contractility. Am J Physiol. 2005; 288: H1477–H1490.
Alcendor RR, Kirshenbaum LA, Imai S-I, Vatner SF, Sadoshima J. Silent information regulator 2, a longevity factor and class III histone deacetylase, is an essential endogenous apoptosis inhibitor in cardiac myocytes. Circ Res. 2004; 95: 971–980.
McKinsey TA, Olson EN. Toward transcriptional therapies for the failing heart: chemical screens to modulate genes. J Clin Invest. 2005; 115: 538–546.
Hoshijima M, Chien KR. Mixed signals in heart failure: cancer rules. J Clin Invest. 2002; 109: 849–855.
Gui CY, Ngo L, Xu WS, Richon VM, Marks PA. Histone deacetylase (HDAC) inhibitor activation of p21WAF1 involves changes in promoter-associated proteins, including HDAC1. Proc Natl Acad Sci U S A. 2004; 101: 1241–1246.
Tamamori M, Ito H, Hiroe M, Terada Y, Marumo F, Ikeda MA. Essential roles for G1 cyclin-dependent kinase activity in development of cardiomyocyte hypertrophy. Am J Physiol. 1998; 275: H2036–H2040.
Westermann S, Weber K. Post-translational modifications regulate microtubule function. Nat Rev Mol Cell Biol. 2003; 4: 938–947.
Kawamura T, Ono K, Morimoto T, Wada H, Hirai M, Hidaka K, Morisaki T, Heike T, Nakahata T, Kita T, Hasegawa K. Acetylation of GATA-4 is involved in the differentiation of embryonic stem cells into cardiac myocytes. J Biol Chem. 2005; 280: 19682–19688.
Kwon HJ, Kim M, Kim DH. Histone deacetylase in carcinogenesis and its inhibitors as anti-cancer agents. J Biochem Mol Biol. 2003; 36: 110–119.(Hae Jin Kee, PhD; Il Suk Sohn, MD, PhD; )
The Heart Center (I.S.S., Y.A., M.H.J.) and Research Institute of Clinical Medicine (J.E.P.) of Chonnam National University Hospital, Gwangju, South Korea
National Research Laboratory for Cancer Epigenetics, Cancer Research Institute, Seoul National University College of Medicine, Seoul, South Korea (Y.-J.B.)
Cardiovascular Institute, University of Pennsylvania, Philadelphia (Z.Y., J.A.E.).
Abstract
Background— A number of distinct stress signaling pathways in myocardium cause cardiac hypertrophy and heart failure. Class II histone deacetylases (HDACs) antagonize several stress-induced pathways and hypertrophy. However, cardiac hypertrophy induced by transgenic overexpression of the homeodomain only protein, HOP, can be prevented by the nonspecific HDAC inhibitors trichostatin A and valproic acid, suggesting that alternate targets that oppose class II HDAC function might exist in myocardium. We tested the effects of several HDAC inhibitors, including a class I HDAC-selective inhibitor, SK-7041, on cardiac hypertrophy induced by angiotensin II (Ang II) treatment or aortic banding (AB).
Methods and Results— Cardiac hypertrophy was induced by chronic infusion of Ang II or by AB in mice or rats and evaluated by determining the ratio of heart weight to body weight or to tibia length, cross-sectional area, or echocardiogram. Cardiac hypertrophy induced by Ang II or AB for 2 weeks was significantly reduced by simultaneous administration of trichostatin A, valproic acid, or SK-7041. Echocardiogram revealed that exaggerated left ventricular systolic dimensions were relieved by HDAC inhibitors. HDAC inhibitors partially reversed preestablished cardiac hypertrophy and improved survival of AB mice. The expressions of atrial natriuretic factor, -tubulin, -myosin heavy chain, and interstitial fibrosis were reduced by HDAC inhibition.
Conclusions— These results suggest that the predominant effect of HDAC inhibition, mainly mediated by class I HDACs, is to prevent cardiac hypertrophy in response to a broad range of agonist and stretch stimuli.
Key Words: angiotensin aortic banding histone deacetylases hypertrophy
Introduction
In contrast to hyperplasia, which involves proliferation of cells, cardiac hypertrophy, an increase in the size of cardiac muscle cells, is often a primary adaptive response to exogenous physiological or pathological signals, such as myocardial infarction, hypertension, aortic stenosis, and valvular dysfunction. These stimuli in animal models and human diseases have generally been thought to induce prohypertrophic gene expression. Reactivation of fetal gene programs and repression of some adult cardiac genes are closely related to deterioration of heart function.1
Clinical Perspective p 59
Posttranslational modifications of histones play an important role in transcriptional regulation.2 In particular, acetylation of histone tails, mediated by histone acetyltransferases, is associated with activation of gene expression in myocardium.3 Conversely, repression of gene expression can be induced by histone deacetylation, which is mediated by a family of histone deacetylases (HDACs). HDACs are divided into 3 subfamilies on the basis of secondary structure.4 Class II HDACs, characterized by an amino-terminal domain that can interact with myocyte enhancer factor 2, have been strongly implicated as repressors of cardiac hypertrophic gene expression. HDAC5 and HDAC9, both class II HDACs, are highly expressed in myocardium, and inactivation of these genes promotes cardiac hypertrophy.5 These results might suggest that HDAC inhibition would promote hypertrophy. However, when isolated myocytes in primary culture are treated with chemical HDAC inhibitors, gene expression characteristic of hypertrophic signaling is paradoxically inhibited.6
Recently, we have shown that cardiac hypertrophy induced by transgenic overexpression of the homeodomain only protein, HOP, a transcriptional corepressor in the developing heart,7 can be prevented by treatment with the nonspecific HDAC inhibitors trichostatin A (TSA) and valproic acid (VAL). TSA also repressed hypertrophy induced by chronic infusion of isoproterenol, a -adrenergic agonist.8 In the present study we sought to determine whether HDAC inhibition would block hypertrophic responses induced by both receptor-mediated agonists and stretch. Our results suggest that nonspecific as well as class I–selective HDAC inhibitors may prove to be useful pharmacological agents for the prevention or treatment of cardiac hypertrophy and heart failure.
Methods
In Vivo Hypertrophy Models
Five- to 8-week-old adult male CD1 mice (n=225) and 6-week-old adult male Sprague-Dawley rats (n=40) were purchased from Daehan Biolink (Daejeon, Korea) and housed individually in plastic cages in a temperature-controlled room. The experimental protocol was approved by the Chonnam National University Medical School Research Institutional Animal Care and Use Committee. All surgical procedures and echocardiography were performed with the animals under anesthesia with ketamine (16.65 mg/kg IM) and xylazine (7.77 mg/kg IM).
Angiotensin II (Ang II) infusion was done at 1.3 mg/kg per day for 14 days. For preparation of aortic banding (AB), the left chest was opened at the second intercostal space with the animal under anesthesia. Partial aortic constriction was performed by ligating the ascending aorta with a 22-gauge needle with a 7-0 braided polyester suture. The increased blood flow velocity was confirmed by Doppler echocardiogram (Figure 1B and 1C). Sham-operated animals underwent the same surgical procedure without constricting the aorta. Establishment of hypertrophy was confirmed by echocardiography by measuring left ventricular (LV) wall thickness and dimensions, ratios of heart weight to body weight (HW/BW), and capacitance measurement in isolated cardiomyocytes after euthanasia.
Blood pressures of mice were evaluated by direct cannulation of the common carotid artery, connected to a polygraph (Grass 7E) through a pressure transducer. After the blood pressure was stabilized, the mean arterial pressure was recorded.
Implantation of osmotic minipumps and intraperitoneal administration of TSA (0.6 mg/kg/d) and VAL (0.71% in drinking water, ad libitum) were described previously.8 SK-7041 (SK) (In2Gen Co), dissolved in dimethyl sulfoxide, was administered 30 mg/kg per day IP 5 times a week for 2 weeks as described previously.9 The dose of HDAC inhibitors used has been reported to inhibit endogenous HDAC activity,9–13 and daily administration of TSA or VAL for a given period was well tolerated because it did not affect overall body weight or HW/BW ratio in control animals compared with those injected with vehicle alone (Figures 1A, 1D, 2A, 2 D). TSA, VAL, or SK did not affect cardiac contractility (Table 1).
Evaluation of Regression of Cardiac Hypertrophy
Regression of cardiac hypertrophy was evaluated by HW/BW or heart weight to tibia length (HW/TL) ratios and by echocardiogram. Cross-sectional areas of cardiomyocytes were also examined. For each experimental group, hearts from 4 to 6 animals were mounted after coronal section and stained with hematoxylin-eosin. Ten cardiomyocytes in LV free wall were randomly chosen, and cross-sectional areas were measured with Multi Gauge software (Fuji Photo Film Co) by a blinded investigator.
Echocardiographic studies were performed with a 15-MHz linear array transducer system (Acuson Sequoia c512, Siemens).8 Two-dimensionally guided M-mode of LV at the papillary level was obtained from the parasternal long-axis view. For each mouse, measurements were made from at least 4 beats. LV cavity dimension and wall thickness were measured, and percent change in LV dimension (fractional shortening [FS]) (LV%FS) was calculated as follows: LV%FS=[(LVDd–LVSd)/LVDd]x100, where LVDd is LV dimension at end-diastole and LVSd is LV dimension at end-systole. For the estimation of flow velocity, pulsed-wave Doppler sample volume was placed on the aorta just proximal and distal to the constriction (Figure 1B and 1C).
To determine whether preexisting cardiac hypertrophy could be affected by HDAC inhibition, 42 AB mice aged 8 weeks were randomly divided into 4 groups. The first group was euthanized at 2 weeks after operation, and hypertrophy was confirmed (AB2w group). TSA was administered daily to the second group from the next day of AB (AB+TSA2w group). The third group was maintained for 5 weeks without TSA (AB5w group). In the last group, 2 weeks after AB operation, daily injection of TSA was started and maintained for 3 additional weeks (AB2w+TSA3w group). For each experimental condition, age-matched mice with sham operation served as control. The long-term effect of HDAC inhibition was also evaluated by administration of VAL for 7 weeks, and survival rate as well as echocardiogram was examined.
Reverse Transcription–Polymerase Chain Reaction, Immunoblotting, and Histology
Reverse transcription–polymerase chain reaction (RT-PCR), immunoblotting, immunostaining, and Masson’s trichrome staining of tissues were described previously.8 Transcript levels of heart-specific genes were examined.7 Total RNA was isolated with TriZol reagent (Invitrogen Life Technologies), and 1 μg of RNA underwent reverse transcription reaction with Superscript first strand synthesis system for RT-PCR kit (Invitrogen Life Technologies). Quantification of the mRNA amounts was further confirmed with SYBR Green PCR kit (Applied Biosystems, Inc). Relative expression levels of genes were compared with those of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by the 2–C(t) method.14
For Western blot, anti–atrial natriuretic factor (ANF) (1:1000), anti–-tubulin antibody (1:1000, Zymed, South San Francisco, Calif), or anti-actin antibody (1:1000, Sigma, St Louis, Mo) was used. Nuclear fractions were extracted from isolated hearts with nuclear extraction kit (Panomics Inc), and the loaded protein amounts were checked by Ponceau S staining after separation on SDS-PAGE gel. The level of acetylation of histone H4 was assessed by immunoblotting with anti-acetyl histone H4 antibody (1:2000, Upstate Biotechnology Inc, Lake Placid, NY), following the manufacturer’s protocol.
For immunohistochemistry, primary antibody dilutions of ANF (Biodesign, Saco, Maine) and type I collagen (Abcam, Cambridge, UK) were 1:200 and 1:100, respectively. Cardiomyocyte apoptosis was evaluated by FragEL DNA fragmentation Detection kit with colorimetric TdT enzyme (Calbiochem), following the manufacturer’s protocol.
Results
Blockade of Cardiac Hypertrophy by Nonspecific HDAC Inhibitors
In previous work, we have shown that cardiac hypertrophy induced by constant infusion of isoproterenol can be significantly attenuated by TSA.8 We sought to determine whether nonspecific HDAC inhibition would also prevent the hypertrophy induced by an unrelated agonist or by pressure overload. Ang II is known to induce cardiac hypertrophy by activating receptor-mediated signaling cascades, including those involving mitogen-activated protein kinases, phosphatidylinositol 3-kinase, Akt, and janus-activating kinases.15 We treated CD1 mice with Ang II (1.3 mg/kg per day), which, as expected, induced cardiac hypertrophy, and HW/BW ratio was increased by 27% compared with the vehicle group. Concomitant treatment with VAL markedly reduced the hypertrophic response to Ang II (Figure 1A).
To determine whether cardiac hypertrophy induced by pressure overload in mice or rats could be prevented by HDAC inhibition, we treated AB mice or rats with TSA or VAL. AB induced a marked increase in flow velocity (Figure 1B and 1C) and LV wall thickness (Figure 3C and 3D) and a 46% increase in HW/BW ratio compared with sham-operated mice. VAL administration significantly attenuated this increase to 18% (Figure 1D), which was also evidenced by changes in HW/TL ratio (Figure 1E).
The Ang II–induced cardiac hypertrophy, as assessed by HW/BW ratio, was also significantly attenuated by TSA (Figure 2A), an unrelated agent with HDAC inhibitory activity.10 Blockade of cardiac hypertrophy by TSA in Ang II–treated animals raised the possibility that TSA might ameliorate the hypertension induced by Ang II, and thus the blockade of the hypertrophy might have been caused secondarily by reduction of afterload rather than by direct cardiac effects. To rule out this possibility, blood pressure was measured. As expected, Ang II markedly increased the blood pressure; however, TSA did not affect the increased or basal level of blood pressure (Figure 2B).
To determine whether regression of cardiac hypertrophy by HDAC inhibitors correlated with increases in histone acetylation in the cardiomyocytes, the effect of TSA treatment on histone H4 acetylation was determined by immunoblot analysis with an anti–acetyl histone H4 antibody. As shown in Figure 2C, TSA increased the acetylation of histone H4 of cardiomyocytes, whereas the total amount of histone was not changed.
Cardiac hypertrophy induced by AB, as shown by HW/BW ratio, was also significantly relieved by TSA (Figure 2D), which was further confirmed by changes in individual cardiomyocyte volume, measured by cross-sectional area (Figure 2E).
We performed similar experiments in rats and observed a comparable protective effect when AB rats were treated with TSA or VAL. AB significantly increased the HW/BW ratio by 47%, but this increase was significantly blunted to 25% by TSA administration (Figure I in the online-only Data Supplement; see http://circ.ahajournals.org/cgi/content/full/ 113/1/51/DC1).
Prevention of Cardiac Hypertrophy by SK-7041, a Class I HDAC-Selective Inhibitor
The present observations as well as the previous reports6,8 are somewhat unexpected and at odds with the previous findings that class II HDACs inhibit cardiac hypertrophy in response to various exogenous stimuli.4,5 However, the lack of specificity of HDAC inhibitors used led us to postulate that class I HDACs oppose class II HDACs in regulating cardiac hypertrophy and that the activity of class I HDACs predominates in the myocardium such that nonspecific HDAC inhibition results in blockade of hypertrophic pathways. Thus, we examined the effects of a selective class I HDAC inhibitor in our model.
Recently, novel hybrid HDAC inhibitors were synthesized by combining the hydroxamic acid of TSA and the pyridyl ring of MS-275, a synthetic benzamide derivative. One of these new HDAC inhibitors, 3-(4-substituted phenyl)-N-hydroxy-2-propenamide (SK-7041 [SK]),13 was found to have high selectivity to HDAC1 and HDAC2, both belonging to the class I HDAC family.9 To test whether cardiac hypertrophy induced by pressure overload could be prevented by class I–selective HDAC inhibition, we treated AB mice with SK. AB-induced cardiac enlargement was almost completely prevented by SK, as shown in Figure 3A, and the reduction of LV dimension was confirmed by M-mode echocardiogram (Figure 3C to 3F, Table 1). Histone acetylation status in SK-treated hearts is shown in Figure 3B. SK increased the histone H4 acetylation in both sham- and AB-operated groups (top panel).
AB increased HW/BW ratio by 46% in the vehicle-treated group; however, SK completely abolished the increase (to 2%) compared with the sham+SK group (Figure 3G). Because SK could induce mild weight loss in some mice, we measured tibia length and calculated HW/TL ratio. Similarly, the 51% increase in HW/TL ratio in the AB group was reduced to 3% by SK (Figure 3H). Table 1 shows the changes of LV dimensions as well as heart weight after administration of 3 HDAC inhibitors to AB mice. Although all 3 inhibitors significantly reduced the thickness of the interventricular septum and posterior wall, the reduction was greatest in the SK-treated group.
Regression of Preestablished Cardiac Hypertrophy and Long-Term Evaluation
We next examined whether HDAC inhibition can reverse preexisting cardiac hypertrophy, which might be of greater clinical significance. As expected, AB increased HW/BW ratio over a 2-week period, and this increase was significantly attenuated by simultaneous administration of TSA (Figure 4B). Maintenance of a cohort of AB mice with vehicle treatment for the subsequent 3 weeks resulted in a further increase in HW/BW ratio, suggesting that cardiac hypertrophy is progressive. Interestingly, however, TSA administration for a 3-week period after 2 weeks of AB relieved the preexisting cardiac hypertrophy and prevented further progression; HW/BW ratio was significantly reduced compared with AB2w as well as AB5w mice (Figure 4B). Reversal of preestablished cardiac hypertrophy was further confirmed by measuring HW/TL ratio, in which the level of regression appeared even more dramatic (Figure II in the online-only Data Supplement). The regression of the heart weight paralleled the reduction of LV wall thickness (Table 2).
The long-term effects of HDAC inhibition on cardiac hypertrophy and survival were evaluated in AB mice treated with or without VAL or TSA for 7 weeks. HW/TL in AB mice was increased by 41% over that in age-matched controls; however, this increase was blunted to 19% by VAL. Figure III in the online-only Data Supplement also shows similar changes in HW/BW. Some AB mice died suddenly and were found to have enlarged hearts with severe myocardial fibrosis. Kaplan-Meier analysis revealed that the survival rate was 54.7% at 40 days after surgery. However, administration with TSA or VAL improved the survival rate to 83.3% (Figure 2E).
Hypertrophic Markers
Cardiac hypertrophy reactivates the fetal gene program, characterized by a switch from -myosin heavy chain (-MHC) to -MHC gene expression in the adult murine heart.1,16 -MHC transcript levels as well as ANF transcripts were increased in Ang II and AB mice (Figure 5A and 5B). These increases were blunted by administration of TSA (Figure 5A) or SK (Figure 5B). The changes in ANF mRNA levels were confirmed by quantification, and both VAL and TSA significantly blunted the increase (Figure 5C).
In addition to ANF, -tubulin is another marker of cardiac hypertrophy and cardiac protein expression increases in response to diverse hypertrophic stimuli.17 As expected, AB increased the protein levels of ANF and -tubulin in mouse hearts. However, this increase was significantly blocked by treatment with TSA (Figure 5D) or SK (Figure 5E). Similar effects with regard to ANF and -tubulin expression were seen in rat heart samples after AB with and without TSA (Figure IV in the online-only Data Supplement).
We examined expression of ANF and deposition of type I collagen18 by immunohistochemistry after AB and Ang II, with and without TSA. Staining for both ANF and type I collagen was significantly enhanced in samples from AB rats (Figure 6B and 6E) compared with sham controls (Figure 6A and 6D). These changes in gene expression were normalized by TSA (Figure 6C and 6F). In AB mice, SK treatment also normalized the changes in ANF (Figure 6G to 6I).
AB for 2 and 7 weeks (Figure 6K and 6N) caused significant interstitial collagen deposition, as demonstrated by Masson’s trichrome staining. However, fibrosis was reduced in AB mice treated with SK for 2 weeks or VAL for 7 weeks (Figure 6L and 6O). Interestingly, in some mice with SK treatment, no evidence of interstitial fibrosis was seen (data not shown).
Previous reports that HDAC inhibitors, including SK, induce apoptosis of transformed cells9,19,20 and thereby can be used for cancer treatment9,21 raise the possibility that apoptosis in cardiomyocytes may occur in our animal models, leading to reduction of cardiac mass. However, terminal deoxynucleotidyl transferase–mediated dUTP nick-end labeling (TUNEL) staining showed no apparent increase in cardiomyocyte apoptosis in TSA- or SK-treated animals compared with the vehicle group (data not shown).
Discussion
Our results clarify that nonspecific HDAC inhibitors can function to attenuate cardiac hypertrophic changes induced by diverse stimuli including receptor-mediated agonists and pressure overload. In addition, we have shown that a class I HDAC-selective inhibitor prevents cardiac hypertrophy and that administration of HDAC inhibitors can induce regression of preestablished cardiac hypertrophy in at least some animal models.
Cardiac hypertrophy induced by transgenic overexpression of HOP or by chronic infusion of either isoproterenol or Ang II is prevented or significantly attenuated by concomitant treatment with TSA. Likewise, hypertrophy induced by AB, in which stretch-activated ion channels, integrins, and sarcomeric Z disks are involved in mediating hypertrophic signaling,22 is blocked by TSA or VAL. These results suggest that HDAC activation is a part of the final common pathway induced by diverse hypertrophic agonists and that inhibition of this step may serve as a therapeutic target for preventing or reversing cardiac hypertrophy and subsequent heart failure. Indeed, in this study, along with improved LV dimensions, as determined by echocardiogram, better survival in the TSA- or VAL-treated group in AB mice supports their beneficial effects on the transition of cardiac hypertrophy to heart failure. In addition, the regression of preestablished cardiac hypertrophy further raises the potential attractiveness for the therapeutic application of HDAC inhibitors.
It is unlikely that reduction in cardiac hypertrophy in the Ang II model was caused by relief of Ang II–induced hypertension, and we suggest that the primary target organ of HDAC inhibitors is heart rather than blood vessels. Likewise, cardiomyocyte apoptosis does not appear to be responsible for the reduction of heart mass. Previous reports6,23 have shown that TSA, VAL, or sodium butyrate, an alternate HDAC inhibitor, does not significantly affect the survival of primary cultured rat cardiomyocytes, and HDAC inhibitors in this study did not increase apoptosis in cardiomyocytes in vivo. Although HDAC inhibitors have significant proapoptotic effects in transformed cells,19 Park et al9 clearly showed that untransformed epithelial cells are much more resistant to SK-induced apoptosis than are cancer cells.
To date, at least 17 distinct HDACs have been reported in humans. Members of all 3 classes of HDACs are expressed in the heart, and, recently, class III HDACs were reported to be endogenous inhibitors of apoptosis in the heart.24 TSA or VAL inhibits both class I and class II HDACs. Given that class II HDACs function to antagonize cardiac hypertrophy,4,5 the antihypertrophic effect of nonspecific HDAC inhibitors is more likely to be mediated by class I HDACs. In this study we clearly demonstrate that class I HDACs in cardiomyocyte are prohypertrophic because SK, a class I HDAC-selective inhibitor, blocked the development of cardiac hypertrophy.
Given the proposed antagonistic actions of class I and class II HDACs, why do nonspecific HDAC inhibitors result in antihypertrophic effects The most plausible explanation is that class I HDAC activity predominates with regard to hypertrophic gene expression in the heart. Indeed, the enzymatic activity of class II HDACs is not required for the transcriptional repression of prohypertrophic genes in the heart, as a splice variant of HDAC9 that lacks a deacetylase domain is highly effective in repressing cardiac hypertrophy.5,25 These reports further support our conclusion that the net functional role of HDAC activity, probably mediated by class I HDACs, in cardiomyocytes is prohypertrophic.
Cell proliferation/growth arrest mechanisms are known to contribute to the regulation of cardiac hypertrophy.26 In cancer cells, for example, HDAC inhibitors relieve histone compaction to upregulate p21,27 which has been implicated as a repressor of hypertrophy.28 It is still unclear, however, whether HDACs may affect other prohypertrophic signal transduction cascades, because several nonhistone targets, such as tubulin and GATA transcription factor,23,29,30 which can affect cardiac remodeling, have been implicated. For example, in primarily cultured rat cardiomyocytes, TSA was shown to increase -MHC expression but to decrease cardiac tubulins. Although early growth response gene 1 (EGR-1) was elucidated as a primary mediator of the responses,23 direct evidence for the functional involvement of EGR-1 in in vivo hypertrophy remains to be demonstrated.
This work relies entirely on the use of pharmacological inhibitors of HDAC activity. Although we have attempted to use several different chemical inhibitors, it remains possible that the effects that we observed on cardiac hypertrophy are produced by effects of the drugs unrelated to their abilities to inhibit HDAC catalytic function. Indeed, alternative cellular functions for HDACs remain possibly unrelated to the regulation of chromatin structure as described above, and unappreciated functions of the pharmacological agents that we have used may exist. Nevertheless, the cardiac effects of these agents are of interest given the increasing likelihood of more widespread clinical use for noncardiac indications, including the treatment of neoplasia.21,31 Therefore, as well as development of novel HDAC inhibitors with selectivity and low toxicity, additional preclinical testing is indicated to validate the use of these inhibitors for prevention or reversal of cardiac hypertrophy and failure in humans.
Acknowledgments
This work was supported by the Korea Science and Engineering Foundation through the Medical Research Center for Gene Regulation (R13-2002-013-03002-0) at Chonnam National University. Dr Kee was supported by a Korea Research Foundation grant (KRF-2004-C00141). Dr Epstein was supported by grants from the National Institutes of Health. The authors are grateful to Do Su Kim and Jin Sung Park for their excellent assistance in surgical procedures, to Gwang Hyeon Eom for preparing pictures, and to Professor Emeritus Young Johng Kook, Chonnam National University Medical School, for reviewing the manuscript.
Disclosures
None.
References
Olson EN, Schneider MD. Sizing up the heart: development redux in disease. Genes Dev. 2003; 17: 1937–1956.
Schreiber SL, Bernstein BE. Signaling network model of chromatin. Cell. 2002; 111: 771–778.
Gusterson RJ, Jazrawi E, Adcock IM, Latchman DS. The transcriptional co-activators CREB binding protein (CBP) and p300 play a critical role in cardiac hypertrophy that is dependent on their histone acetyltransferase activity. J Biol Chem. 2003; 278: 6838–6847.
McKinsey TA, Zhang CL, Olson EN. Signaling chromatin to make muscle. Curr Opin Cell Biol. 2002; 14: 763–772.
Zhang CL, McKinsey TA, Chang S, Antos CL, Hill JA, Olson EN. Class II histone deacetylases act as signal-responsive repressors of cardiac hypertrophy. Cell. 2002; 110: 479–488.
Antos CL, McKinsey TA, Dreitz M, Hollingsworth LM, Zhang CL, Schreiber K, Rindt H, Gorczynski RJ, Olson EN. Dose-dependent blockade to cardiomyocyte hypertrophy by histone deacetylase inhibitors. J Biol Chem. 2003; 278: 28930–28937.
Chen F, Kook H, Milewski R, Gitler AD, Lu MM, Li J, Nazarian R, Schnepp R, Jen K, Biben C, Runke G, Mackay JP, Novotny J, Schwartz RJ, Harvey RP, Mullins MC, Epstein JA. HOP is an unusual homeobox gene that modulates cardiac development. Cell. 2002; 110: 713–723.
Kook H, Lepore JJ, Gitler AD, Lu MM, Wing-Man Yung W, Mackay J, Zhou R, Ferrari V, Gruber P, Epstein JA. Cardiac hypertrophy and histone deacetylase-dependent transcriptional repression mediated by the atypical homeodomain protein HOP. J Clin Invest. 2003; 112: 863–871.
Park JH, Jung Y, Kim TY, Kim SG, Jong HS, Lee JW, Kim DK, Lee JS, Kim NK, Kim TY, Bang YJ. Class I histone deacetylase-selective novel synthetic inhibitors potently inhibit human tumor proliferation. Clin Cancer Res. 2004; 10: 5271–5281.
Yoshida M, Kijima M, Akita M, Beppu T. Potent and specific inhibition of mammalian histone deacetylase both in vivo and in vitro by trichostatin A. J Biol Chem. 1990; 265: 17174–17179.
Nervi C, Borello U, Fazi F, Buffa V, Pelicci PG, Cossu G. Inhibition of histone deacetylase activity by trichostatin A modulates gene expression during mouse embryogenesis without apparent toxicity. Cancer Res. 2001; 61: 1247–1249.
Gottlicher M, Minucci S, Zhu P, Kramer OH, Schimpf A, Giavara S, Sleeman JP, Lo Coco F, Nervi C, Pelicci PG, Heinzel T. Valproic acid defines a novel class of HDAC inhibitors inducing differentiation of transformed cells. EMBO J. 2001; 20: 6969–6978.
Kim DK, Lee JY, Kim JS, Ryu JH, Choi JY, Lee JW, Im GJ, Kim TK, Seo JW, Park HJ, Yoo J, Park JH, Kim TY, Bang YJ. Synthesis and biological evaluation of 3-(4-substituted-phenyl)-N-hydroxy-2-propenamides, a new class of histone deacetylase inhibitors. J Med Chem. 2003; 46: 5745–5751.
Ismat FA, Zhang M, Kook H, Huang B, Zhou R, Ferrari VA, Epstein JA, Patel VV. Homeobox protein Hop functions in the adult cardiac conduction system. Circ Res. 2005; 96: 898–903.
Shah BH, Catt KJ. A centrol role of EGF receptor transactivation in angiotensin II–induced cardiac hypertrophy. Trends Pharmacol Sci. 2003; 24: 239–244.
Izumo S, Lompre AM, Matsuoka R, Koren G, Schwartz K, Nadal-Ginard B, Mahdavi V. Myosin heavy chain messenger RNA and protein isoform transitions during cardiac hypertrophy: interaction between hemodynamic and thyroid hormone-induced signals. J Clin Invest. 1987; 79: 970–977.
Belmadani S, Pous C, Ventura-Clapier R, Fischmeister R, Mery PF. Post-translational modifications of cardiac tubulin during chronic heart failure in the rat. Mol Cell Biochem. 2002; 237: 39–46.
Contard F, Koteliansky V, Marotte F, Dubus I, Rappaport L, Samuel JL. Specific alterations in the distribution of extracellular matrix components within rat myocardium during the development of pressure overload. Lab Invest. 1991; 64: 65–75.
Marks PA, Richon VM, Rifkind RA. Histone deacetylase inhibitors: inducers of differentiation or apoptosis of transformed cells. J Natl Cancer Inst. 2000; 92: 1210–1216.
Ryu JK, Lee WJ, Lee KH, Hwang JH, Kim YT, Yoon YB, Kim CY. SK-7041, a new histone deacetylase inhibitor, induces G(2)-M cell cycle arrest and apoptosis in pancreatic cancer cell lines. Cancer Lett. 2005; xx: 1–12.
Marks PA, Richon VM, Breslow R, Rifkind RA. Histone deacetylase inhibitors as new cancer drugs. Curr Opin Oncol. 2001; 13: 477–483.
Sadoshima J, Izumo S. The cellular and molecular response to cardiac myocytes to mechanical stress. Annu Rev Physiol. 1997; 59: 551–571.
Davis FJ, Pillai JB, Gupta M, Gupta MP. Concurrent opposite effects of trichostatin A, an inhibitor of histone deacetylases, on expression of alpha-MHC and cardiac tubulins: implication for gain in cardiac muscle contractility. Am J Physiol. 2005; 288: H1477–H1490.
Alcendor RR, Kirshenbaum LA, Imai S-I, Vatner SF, Sadoshima J. Silent information regulator 2, a longevity factor and class III histone deacetylase, is an essential endogenous apoptosis inhibitor in cardiac myocytes. Circ Res. 2004; 95: 971–980.
McKinsey TA, Olson EN. Toward transcriptional therapies for the failing heart: chemical screens to modulate genes. J Clin Invest. 2005; 115: 538–546.
Hoshijima M, Chien KR. Mixed signals in heart failure: cancer rules. J Clin Invest. 2002; 109: 849–855.
Gui CY, Ngo L, Xu WS, Richon VM, Marks PA. Histone deacetylase (HDAC) inhibitor activation of p21WAF1 involves changes in promoter-associated proteins, including HDAC1. Proc Natl Acad Sci U S A. 2004; 101: 1241–1246.
Tamamori M, Ito H, Hiroe M, Terada Y, Marumo F, Ikeda MA. Essential roles for G1 cyclin-dependent kinase activity in development of cardiomyocyte hypertrophy. Am J Physiol. 1998; 275: H2036–H2040.
Westermann S, Weber K. Post-translational modifications regulate microtubule function. Nat Rev Mol Cell Biol. 2003; 4: 938–947.
Kawamura T, Ono K, Morimoto T, Wada H, Hirai M, Hidaka K, Morisaki T, Heike T, Nakahata T, Kita T, Hasegawa K. Acetylation of GATA-4 is involved in the differentiation of embryonic stem cells into cardiac myocytes. J Biol Chem. 2005; 280: 19682–19688.
Kwon HJ, Kim M, Kim DH. Histone deacetylase in carcinogenesis and its inhibitors as anti-cancer agents. J Biochem Mol Biol. 2003; 36: 110–119.(Hae Jin Kee, PhD; Il Suk Sohn, MD, PhD; )