PSME4 determines mesenchymal stem cell fate towards cardiac commitment through YAP1 degradation

The regeneration of myocardium following acute circulatory events remains a challenge, despite numerous efforts. Mesenchymal stem cells (MSCs) present a promising cell therapy option, but their differentiation into cardiomyocytes is a time-consuming process. Although it has been demonstrated that PSME4 degrades acetyl-YAP1, the role of PSME4 in the cardiac commitment of MSCs has not been fully elucidated. Here we reported the novel role of PSME4 in MSCs cardiac commitment. It was found that overnight treatment with apicidin in primary-cultured mouse MSCs led to rapid cardiac commitment, while MSCs from PSME4 knock-out mice did not undergo this process. Cardiac commitment was also observed using lentivirus-mediated PSME4 knockdown in immortalized human MSCs. Immunofluorescence and Western blot experiments revealed that YAP1 persisted in the nucleus of PSME4 knockdown cells even after apicidin treatment. To investigate the importance of YAP1 removal, MSCs were treated with shYAP1 and apicidin simultaneously. This combined treatment resulted in rapid YAP1 elimination and accelerated cardiac commitment. However, overexpression of acetylation-resistant YAP1 in apicidin-treated MSCs impeded cardiac commitment. In addition to apicidin, the universal effect of histone deacetylase (HDAC) inhibition on cardiac commitment was confirmed using tubastatin A and HDAC6 siRNA. Collectively, this study demonstrates that PSME4 is crucial for promoting the cardiac commitment of MSCs. HDAC inhibition acetylates YAP1 and facilitates its translocation to the nucleus, where it is removed by PSME4, promoting cardiac commitment. The failure of YAP1 to translocate or be eliminated from the nucleus results in the MSCs' inability to undergo cardiac commitment.

High VEGF Concentrations Accelerate Human Trabecular Meshwork Fibrosis in a TAZ-Dependent Manner

We aimed to investigate the effects of different concentrations of vascular endothelial growth factor (VEGF) on the extracellular matrix (ECM) and fibrotic proteins in human trabecular meshwork (TM) cells. We also explored how the Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) signaling pathway modulates VEGF-induced fibrosis. We determined cross-linked actin network (CLAN) formation using TM cells. Changes in fibrotic and ECM protein expression were determined. High VEGF concentrations (10 and 30 ng/mL) increased TAZ and decreased p-TAZ/TAZ expression in TM cells. Western blotting and real-time PCR revealed no YAP expression changes. Fibrotic and ECM protein expression decreased at low VEGF concentrations (1 and 10 ρg/mL) and significantly increased at high VEGF concentrations (10 and 30 ng/mL). CLAN formation increased in TM cells treated with high VEGF concentrations. Moreover, TAZ inhibition by verteporfin (1 μM) rescued TM cells from high-VEGF-concentration-induced fibrosis. Low VEGF concentrations reduced fibrotic changes, whereas high VEGF concentrations accelerated fibrosis and CLAN formations in TM cells in a TAZ-dependent manner. These findings reflect the dose-dependent influences of VEGF on TM cells. Moreover, TAZ inhibition might be a therapeutic target for VEGF-induced TM dysfunction.

PSME4 Degrades Acetylated YAP1 in the Nucleus of Mesenchymal Stem Cells

Intensive research has focused on minimizing the infarct area and stimulating endogenous regeneration after myocardial infarction. Our group previously elucidated that apicidin, a histone deacetylase (HDAC) inhibitor, robustly accelerates the cardiac commitment of naïve mesenchymal stem cells (MSCs) through acute loss of YAP1. Here, we propose the novel regulation of YAP1 in MSCs. We found that acute loss of YAP1 after apicidin treatment resulted in the mixed effects of transcriptional arrest and proteasomal degradation. Subcellular fractionation revealed that YAP1 was primarily localized in the cytoplasm. YAP1 was acutely relocalized into the nucleus and underwent proteasomal degradation. Interestingly, phosphor-S127 YAP1 was shuttled into the nucleus, suggesting that a mechanism other than phosphorylation governed the subcellular localization of YAP1. Apicidin successfully induced acetylation and subsequent dissociation of YAP1 from 14-3-3, an essential molecule for cytoplasmic restriction. HDAC6 regulated both acetylation and subcellular localization of YAP1. An acetylation-dead mutant of YAP1 retarded nuclear redistribution upon apicidin treatment. We failed to acquire convincing evidence for polyubiquitination-dependent degradation of YAP1, suggesting that a polyubiquitination-independent regulator determined YAP1 fate. Nuclear PSME4, a subunit of the 26 S proteasome, recognized and degraded acetyl YAP1 in the nucleus. MSCs from PSME4-null mice were injected into infarcted heart, and aberrant sudden death was observed. Injection of immortalized human MSCs after knocking down PSME4 failed to improve either cardiac function or the fibrotic scar area. Our data suggest that acetylation-dependent proteasome subunit PSME4 clears acetyl-YAP1 in response to apicidin treatment in the nucleus of MSCs.

Abstract P1135: Psme4 Degrades Acetylated Yap1 In The Nucleus Of Mesenchymal Stem Cells To Induce Cardiac Commitment

Intensive research has focused on minimizing the infarct area and stimulating endogenous regeneration after myocardial infarction. Our group elucidated that apicidin, a histone deacetylase (HDAC) inhibitor, robustly stimulates cardiac commitment of mesenchymal stem cells (MSCs) through acute loss of YAP1. Here we further studied the mechanism of this role of YAP1 in MSCs. We found that acute loss of YAP1 after apicidin treatment resulted in the mixed effects of transcriptional arrest and proteosomal degradation. Subcellular fractionation revealed that YAP1 was primarily localized in the cytoplasm. YAP1 was acutely relocalized into the nucleus and underwent proteosomal degradation. Interestingly, phosphor-S127 YAP1 was shuttled into the nucleus, suggesting that a mechanism other than phosphorylation governed subcellular localization of YAP1. Apicidin successfully induced acetylation and subsequent dissociation of YAP1 from 14-3-3, an essential molecule for cytoplasmic restriction. HDAC6 regulated both acetylation and subcellular localization of YAP1. An acetylation-dead mutant of YAP1 retarded nuclear redistribution upon apicidin treatment. We failed to acquire convincing evidence for polyubiquitination-dependent degradation of YAP1, suggesting that a polyubiquitination-independent regulator determined YAP1 fate. Nuclear PSME4, a subunit of the 26S proteasome, recognized and degraded acetyl YAP1 in the nucleus. MSCs from PSME4-null mice were injected into infarcted heart and aberrant sudden death was observed. Injection of immortalized human MSCs after knocking down PSME4 failed to improve either cardiac function or the fibrotic scar area. Our data suggest that acute ablation of YAP1 in the nucleus by the acetylation-dependent proteasome subunit PSME4 is mandatory for cardiac commitment of MSCs.

Overexpression of Heat Shock Protein 70 Improves Cardiac Remodeling and Survival in Protein Phosphatase 2A-Expressing Transgenic Mice with Chronic Heart Failure

Heat shock protein (HSP) 70 is a molecular chaperone that regulates protein structure in response to thermal stress. In addition, HSP70 is involved in post-translational modification and is related to the severity of some diseases. Here, we tested the functional relevance of long-lasting HSP70 expression in a model of nonischemic heart failure using protein phosphatase 2 catalytic subunit A (PP2CA)-expressing transgenic mice. These transgenic mice, with cardiac-specific overexpression of PP2CA, abruptly died after 12 weeks of postnatal life. Serial echocardiograms to assess cardiac function revealed that the ejection fraction (EF) was gradually decreased in transgenic PP2CA (TgPP2CA) mice. In addition, PP2CA expression exacerbated systolic dysfunction and LV dilatation, with free wall thinning, which are indicators of fatal dilated cardiomyopathy. Interestingly, simultaneous expression of HSP70 in double transgenic mice (dTg) significantly improved the dilated cardiomyopathy phenotype of TgPP2CA mice. We observed better survival, preserved EF, reduced chamber enlargement, and suppression of free wall thinning. In the proposed molecular mechanism, HSP70 preferentially regulates the phosphorylation of AKT. Phosphorylation of AKT was significantly reduced in TgPP2CA mice but was not significantly lower in dTg mice. Signal crosstalk between AKT and its substrates, in association with HSP70, might be a useful intervention for patients with nonischemic heart failure to suppress cardiac remodeling and improve survival.

Statin Use and COVID-19 Infectivity and Severity in South Korea: Two Population-Based Nationwide Cohort Studies

Background

Basic studies suggest that statins as add-on therapy may benefit patients with COVID-19; however, real-world evidence of such a beneficial association is lacking.

Objective

We investigated differences in SARS-CoV-2 test positivity and clinical outcomes of COVID-19 (composite endpoint: admission to intensive care unit, invasive ventilation, or death) between statin users and nonusers.

Methods

Two independent population-based cohorts were analyzed, and we investigated the differences in SARS-CoV-2 test positivity and severe clinical outcomes of COVID-19, such as admission to the intensive care unit, invasive ventilation, or death, between statin users and nonusers. One group comprised an unmatched cohort of 214,207 patients who underwent SARS-CoV-2 testing from the Global Research Collaboration Project (GRCP)-COVID cohort, and the other group comprised an unmatched cohort of 74,866 patients who underwent SARS-CoV-2 testing from the National Health Insurance Service (NHIS)-COVID cohort.

Results

The GRCP-COVID cohort with propensity score matching had 29,701 statin users and 29,701 matched nonusers. The SARS-CoV-2 test positivity rate was not associated with statin use (statin users, 2.82% [837/29,701]; nonusers, 2.65% [787/29,701]; adjusted relative risk [aRR] 0.97; 95% CI 0.88-1.07). Among patients with confirmed COVID-19 in the GRCP-COVID cohort, 804 were statin users and 1573 were matched nonusers. Statin users were associated with a decreased likelihood of severe clinical outcomes (statin users, 3.98% [32/804]; nonusers, 5.40% [85/1573]; aRR 0.62; 95% CI 0.41-0.91) and length of hospital stay (statin users, 23.8 days; nonusers, 26.3 days; adjusted mean difference –2.87; 95% CI –5.68 to –0.93) than nonusers. The results of the NHIS-COVID cohort were similar to the primary results of the GRCP-COVID cohort.

Conclusions

Our findings indicate that prior statin use is related to a decreased risk of worsening clinical outcomes of COVID-19 and length of hospital stay but not to that of SARS-CoV-2 infection.

BRD4 orchestrates genome folding to promote neural crest differentiation

Higher-order chromatin structure regulates gene expression, and mutations in proteins mediating genome folding underlie developmental disorders known as cohesinopathies. However, the relationship between three-dimensional genome organization and embryonic development remains unclear. Here we define a role for bromodomain-containing protein 4 (BRD4) in genome folding, and leverage it to understand the importance of genome folding in neural crest progenitor differentiation. Brd4 deletion in neural crest results in cohesinopathy-like phenotypes. BRD4 interacts with NIPBL, a cohesin agonist, and BRD4 depletion or loss of the BRD4-NIPBL interaction reduces NIPBL occupancy, suggesting that BRD4 stabilizes NIPBL on chromatin. Chromatin interaction mapping and imaging experiments demonstrate that BRD4 depletion results in compromised genome folding and loop extrusion. Finally, mutation of individual BRD4 amino acids that mediate an interaction with NIPBL impedes neural crest differentiation into smooth muscle. Remarkably, loss of WAPL, a cohesin antagonist, rescues attenuated smooth muscle differentiation resulting from BRD4 loss. Collectively, our data reveal that BRD4 choreographs genome folding and illustrates the relevance of balancing cohesin activity for progenitor differentiation.

Nitrosative Stress and Human Disease: Therapeutic Potential of Denitrosylation

Proteins dynamically contribute towards maintaining cellular homeostasis. Posttranslational modification regulates the function of target proteins through their immediate activation, sudden inhibition, or permanent degradation. Among numerous protein modifications, protein nitrosation and its functional relevance have emerged. Nitrosation generally initiates nitric oxide (NO) production in association with NO synthase. NO is conjugated to free thiol in the cysteine side chain (S-nitrosylation) and is propagated via the transnitrosylation mechanism. S-nitrosylation is a signaling pathway frequently involved in physiologic regulation. NO forms peroxynitrite in excessive oxidation conditions and induces tyrosine nitration, which is quite stable and is considered irreversible. Two main reducing systems are attributed to denitrosylation: glutathione and thioredoxin (TRX). Glutathione captures NO from S-nitrosylated protein and forms S-nitrosoglutathione (GSNO). The intracellular reducing system catalyzes GSNO into GSH again. TRX can remove NO-like glutathione and break down the disulfide bridge. Although NO is usually beneficial in the basal context, cumulative stress from chronic inflammation or oxidative insult produces a large amount of NO, which induces atypical protein nitrosation. Herein, we (1) provide a brief introduction to the nitrosation and denitrosylation processes, (2) discuss nitrosation-associated human diseases, and (3) discuss a possible denitrosylation strategy and its therapeutic applications.

Serum Ferritin as a Diagnostic Biomarker for Kawasaki Disease

Diagnosis of Kawasaki disease (KD) is occasionally delayed because it is solely based on clinical symptoms. Previous studies have attempted to identify diagnostic biomarkers for KD. Recently, patients with KD were reported to have elevated serum ferritin levels. We investigated the usefulness of the serum ferritin level as a diagnostic biomarker for distinguishing KD from other acute febrile illnesses. Blood samples were obtained from pediatric patients with KD (N=77) and those with other acute febrile illnesses (N=32) between December 2007 and June 2011 for measuring various laboratory parameters, including serum ferritin levels. In patients with KD, laboratory tests were performed at diagnosis and repeated at 2, 14, and 56 days after intravenous immunoglobulin treatment. At the time of diagnosis, serum ferritin levels in patients with KD (188.8 μg/L) were significantly higher than those in patients with other acute febrile illnesses (106.8 μg/L, P=0.003). The serum ferritin cut-off value of 120.8 μg/L effectively distinguished patients with KD from those with other acute febrile illnesses, with a sensitivity and specificity of 74.5% and 83.3%, respectively. Serum ferritin may be a useful biomarker to distinguish KD from other acute febrile illnesses.

S-Nitrosylation of Histone Deacetylase 2 by Neuronal Nitric Oxide Synthase as a Mechanism of Diastolic Dysfunction

BACKGROUND

Although the clinical importance of heart failure with preserved ejection fraction has been extensively explored, most therapeutic regimens, including nitric oxide (NO) donors, lack therapeutic benefit. Although the clinical characteristics of heart failure with preserved ejection fraction are somewhat heterogeneous, diastolic dysfunction (DD) is one of the most important features. Here we report that neuronal NO synthase (nNOS) induces DD by S-nitrosylation of HDAC2 (histone deacetylase 2).

METHODS

Two animal models of DD-SAUNA (SAlty drinking water/Unilateral Nephrectomy/Aldosterone) and mild transverse aortic constriction mice-as well as human heart samples from patients with left ventricular hypertrophy were used. Genetically modified mice that were either nNOS-ablated or HDAC2 S-nitrosylation-resistant were also challenged. N(ω)-propyl-L-arginine, an nNOS selective inhibitor, and dimethyl fumarate, an NRF2 (nuclear factor erythroid 2-related factor 2) inducer, were used. Molecular events were further checked in human left ventricle specimens.

RESULTS

SAUNA or mild transverse aortic constriction stress impaired diastolic function and exercise tolerance without overt systolic failure. Among the posttranslational modifications tested, S-nitrosylation was most dramatically increased in both models. Utilizing heart samples from both mice and humans, we observed increases in nNOS expression and NO production. N(ω)-propyl-L-arginine alleviated the development of DD in vivo. Similarly, nNOS knockout mice were resistant to SAUNA stress. nNOS-induced S-nitrosylation of HDAC2 was relayed by transnitrosylation of GAPDH. HDAC2 S-nitrosylation was confirmed in both DD mouse and human left ventricular hypertrophy. S-nitrosylation of HDAC2 took place at C262 and C274. When DD was induced, HDAC2 S-nitrosylation was detected in wild-type mouse, but not in HDAC2 knock-in mouse heart that expressed HDAC2 C262A/C274A. In addition, HDAC2 C262A/C274A mice maintained normal diastolic function under DD stimuli. Gene delivery with adenovirus-associated virus 9 (AAV9)-NRF2, a putative denitrosylase of HDAC2, or pharmacological intervention by dimethyl fumarate successfully induced HDAC2 denitrosylation and mitigated DD in vivo.

CONCLUSIONS

Our observations are the first to demonstrate a new mechanism underlying DD pathophysiology. Our results provide theoretical and experimental evidence to explain the ineffectiveness of conventional NO enhancement trials for improving DD with heart failure symptoms. More important, our results suggest that reduction of NO or denitrosylation of HDAC2 may provide a new therapeutic platform for the treatment of refractory heart failure with preserved ejection fraction.

miR-27a-3p Targets ATF3 to Reduce Calcium Deposition in Vascular Smooth Muscle Cells

Vascular calcification, the ectopic deposition of calcium in blood vessels, develops in association with various metabolic diseases and atherosclerosis and is an independent predictor of morbidity and mortality associated with these diseases. Herein, we report that reduction of microRNA-27a-3p (miR-27a-3p) causes an increase in activating transcription factor 3 (ATF3), a novel osteogenic transcription factor, in vascular smooth muscle cells. Both microRNA (miRNA) and mRNA microarrays were performed with rat vascular smooth muscle cells, and reciprocally regulated pairs of miRNA and mRNA were selected after bioinformatics analysis. Inorganic phosphate significantly reduced the expression of miR-27a-3p in A10 cells. The transcript level was also reduced in vitamin D₃-administered mouse aortas. miR-27a-3p mimic reduced calcium deposition, whereas miR-27a-3p inhibitor increased it. The Atf3 mRNA level was upregulated in a cellular vascular calcification model, and miR-27a-3p reduced the Atf3 mRNA and protein levels. Transfection with Atf3 could recover the miR-27a-3p-induced reduction of calcium deposition. Our results suggest that reduction of miR-27a-3p may contribute to the development of vascular calcification by de-repression of ATF3.

Inhibition of heat shock protein 70 blocks the development of cardiac hypertrophy by modulating the phosphorylation of histone deacetylase 2

AIMS

Previously, we reported that phosphorylation of histone deacetylase 2 (HDAC2) and the resulting activation causes cardiac hypertrophy. Through further study of the specific binding partners of phosphorylated HDAC2 and their mechanism of regulation, we can better understand how cardiac hypertrophy develops. Thus, in the present study, we aimed to elucidate the function of one such binding partner, heat shock protein 70 (HSP70).

METHODS AND RESULTS

Primary cultures of rat neonatal ventricular cardiomyocytes and H9c2 cardiomyoblasts were used for in vitro cellular experiments. HSP70 knockout (KO) mice and transgenic (Tg) mice that overexpress HSP70 in the heart were used for in vivo analysis. Peptide-precipitation and immunoprecipitation assay revealed that HSP70 preferentially binds to phosphorylated HDAC2 S394. Forced expression of HSP70 increased phosphorylation of HDAC2 S394 and its activation, but not that of S422/424, whereas knocking down of HSP70 reduced it. However, HSP70 failed to phosphorylate HDAC2 in the cell-free condition. Phosphorylation of HDAC2 S394 by casein kinase 2α1 enhanced the binding of HSP70 to HDAC2, whereas dephosphorylation induced by the catalytic subunit of protein phosphatase 2A (PP2CA) had the opposite effect. HSP70 prevented HDAC2 dephosphorylation by reducing the binding of HDAC2 to PP2CA. HSP70 KO mouse hearts failed to phosphorylate S394 HDAC2 in response to isoproterenol infusion, whereas Tg overexpression of HSP70 increased the phosphorylation and activation of HDAC2. 2-Phenylethynesulfonamide (PES), an HSP70 inhibitor, attenuated cardiac hypertrophy induced either by phenylephrine in neonatal ventricular cardiomyocytes or by aortic banding in mice. PES reduced HDAC2 S394 phosphorylation and its activation by interfering with the binding of HSP70 to HDAC2.

CONCLUSION

These results demonstrate that HSP70 specifically binds to S394-phosphorylated HDAC2 and maintains its phosphorylation status, which results in HDAC2 activation and the development of cardiac hypertrophy. Inhibition of HSP70 has possible application as a therapeutic.

Chimeric Antigen Receptor T Cell Therapy: A Novel Modality for Immune Modulation

Cancer remains a leading cause of death, despite multimodal treatment approaches. Even in patients with a healthy immune response, cancer cells can escape the immune system during tumorigenesis. Cancer cells incapacitate the normal cell-mediated immune system by expressing immune modulation ligands such as programmed death (PD) ligand 1, the B7 molecule, or secreting activators of immune modulators. Chimeric antigen receptor (CAR) T cells were originally designed to target cancer cells. Engineered approaches allow CAR T cells, which possess a simplified yet specific receptor, to be easily activated in limited situations. CAR T cell treatment is a derivative of the antigen-antibody reaction and can be applied to various diseases. In this review, the current successes of CAR T cells in cancer treatment and the therapeutic potential of CAR T cells are discussed.

HDAC2 Regulates Glial Cell Activation in Ischemic Mouse Retina

The current study was undertaken to investigate whether histone deacetylases (HDACs) can modulate the viability of retinal ganglion cells (RGCs) and the activity of glial cells in a mouse model of retinal ischemia-reperfusion (IR) injury. C57BL/6J mice were subjected to constant elevation of intraocular pressure for 60 min to induce retinal IR injury. Expression of macroglial and microglial cell markers (GFAP and Iba1), hypoxia inducing factor (HIF)-1α, and histone acetylation was analyzed after IR injury. To investigate the role of HDACs in the activation of glial cells, overexpression of HDAC1 and HDAC2 isoforms was performed. To determine the effect of HDAC inhibition on RGC survival, trichostatin-A (TSA, 2.5 mg/kg) was injected intraperitoneally. After IR injury, retinal GFAP, Iba1, and HIF-1α were upregulated. Conversely, retinal histone acetylation was downregulated. Notably, adenoviral-induced overexpression of HDAC2 enhanced glial activation following IR injury, whereas overexpression of HDAC1 did not significantly affect glial activation. TSA treatment significantly increased RGC survival after IR injury. Our results suggest that increased activity of HDAC2 is closely related to glial activation in a mouse model of retinal IR injury and inhibition of HDACs by TSA showed neuroprotective potential in retinas with IR injuries.

Antiinflammatory activity of ANGPTL4 facilitates macrophage polarization to induce cardiac repair

Mesenchymal stem cells (MSCs) can suppress pathological inflammation. However, the mechanisms underlying the association between MSCs and inflammation remain unclear. Under coculture conditions with macrophages, MSCs highly expressed angiopoietin-like 4 (ANGPTL4) to blunt the polarization of macrophages toward the proinflammatory phenotype. ANGPTL4-deficient MSCs failed to inhibit the inflammatory macrophage phenotype. In inflammation-related animal models, the injection of coculture medium or ANGPTL4 protein increased the antiinflammatory macrophages in both peritonitis and myocardial infarction. In particular, cardiac function and pathology were markedly improved by ANGPTL4 treatment. We found that retinoic acid-related orphan receptor α (RORα) was increased by inflammatory mediators, such as IL-1β, and bound to ANGPTL4 promoter in MSCs. Collectively, RORα-mediated ANGPTL4 induction was shown to contribute to the antiinflammatory activity of MSCs against macrophages under pathological conditions. This study suggests that the capability of ANGPTL4 to induce tissue repair is a promising opportunity for safe stem cell-free regeneration therapy from a translational perspective.

Abstract 946: Aberrant Activation of Nitric Oxide Synthase 1 in the Heart Accelerates Diastolic Dysfunction Though Protein S-nitrosylation

Heart failure refers to an inappropriate blood supply to the periphery. Among subtype of heart failure, pathophysiology and effective therapeutic strategy of systolic heart failure is well established. However, molecular mechanism and specific regimens for diastolic heart failure (DHF) still remains unclear. Here we propose nitric oxide synthase (NOS) 1 mediated exacerbation of DHF and therapeutic potential for novel therapeutics. We screened alteration of posttranslational modifications in DHF which were induced either by SAUNA (SAlty drinking water/Unilateral Nephrectomy/Aldosterone) model or transverse aortic constriction (TAC) model and observed that protein S-nitrosylation was dramatically increased. Total RNA sequencing revealed that transcription amount of NOS1 was aberrantly increased in DHF, whereas NOS2 or NOS3 was not changed. Either non-selective NOS inhibitor or specific NOS1 inhibitor effectively blocked diastolic dysfunction. To elucidate the molecular target of S-nitrosylation, we performed biotin switch assay and requested protein sequencing which were newly appeared in the presence of GSNO. Among novel signal, we identified and confirmed that Histone deacetylase (HDAC) 2 was target molecule of NOS1. HDAC2 cysteine 262 and cysteine 274 were responsible residue of NOS1-mediated S-nitrosylation. We generated knock-in mice carrying S-nitrosylation defect HDAC2 mutant, HDAC2 C262A/C274A (2CA). HDAC2 2CA knock-in mice underwent SAUNA surgery or TAC and diastolic function of those mice was measured by early diastole (E) and mitral valve annulus movement (E’). When compared to wild type littermates, the diastolic function assessed by E/E’ ratio in HDAC2 2CA knock-in mice were relatively well conserved both in SAUNA- and TAC-induced DHF model. Survival rate after TAC operation was also dramatically ameliorated in HDAC2 2CA knock-in mice. Taken together, we proposed novel molecular axis, NOS1/S-NO HDAC2, accelerating diastolic dysfunction and which implicated notable molecular target for treatment of DHF patients.

Augmentation of NAD+ levels by enzymatic action of NAD(P)H quinone oxidoreductase 1 attenuates adriamycin-induced cardiac dysfunction in mice

BACKGROUND

Adriamycin (ADR) is a powerful chemotherapeutic agent extensively used to treat various human neoplasms. However, its clinical utility is hampered due to severe adverse side effects i.e. cardiotoxicity and heart failure. ADR-induced cardiomyopathy (AIC) has been reported to be caused by myocardial damage and dysfunction through oxidative stress, DNA damage, and inflammatory responses. Nonetheless, the remedies for AIC are even not established. Therefore, we illustrate the role of NAD⁺/NADH modulation by NAD(P)H quinone oxidoreductase 1 (NQO1) enzymatic action on AIC.

METHODS AND RESULTS

AIC was established by intraperitoneal injection of ADR in C57BL/6 wild-type (WT) and NQO1 knockout (NQO1^-/-) mice. All Mice were orally administered dunnione (named NQO1 substrate) before and after exposure to ADR. Cardiac biomarker levels in the plasma, cardiac dysfunction, oxidative biomarkers, and mRNA and protein levels of pro-inflammatory mediators were determined compared the cardiac toxicity of each experimental group. All biomarkers of Cardiac damage and oxidative stress, and mRNA levels of pro-inflammatory cytokines including cardiac dysfunction were increased in ADR-treated both WT and NQO1^-/- mice. However, this increase was significantly reduced by dunnione in WT, but not in NQO1^-/- mice. In addition, a decrease in SIRT1 activity due to a reduction in the NAD⁺/NADH ratio by PARP-1 hyperactivation was associated with AIC through increased nuclear factor (NF)-κB p65 and p53 acetylation in both WT and NQO1^-/- mice. While an elevation in NAD⁺/NADH ratio via NQO1 enzymatic action using dunnione recovered SIRT1 activity and subsequently deacetylated NF-κB p65 and p53, however not in NQO1^-/- mice, thereby attenuating AIC.

CONCLUSION

Thus, modulation of NAD⁺/NADH by NQO1 may be a novel therapeutic approach to prevent chemotherapy-associated heart failure, including AIC.

Histone deacetylase inhibitor, CG200745 attenuates renal fibrosis in obstructive kidney disease

Tubulointerstitial fibrosis is a common feature of kidney disease. Histone deacetylase (HDAC) inhibitors have been reported to attenuate renal fibrosis progression. Here, we investigated the effect of CG200745, a novel HDAC inhibitor, on renal fibrosis development in a mouse model of unilateral ureteral obstruction (UUO). To examine the effects of CG200745 on renal fibrosis in UUO, C57BL/6 J male mice were divided into three groups: control, UUO, and CG200745 (30 mg/kg/day)-treated UUO groups. CG 200745 was administered through drinking water for 1 week. Human proximal tubular epithelial (HK-2) cells were also treated with CG200745 (10 µM) with or without TGF-β (2 ng/mL). Seven days after UUO, plasma creatinine did not differ among the groups. However, plasma neutrophil gelatinase-associated lipocalin (NGAL) levels were markedly increased in the UUO group, which were attenuated by CG200745 treatment. UUO kidneys developed marked fibrosis as indicated by collagen deposition and increased α-smooth muscle actin (SMA) and fibronectin expression. CG200745 treatment attenuated these fibrotic responses and suppressed UUO-induced production of transforming growth factor-beta1 (TGF-β) and phosphorylation of Smad-2/3. CG200745 treatment also attenuated UUO-induced inflammation as indicated by the expression of inflammatory markers. Furthermore, CG200745 attenuated phosphorylation of p38 mitogen-activated protein kinase in UUO kidneys. In HK-2 cells, TGF-β induced the expression of α-SMA and fibronectin, which were attenuated by CG200745 cotreatment. These results demonstrate that CG200745, a novel HDAC inhibitor, has a renoprotective effect by suppressing renal fibrosis and inflammation in a UUO mouse model.

PP2A negatively regulates the hypertrophic response by dephosphorylating HDAC2 S394 in the heart

Cardiac hypertrophy occurs in response to increased hemodynamic demand and can progress to heart failure. Identifying the key regulators of this process is clinically important. Though it is thought that the phosphorylation of histone deacetylase (HDAC) 2 plays a crucial role in the development of pathological cardiac hypertrophy, the detailed mechanism by which this occurs remains unclear. Here, we performed immunoprecipitation and peptide pull-down assays to characterize the functional complex of HDAC2. Protein phosphatase (PP) 2 A was confirmed as a binding partner of HDAC2. PPP2CA, the catalytic subunit of PP2A, bound to HDAC2 and prevented its phosphorylation. Transient overexpression of PPP2CA specifically regulated both the phosphorylation of HDAC2 S394 and hypertrophy-associated HDAC2 activation. HDAC2 S394 phosphorylation was increased in a dose-dependent manner by PP2A inhibitors. Hypertrophic stresses, such as phenylephrine in vitro or pressure overload in vivo, caused PPP2CA to dissociate from HDAC2. Forced expression of PPP2CA negatively regulated the hypertrophic response, but PP2A inhibitors provoked hypertrophy. Adenoviral delivery of a phosphomimic HDAC2 mutant, adenovirus HDAC2 S394E, successfully blocked the anti-hypertrophic effect of adenovirus-PPP2CA, implicating HDAC2 S394 phosphorylation as a critical event for the anti-hypertrophic response. PPP2CA transgenic mice were protected against isoproterenol-induced cardiac hypertrophy and subsequent cardiac fibrosis, whereas simultaneous expression of HDAC2 S394E in the heart did induce hypertrophy. Taken together, our results suggest that PP2A is a critical regulator of HDAC2 activity and pathological cardiac hypertrophy and is a promising target for future therapeutic interventions.

Serial evaluation of myocardial function using the myocardial performance index in Kawasaki disease

BACKGROUND

Kawasaki disease (KD) is known as systemic vasculitis, and more than half of the patients with KD have myocarditis, which can induce ventricular dysfunction. In this study, we evaluate left ventricular (LV) dysfunction in patients with KD based on the myocardial performance index (MPI) using pulse Doppler (PD) and tissue Doppler imaging (TDI), from the acute to convalescent phases.

METHODS

We retrospectively studied 89 children diagnosed with KD from January 2010 to August 2012. We assessed the presence of coronary artery lesions (CALs) and the LV ejection fraction, PD-MPI, and TDI-MPI at diagnosis, and 2, 14, and 56 days after intravenous immunoglobulin (IVIG) treatment. We enrolled 70 healthy children as a control group.

RESULTS

The ejection fraction in patients with KD at diagnosis (67.3 ± 0.9%) was lower than that in the control group (69.8 ± 0.8%, P = 0.035), and the LV TDI-MPIs for patients with KD at diagnosis (0.49 ± 0.01) and 2 days after IVIG treatment (0.48 ± 0.01) were higher than those in the control group (0.45 ± 0.01, P = 0.002, P = 0.033, respectively). No significant differences were found in the LV dysfunction between the patients with complete and incomplete KD. Septal TDI-MPIs in patients with KD with CAL at diagnosis (0.52 ± 0.02) were higher than those in patients with KD without CAL (0.47 ± 0.01, P = 0.019).

CONCLUSIONS

Transient LV dysfunction occurred in patients with complete and incomplete KD in the acute stage. In patients with KD with CAL at diagnosis, the LV dysfunction was more prominent. The PD-MPI and TDI-MPI are useful parameters for assessing LV function in patients with KD.

Novel NTRK1 mutations associated with congenital insensitivity to pain with anhidrosis verified by functional studies

Congenital insensitivity to pain with anhidrosis (CIPA), also known as hereditary sensory and autonomic neuropathy type IV, features loss of pain sensation, decreased or absent sweating (anhidrosis), recurrent episodes of unexplained fever, self-mutilating behavior, and variable mental retardation. Mutations in neurotrophic receptor tyrosine kinase 1 (NTRK1) have been reported to be associated with CIPA. We identified four novel NTRK1 mutations in six Korean patients from four unrelated families. Of the four mutations, we demonstrated using a splicing assay that IVS14+3A>T causes aberrant splicing of NTRK1 mRNA, leading to introduction of a premature termination codon. An NTRK1 autophosphorylation assay showed that c.1786G>A (p.Asp596Asn) abolished autophosphorylation of NTRK1. In addition, Western blotting showed that c.704C>G (p.Ser235*) and c.2350_2363del (p.Leu784Serfs*79) blunted NTRK1 expression to undetectable levels. The four novel NTRK1 mutations we report here will expand the repertoire of NTRK1 mutations in CIPA patients, and further our understanding of CIPA pathogenesis.

Dual Roles of Graphene Oxide To Attenuate Inflammation and Elicit Timely Polarization of Macrophage Phenotypes for Cardiac Repair

Development of localized inflammatory environments by M1 macrophages in the cardiac infarction region exacerbates heart failure after myocardial infarction (MI). Therefore, the regulation of inflammation by M1 macrophages and their timely polarization toward regenerative M2 macrophages suggest an immunotherapy. Particularly, controlling cellular generation of reactive oxygen species (ROS), which cause M1 differentiation, and developing M2 macrophage phenotypes in macrophages propose a therapeutic approach. Previously, stem or dendritic cells were used in MI for their anti-inflammatory and cardioprotective potentials and showed inflammation modulation and M2 macrophage progression for cardiac repair. However, cell-based therapeutics are limited due to invasive cell isolation, time-consuming cell expansion, labor-intensive and costly ex vivo cell manipulation, and low grafting efficiency. Here, we report that graphene oxide (GO) can serve as an antioxidant and attenuate inflammation and inflammatory polarization of macrophages via reduction in intracellular ROS. In addition, GO functions as a carrier for interleukin-4 plasmid DNA (IL-4 pDNA) that propagates M2 macrophages. We synthesized a macrophage-targeting/polarizing GO complex (MGC) and demonstrated that MGC decreased ROS in immune-stimulated macrophages. Furthermore, DNA-functionalized MGC (MGC/IL-4 pDNA) polarized M1 to M2 macrophages and enhanced the secretion of cardiac repair-favorable cytokines. Accordingly, injection of MGC/IL-4 pDNA into mouse MI models attenuated inflammation, elicited early polarization toward M2 macrophages, mitigated fibrosis, and improved heart function. Taken together, the present study highlights a biological application of GO in timely modulation of the immune environment in MI for cardiac repair. Current therapy using off-the-shelf material GO may overcome the shortcomings of cell therapies for MI.

Abstract 241: MDM2 E3 Ligase-mediated Ubiquitination and Degradation of HDAC1 in Vascular Calcification

Vascular calcification (VC) is often associated with cardiovascular and metabolic diseases. However, the molecular mechanisms linking VC to these diseases have yet to be elucidated. Here we report that MDM2-induced ubiquitination of histone deacetylase 1 (HDAC1) mediates VC. Loss of HDAC1 activity via either chemical inhibitor or genetic ablation enhances VC. HDAC1 protein, but not mRNA, is reduced in cell and animal calcification models and in human calcified coronary artery. Under calcification-inducing conditions, proteasomal degradation of HDAC1 precedes VC and it is mediated by MDM2 E3 ubiquitin ligase that initiates HDAC1 K74 ubiquitination. Overexpression of MDM2 enhances VC, whereas loss of MDM2 blunts it. Decoy peptide spanning HDAC1 K74 and RG 7112, an MDM2 inhibitor, prevent VC in vivo and in vitro. These results uncover a previously unappreciated ubiquitination pathway and suggest MDM2-mediated HDAC1 ubiquitination as a new therapeutic target in VC.

Abstract 454: Protein Phosphatase Pp2a Regulates Hypertrophic Response Through Hdac2 Dephosphorylation in the Heart

Rationale: Cardiac hypertrophy is an adaptive process to meet the hemodynamic demands from exogenous stresses, and histone deacetylase (HDAC) 2 plays central role in cardiac remodeling. Recently, we have suggested the importance of acetylation of HDAC2; however, specific phosphatase of HDAC2 remains unclear.

Objective: We aimed to delineate the phosphatase of HDAC2 in the development of cardiac hypertrophy and to suggest therapeutic implications of those phosphatase in cardiac remodeling.

Methods and Results: We performed complex-isolation assay in the heart and found that Hdac2 physically interacted with the Ppp2ca, and Hsp70. Ppp2ca kept Hdac2 unphosphorylated in the absence of hypertrophic stresses. Hypertrophic stresses-induced Hdac2 K75 acetylation, which then allowed Ppp2ca to dissociate from Hdac2, which led to phosphorylate Hdac2. The agonist-induced hypertrophy was significantly attenuated in transgenic mice heart expressing Ppp2ca. Forced expression of phosphorylation mimicking mutant of Hdac2, Hdac2 S394E, successfully overcame to antihypertrophic effects of Ppp2ca, whereas wild type of Hdac2 failed to do so. On the other hand, hypertrophic stresses induced Hsp70, one of the binding partners of Hdac2, which then preferentially bound to phosphorylated Hdac2 rather than to unphosphorylated one. The increase in expression of Hsp70 led to dissociate Ppp2ca from Hdac2. Hsp70 significantly increased phosphorylation of Hdac2 by protection from Ppp2ca. Cardiac hypertrophy was observed in the TgHsp70 mice and hyper-phosphorylation of Hdac2 was also detected. Double transgenic mice expressing both Ppp2ca and Hsp70 showed cardiac hypertrophy, which implicated that Hsp70 functioned as an endogenous regulator of Ppp2ca in the heart. TgHsp70-induced cardiac hypertrophy was significantly inhibited by adeno-Ppp2ca in a dose response fashion.

Conclusion: Taken together, HDAC2 forms a complex with PP2A in the absence of hypertrophic stresses and remains inactivated. HDAC2 acetylation results in dissociation of PP2A and thereby phosphorylation, which is maintained by the association with HSP70 during development of cardiac hypertrophy. Hyun-Ki Min and Somy Yoon contributed equally to this work.

HDAC and HDAC Inhibitor: From Cancer to Cardiovascular Diseases

Histone deacetylases (HDACs) are epigenetic regulators that regulate the histone tail, chromatin conformation, protein-DNA interaction, and even transcription. HDACs are also post-transcriptional modifiers that regulate the protein acetylation implicated in several pathophysiologic states. HDAC inhibitors have been highlighted as a novel category of anti-cancer drugs. To date, four HDAC inhibitors, Vorinostat, Romidepsin, Panobinostat, and Belinostat, have been approved by the United States Food and Drug Administration. Principally, these HDAC inhibitors are used for hematologic cancers in clinic with less severe side effects. Clinical trials are continuously expanding to address other types of cancer and also nonmalignant diseases. HDAC inhibition also results in beneficial outcomes in various types of neurodegenerative diseases, inflammation disorders, and cardiovascular diseases. In this review, we will briefly discuss 1) the roles of HDACs in the acquisition of a cancer's phenotype and the general outcome of the HDAC inhibitors in cancer, 2) the functional relevance of HDACs in cardiovascular diseases and the possible therapeutic implications of HDAC inhibitors in cardiovascular disease.

Role of histone deacetylase 2 and its posttranslational modifications in cardiac hypertrophy

Cardiac hypertrophy is a form of global remodeling, although the initial step seems to be an adaptation to increased hemodynamic demands. The characteristics of cardiac hypertrophy include the functional reactivation of the arrested fetal gene program, where histone deacetylases (HDACs) are closely linked in the development of the process. To date, mammalian HDACs are divided into four classes: I, II, III, and IV. By structural similarities, class II HDACs are then subdivided into IIa and IIb. Among class I and II HDACs, HDAC2, 4, 5, and 9 have been reported to be involved in hypertrophic responses; HDAC4, 5, and 9 are negative regulators, whereas HDAC2 is a pro-hypertrophic mediator. The molecular function and regulation of class IIa HDACs depend largely on the phosphorylation-mediated cytosolic redistribution, whereas those of HDAC2 take place primarily in the nucleus. In response to stresses, posttranslational modification (PTM) processes, dynamic modifications after the translation of proteins, are involved in the regulation of the activities of those hypertrophy-related HDACs. In this article, we briefly review 1) the activation of HDAC2 in the development of cardiac hypertrophy and 2) the PTM of HDAC2 and its implications in the regulation of HDAC2 activity.

Abstract 418: Mdm2 E3 Ligase-mediated Ubiquitination of Histone Deacetylase 1 in Vascular Calcification

Vascular calcification (VC) often associates with many cardiovascular and metabolic diseases. Although VC is the cause of high morbidity and mortality, molecular mechanisms have yet to be elucidated. Here we report that MDM2-induced ubiquitination of histone deacetylase 1 (HDAC1) mediates VC. Loss of HDAC1 activity enhanced VC in vivo and in vitro . HDAC1 protein was reduced in cell and animal calcification models and in human calcified coronary artery and this reduction preceded VC. Calcification stresses induced MDM2 E3 ligase, which resulted in HDAC1 K74 ubiquitination. Forced expression of MDM2 enhanced VC, whereas loss of MDM2 blunted it. A decoy peptide spanning HDAC1 K74 prevented VC. These results demonstrate a previously unknown ubiquitination pathway as well as the involvement of HDAC1 in VC. Our results suggest MDM2-mediated HDAC1 ubiquitination as a new therapeutic target in VC.

Abstract 118: PP2A/HSP70 Dynamically Regulates HDAC2 Phosphorylation and its Activity in Cardiac Hypertrophy

Rationale: Cardiac hypertrophy is an adaptation for increased hemodynamic demands by underlying diseases and histone deacetylase (HDAC) 2 phosphorylation and following its activation are closely associated with those of process. Recently, we have demonstrated that the acetylation of HDAC2 K75 could induce S394 phosphorylation; however, specific mechanism for inter-modifications regulation in the single protein largely remains unclear.

Objective: We aimed to delineate the regulation mechanism how K75 acetylation modulates S394 phosphorylation and which phosphatase regulates HDAC2 phosphorylation in the cardiac hypertrophy.

Methods and Results: We found that the catalytic subunit of protein phosphatase (PP) 2A bound to HDAC2 in the H9c2 cell. PP2A kept HDAC2 unphosphorylated in the absence of hypertrophic stresses. Hypertrophic stresses-induced activation of pCAF, however, induced HDAC2 K75 acetylation, which then allowed PP2A to dissociate from HDAC2. This dissociation leads CK2α1 to bind to and phosphorylate HDAC2. Hypertrophic stresses induced HSP70 which then preferentially bound to phosphorylated HDAC2 rather than to unphosphorylated one. Forced expression of PP2CA not only reduced enzyme activity of HDAC2 but inhibited hypertrophic response in the cardiomyocytes. On the other hand, HSP70 bound to phosphorylated HDAC2 in order to mask the phosphor-HDAC2 from PP2CA. HDAC2 phosphorylation and following activation of intrinsic activity were regulated by binding of PP2CA to HDAC2. PP2A functioned as a negative regulator for cardiac hypertrophy by targeting of HDAC2 S394 phosphorylation.

Conclusion: Taken together, HDAC2 forms a complex with PP2A in the absence of hypertrophic stresses and remains inactivated. HDAC2 acetylation results in both detachment of PP2A and binding of CK2α1 for phosphorylation, which is maintained by the association with HSP70 during development of cardiac hypertrophy.

The microRNA miR-34c inhibits vascular smooth muscle cell proliferation and neointimal hyperplasia by targeting stem cell factor

The fine balance between proliferation and differentiation of vascular smooth muscle cells (VSMCs) is indispensable for the maintenance of healthy blood vessels, whereas an increase in proliferation participates in pathologic cardiovascular events such as atherosclerosis and restenosis. Here we report that microRNA-34c (miR-34c) targets stem cell factor (SCF) to inhibit VSMC proliferation and neointimal hyperplasia. In an animal model, miR-34c was significantly increased in the rat carotid artery after catheter injury. Transient transfection of miR-34c to either VSMCs or A10 cells inhibited cell survival by inducing apoptosis, which was accompanied by an increase in expression of p21, p27, and Bax. Transfection of miR-34c also attenuated VSMC migration. Bioinformatics showed that SCF is a target candidate of miR-34c. miR-34c down-regulated luciferase activity driven by a vector containing the 3'-untranslated region of SCF in a sequence-specific manner. Forced expression of SCF in A10 cells induced proliferation and migration, whereas knocking-down of SCF reduced cell survival and migration. miR-34c antagomir-induced VSMC proliferation was blocked by SCF siRNA. Delivery of miR-34c to rat carotid artery attenuated the expression of SCF and blocked neointimal hyperplasia. These results suggest that miR-34c is a new modulator of VSMC proliferation and that it inhibits neointima formation by regulating SCF.

Abstract 309: Small Heterodimer Partner Blocks Cardiac Hypertrophy By Interfering With GATA6 Signaling

Rationale: Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that lacks a conventional DNA binding domain. By interacting with other transcription factors, SHP regulates diverse biological events including glucose metabolism in liver. The role of SHP in adult heart diseases has not yet been demonstrated.

Objective: We aimed to investigate the role of SHP in adult heart in association with cardiac hypertrophy.

Methods and Results: The roles of SHP in cardiac hypertrophy were tested in primary cultured cardiomyocytes and in animal models. SHP null mice showed a hypertrophic phenotype. Hypertrophic stresses repressed the expression of SHP, whereas forced expression of SHP blocked the development of cardiomyocyte hypertrophy. SHP reduced the protein amount of Gata6. By direct physical interaction with Gata6, SHP interfered with the binding of Gata6 to GATA binding elements in the promoter regions of natriuretic peptide precursor type A. Metformin, an anti-diabetic agent, induced SHP and suppressed cardiac hypertrophy. The metformin-induced anti-hypertrophic effect was attenuated either by SHP siRNA in cardiomyocytes or in SHP null mice.

Conclusions: These results establish SHP as a novel anti-hypertrophic regulator that acts by interfering with GATA6 signaling. SHP may participate in the metformin-induced anti-hypertrophic response.

Abstract 188: Regulation Of Acetylation Of Histone Deacetylase 2 By P300/CBP-associated Factor/histone Deacetylase 5 In The Development Of Cardiac Hypertrophy

Rationale: Histone deacetylases (HDACs) are closely involved in cardiac reprogramming. Although the functional roles of the class I and class IIa HDACs are well established, the significance of interclass crosstalk in the development of cardiac hypertrophy remains unclear.

Objective: Recently, we suggested that casein kinase-2α1-dependent phosphorylation of HDAC2 leads to enzymatic activation, which in turn induces cardiac hypertrophy. Here we report an alternate posttranslational activation mechanism of HDAC2 that involves acetylation of HDAC2 mediated by p300/CBP-associated factor (pCAF)/HDAC5.

Methods and Results: Hdac2 was acetylated in response to hypertrophic stresses in both cardiomyocytes and a mouse model. The acetylation was reduced by a histone acetyltransferase inhibitor but was increased by a nonspecific HDAC inhibitor. The enzymatic activity of Hdac2 was positively correlated with its acetylation status. pCAF bound to Hdac2 and induced acetylation. The HDAC2 K75 residue was responsible for hypertrophic stress-induced acetylation. The acetylationresistant Hdac2 K75R showed a significant decrease in phosphorylation on S394, which led to the loss of intrinsic activity. Hdac5, one of class IIa HDACs, directly deacetylated Hdac2. Acetylation of Hdac2 was increased in Hdac5 null mice. When an acetylation-mimicking mutant of Hdac2 was infected into cardiomyocytes, the anti-hypertrophic effect of either nuclear tethering of Hdac5 with leptomycin B or Hdac5 overexpression was reduced.

Conclusions: Taken together, our results suggest a novel mechanism by which the balance of HDAC2 acetylation is regulated by pCAF and HDAC5 in the development of cardiac hypertrophy.

Ret finger protein mediates Pax7-induced ubiquitination of MyoD in skeletal muscle atrophy

Skeletal muscle atrophy results from the net loss of muscular proteins and organelles and is caused by pathologic conditions such as nerve injury, immobilization, cancer, and other metabolic diseases. Recently, ubiquitination-mediated degradation of skeletal-muscle-specific transcription factors was shown to be involved in muscle atrophy, although the mechanisms have yet to be defined. Here we report that ret finger protein (RFP), also known as TRIM27, works as an E3 ligase in Pax7-induced degradation of MyoD. Muscle injury induced by sciatic nerve transection up-regulated RFP and RFP physically interacted with both Pax7 and MyoD. RFP and Pax7 synergistically reduced the protein amounts of MyoD but not the mRNA. RFP-induced reduction of MyoD protein was blocked by proteasome inhibitors. The Pax7-induced reduction MyoD was attenuated by RFP siRNA and by MG132, a proteasome inhibitor. RFPΔR, an RFP construct that lacks the RING domain, failed to reduce MyoD amounts. RFP ubiquitinated MyoD, but RFPΔR failed to do so. Forced expression of RFP, but not RFPΔR, enhanced Pax7-induced ubiquitination of MyoD, whereas RFP siRNA blocked the ubiquitination. Sciatic nerve injury-induced muscle atrophy as well the reduction in MyoD was attenuated in RFP knockout mice. Taken together, our results show that RFP works as a novel E3 ligase in the Pax7-mediated degradation of MyoD in response to skeletal muscle atrophy.

Small heterodimer partner blocks cardiac hypertrophy by interfering with GATA6 signaling

RATIONALE

Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that lacks a conventional DNA-binding domain. Through interactions with other transcription factors, SHP regulates diverse biological events, including glucose metabolism in liver. However, the role of SHP in adult heart diseases has not yet been demonstrated.

OBJECTIVE

We aimed to investigate the role of SHP in adult heart in association with cardiac hypertrophy.

METHODS AND RESULTS

The roles of SHP in cardiac hypertrophy were tested in primary cultured cardiomyocytes and in animal models. SHP-null mice showed a hypertrophic phenotype. Hypertrophic stresses repressed the expression of SHP, whereas forced expression of SHP blocked the development of hypertrophy in cardiomyocytes. SHP reduced the protein amount of Gata6 and, by direct physical interaction with Gata6, interfered with the binding of Gata6 to GATA-binding elements in the promoter regions of natriuretic peptide precursor type A. Metformin, an antidiabetic agent, induced SHP and suppressed cardiac hypertrophy. The metformin-induced antihypertrophic effect was attenuated either by SHP small interfering RNA in cardiomyocytes or in SHP-null mice.

CONCLUSIONS

These results establish SHP as a novel antihypertrophic regulator that acts by interfering with GATA6 signaling. SHP may participate in the metformin-induced antihypertrophic response.

Regulation of acetylation of histone deacetylase 2 by p300/CBP-associated factor/histone deacetylase 5 in the development of cardiac hypertrophy

RATIONALE

Histone deacetylases (HDACs) are closely involved in cardiac reprogramming. Although the functional roles of class I and class IIa HDACs are well established, the significance of interclass crosstalk in the development of cardiac hypertrophy remains unclear.

OBJECTIVE

Recently, we suggested that casein kinase 2α1-dependent phosphorylation of HDAC2 leads to enzymatic activation, which in turn induces cardiac hypertrophy. Here we report an alternative post-translational activation mechanism of HDAC2 that involves acetylation of HDAC2 mediated by p300/CBP-associated factor/HDAC5.

METHODS AND RESULTS

Hdac2 was acetylated in response to hypertrophic stresses in both cardiomyocytes and a mouse model. Acetylation was reduced by a histone acetyltransferase inhibitor but was increased by a nonspecific HDAC inhibitor. The enzymatic activity of Hdac2 was positively correlated with its acetylation status. p300/CBP-associated factor bound to Hdac2 and induced acetylation. The HDAC2 K75 residue was responsible for hypertrophic stress-induced acetylation. The acetylation-resistant Hdac2 K75R showed a significant decrease in phosphorylation on S394, which led to the loss of intrinsic activity. Hdac5, one of class IIa HDACs, directly deacetylated Hdac2. Acetylation of Hdac2 was increased in Hdac5-null mice. When an acetylation-mimicking mutant of Hdac2 was infected into cardiomyocytes, the antihypertrophic effect of either nuclear tethering of Hdac5 with leptomycin B or Hdac5 overexpression was reduced.

CONCLUSIONS

Taken together, our results suggest a novel mechanism by which the balance of HDAC2 acetylation is regulated by p300/CBP-associated factor and HDAC5 in the development of cardiac hypertrophy.

Abstract 071: Estrogen-related Receptor Gamma Induces Cardiac Hypertrophy By Activating Gata4

Introduction— Estrogen-related receptor gamma (ERRγ) is an orphan nuclear receptor that has biological roles mainly in metabolism and it controls metabolic switching in perinatal heart. In adult heart diseases, however, the functional roles of ERRγ have not yet been elucidated.

Hypothesis— In the present study, we aimed to characterize the role of ERRγ in cardiac hypertrophy. Here we show that ERRγ provokes cardiac hypertrophy by inducing GATA4 and that its inverse agonist, GSK-5182, prevents cardiac hypertrophy.

Methods and Results— The functional roles of ERRγ in association with development of cardiac hypertrophy were examined in primarily cultured cardiomyocytes, in animal models, and in heart samples from human hypertrophic cardiomyopathy patients. ERRγ expression was increased in hearts obtained from human hypertrophic cardiomyopathy patients and in both agonist-induced cellular models and aortic banding-induced animal models of cardiac hypertrophy. Transgenic overexpression in mouse heart as well as forced expression of ERRγ in cardiomyocytes induced hypertrophic phenotypes. Knock-down of ERRγ blocked agonist-induced hypertrophic phenotypes. ERRγ directly bound to the proximal ERR-responsive element in the GATA4 promoter in a sequence-specific manner and thereby induced transcription. ERRγ-induced hypertrophy was blocked by inhibition of GATA4. GSK-5182 completely blocked cardiac hypertrophy in cardiomyocytes. It also prevented aortic banding-induced cardiac hypertrophy and fibrosis in mouse heart.

Conclusion— These findings demonstrate a novel ERRγ/GATA4 signal cascade in the development of cardiac hypertrophy and suggest GSK-5182 as a possible therapeutic.

Abstract 077: Small Heterodimer Partner, An Orphan Nuclear Receptor, Inhibits Cardiac Hypertrophy

Background: Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor lacking DNA binding domain. SHP directly modulates the activities of other nuclear receptors and regulates a variety of cellular events such as cell differentiation, proliferation, and metabolism in various tissues. However, the role of SHP in heart has not yet been elucidated. Thus, in this study, we tried to investigate the functional roles of SHP in heart physiology and in the development of cardiac hypertrophy.

Methods and Results: We observed that SHP knock-out mice elicited cardiac hypertrophic features determined by heart weight to body weight or to tibia length ratios. Fetal genes, such as atrial natriuretic factor (ANF) or beta myosin heavy chain (βMHC) were significantly up-regulated in SHP knockout mice heart. In neonatal rat ventricular cardiomyocytes (NRVCs), phenylephrine (PE) reduced promoter activation of SHP and decreased protein level of SHP. Adenovirus-mediated over-expression of SHP (Adeno-SHP) significantly reduced hypertrophic responses induced by PE as assayed by [3H]-leucine incorporation, Nppa promoter activity, and cell size measurement. Adeno-SHP significantly reduced hypertrophy-associated proteins. In contrast, knock-down of SHP by small hairpin RNA, decreased both Myh7 and Nppa promoter activities, whereas it up-regulated ANF or α-tubulin expressions. Metfomin (N,N-Dimethylimidodicarbonimidic diamide), an anti-diabetic agent, up-regulated SHP in dose-response fashion. PE-induced activation of Nppa promoter and [3H]-leucine incorporation were completely blocked by metformin. PE-induced down-regulation of SHP was blunted by simultaneous treatment of metformin. Metformin-mediated antihypertrophic action was not observed when the SHP was down-regulated by small interfering RNA against to SHP.

Conclusions: These results suggest that atypical orphan nuclear receptor SHP prevents cardiac hypertrophy and it mediates metformin-mediated antihypertrophic responses, implicating that theses signal cascades may serve as a novel therapeutic target of treatment of hypertrophic cardiomyopathy patients.

The microRNA miR-132 targets Lrrfip1 to block vascular smooth muscle cell proliferation and neointimal hyperplasia

OBJECTIVE

The proliferation and remodeling of vascular smooth muscle cells (VSMCs) is an important pathological event in atherosclerosis and restenosis. Here we report that microRNA-132 (miR-132) blocks vascular smooth muscle cells (VSMC) proliferation by inhibiting the expression of LRRFIP1 [leucine-rich repeat (in Flightless 1) interacting protein-1].

METHODS AND RESULTS

MicroRNA microarray revealed that miR-132 was upregulated in the rat carotid artery after catheter injury, which was further confirmed by quantitative real-time RT-PCR. Transfection of a miR-132 mimic significantly inhibited the proliferation of VSMCs, whereas transfection of a miR-132 antagomir increased it. miR-132 mimic inhibited VSMC migration and induced apoptosis. miR-132 mimic increased the protein amounts of both p27 and smooth muscle (SM) α-actin, whereas it decreased SM α-actin and Bcl2. Bioinformatics showed that LRRFIP1 is a target candidate of miR-132. miR-132 down-regulated luciferase activity driven by a vector containing the 3'-untranslated region of Lrrfip1 in a sequence-specific manner. LRRFIP1 induced VSMC proliferation and increased phosphorylation of ERK. Immunohistochemical analysis revealed that Lrrfip1 was clearly expressed along with the basal laminar area of smooth muscle, and its expression pattern was disrupted 7 days after arterial injury. LRRFIP1 mRNA was decreased 14 days after injury. Delivery of miR-132 to rat carotid artery reduced LRRFIP1 expression and attenuated neointimal proliferation in carotid artery injury models.

CONCLUSIONS

Our results suggest that miR-132 is a novel regulator of VSMC proliferation that represses neointimal formation by inhibiting LRRFIP1 expression.

Abstract P187: Casein Kinase 2/Histone Deacetylase 2/Krúppel-like Factor 4 Is a Novel Axis of Development of Cardiac Hypertrophy

Background. Cardiac hypertrophy is characterized by transcriptional reprogramming of fetal gene expression, and histone modifiers are tightly linked to the regulation of those genes. We previously reported that activation of histone deacetylase (HDAC) 2, one of the class I HDACs, mediates hypertrophy. Here we suggest that disinhibiting of kruppel-like factor 4 (Klf4) by casein kinase-2α1 (CK2α1)-dependent phosphorylation of HDAC2 S394 develop the cardiac hypertrophy.

Methods and Results. Hypertrophic stimuli phosphorylated Hdac2 S394, which was necessary for its enzymatic activation and thereby for the development of hypertrophic phenotypes. Transgenic mice overexpressing Hdac2-wild type exhibited cardiac hypertrophy, whereas those expressing phosphorylation-resistant Hdac2 S394A did not. Compared with that in age-matched normal human hearts, phosphorylation of Hdac2 S394 was dramatically increased in hypertrophic cardiomyopathy patients. Hypertrophy-induced phosphorylation of Hdac2 S394 and its enzymatic activity were completely blocked either by CK2-blockers or by CK2a1 siRNA. Hypertrophic stimuli led CK2α1 to be activated, and its chemical inhibitors blocked hypertrophy in both phenylephrine-treated cardiomyocytes and in isoproterenol-administered mice. However, by utilizing KLF4-binding element-disrupted Nppa promoter, treatment with either TBB or TBCA failed to reduce the mutant promoter activity. These results emphasized that CK2α1-induced hypertrophic events are dependent on both Hdac2 and KLF4. CK2α1-transgenic mice developed hypertrophy, which was attenuated by administration of trichostatin A, an HDAC inhibitor. Overexpression of CK2α1 caused hypertrophy in cardiomyocytes, whereas its chemical inhibitors as well as Hdac2 S394A blunted it. Hypertrophy in CK2α1-transgenic mice was exaggerated by crossing these mice with Hdac2-transgenic mice. By contrast, however, it was blocked when CK2α1-transgenic mice were crossed with Hdac2 S394A-transgenic mice.

Conclusions. We have demonstrated a novel mechanism in the development of cardiac hypertrophy by which CK2 activates HDAC2 via phosphorylating HDAC2 S394 and consequence down-regulation of KLF4.

Abstract P226: Small Heterodimer Partner Negatively Regulates Cardiac Hypertrophy Through Upregulation of GATA6

Small heterodimer partner (SHP; NR0B2) is an atypical orphan nuclear receptor that regulates a variety of cellular events such as cell proliferation, differentiation and metabolism in liver and bone. However, the role of SHP in heart has not yet been elucidated. In this study, we investigated the functional roles of SHP in cardiac hypertrophy. In rat neonatal cardiomyocytes model, phenylephrine (PE) down-regulated expression of SHP. Transient transfection of SHP decreased the promoter activity of Nppa (natriuretic polypeptide precursor type A). Adenovirus-mediated overexpression of SHP (Ad-SHP) blocked gene expressions of GATA4, GATA6, and serum response factor (SRF). The increase in [ 3 H]-leucine incorporation induced by PE or fetal bovine serum (FBS) was dramatically reduced by Ad-SHP. Likewise, increases in cell size with those hypertrophic stresses were significantly attenuated by Ad-SHP. The expressions of atrial natriuretic factor (ANF), β-myosin heavy chain (βMHC), and skeletal α-actin were significantly higher in hearts of SHP null mice. SHP physically interacted with GATA6 in mammalian cells. SHP significantly decreased the activation of -3003 Nppa promoter induced by GATA6. The action of SHP on Nppa promoter activity was partially recovered by GATA6. Taken together, these results suggest that SHP works as a novel anti-hypertrophic regulator by repressing GATA6.

Histone methyltransferase SETD3 regulates muscle differentiation

Histone lysine methylation, as one of the most important factors in transcriptional regulation, is associated with a various physiological conditions. Using a bioinformatics search, we identified and subsequently cloned mouse SET domain containing 3 (SETD3) with SET (Su(var)3-9, Enhancer-of-zeste and Trithorax) and Rubis-subs-bind domains. SETD3 is a novel histone H3K4 and H3K36 methyltransferase with transcriptional activation activity. SETD3 is expressed abundantly in muscular tissues and, when overexpressed, activates transcription of muscle-related genes, myogenin, muscle creatine kinase (MCK), and myogenic factor 6 (Myf6), thereby inducing muscle cell differentiation. Conversely, knockdown of SETD3 by shRNA significantly retards muscle cell differentiation. In this study, SETD3 was recruited to the myogenin gene promoter along with MyoD where it activated transcription. Together, these data indicate that SETD3 is a H3K4/K36 methyltransferase and plays an important role in the transcriptional regulation of muscle cell differentiation.

Ret finger protein inhibits muscle differentiation by modulating serum response factor and enhancer of polycomb1

Skeletal myogenesis is precisely regulated by multiple transcription factors. Previously, we demonstrated that enhancer of polycomb 1 (Epc1) induces skeletal muscle differentiation by potentiating serum response factor (SRF)-dependent muscle gene activation. Here, we report that an interacting partner of Epc1, ret finger protein (RFP), blocks skeletal muscle differentiation. Our findings show that RFP was highly expressed in skeletal muscles and was downregulated during myoblast differentiation. Forced expression of RFP delayed myoblast differentiation, whereas knockdown enhanced it. Epc1-induced enhancements of SRF-dependent multinucleation, transactivation of the skeletal α-actin promoter, binding of SRF to the serum response element, and muscle-specific gene induction were blocked by RFP. RFP interfered with the physical interaction between Epc1 and SRF. Muscles from rfp knockout mice (Rfp(-/-)) mice were bigger than those from wild-type mice, and the expression of SRF-dependent muscle-specific genes was upregulated. Myotube formation and myoblast differentiation were enhanced in Rfp(-/-) mice. Taken together, our findings highlight RFP as a novel regulator of muscle differentiation that acts by modulating the expression of SRF-dependent skeletal muscle-specific genes.

Enhancer of polycomb1 acts on serum response factor to regulate skeletal muscle differentiation

Skeletal muscle differentiation is well regulated by a series of transcription factors. We reported previously that enhancer of polycomb1 (Epc1), a chromatin protein, can modulate skeletal muscle differentiation, although the mechanisms of this action have yet to be defined. Here we report that Epc1 recruits both serum response factor (SRF) and p300 to induce skeletal muscle differentiation. Epc1 interacted physically with SRF. Transfection of Epc1 to myoblast cells potentiated the SRF-induced expression of skeletal muscle-specific genes as well as multinucleation. Proximal CArG box in the skeletal alpha-actin promoter was responsible for the synergistic activation of the promoter-luciferase. Epc1 knockdown caused a decrease in the acetylation of histones associated with serum response element (SRE) of the skeletal alpha-actin promoter. The Epc1.SRF complex bound to the SRE, and the knockdown of Epc1 resulted in a decrease in SRF binding to the skeletal alpha-actin promoter. Epc1 recruited histone acetyltransferase activity, which was potentiated by cotransfection with p300 but abolished by si-p300. Epc1 directly bound to p300 in myoblast cells. Epc1+/- mice showed distortion of skeletal alpha-actin, and the isolated myoblasts from the mice had impaired muscle differentiation. These results suggest that Epc1 is required for skeletal muscle differentiation by recruiting both SRF and p300 to the SRE of muscle-specific gene promoters.

Activation of Histone Deacetylase 2 by Inducible Heat Shock Protein 70 in Cardiac Hypertrophy

Diverse cardiac diseases induce cardiac hypertrophy, which leads to dilatation and heart failure. We previously reported that hypertrophy can be blocked by class I histone deacetylase (HDAC) inhibitor, which prompted us to investigate the regulatory mechanism of class I HDACs. Cardiac hypertrophy was introduced by aortic banding, by infusion of isoproterenol or angiotensin II, or by swimming. Hypertrophic stimuli transiently elevated the activity of histone deacetylase-2 (Hdac2), a class I HDAC. In cardiomyocytes, forced expression of Hdac2 simulated hypertrophy in an Akt-dependent manner, whereas enzymatically inert Hdac2 H141A failed to do so. Hypertrophic stimuli induced the expression of heat shock protein (Hsp)70. The induced Hsp70 physically associated with and activated Hdac2. Hsp70 overexpression produced a hypertrophic phenotype, which was blocked either by siHdac2 or by a dominant negative Hsp70ΔABD. In Hsp70.1 −/− mice, cardiac hypertrophy and Hdac2 activation were significantly blunted. Heat shock either to cardiomyocytes or to mice activated Hdac2 and induced hypertrophy. However, heat shock-induced Hdac2 activation was blunted in the cardiomyocytes isolated from Hsp70.1 −/− mice. These results suggest that the induction of Hsp70 in response to diverse hypertrophic stresses and the ensuing activation of HDAC2 trigger cardiac hypertrophy, emphasizing HSP70/HDAC2 as a novel mechanism regulating hypertrophy.

Characterization of a novel WHSC1-associated SET domain protein with H3K4 and H3K27 methyltransferase activity

Evolutionary conserved SET domains were originally identified in three Drosophila proteins: suppressor of variegation (Su (var) 3-9), enhancer of zeste (E(z)), and the trithorax. Some of the SET-domain containing proteins have been known to elicit methylation of histone lysine residues. Based on a search for SET-domain containing proteins using bioinformatic tools, we identified and subsequently named a novel SET domain as WHISTLE, that has histone methyltransferase (HMTase) activity. To characterize WHISTLE, we performed an HMTase assay, mass spectrometric analysis, lysine specificity, and transfection assays. Mass spectrometric and immunoblot analysis revealed that WHISTLE di-methylates H3K4 and di-, and tri-methylates H3K27 of histones. Overexpression of WHISTLE repressed transcription of the SV40 promoter. Our results suggest that WHISTLE is a novel SET domain containing a protein with specific H3K4 and H3K27 HMTase activity.