Cardiac Hypertrophy In Response Research Articles

Co-administration of resveratrol with doxorubicin in young mice attenuates detrimental late-occurring cardiovascular changes.

Doxorubicin (DOX) is among the most effective chemotherapies used in paediatric cancer patients. However, the clinical utility of DOX is offset by its well-known cardiotoxicity, which often does not appear until later in life. Since hypertension significantly increases the risk of late-onset heart failure in childhood cancer survivors, we investigated whether juvenile DOX exposure impairs the ability to adapt to angiotensin II (Ang II)-induced hypertension later in life and tested a treatment that could prevent this. Five-week-old male mice were administered a low dose of DOX (4 mg/kg) or saline once a week for 3 weeks and then allowed to recover for 5 weeks. Following the 5-week recovery period, mice were infused with Ang II or saline for 2 weeks. In another cohort, mice were fed chow containing 0.4% resveratrol 1 week before, during, and 1 week after the DOX administrations. One week after the last DOX administration, p38 mitogen-activated protein kinase (MAPK) was activated in hearts of DOX-treated mice demonstrating molecular signs of cardiac stress; yet, there was no change in cardiac function between groups. However, DOX-treated mice failed to develop compensatory cardiac hypertrophy in response to Ang II-induced hypertension later in life. Of importance, mice receiving DOX with resveratrol co-administration displayed normalization in p38 MAPK activation in the heart and a restored capacity for cardiac hypertrophy in response to Ang II-induced hypertension. We have developed a juvenile mouse model of DOX-induced cardiotoxicity that displays no immediate overt physiological dysfunction; but, leads to an impaired ability of the heart to adapt to hypertension later in life. We also show that co-administration of resveratrol during DOX treatment was sufficient to normalize molecular markers of cardiotoxicity and restore the ability of the heart to undergo adaptive remodelling in response to hypertension later in life.

GUT MICROBIOTA DEPLETION PRESERVES HEART FUNCTION, SUPPRESSES CARDIAC FIBROSIS AND HYPERTROPHY IN A NON‐ISCHEMIC HEART FAILURE MOUSE MODEL

The gut is a major reservoir of T cells and diverse resident microbes, microbiota, which can influence immune responses in sites distant from the mucosal surfaces. Complete sterilization of the gut has proven to be beneficial in some experimental models of T cell mediated diseases, whereas partial recolonization post sterilization leads to microbial perturbations, a process called dysbiosis, and, worsens the outcome. Gut dysbiosis is thus recently becoming associated with the pathogenesis of several diseases, in part, by mechanisms in which certain bacteria promote T cell activation and enhance disease progression in a vicious cycle. The complex syndrome of heart failure (HF), a leading cause of morbidity and mortality affecting more than 24 million people worldwide, is recently becoming associated with gut dysbiosis and T cell mediated systemic inflammation in patients, but the mechanisms regulating this emerging gut‐heart axis, and whether T cell activation and heart infiltration play a role remains unclear. We have previously reported that T cells infiltrate the heart in patients with non‐ischemic HF, and using the transverse aortic constriction (TAC) mouse model of HF, demonstrated that T cells are critical regulators of adverse cardiac remodeling and HF. We hypothesized that sterilization of the gut by microbiota depletion prevents adverse cardiac remodeling and HF in a T cell dependent manner. C57/BL6 mice were orally treated with a well‐established cocktail of antibiotics and antifungal (ABX) and subjected to TAC or Sham surgery. ABX treatment started 1 week before TAC surgery and was terminated 4 weeks after TAC. In vivo transthoracic echocardiography and hemodynamics showed a preserved ejection fraction and fractional shortening in mice treated with ABX as compared to untreated mice. Furthermore, gut microbiota depletion with ABX resulted in decreased left ventricular interstitial and perivascular fibrosis, and decreased cardiac hypertrophy in response to TAC, as compared to non‐ABX treated TAC mice. These changes correlated with significant reduction of CD4 T cell activation in the mediastinal lymph nodes (mLNs) draining the heart, determined by FACS, as well as in the number of CD4 T cells infiltrated in the heart in ABX treated mice. Our findings indicate that ABX treatment results in distal effects in T cell activation occurring during TAC and protects from adverse cardiac remodeling, supporting the potential importance of gut microbiota in pressure overload induced HF. Future studies will determine whether dysbiosis post ABX treatment contributes to pathological cardiac remodeling and the mechanisms regulating the gut‐heart axis in non‐ischemic HF.Support or Funding InformationThis work was supported by the NIH‐RO1‐HL123658 grant.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Phosphodiesterase‐5 inhibitors “Sildenafil and Ordonafil” suppress/reverse L‐NAME induced cardiac hypertrophy in isolated rabbit heart and in phenylephrine induced hypertrophy in isolated neonatal rat myocytes

Phosphodiesterase 5 inhibitors (PDE5Is) have been shown to suppress and reverse myocardial hypertrophy induced by pressure overload. Calcineurin, a protein phosphatase, has been suggested to function as an important hypertrophic factor in cardiac myocytes and its signaling regulates the cardiac hypertrophic response in coordination with mitogen‐activated protein kinases (MAPKs). The present study investigated the effects of two PDE5Is i.e. Sildenafil (SILD) ‘ Viagra’ and Ordonafil (ORD) on N‐nitro‐L‐arginine methyl ester (L‐NAME) induced cardiac hypertrophy and assessed their ability to attenuate the activity of calcineurin, p38 and protein synthesis to exert their effect on hypertrophied cardiac myocytes.MethodsL‐NAME (10 mg/kg/day) was used to induce cardiac hypertrophy in rabbits' hearts and left ventricular thicknesses (LVTs) were measured in L‐NAME and PDE5Is treated hearts. Then, in cultured neonatal rat ventricular myocytes, Western Blot technique was used to assess the ability of these PDE5Is (different doses) to attenuate the activation of calcineurin, p38 and protein synthesis in phenylphrine‐induced ventricular hypertrophy as indicated by the cell surface area of cultured neonatal rat cardiomyocytes.ResultsL‐NAME significantly increased LVT to 6.1± 0.18 mm vs. 4.6±0.13 mm in control rabbit hearts, (p<0.05). SILD and ORD significantly regressed LVT to 4.8 ± 0.2 mm and 5.1 ± 0.1 mm, respectively (p<0.05). Phenylphrine significantly increased neonatal rat ventricular myocyte cell surface area to 131% of control values (p<0.05). This hypertrophic effect of phenylphrine was associated with significant increment in protein synthesis to 143+5% of control values, (p<0.05). Both drugs (in a dose dependent, 0.001–1 mg/L) decreased cell surface area to 95% and 90% of control value respectively, and both decreased protein synthesis to 88% of control values. Phosphatase activity of calcineurin significantly decreased from 1.93±0.09 IU to 1.15±0.05 IU after one hour and to 1.2±0.06 IU after 24 hours incubation with ORD (0.1 mg/l) incubation, (p<0.05). Whereas this activity significantly decreased after 24 hours (1.22±0.04 IU, (p<0.05)), but not after one hour (1.84±0.05 IU) of SILD (0.1 mg/l) incubation. Protein synthesis and p38 activation were significantly attenuated by both drugs (0.1 mg/L).ConclusionsThese results suggest that both SILD and ORD have the ability to reverse L‐NAME induced cardiac hypertrophy in rabbits and suppress phenylphrine induce hypertrophic myocytes. The results indicate these effects are mediated through inhibiting protein synthesis and the attenuation of calcineurin and p38 activity signaling pathways in neonatal rat ventricular myocytes which is reported in this study for the first time.Support or Funding InformationDeanship of Scientific research ‐ Jordan University of Science & TechnologyThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Soluble adenylyl cyclase: A novel player in cardiac hypertrophy induced by isoprenaline or pressure overload.

AimsIn contrast to the membrane bound adenylyl cyclases, the soluble adenylyl cyclase (sAC) is activated by bicarbonate and divalent ions including calcium. sAC is located in the cytosol, nuclei and mitochondria of several tissues including cardiac muscle. However, its role in cardiac pathology is poorly understood. Here we investigate whether sAC is involved in hypertrophic growth using two different model systems.Methods and resultsIn isolated adult rat cardiomyocytes hypertrophy was induced by 24 h β1-adrenoceptor stimulation using isoprenaline (ISO) and a β2-adrenoceptor antagonist (ICI118,551). To monitor hypertrophy cell size along with RNA/DNA- and protein/DNA ratios as well as the expression level of α-skeletal actin were analyzed. sAC activity was suppressed either by treatment with its specific inhibitor KH7 or by knockdown. Both pharmacological inhibition and knockdown blunted hypertrophic growth and reduced expression levels of α-skeletal actin in ISO/ICI treated rat cardiomyocytes. To analyze the underlying cellular mechanism expression levels of phosphorylated CREB, B-Raf and Erk1/2 were examined by western blot. The results suggest the involvement of B-Raf, but not of Erk or CREB in the pro-hypertrophic action of sAC. In wild type and sAC knockout mice pressure overload was induced by transverse aortic constriction. Hemodynamics, heart weight and the expression level of the atrial natriuretic peptide were analyzed. In accordance, transverse aortic constriction failed to induce hypertrophy in sAC knockout mice. Mechanistic analysis revealed a potential role of Erk1/2 in TAC-induced hypertrophy.ConclusionSoluble adenylyl cyclase might be a new pivotal player in the cardiac hypertrophic response either to long-term β1-adrenoceptor stimulation or to pressure overload.

Glucose-6-phosphate dehydrogenase is critical for suppression of cardiac hypertrophy by H2S

Hydrogen Sulfide (H2S), recently identified as the third endogenously produced gaseous messenger, is a promising therapeutic prospect for multiple cardio-pathological states, including myocardial hypertrophy. The molecular niche of H2S in normal or diseased cardiac cells is, however, sparsely understood. Here, we show that β-adrenergic receptor (β-AR) overstimulation, known to produce hypertrophic effects in cardiomyocytes, rapidly decreased endogenous H2S levels. The preservation of intracellular H2S levels under these conditions strongly suppressed hypertrophic responses to adrenergic overstimulation, thus suggesting its intrinsic role in this process. Interestingly, unbiased global transcriptome sequencing analysis revealed an integrated metabolic circuitry, centrally linked by NADPH homeostasis, as the direct target of intracellular H2S augmentation. Within these gene networks, glucose-6-phosphate dehydrogenase (G6PD), the first and rate-limiting enzyme (producing NADPH) in pentose phosphate pathway, emerged as the critical node regulating cellular effects of H2S. Utilizing both cellular and animal model systems, we show that H2S-induced elevated G6PD activity is critical for the suppression of cardiac hypertrophy in response to adrenergic overstimulation. We also describe experimental evidences suggesting multiple processes/pathways involved in regulation of G6PD activity, sustained over extended duration of time, in response to endogenous H2S augmentation. Our data, thus, revealed H2S as a critical endogenous regulator of cardiac metabolic circuitry, and also mechanistic basis for its anti-hypertrophic effects.

New Insights Into the Role of mTOR Signaling in the Cardiovascular System.

The mTOR (mechanistic target of rapamycin) is a master regulator of several crucial cellular processes, including protein synthesis, cellular growth, proliferation, autophagy, lysosomal function, and cell metabolism. mTOR interacts with specific adaptor proteins to form 2 multiprotein complexes, called mTORC1 (mTOR complex 1) and mTORC2 (mTOR complex 2). In the cardiovascular system, the mTOR pathway regulates both physiological and pathological processes in the heart. It is needed for embryonic cardiovascular development and for maintaining cardiac homeostasis in postnatal life. Studies involving mTOR loss-of-function models revealed that mTORC1 activation is indispensable for the development of adaptive cardiac hypertrophy in response to mechanical overload. mTORC2 is also required for normal cardiac physiology and ensures cardiomyocyte survival in response to pressure overload. However, partial genetic or pharmacological inhibition of mTORC1 reduces cardiac remodeling and heart failure in response to pressure overload and chronic myocardial infarction. In addition, mTORC1 blockade reduces cardiac derangements induced by genetic and metabolic disorders and has been reported to extend life span in mice. These studies suggest that pharmacological targeting of mTOR may represent a therapeutic strategy to confer cardioprotection, although clinical evidence in support of this notion is still scarce. This review summarizes and discusses the new evidence on the pathophysiological role of mTOR signaling in the cardiovascular system.

Sphingosine-1-phosphate ameliorates the cardiac hypertrophic response through inhibiting the activity of histone deacetylase-2.

Inhibition of histone deacetylase-2 (HDAC2), which is a prohypertrophic factor in the heart, can functionally attenuate cardiac hypertrophy. The present study aimed to investigate whether sphingosine‑1‑phosphate (S1P), which has recently been reported to suppress HDAC2 activity, could ameliorate the cardiac hypertrophic response and improve cardiac function in mice with transverse aortic constriction(TAC), as well as to determine the underlying mechanisms. Briefly, 8‑week‑old male C57BL/6 mice were randomly divided into sham, TAC and TAC+S1P groups; the results indicated that S1P treatment attenuated TAC‑induced cardiac dysfunction. In addition, heart size and the expression levels of fetalcardiacgenes were reduced in the TAC+S1P group compared with in the TAC group. Furthermore, in cultured H9c2 cells exposed to phenylephrine, S1P was revealed to decrease cardiomyocyte size and the exaggerated expression of fetalcardiacgenes. The present study also demonstrated that S1P had no effect on HDAC2 expression, but it did suppress its activity and increase acetylation of histoneH3 invivo and invitro. Krüppel‑like factor4(KLF4) is an antihypertrophic transcriptional regulator, which mediates HDAC inhibitor‑induced prevention of cardiac hypertrophy; in the present study, KLF4 was upregulated by S1P. Finally, the results indicated that S1P receptor2(S1PR2) may be involved in the antihypertrophic effects, whereas the suppressive effects of S1P on HDAC2 activity were independent of S1PR2. In conclusion, the present study demonstrated that S1P treatment may ameliorate the cardiac hypertrophic response, which may be partly mediated by the suppression of HDAC2 activity and the upregulation of KLF4; it was suggested that S1PR2 may also be involved. Therefore, S1P may be considered a potential therapy for the treatment of heart diseases caused by cardiac hypertrophy.

AT1 receptor blockage impairs NF-κB activation mediated by thyroid hormone in cardiomyocytes.

We have previously demonstrated that calcium-binding protein S100A8 and myeloid differentiation factor-88 (MyD88) are important mediators of nuclear transcription factor kappa-B (NF-κB) activation in cardiomyocytes and that signalling molecules are involved in the hypertrophic response that is stimulated by thyroid hormones (TH). Angiotensin II (Ang II), the main active peptide of the renin-angiotensin system (RAS), binds to type 1 Ang II receptor (AT1R) and subsequently promotes cardiac hypertrophy and the inflammatory response with NF-κB activation underlying the cardiovascular effects. Considering the amount of evidence that RAS is an important mediator of TH actions on the cardiovascular system, we aimed to investigate whether cardiac expression of NF-κB and upstream associated molecules could be altered in hyperthyroidism, as well as whether AT1R could mediate the effects of TH on cardiac tissue and in cardiomyocytes in culture. Wistar rats were subjected to hyperthyroidism with or without the AT1R blocker losartan. The TH serum levels, haemodynamic parameters and cardiac mass were assessed to confirm the hyperthyroid status. The S100A8, MyD88 and nuclear NF-κB expression levels were increased in the hearts of the hyperthyroid rats, and the losartan treatment attenuated these TH effects. In addition, the cultured cardiomyocytes that had been stimulated with losartan exhibited blunted S100A8 upregulation and NF-κB activation compared with the TH-treated cells. Together, our results suggest that AT1R participates in TH-induced cardiac hypertrophy partly by mediating S100A8, MyD88 and NF-κB activation via TH. These findings indicate the important crosstalk between TH and RAS, highlighting the participation of AT1R in the triggered mechanisms of TH that contribute to the cardiac hypertrophy response.

Cardioprotection in mice with a knock-in mutation in Cyclophilin D (CypD-C202S): a site of S-nitrosylation

Our previous study in mouse embryonic fibroblasts showed that cysteine 202 of cyclophilin D (CyPD) is necessary for redox stress-induced activation of the mitochondrial permeability transition pore (mPTP). To further investigate the essential function of this cysteine residue in situ, we used CRISPR to develop a knock-in mouse model (C57BL/6N strain), where CyPD cysteine 202 was mutated to a serine (C202S-KI). The amount of total CyPD expressed in the CyPD C202S-KI did not differ compared to the wild-type (WT). However, the CyPD C202S-KI mouse hearts elicit a significant cardioprotective effect against ischemia-reperfusion (I/R) injury in the Langendorff perfused heart model. After 20 min of global ischemia followed by 90 min of reperfusion, the post-ischemic recovery of rate pressure product (RPP= heart rate x LVDP) was 45.0±4.2% in CyPD WT and 59.6±4.0% in CyPD C202S-KI mice (p=0.0455). Myocardial infarct size was decreased in CyPD C202S-KI mouse hearts versus CyPD WT mice (24.5±4.7% vs 49.8±2.7%, p=0.0095). Isolated heart mitochondria from CyPD C202-KI mice had a higher calcium retention capacity compared to CyPD WT mice (213.3±16.67 vs 140.0±20.82 umol Ca+2/g protein, p=0.0371). However, in contrast to CyPD knockout mice which exhibit more pronounced cardiac hypertrophy in response to pressure overload stimulation than control mice, CyPD C202S-KI mice developed a comparable level of hypertrophy to their WT littermate in an angiotensin II-induced hypertrophy model delivered by implanted osmotic minipumps. In conclusion, these results show that mutated CyPD C202S affords cardioprotection against I/R injury, suggesting that the redox-modification of cysteine 202 might play an important role in the regulation of CyPD and its downstream targets such as mPTP.

Glucose Promotes Cell Growth by Suppressing Branched-chain Amino Acid Degradation

Cell growth is dependent on glucose but the mechanistic role of glucose metabolism in the transduction of growth signaling is not understood. The present study reports that elevation of intracellular glucose during a growth response is required for the activation of mTOR signaling pathway without affecting the signal input through the PI3K or MAPK pathway. This mechanism is independent of ATP provision by glucose but requires intracellular accumulation of branched chain amino acids (BCAAs). Using transcriptome and metabolomics analysis we identified that high glucose inhibited the expression of enzymes in the BCAA degradation pathway through downregulation of KLF15, a transcriptional regulator of development and metabolism. Interruption of the glucose-KLF15-BCAA degradation axis prevented cardiac hypertrophy in response to pressure overload in wildtype mice but not in mutant mice deficient of BCAA degradation gene. Thus, by demonstrating a novel glucose-BCAA cycle through KLF15 the study reveals a cascade of obligatory metabolic responses previously unrecognized for cell growth. Moreover, identification of KLF15 as a glucose responsive gene will stimulate future studies of how cellular metabolism impacts the biological response through transcriptional mechanisms.

O45-6 - Teneligliptin Attenuated AngII-induced Cardiac Hypertrophy by Inhibiting Nox4-HDAC4 Axis

Background: NADPH oxidase 4 (Nox4) mediates nuclear export of histone deacetylase 4 (HDAC4), thereby inducing cardiac hypertrophy in response to hypertrophic stimuli including phenylephrine and pressure overload. Recent studies suggested that teneligliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, inhibited Nox4 expression in aorta and adipocytes. The purpose of this study was to determine whether teneligliptin ameliorates angiotensin II (AngII)-induced cardiac hypertrophy by suppression of Nox4-HDAC4 axis. Methods and Results: AngII (1.44 mg/kg/day) or saline was continuously infused into C57BL/6J mice with or without teneligliptin (30 mg/kg/day) by oral gavage for 1 week. AngII significantly increased blood pressure compared with control mice (125 ± 4 vs. 102 ± 2 mmHg; P < .01). AngII increased heart weight/body weight (LV/BW) and left ventricular wall thickness (LVWT), which were significantly attenuated by teneligliptin (LV/BW 3.9 ± 0.1 vs. 3.6 ± 0.1 mg/g; P < .05, LVWT 0.93 ± 0.04 vs. 0.78 ± 0.05 mm; P < .01) with no significant changes in aortic blood pressure and blood glucose. Histological analysis demonstrated that teneligliptin suppressed AngII-induced increase in cardiomyocyte cross-sectional-area. It also inhibited AngII-induced increases in expression levels of Nox4 mRNA by 22% (P < .05) and phosphorylated HDAC4, a cytosolic localized form of HDAC4, by 40% (P < .05). In cultured neonatal rat ventricular myocytes, teneligliptin or GKT137831, a specific inhibitor of Nox4, directly inhibited AngII-induced phosphorylation of HDAC4 by 39% and 60% (P < .01), respectively. Conclusions: Teneligliptin attenuated AngII-induced cardiac hypertrophy, at least in part, by inhibiting Nox4-HDAC4 axis.

Fibroblast-specific TGF-β-Smad2/3 signaling underlies cardiac fibrosis.

The master cytokine TGF-β mediates tissue fibrosis associated with inflammation and tissue injury. TGF-β induces fibroblast activation and differentiation into myofibroblasts that secrete extracellular matrix proteins. Canonical TGF-β signaling mobilizes Smad2 and Smad3 transcription factors that control fibrosis by promoting gene expression. However, the importance of TGF-β-Smad2/3 signaling in fibroblast-mediated cardiac fibrosis has not been directly evaluated in vivo. Here, we examined pressure overload-induced cardiac fibrosis in fibroblast- and myofibroblast-specific inducible Cre-expressing mouse lines with selective deletion of the TGF-β receptors Tgfbr1/2, Smad2, or Smad3. Fibroblast-specific deletion of Tgfbr1/2 or Smad3, but not Smad2, markedly reduced the pressure overload-induced fibrotic response as well as fibrosis mediated by a heart-specific, latency-resistant TGF-β mutant transgene. Interestingly, cardiac fibroblast-specific deletion of Tgfbr1/2, but not Smad2/3, attenuated the cardiac hypertrophic response to pressure overload stimulation. Mechanistically, loss of Smad2/3 from tissue-resident fibroblasts attenuated injury-induced cellular expansion within the heart and the expression of fibrosis-mediating genes. Deletion of Smad2/3 or Tgfbr1/2 from cardiac fibroblasts similarly inhibited the gene program for fibrosis and extracellular matrix remodeling, although deletion of Tgfbr1/2 uniquely altered expression of an array of regulatory genes involved in cardiomyocyte homeostasis and disease compensation. These findings implicate TGF-β-Smad2/3 signaling in activated tissue-resident cardiac fibroblasts as principal mediators of the fibrotic response.

Bone Marrow-Derived Tenascin-C Attenuates Cardiac Hypertrophy by Controlling Inflammation

BackgroundTenascin-C (TNC) is a highly conserved matricellular protein with a distinct expression pattern during development and disease. Remodeling of the left ventricle (LV) in response to pressure overload leads to the re-expression of the fetal gene program. ObjectivesThe aim of this study was to investigate the function of TNC in cardiac hypertrophy in response to pressure overload. MethodsPressure overload was induced in TNC knockout and wild-type mice by constricting their abdominal aorta or by infusion of angiotensin II. Echocardiography, immunostaining, flow cytometry, quantitative real-time polymerase chain reaction, and reciprocal bone marrow transplantation were used to evaluate the effect of TNC deficiency. ResultsEchocardiographic analysis of pressure overloaded hearts revealed that all LV parameters (LV end-diastolic and -systolic dimensions, ejection fraction, and fractional shortening) deteriorated in TNC-deficient mice compared with their wild-type counterparts. Cardiomyocyte size and collagen accumulation were significantly greater in the absence of TNC. Mechanistically, TNC deficiency promoted rapid accumulation of the CCR2+/Ly6Chi monocyte/macrophage subset into the myocardium in response to pressure overload. Further, echocardiographic and immunohistochemical analyses of recipient hearts showed that expression of TNC in the bone marrow, but not the myocardium, protected the myocardium against excessive remodeling of the pressure-overloaded heart. ConclusionsTNC deficiency further impaired cardiac function in response to pressure overload and exacerbated fibrosis by enhancing inflammation. In addition, expression of TNC in the bone marrow, but not the myocardium, protected the myocardium against excessive remodeling in response to mild pressure overload.

Adult-onset obesity is triggered by impaired mitochondrial gene expression.

Mitochondrial gene expression is essential for energy production; however, an understanding of how it can influence physiology and metabolism is lacking. Several proteins from the pentatricopeptide repeat (PPR) family are essential for the regulation of mitochondrial gene expression, but the functions of the remaining members of this family are poorly understood. We created knockout mice to investigate the role of the PPR domain 1 (PTCD1) protein and show that loss of PTCD1 is embryonic lethal, whereas haploinsufficient, heterozygous mice develop age-induced obesity. The molecular defects and metabolic consequences of mitochondrial protein haploinsufficiency in vivo have not been investigated previously. We show that PTCD1 haploinsufficiency results in increased RNA metabolism, in response to decreased protein synthesis and impaired RNA processing that affect the biogenesis of the respiratory chain, causing mild uncoupling and changes in mitochondrial morphology. We demonstrate that with age, these effects lead to adult-onset obesity that results in liver steatosis and cardiac hypertrophy in response to tissue-specific differential regulation of the mammalian target of rapamycin pathways. Our findings indicate that changes in mitochondrial gene expression have long-term consequences on energy metabolism, providing evidence that haploinsufficiency of PTCD1 can be a major predisposing factor for the development of metabolic syndrome.

1984Innate immune nod1/rip2 signaling is essential for cardiac hypertrophic response with a surprising critical interaction with mitochondrial danger activator

1984Innate immune nod1/rip2 signaling is essential for cardiac hypertrophic response with a surprising critical interaction with mitochondrial danger activator

Abstract 419: OLA1 Regulates GSK3β/eIF2-alpha Signaling Axis in Angiotensin II-treated Human Ventricular Cardiomyocytes

Pathological cardiac hypertrophy in response to stress or disease such as hypertension, myocardial infarction, valvular disease or neurohomonal dysregulation often result in heart failure. Cardiac hypertrophy is associated with changes in key molecular features including protein synthesis, sarcomeric organization, fibrogenesis, cell death and energy metabolism. OBG like ATPase 1 (OLA1) belongs to the translation factor-related (TRAFAC) class, Obg family, and YchF subfamily of P-loop GTPases that play a crucial role in the regulation of diverse cellular processes including protein translation, intracellular transport, signal transduction and growth. Recent study has shown that OLA1 functions as an intrinsic regulator in cellular stress responses, such as oxidative stress and heat shock. However, its role in cardiac hypertrophy is unknown so far. Here, we investigated the effect of OLA1 deficiency on angiotensin II (ANG II)-induced hypertrophic signaling response in immortalized human ventricular cardiomyocytes (hCM) and in heart tissue from OLA1 knockout mice. We observed that ANG II-induced increase in cardiomyocyte cell size was lower in OLA1 knockdown hCM cells as compared to control transfected cells. Interestingly, OLA1 knockdown inhibits the above effect and increases phosphorylation of GSK3β and eIF2α (inactive state). Furthermore, OLA1 homozygous knockout mice showed increase in phosphorylation of GSK3β. Taken together, these findings show that OLA1 deficiency decreases ANG II-induced hypertrophy signaling response in ventricular cardiomyocytes. This study provides the first evidence for the role of OLA1 in ANG II-induced hypertrophic response of human ventricular cardiomyocytes.

Deoxycorticosterone/Salt-Mediated Cardiac Inflammation and Fibrosis Are Dependent on Functional CLOCK Signaling in Male Mice.

Activation of the mineralocorticoid receptor (MR) promotes inflammation, fibrosis, and hypertension. Clinical and experimental studies show that MR antagonists have significant therapeutic benefit for all-cause heart failure; however, blockade of renal MRs limits their widespread use. Identification of key downstream signaling mechanisms for the MR in the cardiovascular system may enable development of targeted MR antagonists with selectivity for pathological MR signaling and lower impact on physiological renal electrolyte handling. One candidate pathway is the circadian clock, the dysregulation of which is associated with cardiovascular diseases. We have previously shown that the circadian gene Per2 is dysregulated in hearts with selective deletion of cardiomyocyte MR. We therefore investigated MR-mediated cardiac inflammation and fibrosis in mice that lack normal regulation and oscillation of the circadian clock in peripheral tissues, that is, CLOCKΔ19 mutant mice. The characteristic cardiac inflammatory/fibrotic response to a deoxycorticosterone (DOC)/salt for 8 weeks was significantly blunted in CLOCKΔ19 mice when compared with wild-type mice, despite a modest increase at "baseline" for fibrosis and macrophage number in CLOCKΔ19 mice. In contrast, cardiac hypertrophy in response to DOC/salt was significantly greater in CLOCKΔ19 vs wild-type mice. Markers for renal inflammation and fibrosis were similarly attenuated in the CLOCKΔ19 mice given DOC/salt. Moreover, increased CLOCK expression in H9c2 cardiac cells enhanced MR-mediated transactivation of Per1, suggesting cooperative signaling between these transcription factors. This study demonstrates that the full development of MR-mediated cardiac inflammation and fibrosis is dependent on intact signaling by the circadian protein CLOCK.

Control of Pathological Cardiac Hypertrophy by Transcriptional Corepressor IRF2BP2 (Interferon Regulatory Factor-2 Binding Protein 2)

The transcription factor NFAT1 (nuclear factor of activated T-cells 1), with the aid of transcriptional coactivators, has been recognized for its necessity and sufficiency to drive pathological cardiac hypertrophy. However, how the transcriptional activity of NFAT1 in terms of cardiac hypertrophy is controlled at the transcriptional level has not been well defined. Herein, we showed that a cardiac-enriched protein IRF2BP2 (interferon regulatory factor-2 binding protein 2) was further upregulated in both human and mouse hypertrophied myocardium and negatively regulated cardiomyocyte hypertrophic response in vitro. By generating cardiomyocyte-specific Irf2bp2 knockout and Irf2bp2-transgenic mouse strains, our in vivo experiments showed that, whereas IRF2BP2 loss-of-function exacerbated both aortic banding- and angiotensin II infusion-induced cardiac hypertrophic response, IRF2BP2 overexpression exerted a strong protective effect against these maladaptive processes. Particularly, IRF2BP2 directly interacted with the C-terminal transactivation domain of NFAT1 by competing with myocyte enhancer factor-2C and disturbing their transcriptional synergism, thereby impeding NFAT1-transactivated hypertrophic transcriptome. As a result, the devastating effect of Irf2bp2 deficiency on cardiac hypertrophy was largely rescued by NFAT1 blockage. Our study, thus, defined IRF2BP2 as a novel negative regulator in controlling pathological cardiac hypertrophy at the transcriptional level.

C33(S), a novel PDE9A inhibitor, protects against rat cardiac hypertrophy through upregulating cGMP signaling.

Phosphodiesterase-9A (PDE9A) expression is upregulated during cardiac hypertrophy and heart failure. Accumulating evidence suggests that PDE9A might be a promising therapeutic target for heart diseases. The present study sought to investigate the effects and underlying mechanisms of C33(S), a novel selective PDE9A inhibitor, on cardiac hypertrophy in vitro and in vivo. Treatment of neonatal rat cardiomyocytes (NRCMs) with PE (100 μmol/L) or ISO (1 μmol/L) induced cardiac hypertrophy characterized by significantly increased cell surface areas and increased expression of fetal genes (ANF and BNP). Furthermore, PE or ISO significantly increased the expression of PDE9A in the cells; whereas knockdown of PDE9A significantly alleviated PE-induced hypertrophic responses. Moreover, pretreatment with PDE9A inhibitor C33(S) (50 and 500 nmol/L) or PF-7943 (2 μmol/L) also alleviated the cardiac hypertrophic responses in PE-treated NRCMs. Abdominal aortic constriction (AAC)-induced cardiac hypertrophy and ISO-induced heart failure were established in SD rats. In ISO-treated rats, oral administration of C33(S) (9, 3, and 1 mg·kg-1·d-1, for 3 consecutive weeks) significantly increased fractional shortening (43.55%±3.98%, 54.79%±1.95%, 43.98%±7.96% vs 32.18%±6.28%), ejection fraction (72.97%±4.64%, 84.29%±1.56%, 73.41%±9.37% vs 49.17%±4.20%) and cardiac output (60.01±9.11, 69.40±11.63, 58.08±8.47 mL/min vs 48.97±2.11 mL/min) but decreased the left ventricular internal diameter, suggesting that the transition to heart failure was postponed by C33(S). We further revealed that C33(S) significantly elevated intracellular cGMP levels, phosphorylation of phospholamban (PLB) and expression of SERCA2a in PE-treated NRCMs in vitro and in ISO-induced heart failure model in vivo. Our results demonstrate that C33(S) effectively protects against cardiac hypertrophy and postpones the transition to heart failure, suggesting that it is a promising agent in the treatment of cardiac diseases.

217 Genetic ablation of microtubule-associated protein 1s (map1s) protects the heart from pathological hypertrophy via regulation of autophagy

BackgroundAutophagy is a process essential in maintaining cellular homeostasis, by degrading and recycling unwanted materials such as misfolded proteins and dysfunctional organelles. In the heart, autophagy is key in mediating...