Hypertrophy In Rat Cardiomyocytes Research Articles

MiR-495-3p promotes cardiac hypertrophy by targeting Pum2.

Pathological cardiac hypertrophy (CH) may lead to heart failure and sudden death. MicroRNAs (miRNAs) have been documented to play crucial parts in CH. The objective of this research was to discuss the potential along with molecule mechanism of miR-495-3p in CH. In vivo CH model was induced by aortic banding (AB) in rats. Cellular hypertrophy in H9c2 rat cardiomyocytes was stimulated by angiotensin II (Ang II) treatment. Haematoxylin and eosin (HE), echocardiography and immunofluorescence staining were used to examine the alterations in cardiac function. The outcomes showed that miR-495-3p expression was high in rat model as well as in Ang II-stimulated cardiomyocytes. Besides, silenced miR-495-3p attenuated CH both in vitro and in vivo. Mechanically, miR-495-3p bound to pumilio RNA binding family member 2 (Pum2) 3'UTR and silenced its expression. Rescue assays further notarized that Pum2 silence abrogated the inhibitory impacts of miR-495-3p inhibitor on CH. In a word, the present research uncovered that miR-495-3p promoted CH by targeting Pum2. Therefore, miR-495-3p may be a novel therapeutic molecule for this disease.

Farrerol Alleviates Diabetic Cardiomyopathy by Regulating AMPK-Mediated Cardiac Lipid Metabolic Pathways in Type 2 Diabetic Rats.

Diabetic cardiomyopathy (DCM) is a prevalent complication of diabetes mellitus characterized by cardiac dysfunction and myocardial remodeling. Farrerol (FA), an active ingredient in Rhododendron with various pharmacological activities, has an unclear specific role in DCM. Therefore, this study aims to investigate the effects of FA on DCM rats and elucidate its mechanism. The type 2 diabetes mellitus (T2DM) model was induced in adult male Sprague-Dawley rats by administering a high-fat diet for 8 weeks along with STZ injection. Subsequent to successful modeling, FA and the positive drug Dapagliflozin (Dapa) were orally administered via gavage for an additional 8-week period. After administration, the rats' body weight, fasting blood glucose, fasting insulin, and blood lipid profiles were quantified. Cardiac function was assessed through evaluation of cardiac function parameters, histopathological examination and measurement of myocardial enzyme markers were conducted to assess myocardial injury and fibrosis, Oil red O staining was utilized to evaluate myocardial lipid accumulation, wheat germ agglutinin (WGA) staining was used for assessing cardiomyocyte hypertrophy, and Western blot analysis was used to detect the proteins expression level of AMP-activated protein kinase (AMPK) pathway. The rat cardiomyocyte H9c2 were induced with palmitic acid to establish an in vitro cell model of myocardial lipid toxicity. Subsequently, the cells were subjected to treatment with FA and AMPK inhibitor Compound C, followed by assessment of lipid formation and expression levels of proteins related to the AMPK signaling pathway. The findings demonstrated that both FA and Dapa exhibited efficacy in ameliorating diabetic symptoms, cardiac dysfunction, myocardial fibrosis, cardiomyocyte hypertrophy, and lipid accumulation in T2DM rats. Additionally, they were found to enhance AMPK phosphorylation and PPARα expression while down-regulating CD36. Similarly, FA was observed to inhibit lipid formation in H9c2 and activate the AMPK signaling pathway. However, the improved effect of FA on lipotoxic cardiomyocytes induced by palmitic acid was partially reversed by Compound C. Therefore, the activation of the AMPK signaling pathway by FA may enhance cardiac lipid metabolism, thereby improving cardiac dysfunction and myocardial fibrosis in DCM rats.

Morphological aspects of the heart of young rats subjected to high and medium intensity progressive resistance physical exercise protocols

Morphological aspects of the heart of young rats subjected to high and medium intensity progressive resistance physical exercise protocols

The effect of physical activity of varying intensity on cardiomyocyte hypertrophy and myocardial polyploidy in rats

Regular exercise improves cognitive function, reduces the risk of premature death from cardiovascular disease, stroke, diabetes and improves quality of life.Aim: To study the morphological parameters of cardiomyocytes of the left ventricle of the heart and the proliferative activity of rat cardiomyocytes during physical activity of different intensity.Methodology and Research Methods. Outbred male rats (n = 30) were taken as experimental animals and divided into three series. The first series of rats were given light physical activity – the animals swam in the bath for 15 minutes. The animals of the second series were in the bath for 30 minutes (moderate severity), the third series were in the bath until they began to lose strength and sink (in 55–59 minutes). Animals were taken out of the experiment after 10 sessions of water loading. Some rats (5 animals per series) were slaughtered 30 days after the end of the experiment. After extraction, the heart was stained with hematoxylin and eosin, the amount of DNA in the nuclei of cardiomyocytes was determined, binuclear and Ki-67 positive cells were counted, and the diameter of cardiomyocytes was measured. Statistical analysis was carried out in the program “Statistica 10.0”.Results. Histological examination revealed changes only in the myocardium of the left ventricle of rats of the third series: pronounced dystrophic changes in cardiomyocytes. There were cells with necrobiosis, focal necrosis of groups of cardiomyocytes. The highest level of cardiomyocyte polyploidy occurred in the second and third series (the ratio of diploid and tetraploid cardiomyocytes in the control corresponded to 91.6 ± 7.4%; 8.2±6.3%). In these series, there was also a change in the number of binuclear cells (in the control – 12.7 ± 1.9‰). In all series of Ki-67 positive nuclei were not detected.Conclusion. Severe physical activity leads to structural disorders of the myocardium, persistent hypertrophy of cardiomyocytes and is accompanied by a decrease in the proliferative activity of cardiomyocytes.

Abstract 18286: Histone Acetyltransferase P300/CBP in Pulmonary Arterial Hypertension and Associated Right Ventricular Failure

INTRODUCTION Pulmonary arterial hypertension (PAH) is defined by increased pulmonary artery (PA) pressure and vascular remodeling, partly due to excessive proliferation and survival of PA smooth muscle cells (PASMCs). Initially, RV hypertrophy allows adaptation to increased resistance, but as the disease progresses, maladaptive remodeling takes place, leading to RV failure and death. Current therapies aim to promote vasodilatation, but none of them directly targets pathological lungs or RV remodeling. The histone acetyltransferases P300/CBP have been identified as central players driving gene expression in various cellular processes such as proliferation/apoptosis and hypertrophy/fibrosis, all of which are critical features of pathological lung and RV remodeling in PAH. Given their role in controlling gene transcription programs, we hypothesized that P300/CBP contributes to maladaptive remodeling. METHODS & RESULTS We show by western blot (WB) and immunofluorescence (IF) increased P300 expression in isolated PASMCs and distal PAs from PAH patients compared to controls (p<0.01) as well as in monocrotaline (MCT) and sugen-hypoxia rat models (p<0.05). Similar results are observed in remodeled RV from PAH patients, MCT- and pulmonary artery banding-subjected rats (WB). In vitro, P300/CBP inhibition (CCS-1477 or siRNA) reduces H3K27 acetylation (WB, p<0.05) in PAH-PASMCs and RV fibroblasts (RVFbs). This effect is accompanied by a decrease in PAH-PASMC proliferation and resistance to apoptosis [WB (PCNA, PLK1, Survivin), IF (Ki67, AnexinV), p<0.01]. Similarly, P300/CBP inhibition reduces proliferation (WB, PCNA, Survivin) and activation/extracellular matrix production (WB, pSMAD2/3, aSMA, Fn, Col1, MMP2) in RVFbs. In addition, P300/CBP inhibition prevents phenylephrine-induced hypertrophy in H9C2 cells and adult rat cardiomyocytes (IF, p<0.05). In vivo, administration of CCS-1477 reduces pulmonary vascular remodeling (Elastica Van Gieson, p<0.05), improves pulmonary hemodynamics (p<0.01) and attenuates RV fibrosis (Masson’s Trichrome, p<0.05) in MCT rats with established PAH. Conclusion: We provide evidence that targeting P300/CBP may represent a promising avenue to tackle both lung and RV maladaptive remodeling in PAH.

Vanillic Acid Alleviates Right Ventricular Function in Rats With MCT-Induced Pulmonary Arterial Hypertension

This study examined the molecular processes behind the effects of vanillic acid (VA) on right ventricular (RV) hypertrophy and function in rats with monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH). There were 40 male Sprague‒Dawley (SD) rats that were separated into 4 groups: Control, PAH, MCT + VA (50 mg/kg/d), and MCT + VA (100 mg/kg/d). Male SD rats were injected with MCT once under the skin to create the PAH model (40 mg/kg). RV morphological properties were evaluated using Masson and hematoxylin and eosin (H&E) staining. Echocardiography was used to evaluate RV functioning and right ventricle–pulmonary artery (RV-PA) coupling. In addition, Rho-associated protein kinase (ROCK) pathway-related factors were evaluated using Western blotting. Enzyme-linked immunosorbent assay (ELISA) was used to detect inflammatory markers as well as atrial natriuretic peptide (ANP) and brain-type natriuretic peptide (BNP) in the blood of PAH rats. As a result, VA effectively reduced the development of RV cardiomyocyte hypertrophy and fibrosis in PAH rats; levels of ANP, BNP, and inflammatory markers in the blood of PAH rats were also significantly decreased by VA intervention. Additionally, VA enhanced RV functioning and RV-PA coupling in PAH rats. In response to VA, the expression of proteins related to the ROCK pathway (ROCK1, ROCK2, NFATc3, P-STAT3, and Bax) was downregulated, whereas Bcl-2 expression was elevated. This study found that VA could attenuate RV remodeling and improve RV-PA coupling in PAH rats. RV remodeling and dysfunction may be linked to the dysregulation of the ROCK pathway, and the protective action of VA on RV function may be due to a block in the ROCK signaling pathway or its downstream signaling molecules.

Heart-targeting exosomes from human cardiosphere-derived cells improve the therapeutic effect on cardiac hypertrophy

Exosomes of human cardiosphere-derived cells (CDCs) are very promising for treating cardiovascular disorders. However, the current challenge is inconvenient delivery methods of exosomes for clinical application. The present study aims to explore the potential to enhance the therapeutic effect of exosome (EXO) from human CDCs to myocardial hypertrophy. A heart homing peptide (HHP) was displayed on the surface of exosomes derived from CDCs that were forced to express the HHP fused on the N-terminus of the lysosomal-associated membrane protein 2b (LAMP2b). The cardiomyocyte-targeting capability of exosomes were analyzed and their therapeutic effects were evaluated in a mouse model of myocardial hypertrophy induced by transverse aorta constriction (TAC). The molecular mechanisms of the therapeutic effects were dissected in angiotensin II-induced neonatal rat cardiomyocyte (NRCMs) hypertrophy model using a combination of biochemistry, immunohistochemistry and molecular biology techniques. We found that HHP-exosomes (HHP-EXO) accumulated more in mouse hearts after intravenous delivery and in cultured NRCMs than control exosomes (CON-EXO). Cardiac function of TAC mice was significantly improved with intravenous HHP-EXO administration. Left ventricular hypertrophy was reduced more by HHP-EXO than CON-EXO via inhibition of β-MHC, BNP, GP130, p-STAT3, p-ERK1/2, and p-AKT. Similar results were obtained in angiotensin II-induced hypertrophy of NRCMs, in which the beneficial effects of HHP-EXO were abolished by miRNA-148a inhibition. Our results indicate that HHP-EXO preferentially target the heart and improve the therapeutic effect of CDCs-exosomes on cardiac hypertrophy. The beneficial therapeutic effect is most likely attributed to miRNA-148a-mediated suppression of GP130, which in turn inhibits STAT3/ERK1/2/AKT signaling pathway, leading to improved cardiac function and remodeling.

Melatonin activates the Mst1-Nrf2 signaling to alleviate cardiac hypertrophy in pulmonary arterial hypertension

Among pulmonary arterial hypertension (PAH) patients, right ventricular (RV) functioning has been considered a major determining factor for cardiac capacity and survival. However, despite the recognition of the clinical importance for preserving RV functioning, no effective treatments are currently available for RV failure. This study aims to suggest one such possible treatment, through investigating the cardio-protective capabilities of the anti-oxidant, melatonin (Mel), for treating adverse RV remodeling in PAH, along with its underlying mechanisms. Arginine vasopressin induced neonatal rat cardiomyocyte hypertrophy in vitro; in vivo, PAH was induced in rats through intraperitoneal monocrotaline (MCT) injections, and Mel was administered intraperitoneally 24 h prior to MCT. Mel reduced rat cardiomyocyte hypertrophy and mitochondrial oxidative stress in vitro by activating the Mst1-Nrf2 pathway, which were all reversed upon siRNA knockdown of Mst1. Likewise, in vivo, Mel pre-treatment significantly ameliorated MCT-induced deterioration in cardiac function, RV hypertrophy, fibrosis and dilation. These beneficial effects were also associated with Mst1-Nrf2 pathway up regulation and its associated reduction in oxidative stress, as evidenced by the decrease in RV malondialdehyde content. Notably, results from Mel treatment were similar, or even superior, to those obtained from N-acetyl cysteine (NAC), which has already been-confirmed as an anti-oxidative treatment for PAH. By contrast, co-treatment with the Mst1 inhibitor XMU-MP-1 reversed all of those Mel-associated beneficial effects. Our findings thus identified Mel as a potent cardio-protective agent against the onset of maladaptive RV remodeling, through enhancement of the anti-oxidative response via Mst1-Nrf2 pathway activation.

Sodium Ferulate Inhibits Rat Cardiomyocyte Hypertrophy Induced by Angiotensin II Through Enhancement of Endothelial Nitric Oxide Synthase/Nitric Oxide/Cyclic Guanosine Monophosphate Signaling Pathway.

Sodium ferulate (SF) is the sodium salt of ferulic acid, which is one of the effective components of Angelica sinensis and Lignsticum chuanxiong , and plays an important role in protecting the cardiovascular system. In this study, myocardial hypertrophy was induced by angiotensin II 0.1 μmol/L in neonatal Sprague-Dawley rat ventricular myocytes. Nine groups were designed, that is, normal, normal administration, model, L-arginine (L-arg 1000 μmol/L), SF (50, 100, 200 μmol/L) group, and N G -nitro-L-arg-methyl ester 1500 μmol/L combined with SF 200 μmol/L or L-arg 1000 μmol/L group, respectively. Cardiomyocyte hypertrophy was confirmed by observing histological changes and measurements of cell diameter, protein content and atrial natriuretic factor, and β-myosin heavy chain levels of the cells. Notably, SF could inhibit significantly myocardial hypertrophy of neonatal rat cardiomyocytes in a concentration-dependent manner without producing cytotoxicity, and the levels of nitric oxide, NO synthase (NOS), endothelial NOS, and cyclic guanosine monophosphate were increased, but the level of cyclic adenosine monophosphate was decreased in cardiomyocytes. Simultaneously, levels of protein kinase C beta, Raf-1, and extracellular regulated protein kinase 1/2 (ERK1/2) were downregulated, whereas levels of mitogen-activated protein kinase phosphatase-1 were significantly upregulated. All the beneficial effects of SF were blunted by N G -nitro-L-arg-methyl ester. Overall, these findings reveal that SF can inhibit angiotensin II-induced myocardial hypertrophy of neonatal rat cardiomyocytes, which is closely related to activation of endothelial NOS/NO/cyclic guanosine monophosphate, and inhibition of protein kinase C and mitogen-activated protein kinase signaling pathways.

Investigating the Therapeutic Potential of Cdk8 Small Molecule Inhibitors to Prevent Pathological Cardiac Remodeling and Heart Failure

Pathological cardiac hypertrophy represents a major risk factor for heart failure (HF). Cardiac hypertrophic responses are coordinated in part through altered transcriptional dynamics involving chromatin structure and accessibility, transcription factor (TF) activation, and enhancer utilization. Mediator is a multiprotein complex that integrates signal‐dependent TFs with basal transcriptional machinery to regulate downstream gene expression. Cyclin‐dependent kinase 8 (Cdk8) is a Mediator kinase demonstrated to have a complex role in transcription regulation, driving both transcription activation and inhibition in context‐specific ways. Previous studies have demonstrated that Cdk8 protein expression is increased in human and mouse HF. Cardiomyocyte‐specific Cdk8 overexpression leads to eccentric cardiac hypertrophy consistent with HF, suggesting that Cdk8 activity may play a significant role in the progression of HF. To investigate the therapeutic potential in regulating Cdk8 activity, we used Cdk8 selective inhibitors SenexinA and CCT251545 in an in vitro neonatal rat cardiomyocyte hypertrophy model, resulting in altered regulation of hypertrophic transcriptional programs and blunted cardiomyocyte hypertrophy. To further assess Cdk8 kinase activity in regulating hypertrophic responses, Cdk8 inhibitor CCT251545 was used in an in vivo angiotensin II‐induced hypertensive mouse model. It was hypothesized that Cdk8 inhibition by CCT251545 in vivo would lead to reduced hypertrophic responses. Results indicate that CCT251545 is effective at inhibiting Cdk8 activity, leading to blunted hypertrophic responses with altered gene expression. These studies demonstrate a role for Cdk8 activity in transcriptional regulation of genes associated with pathological cardiac hypertrophy, which can ultimately lead to heart failure.

Protective Effect of Curcumin on Lipopolysaccharide-Induced Rat Cardiomyocyte Hypertrophy

To study the protective effect of curcumin on lipopolysaccharide-induced rat cardiomyocyte hypertrophy is the main objective of the study. Cardiomyocytes were purified and cultured by differential adherence in in vitro and then they were divided into control group, lipopolysaccharide group, lipopolysaccharide+curcumin low-dose (12.5 mg/l) group, lipopolysaccharide+curcumin medium-dose (25 mg/l) group and lipopolysaccharide+curcumin high-dose (50 mg/l) group. The morphological changes were observed under a phase-contrast inverted microscope and the cell volume was measured. The total protein content of the cell was detected by Coomassie brilliant blue kit. Enzyme-linked immunosorbent assay method was used to detect the level of tumor necrosis factor alpha. The TILL imaging system was used to observe the changes in intracellular calcium ions. Compared with the control group, lipopolysaccharide significantly increased the cardiomyocyte volume, the total cell protein content, the level of tumor necrosis factor alpha (p<0.01) and the instantaneous peak of calcium ions. Compared with the lipopolysaccharide group, 12.5, 25, 50 mg/l curcumin treatment inhibited the increase of cardiomyocyte volume, total protein content, tumor necrosis factor alpha level and the instantaneous peak of calcium ions induced by lipopolysaccharide and showed a dose-dependent effect. Curcumin has a protective effect on rat cardiomyocyte hypertrophy induced by lipopolysaccharides, which may be related to the inhibition of tumor necrosis factor alpha production and the inhibition of calcium ions overload.

Knockout of AMPKα2 Blocked the Protection of Sestrin2 Overexpression Against Cardiac Hypertrophy Induced by Pressure Overload.

Objectives: Sestrin2 (Sesn2) has been demonstrated to be a cysteine sulfinyl reductase and protects cells from multiple stress insults, including hypoxia, endoplasmic reticulum stress, and oxidative stress. However, the roles and mechanisms of Sesn2 in pressure overload-induced mouse cardiac hypertrophy have not been clearly clarified. This study intended to investigate whether sestrin2 (Sesn2) overexpression could prevent pressure overload-induced cardiac hypertrophy via an AMPKα2 dependent pathway through conditional knockout of AMPKα2. Methods and results: Sesn2 expression was significantly increased in mice hearts at 2 and 4 weeks after aortic banding (AB) surgery, but decreased to 60–70% of the baseline at 8 weeks. Sesn2 overexpression (at 3, 6, and 9 folds) showed little cardiac genetic toxicity in transgenic mice. Cardiac dysfunctions induced by pressure overload were attenuated by cardiomyocyte-specific Sesn2 overexpression when measured by echocardiography and hemodynamic analysis. Results of HE and PSR staining showed that Sesn2 overexpression significantly alleviated cardiac hypertrophy and fibrosis in mice hearts induced by pressure overload. Meanwhile, adenovirus-mediated-Sesn2 overexpression markedly suppressed angiotensin II-induced neonatal rat cardiomyocyte hypertrophy in vitro. Mechanistically, Sesn2 overexpression increased AMPKα2 phosphorylation but inhibited mTORC1 phosphorylation. The cardiac protections of Sesn2 overexpression were also via regulating oxidative stress by enhancing Nrf2/HO-1 signaling, restoring SOD activity, and suppressing NADPH activity. Particularly, we first proved the vital role of AMPKα2 in the regulation of Sesn2 with AMPKα2 knockout (AMPKα2-/-) mice and Sesn2 transgenic mice crossed with AMPKα2-/-, since Sesn2 overexpression failed to improve cardiac function, inhibit cardiac hypertrophy and fibrosis, and attenuate oxidative stress after AMPKα2 knockout. Conclusion: This study uniquely revealed that Sesn2 overexpression showed little genetic toxicity in mice hearts and inhibited mTORC1 activation and oxidative stress to protect against pressure overload-induced cardiac hypertrophy in an AMPKα2 dependent pathway. Thus, interventions through promoting Sesn2 expression might be a potential strategy for treating pathological cardiac hypertrophy and heart failure.

Effects of Yiqi Huoxue Decoction on Post-Myocardial Infarction Cardiac Nerve Remodeling and Cardiomyocyte Hypertrophy in Rats.

Myocardial infarction can lead to ventricular remodeling and arrhythmia, which is closely related to nerve remodeling. Our previous study found that Yiqi Huoxue decoction (YQHX) can improve ventricular remodeling and reduce myocardial damage. Therefore, in this study, we observed the effect of YQHX on cardiac neural remodeling and cardiomyocyte hypertrophy and its possible mechanism. This research is composed of two parts: animal and H9c2 cells experiments. The animal model of acute myocardial infarction was established by ligating the left anterior descending coronary artery in Sprague Dawley (SD) rats. H9c2 cells were placed in 94% N2, 5% CO2, and 1% O2 hypoxic environment for 12 hours to replicate the hypoglycemic hypoxia model. The experimental results showed that, compared with the MI group, YQHX can significantly improve heart function after myocardial infarction and reduce nerve remodeling and myocardial hypertrophy. Pathological structure observation demonstrated reducing myocardial tissue damage and decreasing of cell cross-sectional area, diameter, and circumference. The positive rate of TH declined apparently, and the sympathetic nerve density was lower than that of the MI group. After YQHX was given for 28 days, the proneural remodeling factors TH, NGF, and GAP43 in the marginal zone of infarction and stellate ganglion decreased obviously while the inhibitory nerve remodeling factor Sema-3A increased. The myocardial hypertrophic protein ANP and β-MHC were also significantly inhibited with p-ERK1/2 protein expression level prominently reduced. There was no difference between the YQHX group and the Meto group. After myocardial infarction, nerve remodeling was seen in the marginal area of infarction and stellate ganglion, and the neuropeptides released by which promoted myocardial hypertrophy. The mechanism may be related to the ERK1/2 signaling pathway. YQHX could regulate the ERK1/2 signaling pathway, inhibit the release of nerve remodeling factors and myocardial hypertrophy protein to reduce nerve remodeling, and relieve myocardial hypertrophy.

Azilsartan ameliorates ventricular hypertrophy in rats suffering from pressure overload-induced cardiac hypertrophy by activating the Keap1-Nrf2 signalling pathway.

Investigate if azilsartan protects against myocardial hypertrophy by upregulating nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated pathways. Abdominal aortic constriction (AAC)-induced cardiac hypertrophy in rats was applied. Azilsartan or vehicle was administered daily for 6 weeks in sham or AAC rats. Cardiac morphology and ventricular function were determined. Azilsartan effects upon neonatal rat cardiomyocyte (NRCM) hypertrophy and molecular mechanisms were studied in angiotensin (Ang) II-stimulated NRCMs in vitro. Nrf2-small interfering RNA (siRNA) was used to knockdown Nrf2 expression. Messenger RNA (mRNA)/protein expression of Kelch-like erythroid cell-derived protein (Keap)1 and Nrf2 and its downstream antioxidant enzymes was determined by real-time reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. Azilsartan treatment ameliorated cardiac hypertrophy/fibrosis significantly in AAC rats. Azilsartan increased expression of Nrf2 protein but decreased expression of Keap1 protein. Upregulation of protein expression of Nrf2's downstream antioxidant enzymes by azilsartan treatment was observed. Azilsartan inhibited Ang II-induced NRCM hypertrophy significantly and similar effects on the Keap1-Nrf2 pathway were observed in vivo. Nrf2 knockdown markedly counteracted the beneficial effects of azilsartan on NRCM hypertrophy and the Keap1-Nrf2 pathway. Azilsartan restrained pressure overload-induced cardiac remodelling by activating the Keap1-Nrf2 pathway and increasing expression of downstream antioxidant enzymes to alleviate oxidative stress.

Distinct roles of calmodulin and Ca2+/calmodulin-dependent protein kinase II in isopreterenol-induced cardiac hypertrophy

Intracellular calcium is related to cardiac hypertrophy. The CaV1.2 channel and Ca2+/calmodulin-dependent protein kinase II (CaMKII) and CaM regulate the intracellular calcium content. However, the differences in CaMKII and CaM in cardiac hypertrophy are still conflicting and are worthy of studying as drug targets. Therefore, in this study, we aim to investigate the roles and mechanism of CaM and CaMKII on CaV1.2 in pathological myocardial hypertrophy. The results showed that ISO stimulation caused SD rat heart and cardiomyocyte hypertrophy. In vivo, the HW/BW, LVW/BW, cross-sectional area, fibrosis ratio and ANP expression were all increased. There were no differences in CaV1.2 channel expression in the in vivo model or the in vitro model, but the ISO stimulation induced channel activity, and the [Ca2+]i increased. The protein expression levels of CaMKII and p-CaMKII were all increased in the ISO group, but the CaM expression level decreased. AIP inhibited ANP, CaMKII and p-CaMKII expression, and ISO-induced [Ca2+]i increased. AIP also reduced HDAC4, p-HDAC and MEF2C expression. However, CMZ did not play a cardiac hypertrophy reversal role in vitro. In conclusion, we considered that compared with CaM, CaMKII may be a much more important drug target in cardiac hypertrophy reversal.

Combination treatment of perifosine and valsartan showed more efficiency in protecting against pressure overload induced mouse heart failure

The optimum strategy for heart failure (HF) treatment has yet to be elucidated. This study intended to test the benefit of a combination of valsartan (VAL) and perifosine (PER), a specific AKT inhibitor, in protecting against pressure overload induced mouse HF. Mouse were subjected to aortic banding (AB) surgery to establish HF models and then were given vehicle (HF), VAL (50 mg/kg/d), PER (30 mg/kg/d) or combination of VAL and PER for 4 weeks. Mouse with sham surgery treated with VEH were used for control (VEH). VAL or PER treatment could significantly alleviate mouse heart weight, attenuate cardiac fibrosis and improve cardiac function. The combination treatment of VAL and PER presented much better benefit compared with VAL or PER group respectively. PER treatment significantly inhibited AKT/GSK3β/mTORC1 signaling. Besides the classic AT1 inhibition, VAL treatment significantly inhibited MAPK (ERK1/2) signaling. Furthermore, VAL and PER treatment could markedly prevent neonatal rat cardiomyocyte hypertrophy and the activation of neonatal rat cardiac fibroblast. Combination of VAL and PER also presented superior beneficial effects than single treatment of VAL or PER in vitro experiments respectively. This study presented that the combination of valsartan and PER may be a potential treatment for HF prevention.

Myricetin Alleviates Pathological Cardiac Hypertrophy via TRAF6/TAK1/MAPK and Nrf2 Signaling Pathway.

Myricetin (Myr) is a common plant-derived polyphenol and is well recognized for its multiple activities including antioxidant, anti-inflammation, anticancer, and antidiabetes. Our previous studies indicated that Myr protected mouse heart from lipopolysaccharide and streptozocin-induced injuries. However, it remained to be unclear whether Myr could prevent mouse heart from pressure overload-induced pathological hypertrophy. Wild type (WT) and cardiac Nrf2 knockdown (Nrf2-KD) mice were subjected to aortic banding (AB) surgery and then administered with Myr (200 mg/kg/d) for 6 weeks. Myr significantly alleviated AB-induced cardiac hypertrophy, fibrosis, and cardiac dysfunction in both WT and Nrf2-KD mice. Myr also inhibited phenylephrine- (PE-) induced neonatal rat cardiomyocyte (NRCM) hypertrophy and hypertrophic markers' expression in vitro. Mechanically, Myr markedly increased Nrf2 activity, decreased NF-κB activity, and inhibited TAK1/p38/JNK1/2 MAPK signaling in WT mouse hearts. We further demonstrated that Myr could inhibit TAK1/p38/JNK1/2 signaling via inhibiting Traf6 ubiquitination and its interaction with TAK1 after Nrf2 knockdown in NRCM. These results strongly suggested that Myr could attenuate pressure overload-induced pathological hypertrophy in vivo and PE-induced NRCM hypertrophy via enhancing Nrf2 activity and inhibiting TAK1/P38/JNK1/2 phosphorylation by regulating Traf6 ubiquitination. Thus, Myr might be a potential strategy for therapy or adjuvant therapy for malignant cardiac hypertrophy.

Regulation of mitochondrial cristae remodelling by acetylcholine alleviates palmitate-induced cardiomyocyte hypertrophy

Mitochondrial dysfunction is associated with obesity-induced cardiac remodelling. Recent research suggests that the cristae are the true bioenergetic components of cells. Acetylcholine (ACh), the major neurotransmitter of the vagus nerve, exerts cardio-protective effects against ischaemia. This study investigated the role of cristae remodelling in palmitate (PA)-induced neonatal rat cardiomyocyte hypertrophy and explored the beneficial effects of ACh. We found loose, fragmented and even lysed cristae in PA-treated neonatal cardiomyocytes along with declines in mitochondrial network and complex expression and overproduction of mitochondrial reactive oxygen species (ROS); these changes ultimately resulted in increased myocardial size. Overexpression of mitofilin by adenoviral infection partly improved cristae shape, mitochondrial network, and ATP content and attenuated cell hypertrophy. Interestingly, siRNA-mediated AMP-activated protein kinase (AMPK) silencing increased the number of cristae with a balloon-like morphology without disturbing mitofilin expression. Furthermore, AMPK knockdown abolished the effects of mitofilin overexpression on cristae remodelling and inhibited the interaction of mitofilin with sorting and assembly machinery 50 (Sam50) and coiled-coil helix coiled-coil helix domain-containing protein 3 (CHCHD3), two core components of the mitochondrial contact site and cristae organizing system (MICOS) complex. Intriguingly, ACh upregulated mitofilin expression and AMPK phosphorylation via the muscarinic ACh receptor (MAChR). Moreover, ACh enhanced protein-protein interactions between mitofilin and other components of the MICOS complex, thereby preventing PA-induced mitochondrial dysfunction and cardiomyocyte hypertrophy; however, these effects were abolished by AMPK silencing. Taken together, our data suggest that ACh improves cristae remodelling to defend against PA-induced myocardial hypertrophy, presumably by increasing mitofilin expression and activating AMPK to form the MICOS complex through MAChR. These results suggest new and promising therapeutic approaches targeting mitochondria to prevent lipotoxic cardiomyopathy.

2,5-Dimethylcelecoxib prevents isoprenaline-induced cardiomyocyte hypertrophy and cardiac fibroblast activation by inhibiting Akt-mediated GSK-3 phosphorylation

We previously reported that 2,5-dimethylcelecoxib (DM-celecoxib), a celecoxib derivative that is unable to inhibit cyclooxygenase-2, prevented cardiac remodeling by activating glycogen synthase kinase-3 (GSK-3) and prolonged the lifespan of heart failure mice with genetic dilated cardiomyopathy or transverse aortic constriction-induced left ventricular hypertrophy. However, it remained unclear how DM-celecoxib regulated structure and function of cardiomyocytes and cardiac fibroblasts involved in cardiac remodeling. In the present study, therefore, we investigated the effect of DM-celecoxib on isoprenaline-induced cardiomyocyte hypertrophy and cardiac fibroblast activation, because DM-celecoxib prevented isoprenaline-induced cardiac remodeling in vivo. DM-celecoxib suppressed isoprenaline-induced neonatal rat cardiomyocyte hypertrophy by the inhibition of Akt phosphorylation resulting in the activation of GSK-3 and the inhibition of β-catenin and mammalian target of rapamycin (mTOR). DM-celecoxib also suppressed the proliferation and the production of matrix metalloproteinase-2 and fibronectin of rat cardiac fibroblasts. Moreover, we found that phosphatase and tensin homolog on chromosome 10 (PTEN) could be a molecule to mediate the effect of DM-celecoxib on Akt. These results suggest that DM-celecoxib directly improves the structure and function of cardiomyocytes and cardiac fibroblasts and that this compound could be clinically useful for the treatment of β-adrenergic receptor-mediated maladaptive cardiac remodeling.

Inhibitory Effects of Tofogliflozin on Cardiac Hypertrophy in Dahl Salt-Sensitive and Salt-Resistant Rats Fed a High-Fat Diet.

Sodium-glucose cotransporter 2 (SGLT2) inhibitors are drugs for diabetes and might prevent heart failure. In this study, we investigated the effects of tofogliflozin, an SGLT2 inhibitor, on cardiac hypertrophy and metabolism in hypertensive rats fed a high-fat diet. Dahl salt-sensitive (DS) rats, hypertensive model rats, and Dahl salt-resistant (DR) rats, non-hypertensive model rats, were fed a high-salt and high-fat diet containing tofogliflozin (0.005%) for 9 weeks to examine the effects of this drug on cardiac hypertrophy and metabolism. Tofogliflozin tended to suppress a rise of the systolic blood pressure, relative to the control, throughout the treatment period in both DR and DS rats, and significantly suppress a rise of the systolic blood pressure, relative to the control, at the 9th week in DS rats. Tofogliflozin reduced cardiac hypertrophy (heart weight/body weight) not only in DS rats but also in DR rats. Histological analysis showed that tofogliflozin significantly decreased cardiomyocyte hypertrophy and perivascular fibrosis in both DS and DR rats. Tofogliflozin significantly decreased the expression levels of genes related to cardiac hypertrophy (encoding for natriuretic peptides A and B and interleukin-6), and to cardiac fibrosis (encoding for transforming growth factor-β1 and collagen type IV), in DS rats. Recent studies have shown that hypertrophied and failing hearts shift to oxidizing ketone bodies as a significant fuel source. We also performed metabolome analysis for ventricular myocardial tissue. Tofogliflozin reduced 3-hydroxybutyrate, a ketone body, and significantly decreased the expression levels of β-hydroxybutyrate dehydrogenase 1 and 3-oxoacid CoA-transferase, which are related to ketone oxidization. In conclusion, tofogliflozin ameliorated cardiac hypertrophy and fibrosis along with reduction of ketone usage in myocardial tissue.