Mouse strain-specific responses of mitochondrial respiratory function and cardiac hypertrophy to isoproterenol treatment / 生理学报

Cardiac hypertrophy is a common pathological process of various cardiovascular diseases and eventually develops into heart failure. This paper was aimed to study the different pathological characteristics exhibited by different mouse strains after hypertrophy stimulation. Two mouse strains, A/J and FVB/nJ, were treated with isoproterenol (ISO) by osmotic pump to induce cardiac hypertrophy. Echocardiography was performed to monitor heart morphology and function. Mitochondria were isolated from hearts in each group, and oxidative phosphorylation function was assayed in vitro. The results showed that both strains showed a compensatory enhancement of heart contractile function after 1-week ISO treatment. The A/J mice, but not the FVB/nJ mice, developed significant cardiac hypertrophy after 3-week ISO treatment as evidenced by increases in left ventricular posterior wall thickness, heart weight/body weight ratio, cross sectional area of cardiomyocytes and cardiac hypertrophic markers. Interestingly, the heart from A/J mice contained higher mitochondrial DNA copy number compared with that from FVB/nJ mice. Functionally, the mitochondria from A/J mice displayed faster O

Aliskiren attenuates cardiac dysfunction by modulation of the mTOR and apoptosis pathways

Aliskiren (ALS) is well known for its antihypertensive properties. However, the potential underlying the molecular mechanism and the anti-hypertrophic effect of ALS have not yet been fully elucidated. The aim of the present study was to investigate the role of ALS in mammalian target of rapamycin (mTOR) and apoptosis signaling using in vivo and in vitro models of cardiac hypertrophy. A rat model of cardiac hypertrophy was induced by isoproterenol treatment (5 mg·kg-1·day-1) for 4 weeks, with or without ALS treatment at 20 mg·kg-1·day-1. The expression of hypertrophic, fibrotic, and apoptotic markers was determined by RT-qPCR. The protein expression of apoptotic markers mTOR and p-mTOR was assessed by western blot analysis. The proliferation of H9C2 cells was monitored using the MTS assay. Cell apoptosis was analyzed using flow cytometry. In vivo, isoproterenol-treated rats exhibited worse cardiac function, whereas ALS treatment reversed these dysfunctions, which were associated with changes in p-mTOR, Bcl-2, Bax, and cleaved caspase-3 expression, as well as the number of apoptotic cells. In vitro, H9C2 cardiomyocyte viability was significantly inhibited and cardiac hypertrophy was induced by Ang II administration, but ALS reversed Ang II-induced H9C2 cardiomyocyte hypertrophy and death. Furthermore, Ang II triggered the activation of the mTOR and apoptosis pathways in hypertrophic cardiomyocytes that were inhibited by ALS treatment. These results indicated that ALS alleviated cardiac hypertrophy through inhibition of the mTOR and apoptosis pathways in cardiomyocytes.

BMP4 Induces Cardiomyocyte Hypertrophy Through the Activation of ERK 1/2 Signaling Pathway in H9c2 Cells

Abstract Bone morphogenetic protein-4 (BMP4) is a member of the bone morphogenetic protein family which plays an important role in bone formation, inflammation and cardiac hypertrophy. The aim of this study was to investigate the underlying molecular mechanism that BMP4-induced cardiomyocyte hypertrophy. H9c2 cells were used to measure cell surface area and protein synthesis. Western blot was used to examine hypertrophic marker brain natriuretic peptide (BNP) protein expression and phosphorylation of ERK1/2. The results exhibited that cell surface area, protein synthesis and BNP protein expression were increased with BMP4 treatment. While PD98059 inhibited these effects of BMP4. In addition, BMP4 treatment increased phosphorylation of ERK1/2 in a time- and dose-dependent manner. PD98059 treatment decreased phosphorylation of ERK1/2 that was increased by BMP4. These results suggest that BMP4 induces cardiomyocyte hypertrophy through the activation of ERK1/2 cell signaling pathway.

Etanercept protects rat cardiomyocytes against hypertrophy by regulating inflammatory cytokines secretion and cell apoptosis

We aimed to investigate the effect of etanercept, a tumor necrosis factor-α (TNF-α) inhibitor, on rat cardiomyocyte hypertrophy and its underlying mechanism. Primary neonatal rat cardiomyocytes were isolated from Sprague-Dawley rats. The model of rat cardiomyocyte hypertrophy was induced by endothelin, and then treated with different concentrations of etanercept (1, 10, and 50 μM). After treatment, cell counts, viability and cell apoptosis were evaluated. The mRNA levels of myocardial hypertrophy marker genes, including atrial natriuretic factor (ANF), matrix metalloproteinase (MMP)-9 and MMP-13, were detected by qRT-PCR, and the expressions of apoptosis-related proteins (Bcl-2 and Bax) were measured by western blotting. The protein levels of transforming growth factor-β1 (TGF-β1), interleukin (IL)-1β, IL-6, leukemia inhibitory factor (LIF) and cardiotrophin-1 (CT-1) were determined using enzyme linked immunosorbent assay (ELISA) kits. In the present study, TNF-α level in cardiomyocytes with hypertrophy was significantly enhanced (P<0.05). Compared to the model group, cell number and viability were significantly increased and ratio of apoptotic cells was reduced by etanercept (P<0.05, P<0.01, or P<0.001). In addition, etanercept remarkably reduced the mRNA levels of ANF, MMP-9 and MMP-13, inhibited the expression of Bax, and increased the expression of Bcl-2 compared to the model group (P<0.05). ELISA results further showed that etanercept lowered the levels of IL-1β, IL-6, LIF and CT-1 but not TGF-β1 compared to the model group (P<0.05). Etanercept may protect rat cardiomyocytes from hypertrophy by inhibiting inflammatory cytokines secretion and cell apoptosis.

The role of Ca2+/calmodulin-dependent protein kinase II and calcineurin in TNF-α-induced myocardial hypertrophy

We investigated whether Ca2+/calmodulin-dependent kinase II (CaMKII) and calcineurin (CaN) are involved in myocardial hypertrophy induced by tumor necrosis factor α (TNF-α). The cardiomyocytes of neonatal Wistar rats (1-2 days old) were cultured and stimulated by TNF-α (100 μg/L), and Ca2+ signal transduction was blocked by several antagonists, including BAPTA (4 µM), KN-93 (0.2 µM) and cyclosporin A (CsA, 0.2 µM). Protein content, protein synthesis, cardiomyocyte volumes, [Ca2+]i transients, CaMKIIδB and CaN were evaluated by the Lowry method, [³H]-leucine incorporation, a computerized image analysis system, a Till imaging system, and Western blot analysis, respectively. TNF-α induced a significant increase in protein content in a dose-dependent manner from 10 µg/L (53.56 µg protein/well) to 100 μg/L (72.18 µg protein/well), and in a time-dependent manner from 12 h (37.42 µg protein/well) to 72 h (42.81 µg protein/well). TNF-α (100 μg/L) significantly increased the amplitude of spontaneous [Ca2+]i transients, the total protein content, cell size, and [³H]-leucine incorporation in cultured cardiomyocytes, which was abolished by 4 µM BAPTA, an intracellular Ca2+ chelator. The increases in protein content, cell size and [³H]-leucine incorporation were abolished by 0.2 µM KN-93 or 0.2 µM CsA. TNF-α increased the expression of CaMKIIδB by 35.21% and that of CaN by 22.22% compared to control. These effects were abolished by 4 µM BAPTA, which itself had no effect. These results suggest that TNF-α induces increases in [Ca2+]i, CaMKIIδB and CaN and promotes cardiac hypertrophy. Therefore, we hypothesize that the Ca2+/CaMKII- and CaN-dependent signaling pathways are involved in myocardial hypertrophy induced by TNF-α.

La vía de señalización Rho a/ Rho kinasa se encuentra activada en el miocardio en ratas con fibrosis cardíaca inducida por isoprotenerol / Rho A/ Rho kinase pathway is activated in the myocardium of rats with isoprotenerol - induced fibrosis

Antecedentes: En pacientes con insuficiencia cardíaca la actividad adrenérgica está aumentada, lo que induce en el largo plazo, a cardiotoxicidad y mayor deterioro de la función ventricular. La administración experimental de Isoprotenerol, un agonista beta-adrenérgico, produce hipertrofia ventricular, daño y fibrosis miocárdica. La vía de señalización intracelular RhoA/Rho-Kinasa (ROCK) participa en el remodelamiento cardiovascular, no estando clara la relación entre la activación de esta vía y el desarrollo de fibrosis miocárdica. Objetivo: Determinar si existe activación de la vía ROCK en ratas con fibrosis miocárdica inducida experimentalmente por Isoprotenerol, mediante cuantificación de la fosforilación de la proteína blanco 1 de la fosfatasa de la miosina (MYPT1). Métodos: Se utilizaron ratas Sprague-Dawley machos (100 +/- 10 gr.); 10 como grupo control con administración de suero fisiológico y 10 en el grupo experimental con inyección subcutánea de Isoprotenerol Hemisulfato, 5 mg/kilo de peso por día, por un período de 10 días. Se determinó la presión arterial sistólica (PAS), la masa relativa ventricular izquierda (MRVI), la activación de ROCK a través de niveles de MYPT1 por Western Blot y se cuantificó la fibrosis en Ventrículo Izquierdo por análisis morfométrico del colágeno (en tinciones con Rojo de Picrosirio). Resultados (promedio +/- ES, =p<0,05): Los resultados en Presión Arterial Sistólica fueron 119,6 +/- 8,1 mmHg en el grupo control y 113,8 +/- 5,2 mmHg en el grupo tratado con Isoprotenerol, la MRVI fue de 358,3 +/- 10,9 mg/g en las controles y 495,3 +/- 42,02 mg/g en ratas Iso. La fracción volumétrica de colágeno (FVC) en miocardio y subendocardio fueron 3 +/- 0,3 y 3,3 +/- 0,4 en ratas control; en ratas Iso fueron 5,2 +/- 0,7 y 7,4 +/- 1,3 respectivamente.

Background: Patients with heart failure have increased adrenergic activity, which in turn induces cardiotoxicity, and further damage to the myocardium. lsoprotenerol induces ventricular hypertrophy with myocardial fibrosis. RHO A/ RHO Kinase pathway (ROCK) participates in myocardial remodeling, but it is not known whether ROCK is involved in the fibrotic process.Aim: To ascertain whether ROCK is activated in rats with Isoprotenerol -induced myocardial fibrosis, measuring ROCK by phosphon/ation of the myosin phosphatase (MYPTI). Methods: We used male Sprague-Dawley rats (100 +/- 10 g); 10 rats were used as controls and received sq saline,- 10 rats in the experimental group received sq Isoprotenerol (ISO rats) 5 mg/k body weight/day, during 10 days. We measured systolic blood pressure (SBP), left ventricular mass (LVM) and ROCK, which was measured by phophorylation of the MYPTI protein using Western Blot. Myocardial fibrosis was measured by morphometry of collagen in Picrosirius red stained samples, and was expressed as collagen volume fraction (CVF). Results were expressed as average +/- SEM; =p<005Results: SBP was 119,6 +/- 8,1 mmHg in controls and 113,8 +/- 5,2 mmHg in ISO rats; LVM was 358,3 +/- 10,9 mg/g in controls and 495,3 +/- 42,02 mg/g in ISO rats. CVF in the myocardium and subendocardium were 3 +/- 0,3 and 3,3 +/- 0,4 in control rats; values in ISO rats were 2 +/- 0,7 y 7,4 +/- 1,3 respectively. Total CVF were 3,2 +/- 0,4 in controls and 6,3 +/- 1,6 in ISO rats. ROCK, expressed as phosphorylated MYPTI /total MYPTI in control rats was 2,5 +/- 0,8 and 4,7 +/- 2,2 in ISO rats. Conclusion: ROCK pathway is significantly activated in the myocardium of ISO rats. ROCK antagonists for preventing myocardial fibrosis should be evaluated in this experimental model.

Effects of Nigella sativa supplementation for one month on cardiac reserve in rats.

Nigella sativa (N. sativa) has a long history of use in folk medicine. In a current study performed in this laboratory, two-month dietary supplementation with N. sativa extract to normal rats has shown a homogenous cardiac hypertrophy and enhanced cardiac contractility at baseline conditions. In the present study, shorter (one-month) duration of oral N. sativa administration was adopted to detect possible earlier cardiac responses. In addition, in vitro cardiac stress by the beta adrenoceptor agonist isoproterenol was used to assess the intrinsic cardiac reserve mechanisms. The hearts of Nigella-treated rats developed a moderate but significant hypertrophy that was evident by an increase in the heart weight to body weight ratio. The observed Nigella-induced cardiac hypertrophy was associated with an increase in the baseline cardiac inotropic properties as well as the maximal peak tension generation upon progressive cardiac stress by isoproterenol infusion. The demonstrated selective enhancement of the inotropic reserve favours the physiological nature of Nigella-induced cardiac hypertrophy, similar to that provoked by exercise training.

Sodium tanshinone IIA sulfonate depresses angiotensin II-induced cardiomyocyte hypertrophy through MEK/ERK pathway

Cardiomyocyte hypertrophy is a major cause of morbidity and mortality worldwide. The aim of this study is to determine the effects of sodium tanshinone IIA sulfonate (STS) on cardiomyocyte hypertrophy induced by angiotensin II (Ang II) in vivo and in vitro. In long-term treatment, adult Wistar rats were infused with Ang II for three weeks via osmotic mini-pumps and some of them were given intragastrically of STS. Left ventricle was isolated; the ratio of left ventricular weight to body weight and systolic blood pressure (SBP) were determined and heart morphometry was assessed after hematoxylin and eosin staining. Results indicated STS inhibited Ang II-induced increases in myocyte diameter and decreased the LVW/BW ratio independent of decreasing systolic blood pressure. In vitro, treatment of cultured cardiomyocytes with STS inhibited Ang II-induced increase in cell size, protein synthesis, ANP expression, activation of extracellular signal-regulated kinase (ERK) and ERK kinase (MEK). Then we reexamined the mechanism of STS-induced anti-hypertrophic effects. Results revealed MEK inhibitor U0126 (20 microM) markedly enhanced STS-induced depressions in [3H]leucine incorporation and ANP expression. In conclusion, MEK/ERK pathway plays a significant role in the anti-hypertrophic effects of STS.

Caracterizaçäo funcional da hipertrofia miocárdica induzida pelo isoproterenol e de sua regressäo / Functional characterization of myocardial hypertrophy induced by isoproterenol and its regression

OBJETIVO: Analisar as disfunçöes da hipertrofia miocárdica induzida pelo isoproterenol e de sua regressäo. Coraçöes isolados hipertrofiados por isoproterenol (ISO) (8 dias) e após 22 dias de sua suspensäo (regressäo) foram distendidos. MÉTODOS: Até pressäo de repouso (Pr) de 60mmHg, analisaram-se: pressäo desenvolvida máxima (PDmáx.); estresse sistólico (sigmamáx); inclinaçäo da reta estresses/deformaçöes; constante de relaxamento; rigidez da câmara e rigidez miocárdica. RESULTADOS: Nos coraçöes hipertrofiados (H) as variaçöes de volume (deltaV) necessárias para Pr=60mmHg foram heterogêneas. Em alguns (H1; n=10) deltaV equivaleu à dos controle (C) enquanto em outros (H2; n=10) foi inferior, e também diferiram quanto ao peso seco, complacência ventricular, rigidez miocárdica, constante de relaxamento,e sigmamáx. PDmáx dos grupos H1 e H2 foram superiores às de C (n=8) e Regressäo (R) (n=8). Contudo, sigmamáx de H2 foi menor que C, H1 e R. O mecanismo de Frank-Starling foi deprimido nos coraçöes hipertrofiados. A constante de relaxamento de H2 indicou retardo no decaimento da pressäo associado a menor complacência ventricular e rigidez miocárdica acentuada. CONCLUSÄO: Hipertrofia miocárdica induzida pelo ISO näo é homogênea. Alguns coraçöes têm alteraçöes pouco expressivas; outros têm comprometimento das funçöes sistólica e diastólica. A hipertrofia miocárdica reduz a capacidade de gerar força e aprimora a capacidade em variar pressäo por aumento da relaçäo massa/volume. Há, também, comprometimento da complacência ventricular e da rigidez muscular

Envolvimento cardíaco na lipodistrofia total generalizada (síndrome de Berardinelli-Seip) / Cardiac involvement in total generalized lipodystrophy (Berardinelli- Seip syndrome)

Total generalized lipodystrophy (Berardinelli--Seip Syndrome) is a rare hereditary disease characterized by insulin-resistant diabetes mellitus and a small quantity of adipose tissue and is of unknown origin. Common cardiovascular alterations related to this syndrome are cardiac hypertrophy and arterial hypertension. This article reports a case of Berardinelli--Seip syndrome and reviews the literature with special emphasis on the cardiovascular manifestations of this syndrome.

Developed pressure data may provide misinformation when used alone to evaluate systolic function in isovolumetric left ventricle preparations

We report data showing that developed pressure (DPmax) may lead to opposite conclusion with respect to maximal developed circumferential wall stress (max) when used to assess contractile function in left ventricle isovolumic preparations. Isovolumetric left ventricle preparations of rats with cardiac hypertrophy (H; N = 10) induced by isoproterenol administration showed higher DPmax (174 + ou - 14 mmHg) than control (C; N = 8) animals (155 + ou - 12 mmHg) or rats with regression (R; N = 8) of hypertrophy (144 + ouy - 11 mmHg). In contrast, the estimated max for C (145 + ou - 26 kdynes/cm2) and R (133 + ou - 17 kdynes/cm2) was higher than for H (110 + ou - 13 kdynes/cm2). According to Laplace's law, the opposite results of DPmax and max may depend on the increased mass/volume left ventricle ratio of the hypertrophied hearts, which favored pressure generation. These results clearly show that DPmax should be used with caution to analyze systolic function.