Cardioprotective effect of mangiferin on left ventricular remodeling in rats

The purpose of this study was to clarify the protective role of mangiferin on postinfarction myocardial remodeling and potential mechanisms. The myocardial infarction (MI) model was established by ligating the left anterior descending coronary artery. Cardiac function, myocardial apoptosis and fibrosis, serum tumor necrosis factor-α (TNF-α) and phosphorylated p38 mitogen-activated protein kinase (MAPK) were examined by echocardiography, histological staining, ELISA and Western blot, respectively. Mangiferin attenuated MI and prevented the development of intercellular fibrosis. Western blotting underscores that the p38 MAPK cascade plays an important role in the cardioprotective effect of mangiferin during MI. Inhibition of p38 MAPK significantly decreased serum TNF-α levels. Transferase-mediated uridine nick end labeling and Masson staining also showed that mangiferin reduced apoptosis and fibrosis in myocardium remodeling. Based on these results, we conclude that mangiferin has a therapeutic effect on post-MI left ventricular remodeling and improves cardiac function.     

灯盏花素通过激活线粒体自噬途径减轻糖尿病大鼠心肌缺血再灌注损伤

目的 探讨灯盏花素对糖尿病大鼠心肌缺血再灌注损伤(MIRI)及线粒体自噬途径的影响.方法 采用高糖高脂饮食联合链脲佐菌素制备糖尿病模型,糖尿病模型成功后再制备MIRI模型,具体分组为对照组(不做任何处理)、模型组(糖尿病+MIRI)、假手术组(糖尿病),均ip等体积生理盐水;灯盏花素低、高剂量组(糖尿病+MIRI),分...     

Role of p38 mitogen-activated protein kinase in cardiac remodelling

BACKGROUND AND PURPOSE: Mitogen-activated protein kinases (MAPK) are centrally involved in several mechanisms important for heart failure such as apoptosis, activation of inflammatory responses and cell proliferation. We therefore evaluated the effect of the selective p38 MAPK inhibitor SB 239063 on progression of left ventricular remodelling after myocardial infarction (MI) in rats. EXPERIMENTAL APPROACH: Rats were treated for 9 weeks with placebo or SB 239063 by gavage (15 mg kg(-1)) twice daily starting 7 days after ligation of the left anterior descending artery. Serial transthoracic echocardiography was performed at days 7, 36 and 70. KEY RESULTS: Over the 9 weeks, mortality was not different between the groups. On echocardiography, animals after myocardial infarction exhibited significant left ventricular dilatation as expected (week 10, end-systolic diameter, placebo sham 5.21+/- 0.34 vs. placebo MI 8.44+/- 0.57 mm). However, there was no difference between placebo and SB 239063-treated rats (week 10, end-systolic diameter, SB MI 7.76+/- 0.74 mm, not significantly different from placebo MI). Haemodynamics changed accordingly. Moreover, SB 239063 had no effect on left ventricular hypertrophy. Treatment with SB 239063 significantly reduced cytokine expression of tumour necrosis factor and interleukin-1beta after myocardial infarction. However, collagen content was not influenced by the treatment. CONCLUSION: Despite a reduction of inflammation, treatment with the p38 inhibitor SB 239063 does not affect cardiac remodelling and cardiac function when treatment is started 7 days after myocardial infarction.     

Aerobic interval training protects against myocardial infarction‐induced oxidative injury by enhancing antioxidase system and mitochondrial biosynthesis

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小檗碱对心肌缺血再灌注损伤大鼠线粒体自噬及对PINK1/Parkin通路的影响

目的探讨小檗碱对心肌缺血再灌注损伤大鼠线粒体自噬及PTEN诱导激酶1(PTENinducedputativekinase1,PINK1)/帕金森病蛋白(Parkin)通路的影响。方法建立心肌缺血再灌注损伤大鼠模型,随机分组为模型组、小檗碱低、高剂量(75、150 mg/kg)组,自噬抑制剂三甲基腺嘌呤(3-MA,100 mmol/L)组、小檗碱+3-MA(150 mg/kg+100 mmol/L)组,每组12只,另取12只正常大鼠设为假手术组。分组处理后,超声检测大鼠左室功能,记录左室收缩末期内径(LVESD)、左室舒张末期内径(LVEDD)、左心射血分数(LVEF)、左室短轴缩短率(FS);三苯基氯化四氮唑(TTC)染色检测各组大鼠心肌梗死面积,酶联免疫吸附实验(ELISA)检测各组大鼠血清中磷酸肌酸激酶同工酶(CK-MB)、肌钙蛋白I(cTnI)水平;HE染色观察大鼠心肌组织病理变化;透射电镜观察心肌细胞超微结构及线粒体自噬并分析线粒体损伤评分;蛋白免疫印迹法检测各组大鼠心肌组织PINK1、Parkin蛋白及微管轻链蛋白3B(LC3B)、线粒体自噬受体p62(p62)、泛素特异性蛋白酶30(USP30)蛋白表达。结果与假手术组比较,模型组大鼠心肌组织病理损伤严重,线粒体肿胀及空泡化损伤较多,线粒体损伤评分、心肌梗死面积、LVEDD、LVESD、CK-MB、cTnI水平及PINK1、Parkin、LC3B、p62蛋白表达升高(P0.05),LVEF及FS、USP30蛋白表达降低(P0.05)。与模型组比较,3-MA组大鼠心肌组织及线粒体病理损伤加重,LVEF、FS、PINK1、Parkin、LC3B、p62蛋白表达降低(P0.05),线粒体损伤评分、心肌梗死面积、LVEDD、LVESD、CK-MB、cTnI水平、USP30蛋白表达升高(P0.05);小檗碱低、高剂量大鼠心肌组织及线粒体病理损伤减轻,LVEF、FS、PINK1、Parkin、LC3B、p62、USP30蛋白表达升高(P0.05),线粒体损伤评分、心肌梗死面积、LVEDD、LVESD、CK-MB、c TnI水平降低(P0.05)。小檗碱+3-MA组大鼠上述各项指标均与小檗碱高剂量组变化趋势相反,且有统计学差异(P0.05)。结论小檗碱可能通过激活PINK1/Parkin/P62/LC3B通路促进线粒体自噬,升高USP30表达,减少异常自噬,缓解心肌缺血再灌注损伤。     

Comparison of low and high doses of carvedilol on restoration of cardiac function and calcium-handling proteins in rat failing heart

1. The beta-adrenoceptor antagonist carvedilol reverses cardiac dysfunction in the failing heart. A recent study showed that beta-adrenoceptor antagonists indirectly normalize Ca(2+)-regulatory proteins. The relationship between these two phenomena and the suitable dosage of carvedilol remains unclear. 2. We investigated the change in left ventricular (LV) remodelling and function in a rat model of heart failure due to myocardial infarction (MI) with or without carvedilol (30 or 2 mg/kg per day) treatment for 6 weeks. The expression of mRNA and proteins of sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) and phospholamban (PLB) in cardiomyocytes was also measured. 3. There was significant LV remodelling and cardiac contractile dysfunction in MI rats. The expression of SERCA mRNA and protein were downregulated (P < 0.01), but the expression of PLB mRNA and protein were upregulated (P < 0.01) in MI rats compared with sham-operated rats. After treatment with carvedilol, LV remodelling and cardiac contractile dysfunction were clearly improved. Low-dose carvedilol was better at improving some parameters of LV remodelling and function than the high dose. Carvedilol partially restored the low expression of SERCA (P < 0.05), but had no effect on PLB expression (P > 0.05). Moreover, low-dose carvedilol induced a more significant improvement in SERCA expression than did the high dose (P < 0.05). 4. The results of the present study suggest that carvedilol is effective in improving LV remodelling and cardiac contractile dysfunction after MI. This may be related to the normalization of SERCA expression.     

Survival,haemodynamics and cardiac remodelling follow up in mice after myocardial infarction

1. In the present study, the time-course, over a 1 year period, of postischaemic dilated cardiomyopathy and/or development of congestive heart failure was investigated in mice in terms of survival and cardiac functional and structural characteristics. 2. C57BL/6 mice with myocardial infarction (MI mice; coronary ligation n = 78) or sham-operated animals (n = 45) were used and echocardiographic, haemodynamic and histomorphometric parameters were assessed at 3, 6 and 12 months post-MI. 3. At 12 months, the survival rate was 70% in MI mice. Left ventricular dysfunction was evidenced by a strong decrease in ejection fraction (EF; -48 and -53% at 6 and 12 months, respectively; both P < 0.05) and an increase in left ventricular end-diastolic pressure (+100% at both 6 and 12 months; both P < 0.05). There was no major worsening in cardiac function between 6 and 12 months, suggesting strong compensatory mechanisms. Cardiac remodelling was observed, characterized by strong left ventricular hypertrophy (+38 and +62% at 6 and 12 months, respectively; both P < 0.05) and dilatation (+53% at 6 months; P < 0.05), but collagen was not significantly increased. Significant correlations were found between EF (echocardiography) and dP/dtmax, between end-diastolic volume (echocardiography) and left ventricular internal perimeter (histomorphometry) and between left ventricular mass (echocardiography) and weight. 4. In conclusion, despite a high survival rate, the MI mouse model displays most of the hallmarks of postischaemic dilated cardiomyopathy and/or congestive heart failure, thus affording the necessary background for the subsequent evaluation of gene manipulation and/or drug effects. In addition, two-dimensional echocardiography appears to be a suitable tool for the long-term follow up of cardiac function and remodelling in this model.     

Protective effect of Qingre Huoxue decoction against myocardial infarction via PI3K/Akt autophagy pathway based on UPLC-MS,network pharmacology,and in vivo evidence

ContextQingre Huoxue (QRHX) decoction, a traditional Chinese medicine, has been widely used to prevent and treat myocardial infarction (MI).ObjectiveThis study elucidates the possible mechanisms of QRHX in preventing or treating MI in a rat model.Materials and methodsThe chemical constituents of QRHX were identified by UPLC-MS. Sprague-Dawley rats were randomly divided into the Sham (normal saline), Model (normal saline), QRHX-L, QRHX-M and QRHX-H group (n = 10 per group). QRHX decoction was administered by gavage to the rats for 14 days (5, 10 and 20 g/kg/day). The left anterior descending ligation method was performed to develop MI in Model and QRHX groups, and the same surgical procedures excluding ligation sutures were performed for the sham group. Finally, we evaluated cardiac function, myocardial fibrosis degree, serum inflammatory factors, autophagy levels and verified the signalling pathways in vivo.ResultsA total of 68 active components of QRHX corresponding to 223 active targets were obtained and 2558 MI-related disease targets were collected. After integration, 123 QRHX anti-MI targets were obtained, and 70 signalling pathways, such as PI3K/Akt, were identified by enrichment analysis. In vivo experiments suggest that QRHX could reduce the degree of myocardial fibrosis, downregulate serum inflammatory factors, and promote autophagy in MI rats.Discussion and ConclusionsQRHX plays a protective role in the myocardium by mediating PI3K/Akt signalling pathway to activate autophagy and inhibiting inflammatory factor expression. These findings provide a scientific basis for further research and validation of QRHX as a potential therapeutic for MI.     

Effect of high salt intake on local renin-angiotensin system and ventricular dysfunction following myocardial infarction in rats

1. This study was performed to evaluate the effect of chronic high salt intake on local cardiac and renal components of the renin-angiotensin system (RAS) and its impact on cardiac remodelling and function after myocardial infarction (MI). 2. Rats submitted to coronary artery ligation to produce MI or sham operation (SO) were randomized to receive 1% NaCl solution or tap water as drinking water for 4 weeks. Plasma renin activity (PRA) and angiotensin-converting enzyme (ACE) activity were quantified. Tissue angiotensin (Ang) II and ACE activity were determined by ELISA and a fluorimetric assay, respectively. Renal and cardiac AT(1) and AT(2) receptor protein levels were quantified by western blot. 3. Independent of the lower PRA levels, MI promoted a significant increase in the left ventricular/bodyweight ratio and impaired cardiac function. The cardiac RAS was activated after MI with a significant increase in ACE activity, AngII and AT(1) receptor levels. The RAS was slightly attenuated under high-salt conditions. 4. Interestingly, high salt intake increased the expression of the AT(2) receptor by approximately twofold in the kidney of MI rats compared with the SO control group. Because of its natriuretic effect, the AT(2) receptor may counterbalance the salt overload and prevent the additional impairment of cardiac function. 5. The present study indicates that 4 weeks after MI, high salt intake did not further increase cardiac hypertrophy or further impair cardiac function in MI rats. A chronic increase in salt intake significantly suppressed PRA, but did not prevent activation of the local RAS or the progression of cardiac remodelling and left ventricular dysfunction caused by MI. 6. The present results show that inhibition of systemic renin production with salt overload does not affect ventricular remodelling after MI in rats. This suggests that local activation of the RAS in the heart, which was not suppressed by salt overload, exerts a predominant role for local adaptations of the heart after MI.     

曲美他嗪对心肌梗死后心力衰竭大鼠心肌自噬水平的影响

摘要： 目的 观察心肌梗死 （MI） 后心力衰竭 （心衰） 大鼠应用曲美他嗪后左心功能及心肌自噬水平的变化。方法 健康雄性 Wistar 大鼠 20 只结扎左冠状动脉前降支近段, 4 周后随机分为模型组 （M 组）、 曲美他嗪组 （Q 组）, 每组 10 只, 另设假手术组 （S 组） 10 只, Q 组给予曲美他嗪 15 mg·kg-1 ·d-1 , 用药 4 周后, 使用小动物超声仪检测左室心功能水平, PV-Loop 压力-容积系统测量大鼠血流动力学水平, 酶联免疫吸附试验测定 （ELISA） 法检测大鼠血清 N- 末端脑钠肽前体 （NT-proBNP） 和超敏肌钙蛋白 T （hs-TnT） 水平, HE 和 Masson 染色观察心肌病理学改变和纤维化情况, TUNEL 荧光染色检测心肌细胞凋亡情况, Western blot 法和 RT-PCR 检测心肌组织自噬相关蛋白和基因的表达水平。结果 （1） 曲美他嗪显著改善了大鼠 MI 后心衰引起的左室扩张和功能障碍。（2） 曲美他嗪显著改善了心衰引起的压力负荷加重、 左室顺应性降低。（3） 曲美他嗪减轻了心衰大鼠心肌细胞水肿、 坏死以及心肌纤维化。（4） ELISA 结果显示, 曲美他嗪显著改善了大鼠心衰引起的血清 NT-proBNP 和 hs-TnT 水平升高。（5） 曲美他嗪降低了心衰引起的心肌细胞凋亡。（6） Western blot 和 RT-PCR 结果显示, 曲美他嗪可上调心衰大鼠心肌自噬水平, 并且增加心肌自噬流的活化。结论 自噬对心肌细胞有保护作用, 曲美他嗪可通过上调 MI 后心衰大鼠心肌细胞自噬水平, 改善心功能。     

Procyanidins Produce Significant Attenuation of Doxorubicin‐Induced Cardiotoxicity via Suppression of Oxidative Stress

Abstract: Doxorubicin is widely prescribed in the chemotherapy of haematological malignancies and solid tumours. The major side effect of doxorubicin is oxidative injury‐related cardiotoxicity, which has dramatically hindered its usage. Procyanidins from grape seeds are potent free radical scavengers that have been shown to protect against anthracycline‐induced cardiotoxicity. In the present study, we tested whether procyanidins would prevent the doxorubicin‐induced cardiotoxicity in rats. Rats were intraperitoneally treated with doxorubicin at a cumulative dose of 15 mg/kg with and without pre‐administration of procyanidins. Our data showed that doxorubicin led to cardiac function deterioration, myocardial injury and increased oxidative stress in cardiac tissues. The cardiac function deterioration by doxorubicin included increased QT‐interval and ST‐interval in electrocardiograph (ECG) and decreased left ventricular developed pressure. Doxorubicin‐induced myocardial injury was shown by the increased creatine kinase, alanine aminotransferase and aspartate aminotransferase in serum as well as in myocardial lesions. Pretreatment with procyanidin (150 mg/kg daily) effectively hindered the adverse effects of doxorubicin, such as myocardial injury and impaired heart function. Procyanidin pretreatment attenuated cytoplasmic vacuolization, increased left ventricular developed pressure and improved the ECG. The cardioprotective effect of procyanidin corresponded to the decrease of lipid peroxidation and the increase of cardiac antioxidant potency in doxorubicin‐treated rats that were also given procyanidin. An in vitro cytotoxic study showed that procyanidins did not attenuate the antineoplastic activity of doxorubicin to A549 adenocarcinoma cells. All the above lines of evidence suggest that procyanidins protect cardiomyocytes from doxorubicin‐induced cardiotoxicity via suppression of oxidative stress.     

Regulation of endothelial nitric oxide synthase and asymmetric dimethylarginine by matrine attenuates isoproterenol-induced acute myocardial injury in rats

Objectives This study was designed to investigate the cardioprotective effects of matrine on regulation of endothelial nitric oxide synthase (eNOS) and asymmetric dimethylarginine (ADMA) in isoproterenol‐induced acute myocardial ischaemic rats. Methods Male Sprague–Dawley rats were pretreated with matrine (200, 100 and 50 mg/kg) orally for 10 days. Acute myocardial injury was induced in rats by subcutaneous injection of isoproterenol. Serum and haemodynamic parameters, histopathological variables and expression of protein levels were analysed. Key findings Oral administration of matrine (200, 100 and 50 mg/kg) significantly attenuated isoproterenol‐induced cardiac necrosis and left ventricular dysfunction. Matrine treatment restored impaired ventricular Akt and eNOS protein expression with concomitant increased phosphorylation of Akt (Ser473) and eNOS (Ser1177), and also restored glycogen synthase kinase 3β activity, as indicated by increased phosphorylation at Ser 9. Moreover, treatment with matrine had no effect on the isoproterenol‐induced elevated protein arginine methyltransferase 1 protein expression, but could significantly normalize the reduced dimethylarginine dimethylaminohydrolase 2 expression and attenuate the increased serum level of ADMA. The expression of catechol‐o‐methyltransferase and monoamine oxidase did not differ among all groups (all P > 0.05). Conclusions Our results suggested that matrine protects against isoproterenol‐induced myocardial ischaemia via eNOS and ADMA pathway.     

INHIBITION OF BRAIN RENIN–ANGIOTENSIN SYSTEM IMPROVES DIASTOLIC CARDIAC FUNCTION FOLLOWING MYOCARDIAL INFARCTION IN RATS

• 1 Recently, we demonstrated that oral captopril treatment improved diastolic function and attenuated cardiac remodelling after myocardial infarction (MI) in rats. Considering the feasible role of the brain renin–angiotensin system (RAS) in heart failure, in the present study we investigated the role of the captopril injected intracerebroventricularly (i.c.v.) on the progression of cardiac dysfunction.
• 2 Male Wistar rats underwent experimental MI or sham operation. Infarcted animals received daily i.c.v. injections of captopril (approximately 200 mg/kg; MI + Cap) or saline (MI) from 11 to 18 days after infarction. Electro‐ and echocardiogram assessments were performed before and after i.c.v. treatment (10 and 18 days after MI, respectively). Water and hypertonic saline ingestion were determined daily between 12 and 16 days after MI.
• 3 Electrocardiograms from the MI and MI + Cap groups showed signs that resembled large MI before and after i.c.v. treatment. However, despite similar systolic dysfunction observed in both groups, only captopril‐treated rats exhibited reduced left ventricular (LV) dilatation and improved LV filling, as assessed by echocardiograms, and low levels of water ingestion compared with the saline‐treated control group.
• 4 The results of the present study suggest that the brain RAS may participate in the development of cardiac dysfunction induced by ischaemia and that inhibition of the brain RAS may provide a new strategy for the prevention of diastolic dysfunction.

     

Neuregulin‐1 attenuates right ventricular diastolic stiffness in experimental pulmonary hypertension

We have previously shown that treatment with recombinant human neuregulin‐1 (rhNRG‐1) improves pulmonary arterial hypertension (PAH) in a monocrotaline (MCT)‐induced animal model, by decreasing pulmonary arterial remodelling and endothelial dysfunction, as well as by restoring right ventricular (RV) function. Additionally, rhNRG‐1 treatment showed direct myocardial anti‐remodelling effects in a model of pressure loading of the RV without PAH. This work aimed to study the intrinsic cardiac effects of rhNRG‐1 on experimental PAH and RV pressure overload, and more specifically on diastolic stiffness, at both the ventricular and cardiomyocyte level. We studied the effects of chronic rhNRG‐1 treatment on ventricular passive stiffness in RV and LV samples from MCT‐induced PAH animals and in the RV from animals with compensated and decompensated RV hypertrophy, through a mild and severe pulmonary artery banding (PAB). We also measured passive tension in isolated cardiomyocytes and quantified the expression of myocardial remodelling‐associated genes and calcium handling proteins. Chronic rhNRG‐1 treatment decreased passive tension development in RV and LV isolated from animals with MCT‐induced PAH. This decrease was associated with increased phospholamban phosphorylation, and with attenuation of the expression of cardiac maladaptive remodelling markers. Finally, we showed that rhNRG‐1 therapy decreased RV remodelling and cardiomyocyte passive tension development in PAB‐induced RV hypertrophy animals, without compromising cardiac function, pointing to cardiac‐specific effects in both hypertrophy stages. In conclusion, we demonstrated that rhNRG‐1 treatment decreased RV intrinsic diastolic stiffness, through the improvement of calcium handling and cardiac remodelling signalling.     

Calycosin induces apoptosis in adenocarcinoma HT29 cells by inducing cytotoxic autophagy mediated by SIRT1/AMPK‐induced inhibition of Akt/mTOR

Autophagy promotes cell survival or induces apoptosis in cancer cells. While SIRT1 and AMPK induce autophagy in both normal and cancer cells, Akt and mTOR can inhibit it. Calycosin, a methoxyisoflavone, protects against several types of solid tumours including colorectal cancer. However, the mechanisms behind the antitumour effect of Calycosin remain largely unknown. This study investigates if autophagy mediates the anti‐tumourigenesis effect afforded by Calycosin and examines if this effect involves activation of SIRT1 and/or AMPK. Human colorectal (HT29) carcinoma cells were cultured under normal conditions with Calycosin (50 μmol/L) in the presence or absence of chloroquine (10 μmol/L), EX‐527 (100 nmol/L, SIRT1 inhibitor), or IGF‐1 (100 ng/mL, Akt/mTOR activator) for 48 hours. Calycosin inhibited cell growth, proliferation and invasion and increased protein levels of Beclin‐1 and LC3II, markers of autophagy. It significantly increased protein levels of cleaved caspase‐3, Bax, and SIRT1, and activity of AMPK and reduced those of Bcl‐2. These effects were parallel with concomitant reduction in protein levels p‐src, integrin‐β1 and Cyclin‐D1 and activities of Akt and mTOR. Inhibition of autophagy by CQ reversed all these effects except cell invasion. Interestingly, co‐incubating the cells with either EX‐527 or IGF‐1 completely prevented Calycosin‐induced autophagy and all other associated effects and increased cell invasion. Also, blockade of SIRT‐1 prevented the activation of AMPK, Akt, and mTOR, suggesting it to be an upstream regulator of these markers. In conclusion, Calycosin stimulates CRC cell apoptosis and inhibits their invasion by acting as SIRT1 activator which induces activation of AMPK‐induced inhibition of Akt/mTOR axis.     

Novel mouse model of left ventricular pressure overload and infarction causing predictable ventricular remodelling and progression to heart failure

Mouse surgical models are important tools for evaluating mechanisms of human cardiac disease. The clinically relevant comorbidities of hypertension and ischaemia have not been explored in mice. We have developed a surgical approach that combines transverse aortic constriction and distal left anterior coronary ligation (MI) to produce a gradual and predictable progression of adverse left ventricular (LV) remodelling that leads to heart failure (HF). Mice received either sham, MI alone, transverse aortic constriction alone or HF surgery. Infarct size and LV remodelling were evaluated by serial 2‐D echocardiograms. Transverse aortic constriction gradients were measured by the Doppler velocity–time integral ratio between constricted and proximal aortic velocities. At 4 weeks, hearts were weighed and analysed for histology and brain natriuretic peptide, a molecular marker of HF. Echocardiographic analysis of segmental wall motion scores showed similarly small apical infarct sizes in the MI and HF groups at day 1 postsurgery. MI alone showed little change in infarct size over 4 weeks (0.26 ± 0.02 to 0.27 ± 0.04, P = 0.77); however, HF mice showed infarct expansion (0.25 ± 0.06 to 0.39 ± 0.09, P < 0.05). HF mice also showed LV remodelling with increases in LV volumes (1 day = 36.5 ± 5.2 mL, 28 days = 89.1 ± 16.0 mL) versus no significant changes in the other groups. Furthermore, systolic function progressively deteriorated in the HF group only (ejection fraction, 1 day = 55.6 ± 3.6%, 28 days = 17.6 ± 4.1%, P < 0.05) with an increase of brain natriuretic peptide by 3.5‐fold. This surgical model of pressure overload in the setting of a small infarction causes progressive deterioration of cardiac structural and functional properties, and provides a clinically relevant tool to study adverse LV remodelling and heart failure.     

Phosphorylation of GATA4 at serine 105 is required for left ventricular remodelling process in angiotensin II‐induced hypertension in rats

In this study, we investigated whether local intramyocardial GATA4 overexpression affects the left ventricular (LV) remodelling process and the importance of phosphorylation at serine 105 (S105) for the actions of GATA4 in an angiotensin II (AngII)‐induced hypertension rat model. Adenoviral constructs overexpressing wild‐type GATA4 or GATA4 mutated at S105 were delivered into the anterior LV free wall. AngII (33.3 µg/kg/h) was administered via subcutaneously implanted minipumps. Cardiac function and structure were examined by echocardiography, followed by histological immunostainings of LV sections and gene expression measurements by RT‐qPCR. The effects of GATA4 on cultured neonatal rat ventricular fibroblasts were evaluated. In AngII‐induced hypertension, GATA4 overexpression repressed fibrotic gene expression, reversed the hypertrophic adult‐to‐foetal isoform switch of myofibrillar genes and prevented apoptosis, whereas histological fibrosis was not affected. Overexpression of GATA4 mutated at S105 resulted in LV chamber dilatation, cardiac dysfunction and had minor effects on expression of myocardial remodelling genes. Fibrotic gene expression in cardiac fibroblasts was differently affected by overexpression of wild‐type or mutated GATA4. Our results indicate that GATA4 reduces AngII‐induced responses by interfering with pro‐fibrotic and hypertrophic gene expressions. GATA4 actions on LV remodelling and fibroblasts are dependent on phosphorylation site S105.     

Angiotensin II receptor blockade and ventricular remodelling.

Cardiac remodelling is the expression of molecular, cellular and interstitial changes in response to cardiac injury, manifesting as adverse alterations in the size, shape and function of the ventricle. Several clinical studies have documented significant elevations in the levels of renin, angiotensin II (Ang II) and aldosterone attending acute myocardial infarction and/or congestive heart failure. Similar to catecholamines, markedly elevated activity of the renin-angiotensin-aldosterone system (RAAS) is associated with poor prognosis. The effects of Ang II upon cardiac tissue are related to two primary receptors, Ang II type 1 (AT1) and Ang II type 2 (AT2). The AT1-receptor appears to mediate many of the deleterious effects of chronic RAAS activity, while the AT2-receptor is increasingly shown to have potential cardioprotective effects. Attenuating the deleterious effects of sustained Ang II stimulation can be achieved by direct inhibition of angiotensin- converting enzyme (ACE) and/or direct antagonism of AT receptors. ACE inhibition reduces left ventricular (LV) volumes, retards the progression of LV dilatation and hypertrophy and increases systolic function in systolic dysfunction. By blocking at the receptor level, Ang II receptor blockers (ARBs) provide an alternative and more direct approach to inhibiting the effects of Ang II; however, data relating to their effects upon ventricular remodelling, whether used in isolation or in combination with ACE inhibitors (ACE-Is), are less convincing. Data arising from several recent clinical trials suggest that simultaneous use of ACE-Is and ARBs maybe of more benefit in attenuating ventricular remodelling than either agent alone.     

Chronic inhibition of p38MAPK improves cardiac and endothelial function in experimental diabetes mellitus

To investigate the influence of p38 mitogen activated kinase (p38MAPK) on the development of diabetic cardiac and endothelial dysfunction, we assessed left ventricular and vascular function as well as inflammatory markers in diabetic rats after chronic pharmacological inhibition of p38MAPK. Diabetes mellitus was induced in rats by a single injection of streptozotocin. Rats were treated with the p38MAPK inhibitor SB 239063 (40 mg/kg/day, p.o.) or vehicle. 48 days after diabetes mellitus-induction, left ventricular function and vascular function were assessed in vivo by TIP-catheter and the autoperfused hindlimb, respectively. Cell adhesion molecules staining was quantified immunohistochemically in the heart and quadriceps muscle, respectively, as well as cardiac phosphorylation of p38MAPK by Western blot analysis. Treated and untreated diabetic groups displayed similar severe hyperglycemia. Left ventricular and endothelial function were impaired in the untreated diabetic group compared to controls (dp/dtmax: -40%, dp/dtmin: +49%, maximal vasodilatation: -57%; P < 0.05) associated with significantly increased cardiac (3-fold) and peripheral cell adhesion molecules staining, respectively. Treatment of diabetic rats with SB 239063 led to a significant reduction of diabetes-induced enhancement of p38MAPK phosphorylation associated with improved left ventricular function (dp/dtmax: +39%, dp/dtmin: +47%; P < 0.05) and peripheral endothelial function (maximal vasodilatation: +71%; P < 0.05) under diabetic conditions. This was associated with reduced cardiac and peripheral inflammation indexed by reduced adhesion molecules content. Pharmacological inhibition of p38MAPK is sufficient to mitigate the development of diabetic cardiac and endothelial dysfunction despite of hyperglycemia. Our data suggest that the anti-inflammatory properties due to p38MAPK inhibition contribute to these beneficial cardiovascular effects.