Neuroendocrine activation and markers of early reperfusion in the acute phase of myocardial infarction

Potentially harmful stimulation of the neuroendocrine axis occursin the early hours of myocardial infarction. It has been suggestedthat this acute neuroendocrine response might be attentuatedby early therapeutic reperfusion. To test this hypothesis wemeasured plasma concentrations of atrial natriuretic factor(ANF), renin, adrenaline (ADR) and noradrenaline (NADR) on admissionand at 1 h and 4 h in 32 patients undergoing streptokinase treatmentwithin 6 h of myocardial infarction. Fractional changes (FC)in hormone levels were calculated: e.g. ANFO-ANF4/ANFO. Resolutionof ST segment elevation at 4 h was the primary measure of reperfusion.Sixteen patients showed ST segment resolution. There was nodifference in hormone levels at baseline between reperfusedand non-reperfused patients. Fractional changes in ANF, reninand ADR were similar in both groups. NADR fell from admissionto 4 h in reperfused patients but rose in non-reperfused (FC0.28 vs –0.10; P=0.054). There was no difference in thechanges in pulse rate or blood pressure from admission to 4h between the two groups. Thus there is no evidence that earlyreperfusion acutely alters the release of ANF, renin or ADRto myocardial infarction. Although plasma NADR tended to fallacutely in reperfused patients this was not accompanied by othermarkers of sympathetic withdrawal.     

Plasma atrial peptide concentration during acute changes in cardiac filling pressure induced by a contrast agent

Left ventricular end-diastolic pressure and the concentration of atrial peptides in plasma were measured before and after the administration of contrast material into the left ventricle of 12 patients during cardiac catheterization. A positive relationship between changes in left ventricular end-diastolic pressure and the circulating level of atrial peptides was found in all 12 patients. Increases in plasma atrial peptide levels were detected within less than one minute after injection of the contrast agent. We conclude that the release of atrial peptides in the human is modulated rapidly by changes in atrial pressure. The rapid release of peptides from the atria in response to an increase in atrial pressure, coupled with evidence that atrial peptides reduce cardiac filling pressure, is consistent with the possibility that the atrial peptides may serve as part of a negative feedback system that enables the heart to influence its own filling pressure.     

强利尿心钠素对急性心肌缺血犬的心脏及外周循环中肾素-血管紧张素系统的影响

在犬急性缺血性心功能不全模型中，应用冠状动脉（冠脉）内灌注给药的方法观察了两种剂量的强利尿心钠素（ＡＮＰ０．６，０．３μｇｋｇ－１／ｍｉｎ）对外周循环及心脏肾素－血管紧张素（ＲＡＳ）的影响。结果发现，缺血性心功能不全时外周循环及心脏ＲＡＳ均较对照组显著升高；两种剂量均可使循环及心脏ＲＡＳ降低，剂量越大，作用越明显；而且，冠状静脉窦血中激素水平下降幅度及持续时间大于外周静脉（Ｐ＜０．０１）。结论：（１）急性缺血性心功能不全时，外周循环及心脏ＲＡＳ明显激活；（２）冠脉内灌注强利尿心钠素不仅可抑制循环ＲＡＳ，对心脏局部ＲＡＳ也有明显抑制作用。     

Melatonin protects against the pathological cardiac hypertrophy induced by transverse aortic constriction through activating PGC‐1β: In vivo and in vitro studies

Melatonin, a circadian molecule secreted by the pineal gland, confers a protective role against cardiac hypertrophy induced by hyperthyroidism, chronic hypoxia, and isoproterenol. However, its role against pressure overload‐induced cardiac hypertrophy and the underlying mechanisms remains elusive. In this study, we investigated the pharmacological effects of melatonin on pathological cardiac hypertrophy induced by transverse aortic constriction (TAC). Male C57BL/6 mice underwent TAC or sham surgery at day 0 and were then treated with melatonin (20 mg/kg/day, via drinking water) for 4 or 8 weeks. The 8‐week survival rate following TAC surgery was significantly increased by melatonin. Melatonin treatment for 8 weeks markedly ameliorated cardiac hypertrophy. Compared with the TAC group, melatonin treatment for both 4 and 8 weeks reduced pulmonary congestion, upregulated the expression level of α‐myosin heavy chain, downregulated the expression level of β‐myosin heavy chain and atrial natriuretic peptide, and attenuated the degree of cardiac fibrosis. In addition, melatonin treatment slowed the deterioration of cardiac contractile function caused by pressure overload. These effects of melatonin were accompanied by a significant upregulation in the expression of peroxisome proliferator‐activated receptor‐gamma co‐activator‐1 beta (PGC‐1β) and the inhibition of oxidative stress. In vitro studies showed that melatonin also protects against angiotensin II‐induced cardiomyocyte hypertrophy and oxidative stress, which were largely abolished by knocking down the expression of PGC‐1β using small interfering RNA. In summary, our results demonstrate that melatonin protects against pathological cardiac hypertrophy induced by pressure overload through activating PGC‐1β.     

Effect of prolonged inhibition of neutral endopeptidase on cardiac hypertrophy in rats with myocardial infarction

Summary Myocardial infarction was induced in rats by ligation of the left coronary artery. Treatment with TM1, a prodrug of SQ 28,603, an inhibitor of neutral endopeptidase (NEP, EC 3.4.24.11), was started 18–20 hours after ligation and was continued for 4 weeks (100 mg/kg, orally, twice daily). Morphological and biochemical parameters were assessed at the end of therapy. The treatment resulted in a significant reduction of heart hypertrophy, which was restricted to the parts of myocardium hemodynamically upstream of the infarcted left ventricle. The weights of the right ventricle and atria were reduced by 15–20%, whereas the treatment had no effect on the left ventricle and septum weights. Treatment led to an almost complete inhibition of plasma NEP activity and to a slight decrease (-14%, p<0.05) in plasma ACE activity. Plasma ANF level increased 3.8-fold after ligation, and treatment resulted in a slight (+29%) and nonsignificant additional increase in the ANF level. The amount of hydroxyproline in the right ventricle was enhanced by +207% in control ligated rats and by +140% (NS) in treated rats. These data indicate that prolonged NEP inhibition exerts a favorable effect in heart failure by reducing the development of right ventricular and atrial hypertrophy. These effects may result from an improvement in hemodynamic conditions, leading to a reduction in cardiac preload.     

阿托伐他汀在1-磷酸鞘氨醇诱导心肌细胞肥大中的作用

目的研究阿托伐他汀对1-磷酸鞘氨醇(S1P)诱导乳鼠心肌细胞肥大反应中的作用。方法原代培养乳鼠心肌细胞,测定心肌细胞体积和[3H]-亮氨酸掺入量作为心肌细胞肥大的指标。乳鼠心肌细胞使用不同浓度的阿托伐他汀(atorvastatin),加入S1P,[3H]-亮氨酸掺入量作为心肌细胞蛋白摄取量;分别用qPCR和Western blot法检测心肌细胞的β-肌球蛋白(β-MHC)的mRNA和蛋白质表达水平;用qPCR检测心肌细胞的心房利钠肽(ANF)的mRNA表达水平。结果与S1P组比较,阿托伐他汀10μmol/L处理组[3H]-亮氨酸掺入率减少[(234.89%±31.23%)比(342.23%±31.60%),P=0.205],β-MHC的mRNA和蛋白表达水平下降[(0.59±0.14)比(0.84±0.20),P=0.318]和[(0.55±0.09)比(0.98±0.15),P=0.223],ANF的mRNA表达水平降低[(0.51±0.13)比(0.76±0.19),P=0.445];与S1P组比较,阿托伐他汀20μmol/L处理组[3H]-亮氨酸掺入率明显减少[(189.07%±17.69%)比(342.23%±31.60%),P<0.01],β-MHC的mRNA和蛋白表达水平显著下降[(0.50±0.12)比(0.84±0.20),P<0.01]和[(0.35±0.08)比(0.98±0.15),P<0.01],ANF的mRNA水平明显降低[(0.47±0.12)比(0.76±0.19),P<0.01]。结论阿托伐他汀可抑制S1P诱导的心肌细胞肥大,并可减少S1P诱导的β-MHC和ANF表达。     

Cardiomyocyte-restricted over-expression of C-type natriuretic peptide prevents cardiac hypertrophy induced by myocardial infarction in mice

OBJECTIVE: Infused C-type natriuretic peptide (CNP) was recently found to play a cardioprotective role in preventing myocardial ischaemia/reperfusion (I/R) injury and improving cardiac remodelling after myocardial infarction (MI) in rats. Our study aimed to investigate the effect of cardiomyocyte-specific CNP over-expression on I/R injury and MI in transgenic mice. METHODS AND RESULTS: We generated transgenic (TG) mice over-expressing CNP in cardiomyocytes. Elevated CNP expression on RNA and protein levels was demonstrated by RNase-protection assay and radioimmunoassay. Male TG mice and age-matched wild-type (WT) littermates were subjected to 1-hour global myocardial ischaemia and 23 h of reperfusion or permanent ligation of the coronary artery for 3 weeks. Infarct size did not differ between the WT and TG groups in mice subjected to I/R. In mice that underwent permanent ligation of coronary arteries, both left and right ventricular hypertrophy were prevented by CNP over-expression 3 weeks post-MI. Histological analysis revealed less necrosis, muscular degeneration and inflammation in infarcted TG mice. Impairment of cardiac function was less pronounced in transgenic animals than in the wild-type controls. CONCLUSIONS: Over-expression of CNP in cardiomyocytes does not affect I/R-induced infarct size but prevents cardiac hypertrophy induced by MI. Therefore, CNP may represent a potent therapeutic target for the treatment of patients with cardiac hypertrophy induced by myocardial infarction or other aetiology.     

辛伐他汀对大鼠心肌肥厚的防治作用及其与钙通道的关系

目的 探讨辛伐他汀对心肌肥厚的防治作用及其与钙通道活动的关系.方法 采用腹主动脉缩窄术建立心肌肥厚动物模型.尾动脉无创测量大鼠收缩压.称量心脏重量/体重(HW/BW)、左心室重量/体重(LVW/BW)比值.采用超声心动图检测动物心脏构型及射血功能.应用RT-PCR和Western blot分别检测心肌L-型钙通道亚单位Cav1.2(α,C)、T-型钙通道亚单位Cav3.1 (α1G)、Cav3.2(α1H)mRNA及其蛋白表达的变化.结果 (1)腹主动脉缩窄+辛伐他汀组(AAC+SIM组)大鼠收缩压130 mm Hg(1 mm Hg=0.133 kPa)明显低于腹主动脉缩窄组(AAC组)189mm Hg,P<0.05.HW/BW比值AAC+SIM组3.37 mg/g明显低于AAC组3.94 mg/g,P<0.01.LVW/BW比值AAC+SIM组2.33 mg/g明显低于AAC组2.95 mg/g,P<0.01.室间隔厚度AAC+SIM组2.01 mm明显低于AAC组2.31 mm,P<0.01.左心室后壁厚度AAC+SIM组1.89 mm明显低于AAC组2.19 mm,P<0.01.(2)AAC+SIM组大鼠心肌T-型钙通道亚单位α1G、α1H mRNA和蛋白表达均显著低于AAC组,P均<0.01,但L-型钙通道亚单位α1 C mRNA和蛋白表达两组间比较差异无统计学意义.结论 辛伐他汀对腹主动脉缩窄所致的心肌肥厚具有明显的防治作用,其作用机制可能与其抑制T-型钙通道亚单位α1G、α1H mRNA和蛋白的重新再表达有关,但与L-型钙通道亚单位α1C mRNA和蛋白表达无关.     

Molecular mechanisms for hyperinsulinaemia induced by overproduction of selenium-dependent glutathione peroxidase-1 in mice

Aims/hypothesis  We previously observed hyperglycaemia, hyperinsulinaemia, insulin resistance and obesity in Gpx1-overexpressing mice (OE). Here we determined whether these phenotypes were eliminated by diet restriction, subsequently testing whether hyperinsulinaemia was a primary effect of Gpx1 overexpression and caused by dysregulation of pancreatic duodenal homeobox 1 (PDX1) and uncoupling protein-2 (UCP2) in islets. Methods  First, 24 male OE and wild-type (WT) mice (2 months old) were given 3 g (diet-restricted) or 5 g (full-fed) feed per day for 4 months to compare their glucose metabolism. Thereafter, several mechanistic experiments were conducted with pancreas and islets of the two genotypes (2 or 6 months old) to assay for beta cell mass, reactive oxygen species (ROS) levels, mitochondrial membrane potential (Δψ_m) and expression profiles of regulatory proteins. A functional assay of islets was also performed. Results  Diet restriction eliminated obesity but not hyperinsulinaemia in OE mice. These mice had greater pancreatic beta cell mass (more than twofold) and pancreatic insulin content (40%) than the WT, along with an enhanced Δψ_m and glucose-stimulated insulin secretion in islets. With diminished ROS production, the OE islets displayed hyperacetylation of H3 and H4 histone in the Pdx1 promoter, elevated PDX1 and decreased UCP2. Conclusions/interpretation  Overproduction of the major antioxidant enzyme, glutathione peroxidase 1, caused seemingly beneficial changes in pancreatic PDX1 and UCP2, but eventually led to chronic hyperinsulinaemia by dysregulating islet insulin production and secretion. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

硒对砷诱导的大鼠H9c2心肌细胞氧化损伤的抑制作用和可能机制

目的探讨硒对砷诱导的H9c2心肌细胞氧化损伤的保护作用及其可能机制。方法H9c2细胞按处理方法不同分对照组、Na2SeO3（1μmol/L）组、As2O3（5μmol/L）组、As2O3（5μmol/L）＋Na2SeO3（1μmol/L）组以及NF-κB抑制剂PDTC（100 nmol/L）不同处理组。应用MTT法检测细胞存活率;DTNB法检测细胞内还原型谷胱甘肽（GSH）含量;二氢乙啶（Dihydroethidium,DHE）染色法检测细胞活性氧（reactive oxygen species,ROS）产生;提取细胞核蛋白,Western blotting法检测核蛋白中NF-κB的p65亚单位表达。结果与对照组相比,5μmol/L As2O3作用下,H9c2细胞生存率、细胞内GSH含量降低,ROS生成和核蛋白中NF-κB p65的表达增加;1μmol/L Na2SeO3可以提高As2O3损伤的H9c2细胞存活率和细胞内GSH含量,减少ROS生成和p65的表达。PDTC干预可减轻砷所致心肌细胞的损伤,表现为细胞ROS产生减少;Na2SeO3和抑制剂PDTC共同作用时,H9c2细胞生成ROS进一步减少。结论NF-κB信号途径参与了As2O3诱导的H9c2心肌细胞氧化应激反应,Na2SeO3可能通过抑制NF-κB减轻氧化应激诱导的H9c2细胞损伤。     

黄山药总皂苷对晚期糖基化终产物诱导心肌老化的保护作用及机制

目的研究黄山药总皂苷(TSDP)对晚期糖基化终产物(AGEs)诱导的心肌老化产生的作用并初步探讨其机制。方法用不同浓度TSDP干预原代心肌细胞,以CCK-8试剂盒(CCK-8)检测细胞活性。细胞预先TSDP干预2 h后加入AGEs,通过免疫印迹实验检测沉默信息调节因子(SIRT3)、超氧化物歧化酶-2 (SOD2)、及衰老相关蛋白p53和p16水平的表达;2′,7′-二氯二氢荧光素二乙酸酯探针(DCFH-DA)检测细胞内活性氧(ROS)。结果与对照组比较,AGEs干预组β半乳糖苷酶(SA-β-Gal)活性增加,p53和p16蛋白水平增加, SOD2和SIRT3蛋白表达下降,ROS产生增多,差异有统计学意义(P0.05)。与AGEs组相比,TSDP预干预组SA-β-Gal活性降低,SIRT3和SOD2蛋白水平增加,p53和p16下降,ROS增加,差异有统计学意义(P0.05)。结论 TSDP对AGEs诱导的心肌细胞老化起保护作用,其机制可能与升高SIRT3和调节氧化应激有关。     

Analysis of oxidative stress expressed by urinary level of 8-hydroxy-2′-deoxyguanosine and biopyrrin in atrial fibrillation: Effect of sinus rhythm restoration

Background

Oxidative stress is considered to contribute to the pathological consequences of atrial fibrillation (AF). We examined the level of oxidative stress in AF patients and changes in its level following sinus rhythm restoration.

Methods

Oxidative stress level was evaluated by urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, and urinary biopyrrin, an oxidative metabolite of bilirubin. In Study 1, we compared 8-OHdG/creatinine levels between patients with permanent AF (AF-group, n = 40) and sinus rhythm (SR-group, n = 133). In Study 2, we examined the changes in 8-OHdG and biopyrrin levels in 36 patients with persistent AF following sinus rhythm restoration by electrical or pharmacological cardioversion (n = 15) and radiofrequency catheter ablation (n = 21).

Results

In Study 1, 8-OHdG/creatinine levels were significantly higher in AF-group than in SR-group (19.1 ± 8.6 vs. 12.3 ± 5.5 ng/mg, p < 0.001). Multivariate analysis showed that the presence of AF was an independent factor that significantly correlated with 8-OHdG/creatinine level after adjustment for other covariates to oxidative stress (β = 0.36, p < 0.001). Sinus rhythm was maintained at the chronic phase in patients of all Study 2 (7.2 ± 5.8 months after cardioversion or catheter ablation). 8-OHdG/creatinine and biopyrrin/creatinine levels at the chronic phase were significantly lower than those before cardioversion or catheter ablation (8.7 ± 3.2 vs. 21.7 ± 15.1 ng/mg, p < 0.0001 and 1.7 ± 1.1 vs. 3.0 ± 1.9 mU/mg, p < 0.0001).

Conclusions

Oxidative stress level is significantly increased in AF patients, but can be improved by restoration of sinus rhythm. The results suggest that the pathogenic process of AF is promoted by AF itself through the production of oxidative stress.     

SHP2 mediates gp130-dependent cardiomyocyte hypertrophy via negative regulation of skeletal alpha-actin gene

Morphological and biochemical phenotypes of cardiomyocyte hypertrophy are determined by neurohumoral factors. Stimulation of G protein-coupled receptor (GPCR) results in uniform cell enlargement in all directions with an increase in skeletal α-actin (α-SKA) gene expression, while stimulation of gp130 receptor by interleukin-6 (IL-6)-related cytokines induces longitudinal elongation with no increase in α-SKA gene expression. Thus, α-SKA is a discriminating marker for hypertrophic phenotypes; however, regulatory mechanisms of α-SKA gene expression remain unknown. Here, we clarified the role of SH2-containing protein tyrosine phosphatase 2 (SHP2) in α-SKA gene expression. In neonatal rat cardiomyocytes, endothelin-1 (ET-1), a GPCR agonist, but not leukemia inhibitory factor (LIF), an IL-6-related cytokine, induced RhoA activation and promotes α-SKA gene expression via RhoA. In contrast, LIF, but not ET-1, induced activation of SHP2 in cardiomyocytes, suggesting that SHP2 might negatively regulate α-SKA gene expression downstream of gp130. Therefore, we examined the effect of adenovirus-mediated overexpression of wild-type SHP2 (SHP2^WT), dominant-negative SHP2 (SHP2^C/S), or β-galactosidase (β-gal), on α-SKA gene expression. LIF did not upregulate α-SKA mRNA in cardiomyocytes overexpressing either β-gal or SHP2^WT. In cardiomyocytes overexpressing SHP2^C/S, LIF induced upregulation of α-SKA mRNA, which was abrogated by concomitant overexpression of either C3-toxin or dominant-negative RhoA. RhoA was activated after LIF stimulation in the cardiomyocytes overexpressing SHP2^C/S, but not in myocytes overexpressing β-gal. Furthermore, SHP2 mediates LIF-induced longitudinal elongation of cardiomyocytes via ERK5 activation. Collectively, these findings indicate that SHP2 negatively regulates α-SKA expression via RhoA inactivation and suggest that SHP2 implicates ERK5 in cardiomyocyte elongation downstream of gp130.     

Menopause-Related Estrogen Decrease and the Pathogenesis of HFpEF: JACC Review Topic of the Week

Heart failure (HF) is a complex condition affecting >40 million people worldwide. It is defined by failure of the heart to pump (HF with reduced ejection fraction) or by the failure of the heart to relax, resulting in reduced filling but with preserved ejection fraction (HFpEF). HFpEF affects approximately 50% of patients with HF, most of whom are women. Given that the annual mortality ranges from 10% to 30% and as there are no treatments specifically directed for HFpEF, there is a need for better understanding of the underlying mechanisms of this condition. We put forward the hypothesis that the decline of estrogen at menopause might contribute to the pathogenesis of HFpEF and we highlight potential underlying mechanisms of estrogen action, which may attenuate the development of HFpEF. We also discuss areas in which additional research is needed to develop new approaches for prevention and treatment of HFpEF.