低频脉冲磁场调节NO/ONOO-对缺氧/复氧条件下心肌细胞的保护作用

目的:观察低频脉冲磁场（LF-PMFs）对缺氧/复氧（H/R）条件下乳鼠心肌细胞增殖与凋亡的影响,并探讨一氧化氮/过氧亚硝基阴离子（NO/ONOO-）平衡在LF-PMFs保护心肌细胞的作用。方法: 采用酶消化法分离SD乳鼠心肌细胞,随机分为对照组、H/R组和磁场组。用TUNEL法检测心肌细胞凋亡程度,MTT比色法检测心肌细胞增殖活性,以观察LF-PMFs对损伤心肌细胞的效果,用WST-1 法检测超氧阴离子,Griess法测定NO和ONOO-。结果: LF-PMFs磁场可减少H/R诱导的心肌细胞凋亡,并促进心肌细胞的存活,以15 Hz,4.5 mT LF-PMFs磁场的作用效果最为显著。同时LF-PMFs可减少H/R条件下乳鼠心肌细胞超氧阴离子的生成,促进NO生成,提高NO/ONOO-比值。结论: LF-PMFs可通过抗氧化及调节NO/ONOO-平衡减轻H/R导致的心肌细胞损伤。     

NO对凋亡影响的两面性

NO是由 L -精氨酸通过 NO合成酶而合成的。在心脏及血管 ,NO至少由内皮型 (e NOS)及诱导型 (i NOS)二种酶合成。NO可引起各种细胞凋亡 ,在人动脉硬化病变及再狭窄的血管 ,认为有细胞凋亡引起的细胞死亡现象。在实验性心肌梗塞及缺血再灌注模型 ,认为存在有发生凋亡的心肌细胞。已证明从来考虑为坏死的细胞死亡的一部分是细胞凋亡。推测 NO对细胞凋亡有重要的作用。据报导肿瘤坏死因子(TNF- α)、γ干扰素 (IFN- γ)、白细胞介素 1β(IL- 1β)等细胞因子诱导的 i NOS合成大量的 NO而引起心肌细胞和血管平滑肌细胞凋亡 ,但 NO诱…     

缬沙坦对过氧化氢损伤乳鼠心肌细胞的保护作用

目的探讨缬沙坦对过氧化氢（H2O2）致心肌细胞氧化损伤的保护作用及其机制。方法用H2O2作用于新生SD大鼠心肌细胞,建立心肌细胞H2O2损伤模型。用缬沙坦预处理后,观察心肌细胞结构,测定心肌细胞存活率、乳酸脱氢酶（LDH）、丙二醛（MDA）及一氧化氮（NO）水平。结果缬沙坦提高心肌细胞过氧化损伤的细胞存活率（P〈0.05）,减少损伤时LDH、MDA和NO的生成（P〈0.05）。结论缬沙坦通过抗氧化、抗脂质过氧化反应,对心肌细胞过氧化损伤起保护作用。     

胆碱对H2O2诱导的心肌细胞凋亡的保护作用

目的 探讨M3受体激动对H2O2诱导的大鼠培养心肌细胞凋亡的作用.方法 以 H2O2诱导大鼠培养心肌细胞损伤模型为基础,给予M3受体激动剂胆碱和M3受体阻断剂4DAMP进行干预.流式细胞仪检测细胞凋亡;RT-PCR检测凋亡抑制蛋白Bcl-2.结果 ①胆碱可显著降低 H2O2对心肌细胞的损伤,提高心肌细胞存活率,并降低细胞的凋亡率;②胆碱可增加凋亡心肌细胞Bcl-2的表达;③M3受体阻断剂4DAMP可逆转胆碱的上述作用(P＜0.01) .结论 激动M3受体对H2O2诱导的心肌细胞凋亡有保护作用,其机制可能与凋亡抑制蛋白Bcl-2有关.     

白藜芦醇预处理对体外大鼠心肌缺血再灌注损伤的保护作用

目的:观察白藜芦醇预处理对体外大鼠缺血再灌注心肌损伤的保护作用及其作用机制。方法:利用Langendorff灌注系统,建立体外大鼠心肌常温全心心肌缺血30min再灌注120min损伤模型。将56只雄性SD大鼠随机分为4组(每组14只):缺血再灌注损伤(IRI)组、白藜芦醇组、Nω硝基L精氨酸甲酯(LNAME)组、氨基胍(AG)组。检测各组的心功能、心肌一氧化氮合酶(NOS)同工酶(NOSi)活性、一氧化氮(NO)的含量、丙二醛的含量、心肌梗死面积以及心肌细胞凋亡指数。结果:与IRI组相比,白藜芦醇组左室发展压(LVDP)、左室压力上升和下降最大变化速率(±dp/dtmax)明显改善(P<0.05或0.01);心肌梗死面积、心肌细胞凋亡指数、心肌丙二醛含量显著降低(P<0.01);心肌NOSi活性和NO含量显著升高(P<0.01)。LNAME组和AG组LVDP和±dp/dtmax显著低于白藜芦醇组(P<0.05或P<0.01);心肌梗死面积、心肌细胞凋亡指数、心肌丙二醛含量显著升高(P<0.01);心肌NOSi活性和NO含量显著降低(P<0.01)。结论:白藜芦醇对体外大鼠IRI具有保护作用,其机制可通过提高心肌NOSi活性,促进NO产生而介导的。     

热休克蛋白70对大鼠心肌细胞凋亡的保护作用

目的　探讨热休克蛋白 70 (HSP 70 )对大鼠心肌细胞凋亡的保护作用。方法　体外培养大鼠心肌细胞同时温度诱导细胞产生HSP 70 ,用过氧化氢 (H2 O2 )造成心肌细胞损伤。采用免疫组化 ,DNALadder,流式细胞仪 ,细胞色素C氧化酶比活力的测定 ,电镜观察等作为检测指标。结果　温度诱导后HSP 70在胞浆中大量表达 ,损伤组与保护组凋亡率、细胞色素C氧化酶比活力差异有显著意义 (P <0 .0 1)电镜观察损伤组细胞的细胞膜、细胞器损伤明显 ,并出现凋亡小体。结论　HSP 70可延迟细胞凋亡 ,对心肌细胞具有保护作用     

生长激素对阿霉素中毒大鼠心肌细胞的抗凋亡作用

目的 :观察不同剂量生长激素 (GH)对阿霉素中毒所致大鼠心肌细胞凋亡的影响。方法 :建立体外培养的大鼠心肌细胞阿霉素损伤模型 ,加入不同剂量的生长激素 ,采用流式细胞仪 (FCM)检测心肌细胞凋亡和坏死率。以 2 ,3 二苯基溴化四唑 (MTT)比色法绘制心肌细胞生长曲线。结果 :阿霉素可导致心肌细胞损伤 ,表现为心肌细胞细胞坏死和凋亡发生率增高 ;GH能促进心肌细胞增殖并降低其凋亡率 ,在 10 μg·ml- 1 至 5 0 0 μg·ml- 1 范围内 ,其抗凋亡和促增殖作用呈剂量依赖性增强。结论 :GH对阿霉素中毒所致的心肌细胞凋亡有直接的抑制作用     

热诱导延迟损伤大鼠心肌细胞凋亡机理的探讨

目的探讨热诱导延迟过氧化氢(H2O2)造成大鼠心肌细胞凋亡机理。方法体外培养大鼠乳鼠心肌细胞同时温度诱导细胞产生热休克蛋白70(HSP70)，用H2O2造成心肌细胞损伤。采用Western Blottmg、流式细胞仪、Bcl-2原位杂交、免疫组化检测Caspase-3等作为检测指标，观察心肌细胞损伤，以及HSP70对心肌细胞的保护作用。结果温度诱导后HSP70在胞浆中大量表达，保护组凋亡率显著低于损伤组，Bcl-2和Caspase-3在损伤组大量表达。结论HSP70可延迟细胞凋亡，对心肌细胞具有保护作用。     

白藜芦醇通过减弱线粒体损伤对高同型半胱氨酸血症大鼠所致心脏损伤的保护作用

目的探讨白藜芦醇对高同型半胱氨酸血症(HHcy)大鼠心肌细胞凋亡的逆转作用及相关分子机制。方法建立HHcy大鼠模型;超声心动图评估大鼠心功能;苏木素-伊红、Masson和TUNEL染色分析心肌细胞凋亡;TUNEL法检测细胞凋亡;Western印迹确定线粒体凋亡相关因子(NOX)4、细胞色素C和半胱氨酸-天冬氨酸蛋白酶(Caspase)-3表达;透射电镜观察心肌细胞线粒体形态;荧光显微镜观察细胞凋亡;Mitotracker和JC-1染色检测心肌细胞线粒体膜电位。结果 HHcy大鼠心肌细胞线粒体NOX4表达升高,细胞色素C渗漏增多,Caspase-3表达显著升高,细胞凋亡数量增多。HHcy大鼠心肌细胞线粒体膜电位显著下降,线粒体结构和功能破坏。予以白藜芦醇可明显抑制高同型半胱氨酸对心肌细胞的促凋亡和线粒体损伤作用。结论白藜芦醇可通过抑制高同型半胱氨酸对心肌细胞的线粒体相关凋亡和线粒体损伤作用,起到心肌细胞保护作用。     

卡维地洛和美托洛尔对大鼠缺血再灌注损伤心肌细胞凋亡的影响

目的观察卡维地洛和美托洛尔对大鼠缺血再灌注损伤心肌细胞凋亡及caspase-3、p53的影响。方法取SD大鼠32只,随机分为假手术组、I/R组、卡维地洛组、美托洛尔组,每组8只。通过结扎和放松大鼠左冠状动脉前降支(LAD)造成心肌缺血再灌注损伤。采用末端标记原位细胞凋亡法检测心肌凋亡细胞,采用免疫组化法测caspase-3、p53蛋白表达。结果 I/R组caspase-3、p53表达和心肌细胞凋亡指数较假手术组明显升高(P<0.05),卡维地洛组和美托洛尔组各项指标较I/R组明显降低(P<0.05),卡维地洛组各指标较美托洛尔组明显降低(P<0.05)。结论 p53和caspase-3在缺血诱导的心肌细胞凋亡中发挥重要作用。卡维地洛和美托洛尔均可抑制心肌细胞凋亡,对缺血再灌注损伤心肌细胞有保护作用,且卡维地洛作用优于美托洛尔。     

Regulation of basal myocardial function by NO.

The effects of exogenous and endogenous. NO on myocardial functions such as contraction, relaxation and heart rate have recently gained considerable scientific interest. .NO stimulates myocardial soluble guanylate cyclase to produce cGMP, which activates two major target proteins. A small increase in cGMP levels predominantly inhibits phosphodiesterase III, while high cGMP levels activate cGMP-dependent protein kinase. Accordingly, submicromolar .NO concentrations improve myocardial contraction, while submillimolar .NO concentrations decrease contractility. The latter action includes direct inhibitory .NO effects on ATP synthesis and voltage-gated calcium channels. Overall, the inotropic effects of exogenous .NO are small and probably of minor importance for myocardial contractility. Cardiomyocytes are capable of expressing eNOS and iNOS. Endogenous .NO has effects on myocardial contraction, similar to that of exogenous .NO. Various NOS inhibitors can substantially reduce myocardial contractility in vitro and in vivo, suggesting that basal endogenous .NO production supports myocardial contractility. There is also evidence for a .NO-dependent cardiodepressive effect of cytokines that is mediated by expression of iNOS. This is consistent with the negative inotropic effects of .NO at high concentrations. Cardiodepressive actions of endogenous .NO production may play a role in certain forms of heart failure. Finally, .NO also has an effect on heart rate. Physiologic .NO concentrations can stimulate heart rate by activating the hyperpolarization-activated inward current (If) and this effect decreases at submillimolar .NO concentrations. In summary, physiological concentrations of .NO increase contractility and heart rate under basal conditions, while high .NO concentrations induce the opposite effects.     

Beneficial Effects of Nitric Oxide on Cardiac Diastolic Function: 'The Flip Side of the Coin'

Modulation by NO of systolic myocardial function received widespread attention but most studies focused on potential negative inotropic properties of NO. The very original observations on the effects of NO on myocardial contraction already provided evidence that NO modified myocardial contractile performance mainly through a relaxation-hastening effect (i.e. earlier onset of relaxation) and through an increase in myocardial distensibility. The present review discusses the relaxation hastening and distensibility-increasing effects of NO in experimental preparations, in the normal human heart, in left ventricular hypertrophy of aortic stenosis, in the human allograft and in dilated nonischemic cardiomyopathy. This diastolic flip side of the myocardial effects of NO appears to be beneficial especially for patients who are dependent on the LV Frank-Starling response to maintain cardiac output.     

Role of nitric oxide and oxidative stress in ischaemic myocardial injury and preconditioning

Nitric oxide (NO) plays an important role in the physiologic modulation of coronary artery tone and myocardial function. However, increased formation of NO within the myocardium can also have detrimental effects, contributing to the pathophysiology of myocardial dysfunction in ischaemic heart diseases. The role of reactive nitrogen species in the pathogenesis of myocardial dysfunction after ischaemia has been investigated in numerous studies. They reveal divergent and opposed effects of nitric oxide: from a cardioprotective action leading to ischaemic preconditioning after short ischaemic periods to a cardiodepressive action after severe ischaemia/reperfusion injury and heart failure. This review describes the determining role of reactive oxygen species on these opposite myocardial effects of NO. The final action of NO, whether cardioprotective or cardiodepressive, strongly depends on the level of oxidative stress in the myocardium. Nitric oxide disrupts free radical and oxidant-mediated reactions, due to a strong attraction and interaction with superoxide.The level of oxidative stress is positively related to the severity of the ischaemic injury, making the results in different myocardial syndromes more concordant. If the increased production of NO is well in balance with a moderate increase in oxygen radicals, then NO will exert beneficial effects. However, if the oxygen radicals are produced in excess of NO as in prolonged ischaemic injury, then deleterious effects will be induced. Consequently, the balance between NO and free oxygen radicals is crucial in modulating the outcome after an ischaemic insult.     

Nitric oxide in myocardial ischemia/reperfusion injury

Administration of nitric oxide (NO), NO donors or drugs that enhance NO release (statins, calcium antagonists, ACE-inhibitors, dexamethasone) prior to ischemia protects the myocardium against ischemia/reperfusion injury. While this exogenous administration of NO prior to ischemia can initiate a preconditioning-like phenomenon, endogenous NO-synthase (NOS)-derived NO is not involved in triggering or mediating the early phase of ischemic preconditioning's protection, but does play a pivotal role for initiating and mediating the delayed phase of ischemic preconditioning's protection. The present review now summarizes the importance of endogenous and exogenous NO when given at the time of reperfusion for vascular and myocardial function and morphological outcome following ischemia/reperfusion. Given the inconsistency of the published data, potential confounding factors that might affect experimental results on the role of NO in myocardial ischemia/reperfusion were identified, such as (1) the lack of characterization of the involved NOS isoforms in myocardial ischemia/reperfusion injury in different animal species, (2) the lack of direct measurements of myocardial NO concentration and/or NOS activity to assure sufficient NOS inhibition, (3) the lack of consideration of nonenzymatic NO production as a potential source of NO, and (4) the absence of plasma or blood components in in vitro studies influencing NO delivery and metabolism. Future research on the importance of NO in ischemia/reperfusion injury will have to focus more precisely on the identification and standardization of potential confounding experimental factors that influence synthesis, transport, and interaction of NO with various targets in blood and tissue.     

Role of nitric oxide in regulating cardiac electrophysiology

Despite the explosion of new information on nitric oxide (NO), important questions about its role in regulating cardiac electrophysiology remain unanswered. Recent in vitro and in vivo animal studies have discovered a number of new electrophysiological properties of NO, some of which may contribute to a reduction in fatal arrhythmias induced by acute myocardial ischemia. This review summarizes the influences of NO on heart rate, atrioventricular conduction, ventricular repolarization and the development of ventricular arrhythmias during acute myocardial ischemia.     

The ubiquitous role of nitric oxide in cardioprotection

In recent years, major advances have been made toward understanding the role of nitric oxide (NO) in the ischemic biology of the heart. It is now clear that NO, either endogenous or exogenous, represents one of the most important defenses against myocardial ischemia-reperfusion injury. The purpose of this review is to provide an update on the cardioprotective actions of NO, with particular emphasis on the function of the inducible isoform of NO synthase (iNOS) and on the role of mitochondria in NO-mediated protection. This essay underscores some of the more prominent areas of ischemic biology that relate to NO, such as ischemic preconditioning, pharmacological cardioprotection, and gene therapy. The hypothesis that the late phase of preconditioning is mediated by increased iNOS activity resulting in enhanced NO bioavailability, first proposed by our group, is now widely accepted and can be regarded as a proven hypothesis. Likewise, the burgeoning field of postconditioning may share such a requirement for NO. Various drugs (e.g. statins, ACE inhibitors, angiotensin-receptor blockers, etc.) also produce salubrious effects in experimental models of myocardial infarction via their enhancement of NO bioavailability. Thus, NO appears to be a common mediator of the protection afforded by a wide array of seemingly unrelated pharmacological and nonpharmacological interventions, underscoring its fundamental role as a ubiquitous defense of the heart against ischemia and reperfusion. This review challenges the conventional wisdom that iNOS is deleterious during myocardial ischemia-reperfusion and instead proposes the concept that iNOS, when expressed in cardiac myocytes, is a profoundly protective protein. We also emphasize the emerging importance of the mitochondrial actions of NO. Although the precise molecular events remain to be defined, we propose that NO interacts with components of the electron transport chain and/or the mitochondrial permeability transition pore to limit post-ischemic myocardial damage, and that this action potentially provides a fundamental molecular explanation for the mechanism of NO-mediated cardioprotection.     

Opposite effects of nitric oxide and nitroxyl on postischemic myocardial injury

Recent experimental evidence suggests that reactive nitrogen oxide species can contribute significantly to postischemic myocardial injury. The aim of the present study was to evaluate the role of two reactive nitrogen oxide species, nitroxyl (NO(-)) and nitric oxide (NO(.)), in myocardial ischemia and reperfusion injury. Rabbits were subjected to 45 min of regional myocardial ischemia followed by 180 min of reperfusion. Vehicle (0.9% NaCl), 1 micromol/kg S-nitrosoglutathione (GSNO) (an NO(.) donor), or 3 micromol/kg Angeli's salt (AS) (a source of NO(-)) were given i.v. 5 min before reperfusion. Treatment with GSNO markedly attenuated reperfusion injury, as evidenced by improved cardiac function, decreased plasma creatine kinase activity, reduced necrotic size, and decreased myocardial myeloperoxidase activity. In contrast, the administration of AS at a hemodynamically equieffective dose not only failed to attenuate but, rather, aggravated reperfusion injury, indicated by an increased left ventricular end diastolic pressure, myocardial creatine kinase release and necrotic size. Decomposed AS was without effect. Co-administration of AS with ferricyanide, a one-electron oxidant that converts NO(-) to NO(.), completely blocked the injurious effects of AS and exerted significant cardioprotective effects similar to those of GSNO. These results demonstrate that, although NO(.) is protective, NO(-) increases the tissue damage that occurs during ischemia/reperfusion and suggest that formation of nitroxyl may contribute to postischemic myocardial injury.     

Peroxynitrite is a major contributor to cytokine-induced myocardial contractile failure

Proinflammatory cytokines depress myocardial contractile function by enhancing the expression of inducible NO synthase (iNOS), yet the mechanism of iNOS-mediated myocardial injury is not clear. As the reaction of NO with superoxide to form peroxynitrite markedly enhances the toxicity of NO, we hypothesized that peroxynitrite itself is responsible for cytokine-induced cardiac depression. Isolated working rat hearts were perfused for 120 minutes with buffer containing interleukin-1 beta, interferon-gamma, and tumor necrosis factor-alpha. Cardiac mechanical function and myocardial iNOS, xanthine oxidoreductase (XOR), and NAD(P)H oxidase activities (sources of superoxide) were measured during the perfusion. Cytokines induced a marked decline in myocardial contractile function accompanied by enhanced activity of myocardial XOR, NADH oxidase, and iNOS. Cardiac NO content, myocardial superoxide production, and perfusate nitrotyrosine and dityrosine levels, markers of peroxynitrite, were increased in cytokine-treated hearts. The peroxynitrite decomposition catalyst FeTPPS (5,10,15, 20-tetrakis-[4-sulfonatophenyl]-porphyrinato-iron[III]), the NO synthase inhibitor N(G)-nitro-L-arginine, and the superoxide scavenger tiron each inhibited the decline in myocardial function and decreased perfusate nitrotyrosine levels. Proinflammatory cytokines stimulate the concerted enhancement in superoxide and NO-generating activities in the heart, thereby enhancing peroxynitrite generation, which causes myocardial contractile failure.     

Selective NOS inhibition restores myocardial contractility in endotoxemic rats; however, myocardial NO content does not correlate with myocardial dysfunction

The role of nitric oxide (NO) in lipopolysaccharide (LPS)-induced myocardial dysfunction remains controversial as some investigators concluded that inhibition of NO synthesis improves left ventricular (LV) contractility, whereas others did not. We investigated the relationship between LPS-induced LV dysfunction and LV NO production. We postulated that high myocardial NO concentrations would correspond to decreased contractility and low NO concentrations would correspond to recovery. In a rat model of endotoxemia, we used the isolated papillary preparation to assess inotropic dysfunction. We measured LV NO content and hemodynamics at baseline, 4, 16, and 48 h after LPS administration. LPS caused a decrease in LV contractility at 16 h with recovery at 48 h. Myocardial NO levels were elevated at all time periods. However, at 48 h in spite of normalization of LV contractility, myocardial NO content remained elevated. Pretreatment of LPS animals with the nonselective nitric oxide synthase (NOS) inhibitor N (G)-nitro-L-arginine methyl ester (L-NAME) worsened LV contractility, decreased LV NO content, and increased mortality. However, pretreatment with the relatively selective inducible NOS (iNOS) inhibitor S-methylisothiourea sulfate (SMT) restored LV contractility. Myocardial NO content in the SMT was lower than that of the LPS only group, but higher than the L-NAME group. We conclude that SMT is beneficial to myocardial contractility in this model of endotoxemia, whereas pretreatment with L-NAME is associated with further deterioration of contractility and increased mortality. Moreover, our data indicate that high myocardial NO concentrations do not necessarily correlate with decreased contractility.     

Relevance of nitric oxide for myocardial remodeling

Endogenous myocardial nitric oxide (NO) may modulate the transition from adaptive to maladaptive remodeling leading to heart failure. In rodent models of pressure overload or myocardial infarction, the three NO synthase (NOS) isoforms were shown to play a neutral, protective, or even adverse role in myocardial remodeling, depending on the quantity of NO produced, the location of each NOS and their regulators, the prevailing oxidant stress and resultant NO/oxidant balance, as well as NOS coupling/dimerization. Beside neuronal NOS and—in specific conditions—inducible NOS isoforms, endothelial NOS (eNOS) exerts cardioprotective effects on pressure-overload, ischemia/reperfusion, and myocardial infarction-induced myocardial remodeling, provided the enzyme remains in a coupled state. Besides its effects on excitation-contraction coupling in response to stretch, eNOS acts as an ‘endogenous β-blocker’ by restoring the sympathovagal balance, opposing excessive hypertrophy as well as promoting vasodilatation and neoangiogenesis, thereby contributing to tissue repair. As eNOS was also shown to mediate the beneficial effects of cardiovascular drugs commonly used in patients with heart failure, strategies to increase its expression and/or coupled catalytic activity in the myocardium offer new therapeutic avenues for the treatment of this disease.