miRNA与心肌细胞凋亡研究进展

微小RNA是一种单链、非编码的内源性RNA,通常在转录后负向调节基因的表达水平。微小RNA对心肌细胞凋亡具有重要的调控作用。微小RNA可通过心肌细胞凋亡经典通路(包括线粒体凋亡通路、死亡受体凋亡通路、内质网应激凋亡通路)发挥抗心肌细胞凋亡作用或促心肌细胞凋亡作用。     

中药干预慢性心力衰竭心肌细胞凋亡的研究进展

心肌细胞凋亡是心力衰竭的重要病理变化,是心衰从代偿走向失代偿的转折点。中药在调控心衰心肌细胞凋亡中发挥着重要作用,已成为现阶段的研究热点。中药主要通过调控相关凋亡因子及信号通路(线粒体信号通路、死亡受体信号通路、内质网信号通路、Hippo通路、Bcl-2家族、caspase家族、p53等),发挥抑制心肌细胞凋亡的作用,从而改善心脏功能,保护心肌组织。本文主要对与中药作用密切相关的细胞凋亡途径及凋亡因子进行了综述,为临床治疗慢性心衰提供可靠的实验依据。     

Bax/Bak蛋白在凋亡通路中的调控与激活机制

细胞凋亡是机体维持组织稳态和胚胎发育的重要机制之一,受到多种信号分子的严格调控。促凋亡Bcl-2家族蛋白成员Bax和Bak蛋白在细胞凋亡中扮演着非常重要的角色。在凋亡信号的刺激下,Bax和Bak蛋白被激活并在线粒体上互相凝集成簇,使得线粒体膜的通透性增加,引起凋亡因子的释放,并最终诱导细胞的死亡。本文主要介绍Bax和Bak蛋白在细胞凋亡过程中的调控与激活机制,并详细阐述目前它们在线粒体凋亡通路中的几个激活模型,总结二者在激活线粒体凋亡通路中的作用,为进一步研究线粒体凋亡通路作一铺垫。     

内质网应激与心血管疾病研究概述

内质网应激是继死亡受体信号途径和线粒体途径之后新近发现的一条细胞凋亡通路,适度的应激可通过未折叠蛋白反应(UPR)产生细胞保护作用,但当应激过强或长时间不缓解时则会触发CHOP、ASK1/JNK及Caspases等通路诱导细胞凋亡。近年来研究发现内质网应激参与多种心血管疾病的发生发展,通过对相关通路的干预可以产生心肌细胞的保护作用,这有望成为防治心脏疾病的新靶点。     

E2F6在物理性低氧及化学性低氧诱导的凋亡中的表达特征

心肌细胞凋亡性死亡是低氧发生时的重要病理学特征,但低氧诱导的心肌细胞凋亡的调控机制尚未完全阐明.E2F6是E2F转录因子家族成员之一,我们新近的研究证实其具有抑制DNA损伤诱导的细胞凋亡作用.但是,E2F6是否参与了低氧诱导的心肌细胞凋亡的调控尚不清楚.在本研究中,我们初步探讨了E2F6在物理性低氧及化学性低氧模拟物诱导大鼠心肌细胞系H9c2细胞凋亡中的表达特征.结果表明:物理性低氧、化学性低氧模拟物去铁胺(desferrioxamine,DFO)和氯化钻(cobalt chloride,CoCl2)均能有效诱导H9c2细胞发生凋亡.在物理性低氧及CoCl2,诱导的H9c2细胞凋亡中,内源性E2F6 mRNA表达明显下调,但蛋白表达没有明显变化.而在DFO诱导的凋亡中,内源性E2F6 mRNA及蛋白表达均发生明显下调.这些结果提示,E2F6可能参与调控DFO模拟低氧诱导的H9c2细胞凋亡,而对物理性低氧及CoCl2,模拟低氧诱导的细胞凋亡敏感性较低.此外,DFO模拟低氧诱导的细胞凋亡机制可能与物理性低氧及CoCl2.模拟低氧诱导的细胞凋亡机制不同.     

微小RNA在肿瘤中调控细胞凋亡的研究进展

微小RNA (microRNA, miRNA)是一种非编码的小分子RNA,广泛参与基因转录后调控,其表达或功能异常在肿瘤的发生发展中起重要作用。细胞凋亡是程序性死亡的一种形式,能有效地清除受损细胞。细胞凋亡的失调不仅与肿瘤的发生发展有关,而且与肿瘤对治疗的抵抗有关。微小RNA可通过细胞凋亡经典通路(包括线粒体凋亡通路、死亡受体凋亡通路、内质网应激凋亡通路)发挥抗细胞凋亡或促细胞凋亡作用。该文主要对miRNA在肿瘤中调控细胞凋亡的相关研究进展作一综述。     

线粒体动力学与细胞凋亡

线粒体是普遍存在于真核细胞中的双层膜细胞器,通过氧化磷酸化为细胞提供能量。线粒体是高度动态的细胞器,通过持续的融合和分裂改变自身形态来适应各种应激条件以满足细胞的能量代谢及其他生物学需求,这种生物学过程被称为线粒体动力学。细胞凋亡是细胞程序性的死亡方式,而线粒体在内源性细胞凋亡途径中扮演着重要的角色。在受到细胞内部(DNA突变)或者外部刺激时,线粒体外膜通透性改变并释放凋亡因子,如细胞色素C、Smac、AIF等,进而激活细胞凋亡信号通路,促进细胞凋亡。细胞凋亡过程中线粒体形态发生改变,可从管状向颗粒状转变,并伴随着线粒体嵴重构。线粒体形态是由Mfn1、Mfn2、OPA1、Drp1等多种GTP蛋白调控,这些蛋白同时也参与细胞凋亡调控。此外,细胞凋亡调控蛋白如Bax、Bak、Bcl-2等蛋白也可调控线粒体形态。该文主要回顾和阐述细胞凋亡与线粒体动力学的发展历程、基本知识以及它们之间的内在联系。     

常氧及低氧下孵育液中钙浓度改变对心肌线粒体钙含量及其呼吸功能损伤的影响

在常氧孵育中,当孵育介质自由钙离子浓度升高时,离体心肌线粒体钙含量显著增加。同时,线粒体状态4呼吸速率也明显加快并与其钙含量的增加呈正相关关系。在低氧孵育中,当孵育介质自由钙离子浓度升高时,离体心肌线粒体钙含量没有明显的增加,其状态4呼吸速率虽有加快但程度明显较常氧孵育时低。另外,在低孵育介质自由钙离子浓度(pCa8.0)的条件下,低氧可引起轻微的线粒体状态4呼吸速率加快。从以上结果作者推测,低氧引起心肌细胞的线粒体损伤可能主要不是低氧直接对线粒体作用所造成的,而是由低氧引起的心肌细胞胞浆环境变化对线粒体破坏的结果。其中胞浆自由钙离子的升高可能是一个的原因。     

天然提取物诱导人HepG2 细胞凋亡的研究进展

细胞凋亡是机体维持内环境稳定,更好的适应生存环境采取的一种死亡过程。细胞凋亡异常与肿瘤的发生、发展存在密切的关系。细胞凋亡的信号途径主要有死亡受体介导的外源性通路、线粒体介导内源性通路、内质网信号通路及MAPK信号通路。通过作用于凋亡信号通路上一些关键基因,诱导肿瘤细胞凋亡被认为是临床抗肿瘤治疗最有成效的治疗方法之一。研究已证实多种天然提取物作用于凋亡信号途径中一些重要因子可诱导细胞凋亡,并取得较好的抑制肿瘤增殖的效果。本文是关于细胞凋亡机制及各种天然提取物作用于凋亡通路上主要基因进行抗肿瘤治疗研究进展的综述。     

microRNA调控细胞凋亡的研究进展

microRNA(miRNA)是一类非编码小RNA,通过基因转录后调控来调节细胞的各生理过程。其中,细胞凋亡作为细胞自主有序的死亡过程,在维持内环境稳态中起重要作用。同时,miRNA作为细胞凋亡信号通路的关键调节因子,已成为生命科学研究的热点之一。本文综述了miRNA对细胞凋亡相关通路(线粒体通路,死亡受体通路和内质网通路)调控的研究进展,总结了不同组织及细胞中miRNA对凋亡通路的调节作用,为癌症等疾病治疗提供理论指导和新的思路。     

Mitochondrial ca(2+) signaling and cardiac apoptosis

The broad significance of apoptosis in the cardiovascular system only began to be recognized more widely recently. Apoptotic cell death is a normal component of postnatal morphogenesis of the human cardiac conduction system and may also be involved in the pathogenesis of a variety of cardiovascular diseases, including heart failure, myocardial infarction and atherosclerosis. Recently, it has become evident that mitochondria play important role in the signaling machinery of apoptotic cell death by releasing several apoptotic factors such as cytochrome c, apoptosis-inducing factor and procaspases. Furthermore, calcium signals have been identified as one of the major signals that converge on mitochondria to trigger the mitochondrion-dependent pathway of the apoptotic cell death. Calcium signals are also important in the physiological control of mitochondrial energy metabolism and it has not yet been explored how Ca(2+) turns from a signal for life to a signal for death. Since large elevations of cytosolic [Ca(2+)] ([Ca(2+)](c)) occur during each heartbeat in cardiac myocytes and these [Ca(2+)](c) signals may efficiently propagate to the mitochondria, the Ca(2+)-dependent mitochondrial pathways of apoptosis can be particularly important in the heart. This review is concerned with the role of mitochondrial Ca(2+) signaling in the control of cardiac apoptosis.     

Haemin attenuates intermittent hypoxia‐induced cardiac injury via inhibiting mitochondrial fission

Obstructive sleep apnoea (OSA) characterized by intermittent hypoxia (IH) is closely associated with cardiovascular diseases. IH confers cardiac injury via accelerating cardiomyocyte apoptosis, whereas the underlying mechanism has remained largely enigmatic. This study aimed to explore the potential mechanisms involved in the IH‐induced cardiac damage performed with the IH‐exposed cell and animal models and to investigate the protective effects of haemin, a potent haeme oxygenase‐1 (HO‐1) activator, on the cardiac injury induced by IH. Neonatal rat cardiomyocyte (NRC) was treated with or without haemin before IH exposure. Eighteen male Sprague‐Dawley (SD) rats were randomized into three groups: control group, IH group (PBS, ip) and IH + haemin group (haemin, 4 mg/kg, ip). The cardiac function was determined by echocardiography. Mitochondrial fission was evaluated by Mitotracker staining. The mitochondrial dynamics‐related proteins (mitochondrial fusion protein, Mfn2; mitochondrial fission protein, Drp1) were determined by Western blot. The apoptosis of cardiomyocytes and heart sections was examined by TUNEL. IH regulated mitochondrial dynamics‐related proteins (decreased Mfn2 and increased Drp1 expressions, respectively), thereby leading to mitochondrial fragmentation and cell apoptosis in cardiomyocytes in vitro and in vivo, while haemin‐induced HO‐1 up‐regulation attenuated IH‐induced mitochondrial fragmentation and cell apoptosis. Moreover, IH resulted in left ventricular hypertrophy and impaired contractile function in vivo, while haemin ameliorated IH‐induced cardiac dysfunction. This study demonstrates that pharmacological activation of HO‐1 pathway protects against IH‐induced cardiac dysfunction and myocardial fibrosis through the inhibition of mitochondrial fission and cell apoptosis.     

TLR9 deficiency alleviates doxorubicin‐induced cardiotoxicity via the regulation of autophagy

Doxorubicin is a commonly used anthracycline chemotherapeutic drug. Its application for treatment has been impeded by its cardiotoxicity as it is detrimental and fatal. DNA damage, cardiac inflammation, oxidative stress and cell death are the critical links in DOX‐induced myocardial injury. Previous studies found that TLR9‐related signalling pathways are associated with the inflammatory response of cardiac myocytes, mitochondrial dysfunction and cardiomyocyte death, but it remains unclear whether TLR9 could influence DOX‐induced heart injury. Our current data imply that DOX‐induced cardiotoxicity is ameliorated by TLR9 deficiency both in vivo and in vitro, manifested as improved cardiac function and reduced cardiomyocyte apoptosis and oxidative stress. Furthermore, the deletion of TLR9 rescued DOX‐induced abnormal autophagy flux in vivo and in vitro. However, the inhibition of autophagy by 3‐MA abolished the protective effects of TLR9 deletion on DOX‐induced cardiotoxicity. Moreover, TLR9 ablation suppressed the activation of p38 MAPK during DOX administration and may promote autophagy via the TLR9‐p38 MAPK signalling pathway. Our study suggests that the deletion of TLR9 exhibits a protective effect on doxorubicin‐induced cardiotoxicity by enhancing p38‐dependent autophagy. This finding could be used as a basis for the development of a prospective therapy against DOX‐induced cardiotoxicity.     

Multiple antiapoptotic targets of the PI3K/Akt survival pathway are activated by epoxyeicosatrienoic acids to protect cardiomyocytes from hypoxia/anoxia

Epoxyeicosatrienoic acids (EETs) reduce infarction of the myocardium after ischemia-reperfusion injury to rodent and dog hearts mainly by opening sarcolemmal and mitochondrial potassium channels. Other mediators for the action of EET have been proposed, although no definitive pathway or mechanism has yet been reported. Using cultured cells from two rodent species, immortalized myocytes from a mouse atrial lineage (HL-1) and primary myocytes derived from neonatal rat hearts, we observed that pretreatment with EETs (1 microM of 14,15-, 11,12-, or 8,9-EET) attenuated apoptosis after exposure to hypoxia and reoxygenation (H/R). EETs also preserved the functional beating of neonatal myocytes in culture after exposure to H/R. We demonstrated that EETs increased the activity of the prosurvival enzyme phosphatidylinositol 3-kinase (PI3K). In fact, cardiomyocytes pretreated with EET and exposed to H/R exhibited antiapoptotic changes in at least five downstream effectors of PI3K, protein kinase B (Akt), Bcl-x(L)/Bcl-2-associated death promoter, caspases-9 and -3 activities, and the expression of the X-linked inhibitor of apoptosis, compared with vehicle-treated controls. The PI3K/Akt pathway is one of the strongest intracellular prosurvival signaling systems. Our studies show that EETs regulate multiple molecular effectors of this pathway. Understanding the targets of action of EET-mediated protection will promote the development of these fatty acids as therapeutic agents against cardiac ischemia-reperfusion.     

Nuclear respiratory factor 1 protects H9C2 cells against hypoxia-induced apoptosis via the death receptor pathway and mitochondrial pathway

Hypoxia-induced cardiomyocyte apoptosis is one of the leading causes of heart failure. Nuclear respiratory factor 1 (NRF-1) was suggested as a protector against cell apoptosis; However, the mechanism is not clear. Therefore, the aim of this study was to elucidate the role of NRF-1 in hypoxia-induced H9C2 cardiomyocyte apoptosis and to explore its effect on regulating the death receptor pathway and mitochondrial pathway. NRF-1 was overexpressed or knocked down in H9C2 cells, which were then exposed to a hypoxia condition for 0, 3, 6, 12, and 24 h. Changes in cell proliferation, cell viability, reactive oxygen species (ROS) generation, and mitochondrial membrane potential (MMP) were investigated. The activities of caspase-3, -8, and -9, apoptosis rate, and the gene and protein expression levels of the death receptor pathway and mitochondrial pathway were analyzed. Under hypoxia exposure, NRF-1 overexpression improved the proliferation and viability of H9C2 cells and decreased ROS generation, MMP loss, caspase activities, and the apoptosis rate. However, the NRF-1 knockdown group showed the opposite results. Additionally, NRF-1 upregulated the expression of antiapoptotic molecules involved in the death receptor and mitochondrial pathways, such as CASP8 and FADD-like apoptosis regulator, B-cell lymphoma 2, B-cell lymphoma-extra-large, and cytochrome C. Conversely, the expression of proapoptotic molecules, such as caspase-8, BH3-interacting domain death agonist, Bcl-2-associated X protein, caspase-9, and caspase-3 was downregulated by NRF-1 overexpression in hypoxia-induced H9C2 cells. These results suggest that NRF-1 functions as an antiapoptotic factor in the death receptor and mitochondrial pathways to mitigate hypoxia-induced apoptosis in H9C2 cardiomyocytes.     

Chemical hypoxia triggers apoptosis of cultured neonatal rat cardiac myocytes: Modulation by calcium-regulated proteases and protein kinases

Myocardial infarctions and stroke arise primarily as a result of hypoxia/ischemia-induced cell injury. However, the molecular mechanism of cardiac cell death due to hypoxia has not been elucidated. We showed here that chemical hypoxia induced by 1 mM azide triggered apoptosis of isolated neonatal rat ventricular cardiac myocytes but had no effect on cardiac fibroblasts. The azide-induced cardiomyocyte apoptosis could be characterized by a reversible initiation phase (0-6 h after azide exposure) during which cytosolic ATP levels remained little affected. This was followed by an irreversible execution phase (12-18 h) exhibiting prominent internucleosomal DNA fragmentation, cell membrane leakage, mitochondrial dysfunction, and increased calpain messenger RNA. Blocking extracellular calcium influx or intracellular calcium release was each effective in suppressing myocyte apoptosis. Cell death was also found to be mediated by calcium sensitive signal transduction events based on the use of specific antagonists. Consistent with the induction of calpain expression during apoptosis, blocking de novo protein synthesis and calpain activity inhibited cell death. These regulatory features coupled with the ease of the cell system suggest that the myocyte apoptosis model described here should be useful in the study of events leading to the demise of the myocardium.     

Neurohormonal regulation of myocardial cell apoptosis during the development of heart failure

Adult cardiac myocytes are terminally differentiated cells that are no longer able to divide. Accumulating data support the idea that apoptosis in these cells is involved in the transition from cardiac compensation to decompensated heart failure. Since a number of neurohormonal factors are activated in this state, these factors may be involved in the positive and negative regulation of apoptosis in cardiac myocytes. beta1-Adrenergic receptor and angiotensin type 1 receptor pathways, nitric oxide and natriuretic peptides are involved in the induction of apoptosis in these cells, while alpha1- and beta2-adrenergic receptor and endothelin-1 type A receptor pathways and gp130-related cytokines are antiapoptotic. The myocardial protection of the latter is mediated, at least in part, through mitogen-activated protein kinase-dependent pathways, compatible with the findings in other cell types. In contrast, signaling pathways leading to apoptosis in cardiac myocytes are distinct from those in other cell types. The cAMP/PKA pathway induces apoptosis in cardiac myocytes and blocks apoptosis in other cell types. The p300 protein, a coactivator of p53, mediates apoptosis in fibroblasts but appears to play a protective role in differentiated cardiac myocytes. The inhibition of myocardial cell apoptosis in heart failure may be achieved by directly blocking apoptosis signaling pathways or by modulating neurohormonal factors involved in their regulation. These may provide novel therapeutic strategies in some forms of heart failure.