PAR-2对自噬介导的心肌缺血/再灌注损伤的研究进展

心肌再灌注治疗是急性心肌梗死最重要的治疗方法之一,能够显著改善致死、致残率。但再灌注早期仍难以避免增加心肌损害,引起心肌缺血/再灌注(ischemia/reperfusion,I/R)损伤。心肌缺血阶段激活的自噬对心肌具有保护作用,而再灌注阶段激活的自噬对心肌具有损害作用,其机制可能与缺血阶段AMPK-mTOR信号通路,以及再灌注阶段Bcl-2-Beclin 1信号通路介导的自噬诱导I/R损伤的重要途径有关。蛋白酶激活受体2(protease activated receptor2,PAR-2)在缺血心肌细胞高度表达,是自噬的上游标记物之一,能够显著改善I/R损伤,具有心肌保护作用。在缺血阶段,PAR-2可能通过激活AMPK途径,抑制其下游mTOR表达,从而激活自噬,保护心肌;在再灌注阶段,通过Bcl-2下调激活Beclin 1表达,诱导自噬发生,并且能够上调Bcl-2mRNA表达水平。本文就PAR-2对自噬介导的I/R损伤的研究进展进行综述。     

mTOR信号通路与动脉粥样硬化

mTOR是一种丝氨酸/苏氨酸激酶,主要参与到两种信号通路的调节中。mTOR信号通路具有调控细胞生长、自噬、增殖和凋亡等生物学功能。mTOR可以调控动脉粥样硬化发生发展过程中内皮细胞的增殖与迁移、巨噬细胞的自噬和平滑肌细胞的增殖与迁移。通过不同时期抑制或激活mTOR可以稳定动脉粥样硬化易损斑块,防止动脉粥样硬化的发生发展。mTOR信号通路在动脉粥样硬化进展中发挥了多方面效应,本文主要针对mTOR信号通路与动脉粥样硬化做一综述,为临床治疗提供新的研究方向。     

核因子-kB信号通路与自噬在动脉粥样硬化发生发展中的相互调节作用

动脉粥样硬化(atherosclerosis,AS)是一种复杂的慢性血管炎症疾病,由多种AS相关细胞与其表达的促炎因子相互作用促进其发生发展。核因子-k B(NF-kB)信号通路是由多种细胞因子介导的经典信号通路,不仅参与炎症反应,也调控细胞损伤、氧化应激、细胞凋亡等过程。而自噬是细胞稳态的溶酶体降解过程,在一定范围内的自噬激活可调节炎症反应。AS多伴有炎症反应并与自噬密切相关,NF-kB的激活可介导自噬,而自噬的过度激活抑制NF-kB活性。本研究主要对NF-kB与自噬在AS中的相互关系做一综述。     

ROS调节mTOR信号通路参与自噬的研究进展

自噬是真核细胞中普遍存在的一种物质降解途径,通过自噬溶酶体介导,清除自身多余或受损的细胞器,参与正常细胞内稳态的维护,对机体生长、发育和衰老均起重要作用。哺乳动物雷帕霉素靶蛋白(mTOR)是一种丝/苏氨酸蛋白质激酶,接受并整合细胞内外的各种信号,是调节蛋白质翻译与细胞生长等多种生理活动的中心信号分子。而活性氧类(ROS)作为第2信使分子,可介导多种细胞信号通路并发挥广泛的生理效应。研究发现,在自噬的过程中,ROS可通过一定的途径激活或抑制mTOR通路,但其调节机制极其复杂。本文就自噬过程中ROS与mTOR之间相互调节机制的研究进展进行综述。     

PI3K/AKT/mTOR信号通路在糖皮质激素性股骨头坏死中的表达与作用

糖皮质激素性股骨头坏死(steroid-induced avascularnecrosis of femoral head,SANFH)是一类致残率较高的疾病,长期损害人类与社会健康,已成为亟待解决的社会问题。PI3K/AKT/mTOR信号通路是一条与细胞分化凋亡自噬等密切相关的转导通路。近年随着分子生物学和细胞生物学的进步发展,表明以此信号通路为切入点能够对SANFH进行有效的靶向调控,并通过促进成骨分化,抑制凋亡,修复血管内皮细胞以及调控自噬等多种途径,对骨细胞产生显著调控和影响。本文就PI3K/AKT/mTOR通路在SANFH中所发挥的调控机制和作用,以及各部分在激素性股骨头坏死中的表达作简要综述,为以后的研究治疗提供思路与依据。     

DPC4基因通过mTOR信号通路诱导胰腺癌细胞自噬

目的验证过表达DPC4基因对胰腺癌细胞增殖侵袭的抑制作用,探讨mTOR信号通路对其激活自噬的调控作用。方法构建DPC4过表达载体,转染胰腺癌JF305细胞,CCK-8、Transwell检测其对胰腺癌JF305细胞的增殖侵袭能力,透射电镜观察自噬小体,Western blotting法检测自噬相关蛋白Beclin-1、LC3-Ⅱ/Ⅰ、mTOR、p-mTOR、4EBP1、p-4EBP1的表达。结果过表达DPC4可以抑制胰腺癌细胞增殖和侵袭;激活自噬,电镜下DPC4过表达细胞中自噬颗粒明显增多;自噬相关蛋白Beclin-1和LC3-Ⅱ/Ⅰ在过表达DPC4的JF305细胞中表达升高,同时下调p-mTOR和p-4EBP1的表达水平。结论 DPC4基因可以抑制胰腺癌细胞增殖和侵袭能力,其作用机制与抑制mTOR信号通路、激活自噬相关。     

PI3K/AKT/mTOR信号通路在糖皮质激素性股骨头坏死中的表达与作用

糖皮质激素性股骨头坏死(steroid-induced avascularnecrosis of femoral head,SANFH)是一类致残率较高的疾病,长期损害人类与社会健康,已成为亟待解决的社会问题。PI3K/AKT/mTOR信号通路是一条与细胞分化凋亡自噬等密切相关的转导通路。近年随着分子生物学和细胞生物学的进步发展,表明以此信号通路为切入点能够对SANFH进行有效的靶向调控,并通过促进成骨分化,抑制凋亡,修复血管内皮细胞以及调控自噬等多种途径,对骨细胞产生显著调控和影响。本文就PI3K/AKT/mTOR通路在SANFH中所发挥的调控机制和作用,以及各部分在激素性股骨头坏死中的表达作简要综述,为以后的研究治疗提供思路与依据。     

组织因子途径抑制物与无复流

缺血再灌注损伤在无复流病理生理中起核心作用。自噬在缺血再灌注损伤病理过程中起"双刃剑"作用。组织因子途径抑制物对组织因子介导的伴有炎症通路和凝血系统激活的无复流可能起到有效地预防及治疗作用。现就组织因子途径抑制物、心肌无复流与自噬的关系做一综述。     

mTOR信号通路在冠心病的研究进展

哺乳动物雷帕霉素靶蛋白（mTOR）是一种非典型的丝氨酸/苏氨酸激酶,mTOR与特异性蛋白作用形成mTORC1和mTORC2两种复合物。mTOR信号通路在细胞的蛋白质合成、自噬、存活、应激中起着关键的调节作用。越来越多的研究表明mTOR信号通路在冠心病的发生、发展方面起着重要调控作用。本文主要讨论mTOR在冠心病中的作用机制研究。     

自噬在脑缺血中的双重作用

自噬是一种细胞内成分降解过程,分为启动、延伸、成熟以及自噬体降解等不同阶段,其作用与细胞损伤程度有关.自噬在饥饿、低氧等情况下适度激活,可促进细胞存活;而在脑缺血时过度激活,可导致细胞裂解和促进细胞死亡.预处理可能通过适当激活自噬而产生缺血耐受作用.自噬受到多种蛋白激酶、凋亡分子以及氧化应激通路的严格调控.     

Distinct roles of autophagy in the heart during ischemia and reperfusion: roles of AMP-activated protein kinase and Beclin 1 in mediating autophagy

Autophagy is an intracellular bulk degradation process for proteins and organelles. In the heart, autophagy is stimulated by myocardial ischemia. However, the causative role of autophagy in the survival of cardiac myocytes and the underlying signaling mechanisms are poorly understood. Glucose deprivation (GD), which mimics myocardial ischemia, induces autophagy in cultured cardiac myocytes. Survival of cardiac myocytes was decreased by 3-methyladenine, an inhibitor of autophagy, suggesting that autophagy is protective against GD in cardiac myocytes. GD-induced autophagy coincided with activation of AMP-activated protein kinase (AMPK) and inactivation of mTOR (mammalian target of rapamycin). Inhibition of AMPK by adenine 9-beta-d-arabinofuranoside or dominant negative AMPK significantly reduced GD-induced autophagy, whereas stimulation of autophagy by rapamycin failed to cause an additive effect on GD-induced autophagy, suggesting that activation of AMPK and inhibition of mTOR mediate GD-induced autophagy. Autophagy was also induced by ischemia and further enhanced by reperfusion in the mouse heart, in vivo. Autophagy resulting from ischemia was accompanied by activation of AMPK and was inhibited by dominant negative AMPK. In contrast, autophagy during reperfusion was accompanied by upregulation of Beclin 1 but not by activation of AMPK. Induction of autophagy and cardiac injury during the reperfusion phase was significantly attenuated in beclin 1(+/-) mice. These results suggest that, in the heart, ischemia stimulates autophagy through an AMPK-dependent mechanism, whereas ischemia/reperfusion stimulates autophagy through a Beclin 1-dependent but AMPK-independent mechanism. Furthermore, autophagy plays distinct roles during ischemia and reperfusion: autophagy may be protective during ischemia, whereas it may be detrimental during reperfusion.     

mTOR信号介导的自噬在褪黑素减轻心脏缺血/再灌注损伤中的作用

目的 探讨mTOR信号介导的自噬在褪黑素（melatonin,Mel）减轻心脏缺血/再灌注损伤中的作用。方法 将60只8周龄C57BL/6小鼠随机分为假手术（Sham）组、单纯褪黑素10 mg/(kg·d)处理(Mel)组、缺血/再灌注（ischemia reperfusion,I/R）组和褪黑素10 mg/(kg·d)干预I/R（Mel+I/R）组。采用冠状动脉左前降支结扎术制备心肌I/R模型,HE染色观察心肌组织形态学变化,试剂盒检测各组血清中LDH的含量,TUNEL染色检测各组细胞凋亡情况,蛋白印迹法（Western blot）检测自噬相关蛋白微管相关蛋白1轻链3（microtubule-associated protein 1 light chain 3,LC3）I和II、Beclin1和mTOR磷酸化的表达,免疫荧光染色法检测LC3B的表达。结果 与Sham组相比,Mel组各项指标均无明显变化;I/R组心肌纤维断裂明显排列紊乱,血清中LDH含量明显增加（P<0.01）,TUNEL阳性细胞明显增多（P<0.01）,LC3II和Beclin1表达显著升高（P<0.01）,而磷酸化mTOR的表达降低（P<0.01）,免疫荧光结果显示LC3B表达增加（P<0.01）; Mel+I/R组可明显减轻心肌纤维的断裂,降低血清中LDH含量（P<0.01）,减少TUNEL阳性细胞数（P<0.01）,减少LC3II和Beclin1的表达（P<0.01）,降低免疫荧光染色中LC3B的表达（P<0.01）。结论 褪黑素通过调节mTOR信号介导的自噬减轻心脏I/R损伤。     

老年人心肌细胞自噬的变化及其调控机制研究进展

心肌细胞自噬对维持正常心脏结构和功能起重要作用。近年来的研究结果表明老年人心肌细胞自噬功能降低,老年人心肌自噬基因Atg5、Atg7和Beclin1表达降低;心肌细胞自噬下调与磷脂酰肌醇3-激酶/丝氨酸-苏氨酸激酶/雷帕霉素靶蛋白和单磷酸腺苷激活的蛋白激酶及SIRT1信号通路失调有关;此外,活性氧及一些神经内分泌因子也可介导老年人心肌细胞自噬下调。调控心肌细胞自噬将为老年人心肌病的预防和治疗提供新的途径。     

Advances in intervention methods and brain protection mechanisms of in situ and remote ischemic postconditioning

Ischemic postconditioning (PostC) conventionally refers to a series of brief blood vessel occlusions and reperfusions, which can induce an endogenous neuroprotective effect and reduce cerebral ischemia/reperfusion (I/R) injury. Depending on the site of adaptive ischemic intervention, PostC can be classified as in situ ischemic postconditioning (ISPostC) and remote ischemic postconditioning (RIPostC). Many studies have shown that ISPostC and RIPostC can reduce cerebral IS injury through protective mechanisms that increase cerebral blood flow after reperfusion, decrease antioxidant stress and anti-neuronal apoptosis, reduce brain edema, and regulate autophagy as well as Akt, MAPK, PKC, and KATP channel cell signaling pathways. However, few studies have compared the intervention methods, protective mechanisms, and cell signaling pathways of ISPostC and RIPostC interventions. Thus, in this article, we compare the history, common intervention methods, neuroprotective mechanisms, and cell signaling pathways of ISPostC and RIPostC.

     

Urocortin inhibits Beclin1-mediated autophagic cell death in cardiac myocytes exposed to ischaemia/reperfusion injury

Autophagy is known to be a feature of cardiomyopathies and chronic ischaemia. Here we demonstrate that autophagy is also induced by a single cycle of ischaemia/reperfusion (I/R in neonatal and adult rat cardiac myocytes). Consistent with the critical role for Beclin1 in autophagocytosis, reduction of Beclin1 expression in cardiac myocytes by RNAi reduces I/R-induced autophagy and this is associated with enhanced cell survival. Autophagy is also reduced by urocortin, an endogenous cardiac peptide which we have previously shown to reduce other forms of myocyte cell death induced by I/R. The inhibition of autophagy by urocortin is mediated in part by inhibition of Beclin1 expression, an effect which is mediated by activation of the PI3 kinase/Akt pathway but which does not involve activation of p42/p44 MAPK.     

Chronic resistance training activates autophagy and reduces apoptosis of muscle cells by modulating IGF-1 and its receptors,Akt/mTOR and Akt/FOXO3a signaling in aged rats

Resistance exercise training (RET) remains the most effective treatment for the loss of muscle mass and strength in elderly people. However, the underlying cellular and molecular mechanisms are not well understood. Recent evidence suggests that autophagic signaling is altered in aged skeletal muscles. This study aimed to investigate if RET affects IGF-1 and its receptors, the Akt/mTOR, and Akt/FOXO3a signaling pathways and regulates autophagy and apoptosis in the gastrocnemius muscles of 18–20 month old rats. The results showed that 9 weeks of RET prevented the loss of muscle mass and improved muscle strength, accompanied by reduced LC3-II/LC3-I ratio, reduced p62 protein levels, and increased levels of autophagy regulatory proteins, including Beclin 1, Atg5/12, Atg7, and the lysosomal enzyme cathepsin L. RET also reduced cytochrome c level in the cytosol but increased its level in mitochondrial fraction, and inhibited cleaved caspase 3 production and apoptosis. Furthermore, RET upregulated the expression of IGF-1 and its receptors but downregulated the phosphorylation of Akt and mTOR. In addition, RET upregulated the expression of total AMPK, phosphorylated AMPK, and FOXO3a. Taken together, these results suggest that the benefits of RET are associated with increased autophagy activity and reduced apoptosis of muscle cells by modulating IGF-1 and its receptors, the Akt/mTOR and Akt/FOXO3a signaling pathways in aged skeletal muscles.     

New concepts in reactive oxygen species and cardiovascular reperfusion physiology

Increasingly complex behavior of free radicals and reactive oxygen species (ROS) are noted within biological systems. Classically free radicals and ROS were considered injurious, however current mechanisms describe both protective and deleterious effects. A burst of ROS has been well described with the first moments of reperfusion and is associated with injury. However ROS can also be protective as signal preconditioning protection and induce stress responses that lead to survival. ROS generation is appreciated to occur during ischemia despite the low oxygen tension, from a likely mitochondria source, and ROS-induced ROS release may amplify its signal. The burst of ROS seen during reperfusion may originate from a different cellular source than during ischemia and is not yet fully identified. ROS and cellular redox conditions regulate a large number of vital pathways (energy metabolism, survival/stress responses, apoptosis, inflammatory response, oxygen sensing, etc). While cellular systems may demonstrate reperfusion injury, whole organ and animal models continue to report contradictory results on reperfusion injury and the role of antioxidants as a therapy. Collectively, these data may offer insight into why clinical trials of antioxidants have had such mixed and mostly negative results. Future antioxidant therapies are likely to be effective but they must become: more specific for site of action, not have deleterious effects on other signaling pathways, be targeted to a specific reactive oxygen species or cellular compartment, and be "time sensitive" so they deliver the correct therapy at precisely the correct time in ischemia and reperfusion.     

Too much or not enough of a good thing — The Janus faces of autophagy in cardiac fuel and protein homeostasis

Cells respond to changes in their environment and in their intracellular milieu by altering specific pathways of protein synthesis and degradation. Autophagy is a highly conserved catabolic process involved in the degradation of long-lived proteins, damaged organelles, and subcellular structures. The process is orchestrated by the autophagy related protein (Atg) to form the double-membrane structure autophagosomes, which then fuse with lysosomes to generate autophagolysosomes where subcellular contents are degraded for a variety of cellular processes. Alterations in autophagy play an important role in diseases including cancer, neurodegenerative diseases, aging, metabolic diseases, inflammation and cardiovascular diseases. In the latter, dysregulated autophagy is speculated to contribute to the onset and development of atherosclerosis, ischemia/reperfusion injury, cardiomyopathy, diabetes mellitus, and hypertension. Autophagy may be both adaptive and beneficial for cell survival, or maladaptive and detrimental for the cell. Basal autophagy plays an essential role in the maintenance of cellular homeostasis whereas excessive autophagy may lead to autophagic cell death. The point and counterpoint discussion highlights adaptive vs. maladaptive autophagy. In this review, we discuss the molecular control of autophagy, focusing particularly on the regulation of physiologic vs. defective autophagy.     

How does the heart (not) die? The role of autophagy in cardiomyocyte homeostasis and cell death

Autophagy plays a critical and seemingly dual-purposed role in cardiomyocytes, being implicated as a mechanism of both cellular survival, for example, during ischemia/reperfusion injury and a mechanism of cell death at stages in which progressive myocyte alterations are beyond repair. This review aims to highlight the current literature as it relates to autophagy in cardiomyocytes. It provides background into the mechanisms of cell death, discusses the details that are known about the ubiquitin proteasome system and autophagy, delves into the pathways that are known to initiate and inhibit autophagy, and comments on the role of autophagy in cardiomyocyte homeostasis and cell death.