转录因子EB介导的自噬溶酶体途径在心血管疾病中的作用

转录因子EB是自噬和溶酶体的主要调控因子,可调节自噬和溶酶体,改善心血管疾病进程。该文介绍转录因子EB的生物学特点、调控机制及其介导自噬和溶酶体途径参与心血管疾病发生发展的机制。     

心肌肥厚对核转录因子C/EBPβ和心肌自噬的影响

背景心肌肥厚初期心肌细胞自噬机制受到抑制,而核转录因子C/EBPβ和TFEB被认为参与自噬-溶酶体体系的调控。目的探讨核转录因子C/EBPβ和TFEB在腹主动脉结扎型和甲状腺素功能亢进型肥厚心肌中的表达及心肌自噬与心肌肥厚的关系。方法 32只雄性SD大鼠被随机分配到甲状腺素注射(T3)组、生理盐水注射(对照)组、腹主动脉结扎(TAC)组和假手术组。分别采取腹主动脉缩窄法和甲状腺素腹腔注射法构建心肌肥厚早期模型。采用超声和称量评估心室肥厚程度,运用免疫荧光共聚焦显微镜成像技术和免疫印迹检测心肌自噬微管相关蛋白轻链3(LC3)蛋白表达及LC3-Ⅰ转化LC3-Ⅱ程度,通过亚细胞结构技术分离细胞核-细胞质联合蛋白印迹检测核转录因子C/EBPβ和TFEB在细胞核的表达情况。结果称量检测心体比显示,对照组心体比小于T3组(3.12±0.07比4.24±0.11,P<0.01),假手术组心体比小于TAC组(3.20±0.16比4.69±0.20,P<0.01);心脏超声检测显示TAC组和T3组均出现心脏室壁增厚的形态学改变;免疫荧光技术显示TAC组和T3组均出现LC3标记荧光减弱;免疫印迹检测提示,相对于对照组,T3组细胞核C/EBPβ表达下调,而LC3-Ⅰ转化LC3-Ⅱ减少(均P<0.05);相对于假手术组,TAC组细胞核C/EBPβ表达下调,LC3-Ⅰ转化LC3-Ⅱ也减少(均P<0.05)。结论心肌肥厚初期自噬减少促进心肌重构,而核转录因子C/EBPβ下调可能参与其中。     

心肌自噬研究进展

多数学者将细胞的死亡形式分为凋亡性程序性细胞死亡(Apoptosis)、自噬性程序性细胞死亡(Autophagy)和细胞坏死(Necrosis)3种类型.自噬(Autophagy)是凋亡之外的第二种程序性细胞死亡方式,在进化中高度保守,从酵母、果蝇到脊椎动物和人都可以找到参与自噬的同源基因.相对于主要降解短半衰期蛋白质的泛素-蛋白酶体系统,自噬参与降解绝大多数长半衰期蛋白质[1].在正常和轻微应激下,作为一种细胞保护机制,自噬能降解和回收细胞器组分,如长半衰期蛋白并选择性移除受损线粒体.     

自噬调控衰老的研究进展

随着机体老化,组织器官可发生不可逆退行性改变,这些变化与疾病和死亡密切相关。自噬是细胞内一种重要的分解代谢过程,在维持细胞稳态和促进长寿中起重要作用,机体衰老后,其自噬调节能力也随之下降。本文综述了自噬与衰老相关疾病的关系,明确自噬调控衰老的相关分子机制可能为治疗衰老相关疾病提供新的靶点。     

自噬与心肌衰老及心血管疾病关系的研究进展

真核细胞降解细胞内物质主要通过2条途径--蛋白酶体降解和自噬(autophagy)降解[1].蛋白酶体主要降解细胞内短寿命蛋白质;细胞内几乎全部的长寿蛋白质、多数大分子物质以及所有的细胞器都通过自噬作用被运输到溶酶体内降解,以实现细胞本身的代谢需要和细胞器的更新.     

TFEB的翻译后修饰对自噬的调节作用

转录因子EB(TFEB)是小眼畸形相关转录因子家族成员,通过调节自噬-溶酶体相关基因的表达在脂质代谢等多种生物过程中发挥重要作用。TFEB的活性与细胞定位可通过蛋白质的翻译后修饰进行调节。本文就TFEB翻译后修饰对自噬的调节作用进行综述,旨在加深对动脉粥样硬化等自噬异常所致疾病发病机制的理解,为相应疾病的防治提供新的思路和干预靶点。     

细胞自噬对衰老的调节

细胞内损伤物质的积累是所有衰老细胞的普遍特征,能导致生命有机体生存能力降低.细胞自噬能够降解受损蛋白质和衰老或损伤细胞器等细胞结构,是细胞内主要的异化途径,参与衰老以及与衰老相关的各种病理过程.近年来研究发现,衰老进程中,细胞自噬活动下调,而对各种长寿突变体的研究表明自噬活动是寿命延长所必需的,多种自噬相关基因或蛋白直接受长寿途径的调节[1~5],这些发现都支持细胞自噬是各种真核生物衰老非常重要的调节机制.     

自噬与血管衰老的研究进展

<正>自噬是由细胞质起源的自噬体与溶酶体融合降解胞内异常分子和长寿命蛋白的过程,是一种特殊分解代谢途径。它在细胞代谢、存活与分化等方面都具有重要作用。当前社会正朝向老龄化社会演变,关注老龄化相关疾病的研究显得格外重要。随着细胞生物科学与老年医学的相互交叉发展,自噬在老年性心血管疾病、神经退行性疾病、脏器衰老等方面的研究中取得进展。研究已发现通过对自噬调控能够对血管组成细胞的增殖、分化和转归起到重要的调控作用。本文对自噬与血管     

The role of calcium in the age-related decline of neutrophil function

Upon activation by formyl-methionyl-leucyl-phenylalanine (FMLP), either in the presence of absence of cytochalasin B, neutrophils from old subjects generated significantly less superoxide than did neutrophils from the young. This reduction in activity was associated with a significant decrease in the basal cytosolic calcium concentration and a diminished flux of calcium to the cytosol after activation. At all concentrations of FMLP tested, cytosolic calcium remained significantly lower in neutrophils from the old as compared with the young, whereas permeability to extracellular calcium and efflux of calcium from the cell were also significantly diminished. Pretreatment of the cell with the ionophore ionomycin elevated the cytosolic calcium concentration and significantly improved function in old neutrophils. These findings demonstrate that aging results in alterations in neutrophil calcium homeostasis that may play a role in the age-related decline in neutrophil function.     

The role of muscle loss in the age-related decline of grip strength: cross-sectional and longitudinal perspectives

The decline of strength with age has often been attributed to declining muscle mass in older subjects. To investigate factors which might influence changes in strength across the life span, grip strength and muscle mass (as estimated by creatinine excretion and forearm circumference) were measured in 847 healthy volunteers, aged 20-100 years, from the Baltimore Longitudinal Study of Aging. Cross-sectional and longitudinal results concur that grip strength increases into the thirties and declines at an accelerating rate after age 40. However, the grip strength of 48% of subjects less than 40 years old, 29% of individuals 40-59 years old, and 15% of subjects older than 60 did not decline during the average 9-year follow-up. Grip strength is strongly correlated with muscle mass (r = .60, p less than .0001). However, using multiple regression analysis, grip strength is more strongly correlated with age (partial r2 = .38) than muscle mass (partial r2 = .16). Additionally, a residuals analysis demonstrates that younger subjects are stronger and older subjects are weaker than one would predict based on their muscular size. Thus, while strength losses are partially explained by declining muscle mass, there remain other yet undetermined factors beyond declining muscle mass to explain some of the loss of strength seen with aging.     

Chronic akt activation accentuates aging-induced cardiac hypertrophy and myocardial contractile dysfunction: role of autophagy

Aging is often accompanied with geometric and functional changes in the heart, although the underlying mechanisms remain unclear. Recent evidence has described a potential role of Akt and autophagy in aging-associated organ deterioration. This study was to examine the impact of cardiac-specific Akt activation on aging-induced cardiac geometric and functional changes and underlying mechanisms involved. Cardiac geometry, contractile and intracellular Ca²⁺ properties were evaluated using echocardiography, edge-detection and fura-2 techniques. Level of insulin signaling and autophagy was evaluated by western blot. Our results revealed cardiac hypertrophy (enlarged chamber size, wall thickness, myocyte cross-sectional area), fibrosis, decreased cardiac contractility, prolonged relengthening along with compromised intracellular Ca²⁺ release and clearance in aged (24–26 month-old) mice compared with young (3–4 month-old) mice, the effects of which were accentuated by chronic Akt activation. Aging enhanced Akt and mTOR phosphorylation while reducing that of PTEN, AMPK and ACC with a more pronounced response in Akt transgenic mice. GSK3β phosphorylation and eNOS levels were unaffected by aging or Akt overexpression. Levels of beclin-1, Atg5 and LC3-II-to-LC3-I ratio were decreased in aged hearts, the effect of which with the exception of Atg 5 was exacerbated by Akt overactivation. Levels of p62 were significantly enhanced in aged mice with a more pronounced increase in Akt mice. Neither aging nor Akt altered β-glucuronidase activity and cathepsin B although aging reduced LAMP1 level. In addition, rapamycin reduced aging-induced cardiomyocyte contractile and intracellular Ca²⁺ dysfunction while Akt activation suppressed autophagy in young but not aged cardiomyocytes. In conclusion, our data suggest that Akt may accentuate aging-induced cardiac geometric and contractile defects through a loss of autophagic regulation.     

The role and modulation of autophagy in experimental models of myocardial ischemia-reperfusion injury

A physiological sequence called autophagy qualitatively determines cellular viability by removing protein aggregates and damaged cyto-plasmic constituents, and contributes significantly to the degree of myocardial ischemia-reperfusion （I/R） injury. This tightly orchestrated cata-bolic cellular‘housekeeping’ process provides cells with a new source of energy to adapt to stressful conditions. This process was first described as a pro-survival mechanism, but increasing evidence suggests that it can also lead to the demise of the cell. Autophagy has been implicated in the pathogenesis of multiple cardiac conditions including myocardial I/R injury. However, a debate persists as to whether autophagy acts as a protec-tive mechanism or contributes to the injurious effects of I/R injury in the heart. This controversy may stem from several factors including the va-riability in the experimental models and species, and the methodology used to assess autophagy. This review provides updated knowledge on the modulation and role of autophagy in isolated cardiac cells subjected to I/R, and the growing interest towards manipulating autophagy to increase the survival of cardiac myocytes under conditions of stress-most notably being I/R injury. Perturbation of this evolutionarily conserved intracellular cleansing autophagy mechanism, by targeted modulation through, among others, mammalian target of rapamycin （mTOR） inhibitors, adenosine monophosphate-activated protein kinase （AMPK） modulators, calcium lowering agents, resveratrol, longevinex, sirtuin activators, the proapoptotic gene Bnip3, IP3 and lysosome inhibitors, may confer resistance to heart cells against I/R induced cell death. Thus, therapeutic ma-nipulation of autophagy in the challenged myocardium may benefit post-infarction cardiac healing and remodeling.