同型半胱氨酸通过抑制心肌线粒体自噬诱导线粒体损伤

本研究旨在探究同型半胱氨酸(Hcy)与心肌细胞线粒体自噬及线粒体损伤的关系。通过高蛋氨酸饮食法构建高同型半胱氨酸血症(HHcy)大鼠模型,利用免疫荧光共定位染色法和Western blot检测HHcy大鼠心肌的线粒体自噬水平。运用透射电镜观察HHcy大鼠心肌的线粒体形态结构的改变。体外培养H9C2细胞,用Hcy刺激H9C2,利用流式细胞术和JC-1染色法检测线粒体膜电位(MMP)的改变。采用18F-FDG PET/CT在体心肌代谢成像技术检测心肌葡萄糖摄取情况以及直接检测心肌组织的三磷酸腺苷(ATP)含量来评价HHcy大鼠心肌的能量供应情况。结果显示,与正常对照组相比,在HHcy大鼠模型心肌组织中,线粒体自噬水平降低;线粒体排列紊乱,轮廓模糊,膜破损溶解,嵴消失;Hcy刺激的H9C2细胞,线粒体膜电位降低,膜结构完整性受损。HHcy大鼠心肌葡萄糖摄取率增加,ATP含量下降。结果提示,同型半胱氨酸可通过抑制心肌线粒体自噬诱导线粒体损伤。     

PINK1/Parkin介导的线粒体自噬在眼科疾病中作用的研究进展

线粒体自噬作为一种选择性自噬过程,通过清除受损和多余线粒体来维持细胞正常生理功能。线粒体自噬与多种眼科疾病的发生发展有密切联系,而PINK1/Parkin信号通路作为线粒体自噬的主要通路之一,在白内障、青光眼、年龄相关性黄斑变性等多种眼科疾病中发挥了重要作用,靶向该通路的治疗手段也为多种眼科疾病的治疗提供了新思路。本文将对PINK1/Parkin介导的线粒体自噬通路在眼科疾病中的相关作用及机制进行综述,以期深入了解线粒体自噬在眼科相关疾病中的影响与价值。     

Ginseng Saponin Enriched in Rh1 and Rg2 Ameliorates Nonalcoholic Fatty Liver Disease by Inhibiting Inflammasome Activation

Nonalcoholic fatty liver disease (NAFLD) is becoming one of the most common chronic liver diseases in the world. One of the features of NAFLD is hepatic fat accumulation, which further causes hepatic steatosis, fibrosis, and inflammation. Saponins, the major pharmacologically active ingredients isolated from Panax notoginseng, contain several ginsenosides, which have various pharmacological and therapeutic functions. However, the ginsenoside-specific molecular mechanism of saponins in NAFLD remains unknown. This study aimed to elucidate the effects of ginseng saponin extract and its ginsenosides on hepatic steatosis, fibrosis, and inflammation and their underlying action mechanism in NAFLD. Mice were fed a fast food diet (FFD) for 16 weeks to induce NAFLD and then treated with saponin extract (50 or 150 mg/kg) for the remaining nine weeks to determine the effects of saponin on NAFLD. Saponin extract administration significantly alleviated FFD-induced hepatic steatosis, fibrosis, and inflammation. Particularly, saponin extract, compared with conventional red ginseng, contained significantly increased amounts of ginsenosides (Rh1 (10.34-fold) and Rg2 (7.1-fold)). In vitro Rh1 and Rg2 treatments exerted an anti-steatotic effect in primary hepatocytes, an antifibrotic effect in hepatic stellate cells, and anti-inflammatory and pro-mitophagy effects in immortalized mouse Kupffer cells. Mechanistically, saponin extract alleviated lipopolysaccharide-induced NLRP3 inflammasome activation by promoting mitophagy. In conclusion, saponin extract inhibited inflammation-mediated pathological inflammasome activation in macrophages, thereby preventing NAFLD development. Thus, saponin extract administration may be an alternative method for NAFLD prevention.     

Melatonin attenuates myocardial ischemia‐reperfusion injury via improving mitochondrial fusion/mitophagy and activating the AMPK‐OPA1 signaling pathways

Optic atrophy 1 (OPA1)‐related mitochondrial fusion and mitophagy are vital to sustain mitochondrial homeostasis under stress conditions. However, no study has confirmed whether OPA1‐related mitochondrial fusion/mitophagy is activated by melatonin and, consequently, attenuates cardiomyocyte death and mitochondrial stress in the setting of cardiac ischemia‐reperfusion (I/R) injury. Our results indicated that OPA1, mitochondrial fusion, and mitophagy were significantly repressed by I/R injury, accompanied by infarction area expansion, heart dysfunction, myocardial inflammation, and cardiomyocyte oxidative stress. However, melatonin treatment maintained myocardial function and cardiomyocyte viability, and these effects were highly dependent on OPA1‐related mitochondrial fusion/mitophagy. At the molecular level, OPA1‐related mitochondrial fusion/mitophagy, which was normalized by melatonin, substantially rectified the excessive mitochondrial fission, promoted mitochondria energy metabolism, sustained mitochondrial function, and blocked cardiomyocyte caspase‐9‐involved mitochondrial apoptosis. However, genetic approaches with a cardiac‐specific knockout of OPA1 abolished the beneficial effects of melatonin on cardiomyocyte survival and mitochondrial homeostasis in vivo and in vitro. Furthermore, we demonstrated that melatonin affected OPA1 stabilization via the AMPK signaling pathway and that blockade of AMPK repressed OPA1 expression and compromised the cardioprotective action of melatonin. Overall, our results confirm that OPA1‐related mitochondrial fusion/mitophagy is actually modulated by melatonin in the setting of cardiac I/R injury. Moreover, manipulation of the AMPK‐OPA1‐mitochondrial fusion/mitophagy axis via melatonin may be a novel therapeutic approach to reduce cardiac I/R injury.     

Three‐dimensional analysis of somatic mitochondrial dynamics in fission‐deficient injured motor neurons using FIB/SEM

Mitochondria undergo morphological changes through fusion and fission for their quality control, which are vital for neuronal function. In this study, we examined three‐dimensional morphologies of mitochondria in motor neurons under normal, nerve injured, and nerve injured plus fission‐impaired conditions using the focused ion beam/scanning electron microscopy (FIB/SEM), because the FIB/SEM technology is a powerful tool to demonstrate both 3D images of whole organelle and the intra‐organellar structure simultaneously. Crossing of dynamin‐related protein 1 (Drp1) gene‐floxed mice with neuronal injury‐specific Cre driver mice, Atf3:BAC Tg mice, allowed for Drp1 ablation specifically in injured neurons. FIB/SEM analysis demonstrated that somatic mitochondrial morphologies in motor neurons were not altered before or after nerve injury. However, the fission impairment resulted in prominent somatic mitochondrial enlargement, which initially induced complex morphologies with round regions and long tubular processes, subsequently causing a decrease in the number of processes and further enlargement of the round regions, which eventually resulted in big spheroidal mitochondria without processes. The abnormal mitochondria exhibited several degradative morphologies: local or total cristae collapse, vacuolization, and mitophagy. These suggest that mitochondrial fission is crucial for maintaining mitochondrial integrity in injured motor neurons, and multiple forms of mitochondria degradation may accelerate neuronal degradation.     

Loss of autophagy in erythroid cells leads to defective removal of mitochondria and severe anemia in vivo

Timely elimination of damaged mitochondria is essential to protect cells from the potential harm of disordered mitochondrial metabolism and release of proapoptotic proteins. In mammalian red blood cells, the expulsion of the nucleus followed by the removal of other organelles, such as mitochondria, are necessary differentiation steps. Mitochondrial sequestration by autophagosomes, followed by delivery to the lysosomal compartment for degradation (mitophagy), is a major mechanism of mitochondrial turnover. Here we show that mice lacking the essential autophagy gene Atg7 in the hematopoietic system develop severe anemia. Atg7^−/− erythrocytes accumulate damaged mitochondria with altered membrane potential leading to cell death. We find that mitochondrial loss is initiated in the bone marrow at the Ter119⁺/CD71^High stage. Proteomic analysis of erythrocyte ghosts suggests that in the absence of autophagy other cellular degradation mechanisms are induced. Importantly, neither the removal of endoplasmic reticulum nor ribosomes is affected by the lack of Atg7. Atg7 deficiency also led to severe lymphopenia as a result of mitochondrial damage followed by apoptosis in mature T lymphocytes. Ex vivo short-lived hematopoietic cells such as monocytes and dendritic cells were not affected by the loss of Atg7. In summary, we show that the selective removal of mitochondria by autophagy, but not other organelles, during erythropoeisis is essential and that this is a necessary developmental step in erythroid cells.     

Induced pluripotent stem cell‐based modeling of mutant LRRK2‐associated Parkinson's disease

Recent advances in cell reprogramming have enabled assessment of disease‐related cellular traits in patient‐derived somatic cells, thus providing a versatile platform for disease modeling and drug development. Given the limited access to vital human brain cells, this technology is especially relevant for neurodegenerative disorders such as Parkinson's disease (PD) as a tool to decipher underlying pathomechanisms. Importantly, recent progress in genome‐editing technologies has provided an ability to analyze isogenic induced pluripotent stem cell (iPSC) pairs that differ only in a single genetic change, thus allowing a thorough assessment of the molecular and cellular phenotypes that result from monogenetic risk factors. In this review, we summarize the current state of iPSC‐based modeling of PD with a focus on leucine‐rich repeat kinase 2 (LRRK2), one of the most prominent monogenetic risk factors for PD linked to both familial and idiopathic forms. The LRRK2 protein is a primarily cytosolic multi‐domain protein contributing to regulation of several pathways including autophagy, mitochondrial function, vesicle transport, nuclear architecture and cell morphology. We summarize iPSC‐based studies that contributed to improving our understanding of the function of LRRK2 and its variants in the context of PD etiopathology. These data, along with results obtained in our own studies, underscore the multifaceted role of LRRK2 in regulating cellular homeostasis on several levels, including proteostasis, mitochondrial dynamics and regulation of the cytoskeleton. Finally, we expound advantages and limitations of reprogramming technologies for disease modeling and drug development and provide an outlook on future challenges and expectations offered by this exciting technology.     

Mitochondrial integrity in neurodegeneration

The mitochondrion is a unique organelle with a diverse range of functions. Mitochondrial dysfunction is a key pathological process in several neurodegenerative diseases. Mitochondria are mostly important for energy production; however, they also have roles in Ca²⁺ homeostasis, ROS production, and apoptosis. There are two major systems in place, which regulate mitochondrial integrity, mitochondrial dynamics, and mitophagy. These two processes remove damaged mitochondria from cells and protect the functional mitochondrial population. These quality control systems often become dysfunctional during neurodegenerative diseases, such as Parkinson's and Alzheimer's disease, causing mitochondrial dysfunction and severe neurological symptoms.     

BNIP3表达变化与脑缺血损伤关系的研究

目的观察大鼠永久性大脑中动脉闭塞(permanent middle cerebral artery occlusion,pMCAO)不同时间点脑损伤情况、Bcl-2/腺病毒E1B19kD相互作用蛋白3(Bcl-2/adenovirus E1B-19kDa-interacting protein 3,BNIP3)及线粒体自噬相关蛋白的表达,探讨BNIP3与脑缺血损伤程度的关系。方法将健康雄性SD大鼠随机分为假手术组(sham组,即pMCAO 0h组)、pMCAO 3h组、9h组和24h组,每组12只。分别采用TTC染色检测大鼠脑梗死体积、透射电镜观察线粒体形态变化、Western blot检测BNIP3及相关蛋白表达。结果 (1)各组大鼠脑梗死体积变化:sham组TTC染色显示无梗死发生,其余3组均存在脑梗死区。pMCAO 3h、9h、24h组矫正脑梗死体积〔分别为(12.12±2.15)%、(37.00±4.24)%和(51.82±4.39)%〕均明显高于sham组(均P0.01),且随缺血时间延长而矫正脑梗死体积增加(四组间两两比较,均P0.01)。(2)各组大鼠脑组织中线粒体形态变化:sham组透射电镜可以观察到完整的双层线粒体膜结构;pMCAO 3h和9h组观察到典型的线粒体自噬现象:具有双层膜结构的线粒体自噬溶酶体;pMCAO 24h组线粒体受损严重,嵴消失,膜破损,线粒体肿胀加剧,未观察到线粒体自噬现象。(3)各组BNIP3和线粒体自噬相关蛋白表达:与sham组比较,pMCAO 3h和9h组BNIP3和自噬诱导分子Beclin-1表达增加,自噬标记分子LC3-Ⅱ/Ⅰ比值升高,接头蛋白P62和线粒体标记分子热休克蛋白60(heat shockprotein-60,HSP60)、线粒体外膜易位酶(translocase of outer mitochondrial membrane 20,TOM20)表达下降(均P0.01);与pMCAO 9h组比较,pMCAO 24h组BNIP3和Beclin-1表达下降,LC3-Ⅱ/Ⅰ比值降低,P62和TOM20、HSP60表达增加(均P0.01)。结论 BNIP3很可能在脑缺血早期通过促进线粒体自噬来发挥对脑缺血损伤的保护作用。     

心磷脂外化在创伤性脑损伤中的研究进展

创伤性脑损伤(TBI)造成严重的神经损伤,为社会和个人带来巨大经济负担,然而目前保护神经的有效治疗方法还比较缺乏,成为一个亟待解决的问题.线粒体特异性脂质-心磷脂(CL)对TBI的治疗作用在基础研究中显示出希望.本文围绕CL在神经细胞凋亡和线粒体自噬两方面的研究作一综述,重点介绍CL外化介导的线粒体自噬机制及其在脑损伤...