Changes in autophagy proteins in a rat model of controlled cortical impact induced brain injury

Autophagy has been implicated in several neurodegenerative diseases and recently its role in acute brain injury has received increased interest. In our study, we investigated the profiles of autophagy-linked proteins (MAP-LC3 (Atg8), beclin-1 (Atg6) and the beclin-1-binding protein, bcl-2, following controlled cortical impact injury in rats—a model for moderate-to-severe traumatic brain injury. We observed significant increases in the levels of the processed form of LC3 (LC3-II) in the ipsilateral cortex 2 h to 2 days after injury when compared to sham. Furthermore, the beclin-1/bcl-2 ratio in the ipsilateral cortex was found to have increased from 1 and 2 days after injury. Since both of these changes are established autophagy-enabling events, and, based on these data, we propose that autophagy, plays a role in the manifestation of cell injury following brain trauma.     

自噬在肝脏蛋白质和脂质代谢中的作用

自噬是一个通过降解细胞组分如细胞器和蛋白质等以维持细胞存活和功能的重要的溶酶体途径。肝脏作为新陈代谢的中枢器官,肝脏高度依赖于自噬以发挥正常功能并防止疾病发展。肝细胞自噬的改变参与肝损伤,脂肪肝等肝病的病理变化,以自噬为靶点寻求治疗各种肝病的方法已成为热点研究领域,但自噬在肝脏蛋白质和脂质代谢中的作用极其机制尚不清楚。本文对自噬在肝脏蛋白质和脂质代谢中的作用的最新进展进行综述。     

自噬在肝再生中的作用

自噬是存在于真核细胞内的一种溶酶体依赖性的降解途径,在肝脏生理和病理过程中发挥着重要作用。肝脏具有强大的再生能力,在受到急、慢性损伤时,残肝细胞将会被激活进入细胞周期进行细胞增殖,以补偿丢失的肝组织和恢复肝功能。文章阐述了各种类型损伤之后的肝再生与自噬的关系。在物理性、酒精、食源性等因素引起的肝损伤中,肝脏通过启动自噬来促进肝再生;在化学性损伤的肝再生模型中,自噬在其中的作用仍然有争议;在病毒感染之后的肝再生中,一些嗜肝病毒（如丙肝病毒和乙肝病毒等）反而利用自噬来促进病毒颗粒复制,抑制肝再生。对自噬和肝再生机制的研究,将有助于进一步阐明再生过程,为治疗肝脏疾病提供新方法。     

Intersection of autophagy regulation and circadian rhythms in the heart

Autophagy is a vital cellular mechanism that controls the removal of damaged or dysfunctional cellular components. Autophagy allows the degradation and recycling of damaged proteins and organelles into their basic constituents of amino acids and fatty acids for cellular energy production. Under basal conditions, autophagy is essential for the maintenance of cell homeostasis and function. However, during cell stress, excessive activation of autophagy can be destructive and lead to cell death. Autophagy plays a crucial role in the cardiovascular system and helps to maintain normal cardiac function. During ischemia- reperfusion, autophagy can be adaptive or maladaptive depending on the timing and extent of activation. In this review, we highlight the molecular mechanisms and signaling pathways that underlie autophagy in response to cardiac stress and therapeutic approaches to modulate autophagy by pharmacological interventions. Finally, we also discuss the intersection between autophagy and circadian regulation in the heart. Understanding the mechanisms that underlie autophagy following cardiac injury can be translated to clinical cardiology use toward improved patient treatment and outcomes.     

Autophagy is increased in mice after traumatic brain injury and is detectable in human brain after trauma and critical illness

Autophagy is a homeostatic process for recycling of proteins and organelles, that increases during times of nutrient deprivation and is regulated by reactive oxygen species. We reported that autophagy can also be induced after traumatic brain injury (TBI) in mice.1 Specifically, autophagosomes and multilamellar bodies were frequently observed in cell processes and axons in injured brain regions by electron microscopy, and lipidated microtubule-associated protein light chain 3 (LC3-II), was increased after TBI vs. controls. To determine if antioxidants could reduce autophagy, separate mice were treated with the antioxidant ?-glutamylcysteinyl ethyl ester (GCEE). Treatment with GCEE preserved total antioxidant reserves, reduced LC3-II in injured brains, and improved both behavioral and histological outcome after TBI. Here we report that LC3-II and autophagosomes were detectable in brain tissue from humans after TBI. Taken together, we show that autophagy occurs after both experimental and clinical TBI, and that oxidative stress contributes to overall neuropathology after TBI in mice, at least in part by initiating or influencing autophagy.     

Role of autophagy in early brain injury after subarachnoid hemorrhage in rats

Early brain injury (EBI) occurred after aneurismal subarachnoid hemorrhage (SAH) strongly determined the patients’ prognosis. Autophagy was activated in neurons in the acute phase after SAH, while its role in EBI has not been examined. This study was designed to explore the effects of autophagy on EBI post-SAH in rats. A modified endovascular perforating SAH model was established under monitoring of intracranial pressure. Extent of autophagy was regulated by injecting autophagy-regulating drugs (3-methyladenine, wortmannin and rapamycin) 30 min pre-SAH intraventricularly. Simvastatin (20 mg/kg) was prophylactically orally given 14 days before SAH induction. Mortality, neurological scores, brain water content and blood–brain barrier (BBB) permeability were evaluated at 24 h post-SAH. Microtubule-associated protein light chain-3 (LC3 II/I) and beclin-1 were detected for monitoring of autophagy flux. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick end labeling, expression of cleaved caspase-3 and cytoplasmic histone-associated DNA fragments were used to detect apoptosis. The results showed that mortality was reduced in rapamycin and simvastatin treated animals. When autophagy was inhibited by 3-methyladenine and wortmannin, the neurological scores were decreased, brain water content and BBB permeability were further aggravated and neuronal apoptosis was increased when compared with the SAH animals. Autophagy was further activated by rapamycin and simvastatin, and apoptosis was inhibited and EBI was ameliorated. The present results indicated that activation of autophagy decreased neuronal apoptosis and ameliorated EBI after SAH. Aiming at autophagy may be a potential effective target for preventing EBI after SAH.     

自噬及其在肺部疾病中作用研究进展

自噬作为一种新的细胞程序化死亡方式,在维持细胞内环境稳态中起着重要作用。它由溶酶体介导,对细胞内衰老细胞器或受损蛋白质进行再次利用,以补充细胞在"饥饿"状态下的物质供给。自噬曾被认为是细胞对氧化应激的随机自我保护性反应,然而最近研究发现自噬体的形成具有选择性和高度保守性的特点。目前研究发现自噬在COPD、肺气肿、肺纤维化、肺动脉高压、急性肺损伤、肺肿瘤等肺部疾病中起重要作用。本文通过分析总结自噬信号传导机制及其在肺部疾病中的相关作用,以阐明肺部疾病的可能发生机制,从而指导相关疾病的临床治疗。     

Targeting autophagy for drug-induced hepatotoxicity

Autophagy is a lysosomal degradation pathway for bulk cytosolic proteins and damaged organelles, and is well known to act as a cell survival mechanism. Acetaminophen (APAP) overdose can cause liver injury in animals and humans by inducing necrosis due to mitochondrial damage. We recently found that pharmacological induction of autophagy by rapamycin protects against, whereas pharmacological suppression of autophagy by chloroquine exacerbates, APAP-induced liver injury in mice. Autophagy is induced to remove APAP-induced damaged mitochondria and thus attenuates APAP-induced hepatocyte necrosis. To our surprise, we found that liver-specific Atg5 knockout mice are not more susceptible, but are resistant to APAP-induced liver injury due to compensatory effects. Our work suggests that pharmacological modulation of autophagy is a novel therapeutic approach to ameliorate APAP-induced liver injury. Moreover, our work also suggests that caution needs to be exercised when using genetic autophagy gene knockout mice for pathophysiological studies.     

Autophagy and genomic integrity

DNA lesions, constantly produced by endogenous and exogenous sources, activate the DNA damage response (DDR), which involves detection, signaling and repair of the damage. Autophagy, a lysosome-dependent degradation pathway that is activated by stressful situations such as starvation and oxidative stress, regulates cell fate after DNA damage and also has a pivotal role in the maintenance of nuclear and mitochondrial genomic integrity. Here, we review important evidence regarding the role played by autophagy in preventing genomic instability and tumorigenesis, as well as in micronuclei degradation. Several pathways governing autophagy activation after DNA injury and the influence of autophagy upon the processing of genomic lesions are also discussed herein. In this line, the mechanisms by which several proteins participate in both DDR and autophagy, and the importance of this crosstalk in cancer and neurodegeneration will be presented in an integrated fashion. At last, we present a hypothetical model of the role played by autophagy in dictating cell fate after genotoxic stress.     

几个能量代谢相关蛋白在HeLa细胞自噬过程中表达下调

自噬是真核细胞中的一种保守的代谢信号通路。人们已经知道自噬与肿瘤发生等疾病密切相关,但对于自噬的分子机制仍然不是很清楚。鉴定更多的自噬相关蛋白对于进一步阐明自噬的分子机制具有重要意义。该研究使用饥饿法处理HeLa细胞,通过电镜观察以及检测自噬标记蛋白LC3-I的转换,证实HeLa细胞发生了明显的自噬。之后,使用双向电泳结合串联质谱分析鉴定细胞自噬时发生变化的蛋白质。结果发现果糖二磷酸醛缩酶A、GAPDH和ATP合成酶O亚基的量在HeLa细胞发生自噬后明显降低。实时定量PCR结果证明饥饿诱导后,这三种蛋白的mRNA水平都发生了明显的下降。使用自噬抑制剂3-Methyladenine预处理HeLa细胞后再行饥饿,三种蛋白mRNA的表达水平与正常细胞相当而明显高于饥饿诱导的细胞。结果表明这三种蛋白在饥饿诱导的自噬中表达下调,其分子机制还有待进一步研究。     

The dynamic changes in autophagy activity and its role in lung injury after deep hypothermic circulatory arrest

Deep hypothermic circulatory arrest (DHCA) can cause acute lung injury (ALI), and its pathogenesis mimics ischaemia/reperfusion (I/R) injury. Autophagy is also involved in lung I/R injury. The present study aimed to elucidate whether DHCA induces natural autophagy activation and its role in DHCA‐mediated lung injury. Here, rats were randomly assigned to the Sham or DHCA group. The sham group (n = 5) only received anaesthesia and air intubation. DHCA group rats underwent cardiopulmonary bypass (CPB) followed by the DHCA procedure. The rats were then sacrificed at 3, 6 and 24 h after the DHCA procedure (n = 5) to measure lung injury and autophagy activity. Chloroquine (CQ) was delivered to evaluate autophagic flux. DHCA caused lung injury, which was prominent 3–6 h after DHCA, as confirmed by histological examination and inflammatory cytokine quantification. Lung injury subsided at 24 h. Autophagy was suppressed 3 h but was exaggerated at 6 h. At both time points, autophagic flux appeared uninterrupted. To further assess the role of autophagy in DHCA‐mediated lung injury, the autophagy inducer rapamycin and its inhibitor 3‐methyladenine (3‐MA) were applied, and lung injury was reassessed. When rapamycin was administered at an early time point, lung injury worsened, whereas administration of 3‐MA at a late time point ameliorated lung injury, indicating that autophagy contributed to lung injury after DHCA. Our study presents a time course of lung injury following DHCA. Autophagy showed adaptive yet protective suppression 3 h after DHCA, as induction of autophagy caused worsening of lung tissue. In contrast, autophagy was exaggerated 6 h after DHCA, and autophagy inhibition attenuated DHCA‐mediated lung injury.     

Aristolochic acid I induced autophagy extenuates cell apoptosis via ERK 1/2 pathway in renal tubular epithelial cells

Autophagy is a lysosomal degradation pathway that is essential for cell survival and tissue homeostasis. However, limited information is available about autophagy in aristolochic acid (AA) nephropathy. In this study, we investigated the role of autophagy and related signaling pathway during progression of AAI-induced injury to renal tubular epithelial cells (NRK52E cells). The results showed that autophagy in NRK52E cells was detected as early as 3-6 hrs after low dose of AAI (10 μM) exposure as indicated by an up-regulated expression of LC3-II and Beclin 1 proteins. The appearance of AAI-induced punctated staining of autophagosome-associated LC3-II upon GFP-LC3 transfection in NRK52E cells provided further evidence for autophagy. However, cell apoptosis was not detected until 12 hrs after AAI treatment. Blockade of autophagy with Wortmannin or 3-Methyladenine (two inhibitors of phosphoinositede 3-kinases) or small-interfering RNA knockdown of Beclin 1 or Atg7 sensitized the tubular cells to apoptosis. Treatment of NRK52E cells with AAI caused a time-dependent increase in extracellular signal-regulated kinase 1 and 2 (ERK1/2) activity, but not c-Jun N-terminal kinase (JNK) and p38. Pharmacological inhibition of ERK1/2 phosphorylation with U0126 resulted in a decreased AAI-induced autophagy that was accompanied by an increased apoptosis. Taken together, our study demonstrated for the first time that autophagy occurred earlier than apoptosis during AAI-induced tubular epithelial cell injury. Autophagy induced by AAI via ERK1/2 pathway might attenuate apoptosis, which may provide a protective mechanism for cell survival under AAI-induced pathological condition.     

Autophagy Activation Contributes to the Neuroprotection of Remote Ischemic Perconditioning Against Focal Cerebral Ischemia in Rats

Remote ischemic perconditioning (RIPer) has been proved to provide potent cardioprotection. However, there are few studies on neuroprotection of RIPer. This study aims to clarify the neuroprotective effect of RIPer and the role of autophagy induced by RIPer against cerebral ischemia reperfusion injury in rats. Using a transient middle cerebral artery occlusion (MCAO) model in rats to imitate focal cerebral ischemia. RIPer was carried out 4 cycles of 10 min ischemia and 10 min reperfusion, with a thin elastic band tourniquet encircled on the bilateral femoral arteries at the start of 10 min after MCAO. Autophagy inhibitor 3-methyladenine (3-MA) and autophagy inducer rapamycin were administered respectively to determine the contribution of autophagy in RIPer. Neurologic deficit scores, infarct volume, brain edema, Nissl staining, TUNEL assay, immunohistochemistry and western blot was performed to analyze the neuroprotection of RIPer and the contribution of autophagy in RIPer. RIPer significantly exerted neuroprotective effects against cerebral ischemia reperfusion injury in rats, and the autophagy-lysosome pathway was activated by RIPer treatment. 3-MA reversed the neuroprotective effects induced by RIPer, whereas rapamycin ameliorated the brain ischemic injury. Autophagy activation contributes to the neuroprotection by RIPer against focal cerebral ischemia in rats.     

ATGPred-FL: sequence-based prediction of autophagy proteins with feature representation learning

Amino Acids - Autophagy plays an important role in biological evolution and is regulated by many autophagy proteins. Accurate identification of autophagy proteins is crucially important to reveal...     

Targeting autophagy for drug-induced hepatotoxicity

Autophagy is a lysosomal degradation pathway for bulk cytosolic proteins and damaged organelles, and is well known to act as a cell survival mechanism. Acetaminophen (APAP) overdose can cause liver injury in animals and humans by inducing necrosis due to mitochondrial damage. We recently found that pharmacological induction of autophagy by rapamycin protects against, whereas pharmacological suppression of autophagy by chloroquine exacerbates, APAP-induced liver injury in mice. Autophagy is induced to remove APAP-induced damaged mitochondria and thus attenuates APAP-induced hepatocyte necrosis. To our surprise, we found that liver-specific Atg5 knockout mice are not more susceptible, but are resistant to APAP-induced liver injury due to compensatory effects. Our work suggests that pharmacological modulation of autophagy is a novel therapeutic approach to ameliorate APAP-induced liver injury. Moreover, our work also suggests that caution needs to be exercised when using genetic autophagy gene knockout mice for pathophysiological studies.     

Autophagy,a guardian against neurodegeneration

Autophagy is an intracellular degradation process responsible for the clearance of most long-lived proteins and organelles. Cytoplasmic components are enclosed by double-membrane autophagosomes, which subsequently fuse with lysosomes for degradation. Autophagy dysfunction may contribute to the pathology of various neurodegenerative disorders, which manifest abnormal protein accumulation. As autophagy induction enhances the clearance of aggregate-prone intracytoplasmic proteins that cause neurodegeneration (like mutant huntingtin, tau and ataxin 3) and confers cytoprotective roles in cell and animal models, upregulating autophagy may be a tractable therapeutic strategy for diseases caused by such proteins. Here, we will review the molecular machinery of autophagy and its role in neurodegenerative diseases. Drugs and associated signalling pathways that may be targeted for pharmacological induction of autophagy will also be discussed.     

Autophagy: a barrier or an adaptive response to cancer

Macroautophagy or autophagy is a degradative pathway terminating in the lysosomal compartment after the formation of a cytoplasmic vacuole that engulfs macromolecules and organelles. The recent discovery of the molecular controls of autophagy that are common to eukaryotic cells from yeast to human suggests that the role of autophagy in cell functioning is far beyond its nonselective degradative capacity. The involvement of proteins with properties of tumor suppressor and oncogenic properties at different steps of the pathway implies that autophagy must be considered in tumor progression. Autophagy as a stress response mechanism protects cancer cells from low nutrient supply or therapeutic insults. Autophagy is also involved in the elimination of cancer cells by triggering a non-apoptotic cell death program, suggesting a negative role in tumor development. These two aspects of autophagy will be discussed in this review.     

Autophagy promotes survival of retinal ganglion cells after optic nerve axotomy in mice

Autophagy is an essential recycling pathway implicated in neurodegeneration either as a pro-survival or a pro-death mechanism. Its role after axonal injury is still uncertain. Axotomy of the optic nerve is a classical model of neurodegeneration. It induces retinal ganglion cell death, a process also occurring in glaucoma and other optic neuropathies. We analyzed autophagy induction and cell survival following optic nerve transection (ONT) in mice. Our results demonstrate activation of autophagy shortly after axotomy with autophagosome formation, upregulation of the autophagy regulator Atg5 and apoptotic death of 50% of the retinal ganglion cells (RGCs) after 5 days. Genetic downregulation of autophagy using knockout mice for Atg4B (another regulator of autophagy) or with specific deletion of Atg5 in retinal ganglion cells, using the Atg5(flox/flox) mice reduces cell survival after ONT, whereas pharmacological induction of autophagy in vivo increases the number of surviving cells. In conclusion, our data support that autophagy has a cytoprotective role in RGCs after traumatic injury and may provide a new therapeutic strategy to ameliorate retinal diseases.