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      Activation of autophagy in rat brain cells following focal cerebral ischemia reperfusion through enhanced expression of Atg1/pULK and LC3

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          Abstract

          The present study aimed to investigate the activation of Atg1/pULK, and LC3 in the cerebral cortex following focal cerebral ischemia reperfusion (CIR) injury, thereby examining its effect on autophagy in brain cells. Rat CIR models were established using the technique of middle cerebral artery occlusion. The neurological function score, TTC staining and the water content of brain tissue were used to evaluate the CIR model. Levels of autophagy in the brain cells were examined at different time-points following CIR damage using electron microscopy. Immunohistochemistry and western blot analysis were also used for the qualitative and quantitative detection of levels of Atg1/pULK and LC3 in the cerebral cortex. Autophagy was observed in the early stage of CIR, and the expression of Atg1/pULK and LC3 were observed 1 h following CIR in the rats and reached peak expression levels after12 h, which following which the they gradually decreased. These results suggested Atg1/pULK and LC3 are key in the regulation of autophagy following CIR in the rat brain.

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          Cerebral ischemia-reperfusion-induced autophagy protects against neuronal injury by mitochondrial clearance.

          Cerebral ischemia-reperfusion (I-R) is a complex pathological process. Although autophagy can be evoked by ischemia, its involvement in the reperfusion phase after ischemia and its contribution to the fate of neurons remains largely unknown. In the present investigation, we found that autophagy was activated in the reperfusion phase, as revealed in both mice with middle cerebral artery occlusion and oxygen-glucose deprived cortical neurons in culture. Interestingly, in contrast to that in permanent ischemia, inhibition of autophagy (by 3-methyladenine, bafilomycin A 1, Atg7 knockdown or in atg5(-/-) MEF cells) in the reperfusion phase reinforced, rather than reduced, the brain and cell injury induced by I-R. Inhibition of autophagy either with 3-methyladenine or Atg7 knockdown enhanced the I-R-induced release of cytochrome c and the downstream activation of apoptosis. Moreover, MitoTracker Red-labeled neuronal mitochondria increasingly overlapped with GFP-LC3-labeled autophagosomes during reperfusion, suggesting the presence of mitophagy. The mitochondrial clearance in I-R was reversed by 3-methyladenine and Atg7 silencing, further suggesting that mitophagy underlies the neuroprotection by autophagy. In support, administration of the mitophagy inhibitor mdivi-1 in the reperfusion phase aggravated the ischemia-induced neuronal injury both in vivo and in vitro. PARK2 translocated to mitochondria during reperfusion and Park2 knockdown aggravated ischemia-induced neuronal cell death. In conclusion, the results indicated that autophagy plays different roles in cerebral ischemia and subsequent reperfusion. The protective role of autophagy during reperfusion may be attributable to mitophagy-related mitochondrial clearance and inhibition of downstream apoptosis. PARK2 may be involved in the mitophagy process.
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            Neuronal injury in rat model of permanent focal cerebral ischemia is associated with activation of autophagic and lysosomal pathways.

            It has been reported that ischemic insult increases the formation of autophagosomes and activates autophagy. However, the role of autophagy in ischemic neuronal damage remains elusive. This study was taken to assess the role of autophagy in ischemic brain damage. Focal cerebral ischemia was introduced by permanent middle cerebral artery occlusion (pMCAO). Activation of autophagy was assessed by morphological and biochemical examinations. To determine the contribution of autophagy/lysosome to ischemic neuronal death, rats were pretreated with a single intracerebral ventricle injection of the autophagy inhibitors 3-methyl-adenine (3-MA) and bafliomycin A1 (BFA) or the cathepsin B inhibitor Z-FA-fmk after pMCAO. The effects of 3-MA and Z-FA-fmk on brain damage, expression of proteins involved in regulation of autophagy and apoptosis were assessed with 2,3,5-triphenyltetrazolium chloride (TTC) staining and immunoblotting. The results showed that pMACO increased the formation of autophagosomes and autolysosomes, the mRNA and protein levels of LC3-II and the protein levels of cathepsin B. 3-MA, BFA and Z-FA-fmk significantly reduced infarct volume, brain edema and motor deficits. The neuroprotective effects of 3-MA and Z-FA-fmk were associated with an inhibition on ischemia-induced upregulation of LC3-II and cathepsin B and a partial reversion of ischemia-induced downregulation of cytoprotective Bcl-2. These results demonstrate that ischemic insult activates autophagy and an autophagic mechanism may contribute to ischemic neuronal injury. Thus, autophagy may be a potential target for developing a novel therapy for stroke.
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              Focal cerebral ischemia induces upregulation of Beclin 1 and autophagy-like cell death.

              Autophagy is a highly regulated cellular mechanism for the bulk degradation of cytoplasmic contents which seems to be implicated in a variety of physiological and pathological conditions relevant to neurological diseases. We were prompted to examine whether autophagy is involved in mechanisms of cell death after focal cerebral ischemia. To do so, we examined the protein level and distribution of Beclin 1 (Bcl2 interacting protein) and microtubule-associated protein 1 light chain 3 (LC3) which were previously found to promote autophagy. We found a dramatic elevation in Beclin 1 levels in the penumbra of rats challenged by cerebral ischemia. Beclin 1 elevations start at early stages postischemia (6 h) and it lasts for at least 48 h. A subpopulation of Beclin 1-upregulating cells is also expressing the active form of caspase-3. In addition, not all Beclin 1-upregulating cells display dense staining of LC3. Neuronal cells that overexpress Beclin 1 may exhibit damaged DNA but without changes in nuclear morphology, which indicates that not all the Beclin 1-upregulating cells are predestined to die. The upregulation of Beclin 1 and related changes of LC3 in the ischemic penumbra may represent enhanced autophagy either as a mechanism to recycle injured cells and reduce damage or a process leading to cell demise.
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                Author and article information

                Journal
                Mol Med Rep
                Mol Med Rep
                Molecular Medicine Reports
                D.A. Spandidos
                1791-2997
                1791-3004
                September 2015
                26 May 2015
                26 May 2015
                : 12
                : 3
                : 3339-3344
                Affiliations
                [1 ]Department of Histology and Embryology, Liaoning Medical University, Jinzhou, Liaoning 121001, P.R. China
                [2 ]Key Laboratory of Molecular Cell Biology and New Drug Development, Liaoning Medical University, Jinzhou, Liaoning 121001, P.R. China
                Author notes
                Correspondence to: Ms. Xia Liu, Department of Histology and Embryology, Liaoning Medical University, 3-40 Songpo Road, Jinzhou, Liaoning 121001, P.R. China, E-mail: dongyanru530@ 123456163.com
                Article
                mmr-12-03-3339
                10.3892/mmr.2015.3850
                4526088
                26018745
                c4fe2616-c5f7-426b-b0d1-ba6675311aed
                Copyright © 2015, Spandidos Publications

                This is an open-access article licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. The article may be redistributed, reproduced, and reused for non-commercial purposes, provided the original source is properly cited.

                History
                : 19 August 2014
                : 30 April 2015
                Categories
                Articles

                autophagy,focal cerebral ischemia reperfusion injury,atg1/pulk,lc3

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