title: Neuroprotection of hypoxic postconditioning against global cerebral ischemia through influencing posttranslational regulations of heat shock protein 27 in adult rats.
abstract: We previously reported that hypoxic postconditioning (HPC) ameliorated hippocampal neuronal death induced by transient global cerebral ischemia (tGCI) in adult rats. However, the mechanism of HPC-induced neuroprotection is still elusive. Notably, heat shock protein 27 (Hsp27) has recently emerged as a potent neuroprotectant in cerebral ischemia. Although its robust protective effect on stroke has been recognized, the mechanism of Hsp27-mediated neuroprotection is largely unknown. Here, we investigated the potential molecular mechanism by which HPC modulates the posttranslational regulations of Hsp27 after tGCI. We found that HPC increased expression of Hsp27 in CA1 subregion after tGCI. Inhibition of Hsp27 expression with lentivirus-mediated short hairpin RNA (shRNA) abolished the neuroprotection induced by HPC in vivo. Furthermore, pretreatment with cycloheximide, a protein synthesis inhibitor, resulted in a significant decrease in the degradation rate of Hsp27 protein in postconditioned rats, suggesting that the increase in the expression of Hsp27 after HPC might result from its decreased degradation. Next, pretreatment with leupeptin, a lysosomal inhibitor, resulted in an accumulation of Hsp27 after tGCI, indicating that autophagic pathway may be responsible for the degradation of Hsp27. We further showed that the formation of LC3-II and autophagosomes increased after tGCI. Meanwhile, the degradation of Hsp27 was suppressed and neuronal damage was reduced when blocking autophagy with 3-Methyladenine, whereas activating autophagy with rapamycin showed an opposite tendency. Lastly, we confirmed that HPC increased the expression of phosphorylated MAPKAP kinase 2 (MK2) and Hsp27 after tGCI. Also, administration of SB203580, a p38 mitogen-activated protein kinase inhibitor, decreased the expressions of phosphorylated MK2 and Hsp27. Our results suggested that inhibition of Hsp27 degradation mediated by down-regulation of autophagy may induce ischemic tolerance after HPC. Additionally, phosphorylation of Hsp27 induced by MK2 might be associated with the neuroprotection of HPC.
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Lixuan
authors.initials: L
authors.lastname: Zhan
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Liu
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Kongping
authors.initials: K
authors.lastname: Li
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Baoxing
authors.initials: B
authors.lastname: Wu
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Liu
authors.affiliation: Department of Environmental Health Sciences, Rollins School of Public Health, Emory University, 1518 Clifton Road, 2040K, Atlanta, GA, 30322.
authors.forename: Donghai
authors.initials: D
authors.lastname: Liang
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Haixia
authors.initials: H
authors.lastname: Wen
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Yanmei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Weiwen
authors.initials: W
authors.lastname: Sun
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: Weiping
authors.initials: W
authors.lastname: Liao
authors.affiliation: Institute of Neurosciences and the Second Affiliated Hospital of Guangzhou Medical University, Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China, Collaborative Innovation Center for Neurogenetics and Channelopathies, Guangzhou, 510260, China.
authors.forename: En
authors.initials: E
authors.lastname: Xu
mesh_terms: D000818:Animals; D001343:Autophagy; D002545:Brain Ischemia / Q000150:complications / Q000473:pathology*; D002544:Cerebral Infarction; D005786:Gene Expression Regulation / Q000502:physiology; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D006624:Hippocampus / Q000378:metabolism; D000860:Hypoxia / Q000378:metabolism; D057775:Ischemic Postconditioning / Q000379:methods*; D008297:Male; D009474:Neurons / Q000378:metabolism; D000066829:Neuroprotection / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
chemical_list: D055551:HSP27 Heat-Shock Proteins; D018696:Neuroprotective Agents
keywords: Autophagy; MAPKAP kinase 2; cerebral ischemia; heat shock protein 27; hypoxic postconditioning; neuroprotection