Neuroprotection of hypoxic postconditioning against global cerebral ischemia through influencing posttranslational regulations of heat shock protein 27 in adult rats.
Neuroprotection of hypoxic postconditioning against global cerebral ischemia through influencing posttranslational regulations of heat shock protein 27 in adult rats.
复制标题
通过影响成年大鼠热休克蛋白 27 的翻译后调节，对低氧后处理对全脑缺血进行神经保护。
作者：
Zhan Lixuan;Liu Liu;Li Kongping;Wu Baoxing;Liu D;an;Liang Donghai;Wen Haixia;Wang Yanmei;Sun Weiwen;Liao Weiping;Xu En
我们以前报道过低氧后处理（HPC）可减轻成年大鼠短暂性全脑缺血（tGCI）引起的海马神经元死亡。然而，HPC诱导的神经保护机制仍然是难以捉摸的。值得注意的是，热休克蛋白27（Hsp 27）最近出现作为一个有效的神经保护剂在脑缺血。虽然其对中风的强大保护作用已被认可，但Hsp 27介导的神经保护机制在很大程度上尚不清楚。在这里，我们研究了潜在的分子机制，HPC调制tGCI后的Hsp 27的翻译后调节。我们发现HPC增加了tGCI后CA 1亚区Hsp 27的表达。用慢病毒介导的短发夹RNA（shRNA）抑制Hsp 27的表达可在体内消除HPC诱导的神经保护作用。此外，放线菌酮，蛋白质合成抑制剂，预处理后，在后处理大鼠的Hsp 27蛋白的降解率显着下降，表明Hsp 27的表达增加后HPC可能是由于其降解减少。接下来，用亮抑酶肽（leupeptin）（一种溶酶体抑制剂）预处理导致tGCI后Hsp 27的积累，表明自噬途径可能是Hsp 27降解的原因。我们进一步表明，tGCI后LC 3-II和自噬体的形成增加。同时，当用3-甲基腺嘌呤阻断自噬时，Hsp 27的降解受到抑制，神经元损伤减轻，而用雷帕霉素激活自噬则表现出相反的趋势。最后，我们证实了HPC增加了tGCI后磷酸化MAPKAP激酶2（MK 2）和Hsp 27的表达。此外，施用SB 203580（一种p38丝裂原活化蛋白激酶抑制剂）降低了磷酸化MK2和Hsp 27的表达。我们的研究结果表明，抑制Hsp 27降解介导的自噬下调可能诱导缺血耐受后HPC。此外，MK 2诱导的Hsp 27磷酸化可能与HPC的神经保护作用有关。
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 HPCin 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.