Endoplasmic Reticulum Stress And Apoptosis Via PERK-eIF2?-CHOP Signaling In The Methamphetamine-induced Chronic Pulmonary Injury

Objective:Methamphetamine(MA)is one of the most widely abused addictive drugs in the world,which caused the dysfunction and injury of multiple organs,such as brain,heart and lung.Endoplasmic reticulum stress is the imbalance between the capacity of the endoplasmic reticulum to fold protein and its demand,which usually leads to a large accumulation of unfolded and misfolded proteins,and then leads to the unfolded protein reaction(UPR).GRP78 will be significantly increased with the occurrence of ERS.Hence,increasing GRP78 expression is an important indication of ERS.After dissociated with GRP78,PERK will induce self phosphorylation and oligomerization to activate eukaryotic initiation factor 2 alpha(e IF2?),and reduce the initiation of translation of most cellular proteins,so as to resist the cytotoxicity caused by the accumulation of misfolded proteins.Activated e IF2?mediates transcription of the transcription activation factor 4(ATF4).ATF4 induced apoptosis factor C/EBP homologous protein(CHOP)expression and induce increased expression of BAX from cytoplasm to mitochondria,and increased Ca~+concentration in cytoplasm to activate caspase-12 and the Caspase cascade.Endoplasmic reticulum stress PERK-e IF2?signaling pathway is widely existed in the pathological process of pulmonary fibrosis,lung cancer,emphysema,neutrophilic asthma and pulmonary vascular remodeling,but whether it exists in chronic lung injury caused by methamphetamine is still unclear.Therefore,the aim of this experiment is to investigate whether endoplasmic reticulum stress and PERK-eIF2?-CHOP signaling pathway are involved in chronic lung injury induced by methamphetamine.Methods:30 male Wistar rats were randomly divided into 3 groups:Control group(CON),5 mg/kg MA group(M5),and 10 mg/kg MA group(M10).The rats in MA-treated groups were intraperitoneally injected(i.p.)with MA 5 mg/kg and 10mg/kg,respectively(twice per day for 5 weeks).The rats in control group were administrated with an equivalent volume of 0.9%saline(i.p.)everyday.The survival rate of the first week and the last week after administration of the rats in each group was calculated.After five weeks,all the surviving rats were dissected and the lung tissues were stored at-80?.Three rat lung tissues in each group were dehydrated with paraformaldehyde and embedded in paraffin for HE staining and IHC.Western blot were used to detect the expression of GRP78,PERK,e IF2?,p-eIF2?,ATF4,CHOP,BAX and Caspase-12;IHC were used to detect the expression of GRP78,CHOP and BAX.Result:In our study,methamphetamine decreased the survival rate of rats,and caused the loss of epithelium of alveolar wall,alveolar fusion,decreased numbers of alveoli,and even infiltration inflammatory cells.Compared with the control group,in the M10group the expressions of GRP78 and PERK signaling protein(PERK,p-e IF2?,ATF4and CHOP)were markedly up-regulated,and apoptosis indicators,BAX and caspase-12 were obviously increased.Conclusion:Endoplasmic reticulum stress is involved in the chronic lung injury induced by methamphetamine.PERK-eIF2-ATF4 signaling pathway is activated,and finally activated apoptotic factor CHOP and BAX to activate apoptosis signaling pathway and Caspase-12.This study provides a new perspective on the toxicity of MA in the lung.