Neuroprotective effects of atorvastatin against cerebral ischemia/reperfusion injury through the inhibition of endoplasmic reticulum stress

Cerebral ischemia triggers secondary ischemia/reperfusion injury and endoplasmic reticulum stress initiates cell apoptosis. However, the regulatory mechanism of the signaling pathway remains unclear. We hypothesize that the regulatory mechanisms are mediated by the protein kinase-like endoplasmic reticulum kinase/eukaryotic initiation factor 2α in the endoplasmic reticulum stress signaling pathway. To verify this hypothesis, we occluded the middle cerebral artery in rats to establish focal cerebral ischemia/reperfusion model. Results showed that the expression levels of protein kinase-like endoplasmic reticulum kinase and caspase-3, as well as the phosphorylation of eukaryotic initiation factor 2α, were increased after ischemia/reperfusion. Administration of atorvastatin decreased the expression of protein kinase-like endoplasmic reticulum kinase, caspase-3 and phosphorylated eukaryotic initiation factor 2α, reduced the infarct volume and improved ultrastructure in the rat brain. After salubrinal, the specific inhibitor of phosphorylated eukaryotic initiation factor 2α was given into the rats intragastrically, the expression levels of caspase-3 and phosphorylated eukaryotic initiation factor 2α in the were decreased, a reduction of the infarct volume and less ultrastructural damage were observed than the untreated, ischemic brain. However, salubrinal had no impact on the expression of protein kinase-like endoplasmic reticulum kinase. Experimental findings indicate that atorvastatin inhibits endoplasmic reticulum stress and exerts neuroprotective effects. The underlying mechanisms of attenuating ischemia/reperfusion injury are associated with the protein kinase-like endoplasmic reticulum kinase/eukaryotic initiation factor 2α/caspase-3 pathway.

Sodium fluoride induces apoptosis through reactive oxygen species-mediated endoplasmic reticulum stress pathway in Sertoli cells

Excessive fluoride exposure is known to contribute to reproductive system dysfunction,ultimately leading to pathological damage and apoptosis in cells. Although both oxidative and endoplasmic reticulum（ER） stresses have been implicated in fluorosis, the signaling pathways and their roles in sodium fluoride（Na F）-induced apoptosis of Sertoli cells have been sparsely described. In this study, oxidative damage, ER stress, and apoptosis were analyzed after Sertoli cells were treated with varying doses of Na F for 24 hr. Moreover, the antioxidant N-acetylcysteine（NAC） and pro-apoptotic transcription factor CHOP knockdown were used to clarify the precise interplay between reactive oxygen species（ROS）, ER stress and their roles in NaF-induced apoptosis in Sertoli cells. The present study indicated that NaF significantly decreased cell viability and induced apoptosis in Sertoli cells. In addition, NaF exposure facilitated the accumulation of ROS and increased nuclear translocation of nuclear factor erythroid 2-related factor 2（Nrf2） in Sertoli cells. Treatment with NAC caused remarkable recovery from these NaF-induced responses. Meanwhile, excessive NaF triggered ER stress as evidenced by up-regulated glucose-regulated protein 78 k Da（GRP78）, PKR-like ER kinase（PERK）, phosphorylation of eukaryotic translation initiation factor 2α（p-eI F2α） and CCAAT/enhancer-binding protein-homologous protein（CHOP）, without affecting total eukaryotic translation initiation factor 2α（e IF2α）. NAC effectively blocked the activation of ER stress, suggesting that Na F-induced ROS is an early event that triggers ER stress. Taken together, the results demonstrate that the ROS-mediated ER stress pathway is the crucial mechanistic event involved in NaF-induced apoptosis of Sertoli cells.

Endoplasmic Reticulum Stress Induces the Early Appearance of Pro-apoptotic and Anti-apoptotic Proteins in Neurons of Five Familial Alzheimer＇s Disease Mice

Background： Amyloid β （Aβ） deposits and the endoplasmic reticulum stress （ERS） are both well established in the development and progression of Alzheimer＇s disease （AD）. However, the mechanism and role of Aβ-induced ERS in AD-associated pathological progression remain to be elucidated. Methods： The five familial AD （5×FAD） mice and wild-type （WT） mice aged 2, 7, and 12 months were used in the present study. Monis water maze test was used to evaluate their cognitive performance, lmmunofluorescence and Western blot analyses were used to examine the dynamic changes of pro-apoptotic （CCAAT/enhancer-binding protein homologous protein [CHOP] and cleaved caspase-12） and anti-apoptotic factors （chaperone glucose-regulated protein [GRP] 78 and endoplasmic reticulum-associated protein degradation-associated ubiquitin ligase synovial apoptosis inhibitor 1 [SYVN 1]） in the ERS-associated unfolded protein response （UPR） pathway. Results： Compared with age-matched WT mice, 5 xFAD mice showed higher cleaved caspase-3, lower neuron-positive staining at the age of 12 months, but earlier cognitive deficit at the age of 7 months （all P 〈 0.05）. Interestingly, for 2-month-old 5×FAD mice, the related proteins involved in the ERS-associated UPR pathway, including CHOP, cleaved caspase-12, GRP 78, and SYVN 1, were significantly increased when compared with those in age-matched WT mice （all P 〈 0.05）. Moreover, ERS occurred mainly in neurons, not in astrocytes. Conclusions： These findings suggest that compared with those of age-matched WT mice, ERS-associated pro-apoptotic and anti-apoptotic proteins are upregulated in 2-month-old 5×FAD mice, consistent with intracellular Aβ aggregation in neurons.