Nianxiu Tian,Yanbin Gao,Xiaolei Wang,Xiaoming Wu,Dawei Zou,Zhiyao Zhu,ZheJi Han,Tao Wang,Yimin Shi
Background Endoplasmic reticulum stress is associated with podocyte apoptosis in the pathogenesis of diabetic nephropathy (DN). A previous study has demonstrated that emodin has a protective effect in the kidney by suppressing proliferation of mesangial cells and inhibiting the renal tubular epithelial-to-mesenchymal transition. However, the effects of emodin on the podocyte apoptosis in DN and its mechanisms are unknown.Aim This study aimed to explore the effect of emodin on DN model KK-Ay mice and high glucose induced podocytes apoptosis via the PERK–eIF2α pathway.Methods KK-Ay mice model of DN were treated with emodin at dose of 40 and 80 mg/kg/day for 8 weeks. Urine albumin, serum creatinine, blood urea nitrogen levels and the renal histopathology in mice were performed. In vitro, conditionally immortalized mouse podocytes exposed to HG (30mM) were incubated with emodin. Cell viability was measured by CCK-8 assay. Additionally, we performed RNA interference and measured the apoptosis in cultured podocytes treated with emodin. Immunohistochemistry, immunofluorescence, western blot, and real-time PCR were used to detect gene and protein expression both in vivo and in vitro.Results The results showed that emodin treatment ameliorated urine albumin, serum creatinine, and blood urea nitrogen of DN mice. The pathological damage of kidney tissue was also improved after treatment with emodin. Moreover, emodin increased nephrin expression. Podocytes apoptosis and endoplasmic reticulum stress markers (GRP78) were significantly reduced upon emodin treatment. Furthermore, emodin treatment decreased the expression of phosphorylated protein kinase RNA-like endoplasmic reticulum kinase (P-PERK), phosphorylated P-eIF2α, ATF4, and CHOP. In vitro, emodin treatment was further found to decrease the GRP78 level induced by high glucose or tunicamycin (TM). Besides, emodin and PERK knockdown inhibited the apoptosis of podocytes cultured in high glucose by counteracting the upregulation of phosphorylated PERK, phosphorylated eIF2α, ATF4, and CHOP.Conclusion Overall, the findings indicate that emodin mitigates podocytes apoptosis by inhibiting the PERK-eIF2α signaling pathway in vivo and in vitro, and, therefore, exerts a protective action on podocytes in DN.
Xing Li,Bingtian Xu,Lu Long,Yuting Li,Xuan Xiao,Shuqin Qiu,Jiangping Xu,Li-Wen Tian,Haitao Wang
Mitochondrial dysfunction and endoplasmic reticulum (ER) stress play pivotal roles in the pathology of cerebral ischemia. In this study, we investigated whether phelligridimer A (PA), an active compound isolated from the medicinal and edible fungus Phellinus igniarius , ameliorates ischemic cerebral injury by restoring mitochondrial function and restricting ER stress. An in vitro cellular model of ischemic stroke-induced neuronal damage was established by exposing HT-22 neuronal cells to oxygen-glucose deprivation/reoxygenation (OGD/R). An in vivo animal model was established in rats subjected to middle cerebral artery occlusion/reperfusion (MCAO/R). The results showed that PA (1–10 μM) dose-dependently increased HT-22 cell viability, reduced OGD/R-induced lactate dehydrogenase release, and reversed OGD/R-induced apoptosis. PA reduced OGD/R-induced accumulation of reactive oxygen species, restored mitochondrial membrane potential, and increased ATP levels. Additionally, PA reduced the expression of the 78-kDa glucose-regulated protein (GRP78) and the phosphorylation of inositol-requiring enzyme-1α (p-IRE1α) and eukaryotic translation-initiation factor 2α (p-eIF2α). PA also inhibited the activation of the mitogen-activated protein kinase (MAPK) pathway in the OGD/R model. Moreover, treatment with PA restored the expression of mitofusin 2 (Mfn-2), a protein linking mitochondria and ER. The silencing of Mfn-2 abolished the protective effects of PA. The results from the animal study showed that PA (3–10 mg/kg) significantly reduced the volume of cerebral infarction and neurological deficits, which were accompanied by an increased level of Mfn-2, and decreased activation of the ER stress in the penumbra of the ipsilateral side after MCAO/R in rats. Taken together, these results indicate that PA counteracts cerebral ischemia-induced injury by restoring mitochondrial function and reducing ER stress. Therefore, PA might be a novel protective agent to prevent ischemia stroke-induced neuronal injury.
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