Mechanism of total flavonoids of Rhododendra simsii in alleviating ischemic brain injury / 中国中药杂志

This study explores the effect of total flavonoids of Rhododendra simsii(TFR) on middle cerebral artery occlusion(MCAO)-induced cerebral injury in rats and oxygen-glucose deprivation/reoxygenation(OGD/R) injury in PC12 cells and the underlying mechanism. The MCAO method was used to induce focal ischemic cerebral injury in rats. Male SD rats were randomized into sham group, model group, and TFR group. After MCAO, TFR(60 mg·kg~(-1)) was administered for 3 days. The content of tumor necrosis factor-α(TNF-α), interleukin-1(IL-1), and interleukin-6(IL-6) in serum was detected by enzyme-linked immunosorbent assay(ELISA). The pathological changes of brain tissue and cerebral infarction were observed based on hematoxylin and eosin(HE) staining and 2,3,5-triphenyltetrazolium chloride(TTC) staining. RT-qPCR and Western blot were used to detect the mRNA and protein levels of calcium release-activated calcium channel modulator 1(ORAI1), stromal interaction molecule 1(STIM1), stromal intera-ction molecule 2(STIM2), protein kinase B(PKB), and cysteinyl aspartate specific proteinase 3(caspase-3) in brain tissues. The OGD/R method was employed to induce injury in PC12 cells. Cells were randomized into the normal group, model group, gene silencing group, TFR(30 μg·mL~(-1)) group, and TFR(30 μg·mL~(-1))+gene overexpression plasmid group. Intracellular Ca~(2+) concentration and apoptosis rate of PC12 cells were measured by laser scanning confocal microscopy and flow cytometry. The effect of STIM-ORAI-regulated store-operated calcium entry(SOCE) pathway on TFR was explored based on gene silencing and gene overexpression techniques. The results showed that TFR significantly alleviated the histopathological damage of brains in MCAO rats after 3 days of admini-stration, reduced the contents of TNF-α, IL-1, and IL-6 in the serum, down-regulated the expression of ORAI1, STIM1, STIM2, and caspase-3 genes, and up-regulated the expression of PKB gene in brain tissues of MCAO rats. TFR significantly decreased OGD/R induced Ca~(2+) overload and apoptosis in PC12 cells. However, it induced TFR-like effect by ORAI1, STIM1 and STIM2 genes silencing. However, overexpression of these genes significantly blocked the effect of TFR in reducing Ca~(2+) overload and apoptosis in PC12 cells. In summary, in the early stage of focal cerebral ischemia-reperfusion injury and OGD/R-induced injury in PC12 cells TFR attenuates ischemic brain injury by inhibiting the STIM-ORAI-regulated SOCE pathway and reducing Ca~(2+) overload and inflammatory factor expression, and apoptosis.

Effects of total flavonoids of Rhododendra simsii on ameliorating brain injury via G protein-coupled SOCE pathway mediated by STIM and Orai in subacute phase of ischemia/reperfusion / 中国药理学与毒理学杂志

OBJECTIVE To explore the effect of total flavonoids of Rhododendra simsii (TFR) on improving cerebral ischemia/reperfusion injury (CIRI) and its relationship with STIM/Orai-regulated operational Ca2+influx (SOCE) pathway. METHODS Oxygen-glucose deprivation/reoxygenation (OGD/R) PC12 cells were used to simulate CIRI in vitro, and the intracellular Ca2+ concentration and apoptosis rate of PC12 cells were detected by laser confocal microscope and flow cytometry, respectively. The regulation of STIM/Orai on SOCE was analyzed by STIM/Orai gene silencing and STIM/Orai gene overexpression. The CIRI model was established by MCAO in SD rats. The activities of inflammatory cyto?kines IL-1, IL-6 and TNF-αin serum were detected by ELISA. The pathological changes of ischemic brain tissue and the infarction of rat brain tissue were detected by HE staining and TTC staining. The protein and mRNA expression levels of STIM1, STIM2, Orai1, caspase-3 and PKB in brain tissue were detected by Western blotting and RT-qPCR, respectively. RESULTS The results of in vitro experiment showed that the fluorescence intensity of Ca2+ and apoptosis rate in PC12 cells treated with TFR were significantly lower than those in OGD/R group, and this trend was enhanced by SOCE antagonist 2-APB. STIM1/STIM2/Orai1 gene silencing significantly reduced apoptosis and Ca2+overload in OGD/R model, while TFR combined with overexpression of STIM1/STIM2/Orai1 aggravated apoptosis and Ca2+overload. In the in vivo experiment, TFR significantly reduced the brain histopathological damage, infarction of brain tissue, the contents of IL-1, IL-6 and TNF-α in the serum in MCAO rats and down-regulated the expression of STIM1, STIM2, Orai1 and caspase-3 protein and mRNA in the brain tissue, and up-regulated the expression of PKB. The above effects were enhanced by the addition of 2-APB. CONCLUSION The above results indicate that TFR may reduce the contents of inflammatory factors and apoptosis, decrease Ca2+ overload and ameliorate brain injury by inhibiting SOCE pathway mediated by STIM and Orai, suggesting that it has a protective effect against subacute CIRI.