下调孕烷X受体表达对谷氨酸诱导的小鼠脑微血管内皮细胞P-糖蛋白表达和功能的影响

Effects of downregulated pregnane X receptor on glutamate-induced expression and activity of P-glycoprotein in the mouse brain microvascular endothelial cells

目的探索下调孕烷X受体(PXR)表达对谷氨酸(GLU)模拟癫痫发作环境下小鼠脑微血管内皮细胞(m BMEC) P-糖蛋白(P-gp)表达和功能的影响。方法体外培养小鼠脑微血管内皮b End. 3细胞,分为不同浓度GLU处理组(以0μmol/L、10μmol/L、50μmol/L、100μmol/L GLU处理细胞30 min),GLU不同时间处理组(以100μmol/L GLU处理细胞0 min、15 min、30 min);使用siRNA-PXR特异性抑制PXR表达,分为对照siRNA(NC siRNA)+GLU组、siRNA-PXR+GLU组。Western blotting检测细胞PXR和P-gp蛋白表达,细胞免疫荧光法检测细胞核内PXR蛋白表达,RT-qPCR检测细胞P-gp mRNA表达,罗丹明123(Rh123)细胞蓄积实验检测P-gp外排功能。结果与空白组相比,50μmol/L和100μmol/L GLU组PXR和P-gp蛋白表达均增高(均P <0. 05),尤以100μmol/L组PXR和P-gp蛋白表达最明显。与空白组相比,15 min和30 min组PXR蛋白表达均增加(均P <0. 05),30 min组P-gp蛋白表达增加(P <0. 05)。与空白组相比,100μmol/L GLU组胞核内PXR表达增加(P <0. 05)。与NC siRNA+GLU组相比,siRNA-PXR+GLU组PXR蛋白表达下调了37%[(1. 00±0. 00) vs (0. 63±0. 18); t=3. 41,P=0. 02],P-gp蛋白表达下调了43%[(1. 00±0. 00) vs(0. 57±0. 09); t=7. 94,P=0. 00],P-gp mRNA表达下调了52%[(1. 00±0. 04) vs (0. 48±0. 08); t=10. 98,P=0. 00]。GLU组细胞内Rh123荧光强度(0. 72±0. 01)较空白组降低[(1. 00±0. 03); t=9. 66,P=0. 00];GLU+维拉帕米(P-gp抑制剂)组(1. 07±0. 04)较GLU组增高(t=-11. 93,P=0. 00); siRNA-PXR+GLU组(0. 91±0. 03)较NC siRNA+GLU组增高[(0. 69±0. 05); t=-7. 52,P=0. 00]。结论下调PXR表达能够抑制m BMEC在GLU模拟癫痫发作环境下的P-gp表达及其功能,提示PXR参与调控癫痫发作诱导血-脑屏障P-gp表达及其功能。

Objective To investigate the effects of downregulated pregnane X receptor (PXR)on expression and activity of P-glycoprotein(P-gp)in mouse brain microvascular endothelial cells (mBMEC)exposed to glutamate (GLU)to mimic conditions during seizures. Methods The bEnd.3 cells,were cultured in vitro and treated with culture medium containing 0 μmol,10 μmol,50 μmol,100 μmol GLU for 30 min and exposed to 100 μM GLU for different durations (0 min,15 min,30 min). With PXR knockdown using siRNA,the cells were divided into NC siRNA plus GLU group and siRNA-PXR plus GLU group. Western blotting was used to detect the protein expressions of P-gp and PXR in each group. Immunofluorescence assay was used to detect localization of PXR in cells. The expression of P-gp mRNA was detected by RT-qPCR. Rhodamine123 (Rh123)accumulation assay was used to study the activity of the P-gp in cells.Results PXR and P-gp protein expressions in the 50 μmol and 100 μmol GLU group were significantly higher than that in the blank group(P<0.05),especially maximal expressions occurred in the 100 μmol GLU group. GLU exposures as short as 15 min and 30 min significantly increased PXR expressions(all P<0.05);P-gp expression in the 30 min groups was higher than that in the blank group (P<0.05 ). The data of immunofluorescence analysis suggested that the PXR nuclear accumulation increased in the 100 μM GLU group, compared with the blank group(P<0.05). Compared with NC siRNA plus GLU group,the protein level of PXR was decreased by approximately 37%[(1.00 ± 0.00)vs(0.63 ± 0.18);t=3.41,P=0.02]and the levels of P-gp protein and mRNA were respectively decreased by 43%[(1.00 ± 0.00)vs (0.57 ± 0.09);t=7.94,P=0.00] and 52%[(1.00 ± 0.04)vs (0.48 ± 0.08);t =10.98,P=0.00]in the siRNA-PXR plus GLU group. The fluorescence intensity of intracellular Rh123 in the GLU group (0.72 ± 0.01)was lower than that in the blank group [(1.00 ± 0.03);t =9.66,P=0.00]. The fluorescence intensity of Rh123 in the GLU plus verapamil (P-gp inhibitor)group (1.07 ± 0.04)was higher than that in the GLU group (t= -11.93,P=0.00). The fluorescence intensity of Rh123 in the siRNA-PXR plus GLU group (0.91 ± 0.03)was higher than that in the NC siRNA plus GLU group[(0.69 ± 0.05);t= -7.52,P=0.00]. Conclusions Downregulation of PXR expression results in the inhibition of P-gp expression and activity in the mBMEC exposed to GLU to mimic seizures. PXR may play an important role in the regulation of seizure-induced expression and activity of P-gp in the blood-brain barrier.