Felix Robert A, Barrand Margery A
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, UK.
J Neurochem. 2002 Jan;80(1):64-72. doi: 10.1046/j.0022-3042.2001.00660.x.
During ischaemia/reperfusion, cells of the blood-brain barrier are subjected to oxidative stress. This study uses primary cultured rat brain endothelial cells to examine the effect of such stresses on expression of multidrug transporters. H(2)O(2) up to 500 microm applied to cell monolayers caused a concentration-dependent increase in expression of P-glycoprotein (Pgp) but not of multidrug resistance-associated protein (Mrp1). Concentrations > 250 microm H(2)O(2) decreased cell viability. Application of 100 microm H(2)O(2) caused a significant increase after 48 h in Pgp functional activity, as assessed from [(3)H]vincristine accumulation experiments. At this concentration, H(2)O(2) produced a transient increase within 10 min followed by a sustained decrease in levels of intracellular reactive oxygen species (iROS), detectable by flow cytometry. Reoxygenation of cell monolayers after 6 h hypoxia gave rise to a similar transient increase in iROS and this also led to increased Pgp expression by 24 h. Increases were also observed within 4 h after both H(2)O(2) and hypoxia/reoxygenation treatments in mdr1a and mdr1b mRNA. Evidence suggests this was due to enhanced transcription rather than mRNA stabilization. Therefore, oxidative stress, by changing Pgp expression, may affect movement of Pgp substrates in and out of the brain.
在缺血/再灌注期间，血脑屏障的细胞会受到氧化应激。本研究使用原代培养的大鼠脑内皮细胞来检测这种应激对多药转运蛋白表达的影响。向细胞单层施加高达500微摩尔的过氧化氢会导致P-糖蛋白（Pgp）表达呈浓度依赖性增加，但多药耐药相关蛋白（Mrp1）的表达则不会增加。浓度大于250微摩尔的过氧化氢会降低细胞活力。根据[³H]长春新碱积累实验评估，施加100微摩尔的过氧化氢48小时后会导致Pgp功能活性显著增加。在此浓度下，过氧化氢在10分钟内会使细胞内活性氧（iROS）水平产生短暂升高，随后持续下降，这可通过流式细胞术检测到。细胞单层在缺氧6小时后再给氧会导致iROS出现类似的短暂升高，这也会导致24小时后Pgp表达增加。在过氧化氢和缺氧/再灌注处理后4小时内，mdr1a和mdr1b mRNA也出现增加。有证据表明这是由于转录增强而非mRNA稳定性增加所致。因此，氧化应激通过改变Pgp表达，可能会影响Pgp底物进出大脑的转运。
