Molecular pharmacokinetic studies on changes in the expression and function of drug transporters in endotoxemia

肺炎克雷伯菌内毒素对肝乳腺癌耐药蛋白(BCRP)功能和表达的影响尚不清楚。在本研究中，我们研究了肺炎克雷伯菌内毒素对小鼠腹腔注射内毒素(10 mg/kg体重)后不同时间肝胆排泄米托蒽醌的影响。注射内毒素后6h和2 4h，米托蒽醌的胆汁清除率分别下降40%和70%。免疫印迹和免疫荧光分析显示，注射内毒素后6h和24h，BCRP的表达均下降，这与体内实验结果一致。这些结果表明，内毒素诱导的BCRP介导的肝胆排泄减少，部分是由于下调了肝脏BCRP的表达。内毒素可显著诱导IL-6和IL-1β等细胞因子的产生。IL-1β不能减少肝胆汁中米托蒽醌的排泄量，也不能下调肝BCRP的表达。而IL-6可显著降低米托蒽醌对肝胆的排泄量。免疫印迹和免疫荧光分析还显示，IL-6预处理降低了BCRP的表达，这与体内实验结果一致。这些结果提示肺炎克雷伯菌内毒素通过降低肝脏BCRP的表达来减少BCRP介导的米托蒽醌的排泄，这可能是通过增加血浆IL-6水平来实现的。

The effect of Klebsiella pneumoniae endotoxin on the function and expression of hepatic breast cancer resistance protein (BCRP) remains unknown. In the present study, we investigated the effect of K.pneumoniae endotoxin on the hepatobiliary excretion of mitoxantrone, a typical substrate of BCRP in mice at different times after intraperitoneal injection of endotoxin (10mg/kg of body weight). The biliary clearance of mitoxantrone significantly decreased by 40% and 70% 6 and 24 h after endotoxin injection, respectively. Both Western blot and immunofluorescence analyses revealed that BCRP expression decreased 6 and 24 h after injection of endotoxin, which were consistent with the results from in vivo experiments. These results suggest that endotoxin-induced decrease in BCRP-mediated hepatobiliary excretion is caused, in part, by down-regulation of hepatic BCRP expression. Endotoxin significantly induced the production of cytokines including interleukin-6 (IL-6) and IL-1β. Pretreatment with IL-1β did not decrease the hepatobiliary excretion of mitoxantrone and down-regulate hepatic BCRP expression. However, pretreatment with IL-6 significantly decreased the hepatobiliary excretion of mitoxantrone. Western blot and immunofluorescence analyses also revealed that pretreatment with IL-6 decreased the expression of BCRP, which is in line with in vivo experiments. These findings suggest that K.pneumoniae endotoxin decreases BCRP-mediated hepatobiliary excretion of mitoxantrone by decreasing the expression of hepatic BCRP, which is likely due to increased plasma IL-6 levels.