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性乳腺癌耐药蛋白（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在小鼠腹腔注射（10mg/kg体重）内毒素后不同时间对BCRP典型底物米托蒽醌（mitoxantrone）肝脏胆道排泄的影响。内毒素注射后6和24 h，米托蒽醌的胆道清除率分别显著降低40%和70%。Western blot和免疫荧光分析显示，注射内毒素后6和24 h BCRP表达下降，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肝脏BCRP表达下调引起的。内毒素显著诱导白细胞介素-6 （IL-6）和IL-1β等细胞因子的产生。IL-1β预处理不能降低米托蒽醌的肝胆排泄，也不能下调肝脏BCRP的表达。然而，IL-6预处理可显著降低米托蒽醌的肝胆排泄。Western blot和免疫荧光分析也显示，IL-6预处理能降低BCRP的表达，这与体内实验结果一致。这些研究结果表明，肺炎克雷伯菌内毒素通过降低肝脏BCRP的表达来降低BCRP介导的米托蒽醌的肝胆排泄，这可能是由于血浆IL-6水平升高所致。

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.