Abstract

P-glycoprotein (P-gp) is an ABC transporter exhibiting high pharmacotoxicological relevance by extruding a wide range of cytotoxic compounds out of the cells. Previously, we demonstrated that the phytoestrogen genistein (GNT) modulates P-gp expression in hepatocellular carcinoma in vitro. Although several beneficial effects (e.g., antioxidant, antimutagenic, anticancer) have been attributed to GNT, the molecular mechanisms have not been totally elucidated. In the present work, we evaluated the effect of GNT on P-gp expression in rat liver, kidney and ileum. We found that GNT (5 mg/kg daily s.c. 3 days) increased hepatic P-gp expression and also Mdr1a (one of the genes encoding P-gp) mRNA levels. Renal and intestinal P-gp remained unchanged after GNT treatment. Hepatic P-gp activity measured with rhodamine-123 and digoxin, both well-known P-gp substrates, was also increased. In vitro experiments using hepatocyte primary cell culture demonstrated that inhibition of ER-α with ICI182/780 did not prevent Mdr1a mRNA up-regulation by GNT (10 µM). In contrast, Mdr1a induction was suppressed after pregnane X receptor (PXR) inhibition by sulforaphane and knockdown of this nuclear receptor. These findings were confirmed in vivo by using the PXR antagonist ketoconazole. In conclusion, we demonstrated the induction of hepatic P-gp expression and activity by GNT in vivo, with PXR being a likely mediator. This suggests that GNT, at concentrations observed in plasma of individuals consuming the phytoestrogen in the diet or through supplements, could affect the clearance of relevant P-gp substrates of therapeutic use as well as toxicity of environmental and food toxicants.

中文翻译：

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金雀异黄素对大鼠肝脏P-gp表达和活性的调节。

摘要

P-糖蛋白（P-gp）是一种ABC转运蛋白，通过将多种细胞毒性化合物挤出细胞而具有很高的药理学相关性。以前，我们证明了植物雌激素染料木黄酮（GNT）在体外可调节肝细胞癌中P-gp的表达。尽管几种有益的作用（例如抗氧化剂，抗诱变剂，抗癌剂）已归因于GNT，但其分子机制尚未完全阐明。在目前的工作中，我们评估了GNT对大鼠肝脏，肾脏和回肠中P-gp表达的影响。我们发现，GNT（5 mg / kg每天皮下注射3天）增加了肝P-gp表达，同时也增加了Mdr1a（编码P-gp的基因之一）mRNA水平。GNT治疗后，肾脏和肠道P-gp保持不变。用罗丹明-123和地高辛这两种众所周知的P-gp底物测得的肝P-gp活性也增加了。使用肝细胞原代细胞培养的体外实验表明，用ICI182 / 780抑制ER-α不会阻止GNT（10 µM）对Mdr1a mRNA的上调。相反，Mdr1a萝卜硫烷抑制孕烷X受体（PXR）并抑制该核受体后，诱导被抑制。通过使用PXR拮抗剂酮康唑在体内证实了这些发现。总之，我们证明了GNT在体内可诱导肝P-gp表达和活性，其中PXR可能是介体。这表明，在饮食中或通过补充剂消耗饮食中的植物雌激素的个体的血浆中观察到的浓度下的GNT，可能会影响治疗用途的相关P-gp底物的清除以及环境和食物中毒物的毒性。