Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Kobe Gakuin University, Chuo-ku, Kobe 650-8586, Japan.
J Pharm Sci. 2013 Mar;102(3):1095-105. doi: 10.1002/jps.23441. Epub 2013 Jan 9.
Previously, we reported that repeated oral treatment with etoposide (ETP) causes attenuation of oral morphine analgesia through upregulation of ileal P-glycoprotein (P-gp) mediated by Ras homolog gene family, member A (RhoA) activation. However, the detailed mechanism of the increase in ileal P-gp via RhoA activation remains unknown. Recently, it has been reported that ezrin-radixin-moesin (ERM) proteins, linking several plasma-membrane proteins to the actin cytoskeleton, are involved in the membrane localization and functional activity of P-gp. Moreover, the cross-linking activities of ERM are known to be regulated by RhoA and Rho-associated coiled-coil containing kinase (ROCK). Here, we examined the involvement of ERM in the changes in expression of P-gp via RhoA and ROCK in ileal membrane induced by ETP. Repeated oral treatment with ETP significantly increased the ileal membrane localization of ERM and phosphorylated ERM (p-ERM) in association with upregulation of P-gp and activation of RhoA and ROCK. Interestingly, coadministration of rosuvastatin (inhibitor of RhoA activation) and fasudil (ROCK inhibitor) prevented increments in the activation and phosphorylation of ERM, respectively. In conclusion, upregulation of ileal membrane localization of ERM and p-ERM via activation of RhoA/ROCK induced by ETP treatment may be involved in the regulation of ileal membrane localization of P-gp.
先前，我们曾报道，依托泊苷（ETP）的重复口服治疗通过激活 Ras 同源基因家族成员 A（RhoA）引起的回肠 P-糖蛋白（P-gp）上调，导致口服吗啡镇痛作用减弱。然而，RhoA 激活导致回肠 P-gp 增加的详细机制尚不清楚。最近，有报道称，ezrin-radixin-moesin（ERM）蛋白将几种质膜蛋白与肌动蛋白细胞骨架连接起来，参与 P-gp 的膜定位和功能活性。此外，ERM 的交联活性受 RhoA 和含 Rho 相关卷曲螺旋的蛋白激酶（ROCK）调节。在这里，我们研究了在 ETP 诱导的回肠膜中，RhoA 和 ROCK 通过 ERM 参与 P-gp 表达变化的情况。重复口服 ETP 治疗可显著增加 ERM 和磷酸化 ERM（p-ERM）在回肠膜中的定位，同时 P-gp 上调和 RhoA 和 ROCK 激活。有趣的是，同时给予罗伐他汀（RhoA 激活抑制剂）和法舒地尔（ROCK 抑制剂）可分别防止 ERM 的激活和磷酸化增加。总之，ETP 处理通过激活 RhoA/ROCK 引起的回肠膜中 ERM 和 p-ERM 的上调可能参与了 P-gp 回肠膜定位的调节。
