A Mechanism for P-Glycoprotein-Mediated Apoptosis As Revealed by Verapamil Hypersensitivity
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- 作者：Joel Karwatsky ; Maximilian C. Lincoln ; and Elias Georges
- 刊名：Biochemistry
- 出版年：2003
- 出版时间：October 28, 2003
- 年：2003
- 卷：42
- 期：42
- 页码：12163 - 12173
- 全文大小：288K
- 年卷期：v.42,no.42(October 28, 2003)
- ISSN：1520-4995
文摘
Selection of tumor cell lines with anticancer drugs has led to the appearance of multidrug-resistant (MDR) subclones with P-glycoprotein 1 (P-gp1) expression. These cells are cross-resistant toseveral structurally and functionally dissimilar drugs. Interestingly, in the process of gaining resistance,MDR cells become hypersensitive or collaterally sensitive to membrane-active agents, such as calciumchannel blockers, steroids, and local anaesthetics. In this report, hypersensitivity to the calcium channelblocker, verapamil, was analyzed in sensitive and resistant CHO cell lines. Our results show that treatmentwith verapamil preferentially induced apoptosis in MDR cells compared to drug-sensitive cells. This effectwas independent of p53 activity and could be inhibited by overexpression of the Bcl-2 gene. The inductionof apoptosis by verapamil had a biphasic trend in which maximum cell death occurred at 10 
M, followedby improved cell survival at higher concentrations (50 M). We correlated this effect to a similar biphasictrend in P-gp1 ATPase activation by verapamil in which low concentrations of verapamil (10 M) activatedATPase, followed by inhibition at higher concentrations. To confirm the relationship between apoptosisand ATPase activity, we used two inhibitors of P-gp1 ATPase, PSC 833 and ivermectin. These ATPaseinhibitors reduced hypersensitivity to verapamil in MDR cells. In addition, low concentrations of verapamilresulted in the production of reactive oxygen species (ROS) in MDR cells. Taken together, these resultsshow that apoptosis was preferentially induced by P-gp1 expressing cells exposed to verapamil, an effectthat was mediated by ROS, produced in response the high ATP demand by P-gp1.
M, followedby improved cell survival at higher concentrations (50 M). We correlated this effect to a similar biphasictrend in P-gp1 ATPase activation by verapamil in which low concentrations of verapamil (10 M) activatedATPase, followed by inhibition at higher concentrations. To confirm the relationship between apoptosisand ATPase activity, we used two inhibitors of P-gp1 ATPase, PSC 833 and ivermectin. These ATPaseinhibitors reduced hypersensitivity to verapamil in MDR cells. In addition, low concentrations of verapamilresulted in the production of reactive oxygen species (ROS) in MDR cells. Taken together, these resultsshow that apoptosis was preferentially induced by P-gp1 expressing cells exposed to verapamil, an effectthat was mediated by ROS, produced in response the high ATP demand by P-gp1.