Cyclosporin A has low potency as a calcineurin inhibitor in cells expressing high levels of P-glycoprotein.
Cyclosporin A has low potency as a calcineurin inhibitor in cells expressing high levels of P-glycoprotein.
复制标题
在表达高水平 P-糖蛋白的细胞中，环孢菌素 A 作为钙调神经磷酸酶抑制剂的效力较低。
DOI：
10.1016/s0024-3205(98)00227-6
复制
发表时间：
1998
期刊：
影响因子：
6.1
通讯作者：
Stemmer,PM
中科院分区：
文献类型：
--
作者：
Fakata,KL;Elmquist,WF;Swanson,SA;Vorce,RL;Prince,C;Stemmer,PM
环孢菌素A（CsA）是一种广泛使用的免疫抑制剂，其治疗和毒性作用是通过抑制钙调磷酸酶（CN）介导的，钙调磷酸酶是钙和钙调蛋白依赖性磷酸酶。CsA对CN的抑制作用需要药物与其蛋白质辅因子亲环素结合。由于亲环蛋白是CsA的高亲和力靶点，因此预期该蛋白质可作为细胞中药物的储库，并可能能够抑制CsA的细胞外排。已知P-糖蛋白（P-gp）可增加CsA负载细胞的CsA外排速率，但尚不清楚P-gp药物外排泵是否可在治疗相关浓度的CsA下与亲环素有效竞争。为了检验P-gp表达增加可保护CN磷酸酶活性免受CsA依赖性抑制的假设，分析了表达不同水平P-gp的KB-V细胞，以确定CsA作为CN抑制剂的效力。当用CsA处理完整细胞时，观察到P-gp表达与对CN的CsA依赖性抑制的抗性之间存在正相关性：在多药耐药表皮癌细胞系KB-V中，IC 50大约是在表达极低水平P-gp的亲本KB细胞系中的20倍。KB-V细胞显示的耐药性通过共同施用P-gp抑制剂维拉帕米而消除，而维拉帕米对对照KB细胞中的CsA效力没有影响。在来自KB-V细胞的细胞裂解物中，具有不同量的P-gp CsA表现出等效效力，表明细胞类型之间对CsA的敏感性差异需要维持细胞完整性。这些观察结果支持这样的观点，即在P-gp活性中度升高的细胞中发生CsA对CN抑制的抗性。因此，P-gp活性似乎是CsA细胞特异性治疗和毒性作用的重要决定因素。
Cyclosporin A (CsA) is a widely-used immunosuppressant drug whose therapeutic and toxic actions are mediated through inhibition of calcineurin (CN), a calcium- and calmodulin-dependent phosphatase. Inhibition of CN by CsA requires drug binding to its protein cofactor in the inhibition, cyclophilin. Because cyclophilin is a high affinity target for CsA it is expected that this protein can act as a reservoir for the drug in the cell and may be able to inhibit cellular efflux of CsA. P-glycoprotein (P-gp) is known to increase the rate of CsA efflux from CsA loaded cells but it is not clear if the P-gp drug efflux pump can compete effectively with cyclophilin at therapeutically relevant concentrations of CsA. To test the hypothesis that increased expression of P-gp confers protection against CsA-dependent inhibition of CN phosphatase activity, KB-V cells expressing varying levels of P-gp were analyzed to determine the potency of CsA as a CN inhibitor. When intact cells were treated with CsA, a positive correlation was observed between P-gp expression and resistance to CsA-dependent inhibition of CN: the IC50is approximately 20-fold higher in the multidrug resistant epidermal carcinoma cell line, KB-V, which expresses P-gp at a high level than in the parental, KB, cell line expressing very low levels of P-gp. The resistance displayed by KB-V cells is abrogated by co-administration of the P-gp inhibitor verapamil, whereas verapamil has no effect on CsA potency in control KB cells. In cell lysates from KB-V cells with different amounts of P-gp CsA exhibits equivalent potency, indicating that the difference in sensitivity to CsA among the cell types requires maintenance of cell integrity. These observations support the view that resistance to CN inhibition by CsA occurs in cells with moderately elevated P-gp activity. Therefore, P-gp activity appears to be an important determinant of CsA cellular specificity for both therapeutic and toxic effects.