Inhibition of cell-mediated cytolysis and P-glycoprotein function in natural killer cells by verapamil isomers and cyclosporine a analogs

Walter T. Klimecki, Charles W. Taylor, William S. Dalton

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

We have previously shown that among normal leukocytes, CD56+ and CD8+ cells express relatively high levels of P-glycoprotein (P-gp), a transmembrane efflux pump. While the physiologic significance of P-gp expression in leukocytes is unknown, the relatively high levels of P-gp in CD56+ and CD8+ cells suggest that P-gp may function in cell-mediated cytolysis. To explore this possibility we examined the effect of four inhibitors of P-gp efflux [(R)-verapamil (R-ver), (S) -verapamil (S-ver), cyclosporine A (CsA), and PSC833 (PSC)] on both the inhibition of natural killer cell (NK) function and on P-gp efflux. NK function was assayed by measuring the lysis of51Cr-labeled K562 target cells in the presence and absence of inhibitors. All four P-gp efflux inhibitors inhibited NK-mediated cytolysis in a dose-dependent manner. The stereoisomers of verapamil were more potent inhibitors of cell-mediated cytolysis than the cyclosporines CsA and PSC. In contrast, CsA and PSC were more potent as inhibitors of P-gp-mediated rhodamine 123 dye efflux than the verapamil isomers. Both CsA and PSC maximally inhibited P-gp efflux at 3 μM, but only minimally inhibited cell-mediated cytolysis. The verapamil compounds demonstrated closer correlation between efflux inhibition and inhibition of NK-mediated cytolysis. The data support a role for P-gp in NK-mediated cytolysis; however, these studies also suggest that the NK cytolytic process is multifaceted and that inhibition of the P-gp-mediated efflux mechanism only partially abrogates this process.

Original languageEnglish (US)
Pages (from-to)152-158
Number of pages7
JournalJournal of Clinical Immunology
Volume15
Issue number3
DOIs
StatePublished - May 1995

Keywords

  • NK cells
  • P-Glycoprotein
  • cytolysis inhibition
  • efflux inhibition

ASJC Scopus subject areas

  • Immunology and Allergy
  • Immunology

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