title: Additive inhibition of afferent and efferent immunological responses of human peripheral blood mononuclear cells by verapamil and cyclosporine.
abstract: We have studied the effects of verapamil (0-50 microM) on the in vitro immunological function of human peripheral blood mononuclear cells in the presence or absence of cyclosporine (0-600 ng/ml). The proliferative response to phytohemagglutinin, OKT3, and alloantigens, the generation of cytotoxic T lymphocytes following allogeneic stimulation, and mitogen-induced reduction of intracellular ATP were inhibited in a concentration-dependent fashion by verapamil alone and by cyclosporine alone. When the two drugs were added to the same culture, additive inhibition was observed. A verapamil concentration of 5 microM usually reduced by at least 50% the amount of cyclosporine necessary to cause the same level of inhibition seen when no verapamil was present. The additive inhibition of the two drugs was likely not due to additive inhibition of IL-2 responsiveness, since neither drug alone inhibited the response of an IL-2-dependent T cell clone (CTLL-2) to recombinant IL-2 except at the highest concentrations tested, where a mild additive effect was noted. Nor was the additive inhibition related to an additive effect on total IL-2 receptor expression since an additive inhibitory effect on PHA-induced IL-2 receptor expression was only seen with 50 microM verapamil, while additive functional effects on mitogen- and antigen-induced proliferation and alloantigen-induced CTL generation were seen with 5 microM verapamil doses. Verapamil or cyclosporine alone inhibited IL-2 production of PHA- and phorbol ester-stimulated peripheral blood mononuclear cells--however, no additive effect was seen when the two drugs were both added to culture, probably because of the very potent inhibition by cyclosporine alone. Natural killer cell activity of human peripheral blood mononuclear cells against K562 target cells was significantly inhibited by verapamil in a concentration-dependent fashion, while cyclosporine had a more modest concentration-dependent effect. The combination of both drugs demonstrated additive inhibition. Effector function of cytotoxic T lymphocytes was modestly inhibited by either verapamil or cyclosporine alone. A combination of the highest concentrations of verapamil and cyclosporine caused an additive inhibitory effect. In summary, these data demonstrate that verapamil and cyclosporine have concentration-dependent inhibitory activities on both the afferent and efferent limbs of immunity that were additive when verapamil was used in a concentration of at least 5 microM. The additive effects are probably not related to effects on IL-2 circuitry.
authors.affiliation: Department of Medicine, University of Maryland Hospital, Baltimore 21201.
authors.forename: M R
authors.initials: MR
authors.lastname: Weir
authors.forename: R
authors.initials: R
authors.lastname: Peppler
authors.forename: D
authors.initials: D
authors.lastname: Gomolka
authors.forename: B S
authors.initials: BS
authors.lastname: Handwerger
mesh_terms: D000328:Adult; D000917:Antibody Formation / Q000187:drug effects; D003524:Cyclosporins / Q000494:pharmacology*; D003864:Depression, Chemical; D004357:Drug Synergism; D006801:Humans; D007694:Killer Cells, Natural / Q000187:drug effects; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008213:Lymphocyte Activation / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology*
chemical_list: D003524:Cyclosporins; D014700:Verapamil