title: Cyclosporine A, an in vitro calmodulin antagonist, induces nuclear lobulations in human T cell lymphocytes and monocytes.
abstract: Cyclosporine A is a noncytotoxic, natural, 11 amino acid cyclic peptide used clinically as an immunosuppressant to prevent organ rejection after transplantation. Cyclosporine A is an in vitro calmodulin antagonist. At the low concentrations required to inhibit calmodulin-dependent phosphodiesterase in vitro, cyclosporine A causes a dramatic alteration in the nuclear morphology of 23% of human peripheral blood mononuclear leukocytes in vitro without loss of viability. The shape of the nucleus changes from ovoid to a distinctive, radially splayed lobulated structure. The changes occur in a dose-dependent manner in 60 min at 37 degrees C. Specific monoclonal antibodies to human leukocytes identify the cells susceptible to nuclear lobulation by cyclosporine A as OKT4 antigen-positive T cell lymphocytes and monocytes. The lobulated nuclei are 2N as determined by flow cytometric measurement of ethidium bromide fluorescence of DNA. The cyclosporine A-induced lobulation of T cell nuclei requires both physiologic temperature and metabolic energy. Although structurally different than cyclosporine A, the calmodulin antagonists R24571 and W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide] also produce T cell nuclear lobulations that are indistinguishable from the nuclear lobulations caused by cyclosporine A. These data indicate that nonmitotic structural elements that govern normal nuclear morphology in a subset of mononuclear leukocytes appear to require a calmodulin-mediated process. Cyclosporine A may be a useful noncytotoxic inhibitor of calmodulin-dependent systems that influence nuclear structure and function.
mesh_terms: D000954:Antigens, Surface / Q000032:analysis; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002467:Cell Nucleus / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D003524:Cyclosporins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects* / Q000276:immunology; D012323:RNA Processing, Post-Transcriptional / Q000187:drug effects; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D013696:Temperature; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D000954:Antigens, Surface; D002147:Calmodulin; D003524:Cyclosporins; D007093:Imidazoles; C031938:calmidazolium