Delta 9-tetrahydrocannabinol suppresses concanavalin A induced increase in cytoplasmic free calcium in mouse thymocytes.
It has been shown that delta-9-tetrahydrocannabinol (THC) suppresses thymocyte, lymph node, and splenic lymphocyte proliferation in response to a mitogenic stimulus. It has also been reported that increases occur in the cytosolic free calcium concentration (Ca2+) in mitogen treated lymphocytes. In an attempt to understand a portion of the molecular basis of the THC induced suppression of lymphocyte proliferation, we have examined the effects of THC on the Concanavalin A (Con A) induced cytosolic free Ca2+ mobilization in mouse thymocytes measured by fluorescent Ca2+ probes and spectrofluorometry. The results show that a 10 minute pretreatment with THC suppresses the normal rise in intracellular free Ca2+ in response to Con A. A THC concentration of 4 micrograms/ml (13 microM) was suppressive and the drug vehicle, DMSO, had no effect. In addition, we found that THC pretreatment did not inhibit the binding of FITC labeled Con A to the thymocytes suggesting that the drug did not interfere with lectin binding to the cell surface. To further define the nature of the Ca2+ response affected by THC, mouse thymocytes containing fura-2 were exposed to Con A either in the presence or absence of Ca(2+)-containing medium. It was observed that THC abrogated both intracellular release (measured in Ca(2+)-free medium) as well as extracellular Ca2+ influx. These results suggest that a portion of the proliferation defect in THC treated lymphocytes may be related to a drug induced inhibition of Ca2+ mobilization that normally occurs following mitogen treatment.
Yebra
M
M
Department of Medical Microbiology and Immunology, University of South Florida College of Medicine, Tampa 33612.
Klein
T W
TW
Friedman
H
H
D000634:Aminoquinolines / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003208:Concanavalin A / Q000494:pharmacology*; D003593:Cytoplasm / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D013759:Dronabinol / Q000494:pharmacology*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D013053:Spectrophotometry; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology
D000634:Aminoquinolines; D005456:Fluorescent Dyes; D003208:Concanavalin A; D013759:Dronabinol; C035739:Quin2; D002118:Calcium; D016257:Fura-2