Hydrocortisone inhibits antigen-induced rise in intracellular free calcium concentration and abolishes leukotriene C4 production in leukemic basophils.
Antigenic stimulation of rat basophilic leukemia cells (RBL-3H3) elevates intracellular free Ca2+ concentration ([Ca2+]i) and induces production of leukotriene C4 (LTC4). This model was used to examine the role of Ca2+ in LTC4 formation, and inhibition by hydrocortisone (HC). HC, at a physiological concentration (2 x 10(-7) M), selectively prevented the stimulatory effect of the antigen on LTC4 production whereas the response to calcium ionophore (A23187) remained unimpaired. The inhibition by HC was time-dependent: half maximal response was reached at 2 hour and maximal response at 3 hours. Addition of arachidonic acid (3 micrograms/ml) did not overcome the inhibitory action of HC. An elevated [Ca2+]i is known to be essential for the activation of both 5-lipoxygenase and phospholipase A2. The stimulatory effect of the antigen on LTC4 production was abolished when the cells were incubated in Ca2+-deficient medium. Likewise, calcium ionophore stimulation shows dependence on extracellular Ca2+. Half maximal stimulation by the antigen and calcium ionophore was observed at external Ca2+ concentration of 150 microM and 40 microM respectively. Treatment with HC largely prevented the antigen-induced rise in [Ca2+]i, measured by Quin 2. In addition, HC reduced by 70% the accumulation of 45Ca2+ induced by the antigen. Collectively, these results demonstrate for the first time that HC reduces antigen-induced elevation of [Ca2+]i, and this may be associated with the inhibitory action of HC on LTC4 formation. This property could be partly responsible for the antiallergic and antiinflammatory activities of HC.
Department of Hormone, Research, Weizmann Institute of Science, Rehovot, Israel.
U
U
Zor
E
E
Her
J
J
Talmon
F
F
Kohen
T
T
Harell
S
S
Moshonov
B
B
Rivnay
D000818:Animals; D000941:Antigens / Q000276:immunology*; D001491:Basophils / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006854:Hydrocortisone / Q000494:pharmacology*; D007942:Leukemia, Experimental / Q000378:metabolism; D013189:SRS-A / Q000096:biosynthesis*; D013050:Spectrometry, Fluorescence; D014407:Tumor Cells, Cultured / Q000378:metabolism
D000941:Antigens; D013189:SRS-A; D002118:Calcium; D006854:Hydrocortisone