Calcium signaling and protein kinase C for TNF-alpha secretion in a rat mast cell line.
In mast cells, like other nonexcitable cells, receptor activation produces Ca2+-mobilizing second messengers such as inositol 1,4,5-triphosphate or sphingosine-1-phosphate, which induce Ca2+ release from internal stores. The resulting depletion of Ca2+ stores activates Ca2+ channels in plasma membranes designated as Ca2+ release-activated Ca2+ (CRAC) channels. Ionomycin appears to cause activation of CRAC channels by depleting intracellular Ca2+ stores rather than by acting as an ionophore. We compared the effects of azelastine, an anti-allergic drug, on TNF-alpha secretion, on Ca2+ signal, and on degranulation in an antigen- or ionomycin-stimulated rat mast RBL-2H3 cell line. Azelastine inhibited TNF-alpha release at concentrations lower than those needed for the inhibition of degranulation. In antigen-stimulated cells, azelastine also inhibited equipotently TNF-alpha mRNA expression/protein synthesis, TNF-alpha release and Ca2+ influx. In ionomycin-stimulated cells, however, azelastine inhibited TNF-alpha release to a greater extent than TNF-alpha mRNA expression/protein synthesis and Ca2+ influx, indicating that azelastine inhibits the release process more potently than transcription or production of TNF-alpha by interfering with a signal other than Ca2+. Pretreatment with 1 microM azelastine inhibited ionomycin-induced, but not antigen-induced, protein kinase C translocation to the membranes. These results suggest that TNF-alpha transcription/production is mainly regulated by Ca2+ influx, but the release process of TNF-alpha is regulated by additional mechanism(s) possibly involving activation of protein kinase C.
Nakata
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Department of Pharmacology, Institute of Pharmaceutical Sciences, Hiroshima University School of Medicine, Japan. ynakata@ipc.hiroshima-u.ac.jp
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D000818:Animals; D000941:Antigens / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015550:Cell Degranulation / Q000187:drug effects / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism*; D010793:Phthalazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000378:metabolism*
D000941:Antigens; D002121:Calcium Channel Blockers; D007093:Imidazoles; D007476:Ionophores; D016859:Lipoxygenase Inhibitors; D010793:Phthalazines; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D015759:Ionomycin; D011493:Protein Kinase C; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium; C020976:azelastine