Nakata Y, Hide I
Department of Pharmacology, Institute of Pharmaceutical Sciences, Hiroshima University School of Medicine, Japan.
Life Sci. 1998;62(17-18):1653-7. doi: 10.1016/s0024-3205(98)00123-4.
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.
在肥大细胞中，与其他非兴奋性细胞一样，受体激活会产生动员钙离子的第二信使，如肌醇1,4,5-三磷酸或鞘氨醇-1-磷酸，它们会诱导细胞内储存的钙离子释放。由此导致的钙离子储存耗竭会激活质膜上被称为钙离子释放激活钙离子（CRAC）通道的钙离子通道。离子霉素似乎是通过耗尽细胞内钙离子储存而非作为离子载体来引起CRAC通道的激活。我们比较了抗组胺药氮卓斯汀对抗原或离子霉素刺激的大鼠肥大RBL-2H3细胞系中肿瘤坏死因子-α（TNF-α）分泌、钙离子信号和脱颗粒的影响。氮卓斯汀在低于抑制脱颗粒所需浓度时就能抑制TNF-α释放。在抗原刺激的细胞中，氮卓斯汀还能同等程度地抑制TNF-α mRNA表达/蛋白质合成、TNF-α释放和钙离子内流。然而，在离子霉素刺激的细胞中，氮卓斯汀对TNF-α释放的抑制作用比对TNF-α mRNA表达/蛋白质合成和钙离子内流的抑制作用更强，这表明氮卓斯汀通过干扰钙离子以外的信号，比TNF-α的转录或产生更有效地抑制释放过程。用1微摩尔/升氮卓斯汀预处理可抑制离子霉素诱导的而非抗原诱导的蛋白激酶C转位至细胞膜。这些结果表明，TNF-α的转录/产生主要受钙离子内流调节，但TNF-α的释放过程受可能涉及蛋白激酶C激活的其他机制调节。
