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Leukotriene receptor antagonists,LY293111 and ONO-1078, protect neurons from the sPLA2-IB-induced neuronal cell death independently of blocking their receptors
Authors:Tatsurou Yagami  Yasuhiro Yamamoto  Hiromi Kohma
Institution:1. Faculty of Pharmaceutical Sciences, Himeji Dokkyo University, 2-1, kami-ohno 7-Chome, Himeji, Hyogo 670-8524, Japan;2. Discovery Research Laboratories, Shionogi and Co. Ltd., 3-1-1 Futaba-cho, Toyonaka, Osaka 561-0825, Japan
Abstract:In the ischemic brain, leukotrienes (LTs) are increased and their receptor antagonists protect neurons. However, it has not yet been sufficiently clarified how antagonists for LT receptors exhibit neuroprotective effects. In the present study, we evaluated protective effects of receptor antagonists for LTB4 (LY293111) and cysteinyl LTs (ONO-1078) in the primary culture of rat cortical neurons. The group IB secretory phospholipase A2 (sPLA2-IB)-induced neuronal cell death had been established as the in vitro model for cerebral ischemia. sPLA2-IB triggered the influx of Ca2+ into neurons via L-type voltage-dependent calcium channel (L-VDCC). Subsequently, the enzyme produced eicosanoids including LTB4 before neuronal cell death. Neither administration of LTB4 nor cysteinyl LTs such as LTC4, LTD4 and LTE4 killed neurons. However, both LY293111 and ONO-1078 significantly prevented neurons from the neurotoxicity of sPLA2-IB, suggesting that the two LT receptor blockers protected neurons through alternative pathways beside LT receptors. An L-VDCC blocker does not only inhibit the influx of Ca2+ into neurons but also rescues neurons from the sPLA2-IB-induced neuronal cell death. The two LT receptor antagonists also blocked the sPLA2-IB-induced Ca2+ influx significantly. Thus, LTs exhibited no neurotoxicity, but their receptor antagonists protected neurons directly in the in vitro ischemic model. Furthermore, the suppression of L-VDCC appeared to be involved in the neuroprotective effects of LY293111 and ONO-1078 independent of blocking their receptors.
Keywords:LY293111  ONO-1078  Group IB secretory phospholipase A2  L-type voltage-dependent calcium channel  Cerebral cortex  Neuroprotection
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