The roles of arachidonic acid metabol in the pathogenesis of inflammatory diseases in childhood: Regulation of related enzymes by various cytokines

在儿童时期的各种过敏性和炎症性疾病中，一系列负责合成前列腺素(PG)、血栓素(TX)和白三烯(LTS)的酶被激活。可能的调控机制之一是各种细胞因子和炎症介质在转录和/或翻译水平上上调每种酶的转录。本研究采用RT-PCR和Northern印迹技术，研究了中性粒细胞和HL-60细胞胞浆PLA2、环氧合酶(COX)-1、COX-2，5-脂氧合酶(5-LO)、LTC4合成酶(LTC4syn)、LTA4水解酶和5-LO激活蛋白(FLAP)的上调机制。在中性粒细胞中，IL-3和GM/CSF刺激30-60分钟后，LTB_4和TXB_2的合成增加，随后减少。几小时后，TXB2的合成再次增加，而LTB4的合成没有增加，这与COX-2mRNA的表达增强有关。IL-8刺激60min后，LTB4的合成暂时增加，提示IL-8对5-LO或LTA4水解酶有启动作用。IL-4和IL-13作用6h后可促进LTB4合成，这与LTA4水解酶基因表达增强有关。细菌内毒素脂多糖(LPS)通过诱导中性粒细胞产生新的cPLA2和COX-2而增加TXB2的产生。在DMSO处理的HL-60细胞中，通过转录上调5-LO、LTC4syn和LTA4水解酶，LTB4和LTC4的合成增加。我们还研究了抗炎和抗过敏药物如何调节这些酶的活性。

A series of enzymes which are responsible for the synthesis of prostaglandins(PGs), thromboxane(TX) and leukotriens(LTs) are activated in a variety of allergic and inflammatory disease in childhood. One of the possible regulatory mechanisms is a transcriptional up-regulation by various cytokines and inflammatory mediators at the transcriptional and/or translational levels of each enzyme. In this study, we have investigated up-regulatory mechanisms of cytosolic PLA2, cyclooxygenase(COX)-1, COX -2, 5-lipoxygenase (5-LO), LTC4 synthase (LTC4syn), LTA4 hydrolase and 5-LO activating protein (FLAP) in PMNs and HL-60 cells by using RT-PCR and Northern blotting techniques. In PMNs, the synthesis of LTB4 and TXB2 was increased by the stimulation with IL-3 and GM/CSF for 30-60 min, the production was then decreased. After several hours, the synthesis of TXB2 but not LTB4 was increased again, which was associated with enhanced expression of COX-2 mRNA. IL-8 temporarily increased the synthesis of LTB4 after 60 min stimulation, indicating a priming effect on 5-LO or LTA4 hydrolase. LTB4 synthesis was enhanced by IL-4 and IL-13 after 6 hour incubation, which was associated the enhanced expression of LTA4 hydrolase mRNA. Lipopolysaccharide(LPS), a bacterial endotoxin, increased the production of TXB2 by new induction of cPLA2 and COX-2 in PMNs. In DMSO-treated HL-60 cells, the synthesis of LTB4 and LTC4 was increased by transcriptionaly up-regulating 5-LO, LTC4syn and LTA4 hydrolase. We also investigated how anti-inflammatory and anti-allergy medicines modulate these enzyme activities.