Regulatory mechanisms of leukotrene(LT) synthesizing and degrading enzymes, and LT receptos

白三烯（Leukotrienes， LT）是由膜磷脂在各种内外刺激下合成的重要脂质代谢物，在儿童哮喘变应性炎症的发展中起重要作用。研究LT合成和降解酶的调控机制以及这些生物活性脂质的受体的功能是一个重要的目标。LT合成酶主要在骨髓源性白细胞中表达。另一方面，降解酶和受体广泛分布于各种细胞类型中，表明LTs在各器官中具有多种病理生理作用。培养人转化支气管上皮细胞，与Th2细胞因子IL-13、IL-10、IL-4、IL-5等多种生物活性物质共同培养，观察LT合成和降解酶的mRNA和蛋白表达；胞质磷脂酶a2、5-脂氧合酶、lta4水解酶、ltc4合酶、5- lo活化肽、γ -谷氨酰转肽酶、γ -谷氨酰转肽酶相关酶和LTs受体；采用RT-PCR和western blot检测半胱氨酸LT受体-1、半胱氨酸LT受体-2和BLT。我们发现IL-13和TNFa上调了半胱氨酸LT受体1的表达，这表明在Th2细胞因子优势条件下，半胱氨酸LT的作用通过受体的转录上调机制得到增强。我们还发现IL-4和IL-13在人支气管上皮细胞中主要诱导eotaxin-3，这是一种对嗜酸性粒细胞有效的化学引诱剂。干扰素γ，一种Th1细胞因子；抑制IL-13诱导的eotaxin-3。这些发现提示病毒感染可能参与支气管哮喘的发病机制。

Leukotrienes(LT) are very important lipid metabolites synthesized from membrane phospholipids by various internal and/or external stimuli, which play significant roles in the development of allergic inflammation in childhood asthma. It is an essential target to investigate the regulatory mechanisms of LT synthesizing and degrading enzymes as well as the function of receptors of these bioactive lipids. LT synthesizing enzymes are predominantly expressed in bone marrow-derived leukocytes. On the other hands, the degrading enzymes and receptors are widely distributed in various cell types, indicating a variety of patho-physiological roles of LTs in various organs.Cultured human transformed bronchoepithelial cells were grown and incubated with various bioactive substances including Th2 cytokines such as IL-13,IL-10,IL-4 and IL-5,and then mRNA- and protein-expression of LT synthesizing and degrading enzymes ; cytosolic phospholipaseA2,5-lipoxygenase, LTA4-hydrolase, LTC4-synthase,5-LO-aetivating peptide, ganmma-glutamyl transpeptidase, ganmma-glutamyl transpeptidase related enzyme, and receptors of LTs ; cysteinyl LT receptor-1,cysteinyl LT receptor-2 and BLT were evaluated by RT-PCR and western blotting.We have found that expression of cysteinyl LT receptor-1 is up-regulated by IL-13 and TNFa, which indicates that action of cysteinyl LTs are enhanced in Th2 cytokine dominant conditions through the transcriptional up-regulatory mechanism of the receptor.We have also found that IL-4 and IL-13 predominantly induce eotaxin-3, a potent chemoattractant to eosinophils, in human bronchoepithelial cells. Interferon ganmma, a Th1 cytokine ; produced by viral infection, inhibits IL-13 induced eotaxin-3. These findings suggest that viral infection may be involved in pathogenesis of bronchial asthma.