mPGES-1来源的PGE2通过活化NLRP3炎症小体介导腹膜透析相关性腹膜纤维化

Peritoneal mesangial cells undergoing mesothelial-to-mesenchymal transition (MMT) induced by chronic non-bacterial inflammation promotes peritoneal fibrosis, but the exact molecular mechanism is still unclear. It’s reported that mPGES-1-derived PGE2 plays an important role in inflammatory diseases. Besides, previous studies have shown that the secretion of PGE2 increased significantly in peritoneal mesothelial cells under the circumstance of high glucose. Emerging evidence indicated that mPGES-1 is highly expressed in peritoneal mesangial cells treated with high glucose. Meantime, down regulation of mPGES-1 in peritoneal mesangial cells treated with high glucose resulted in the decrease of fibronectin, which suggested that mPGES-1 may promote fibrosis. In addition, NLRP3 and caspase-1 expression are also enhanced in peritoneal mesangial cells treated with high glucose. More importantly, when mPGES-1 was silenced in peritoneal mesangial cells, the components NLRP3 inflammasome of NLRP3 and caspase-1 expression was reduced following high glucose treatment. Since the NLRP3 inflammasome promoted liver fibrosis via activating Smad pathway. Thus, we hypothesized that mPGES-1-derived PEG2 might mediate high glucose induced peritoneal mesangial cells injury via triggering NLRP3 inflammasomes which activated Smad pathway. In the present proposal, employing the peritoneal tissues of peritoneal ultrafiltration failure, animal models of peritoneal dialysis-associated peritoneal fibrosis, cell damage models induced by high glucose, we will fully explore the contribution of this pathway in peritoneal dialysis-associated peritoneal fibrosis, which will offer new insights into the prevention and therapies of peritoneal dialysis-associated fibrosis.

慢性炎症反应是导致腹膜透析相关性腹膜纤维化的关键因素，但具体分子机制尚不清楚。mPGES-1来源的PGE2在炎症性疾病中发挥了重要作用，但在腹膜纤维化中的作用尚无报道。我们前期发现高糖显著上调腹膜间皮细胞mPGES-1表达，而敲低mPGES-1可抑制高糖诱导的腹膜间皮细胞外基质FN的上调。进一步，我们发现高糖上调了腹膜间皮细胞NLRP3及caspase-1的表达，而敲低mPGES-1显著抑制了NLRP3及caspase-1水平，提示高糖诱导的mPGES-1/PGE2可活化NLRP3炎症小体。而NLRP3炎症小体可通过活化Smads参与肝脏纤维化。故推测：高糖环境下，mPGES-1/PGE2活化NLRP3炎症小体，产生持续的慢性炎症反应，促进Smads活化，进而介导了腹膜纤维化。本课题将在整体、细胞及分子层面研究这一通路在腹膜透析相关性腹膜纤维化中的作用，为临床防治腹膜纤维化提供新思路。

腹膜透析（peritoneal dialysis, PD）是利用人体自身腹膜作为半透膜进行溶质和水的跨膜转运的一种透析方式，其具有可家居实施、治疗费用相对低廉及更好保护残余肾功能等优势，目前已成为ESRD患者肾脏替代治疗的主要方式之一。慢性非细菌性炎症反应是导致腹膜透析相关性腹膜纤维化的关键因素之一，但具体分子机制尚不清楚。前列腺素E2（prostaglandin E2,PGE2）是体内重要的促炎及调节免疫的介质，膜结合型前列腺素E2合酶1 （microsomal prostaglandin E synthase-1, mPGES-1）是特异性的PGE2合成酶， PGE2可通过EP4受体介导炎症反应。研究显示mPGES-1在博来霉素诱导的皮肤纤维化进程中起到了重要的作用；而高糖刺激腹膜间皮细胞后，PGE2分泌显著增加，提示mPGES-1/PGE2可能参与腹膜纤维化。我们在前期研究也发现与正常糖浓度培养的大鼠腹膜间皮细胞系相比，高糖刺激可使mPGES-1、EP4的表达显著增加，提示高糖环境下mPGES-1/PGE2/EP4通路被诱导活化。而敲低mPGES-1可抑制高糖诱导的腹膜间皮细胞外基质纤维连接蛋白的上调，提示干涉mPGES-1/PGE2/EP4通路可减缓腹膜纤维化。因此，本项目以mPGES-1/PGE2/EP4通路为研究切入点，将在患者、动物及细胞层面阐明这一通路在腹膜透析相关腹膜纤维化中的作用，开拓基于靶向调控慢性非细菌性炎症反应减缓腹膜透析相关腹膜纤维化的防治策略。本项目在研究过程中发现：1.腹膜超滤衰竭患者腹膜组织中mPGES-1及EP4表达增加，且表达位于腹膜间皮细胞中，随着PD治疗时间延长，PD患者腹腔PGE2分泌增加；2.高浓度葡萄糖可诱导大鼠腹膜间皮细胞系mPGES-1和EP4的表达，体外抑制mPGES-1的表达或抑制EP4受体可使高浓度葡萄糖诱导的大鼠腹膜间皮细胞系细胞外基质蛋白合成减少；3.体内抑制EP4受体可减轻PD大鼠腹膜病理损伤及改善腹膜功能，同时可改善PD大鼠腹腔微炎症及减轻PD大鼠腹膜纤维化；4.mPGES-1/PGE2/EP4通路可通过活化NLRP3炎症小体和NF-κB介导大鼠腹膜间皮细胞系细胞外基质蛋白的合成。