SphK2激活肾脏成纤维细胞进而引起肾纤维化的作用机制研究

Renal fibrosis is the common final manifestation of almost all types of chronic kidney diseases which leads to renal failure. The activation of renal fibroblasts that secrete massive extracellular matrix plays crucial roles in renal fibrosis. Previous studies have reported that S1P induced renal fibrosis. However, there's no report on the role of SphK2, the kinase producing S1P. Our preliminary data showed elevated SphK2 in the kidney after UUO surgery and ameliorated renal fibrosis after UUO surgery in SphK2-/- mice compared with wild type mice. In this project, in vivo and in vitro experiments will be performed to explore (1) the role of SphK2 in renal fibrosis and renal function; (2) the effect of SphK2 on activation of renal fibroblast and associated mechanisms; (3) and we will confirm the association between the severity of renal fibrosis and SphK2 level. Our study will be helpful in further understanding the mechanism of renal fibrosis induced by SphK2 and contributes to developing new therapeutic strategies for renal fibrosis.

肾纤维化是所有慢性肾脏疾病的共同终末通路，最终引起肾衰竭，在此过程中成纤维细胞活化分泌细胞外基质是关键步骤。已有研究发现S1P在其中起着促纤维化的作用，而诱导S1P产生的激酶SphK2的作用尚未见报道。我们在前期工作中发现肾纤维化小鼠肾脏中SphK2表达水平升高，且SphK2-/-小鼠经单侧输尿管梗阻（UUO）术后肾纤维化程度较野生型UUO小鼠显著减轻。本项目将通过体内外实验，继续探索（1）SphK2对肾纤维化程度及肾功能的影响，（2）SphK2在肾纤维化过程中对肾脏成纤维细胞的作用，以及SphK2激活肾脏成纤维细胞的分子机制，（3）分析SphK2水平与临床肾纤维化疾病的相关性。通过研究以上几个问题，本课题将有助于深入理解SphK2在肾纤维化过程中的作用机制，为临床肾纤维化患者的治疗提供新策略。

肾纤维化是所有慢性肾脏疾病的共同终末通路，最终引起肾衰竭，在此过程中成纤维细胞活化分泌细胞外基质是关键步骤。已有研究发现1磷酸鞘氨醇S1P在其中起着促纤维化的作用，而诱导S1P产生的鞘氨醇激酶SphK2的作用尚未见报道。本课题发现在单侧输尿管梗阻（UUO）肾纤维化小鼠模型中，肾脏中SphK2水平随着疾病进展而上调。SphK2-/-小鼠UUO术后肾纤维化程度及肾脏炎症水平较野生型小鼠显著减轻。TGF-β1可诱导肾脏成纤维细胞中SphK2表达上调，抑制SphK2（SphK2 siRNA或SphK2抑制剂ABC294640）可减少细胞外基质沉积，此效应通过减轻STAT3和AKT的磷酸化来实现，而非Smad通路。我们还发现SphK2可与Fyn结合促进其磷酸化，抑制Fyn可减轻STAT3、AKT的磷酸化水平及肾脏成纤维细胞的激活。此外，在临床肾纤维化患者肾活检标本中检测到SphK2阳性细胞数量与肾纤维化严重程度呈正相关。我们用SphK2抑制剂ABC294640治疗UUO小鼠，其肾纤维化程度显著缓解。总之，我们的研究证明SphK2通过磷酸化Fyn来激活下游STAT3和AKT信号，促进细胞外基质沉积，阐明了SphK2促进肾纤维化的分子机制，为进一步寻求治疗肾纤维化的新靶点提供坚实的实验依据。