Yu Ruichao, Bo Hong, Villani Vincenzo, Spencer Philip J, Fu Ping
Sichuan University, West China Hospital, Department of Nephrolog, Wuhou District, Chengdu, Sichuan, China.
Kidney Blood Press Res. 2016;41(1):55-69. doi: 10.1159/000368547. Epub 2016 Feb 7.
BACKGROUND/AIMS: There is increasing evidence showing that innate immune responses and inflammatory processes play an important role in the development and progression of diabetic nephropathy (DN). The potential effect of innate immunity in the early stage of DN is still unclear. Toll-Like-Receptor 4 (TLR4) is vigorously involved in the progress of kidney diseases in a sterile environment. The activation of the interleukin 17 (IL-17) pathway produces inflammatory cytokines, appearing in various kidney diseases. Unfortunately the relationship between TLR4 and IL-17 has not been investigated in diabetic nephropathy to date. The aim of this study is to investigate whether mammalian target of rapamycin (mTOR) inhibition may be dependent on TLR4 signaling and the pro-inflammatory factor IL-17 to delay the progression of DN.
Streptozotocin (STZ)-induced diabetic rats were randomly assigned to 3 experimental groups: a diabetic nephropathy group (DN, n = 6); and a diabetic nephropathy treated with rapamycin group (Rapa, n = 6) and a control group (Control, n =6). Body weight, fasting blood sugar, and 24h urine albumin were assessed at week 2, week 4 and week 8. Renal tissues were harvested for H&E, PAS staining, as well as an immunohistochemistry assay for TLR4 and IL-17. TLR4 quantitative expression was measured by Western-Blot analysis and RT-PCR.
Our results demonstrated that the expression of both TLR4 and IL-17 were upregulated in early stage DN and reduced by rapamycin. TLR4 and IL-17 both increased and positively related to 24h urinary albumin and kidney/weight ratio. However, neither TLR4 nor IL-17 made a significant difference on fasting blood sugar.
Taken together, our results confirm and extend previous studies identifying the significance of the TLR4 and Th17 pathways in development of early stage DN. Furthermore, we suggest this overexpression of TLR4 might be involved in the immunopathogenesis of DN through activation of Th17 cells. Rapamycin may attenuate DN via reduction of the TLR4 signaling pathway and Th17 cells signaling. Although the underlying mechanisms need to be explored, the observed increase of TLR4 and IL-17 during the early stages of DN and their suppression with rapamycin treatment suggest the importance of TLR4 and IL-17 in DN pathophysiology.
背景/目的：越来越多的证据表明，固有免疫反应和炎症过程在糖尿病肾病（DN）的发生和发展中起重要作用。固有免疫在DN早期的潜在作用仍不清楚。Toll样受体4（TLR4）在无菌环境下积极参与肾脏疾病的进展。白细胞介素17（IL-17）通路的激活会产生炎症细胞因子，见于各种肾脏疾病。遗憾的是，迄今为止，TLR4与IL-17之间的关系在糖尿病肾病中尚未得到研究。本研究的目的是探讨雷帕霉素靶蛋白（mTOR）抑制是否可能依赖于TLR4信号传导和促炎因子IL-17来延缓DN进展。
将链脲佐菌素（STZ）诱导的糖尿病大鼠随机分为3个实验组：糖尿病肾病组（DN，n = 6）；雷帕霉素治疗糖尿病肾病组（Rapa，n = 6）和对照组（Control，n = 6）。在第2周、第4周和第8周评估体重、空腹血糖和24小时尿白蛋白。收集肾组织进行苏木精-伊红（H&E）、过碘酸-雪夫（PAS）染色，以及TLR4和IL-17的免疫组化检测。通过蛋白质免疫印迹分析和逆转录-聚合酶链反应（RT-PCR）测量TLR4定量表达。
我们的结果表明，TLR4和IL-17的表达在DN早期均上调，并被雷帕霉素降低。TLR4和IL-17均升高，且与24小时尿白蛋白和肾重比呈正相关。然而，TLR4和IL-17对空腹血糖均无显著影响。
综上所述，我们的结果证实并扩展了先前的研究，确定了TLR4和Th17通路在早期DN发生中的重要性。此外，我们认为TLR4的这种过表达可能通过激活Th17细胞参与DN的免疫发病机制。雷帕霉素可能通过减少TLR4信号通路和Th17细胞信号传导来减轻DN。尽管潜在机制有待探索，但在DN早期观察到的TLR4和IL-17增加以及雷帕霉素治疗对它们的抑制表明TLR4和IL-17在DN病理生理学中的重要性。
