C-Reactive Protein promotes diabetic nephropathy via Smad3 mediated NLRP3 inflammasome activation

Abstract

<p>Introduction:<br>Diabetic nephropathy (DN) is the leading microvascular complications of diabetic mellitus. Our previous research revealed that C-reactive protein (CRP) enhances DN and acute kidney injury (AKI)[1], by exacerbating renal fibrosis or inflammation via Smad3 signalling pathways[2]. Our analysis of RNAseq results indicated that NLRP3 is a potential targeted RNA for CRP. The study determined whether CRP promotes inflammation via Smad3-mediated NLRP3 inflammasome activation in DN.</p><p>Methods:<br>CRP transgenic (Tg)×db/db, CRPtg×db/dm mice, Smad3 knockout (KO)×db/db and Smad3 KO×db/m mice were used in the study. The human tubular epithelial cells (TECs), HK-2 and mouse mesangial cells (MCs) were treated with CRP with/without the pre-treatment of CRP receptor CD32b antibody or SIS3, the specific Smad3 inhibitor. In vivo and in vitro kidney injury and inflammation indexes were measured by immunofluorescence, western-blot and qRT-PCR. Cellular mechanism was measured by ChIP and Dual luciferase reporter assay.</p><p>Results:<br>The overexpression of CRP in diabetic mice significantly enhanced kidney injuries (IL-1β, TNF-α), activation of NLRP3 inflammasome (NLRP3, NEK7, and Caspase-1) and phosphorylation of Smad3. The deletion of Smad3 alleviated the diabetic kidney injury and activation of NLRP3 inflammasome in diabetic mice. Consistently, CRP induced cell injury and NLRP3 inflammasome activation in high glucose treated TECs and MCs were reversed by Smad3 inhibitor SIS3 or CRP receptor CD32b antibody. Notably, we identified that CRP promoted NLRP3 activation by P-Smad3 binding to NLRP3 promoter area.</p><p>Conclusion:<br>CRP promotes diabetic nephropathy via Smad3 mediated NLRP3 inflammasome activation. Smad3 is a potential therapeutic target for the treatment of inflammation in diabetic patients.</p><p>Keywords:<br>CRP, Diabetic nephropathy, NLRP3, Smad3</p><p>Reference<br>1. Lai W, Tang Y, Huang XR, Ming-Kuen Tang P, Xu A, Szalai AJ, et al. C-reactive protein promotes acute kidney injury via Smad3-dependent inhibition of CDK2/cyclin E. Kidney international. 2016;90(3):610-26.<br>2. You Y-K, Huang X-R, Chen H-Y, Lyu X-F, Liu H-F, Lan HY. C-Reactive Protein Promotes Diabetic Kidney Disease in db/db Mice via the CD32b-Smad3-mTOR signaling Pathway. Scientific reports. 2016;6(1):26740-.</p>