Expression And Regulation Of A Novel Identified TNFAIP8 Family Is Associted With Diabetic Nephropathy

Objective:Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes and the most common cause of end stage of renal diseases (ESRD). DN can be characterized by both glomerular and tubulointerstitial injury. An important histological hallmark of DN is mesangial cell proliferation, resulting in the expansion of extracellular matrix (ECM) in the mesangium. Thickening of the glomerular basement membrane (GBM) is another feature of DN. Although the pathogenesis of DN is multifactorial, a number of clinical and animal model studies have implicated inflammatory mechanisms as important pathogenic factors in DN. Tumor necrosis factor-a-inducible protein 8 (TNFAIP8) family (include TNFAIP8, TIPE1, TIPE2, TIPE3) are very recently identified proteins which share considerable sequence homology to regulate cellular and immune homeostasis. Therefore, the present study was designed to characterize the members of TNFAIP8 family in the kidney and to explore their possible roles in the development and progression of DN.Methods:1. In in vivo study Male Sprague-Dawley rats were randomly divided into control and diabetic animal model (induced by tail-vein injection of streptozotocin at 50 mg/kg). After 12 weeks, the determination of urinary albumin and HE staining to determine the glomerular damages; By immunofluorescence or immunohistochemistry to determine the distribution of the TNFAIP8 family in renal biopsies; By real time RT-PCR and Western blot analyses to detect the expression changes of the TNFAIP8 family and to measure the activity of NADPH oxidase activity in the kidney.2. In in vitro study To determine the expression and change of the TNFAIP8 family in glomerular mesangial cells (MC) and podocyte cells (PC).3. Anaylsis of the expression levels of TNFAIP8 family in the renal biopsies from DN patients and explore the related regulatory mechanisms.Results:The activity of NADPH oxidase and the exepression of TNF-αmRNA were increased in the renal cortex from streptozotocin (STZ)-induced diabetic rats.By real time RT-PCR and Western blot analyses, it was found that that all members of TNFAIP8 family were detected in the kidney. TNFAIP8 and TIPE2 expression was significantly increased in the renal cortex from streptozotocin (STZ)-induced diabetic rats, and this upregulation was further confirmed in renal biopsies of diabetic patients. In in vitro study, TNFAIP8 was upregulated in response to high glucose in mesangial cells rather than podocytes. However, we failed to observe the upregulation of TIPE2 in both mesangial cells and podocytes in response to high glucose.Conclusions:We found that, among four members of this family, TNFAIP8 and TIPE2 were upregulated in DN, indicating that they may participate in the pathogenesis of DN. A direct correlation was observed between expression of TNFAIP8 and cell proliferation in high glucose-treated mesangial cells. We further demonstrated that this regulation is associated with NADPH oxidase-mediated signaling pathways.