Effects Of Mycophenolate Mofetil On Podocyte-associated Proteins And Its Mechanism In Diabetic Rats

Background and objective Diabetic nephropathy (DN) has become one of the main cause of end-stage renal disease (ESRD). Experimental and clinical evidence suggests that inflammation plays a role in the pathogenesis of diabetic nephropathy. in addition to. or in concert with the associated hemodynamic and metabolic changes. Proteinuria is not only a cardinal manifestation of glomerular injury in diabetes, but also an important pathogenetic factor in the progression of renal dysfunction. Recent studies in vivo have shown that mycophenolate mofetil (MMF) administration to streptozotocin-induced diabetic rats could decrease urinary albumin excretion, but the pathophysiologic mechanisms are unclear. Recent studies suggest that podocyte dysfunction plays an essential role in the pathogenesis of proteinuria in diabetic nephropathy. and podocyte-associated molecules such as Nephrin and Podocin make a pivotal contribution to the maintenance of the selective filtration barrier of the nomal glomerulus.The study in vitro indicated that macrophages as well as macrophage-derived cytokines markedly suppressed activity of the Nephrin gene promoter and thereby repress expression of its protein, revealed that inflammation play a crucial role in the injury of podocytes. In the present study, we investigate the effect of MMF on proteinuria and podocyte injury and its mechanism in diabetic rats. Methods Diabetes was induced by injection streptozotocin after uninephrectomy. Rats were randomly divided into three groups: control group(C), diabetic group (DM) and diabetic group treated with MMF (DM+MMF, 10 mg·kg^-1·d^-1, by gavage ). Relative kidney weight (RKW),blood glucose(BG),24 hours urinary albumin excretion rate (AER) were measured and renal morphology was observed by light microscopy after 8 weeks. The expression of ED-1. Nephrin, Podocin, interleukin-1 (IL-1) and tumor necrosis factor-α(TNF-α) protein were determined by immunohistochemistry or Western blot analysis in the kidney. Results 1. BG, RKW, AER: There was a significant increase in BG (P<0.01) in diabetic rats compared with control group. The BG level of diabetic group treated with MMF had no statistically significant difference compared with diabetic group(P>0.05). Increased RKW was significantly reduced by MMF treatment (P<0.05 ) , elevated AER was markedly attenuated by MMF treatment ( P<0.05 ). 2. Renal pathologic morphology: Compared with control group, glomerular area(A_G), mesangial area(A_M), glomerular volume(V_G) were significantly increased in diabetic group (p<0.05, 0.01), which were markedly attenuated by MMF treatment (P <0.05). 3. ED-1 protein expression in renal tissue: ED-1-positive cells were significantly increased in glomeruli in diabetic rats(3.90±0.88/gcs virus 0.70±0.48/gcs, p<0.01), which were effectively suppressed by MMF treatment (1.60±0.52/gcs virus 3.90±0.88/gcs, p<0.05). 4. Nephrin and Podocin protein expression in renal tissue: Western blot analysis noted that the expression of Nephrin and Podocin protein were reduced in the kidney in diabetic group by 80.2% and 65.1%, and MMF treatment significantly increased the expression of Nephrin and Podocin protein (p<0.01).5. IL-1 and TNF-αprotein expression in renal tissue: Western blot analysis noted that the expression of IL-1 and TNF-αprotein was increased 2.8 and 3.8 fold in the kidney in model group(P<0.01), MMF treatment could reduce the increased expression of IL-1 and TNF-αprotein by 73.6% and 70.0%(P<0.01). Conclusion MMF could decrease AER and upregulated the expression of Nephrin and Podocin in the kidney in diabetic rat, which mechanism may be at least partly correlated with its anti-inflammatory effect via suppression of macrophage infiltration and IL-1 , TNF-αprotein production in kidney tissue .