Expression and Co-Localization of Nephrin and Podocin in Adriamycin-Induced Nephrotic Rats

Abstract

Objective To observe the expression and distribution of nephrin and podocin in adriamycin-inducing nephrotic (ADN) rats, and explore the possible mechanisms of nephrin and podocin during the progression of nephrotic syndrome(NS). Methods Sixty Spraque-Dawley(SD) rats were divided into ADN model group(injected 6.5 mg/kg adriamycin in tail vein, n=30)and control group (injected 0.8 mL saline solution in tail vein, n=30). After the nephropathy model was established, rats were killed at the end of 1st, 2nd, 4th, 6th, 8th week. The changes of the following indicators were observed: ① 24-hour urinary protein, serum albumin, serum cholesterol, serum creatinine and serum urea nitrogen were detected; ② The characters of renal cortex detected by optical microscope and electron microscope at different time points were observed; ③ The expression of podocin mRNA and nephrin mRNA in cortex of kidney were examined by real time RT-PCR; ④ The co-localization of nephrin and podocin in glomerular was observed by dual-labeling immunofluorescence. Results ①ADN model group came out massive proteinuria, hypoalbuminemia, hypercholesterolaemia, renal failure, and presented as nephrotic syndrome. ADN model group developed from minimal change diseases to focal segmental glomerulosclerosis. The ultrastructure of podocyte showed that foot process conflurence in the early stage, foot process disappeared and chromatin raritas in the end stage. ② ADN model group compared with control group: podocin mRNA expression of AND model group increased 95.8% (P<0.01)at the end of the first week, increased 252.5%( P<0.01) at the end of the second week and reached the peak value, then began to decrease 27.6%(P<0.05)at the end of the fourth week, and decreased 52.9%(P<0.01)at the end of the sixth week, and decreased 48.0%(P<0.01)at the end of the eighth week. Nephrin mRNA expression of ADN model group increased 140.8% (P<0.05) at the end of the first week and reached the peak value, then increased 80.4%( P<0.05)at the end of the second week, decreased 39.2%(P<0.01)at the end of the fourth week, decreased 47.5%(P<0.01)at the end of the sixth week, decreased 52.5%(P<0.01)at the end of the eighth week. ③In ADN model group, the distribution of nephrin and podocin gradually shifted from a linear-like pattern along the capillary loops of glomerulus to a discontinuous coarse granular pattern, and the degree of overlapping localization decreased. Conclusion The abnormal expression and distribution of nephrin and podocin during the progression of adriamycin nephropathy lead nephrin and podocin can not form normal complex, but it may be the important molecular mechanism of proteinuria. Key words: podocin; nephrin; adriamycin-inducing nephrotic (ADN); nephrotic syndrome(NS); proteinuria