P-Cadherin is Decreased in Glucose-Stimulated Podocytes and in Experimental Diabetic Nephropathy

Ryu, Dong Ryeol; Xu, Zhong Gao; Yoo, Tae Hyun; Chang, Jae Hyun; Jung, Dong Sub; Lee, Su Hyun; Kim, Jin Ju; Choi, Kyu Hun; Lee, Ho Yung; Han, Dae Suk; Kang, Shin Wook

Abstract

BACKGROUND
Proteinuria is a cardinal feature of glomerular disease including diabetic nephropathy, and glomerular filtration barrier is considered as a filter restricting protein excretion in urine. We tested whether the expression of P-cadherin, a molecule known to be located at the slit diaphragm, was altered by high glucose in cultured podocytes in vitro and by diabetes in vivo. METHODS: In vitro, immortalized mouse podocytes were cultured in media with 5.6 mM glucose (NG), NG+24.4 mM mannitol (NG+M), or 30 mM glucose (HG) for 7 days at 37dgrees C. Cell lysates were used for RT-PCR and Western blot. For animal studies, twelve Sprague-Dawley rats were injected with diluent (Control, C, N=6) or streptozotocin (DM, N=6) intraperitoneally, and were sacrificed after 6 weeks. RT-PCR and Western blot for P-cadherin mRNA and protein expression, respectively, were performed with sieved glomeruli, and immunohistochemistry with renal tissue. RESULTS: HG significantly reduced P-cadherin mRNA and protein expression in cultured podocytes by 47% and 62%, respectively (p<0.05). Twenty-four hour urinary albumin excretion was significantly higher in DM (12.80+/-1.12 mg/day) compared to C rats (3.15+/-0.24 mg/day) (p<0.05). Glomerular P-cadherin mRNA expression was significantly lower in DM than that in C rats (p<0.05). P-cadherin protein expression assessed by Western blot and immunohistochemistry showed a similar pattern. CONCLUSION: Exposure of podocytes to HG in vitro and diabetes in vivo reduced P-cadherin mRNA and protein expression. These findings suggest that the decrease in P-cadherin expression is connected to the early changes of diabetic nephropathy and thus may contribute to the development of proteinuria.