The Proteasome Inhibitor, MG132, Attenuates Diabetic Nephropathy by Inhibiting SnoN Degradation In Vivo and In Vitro

• Main Authors: Wei Huang, Chen Yang, Qinling Nan, Chenlin Gao, Hong Feng, Fang Gou, Guo Chen, Zhihong Zhang, Pijun Yan, Juan Peng, Yong Xu
• Format: Article
• Language: English
• Published: Hindawi Limited 2014-01-01
• Series: BioMed Research International
• Online Access: http://dx.doi.org/10.1155/2014/684765
• ISSN: 2314-6133; 2314-6141

Transforming growth factor-β (TGF-β) has been shown to be involved in diabetic nephropathy (DN). The SnoN protein can regulate TGF-β signaling through interaction with Smad proteins. Recent studies have shown that SnoN is mainly degraded by the ubiquitin-proteasome pathway. However, the role of SnoN in the regulation of TGF-β/Smad signaling in DN is still unclear. In this study, diabetic rats were randomly divided into a diabetic control group (DC group) and a proteasome inhibitor (MG132) diabetes therapy group (DT group). Kidney damage parameters and the expression of SnoN, Smurf2, and TGF-β were observed. Simultaneously, we cultured rat glomerular mesangial cells (GMCs) stimulated with high glucose, and SnoN and Arkadia expression were measured. Results demonstrated that 24-hour urine protein, ACR, BUN, and the expression of Smurf2 and TGF-β were significantly increased (P<0.05), whereas SnoN was significantly decreased in the DC group (P<0.05). However, these changes diminished after treatment with MG132. SnoN expression in GMCs decreased significantly (P<0.05), but Arkadia expression gradually increased due to high glucose stimulation (P<0.05), which could be almost completely reversed by MG132 (P<0.05). The present results support the hypothesis that MG132 may alleviate kidney damage by inhibiting SnoN degradation and TGF-β activation, suggesting that the ubiquitin-proteasome pathway may become a new therapeutic target for DN.