benzyloxycarbonylleucyl-leucyl-leucine-aldehyde and Proteinuria

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.

Topics: Animals; Diabetic Nephropathies; Down-Regulation; Glucose; Kidney Function Tests; Kidney Glomerulus; Leupeptins; Male; Mesangial Cells; Nerve Tissue Proteins; Proteasome Inhibitors; Proteinuria; Proteolysis; Rats, Wistar; Streptozocin; Transcription Factors; Transforming Growth Factor beta

Oxidative stress may play an important role in the pathogenesis of diabetic nephropathy (DN). Recent studies have shown that the ubiquitin-proteasome pathway (UPP) and oxidative stress have interaction. We aimed to investigate whether inhibiting the proteasome has a preventive effect on DN through suppression of renal oxidative stress.. Male Sprague-Dawley rats were randomly divided into three groups: a normal control (NC) group, a streptozotocin-induced DN model group, and a DN plus MG132 (10 μg/kg) treatment group.. Increased 24-h urinary protein excretion rate (UPER) and renal pathological changes were all improved after MG132 administration. Furthermore, enhanced renal 26S proteasome activity and concentration in DN rats were effectively reduced after MG132 administration. Increased p47phox and nitrotyrosine (NT) expressions in kidneys of DN rats were decreased after MG132 treatment. Renal mRNA and protein expressions of NF-E2 related factor 2 (Nrf2) were up-regulated by MG132 in comparison to DN alone. Decreased renal mRNA expression of superoxide dismutase 1 (SOD1), catalase (CAT) and glutathione peroxidase (GPx) in DN rats was heightened after MG132 intervention. Depressed activities of renal SOD, CAT and GPx in DN rats were also improved by MG132 treatment. Increased renal nuclear factor κB (NF-κB) activity was inhibited after MG132 administration in DN rats at the end of 12 weeks.. Our present data suggest that inhibition of the proteasome by low-dose MG132 has a preventive effect on DN development and progression in rats through the up-regulation of antioxidant genes.

Topics: Animals; Antioxidants; Blotting, Western; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Electrophoretic Mobility Shift Assay; Enzyme-Linked Immunosorbent Assay; Kidney; Leupeptins; Male; Oxidative Stress; Protease Inhibitors; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proteinuria; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction