Effect of MG132 on expression of Smad7 in cultured glomerular mesangial cells induced by high concentration of glucose

Objective To observe the expression of Smad7 in rat glomerular mesangial cells(GMC) stimulated by the high glucose of different concentration,and to investigatiethe the effect of the ubiquition in this smad signal by adding MG132 as a proteasome differential inhibitor.Methods Cultured rat GMC were divided into normal group(the concentration of glucose:5.6 mmol/L),high glucose group(20 mmol/L,30 mmol/L respectively),therapy group(30 mmol/L high glucose with MG132),mannital group,normal glucose+MG132 group,30 mmol/L glucose+solvent group.The expression of Smad7 mRNA of each group was measured by quantitative PT-PCR and protein was measured by indirect immunfluorescence and laser scanning confocal microscope respectively.Results(1)Compared with normal control group,the expression of Smad7 mRNA had no significant change.(2)The expression of Smad7 protein was decreased significantly in a dose dependent manner in high glucose(P0.05);in therapy group,the expression of Smad7 protein was enhanced.Conclusion(1)High glucose can increase the ubiquitinated degradation of Smad7 protein in glomerular mesangial cells.(2)Compared with 30 mmol/L glucose group,the degradation of Smad7 protein could be reverted mostly by MG132(P0.05).Ubiquition-proteasome pathway(UPP) is related with the regulation of Smad signal transduction pathways in diabetic nephropathy(DN).