ABSTRACT
Objective To investigate whether and how murine double minute 2(MDM2) was involved in aldosterone (ALD)-induced human mesangial cells line (HMCLs) proliferation. Methods RT-PCR and immunofluorescence were used to confirm the expression of MDM2 in HMCLs. Western blotting was used to estimate the relationship between ALD dose and MDM2 expression. Spironolactone, a mineralocorticoid receptor (MR) blocker, was used to estimate the role of MR on the up-regulation of MDM2 induced by ALD. Cycloheximide (CHX), a protein synthesis inhibitor, was used to estimate whether the rapid nongenomic mechanism was involved in the upregulation. To confirm the relationship among ALD, MDM2 expression and proliferation of HMCLs, small interference RNA of MDM2 was applied. Results Both MR and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) mRNAs were detected in HMCLs. MDM2 protein expression was also detected in both the nucleus and the cytoplasm. ALD significantly stimulated MDM2 expression, which implied that MDM2 was a novel mineralocorticoid-responsive gene in HMCLs. MR was involved in this process as spironolactone did not promote the expression of MDM2 mRNA or protein. ALD with CHX did not increase the expression of MDM2 protein, which indicated it was not directly regulated by the rapid nongenomic mechanisms. MDM2 protein was decreased by using the transfection of MDM2 siRNA and ALD did not promote the cell proliferation of HMCLs under the same conditions. All of which implied that MDM2 participated in ALQ-induced HMCLs proliferation. Conclusions MDM2 is a novel mineralocorticoid-responsive gene in HMCLs. MR is involved in ALD-induced MDM2 expression which is inhibited by spironolactone. The increased expression of MDM2 protein induced by ALD is not directly regulated by the rapid nongenomic mechanisms. MDM2 participates in ALD induced HMCLs proliferation.