Objective: To determine the effect of aldosterone and its antagonist, spironolactone on epithelial-mesenchymal transition (EMT) of normal rat kidney epithelial cells (NRK-52E) in a high glucose milieu,and to explore the mechanism of renoprotection in diabetic nephropathy (DN ) in rats involving aldosterone and spironolacton.
Methods: NRK-52E cells were simultaneously cultured in the serum-free Dulbecco's modification of Eagle's medium Dulbecco (DMEM) for 12 hours. Then the low glucose (LG) group was cultured in LG (1000 mg/L) DMEM:The high glucose (HG) group was cultured in high glucose (4,500 mg/L) DMEM. The aldosterone (Aldo) groups were cultured in high glucose DMEM with the addition of 10,50 and 100 nmol/L aldosterone respectively. The SP group was cultured in high glucose (4,500 mg/L) DMEM plus 10(-7)mol/L spironolactone. Immunohistochemistry, RT-PCR and Western blot were used to detect E-cadherin and alpha smooth muscle actin(alpha-SMA) mRNA expression.
Results: RT-PCR showed that compared with the LG Group, E-cadherin mRNA expression in the HG group was significantly lower, and alpha-SMA mRNA expression was significantly increased(P<0.05). E-cadherin mRNA expression in the 50 nmol/L Aldo group and 100 nmol/L Aldo group was significantly lower than that in the HG group, while the expression of alpha-SMA mRNA was significantly increased in the HG group(P<0.05), with a dose-dependent relationship with aldosterone(r=-0.70,P<0.05;r=0.67, P<0.05). E-cadherin mRNA in the SP group was significantly higher,while alpha-SMA mRNA expression was lower than that in the HG group(P<0.01). Immunohistochemistry and Western blot showed that compared with the LG group, E-cadherin protein expression was significantly reduced, and alpha-SMA expression was significantly increased in the HG group(P<0.01). In the 10 nmol/L Aldo, 50 nmol/L Aldo, and the 100 nmol/L Aldo groups, E-cadherin protein expression was significantly lower, and alpha-SMA protein expression was significantly higher than that in the HG group(P<0.05), with a dose-dependent relationship with aldosterone(r=-0.83,P<0.05;r=0.81, P<0.05). In the SP group, E-cadherin protein expression was higher, and alpha-SMA protein level was lower than that in the HG group(P<0.05).
Conclusion: Aldosterone can promote EMT of tubular epithelial cells in a high sugar milieu, leading to renal interstitial fibrosis in Diabetic nephropathy. Spironolactone can inhibit high glucose-induced renal tubular epithelial cells EMT, which may be an important mechanism for the inhibition of renal interstitial fibrosis.