OBJECTIVETo study the effects of p38 MAPK signaling pathway and aldose reductase (AR) on the transforming growth factor (TGF)-β1-induced expression of fibronectin (FN).

METHODSHuman mesangial cells (HMCs) were cultured, and transfected with pCDNA3-AR. AR gene silencing was induced by small interfering RNA (siRNA). AR expression in HMCs was examined by immunofluorescence analysis. RT-PCR and real-time PCR were performed to detect the mRNA expression of AR in the HMCs and Western blotting was used to detect the protein expression of AR, FN and p38. AR inhibitors (ARIs), Sorbinil and Zopolrestat were added and co-incubated, followed by addition of TGF-β1. Western blotting was used to document protein expression of FN and p38 mitogen-activated protein kinases (p38 MAPKs) in the HMCs.

RESULTSImmunofluorescence analysis showed a stronger expression of AR in HMCs transfected with AR than that of normal HMCs and HMCs transfected with blank vector. In comparison with normal HMCs and those transfected with blank vector, HMCs transfected with AR showed stronger protein expression of FN (P<0.05). After incubation of ARIs, protein expression of FN decreased in HMCs transfected with AR (P<0.05). After stimulation of TGF-β1, FN protein expression increased in both normal HMCs and those transfected with AR (P<0.05). After preincubation with ARI, FN protein expression in HMCs transfected decreased significantly (P<0.05). After stimulation of TGF-β1, naïve HMCs showed increased expression of phosphor-p38. In contrast, HMCs preincubated with ARIs showed reduced expression of phosphor-p38, and HMCs transfected with AR showed increased expression of phosphor-p38 (P<0.05).

CONCLUSIONSAR regulates the expression of FN through the stimulation of TGF-β1, which may involve the activation of p38-MAPK signaling pathway. AR may play a role in the pathogenesis of glomerulosclerosis.