Effect of serum IgA1 from patients with IgA nephropathy on the transforming growth factor -β1/Smads signaling pathway in human glomerular mesangial cells

Abstract

Objective To explore the effect of serum IgA1 from patients with IgA nephropathy(IgAN) on transforming growth factor beta- 1 ( TGF-β 1 ), phosphorylated Smad3 (p-Smad3) and fibronectin(FN) in human glomerular mesangial cells (HMC). Methods HMC was cultured in vitro and divided into 5 groups: IgA1 free control (health control group), stimulated with serum IgA1 from healthy people (NIgA1group) , stimulated with serum aggregated IgA1 from healthy people (aNIgA1 group) , stimulated with serum IgA1 from patients with IgA nephropathy (IgAN) (PIgA1 group), and stimulated with serum aggregated IgA 1 from patients with IgAN (aPIgA1 group). The expression of TGF-β1, p-Smad3 and FN mRNA was assayed by RT-PCR. The expression of p-Smad3 protein was analyzed by Western blot. The expression of TGF-β1 and FN protein in the culture supematant of HMC was analyzed by ELISA. Results PIgA1 and aPIgA1 significantly up-regnlated TGF-β1, p-Smad3, FN mRNA and protein expression. The TGF-β1, p-Smad3 and FN mRNA were increased by 1.5-fold(P<0.01), 1.3-fold(P<0.05) and 1.5-fold(P< 0.01 ) in aPIgA1 group as compared with PIgA1 group. The TGF-β1 and p-Smad3 protein were increased by 2.1-fold and 1.6-fold (P<0.01) in aPIgA1 group as compared with PIgA1 group. In aPIgA1 group, the expression of TGF-β1 and p-Smad3 mRNA with aPIgA1 was increased gradually, peaked at 12 h (0.866± 0.055,0.891±0.251 ), and then decreased to the basic levels at 24 h, but the the expression of FN mRNA peaked at 24 h(0.968±0.031 ). The expression of TGF-β1 and p-Smad3 protein was increased , peaked at 12 h for TGF-β1 [(246.960±1.270) ng/L], at 6 h for p-Smad3(0.490±0.046), then decreased. The expression of FN protein was increased , peaked at 24 h [(1.804±0.038) mg/L] (P<0.01). Conclusions PIgA1 and aPIgA1 significantly up-regulate TGF-β, p-Smad3, FN mRNA and protein expression. The effect of aPIgA1 is stronger than that of PIgA1. It is suggested that serum IgA1, mainly aIgA1 from patients with IgAN may play an important role in the progression of IgAN through TGF-β1/Smads signaling pathway. Key words: Glomerulonephritis; IgA; Mesangial cells; Transforming growth factor beta1; Phosphorylated Smad3; Fibronectins