Serum IgA1 from IgA nephropathy patients induces apoptosis in podocytes through direct and indirect pathways.

PURPOSE To investigate apoptosis of podocytes induced by IgA1 isolated from IgA nephropathy (IgAN) patients through direct and indirect pathways. METHODS Jacalin affinity chromatography and Sephacryl S-200 molecular sieve chromatography were used to isolate IgA1 from blood of IgAN patients made as aggregated IgA1 (aIgA1). Podocytes were incubated with aIgA1 or special treated medium from mesangial cells after co-incubation with aIgA1 from IgAN patients. Apoptosis of podocytes was assessed by TUNEL staining and flow cytometry. Real-time PCR was used to detect the mRNA expression of Bcl-2, Bax, Fas and Fas-L. RESULTS AIgA1 from IgAN patients induced more apoptosis of podocytes by both time and concentration-dependent patterns than control (30.5+/-5.4% vs 20.5+/-4.5, respectively, P < 0.05). The percentage of apoptotic podocytes exposed to treated medium was higher than control (28.5+/-5.9 % vs 20.5+/-4.5%, respectively, P < 0.05). The level of normalized Fas mRNA expression in podocytes exposed to aIgA1 was 2.4-fold higher than control (P < 0.05), while the level in podocytes exposed with treated medium was 1.89-fold higher than control (P < 0.05), and the level of normalized Bcl-2 mRNA expression in this group was 72% lower than control (P < 0.05) CONCLUSION IgA1 from IgAN patients may induce apoptosis of podocytes through direct and indirect pathways. IgA1 may accelerate progression of IgAN by inducing apoptosis of podocytes.