Effect of aggregated immunoglobulin A1 from immunoglobulin A nephropathy patients on nephrin expression in podocytes.

Aim: Abnormal immunoglobulin (Ig)A1 is considered to play a pivotal role in IgA nephropathy. We used mouse podocytes as the experimental model to investigate the effect of aggregated IgA1 (algA1) isolated from IgA nephropathy (IgAN) patients on nephrin expression in podocytes 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 which was therefore became algA1. Podocytes were incubated with algA1 or special mesangial medium. Nephrin expression in podocytes was measured by real-time polymerase chain reaction and western blot analysis. Results: Aggregated IgA1 from IgAN patients and healthy controls reduced nephrin expression in podocytes at mRNA and protein levels when compared with podocytes incubated with control medium (RPMI-1640 with 0.5% foetal bovine serum) (P < 0.05). While medium from mesangial cells incubated with algA1 from IgAN inhibited nephrin expression in podocytes at mRNA and protein levels when compared with podocytes incubated with medium from mesangial cells with algA1 from healthy controls (P < 0.05). Conclusion: Our findings implicate that algA1 from IgAN patients could inhibit nephrin expression through direct and indirect pathways, although these mechanisms remain to be clarified.