Serum IgA1 from patients with IgA nephropathy up-regulates integrin-linked kinase synthesis and inhibits adhesive capacity in podocytes through indirect pathways.

Purpose: To investigate the influence of IgA1 isolated from IgA nephropathy (IgAN) patients on integrin-linked kinase (ILK) synthesis and adhesive capacity of podocytes through indirect pathways.

Methods: IgA1 was isolated from healthy control or IgAN patients' sera using jacalin affinity chromatography and S-200 chromatography. Podocytes were treated with medium from mesangial cells incubated with aggregated IgA1 (aIgA1, 100 microg/ml), in the presence or absence of valsartan (10(-5)M) or neutralizing antibodies of tumor necrosis factor-alpha (TNF-alpha, 50 ng/ml). Adhesive capacity of podocytes was assessed by cell counting manually and hexosaminidase assay. Real-time PCR and western blotting were used to detect the expression of ILK.

Results: Medium from mesangial cells incubated with aIgA1 from IgAN patients reduced podocyte adhesion to collagen compared with medium from mesangial cells incubated with control medium(RPMI-1640 with 0.5% FBS) (35.0+/-4.8% vs. 60.0+/-2.0%; P < 0.05). While medium from mesangial cells incubated with aIgA1 from IgAN patients upregulated ILK expression in podocytes at mRNA and protein levels compared with medium from mesangial cells without aIgA1 incubated (1.6-fold and 1.38-fold higher than control, respectively, P < 0.05). Defects in podocyte adhesion and up-regulation of ILK synthesis induced by medium from mesangial cells incubated with aIgA1 from IgAN patients can be partially reversed by the pre-treatment for 1 hour with valsartan(P < 0.05), while pre-treatment with neutralizing antibodies of TNF-alpha produced no protective effect on podocytes (P > 0.05).

Conclusion: Serum IgA1 from IgAN patients may inhibit adhesive capacity and up-regulate ILK synthesis in podocytes through indirect pathways.