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 (aI-gA1, 100 mu g/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 aI-gA1 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 aI-gA1 from IgAN patients upregulated ILK expression in podocytes at mRNA and protein levels compared with medium from mesangial cells without aI-gA1 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 aI-gA1 from IgAN patients can be partially reversed by the pretreatment for 1 hour with valsartan(P<0.05), while pretreatment 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.