Kidney Week

Abstract: SA-PO643

Serum IgA1-IgG-Containing Immune Complexes From Patients With IgA Nephropathy Activate Cultured Human Mesangial Cells and Associate With Cellular Integrin β1

Session Information

• Glomerular Diseases: IgA and Complement-Mediated GN
  November 05, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
  Abstract Time: 10:00 AM - 12:00 PM

Category: Glomerular Diseases

• 1302 Glomerular Diseases: Immunology and Inflammation

Authors

• Huang, Zhi qiang, University of Alabama at Birmingham, Birmingham, Alabama, United States

Zhi qiang Huang,

• Zhang, Xianwen, Long Hua Hospital, Shanghai, Shanghai, China

Xianwen Zhang,

• Hall, Stacy D., University of Alabama at Birmingham, Birmingham, Alabama, United States

Stacy D. Hall,

• Wang, Lin, Long Hua Hospital, Shanghai, Shanghai, China

Lin Wang,

• Chen, Yiping, Long Hua Hospital, Shanghai, Shanghai, China

Yiping Chen,

• Rizk, Dana, University of Alabama at Birmingham, Birmingham, Alabama, United States

Dana Rizk,

• Julian, Bruce A., University of Alabama at Birmingham, Birmingham, Alabama, United States

Bruce A. Julian,

• Novak, Jan, University of Alabama at Birmingham, Birmingham, Alabama, United States

Jan Novak,

Background

Circulatory IgA1-IgG-containing immune complexes of patients with IgA nephropathy (IgAN) induce cellular proliferation of cultured human mesangial cells. This process involves activation of multiple protein-tyrosine kinases. However, whether IgA1-IgG immune complexes associate with mesangial cells and any role of integrin β1 in this process are not known.

Methods

IgA1-IgG immune complexes were isolated from sera of patients with IgAN by size-exclusion chromatography and added to quiescent human primary mesangial cells in culture. After 15 min incubation at 37^oC, with or without different inhibitors, the cells were washed and lysed. Cell lysates or immunoprecipitated products were analyzed by SDS-PAGE immunoblotting. Inhibitors of integrin α1β1 (obtustatin) and α5β1 (Arg-Gly-Asp peptide; RGD), and protein-tyrosine kinases (dasatinib) and Sheng Ping (a herbal medicine for treatment of patients with IgAN in China), were tested for their inhibitory effects. Antibodies specific for integrin α1β1, integrin α5β1, or platelet-derived growth factor receptor β (PDGFR-β) were used for immunoprecipitation. Antibodies specific for IgA, IgG, different subtypes of integrins and their associated proteins, several protein-tyrosine kinases and their phosphorylated variants were used for immunoblotting.

Results

The mesangial cell lysates contained IgG and IgA, indicating that IgA1-IgG immune complexes associated with the cells, either bound at the surface or within the cells. Immunoprecipitation indicated that the IgA/IgG were associated with integrin α1β1 and α5β1. The complexes induced phosphorylation of ERK1/2, AXL, PDGFR-β, and integrin β1. Analysis of immunoprecipitated products indicated association of integrin β1 with PDGFR-β. Obtustatin, RGD, dasatinib, and Sheng Ping inhibited phosphorylation of integrin β1, PDGFR-β, and ERK1/2; all inhibitors except RGD also inhibited phosphorylation of AXL.

Conclusion

Thus, IgA1-IgG immune complexes associated with mesangial cells and this process was, at least in part, mediated by integrin α1β1 and α5β1 and involved activation of multiple signaling pathways. A better understanding of the pathways activated by IgA1-IgG immune complexes may provide new therapeutic approaches for IgAN.

Funding

• NIDDK Support