Autoantigen spermatid nuclear transition protein 1 enhances pro-inflammatory cytokine production stimulated by anti-DNA autoantibodies in macrophages

Abstract

Introduction Lupus nephritis (LN), a severe manifestation of systemic lupus erythematosus (SLE), is associated with high fatality rate in patients. The pathogenesis of lupus nephritis is complex and has not been fully elucidated. Kidney inflammation, renal cell damage, and accumulation of immune complexes in the glomerular basement membrane often occur in patients with lupus nephritis. Spermatid nuclear transition protein 1 (TNP1) might be a potentially interesting autoantigen in exploring the pathogenesis and therapy of lupus nephritis. Objective This study aimed to explore the effect of TNP1 and its complexes with anti-double-stranded DNA antibodies on the levels of interleukin-6 (IL-6) and interferon-α (IFN-α) in vitro. Methods We studied the effect of the synthetic peptide of the autoantigen on the pathogenic characteristics of the G2-6 and G5-8 antibodies in mouse macrophages, using enzyme-linked immunosorbent assay, quantitative RT-PCR, western blotting, and flow cytometry. Results The antibodies exhibited cross-reactivity to spermatid TNP1 in direct-binding and competitive enzyme-linked immunosorbent assay. Results of quantitative RT-PCR and western blotting revealed that the antibodies alone enhanced the levels of IL-6 and IFN-α transcripts and proteins, respectively. Flow cytometry revealed that treatment with the autoantigen enhanced the cell-penetrating activities of G2-6 and G5-8 and remarkably increased the cytokine levels. Conclusion TNP1 enhanced the cell-penetrating activities of anti-dsDNA auto-Abs, G2-6 and G5-8, and remarkably increased the levels of IL-6 and IFN-α in macrophages, suggesting that TNP1 and cell-penetrating pathogenic anti-dsDNA auto-Abs is potential targets for future therapeutic approaches to treat LN/SLE.