Neutrophil Gelatinase Associated Lipocalin (NGAL) regulates the onset of serum autoantibodies in pristane induced lupus (P4059)

Abstract NGAL (lipocalin-2), a member of the lipocalin superfamily, is expressed by neutrophils, hepatocytes, and renal resident cells following inflammatory conditions, and is involved in innate immunity during infection. Previously, we found that NGAL worsens renal disease in nephrotoxic nephritis. However, its relevance to adaptive immunity has not been fully explored. To investigate a possible role for NGAL in autoreactive antibody responses in experimental lupus, we injected pristane into B6 (n=10) and NGAL-deficient B6 (NGAL-/-) (n=10) mice. Analyzing the levels of serum autoantibodies at 3 months post injection, we found that B6 NGAL-/- mice had significant increases in IgG2a and IgG2b anti-double stranded DNA antibodies. Similarly, the titers of IgG2a and IgG2b antibodies to single stranded DNA and histone were significantly increased in pristane challenged NGAL-/- mice as compared to NGAL sufficient mice. Furthermore, elevated serum anti-ribonucleoprotein antibodies were found in pristane treated NGAL-/- mice by immunoprecipitation. Although autoantibody titers in NGAL-/- mice were not increased at baseline, our results are consistent with the apoptotic defects and accumulation of lymphoid cells reported previously in these mice. We also found significant upregulation of IRF5, IP-10, CXCL13, CXCR5, CxCR3, PD-1, PD-L1, and activation induced cytidine deaminase (AID) in spleens of NGAL-/- mice compared to WT mice. In vitro, we found that pristane and other inflammatory mediators promoted NGAL secretion by splenocytes. In conclusion, NGAL deficiency accelerates the onset of anti-nuclear antibodies in pristane induced lupus, suggesting that NGAL may regulate the spontaneous or induced humoral autoimmunity.