Background:Systemic lupus erythematosus (SLE) is associated with high levels of inflammatory cytokines as well as increased autoantibodies. Accumulating evidences show that transcription factor interferon regulatory factor 5 (Irf5) deficiency ameliorates disease severity.Here we assessed the therapeutic outcome of a peptide inhibitor targeting IRF5 activation in the NZB/W F1 murine model.
Methods:For proof-of-principle that the peptide inhibits IRF5 activation, RAW264.7 macrophages were pre-incubated with peptide inhibitor for 1 hour before stimulating with 5ug/mL LPS for 2 hours. Nuclear extracts were subjected to Western blotting. For acute in vivo studies, 10 week-old WT Balb/c female mice were IP-injected with 200ug inhibitor followed by 100ug R848 1 hour post. Plasma IL-6 production was then measured 90min later by ELISA (Cayman). For chronic in vivo studies, 8 week-old NZB/W F1 mice (Jacksons) were IP-injected with control (n=6) or inhibitor (n=6) at a dose of 100ug/mouse/injection on D0, D1, D4, D7 and D14. Body weight and proteinuria were monitored. Serum auto-antibodies were measured by ANA-HEp-2 (Bio-rad). Immune cell population differences were measured by flow cytometry.
Results: The inhibitor decreased LPS-induced IRF5 nuclear translocation in a dose dependent manner in RAW 264.7 macrophages. Acute IL-6 production stimulated by R848 in Balb/c mice was blocked by N5-1. Urine protein levels were significantly elevated as disease progressed in the control group, while the inhibitor-treated group retained low protein levels. At week 27, 1/11 from the treated group showed positive autoantibody staining on HEp-2 cells while 6/11 from the control group showed positive ANA.Body weights remained similar between control and treated groups over time. CD4/CD8 ratios were increased in the treated group.
Conclusion:Our data show for the first time that direct inhibition of IRF5 in an in vivo SLE model ameliorates disease onset and severity. The inhibitor was well-tolerated supporting the therapeutic utility of IRF5 inhibitors in the clinic.