Abstract
Purpose :
We recently reported the activation of the IRG1/itaconate axis in promoting inflammation resolution during endophthalmitis. This study aims to determine the immunomodulatory role of IRG1 in the pathogenesis of autoimmune uveitis (EAU), the predominant cause of intraocular inflammation in autoimmune patients.
Methods :
EAU was induced in wild-type (C57BL/6J) or Irg1 knock-out (KO) mice by immunization with interphotoreceptor retinoid-binding protein (IRBP). Disease severity was assessed based on fundus examination and retinal function (ERG) testing. Ocular tissue (retina) and cervical lymph nodes were harvested at 21 days post-immunization. Flow cytometry was used to determine the frequencies of myeloid (macrophages, monocytes, and neutrophils) and lymphoid (Th1, Th17, and Tregs) cells. In vitro, studies were performed using mice splenocytes and challenging them with IRBP in the presence or absence of itaconate, a metabolite produced by IRG1 activity. The metabolic activity was assessed using the Seahorse analyzer. ELISA and qPCR assays were performed to measure inflammatory cytokines/chemokines.
Results :
Our findings indicate that Irg1 KO mice developed severe EAU in comparison to wild-type mice. The exacerbated EAU in Irg1 KO mice is accompanied by increased frequencies of macrophages, as well as Th17 cells, and a decreased percentage of regulatory T cells in the retina. In vitro, experiments utilizing Irg1 KO mice cervical lymph nodes further confirmed enhanced Th17 cells and diminished Tregs percentages. Mechanistically, splenocytes from IRBP-immunized Irg1 KO mice exhibited higher glycolysis compared to wild-type mice. Moreover, splenocytes treated with an itaconate derivative (4-OI), exhibited enhanced regulatory T cells, suppressed Th 17 cells, and decreased production of inflammatory mediators.
Conclusions :
Our study demonstrates that itaconate is a crucial metabolic regulator in both innate and adaptive immune responses during EAU. Itaconate supplementation exerts anti-inflammatory effects and maintains the crucial balance of Th17/Treg cell balance, indicating its therapeutic potential in the treatment of EAU.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.