Abstract
Purpose :
Th17 cells play a crucial role in the pathogenesis of autoimmune ocular inflammation. Our previous studies found that growth hormone releasing hormone (GHRH) signaling promotes Th17 cell differentiation and pathogenicity through the GHRHR-JAK2-STAT3 pathway. The inhibition of GHRH signaling by GHRH antagonists results in reduced Th17 cell differentiation, mitochondrial functions, and ocular inflammation. However, the inhibition of GHRH may also reduce the production of growth hormone, an important hormone regulating growth and metabolism, which may lead to severe side effects. In this study, we aim to block GHRH signaling by inhibiting the downstream protein JAK2 by using ruxolitinib (Rux), a JAK2 inhibitor, to indirectly regulate Th17 cell differentiation and ocular inflammation.
Methods :
Naïve CD4+ T cells isolated from female C57BL/6 mice (6-8 weeks) were cultured under Th17 cell-polarizing conditions with (1) DMSO, (2) 0.1 μM Rux, and (3) 1 μM Rux for 3 days. IL-17A production was determined by flow cytometry (n=5). Mitochondrial respiration was analyzed by measuring the oxygen consumption rate (OCR) using XF-96 extracellular flux analyzer (n=5). C57BL/6 mice were immunized with IRBP1-20 to induce experimental autoimmune uveitis (EAU). EAU mice were treated with DMSO and 16 mg/kg Rux orally or intraperitoneally on days 1-21 after immunization (n=6). EAU was evaluated using confocal scanning laser ophthalmoscopy (cSLO). Retinal-choroidal thickness (RCT) was quantified using optical coherence tomography (OCT).
Results :
Compared with DMSO, cells treated with 1 μM Rux showed reduced IL-17 production (P=0.0009) under Th17 cell differentiation conditions for 3 days. During the differentiation, cells treated with Rux had significantly lower basal respiration (p=0.0045), maximal respiration (p=0.0028), and spare respiratory capacity (p=0.0042). In vivo, compared with mice treated with DMSO, mice treated with either Rux orally or intraperitoneally had a lower disease score (p=0.012), decreased fold change of RCT (p=0.0064), and attenuated inflammatory characteristics in terms of optic nerve head inflammation, vitreous and retinal infiltrates, retinal edema, and vasculitis.
Conclusions :
Our results indicate that the inhibition of JAK2 by Rux reduces Th17 cell differentiation, mitochondrial functions, and autoimmune ocular inflammation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.