Inhibition of bruton’s tyrosine kinase directly alleviates pathogenic CD4+ T cell response via PPAR-γ signaling in autoimmune uveitis

Bruton’s tyrosine kinase (BTK), a key regulator of immune responses, has been extensively studied in B cells and innate immunocytes. Small-molecule BTK inhibitors (BTKi) have shown remarkable efficacy in multiple preclinical and clinical studies for autoimmune diseases via mediating the activation of B cells and innate immunocytes. Recent studies have demonstrated functional BTK expression in T cells, contributing to T cell activation and the pathogenesis of aplastic anemia. Whether BTK is involved in uveitis, the CD4+ T cell-mediated autoimmune disease, and whether it could be a therapeutic target remain unclear. We assessed BTK expression and phosphorylation levels in CD4+ T cells from Autoimmune uveitis (AU) patients and experimental autoimmune uveitis (EAU) mice. By administering BTKi to EAU mice, we evaluated its effects on ocular and systemic inflammation levels through fundus photography, histopathology, qPCR, and flow cytometry. In vitro, we assessed its impact on the Th1/Th17/Treg differentiation, and the pathogenicity of CD4+ T cells. Transcriptomic sequencing and flow cytometry were employed to explore the potential mechanism by which BTK regulates CD4+ T cells. BTK expression and activation were upregulated in CD4+ T cells from AU patients and EAU mice. BTK inhibition suppressed the polarization of Th17 and Th1 cells, but not Treg differentiation. BTK inhibition upregulated the PPAR-γ signaling, alleviating oxidative stress and inflammatory responses in CD4+ T cells, thereby reducing ocular and systemic inflammation in EAU mice. Additionally, BTKi exhibited significant anti-inflammatory effects in CD4+ T cells from AU patients. This study demonstrates the critical role of BTK in CD4+ T cell-driven AU. BTK inhibition ameliorates oxidative stress and inflammatory responses via PPAR-γ involved signaling in CD4+ T cells and suppresses their differentiation to Th1/Th17 to restore immune homeostasis, thereby mitigating AU. These findings identify BTK as a potential therapeutic target and provide a theoretical foundation for the clinical application of BTKi in AU.