Glucocorticoids improve the balance of M1/M2 macrophage polarization in experimental autoimmune uveitis through the P38MAPK-MEF2C axis

Uveitis is a common ocular disease that can induce serious complications and sequelae. It is one of the major causes of blindness. Currently, mounting evidence suggests that glucocorticoids (GCs) can suppress ocular inflammation and promote the healing of damaged ocular tissues, but the underlying mechanism remains unclear. The present study aimed to elucidate the mechanism by which GCs modulate the homeostasis of M1/M2 macrophage polarization in experimental autoimmune uveitis (EAU) through the p38MAPK-MEF2C axis. Female Lewis rats were randomly divided into four groups: a normal control (NC) group, an EAU group, an EAU + glucocorticoid (EAU + GC) group, and an EAU + p38MAPK inhibitor (EAU + SB) group. The EAU model was induced in EAU, EAU + GC, and EAU + SB groups, followed by the treatments of normal saline, GC (predisione), and SB203580, respectively. The findings demonstrated that the rats in GC and SB groups had much less ocular inflammation, and the clinical and pathological scores decreased. Further research revealed that GC and SB treatment could inhibit iNOS and CD86 expression while promoting Arg-1 and CD206 secretion in IRBP-induced uveitis rats. Moreover, we found that the role of GC was similar to the results of SB203580, but the role of GC was masked by the C16-PAF (a p38MAPK activator) treatment. Molecular docking and western blot results confirmed that GC's therapeutic action against EAU is mediated via the p38MAPK-MEF2C axis. It regulates macrophage polarization by encouraging M1 to M2 transition and releasing anti-inflammatory factors.