IL-36α Enhances Host Defense against <i>Pseudomonas aeruginosa</i> Keratitis in C57BL/6 Mouse Corneas

Abstract

The IL-36 cytokines are known to play various roles in mediating the immune response to infection in a tissue- and pathogen-dependent manner. The present study seeks to investigate the role of IL-36R signaling in C57BL/6 mouse corneas in response to <i>Pseudomonas aeruginosa</i> infection. IL-36α^-/-, IL-36γ^-/-, and IL-36R^-/- mice had significantly more severe keratitis than wild-type mice. At six hours postinfection, IL-36α pretreatment augmented <i>P. aeruginosa</i>-induced expression of IL-1Ra, IL-36γ, LCN2, and S100A8/A9. At one day postinfection, exogenous IL-36α suppressed, whereas IL-36α deficiency promoted, the expression of IL-1β. At three days postinfection, exogenous IL-36α suppressed Th1 but promoted Th2 immune response. IL-36α stimulated the infiltration of IL-22-expressing immune cells, and IL-22 neutralization resulted in more severe keratitis. IL-36α alone stimulated dendritic cell infiltration in B6 mouse corneas. Taken together, our study suggests that IL-36R signaling plays a protective role in the pathogenesis of <i>P. aeruginosa</i> keratitis by promoting the innate immune defense, Th2, and/or Th22/IL-22 immune responses. Exogenous IL-36α might be a potential therapy for improving the outcome of <i>P. aeruginosa</i> keratitis.