Inhibition of STAT6 signaling by rebamipide attenuates IL-4- and IL-13-induced eotaxin expression in corneal fibroblasts.

Giant papillae formation along with corneal damage in vernal keratoconjunctivitis (VKC) is primarily mediated by type 2 inflammation and eosinophils. Corneal keratocytes are the primary cellular source of eotaxin at the ocular surface, facilitating eosinophil migration to the cornea. We aimed to elucidate the role of the transcription factor signal transducer and activator of transcription 6 (STAT6) in eotaxin expression by corneal fibroblasts and to evaluate the inhibitory effects of rebamipide-a mucin secretagogue with reported therapeutic potential in VKC-on this pathway. Human corneal fibroblasts were cultured and stimulated with interleukin (IL)-4 or IL-13, and subsequently preincubated with either a STAT6 inhibitor (AS1517499) or rebamipide prior to cytokine stimulation. STAT6 phosphorylation was evaluated by Western blotting. Eotaxin expression was assessed using an enzyme-linked immunosorbent assay and a real-time polymerase chain reaction. IL-4 and IL-13 stimulation induced STAT6 phosphorylation and increased eotaxin production at mRNA and protein levels. Preincubation with both AS1517499 and rebamipide suppressed IL-4- or IL-13-induced STAT6 phosphorylation, significantly reducing eotaxin mRNA and protein expression. These findings demonstrate that IL-4- or IL-13-stimulated eotaxin production in human corneal fibroblasts is mediated through the STAT6 signaling pathway. Rebamipide inhibited STAT6 activation, leading to reduced eotaxin production, suggesting that its therapeutic effect in VKC is due to the suppression of STAT6-mediated eotaxin production, which may reduce eosinophil accumulation to the cornea.