Protective Effect of Calcitonin Gene-Related Peptide on Corneal Epithelial Barrier in Experimental Dry Eye Models

Purpose: To investigate the role of calcitonin gene-related peptide (CGRP) in corneal epithelial barrier dysfunction in dry eye disease (DED). Methods: Benzalkonium chloride (BAC)-induced murine dry eye models and hyperosmotic-stressed human corneal epithelial cells-transformed (HCE-T) were used. Corneal nerve density and CGRP expression were assessed via whole-mount staining and Western blot. CGRP receptor components, including CRLR, RAMP-1, and CRCP, were evaluated by quantitative real-time PCR and immunofluorescence. Mice received a topical CGRP solution (50 µM) for four days. Barrier function was analyzed using Oregon Green Dextran (OGD) staining and transepithelial electrical resistance (TEER). Tight junction proteins, inflammatory markers, and PKA/CREB/NF-κB signaling pathways were examined via immunofluorescence, qPCR, and Western blot. Results: BAC exposure caused significant corneal nerve damage (P < 0.05) and a reduction of CGRP levels (P < 0.001), accompanied by upregulation of CGRP receptor components (CRLR, RAMP-1, CRCP; P < 0.05). Exogenous CGRP treatment restored corneal epithelial barrier function, as indicated by decreased OGD staining intensity (P < 0.001) and improved TEER (P < 0.001), while maintaining the localization of tight junction proteins. Mechanistically, CGRP increased p-PKACα (T197)/PKACα and p-CREB (S133)/CREB (P < 0.01), while reducing p-p65 and IL-1β, IL-6, TNF-α, MMP-9 (P < 0.01). These effects were observed in both BAC-induced DED mice and in hyperosmotic-stressed human corneal epithelial cells, demonstrating that CGRP exerts dual mechanisms in barrier repair and anti-inflammatory protection. Conclusions: CGRP deficiency and receptor upregulation may be involved in the pathological process of DED. Exogenous CGRP ameliorates corneal barrier dysfunction, which is associated with modulation of the PKA/CREB and NF-κB pathways.