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.