BRD4 Inhibition Mitigates Acute and Chronic Corneal Injury Following Topical Nitrogen Mustard Exposure

Corneal chemical injury, including mustard vesicant injury, remains a clinical challenge with limited therapeutic options. To enable effective mechanistic and therapeutic studies, we developed a mouse model of nitrogen mustard (NM)-induced corneal injury using a 3D-molded, cap-shaped filter paper conforming to the corneal surface to generate reproducible injuries. Multimodal in vivo imaging and histological assessment revealed an injury course characterized by acute epithelial disruption, stromal edema, and inflammation, followed by transient partial recovery and chronic stromal remodeling with persistent endothelial loss. After NM exposure, bromodomain (BD)-containing protein 4 (BRD4) expression and activity were upregulated. Short-term topical BRD4 inhibition with JQ1 reduced acute corneal inflammation (e.g., reducing CD45⁺ cells by 86%) and oxidative stress, and conferred long-term preservation of corneal clarity, stromal organization, and endothelial integrity. Selective inhibition of BD1 or BD2 recapitulated JQ1's effects, indicating that blockade of either bromodomain is sufficient. BRD4 inhibition also significantly attenuated NM-induced corneal pathology in a rabbit model, supporting cross-species efficacy and translational relevance. Mechanistically, BRD4 inhibition selectively counteracted key NM-driven pathogenic programs, including inflammation, oxidative stress, and extracellular matrix remodeling. These findings identify BRD4 as a central epigenetic driver of vesicant-induced corneal injury and position BRD4 inhibition as a promising translational therapeutic strategy.