Histopathological and Molecular Changes in the Rabbit Cornea From Arsenical Vesicant Lewisite Exposure.

Lewisite (LEW), a potent arsenical vesicating chemical warfare agent, poses a continuous risk of accidental exposure in addition to its feared use as a terrorist weapon. Ocular tissue is exquisitely sensitive to LEW and exposure can cause devastating corneal lesions. However, detailed pathogenesis of corneal injury and related mechanisms from LEW exposure that could help identify targeted therapies are not available. Using an established consistent and efficient exposure system, we evaluated the pathophysiology of the corneal injury in New Zealand white rabbits following LEW vapor exposure (at 0.2 mg/L dose) for 2.5 and 7.5 min, for up to 28 day post-exposure. LEW led to an increase in total corneal thickness starting at day 1 post-exposure and epithelial degradation starting at day 3 post-exposure, with maximal effect at day 7 postexposure followed by recovery at later time points. LEW also led to an increase in the number of blood vessels and inflammatory cells but a decrease in keratocytes with optimal effects at day 7 postexposure. A significant increase in epithelial-stromal separation was observed at days 7 and 14 post 7.5 min LEW exposure. LEW also caused an increase in the expression levels of cyclooxygenase-2, IL-8, vascular endothelial growth factor, and matrix metalloproteinase-9 at all the study time points indicating their involvement in LEW-induced inflammation, vesication, and neovascularization. The outcomes here provide valuable LEW-induced corneal injury endpoints at both lower and higher exposure durations in a relevant model system, which will be helpful to identify and screen therapies against LEW-induced corneal injury.