Changes in Rabbit Conjunctival Mucins Following Exposure to Sulfur Mustard

Abstract

Sulfur mustard (SM) is a vesicating chemical warfare agent that is relatively easy to synthesize, stockpile, and deliver. It is known to cause severe injury to the eye damaging both the conjunctiva and cornea; developing approaches to counter SM-induced acute and chronic ocular toxicities is a high priority. In the present studies, we characterized the ocular effects of SM in New Zealand white rabbits. Within one day of exposure to SM, edema and hazing of the cornea were observed, followed by neovascularization which persisted for at least 28 days. This was associated with upper and lower eyelid hyperemia, edema and conjunctival inflammation. The conjunctiva is composed of a proliferating epithelium largely consisting of stratified columnar and squamous epithelial cells overlying a well-defined dermis. Superficial layers of the conjunctival epithelium expressed keratin 1, a marker of differentiating squamous epithelium, while keratin 17, a marker of proliferating stratified squamous epithelium, was expressed in cells overlying the basement membrane. SM treatment increased the number of keratin 17 expressing epithelial cells. Mucin 5AC producing goblet cells were interspersed within the superficial layers of the conjunctival epithelium. Alcian blue/periodic acid-Schiff staining revealed that these cells generated both acidic and neutral mucins. SM was found to increase the number of goblet cells producing neutral mucins. SM also increased expression of membrane-associated mucin 1 and mucin 4 in the superficial layers of the conjunctiva. These data demonstrate that ocular exposure of rabbits to SM causes significant damage not only to the cornea, but to the eyelid and conjunctiva, altering conjunctival mucins which are important in protecting the eye from injury. Multiple targets within the eye should be assessed when evaluating the efficacy of potential SM ocular countermeasures.