Proteomic characterization of ocular tear fluid reveals preclinical markers of sulfur mustard toxicity.
Sulfur mustard (SM) vapor causes ocular injury after a short latent period, when molecular damage has occurred, but clinical signs are not yet apparent. Characterizing ocular responses during this early phase is important for understanding SM pathogenesis, identifying molecular readouts of injury progression, and developing biomarkers of exposure. Tear fluid is well-suited for this purpose because it can be collected noninvasively and captures responses from injured ocular tissues. We tested whether temporal changes in the tear fluid proteome reflect cellular and molecular responses to corneal SM exposure. Rabbits were exposed to SM vapor using a corneal vapor cap, and tear fluid was collected at baseline, 4 h, 1 d, and 5 d, corresponding to the latent period, acute lesion, and early recovery. A large proteomic response was detected at 4 h, involving extracellular injury signaling, epithelial injury, and innate immune activation. By 1 d, the tear fluid proteome transitioned to inflammatory cell activation with metabolic, redox, and proteostasis stress. By 5 d, evidence of acute injury response was reduced but the proteome retained a residual signature of immune, epithelial, and stress responses. This temporal progression is consistent with the molecular mechanisms of SM toxicity and provides insight into acute ocular vesicant injury. These findings establish tear fluid as a noninvasive molecular reporter of ocular SM injury progression. They also reveal a molecular signature of vesicant exposure, which emerges prior to clinical signs, and provide foundational data for developing tear-based biomarkers of chemical exposure, injury assessment, and therapeutic testing.