Comparison of Mustard and Urticant Vesicating Agents' Induced Cutaneous Lesions in Wild Type and Mast Cell Deficient Mice

Abstract

<b>Abstract ID 25825</b> <b>Poster Board 223</b> Cutaneous exposure to mustards [Sulfur mustard (SM) and Nitrogen mustard (NM)] and urticant (Phosgene Oxime, CX) vesicating chemical threat agents9 is known to cause devastating injuries that include skin erythema, edema and necrosis, and systemic toxic effects. The symptoms of CX-exposure appear instantaneously with skin blanching and urticaria while SM and NM-induced lesions appear a few hours after the exposure. The mechanisms underlying the injury from these agents is not fully known and there are no effective approved therapies to alleviate the injury. Our previous studies have shown that NM and CX-exposure causes significant increase in mast cell degranulation suggesting their role in vesicant injury. To further analyze the effect of mast cell activation in NM- and CX-induced clinical injury parameters, we compared the toxicity of these agents in wild type (WT; C57BL/6) and mast cell deficient (MCD; B6.Cg-KitW-sh/HNihrJaeBsmJ) mice. Mice were exposed to NM (0.5mg NM/100μL of acetone) or CX (10 μL CX for 0.5 or 1.0 min using two 12 mm vapor caps) on the dorsal skin. CX exposures were carried out at MRIGlobal (Kansas City, MO). Clinical assessments including body weight, skin bi-fold thickness, and scoring for erythema, edema, and necrosis were carried out. Mice were sacrificed at different time points (24 h and/or 14 Day) post-exposure, and skin and other tissues were harvested for analyses. NM and CX-exposures led to significant increases in mast cell degranulation in the skin of the WT mice. The increase in mast cell degranulation was more robust and instant upon CX-exposure compared to NM. Increased mast cell degranulation was accompanied with increases in mast-cell associated protease, tryptase in the skin of the WT mice upon NM and CX-exposure. MCD mice showed improved survival upon NM-exposure compared to WT mice. MCD mice also fared better in terms of NM-induced body weight-loss and increase in skin-bi-fold thickness compared to WT mice. MCD mice also exhibited reduced erythema, edema, and decreased wound size compared to WT mice. In case of CX-exposure, MCD mice also showed reduced erythema (at 2 h, and 24h post-exposure), and edema (at 2h post CX-exposure) compared to WT mice. MCD mice also had reduced necrosis compared to WT mice at day 3 post CX-exposure. Together, our results show that MCD mice developed less severe clinical lesions compared to WT mice upon cutaneous exposure to both NM and CX, suggesting the role of mast cells in the skin injury. A more robust increase in mast cell degranulation and urticaria like symptoms upon CX-exposure suggest that mast cells could play a more crucial role in CX-induced skin injury; however, this remains to be investigated. Further histopathological and molecular analyses are being carried out to delineate the role of mast cells in vesicant injury and to identify the underlying molecular pathways. <b>Support/Funding Information:</b> Department of Defense (W81XWH-18-1-0169) and Countermeasures Against Chemical Threats (CounterACT) Program, Office of the Director National Institutes of Health (NIH OD) and the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) [Grant Numbers R21 AR073544 and U01 AR075470].