Investigation of inflammatory mechanisms induced by mechlorethamine in mouse ear

Mechlorethamine (HN2) is toxic to the skin and causes inflammation accompanied by disruption of the dermal-epidermal junction (DEJ), commonly known as vesication. HN2 is a sulfur mustard mimic used in research settings to investigate the pharmaco-toxic effects of vesicants. Effective medical countermeasures for vesicant-induced injury remain limited, underscoring the need to identify novel targets for reducing vesication. The present study used HN2 dissolved in dimethyl sulfoxide (DMSO) to induce mouse ear edema and investigate the contribution of the complement system (CS) to skin responses 24 h after exposure to HN2, with DMSO serving as the vehicle control. Tissues were homogenized and processed for proteomic analysis to examine the protein milieu in skin actively responding to HN2-mediated cutaneous injury. Comparative analysis identified 695 proteins that were differentially expressed between the vehicle- and HN2-treated groups (p < 0.05, fold change ≥1). Of these, 134 proteins were upregulated and 561 were downregulated in HN2-exposed tissues relative to DMSO-treated control tissues, with several complement proteins significantly upregulated. Protein enrichment and protein-protein interaction analyses identified the complement pathway as the most significantly enriched pathway in mouse ear skin 24 h after HN2 exposure. ELISA analysis of protein extracts confirmed increased levels of complement factor B, complement C3a, complement C5a, and complement C5b-9, also known as the membrane attack complex. Taken together, these data suggest that activation of the complement pathway may represent a novel target for vesicant countermeasure development.