Comprehensive Epigenetic Landscape of Sulfur Mustard (SM) Exposure in HaCaT Keratinocytes.

Sulfur Mustard (SM) is a potent vesicant chemical agent with profound and complex toxic effects. Traditionally, its toxic mechanism has been attributed to DNA alkylation-induced cytotoxicity and genomic instability. However, growing evidence indicates that dysregulation of epigenetic regulatory mechanisms constitutes a central link in SM toxicity, particularly in its long-term and delayed effects. Our study establishes an in vitro SM exposure model and employs integrated multi-omics profiling-including six histone modifications, DNA methylation, transcriptomic, and non-coding RNA analyses-to systematically investigate SM-induced epigenetic reprogramming. Our results demonstrate that SM drives extensive chromatin state remodeling, accompanied by altered expression of genes involved in DNA damage repair, cell cycle regulation, and immune response. We further constructed a predicted ceRNA network, identifying key lncRNAs, potentially associated with promoter hypomethylation, that may participate in ceRNA interactions involving cancer- and apoptosis-related genes. Additionally, we developed and validated a mass spectrometry-based method for precise quantification of 37 histone H3 modifications, providing a robust tool for profiling epigenetic biomarkers of exposure. These findings provide systems-level evidence for acute epigenetic reprogramming induced by SM exposure and reveal relevant associations between epigenomic dysregulation and genomic instability-related pathways in keratinocytes, suggesting candidate targets for future functional validation and early intervention studies.