Mustard
vesicants, including
sulfur mustard (2,2'-
dichlorodiethyl sulfide, SM) and
nitrogen mustard (bis(2-chloroethyl)methylamine, HN2) are cytotoxic blistering agents synthesized for chemical warfare. Because they contain highly reactive electrophilic chloroethyl side chains, they readily react with cellular macromolecules like
DNA forming monofunctional and bifunctional adducts. By targeting
DNA, mustards can compromise genomic integrity, disrupt the cell cycle, and cause mutations and cytotoxicity. To protect against genotoxicity following exposure to mustards, cells initiate
a DNA damage response (DDR). This involves activation of signaling cascades including ATM (
ataxia telangiectasia mutated), ATR (
ataxia telangiectasia and Rad3-related) and
DNA-
PKcs (
DNA-dependent protein kinase, catalytic unit). Signaling induced by the DDR leads to the recruitment and activation of repair related
proteins such as phospho H2AX and phospho p53 to sites of DNA lesions. Excessive
DNA modifications by mustards can overwhelm DNA repair leading to single and double strand DNA breaks, cytotoxicity and tissue damage, sometimes leading to
cancer. Herein we summarize DDR signaling pathways induced by SM, HN2 and the half mustard,
2-chloroethyl ethyl sulfide (
CEES). At the present time, little is known about how mustard-induced DNA damage leads to the activation of DDR signaling. A better understanding of mechanisms by which mustard
vesicants induce the DDR may lead to the development of countermeasures effective in mitigating tissue injury.