Fas targeted siRNA markedly attenuates sulfur mustard‐induced apoptosis in human airway epithelial cells

Abstract

Sulfur mustard (SM), known as mustard gas, causes debilitating skin blisters and injuries to the eyes and the respiratory tract; these effects are attributed to SM‐induced epithelial damage, mainly basal cell apoptosis. Previous studies have shown that SM‐induced apoptosis is mediated by caspases‐8 (death receptor pathway) and ‐9 (mitochondrial pathway). Our earlier results have suggested the Fas receptor is the major activator of caspase‐8 in human bronchial/tracheal epithelial cells (NHBE, upper lung model). To elucidate the role that Fas plays in SM‐induced apoptosis, we designed a siRNA construct targeted towards the Fas receptor. By utilizing siRNA technology we are able to block the Fas receptor more selectively than with other methods (e.g., by using a Fas antagonistic antibody ZB4). Since caspase‐8 activates the executioner caspase‐3, we studied Fas activation by measuring caspase‐3 using a fluorogenic caspase substrate hydrolysis assay. Validation of the siRNA construct was at both protein (western blot for Fas) and functional (caspase‐3 activation) levels. We found that siRNA was able to substantially (∼50%) decrease the SM‐induced apoptosis. These results suggest a high degree of involvement of Fas receptor in SM‐induced apoptosis. Research supported by JSTO‐DTRA Award # M0005_04_RC_C to R. Ray. The views represented are those of the authors and are not necessarily endorsed by the US Army.