Formation of di-cysteine acrolein adduct decreases cytotoxicity of acrolein by ROS alleviation and apoptosis intervention

Acrolein (ACR) is a toxic contaminant for humans. Our previous research indicated that L-cysteine (Cys) decreased the cytotoxicity of acrolein possibly via adduct formation, but which adduct contributed to the toxicity-lowering effect remains unknown. In this work, we identified a di-cysteine acrolein adduct (ACR-di-Cys) and investigated its toxicity against human bronchial epithelial cell line HBE and colon cancer cell line Caco-2. ACR-di-Cys tremendously decreased acrolein-induced cytotoxicity via alleviating ROS and apoptosis intervention. In the condition of no presence of free cysteine, however, this adduct can convert to mono-ACR-Cys in PBS solution by losing a molecule of cysteine conjugated at C=C bond. ACR-mono-Cys showed much higher toxicity than ACR-di-Cys, and even higher than acrolein after 48h exposure. This study indicated that cysteine can react with acrolein to form adducts with different acrolein-detoxifying capacity, and a sufficient intake of cysteine or cysteine-containing proteins can maximize the detoxifying effect for acrolein via the formation of a highly detoxifying agent, ACR-di-Cys.