3-Chloro-1,2-propanediol (3-MCPD) and 2-chloro-1,3-propanediol (2-MCPD) are heat-induced food contaminants being present either as free substances or as fatty acid esters in numerous foods. 3-MCPD was classified to be possibly carcinogenic to humans (category 2B) with kidney and testis being the primary target organs according to animal studies. A previous 28-day oral feeding study with rats revealed that the endogenous antioxidant protein DJ-1 was strongly deregulated at the protein level in kidney, liver, and testis of the experimental animals that had been treated either with 3-MCPD, 2-MCPD or their dipalmitate esters. Here we show that this deregulation is due to the oxidation of a conserved, redox-active cysteine residue (Cys106) of DJ-1 to a cysteine sulfonic acid which is equivalent to loss of function of DJ-1. Irreversible oxidation of DJ-1 is associated with a number of oxidative stress-related diseases such as Parkinson, cancer, and type II diabetes. It is assumed that 3-MCPD or 2-MCPD do not directly oxidize DJ-1, but that these substances induce the formation of reactive oxygen species (ROS) which in turn trigger DJ-1 oxidation. The implications of 3-MCPD/2-MCPD-mediated ROS formation in vivo for the ongoing risk assessment of these compounds as well as the potential of oxidized DJ-1 to serve as a novel effect biomarker for 3-MCPD/2-MCPD toxicity are being discussed.
Keywords: 2-MCPD; 3-MCPD; Cysteine oxidation; DJ-1; Oxidative stress.