In vitro toxicological assessment of free 3-MCPD and select 3-MCPD esters on human proximal tubule HK-2 cells

Chloropropanols are chemical contaminants that can be formed during industrial processing of foods, such as lipids used in commercially available infant and toddler formula in the USA. Many researchers have studied the most common chloropropanol contaminant, 3-monochloropropane-1,2-diol (3-MCPD), as well as its lipid ester derivatives. A plethora of toxicological outcomes have been described in vivo, including effects on the heart, nervous system, reproductive organs, and kidneys. To better understand the concordance of some of these effects to in vitro outcomes, we focused our research on using an in vitro cellular model to investigate whether the proximal tubule cells of the kidney would be vulnerable to the effects of free 3-MCPD and nine of its common esters in commercial formula. Using the established human kidney proximal tubule cell line, HK-2, we performed 24-h treatments using 3-MCPD and nine mono- or di-esters derived from palmitate, oleate, and linoleate. By directly exposing HK-2 cells at treatment doses ranging from 0 to 100 μM, we could evaluate their effects on cell viability, mitochondrial health, reactive oxygen species (ROS) production, and other endpoints of toxicity. Since chloropropanols reportedly inhibit cellular metabolism through interference with glycolysis, we also tested the extent of this mechanism. Overall, we found mild but statistically significant evidence of cytotoxicity at the highest tested treatment concentrations, which were also associated with mitochondrial dysfunction and transient perturbations in cellular metabolism. Based on these findings, further studies will be required to better understand the effects of these compounds under conditions that are more physiologically relevant to human infant and toddler proximal tubules in order to mimic their exposure to chloropropanol-containing foods.