Correlation between 3-MCPD-induced organ toxicity and oxidative stress response in male mice

Abstract

 The transgenic HOTT reporter mouse was employed to examine 3-MCPD-mediated induction of oxidative stress  3-MCPD induces oxidative stress in mouse kidney, testes and brain  3-MCPD leads to the irreversible oxidation of the redox sensor protein DJ-1  3-MCPD does not severely affect Nrf2-dependent gene expression in different mouse organs Abstract 3-Chloro-1,2-propanediol (3-MCPD) is a food contaminant which has been classified as a non-genotoxic carcinogen (category 2B). Previous studies suggested that oxidative stress might play a role in 3-MCPD toxicity. To elucidate the impact of 3-MCPD-mediated organ toxicity in more detail, transgenic reporter mice were employed which contain a lacZ reporter under the control of the heme oxygenase 1 (Hmox1) promoter which is responsive to oxidative stress. The mice received daily doses of up to 100 mg/kg body weight 3-MCPD per day in a 28-day feeding study. Subsequently, tissue slices from different organs were subjected to X-Gal staining as the readout for lacZ gene expression. A dose-dependent increase of blue stain was observed in mouse kidney that was exclusively visible in the renal cortex but not in the renal medulla. Moreover, blue-stained regions were detected in the basal membrane of the seminiferous tubules in testes and also in specific brain regions (cerebellum, midbrain and pons). Notably, gene expression of a number of Nrf2-dependent target genes except Hmox1 was not severely affected by 3-MCPD. In all three organs, however, the amount of irreversibly oxidized DJ-1 protein, which is a biomarker for oxidative stress, was significantly increased already by low doses of 3-MCPD.

Effects of 2-MCPD on oxidative stress in different organs of male mice

“…Heart hypertrophy was a possible toxic effect, which was bioinformatically predicted in the rat heart proteome study. However, neither in the rat proteome study nor in the present mouse study the heart-to-body weight was increased (Schultrich et al 2017;Schultrich et al 2020). Although the specific mechanism of action of 2-MCPD is unclear, the data show that 2-MCPD not only targets other organs compared to 3-MCPD, but also triggers different toxic mechanisms at the molecular level.…”

“…The animals showed no signs of acute toxicity after treatment and were in a healthy condition during the entire study. In a previous animal experiment with analogous study design using 3-MCPD, mice of the high dose group (100 mg 3-MCPD per kg body weight per day) showed a severe decrease in body weight of more than 20% within seven days (Schultrich et al 2020). This clearly shows that a daily oral application of 100 mg 3-MCPD per kg body weight caused acute toxic effects in male HOTT mice, whereas identical doses of 2-MCPD did not lead to any clinical symptoms or significant toxicity, indicating that, at least in mice, 2-MCPD is less toxic than 3-MCPD.…”

“…Slides with 10 µm tissue slices were stained as detailed described in (Schultrich et al 2020).In brief, the tissue sections were rehydrated and stained at 37°C overnight by using an X-Gal staining solution. Afterwards, slides were washed with PBS, counterstained with Nuclear Fast Red and again washed twice with double-distilled water.…”

“…The reporter mice were treated with PBS, 1, 10 or 100 mg 2-MCPD per kg body weight for 28 days. As positive control, microscopic images of X-Gal stained kidney, testes and cerebellum of HOTT mice treated with 100 mg 3-MCPD per kg body weight over a period of 7 days are depicted (Schultrich et al, 2020).…”

“…2-MCPD, however, led to a substantially less pronounced oxidation of the thiol group of DJ-1/Park7 in rat, as compared to 3-MCPD (Buhrke et al 2018), possibly indicating a lower toxic potential of 2-MCPD regarding the induction of oxidative stress. Moreover, an in vivo study with HOTT (heme oxygenase transgenic triple reporter) mice has demonstrated substantial effects of 3-MCPD in mice (Schultrich et al 2020). The HOTT mouse serves as a model to monitor substance-induced oxidative stress in different target organs.…”