In Vivo acrylamide exposure may cause severe toxicity to mouse oocytes through its metabolite glycidamide

Abstract

High acrylamide (ACR) content in heat-processed carbohydrate-rich foods, as well as roasted products such as coffee, almonds etc., has been found to be as a risk factor for carcinogenicity and genotoxicity by The World Health Organization. Glycidamide (GLY), the epoxide metabolite of ACR, is processed by the cytochrome P-450 enzyme system and has also been found to be a genotoxic agent. The aim of this study was to determine whether ACR and/or GLY have any detrimental effect on the meiotic cell division of oocytes. For this purpose, germinal vesicle-stage mouse oocytes were treated with 0, 100, 500, or 1000 μM ACR or 0, 25, or 250 μM GLY in vitro. In vivo experiments were performed after an intraperitoneal injection of 25 mg/kg/day ACR of female BALB/c mice for 7 days. The majority of in vitro ACR-treated oocytes reached the metaphase-II stage following 18 hours of incubation, which was not significantly different from the control group. Maturation of the oocytes derived from in vivo ACR-treated mice was impaired significantly. Oocytes, reaching the M-II stage in the in vivo ACR-treated group, were characterized by a decrease in meiotic spindle mass and an increase in chromosomal disruption. In vitro GLY treatment resulted in the degeneration of all oocytes, indicating that ACR toxicity on female germ cells may occur through its metabolite, GLY. Thus, ACR exposure must be considered, together with its metabolite GLY, when female fertility is concerned.

Fig 1. In vitro Effect of ACR on Oocyte Maturation.

In vitro maturation stages of 0, 100, 500 and 1000 μM ACR-treated oocytes following 18 hours of incubation. There was no significant difference between control and ACR-treated groups in terms of oocytes reaching the M-II stage or degenerated oocytes.

Fig 2. In vitro and In vivo Effects of ACR on Meiotic Spindle.

In vitro-matured M-II stage oocytes in control (A-C), in vitro ACR-treated (D-F) and in vivo ACR-treated (25 mg/kg) groups (G-I). Representative images in D-F were taken from a 1000 μM ACR-treated group. In vitro ACR-treated M-II stage oocytes showed no disruption in the meiotic spindle (green signal) and chromosome organization (red signal) appeared to be intact. In vivo ACR-treatment caused a decrease in spindle microtubule mass and disruption in the chromosome alignment. Multiple microtubule-organizing centers (MTOCs) were detected (arrows). PB: polar body. Scale bar: 10 μm.

Fig 3. In vivo Effect of ACR on Oocyte Maturation.

Maturation stages of oocytes isolated from control and ACR-treated mice were presented. *The percentage of M-II stage oocytes was significantly higher in the control group compared to the ACR-treated group (p = 0.001).

Fig 4. In vitro Effect of GLY on Oocyte Maturation.

In vitro-maturated oocytes were presented in control (A) and in vitro GLY-treated (B) groups. Bar graphs show the in vitro maturation stages of 0, 25 and 250 μM ACR-treated oocytes following 18 hours of incubation (C). The representative image in B was taken from a 25 μM GLY-treated group. The majority of the GV-stage oocytes reached the M-II stage in the control group, whereas all GLY-treated oocytes were degenerated following 18 hours of incubation (A-C). Scale bar: 200 μm.