Exposure to 7,12-dimethylbenz[a]anthracene impacts ovarian DNA damage sensing and repair proteins differently in lean and obese female mice and weight loss may mitigate obesity-induced ovarian dysfunction.

Obesity impairs oocyte quality, fertility, pregnancy maintenance, and is associated with offspring birth defects. The model ovotoxicant, 7,12-dimethylbenz[a]anthracene (DMBA), causes ovarian DNA damage and follicle loss. Both DMBA-induced chemical biotransformation and the DNA damage response are partially attenuated in obese relative to lean female mice but whether weight loss could improve the DNA damage response to DMBA exposure has not been explored. Thus, at six weeks of age, C57BL/6 J female mice were divided in three groups: 1) Lean (L; n = 20) fed a chow diet for 12 weeks, 2) obese (O; n = 20) fed a high fat high sugar (HFHS) diet for 12 weeks and, 3) slim-down (S; n = 20). The S group was fed with HFHS diet for 7 weeks until attaining a higher body relative to L mice on week 7.5 and switched to a chow diet for 5 weeks to achieve weight loss. Mice then received either corn oil (CT) or DMBA (D; 1 mg/kg) for 7 d via intraperitoneal injection (n = 10/treatment). Obesity increased (P < 0.05) kidney and spleen weight, and DMBA decreased uterine weight (P < 0.05). Ovarian weight was reduced (P < 0.05) in S mice, but DMBA exposure increased ovary weight in the S mice. LC-MS/MS identified 18, 64, and 7 ovarian proteins as altered (P < 0.05) by DMBA in the L, S and O groups, respectively. In S and O mice, 24 and 8 proteins differed, respectively, from L mice. These findings support weight loss as a strategy to modulate the ovarian genotoxicant response.

Biological sex differences in hepatic response to in utero dimethylbenz(a)anthracene exposure.

Fetal hepatic dimethylbenz(a)anthracene (DMBA) biotransformation is not defined, thus, this study investigated whether the fetal liver metabolizes DMBA and differs with biological sex. KK.Cg-a/a (lean; n = 20) or KK.Cg-Ay/J (obese; n = 20) pregnant mice were exposed to corn oil (CT) or DMBA (1 mg/kg bw/day) by intraperitoneal injection (n = 10/treatment) from gestation day 7-14. Postnatal day 2 male or female offspring livers were collected. Total RNA (n = 6) and protein (n = 6) were analyzed via a PCR-based array or LC-MS/MS, respectively. The level of Mgst3 was lower (P < 0.05) in livers of female compared to male offspring. Furthermore, in utero DMBA exposure increased (P < 0.1) Cyp2c29 and Gpx3 levels (P < 0.05) in female offspring. In male offspring, the abundance of Ahr, Comt (P < 0.1), Alox5, and Asna1 (P < 0.05) decreased due to DMBA exposure. Female and male offspring had 34 and 21 hepatic proteins altered (P < 0.05) by in utero DMBA exposure, respectively. Opposing patterns for hepatic CD81 and KRT78 occurred, being decreased in females but increased in males, while YWHAG was decreased by DMBA exposure in both. Functional KEGG pathway analysis identified enrichment of 26 and 13 hepatic metabolic proteins in male and female offspring, respectively, due to in utero DMBA exposure. In silico transcription factor analysis of differentially expressed proteins predicted involvement of female NRF1 but male AHR. Thus, hepatic biological sex differences and capacity to respond to toxicants in utero are supported.

Lessons Learned from ToxMSDT: A Pilot Innovative Toxicology Research Education Pipeline Program Targeting Underrepresented Undergraduate Students to the Field of Toxicology.

Toxicology, as a profession, lacks diversity. Undergraduate students, and especially underrepresented students, are not commonly introduced to toxicology at US colleges and universities. The Toxicology Mentoring and Skills Development Training Program (ToxMSDT) seeks to acquaint underrepresented undergraduates enrolled in STEM fields with toxicology fundamentals and skills to aid their entry into graduate programs and, ultimately, careers in toxicology. ToxMSDT is a collaboration among three universities. It is a year-long holistic training and mentoring program comprised of web resources accessible 24/7 and extensive one-to-one mentor-mentee interactions throughout the year. Evaluation of the two-year pilot program shows that students expressed a significant increase in knowledge about toxicology careers, networking with people involved in the field of toxicology, feelings of being part of the toxicology community, and seeing themselves as someone who will study toxicology, compared with their feelings prior to their participation in the ToxMSDT program. Thirty students have completed the ToxMSDT program and all 10 (100%) of those who have graduated have joined graduate school in toxicology or toxicology-related STEM fields. Of the 20 (66.6%) program alumni still enrolled as undergraduates, five (25%) are in the process of applying to graduate programs and medical schools as of August 2019.