Chronic prenatal cannabinoid exposure in rats drives differences in fetal and placental size, placental oxidative stress genes, and placental SIRT1 expression

Abstract Authors: Rachel C. West1, Adrian H. Courville2, Paige M. Drotos1, Carly Parker1, Cristine R. Camp1, Victoria T. Caravaggio1, Miranda N. Reed²

1. Anatomy, Physiology, Pharmacology Department, College of Veterinary Medicine, Auburn University, Auburn, USA
2. Department of Drug Discovery and Development, Harrison College of Pharmacy, Auburn University, Auburn, USA

Abstract Text:

Recreational use of marijuana during pregnancy has sharply increased as general attitudes towards marijuana have become more relaxed. There is a growing body of work demonstrating that prenatal cannabinoid exposure negatively impacts fetal and neonatal development and leads to increased risk of preterm birth and NICU admissions. As the placenta serves as a mediator of communication between the mother and the fetus, we aimed to assess the effect of prenatal cannabinoid exposure on placental development using a rat model. On gestational day (GD) 5, we exposed pregnant dams to a vaporized dose of 100 mg/mL Δ9-tetrahydrocannabinol (THC) or polyethylene glycol (PEG). The dams received a daily dose of either THC or PEG until GD19 when dams were euthanized and fetuses and placentas collected. Compared to the PEG control fetuses, THC exposed fetuses were significantly heavier (p < 0.001). The average weight of the THC exposed placentas was also significantly heavier (p < 0.05), suggesting that prenatal cannabinoid exposure affects metabolism and growth in both the fetus and placenta. Interestingly, after re-assessing the fetal and placental weights while using genetic sex as a biological variable, we found that only the male THC fetuses were significantly heavier (p < 0.05) than the male and female PEG fetuses. Alternatively, we found that female THC placentas were significantly heavier (p < 0.05) than the PEG male placentas and were slightly heavier, although not significantly (p < 0.079) than the PEG female placentas. There were no significant differences in weight between the male THC and PEG placentas. We next isolated RNA from 20 (10 male, 10 female) PEG and 20 (10 male, 10 female) THC-exposed placentas and performed RNA-sequencing (RNAseq). RNAseq revealed 824 total differentially expressed genes between the PEG and THC placentas, with 452 upregulated genes in the THC group and 372 downregulated genes in the THC group (padj < 0.025, log2FoldChange > 0). Gene ontology (GO) revealed several functional pathways related to oxidation-reduction, antioxidant activity, cellular detoxification, and lipid metabolism were enriched in the THC placenta group. Alternatively, pathways related to cell proliferation, methylation, and histone modification were decreased in the THC placenta group. Based on the GO data, we began to assess differences in protein expression of genes related to redox reactions and oxidative stress. One gene of interest that was significantly downregulated (padj < 0.05) in the THC exposed placentas was Sirtuin-1 (Sirt1). SIRT1 is a NAD+-dependent histone deacetylase protein involved in many biological processes including modulation of inflammation and protection against oxidative stress. Western blotting confirmed that protein levels of SIRT1 were also significantly decreased (p < 0.005) in THC placentas. In summary, this study demonstrates that prenatal cannabinoid exposure alters fetal and placental growth in a sex-dependent manner and that THC exposure impacts several important placental pathways related to redox reactions, oxidative stress, and lipid metabolism. Finally, we also have demonstrated significant decreases in SIRT1 mRNA and protein levels in THC exposed placentas. As decreased levels of SIRT1 have been linked to premature placental senescence and preeclampsia, these data suggest a new link between prenatal cannabinoid exposure and placental dysfunction and adverse pregnancy outcomes.

Funding: Auburn Startup Funds (West) and NIH/NIDA R01 DA046723 (Reed)