Co-trimoxazole-induced reproductive toxicity and placental-barrier disruption: impact on cell-cell junctions and ERK signaling pathway

Co-trimoxazole (CTX), a combination of sulfamethoxazole (SMZ) and trimethoprim (TMP), is used during pregnancies complicated by infections like Urinary Tract Infections (UTI) and Human Immunodeficiency Virus (HIV), despite potential fetal safety concerns. This study examines CTX's effects on the placenta using both in vivo and in vitro models. Pregnant mice received CTX for 4 days during both early and late gestation. On gestational day 19, tissues were collected for analysis. Furthermore, in vitro, human BeWo placental cells were exposed to non-cytotoxic concentrations of CTX for 24 h. Gene expression was analyzed by bulk RNA sequencing with pathway analysis, and placental barrier function was assessed by measuring transepithelial electrical resistance (TEER) and fluorescein isothiocyanate-dextran (FITC-D) permeability. In vivo, CTX significantly reduced uterine weight and litter size (p < 0.05), indicating potential reproductive toxicity, which was supported by placental transcriptomic analysis. In vitro, bulk RNA-sequencing of CTX-treated BeWo cells exhibited differential expression of genes related to tight and adherens junctions, indicating impaired placental barrier integrity. This was accompanied by a significant reduction in TEER (p < 0.0001) and an increase in FITC-D permeability (p < 0.001). In addition, CTX activated the ERK1/2 (MAPK3) pathway, as indicated by increased ERK1/2 (p < 0.01) phosphorylation and downregulation of the ERK pathway negative regulators (DUSP genes). Additionally, IL-6 expression levels were reduced in the amniotic fluid (p < 0.01) and placenta of CTX-treated mice, and a similar reduction was observed in CTX-treated BeWo cells at both the transcript (p < 0.05) and protein (p < 0.001) levels. In conclusion, CTX may induce reproductive toxicity and compromise placental barrier integrity, warranting further investigation into its safety during pregnancy.