123 Cytokine upregulation in female placentas of nano-titanium dioxide exposed rat dams

Abstract The placenta plays a vital role for the developing foetus by providing nutrient and waste exchange in the labyrinth zone (LZ), hormone production within the junctional zone (JZ), and a protective barrier. Poor placental protection or nutrient delivery can result in preeclampsia, foetal growth restriction, and/or fatal mortality. Because immune responses are known to be sexually dimorphic, we sought to determine if placentas exposed to nTiO2 have sex and zone-specific immune responses. Female Sprague Dawley (SD) rats (n = 4 to 6 per group; 8-week-old) were were randomly assigned to nTiO2 (12 mg/m3) or HEPA-filtered air (25 mL/min) exposure for 6 h/day for 6 non-consecutive days between gestational days (GD) 12 to 19. On GD 20, placentas were collected, divided by foetal sex, and zones isolated. One male and female placenta per dam was fixed for immunofluorescence of Hofbauer cell polarization, and snap frozen for protein and RNA analysis. A 79-cytokine proteome array was used to screen whole placentas, and relative mRNA levels of cytokines, chemokines, and pro-inflammatory ER stress pathways were determined RT-qPCR. nTiO2 exposure resulted in increased cytokine upregulation in female placentas (IL-6, IFNγ, CCL2) and increased downregulation in male placentas (IGF-1, IL-1β, CCL2). Exposed male JZs had more IL-10 (355%, P = 0.06) and IFNγ (305%, P = 0.06), while female JZs had a trending increase in IL-10 (487%, P = 0.1). Overall, nTiO2 exposure increased cytokine protein concentrations in female placentas, which may contribute to the growth restriction and placental zone adaptations. Revealing sex-driven differences in placental responses can identify mechanisms, pharmacological targets, and markers of poor pregnancy outcomes specific to the foetal sex.