Sex-Dependent Effects of Early Life Stress and Bisphenol S Exposure on Molecular Elements of the Heart

Early life stress (ELS) is a risk for adult-onset cardiovascular disease (CVD), although the molecular mechanisms of risk remain poorly understood. Studies have reported sex differences in the physiological response to ELS, but no study has investigated sex differences in the cardiac response. Exposure to bisphenol A (BPA) and other ubiquitous plasticizers also increase CVD risk, and exposure is disproportionately high in vulnerable populations, including people who experience ELS. Bisphenol S (BPS) was touted as a safer replacement for BPA, but studies show similarly negative cardiovascular effects. We have previously shown sex-dependent effects of acute BPS exposure on the heart. How chronic exposure to environmental chemicals impacts the cardiac response to ELS is unknown. We hypothesized that ELS and BPS exposure, in isolation and together, mediate sex-dependent effects on the heart, including activation of cardiac stress responses. Maternal separation with early weaning (MSEW) is an established model for ELS. Pups are separated from the dam 4h/day from postnatal day (PD) 2 to PD5, and 8h/day from PD6 to 16 before being weaned early at PD17. Controls remain with the dam until normal weaning at PD21. A low concentration of BPS (250 nM) or vehicle was added to the drinking water in glass containers starting at PD21 until 12 weeks of age. Water volume consumed per day and body weight at time of sacrifice were recorded and no differences were observed between groups. Cardiac myofilament function was assessed using a colourimetric actomyosin MgATPase assay (N=4-7 per group). BPS exposure depressed maximum cardiac myofilament function by 12% in female mice (P=0.02), and MSEW reduced activity by a further 10% (P< 0.01). The combination of MSEW + BPS yielded lower activity compared to controls (P< 0.01), similar to MSEW alone. By contrast, cardiac myofilament function in males was not significantly affected in any group. Immunoblotting (N=3 per group) found reduced nitrotyrosine levels in myocardial samples from female mice exposed to BPS or MSEW by 73% and 44% respectively, but no difference when subjected to both. Male samples had similar, but smaller nitrotyrosine reductions of ~30% in BPS or MSEW groups, but a 3-fold increase in the MSEW + BPS group. Beclin, a marker of autophagy did not change in any male group, but decreased by 30% in females exposed to BPS, and increased by 32% and 97% in females exposed to MSEW and MSEW + BPS respectively. Bcl-2 expression and CamKII phosphorylation did not exhibit differences in any group of either sex. Together these data demonstrate significant sex differences in the cardiac response to ELS, BPS, or a combination of both. Both sexes exhibited markers of stress including protein nitrosylation and autophagy in a manner that depended on the stressor and animal sex. This study provides novel insight into the molecular mechanisms that underlie CVD risks presented by environmental BPS exposure and ELS, and underscores the need to consider sex in the development of interventions to mitigate disease risk. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.