In-utero exposure to estrogen-mimicking bisphenols alters bone mineralization in the offspring

Abstract

Exposure to plastic-derived estrogen-mimicking endocrine-disrupting bisphenols can have a long-lasting effect on bone health. However, gestational exposure to below tolerable daily intake (TDI) of bisphenol A (BPA) and its substitute, bisphenol S (BPS), on offspring’s bone mineralization is unclear. This study examined the effects of in-utero bisphenol exposure on the growth and bone density of the offspring rats. Pregnant Wistar rats were exposed to BPA and BPS (0.0, 0.4 μg/kg bw) via oral gavage from gestational day 4 to 21. The bone density, IGF-1, osteocalcin, and calcium levels were measured by DEXA, ELISA and AAS, respectively. The bisphenol’s action on canonical BMP signaling was examined in osteoblast SaOS-2 cells. Maternal exposure to bisphenols (BPA and BPS) increased the body weight, bone mineral content, and density in the offspring aged 30 and 90 days (p<0.05). Plasma IGF-1, calcium, osteocalcin, and alkaline phosphatase activities were altered in BPA-exposed offspring (p<0.05). The bisphenols exposure to SaOS-2 cells decreased its viability in a dose-dependent manner and promoted the cell cycle progression of the S/G2-M phase (p<0.05). The expression of BMP1, BMP4, and intracellular signalling mediators SMAD1, SMAD5, and RUNX2 mRNAs was altered upon bisphenol exposure in these cells (p<0.05). The bone mineralization index and expression of extracellular matrix proteins such as ALPL, COL1A1, DMP1, and FN1 were downregulated (p<0.05). Bisphenol co-incubation with noggin decreased TGF-β1 expression, indicating its involvement in bone mineralization. Overall, exposure to bisphenols (BPA and BPS) during gestation altered growth and bone mineralization in the offspring by modulating canonical BMP/ TGF-β1 signalling mediators.HighlightsGestational exposure to low doses of bisphenol increases whole-body BMC and BMD in the offspring.In-utero BPA exposure increased plasma IGF-1 and gla-type osteocalcin, a marker of osteoblast activity in the offspring.Bisphenol exposure modulates Smad-dependent BMP signaling in the SaOS-2 cells.