Bisphenol A in the Gut: Another Break in the Wall?

The intestinal microbiota as mediators between dietary contaminants and host health

The gut microbiota sit at an important interface between the host and the environment, and are exposed to a multitude of nutritive and non-nutritive substances. These microbiota are critical to maintaining host health, but their supportive roles may be compromised in response to endogenous compounds. Numerous non-nutritive substances are introduced through contaminated foods, with three common groups of contaminants being bisphenols, phthalates, and mycotoxins. The former contaminants are commonly introduced through food and/or beverages packaged in plastic, while mycotoxins contaminate various crops used to feed livestock and humans alike. Each group of contaminants have been shown to shift microbial communities following exposure; however, specific patterns in microbial responses have yet to be identified, and little is known about the capacity of the microbiota to metabolize these contaminants. This review characterizes the state of existing research related to gut microbial responses to and biotransformation of bisphenols, phthalates, and mycotoxins. Collectively, we highlight the need to identify consistent, contaminant-specific responses in microbial shifts, whether these community alterations are a result of contaminant effects on the host or microbiota directly, and to identify the extent of contaminant biotransformation by microbiota, including if these transformations occur in physiologically relevant contexts.

Visible-light-driven photocatalytic dual-layer hollow fibre membrane ameliorates the changes of bisphenol A exposure in gastrointestinal tract

Various treatments of choice are available to overcome contamination of bisphenol A (BPA) in the environment including membrane technologies; however, the treatment still releases contaminants that threaten the human being. Therefore, the present study is conducted to investigate the degradation of BPA by recently developed visible-light-driven photocatalytic nitrogen-doping titanium dioxide (N-doped TiO₂) dual-layer hollow fibre (DLHF) membrane and its efficiency in reducing the level of BPA in contaminated water. Fabricated with suitable polymer/photocatalyst (15/7.5 wt.%) via co-extrusion spinning method, the DLHF was characterized morphologically, evaluated for BPA degradation by using submerged photocatalytic membrane reactor under visible light irradiations followed by the investigation of intermediates formed. BPA exposure effects were accessed by immunohistochemistry staining of gastrointestinal sample obtained from animal model. BPA has been successfully degraded up to 72.5% with 2 intermediate products, B1 and B2, being identified followed by total degradation of BPA. BPA exposure leads to the high-intensity IHC staining of Claudin family which indicated the disruption of small intestinal barrier (SIB) integrity. Low IHC staining intensity of Claudin family in treated BPA group demonstrated that reducing the level of BPA by N-doped TiO₂ DLHF is capable of protecting the important component of SIB. Altogether, the fabricated photocatalytic DLHF membrane is expected to have an outstanding potential in removing BPA and its health effect for household water treatment to fulfil the public focus on the safety of their household water and their need to consume clean water.

MAIT cell activation is reduced by direct and microbiota-mediated exposure to bisphenols

Oral uptake is the primary route of human bisphenol exposure, resulting in an exposure of the intestinal microbiota and intestine-associated immune cells. Therefore, we compared the impact of bisphenol A (BPA), bisphenol F (BPF) and bisphenol S (BPS) on (i) intestinal microbiota, (ii) microbiota-mediated immunomodulatory effects and (iii) direct effects on mucosal-associated invariant T (MAIT) cells in vitro. We acutely exposed human fecal microbiota, Bacteroides thetaiotaomicron and Escherichia coli to BPA and its analogues BPF and BPS referring to the European tolerable daily intake (TDI), i.e. 2.3 µg/mL, 28.3 µg/mL and 354.0 µg/mL. Growth and viability of E. coli was most susceptible to BPF, whereas B.thetaiotaomicron and fecal microbiota were affected by BPA > BPF > BPS. At 354.0 µg/mL bisphenols altered microbial diversity in compound-specific manner and modulated microbial metabolism, with BPA already acting on metabolism at 28.3 µg/mL. Microbiota-mediated effects on MAIT cells were observed for the individual bacteria at 354.0 µg/mL only. However, BPA and BPF directly modulated MAIT cell responses at low concentrations, whereby bisphenols at concentrations equivalent for the current TDI had no modulatory effects for microbiota or for MAIT cells. Our findings indicate that acute bisphenol exposure may alter microbial metabolism and impact directly on immune cells.

Effects of bisphenol A and its alternative bisphenol F on Notch signaling and intestinal development: A novel signaling by which bisphenols disrupt vertebrate development

We previously found bisphenol A (BPA) alternative, bisphenol F (BPF) upregulated Notch-related gene expression in intestines of the African clawed frog Xenopus laevis, suggesting an agonistic action on Notch signaling, a crucial signaling in multiple biological processes during development. Here, we aimed to confirm the actions of BPA and BPF on Notch signaling and to reveal their effects on intestinal development. Using X. laevis, an excellent model for developmental biology, we found that 10-1000 nM BPA and BPF significantly elevated Notch-related gene expression in a concentration-dependent manner. Subsequently, exceptional cell proliferation as well as intestinal histological changes were observed in treated intestines. Importantly, Notch inhibitor markedly suppressed the effects of BPA and BPF described above. Furthermore, we employed rat intestinal epithelium cells (IEC-6), an ideal in vitro model of intestinal epithelial cell differentiation, to confirm the effects of bisphenols. As expected, BPA and BPF upregulated Notch-related gene expression and induced the translocation of the Notch intracellular domain to the nucleus, followed by exceptional cell proliferation and differentiation, whereas Notch inhibitor antagonized the effects caused by BPA and BPF. All results strongly demonstrate that both BPA and BPF activate Notch signaling and subsequently disrupt intestinal development in vertebrates. Given its fundamental roles in multiple developmental processes, we propose that Notch signaling is an important and general target signaling of bisphenols in many developing tissues of vertebrates including humans.