Bisphenol-C is the strongest bifunctional ERα-agonist and ERβ-antagonist due to magnified halogen bonding

Mixture Effects of Bisphenol A and Its Structural Analogs on Estrogen Receptor Transcriptional Activation

Bisphenol A (BPA) exposure has been widely linked to endocrine-disrupting effects. Recently, many substitutes for BPA have been developed as safe structural analogs. However, they have still been reported to have similar adverse effects. The current study evaluated the effects of bisphenol A and eight structural analogs on the transcription of estrogen receptor alpha (ERα). The effects of binary and ternary mixtures prepared from different combinations of BPA analogs were also evaluated for transcription activity. The measured data of the mixtures were compared to the predicted data obtained by the full logistic model, and the model deviation ratio (MDR) was calculated to determine whether the effects were synergistic, antagonistic, or additive. Overall, the results suggest that the effect of bisphenol compound are additive in binary and ternary mixtures.

Combined Toxic Effects of BPA and Its Two Analogues BPAP and BPC in a 3D HepG2 Cell Model

Bisphenol A (BPA) is one of the most commonly used substances in the manufacture of various everyday products. Growing concerns about its hazardous properties, including endocrine disruption and genotoxicity, have led to its gradual replacement by presumably safer analogues in manufacturing plastics. The widespread use of BPA and, more recently, its analogues has increased their residues in the environment. However, our knowledge of their toxicological profiles is limited and their combined effects are unknown. In the present study, we investigated the toxic effects caused by single bisphenols and by the combined exposure of BPA and its two analogues, BPAP and BPC, after short (24-h) and prolonged (96-h) exposure in HepG2 spheroids. The results showed that BPA did not reduce cell viability in HepG2 spheroids after 24-h exposure. In contrast, BPAP and BPC affected cell viability in HepG2 spheroids. Both binary mixtures (BPA/BPAP and BPA/BPC) decreased cell viability in a dose-dependent manner, but the significant difference was only observed for the combination of BPA/BPC (both at 40 µM). After 96-h exposure, none of the BPs studied affected cell viability in HepG2 spheroids. Only the combination of BPA/BPAP decreased cell viability in a dose-dependent manner that was significant for the combination of 4 µM BPA and 4 µM BPAP. None of the BPs and their binary mixtures studied affected the surface area and growth of spheroids as measured by planimetry. In addition, all BPs and their binary mixtures studied triggered oxidative stress, as measured by the production of reactive oxygen species and malondialdehyde, at both exposure times. Overall, the results suggest that it is important to study the effects of BPs as single compounds. It is even more important to study the effects of combined exposures, as the combined effects may differ from those induced by single compounds.

Interaction of various types of bisphenols with enzymes involved in melanin synthesis

Objectives

Bisphenol is one of the commercial chemical compounds which finds application in the manufacture of phenol, polyesters, polycarbonates, epoxy resins, etc. Bisphenol A is the most commonly found bisphenol derivative, although there are various analogues such as Bisphenol S, Bisphenol B, Bisphenol C, Bisphenol E, Bisphenol AF, which vary with their structures. Bisphenols majorly get into us by means of food as they are found in food packaging and beverage containers and can be easily absorbed by the body. They can make way into the body systems either by direct means like skin contact or by indirect means through food that is stored in a bisphenol-coated containers. Exposure of the human system to this compound may bring about mild to adverse ailments ranging from skin irritations to infertility. Pigmentation disorder is one such health condition that occurs due to melanocyte destruction and is caused by bisphenol exposures. They interact with various proteins and enzymes that have been involved in the melanocyte synthesis pathway, thereby disrupting their normal functions.

Methods

In silico analysis has been done to predict the interaction and other descriptive binding parameters when the bisphenol derivatives BPA. BPB, BPC, BPE, BPS and BPAF have been docked with some of the essential proteins for melanin synthesis such as tyrosinase, tyrosinase-related protein 1(TRP-1), dopachrome tautomerase/tyrosinase-related protein-2(TRP-2).

Results

The interaction has been quantified with the binding energies, and the interacting amino acid residues have also been identified. The results showed strong interactions for both the proteins TRP-1 and TRP-2 with BPA. BPB, BPC, BPE, BPS and BPAF.

Conclusions

The risk and threats caused by the commercial products made of bisphenol are at higher levels, and thereby, the need for a safe and desirable alternative has been insisted.

Dissection of the Origin of π-Holes and the Noncovalent Bonds in Which They Engage

Accompanying the rapidly growing list of σ-hole bonds has come the acknowledgment of parallel sorts of noncovalent bonds which owe their stability in large part to a deficiency of electron density in the area above the molecular plane, known as a π-hole. The origins of these π-holes are probed for a wide series of molecules, comprising halogen, chalcogen, pnicogen, tetrel, aerogen, and spodium bonds. Much like in the case of their σ-hole counterparts, formation of the internal covalent π-bond in the Lewis acid molecule pulls density toward the bond midpoint and away from its extremities. This depletion of density above the central atom is amplified by an electron-withdrawing substituent. At the same time, the amplitude of the π*-orbital is enhanced in the region of the density-depleted π-hole, facilitating a better overlap with the nucleophile's lone pair orbital and a stabilizing n → π* charge transfer. The presence of lone pairs on the central atom acts to attenuate the π-hole and shift its position somewhat, resulting in an overall weakening of the π-hole bond. There is a tendency for π-hole bonds to include a higher fraction of induction energy than σ-bonds with proportionately smaller electrostatic and dispersion components, but this distinction is less a product of the σ- or π-character and more a function of the overall bond strength.

ERα-agonist and ERβ-antagonist bifunctional next-generation bisphenols with no halogens: BPAP, BPB, and BPZ

As demonstrated for bisphenol AF (BPAF), the electrostatic halogen bond based on the London dispersion force of halogen atoms was found to be a major driving force of their bifunctional ERα-agonist and ERβ-antagonist activities. Because similar electronic effects are anticipated for hydrocarbon groups (alkyl or aryl groups), we hypothesized that bisphenol compounds consisting of such groups also work bifunctionally. In the present study, we examined bisphenol AP (BPAP), B (BPB), and Z (BPZ). After recognizing their considerably strong receptor binding affinities, we evaluated the abilities of BPAP, BPB, and BPZ to activate ERα and ERβ in a luciferase reporter gene assay. These bisphenols were fully active for ERα but completely inactive for ERβ. When we examined their inhibitory activities for 17β-estradiol in ERβ by two different qualitative and quantitative analytical methods, we found that those bisphenols worked as definite antagonists. Consequently, they were established as bifunctional ERα-agonists and ERβ-antagonists. The present structure-activity analyses revealed that the dispersion force works not only on the halogens but also on the hydrocarbon groups, and that it is a major driving force of bifunctional ERα-agonist and ERβ-antagonist activities.