Butylated hydroxyanisole alters rat 5α-reductase and 3α-hydroxysteroid dehydrogenase: Implications for influences of neurosteroidogenesis

Paraben preservatives exhibit inhibition on human and rat steroid 5α-reductase 1: A comprehensive 3D-QSAR and computational analysis

Parabens are preservatives used in personal care products, cosmetics, and pharmaceuticals. Steroid 5α-reductase 1 (SRD5A1) catalyzes the conversion of testosterone to dihydrotestosterone and is present in the brain, contributing to neurosteroid production. This study aimed to assess the effects of nine paraben preservatives on SRD5A1 in human SF126 glioblastoma cell and rat brain microsomes, particularly focusing on dihydrotestosterone production in SF126 cells. The results showed that methyl, ethyl, propyl, butyl, hexyl, heptyl, nonyl, phenyl, and benzyl paraben inhibited human SRD5A1, with nonylparaben having the strongest effect (7.59 μM). Additionally, kinetic analysis indicated that parabens acted as mixed/noncompetitive inhibitors, leading to a significant decrease in dihydrotestosterone production in SF126 cells. While rat SRD5A1 exhibited lower sensitivity to parabens, docking analysis revealed that parabens bind to the NADPH-binding site of both human and rat SRD5A1. In conclusion, these results highlight the inhibitory effects of paraben preservatives on SRD5A1 and elucidate their binding mechanisms, underscoring their role in hormone production.

Carbon-chain length determines the binding affinity and inhibitory strength of per- and polyfluoroalkyl substances on human and rat steroid 5α-reductase 1 activity

Per- and polyfluoroalkyl substances (PFAS) are widely used synthetic chemicals that persist in the environment and bioaccumulate in animals and humans. There is growing evidence that PFAS exposure adversely impacts neurodevelopment and neurological health. Steroid 5α-reductase 1 (SRD5A1) plays a key role in neurosteroidogenesis by catalyzing the conversion of testosterone or pregnenolone to neuroactive steroids, which influence neural development, cognition, mood, and behavior. This study investigated the inhibitory strength and binding interactions of 18 PFAS on human and rat SRD5A1 activity using enzyme assays, molecular docking, and structure-activity relationship analysis. Results revealed that C9-C14 PFAS carboxylic acid at 100 μM significantly inhibited human SRD5A1, with IC50 values ranged from 10.99 μM (C11) to 105.01 μM (C14), and only one PFAS sulfonic acid (C8S) significantly inhibited human SRD5A1 activity, with IC50 value of 8.15 μM. For rat SRD5A1, C9-C14 PFAS inhibited rat SRD5A1, showing the similar trend, depending on carbon number of the carbon chain. PFAS inhibit human and rat SRD5A1 in a carbon chain length-dependent manner, with optimal inhibition around C11. Kinetic studies indicated PFAS acted through mixed inhibition. Molecular docking revealed PFAS bind to the domain between NADPH and testosterone binding site of both SRD5A1 enzymes. Inhibitory potency correlated with physicochemical properties like carbon number of the carbon chain. These findings suggest PFAS may disrupt neurosteroid synthesis and provide insight into structure-based inhibition of SRD5A1.

3-tert-Butyl-4-hydroxyanisole Impairs Hepatic Lipid Metabolism in Male Mice Fed with a High-Fat Diet

3-tert-Butyl-4-hydroxyanisole (3-BHA), one of the widely used food antioxidants, has been found to act as a potential obesogen by promoting adipogenesis in vitro and inducing white adipose tissue development in vivo. Whether 3-BHA-induced visceral obesity was accompanied by a disruption of hepatic lipid homeostasis in mammals remained unclear. In this study, we evaluated the effect of 3-BHA on the development of nonalcoholic fatty liver disease (NAFLD) in male C57BL/6J mice. After 18 weeks of oral administration of 10 mg/kg 3-BHA, the mice fed with a high-fat diet (HFD) had higher hepatic triglyceride concentrations (0.32 mg/mg protein) and severer steatosis (1.57 for the NAFLD score) than the control ones. The in vivo hepatic lipid deposition disturbed by 3-BHA was transcriptionally regulated by the genes involved in lipid uptake, de novo lipogenesis, fatty acid oxidation, and lipid export. The in vitro studies further confirmed that 24 h of exposure to 50 μM 3-BHA could induce intracellular oleic acid (OA) uptake and triglyceride accumulation (1.5-fold of the OA control) in HepG2 cells. Lipidomic analysis indicated the perturbation of 3-BHA in the levels of 30 lipid species related to sphingolipids, glycerophospholipids, and glycerolipids under HFD conditions. The findings herein first revealed the disruption effect of 3-BHA on hepatic lipid homeostasis, thus exacerbating the development of HFD-induced NAFLD.

Exploring the mode of binding between butylated hydroxyanisole with bovine serum albumin: Multispectroscopic and molecular docking study

Considering the harm of BHA on humans, thorough research of the effect of BHA on the structure of serum albumin is necessary. The binding mechanisms of BHA with bovine serum albumin (BSA) and the effects of other three food additives (butylated hydroxytoluene, benzoic acid and citric acid) on BHA-BSA system were researched by multispectroscopy and molecular docking. The fluorescence quenching experiment results showed that the fluorescence quenching mechanism of BSA by BHA was static quenching. The binding constant ((5.70 ± 0.38) × 103 M-1 at 298 K) and thermodynamic parameters (ΔH = 110.8 ± 2.91 kJ·mol-1 and ΔS = 443.3 ± 9.30 J·mol-1·K-1) indicated that BHA and BSA formed a relatively stable complex through hydrophobic interaction. Three-dimensional fluorescence spectra confirmed the conformation changes of BSA due to the binding of BHA. Site marker competitive experiments and molecular docking proved that BHA could bind BSA into site I in subdomain IIA. The results of molecular docking showed that BHA formed hydrophobic interactions with amino acid residues (Ala290, Leu237, Leu259, Ile263 and Ile289). The presence of other food additives weakened the binding of BHA to BSA.

Butylated hydroxyanisole induces testicular dysfunction in mouse testis cells by dysregulating calcium homeostasis and stimulating endoplasmic reticulum stress

Butylated hydroxyanisole (BHA), a synthetic phenolic antioxidant (SPA), has been used as a food additive. However, BHA acts as an environmental hormone, i.e., endocrine disruptor. Here, we investigated BHA-induced male reproductive dysfunction in mouse Leydig and Sertoli cells. We found that BHA suppressed proliferation and induced cell cycle arrest in TM3 and TM4 cells. Furthermore, we investigated mitochondrial permeabilization, expression profiles of pro-apoptotic and anti-apoptotic proteins, calcium influx, and endoplasmic reticulum (ER) stress in testicular cells after BHA treatment. The results indicated that BHA-mediated calcium dysregulation and ER stress downregulated steroidogenesis- and spermatogenesis-related genes in mouse testis cell lines. Additionally, proliferation of both TM3 and TM4 cells in response to BHA treatment was regulated via the Mapk and Akt signaling pathways. Therefore, constant BHA exposure may lead to testicular toxicity via mitochondrial dysfunction, ER stress, and abnormal calcium levels in the testis.

Butylated Hydroxyanisole Exerts Neurotoxic Effects by Promoting Cytosolic Calcium Accumulation and Endoplasmic Reticulum Stress in Astrocytes

Astrocytes provide nutritional support, regulate inflammation, and perform synaptic functions in the human brain. Although butylated hydroxyanisole (BHA) is a well-known antioxidant, several studies in animals have indicated BHA-mediated liver toxicity, retardation in reproductive organ development and learning, and sleep deficit. However, the specific effects of BHA on human astrocytes and the underlying mechanisms are yet unclear. Here, we investigated the antigrowth effects of BHA through cell cycle arrest and downregulation of regulatory protein expression. The typical cell proliferative signaling pathways, phosphoinositide 3-kinase/protein kinase B and extracellular signal-regulated kinase 1/2, were downregulated in astrocytes after BHA treatment. BHA increased the levels of pro-apoptotic proteins, such as BAX, cytochrome c, cleaved caspase 3, and cleaved caspase 9, and decreased the level of anti-apoptotic protein BCL-XL. It also increased the cytosolic calcium level and the expression of endoplasmic reticulum stress proteins. Treatment with BAPTA-AM, a calcium chelator, attenuated the increased levels of ER stress proteins and cleaved members of the caspase family. We further performed an in vivo evaluation of the neurotoxic effect of BHA on zebrafish embryos and glial fibrillary acidic protein, a representative astrocyte biomarker, in a gfap:eGFP zebrafish transgenic model. Our results provide clear evidence of the potent cytotoxic effects of BHA on human astrocytes, which lead to disruption of the brain and nerve development.

Gossypol inhibits 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase: Its possible use for the treatment of prostate cancer

Gossypol is a yellow polyphenol isolated from cotton seeds. It has the antitumor activity and it is being tested to treat prostate cancer. However, its underlying mechanisms are still not well understood. The present study investigated the inhibitory effects of gossypol acetate on rat 5α-reductase 1, 3α-hydroxysteroid dehydrogenase, and retinol dehydrogenase 2 for androgen metabolism. Rat 5α-reductase 1, 3α-hydroxysteroid dehydrogenase, and retinol dehydrogenase 2 were expressed in COS-1 cells. Immature Leydig cells that contain these enzymes were isolated from 35-day-old male Sprague Dawley rats. The potency and mode of action of gossypol acetate to inhibit these enzymes in both enzyme-expressed preparations and immature Leydig cells were examined. Molecular docking study of gossypol on the crystal structure of 3α-hydroxysteroid dehydrogenase was performed. Gossypol acetate inhibited 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase with IC₅₀ values of 3.33 ± 0.07 and 0.52 ± 0.06 × 10^-6 M in the expressed enzymes as well as 8.512 ± 0.079 and 1.032 ± 0.068 × 10^-6 M in intact rat immature Leydig cells, respectively. Gossypol acetate inhibited rat 5α-reductase 1 in a noncompetitive mode and 3α-hydroxysteroid dehydrogenase in a mixed mode when steroid substrates were supplied. Gossypol acetate weakly inhibited retinol dehydrogenase 2 with IC₅₀ value over 1 × 10^-4 M. Molecular docking analysis showed that gossypol partially bound to the steroid-binding site of the crystal structure of rat 3α-hydroxysteroid dehydrogenase. Gossypol acetate is a potent inhibitor of rat 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase, possibly inhibiting the formation of androgen in the prostate cancer cells.