Low concentrations of bisphenol A induce lipid accumulation mediated by the production of reactive oxygen species in the mitochondria of HepG2 cells

Bisphenol A (BPA) is an endocrine-disrupting chemical that leaches from polycarbonate plastics that consequently leads to low-dose human exposure. In addition to its known xenoendocrine action, BPA exerts a wide variety of metabolic effects, but no data are available on its actions on the functions of liver mitochondrial. To assess these effects, HepG2 cells were exposed to BPA (10^?4–10^?12 M) and physiological parameters were measured by flow cytometry. We demonstrated a significant mitochondrial dysfunction including ROS production, ΔΨ_M hyperpolarization, lipid accumulation, lipoperoxidation and the release of pro-inflammatory cytokines. In conclusion, we showed that low concentrations of BPA promote lipid accumulation in hepatic cells triggered by disturbances in mitochondrial function, alterations in lipid metabolism and by inflammation that can therefore contribute to steatosis.     

Role of oxidative stress in carbon nanotube-generated health effects

The development of products containing carbon nanotubes (CNTs) is a major achievement of nanotechnology, although concerns regarding risk of toxic effects linger if the hazards associated with these materials are not thoroughly investigated. Exposure to CNTs has been associated with depletion of antioxidants, increased intracellular production of reactive oxygen species and pro-inflammatory signaling in cultured cells with primary function in the immune system as well as epithelial, endothelial and stromal cells. Pre-treatment with antioxidants has been shown to attenuate these effects, indicating a dependency of oxidative stress on cellular responses to CNT exposure. CNT-mediated oxidative stress in cell cultures has been associated with elevated levels of lipid peroxidation products and oxidatively damaged DNA. Investigations of oxidative stress endpoints in animal studies have utilized pulmonary, gastrointestinal, intravenous and intraperitoneal exposure routes, documenting elevated levels of lipid peroxidation products and oxidatively damaged DNA nucleobases especially in the lungs and liver, which to some extent occur concomitantly with altered levels of components in the antioxidant defense system (glutathione, superoxide dismutase or catalase). CNTs are biopersistent high aspect ratio materials, and some are rigid with lengths that lead to frustrated phagocytosis and pleural accumulation. There is accumulating evidence showing that pulmonary exposure to CNTs is associated with fibrosis and neoplastic changes in the lungs, and cardiovascular disease. As oxidative stress and inflammation responses are implicated in the development of these diseases, converging lines of evidence indicate that exposure to CNTs is associated with increased risk of cardiopulmonary diseases through generation of a pro-inflammatory and pro-oxidant milieu in the lungs.     

Bisphenol A differently inhibits CaV3.1, CaV3.2 and CaV3.3 calcium channels

Bisphenol A (BPA) is a widespread environmental contaminant detected in urine of 93 % of investigated US population. Recent epidemiological studies found correlation between BPA exposure and diseases including cardiovascular and neuronal disorders. BPA targets include hormone receptors and voltage-dependent ion channels. T-type calcium channels are important regulatory elements in both cardiovascular and neuronal system. Therefore, we investigated effects of BPA on T-type calcium channels. Calcium current flowing through recombinant T-type calcium channels expressed in HEK 293 cells was measured using whole-cell patch clamp. BPA inhibited the current through individual T-type calcium channel subtypes in a concentration-dependent manner with two distinguishable components in these concentration-dependencies. Nanomolar concentrations of BPA inhibited calcium current through T-type calcium channels in the order of efficiency Ca_V3.2?≥?Ca_V3.1?>?Ca_V3.3 without affecting voltage dependence and kinetics of channel gating. Micromolar concentrations of BPA accelerated kinetics of current decay, shifted voltage dependence of steady-state inactivation towards more negative values and inhibited current amplitudes. We suggest that BPA acts as a modifier of channel gating and directly plugs conductive channel pore at high concentration. Concentration range in which inhibition was observed corresponds to concentrations detected in human fluids and therefore may be relevant for evaluation of health effects of BPA.     

Green tea polyphenols as an anti-oxidant and anti-inflammatory agent for cardiovascular protection

Our review aims to examine the cellular and molecular mechanisms of cardiovascular protection of green tea polyphenols, particularly epigallocatechin gallate (EGCG), which focuses on the anti-oxidative and anti-inflammatory effects. EGCG is the major and the most active component in green tea. Studies have shown that EGCG protects cellular damage by inhibiting DNA damage and oxidation of LDL. One of the protective properties of EGCG is its ability to scavenge free radicals. EGCG can also reduce the inflammatory response associated with local tissue injuries such as the hepatocellular necrosis in acute liver injury induced by carbon tetrachloride. The protective effect of EGCG is due to its ability to decrease lipid peroxidation, oxidative stress and the production of nitric oxide (NO) radicals by inhibiting the expression of iNOS. EGCG also ameliorates the overproduction of pro-inflammatory cytokines and mediators, reduces the activity of NF-kappaB and AP-1 and the subsequent formation of peroxynitrite with NO and reactive oxygen species. Thus, EGCG effectively mitigates cellular damage by lowering the inflammatory reaction and reducing the lipid peroxidation and NO generated radicals leading to the oxidative stress. Green tea is proposed to be a dietary supplement in the prevention of cardiovascular diseases in which oxidative stress and proinflammation are the principal causes.     

Neuroprotective effects of 17beta-estradiol and nonfeminizing estrogens against H2O2 toxicity in human neuroblastoma SK-N-SH cells

Neuroprotective effects of estrogens have been shown in various in vitro and in vivo models, but the mechanisms underlying protection by estrogen are not clear. Mounting evidence suggests antioxidant effects contribute to the neuroprotective effects of estrogens. In the present study, we assessed the protective effects of estrogens against H2O2-induced toxicity in human neuroblastoma cells and the potential mechanisms involved in this protection. We demonstrate that 17beta-estradiol (17beta-E2) increases cell survival against H2O2 toxicity in human neuroblastoma cells. 17beta-E2 effectively reduced lipid peroxidation induced by 5-min H2O2 exposure. Furthermore, 17beta-E2 exerts the protective effects by maintaining intracellular Ca2+ homeostasis, attenuating ATP depletion, ablating mitochondrial calcium overloading, and preserving mitochondrial membrane potential. Two nonfeminizing estrogens, 17alpha- and ent-estradiol, were as effective as 17beta-E2 in increasing cell survival, alleviating lipid peroxidation, preserving mitochondrial function, and maintaining intracellular glutathione levels and Ca2+ homeostasis against H2O2 insult. Moreover, the estrogen receptor antagonist fulvestrant (ICI 182,780) did not block effects of 17beta-E2, but increased cell survival and blunted intracellular Ca2+ increases. However, these estrogens failed to reduce cytosolic reactive oxygen species, even at concentrations as high as 10 microM. In conclusion, estrogens exert protective effects against oxidative stress by inhibiting lipid peroxidation and subsequently preserving Ca2+ homeostasis, mitochondrial membrane potential, and ATP levels.     

Protective effects of breviscapine on ischemic vascular dementia in rats

Breviscapine, a traditional Chinese medicine, is extensively used in clinic to treat cardiovascular diseases and cerebrovascular injury. In this study, we demonstrated the effects of breviscapine on vascular dementia (VD) rats, which were mimicked by permanent occlusion of bilateral common carotid arteries. Breviscapine (2 mg/kg for 14 d) improved the performance of learning and memory of VD rats in Morris water maze, decreased the level of lipid peroxidation and free radicals, and attenuated the pathological alterations, such as nuclear shrink, cellular edema and irregular arrangement of pyramidal layer in the hippocampal CA(1) area. In vitro experiment, breviscapine (50 microg/l) protected cortical neuron from injury and decreased intracellular calcium overloading induced by H2O2 (10 mM). The results suggest that breviscapine has therapeutic effect on cerebral ischemia and vascular dementia.     

Effects of rutin and harmaline on rat reflux oesophagitis

1. This study was aimed at evaluating the effect of rutin and harmaline (1-methyl-7-methoxy-3,4-dihydro-beta-carboline) on the development of the surgically induced reflux oesophagitis, on gastric secretion, lipid peroxidation, polymorphonucleocytes (PMNs) accumulation, superoxide and hydroxyl radical production in PMNs, cytokine [interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha)] production in blood and [Ca2+]i mobilization in PMNs. 2. Rutin and harmaline significantly prevented the development of reflux oesophagitis and gastric secretion. Treatments of oesophagitis rats with rutin and harmaline inhibited lipid peroxidation, and myeloperoxidase (MPO) in the oesophagus in comparison with untreated rats. 3. Superoxide anion and hydrogen peroxide production in 1 microm formylmethionylleucylphenylalanine (fMLP)- or 0.1 microg ml-1N-phorbol 12-myristate 13-acetate (PMA)-activated PMNs was inhibited by rutin and harmaline in a dose-dependent fashion. Rutin and harmaline effectively scavenged the hydroxyl radical and hydrogen peroxide. Treatments of oesophagitis rats with rutin and harmaline inhibited IL-1beta production in the oesophagus in comparison with untreated rats, but TNF-alpha production was not affected by rutin and harmaline. The fMLP-induced elevation of [Ca2+]i was inhibited by rutin. 4. The results of this study suggest that rutin and harmaline may have beneficial protective effects against reflux oesophagitis by the inhibition of gastric acid secretion, oxidative stress, inflammatory cytokine production (i.e. IL-1beta), and intracellular calcium mobilization in PMNs in rats.     

Melatonin ameliorates bisphenol A-induced biochemical toxicity in testicular mitochondria of mouse

Bisphenol A (BPA) is a monomer of polycarbonate plastic used to manufacture plastic baby bottles and lining of food cans. It has endocrine-disrupting potential and exerts both toxic and estrogenic effects on mammalian cells. We studied BPA-induced perturbation of mitochondrial marker enzymes in testes of Swiss albino mice and its amelioration by melatonin. Mice exposed to standardized dose of BPA (10 mg/kg body weight) orally for 14 days showed decrease in activities of marker mitochondrial enzymes such as succinate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase, monoamine oxidase and NADH dehydrogenase. Besides, it also affected activities of antioxidant enzymes such as superoxide dismutase, glutathione reductase and glutathione peroxidase. BPA also caused lipid peroxidation (LPO) and decrease in reduced glutathione (GSH) content of mitochondria. Concomitant melatonin administration (10 mg/kg body weight; intraperitoneally for 14 days) lowered mitochondrial lipid peroxidation. It also restored the activity of mitochondrial marker enzymes and ameliorated decreased enzymatic and non-enzymatic antioxidants of mitochondria. These results demonstrate that melatonin has a potential role in ameliorating BPA-induced mitochondrial toxicity and the protection is due to its antioxidant property or by the direct free radical scavenging activity.     

Biotransformation and cytotoxicity of a brominated flame retardant, tetrabromobisphenol A, and its analogues in rat hepatocytes

The metabolism and cytotoxic effects of tetrabromobisphenol A (TBBPA), a phenolic flame retardant, and its analogues were studied in freshly isolated rat hepatocytes and isolated hepatic mitochondria, respectively. The exposure of hepatocytes to TBBPA caused not only concentration (0.25-1.0 mM)- and time- (0-3 h) dependent cell death accompanied by the loss of cellular ATP, adenine nucleotide pools, reduced glutathione, and protein thiols, but also the accumulation of oxidized glutathione and malondialdehyde, indicating lipid peroxidation. TBBPA at a weakly toxic level (0.25 mM) was metabolized to monoglucuronide and monosulfate conjugates: the amounts of glucuronide rather than sulfate conjugate predominantly increased, accompanied by a loss of the parent compound, with time. In comparative effects based on cell viability, mitochondrial membrane potential and some toxic parameters, bisphenol A (BPA) was less toxic than TBBPA and tetrachlorobisphenol A (TCBPA), which are not significant differences in these parameters. In mitochondria isolated from rat liver, TBBPA and TCBPA caused an increase in the rate of State 4 oxygen consumption in the presence of succinate, indicating an uncoupling effect and a decrease in the rate of State 3 oxygen consumption in a concentration-dependent manner (5-25 microM). Taken collectively, our results indicate that (i) mitochondria are target organelles for TBBPA, which elicits cytotoxicity through mitochondrial dysfunction related to oxidative phosphorylation at an early stage and subsequently lipid peroxidation at a later stage; and (ii) the toxicity of TBBPA and TCBPA is greater than that of BPA, suggesting the participation of halogen atoms such as bromine and chlorine in the toxicity.     

The inhibition of lipid peroxidation by cinnarizine. Possible implications to its therapeutic and side-effects

Cinnarizine has antivasoconstrictor properties and improves red-cell deformability. Its major side-effects are the induction of extrapyramidal reactions. It is a calcium antagonist, but it was suggested that its effects may depend on other mechanisms, namely on antiperoxidant properties. We have studied these properties in different biological systems, intact red-cells included. The occurrence of lipid peroxidation was determined by the formation of 2-thiobarbituric acid reactive products. Cinnarizine was found to inhibit spontaneous lipid peroxidation in rat liver homogenates, copper-induced lipid peroxidation in human plasma and copper-induced and hydrogen peroxide-induced lipid peroxidation in human red-cells. In red-cells, the inhibition of lipid peroxidation is accompanied by the inhibition of hemolysis. Copper-induced red-cell lipid peroxidation is 85% inhibited by as little as 5 microM cinnarizine. The antioxidant activity of cinnarizine may contribute to explain some of the effects of this drug.     

Nitroaryl-1,4-dihydropyridines as antioxidants against rat liver microsomes oxidation induced by iron/ascorbate, Nitrofurantoin and naphthalene

1,4-Dihydropyridines (DHPs) used in the treatment of cardiovascular diseases, are calcium channel antagonists and also antioxidant agents. These drugs are metabolized through cytochrome P₄₅₀ oxidative system, majority localized in the hepatic endoplasmic reticulum. Several lipophilic drugs generate oxidative stress to be metabolized by this cellular system. Thus, DHP antioxidant properties may prevent the oxidative stress associated with hepatic biotransformation of drugs.

In this work, we tested the antioxidant capacity of several synthetic nitro-phenyl-DHPs. These compounds (I–IV) inhibited the microsomal lipid peroxidation, UDPGT oxidative activation and microsomal thiols oxidation; all phenomena induced by Fe³⁺/ascorbate, a generator system of oxygen free radicals. As the same manner, these compounds inhibited the oxygen consumption induced by Cu²⁺/ascorbate in the absence of microsomes. Furthermore, compound III (2,6-dimethyl-4-(4-nitrophenyl)-1,4-dihydropyridin-3,5-ethyl-dicarboxylate) and compound V (N-ethyl-2,6-dimethyl-4-(4-nitrophenyl)-1,4-dihydropyridin-3,5-methyl-dicarboxylate) inhibited the microsomal lipid peroxidation induced by Nitrofurantoin and naphthalene in the presence of NADPH. Oxidative stress induced on endoplasmic reticulum may alter the biotransformation of drugs, so, modifying their plasmatic concentrations and therapeutic effects. When drugs which are activated by biotransformation are administered together with antioxidant drugs, such as DHPs, oxidative stress induced in situ may be prevented.     

The cytotoxic and mutagenic properties of cholesterol oxidation products

The oxidation of cholesterol proceeds as part of the lipid peroxidation process in membranes. Several oxidation products characteristic of a free-radical mechanism are formed and some can serve as indices of the nature and extent of cholesterol oxidation and of lipid peroxidation in general. Among the most typical oxidation products of lipid peroxide-dependent propagation reactions are the enantiomeric 5,6-epoxides and 7-ketocholestanol. Small amounts of these compounds may persist in tissues experiencing lipid peroxidation at a low but steady flux of free-radical reactions. Supporting evidence includes the routine detection of small quantities of cholesterol epoxides in tissues of normal animals, and the increase of these epoxides under conditions of oxidant stress or antioxidant deficiency. Conversion of cholesterol epoxides to cholestane triol is expected in cells possessing cholesterol epoxide hydrolase. All of these oxidation products possess remarkable cytotoxicity (at least part of which may be due to effects on the cell membrane) causing an increase in intracellular calcium. The cholesterol epoxides are also weakly mutagenic, although the mechanism for this mutagenicity remains to be clarified. In contrast, the other lipid epoxides normally encountered in tissues (chiefly fatty acid epoxides) are not mutagenic, and are much less toxic than the oxysterols described. The cytotoxicity of several oxysterols may be due to a number of mechanisms. That only the epoxides are mutagenic suggests that genotoxicity is a function of their electrophilic reactivity. This is not consistently apparent with the other compounds examined.     

Effects of gentianine on the production of pro-inflammatory cytokines in male Sprague-Dawley rats treated with lipopolysaccharide (LPS)

This study was undertaken to elucidate the mechanism of anti-inflammatory action of gentianine, a constituent of Gentiana Macrophylla. The effects of gentianine on lipopolysacharide (LPS)-induced production of pro-inflammatory cytokines were investigated in male Sprague-Dawley rats. For the first time, we found that oral administration of gentianine (10-100 mg/kg) suppressed the increases in tumor necrosis factor-alpha (TNF-alpha) (ED(50), 37.7 mg/kg) and interleukin (IL)-6 (ED(50), 38.5 mg/kg) in the sera from the rats challenged with bacterial LPS (100 microg/kg; i.p.). However, LPS induced production of other interleukins, such as IL-alpha, was not significantly altered by gentianine. These results suggest that the potential anti-inflammatory action of gentianine might be at least partly based on the suppressed production of TNF-alpha and IL-6.     

Is hyperthermia the triggering factor for hepatotoxicity induced by 3,4-methylenedioxymethamphetamine (ecstasy)? An in vitro study using freshly isolated mouse hepatocytes

The consumption of 3,4-methylenedioxymethamphetamine (ecstasy; MDMA) may cause hepatocellular damage in humans, a toxic effect that has been increasing in frequency in the last few years, although the underlying mechanisms are still unknown. The metabolism of MDMA involves the production of reactive metabolites which form adducts with intracellular nucleophilic sites, as is the case with glutathione (GSH). Also, MDMA administration elicits hyperthermia, a potentially deleterious condition that may aggravate its direct toxic effects. Thus, the objective of this study was to evaluate the extent of MDMA-induced depletion of GSH, induction of lipid peroxidation and loss of cell viability in freshly isolated mouse hepatocytes under normothermic conditions (37 degrees C) and to compare the results with the effects obtained under hyperthermic conditions (41 degrees C). By itself, hyperthermia was an important cause of cell toxicity. A rise in incubation temperature from 37 degrees C to 41 degrees C caused oxidative stress in freshly isolated mouse hepatocytes, reflected as a time-dependent induction of lipid peroxidation and consequent loss of cell viability (up to 40-45%), although the variations in GSH and GSSG levels were similar to those under normothermic conditions. MDMA (100, 200, 400, 800 and 1600 microM) induced a concentration- and time-dependent GSH depletion at 37 degrees C but had a negligible effect on lipid peroxidation and cell viability at this temperature. It is particularly noteworthy that hyperthermia (41 degrees C) potentiated MDMA-induced depletion of GSH, production of lipid peroxidation and loss of cell viability (up to 90-100%). It is therefore concluded that hyperthermia potentiates MDMA-induced toxicity in freshly isolated mouse hepatocytes.     

Toxic Effects of Free and DNA-linked Daunorubicin on Isolated Rat Cardiac Myocytes

Abstract: Isolated cardiac myocytes from adult rats were used as a model to study the cardiotoxicity of free and DNA-linked daunorubicin. The toxic effects on the myocytes were evaluated by studying morphological changes, trypan blue exclusion and cell membrane permeability to NADH, as determined by LDH-activity. At a concentration of 100 μM daunorubicin caused an increased plasma membrane permeability within 30 min. Using light microscopy, the myocytic injury induced by daunorubicin could be distinguished from that induced by anoxia or elevated pH. In contrast to the effect of the free drug, no toxic effects could be demonstrated after incubation with DNA-linked daunorubicin (100 μM) for 5 hours. The higher toxicity of the free drug was related to a much higher intracellular accumulation of daunorubicin. No fluorescent metabolites of daunorubicin could be detected in the myocardial cells. Daunorubicin did not induce lipid peroxidation, as judged by the absence of malondialdehyde production and evolution of ethane. It is concluded that daunorubicin exerts toxic effects on rat cardiac myocytes by mechanisms that do not involve lipid peroxidation. Isolated cardiac cells from adult rats seem to be a useful model for the further study of such mehanisms.     

Experimental exposure to wood-smoke particles in healthy humans: effects on markers of inflammation, coagulation, and lipid peroxidation

Particulate air pollution is known to increase cardiovascular morbidity and mortality. Proposed mechanisms underlying this increase include effects on inflammation, coagulation factors, and oxidative stress, which could increase the risk of coronary events and atherosclerosis. The aim of this study was to examine whether short-term exposure to wood smoke affects markers of inflammation, blood hemostasis, and lipid peroxidation in healthy humans. Thirteen subjects were exposed to wood smoke and clean air in a chamber during two 4-h sessions, 1 wk apart. The mass concentrations of fine particles at wood smoke exposure were 240-280 mug/m3, and number concentrations were 95,000-180,000/cm3. About half of the particles were ultrafine (< 100 nm). Blood and urine samples were taken before and after the experiment. Exposure to wood smoke increased the levels of serum amyloid A, a cardiovascular risk factor, as well as factor VIII in plasma and the factor VIII/von Willebrand factor ratio, indicating a slight effect on the balance of coagulation factors. Moreover, there was an increased urinary excretion of free 8-iso-prostaglandin2alpha, a major F2-isoprostane, though this was based on nine subjects only, indicating a temporary increase in free radical-mediated lipid peroxidation. Thus, wood-smoke particles at levels that can be found in smoky indoor environments seem to affect inflammation, coagulation, and possibly lipid peroxidation. These factors may be involved in the mechanisms whereby particulate air pollution affects cardiovascular morbidity and mortality. The exposure setup could be used to establish which particle characteristics are critical for the effects.     

Chronic exposure of bisphenol A impairs carbohydrate and lipid metabolism by altering corresponding enzymatic and metabolic pathways

Bisphenol-A (BPA), a widespread endocrine-disrupting chemical, has been recognized as a risk factor for metabolic disorders. BPA is considered to be involved in the impairment of carbohydrate and lipid metabolism but the underlying mechanisms still need to be elucidated. Present study was aimed to investigate the impact of BPA exposure on enzymatic and metabolic pathways that are responsible to regulate the carbohydrate and lipid metabolism. Experimental rats were exposed to different doses of BPA (50, 500, 2500 and 5000 μg/kg/day orally) dissolved in 1.5% dimethyl sulfoxide for a period of 3 months. Serum level of key metabolic enzymes (α-amylase, α-glucosidase, hexokinase, glucose-6-phosphatase and HMG-CoA-reductase) was measured by ELISA method. BPA-exposure suppressed the mRNA expression of gene encoding insulin resulting in poor insulin production. While hexokinase, acetyl-CoA carboxylase and squalene epoxide were up-regulated upon BPA exposure that justified the increased lipid profile. Moreover, BPA exposure showed considerably decreased glucose uptake through insulin signaling via Akt/GLUT4 pathways. There was a significant (p < 0.001) reduction in tissue level of glucose transporters. BPA significantly (p < 0.001) decreased the serum levels of oxidative stress biomarkers (GSH, CAT, and SOD). Serum levels of leptin, TNF-α, and IL-6 were rapidly increased upon exposure to BPA (p < 0.001). It was clearly evident from this study that BPA disturbed the carbohydrate and lipid metabolism after chronic exposure. It also accelerated the inflammatory processes by increasing the oxidative stress which ultimately lead towards the insulin resistance and impaired carbohydrate and lipid metabolism.     

Proangiogenic effects of environmentally relevant levels of bisphenol A in human primary endothelial cells

Bisphenol A (BPA) is widely used in the manufacturing of consumer products such as plastic food containers and food cans. Experimental studies suggest a relationship between exposure to BPA and changes in metabolic processes and reproductive organs. Also, epidemiological studies report an association between elevated exposure to BPA and cardiovascular disease and diabetes. Although alterations in the vascular endothelium are implicated in pathological conditions associated with BPA, little is known about the effects of BPA in the human endothelium. This study aimed to investigate the effects of 0.1 nM–1 μM of BPA on selected biomarkers of endothelial dysfunction, inflammation, and angiogenesis in human umbilical vein endothelial cells (HUVEC). The mRNA expression of biomarkers was assayed using qRT-PCR, and the production of nitric oxide and reactive oxygen species was measured using the H₂DCFDA and the DAF-FM assays. The effect of BPA on phosphorylated eNOS was examined using Western blot and immunofluorescence, and the endothelial tube formation assay was used to investigate in vitro angiogenesis. BPA (≤1 μM) increased the mRNA expression of the proangiogenic genes VEGFR-2, VEGF-A, eNOS, and Cx43 and increased the production of nitric oxide in HUVEC. Furthermore, BPA increased the expression of phosphorylated eNOS and endothelial tube formation in HUVEC. These studies demonstrate that environmentally relevant levels of BPA have direct proangiogenic effects on human primary endothelial cells in vitro suggesting that the human endothelium may be an important target for BPA.     

Stimulative effects of chelating agents, 2,2'-bipyridine and 1,10-phenanthroline, on lipid peroxidation in rat liver microsomes.

Well known lipid peroxidation inhibitors, 1,10-phenanthroline and 2,2'-bipyridine, stimulated microsomal NADPH- and ascorbic acid-dependent lipid peroxidation when low concentrations of these chelating agents were added to incubation mixture. The stimulatory effects of the chelating agents on lipid peroxidation were enhanced when ferrous ion was added together with the chelating agents to the mixture at a molar ratio of 1:1. Ethylenediaminetetraacetic acid (EDTA) had no stimulatory effect on lipid peroxidation. Ferrous ion-EDTA complex increased lipid peroxidation by only 20-30%, which was lower than that obtained by addition of the same concentration of ferrous ion alone. On the other hand, manganese and calcium ions, which are also inhibitors of lipid peroxidation, had no ability to stimulate lipid peroxidation even in the presence of extra ferrous ions. Changes in the lipid peroxidation by chelating agents affected the apparent activity of ethylmorphine N-demethylation.     

BPA‐toxicity via superoxide anion overload and a deficit in β‐catenin signaling in human bone mesenchymal stem cells

Bisphenol A (BPA), used in the manufacture of products based on polycarbonate plastics and epoxy resins, is well known as an endocrine‐disrupting monomer. In the current study, BPA increased cytotoxicity in hBMSCs in a dose‐ and time‐dependent manner, concomitantly with increased lipid peroxidation. Increased cell death in BPA‐treated cells was markedly blocked by pretreatment with the superoxide dismutase mimetic MnTBAP and MnTMPyP, but not by catalase, glutathione, the glutathione peroxidase mimetic ebselen, the NOS inhibitor NAME, or the xanthine oxidase inhibitor allopurinol. Furthermore, the decline in nuclear β‐catenin and cyclin D1 levels in hBMSCs exposed to BPA was reversed by MnTBAP treatment. Finally, treatment of hBMSCs with the GSK3β inhibitor LiCl₂ increased nuclear β‐catenin levels and significantly attenuated cytotoxicity compared with BPA treatment. Our current results in hBMSCs exposed to BPA suggest that BPA causes a disturbance in β‐catenin signaling via a superoxide anion overload. © 2016 The Authors Environmental Toxicology Published by Wiley Periodicals, Inc. Environ Toxicol 32: 344–352, 2017.