Dibutyl Phthalate (DBP)-Induced Apoptosis and Neurotoxicity are Mediated via the Aryl Hydrocarbon Receptor (AhR) but not by Estrogen Receptor Alpha (ERα), Estrogen Receptor Beta (ERβ), or Peroxisome Proliferator-Activated Receptor Gamma (PPARγ) in Mouse Cortical Neurons

MEHP/ethanol co-exposure favors the death of steatotic hepatocytes, possibly through CYP4A and ADH involvement

Liver steatosis has been associated with various etiological factors (obesity, alcohol, environmental contaminants). How those factors work together to induce steatosis progression is still scarcely evaluated. Here, we tested whether phthalates could potentiate death of steatotic hepatocytes when combined with ethanol. Pre-steatotic WIF-B9 hepatocytes were co-exposed to mono (2-ethylhexyl) (MEHP, 500 nM; main metabolite of di (2-ethylhexyl) phthalate or DEHP) and ethanol (5 mM) for 5 days. An increased apoptotic death was detected, involving a DNA damage response. Using 4-Methypyrazole to inhibit ethanol metabolism, and CH-223191 to antagonize the AhR receptor, we found that an AhR-dependent increase in alcohol dehydrogenase (ADH) activity was essential for cell death upon MEHP/ethanol co-exposure. Toxicity was also prevented by HET0016 to inhibit the cytochrome P450 4A (CYP4A). Using the antioxidant thiourea, a role for oxidative stress was uncovered, notably triggering DNA damage. Finally, co-exposing the in vivo steatosis model of high fat diet (HFD)-zebrafish larvae to DEHP (2.56 nM)/ethanol (43 mM), induced the pathological progression of liver steatosis alongside an increased Cyp4t8 (human CYP4A homolog) mRNA expression. Altogether, these results further emphasized the deleterious impact of co-exposures to ethanol/environmental pollutant towards steatosis pathological progression, and unraveled a key role for ADH and CYP4A in such effects.

Activation of the RhoA/ROCK pathway contributes to renal fibrosis in offspring rats induced by maternal exposure to di-n-butyl phthalate

Maternal exposure to di-n-butyl phthalate (DBP) can cause renal fibrosis in adult offspring rats. However, its underlying mechanisms have not yet been fully understood. In this study, we investigated whether the RhoA/ROCK pathway plays an important role in offspring renal fibrosis induced by maternal exposure to DBP. Our results showed that maternal exposure to DBP (850 mg/kg/day orally feeding during gestational days 14-18) activated the RhoA/ROCK pathway and induced epithelial-mesenchymal transition (EMT) in kidneys of offspring rats. Compared with the control group treated with normal saline, EMT in the kidneys of offspring rats undergoing 8 weeks of ROCK inhibitor Y-27632 treatment (at a dose of 30 mg/kg) was significantly inhibited, the degree of renal fibrosis was significantly reduced, and the renal function was significantly improved. DBP (10 μmol/L) activated the RhoA/ROCK pathway and induced EMT in NRK-52E cells in vitro. Both 5 μM and 10 μM Y-27632, a ROCK inhibitor, significantly reduced the EMT of NRK-52E cells. Taken together, our findings suggest that the RhoA/ROCK pathway plays an important role in the pathogenesis of renal fibrosis in offspring rats induced by maternal exposure to DBP via promoting EMT of renal tubular epithelial cells.

Evaluation of the protective effects of quercetin and gallic acid against oxidative toxicity in rat's kidney and HEK-293 cells

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Gallic acid has better antioxidant protective effect than quercetin in vivo.

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Quercetin has better antioxidant protective effect than gallic acid in vitro.

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The antioxidant effect of quercetin was at the least concentration tested.

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The antioxidant effect of gallic acid was at a higher concentrated tested.

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The in vivo dosage for the antioxidant effects of quercetin in the kidney is low.

Quercetin and gallic acid are phytochemicals with interesting pharmacological properties. We herein investigated the protective effect of quercetin (QUE) in comparison with gallic acid (GAL) against exogenously-induced oxidative damage in rats’ kidney and human embryonic kidney (HEK-293) cell lines. Adult Wistar rats were treated with QUE and GAL (50 mg/kg) separately or in combination with di-n-butylphthalate (DnBP) for 14 days; and HEK-293 cells were treated with different concentrations of GAL (25−294 μM) or QUE (2−17 μM or 28−165.43 μM) singly or in combination with H₂O₂ (200 μM). After treatment, the kidney and cell extracts were processed for biochemical analysis and histopathology. We found that GAL but not QUE prevented DnBP-induced increase in lipid peroxidation (2.603 ± 0.25 vs. 3.65 ± 0.21 μmol/mL). Treatment with QUE but not GAL was associated with increased plasma creatinine (729.09 ± 55.68 vs. 344.25 ± 50.78 μmol/l) and tissue malondialdehyde (3.72 ± 0.62 vs. 1.67 ± 0.47 μmol/mL) concentrations, along with histo-pathological changes such as glomerular and tubular degenerations. However, QUE exhibited wider therapeutic concentration ranges than GAL at which it inhibits lipid peroxidation in HEK-293 cells, and was found to inhibit H₂O₂-induced lipid peroxidation even at the lowest concentration (2 μM) that was tested (0.607 ± 0.074 vs. 0.927 ± 0.106 μmol/l). These suggest that the in vivo dosages required for the antioxidant protective effects of QUE in renal tissues are low.

Acute exposure to bis(2-ethylhexyl)phthalate disrupts calcium homeostasis, energy metabolism and induces oxidative stress in the testis of Danio rerio

Bis(2-ethylhexyl)phthalate (BEHP) negatively affects testicular functions in different animal species, disturbing reproductive physiology and male fertility. The present study investigated the in vitro acute effect of BEHP on the mechanism of action of ionic calcium (Ca²⁺) homeostasis and energy metabolism. In addition, the effect of BEHP on oxidative stress was studied in vitro and in vivo in the testis of Danio rerio (D. rerio). Testes were treated in vitro for 30 min with 1 μM BEHP for ⁴⁵Ca²⁺ influx measurements. Testes were also incubated with 1 μM BEHP for 1 h (in vitro) or 12 h (in vivo) for the measurements of lactate content, ¹⁴C-deoxy-d-glucose uptake, lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT) activity, total reactive oxygen species (ROS) production and lipid peroxidation. In addition, the effect of BEHP (1 μM) on GGT, glutamic oxaloacetic transferase (GOT) and glutamic pyruvic transferase (GPT) activity in the liver was evaluated after in vivo treatment for 12 h. BEHP disturbs the Ca²⁺ balance in the testis when given acutely in vitro. BEHP stimulated Ca²⁺ influx occurs through L-type voltage-dependent Ca²⁺ channels (L-VDCC), transitory receptor potential vaniloid (TRPV1) channels, reverse-mode Na⁺/Ca²⁺ exchanger (NCX) activation and inhibition of sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA). BEHP affected energy metabolism in the testis by decreasing the lactate content and LDH activity. In vitro and in vivo acute effects of BEHP promoted oxidative stress by increasing ROS production, lipid peroxidation and GGT activity in the testis. Additionally, BEHP caused liver damage by increasing GPT activity.

Disruption of androgen signaling during puberty affects Notch pathway in rat seminiferous epithelium

BACKGROUND

Onset of spermatogenesis at puberty is critically dependent on the activity of hypothalamic-pituitary-gonadal axis and testosterone production by Leydig cells. The aim of this study was to examine whether activation of Notch receptors and expression of Notch ligands and effector genes in rat seminiferous epithelium are controlled by androgen signaling during puberty.

METHODS

Peripubertal (5-week-old) Wistar rats received injections of flutamide (50 mg/kg bw) daily for 7 days to reduce androgen receptor (AR) signaling or a single injection of ethanedimethane sulphonate (EDS; 75 mg/kg bw) to reduce testosterone production. Gene and protein expressions were analyzed by real-time RT-PCR and western blotting, respectively, protein distribution by immunohistochemistry, and steroid hormone concentrations by enzyme-linked immunosorbent assay. Statistical analyses were performed using one-way ANOVA followed by Tukey's post hoc test or by Kruskal-Wallis test, followed by Dunn's test.

RESULTS

In both experimental models changes of a similar nature in the expression of Notch pathway components were found. Androgen deprivation caused the reduction of mRNA and protein expression of DLL4 ligand, activated forms of Notch1 and Notch2 receptors and HES1 and HEY1 effector genes (p < 0.05, p < 0.01, p < 0.001). In contrast, DLL1, JAG1 and HES5 expressions increased in seminiferous epithelium of both flutamide and EDS-treated rats (p < 0.05, p < 0.01, p < 0.001).

CONCLUSIONS

Androgens and androgen receptor signaling may be considered as factors regulating Notch pathway activity and the expression of Hes and Hey genes in rat seminiferous epithelium during pubertal development. Further studies should focus on functional significance of androgen-Notch signaling cross-talk in the initiation and maintenance of spermatogenesis.

Bisphenol F-Induced Neurotoxicity toward Zebrafish Embryos

In this study, the influence of bisphenol F (BPF) toward central nervous system (CNS) was assessed using zebrafish embryos. We found that BPF could induce significant neurotoxicity toward zebrafish embryos, including inhibited locomotion, reduced moving distance, and CNS cell apoptosis at an effective concentration of 0.0005 mg/L. Immunofluorescence assay showed that both microglia and astrocyte in zebrafish brain were significantly activated by BPF, indicating the existence of neuroinflammatory response. Peripheral motor neuron development was significantly inhibited by BPF at 72 hpf. RNA-seq data indicated that neuronal developmental processes and cell apoptosis pathways were significantly affected by BPF exposure, which was consistent with the phenotypic results. Chip-seq assay implied that the transcriptional changes were not mediated by ERα. Additionally, no significant change was found in neurotransmitter levels (5-hydroxytryptamine, dopamine, and acetylcholine) or acetylcholinesterase (Ache) enzyme activity after BPF exposure, indicating that BPF may not affect neurotransmission. In conclusion, BPF could lead to abnormal neural outcomes during zebrafish early life stage through inducing neuroinflammation and CNS cell apoptosis even at environmentally relevant concentration.

Elastin-derived peptide VGVAPG affects the proliferation of mouse cortical astrocytes with the involvement of aryl hydrocarbon receptor (Ahr), peroxisome proliferator-activated receptor gamma (Pparγ), and elastin-binding protein (EBP)

During aging and ischemic and hemorrhagic stroke, elastin molecules are degraded and elastin-derived peptides are released into the brain microenvironment. Val-Gly-Val-Ala-Pro-Gly (VGVAPG) is a repeating hexapeptide in the elastin molecule. It is well documented that the peptide sequence binds with high affinity to elastin-binding protein (EBP) located on the cell surface, thereby transducing a molecular signal into the cell. The aim of our study was to investigate whether EBP, aryl hydrocarbon receptor (Ahr), and peroxisome proliferator-activated receptor gamma (Pparγ) are involved in VGVAPG-stimulated proliferation. Primary astrocytes were maintained in DMEM/F12 medium without phenol red, supplemented with 10 or 1% charcoal/dextran-treated fetal bovine serum (FBS). The cells were exposed to increasing concentrations of VGVAPG peptide, and resazurin reduction was measured. In addition, Glb1, Pparγ, and Ahr genes were silenced. After 48 h of exposure to 10 nM and 1 µM of VGVAPG peptide, the level of estradiol (E₂) and the expression of Ki67 and S100B proteins were measured. The results showed that at a wide range of concentrations, VGVAPG peptide increased the metabolism of astrocytes depending on the concentration of FBS. After silencing of Glb1, Pparγ, and Ahr genes, VGVAPG peptide did not affect the cell metabolism which suggests the involvement of all the mentioned receptors in its mechanism of action. Interestingly, in the low-FBS medium, the silencing of Glb1 gene did not result in complete inhibition of VGVAPG-stimulated proliferation. On the other hand, in the medium with 10% FBS VGVAPG increased Ki67 expression after Pparγ silencing, whereas in the medium with 1% FBS VGVAPG decreased Ki67 expression. Following the application of Ahr siRNA, VGVAPG peptide decreased the production of E₂ and increased the expression of Ki67 and S100B proteins.

Di-butyl phthalate (DBP) induces craniofacial defects during embryonic development in zebrafish

Di-butyl phthalate (DBP) is commonly added to make plastics softer and more pliable and is found in a variety of consumer and industrial products. Alarmingly high levels of DBP have been detected in water and sediment as DBP leaches from products. These levels are concerning and have led the Environmental Protection Agency to label DBP as a priority environmental pollutant and the European Commission to label DBP as a priority substance. Given the ubiquitous presence of DBP globally and continuous exposure to DBP, studies on the developmental toxicity of DBP are needed. The endocrine disrupting effects of DBP are well documented, but developmental toxicity of DBP during critical developmental time windows is understudied. Here, we investigate the developmental effects of DBP exposure during early development. We find defects in craniofacial development including a decrease in overall cranial size in DBP treated embryos, but the intraocular distance was increased compared to controls. Further investigation of jawbone development demonstrated loss of and disorganization of cartilage development. Defects in vascular innervation and neuronal patterning were also noted. Here we conclude that exposure to DBP during crucial time windows of embryonic development is toxic to craniofacial development.

Dibutyl phthalate exposure disrupts the progression of meiotic prophase I by interfering with homologous recombination in fetal mouse oocytes

Dibutyl phthalate (DBP), one of the most widely used plasticizers, is a known environmental endocrine disruptor that impairs male and female fertility. In this study, oral administration of DBP was given to pregnant mice on 14.5 days post coitus (dpc) for 3 days; and additionally, DBP was added into the culture of 14.5 dpc fetal ovaries for 3 days. DBP exposure during gestation disturbed the progression of meiotic prophase I of mouse oocytes, specifically from the zygotene to pachytene stages. Meanwhile, the DBP-exposed pachytene oocytes showed increased homologous recombination sites and unrepaired DNA damage. Furthermore, DBP caused DNA damage by increasing oxidative stress, decreased the expression of multiple critical meiotic regulators, and consequently induced oocyte apoptosis. Moreover, the effect of DBP on meiosis I prophase involved estrogen receptors α and β. Collectively, these results demonstrated a set of meiotic defects in DBP-exposed fetal oocytes. As aberrations in homologous recombination can result in aneuploid gametes and embryos, this study provides new support for the deleterious effects of phthalates.

Di-n-butyl phthalate, butylbenzyl phthalate, and their metabolites exhibit different apoptotic potential in human peripheral blood mononuclear cells

Human peripheral blood mononuclear cells (PBMCs) are one of the main cell models used in studies concerning the exposure of humans (in vitro) to various chemical substances. Changes in PBMCs may reflect the general reaction of the organism regarding the effect of xenobiotics. The aim of this work was to evaluate the effect of di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP) and their metabolites: mono-n-butylphthalate (MBP), mono-benzylphthalate (MBzP) upon the induction of apoptosis in human peripheral blood mononuclear cells in vitro. PBMCs were incubated with the studied compounds at concentrations from 1 to 100 μg/mL for 12 h and/or 24 h. In order to clarify the mechanism of phthalates-induced programmed cell death, the changes in the calcium ions (Ca²⁺) level, alterations in the transmembrane mitochondrial potential (ΔѰm) and caspase-8, -9, -3 activity as well as externalization of phosphatidylserine have been determined. An increased Ca²⁺ level and a reduction of the ΔѰm were observed in PBMCs incubated with all of the studied compounds, and particularly with DBP and BBP. Phthalates caused an increase of caspases activity. The most pronounced increase was observed for caspase -9. The most pronounced pro-apoptotic changes were caused by DBP followed by BBP and then by their metabolites.

Bioactive Compounds in the Ethanol Extract of Marine Sponge Stylissa carteri Demonstrates Potential Anti-Cancer Activity in Breast Cancer Cells

Objective:

Despite advanced treatment options available, drug resistance develops in breast cancer (BC) patients requiring novel effective drugs. Stylissa carteri, a marine sponge predominantly living in Indonesia territories, has not been extensively studied as anti-cancer. Therefore, this study targeted to assess the anti-tumor activity of the ethanol extract of S. carteri in BC cells.

Methods:

S. carteri was collected from Pramuka Island, at Kepulauan Seribu National Park, Jakarta, Indonesia and extracted using ethanol. Different BC cells including MDA MB 231, MDA MB 468, SKBR3, HCC-1954 and MCF-7 cells were treated with this extract for cytotoxic analysis using MTT assay. Spheroid growth assay and apoptosis assay were conducted in HCC-1954 cells. In addition, cell migration analysis and synergistic activity with doxorubicin or paclitaxel were conducted in MDA MB 231 cells. This extract was subjected also for GC-MS analysis.

Results:

The results show that ethanol extract of S. carteri demonstrated a cytotoxic activity in BC cells. The IC₅₀ of this extract was lower 15 μg/ml in MDA MB 231, MDA MB 468, SKBR3, and HCC-1954 cells. Moreover, this extract inhibited spheroids growth and induced apoptosis in HCC-1954 cells. It inhibited cell migration and demonstrated a synergistic activity with doxorubicin or paclitaxel on triggering cell death in MDA MB 231 cells. Furthermore, GC-MS analysis indicated that this extract contained 1,2-Benzenediol, Dibutyl phthalate and 9,12-Octadecadienoic acid, ethyl ester.

Conclusion:

Our preliminary data indicate a potential anti-tumor activity of ethanol extract of S. carteri in breast cancer cells.

Environmental ototoxicants, a potential new class of chemical stressors

Hearing loss is an injury that can develop over time, and people may not even be aware of it until it becomes a severe disability. Ototoxicants are substances that may damage the inner ear by either affecting the structures in the ear itself or by affecting the nervous system. We have examined the possibility that ototoxicants may present a health hazard in association with environmental exposures, adding to existing knowledge of their proven hazards under medical therapeutic conditions or occupational activities. In addition to the already described human environmental ototoxicants, mainly organochlorines such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), dichlorodiphenyltrichloroethane (DDT), dichlorodiphenyldichloroethylene (DDE), hexachlorocyclohexane (HCH) and hexachlorobenzene (HCB), we have examined the ubiquitous chemical stressors phthalates, bisphenol A/S/F/, PFCs, flame retardants (FRs) and cadmium for potential ototoxic properties, both as single substances or as chemical mixtures. Our literature review confirmed that these chemicals may disturb thyroid hormones homeostasis, activate aryl hydrocarbon receptor (AhR), and induce oxidative stress, which in turn may initiate a chain of events resulting in impairment of cochlea and hearing loss. With regard to auditory plasticity, diagnostics of a mixture of effects of ototoxicants, potential interactions of chemical and physical agents with effects on hearing, parallel deterioration of hearing due to chemical exposures and ageing, metabolic diseases or obesity, even using specific methods as brainstem auditory evoked potentials (BAEP) or otoacoustic emissions (OAEs) registration, may be difficult, and establishment of concentration-response relationships problematic. This paper suggests the establishment of a class of environmental oxotoxicants next to the established classes of occupational and drug ototoxicants. This will help to properly manage risks associated with human exposure to chemical stressors with ototoxic properties and adequate regulatory measures.

Combined use of vitamin E and nimodipine ameliorates dibutyl phthalate-induced memory deficit and apoptosis in mice by inhibiting the ERK 1/2 pathway

Learning disabilities (LDs) in children are a serious global problem. Dibutyl phthalate (DBP), a plasticizer widely used in daily life, has been linked to triggering childhood LDs, however the mechanism underlying this remains unclear. Studies have shown that the ERK 1/2 pathway is closely related to apoptosis of hippocampal neurons. On the basis of these links between LDs, DBP and the ERK 1/2 pathway, we explore whether DBP induces hippocampal neuron apoptosis and increases behavioral disorders in mice via the ERK 1/2 pathway. We looked at oxidative stress, examined the calcium signal, detected the ERK 1/2 pathway and evaluated apoptosis as well as using histological observations, and found that DBP significantly increased oxidative damage and apoptosis in hippocampal neurons via the ERK 1/2 pathway in mice. We also found that pretreatment with the dihydropyridine's (DHP's) Ca²⁺ antagonist, nimodipine (NMDP), combined with the antioxidant Vitamin E (VE), attenuated ERK 1/2 phosphorylation and DBP-mediated disorders, suggesting that a combined use of VE and NMDP can ameliorate DBP-induced memory deficit and apoptosis via inhibiting the ERK 1/2 pathway. These results indicate that DBP predisposes oxidative damage and apoptosis in hippocampal neurons by activation of the ERK 1/2 pathway, and may be proposed as a possible mechanism underlying LDs in children. Moreover, VE and NMDP may play a certain protective role in the targeted treatment of childhood LDs.

Neurochemical alterations following the exposure to di-n-butyl phthalate in rats

Due to its ability to cross blood brain barrier and placenta, dibutyl phthalate (di-n-butyl phthalate, DBP) is expected to cause severe side effects to the central nervous system of animals and humans. A little data is available about the potential DBP neurotoxicity; therefore, this work was designed to investigate the brain tissue injury induced by DBP exposure. Forty Wister albino rats were allocated randomly into 4 groups (10 rats each). Group 1 served as control and the rats administered with physiological saline (0.9% NaCl) orally for 12 weeks. Groups 2, 3 and 4 were orally treated with DPB (100, 250 and 500 mg/kg) respectively for 12 weeks. DBP-intoxicated rats showed a disturbance in the oxidative status in cerebral cortex, striatum and brainstem, as represented by the elevated oxidants [malondialdehyde (MDA), nitric oxide (NO), 8-hydroxy-2-deoxyguanosine (8-OHdG)] and the decreased antioxidant molecules [reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR)]. DBP also enhanced a pro-inflammatory state through increasing the release of tumor necrosis factor- α (TNF-α) and interleukin-1β (IL-1β). The increase of these cytokines was associated with the increase of pro-apoptotic proteins [Bcl-2 associated X protein (Bax) and caspase-3] and the decrease of the anti-apoptotic protein, B cell lymphoma 2 (Bcl-2). In addition, the levels of norepinephrine (NE), dopamine (DA) and acetylcholine esterase (AChE) activity were decreased. This was accompanied by the alterations in the major excitatory and inhibitory amino acids neurotransmitters levels. The present findings indicated that DBP could exert its neuronal damage through oxidative stress, DNA oxidation, neuroinflammation, activation of apoptotic proteins and altering the monoaminergic, cholinergic and amino acids transmission.

The Action of Di-(2-Ethylhexyl) Phthalate (DEHP) in Mouse Cerebral Cells Involves an Impairment in Aryl Hydrocarbon Receptor (AhR) Signaling

Di-(2-ethylhexyl) phthalate (DEHP) is used as a plasticizer in various plastic compounds, such as polyvinyl chloride (PVC), and products including baby toys, packaging films and sheets, medical tubing, and blood storage bags. Epidemiological data suggest that phthalates increase the risk of the nervous system disorders; however, the impact of DEHP on the brain cells and the mechanisms of its action have not been clarified. The aim of the present study was to investigate the effects of DEHP on production of reactive oxygen species (ROS) and aryl hydrocarbon receptor (AhR), as well as Cyp1a1 and Cyp1b1 mRNA and protein expression in primary mouse cortical neurons and glial cells in the in vitro mono-cultures. Our experiments showed that DEHP stimulated ROS production in both types of mouse neocortical cells. Moreover, the results strongly support involvement of the AhR/Cyp1A1 signaling pathway in the action of DEHP in neurons and glial cells. However, the effects of DEHP acting on the AhR signaling pathways in these two types of neocortical cells were different. In neurons, AhR mRNA expression did not change, but AhR protein expression decreased in response to DEHP. A similar trend was observed for Cyp1a1 and Cyp1b1 mRNA and protein expression. Failure to induce Cyp1a1 in neurons was confirmed by EROD assay. In primary glial cells, a decrease in AhR protein level was accompanied by a decrease in AhR mRNA expression. In glial cells, mRNA and protein expression of Cyp1a1 as well as Cyp1a1-related EROD activity were significantly increased. As for Cyp1b1, both in neurons and glial cells Cyp1b1 mRNA expression did not significantly change, whereas Cyp1b1 protein level were decreased. We postulate that developmental exposure to DEHP which dysregulates AhR/Cyp1a1 may disrupt defense processes in brain neocortical cells that could increase their susceptibility to environmental toxins.

Short-term toxicity of dibutyl phthalate to mice intestinal tissue

The objective of this study was to investigate changes in intestinal histopathology and expression of heat-shock proteins (HSPs) in the small intestinal tissue of mouse after acute exposure to dibutyl phthalate (DBP). Forty-eight 60-day-old Institute of Cancer Research (ICR) mice were administered DBP by gavage once a day for 10 days. The mice were divided into three groups of 16 mice each: the high-dose group was administered 500 mg/kg body weight (BW) DBP; the low-dose group was administered 50 mg/kg BW; and the control group was not administered DBP. Significant increases in the uterine index, ovary index, and testicular index were observed in the DBP-exposed groups compared to those in the control group. Villus height and V/ C ratio significantly increased ( p < 0.05) in the duodenum and decreased ( p < 0.05) in the jejunum after the administration of DBP. The goblet cell number decreased in both the duodenum and the jejunum of mice exposed to DBP ( p < 0.05) compared to the number in the control group mice. Damage to the structure of the small intestine was accompanied by a marked increase in HSP27 expression and a decrease in the expression of HSP70 and HSP90 in both high-dose and low-dose groups. These results indicate that elevated HSP27 levels in the duodenum and jejunum may be important markers for acute DBP exposure and that HSP27 may act as a protective protein involved in intestinal mucosa repair.

Functional genomic analysis of phthalate acid ester (PAE) catabolism genes in the versatile PAE-mineralising bacterium Rhodococcus sp. 2G

Microbial degradation is considered the most promising method for removing phthalate acid esters (PAEs) from polluted environments; however, a comprehensive genomic understanding of the entire PAE catabolic process is still lacking. In this study, the repertoire of PAE catabolism genes in the metabolically versatile bacterium Rhodococcus sp. 2G was examined using genomic, metabolic, and bioinformatic analyses. A total of 4930 coding genes were identified from the 5.6 Mb genome of the 2G strain, including 337 esterase/hydrolase genes and 48 transferase and decarboxylase genes that were involved in hydrolysing PAEs into phthalate acid (PA) and decarboxylating PA into benzoic acid (BA). One gene cluster (xyl) responsible for transforming BA into catechol and two catechol-catabolism gene clusters controlling the ortho (cat) and meta (xyl &mhp) cleavage pathways were also identified. The proposed PAE catabolism pathway and some key degradation genes were validated by intermediate-utilising tests and real-time quantitative polymerase chain reaction. Our results provide novel insight into the mechanisms of PAE biodegradation at the molecular level and useful information on gene resources for future studies.

The Aryl Hydrocarbon Receptor and the Nervous System

The aryl hydrocarbon receptor (or AhR) is a cytoplasmic receptor of pollutants. It translocates into the nucleus upon binding to its ligands, and forms a heterodimer with ARNT (AhR nuclear translocator). The heterodimer is a transcription factor, which regulates the transcription of xenobiotic metabolizing enzymes. Expressed in many cells in vertebrates, it is mostly present in neuronal cell types in invertebrates, where it regulates dendritic morphology or feeding behavior. Surprisingly, few investigations have been conducted to unravel the function of the AhR in the central or peripheral nervous systems of vertebrates. In this review, we will present how the AhR regulates neural functions in both invertebrates and vertebrates as deduced mainly from the effects of xenobiotics. We will introduce some of the molecular mechanisms triggered by the well-known AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which impact on neuronal proliferation, differentiation, and survival. Finally, we will point out the common features found in mice that are exposed to pollutants, and in AhR knockout mice.

Antiproliferative and Antioxidative Bioactive Compounds in Extracts of Marine-Derived Endophytic Fungus Talaromyces purpureogenus

Endophytic fungi are now recognized as sources of pharmacologically beneficial, novel bioactive compounds. This study was carried out to evaluate antiproliferative and antioxidative potential of a seaweed endophytic fungus Talaromyces purpureogenus. Extracts with different solvents of the fungus grown on different liquid media were assayed for the antiproliferative and antioxidative activities. Tested 6 cancer cell lines, the highest antiproliferative activity was observed in ethyl acetate extract of total culture grown in Potato Dextrose Broth for 28 days in a dose-dependent manner. The highest antioxidative activity was observed in hexane extract of fungal culture grown in Malt Extract Broth for 21 days. Analyzed for secondary metabolites, the extract revealed the presence of phenolics, alkaloids, flavonoids, steroids and terpenoids. Further, Gas Chromatography Mass Spectroscopy (GCMS) analysis of the extract revealed the presence of several compounds including 3-nitropropanoic acid, 4H-pyran-4-one 5-hydroxy-2-(hydroxymethyl), hexadecanoic acid, and octadecanoic acid, known to be cytotoxic or antioxidative. Among different cell lines tested, HeLa cells were the most vulnerable to the treatment of the fungal extract with an IC50 value of 101 ± 1 μg/mL. The extract showed no significant cytotoxicity to the normal human embryonic kidney cell line (HEK 293 T) in the MTT assay. The ethyl acetate extract induced membrane damage and mitochondrial depolarization and thereby apoptosis and cytotoxicity in HeLa cells. The study marks marine-derived endophytes as potential sources for discovery of novel drugs.

Perinatal Exposure to an Environmentally Relevant Mixture of Phthalates Results in a Lower Number of Neurons and Synapses in the Medial Prefrontal Cortex and Decreased Cognitive Flexibility in Adult Male and Female Rats

The growth and organization of the developing brain are known to be influenced by hormones, but little is known about whether disruption of hormones affects cortical regions, such as mPFC. This region is particularly important given its involvement in executive functions and implication in the pathology of many neuropsychiatric disorders. Here, we examine the long-term effects of perinatal exposure to endocrine-disrupting compounds, the phthalates, on the mPFC and associated behavior. This investigation is pertinent as humans are ubiquitously exposed to phthalates through a variety of consumer products and phthalates can readily cross the placenta and be delivered to offspring via lactation. Pregnant dams orally consumed an environmentally relevant mixture of phthalates at 0, 200, or 1000 μg/kg/d through pregnancy and for 10 d while lactating. As adults, offspring were tested in an attentional set-shifting task, which assesses cognitive flexibility. Brains were also examined in adulthood for stereological quantification of the number of neurons, glia, and synapses within the mPFC. We found that, independent of sex, perinatal phthalate exposure at either dose resulted in a reduction in neuron number, synapse number, and size of the mPFC and a deficit in cognitive flexibility. Interestingly, the number of synapses was correlated with cognitive flexibility, such that rats with fewer synapses were less cognitively flexible than those with more synapses. These results demonstrate that perinatal phthalate exposure can have long-term effects on the cortex and behavior of both male and female rats.SIGNIFICANCE STATEMENT Humans globally are exposed on a daily basis to a variety of phthalates, which are endocrine-disrupting chemicals. The effects of phthalate exposure on the developing brain, especially on cognitively relevant regions, such as the mPFC, are not known. Here, we use a rat model of human prenatal exposure to an environmentally relevant mixture of phthalates and find that there is an appreciable reduction in neuron number, synapse number, and size of the mPFC and a deficit in cognitive flexibility. These results may have serious implications for humans given that the mPFC is involved in executive functions and is implicated in the pathology of many neuropsychiatric disorders.

Di-n-butyl phthalate, butylbenzyl phthalate and their metabolites induce haemolysis and eryptosis in human erythrocytes

Phthalates have been extensively used as plasticizers in various fields, including food, cosmetic, and pharmaceutical industry. Those compounds do not form covalent bonds to substances they are being added to, and thus they may migrate easily and penetrate various products used every day. They may reach organisms with air, food, or by a direct skin contact. Significant levels of phthalates and their metabolites are found in urine, breast milk, blood serum, venous blood, and cord blood. The purpose of this study was to assess the simple toxicity (haemolysis) and programmed death (eryptosis) caused by following phthalates: di-n-butyl phthalate (DBP), butylbenzyl phthalate (BBP) and their metabolites: mono-n-butyl phthalate (MBP) and mono-benzyl phthalate (MBzP) in vitro in human RBCs. RBCs were incubated with the above mentioned compounds at concentrations ranging between 0.5 and 500 μg/mL for 24 h. Obtained results demonstrated that DBP and BBP possess higher haemolytic properties compared to their metabolites. The lethal concentration (LC₅₀) was determined. The value was 126.37 ± 5.94 μg/mL for DBP, and 103.65 ± 4.03 μg/mL for BBP, and for metabolites the LC₅₀ value was over 500 μg/mL. All compounds induced eryptosis causing translocation of phosphatidylserine, increased cytosolic calcium ions level, increased caspase-3 and calpain activation in human erythrocytes. BBP caused translocation of phosphatidylserine at a lower concentration compared to DBP. In case of other parameters, more pronounced changes were evoked by DBP at lower concentrations. Metabolites showed a significantly lower toxicity compared to parent compounds.

DEP and DBP induce cytotoxicity in mouse embryonic stem cells and abnormally enhance neural ectoderm development

Diethyl phthalate (DEP) and dibutyl phthalate (DBP) are two typical small phthalate esters, extensively used in personal care and consumer products. Although previous studies have linked phthalate esters to several health issues, it is still unclear whether they can affects the early stages of embryonic development. In this study, we evaluated the early developmental neurotoxicity as well as the cytotoxicity of DEP and DBP, using mouse embryonic stem cells (mESCs). Our results showed that both DEP and DBP could decrease mESC viability in a dose-dependent manner. Moreover, while DBP could activate the caspase-3/7 enzymes and cause cell membrane damage as well as intracellular ROS accumulation, interestingly DEP treatment only showed stimulation of ROS production. In addition, DEP and DBP treatment at non-cytotoxic concentrations, abnormally altered the expression levels of several vitally important regulators of embryo development. For instance, neural ectoderm markers, such as Pax6, Nestin, Sox1 and Sox3, were significantly up-regulated upon DEP and DBP exposure. In conclusion, our work suggests a potential developmental toxicity of DEP and DBP on mammals, especially for neural ectoderm specification. Our findings help better understand the association between health problems and DEP/DBP exposure and most significantly remind us of the importance of additional health risk tests for these two largely used chemicals.

Bazedoxifene and raloxifene protect neocortical neurons undergoing hypoxia via targeting ERα and PPAR-γ

Selective estrogen receptor modulators (SERMs) such as bazedoxifene and raloxifene are recognized to mainly act via estrogen receptors (ERs), but there is no study examining the involvement of PPAR-γ in their actions, especially in neurons undergoing hypoxia. Little is also known about age-dependent actions of the SERMs on neuronal tissue challenged with hypoxia. In this study, bazedoxifene and raloxifene protected neocortical cells against hypoxia at early and later developmental stages. Both SERMs evoked caspase-3-independent neuroprotection and increased protein levels of ERα (66 and 46 kDa isoforms) and PPAR-γ. In addition, bazedoxifene enhanced expression of ERα-regulated Cyp19a1 mRNA. Using double siRNA silencing, for the first time we demonstrated a key role of ERα and PPAR-γ in the neuroprotective action of the SERMs in neocortical neurons undergoing hypoxia. This study provides prospects for the development of a new therapeutic strategies against hypoxic brain injury that selectively target ERα and/or PPAR-γ.

Steroid and Xenobiotic Receptor Signalling in Apoptosis and Autophagy of the Nervous System

Apoptosis and autophagy are involved in neural development and in the response of the nervous system to a variety of insults. Apoptosis is responsible for cell elimination, whereas autophagy can eliminate the cells or keep them alive, even in conditions lacking trophic factors. Therefore, both processes may function synergistically or antagonistically. Steroid and xenobiotic receptors are regulators of apoptosis and autophagy; however, their actions in various pathologies are complex. In general, the estrogen (ER), progesterone (PR), and mineralocorticoid (MR) receptors mediate anti-apoptotic signalling, whereas the androgen (AR) and glucocorticoid (GR) receptors participate in pro-apoptotic pathways. ER-mediated neuroprotection is attributed to estrogen and selective ER modulators in apoptosis- and autophagy-related neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, stroke, multiple sclerosis, and retinopathies. PR activation appeared particularly effective in treating traumatic brain and spinal cord injuries and ischemic stroke. Except for in the retina, activated GR is engaged in neuronal cell death, whereas MR signalling appeared to be associated with neuroprotection. In addition to steroid receptors, the aryl hydrocarbon receptor (AHR) mediates the induction and propagation of apoptosis, whereas the peroxisome proliferator-activated receptors (PPARs) inhibit this programmed cell death. Most of the retinoid X receptor-related xenobiotic receptors stimulate apoptotic processes that accompany neural pathologies. Among the possible therapeutic strategies based on targeting apoptosis via steroid and xenobiotic receptors, the most promising are the selective modulators of the ER, AR, AHR, PPARγ agonists, flavonoids, and miRNAs. The prospective therapies to overcome neuronal cell death by targeting autophagy via steroid and xenobiotic receptors are much less recognized.

Neurotoxicity of fragrance compounds: A review

Fragrance compounds are chemicals belonging to one of several families, which are used frequently and globally in cosmetics, household products, foods and beverages. A complete list of such compounds is rarely found on the ingredients-list of such products, as "fragrance mixtures" are defined as "trade secrets" and thus protected by law. While some information regarding the general toxicity of some of these compounds is available, their neurotoxicity is known to a lesser extent. Here, we discuss the prevalence and neurotoxicity of fragrance compounds belonging to the three most common groups: phthalates, synthetic musks and chemical sensitizers.

Short-term social memory deficits in adult female mice exposed to tannery effluent and possible mechanism of action

The accumulated organic residues in tannery-plant courtyards are an eating attraction to small rodents; however, the contact of these animals with these residues may change their social behavior. Thus, the aim of the present study is to investigate whether the exposure to tannery effluent (TE) can damage the social recognition memory of female Swiss mice, as well as to assess whether vitamin C supplementation could provide information about how TE constituents can damage these animals' memory. We have observed that resident females exposed to TE (without vitamin supplementation) did not explore the anogenital region, their body or chased intruding females for shorter time or with lower frequency during the retest session of the social recognition test, fact that indicates social recognition memory deficit in these animals. Such finding is reinforced by the confirmation that there was no change in the animals' olfactory function during the buried food test, or locomotor changes in females exposed to the pollutant. Since no behavioral change was observed in the females exposed to TE and treated with vitamin C (before or after the exposure), it is possible saying that these social cognitive impairments seem to be directly related to the imbalance between the cellular production of reactive oxygen species and the counteracting antioxidant mechanisms (oxidative stress) in female mice exposed to the pollutant (without vitamin supplementation). Therefore, the present study evidences that the direct contact with tannery effluent, even for a short period-of-time, may cause short-term social memory deficits in adult female Swiss mice.

Potential involvement of Fgf10/Fgfr2 and androgen receptor (AR) in renal fibrosis in adult male rat offspring subjected to prenatal exposure to di-n-butyl phthalate (DBP)

BACKGROUND

We previously demonstrated that maternal exposure to di-n-butyl phthalate (DBP) induces dysplasia of the kidney in newborn male offspring and renal fibrosis in adults. But the underlying mechanisms remain elusive. Fgf10/Fgfr2 and androgen receptor (AR) are known to be important for renal development. We therefore investigated whether these genes are involved in DBP-induced renal fibrosis.

MATERIALS AND METHODS

Using Sprague-Dawley rats and rat renal proximal tubular cells (NRK52E), we determined the potential involvement of Fgf10, Fgfr2 and AR in DBP-induced renal fibrosis.

RESULTS

We found that maternal exposure to DBP induces renal fibrosis in adult male offspring. A lower serum testosterone concentration and reduced expression of Fgf10, Fgfr2 and AR were detected in these animals. These was a trend toward lower expression of Fgf10, Fgfr2 and AR in NRK52E cells subjected to DBP exposure. Furthermore, higher expression levels of TGF-β and α-SMA were observed in abnormal renal tissue and DBP-treated NRK52E cells.

CONCLUSION

Our findings suggest the potential involvement of Fgf10/Fgfr2 and AR in renal fibrosis of adult male rat offspring induced by prenatal exposure to DBP. The anti-androgenic effects of DBP might play an important role in this pathological process.

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.

Gestational di-n-butyl phthalate exposure induced developmental and teratogenic anomalies in rats: a multigenerational assessment

With the limited but ongoing usage of di-n-butyl phthalate (DBP) as plasticizer, the health effects of both phthalate and its alternatives are far from being understood. Multigenerational effects of phthalates were evaluated in rats upon exposure to DBP, aiming to provide some evidences about its potential in causing developmental teratogenicity. Gestational rats were exposed to DBP (500 mg/kg bw/day) and control groups with olive oil. On the 18th day of gestation, fetuses (F₁) isolated from a few dams were subjected to prenatal screening, and the other rats were allowed to litter, and later postnatal screening was made. DBP-toxicated (F₁) rats were crossed and reared up to three generations (F₂ and F₃) by adopting the same experimental design. A considerable decrease in the weight of placenta, low number of corpora lutea and increased resorptions, and pre- and postimplantation loss were observed in F₁, F₂, and F₃ generations. Further, there was a decrease in the number of live births and fetal body weight with high mortality, the developmental indices showed reduction in litter size and sex ratio, and a considerable incidence of skeletal and malformation complex involving face and eye was observed in later generations compared to the first. The pre-weaning indices in neonates showed a considerable delay in physical growth milestones and poor scores in sensory motor development. Alterations noticed in the levels of thyroid profile and testosterone found to have a role in sensory motor, craniofacial development, and eye formation. In brief, results confirm multigenerational and fetotoxic effects of DBP; thereby, findings imply that developing tissues are the targets and endocrine disruption appears to be the underlying mechanism of phthalate action.