Alterations in central monoaminergic neurotransmission induced by polycyclic aromatic hydrocarbons in rats

Aquilaria crassna Extract Exerts Neuroprotective Effect against Benzo[a]pyrene-Induced Toxicity in Human SH-SY5Y Cells: An RNA-Seq-Based Transcriptome Analysis

Benzo[a]pyrene (B[a]P) is known to inhibit neurodifferentiation and induce neurodegeneration. Agarwood or Aquilaria crassna (AC), a plant with health-promoting properties, may counteract the neurotoxic effects of B[a]P by promoting neuronal growth and survival. This study investigated the protective effect of AC leaf ethanolic extract (ACEE) on the B[a]P-induced impairment of neuronal differentiation. A transcriptomic analysis identified the canonical pathway, the biological network, and the differentially expressed genes (DEGs) that are changed in response to neuronal differentiation and neurogenesis. Several genes, including CXCR4, ENPP2, GAP43, GFRA2, NELL2, NFASC, NSG2, NGB, BASP1, and NEUROD1, in B[a]P-treated SH-SY5Y cells were up-regulated after treatment with ACEE. Notably, a Western blot analysis further confirmed that ACEE increased the protein levels of GAP43 and neuroglobin. B[a]P treatment led to decreased phosphorylation of Akt and increased phosphorylation of ERK in SH-SY5Y cells; however, ACEE was able to reverse these effects. Clionasterol and lupenone were identified in ACEE. Molecular docking showed that these two phytochemicals had significant interactions with CXCR4, GDNF family receptor alpha (GFRA), and retinoid X receptors (RXRs). In conclusion, ACEE may be a potential alternative medicine for the prevention of impaired neuronal differentiation and neurodegenerative diseases.

Urinary polycyclic aromatic hydrocarbons and adult obesity among the US population: NHANES 2003-2016

Polycyclic aromatic hydrocarbons (PAHs) are naturally occurring environmental pollutants that may contribute to obesity in the adult population. To investigate the relationship between the urinary concentrations of PAH metabolites and adult obesity among the US population, the National Health and Nutritional Examination Survey (NHANES, 2003-2016) was used as a data source for this study. As many as 4464 participants in the NHANES 2003-2016 were included in the final analyses. We used logistic regression to look at the link between urinary PAH metabolites and obesity, using odds ratios (ORs) and 95% confidence intervals (CIs). The study sample comprised 4464 individuals aged ≥18 years, 2199 were male and 2265 were female. The study characteristics for four different quartiles were analyzed, and the average ages of the four urinary PAH quartiles were 49.61 ± 20.01, 46.63 ± 20.33, 44.28 ± 19.19, and 43.27 ± 17.68 years, respectively. In the quartile analysis of all participants, the third quartile was significantly associated with an increased prevalence of obesity (OR = 1.33, 95% CI = 1.12-1.59) with p-values <.05. In addition, females, but not males, had a strong link between the second, third, and fourth quartiles of urinary PAH and a higher risk of obesity (OR = 1.27, 95% CI = 1.00-1.61; OR = 1.52, 95% CI = 1.19-1.94; and OR = 1.39, 95% CI = 1.09-1.78). In conclusion, the study observed that urinary PAH metabolites were associated with the prevalence of obesity among the US population.

Exposure to Benzo[a]pyrene Decreases Noradrenergic and Serotonergic Axons in Hippocampus of Mouse Brain

Epidemiological studies showed the association between air pollution and dementia. A soluble fraction of particulate matters including polycyclic aromatic hydrocarbons (PAHs) is suspected to be involved with the adverse effects of air pollution on the central nervous system of humans. It is also reported that exposure to benzopyrene (B[a]P), which is one of the PAHs, caused deterioration of neurobehavioral performance in workers. The present study investigated the effect of B[a]P on noradrenergic and serotonergic axons in mouse brains. In total, 48 wild-type male mice (10 weeks of age) were allocated into 4 groups and exposed to B[a]P at 0, 2.88, 8.67 or 26.00 µg/mice, which is approximately equivalent to 0.12, 0.37 and 1.12 mg/kg bw, respectively, by pharyngeal aspiration once/week for 4 weeks. The density of noradrenergic and serotonergic axons was evaluated by immunohistochemistry in the hippocampal CA1 and CA3 areas. Exposure to B[a]P at 2.88 µg/mice or more decreased the density of noradrenergic or serotonergic axons in the CA1 area and the density of noradrenergic axons in the CA3 area in the hippocampus of mice. Furthermore, exposure to B[a]P dose-dependently upregulated Tnfα at 8.67 µg/mice or more, as well as upregulating Il-1β at 26 µg/mice, Il-18 at 2.88 and 26 µg/mice and Nlrp3 at 2.88 µg/mice. The results demonstrate that exposure to B[a]P induces degeneration of noradrenergic or serotonergic axons and suggest the involvement of proinflammatory or inflammation-related genes with B[a]P-induced neurodegeneration.

Concentration of Polycyclic Aromatic Hydrocarbons (PAHs) in Human Serum and Adipose Tissues and Stimulatory Effect of Naphthalene in Adipogenesis in 3T3-L1 Cells

Polycyclic aromatic hydrocarbons (PAHs) are one of the most prevalent classes of environmental pollutants. Some evidence shows that PAHs could be involved in human obesity. However, little is known about the distribution patterns of PAHs in human adipose tissue (AT) and the role of PAHs on adipogenesis/lipogenesis. The aims of this pilot study were to determine concentrations of 16 PAHs defined as high-priority pollutants in the plasma and adipose tissue of French and Polish bariatric patients, as well as their correlation with body mass index (BMI), plasma and AT adipokines expression levels. We finally investigated the role of naphthalene on cell proliferation, viability, and differentiation in 3T3-L1 preadipocytes. The concentration of most PAHs was similar in the three types of AT and it was significantly higher in AT as compared to plasma, suggesting bioaccumulation. Polish patients had higher PAH levels in AT than French ones. Only the concentration of naphthalene in AT was positively correlated with the BMI and serum or adipose chemerin, adiponectin and resistin expression, in French but not in Polish patients, who had significantly higher BMIs. Moreover, naphthalene exposure increased the cell proliferation of 3T3-L1 preadipocytes and lipogenesis, and increased the expression of genes involved in adipogenesis after cell differentiation. Taken together, PAHs and more particularly naphthalene could be an obesogenic molecule and increase the risk of obesity.

Effect of benzo(a)pyrene on oxidative stress and inflammatory mediators in astrocytes and HIV-infected macrophages

BACKGROUND

Benzo(a)pyrene (BaP), an important polycyclic aromatic hydrocarbons (PAH) component of cigarette/tobacco smoking, is known to cause adverse health effects and is responsible for various life-threatening conditions including cancer. However, it is not yet clear whether BaP contributes to the macrophage- and astrocyte-mediated inflammatory response.

METHODS

We examined the acute (up to 72 h) effects of BaP on the expression of antioxidant enzymes (AOEs), cytokines/chemokines, and cytochromes P450 (CYP) enzymes in astrocytic cell lines, SVGA, and chronically HIV-infected U1 macrophage. The treated cells were examined for mRNA, protein levels of CYPs, AOEs superoxide dismutase-1 (SOD1) and catalase (CAT), cytokines/chemokines, using Western blot, multiplex ELISA, and reactive oxygen species (ROS) by flow cytometry analysis.

RESULTS

Upon acute exposure, BaP (1 μM) showed a significant increase in the mRNA levels of CYPs (CYP1A1 and CYP1B1), and pro-inflammatory cytokine IL-1β in SVGA cells following BaP for 24, 48, and 72h. In addition, we observed a significant increase in the mRNA levels of SOD1 and CAT at 24h of BaP treatment. In contrast, BaP did not exert any change in the protein expression of AOEs and CYP enzymes. In U1 cells, however, we noticed an interesting increase in the levels of MCP-1 as well as a modest increase in TNFα, IL-8 and IL-1β levels observed at 72 h of BaP treatment but could not reach to statistically significant level.

CONCLUSIONS

Overall, these results suggest that BaP contributes in part to macrophage and astrocyte-mediated neuroinflammation by mainly inducing IL-1β and MCP-1 production, which is likely to occur with the involvement of CYP and/or oxidative stress pathways.

Urinary polycyclic aromatic hydrocarbon excretion and regional body fat distribution: evidence from the U.S. National Health and Nutrition Examination Survey 2001-2016

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that may contribute to the etiology of obesity. However, it is unclear whether PAHs from environmental sources are associated with regional body fat distribution, and whether the association varies across racial/ethnic groups who may have differential PAH exposure patterns.

OBJECTIVES

To examine correlations between PAHs and body fat distribution, and potential racial/ethnic differences among U.S. adults.

METHODS

Ten PAHs were measured in spot urine samples from 2691 non-smoking adults (age ≥ 20 years) in the NHANES 2001-2016. Dual-energy X-ray absorptiometry was used to measure fat mass percent (FM%). Partial Pearson correlation coefficients (r) with multivariable adjustment were used to assess PAH-FM% associations.

RESULTS

In the total population, 1-naphthalene, 3-fluorene, and 1-pyrene were inversely correlated with total FM% or trunk FM% (adjusted r ranged: - 0.06 to - 0.08), while 2-naphthalene, 9-fluorene, and 4-phenanthrene were positively correlated with the FM% measurements (r: 0.07-0.11). PAH levels are highest among non-Hispanic Blacks, followed by Hispanics and Whites and some of the correlations were different by these races/ethnicities. Among non-Hispanic Whites, no PAH was correlated with FM%. In contrast, 9-fluorene was positively correlated with total FM% (r = 0.20) and trunk FM% (r = 0.22) among Blacks, and 4-phenanthrene was positively correlated with total FM% (r = 0.23) and trunk FM% (r = 0.24) among Hispanics (P-interaction: 0.010-0.025).

DISCUSSION

In this US adult population, certain PAHs are significantly associated with higher body fat contents among non-Hispanic Blacks and Hispanics but not non-Hispanic Whites, suggesting that minority groups might be particularly susceptible to PAH's obesogenic effects or the effects of other factors that determine the PAH exposure levels. Alternatively, differences in body composition may contribute to differential PAH metabolism in minority groups. Future studies are warranted to explore the racial/ethnic disparity in PAH exposures, drivers of these exposure differences, and mechanisms through which PAHs may influence body composition by races/ethnicities.

Acute benzo[a]pyrene exposure induced oxidative stress, neurotoxicity and epigenetic change in blood clam Tegillarca granosa

The blood clam (Tegillarca granosa) is being developed into a model bivalve mollusc for assessing and monitoring marine pollution on the offshore seabed. However, the information on the response of blood clam to PAHs, an organic pollutant usually deposited in submarine sediment, remains limited. Herein, we employed multiple biomarkers, including histological changes, oxidative stress, neurotoxicity and global DNA methylation, to investigate the effects of 10 and 100 μg/L Bap exposure on the blood clams under laboratory conditions, as well as the potential mechanisms. Acute Bap exposure can induce significant morphological abnormalities in gills as shown through hematoxylin–eosin (H.E) staining, providing an intuitive understanding on the effects of Bap on the structural organization of the blood clams. Meanwhile, the oxidative stress was significantly elevated as manifested by the increase of antioxidants activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST), lipid peroxidation (LPO) level and 8-hydroxy-2′-deoxyguanosine (8-OHdG) content. The neurotoxicity was also strengthened by Bap toxicity manifested as inhibited acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) activities. In addition, the global DNA methylation level was investigated, and a significant DNA hypomethylation was observed in Bap exposed the blood clam. The correlation analysis showed that the global DNA methylation was negatively correlated with antioxidants (SOD, CAT and POD) activities, but positively correlated choline enzymes (AChE and ChAT) activities. These results collectively suggested that acute Bap exposure can cause damage in gills structures in the blood clam possibly by generating oxidative stress and neurotoxicity, and the global DNA methylation was inhibited to increase the transcriptional expression level of antioxidants genes and consequently elevate antioxidants activities against Bap toxicity. These results are hoped to shed some new light on the study of ecotoxicology effect of PAHs on marine bivalves.

[Effect of benzo(a)pyrene on dopaminergic neurons and α-synuclein in brain and its mechanism involved]

OBJECTIVE

To analyze the effect of benzopyrene on the decrease of dopaminergic neurons, and the increase and aggregation of α-synuclein, which are the pathological features of Parkinson's disease, and to explore its possible mechanisms.

METHODS

Eight-month-old transgenic mice with human SNCA gene were randomly divided into a BaP-exposed group and a control group. BaP and solvent corn oil were injected intraperitoneally to BaP-exposed group and control group respectively, once a day for 60 days. The motor dysfunction of mice was tested by rotarod test. The effects of BaP on the decrease of dopaminergic neurons and increase and aggregation of α-synuclein were observed by immunohistochemistry and Western blot experiments respectively, and the expression of related mRNA was detected by quantitative real-time PCR (qRT-PCR). Twenty genes were tested in the study, mainly related to neurotransmitter transporter (2 genes), neurotransmitter receptor function (10 genes), cellular autophagy (5 genes), and α-synuclein aggregation and degradation (3 genes).

RESULTS

After BaP exposure, the movement time of the mice in the rotarod test was significantly reduced (P<0.05). The substantia nigra dopami-nergic neurons in the mice were significantly reduced, which was 62% of the control group (P<0.05), and the expression of α-synuclein in the midbrain increased, which was 1.36 times that of the control group (P<0.05). After BaP exposure, mRNA expressions of 14 genes in the midbrain of the mice were significantly down-regulated (P<0.05). Alpha-synuclein degradation and cell autophagy (5 genes), neuron transporters (2 genes), and neurotransmitter receptor functions (5 genes) were involved. The expression of one gene, Synphilin-1, was significantly up-regulated (P<0.01), which was related to α-synuclein aggregation.

CONCLUSION

BaP exposure not only inhibited function of neurotransmitter receptor and dopamine transporter, but also interfered cell autophagy, thereby hindering the degradation of α-synuclein, which could lead to decrease of dopaminergic neurons in substantia nigra and increase and aggregation of α-synuclein in midbrain, as the significant pathology of Parkinson's disease. Therefore, BaP exposure may increase the risk of Parkinson's disease.

Association of urinary polycyclic aromatic hydrocarbons and obesity in children aged 3-18: Canadian Health Measures Survey 2009-2015

Polycyclic aromatic hydrocarbons (PAHs) may contribute to obesity. Childhood obesity is a strong predictor of adult obesity and morbidity; however, the relationship between PAHs and obesity in young children (e.g., aged 3-5) has not been studied. We examined the association between urinary PAH metabolites and measures of obesity in children. We analyzed data from 3667 children aged 3-18 years who participated in the Canadian Health Measures Survey (CHMS, 2009-2015). We ran separate multivariable linear models to estimate the association between quartiles of PAH metabolites and each of body mass index (BMI) percentile, waist circumference (WC), and waist-to-height ratio (WHtR) in the total population, as well as in the age subgroups 3-5, 6-11, and 12-18, adjusting for age, sex, ethnicity, education, income quintile, diet, creatinine, and exposure to environmental tobacco smoke. A multinomial logistic regression model estimated adjusted odds ratios for risk of central obesity. BMI, WC, and WHtR were positively associated with total PAH and naphthalene metabolites in the total population aged 3-18 and in age groups 6-11 and 12-18. In 3-5 year olds, WHtR, but not BMI, was significantly associated with total PAH, naphthalene, and phenanthrene metabolites. Overall, those in the highest quartile for naphthalene or total PAH metabolites had three times greater odds of having central obesity compared with those in the lowest quartile. Urinary PAH metabolites are associated with WHtR, an indicator of central obesity and predictor of health risks associated with obesity, in children as young as 3-5.

Health, wealth and behavioural change: an exploration of role responsibilities in the wake of epigenetics

The field of epigenetics is leading to new conceptualizations of the role of environmental factors in health and genetic disease. Although more evidence is required, epigenetic mechanisms are being implicated in the link between low socioeconomic status and poor health status. Epigenetic phenomena work in a number of ways: they can be established early in development, transmitted from previous generations and/or responsive to environmental factors. Knowledge about these types of epigenetic traits might therefore allow us to move away from a genetic deterministic perspective, and provide individuals with the opportunity to change their health status. Although this could be equated with patient empowerment, it could also lead to stigmatization and discrimination where individuals are deemed responsible for their health, even if they are not in social situations where they are able to enact change that would alter their health status. In this paper, we will explore the responsibilities of different actors in the healthcare sphere in relation to epigenetics across four different contexts: (1) genetic research, (2) clinical practice, (3) prenatal care and (4) the workplace. Within this exploration of role responsibilities, we will also discuss the potential constraints that might prevent the patient, mother-to-be, research participant or employee, from enacting any necessary steps in order to increase their health status in response to epigenetic information.

Changes in Brain Monoamines Underlie Behavioural Disruptions after Zebrafish Diet Exposure to Polycyclic Aromatic Hydrocarbons Environmental Mixtures

Zebrafish were exposed through diet to two environmentally relevant polycyclic aromatic hydrocarbons (PAHs) mixtures of contrasted compositions, one of pyrolytic (PY) origin and one from light crude oil (LO). Monoamine concentrations were quantified in the brains of the fish after six month of exposure. A significant decrease in noradrenaline (NA) was observed in fish exposed to both mixtures, while a decrease in serotonin (5HT) and dopamine (DA) was observed only in LO-exposed fish. A decrease in metabolites of 5HT and DA was observed in fish exposed to both mixtures. Several behavioural disruptions were observed that depended on mixtures, and parallels were made with changes in monoamine concentrations. Indeed, we observed an increase in anxiety in fish exposed to both mixtures, which could be related to the decrease in 5HT and/or NA, while disruptions of daily activity rhythms were observed in LO fish, which could be related to the decrease in DA. Taken together, these results showed that (i) chronic exposures to PAHs mixtures disrupted brain monoamine contents, which could underlie behavioural disruptions, and that (ii) the biological responses depended on mixture compositions.

Neurotoxic Effect of Benzo[a]pyrene and Its Possible Association with 6-Hydroxydopamine Induced Neurobehavioral Changes during Early Adolescence Period in Rats

Exposure to persistent genotoxicants like benzo[a]pyrene (B[a]P) during postnatal days causes neurobehavioral changes in animal models. However, neurotoxic potential of B[a]P and its association with 6-hydroxydopamine (6-OHDA) induced neurobehavioral changes are yet to be explored. The growth of rat brain peaks at the first week of birth and continues up to one month with the attainment of adolescence. Hence, the present study was conducted on male Wistar rats at postnatal day 5 (PND 5) following single intracisternal administration of B[a]P to compare with neurobehavioral and neurotransmitter changes induced by 6-OHDA at PND 30. Spontaneous motor activity was significantly increased by 6-OHDA showing similar trend following B[a]P administration. Total distance travelled in novel open field arena and elevated plus maze was significantly increased following B[a]P and 6-OHDA administration. Neurotransmitter estimation showed significant alleviation of dopamine in striatum following B[a]P and 6-OHDA administration. Histopathological studies of striatum by hematoxylin and eosin (H&E) staining revealed the neurodegenerative potential of B[a]P and 6-OHDA. Our results indicate that B[a]P-induced spontaneous motor hyperactivity in rats showed symptomatic similarities with 6-OHDA. In conclusion, early postnatal exposure to B[a]P in rats causing neurobehavioral changes may lead to serious neurodegenerative consequences during adolescence.

Chronic Administration of Benzo(a)pyrene Induces Memory Impairment and Anxiety-Like Behavior and Increases of NR2B DNA Methylation

Background

Recently, an increasing number of human and animal studies have reported that exposure to benzo(a)pyrene (BaP) induces neurological abnormalities and is also associated with adverse effects, such as tumor formation, immunosuppression, teratogenicity, and hormonal disorders. However, the exact mechanisms underlying BaP-induced impairment of neurological function remain unclear. The aim of this study was to examine the regulating mechanisms underlying the impact of chronic BaP exposure on neurobehavioral performance.

Methods

C57BL mice received either BaP in different doses (1.0, 2.5, 6.25 mg/kg) or olive oil twice a week for 90 days. Memory and emotional behaviors were evaluated using Y-maze and open-field tests, respectively. Furthermore, levels of mRNA expression were measured by using qPCR, and DNA methylation of NMDA receptor 2B subunit (NR2B) was examined using bisulfate pyrosequencing in the prefrontal cortex and hippocampus.

Results

Compared to controls, mice that received BaP (2.5, 6.25 mg/kg) showed deficits in short-term memory and an anxiety-like behavior. These behavioral alterations were associated with a down-regulation of the NR2B gene and a concomitant increase in the level of DNA methylation in the NR2B promoter in the two brain regions.

Conclusions

Chronic BaP exposure induces an increase in DNA methylation in the NR2B gene promoter and down-regulates NR2B expression, which may contribute to its neurotoxic effects on behavioral performance. The results suggest that NR2B vulnerability represents a target for environmental toxicants in the brain.

Dopamine D2-Receptor Antagonists Down-Regulate CYP1A1/2 and CYP1B1 in the Rat Liver

Dopaminergic systems regulate the release of several hormones including growth hormone (GH), thyroid hormones, insulin, glucocorticoids and prolactin (PRL) that play significant roles in the regulation of various Cytochrome P450 (CYP) enzymes. The present study investigated the role of dopamine D₂-receptor-linked pathways in the regulation of CYP1A1, CYP1A2 and CYP1B1 that belong to a battery of genes controlled by the Aryl Hydrocarbon Receptor (AhR) and play a crucial role in the metabolism and toxicity of numerous environmental toxicants. Inhibition of dopamine D₂-receptors with sulpiride (SULP) significantly repressed the constitutive and benzo[a]pyrene (B[a]P)-induced CYP1A1, CYP1A2 and CYP1B expression in the rat liver. The expression of AhR, heat shock protein 90 (HSP90) and AhR nuclear translocator (ARNT) was suppressed by SULP in B[a]P-treated livers, whereas the AhRR expression was increased by the drug suggesting that the SULP-mediated repression of the CYP1 inducibility is due to inactivation of the AhR regulatory system. At signal transduction level, the D₂-mediated down-regulation of constitutive CYP1A1/2 and CYP1B1 expression appears to be mediated by activation of the insulin/PI3K/AKT pathway. PRL-linked pathways exerting a negative control on various CYPs, and inactivation of the glucocorticoid-linked pathways that positively control the AhR-regulated CYP1 genes, may also participate in the SULP-mediated repression of both, the constitutive and induced CYP1 expression. The present findings indicate that drugs acting as D₂-dopamine receptor antagonists can modify several hormone systems that regulate the expression of CYP1A1, CYP1A2 and CYP1B1, and may affect the toxicity and carcinogenicity outcome of numerous toxicants and pre-carcinogenic substances. Therefore, these drugs could be considered as a part of the strategy to reduce the risk of exposure to environmental pollutants and pre-carcinogens.

Role of serotonin in fish reproduction

The neuroendocrine mechanism regulates reproduction through the hypothalamo-pituitary-gonadal (HPG) axis which is evolutionarily conserved in vertebrates. The HPG axis is regulated by a variety of internal as well as external factors. Serotonin, a monoamine neurotransmitter, is involved in a wide range of reproductive functions. In mammals, serotonin regulates sexual behaviors, gonadotropin release and gonadotropin-release hormone (GnRH) secretion. However, the serotonin system in teleost may also play unique role in the control of reproduction as the mechanism of reproductive control in teleosts is not always the same as in the mammalian models. In fish, the serotonin system is also regulated by natural environmental factors as well as chemical substances. In particular, selective serotonin reuptake inhibitors (SSRIs) are commonly detected as pharmaceutical contaminants in the natural environment. Those factors may influence fish reproductive functions via the serotonin system. This review summarizes the functional significance of serotonin in the teleosts reproduction.

Late effects of a perinatal exposure to a 16 PAH mixture: Increase of anxiety-related behaviours and decrease of regional brain metabolism in adult male rats

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous pollutants originated from incomplete combustion processes. Ingestion of contaminated food is the main route of exposure for humans. These molecules are able to cross the placental barrier and are also found in breast milk. Since PAHs are neurotoxic agents, the potential adverse effects of a perinatal exposure of the developing brain is a key issue for public health especially concerning PAH mixture. In this study, female rats were exposed trough diet to a mixture of 16 PAHs, at doses of 2 μg/kg/day or 200 μg/kg/day during gestation and 1.5 μg/kg/day or 150 μg/kg/day during breast-feeding period. To assess late neurotoxic effects in male offsprings, behavioural and cognitive tests were carried out and histochemical analyses using cytochrome oxidase as a cerebral metabolism marker were performed on adult animals. Results showed that anxiety-related behaviours significantly increased in exposed animals, but there was no significant alteration of motor activity and learning and memory abilities. Several brain areas of the limbic system showed a neuronal hypometabolism in exposed animals. This work highlights that exposure to PAHs at early stages of brain development can cause later troubles on behaviour and that PAHs are able to partly alter the central nervous system metabolism on adulthood.

Benzo[α]pyrene-induced anti-depressive-like behaviour in adult female mice: role of monoaminergic systems

Benzo[α]pyrene (B[α]P) is a ubiquitous environmental pollutant exhibiting adverse effects on cognitive function and behaviour. In this study, depressive or antidepressive effects of B[α]P were investigated. Here, we report that a subacute B[α]P oral exposure (0.02-0.2 mg/kg) increases mobility behaviour in female adult mice in the tail suspension test, but not in the forced swimming test, without altering locomotion, suggesting that the tail suspension test was a more sensitive indicator of B[α]P-induced neurobehavioural disturbance. This might be because of differences in neurochemical substrates and pathways, mediating the performance in these behavioural models of depression. The effect of B[α]P on female adult mice in the tail suspension test was similar to that obtained with subacute treatment of the antidepressant reference drug imipramine (10 mg/kg). Therefore, B[α]P at 0.02 mg/kg and 0.2 mg/kg induces an antidepressant-like effect in mice, suggesting a neurobehavioural disturbance after oral exposure to this environmental compound. Furthermore, oral exposure to B[α]P at 0.02 mg/kg significantly increased gene expression levels of the brain receptors 5-hydroxytryptamine (serotonin) 1A (5HT(1A)) and alpha-1D adrenergic (ADRA(1D)). In summary, the presented findings suggest that subacute oral exposure to B[α]P results in behavioural changes in female adult mice, possibly caused by alterations in the serotoninergic and adrenergic systems.

Prenatal environmental exposures, epigenetics, and disease

This review summarizes recent evidence that prenatal exposure to diverse environmental chemicals dysregulates the fetal epigenome, with potential consequences for subsequent developmental disorders and disease manifesting in childhood, over the lifecourse, or even transgenerationally. The primordial germ cells, embryo, and fetus are highly susceptible to epigenetic dysregulation by environmental chemicals, which can thereby exert multiple adverse effects. The data reviewed here on environmental contaminants have potential implications for risk assessment although more data are needed on individual susceptibility to epigenetic alterations and their persistence before this information can be used in formal risk assessments. The findings discussed indicate that identification of environmental chemicals that dysregulate the prenatal epigenome should be a priority in health research and disease prevention.

Hepatic drug metabolizing profile of Flinders Sensitive Line rat model of depression

The Flinders Sensitive Line (FSL) rat model of depression exhibits some behavioral, neurochemical, and pharmacological features that have been reported in depressed patients and has been very effective in screening antidepressants. Major factor that determines the effectiveness and toxicity of a drug is the drug metabolizing capacity of the liver. Therefore, in order to discriminate possible differentiation in the hepatic drug metabolism between FSL rats and Sprague-Dawley (SD) controls, their hepatic metabolic profile was investigated in this study. The data showed decreased glutathione (GSH) content and glutathione S-transferase (GST) activity and lower expression of certain major CYP enzymes, including the CYP2B1, CYP2C11 and CYP2D1 in FSL rats compared to SD controls. In contrast, p-nitrophenol hydroxylase (PNP), 7-ethoxyresorufin-O-dealkylase (EROD) and 16alpha-testosterone hydroxylase activities were higher in FSL rats. Interestingly, the wide spread environmental pollutant benzo(alpha)pyrene (B(alpha)P) induced CYP1A1, CYP1A2, CYP2B1/2 and ALDH3c at a lesser extend in FSL than in SD rats, whereas the antidepressant mirtazapine (MIRT) up-regulated CYP1A1/2, CYP2C11, CYP2D1, CYP2E1 and CYP3A1/2, mainly, in FSL rats. The drug also further increased ALDH3c whereas suppressed GSH content in B(alpha)P-exposed FSL rats. In conclusion, several key enzymes of the hepatic biotransformation machinery are differentially expressed in FSL than in SD rats, a condition that may influence the outcome of drug therapy. The MIRT-induced up-regulation of several drug-metabolizing enzymes indicates the critical role of antidepressant treatment that should be always taken into account in the designing of treatment and interpretation of insufficient pharmacotherapy or drug toxicity.

Subacute oral exposure to benzo[alpha]pyrene (B[alpha]P) increases aggressiveness and affects consummatory aspects of sexual behaviour in male mice

Benzo[alpha]pyrene (B[alpha]P) is a neurotoxic pollutant which is also able to affect some behaviour and cognitive function. Here we report that a subacute oral exposure to B[alpha]P increases aggressiveness and affects copulatory behaviour in male mice. Indeed, after 3 weeks of exposure to B[alpha]P at 0.02 and 0.2mg/kg, we have observed that B[alpha]P 0.02 mg/kg-treated male mice are more aggressive than control mice in resident-intruder test because a significant decrease in the latency time of the first attack and a significant increase in the number of attacks in B[alpha]P 0.02 mg/kg-treated mice were found. On the other hand, we have found that subacute exposure (4 weeks) to B[alpha]P, does not affect the appetitive aspects and sexual motivation in copulatory behaviour because the latency to the first mount between control and B[alpha]P-treated male mice was not significantly different. We have nevertheless, surprisingly found that B[alpha]P (0.02-0.2)mg/kg-treated mice have performed significantly more sexual behavioural acts including mounting, intromission latency and intromission frequency than control mice. Although these last results suggest that B[alpha]P improves the consummatory aspects of sexual behaviour, we cannot conclude that this neurotoxic pollutant has advantage of sexual function because B[alpha]P has been shown to alter the monoaminergic neurotransmitter system and causes endocrine dysregulation via toxic effect.

Effects of lactational exposure to benzo[alpha]pyrene (B[alpha]P) on postnatal neurodevelopment, neuronal receptor gene expression and behaviour in mice

The harmful effects of exposure to benzo[alpha]pyrene (B[alpha]P), which is a neurotoxic pollutant, on mammalian neurodevelopment and/or behaviour as yet remain widely unclear. In the present investigation, we evaluated the impact of the lactational exposure to B[alpha]P on postnatal development of pups and behaviour of young mice. The neurobiological effects of B[alpha]P during lactation were also evaluated on pups' brain. Here, we found that lactational exposure to B[alpha]P at 2 and 20mg/kg affects the neuromaturation of pups by significantly decreasing their reflex as highlighted in surface righting reflex and negative geotaxis tests. However, we noted a significant increase in muscular strength of lactationally B[alpha]P mg/kg-exposed pups, which was probably due to the impact of the exposure to this toxic compound on body weight gain. At the pup stage, lactational exposure to B[alpha]P also provoked a neurobiological change, which was assessed by determination of neuronal receptor gene expression. Indeed, a significant reduction in gene expression of 5HT(1A) receptors in pups exposed to B[alpha]P through lactation was found in comparison to controls. Additionally, attenuation in the expression of MOR(1) mRNA was observed, but statistically significant only in animals receiving the higher dose. Neither the expression levels of ADRA(1D) nor GABA(A) mRNA were altered. Interestingly, the harmful effects of lactational exposure to B[alpha]P on behaviour and cognitive function were still found despite a long post-weaning period. Young mice whose mothers were exposed to B[alpha]P displayed a disinhibition behaviour towards the aversive spaces of the elevated plus maze. Furthermore, a significant increase of spontaneous alternation in the Y-maze was observed, but only in young mice whose mothers were orally exposed to the lower dose of B[alpha]P. Our results suggest a close link between the neurobiological change highlighted in pups' brain and the different behavioural disturbances observed during postnatal development period until young adult stage.

Predominant role of peripheral catecholamines in the stress-induced modulation of CYP1A2 inducibility by benzo(alpha)pyrene

The potential involvement of catecholamines and in particular of alpha(2)-adrenoceptor-related signalling pathways, in the regulation of drug-metabolizing enzymes by stress was investigated in Wistar rats after exposure to the environmental pollutant benzo(alpha)pyrene. For this purpose, total cytochrome P450 content, the CYP1A2 mRNA levels, 7-methoxyresorufin-O-dealkylase (MROD), 7-pentoxyresorufin-O-dealkylase (PROD) and p-nitrophenol hydroxylase activity levels were determined in the livers of rats exposed to repeated restraint stress after treatment with benzo(alpha)pyrene coupled with pharmacological manipulations of peripheral and/or central catecholamines and alpha(2)-adrenoceptors. The data show that stress is a significant factor in the regulation of CYP1A2 induction and that catecholamines play a central role in the stress-mediated modulation of hepatic CYP1A2 inducibility by benzo(alpha)pyrene. The up-regulating effect of stress on benzo(alpha)pyrene-induced CYP1A2 gene expression was eliminated after a generalized catecholamine depletion with reserpine. Similarly, in a state where only peripheral catecholamines were depleted and central catecholamines remained intact after guanethidine administration, the up-regulating effect of stress was eliminated. It is apparent that stress up-regulates the induction of CYP1A2 by benzo(alpha)pyrene mainly via peripheral catecholamines, while central catecholamines hold a minor role in the regulation. Pharmacological manipulations of alpha(2)-adrenoceptors appear to interfere with the effect of stress on the regulation of CYP1A2 inducibility. Either blockade or stimulation of alpha(2)-adrenoceptors with atipamezole and dexmedetomidine respectively, eliminated the up-regulating effect of stress on CYP1A2 benzo(alpha)pyrene-induced expression, while it enhanced MROD activity. In contrast, stress and pharmacological manipulations of catecholamines and alpha(2)-adrenoceptors did not affect total P450 content, the CYP2B1/2-dependent PROD and the CYP2E1-dependent p-nitrophenol hydroxylase activities. In conclusion, stress is a significant factor in the regulation of the CYP1A2 inducibility by benzo(alpha)pyrene, which in turn is involved in the metabolism of a large spectrum of toxicants, drugs and carcinogenic agents. Although the mechanism underlying the stress effect on CYP1A2 induction has not been clearly elucidated, it appears that peripheral catecholamines hold a predominant role, while central catecholamines and in particular, central noradrenergic pathways hold a minor role.

D2-receptor-linked signaling pathways regulate the expression of hepatic CYP2E1

This study investigated the role of catecholamine-related signaling pathways in the regulation of hepatic cytochrome P450 (CYP2E1). Central and peripheral catecholamine depletion with reserpine down-regulated CYP2E1. On the other hand, selective peripheral catecholamine depletion with guanethidine increased CYP2E1 apoprotein levels. Enrichment of peripheral catecholamines with adrenaline suppressed p-nitrophenol hydroxylase activity (PNP). PNP activity was also markedly suppressed by l-DOPA. Stimulation of D(2)-receptors with bromocriptine up-regulated CYP2E1, as assessed by enzyme activity and protein levels, whereas blockade of D(2)-dopaminergic receptors with sulpiride down-regulated this isozyme. These findings indicate that central and peripheral catecholamines have different effects on CYP2E1. Central catecholamines appear related to the up-regulation, whereas the role of peripheral catecholamines is clearly related to the type and location of adrenoceptors involved. D(2)-receptor-linked signaling pathways have an up-regulating effect on CYP2E1, while D(1)-receptor pathways may down-regulate this isozyme. It is worth noting that the widespread environmental pollutant benzo(alpha)pyrene (B(alpha)P) altered the modulating effect of catecholaminergic systems on CYP2E1 regulation. In particular, whereas stimulation or blockade of adrenoceptors had no effect on constitutive PNP activity, exposure to B(alpha)P modified the impact of central and peripheral catecholamines and alpha(2)-adrenoceptors on CYP2E1 expression. It appears that under the influence of B(alpha)P, alpha(2)-adrenergic receptor-linked signaling pathways increased CYP2E1 apoprotein levels. Given that a wide range of xenobiotics and clinically used drugs are activated by CYP2E1 to toxic metabolites, including the production of reactive oxygen species (ROS), it is possible that therapies challenging dopaminergic receptor- and/or alpha(2)-adrenoceptor-linked signaling pathways may alter the expression of CYP2E1, thus affecting the progress and development of several pathologies.

Benzo(a)pyrene-induced acute neurotoxicity in the F-344 rat: role of oxidative stress

Given the link between neurotoxicity and exposure to pollutants, the potential behavioral neurotoxicity of benzo(a)pyrene [B(a)P] was investigated. Studies have established that B(a)P requires metabolic activation to highly reactive species to elicit many of its adverse effects. This study investigated the perturbation of nervous system function by correlating behavioral changes with the metabolism of B(a)P, antioxidant enzyme levels and lipid peroxidation in selected brain regions. The neurobehavioral effects of single oral doses of B(a)P (25-200 mg kg(-1) body weight) on motor activity were examined in male F-344 rats at 2, 4, 6, 12, 24, 48, 72 and 96 h post treatment. Parent B(a)P and metabolites were measured at the above mentioned time points by reverse phase HPLC. The activity of several antioxidant enzymes (superoxide dismutase, catalase and glutathione peroxidase) and levels of malondialdehyde were determined at 6 and 96 h in both the striatum and hippocampus of B(a)P exposed rats. Suppression of motor activity (up to 70%) reached a maximum at 6 h, but was reversible at 96 h in all dose groups. The kinetics of disposition data show a strong link between B(a)P metabolism and the onset and duration of behavioral effects. Benzo(a)pyrene caused a 15-70% inhibition in the activity of superoxide dismutase and glutathione peroxidase and an enhancement in catalase and lipid peroxidation (up to 68%) in the striatum and hippocampus at 6 and 96 h post treatment, respectively. These findings suggest that B(a)P-induced acute neurobehavioral toxicity may occur through oxidative stress due to inhibition of the brain antioxidant scavenging system.

Modification of inherent and drug-induced dopaminergic activity after exposure to benzo(alpha)pyrene

The aim of this study was to investigate the effect of benzo(alpha)pyrene (B(alpha)P), a representative polycyclic aromatic hydrocarbon (PAH), on dopaminergic activity in brain. (B(alpha)P) altered dopaminergic activity in discrete regions of the rat brain, including the hippocampus, hypothalamus, caudate putamen and nucleus accumbens. Specifically, B(alpha)P increased DA levels in the hippocampus and DA turnover in the caudate putamen. In addition, B(alpha)P suppressed DA levels in the caudate putamen and DA turnover in the nucleus accumbens. B(alpha)P also altered the effect of several dopaminergic agents, L-DOPA, sulpiride and bromocriptine, on DA activity. In particular, B(alpha)P enhanced the L-DOPA-induced increase in the DA turnover ratio in the caudate putamen and increased DA levels in the nucleus accumbens. B(alpha)P also reversed the sulpiride-induced increase of DA turnover in the nucleus accumbens and the bromocriptine-induced increase of DA turnover in the hippocampus. In addition, DA turnover was increased by B(alpha)P in the nucleus accumbens and caudate putamen and DA levels were suppressed in the nucleus accumbens of bromocriptine treated rats, though the drug alone had no effect. These changes indicate that exposure to B(alpha)P and related compounds may affect dopaminergic function in discrete brain regions that are implicated in cognitive functions, psychosis, depression and Parkinson's disease, and may possibly interfere with their pharmacological intervention.

Role of adrenoceptor-linked signaling pathways in the regulation of CYP1A1 gene expression

Alpha2-adrenoceptor agents as well as stress affect the activity of several hepatic monoxygenases including those related to CYP1A enzymes. This study was therefore designed to assess the role of central and/or peripheral catecholamines and, in particular, of adrenoceptors in the regulation of B(alpha)P-induced cytochrome CYP1A1 expression. In order to discriminate the role of central from that of peripheral catecholamines in the regulation of CYP1A1 induction, the effect of central and peripheral catecholamine depletion using reserpine versus only peripheral catecholamine depletion using guanethidine was assessed. By using selected agonists and antagonists, the role of alpha and beta-adrenoceptors in the regulation of CYP1A1 induction was evaluated. The results showed that the central catecholaminergic system has a negative regulatory effect on 7-ethoxyresorufin O-deethylase (EROD) inducibility by benzo(alpha)pyrene (B(alpha)P), and that this may be mediated via alpha1-, alpha2- and beta-adrenoceptors. Specifically, stimulation of alpha2-adrenoceptors with dexmedetomidine and blockade of alpha1- or beta-adrenoceptors with prazosin or propranolol respectively, resulted in a further increase of EROD inducibility. Adrenoceptors were found to be involved in the regulation of the CYP1A1 gene at mRNA level. Both, reduced noradrenaline release in central nervous system induced with dexmedetomidine and central catecholamine depletion, as well as blockade of central alpha1-adrenoceptors induced with prazosin, all were associated with up-regulation of CYP1A1 expression. In contrast, stimulation of central beta-adrenoceptors with isoprenaline resulted in a down-regulation of CYP1A1 expression. Our observations indicate that drugs, which stimulate or block adrenoceptors and catecholamine release may lead to complications in drug therapy and modulate the toxicity or carcinogenicity of drugs that are substrates for the CYP1A1.

Stress-mediated modulation of B(α)P-induced hepatic CYP1A1: role of catecholamines

The present study investigated the involvement of catecholamines in stress-mediated alterations in CYP1A1 induction by benzo(alpha)pyrene (B(alpha)P) in Wistar rats. This was achieved by measuring EROD activity and CYP1A1 mRNA levels in liver tissue from rats exposed to restraint stress and B(alpha)P coupled with pharmacological modulation of peripheral and central catecholamine levels and different adrenoceptors. In a state of reserpine-induced central and peripheral catecholamine depletion, stress strongly suppressed EROD induction. Peripheral catecholamines do not appear to play a critical role in the stress-mediated modulation of EROD inducibility by B(alpha)P. Stress did not alter EROD inducibility by B(alpha)P when peripheral catecholamines were either depleted by guanethidine or supplemented by peripheral adrenaline administration. On the other hand, central noradrenergic systems appear to have a role in the stress-mediated changes in B(alpha)P-induced EROD activity and Cyp1A1 gene expression. Stimulation or blockade of noradrenaline release with atipamezole and dexmedetomidine, respectively, significantly modified the up-regulating effect of stress. Alpha1 adrenoceptors also appear to participate in the effect of stress on EROD inducibility. Alpha1-blockade with prazosin potentiated the up-regulating effect of stress, possibly preventing the down-regulating effect of noradrenaline. Beta adrenoceptors also seem to be involved directly or indirectly in the stress-mediated modulation of Cyp1A1, as propranolol (beta-antagonist) blocked the down-regulating effect of stress on B(alpha)P-induced Cyp1A1 gene expression. Plasma corticosterone alterations after stress were not related to alterations in the B(alpha)P-induced EROD activity and Cyp1A1 gene expression. In conclusion, stress appears to interfere in the regulation of B(alpha)P-induced hepatic CYP1A1 in an unpredictable manner and via signalling pathways not always directly related to catecholamines. In particular, whenever drug treatment disrupts noradrenergic neurotransmission, other stress-stimulated factors appear to modify the induction of CYP1A1. In summary, regulation of induction of hepatic CYP1A1 during stress appears to involve various components of the stress system, including central and peripheral catecholamines, which interact in a complex manner, yet to be elucidated.

Assessment of metabolites and AhR and CYP1A1 mRNA expression subsequent to prenatal exposure to inhaled benzo(a)pyrene

Few studies have focused on environmental aerosol contaminant, mechanistically-based, dose-related neurotoxicity with respect to development of the central nervous system. To fill this important data gap and to highlight possible mechanistic pathways, a study was undertaken to determine metabolite concentrations associated with the transplacental disposition of inhaled benzo(a)pyrene (B(a)P) and the resulting effects on the status of aryl hydrocarbon receptor (AhR), and cytochrome P450 1A1 (CYP1A1) mRNA in preweaning F1 generation animals. In this study, laparotomy on GD 8 was performed on timed-pregnant rats followed by dosing via nose-only exposure for 4h a day for 10 days (GD 11-GD 20) to three concentrations of a B(a)P: carbon black aerosol (25, 75 and 100 microg/m(3)). A dose-dependent decrease in birth index was observed in the B(a)P exposed group as compared to the controls (P<0.05). Analysis of cerebrocortical extracts from F1 generation pups revealed a dose-dependent (P<0.05) increase in total B(a)P metabolites. Analysis of cerebrocortical and hippocampal mRNA developmental expression profiles for AhR and CYP1A1 using 18sRNA as the internal standard, revealed that inhaled B(a)P upregulates AhR during the first postnatal month. The present study suggest that prenatal exposure to inhaled B(a)P upregulates hepatic aryl hydrocarbon receptor dependent mechanisms in the F1 generation. Hepatic upregulation of the aryl hydrocarbon receptor may modulate the potential for benzo(a)pyrene toxicity via the activation of cytochrome P450 and the subsequent deposition of lipophillic metabolites to developing central nervous system structures such as cerebral cortex and hippocampus.

Fluoranthene-induced neurobehavioral toxicity in F-344 rats

Fluroanthene (FLA) is a nonalternant representative of polycyclic aromatic hydrocarbon (PAH) family of toxic chemicals that are widely distributed in the environment. The effects of single acute doses of FLA on locomotor activities and the functional observational battery (FOB) were investigated in 8-week-old male and female F-344 rats. FLA was dissolved in peanut oil and administered by oral gavage as single doses of 0, 100, 200 and 400 mg/kg. Immediately after dosing, animals were placed in activity cages and monitored for nocturnal locomotor activities at 2-hour intervals and for a total of 12 hours for 5 consecutive days post treatment. Significant (p <.001) reductions in horizontal activity, total distance, stereotypy, and vertical activity were observed. Rats administered acute doses of FLA were also subjected to the functional observational battery (FOB) tests that were conducted at 0, 2, 4, 6, 12, 24, 48, 72 and 96 hours after FLA administration. FLA-exposed animals showed significant (p <.05) dysfunction, including ataxia, decreased grip strengths, increased landing foot splay, loss of aerial righting, increased urination and defecation, and decreased responses to sensory stimuli in both sexes. Neurological deficits in the FOB peaked at 6 hours and lasted for 48 hours post treatment. Significant (p <.05) gender-related differences were noted in behavioral end points, with male rats showing greater sensitivity to FLA administration than females, as evidenced by their greater mean severity scores in FOB parameters and lower motor activity counts. These findings suggest that FLA can produce behavioral toxicity in F-344 rats and that motor activity and the FOB may serve as end points for the detection of acute FLA toxicity.

Modulation of neurotoxic behavior in F-344 rats by temporal disposition of benzo(a)pyrene

The behavioral changes caused by benzo(a)pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH) compound, were monitored, and also its metabolite levels in cerebellum and cortex were measured in BaP treated rats to see if any relationship existed between these two aspects. Rats were administered 0, 25, 50, 100, and 200 mg/kg of BaP in peanut oil by oral gavage. Plasma, and brain tissue (cerebellum and cortex) samples were collected at 0, 2, 4, 6, 12, 24, 48, 72 and 96 h post administration. Neurotoxic effects peaked at 2 h after dosing and lasted 48 h after dosing for all dose groups. The metabolite levels remained the same from 2 to 4 h, reached a peak at 6 h post gavage and showed a gradual decline returning to baseline levels at 72 h when the motor activity of treatment groups also returned to control levels, indicating recovery from the effects of BaP. A significant (P<0.05) correlation between neurotoxic effects and BaP plasma, and brain metabolite concentrations suggests that metabolism plays an important role in modulating the neurobehavioral effects of BaP.

Behavioral effects induced by acute exposure to benzo(a)pyrene in F-344 rats

Polycyclic aromatic hydrocarbons (PAHs) are highly persistent environmental pollutants which pose potential adverse effects on human health. Benzo(a)-pyrene (B(a)P) is the prototypical representative of these widely dispersed lipophylic contaminants. (B(a)P) exposure in experimental animals results in an array of tissue- and organ-specific responses including carcinogenicity, teratogenicity, reproductive and immunotoxicity. However, no previous studies have examined the potential neurobehavioral toxicity of B(a)P in vivo. The present study was conducted to investigate the behavioral effects induced by single oral doses of (B(a)P) in 8-week-old male and female F-344 rats. Rats were exposed to 0, 12.5, 25, 50, 100 and 200 mg/kg of B(a)P by oral gavage. Motor activity measurements and the functional observational battery (FOB) were used to assess behavioral changes induced by B(a)P at 2, 4, 6, 8, 10, 12, 24, 48, 72 and 96 h post treatment. Statistical analyses revealed significant (p <0.001) dose, sex and time interactions. (B(a)P) doses ranging from 25 to 200 mg/kg produced a significant suppression (up to 60%) in four motor activity parameters: horizontal activity, total distance, stereotype and vertical activity in both sexes within 2 and 4h of dosing. B(a)P treated male and female animals also showed significant (p <0.001) changes in neuromuscular, autonomic, sensorimotor and physiological functions within 2 and 4h post B(a)P administration except in the 12.5 mg/kg treatment group. The 12.5 mg/kg dose did not produce significant (p > 0.05) behavioral toxicity in either males or females. All treated animals (25-200 mg/kg) recovered from the toxic effects of B(a)P by 72 h. Significant (p < 0.05) gender differences were noted in FOB test measures with males displaying greater sensitivity to B(a)P. These data suggest that motor activity and FOB measurements can be used as indices to detect B(a)P neurotoxicity.

Stress modulates the enzymatic inducibility by benzo[alpha]pyrene in the rat liver

The role of stress on the inducibility by benzo[alpha]pyrene (B[alpha]P), a representative polycyclic aromatic hydrocarbon, of several drug-metabolizing enzymes was investigated in rats, using restraint stress and mild unpredictable stress as models of psychological stress. Restraint stress was found to significantly suppress basal ethoxyresorufin 7-dealkylase (EROD) and pentoxyresorufin 7-dealkylase (PROD) activities (two-fold). In contrast, mild unpredictable stress markedly increased basal EROD activity, while PROD activity was not affected. In addition, both types of stress resulted in a significant reduction of basal p -nitrophenol hydroxylation (PNP). It is worth noting that restraint stress greatly enhanced the inducibility of EROD, methoxyresorufin 7-dealkylase (MROD) and to a lesser extent PROD activities by B[alpha]P, while mild unpredictable stress had no, or only a mild effect on the inducibility of cytochrome P450s (CYPs) by B[alpha]P. In conclusion, psychological stress may modulate different enzymatic systems which are vital elements of the detoxification mechanisms of the body. The two distinct types of psychological stress used in this study appear to affect the enzymatic systems under investigation in a stress-specific manner at the basal level and at the induced state by B[alpha]P.

Modulation in the developmental expression profile of Sp1 subsequent to transplacental exposure of fetal rats to desorbed benzo[a]pyrene following maternal inhalation

Any alteration of the critical sequence of genes that are required to coordinate the differentiation of cells, the promotion of migration, dendritic arborization, synapse formation, and myelination in the developing nervous system would be expected to have deleterious consequences. The focus of this article is a molecular evaluation of the neurotoxicological effects that result subsequent to the transplacental exposure of fetal rats to desorbed benzo(a)pyrene (BaP) following maternal inhalation. A state-of-the-art, newly designed, fabricated, and tested model aerosol generation system was utilized in these studies. Timed-pregnant Sprague Dawley rats were exposed for 4 h on gestation day 15 of a 21-day gestation period to an acute dose of BaP:carbon black aerosol (100 microg/m(3)). Controls received carbon black only. Nominal and chamber concentrations of the particulate aerosol were determined gravimetrically with a seven-stage cascade impactor. The aerosol exhibited a trimodal distribution with 95% cumulative mass less than 15.85 microm, 90% cumulative mass less than 10 microm, 67. 5% cumulative mass less than 2.5 microm and 66.2% cumulative mass less than 1.0 microm. Time-course bioavailability results indicated that greater than 95% of the parent compound is cleared from blood 240 min postexposure. An Sp1 transcription factor consensus sequence was examined by electrophoretic mobility shift analysis of nuclear extracts from various brain regions of resulting pups on postnatal days 3, 5, 7, 10, and 15. It revealed perturbations in the developmental expression profile of Sp1 abundance as a result of nose-only particulate aerosol exposure to the timed-pregnant dam. The data obtained on the temporal and spatial regulation of gene expression in the brain indicate that (1) Sp1 DNA-binding is developmentally regulated and expressed very highly in actively developing brain regions, and (2) a consequence of the transplacental deposition of desorbed BaP to the fetus is in utero neurotoxicity.

Noradrenaline, dopamine, serotonin: different effects of psychological stress on brain biogenic amines in mice and rats

The effect of restraint stress on central neurotransmission was evaluated in mice and rats. Noradrenaline (NA), dopamine (DA) and serotonin (5-HT) levels and their primary metabolites were measured in discrete brain regions following exposure to stress. Mice and rats demonstrated a similar response to stress in some brain regions. Both species responded to stress with lower NA and 5-HT in the locus coeruleus compared to non-stressed controls. Dopaminergic activity, assessed by DA turnover, was elevated in the hypothalamus. While DA turnover was suppressed in the amygdala, 5-HT turnover was similarly elevated in both species. In most cases, however, there were differences in biogenic neurotransmission between mice and rats in response to stress. In particular, NA levels were suppressed by stress in the dorsal cortex of mice, but in the rats NA levels were decreased in the hypothalamus. While stress produced lower DA levels in the hypothalamus, DA levels demonstrated a marked increase in the amygdala of mice. Stress was also associated with a decrease in DA levels in the rat striatum and with an increase of DA turnover in the locus coeruleus of mice. On the other hand, 5-HT was suppressed in the mouse striatum and in the rat hypothalamus and amygdala, while 5-HT turnover was markedly decreased in the hippocampus and dorsal cortex of rats alone. In conclusion, the changes in the central neurotransmission which are evoked by stress appear to be species-specific in most cases, a fact which may trigger discrete alterations in homeostatic mechanisms.