Polychlorinated biphenyls induced oxidative stress mediated neurodegeneration in hippocampus and behavioral changes of adult rats: Anxiolytic-like effects of quercetin

The protective effect of arbutin against potassium bromate-induced oxidative damage in the rat brain

This study aimed to investigate the protective effects of arbutin (ARB) against brain injury induced in rats with potassium bromate (KBrO₃ ). The rats were divided into four groups as Group 1: Control (0.9% NaCl ml/kg/day p.), Group 2: KBrO₃ (100 mg/kg (gavage), Group 3: ARB (50 mg/kg/day p.), and Group 4: KBrO₃  + ARB (100 mg/kg (gavage) + 50 mg/kg/day p.). At the end of the fifth day of the study, the rats in all groups were killed, and their brain tissues were collected. In the collected brain tissues, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels were measured, and routine histopathological examinations were made. The MDA levels in the group that was exposed to KBrO₃ were significantly higher than those in the control group (p ˂ 0.001). In comparison to the KBrO₃ group, the MDA levels in the KBrO₃  + ARB group were significantly lower (p ˂ 0.001). It was observed that SOD and CAT enzyme activity levels were significantly lower in the KBrO₃ group compared to the control group (p ˂ 0.001), while these levels were significantly higher in the KBrO₃  + ARB group than in the KBrO₃ group (p ˂ 0.001). Additionally, the group that was subjected to KBrO₃ toxicity, as well as ARB administration, had much lower levels of histopathologic signs than the group that was subjected to KBrO₃ toxicity only. Consequently, it was found that KBrO₃ exposure led to injury in the brain tissues of the rats, and using ARB was effective in preventing this injury.

Determination of six thyroid hormones in dog brain and liver using acidic extraction, mixed-mode cleanup, and liquid chromatography-tandem mass spectrometry

Thyroid hormones (THs) play a critical role in the regulation of biological processes, such as growth, metabolism, and development, in various animal species. Prohormone L-thyroxine (T4) is secreted from the thyroid gland and carried to peripheral tissues. T4 is then biotransformed to several metabolites which play different roles, mainly by iodothyronine deiodinases. Determination of deiodinated TH metabolites in key organs such as liver and brain would help to understand tissue-specific TH metabolism and homeostasis. In this study, we thus developed a highly sensitive method for the determination of six THs [T4, 3,5,3'-triodo-L-thyronine (T3), 3,3',5'-triiodo-L-thyronine (rT3), 3,5-diiodo-l-thyronine (3,5-T2), 3,3'-diiodo-l-thyronine (3,3'-T2), and 3-iodo-l-thyronine (3-T1)] in the brain and liver by using stored dog samples. The analytical method consisted of ultrasonic-assisted extraction in acetone acidified with formic acid, cleanup with a EVOLUTE® EXPRESS CX cartridge (reversed-phase combined with strong cation-exchange cartridge), and quantification with liquid chromatography-tandem mass spectrometry. Acceptable accuracy (internal standard-corrected recovery: 80%-120%) and intra- and inter-day precision (coefficient of variation: <6% and <15%, respectively) (n = 3/ batch, three days) were obtained for both brain and liver samples. In addition, low method detection limits were achieved for both brain (0.013-0.12 ng g^-1) and liver (0.030-0.78 ng g^-1), which resulted in the quantitation of not only T4, T3, and rT3, but also 3,3'-T2 in both dog brain and liver samples. The developed method was successfully applied to the analysis of THs in the brain and liver of dogs (Canis lupus familiaris) which were exposed to polychlorinated biphenyls (PCBs). As a result, concentration ratios of rT3/T4 and 3,3'-T2/T3 in the PCB-exposed dogs were significantly higher than those in the control groups, suggesting the enhanced inner (tyrosyl)-ring deiodination (5-deiodination) by PCB exposure. The analytical method developed in the present study enables comprehensive evaluation of alterations in peripheral TH metabolism which are caused by exposure to environmental pollutants.

Quercetin and/or Ascorbic Acid Modulatory Effect on Phenobarbital-Induced Sleeping Mice Possibly through GABAA and GABAB Receptor Interaction Pathway

Depressive disorder is a recurrent illness that affects large numbers of the general population worldwide. In recent years, the goal of depression treatment has moved from symptomatic response to that of full remission. However, treatment-resistant depression is a major challenge in the treatment of depression or depression-related disorders. Consensus opinion, therefore, suggests that effective combined aggressive initial treatment is the most appropriate strategy. This study aimed to evaluate the effects of quercetin (QUR) and/or ascorbic acid (AA) on Phenobarbital-induced sleeping mice. QUR (50 mg/kg) and/or AA (25 mg/kg) with or without intraperitoneally pre-treated with GABA receptor agonist (diazepam: 2 mg/kg, i.p.) or antagonist (Flumazenil: 2.5 mg/kg, i.p.) to underscore the effects, as well as the possible involvement of the GABA receptor in the modulatory action of QUR and AA in sleeping mice. Additionally, an in silico study was undertaken to predict the involvement of GABA receptors in the sleep mechanism. Findings suggest that the pretreatment of QUR and AA modulated the onset and duration of action of the standard drugs in experimental animals. The acute administration of QUR and/or AA significantly (p < 0.05) reversed the DZP-mediated onset of action and slightly reversed the duration of sleep time in comparison to the vehicle (control) group. A further combination of QUR or AA with the FLU resulted in an enhancement of the onset of action while reducing the duration of action, suggesting a FLU-like effect on the test animals. In in silico studies, AA and QUR showed good to moderate binding affinities with GABA_A and GABA_B receptors. Both QUR and AA produced a stimulatory-like effect on mice, possibly through the GABA_A and GABA_B receptor interaction pathways. Further studies are necessary to verify this activity and clarify the exact mechanism of action(s) involved.

Quercetin: A Bioactive Compound Imparting Cardiovascular and Neuroprotective Benefits: Scope for Exploring Fresh Produce, Their Wastes, and By-Products

Quercetin, a bioactive secondary metabolite, holds incredible importance in terms of bioactivities, which has been proved by in vivo and in vitro studies. The treatment of cardiovascular and neurological diseases by quercetin has been extensively investigated over the past decade. Quercetin is present naturally in appreciable amounts in fresh produce (fruits and vegetables). However, today, corresponding to the growing population and global demand for fresh fruits and vegetables, a paradigm shift and focus is laid towards exploring industrial food wastes and/or byproducts as a new resource to obtain bioactive compounds such as quercetin. Based on the available research reports over the last decade, quercetin has been suggested as a reliable therapeutic candidate for either treating or alleviating health issues, mainly those of cardiovascular and neurological diseases. In the present review, we have summarized some of the critical findings and hypotheses of quercetin from the available databases foreseeing its future use as a potential therapeutic agent to treat cardiovascular and neurological diseases. It is anticipated that this review will be a potential reference material for future research activities to be undertaken on quercetin obtained from fresh produce as well as their respective processing wastes/byproducts that rely on the circular concept.

Altered functional activations of prefrontal brain areas during emotional processing of fear in Inuit adolescents exposed to environmental contaminants

Exposure to mercury, lead and polychlorinated biphenyls (PCBs) have been associated with emotional dysregulation, but their neuronal correlates have yet to be examined. Inuit from Nunavik (Northern Quebec, Canada) face internalizing problems and are among the most exposed individuals to these environmental contaminants in the world. The aim of this study was to examine the link between pre- and postnatal exposure to these contaminants and brain fear-circuitry in Inuit adolescents. Facial expression stimuli were presented to participants (mean age = 18.3 years) in a magnetic resonance imaging (MRI) scanner. Fear conditioning and extinction tasks included neutral faces as the conditioned threat and safety cues and a fearful face paired with a shrieking scream as the unconditioned stimulus. Functional MRI data were gathered at the conditioning phase (n = 71) and at the extinction phase (n = 62). Mercury, lead and PCB 153 concentrations were measured in blood samples at birth (cord blood) and at the time of the adolescent testing to estimate pre- and postnatal exposure, respectively. For each time point, exposures were categorized in tertiles (low, moderate and high exposed groups). Mixed analyses of variance were conducted for each contaminant of interest controlling for sex, age, socioeconomic status, drug/alcohol use, food insecurity and contaminant co-exposure. Results revealed greater differential activation during the conditioning phase in the right orbitofrontal cortex in participants with moderate and high concentrations of cord blood PCB 153 compared to those in the low exposure group. During the extinction phase, the high prenatal mercury exposed group showed a lower differential activation in the right and left anterior cingulate cortex compared to those in the low-exposed group; whereas there was a higher differential activation in right dorsolateral prefrontal cortex in the high postnatal lead exposed group compared to the moderate- and low-exposed groups. Our study is the first to show alterations in the prefrontal brain areas in fear conditioning and extinction tasks in relation to environmental contaminant exposures. The observed brain correlates may advance our understanding of the emotional problems associated with environmental chemical toxicity.

Comprehensive Subchronic Inhalation Toxicity Assessment of an Indoor School Air Mixture of PCBs

Few in vivo inhalation studies have explored the toxicity of environmentally relevant mixtures of polychlorinated biphenyls (PCBs). The manufacture of industrial PCBs was banned in 1978, but PCBs continue to be formed in industrial and consumer products. Schools represent a significant source of airborne exposures to legacy and nonlegacy PCBs, placing children at risk. To evaluate the impact of these exposures, we generated an airborne mixture of PCBs, called the School Air Mixture (SAM), to match the profile of an older school from our adolescent cohort study. Female Sprague-Dawley rats were exposed either to SAM or filtered air in nose-only exposure systems, 4 h/day for 4 weeks. Congener-specific air and tissue PCB profiles were assessed using gas chromatography with tandem mass spectrometry (GC-MS/MS). PCB exposures recapitulated the target school air profile with a similarity coefficient, cos θ of 0.83. PCB inhalation yielded μg/g ∑209 PCB levels in tissues. Neurobehavioral testing demonstrated a modest effect on spatial learning and memory in SAM-exposed rats. PCB exposure induced oxidative stress in the liver and lungs, affected the maturational stages of hematopoietic stem cells, reduced telomerase activity in bone marrow cells, and altered the gut microbiota. This is the first study to emulate PCB exposures in a school and comprehensively evaluate toxicity.

Quercetin affects shoaling and anxiety behaviors in zebrafish: Involvement of neuroinflammation and neuron apoptosis

Quercetin, a potential fish food supplement, has been reported to process many beneficial properties. However, some negative effects of quercetin have been observed, which pointed out necessity for additional studies to evaluate its safety. Therefore, the present study investigated effects of quercetin (0.01, 0.1, 1, 10, 100 and 1000 μg/L) on shoaling and anxiety behaviors through novel tank tests in zebrafish (Danio rerio). Furthermore, oxidative stress, neuroinflammation and apoptosis in the brains were examined to learn more about mechanisms of action related to quercetin. The results showed that quercetin at the lower concentrations exerted beneficial effects on shoaling and anxiety behaviors. On the contrary, when quercetin was up to 1000 μg/L, it exerted detrimental effects shown as decreases of movement and increases of anxiety behaviors. Generally, U-shaped responses of antioxidant enzyme activities (superoxide dismutase and catalase), and inversed U-shaped responses of inflammatory mediators (cyclooxygenase-2) and cytokines (interleukin-1β, interleukin-6, interleukin-10, and tumor necrosis factor α) to quercetin treatment were found in the brains. In addition, quercetin at the lower concentrations attenuated cell apoptosis, while even more apoptosis was found at the 1000 μg/L quercetin group. In conclusion, quercetin could exert beneficial or detrimental effects on the shoaling and anxiety behaviors depending on the treatment concentrations, and the underlying mechanisms are potentially associated with neuroinflammation and neuron apoptosis.

The influence of polyphenols on metabolic disorders caused by compounds released from plastics - Review

Persistent organic pollutants (POPs) released from plastics into water, soil and air are significant environmental and health problem. Continuous exposure of humans to these substances results not only from the slow biodegradation of plastics but also from their ubiquitous use as industrial materials and everyday products. Exposure to POPs may lead to neurodegenerative disorders, induce inflammation, hepatotoxicity, nephrotoxicity, insulin resistance, allergies, metabolic diseases, and carcinogenesis. This has spurred an increasing intense search for natural compounds with protective effects against the harmful components of plastics. In this paper, we discuss the current state of knowledge concerning the protective functions of polyphenols against the toxic effects of POPs: acrylonitrile, polychlorinated biphenyls, dioxins, phthalates and bisphenol A. We review in detail papers from the last two decades, analyzing POPs in terms of their sources of exposure and demonstrate how polyphenols may be used to counteract the harmful environmental effects of POPs. The protective effect of polyphenols results from their impact on the level and activity of the components of the antioxidant system, enzymes involved in the elimination of xenobiotics, and as a consequence - on the level of reactive oxygen species (ROS). Polyphenols present in daily diet may play a protective role against the harmful effects of POPs derived from plastics, and this interaction is related, among others, to the antioxidant properties of these compounds. To our knowledge, this is the first extensive review of in vitro and in vivo studies concerning the molecular mechanisms of interactions between selected environmental toxins and polyphenols.

Adolescent exposure to environmental level of PCBs (Aroclor 1254) induces non-alcoholic fatty liver disease in male mice

Polychlorinated biphenyls (PCBs) are persistent organic pollutants found in various environmental media, and there is growing evidence that PCBs may contribute to the pathogenesis of non-alcoholic fatty liver disease (NAFLD). The purposes of this study were to investigate whether environmental level of Aroclor 1254 (a commercial mixture of PCBs) exposure to adolescent male mice could induce the development of NAFLD and the mechanisms involved. Twenty-one-day-old male C57BL/6 mice were exposed to Aroclor 1254 (0.5-500 μg/kg body weight) by oral gavage once every third day for 60 days. The results showed that exposure to Aroclor 1254 increased body weight and decreased the liver-somatic index in a dose-dependent manner. Aroclor 1254 administration increased lipid accumulation in the liver and induced the mRNA expression of genes associated with lipogenesis, including acetyl-CoA carboxylase 1 (Acc1), acetyl-CoA carboxylase 2 (Acc2) and fatty acid synthase (Fasn). Moreover, Aroclor 1254 decreased peroxisome proliferator-activated receptor alpha (PPARα) signaling and lipid oxidation. In addition, we found that Aroclor 1254 administration induced oxidative stress in mouse liver and elevated the protein level of cyclooxygenase 2 (COX-2), an inflammatory molecule, possibly via the endoplasmic reticulum (ER) stress inositol-requiring enzyme 1α-X-box-binding protein-1 (IRE1α-XBP1) pathway, but not the nuclear factor-κB (NF-κB) pathway. In summary, adolescent exposure to environmental level of PCBs stimulated oxidative stress, ER stress and the inflammatory response and caused NAFLD in male mice. This work provides new insight into the idea that adolescent exposure to environmental level of PCBs might induce the development of NAFLD under the regulation of ER stress in males.

The role of the gut microbiome in mediating neurotoxic outcomes to PCB exposure

A series of complex physiological processes underlie the development of the microbiota, gut, and brain in early life, which together communicate via the microbiota-gut-brain axis to maintain health and homeostasis. Disruption of these processes can lead to dysbiosis of the microbiota, pathophysiology of the gut and behavioral deficits including depression, anxiety and cognitive deficits. Environmental exposures, particularly in early life, can interfere with development and impact these pathways. This review will focus on the role of the microbiome and the gut in neurodevelopment and neurodegeneration as well as the impacts of environmental exposures, particularly to the neurotoxicant polychlorinated biphenyls (PCBs), given that the gut serves as the primary exposure route. There exists extensive research on the importance of the microbiome in the developing brain and connections with autism spectrum disorder (ASD) and increasing links being established between the microbiome and development of Alzheimer's disease (AD) in the elderly. Finally, we will speculate on the mechanisms through which PCBs can induce dysbiosis and dysregulate physiology of the gut and brain.

Deleterious effects of perinatal exposure to potassium bromate on the development of offspring of Swiss mice

The present study aimed to investigate the impact of perinatal potassium bromate (KBrO₃) exposure on the development of sensorimotor reflexes and redox status, and on the histological architecture of the brain, liver, and kidney of newborn mice. Pregnant mice received 1-ml bottled drinking water daily by oral intubation and served as the control group. Another group of pregnant mice were supplemented orally with 200 mg/kg body weight KBrO₃ dissolved in drinking water from gestation day 5 to postnatal day 21. KBrO₃ induced a decrease in the postnatal body weight in the newborn mice. KBrO₃-exposed newborn mice showed poor performance and delayed development of the sensorimotor reflexes. Histological changes, increased lipid peroxidation, and altered antioxidants were reported in the cerebrum, cerebellum, medulla oblongata, liver, and kidney of the KBrO₃-exposed newborn mice. In conclusion, these findings demonstrated that perinatal exposure to bromate induced oxidative stress, histological and behavioral alterations, and was a potential teratogen in newborn mice.

Protection of Taurine Against PFOS-Induced Neurotoxicity in PC12 Cells

As a new member of persistent organic pollutants, the potent neurotoxicity of perfluorooctane sulfonates (PFOS) found in epidemiological studies and laboratory research has drawn increasing attention around the world. Previous studies showed that apoptosis driven by oxidative stress and autophagy were both observed in PFOS-induced toxicity. Taurine has been demonstrated to exert potent protections against oxidative stress as an efficient antioxidant. Whether taurine could protect against the PFOS neurotoxicity is not known. In the present study, PC12 cells were treated with several concentrations of PFOS (31.25, 250 μM) for 24 h. 3-(4,5-Dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay was applied to assess the cell viability. DCFH-DA detector was used to explore the production of ROS. Caspase 3 activity was used to reflect the possible apoptosis pathway. The lyso-tracker red dying was invited to evaluate the autophagy. Our data showed that taurine could significantly reverse the decreased viability and the increased ROS production in PC12 cells treated with PFOS. Moreover, the increased autophagy and apoptosis elicited by PFOS in PC12 cells could also be attenuated by taurine. Collectively, our results indicate that taurine may be an effective antioxidant in fighting against PFOS cytotoxicity and therefore could potentially serve as a preventative and therapeutic agent for environmental pollution-related toxicities.

Pesticides, polychlorinated biphenyls and polycyclic aromatic hydrocarbons in cerebrospinal fluid of amyotrophic lateral sclerosis patients: a case-control study

Neurotoxic chemicals including several pesticides have been suggested to play a role in the etiology of amyotrophic lateral sclerosis (ALS). We investigated the relation between organochlorine pesticides and their metabolites (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in the etiology of sporadic ALS, determining for the first time their levels in cerebrospinal fluid as indicator of antecedent exposure. We recruited 38 ALS patients and 38 controls referred to an Italian clinical center for ALS care, who underwent a lumbar puncture for diagnostic purposes between 1994-2013, and had 1mL of cerebrospinal fluid available for the determination of OCPs, PCBs and PAHs. Many chemicals were undetectable in both case and control CSF samples, and we found little evidence of any increased disease risk according to higher levels of exposure. Among males >60 years, we found a slight but statistically very unstable increased ALS risk with higher levels of the congener PCB 28 and the OCP metabolite p,p'-DDE. Overall, these results do not suggest an involvement of the neurotoxic chemicals investigated in this study in disease etiology, although small numbers limited the precision of our results.

Serum Polychlorinated Biphenyls Increase and Oxidative Stress Decreases with a Protein-Pacing Caloric Restriction Diet in Obese Men and Women

The purposes were to compare the effects of a: (1) 12-week P-CR weight loss (WL) diet (Phase 1) between obese men and women and; (2) 52-week modified P-CR (mP-CR) vs. heart healthy (HH) weight maintenance (WM) diet (Phase 2) on serum PCBs and oxidative stress biomarkers (thiobarbituric acid reactive substances, TBARS; total antioxidant capacity, TAC) in 40 obese participants (men, n = 21; women, n = 19). Participants received dietary counseling and monitoring of compliance. PCBs, TBARS, and TAC were assessed at weeks -1 (CON), 12 (WL), and 64 (WM). Following WL (Week 12), concomitant with reductions in TBARS (0.24 ± 0.15 vs. 0.18 ± 0.11 µM; p < 0.01), PCB serum concentrations (86.7 ± 45.6 vs. 115.6 ± 65.9 ng/g lipid; p < 0.01) and TAC (18.9 ± 2.6 vs. 19.9 ± 2.3 nmol/mL; p < 0.02) were increased similarly in men and women. At the end of WM (Week 64), a significant effect of time × group interaction was observed for % change in PCB 170 and 187; whereby mP-CR values were higher compared to HH (PCB170: 19.31% ± 26.48% vs. -6.61% ± 28.88%, p = 0.02; PCB187: -3.04% ± 17.78% vs. -21.4% ± 27.31%, p = 0.04). PCB changes were positively correlated with TBARS levels (r > 0.42, p < 0.05) and negatively correlated with body weight, fat mass, and abdominal fat (r < -0.46, p < 0.02). Our results support mobilization of stored PCBs as well as enhanced redox status following a 12-week P-CR WL diet. Additionally, a 52-week mP-CR WM diet demonstrated an advantage in preventing weight gain relapse accompanied by an increase in circulating PCBs compared to a traditional HH diet.

Lactational exposure effect of polychlorinated biphenyl on rat Sertoli cell markers and functional regulators in prepuberal and puberal F1 offspring

PURPOSE

Polychlorinated biphenyls (PCBs) are persistent and bioaccumulative environmental toxicants acting as endocrine disruptors. Many researches evidenced that PCBs affect the male reproductive system in adult rats and it can transfer from mother to offspring through milk. We investigated whether the lactational exposure to PCBs affects the Sertoli cell function in F₁ offspring.

METHODS

Dams were orally treated with different doses of PCB-Aroclor 1254 (1, 2 and 5 mg/kg bw/day, respectively) from postpartum day 1-20. Male offspring rats were killed on PND 21 and PND 60. Testes were used both for histological study and to isolate Sertoli cell. Serum and testicular interstitial fluid (TIF) levels of testosterone, ABP and estradiol were analyzed by ELISA method. The mRNA and protein expressions of follicle-stimulating hormone (FSHR), androgen-binding protein (ABP), Inhibinβ, androgen receptor (AR) and estrogen receptor (ERβ) were studied using real-time PCR and immunoblotting, respectively.

RESULTS

The testicular architecture was altered in PCB-treated groups of both prepuberal and puberal rats. Testosterone, estradiol and androgen-binding protein levels were altered in both serum and TIF in PCB treated groups. The gene expression level of FSHR, ABP, ERβ and AR was decreased in a dose-dependent manner, whereas Inhibinβ gene expression level was increased in PCB-treated groups.

CONCLUSION

Lactational exposure to PCB affects both the histoarchitecture of testis, Sertoli cell maker and functional regulators in both prepuberal and puberal F₁ male progeny.

Neurodegenerative Diseases: Might Citrus Flavonoids Play a Protective Role?

Neurodegenerative diseases (ND) result from the gradual and progressive degeneration of the structure and function of the central nervous system or the peripheral nervous system or both. They are characterized by deterioration of neurons and/or myelin sheath, disruption of sensory information transmission and loss of movement control. There is no effective treatment for ND, and the drugs currently marketed are symptom-oriented, albeit with several side effects. Within the past decades, several natural remedies have gained attention as potential neuroprotective drugs. Moreover, an increasing number of studies have suggested that dietary intake of vegetables and fruits can prevent or delay the onset of ND. These properties are mainly due to the presence of polyphenols, an important group of phytochemicals that are abundantly present in fruits, vegetables, cereals and beverages. The main class of polyphenols is flavonoids, abundant in Citrus fruits. Our review is an overview on the scientific literature concerning the neuroprotective effects of the Citrus flavonoids in the prevention or treatment of ND. This review may be used as scientific basis for the development of nutraceuticals, food supplements or complementary and alternative drugs to maintain and improve the neurophysiological status.

The protective effect of Hypericum connatum on stress-induced escape deficit in rat is related to its flavonoid content

Context Hypericum perforatum L. (Hypericaceae), used in moderate depression treatment, is active in experimental tests for antidepressant activity. For H. connatum Lam., a South American species lacking hyperforin, antidepressant effects have not been demonstrated. Objective This study evaluates the antidepressant-like effect of H. connatum in rats and identifies the components involved in this activity. Materials and methods First, the effects of acute and 14-d oral administrations of an extract derived from H. connatum aerial parts were studied using the Escape Deficit (ED) test. Next, methanol-extracted flavonoid-enriched fractions B and C and fraction-purified flavonoids (quercetin, rutin and isoquercitrin) were evaluated in the ED test after acute administration. To rule out possible confounding effects of the flavonoids, we examined nociceptive threshold using the tail-flick test and anxious behaviour using the elevated plus maze (EPM) test. Results Hypericum connatum increased reactivity of unavoidable stress-exposed rats after acute (0.5 and 1 g/kg: ED = 18.6/30 and 19.8/30, respectively) and repeated administration (0.5 g/kg twice daily: ED = 17.8/30). Protective effects were observed for fractions B and C (250 mg/kg: ED = 18.1/30 and 18.8/30, respectively), quercetin (2.5, 5 and 10 mg/kg: ED = 15.3/30, 18.3/30 and 21.6/30, respectively), rutin (5 and 10 mg/kg: ED = 15.4/30 and 13.0/30, respectively) and isoquercitrin (2.5 mg/kg: ED = 19.2/30). The flavonoids did not modify nociceptive threshold or performance in the EPM test. Discussion and conclusion Hypericum connatum showed protective activity in the ED test, a correlate of potential antidepressant-like effects that appeared to be related to the flavonoid components of this species.

Oral administration of potassium bromate induces neurobehavioral changes, alters cerebral neurotransmitters level and impairs brain tissue of swiss mice

Background

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. The present study reports the side effects of KBrO₃ administration on the brain functions and behaviour of albino mice.

Methods

Animals were divided into three groups: control, low dose KBrO₃ (100 mg/kg/day) and high dose KBrO₃ (200 mg/kg/day) groups.

Results

Administration of KBrO₃ led to a significant change in the body weight in the animals of the high dose group in the first, second and the last weeks while water consumption was not significantly changed. Neurobehavioral changes and a reduced Neurotransmitters levels were observed in both KBrO₃ groups of mice. Also, the brain level of reduced glutathione (GSH) in KBrO₃ receiving animals was decreased. Histological studies favoured these biochemical results showing extensive damage in the histological sections of brain of KBrO₃-treated animals.

Conclusions

These results show that KBrO₃ has serious damaging effects on the central nervous system and therefore, its use should be avoided.

Quercetin ameliorates polychlorinated biphenyls-induced testicular DNA damage in rats

Polychlorinated biphenyls (PCBs) are a group of environmental contaminants widely reported to cause gonadal toxicity in both humans and animals. This study investigated the amelioratory role of quercetin in PCBs-induced DNA damage in male Wistar rats. Polychlorinated biphenyls were administered intraperitoneally at a dose of 2 mg kg(-1) alone or in combination with quercetin (orally) at 50 mg kg(-1) for 25 days. Quercetin modulation of PCBs-induced gonadal toxicity was evaluated using selected oxidative stress indices, comet assay, measurement of DNA concentration and histology of the testes. Administration of PCBs alone caused a significant (P < 0.05) depletion in the total thiol level in testes of treated rats. Conversely, the levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) production were markedly elevated in testes of PCBs-treated rats compared with control. Further, PCBs exposure produced statistically significant increases in DNA tail migration, degraded double-stranded DNA (dsDNA) concentration and histological alterations of testes of the treated rats compared to control. Quercetin cotreatment significantly improved the testicular antioxidant status, decreased DNA fragmentation and restored the testicular histology, thus demonstrating the protective effect of quercetin in PCBs-treated rats.

Farnesol quells oxidative stress, reactive gliosis and inflammation during acrylamide-induced neurotoxicity: Behavioral and biochemical evidence

Acrylamide (ACR) is an industrial pollutant, to which humans are exposed through chemicals associated with day to day human life and contributes to neurological disorders. The role of reactive gliosis upon toxic insults remains paradoxical, and the immunomodulatory events during ACR intoxication remain obscure. In view of this, the present study investigated ACR-induced (20mg/kgb.wt for 4weeks) neurodegeneration in the context of oxidative stress and associated inflammatory events and the ability of farnesol, a sesquiterpene, to mitigate reactive gliosis in the brain of Swiss albino mice. Farnesol supplementation (100mg/kgb.wt.) showed a marked improvement in gait performance, neuromuscular function and fine motor coordination and attenuated ACR-induced diminution in glutathione (GSH) with parallel reduction in lipid peroxidation (LPO), protein carbonyls, hydroxide, hydroperoxide and nitrite levels. Farnesol treatment significantly ameliorated ACR-mediated histological aberrations and reactive gliosis by downregulating Glial fibrillary acidic protein (GFAP) and Ionizsed calcium-binding adapter molecule-1 ​(Iba-1) in the cortex, hippocampus and striatum. Further, ACR stimulated increase in levels of pro-inflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β) and inducible form of nitric oxide synthase (iNOS) were considerably decreased by farnesol. In conclusion, our findings indicate that farnesol exerts neuroprotective efficacy during ACR-induced neuropathology by suppressing reactive gliosis and associated inflammatory events.

Effect of Melatonin on Glutamate: BDNF Signaling in the Cerebral Cortex of Polychlorinated Biphenyls (PCBs)-Exposed Adult Male Rats

Various epidemiological survey suggests that the central nervous system is the target for many environmental contaminants. One among them is Aroclor 1254, a mixture of polychlorinated biphenyls (PCBs) which explore a spectrum of biochemical and neurotoxic responses in humans and laboratory animals. Learning and motor coordination deficits are the profound effects of PCBs which may be related to cerebral dysfunction. The aim of the study is to elicit the protective effect of melatonin (Mel), a potent, blood brain permeable antioxidant against the effect of Aroclor 1254 on the signaling of glutamate-principal excitatory neurotransmitter and brain derived neurotrophic factor (BDNF) in the cerebral cortex of adult rats which plays a key role in brain functions. Adult male Wistar rats were grouped into four and treated intraperitonealy (i.p) Group I with corn oil (Control), Group II with PCBs (2 mg/kg/bwt), Group III with PCBs + Mel (2 mg/kg/bwt + 5 mg/kg/bwt) and Group IV with Mel (5 mg/kg/bwt). The protein expression of glutamate signaling molecules and mRNA expressions of GLAST, BDNF signaling molecules were analyzed. The results suggest that simultaneous melatonin treatment significantly attenuated the NMDA receptor mediated glutamate excitotoxicity and protects the inhibition of BDNF signaling caused by PCBs exposure in cerebral cortex of adult male rats. Schematic pathway illustrating the proposed mechanism by which melatonin protects against A1254 mediated glutamate induced neurodegeneration in the cerebral cortex of adult male rats. PCBs induced neurodegeneration is caused by the overactivation of NMDAR, followed by the activation of voltage dependent calcium channels leading to the increase in intracellular Ca(2+) that stimulates calpain. Calpain inturn inhibits the PKA α and neurtrophin BDNF, its receptor and downstream signaling MAPK pathway leading to neurodegeneration. Melatonin had scavenged the ROS produced by PCBS and decreased the NMDAR expression which inturn protected the cells from neurodegeneration.

Lipid rafts regulate PCB153-induced disruption of occludin and brain endothelial barrier function through protein phosphatase 2A and matrix metalloproteinase-2

Occludin is an essential integral transmembrane protein regulating tight junction (TJ) integrity in brain endothelial cells. Phosphorylation of occludin is associated with its localization to TJ sites and incorporation into intact TJ assembly. The present study is focused on the role of lipid rafts in polychlorinated biphenyl (PCB)-induced disruption of occludin and endothelial barrier function. Exposure of human brain endothelial cells to 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) induced dephosphorylation of threonine residues of occludin and displacement of occludin from detergent-resistant membrane (DRM)/lipid raft fractions within 1h. Moreover, lipid rafts modulated the reduction of occludin level through activation of matrix metalloproteinase 2 (MMP-2) after 24h PCB153 treatment. Inhibition of protein phosphatase 2A (PP2A) activity by okadaic acid or fostriecin markedly protected against PCB153-induced displacement of occludin and increased permeability of endothelial cells. The implication of lipid rafts and PP2A signaling in these processes was further defined by co-immunoprecipitation of occludin with PP2A and caveolin-1, a marker protein of lipid rafts. Indeed, a significant MMP-2 activity was observed in lipid rafts and was increased by exposure to PCB153. The pretreatment of MMP-2 inhibitors protected against PCB153-induced loss of occludin and disruption of lipid raft structure prevented the increase of endothelial permeability. Overall, these results indicate that lipid raft-associated processes, such as PP2A and MMP-2 activation, participate in PCB153-induced disruption of occludin function in brain endothelial barrier. This study contributes to a better understanding of the mechanisms leading to brain endothelial barrier dysfunction in response to exposure to environmental pollutants, such as ortho-substituted PCBs.

Endocrine-disrupting actions of PCBs on brain development and social and reproductive behaviors

Polychlorinated biphenyls are among the most well-studied endocrine-disrupting chemicals (EDCs) for their neurobehavioral effects, especially neurodevelopment and cognitive performance. In addition, past research has demonstrated effects of PCBs on circulating hormones and associated changes in reproductive behaviors. This article will focus on recent advances that have been made in characterizing developmental PCB effects on reproductive function, broader social and affective behaviors, and the neuroendocrine mechanisms behind such changes. In general, PCBs seem to inhibit reproductive function by suppressing multiple aspects of the associated hypothalamic circuitry. Additionally, PCBs may also reduce motivation for social behaviors and induce depressive-like symptoms via overall reductions in dopaminergic and glutamatergic functions in the limbic system. However, more work with human-relevant exposure paradigms is needed to fully support these conclusions.

Current concepts in neuroendocrine disruption

In the last few years, it has become clear that a wide variety of environmental contaminants have specific effects on neuroendocrine systems in fish, amphibians, birds and mammals. While it is beyond the scope of this review to provide a comprehensive examination of all of these neuroendocrine disruptors, we will focus on select representative examples. Organochlorine pesticides bioaccumulate in neuroendocrine areas of the brain that directly regulate GnRH neurons, thereby altering the expression of genes downstream of GnRH signaling. Organochlorine pesticides can also agonize or antagonize hormone receptors, adversely affecting crosstalk between neurotransmitter systems. The impacts of polychlorinated biphenyls are varied and in many cases subtle. This is particularly true for neuroedocrine and behavioral effects of exposure. These effects impact sexual differentiation of the hypothalamic-pituitary-gonadal axis, and other neuroendocrine systems regulating the thyroid, metabolic, and stress axes and their physiological responses. Weakly estrogenic and anti-androgenic pollutants such as bisphenol A, phthalates, phytochemicals, and the fungicide vinclozolin can lead to severe and widespread neuroendocrine disruptions in discrete brain regions, including the hippocampus, amygdala, and hypothalamus, resulting in behavioral changes in a wide range of species. Behavioral features that have been shown to be affected by one or more these chemicals include cognitive deficits, heightened anxiety or anxiety-like, sociosexual, locomotor, and appetitive behaviors. Neuroactive pharmaceuticals are now widely detected in aquatic environments and water supplies through the release of wastewater treatment plant effluents. The antidepressant fluoxetine is one such pharmaceutical neuroendocrine disruptor. Fluoxetine is a selective serotonin reuptake inhibitor that can affect multiple neuroendocrine pathways and behavioral circuits, including disruptive effects on reproduction and feeding in fish. There is growing evidence for the association between environmental contaminant exposures and diseases with strong neuroendocrine components, for example decreased fecundity, neurodegeneration, and cardiac disease. It is critical to consider the timing of exposures of neuroendocrine disruptors because embryonic stages of central nervous system development are exquisitely sensitive to adverse effects. There is also evidence for epigenetic and transgenerational neuroendocrine disrupting effects of some pollutants. We must now consider the impacts of neuroendocrine disruptors on reproduction, development, growth and behaviors, and the population consequences for evolutionary change in an increasingly contaminated world. This review examines the evidence to date that various so-called neuroendocrine disruptors can induce such effects often at environmentally-relevant concentrations.