Saffron stigma extract and crocin play an important neuroprotective role in therapeutic measures against benzo[a]pyrene-induced behavioral alterations in zebrafish.

Saffron is a well-known expensive spice, which has many pharmacological properties against a variety of ailments. Saffron stigma and leaf contain apocarotenoids and bioactive phytochemicals having therapeutic potential against human disorders. Polycyclic aromatic hydrocarbons (PAHs) are one of the most common toxins in today's aquatic environment. Benzo[a]pyrene (B[a]P), a high molecular weight PAHs prototype, and reported as a potent neurotoxicant, which is profoundly contaminating the environment. The present study investigated the therapeutic efficacy of Saffron stigma extracts and crocin, on B[a]P-induced behavioral changes, altered antioxidant activities, and neurodegeneration in zebrafish. The behavioral responses monitored through the light-dark preference test and novel tank diving test suggested that B[a]P treated zebrafish group showed alteration in anxiolytic-like behavior. Animals exhibited their native behavior when treated alone with Saffron Stigma Extract (SSE) and crocin, an apocarotenoid which also reduced the altered behavior induced by B[a]P. The SSE and crocin stimulated the antioxidant activities with an accumulation of reduced glutathione and catalase enzymes, indicating a protective role against B[a]P-induced oxidative stress and behavioral deficits. The histopathological studies showed the percentage change of pyknotic cell counts in the Periventricular Gray Zone region of the Optic Tectum was 1.74 folds high in B[a]P treated animals as compared to control. Furthermore, the treatment of SSE and crocin reduced the pyknosis process induced by B[a]P-mediated neurodegeneration, possibly due to a better protective mechanism. Future studies may reveal the detailed mechanisms of action of potent SSE and crocin like bioactive compounds having neuroprotective potentials against neurodegenerative diseases.

Lactobacillus rhamnosus GG treatment potentiates ethanol-induced behavioral changes through modulation of intestinal epithelium in Danio rerio / El tratamiento con Lactobacillus rhamnosus GG potencia los cambios de comportamiento inducidos por etanol a través de la modulación del epitelio intestinal en Danio rerio

The gut-brain axis directly regulates the brain homeostatic environment; an imbalance in gut microbial composition following ethanol exposure is maleficent. In this context, involvement of probiotics as prophylactic intervention against ethanol-induced neurotoxicity is elusive in the literature. Therefore, the present study was aimed to determine the impact of chronic ethanol exposure on the neurobehavioral response of zebrafish and possible neuroprotection through co-supplementation of probiotic Lactobacillus rhamnosus GG (LGG). Zebrafish were divided into naive, control, ethanol (0.01% v/v), LGG, and ethanol co-supplemented with LGG groups. Neurobehavioral assessment was performed after 7 days of chronic waterborne exposure to ethanol with LGG co-supplementation followed by histopathological studies. The findings indicated that there was a clear alteration in locomotor activity and habitat preference, with animals preferentially migrating toward altered zones on exposure to ethanol. However, co-supplementation of LGG showed restoration against ethanol-induced neurobehavioral and cognitive dysfunction. Brain tissue pyknosis and intestinal epithelial disruption were significantly mitigated on LGG co-supplementation against ethanol in zebrafish. The present study provides a novel approach toward supplementation of probiotics such as LGG in modulation of gut commensal microbiota influencing zebrafish behavior. Moreover, the findings delineate the possible role of probiotics as a curative administration to counter ethanol-persuaded neurological outcomes.(AU)

Lactobacillus rhamnosus GG treatment potentiates ethanol-induced behavioral changes through modulation of intestinal epithelium in Danio rerio.

The gut-brain axis directly regulates the brain homeostatic environment; an imbalance in gut microbial composition following ethanol exposure is maleficent. In this context, involvement of probiotics as prophylactic intervention against ethanol-induced neurotoxicity is elusive in the literature. Therefore, the present study was aimed to determine the impact of chronic ethanol exposure on the neurobehavioral response of zebrafish and possible neuroprotection through co-supplementation of probiotic Lactobacillus rhamnosus GG (LGG). Zebrafish were divided into naive, control, ethanol (0.01% v/v), LGG, and ethanol co-supplemented with LGG groups. Neurobehavioral assessment was performed after 7 days of chronic waterborne exposure to ethanol with LGG co-supplementation followed by histopathological studies. The findings indicated that there was a clear alteration in locomotor activity and habitat preference, with animals preferentially migrating toward altered zones on exposure to ethanol. However, co-supplementation of LGG showed restoration against ethanol-induced neurobehavioral and cognitive dysfunction. Brain tissue pyknosis and intestinal epithelial disruption were significantly mitigated on LGG co-supplementation against ethanol in zebrafish. The present study provides a novel approach toward supplementation of probiotics such as LGG in modulation of gut commensal microbiota influencing zebrafish behavior. Moreover, the findings delineate the possible role of probiotics as a curative administration to counter ethanol-persuaded neurological outcomes.

In silico discovery and evaluation of phytochemicals binding mechanism against human catechol-O-methyltransferase as a putative bioenhancer of L-DOPA therapy in Parkinson disease.

Levodopa (L-DOPA) therapy is normally practised to treat motor pattern associated with Parkinson disease (PD). Additionally, several inhibitory drugs such as Entacapone and Opicapone are also cosupplemented to protect peripheral inactivation of exogenous L-DOPA (~80%) that occurs due to metabolic activity of the enzyme catechol-O-methyltransferase (COMT). Although, both Entacapone and Opicapone have U.S. Food and Drug Administration approval but regular use of these drugs is associated with high risk of side effects. Thus, authors have focused on in silico discovery of phytochemicals and evaluation of their effectiveness against human soluble COMT using virtual screening, molecular docking, drug-like property prediction, generation of pharmacophoric property, and molecular dynamics simulation. Overall, study proposed, nine phytochemicals (withaphysalin D, withaphysalin N, withaferin A, withacnistin, withaphysalin C, withaphysalin O, withanolide B, withasomnine, and withaphysalin F) of plant Withania somnifera have strong binding efficiency against human COMT in comparison to both of the drugs i.e., Opicapone and Entacapone, thus may be used as putative bioenhancer in L-DOPA therapy. The present study needs further experimental validation to be used as an adjuvant in PD treatment.

Benzo[a]pyrene exposure and overcrowding stress impacts anxiety-like behavior and impairs learning and memory in adult zebrafish, Danio rerio.

Benzo[a]pyrene (B[a]P), a prototype of polycyclic aromatic hydrocarbons and ubiquitous environmental pollutant, alters neurobehavioral responses in aquatic organisms like zebrafish. Increasing organic load on water bodies causes population explosion leading to overcrowding (OC) stress. The effect of OC stress on neurobehavioral alterations remains unclear. The objective of our study is to elucidate the impact of OC stress on behavioral alterations and neurodegenerative phenotypes on exposure to B[a]P in zebrafish. We demonstrate the effects of OC stress (12 fish/L) on acute waterborne exposure to B[a]P (0.2 mg L-1 ) in adult wild zebrafish. Anxiety-like behavior, learning, and memory impairment were assayed by novel tank diving test, light/dark preference test, and T-maze test. Oxidative stress bio-markers were assayed along with histopathological changes in zebrafish brain. OC stress significantly impaired the learning ability and mood behavior by increasing the number of transition and time spent in the alter zones. Increased lipid peroxidation and protein carbonyl formation with significant decreased catalase activity and reduced glutathione level showed oxidative stress on exposure to OC stress and B[a]P. Pyknotic neuronal counts dramatically increased in periventricular grey zone of optic tectum brain region of zebrafish. Our findings showed that OC stress modulates the B[a]P-induced behavioral alterations causing learning and memory deficiency with histopathological changes in adult zebrafish brain. OC stress may act as an early risk factor for the eventual development of cognitive impairments and B[a]P exposure plays a key role in mediating both the facilitating and impairing actions of OC stress in memory processes.

Microbial communities modulating brain functioning and behaviors in zebrafish: A mechanistic approach.

Microbiota plays a vital role in maintaining their host's physiology, development, reproduction, immune system, nutrient metabolism, brain chemistry and its behavior. How the gut microbiota modulates the brain function altering cognitive and fundamental behavior patterns related to specific functional changes is unclear. Recent studies provide holistic approaches which show gut microbiota can greatly sway all aspects of physiology including gut-brain communication, brain function and behavior by establishing a bi-directional link between the gut and brain. Among these studies, to our knowledge, the present review focus on the new mechanistic basis that relates the microbiota of the intestine with diseases of the nervous system causing behavioral alteration in zebrafish (Danio rerio) during development. The current review on microbiota-gut-brain axis communication showed a high instability of the microbiome at early stage of development in zebrafish. Probiotics restore the composition of the gut microbiota by producing neuroactive compounds and introduce beneficial functions to gut microbial communities, resulting in amelioration of gut inflammation and other intestinal disease phenotypes. Therefore, the present review mainly highlights the mechanistic way of gut-brain function, including neuronal, hormonal, immunological signaling with production of bacterial metabolites. This study consider current knowledge that may enable us to increase our understanding to know how the gut microbiota establishes a connection with brain modulating the gut-brain signaling by alteration of the neurochemistry such as GABA and serotonin levels in brain to control host behavior. Further studies are needed to define the exact microbial and host mechanism in GI disease states and functional syndromes.

Understanding ligands driven mechanism of wild and mutant aryl hydrocarbon receptor in presence of phytochemicals combating Parkinson's disease: an in silico and in vivo study.

Aryl Hydrocarbon Receptor (AhR) is a key player to regulate the expression of a group of enzymes known as cytochrome P450s (CYPs) super family (CYP1A1, CYP1B1, CYP2B6, and CYP2E1) which metabolites diverse endogenous as well as toxic compounds such as Benzo[a] Pyrene (B[a] P) and TCDD. B[a] P induces oxidative stress and causes degeneration of dopaminergic neurons in the midbrain, may leads to Parkinson's disease (PD). The metabolism of B[a] P through the expression of CYPs is mainly triggered after binding of B[a] P within ligand binding domain of AhR. But, the molecular mechanism of AhR mediated xenobiotic metabolism in presence of diverse phytochemicals is yet to be studied. The solved AhR (PDB ID: 5NJ8, 23-273aa) structure lacks information for ligand binding domain therefore both wild type and mutant models were predicted and screened virtually against sixty one natural compounds. The result proposed withaferin A, withanolide A, withanolide B, withanolide D and withanone of plant Withania Somnifera as efficient ligand against both wild type and mutants (V381A and V381D) AhR models. However, in silico studies hypothesised withanolide A as a potent phytochemical to trigger the AhR mediated gene regulation activity of CYPs. The in vivo study in zebra fish model proposed about the neuro protective role of W. Somnifera leaf extract in presence of B[a]P. The present study would throw lights on the molecular mechanism of phytochemicals mediated AhR activity which may be useful in treatment of PD. [Formula: see text] Communicated by Ramaswamy H. Sarma.

Chronic waterborne exposure to benzo[a]pyrene induces locomotor dysfunction and development of neurodegenerative phenotypes in zebrafish.

Benzo[a]pyrene (B[a]P), a prototype of polycyclic aromatic hydrocarbons (PAHs), is an ubiquitous and notable anthropogenic toxicant. The escalating load of anthropogenic organic pollutants on water bodies and its momentous impact on aquatic life may lead to the development of potent neurodegenerative diseases. Thus, the present study was conducted on zebrafish model to address the potential role of B[a]P in inducing neurodegenerative disease like phenotypes. Waterborne B[a]P exposure was performed for a stipulated period of 21 days at a concentration of 0.4 µg/ml. Separate groups of zebrafish were subjected to methylphenidate hydrochloride (MPH: 0.15 mg/L) bath exposure to study the effect on their behaviour before B[a]P exposure. The findings of the present study advocate that chronic exposure to B[a]P significantly impairs the locomotor activity in zebrafish, which showed reduction in total distance travelled and velocity. Histopathological observation by cresyl violet staining showed that there was significant increase in pyknotic neuronal counts in the diencephalon and telencephalic region of zebrafish brain after B[a]P exposure. Protein expression study showed that there was a significant increase in α-synuclein and decrease in UCH-L1, PSEN2, Nurr1 and NeuN expression in whole brain lysate of B[a]P-exposed zebrafish. Tyrosine hydroxylase (TH), as a marker of dopaminergic neurons, was significantly reduced in the B[a]P-exposed group. MPH co-supplementation significantly ameliorated the B[a]P induced altered expression of Parkinson's relevant proteins in zebrafish brain. These findings advocate that the locomotor impairment following chronic B[a]P exposure is associated with development of neurodegenerative phenotypes typically affecting the dopaminergic system in zebrafish.

Adolescence benzo[a]pyrene treatment induces learning and memory impairment and anxiolytic like behavioral response altering neuronal morphology of hippocampus in adult male Wistar rats.

Exposure to benzo[a]pyrene (B[a]P), a prototype of polycyclic aromatic hydrocarbons (PAHs) easily cross blood brain barrier (BBB) and is associated with impaired learning and memory in adult rats. However, there is no symmetric study reported on association between B[a]P exposure during the early development and hippocampal dendritic architecture causing behavioral changes like learning and memory deficit of adult rats. We investigated a fourteen day consecutive B[a]P administration, intraperitonial (i.p.), with two different doses (0.1 and 1µM) during early adolescence at PND30-44 and learning behavior assessed between PND 45-60 in adult male rats. The anxiolytic like behavioural analysis was done by LDPT. Depressive like behaviour was estimated through sucrose preference and learning and memory by T-maze. After B[a]P administration oxidative stress markers like glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), reduced (GSH) and oxidized glutathione (GSSG) were evaluated. To parallel these behavioral and antioxidant level changes to alteration in dendritic morphology, Golgi-Cox staining was performed in the hippocampus. Our study showed anxiolytic like behavioral response with significant increase in time spent in light zone and significant (p < 0.05) decrease in preference for sucrose and a reduction in percentage of spontaneous responses in T-maze test in B[a]P administered group as compared to vehicle control. B[a]P exposed male rats showed significant increase in GST activity (p < 0.05) and concentration of GSSG with a decay in GSH, GPx and GR in both the groups as compared to control. B[a]P administered rats showed significant loss in total dendritic length and number (28%) with reduced spine density (18%) in both higher and lower doses. These results suggested that B[a]P administration can be associated with an increase ROS production showing altered antioxidant defence system through glutathione biosynthesis and causing profound alterations in dendritic length and spine density of hippocampal neurons leading towards learning and memory deficits in adult rats.

Protective effects of noradrenaline on benzo[a]pyrene-induced oxidative stress responses in brain tumor cell lines.

Benzo[a]pyrene (B[a]P) is an ubiquitous environmental pollutant that is generated during combustion of fossil fuels. We examine the effect of noradrenaline (NA) on B[a]P-induced neurotoxicity in brain tumor cell lines like neuroblastoma (Neuro2a) and glioma (C6). We pre-treated tumor cells with NA for 6 h, followed by addition of B[a]P for additional 24 h. Cell viability was measured using trypan blue dye-exclusion assay and comet assay was performed to measure DNA damage. Cell cycle status was analyzed using flow cytometry and oxidative DNA damage (8-oxodG) production was examined by immunostaining. The intracellular Ca2+ concentration was analyzed using Fura-2AM. Our results showed viability of Neuro2a and C6 cells declined (24% and 20%) in B[a]P-treated groups. However, pre-treating with NA increased viability of cells by reducing percentage of cell death in both. Furthermore, B[a]P-induced deregulation of cell cycle (G2/M and S phase cell arrest) was significantly restored by pre-treatment with NA in Neuro2a cells as compared to C6 cells. We further observed increased 8-oxodG production in B[a]P-treated cells; however, NA pre-treatment significantly (p < 0.05) reduced the 8-oxodG production in Neuro2a, while C6 cells were less affected possibly due to better protective machinery. B[a]P-induced intracellular Ca2+ influx was significantly reduced in both the cell lines due to co-treatment of NA possibly by reducing Ca2+ influx. NA protects brain tumor cells against B[a]P-induced neurotoxicity may be by decreasing percentage of G2 cell arrest, oxidative DNA damage, and reducing intracellular Ca2+ influx. These findings suggested that NA may be considered as a natural potential protective agent against B[a]P-induced neurotoxicity. Graphical abstract Graphical abstract showing differential protective mechanism of NA against B[a]P-induced toxicity through antioxidant mechanism maintaining homeostasis for oxidative stress in Neuro2a and C6 cell lines. The schematic graph showed the biological significance of the NA that regulates the induction of metabolic processes of cell cycle after exposure to the environmental pollutants. B[a]P increases the intracellular levels of Ca2+, but also induces damage to cellular molecules including DNA causing cell cycle arrest. The B[a]P-induced DNA damage due to base lesions generated in the genome, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is one of the most abundant because of guanine's lowest redox potential among DNA bases through intracellular calcium homoeostasis.

Modulation of Benzo[a]Pyrene Induced Anxiolytic-Like Behavior by Retinoic Acid in Zebrafish: Involvement of Oxidative Stress and Antioxidant Defense System.

Benzo[a]pyrene (B[a]P) is commonly associated with oxidative stress-induced neurotoxicity. Retinoic acid (RA) has been shown to exhibit neuroprotection in brain, and disruption of RA signaling via excess or deficient RA can lead to oxidative stress. B[a]P contamination in aquatic environment has been shown to lower the internal RA level. Thus, the present study was conducted in wild-type zebrafish to ameliorate the neurotoxic effect of B[a]P by waterborne RA co-supplementation. Findings showed that B[a]P induced anxiolytic-like behavioral response, and altered antioxidant activity in zebrafish is attenuated by RA. Our study also advocated the neurotoxic potential of RA treatment alone in control condition. Previous findings showed that periventricular gray zone (PGZ) of optic tectum (TeO) in zebrafish brain regulates anxiety-like behavior. The augmented pyknotic neuronal counts in PGZ following B[a]P treatment was ameliorated by RA co-supplementation. Further, presence of B[a]P in the cell milieu is known to induce oxidative stress through increase expression of cytochrome P450 1A1 (CYP1A1), an enzyme necessary for metabolic breakdown of both B[a]P and RA. Any deviation from the required concentration of RA leads to production of reactive oxygen species. Further, low availability of RA in cell milieu is known to decrease the expression of Nrf2, a transcription factor necessary for the expression of several antioxidants and antioxidant enzymes. Recent studies also showed that RA increases glutathione synthesis and exhibits neuroprotective properties in brain cells. The findings of the present study address the potential role of exogenous RA co-supplementation as a therapeutic intervention against B[a]P-induced depletion of RA, causing neurotoxicity in zebrafish.

Neuropeptide Y expression confers benzo[a]pyrene induced anxiolytic like behavioral response during early adolescence period of male Wistar rats.

Environmental neurotoxicant like benzo[a]pyrene (B[a]P) is known to induce neurobehavioral changes. Our previous reports address the adverse effect of B[a]P on the neurobehavioral responses and neuromorphology of sensitive brain regions in adolescent rats. Present study was conducted on male Wistar rat neonates at postnatal day 5 (PND5) to ascertain B[a]P induced anxiolytic like behavioral response could be an outcome of neuropeptide Y (NPY) overexpression in brain. Single intracisternal administration of B[a]P was carried out at PND5 to elucidate the role of NPY on neurobehavioral responses at PND30. The behavioral studies showed anxiolytic like effect of B[a]P in both light and dark box and elevated plus maze tests. Antioxidant assay involving glutathione peroxidase activity was significantly decreased where as lipid peroxidation was significantly augmented in both hippocampus and hypothalamus of B[a]P treated group as compared to naive and control. The neurotransmitter estimation by HPLC-ECD showed significant increase in 5-HT level in both hippocampus and hypothalamus of B[a]P treated group. Significant elevation in NPY expression was observed in both hippocampus and hypothalamus of B[a]P group. Intracellular Ca2+ estimation using Fura-2AM by fluorometry showed that B[a]P induced increase in Ca2+ influx was associated with augmented NPY expression in brain. As NPY has orexigenic effect, our result revealed that there was a significant increase in body weight at PND30 following B[a]P administration to rat neonates at PND5. These findings suggested that NPY overexpression in brain regions might be associated with anxiolytic like behavioral response and orexigenic effect in rats following single intracisternal B[a]P administration. Future research directing towards understanding the signaling cascades of B[a]P induced biochemical and neuromorphological alteration might address the independent pathway which induce neurodegeneration despite NPY overexpression in brain regions of adolescent rats.

Neonatal Benzo[a]pyrene Exposure Induces Oxidative Stress and DNA Damage Causing Neurobehavioural Changes during the Early Adolescence Period in Rats.

Humans are exposed to polycyclic aromatic hydrocarbons (PAHs) by ingestion of contaminated food and water. Prenatal exposure to benzo[a]pyrene (B[a]P) like PAHs through the placental barrier and neonatal exposure by breast milk and the environment may affect early brain development. In the present study, single intracisternal administration of B[a]P (0.2 and 2.0 µg/kg body weight) to male Wistar rat pups at postnatal day 5 (PND5) was carried out to study its specific effect on neonatal brain development and its consequences at PND30. B[a]P administration showed a significant increase in exploratory and anxiolytic-like behaviour with elevated hippocampal lipid peroxidation and protein oxidation at PND30. Further, DNA damage was estimated in vitro (Neuro2a and C6 cell lines) by the comet assay, and oxidative DNA damage of hippocampal sections was measured in vivo following exposure to B[a]P. DNA strand breaks (single and double) significantly increased due to B[a]P at PND30 in hippocampal neurons and increased the nuclear tail moment in Neuro2a cells. Hippocampal 8-oxo-2'-deoxyguanosine production was significantly elevated showing expression of more TUNEL-positive cells in both doses of B[a]P. Histological studies also revealed a significant reduction in mean area and perimeter of hippocampal neurons in rats treated with B[a]P 2.0 µg/kg, when compared to naïve and control rats. B[a]P significantly increased anxiolytic-like behaviour and oxidative DNA damage in the hippocampus causing apoptosis that may lead to neurodegeneration in adolescence. The findings of the present study address the potential role of B[a]P in inducing oxidative stress-mediated neurodegeneration in the hippocampus through oxidative DNA damage in the early adolescence period of rats.

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.

Neonatal exposure to benzo[a]pyrene induces oxidative stress causing altered hippocampal cytomorphometry and behavior during early adolescence period of male Wistar rats.

Environmental neurotoxicants like benzo[a]pyrene (B[a]P) have been well documented regarding their potential to induce oxidative stress. However, neonatal exposure to B[a]P and its subsequent effect on anti-oxidant defence system and hippocampal cytomorphometry leading to behavioral changes have not been fully elucidated. We investigated the effect of acute exposure of B[a]P on five days old male Wistar pups administered with single dose of B[a]P (0.2 µg/kg BW) through intracisternal mode. Control group was administered with vehicle i.e., DMSO and a separate group of rats without any treatment was taken as naive group. Behavioral analysis showed anxiolytic-like behavior with significant increase in time spent in open arm in elevated plus maze. Further, significant reduction in fall off time during rotarod test showing B[a]P induced locomotor hyperactivity and impaired motor co-ordination in adolescent rats. B[a]P induced behavioral changes were further associated with altered anti-oxidant defence system involving significant reduction in the total ATPase, Na(+) K(+) ATPase, Mg(2+) ATPase, GR and GPx activity with a significant elevation in the activity of catalase and GST as compared to naive and control groups. Cytomorphometry of hippocampus showed that the number of neurons and glia in B[a]P treated group were significantly reduced as compared to naive and control. Subsequent observation showed that the area and perimeter of hippocampus, hippocampal neurons and neuronal nucleus were significantly reduced in B[a]P treated group as compared to naive and control. The findings of the present study suggest that the alteration in hippocampal cytomorphometry and neuronal population associated with impaired antioxidant signaling and mood in B[a]P treated group could be an outcome of neuromorphological alteration leading to pyknotic cell death or impaired differential migration of neurons during early postnatal brain development.

Withania somnifera Leaf Extract Ameliorates Benzo[a]pyrene-Induced Behavioral and Neuromorphological Alterations by Improving Brain Antioxidant Status in Zebrafish (Danio rerio).

The aquatic environment provides a sink for the environmental pollutants that have potential to induce oxidative stress by altering neurobehavioral response of aquatic animals. Benzo[a]pyrene (B[a]P), a polycyclic aromatic hydrocarbon is known to induce oxidative stress in the brain. Withania somnifera has been used traditionally for its neuroprotective effect in experimental models of neurological disorders. The present study is aimed to evaluate the neuroprotective potential of Withania somnifera leaf extract (WSLE) following exposure to waterborne B[a]P. Wild-type zebrafish (Danio rerio) were designated as naive, control (dimethyl sulfoxide), WSLE, B[a]P, and B[a]P + WSLE groups. Behavioral studies showed reversal in scototaxis (anxiety-like) behavior in B[a]P group and was restored by WSLE cosupplementation in B[a]P + WSLE group. B[a]P-induced altered antioxidant status was ameliorated by WSLE in the B[a]P + WSLE group. Previous studies showed that the periventricular gray zone (PGZ) of the optic tectum in zebrafish brain regulates scototaxis (anxiety-like) behavior. Our histopathological observation showed a significant increase in the pyknotic neuronal counts in PGZ of the B[a]P group and was ameliorated by WSLE cosupplementation. The study showed that the reversal in scototaxis behavior following exposure to waterborne B[a]P might be associated with neuromorphological alterations in PGZ, whereas a pioneer ethnopharmacological approach of WSLE cosupplementation showed its neuroprotective role to restore normal scototaxis of zebrafish. Future research directing toward understanding the role of visual circuit involved with impaired scototaxis behavior in zebrafish might provide new pathological outcomes following exposure to B[a]P.

Protective role of noradrenaline in benzo[a]pyrene-induced learning impairment in developing rat.

Benzo[a]pyrene (B[a]P), a carcinogen, affects brain development, learning, and memory. Isolated studies have reported that B[a]P elevates noradrenaline (NA) level that may modulate neuronal growth, learning, and memory. Therefore, we investigated in vivo and in vitro the effects of B[a]P on learning and memory and its possible mechanism of action. Intracisternal administration of B[a]P on postnatal day 5 significantly reduced learning and memory in adolescent rats as observed by probe test using the Morris water maze. The density of both the subunits of the N-methyl-D-aspartate (NMDA) receptor, NMDAR1 and NMDAR2B, significantly increased in the hippocampus. In vitro, B[a]P significantly increased NMDAR1 in both C6 and Neuro2a cell lines, whereas NMDAR2B was significantly increased in C6 but was significantly decreased in Neuro2a. Pretreatment with NA prevented the B[a]P-induced effect on NMDAR1 expression in both cell lines. However, although NA prevented the B[a]P-mediated increase in NMDAR2B expression in C6, it further potentiated the decrease of NMDAR2B in Neuro2a cells. Also, NA prevented the B[a]P-induced increase in intracellular Ca(2+) both in C6 and in Neuro2a. Our findings show that postnatal exposure of developing rats to B[a]P impairs learning and memory even when the rats became adolescent. We also observed that the effects were mediated by elevated intracellular Ca(2+) levels and increased expression of NMDAR; furthermore, NA exerted a protective effect by modulating those factors. NA differentially affects neurons and glia, which may have a compensatory role during toxic insults, especially from B[a]P.