The influence of acute dopamine transporter inhibition on manic-, depressive-like phenotypes, and brain oxidative status in adult zebrafish

Functional changes in dopamine transporter (DAT) are related to various psychiatric conditions, including bipolar disorder (BD) symptoms. In experimental research, the inhibition of DAT induces behavioral alterations that recapitulate symptoms found in BD patients, including mania and depressive mood. Thus, developing novel animal models that mimic BD-related conditions by pharmacologically modulating the dopaminergic signaling is relevant. The zebrafish (Danio rerio) has been considered a suitable vertebrate system for modeling BD-like responses, due to the well-characterized behavioral responses and evolutionarily conservation of the dopaminergic system of this species. Here, we investigate whether GBR 12909, a selective inhibitor of DAT, causes neurobehavioral alterations in zebrafish similar to those observed in BD patients. Behaviors were recorded after a single intraperitoneal (i.p.) administration of GBR 12909 at different doses (3.75, 7.5, 15 and 30 mg/kg). To observe temporal effects on behavior, swim path parameters were measured immediately after the administration period during 30 min. Locomotion, anxiety-like behavior, social preference, aggression, despair-like behavior, and oxidative stress-related biomarkers in the brain were measured 30 min post administration. GBR 12909 induced prominent effects on locomotor activity and vertical exploration during the 30-min period. Hyperactivity was observed in GBR 30 group after 25 min, while all doses markedly reduced vertical drifts. GBR 12909 elicited hyperlocomotion, anxiety-like behavior, decreased social preference, aggression, and induced depressive-like behavior in a behavioral despair task. Depending on the dose, GBR 12909 also decreased SOD activity and TBARS levels, as well as increased GR activity and NPSH content. Collectively, our novel findings show that a single GBR 12909 administration evokes neurobehavioral changes that recapitulate manic- and depressive-like states observed in rodents, fostering the use of zebrafish models to explore BD-like responses in translational neuroscience research.

Diphenyl Diselenide Through Reduction of Inflammation, Oxidative Injury and Caspase-3 Activation Abates Doxorubicin-Induced Neurotoxicity in Rats

Neurotoxicity associated with chemotherapy is a debilitating side effect of cancer management in humans which reportedly involves inflammatory and oxidative stress responses. Diphenyl diselenide (DPDS) is an organoselenium compound which exhibits its anti-tumoral, anti-oxidant, anti-inflammatory and anti-mutagenic effects. Nevertheless, its possible effect on chemotherapy-induced neurotoxicity is not known. Using rat model, we probed the behavioral and biochemical effects accompanying administration of antineoplastic agent doxorubicin (7.5 mg/kg) and DPDS (5 and 10 mg/kg). Anxiogenic-like behavior, motor and locomotor insufficiencies associated with doxorubicin were considerably abated by both DPDS doses with concomitant enhancement in exploratory behavior as demonstrated by reduced heat maps intensity and enhanced track plot densities. Moreover, with exception of cerebral glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, biochemical data demonstrated reversal of doxorubicin-mediated decline in cerebral and cerebellar antioxidant status indices and the increase in acetylcholinesterase (AChE) activity by both doses of DPDS. Also, cerebellar and cerebral lipid peroxidation, hydrogen peroxide as well as reactive oxygen and nitrogen species levels were considerably diminished in rats administered doxorubicin and DPDS. In addition, DPDS administration abated myeloperoxidase activity, tumour necrosis factor alpha and nitric oxide levels along with caspase-3 activity in doxorubicin-administered rats. Chemoprotection of doxorubicin-associated neurotoxicity by DPDS was further validated by histomorphometry and histochemical staining. Taken together, DPDS through offsetting of oxido-inflammatory stress and caspase-3 activation elicited neuroprotection in doxorubicin-treated rats.

Exogenous taurine administration abates reproductive dysfunction in male rats exposed to silver nanoparticles

The broad contemporary applications of silver nanoparticles (AgNPs) have been associated with various toxicities including reproductive toxicity. Taurine is well acknowledged for its potent pharmacological role in numerous disease models and chemically-mediated toxicity. We investigated the effect of taurine on AgNPs-induced reproductive toxicity in male rats. The animals were intraperitoneally injected with AgNPs (200 μg/kg) alone or co-administered with taurine at 50 and 100 mg/kg for 21 successive days. Exogenous taurine administration significantly abated AgNPs-induced oxidative injury by decreasing the levels of oxidative stress indices while boosting antioxidant enzymes activities and glutathione level in the hypothalamus, testes and epididymis of exposed animals. Taurine administration alleviated AgNPs-induced inflammatory response and caspase-3 activity, an apoptotic biomarker. Moreover, taurine significantly improved spermiogram, reproductive hormones and the marker enzymes of testicular function in AgNPs-treated animals. The ameliorative effect of taurine on pathological lesions induced by AgNPs in the exposed animals was substantiated by histopathological data. This study provides the first mechanistic evidence that taurine supplementation affords therapeutic effect against reproductive dysfunction associated with AgNPs exposure in male rats.

Metoprolol elicits neurobehavioral insufficiency and oxidative damage in nontarget Nauphoeta cinerea nymphs

Metoprolol, a drug for hypertension and cardiovascular diseases, has become a contaminant of emerging concern because of its frequent detection in various environmental matrices globally. The dwindling in the biodiversity of useful insects owing to increasing presence of environmental chemicals is currently a great interest to the scientific community. In the current research, the toxicological impact of ecologically relevant concentrations of metoprolol at 0, 0.05, 0.1, 0.25, and 0.5 μg/L on Nauphoeta cinerea nymphs following exposure for 42 consecutive days was evaluated. The insects' behavior was analyzed with automated video-tracking software (ANY-maze, Stoelting Co, USA) while biochemical assays were done using the midgut, head and fat body. Metoprolol-exposed nymphs exhibited significant diminutions in the path efficiency, mobility time, distance traveled, body rotation, maximum speed and turn angle cum more episodes, and time of freezing. In addition, the heat maps and track plots confirmed the metoprolol-mediated wane in the exploratory and locomotor fitness of the insects. Compared with control, metoprolol exposure decreased acetylcholinesterase activity in insects head. Antioxidant enzymes activities and glutathione level were markedly decreased whereas indices of inflammation and oxidative injury to proteins and lipids were significantly increased in head, midgut and fat body of metoprolol-exposed insects. Taken together, metoprolol exposure induces neurobehavioral insufficiency and oxido-inflammatory injury in N. cinerea nymphs. These findings suggest the potential health effects of environmental contamination with metoprolol on ecologically and economically important nontarget insects.

Cellular and molecular mechanisms of aflatoxin B1-mediated neurotoxicity: The therapeutic role of natural bioactive compounds

Aflatoxin B1 (AFB1), a dietary toxin from the mold Aspergillus species, is well acknowledged to elicit extra-hepatic toxicity in both animals and humans. The neurotoxicity of AFB1 has become a global public health concern. Contemporary research on how AFB1 enters the brain to elicit neuronal dysregulation leading to noxious neurological outcomes has increased greatly in recent years. The current review discusses several neurotoxic outcomes and susceptible targets of AFB1 toxicity at cellular, molecular and genetic levels. Specifically, neurotoxicity studies involving the use of brain homogenates, neuroblastoma cell line IMR-32, human brain microvascular endothelial cells, microglial cells, and astrocytes, as well as mammalian and non-mammalian models to unravel the mechanisms associated with AFB1 exposure are highlighted. Further, some naturally occurring bioactive compounds with compelling therapeutic effects on AFB1-induced neurotoxicity are reviewed. In conclusion, available data from literature highlight AFB1 as a neurotoxin and its possible pathological contribution to neurological disorders. Further mechanistic studies aimed at discovering and developing effective therapeutics for AFB1 neurotoxicity is warranted.

Amelioration of neurobehavioral, biochemical, and morphological alterations associated with silver nanoparticles exposure by taurine in rats

The adverse effect of silver nanoparticles (AgNPs) on the nervous system is an emerging concern of public interest globally. Taurine, an essential amino acid required for neurogenesis in the nervous system, is well-documented to possess antioxidant, anti-inflammatory, and antiapoptotic activities. Yet, there is no report in the literature on the effect of taurine on neurotoxicity related to AgNPs exposure. Here, we investigated the neurobehavioral and biochemical responses associated with coexposure to AgNPs (200 µg/kg body weight) and taurine (50 and 100 mg/kg body weight) in rats. Locomotor incompetence, motor deficits, and anxiogenic-like behavior induced by AgNPs were significantly alleviated by both doses of taurine. Taurine administration enhanced exploratory behavior typified by increased track plot densities with diminished heat maps intensity in AgNPs-treated rats. Biochemical data indicated that the reduction in cerebral and cerebellar acetylcholinesterase activity, antioxidant enzyme activities, and glutathione level by AgNPs treatment were markedly upturned by both doses of taurine. The significant abatement in cerebral and cerebellar oxidative stress indices namely reactive oxygen and nitrogen species, hydrogen peroxide, and lipid peroxidation was evident in rats cotreated with AgNPs and taurine. Further, taurine administration abated nitric oxide and tumor necrosis factor-alpha levels cum myeloperoxidase and caspase-3 activities in AgNPs-treated rats. Amelioration of AgNPs-induced neurotoxicity by taurine was confirmed by histochemical staining and histomorphometry. In conclusion, taurine via attenuation of oxido-inflammatory stress and caspase-3 activation protected against neurotoxicity induced by AgNPs in rats.

Perfluorooctanoic acid induces behavioral impairment and oxidative injury in Nauphoeta cinerea nymphs

Perfluorooctanoic acid (PFOA) is a persistent organic contaminant with potential health threats to both animals and humans. However, the impact of PFOA on insects, which play significant roles in ecosystems, is understudied. We evaluated the toxicological impact of ecologically relevant concentrations of PFOA (0, 25, 50, 100, and 200 µg L-1) on Nauphoeta cinerea nymphs following exposure for 42 consecutive days. We analyzed the behavior of the insects with automated video-tracking software and processed the head, midgut, and fat body for biochemical assays. PFOA-exposed insects exhibited significant reductions in locomotory abilities and an increase in freezing time. Furthermore, PFOA exposure reduced acetylcholinesterase activity in the insect head. PFOA exposure increased the activities of superoxide dismutase, glutathione peroxidase, and catalase in the head and midgut, but decreased them in the fat body. PFOA also significantly increased glutathione-S transferase activity, while decreasing glutathione levels in the head, midgut, and fat body. Additionally, PFOA exposure increased reactive oxygen and nitrogen species, nitric oxide, lipid peroxidation, and protein carbonyl contents in the head, midgut, and fat body of the insects. In conclusion, our findings indicate that PFOA exposure poses an ecological risk to Nauphoeta cinerea.

Neurotoxicity of ochratoxin A: Molecular mechanisms and neurotherapeutic strategies

Data from epidemiological and experimental studies have evidenced that some chemical contaminants in food elicit their harmful effects by targeting the central nervous system. Ochratoxin A is a foodborne mycotoxin produced by Aspergillus and Penicillium species. Research on neurotoxicity associated with ochratoxin A exposure has increased greatly in recent years. The present review accrued substantial evidence on the neurotoxicity associated with ochratoxin A exposure as well as discussed notable susceptible targets of noxious ochratoxin A at molecular, cellular and genetic levels. Specifically, the neurotoxic mechanisms associated with ochratoxin A exposure were unequivocally unraveled in vitro using human neuroblastoma SH-SY5Y cells, mouse hippocampal HT22 cells, human astrocyte (NHA-SV40LT) cells and microglia cells as well as in vivo using mammalian and non-mammalian models. Data from human biomonitoring studies on plasma ochratoxin A levels in patients with neurodegenerative diseases with some age- and sex-related responses were also highlighted. Moreover, the neurotherapeutic mechanisms of some naturally occurring bioactive compounds against ochratoxin A neurotoxicity are reviewed. Collectively, accumulated data from literature demonstrate that ochratoxin A is a neurotoxin with potential pathological involvement in neurological disorders. Cutting edge original translational research on the development of neurotherapeutics for neurotoxicity associated with foodborne toxicants including ochratoxin A is indispensable.

Neurotoxicity of furan in juvenile Wistar rats involves behavioral defects, microgliosis, astrogliosis and oxidative stress

Evidence suggests that furan, a widespread environmental and food contaminant, causes liver toxicity and cancer, but its implications in the brain are not well defined. We measured behavioral, glial, and biochemical responses in male juvenile rats exposed orally to 2.5, 5 and 10 mg/kg furan and vitamin E after 28 days. Furan-mediated hyperactivity peaked at 5 mg/kg and did not exacerbate at 10 mg/kg. Enhanced motor defect was also observed at 10 mg/kg. Furan-treated rats elicited inquisitive exploration but showed impaired working memory. Without compromising the blood-brain barrier, furan induced glial reactivity with enhanced phagocytic activity, characterized by parenchyma-wide microglial aggregation and proliferation, which switched from hyper-ramified to rod-like morphology with increasing doses. Furan altered the glutathione-S-transferase-driven enzymatic and non-enzymatic antioxidant defence systems differentially and dose-dependently across brain regions. Redox homeostasis was most perturbed in the striatum and least disrupted in hippocampus/cerebellum. Vitamin E supplementation attenuated exploratory hyperactivity and glial reactivity but did not affect impaired working memory and oxidative imbalance. Overall, sub-chronic exposure of juvenile rats to furan triggered glial reactivity and behavioral defects suggesting the brain's vulnerability during juvenile development to furan toxicity. It remains to be determined whether environmentally relevant furan concentrations interfere with critical brain developmental milestones.

Attenuation of doxorubicin-induced hypothalamic-pituitary-testicular axis dysfunction by diphenyl diselenide involves suppression of hormonal deficits, oxido-inflammatory stress and caspase 3 activity in rats

BACKGROUND

Doxorubicin (DOX) is one of the popular anti-cancer drugs in the world and several literatures have implicated it in various toxicities especially cardiotoxicity and reproductive toxicity. Diphenyl diselenide (DPDS) is well acknowledged for its compelling pharmacological effects in numerous disease models and chemically-mediated toxicity. This study was carried out to investigate the effect of DPDS on DOX-induced changes in the reproductive indices of male Wistar rats.

METHODS

Rats were intraperitoneally injected with 7.5 mg/kg body weight of DOX alone once followed by treatment with DPDS at 5 and 10 mg/kg for seven successive days. Excised hypothalamus, testes and epididymis were processed for biochemical and histological analyses.

RESULTS

DPDS treatment significantly (p < 0.05) abated DOX-induced oxidative damage by decreasing the levels of oxidative stress indices such as hydrogen peroxide, reactive oxygen and nitrogen species, and lipid peroxidation with a respective improvement in the level of glutathione in the hypothalamic, testicular and epididymal tissues of DOX-treated rats. The activities of antioxidant enzymes such as catalase, superoxide dismutase, glutathione S-transferase and glutathione peroxidase were upregulated in the DPDS co-treated group. DPDS co-treatment alleviates the burden of DOX-induced inflammation by significant reductions in myeloperoxidase activity, levels of nitric oxide and tumor necrosis factor alpha with concomitant decline in the activity of caspase-3, an apoptotic biomarker. Consequently, significant improvement in the spermiogram, levels of reproductive hormones (follicle stimulating hormone, luteinizing hormone, prolactin, serum testosterone and intra-testicular testosterone) levels in the DPDS co-treatment group in comparison to DOX alone-treated group were observed. Histology results of the testes and epididymis showed that DPDS significantly alleviated pathological lesions induced by DOX in the animals.

CONCLUSION

DPDS may modulate reproductive toxicity associated with DOX therapy in male cancer patients.

Persistent oxidative injury and neurobehavioral impairment in adult male and female Nauphoeta cinerea exposed to perfluorooctanoic acid

This study aimed to elucidate if the toxicity of perfluorooctanoic acid (PFOA), an emerging persistent organic contaminant, is reversible or not in adult male and female Nauphoeta cinerea. Both sexes of Nauphoeta cinerea were separately exposed to 0, 1 and 5 mg/L PFOA in drinking water for 21 consecutive days. PFOA-exposed Nauphoeta cinerea exhibited significant deficits in the locomotor and exploratory capabilities with concomitant increase in anxiogenic behaviors which persisted after cessation of PFOA exposure. Moreover, PFOA-induced decrease in acetylcholinesterase activity persisted after cessation of PFOA exposure in both insects' sexes. Catalase and superoxide dismutase activities were increased in the midgut but restored to control following cessation of PFOA exposure. The increased reactive oxygen and nitrogen species, nitric oxide and hydrogen peroxide levels persisted in the head whereas they were abated in the midgut after cessation of PFOA exposure. However, PFOA-induced persistent increase in lipid peroxidation and protein carbonyl levels in the head and midgut of insects. Collectively, PFOA exposure elicited persistent neurobehavioral and oxidative injury similarly in both sexes of adult Nauphoeta cinerea during this investigation.

Dietary myricetin assuages atrazine-mediated hypothalamic-pituitary-testicular axis dysfunction in rats

Atrazine (ATZ) exposure is associated with reproductive dysfunction in both animals and humans. Myricetin, a flavonoid compound, is well documented for its numerous pharmacological activities. However, the impact of myricetin on the atrazine-mediated dysfunctional hypothalamic-pituitary-testicular axis is not known. This study investigated the role of myricetin on the atrazine-induced alterations in the male reproductive axis in rats orally gavaged with ATZ alone (50 mg/kg) or co-treated with ATZ + myricetin (MYR) at 5, 10, and 20 mg/kg for 30 consecutive days. Myricetin assuaged ATZ-induced reductions in intra-testicular testosterone, serum follicle-stimulating hormone, luteinizing hormone, and testosterone, coupled with decreases in alkaline phosphatase, acid phosphatase, lactate dehydrogenase, and glucose-6-phosphate dehydrogenase activities. Also, MYR treatment improved epididymal sperm count and motility and decreased sperm defects in ATZ-treated rats. Testicular sperm number, daily sperm production, and sperm viability remained unchanged in all treatment groups. Administration of MYR abated ATZ-mediated depletion in antioxidant status, an increase in myeloperoxidase activity, nitric oxide, hydrogen peroxide, malondialdehyde levels, and reactive oxygen and nitrogen species, as well as the histological lesions in the hypothalamus, epididymis, and testes of treated animals. All in all, MYR mitigated atrazine-mediated functional changes in the reproductive axis via anti-inflammatory and antioxidant mechanisms in atrazine-exposed rats. Dietary intake of MYR could be a worthy chemoprotective approach against reproductive dysfunction related to ATZ exposure.

Neurotoxic and behavioral deficit in Drosophila melanogaster co-exposed to rotenone and iron

Exposure to environmental toxicants has been linked with the onset of different neurodegenerative diseases in animals and humans. Here, we evaluated the toxic effects of co-exposure to iron and rotenone at low concentrations in Drosophila melanogaster. Adult wild-type flies were orally exposed to rotenone (50.0 µM) and ferrous sulfate (FeSO₄; 1.0 and 10.0 µM) through the diet for 10 days. Thereafter, we evaluated markers of oxidative damage (Hydrogen Peroxide (H₂O₂), Nitric Oxide (NO), Protein Carbonyl, and malondialdehyde (MDA)), antioxidant status (catalase, Glutathione S-Transferase (GST), Total Thiol (T-SH) and Non-protein Thiol (NPSH), neurotransmission (monoamine oxidase; MAO and acetylcholinesterase, AChE) and mitochondrial respiration. The results indicated that flies fed rotenone and FeSO₄ had impaired locomotion, reduced survival rate, and AChE activity with a corresponding increase in MAO activity when compared with the control (p < 0.05). Furthermore, rotenone and FeSO₄ significantly decreased the antioxidant status with a concurrent accumulation of NO, MDA, and H₂O₂. Additionally, the activity of complex 1 and mitochondria bioenergetic capacity was compromised in the flies. These findings suggest that the combination of rotenone and FeSO₄ elicited a possible synergistic toxic response in the flies and therefore provided further insights on the use of D. melanogaster in toxicological studies.

Influence of furan and lead co-exposure at environmentally relevant concentrations on neurobehavioral performance, redox-regulatory system and apoptotic responses in rats

Furan and lead are contaminants of global concern due to the potential public health threat associated with their exposure. Herein, the neurobehavioral performance, biochemical effects and histological alterations associated with co-exposure to furan (8 mg/kg) and lead acetate at low, environmentally realistic concentrations (1, 10 and 100 µg PbAc/L) for 28 uninterrupted days were investigated in rats. The results demonstrated that locomotor, motor and exploratory deficits associated with separate exposure to furan and lead was exacerbated in the co-exposed rats. Furan and lead co-exposure aggravated the marked decrease in acetylcholinesterase activity and antioxidant status, elevation in oxido-inflammatory stress indices and caspases activation in the cerebrum and cerebellum of exposed rats compared with control. Furan and lead co-exposure worsened neuronal degeneration as verified by histomorphometry and histochemical staining. Collectively, furan and lead acts together to exacerbate neurotoxicity via inhibition of cholinergic system, induction of oxido-inflammatory stress and caspases activation in rats.

A novel behavioral paradigm to measure anxiety-like behaviors in zebrafish by the concomitant assessment of geotaxis and scototaxis

Pathological anxiety is a set of diseases characterized by specific clinical manifestations and the use of alternative models may provide novel insights in translational neurobehavioral research. In zebrafish, the separate performance of novel tank and light dark tests in different order to assess anxiety using a same animal may provide conflicting data due to the battery effect and/or time-drug-response and variability across tests. To improve data reliability, we aimed to characterize a novel behavioral paradigm to measure geotaxis and scototaxis as anxiety-like responses in the same trial. The novel apparatus consisted of four colored-compartments, with specific white- and black sections delimited in both bottom and upper areas of the tank. The main baseline responses of zebrafish in the novel apparatus were measured and animals were further exposed to modulators of anxiety. Zebrafish showed robust habituation to novelty stress during the 6-min trial with preference for the black section while exploring the top area. Fluoxetine (100 μg/L, 15 min) reduced geotaxis and scototaxis and ketamine (20 mg/L, 20 min) decreased geotaxis and increased the distance traveled in the black section while exploring the top, possibly due to the increased circling behavior. As anxiogenic modulators, conspecific alarm substance (3.5 mL/L, 5 min) exacerbated risk assessment, geotaxis, and scototaxis, whereas caffeine (10 mg/L, 15 min) increased geotaxis and exploration in the black section of the top area. Since important correlations were also found for relevant anxiety-like behaviors, our findings support the predictive validity of this novel paradigm to simultaneously assess geotaxis and scototaxis in zebrafish. Moreover, it fully adheres to the 3Rs principle of animal experimentation of reducing the number of subjects tested, execution time, also minimizing a potential battery effect.

Utility of cockroach as a model organism in the assessment of toxicological impacts of environmental pollutants

Environmental pollution is a global concern because of its associated risks to human health and ecosystem. The bio-monitoring of environmental health has attracted much attention in recent years and efforts to minimize environmental contamination as well as to delineate toxicological mechanisms related to toxic exposure are essential to improve the health conditions of both humans and animals. This review aims to substantiate the need and advantages in utilizing cockroaches as a complementary, non-mammalian model to further understand the noxious impact of environmental contaminants on humans and animals. We discuss recent advances in neurotoxicology, immunotoxicology, reproductive and developmental toxicology, environmental forensic entomotoxicology, and environmental toxicology that corroborate the utility of the cockroach (Periplaneta americana, Blaptica dubia, Blattella germanica and Nauphoeta cinerea) in addressing toxicological mechanisms as well as a sensor of environmental pollution. Indeed, recent improvements in behavioural assessment and the detection of potential biomarkers allow for the recognition of phenotypic alterations in cockroaches following exposure to toxic chemicals namely saxitoxin, methylmercury, polychlorinated biphenyls, electromagnetic fields, pharmaceuticals, polycyclic aromatic hydrocarbon, chemical warfare agents and nanoparticles. The review provides a state-of-the-art update on the current utility of cockroach models in various aspects of toxicology as well as discusses the potential limitations and future perspectives.

Induction of aggression and anxiety-like responses by perfluorooctanoic acid is accompanied by modulation of cholinergic- and purinergic signaling-related parameters in adult zebrafish

Perfluorooctanoic acid (PFOA) is a contaminant of global concern owing to its prevalent occurrence in aquatic and terrestrial environments with potential hazardous impact on living organisms. Here, we investigated the influence of realistic environmental concentrations of PFOA (0, 0.25, 0.5, or 1.0 mg/L) on relevant behaviors of adult zebrafish (Danio rerio) (e.g., exploration to novelty, social preference, and aggression) and the possible role of PFOA in modulating cholinergic and purinergic signaling in the brain after exposure for 7 consecutive days. PFOA significantly increased geotaxis as well as reduced vertical exploration (a behavioral endpoint for anxiety), and increased the frequency and duration of aggressive episodes without affecting their social preference. Exposure to PFOA did not affect ADP hydrolysis, whereas ATP and AMP hydrolysis were significantly increased at the highest concentration tested. However, AChE activity was markedly decreased in all PFOA-exposed groups when compared with control. In conclusion, PFOA induces aggression and anxiety-like behavior in adult zebrafish and modulates both cholinergic and purinergic signaling biomarkers. These novel data can provide valuable insights into possible health threats related to human activities, demonstrating the utility of adult zebrafish to elucidate how PFOA affects neurobehavioral responses in aquatic organisms.

Zebrafish as a potential non-traditional model organism in translational bipolar disorder research: Genetic and behavioral insights

Bipolar disorder (BD) is a severe and debilitating illness that affects 1-2% of the population worldwide. BD is characterized by recurrent and extreme mood swings, including mania/hypomania and depression. Animal experimental models have been used to elucidate the mechanisms underlying BD and different strategies have been proposed to assess BD-like symptoms. The zebrafish (Danio rerio) has been considered a suitable vertebrate system for modeling BD-like responses, due to the genetic tractability, molecular/physiological conservation, and well-characterized behavioral responses. In this review, we discuss how zebrafish-based models can be successfully used to understand molecular, biochemical, and behavioral alterations paralleling those found in BD. We also outline some advantages and limitations of this aquatic species to examine BD-like phenotypes in translational neurobehavioral research. Overall, we reinforce the use of zebrafish as a promising tool to investigate the neural basis associated with BD-like behaviors, which may foster the discovery of novel pharmacological therapies.

Influence of acid-sensing ion channel blocker on behavioral responses in a zebrafish model of acute visceral pain

Acid-sensing ion channels (ASICs) play significant roles in numerous neurological and pathological conditions, including pain. Although acid-induced nociception has been characterized previously in zebrafish, the contribution of ASICs in modulating pain-like behaviors is still unknown. Here, we investigated the role of amiloride, a nonselective ASICs blocker, in the negative modulation of specific behavioral responses in a zebrafish-based model of acute visceral pain. We verified that intraperitoneal injection (i.p.) of 0.25, 0.5, 1.0, and 2.0 mg/mL amiloride alone or vehicle did not change zebrafish behavior compared to saline-treated fish. Administration of 2.5% acetic acid (i.p.) elicited writhing-like response evidenced by the abnormal body curvature and impaired locomotion and motor activity. Attenuation of acetic acid-induced pain was verified at lower amiloride doses (0.25 and 0.5 mg/mL) whereas 1.0 and 2.0 mg/mL abolished pain-like responses. The protective effect of the highest amiloride dose tested was evident in preventing writhing-like responses and impaired locomotion and vertical activity. Collectively, amiloride antagonized abdominal writhing-like phenotype and aberrant behaviors, supporting the involvement of ASICs in a zebrafish-based model of acute visceral pain.

Indole-3-propionic acid mitigates chlorpyrifos-mediated neurotoxicity by modulating cholinergic and redox-regulatory systems, inflammatory stress, apoptotic responses and DNA damage in rats

This study probed the neuroprotective influence of indole-3-propionic acid (IPA) in rats exposed to chlorpyrifos (CPF) alone at 5 mg/kg body weight or co-administered with IPA at 12.5 and 25 mg/kg for 14 days. Behavioral data indicated that IPA significantly (p < 0.05) abated CPF-mediated anxiogenic-like behaviors with concomitant improvement in the locomotor and exploratory behaviors as substantiated by track plots and heat maps data. Also, IPA mitigated CPF-mediated diminution in cholinergic and antioxidant defense systems whereas it markedly improved thioredoxin level and thioredoxin reductase activity in cerebral and cerebellar tissues of the animals. Co-administration of IPA significantly enhanced anti-inflammatory cytokine, interleukin-10 but suppressed oxidative and inflammatory stress, caspase-9 and caspase-3 activation with concomitant reduction in 8-hydroxy-2'-deoxyguanosine (8-OHdG) level and histological damage. Collectively, IPA-mediated neuroprotection involves modulation of cholinergic and redox-regulatory systems, inflammatory stress, apoptotic responses and DNA damage in cerebrum and cerebellum of rats.

Chronic ciprofloxacin and atrazine co-exposure aggravates locomotor and exploratory deficits in non-target detritivore speckled cockroach (Nauphoeta cinerea)

The global detection of ciprofloxacin and atrazine in soil is linked to intensive anthropogenic activities in agriculture and inadvertent discharge of industrial wastes to the environment. Nauphoeta cinerea is a terrestrial insect with cosmopolitan distribution and great environmental function. The current study probed the neurobehavioral and cellular responses of N. cinerea singly and jointly exposed to atrazine (1.0 and 0.5 μg g^-1 feed) and ciprofloxacin (0.5 and 0.25 μg g^-1 feed) for 63 days. Results demonstrated that the reductions in the body rotation, maximum speed, turn angle, path efficiency, distance traveled, episodes, and time of mobility induced by atrazine or ciprofloxacin per se was exacerbated in the co-exposure group. The altered exploratory and locomotor in insects singly and jointly exposed to ciprofloxacin and atrazine were verified by track plots and heat maps. Furthermore, we observed a decrease in acetylcholinesterase and anti-oxidative enzyme activities with concomitant elevation in the levels of lipid peroxidation, nitric oxide, and reactive oxygen and nitrogen species were significantly intensified in the midgut, hemolymph, and head of insects co-exposed to ciprofloxacin and atrazine. In conclusion, exposure to binary mixtures of ciprofloxacin and atrazine elicited greater locomotor and exploratory deficits than upon exposure to the individual compound by inhibiting acetylcholinesterase activity and induction of oxido-inflammatory stress responses in the insects. N. cinerea may be a usable model insect for checking contaminants of ecological risks.

Abatement of the dysfunctional hypothalamic-pituitary-gonadal axis due to ciprofloxacin administration by selenium in male rats

The present study examined the influence of selenium on ciprofloxacin-mediated reproductive dysfunction in rats. The research design consisted of five groups of eight animals each. The rats were administered 135 mg/kg body weight of ciprofloxacin per se or simultaneously with selenium at 0.25 and 0.5 mg/kg for 15 uninterrupted days. Antioxidant and inflammatory indices were assayed using the testes, epididymis, and hypothalamus of the animals after sacrifice. Results revealed that ciprofloxacin treatment per se interfered with the reproductive axis as demonstrated by diminished serum hormonal levels, sperm quality, and enzymatic indices of testicular function, which were, however, abrogated following selenium co-treatment. Besides this, administration of selenium attenuated the depletion of glutathione level, inhibition of catalase, superoxide dismutase, glutathione-S-transferase and glutathione peroxidase activities with a concomitant reduction in reactive oxygen and nitrogen species, and lipid peroxidation in ciprofloxacin-treated in rats. Selenium treatment also mitigated ciprofloxacin-mediated elevation in nitric oxide level and of myeloperoxidase activity as well as histological lesions in the animals. Overall, selenium attenuated impairment in the male reproductive axis due to ciprofloxacin treatment through abatement of inflammation and oxidative stress in rats.

Toxicological outcome of exposure to psychoactive drugs carbamazepine and diazepam on non-target insect Nauphoeta cinerea

The continuous detection of human pharmaceuticals during environmental biomonitoring is a global concern because of the menaces they may exert on non-target organisms. Carbamazepine (CBZ) and diazepam (DZP) are commonly prescribed psychotropic drugs which have been reported to coexist in the environment globally. Nauphoeta cinerea is a common insect with high ecological impact. This study elucidated the influence of co-exposure to DZP (0.5 and 1.0 μg kg^-1 diet) and CBZ (1.5 and 3.0 μg kg^-1 diet) for 42 days on the behavior and biochemical responses in Nauphoeta cinerea. Results showed that DZP alone did not induce adverse effect on the behavior and antioxidant status in the exposed insects. However, exposure to CBZ alone and binary mixtures of DZP and CBZ significantly decreased locomotor and exploratory accomplishments evidenced by decreased mobile episodes, total mobile time, maximum speed, total distance traveled, absolute turn angle, body rotation and path efficiency in comparison with control. The decline observed in the exploratory activities of insects fed with CBZ alone and the mixtures was confirmed by track plots and heat maps. Further, acetylcholinesterase and antioxidant enzyme activities decreased significantly whereas reactive oxygen and nitrogen species, nitric oxide and lipid peroxidation levels increased significantly in the hemolymph, head and midgut of insects exposed to CBZ alone and the mixtures. Collectively, CBZ alone and binary mixtures of CBZ and DZP caused neurotoxicity via induction of inflammatory and oxidative stress in insects. Nauphoeta cinerea may be a potential non-target insect model for monitoring ecotoxicological hazard of pharmaceuticals.

Kolaviron ameliorates hepatic and renal dysfunction associated with multiwalled carbon nanotubes in rats

The increase in the exposure to carbon nanotubes (CNTs) and their incorporation into industrial, electronic, and biomedical products have required several scientific investigations into the toxicity associated with CNTs. Studies have shown that the metabolism and clearance of multiwalled CNTs (MWCNTs) from the body involve biotransformation in the liver and its excretion via the kidney. Since oxidative stress and inflammation underlines the toxicity of MWCNT, we investigated the ameliorative effect of kolaviron (KV), a natural antioxidant and anti-inflammatory agent, on hepatorenal damage in rats. Exposure to MWCNTs for 15 days significantly increased serum activities of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, and lactate dehydrogenase thereby suggesting hepatic dysfunction. Kidney function, which was monitored by urea and creatinine levels, was also impaired by MWCNTs. Additionally, MWCNTs markedly increased myeloperoxidase activity, nitric oxide level, reactive oxygen and nitrogen species, and tumor necrosis factor level in both tissues. However, KV in a dose-dependent manner markedly attenuated MWCNT-induced markers of hepatorenal function in the serum and MWCNT-associated inflammation in the liver and kidney. Also, MWCNTs elicited significant inhibition of superoxide dismutase, catalase, glutathione peroxidase, and glutathione-S-transferase activities. There was a significant diminution in glutathione level (GSH) and enhanced production of malondialdehyde (MDA) in MWCNTs-exposed rats. KV treatment was able to significantly increase the antioxidant enzymes and enhance the GSH level with a subsequent reduction in the MDA level. Taken together, KV elicited ameliorative effects against hepatorenal damage via its anti-inflammatory and antioxidant properties. Thus, KV could be an important intervention strategy for the hepatorenal damage associated with MWCNTs exposure.

Neuroprotective role of gallic acid in aflatoxin B1 -induced behavioral abnormalities in rats

The neurotoxic impact of dietary exposure to aflatoxin B₁ (AFB₁ ) is documented in experimental and epidemiological studies. Gallic acid (GA) is a triphenolic phytochemical with potent anticancer, anti-inflammatory, and antioxidant activities. There is a knowledge gap on the influence of GA on AFB₁ -induced neurotoxicity. This study probed the influence of GA on neurobehavioral and biochemical abnormalities in rats orally treated with AFB₁ per se (75 µg/kg body weight) or administered together with GA (20 and 40 mg/kg) for 28 uninterrupted days. Behavioral endpoints obtained with video-tracking software demonstrated significant (p < .05) abatement of AFB₁ -induced anxiogenic-like behaviors (increased freezing, urination, and fecal bolus discharge), motor and locomotor inadequacies, namely increased negative geotaxis and diminished grip strength, absolute turn angle, total time mobile, body rotation, maximum speed, and total distance traveled by GA. The improvement of exploratory behavior in animals that received both AFB₁ and GA was confirmed by track plots and heat maps appraisal. Abatement of AFB₁ -induced decreases in acetylcholinesterase activity, antioxidant status and glutathione level by GA was accompanied by a marked reduction in oxidative stress markers in the cerebellum and cerebrum of rats. Additionally, GA treatment abrogated AFB₁ -mediated decrease in interleukin-10 and elevation of inflammatory indices, namely tumor necrosis factor-α, myeloperoxidase activity, interleukin-1β, and nitric oxide. Further, GA treatment curtailed caspase-3 activation and histological injuries in the cerebral and cerebellar tissues. In conclusion, abatement of AFB₁ -induced neurobehavioral abnormalities by GA involves anti-inflammatory, antioxidant, and antiapoptotic mechanisms in rats.

Ethanol exacerbates manganese-induced oxidative/nitrosative stress, pro-inflammatory cytokines, nuclear factor-κB activation, and apoptosis induction in rat cerebellar cortex

Manganese (Mn) exposure is causing public health concerns as well as heavy alcohol consumption. This study investigates the mechanisms of neurotoxicity associated with Mn and ethanol (EtOH) exposure in the rat cerebellar cortex. Experimental animals received 30 mg/kg of Mn alone, 5 g/kg of EtOH alone, co-exposed with 30 mg/kg of Mn and 1.25 or 5 g/kg EtOH, while control animals received water by oral gavage for 35 days. Subsequently, alterations in the neuronal morphology of the cerebellar cortex, oxidative/nitrosative stress, acetylcholinesterase (AChE) activity, neuro-inflammation and protein expression of p53, BAX, caspase-3, and BCL-2 were investigated. The results indicate that Mn alone and EtOH alone induce neuronal alterations in the cerebellar cortex, decrease glutathione level and antioxidant enzyme activities, along with an increase in AChE activity, lipid peroxidation, and hydrogen peroxide generation. Mn alone and EtOH alone also increased neuro-inflammatory markers, namely nitric oxide, myeloperoxidase activity, interleukin-1β, tumor necrosis factor-α, and nuclear factor-κB (NF-κB) levels in the cerebellar cortex. Immunohistochemistry analysis further revealed that exposure of Mn alone and EtOH alone increases the protein expression of cyclooxygenase-2, BAX, p53, and caspase-3 and decrease BCL-2 in the rat cerebellar cortex. Furthermore, the results indicated that Mn co-exposure with EtOH at 1.25 and 5 g/kg EtOH significantly (p ≤ .05) increases the toxicity in the cerebellum when compared with the toxicity of Mn or EtOH alone. Taken together, co-exposure of Mn and EtOH exacerbates neuronal alterations, oxidative/nitrosative stress, AChE activity, pro-inflammatory cytokines, NF-κB signal transcription, and apoptosis induction in the rat cerebellar cortex.

Hazardous impact of diclofenac exposure on the behavior and antioxidant defense system in Nauphoeta cinerea

Environmental pollution by pharmaceuticals such as diclofenac (DCF) is globally acknowledged to be a threat to the ecosystems. Nauphoeta cinerea is an important insect with valuable ecological role. The present investigation aimed to elucidate the impact of DCF on insects by assessing the behavior and antioxidant defense response in nymphs of N. cinerea exposed to DCF-contaminated food at 0, 0.5, 1.0 and 2.0 μg kg^-1 feed for 42 successive days. Subsequent to exposure period, neurobehavioral analysis using video-tracking software in a novel apparatus was performed before estimation of biochemical endpoints in the head, midgut and hemolymph of the insects. Results indicated that DCF-exposed insects exhibited marked reduction in the maximum speed, total distance traveled, mobile episodes, total mobile time, body rotation, absolute turn angle and path efficiency, whereas the total freezing time was increased compared with the control. The diminution in the exploratory activities of DCF-exposed insects was substantiated by heat maps and track plots. Additionally, DCF elicited marked diminution in antioxidant enzyme and acetylcholinesterase (AChE) activities along with increase in nitric oxide (NO), reactive oxygen and nitrogen species (RONS), and lipid peroxidation (LPO) levels in the head, midgut and hemolymph of the insects. Taken together, DCF elicited neurotoxicity and oxido-inflammatory stress in exposed insects. N. cinerea may be a suitable model insect for environmental risk assessment of pharmaceuticals in non-target insect species.

Nigral and ventral tegmental area lesioning induces testicular and sperm morphological abnormalities in a rotenone model of Parkinson's disease

Although sexual health is affected by Parkinson's disease (PD), the effect on testicular health and/or sperm quality is not well discussed. After 21 days of rotenone lesioning, we observed dopaminergic neuronal degeneration in the substantia nigra and hypothalamus. There were minimal SPACA-1-expressing epididymal spermatozoa with morphological abnormalities, scanty luminal spermatozoa and reduced testicular spermatids and post-meiotic germ cells indicating hypospermatogenesis. Occludin-expressing sertoli cells were dispersed over a wide area indicating compromised blood-testes barrier. Activated caspase-3 expression was intense while immunoreactivity of spermatogenic-enhancing SRY and GADD45 g was weak. Although serum follicle stimulating hormone level was not affected, the lesion was associated with reduced serum testosterone level, testicular oxidative damage and inhibition of acetylcholinesterase activity, even when rotenone was not detected in the testes. Together, dopaminergic lesions may mediate testicular and sperm abnormalities via the brain-hypothalamic-testicular circuit independent of the pituitary, thereby establishing a causal link between Parkinsonism and reproductive dysfunction.

Abstract A39: 6-Gingerol, a chemopreventive phytochemical as speed breaker in inflammatory and stress signaling cascade triggered by benzo(a)pyrene and dextran sulphate sodium-mediated colorectal cancer in mice

Preclinical and clinical investigations have identified unresolved inflammation and oxidative/nitrosative stress as two coconspirators, which play a multifaceted role and serve as driving force in the journey to cancer development. Ulcerative colitis is an inflammatory disease of the colon that predisposes to colorectal cancer, the fourth leading cause of cancer worldwide. Overexpression of proinflammatory mediators, a distinct network of intracellular signaling molecules including upstream kinases and transcription factors, facilitates tumor promotion and CRC progression. Current therapeutic drugs for CRC have severe adverse effects. Several investigations indicate that a plant-based diet rich in a wide variety of fruits and vegetables is effective in preventing or reversing premalignant lesions. Thus, the search for novel chemopreventive agents of physiologic relevance acting on specific and/or multiple molecular and cellular targets holds promise as a rational strategy for the control of health-threatening diseases such as ulcerative colitis and CRC. A bioactive component, 6-gingerol from ginger (Zingiber officinale) has been reported to possess antioxidant and anti-inflammatory activities. Our study demonstrates that 6-gingerol protects against dextran sulfate sodium (DSS)-induced ulcerative colitis in BalBc mice. 6-Gingerol attenuated DSS-mediated increase in immunoexpression of nuclear factor kappa B (NF-κB [p65]), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1 β), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), mitogen-activated kinase (P 38), RANTES, Bcl2, monocyte chemoattractant protein (MCP-1), and β-catenin expression. Similarly, 6-gingerol modulated DSS decrease in adenomatous polyposis coli (APC), DESMIN, Interleukin 10, and levels of antioxidant enzymes. In the two-stage (DMBA initiation and TPA promotion) mouse skin carcinogenesis model, 6-gingerol downregulated the expression of COX-2 and NF-κB. Also, in the benzo(a)pyrene and DSS (BDS) model of colorectal cancer, BDS induced adenocarcinoma and decreased APC, p53 expression, and number of apoptotic cells. In addition, tumor incidence, β-catenin, and cyclin D1 expressions were increased. Treatment with 6-gingerol decreased adenocarcinoma significantly and modulated the expression of these proteins and transcription factors. This anti-inflammatory phytochemical exerted chemopreventive effects by modulating intracellular signaling cascades and proinflammatory mediators and therefore qualifies as therapeutic signature for chemoprevention of inflammation-associated CRC.

Citation Format: Ebenezer O. Farombi, Babajide O. Ajayi, Isaac A. Adedara, Solomon E. Owumi. 6-Gingerol, a chemopreventive phytochemical as speed breaker in inflammatory and stress signaling cascade triggered by benzo(a)pyrene and dextran sulphate sodium-mediated colorectal cancer in mice [abstract]. In: Proceedings of the AACR Special Conference on Environmental Carcinogenesis: Potential Pathway to Cancer Prevention; 2019 Jun 22-24; Charlotte, NC. Philadelphia (PA): AACR; Can Prev Res 2020;13(7 Suppl): Abstract nr A39.

Gallic acid enhances reproductive function by modulating oxido-inflammatory and apoptosis mediators in rats exposed to aflatoxin-B1

IMPACT STATEMENT

Infertility resulting from reproductive deficiency can be stressful. Exposure to aflatoxin B1, a dietary mycotoxin prevalent in improperly stored grains, is reported to elicit reproductive insufficiencies and infertility. We, therefore, examined the likely beneficial effect of gallic acid (GA) a phytochemical, recognized to exhibit in vitro and in vivo pharmacological bioactivities against oxidative stress and related inflammatory damages in rats, since AFB1 toxicities are predicated on oxidative epoxide formation, in a bid to proffer new evidence to advance the field of nutriceutical application from plant-derived chemopreventive agents. Our findings will advance the field of chemoprevention by presenting data absent in the literature on GA. Our results demonstrate further evidence for GA conferred protection against AFB1-mediated histological lesions in testes, epididymis, and hypothalamus of treated rats; suppresses oxidative damages, relieved inflammatory and apoptotic responses, restored sperm functional characteristics, and hormonal levels relevant for reproductive integrity and function.

Correction to: Kolaviron via anti-inflammatory and redox regulatory mechanisms abates multi-walled carbon nanotubes-induced neurobehavioral deficits in rats

After publication of this paper, the authors discovered that the name of the first author, Isaac Adegboyega Adedara, was missing in the proof. Dr. Adedara's intellectual contributions to the present article include conception and design of the study, manuscript writing and approval of the final version of the manuscript.

Kolaviron via anti-inflammatory and redox regulatory mechanisms abates multi-walled carbon nanotubes-induced neurobehavioral deficits in rats

Exposure to multi-walled carbon nanotubes (MWCNTs) reportedly elicits neurotoxic effects. Kolaviron is a phytochemical with several pharmacological effects namely anti-oxidant, anti-inflammatory, and anti-genotoxic activities. The present study evaluated the neuroprotective mechanism of kolaviron in rats intraperitoneally injected with MWCNTs alone at 1 mg/kg body weight or orally co-administered with kolaviron at 50 and 100 mg/kg body weight for 15 consecutive days. Following exposure, neurobehavioral analysis using video-tracking software during trial in a novel environment indicated that co-administration of both doses of kolaviron significantly (p < 0.05) enhanced the locomotor, motor, and exploratory activities namely total distance traveled, maximum speed, total time mobile, mobile episode, path efficiency, body rotation, absolute turn angle, and negative geotaxis when compared with rats exposed to MWCNTs alone. Further, kolaviron markedly abated the decrease in the acetylcholinesterase activity and antioxidant defense system as well as the increase in oxidative stress and inflammatory biomarkers induced by MWCNT exposure in the cerebrum, cerebellum, and mid-brain of rats. The amelioration of MWCNT-induced neuronal degeneration in the brain structures by kolaviron was verified by histological and morphometrical analyses. Taken together, kolaviron abated MWCNT-induced neurotoxicity via anti-inflammatory and redox regulatory mechanisms.

Neurobehavioural and biochemical responses associated with exposure to binary waterborne mixtures of zinc and nickel in rats

Environmental and occupational exposure to metal mixtures due to various geogenic and anthropogenic activities poses a health threat to exposed organisms. The outcome of systemic interactions of metals is a topical area of research because it may cause either synergistic or antagonistic effect. The present study investigated the impact of co-exposure to environmentally relevant concentrations of waterborne nickel (75 and 150 μg NiCl ₂ L^-1) and zinc (100 and 200 μg ZnCl₂ L^-1) mixtures on neurobehavioural performance of rats. Locomotor, motor and exploratory activities were evaluated using video-tracking software during trial in a novel arena and thereafter, biochemical and histological analyses were performed using the cerebrum, cerebellum and liver. Results indicated that zinc significantly (p < 0.05) abated the nickel-induced locomotor and motor deficits as well as improved the exploratory activity of exposed rats as verified by track plots and heat map analyses. Moreover, zinc mitigated nickel-mediated decrease in acetylcholinesterase activity, elevation in biomarkers of liver damage, levels of reactive oxygen and nitrogen species as well as lipid peroxidation in the exposed rats when compared with control. Additionally, nickel mediated decrease in antioxidant enzyme activities as well as the increase in tumour necrosis factor alpha, interleukin-1 beta and caspase-3 activity were markedly abrogated in the cerebrum, cerebellum and liver of rats co-exposed to nickel and zinc. Histological and histomorphometrical analyses evinced that zinc abated nickel-mediated neurohepatic degeneration as well as quantitative reduction in the widest diameter of the Purkinje cells and the densities of viable granule cell layer of dentate gyrus, pyramidal neurones of cornu ammonis 3 and cortical neurons in the exposed rats. Taken together, zinc abrogated nickel-induced neurohepatic damage via suppression of oxido-inflammatory stress and caspase-3 activation in rats.

Impact of binary waterborne mixtures of nickel and zinc on hypothalamic-pituitary-testicular axis in rats

Several evidences from the literature showed that the coexistence of nickel and zinc in polluted waters is related to the similarity in their geogenic and anthropogenic factors. Although most environmental exposures to metals do not occur singly, there is a paucity of scientific knowledge on the effects of zinc and nickel co-exposure on mammalian reproductive health. The present study investigated the influence of co-exposure to nickel and zinc on male reproductive function in rats. Experimental rats were co-exposed to environmentally relevant concentrations of waterborne nickel (75 and 150 μg NiCl₂ L^-1) and zinc (100 and 200 μg ZnCl₂ L^-1) for 45 successive days. Subsequently, reproductive hormones were assayed whereas the hypothalamus, epididymis and testes of the rats were processed for the assessment of oxidative stress and inflammation indices, caspase-3 activity and histology. Results indicated that co-exposure to nickel and zinc significantly (p < 0.05) abolished nickel-mediated diminution of antioxidant defense mechanisms while diminishing levels of reactive oxygen and nitrogen species and lipid peroxidation in the hypothalamus, epididymis and testes of the exposed rats. Additionally, co-exposure to zinc abated nickel-mediated diminutions in luteinizing hormone, follicle-stimulating hormone, serum and intra-testicular testosterone with concomitant enhancement of sperm production and quality. Further, zinc abrogated nickel-mediated elevation in inflammatory biomarkers including nitric oxide, tumor necrosis factor alpha, interleukin-1 beta as well as caspase-3 activity. The protective influence of zinc on nicked-induced reproductive toxicity was well supported by histological data. Overall, zinc ameliorated nickel-induced reproductive dysfunction via its anti-oxidant, anti-inflammatory, anti-apoptotic and spermato-protective activities in rats.

Protective role of resveratrol, a natural polyphenol, in sodium fluoride-induced toxicity in Drosophila melanogaster

Sodium fluoride (NaF) is used in water fluoridation and dental products such as mouth rinses and toothpastes. Resveratrol is a natural polyphenol with antioxidant and anti-inflammatory properties. The present study was carried out to evaluate the toxicity of NaF and the protective role of resveratrol in Drosophila melanogaster. For longevity assay, Harwich strain of D. melanogaster was treated with NaF (0, 10, 30, 50, 70 and 90 mg/kg diet) throughout the lifespan and daily mortality recorded. Then, flies were again treated with similar doses of NaF for seven days to evaluate survival rate and oxidative stress markers. Thereafter, 60 mg resveratrol/kg diet was selected to determine its ameliorative role in NaF (70 mg/kg)-induced toxicity in flies: Group A (control), Group B (60 mg resveratrol/kg diet), Group C (70 mg NaF/kg diet), and Group D (resveratrol, 60 mg/kg diet) + NaF, 70 mg/kg diet). Thereafter, Glutathione-S-transferase (GST), catalase and acetylcholinesterase (AchE) activities, as well as total thiol (T-SH), nitrites/nitrates and hydrogen peroxide (H2O2) levels were determined. The results showed that resveratrol prevented NaF-induced elevation of H2O2and nitrites/nitrates levels, as well as catalase activity. In addition, resveratrol restored NaF-induced inhibition of GST and AChE activities and depletion of T-SH content ( P < 0.05). Conclusively, resveratrol offered protective benefit against NaF-mediated toxicity in flies due to its antioxidant and anti-inflammatory properties.

Impact statement

D. melanogaster was used to understand the impact of NaF on lifespan and emergence rate as well as the rescue role of resveratrol. These parameters are difficult to carry out in previously used models such as rodents. This further enforces in part, the suitability of D. melanogaster in studying NaF-induced toxicity and the therapeutic effects of drugs. Additionally, we found that resveratrol rescued D. melanogaster from oxidative stress-induced by sodium fluoride (NaF) administration. This study is of public health significance as it indicated that the consumption of fruits rich in resveratrol such as grapes may offer protective role against inadvertent exposure to NaF and related chemicals.

Selenium abates reproductive dysfunction via attenuation of biometal accumulation, oxido-inflammatory stress and caspase-3 activation in male rats exposed to arsenic

Frequent exposure to arsenic is well documented to impair reproductive function in humans and animals. Biological significance of inorganic selenium and organoselenium, diphenyl diselenide (DPDS), has been attributed to their pharmacological activities. However, their roles in arsenic-mediated reproductive toxicity is lacking in literature. The present study evaluated the protective effects elicited by selenium and DPDS in arsenic-induced reproductive deficits in rats. Animals were either exposed to arsenic alone in drinking water at 60 μg AsO₂Na L^-1 or co-treated with selenium at 0.25 mg kg^-1 or DPDS at 2.5 mg kg^-1 body weight for 45 consecutive days. Results indicated that arsenic-mediated deficits in spermatogenic indices and marker enzymes of testicular function were significantly abrogated in rats co-treated with selenium or DPDS. Additionally, selenium or DPDS co-treatment prevented arsenic-mediated elevation in oxidative stress indices and significantly suppressed arsenic-mediated inflammation evidenced by diminished myeloperoxidase activity, nitric oxide, tumor necrosis factor alpha and interleukin-1 beta levels in hypothalamus, testes and epididymis of the rats. Moreover, selenium or DPDS abrogated arsenic mediated activation of caspase-3 activity and histological lesions in the treated rats. Taken together, selenium or DPDS improved reproductive function in arsenic-exposed rats via suppression of inflammation, oxidative stress and caspase-3 activation in rats.

Ethanol Exacerbates Manganese-Induced Neurobehavioral Deficits, Striatal Oxidative Stress, and Apoptosis Via Regulation of p53, Caspase-3, and Bax/Bcl-2 Ratio-Dependent Pathway

This study investigated the effects of ethanol (EtOH) on manganese (Mn)-induced striatal toxicity in rat by evaluating the neurobehavioral changes, biochemical and molecular events in rats exposed to Mn alone at 30 mg/kg, or their combination with EtOH at 1.25- and 5-g/kg body weight for 35 consecutive days. Locomotive and exploratory profiles were assessed using a video tracking software (ANY-Maze software) during a 5-min trial in a novel environment. Subsequently, acetylcholinesterase (AChE) activity, oxidative stress markers, histological morphology, and expression of apoptotic proteins (p53 and Bax and caspase-3) and anti-apoptotic protein (Bcl-2) were assessed in the striatum. Results showed that Mn, EtOH, and their combination induced locomotor and motor deficits. Track plot analysis indicated that EtOH exacerbated the Mn-induced reduction in exploratory profiles of exposed rats. Similarly, exposure of rats to Mn, EtOH, or combination of Mn and EtOH resulted in decreased activities of anti-oxidant enzymes, diminished level of reduced glutathione, downregulated Bcl-2 expression, increased AChE activity, enhanced hydrogen peroxide and lipid peroxidation levels, and upregulated expressions of p53, Bax, and caspase-3. Moreover, potentiation of Mn-induced striatal toxicity by EtOH co-exposure was dose dependent. Taken together, it seems that EtOH exacerbates Mn-induced neurobehavioral deficits, oxidative stress, and apoptosis induction via the regulation of p53, caspase-3, and Bax/Bcl-2 ratio-dependent pathway in rat striatum.

Ethanol via Regulation of NF-κB/p53 Signaling Pathway Increases Manganese-Induced Inflammation and Apoptosis in Hypothalamus of Rats

The diet is a major route of manganese (Mn) exposure for humans. Interestingly, several epidemiological data demonstrated an increase in the incidence of alcohol consumption globally. Chemical-chemical interaction subsequent to chemical mixtures exposure may result in a synergism or antagonism effects. The present study investigated the influence of co-exposure to ethanol (EtOH) and Mn on inflammation and apoptosis in the hypothalamus of rats. The study consisted of five groups of rats that were exposed to drinking water alone, EtOH alone at 5 g/kg, Mn alone at 30 mg/kg or co-expose with EtOH at 1.25 and 5 g/kg body weight by oral gavage for 35 consecutive days. The results indicated that the significant (p < 0.05) increases in pro-inflammatory cytokines, namely tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) as well as cyclooxygenase-2 (COX-2) and nuclear factor kappa B (NF-κB) activation in the hypothalamus following individual exposure to Mn and EtOH to rats were intensified in the co-exposure group. Moreover, immunohistochemistry analysis showed marked decrease in B cell lymphoma-2 (Bcl-2) protein expression as well as the increases in the apoptotic proteins, namely Bax and caspase-3 along with p53 in the hypothalamus of rats treated with Mn or EtOH alone were intensified in the co-exposure group. Taken together, these findings highlight that EtOH exacerbated the induction of inflammatory and apoptotic biomarkers via regulation of NF-κB/p53 signaling pathways in the hypothalamus of rats. These alterations may have profound disrupting effects on the hypothalamus functions such as impairment of it metabolic and autonomic nervous system functions.

6-Gingerol abates benzo[a]pyrene-induced colonic injury via suppression of oxido-inflammatory stress responses in BALB/c mice

Exposure to benzo[a]pyrene (BaP), the most toxic polycyclic aromatic hydrocarbon and a procarcinogen, is a global health concern which necessitates preventive measures. [6]-Gingerol (6-G), the most pharmacologically active constituent of ginger has been reported to promote gut health in various experimental settings. This study investigated the role of 6-G in BaP-induced colonic oxidative and inflammatory stress responses in mice. Experimental mice were randomly assigned into five groups of eight mice each and were orally gavage with BaP (125 mg/kg) singly or in combination with 6-G at 50 and 100 mg/kg for 14 consecutive days. Following sacrifice, the colonic activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), myeloperoxidase (MPO) as well as levels of glutathione (GSH), nitrites and lipid peroxidation (LPO) were assessed spectrophotometrically. Moreover, colonic concentration of epoxide hydrolase (EPXH), tumor necrosis factor alpha (TNF-α), interleukin-1 β (IL-1β), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were assessed using ELISA. Administration of 6-G augmented BaP detoxification and colonic antioxidant status by increasing the EPXH, GST, SOD and CAT activities, GSH level with concomitant decrease in MDA level when compared with BaP alone group. In addition, 6-G suppressed BaP-induced colonic inflammation by decreasing MPO activity as well as nitrites, TNF-α, IL-1β, COX-2 and iNOS levels when compared with BaP alone group. In conclusion, 6-G protected against a decrease in colonic epoxide detoxifying enzymes and antioxidant defense mechanisms caused by BaP.

Dietary co-exposure to methylmercury and monosodium glutamate disrupts cellular and behavioral responses in the lobster cockroach, Nauphoeta cinerea model

The present study aims to investigate the effect of monosodium glutamate (MSG) both separately and combined with a low dose of methylmercury (MeHg) on behavioral and biochemical parameters in Nauphoeta cinerea (lobster cockroach). Cockroaches were fed with the basal diet alone, basal diet + 2% NaCl, basal diet + 2% MSG; basal diet + 0.125 mg/g MeHg, basal diet + 0.125 mg/g MeHg + 2% NaCl; and basal diet + 0.125 mg/g MeHg + 2% MSG for 21 days. Behavioral parameters such as distance traveled, immobility and turn angle were automatically measured using ANY-maze video tracking software (Stoelting, CO, USA). Biochemical end-points such as acetylcholinesterase (AChE), glutathione-S-transferase (GST), total thiol and TBARS were also evaluated. Results show that MeHg + NaCl, increased distance traveled while MeHg + MSG increased time immobile. AChE activity was significantly reduced in cockroaches across all the groups when compared to the control. There was no significant alteration in GST activity and total thiol levels. It could be that both NaCl and MSG potentiates the neurotoxic effect of MeHg in cockroaches.

Protective mechanisms of 6-gingerol in dextran sulfate sodium-induced chronic ulcerative colitis in mice

Ulcerative colitis (UC) is a relapsing and remitting inflammatory disease of the colon, with an increasing incidence worldwide. 6-Gingerol (6G) is a bioactive constituent of Zingiber officinale, which has been reported to possess various biological activities. This study was designed to evaluate the role of 6G in chronic UC. Chronic UC was induced in mice by three cycles of 2.5% dextran sulfate sodium (DSS) in drinking water. Each cycle consisted of 7 days of 2.5% DSS followed by 14 days of normal drinking water. 6G (100 mg/kg) and a reference anti-colitis drug sulfasalazine (SZ) (100 mg/kg) were orally administered daily to the mice throughout exposure to three cycles of 2.5% DSS. Administration of 6G and SZ significantly prevented disease activity index and aberrant crypt foci formation in DSS-treated mice. Furthermore, 6G and SZ suppresses immunoexpression of tumor necrosis factor alpha, interleukin-1β, inducible nitric oxide synthase, Regulated on activation, normal T cell expressed and secreted (RANTES), and Monocyte chemoattractant protein-1 (MCP-1) in the DSS-treated mice. 6G effectively protected against colonic oxidative damage by augmenting the antioxidant status with marked decrease in lipid peroxidation levels in DSS-treated mice. Moreover, 6G significantly inhibited nuclear factor kappa B (P65), p38, cyclooxygenase-2, and β-catenin whereas it enhanced IL-10 and adenomatous polyposis coli expression in DSS-treated mice. In conclusion, 6G prevented DSS-induced chronic UC via anti-inflammatory and antioxidative mechanisms and preservation of the Wnt/β-catenin signaling pathway.

Diphenyl diselenide abrogates brain oxidative injury and neurobehavioural deficits associated with pesticide chlorpyrifos exposure in rats

Exposure to pesticide chlorpyrifos (CPF) is associated with neurodevelopmental toxicity both in humans and animals. Diphenyl diselenide (DPDS) is a simple synthetic organoselenium well reported to possess antioxidant, anti-inflammatory and neuroprotective effects. However, there is paucity of information on the beneficial effects of DPDS on CPF-mediated brain injury and neurobehavioural deficits. The present study investigated the neuroprotective mechanism of DPDS in rats sub-chronically treated with CPF alone at 5 mg/kg body weight or orally co-treated with DPDS at 2.5 and 5 mg/kg body weight for 35 consecutive days. Endpoint analyses using video-tracking software in a novel environment revealed that co-treatment with DPDS significantly (p < 0.05) protected against CPF-mediated locomotor and motor deficits precisely the decrease in maximum speed, total distance travelled, body rotation, absolute turn angle, forelimb grip strength as well as the increase in negative geotaxis and incidence of fecal pellets. The enhancement in the neurobehavioral activities of rats co-treated with DPDS was verified by track plot analyses. Besides, DPDS assuaged CPF-induced decrease in acetylcholinesterase and antioxidant enzymes activities and the increase in myeloperoxidase activity and lipid peroxidation level in the mid-brain, cerebral cortex and cerebellum of the rats. Histologically, DPDS co-treatment abrogated CPF-mediated neuronal degeneration in the cerebral cortex, dentate gyrus and cornu ammonis3 in the treated rats. In conclusion, the neuroprotective mechanisms of DPDS is related to the prevention of oxidative stress, enhancement of redox status and acetylcholinesterase activity in brain regions of the rats. DPDS may be a promising chemotherapeutic agent against brain injury resulting from CPF exposure.

[6]-Gingerol modulates spermatotoxicity associated with ulcerative colitis and benzo[a]pyrene exposure in BALB/c mice

BACKGROUND

The deterioration of male reproductive health may represent an outcome of an active disease and environmental factors. The present study investigated the modulatory role of [6]-gingerol in spermatotoxicity resulting from colitis and benzo[a]pyrene (B[a]P), an environmental and food-borne pollutant.

METHODS

Group I (control) mice received corn oil alone, while group II ([6]-gingerol alone) mice orally received [6]-gingerol alone at 100 mg/kg body weight. Group III [benzo[a]pyrene+dextran sulfate sodium (BDS) alone] mice were orally exposed to B[a]P at 125 mg/kg for 7 days followed by three cycles of 4% dextran sulfate sodium (DSS) in drinking water. A cycle consisted of seven consecutive days of exposure to DSS-treated water followed by 14 consecutive days of normal drinking water. Group IV (BDS+[6]-gingerol) mice were orally treated daily with 100 mg/kg of [6]-gingerol during exposure to B[a]P and DSS in the same manner as those of group III.

RESULTS

[6]-Gingerol significantly abrogated BDS-mediated increase in disease activity index and restored the colon wet weight, colon length and colon mass index to near normal when compared to BDS alone group. Moreover, [6]-gingerol significantly prevented BDS-induced decreases in the daily sperm production (DSP), testicular sperm number (TSN), epididymal sperm number, sperm progressive motility and sperm membrane integrity when compared with the control. [6]-Gingerol markedly increased the sperm antioxidant enzymes activities and decreased the sperm head, mid-piece and tail abnormalities as well as suppressed oxidative stress and inflammatory biomarkers in BDS-exposed mice.

CONCLUSIONS

[6]-Gingerol protected against spermatotoxicity in experimental model of interaction of colitis with environmental pollutant B[a]P.

Low doses of multi-walled carbon nanotubes elicit hepatotoxicity in rats with markers of oxidative stress and induction of pro-inflammatory cytokines

The investigation into the potential health risks associated with the use of engineered nanoparticles is a major scientific interest in recent years. The present study elucidated the involvement of pro-inflammatory cytokines, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in carboxylated multi-walled carbon nanotubes (MWCNTs)-induced hepatotoxicity. Pubertal rats were exposed to purified MWCNTs at 0, 0.25, 0.50, 0.75 and 1.0 mg/kg for 5 consecutive days. Results indicated that exposure to MWCNTs caused liver damage evidenced by significant elevation in serum activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma glutamyl transferase (GGT) when compared with control. Moreover, MWCNTs significantly decreased superoxide dismutase (SOD) and glutathione S-transferase (GST) activities as well as glutathione level whereas it significantly increased catalase (CAT) and glutathione peroxidase (GPx) activities in liver of the treated rats. Moreover, the dose-dependent increase in hepatic hydrogen peroxide (H₂O₂) and lipid peroxidation levels were accompanied by marked increase in micronucleated polychromatic erythrocytes (MNPCE) in the MWCNTs-treated rats. Administration of MWCNTs significantly increased serum concentrations of pro-inflammatory cytokines namely interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in the treated rats. Immunohistochemical analysis showed significantly increased COX-2 and iNOS protein expressions in the liver of MWCNTs-treated rats. In conclusion, carboxylated MWCNTs induces hepatic damage via disruption of antioxidant defense systems, promotion of pro-inflammatory cytokines generation and expression of COX-2 and i-NOS in rats.