Mechanistic exploration of quercetin against metronidazole induced neurotoxicity in rats: Possible role of nitric oxide isoforms and inflammatory cytokines

The potential liver injury induced by metronidazole-provoked disturbance of gut microbiota: modulatory effect of turmeric supplementation

It has been reported that the gut-liver axis and intestinal microbiome contribute crucially to different liver diseases. So, targeting this hepato-intestinal connection may provide a novel treatment modality for hepatic disorders such as drug-induced liver injury (DILI). The present study thought to investigate the protective effect of turmeric (TUR) on metronidazole (MNZ)-induced liver damage and the possible association of the gut-liver axis and gut microbiota as a suggested underlying mechanism. In the first experiment, a MNZ-induced liver injury rat model was reproduced after 130 mg/kg oral MNZ administration for 30 days. Meanwhile, the treatment group was orally treated with 100 mg/kg turmeric daily. In the second experiment, fecal microbiome transplantation (FMT) was conducted, in which the fecal microbiome of each group in the first experiment was transplanted to a healthy corresponding group in the second experiment. The liver enzymes (aminotransferase (ALT) and aspartate aminotransferase (AST)) and histopathological examination were estimated to assess liver function. Inflammatory cytokines and oxidative markers were evaluated in the liver tissues. Histological analysis, intestinal barrier markers, and expression of tight junction proteins were measured for assessment of the intestinal injury. Changes in the gut microbial community and possible hepatic bacterial transmission were analyzed using 16S rRNA sequencing. MNZ induced intestinal and liver injuries which were significantly improved by turmeric. Increased firmicutes/bacteroidetes ratio and bacterial transmission due to gut barrier disruption were suggested. Moreover, TUR has maintained the gut microbial community by rebalancing and restoring bacterial proportions and abundance, thereby repairing the gut mucosal barrier and suppressing bacterial translocation. TUR protected against MNZ-induced gut barrier disruption. Reshaping of the intestinal bacterial composition and prohibition of the hepatic microbial translocation were suggested turmeric effects, potentially mitigating MNZ-related liver toxicity.

Bacteroidota inhibit microglia clearance of amyloid-beta and promote plaque deposition in Alzheimer's disease mouse models

The gut microbiota and microglia play critical roles in Alzheimer's disease (AD), and elevated Bacteroides is correlated with cerebrospinal fluid amyloid-β (Aβ) and tau levels in AD. We hypothesize that Bacteroides contributes to AD by modulating microglia. Here we show that administering Bacteroides fragilis to APP/PS1-21 mice increases Aβ plaques in females, modulates cortical amyloid processing gene expression, and down regulates phagocytosis and protein degradation microglial gene expression. We further show that administering Bacteroides fragilis to aged wild-type male and female mice suppresses microglial uptake of Aβ1-42 injected into the hippocampus. Depleting murine Bacteroidota with metronidazole decreases amyloid load in aged 5xFAD mice, and activates microglial pathways related to phagocytosis, cytokine signaling, and lysosomal degradation. Taken together, our study demonstrates that members of the Bacteroidota phylum contribute to AD pathogenesis by suppressing microglia phagocytic function, which leads to impaired Aβ clearance and accumulation of amyloid plaques.

Exercise mitigates a gut microbiota-mediated reduction in adult hippocampal neurogenesis and associated behaviours in rats

Lifestyle factors, especially exercise, impact the manifestation and progression of psychiatric and neurodegenerative disorders such as depression and Alzheimer's disease, mediated by changes in hippocampal neuroplasticity. The beneficial effects of exercise may be due to its promotion of adult hippocampal neurogenesis (AHN). Gut microbiota has also been showed to be altered in a variety of brain disorders, and disturbances of the microbiota have resulted in alterations in brain and behaviour. However, whether exercise can counteract the negative effects of altered gut microbiota on brain function remains under explored. To this end, chronic disruption of the gut microbiota was achieved using an antibiotic cocktail in rats that were sedentary or allowed voluntary access to running wheels. Sedentary rats with disrupted microbiota displayed impaired performance in hippocampal neurogenesis-dependent tasks: the modified spontaneous location recognition task and the novelty suppressed feeding test. Performance in the elevated plus maze was also impaired due to antibiotics treatment. These behaviours, and an antibiotics-induced reduction in AHN were attenuated by voluntary exercise. The effects were independent of changes in the hippocampal metabolome but were paralleled by caecal metabolomic changes. Taken together these data highlight the importance of the gut microbiota in AHN-dependent behaviours and demonstrate the power of lifestyle factors such as voluntary exercise to attenuate these changes.

Novel protective aspects of dietary polyphenols against pesticidal toxicity and its prospective application in rice-fish mode: A Review

The rice fish system represents an innovative and sustainable approach to integrated farming, combining rice cultivation with fish rearing in the same ecosystem. However, one of the major challenges in this system is the pesticidal pollution resulting from various sources, which poses risks to fish health and overall ecosystem balance. In recent years, dietary polyphenols have emerged as promising bioactive compounds with potential chemo-preventive and therapeutic properties. These polyphenols, derived from various plant sources, have shown great potential in reducing the toxicity of pesticides and improving the health of fish within the rice fish system. This review aims to explore the novel aspects of using dietary polyphenols to mitigate pesticidal toxicity and enhance fish health in the rice fish system. It provides comprehensive insights into the mechanisms of action of dietary polyphenols and their beneficial effects on fish health, including antioxidant, anti-inflammatory, and detoxification properties. Furthermore, the review discusses the potential application methods of dietary polyphenols, such as direct supplementation in fish diets or through incorporation into the rice fields. By understanding the interplay between dietary polyphenols and pesticides in the rice fish system, researchers can develop innovative and sustainable strategies to promote fish health, minimize pesticide impacts, and ensure the long-term viability of this integrated farming approach. The information presented in this review will be valuable for scientists, aqua-culturists, and policymakers aiming to implement eco-friendly and health-enhancing practices in the rice fish system.

Neuroprotective responses of quercetin in regulation of biochemical, structural, and neurobehavioral effects in 28-day oral exposure of iron in rats

BACKGROUND

Iron is one of the essential metals that functions as a cofactor in various biological cascades in the brain. However, excessive iron accumulation in the brain may lead to neurodegeneration and may show toxic effects. Quercetin, a pigment flavonoid compound, has been proven to be a potent antioxidant and anti-inflammatory that can inhibit lipid peroxidation during metal-induced neurotoxicity. Although iron-induced neuroinflammation and neurodegeneration have been reported in many studies, but the proof for its exact mechanisms needs to be explored.

PURPOSE

The key target of the study was to explore the neuroprotective effect of quercetin after oral exposure of iron in rats and explore its underlying molecular mechanisms.

RESULTS

The outcomes of the study have shown that oral exposure to ferrous sulfate may modulate behavioral paradigms such as locomotor activity, neuromuscular coordination, and increased anxiety level. The pro-inflammatory cytokines (TNF-α, IL-1β and IL-6), apoptotic protein (caspase 3), beta-amyloid and phosphorylated tau were found to be increased on iron exposure. Also, the expressions of ferritin heavy and light chain, BACE-1 and GFAP expressions were altered. These behavioral, structural, and biochemical alterations in the brain were significantly and dose-dependently reversed by treatment with quercetin.

CONCLUSION

The current study provides a fundamental understanding of molecular signaling pathways, and structural proteins implicated in iron-induced neurotoxicity along with the ameliorative effects of quercetin.

Mechanistic Assessment of Anise Seeds and Clove Buds against the Neurotoxicity Caused by Metronidazole in Rats: Possible Role of Antioxidants, Neurotransmitters, and Cytokines

Long-term use of the nitroimidazole-derived antibiotic metronidazole has been associated with neuronal damage due to its ability to cross the blood-brain barrier. Polyphenol-rich plants, such as anise seeds and clove buds, are suggested to have neuroprotective effects. However, their intracellular protective pathway against metronidazole-induced neurotoxicity remains unexplored. This study aims to evaluate the potential neuroprotective benefits of anise seeds and clove buds and elucidate the proposed metronidazole-induced neurotoxicity mechanism. This study divided rats into six groups, each containing six rats. In Group I, the control group, rats were administered saline orally. Group II rats received 200 mg/kg of metronidazole orally. Group III rats received 250 mg/kg b.w. of anise seed extract and metronidazole. Group IV rats received 500 mg/kg b.w. of anise seed extract (administered orally) and metronidazole. Group V rats received 250 mg/kg b.w. of clove bud extract (administered orally) and metronidazole. Group VI rats were administered 500 mg/kg b.w. of clove bud extract and metronidazole daily for 30 consecutive days. The study evaluated the phenolic compounds of anise seeds and clove buds. Moreover, it assessed the inflammatory and antioxidant indicators and neurotransmitter activity in brain tissues. A histological examination of the brain tissues was conducted to identify neuronal degeneration, brain antioxidants, and apoptotic mRNA expression. The study found that metronidazole treatment significantly altered antioxidant levels, inflammatory mediators, and structural changes in brain tissue. Metronidazole also induced apoptosis in brain tissue and escalated the levels of inflammatory cytokines. Oral administration of metronidazole resulted in a decrease in GABA, dopamine, and serotonin and an increase in ACHE in brain tissue. Conversely, oral administration of anise and clove extracts mitigated the harmful effects of metronidazole. The neurotoxic effects of metronidazole appear to stem from its ability to reduce antioxidants in brain tissue and increase nitric oxide production and apoptosis. The study concludes that neuronal damage caused by metronidazole is significantly mitigated by treatment with anise and clove extracts.

The protective effects of quercetin on the physiological responses in malathion-exposed common carp, Cyprinus carpio

This study aimed to evaluate the protective effects of quercetin on the biochemical parameters, immunity, and growth performance in malathion-exposed common carp, Cyprinus carpio. The methods six experimental groups, including the control group, fish exposed to concentrations of 1.04 and 2.08 mg/l malathion, fish supplemented with quercetin (200 mg/kg diet), and fish treated with quercetin + malathion for 21 days, were considered for the experiment. After the feeding period, in results the activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione S-transferase (GST) were significantly decreased in the hepatocyte, while malondialdehyde (MDA) content increased in response to malathion. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and glucose, cortisol, and urea levels significantly increased after exposure to malathion. Exposure of fish to malathion-induced decreases in protease, lysozyme, and alternative complement (ACH50) activities and total immunoglobulin (total Ig) in the mucosa. Changes in other parameters were different depending on malathion concentrations. The supplementation of fish with quercetin had no ameliorating effect on the malathion-related alternations of mucosal lysozyme and protease activities. However, quercetin ameliorated the depressing effects of malathion on biochemical and immunological parameters. Changes in the growth performance and hematological parameters indicated the toxic effect of malathion. In conclusion, quercetin could efficiently reduce the toxic effects of malathion on the biochemical, immune, and hematological parameters of the common carp.

Quercetin Abrogates Oxidative Neurotoxicity Induced by Silver Nanoparticles in Wistar Rats

This study aimed to investigate the oxidative neurotoxicity induced by silver nanoparticles (AgNPs) and assess the neuroprotective effects of quercetin against this toxicity. Forty adult male rats were divided into four equal groups: control, AgNPs (50 mg/kg intraperitoneally), quercetin (50 mg/kg orally), and quercetin + AgNPs. After 30 days, blood and brain tissue samples were collected for further studies. AgNP exposure increased lipid peroxidation and decreased glutathione peroxidase, catalase, and superoxide dismutase activities in brain tissue. AgNPs decreased serum acetylcholine esterase activity and γ-aminobutyric acid concentrations. AgNPs upregulated tumor necrosis factor-α, interleukin-1β, and Bax transcript levels. AgNPs reduced the transcripts of claudin-5, brain-derived neurotrophic factor, paraoxonase, nuclear factor-erythroid factor 2 (Nrf2), and Bcl-2. Histopathologically, AgNPs caused various degenerative changes and neuronal necrosis associated with glial cell reactions. AgNPs increased the immunohistochemical staining of glial fibrillary acidic protein (GFAP) in the cerebrum and cerebellum. Oral treatment with quercetin efficiently counteracted the opposing effects of AgNPs on brain tissue via modulation of tight junction proteins, Nrf2, and paraoxonase, and its positive mechanism in modulating pro-inflammatory cytokines and the downregulation of GFAP expression, and the apoptotic pathway. AgNPs also altered the severity of histopathological lesions and modulated GFAP immunostaining in the examined tissue.

Isoformononetin, a dietary isoflavone protects against streptozotocin induced rat model of neuroinflammation through inhibition of NLRP3/ASC/IL-1 axis activation

AIMS

Isoformononetin (IFN), a methoxyl isoflavone present in most of human dietary supplements. However, being a highly potent antioxidant and anti-inflammatory molecule, its activity against neuronal oxidative stress and neuroinflammation has not been explored till now. The present study was inquested to assess the antioxidant, anti-apoptotic and anti-inflammatory activity of IFN against streptozotocin induced neuroinflammation in different brain regions of rat.

MAIN METHODS

Four groups of animals were subjected to treatment as control, toxic control (STZ; single intracerebrovascular injection), third group (STZ + IFN; 20 mg/kg p.o.), fourth group (IFN) for 14 days. The different brain regions of rats were evaluated for inflammatory, apoptotic and biochemical antioxidant markers. The brain tissues were further assessed for gene expression, immunohistochemical and western blotting examination for localization of inflammasome cascade expression that plays a pivotal role in neuroinflammation.

KEY FINDINGS

The modulation in oxidant/antioxidant status after exposure of STZ was significantly balanced after administration of IFN to rats. Further, IFN was also found to be an apoptotic agent as it modulates the apoptotic gene (Bax) and anti-apoptotic gene (BcL₂) expression. IFN significantly curtailed the augmented protein expression of NLRP3, NLRP2, ASC, NFκBP65, IL-1β and caspase-1 due to STZ administration in cortex and hippocampus rat brain regions.

SIGNIFICANCE

The aforementioned results proclaim the neuroprotective functioning of IFN against STZ induced inflammation. IFN significantly prevents the neuroinflammation by decreasing the generation of ROS that reduces the activation of NLRP3/ASC/IL-1 axis thereby exerting neuroprotection as evidenced in rat model of STZ induced neuroninflammation.

Esters of quinoxaline-7-carboxylate-1,4-di-N-oxide as Trichomonas vaginalis triosephosphate isomerase inhibitors

Trichomoniasis is a public health problem worldwide. Trichomoniasis treatment consists of the use of nitroimidazole derivatives; however, therapeutic ineffectiveness occurs in 5 to 20 % of the cases. Therefore, it is essential to propose new pharmacological agents against this disease. In this work, esters of quinoxaline-7-carboxylate-1,4-di-N-oxide (EQX-NO) were evaluated in in vitro assays as novel trichomonicidal agents. Additionally, an in vitro enzyme assay and molecular docking analysis against triosephosphate isomerase of Trichomonas vaginalis to confirm their mechanism of action were performed. Ethyl (compound 12) and n-propyl (compound 37) esters of quinoxaline-7-carboxy-late-1,4-di-N-oxide derivatives showed trichomonicidal activity comparable to nitazoxanide, whereas five methyl (compounds 5, 15, 19, 20 and 22), four isopropyl (compounds 28, 29, 30 and 34), three ethyl (compounds 4, 13 and 23) and one npropyl (compound 35) ester derivatives displayed activity comparable to albendazole. Compounds 6 and 20 decreased 100 % of the enzyme activity of recombinant protein triosephosphate isomerase.

Chemical screening reveals Ronidazole is a superior prodrug to Metronidazole for nitroreductase-induced cell ablation system in zebrafish larvae

The Metronidazole (MTZ)/nitroreductase (NTR)-mediated cell ablation system is the most commonly used chemical-genetic cell ablation method in zebrafish. This system can specifically ablate target cells under spatial and temporal control. The MTZ/NTR system has become a widely used cell ablation system in biological, developmental, and functional studies. However, the inadequate cell-ablation ability of some cell types and the side effects of high concentration MTZ impede extensive applications of the MTZ/NTR system. In the present study, the US drug collection library was searched to extend the NTR system. Six MTZ analogs were found, and the cell-ablation ability of these analogs was tested in zebrafish larvae. The results revealed that two of the NTR substrates, Furazolidone and Ronidazole, ablated target cells more efficiently than MTZ at lower concentrations. Furthermore, the working concentration of Ronidazole, but not Furazolidone and MTZ, did not affect axonal bridge formation during spinal cord regeneration. Our results, taken together, indicate that Ronidazole is a superior prodrug to MTZ for the NTR system, especially for the study of neuron regeneration in zebrafish larvae.

Unmasking antibiotic-associated neurological disorders: The underminer in Intensive Care Unit

Psychosis is a common and intractable disorder of hospitalization, especially in patients hospitalized in Intensive Care Unit (ICU). Along with the widely use of multiple antibiotics in community-acquired infection and hospital-acquired infection, the occurrence of antibiotic-associated neurological disorders has become more frequently. However, antibiotic neurotoxicity is often overlooked or misinterpreted. In this review, we summarized the neurological disorders caused by antibacterial agent usage and firstly systematically formulated the pathogenesis of antibiotic-associated neurotoxic reactions. Precautions of the complications are critical in preventing serious clinical outcome as the inducement is curable. Regular neurological physical examination, electroencephalogram (EEG) examination, lumbar puncture and therapeutic drug monitoring closely are essential for early diagnosis and differential diagnosis.

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

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