Neuroprotective effects of zafirlukast, piracetam and their combination on L-Methionine-induced vascular dementia in rats

Zebrafish models for studying cognitive enhancers

Cognitive decline is commonly seen both in normal aging and in neurodegenerative and neuropsychiatric diseases. Various experimental animal models represent a valuable tool to study brain cognitive processes and their deficits. Equally important is the search for novel drugs to treat cognitive deficits and improve cognitions. Complementing rodent and clinical findings, studies utilizing zebrafish (Danio rerio) are rapidly gaining popularity in translational cognitive research and neuroactive drug screening. Here, we discuss the value of zebrafish models and assays for screening nootropic (cognitive enhancer) drugs and the discovery of novel nootropics. We also discuss the existing challenges, and outline future directions of research in this field.

Neuroprotective effect of piracetam-loaded magnetic chitosan nanoparticles against thiacloprid-induced neurotoxicity in albino rats

Thiacloprid (TH) is a neurotoxic agricultural insecticide and potential food contaminant. The purpose of this study was to investigate the relationship between TH exposure and memory dysfunction in rats, as well as the potential protective effect of piracetam and piracetam-loaded magnetic chitosan nanoparticles (PMC NPs). Rats were divided into five equal groups (six rats/group). The control group received saline. Group II was treated with PMC NPs at a dose level of 200 mg/kg body weight (Bwt); Group III was treated with 1/10 LD₅₀ of TH (65 mg/kg Bwt); Group IV was treated with TH (65 mg/kg Bwt) and piracetam (200 mg/kg Bwt); Group V was co-treated with TH (65 mg/kg Bwt) and PMC NPs (200 mg/kg Bwt). All animal groups were dosed daily for 6 weeks by oral gavage. Footprint analysis, hanging wire test, open field test, and Y-maze test were employed to assess behavioral deficits. Animals were euthanized, and brain tissues were analyzed for oxidative stress biomarkers, proinflammatory cytokines, and gene expression levels of glial fibrillary acidic protein (GFAP), amyloid-beta precursor protein (APP), B-cell lymphoma 2 (Bcl-2), and caspase-3. Brain and sciatic nerve tissues were used for the evaluation of histopathological changes and immunohistochemical expression of tau protein and nuclear factor kappa B (NF-κB), respectively. The results revealed that TH-treated rats suffered from oxidative damage and inflammatory effect on the central and peripheral nerves. The administration of PMC NPs considerably protected against TH-induced neuronal damage, increased antioxidant enzyme activity, decreased inflammatory markers, and improved behavioral performance than the group treated with piracetam. The neuroprotective effect of PMC NPs was mediated through the inhibition of GFAP, APP, caspase-3, Tau, and NF-κB gene expression with induction of Bcl-2 expression. In conclusion, TH could induce oxidative stress, inflammatory and neurobehavior impairment in rats. However, PMC NPs administration markedly mitigated TH-induced brain toxicity, possibly via oxidative and inflammatory modulation rather than using piracetam alone.

Antagonism of cysteinyl leukotriene receptors by zafirlukast modulated acute inflammatory reaction in tilapia, Oreochromis niloticus

To identify activation pathways and effector mechanisms of innate immunity in fish has become relevant for the sanitary management of intensive fish farming. However, little is known about the blocking of cysteinyl leukotrienes receptors (CysLTRs) and their effects in teleost fish. Our study evaluated the anti-inflammatory effect of 250 and 500 μg zafirlukast (antagonist of CysLTRs)/kg b.w., administered orally in the diet, during acute inflammatory reaction induced by Aeromonas hydrophila bacterins in Oreochromis niloticus. 80 tilapia were distributed in 10 aquariums (100L of water each, n = 8) to constitute three treatments: Control (inoculated with A. hydrophila bacterin and untreated); Treated with 250 μg or 500 μg of zafirlukast/kg b.w. and inoculated. To be evaluated in three periods: 6, 24 and 48 h post-inoculation (HPI), totaling nine aquariums. A tenth group was sampled without any stimulus to constitute reference values (Physiological standards). Tilapia treated with zafirlukast demonstrated dose-response effect in the decrease of accumulated inflammatory cells, strongly influenced by granulocytes and macrophages. Zafirlukast treated-tilapia showed decrease in blood leukocyte counts (mainly neutrophils, and monocytes) and reactive oxygen species production. Treatment with zafirlukast resulted in down-regulation of ceruloplasmin, complement 3, alpha2-macroglobulin, transferrin and apolipoprotein A1, as well as up-regulation of haptoglobin. Our study provided convincing results in the pathophysiology of tilapia inflammatory reaction, considering that treatment with zafirlukast, antagonist of cysteinyl leukotriene receptors, resulted in a dose-response effect by suppressing the dynamics between leukocytes in the bloodstream and cell accumulation in the inflamed focus, as well as modulated the leukocyte oxidative burst and the acute phase protein response.

L-Methionine prevents β-cell damage by modulating the expression of Arx, MafA and regulation of FOXO1 in type 1 diabetic rats

L-Methionine (L-Met) is an essential sulphur-containing amino acid having a vital role in various key cellular processes. Here we investigated the effect of L-Met on streptozotocin-induced β-cell damage model of diabetes mellitus in Sprague Dawley rats. At the end of study biochemical parameters, immunoblotting, qRT-PCR and ChIP-qPCR are performed. L-Met was administered orally (250 and 500 mg/kg/day) to diabetic animals for 8 weeks improved plasma glucose and insulin levels. Pancreas immunohistochemistry showed significant increase in insulin expression, decrease in glucagon and Bax expression. Interestingly, L-Met inhibited the expression of Arx; upregulated MafA and FOXO1 which play a critical role in the maintenance of β-cell identity. Our data also showed a decrease in H3K27me3 and an increase in H3K4me3 ("bivalent domain" alteration) in diabetic rats and these recovered by L-Met. Furthermore, the chromatin-immunoprecipitation assay showed a decreased enrichment of H3K27me3 on the promoter of the FOXO1 gene in diabetic rats and L-Met prevents this decrease. Our results showed the first evidence of the involvement of H3K27me3 in regulating the expression of the FOXO1 gene and the prevention of β-cell injury by L-Met treatment. In conclusion, we report the involvement of L-Met in the modulation of α-cell identity marker (Arx), β-cell identity marker (MafA) and regulation of FOXO1 by histone methylation marks for the first time. We are of the opinion that this employed as a novel therapeutic approach for mitigating diabetes-induced β-cell death.

Sitagliptin Attenuates the Cognitive Deficits in L-Methionine-Induced Vascular Dementia in Rats

Vascular dementia (VaD) is the second most prevalent type of dementia characterized by progressive cognitive deficits and is a major risk factor for the development of Alzheimer's disease and other neurodegenerative disorders. This study is aimed at determining the potential neuroprotective effect of sitagliptin (STG) on cognitive deficits in L-methionine-induced VaD in rats and the possible underlying mechanisms. 30 adult male Wistar albino rats were divided equally (n = 10) into three groups: control, VaD, and VaD + STG groups. The cognitive performance of the animals was conducted by open field, elevated plus maze, Y-maze, novel object recognition, and Morris water maze tests. Serum homocysteine, TNF-α, IL-6, IL-10, total cholesterol, and triglycerides levels were assessed together with hippocampal MDA, SOD, and BDNF. Histopathological and immunohistochemical assessments of the thoracic aorta and hippocampus (CA1 region) were also performed. Chronic L-methionine administration impaired memory and learning and induced anxiety. On the other hand, STG protected against cognitive deficits through improving oxidative stress biomarkers, inflammatory mediators, lipid profiles, and hippocampus level of BDNF as well as decreasing caspase-3 and GFAP and increasing Ki-67 immunoreactions in the hippocampus. Also, STG improved the endothelial dysfunction via upregulation of aortic eNOS immunoreaction. STG improved the cognitive deficits of L-methionine-induced VaD by its antioxidant, anti-inflammatory, antiapoptotic, and neurotrophic effects. These findings suggest that STG may be a promising future agent for protection against VaD.

Methionine as a double-edged sword in health and disease: Current perspective and future challenges

Methionine is one of the essential amino acids and plays a vital role in various cellular processes. Reports advocate that methionine restriction and supplementation provide promising outcomes, and its regulation is critical for maintaining a healthy life. Dietary methionine restriction in houseflies and rodents has been proven to extend lifespan. Contrary to these findings, long-term dietary restriction of methionine leads to adverse events such as bone-related disorders, stunted growth, and hyperhomocysteinemia. Conversely, dietary supplementation of methionine improves hepatic steatosis, insulin resistance, inflammation, fibrosis, and bone health. However, a high level of methionine intake shows adverse effects such as hyperhomocysteinemia, reduced body weight, and increased cholesterol levels. Therefore, dietary methionine in a safe dose could have medicinal values. Hence, this review is aimed to provide a snapshot of the dietary role and regulation of methionine in the modulation of health and age-related diseases.

The protective effects of pioglitazone against cognitive impairment caused by L-Methionine administration in a rat model

PURPOSE

Accumulating evidence indicates that elevated levels of methionine are associated with cognitive decline including loss of memory. The exact mechanisms behind this observation are not completely understood but could be related to an increase in oxidative stress markers in hippocampal tissues. The above increase in oxidative stress could be directly caused by an increase in the blood levels of methionine (hypermethioninemia) or one of its metabolites, such as homocysteine. Pioglitazone is a drug primarily used for the treatment of type 2 diabetes mellitus. Several reports showed that using pioglitazone protects against cognitive decline observed in Alzheimer's disease. Pioglitazone has antioxidant properties independent of its hypoglycemic effects. Taken together, we hypothesized that pioglitazone protects against memory loss triggered by elevated levels of methionine through lowering of oxidative stress in the hippocampus.

METHOD

To test this hypothesis, we used chronic administration of L-methionine in a rat model. Spatial learning and memory were evaluated in the model using a radial arm water maze (RAWM). The levels of several markers related to oxidative stress were measured in hippocampal tissues recovered from experimental rats.

RESULTS

Current results showed that administration of L-methionine was associated with a significant loss of short- and long-term memory and an increase in blood homocysteine levels. The above memory changes were associated with an increase in lipid peroxidation and a decrease in the activity of catalase and glutathione peroxidase antioxidant enzymes in the hippocampus. The combined treatment of pioglitazone with L-methionine protected rat model from memory loss. It also prevented changes observed in lipid peroxidation and changes in the activity of catalase and glutathione peroxidase enzymes.

CONCLUSION

Current findings indicate that pioglitazone is a viable therapeutic option that protects against cognitive changes observed upon administration of L-methionine.

Zafirlukast protects blood-brain barrier integrity from ischemic brain injury

Stroke has been considered the second leading cause of death worldwide, and ischemic stroke accounts for the vast majority of stroke cases. Some of the main features of ischemic stroke are increased brain permeability, ischemia/reperfusion injury, oxidative stress, and acute inflammation. Antagonism of cysLT1R has been shown to provide cardiovascular and neural benefits. In the present study, we investigated the effects of the cysLT1R antagonist zafirlukast both in vivo and in vitro using a middle cerebral artery occlusion (MCAO) mouse model and human brain microvascular endothelial cells (HBMVECs). In vivo, we found that zafirlukast pretreatment could reduce MCAO-induced increased brain permeability by rescuing the expression levels of the tight junction proteins occludin and ZO-1. In vitro, we found that zafirlukast could suppress the increase in endothelial monolayer permeability induced by OGD/R via rescue of occludin and ZO-1 expression; additionally, we found that zafirlukast prevented OGD/R-induced degradation of the extracellular matrix via inhibition of MMP-2 and MMP-9 expression. Finally, we found that zafirlukast could also inhibit OGD/R-induced activation of the critical proinflammatory regulator NF-κB by preventing phosphorylation and nuclear translocation of p65 protein. Together, our findings demonstrate a promising role for zafirlukast in preventing damage induced by ischemic stroke and reperfusion injury.