Effects of thymol on amyloid-β-induced impairments in hippocampal synaptic plasticity in rats fed a high-fat diet

Thymol as a Potential Neuroprotective Agent: Mechanisms, Efficacy, and Future Prospects

Neurodegenerative diseases pose a growing global health challenge, with limited effective therapeutic options. Mitochondrial dysfunction, oxidative stress, neuroinflammation, apoptosis, and autophagy are common underlying mechanisms in these diseases. Thymol is a phenolic monoterpene compound that has gained attention for its diverse biological properties, including antioxidant, anti-inflammatory, and immunomodulatory activities. Thymol supplementation could provide potential neuroprotection and improve cognitive deficits, depressant-like effects, learning, and memory impairments in rodents. Mechanistic investigations reveal that the neuroprotective effects of thymol involve the improvement of oxidative stress, mitochondrial dysfunction, and inflammatory response. Several signaling pathways, including mitochondrial apoptotic, NF-κB, AKT, Nrf2, and CREB/BDNF pathways are also involved. In this review, the neuroprotective effects of thymol, the potential molecular mechanisms, safety, applications, and current challenges toward development as a neuroprotective agent were summarized and discussed. We hope that this review provides valuable insights for the further development of this promising natural product as a promising neuroprotective agent.

The effects of carvacrol and p-cymene on Aβ1-42 -induced long-term potentiation deficit in male rats

AIMS

Alzheimer's disease (AD) is the most common type of dementia in which oxidative stress plays an important role. In this disease, learning and memory and the cellular mechanism associated with it, long-term potentiation (LTP), are impaired. Considering the beneficial effects of carvacrol (CAR) and p-cymene against AD, their effect was assessed on in vivo hippocampal LTP in the perforant pathway (PP)-dentate gyrus (DG) pathway in an Aβ1-42 -induced rat model of AD.

METHODS

Male Wistar rats were randomly assigned to five groups: sham: intracerebroventricular (ICV) injection of phosphate-buffered saline, Aβ: ICV Aβ1-42 injections, Aβ + CAR (50 mg/kg), Aβ + p-cymene (50 mg/kg), and Aβ + CAR + p-cymene. Administration of CAR and p-cymene was done by gavage daily 4 weeks before and 4 weeks after the Aβ injection. The population spike (PS) amplitude and field excitatory postsynaptic potentials (fEPSP) slope were determined in DG against the applied stimulation to the PP.

RESULTS

Aβ-treated rats exhibited impaired LTP induction in the PP-DG synapses, resulting in significant reduction in both fEPSP slope and PS amplitude compared to the sham animals. Aβ-treated rats consumed either CAR or p-cymene separately (but not their combination), and showed an enhancement in fEPSP slope and PS amplitude of the DG granular cells.

CONCLUSIONS

These data indicate that CAR or p-cymene can ameliorate Aβ-associated changes in synaptic plasticity. Surprisingly, the combination of CAR and p-cymene did not yield the same effect, suggesting a potential interaction between the two substances.

The Protective Effects of High-Intensity Interval Training Combined with Q10 Supplementation on Learning and Memory Impairments in Male Rats with Amyloid-β-Induced Alzheimer's Disease

Background

Oxidative stress plays a major role in the progression of Alzheimer's disease (AD)-related cognitive deficits.

Objective

This study was done to determine the protective effects of coenzyme Q10 (CoQ10) and high-intensity interval training (HIIT) alone and in combination for eight continuous weeks, on oxidative status, cognitive functions, and histological changes in the hippocampus in amyloid-β (Aβ)-induced AD rats.

Methods

Ninety male Wistar rats were randomly assigned to the sham, control, Q10 (50 mg/kg of CoQ10; P.O.), HIIT (high intensity: 4 min running at 85-90% VO2max, low intensity: 3 min running at 50-60% VO2max), Q10 + HIIT, AD, AD+Q10, AD+HIIT, and AD+Q10 + HIIT groups.

Results

The results showed that Aβ injection reduced cognitive functions in the Morris water maze (MWM) test and recognition memory in the novel object recognition test (NORT), which was accompanied by a decrease in total thiol groups, catalase, and glutathione peroxidase activities, an increase in malondialdehyde levels, and neuronal loss in the hippocampus. Interestingly, pretreatment with CoQ10, HIIT, or both, could markedly improve the oxidative status and cognitive decline in the MWM and NOR tests, and hinder neuronal loss in the hippocampus of Aβ-induced AD rats.

Conclusion

Therefore, a combination of CoQ10 and HIIT can improve Aβ-related cognitive deficits, probably through an amelioration in hippocampal oxidative status and prevention of neuronal loss.

Association between erythrocyte membrane fatty acids and gut bacteria in obesity-related cognitive dysfunction

Obesity increases the risk of cognitive impairment and dementia, and the gut microbiota can affect brain cognitive function and obesity through a variety of pathways such as the gut-brain axis. This study aimed to discover how fatty acid affect cognitive function by regulating intestinal flora in obesity. Obese subjects were recruited for cognitive function assessment, and participants were divided into obese group with cognitive impairment (MCI, n = 49) and obese cognitively normal group (Non_MCI, n = 55). In the erythrocyte membrane, the proportion of polyunsaturated fatty acids (PUFA), linoleic acid (C18:2 n-6) and arachidonic acid (C20:4 n-6) and n-6/n-3 ratio was higher in the MCI group than in the Non_MCI group. However, the α-linolenic acid (C18:3 n-3) percentage of the erythrocyte membrane was lower in the MCI group. We found that Coriobacteriales_Incertae_Sedis was positively correlated with erythrocyte membrane C20:4 n-6 and n-6 PUFA and negatively correlated with cognitive scores in obese patients. In addition, several of the functional pathways we predicted were significantly different in the MCI and Non_MCI groups. Higher levels of n-6/n-3 polyunsaturated fatty acids ratio in the erythrocyte membranes may influence the inflammatory response in the organism causing obesity induced cognitive damage. Moreover, high levels of n-6/n-3 polyunsaturated fatty acids ratio may also affect the intestinal flora of obese patients, which in turn may affect the cognitive function of obese patients.

Oxidative stress in animal models of obesity caused by hypercaloric diets: A systematic review

Obesity is a global health difficulty characterized by an excessive accumulation of fat that increases body weight. Obesity has been studied in multiple animal models, of which those in which it is induced by diet stand out. Due to the increase in this condition, other mechanisms have been addressed that are triggered by states of overweight or obesity, such as the appearance of oxidative stress. These models aim to relate obesity caused by diet and how it influences the development of oxidative stress. In this study, a systematic review of the literature of 39 articles that studied obesity due to the consumption of hypercaloric diets and the appearance of oxidative stress in different animal models was carried out. This review identified the models with the most excellent use and the characteristics of the most appropriate diets to characterize states of oxidative stress due to obesity. In addition, the advantages and disadvantages of each model used are provided, as well as the techniques used for the assessment of obesity, and oxidative stress, providing the information in such a way that there is a general overview of the existing models of the parameters that allow to adequately establish both variables studied, providing information that allows the researcher to choose the appropriate model and factors according to the interest and objectives of the present research.

Gut microbiota dysbiosis and Huntington's disease: Exploring the gut-brain axis and novel microbiota-based interventions

Huntington's disease (HD) is a complex progressive neurodegenerative disorder affected by genetic, environmental, and metabolic factors contributing to its pathogenesis. Gut dysbiosis is termed as the alterations of intestinal microbial profile. Emerging research has highlighted the pivotal role of gut dysbiosis in HD, focusing on the gut-brain axis as a novel research parameter in science. This review article provides a comprehensive overview of gut microbiota dysbiosis and its relationship with HD and its pathogenesis along with the future challenges and opportunities. The focuses on the essential mechanisms which link gut dysbiosis to HD pathophysiology including neuroinflammation, immune system dysregulation, altered metabolites composition, and neurotransmitter imbalances. We also explored the impacts of gut dysbiosis on HD onset, severity, and symptoms such as cognitive decline, motor dysfunction, and psychiatric symptoms. Furthermore, we highlight recent advances in therapeutics including microbiota-based therapeutic approaches, including dietary interventions, prebiotics, probiotics, fecal microbiota transplantation, and combination therapies with conventional HD treatments and their applications in managing HD. The future challenges are also highlighted as the heterogeneity of gut microbiota, interindividual variability, establishing causality between gut dysbiosis and HD, identifying optimal therapeutic targets and strategies, and ensuring the long-term safety and efficacy of microbiota-based interventions. This review provides a better understanding of the potential role of gut microbiota in HD pathogenesis and guides the development of novel therapeutic approaches.

The Protective Effects of Policosanol on Learning and Memory Impairments in a Male Rat Model of Alzheimer's Disease

Alzheimer's disease (AD), the most common form of dementia, is characterized by a progressive decline in cognitive performance and memory formation. The present study was designed to investigate the effect of policosanol (PCO) on cognitive function, oxidative-antioxidative status, and amyloid-beta (Aβ) plaque formation in an AD rat model induced by intracerebroventricular (ICV) injection of Aβ_1-40. Healthy adult male Wistar rats were randomly divided into seven groups: control, sham (5 μL, ICV injection of phosphate-buffered saline), AD model (5 μL, ICV injection of Aβ), acacia gum (50 mg/kg, 8 weeks, gavage), PCO (50 mg/kg, 8 weeks, gavage), AD + acacia gum (50 mg/kg, 8 weeks, gavage), and AD + PCO (50 mg/kg, 8 weeks, gavage). During the ninth and tenth weeks of the study, the cognitive function of the rats was assessed by commonly used behavioral paradigms. Subsequently, oxidative-antioxidative status was examined in the serum. Moreover, compact Aβ plaques were detected by Congo red staining. The results showed that injection of Aβ impaired recognition memory in the novel object recognition test, reduced the spatial cognitive ability in the Morris water maze, and alleviated retention and recall capability in the passive avoidance task. Additionally, injection of Aβ resulted in increased total oxidant status, decreased total antioxidant capacity, and enhanced Aβ plaque formation in the rats. Intriguingly, PCO treatment improved all the above-mentioned neuropathological changes in the Aβ-induced AD rats. The results suggest that PCO improves Aβ-induced cognitive decline, possibly through modulation of oxidative-antioxidative status and inhibition of Aβ plaque formation.

Geraniol improves passive avoidance memory and hippocampal synaptic plasticity deficits in a rat model of Alzheimer's disease

Alzheimer's disease (AD) is the most progressive and irreversible neurodegenerative disease that leads to synaptic loss and cognitive decline. The present study was designed to evaluate the effects of geraniol (GR), a valuable acyclic monoterpene alcohol, with protective and therapeutic effects, on passive avoidance memory, hippocampal synaptic plasticity, and amyloid-beta (Aβ) plaques formation in an AD rat model induced by intracerebroventricular (ICV) microinjection of Aβ_1-40. Seventy male Wistar rats were randomly into sham, control, control-GR (100 mg/kg; P.O. (orally), AD, GR-AD (100 mg/kg; P.O.; pretreatment), AD-GR (100 mg/kg; P.O.; treatment), and GR-AD-GR (100 mg/kg; P.O.; pretreatment & treatment). Administration of GR was continued for four consecutive weeks. Training for the passive avoidance test was carried out on the 36^th day and a memory retention test was performed 24 h later. On day 38, hippocampal synaptic plasticity (long-term potentiation; LTP) was recorded in perforant path-dentate gyrus (PP-DG) synapses to assess field excitatory postsynaptic potentials (fEPSPs) slope and population spike (PS) amplitude. Subsequently, Aβ plaques were identified in the hippocampus by Congo red staining. The results showed that Aβ microinjection increased passive avoidance memory impairment, suppressed of hippocampal LTP induction, and enhanced of Aβ plaque formation in the hippocampus. Interestingly, oral administration of GR improved passive avoidance memory deficit, ameliorated hippocampal LTP impairment, and reduced Aβ plaque accumulation in the Aβ-infused rats. The results suggest that GR mitigates Aβ-induced passive avoidance memory impairment, possibly through alleviation of hippocampal synaptic dysfunction and inhibition of Aβ plaque formation.

Effectiveness of coenzyme Q10 on learning and memory and synaptic plasticity impairment in an aged Aβ-induced rat model of Alzheimer's disease: a behavioral, biochemical, and electrophysiological study

RATIONALE

Aging is the major risk factor for Alzheimer's disease (AD), and cognitive and memory impairments are common among the elderly. Interestingly, coenzyme Q10 (Q10) levels decline in the brain of aging animals. Q10 is a substantial antioxidant substance, which has an important role in the mitochondria.

OBJECTIVE

We assessed the possible effects of Q10 on learning and memory and synaptic plasticity in aged β-amyloid (Aβ)-induced AD rats.

METHODS

In this study, 40 Wistar rats (24-36 months old; 360-450 g) were randomly assigned to four groups (n = 10 rats/group)-group I: control, group II: Aβ, group III: Q10; 50 mg/kg, and group IV: Q10+Aβ. Q10 was administered orally by gavage daily for 4 weeks before the Aβ injection. The cognitive function and learning and memory of the rats were measured by the novel object recognition (NOR), Morris water maze (MWM), and passive avoidance learning (PAL) tests. Finally, malondialdehyde (MDA), total antioxidant capacity (TAC), total thiol group (TTG), and total oxidant status (TOS) were measured.

RESULTS

Q10 improved the Aβ-related decrease in the discrimination index in the NOR test, spatial learning and memory in the MWM test, passive avoidance learning and memory in the PAL test, and long-term potentiation (LTP) impairment in the hippocampal PP-DG pathway in aged rats. In addition, Aβ injection significantly increased serum MDA and TOS levels. Q10, however, significantly reversed these parameters and also increased TAC and TTG levels in the Aβ+Q10 group.

CONCLUSIONS

Our experimental findings suggest that Q10 supplementation can suppress the progression of neurodegeneration that otherwise impairs learning and memory and reduces synaptic plasticity in our experimental animals. Therefore, similar supplemental Q10 treatment given to humans with AD could possibly provide them a better quality of life.

Thymol improves autism-like behaviour in VPA-induced ASD rats through the Pin1/p38 MAPK pathway

Inflammation plays an essential role in the pathogenesis of autism spectrum disorder (ASD). Thymol is a bioactive monoterpene isolated from Thymus vulgaris that has anti-inflammatory properties and is helpful in neurodevelopmental disorders. The purpose of this study was to investigate the effects of thymol on autism-like behaviours in rats with VPA-induced ASD and to assess the related molecular mechanisms. In the prefrontal cortex (PFC) of the valproic acid (VPA)-exposed rat model, the levels of Pin1, phosphorylated p38 MAPK, interleukin-1β (IL-1β) and tumour necrosis factor (TNF)-α, were increased, and the levels of PSD95 and synaptophysin (SYP) decreased. After thymol treatment (30 mg/kg), the VPA-induced autism-like behaviours were alleviated. Moreover, thymol also rescued the dysregulated levels of Pin1, phosphorylated p38 MAPK, IL-1β, TNF-α, PSD95, and SYP. In addition, immunofluorescence experiments showed that thymol treatment decreased the correlation between Pin1 and phosphorylated p38 MAPK. Mechanistically, Pin1 knockdown by RNA interference confirmed that Pin1 promotes inflammation via phosphorylation of p38 MAPK in the VPA exposure rat model. In conclusion, thymol improved autism-like behaviours in VPA-induced ASD rats by reducing inflammation and improving neurodevelopment. This effect was mediated by the Pin1/p38 MAPK pathway. These results experimentally provide the potential for thymol in new therapeutic avenues for autism.

Effects of sesamin on Aβ1-42-induced oxidative stress and LTP impairment in a rat model of Alzheimer's disease

The present study examined the protective effect of sesamin (Ses) on β-amyloid (Aβ)-induced long-term potentiation (LTP) impairment at the PP-DG synapses in male rats. Wistar rats were randomly assigned to seven groups: control, sham, Aβ; ICV Aβ_1-42 microinjection, Ses, Aβ + Ses; first, ICV Aβ injections and then receiving Ses, Ses + Aβ: four weeks of pretreatment with Ses and then Aβ injection, and Ses + Aβ + Ses: pre (four weeks) and post (four weeks) treatment with Ses. Ses-treated groups received 30 mg/kg of Ses once a day by oral gavage for four weeks. After the treatment period, the animals were positioned in a stereotaxic device for surgery and field potential recording. The population spike (PS) amplitude and slope of excitatory postsynaptic potentials (EPSP) were evaluated in the DG region. Serum oxidative stress biomarkers (total oxidant status (TOS) and total antioxidant capacity (TAC)) were measured. Aβ impaired LTP induction at the PP-DG synapses evidenced by a decrease in EPSP slope and PS amplitude of LTP. In Aβ rats, Ses increased EPSP slope and PS amplitude of LTP in the DG granular cells. Also, an increase in TOS and a reduction in TAC caused by Aβ were significantly corrected by Ses. Ses could prevent Aβ-induced LTP impairment at the PP-DG synapses in male rats, which can be due to its preventive effects on oxidative stress.

The effect of minocycline on beta-amyloid-induced memory and learning deficit in male rats: A behavioral, biochemical, and histological study

OBJECTIVES

Minocycline hydrochloride is a semi-synthetic, second-generation tetracycline with neuroprotective, neurorestorative, anti-amyloidogenic, anti-inflammatory, antioxidant, and anti-apoptotic properties. The present study was designed to investigate the potential protective effects of minocycline against beta-amyloid (Aβ)-induced Alzheimer's disease (AD), recognition memory decline, and the possible involved anti-apoptotic mechanisms.

METHODS

The rats were treated with minocycline (50 and 100 mg/kg/day; P.O.) after AD induction for 30 days. Behavioral functions were assessed by employing standard behavioral tests, including novel object recognition (NOR) and passive avoidance learning (PAL) tasks. Then, total antioxidant capacity (TAC) and total oxidant status (TOS) were measured in blood serum using ELISA kits. Apoptosis and the number of Aβ plaques were examined by the TUNEL and Congo red staining, respectively.

RESULTS

Treatment of Aβ rats with minocycline improved memory deficit in the PAL task and a decline in recognition memory in the NOR test. Minocycline at 50 and 100 mg/kg significantly reduced the TOS levels and increased the TAC levels (P < 0.0001). Also, minocycline at 50 and 100 mg/kg reduced the apoptotic index in the hippocampus of Aβ rats. After Congo red staining, the minocycline group showed improved cell morphology and markedly fewer Aβ plaques.

CONCLUSIONS

Minocycline reduced memory and learning deficit in behavioral experiments after Aβ injection, which may be due to its anti-inflammatory and anti-apoptotic effects.

Thymol ameliorated neurotoxicity and cognitive deterioration in a thioacetamide-induced hepatic encephalopathy rat model; involvement of the BDNF/CREB signaling pathway

In the present study, we aimed to delineate the neuroprotective potential of thymol (THY) against neurotoxicity and cognitive deterioration induced by thioacetamide (TAA) in an experimental model of hepatic encephalopathy (HE). Rats received TAA (100 mg kg^-1, intraperitoneally injected, three times per week) for two weeks. THY (30 and 60 mg kg^-1), and Vit E (100 mg k^-1) were administered daily by oral gavage for 30 days after HE induction. Supplementation with THY significantly improved liver function, reduced serum ammonia level, and ameliorated the locomotor and cognitive deficits. THY effectively modulated the alteration in oxidative stress markers, neurotransmitters, and brain ATP content. Histopathology of liver and brain tissues showed that THY had ameliorated TAA-induced damage, astrocyte swelling and brain edema. Furthermore, THY downregulated NF-kB and upregulated GFAP protein expression. In addition, THY significantly promoted CREB and BDNF expression at both mRNA and protein levels, together with enhancing brain cAMP level. In conclusion, THY exerted hepato- and neuroprotective effects against HE by mitigating hepatotoxicity, hyperammonemia and brain ATP depletion via its antioxidant, anti-inflammatory effects in addition to activation of the CREB/BDNF signaling pathway.

Therapeutic Effects of High-Intensity Interval Training Exercise Alone and Its Combination with Ecdysterone Against Amyloid Beta-Induced Rat Model of Alzheimer's Disease: A Behavioral, Biochemical, and Histological Study

Hippocampal oxidative stress has a vital role in the pathophysiology of Alzheimer's disease (AD)-associated behavioral deficits. Ecdysterone (Ecdy), a natural product and primary steroid hormone, exhibits anti-oxidative and neuroprotective effects. High-intensity interval training (HIIT) has emerged as an effective method for improving physiological brain functions. The present study was designed to investigate the comparative effects of separate and combined HIIT and Ecdy treatment on behavioral functions, hippocampal oxidative status, histological changes in an amyloid-beta (Aβ)-induced rat model of AD. Adult male rats were treated simultaneously with HIIT exercise and Ecdy (10 mg/kg/day; P.O.), starting ten days after Aβ-injection, and they continued for eight consecutive weeks. At the end of the treatment course, the behavioral functions of the rats were assessed by commonly-used behavioral paradigms. Subsequently, brain samples were collected for histological analysis and hippocampus samples were collected for biochemical analysis. Results illustrated that Aβ injection impaired learning and memory performances in both novel object recognition and Barnes maze tests, reduced exploratory/locomotor activities in open field test, enhanced anxiety-like behavior in elevated plus-maze (P < 0.05). These behavioral deficits accompanied hippocampal oxidative stress (decreased total antioxidant capacity content and glutathione peroxidase enzyme activity, increased total oxidant status and malondialdehyde level) and neuronal loss in the cerebral cortex and hippocampus in H&E staining (P < 0.05). HIIT and Ecdy improved anxiety-like behavior, attenuated total oxidant status and malondialdehyde, and prevented the neuronal loss (P < 0.05). However, their combination resulted in a more complete and powerful improvement in all the above-mentioned Aβ-related deficits (P < 0.05). Overall, these data provide evidence that a combination of HIIT and Ecdy treatment improves Aβ-induced behavioral deficits, possibly through ameliorating hippocampal oxidative status and preventing neuronal loss.

Chronic stimulation of the serotonergic 5-HT4 receptor modulates amyloid-beta-related impairments in synaptic plasticity and memory deficits in male rats

Alzheimer's disease (AD) is a neurodegenerative disease characterized by memory decline and impaired hippocampal synaptic plasticity. The serotonin 5-HT4 receptor is involved in learning and memory processes. This study explored the effects of chronic stimulation of 5-HT4R on cognition, memory, long-term potentiation (LTP), paired-pulse ratio (PPR), and neuronal apoptosis in a rat model of amyloid-beta (Aβ)-induced AD. Thirty-five male Wistar rats were randomly divided into three groups as follows: the sham, Aβ, and Aβ + BIMU8 groups. Aβ (6 µg/µl) was administrated by intracerebroventricular (icv) injection. The animals were treated with BIMU8 (1 μg/μL, ICV) as a 5-HT4R agonist for 30 days. Memory and behavioral changes were assessed by the passive avoidance learning, novel object recognition, open field, and elevated plus maze tests. Hippocampal synaptic plasticity was evaluated in the dentate gyrus (DG) in response to the stimulation applied to the perforant pathway. Furthermore, neuronal apoptosis was measured in the hippocampus. Data were analyzed by SPSS version 19 using one-way ANOVA, followed by Tukey's post hoc test. Aβ induced memory deficits and neuronal loss and inhibited LTP induction. Aβ also increased the normalized PPR. BIMU8 enhanced the slope of the field excitatory postsynaptic potential in LTP and improved cognition behavior. Paired-pulse inhibition or facilitation was not affected by LTP induction in Aβ animals receiving the BIMU8. It can be concluded that the stimulation of the 5-HT₄ receptor modulated the Aβ-induced cognition and memory deficits, probably via a decrease in the hippocampal apoptotic neurons and an improvement in the hippocampal synaptic functions without involving its inhibitory interneurons.

The effect of sodium channels on neurological/neuronal disorders: A systematic review

Neurological and neuronal disorders are associated with structural, biochemical, or electrical abnormalities in the nervous system. Many neurological diseases have not yet been discovered. Interventions used for the treatment of these disorders include avoidance measures, lifestyle changes, physiotherapy, neurorehabilitation, pain management, medication, and surgery. In the sodium channelopathies, alterations in the structure, expression, and function of voltage-gated sodium channels (VGSCs) are considered as the causes of neurological and neuronal diseases. Online databases, including Scopus, Science Direct, Google Scholar, and PubMed were assessed for studies published between 1977 and 2020 using the keywords of review, sodium channels blocker, neurological diseases, and neuronal diseases. VGSCs consist of one α subunit and two β subunits. These subunits are known to regulate the gating kinetics, functional characteristics, and localization of the ion channel. These channels are involved in cell migration, cellular connections, neuronal pathfinding, and neurite outgrowth. Through the VGSC, the action potential is triggered and propagated in the neurons. Action potentials are physiological functions and passage of impermeable ions. The electrophysiological properties of these channels and their relationship with neurological and neuronal disorders have been identified. Subunit mutations are involved in the development of diseases, such as epilepsy, multiple sclerosis, autism, and Alzheimer's disease. Accordingly, we conducted a review of the link between VGSCs and neurological and neuronal diseases. Also, novel therapeutic targets were introduced for future drug discoveries.

Mechanistic Aspects of Apiaceae Family Spices in Ameliorating Alzheimer's Disease

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases worldwide. In an effort to search for new strategies for treating AD, natural products have become candidates of choice. Plants are a rich source of bioactive and effective compounds used in treating numerous diseases. Various plant extracts are known to display neuroprotective activities by targeting different pathophysiological pathways in association with the diseases, such as inhibiting enzymes responsible for degrading neurotransmitters, reducing oxidative stress, neuroprotection, inhibiting amyloid plaque formation, and replenishing mitochondrial function. This review presented a comprehensive evaluation of the available scientific literature (in vivo, in vitro, and in silico) on the neuroprotective mechanisms displayed by the extracts/bioactive compounds from spices belonging to the Apiaceae family in ameliorating AD.

Vanillic acid attenuates amyloid β1-40-induced long-term potentiation deficit in male rats: an in vivo investigation

Objectives: Alzheimer disease (AD) is a neurodegenerative disorderliness that involves deductible progressive cognition function caused by amyloid-beta (Aβ) peptide accumulation in the interstitial space. The increase of Aβ stimulates all kinds of active oxygen and causes oxidative stress and apoptosis. In this investigation, we researched the neuroprotective impacts of vanillic acid (VA) on the Aβ-induced (Aβ1-40) long-term potentiation (LTP) of the hippocampus - a commonly probed synaptic plasticity model that happens at the same time as memory and learning - in the AD rats.Methods: Forty-five male Wistar rats were categorized into five groups (n = 8 rats/group, 200-220 g), and studied as control (standard diet), sham (vehicle), VA (50 mg/kg), Aβ and Aβ + VA (50 mg/kg) groups. In vivo electrophysiological recordings were implemented after the stereotaxic surgery to gauge the excitatory postsynaptic potential (EPSP) slope and population spike (PS) amplitude in the dentate gyrus of the hippocampus. By the stimulation at high-frequency of the perforate pathway, long-term potentiation (LTP) was induced. To assess the plasma levels of malondialdehyde (MDA) and total thiol group (TTG), blood samples were garnered.Results: In the Aβ-injected rats, EPSP slope, and PS amplitude were significantly reduced after the induction of LTP. Thus, the findings demonstrate that VA decreases the impacts of Aβ on LTP; also, the treatments through VA neuroprotective against the negative effects of Aβ on the synaptic plasticity of the hippocampus can decrease the MDA levels and also increase the TTG levels significantly.Discussion: Therefore, based on this experiment on male rats, VA has neuroprotective effects and antioxidants benefits against the Aβ-mediated inhibition of long-term potentiation.

Effects of the hydroalcoholic extract of Rosa damascena on hippocampal long-term potentiation in rats fed high-fat diet

High-fat diets (HFDs) and obesity can cause serious health problems, such as neurodegenerative diseases and cognitive impairments. Consumption of HFD is associated with reduction in hippocampal synaptic plasticity. Rosa damascena (R. damascena) is traditionally used as a dietary supplement for many disorders. This study was carried out to determine the beneficial effect of hydroalcoholic extract of R. damascena on in vivo hippocampal synaptic plasticity (long-term potentiation, LTP) in the perforant pathway (PP)-dentate gyrus (DG) pathway in rats fed with an HFD. Male Wistar rats were randomly assigned to four groups: Control, R. damascena extract (1 g/kg bw daily for 30 days), HFD (for 90 days) and HFD + extract. The population spike (PS) amplitude and slope of excitatory post-synaptic potentials (EPSP) were measured in DG area in response to stimulation applied to the PP. Serum oxidative stress biomarkers [total thiol group (TTG) and superoxide dismutase (SOD)] were measured. The results showed the HFD impaired LTP induction in the PP-DG synapses. This conclusion is supported by decreased EPSP slope and PS amplitude of LTP. R. damascena supplementation in HFD animals enhanced EPSP slope and PS amplitude of LTP in the granular cell of DG. Consumption of HFD decreased TTG and SOD. R. damascena extract consumption in the HFD animals enhanced TTG and SOD. These data indicate that R. damascena dietary supplementation can ameliorate HFD-induced alteration of synaptic plasticity, probably through its significant antioxidant effects and activate signalling pathways, which are critical in controlling synaptic plasticity.

Effects of vanillic acid on Aβ1-40-induced oxidative stress and learning and memory deficit in male rats

Alzheimer's disease (AD) is a neurodegenerative disease, in which the accumulation of β-amyloid (Aβ) peptide in the extracellular space causes a progressive reduction in cognitive performance. Aβ stimulates active oxygen species generation leading to oxidative stress and neural cell death. Vanillic Acid (VA) is the oxidant form of vanillin widely found in vanilla beans. VA has many properties, such as suppressing apoptosis and eliminating the harmful effects of oxidative stress in animal models. The VA effects on impaired learning and memory in Aβ rats were assessed. Forty adults male Wistar rats were assigned to the following five groups in random: the control, sham (received saline (vehicle) via intracerebroventricular (ICV) injection), Aβ (received Aβ1-40 via ICV injection), VA (50 mg/kg by oral gavage once a day through four weeks), and Aβ + VA (50 mg/kg) groups. Open field test, novel object recognition (NOR) test, Morris water maze (MWM) test, and passive avoidance learning (PAL) task were performed, and finally, we determined the malondialdehyde (MDA), total antioxidant capacity (TAC) and total oxidant status (TOS) levels. Aβ decreased the cognitive memory in NOR, spatial memory in MWM, and passive avoidance memory in PAL tests. In contrast, VA improved learning and memory in the treated group. Aβ significantly increased MDA and TOS and decreased TAC levels, whereas VA treatment significantly reversed TAC, TOS and MDA levels. In conclusion, VA decreased the Aβ effects on learning and memory by suppressing oxidative stress and can be regarded as a neuroprotective substance in AD.

Chamomile decoction mitigates high fat diet-induced anxiety-like behavior, neuroinflammation and cerebral ROS overload

An abundant literature suggests that obesity-associated with taking a high fat diet is related to an elevated risk of type 2 diabetes and metabolic syndrome. However, metabolic disorders may be involved in the induction of the anxiogenic-like symptoms. The current study was designed to elucidate the mechanisms by which a high fat diet (HFD) can cause several complications in the WISTAR rats (Rattus norvegicus) brain. Oxidative stress and inflammation as well as the putative protection afforded by chamomile decoction extract (CDE) were also studied.The results demonstrated that the increased body and brain weight, acetylcholinesterase and butyrylcholinesterase activities as well as hypercholezterolaemia in response to HFD taking were correlated with anxiogenic-like symptoms. Moreover, HFD feed caused a brain oxidative stress characterized by increased lipoperoxidation, inhibition of antioxidant enzyme activities such as SOD, CAT and GPx, depletion of a non-enzymatic antioxidant such as sulfhydryl groups and GSH. Importantly, the results also show that HFD also provoked a cerebral overload in reactive oxygen species such as OH^•, H₂O₂ and O2∙- as well as brain inflammation assessed by the overproduction of cytokines such as IL-1β and IL-6.Interestingly, all neurobehavioral changes and all the biochemical and molecular disturbances were abolished in HFD-fed rats treated with CDE.Our results provide clear evidence that obesity and depression as well as anxiety are finely correlated and that M. recutita's decoction may prove to be a potential therapeutic agent to mitigate the behavioral disorders, the biochemical alterations and the neuroinflammation associated to the obesity.

Critical Review of the Alzheimer's Disease Non-Transgenic Models: Can They Contribute to Disease Treatment?

Alzheimer's disease (AD) is a growing neurodegenerative disease without effective treatments or therapies. Despite the use of different approaches and an extensive variety of genetic amyloid based models, therapeutic strategies remain elusive. AD is characterized by three main pathological hallmarks that include amyloid-β plaques, neurofibrillary tangles, and neuroinflammatory processes; however, many other pathological mechanisms have been described in the literature. Nonetheless, the study of the disease and the screening of potential therapies is heavily weighted toward the study of amyloid-β transgenic models. Non-transgenic models may aid in the study of complex pathological states and provide a suitable complementary alternative to evaluating therapeutic biomedical and intervention strategies. In this review, we evaluate the literature on non-transgenic alternatives, focusing on the use of these models for testing therapeutic strategies, and assess their contribution to understanding AD. This review aims to underscore the need for a shift in preclinical research on intervention strategies for AD from amyloid-based to alternative, complementary non-amyloid approaches.

Dietary Pattern, Gut Microbiota, and Alzheimer's Disease

Alzheimer's disease is the most common neurodegenerative disease. Until now, there has been no specific medicine that can cure Alzheimer's disease or effectively reverse the disease process. A good dietary pattern is an efficient way to prevent or delay the progression of the disease. Evidence suggests that diet may affect β-amyloid production and tau processing or may regulate inflammation, metabolism, and oxidative stress associated with Alzheimer's disease, which can be exerted by gut microbiota. The gut microbiota is a complex microbial community that affects not only various digestive diseases but also neurodegenerative diseases. Studies have shown that gut microbial metabolites, such as pro-inflammatory factors, short-chain fatty acids, and neurotransmitters, can affect the pathogenesis of Alzheimer's disease. Clinical studies suggested that the gut microbial composition of patients with Alzheimer's disease is different, in particular to lower abundances of Eubacterium rectale and Bacteroides fragilis, which have an anti-inflammatory activity. The purpose of this review is to summarize the neuropathological pathogenesis of Alzheimer's disease, and the modulation of dietary patterns rather than single dietary components on Alzheimer's disease through the gut-brain axis was discussed.

Anti-Amnesic Effect of Walnut via the Regulation of BBB Function and Neuro-Inflammation in Aβ1-42-Induced Mice

This study was conducted to assess the protective effect of walnut (Juglans regia L.) extract on amyloid beta (Aβ)_1-42-induced institute of cancer research (ICR) mice. By conducting a Y-maze, passive avoidance, and Morris water maze tests with amyloidogenic mice, it was found that walnut extract ameliorated behavioral dysfunction and memory deficit. The walnut extract showed a protective effect on the antioxidant system and cholinergic system by regulating malondialdehyde (MDA) levels, superoxide dismutase (SOD) contents, reduced glutathione (GSH) contents, acetylcholine (ACh) levels, acetylcholinesterase (AChE) activity, and protein expression of AChE and choline acetyltransferase (ChAT). Furthermore, the walnut extract suppressed Aβ-induced abnormality of mitochondrial function by ameliorating reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and ATP contents. Finally, the walnut extract regulated the expression of zonula occludens-1 (ZO-1) and occludin concerned with blood–brain barrier (BBB) function, expression of tumor necrosis factor-alpha (TNF-α), tumor necrosis factor receptor 1 (TNFR1), phosphorylated c-Jun N-terminal kinase (p-JNK), phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor (p-IκB), cyclooxygenase-2 (COX-2), and interleukin 1 beta (IL-1β), related to neuroinflammation and the expression of phosphorylated protein kinase B (p-Akt), caspase-3, hyperphosphorylation of tau (p-tau), and heme oxygenase-1 (HO-1), associated with the Aβ-related Akt pathway.

Cardioprotective effect of thymol against adrenaline-induced myocardial injury in rats

Cardiovascular disease represents a vital global disease burden. This study aims to assess the possible cardioprotective effect of thymol against adrenaline-induced myocardial injury (MI) in rats. Furthermore the effect of thymol on cardiac function biomarkers, electrocardiogram (ECG) alterations, oxidative stress, inflammation, apoptosis and histopathological changes was assessed. MI was induced by adrenaline (2 mg/kg, s.c.) injected as a single dose for 2 consecutive days (24 h apart). Normal and control groups received the vehicle for 21 consecutive days. The other 3 groups were orally administered thymol (15, 30, 60 mg/kg) for 21 consecutive days and on day 22, adrenaline was injected as a single dose for 2 consecutive days. Then ECG examination, biochemical, histopathological, immunohistochemical analyses were carried out. Thymol reversed adrenaline-induced reduction of heart rate, prolongation of RR interval and elevation of ST interval. Thymol pretreatment significantly reduced serum aspartate dehydrogenase (AST), lactate dehydrogenase (LDH), and creatine kinase (CK) levels in MI rats. Oral pretreatment with thymol increased reduced glutathione (GSH), reduced malondialdehyde (MDA), nuclear factor-kappa B (NF-κB), and interleukin-1β (IL-1β) cardiac contents in MI rats. Additionally, thymol administration significantly decreased protein expression of caspase-3, increased Bcl-2 protein expression in cardiac tissue and ameliorated histopathological changes. This study reveals that thymol exerted cardioprotective effect against adrenaline-induced MI in rats evidenced by improving cardiac function, attenuating ECG and histopathological changes which may be partly mediated through its anti-oxidant, anti-inflammatory and anti-apoptotic effect.

The Protective Effects of Acer okamotoanum and Isoquercitrin on Obesity and Amyloidosis in a Mouse Model

Obesity increases risk of Alzheimer's Disease (AD). A high fat diet (HFD) can lead to amyloidosis and amyloid beta (Aβ) accumulation, which are hallmarks of AD. In this study, protective effects of the ethyl acetate fraction of Acer okamotoanum (EAO) and isoquercitrin were evaluated on obesity and amyloidosis in the HFD- and Aβ-induced mouse model. To induce obesity and AD by HFD and Aβ, mice were provided with HFD for 10 weeks and were intracerebroventricularly injected with Aβ_25-35. For four weeks, 100 and 10 mg/kg/day of EAO and isoquercitrin, respectively, were administered orally. Administration of EAO and isoquercitrin significantly decreased body weight in HFD and Aβ-injected mice. Additionally, EAO- and isoquercitrin-administered groups attenuated abnormal adipokines release via a decrease in leptin and an increase in adiponectin levels compared with the control group. Furthermore, HFD and Aβ-injected mice had damaged liver tissues, but EAO- and isoquercitrin-administered groups attenuated liver damage. Moreover, administration of EAO and isoquercitrin groups down-regulated amyloidosis-related proteins in the brain such as β-secretase, presenilin (PS)-1 and PS-2 compared with HFD and Aβ-injected mice. This study indicated that EAO and isoquercitrin attenuated HFD and Aβ-induced obesity and amyloidosis, suggesting that they could be effective in preventing and treating both obesity and AD.

Effects of Hypericum scabrum extract on dentate gyrus synaptic plasticity in high fat diet-fed rats

High-fat diet (HFD) can induce deficits in neural function, oxidative stress, and decrease hippocampal neurogenesis. Hypericum (H.) scabrum extract (Ext) contains compounds that could treat neurological disorders. This study aimed to examine the neuroprotective impacts of the H. scabrum Ext on hippocampal synaptic plasticity in rats that were fed HFD. Fifty-four male Wistar rats (220 ± 10 g) were randomly arranged in six groups: (1) HFD group; (2) HFD + Ext300 group; (3) HFD + Ext100 group; (4) Control group; (5) Ext 300 mg/kg group; (6) Ext 100 mg/kg group. These protocols were administrated for 3 months. After this stage, a stimulating electrode was implanted in the perforant pathway (PP), and a bipolar recording electrode was embedded into the dentate gyrus (DG). Long-term potentiation (LTP) was provoked by high-frequency stimulation (HFS) of the PP. Field excitatory postsynaptic potentials (EPSP) and population spikes (PS) were recorded at 5, 30, and 60 min after HFS. The HFD group exhibited a large and significant decrease in their PS amplitude and EPSP slope as compared to the control and extract groups. In reverse, H. scabrum administration in the HFD + Ext rats reversed the effect of HFD on the PS amplitude and EPSP slope. The results of the study support that H. scabrum Ext can inhibit diminished synaptic plasticity caused by the HFD. These effects are probably due to the extreme antioxidant impacts of the Ext and its capability to scavenge free radicals.

The protective and therapeutic effects of vinpocetine, a PDE1 inhibitor, on oxidative stress and learning and memory impairment induced by an intracerebroventricular (ICV) injection of amyloid beta (aβ) peptide

Alzheimer's disease (AD) is a neurodegenerative disease leading to cognitive and memory impairment. This study aimed at investigating the therapeutic and preserving effects of vinpocetine on amyloid beta (Aβ)-induced rat model of AD. Sixty male adult Wistar rats were randomly divided into 6 groups (n = 10 per group) as follows: 1; control, 2; sham, 3; Aβ, 4; pre-treatment (vinpocetine + Aβ): oral gavage administration of vinpocetine at 4 mg/kg for 30 days followed by intracerebroventricular (ICV) injection of Aβ, 5; treatment (Aβ + vinpocetine): Aβ ICV injection followed by vinpocetine administration for 30 days, 6; pre-treatment + treatment (vinpocetine + Aβ + vinpocetine): vinpocetine administration for 30 days before and 30 days after AD induction. Following treatments, the animals' learning and memory were investigated using passive avoidance learning (PAL) task, Morris water maze (MWM), and novel object recognition (NOR) tests. The results demonstrated that Aβ significantly enhanced escape latency and the distance traveled in the MWM, decreased step-through latency, and increased time spent in the dark compartment in PAL. Vinpocetine ameliorated the Aβ-infused memory deficits in both MWM and PAL tests. Administration of vinpocetine in the Aβ rats increased the discrimination index of the NOR test. It also significantly diminished the nitric oxide and malondialdehyde levels and restored the reduced glutathione (GSH) levels. Vinpocetine can improve memory and learning impairment following Aβ infusion due to its different properties, including antioxidant effects, which indicates that vinpocetine administration can lead to the amelioration of cognitive dysfunction in AD.

Carvacrol and Thymol Attenuate Cytotoxicity Induced by Amyloid β25-35 via Activating Protein Kinase C and Inhibiting Oxidative Stress in PC12 Cells

Background

Our previous findings indicated that carvacrol and thymol alleviate cognitive impairments caused by Aβ in rodent models of Alzheimer's disease (AD). In this study, the neuroprotective effects of carvacrol and thymol against Aβ25-35-induced cytotoxicity were evaluated, and the potential mechanisms were determined.

Methods

PC12 cells were pretreated with Aβ25-35 for 2 h, followed by incubation with carvacrol or thymol for additional 48 h. Cell viability was measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method. A flurospectrophotometer was employed to observe the intracellular reactive oxygen species (ROS) production. Protein kinase C (PKC) activity was analyzed using ELISA.

Results

Our results indicated that carvacrol and thymol could significantly protect PC12 cells against Aβ25-35-induced cytotoxicity. Furthermore, Aβ25-35 could induce intracellular ROS production, while carvacrol and thymol could reverse this effect. Moreover, our findings showed that carvacrol and thymol elevate PKC activity similar to Bryostatin-1, as a PKC activator.

Conclusion

This study provided the evidence regarding the protective effects of carvacrol and thymol against Aβ25–35-induced cytotoxicity in PC12 cells. The results suggested that the neuroprotective effects of these compounds against Aβ25-35 might be through attenuating oxidative damage and increasing the activity of PKC as a memory-related protein. Thus, carvacrol and thymol were found to have therapeutic potential in preventing or modulating AD.

Anticonvulsant Essential Oils and Their Relationship with Oxidative Stress in Epilepsy

Epilepsy is a most disabling neurological disorder affecting all age groups. Among the various mechanisms that may result in epilepsy, neuronal hyperexcitability and oxidative injury produced by an excessive formation of free radicals may play a role in the development of this pathology. Therefore, new treatment approaches are needed to address resistant conditions that do not respond fully to current antiepileptic drugs. This paper reviews studies on the anticonvulsant activities of essential oils and their chemical constituents. Data from studies published from January 2011 to December 2018 was selected from the PubMed database for examination. The bioactivity of 19 essential oils and 16 constituents is described. Apiaceae and Lamiaceae were the most promising botanical families due to the largest number of reports about plant species from these families that produce anticonvulsant essential oils. Among the evaluated compounds, β-caryophyllene, borneol, eugenol and nerolidol were the constituents that presented antioxidant properties related to anticonvulsant action. These data show the potential of these natural products as health promoting agents and use against various types of seizure disorders. Their properties on oxidative stress may contribute to the control of this neurological condition. However, further studies on the toxicological profile and mechanism of action of essential oils are needed.

Coenzyme Q10 supplementation reverses diabetes-related impairments in long-term potentiation induction in hippocampal dentate gyrus granular cells: An in vivo study

Diabetes mellitus (DM) is associated with impaired hippocampal synaptic plasticity. Coenzyme Q10 (CoQ10) acts as an antioxidant and exerts neuroprotective effects. Accordingly, this study aimed at evaluating the effects of CoQ10 on hippocampal long-term potentiation (LTP) and paired-pulse facilitation (PPF) in streptozotocin (STZ)-induced diabetic rats. Male Wistar rats were randomly divided into six groups (n = 8 per group) as follows and treated for 90 days: the control, control + low dose of CoQ10 (100 mg/kg), control + high dose of CoQ10 (600 mg/kg), diabetic, diabetic + low dose of CoQ10, and diabetic + high dose of CoQ10 groups. Diabetes was induced by a single intraperitoneal injection of 50 mg/kg STZ. The population spike (PS) amplitude and slope of excitatory post synaptic potentials (EPSPs) were measured in dentate gyrus (DG) area in response to the stimulation applied to the perforant path (PP). The results showed that the STZ-induced diabetes impaired LTP induction in the PP-DG synapses. This finding is supported by the decreased EPSP slope and PS amplitude of LTP (P < 0.05). Both low- and high-dose CoQ10 supplementation in the control and diabetic animals enhanced EPSP slope and PS amplitude of LTP in the granular cells of DG (P < 0.05). PPF was affected by LTP induction in diabetic animals receiving the high dose of CoQ10 (P < 0.05). It is suggested that CoQ10 administration could attenuate deteriorative effect of STZ-induced diabetes on in vivo LTP in the DG. The enhanced transmitter release can be partly one of the possible underlying mechanism(s) responsible for the LTP induction in the diabetic animals treated with CoQ10.

Cellular and Molecular Differences Between Area CA1 and the Dentate Gyrus of the Hippocampus

A distinct feature of the hippocampus of the brain is its unidirectional tri-synaptic pathway originating from the entorhinal cortex and projecting to the dentate gyrus (DG) then to area CA3 and subsequently, area CA1 of the Ammon's horn. Each of these areas of the hippocampus has its own cellular structure and distinctive function. The principal neurons in these areas are granule cells in the DG and pyramidal cells in the Ammon's horn's CA1 and CA3 areas with a vast network of interneurons. This review discusses the fundamental differences between the CA1 and DG areas regarding cell morphology, synaptic plasticity, signaling molecules, ability for neurogenesis, vulnerability to various insults and pathologies, and response to pharmacological agents.

Acer okamotoanumand isoquercitrin improve cognitive functionviaattenuation of oxidative stress in high fat diet- and amyloid beta-induced mice

High fat diet (HFD) and accumulation of amyloid beta (Aβ) are known as a risk factor of Alzheimer's disease.Acer okamotoanumand isoquercitrin improved cognition function against both HFD and Aβ accumulation by inhibiting oxidative stress.

TGF-β1 Restores Hippocampal Synaptic Plasticity and Memory in Alzheimer Model via the PI3K/Akt/Wnt/β-Catenin Signaling Pathway

Alzheimer's disease (AD) is the most common neurodegenerative disturbances. Dysfunction of synaptic plasticity and decline in cognitive functions are the most prominent features of AD, but the mechanisms of pathogenesis have not been well elucidated. In this paper, transforming growth factor-β1 (TGF-β1) was found to be reduced in the hippocampus of AD mouse which was accompanied by impaired pine density, synaptic plasticity, and memory function. Hippocampal injection of TGF-β1 rescued the AD-induced memory function impairment. In addition, TGF-β1 ameliorated synaptic plasticity and increased synaptic plasticity-associated protein expression including Arc, NR2B, and PSD-95 in mouse model of AD. Furthermore, we demonstrated that Akt/Wnt/β-catenin pathway protein expression in the hippocampus was suppressed in a mouse model of AD and TGF-β1 significantly enhanced the phosphorylation Akt, GSK3β, and increased the nuclear β-catenin. These results indicate that TGF-β1activates PI3K/Akt/Wnt/β-catenin signaling in mouse model of AD, which is important for promoting synaptic plasticity related to memory function. More importantly, suppression of PI3K/Akt/Wnt/β-catenin pathway compromised the beneficial effects of TGFβ1 in Alzheimer's model. Hence, TGF-β1 shows protective effect on neurons, which might be through the PI3K/Akt/Wnt/β-catenin signaling pathway, serving as a potential target in AD pathology.

Treadmill exercise restores high fat diet-induced disturbance of hippocampal neurogenesis through β2-adrenergic receptor-dependent induction of thioredoxin-1 and brain-derived neurotrophic factor

A high-fat diet (HFD) is known to induce metabolic disturbances that may lead to cognitive impairment. In the present study, we investigated whether a regular treadmill exercise program would improve HFD-induced hippocampal-dependent memory deficits in C57BL/6 mice. Weight gain and hepatic triglyceride levels were profoundly elevated following administration of a 60% HFD for 23 weeks, and this change was attenuated by 23-weeks of treadmill running. The exercise regimen attenuated impairments in memory function of HFD-fed mice in a water maze test and recovered HFD-induced anti-neurogenic effects as shown by immunohistochemistry data with Ki-67 and doublecortin (DCX) antibodies. Moreover, the treadmill exercise resulted in anti-inflammatory, antioxidant, and neuroprotective effects in the HFD-fed brain. The exercise inhibited HFD-induced microglial activation, expression of proinflammatory cytokines (tumor necrosis factor-α and interleukin-1β), and NF-κB activity in the dentate gyrus (DG) of the hippocampus. In addition, the exercise reduced malondialdehyde levels elevated by HFD and recovered antioxidant superoxide dismutase and glutathione levels in hippocampal DG of HFD-mice. The exercise also reduced the number of apoptotic cells induced by HFD, as shown by TUNEL staining in the DG region. Finally, we demonstrated that the thioredoxin-1 (TRX-1) and brain-derived neurotrophic factor (BDNF) levels were recovered by exercise, which was demonstrated to act via β2-adrenergic receptor enriched in synaptosomes of the DG. Therefore, our data collectively suggests that regular exercise may be a promising approach to preventing HFD-induced memory impairments via anti-inflammatory, antioxidant and neuroprotective mechanisms in the hippocampal DG region.

Effect of a 5-HT1D receptor agonist on the reinstatement phase of the conditioned place preference test and hippocampal long-term potentiation in methamphetamine-treated rats

Methamphetamine (METH)-seeking relapse is associated with memory and synaptic plasticity changes. Serotonin is a key neuromodulator in this process. While there is a known distribution of 5-HT_1D receptors in reward and memory areas, such as the hippocampus, its physiological function is currently unknown. Here, we evaluated effect of a 5-HT_1D receptor agonist, PNU142633, on the reinstatement of METH-seeking behavior and long-term potentiation. Rats were implanted with a cannula into lateral ventricle, then treated with saline or METH (5 mg/kg) during the acquisition phase of the conditioned place preference (CPP) test. On day 13 of the extinction phase, METH groups were divided into four groups: METH (0: saline, 1, or 2.5 (priming METH) mg/kg; i.p.) + vehicle (5 µl/rat) or a priming dose of METH (2.5 mg/kg; i.p.) + PNU (2 µg/5 µl; i.c.v.) and their preference scores were calculated on reinstatement day (day 14). Immediately following this, electrophysiology was performed to assay the field excitatory postsynaptic potential (fEPSP) slope and population spike (PS) amplitude between groups. The results showed that CPP induction by METH gradually declined to extinction on days 12 and 13. A priming METH treatment significantly increased preference for the METH-paired chamber when compared with other groups, but pre-treatment with PNU significantly attenuated this effect. PS amplitude and fEPSP slopes in vehicle + priming METH rats were greater when compared with other groups. Furthermore, PNU attenuated the priming METH-induced increase in PS amplitude. These findings suggest that PNU can decrease synaptic transmission and prevent METH reinstatement in rats.

Purinergic system as a potential target for inflammation and toxicity induced by thymol in immune cells and tissues

Thymol is a phytochemical component present in many plants used as food additive in order to promote animal growth due to its several biological properties. However, possible side effects of thymol remain poorly known limited to few reports. In this sense, we evaluated the enzymes of the purinergic signaling such as, ectonucleoside triphosphate diphosphohydrolase (NTPDase), 5'-nucleotidase and adenosine deaminase (ADA), that play an important role on toxicity induced by excessive adenosine triphosphate (ATP) content in the extracellular environment. Thus, the aim of this study was to evaluate whether purinergic signaling could be considered a potential target of thymol-induced inflammation, and the toxicity in tissues and immune cells of mice after thymol administration. NTPDase activity (ATP as substrate) in serum, spleen, and splenic lymphocytes was lower after 30 days of oral treatment at doses of 10, 20, and 40 mg/kg of thymol, while ADA activity was stimulated at 20 and 40 mg/kg. No differences were observed between groups regarding NTPDase (ADP as substrate) and 5'-nucleotidase activities in all evaluated tissues. Based on these evidences, adenine nucleotide hydrolysis is modified in serum, spleen, and splenic lymphocytes of mice treated with thymol, contributing to inflammation and toxicity by a reduction on ATP hydrolyses and its possible accumulation in the extracellular medium and increased Ado desamination and its possible reduction in the extracellular environment, leading to a self-sustained pro-inflammatory deleterious cycle. In summary, all tested thymol concentrations induced inflammation and toxicity in tissues and immune cells of treated mice.