Protective effect of transient receptor potential vanilloid subtype 1 (TRPV1) modulator, against behavioral, biochemical and structural damage in experimental models of Alzheimer's disease

Selective inhibition of T-type calcium channel preserves ischemic pre-conditioning mediated neuroprotection during cerebral ischemia reperfusion injury in diabetic mice

Ischemic preconditioning (IPC) provides ischemic tolerance and neuroprotection during cerebral ischemia reperfusion (CI/R) injury. Diabetes abolishes the beneficial effects of conditioning phenomenon during CI/R. The study investigates the role of T-type calcium ion channel in IPC mediated protection during diabetes mellitus. The study employed Swiss Albino mice. Animals were divided into 3 normoglycaemic groups (Sham, CI/R, and IPC) and 4 hyperglycaemic groups (Sham, CI/R, IPC, and ML218 + IPC). CI/R injury was induced in Swiss Albino mice by occlusion of common carotid arteries followed by reperfusion. IPC was given prior to CI/R injury and diabetes was induced using streptozotocin (STZ). Animals were assessed for learning, memory, motor coordination, neurological function, cerebral infarction, edema, and histopathological alterations. Biochemical assessments were performed for calcium binding proteins (Calmodulin (CaM), calcium/calmodulin-dependent protein kinase II (CaMKII), and S100B), oxidative stress (4-hydroxy-2-nonenal (4-HNE)), glutathione (GSH), inflammation (nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), tumor necrosis factor (TNF-α), interleukin (IL-10)), inducible nitric oxide synthase (iNOS) levels, and acetylcholinesterase activity (AChE) in brain supernatants. NF-kB, iNOS, and S100B serum levels were also assessed. CI/R animals (normoglycemic and hyperglycaemic) showed impairment in learning, memory, motor coordination, and neurological function along with increase in cerebral infarction, edema, and histopathological alterations. Furthermore, increase in brain calcium-binding proteins, oxidative stress, inflammation, and AChE along with serum NF-kB, iNOS, and S100B levels were recorded in CI/R animals. IPC ameliorated CI/R induced behavioral, biochemical, and histopathological impairment, however no beneficial effects were observed in IPC (diabetic) mice. Administration of ML218 (10 mg/kg; i.p.), a selective T-type calcium channel re-established the IPC mediated neuroprotection in CI/R diabetic animals. In conclusion, IPC-mediated neuroprotection was abolished in diabetic mice. T-type calcium ion channel antagonism plays an important role in the IPC-mediated neuroprotection during hyperglycaemia.

Olfactory stimulation with multiple odorants prevents stress-induced cognitive and psychological alterations

Acute and chronic stress markedly affects behavior by triggering sympathetic nervous system activation and several hypothalamus-pituitary-adrenal-dependent responses. Brain regions of the limbic system are responsible for the regulation of stress response, and different reports have demonstrated that their activity can be influenced by olfactory stimuli. Here we report that, in mice exposed to acute restraint stress, olfactory stimulation employing a combination of three odorants, i.e. vanillin, limonene and green odor (trans-2-hexenal and cis-3-hexenol) decreased anxiety behavior, assessed in the elevated plus maze, and halted recognition and spatial memory deficits, as appraised in two different object recognition tasks. Of note, when applied singularly, the same odorants were unable to block the detrimental effects of stress. We also found that the multiple odorants stimulation prevented the development of depressive symptoms assessed by the sucrose splash test and forced swim test in an experimental model of depression, i.e. mice exposed to a chronic unpredictable stress paradigm, and reduced interleukin 1β levels in the prefrontal cortex of depressed mice. Collectively, our data indicate that olfactory stimulation counteracts the detrimental effects of acute and chronic stress on mood regulation and cognitive functions, thus representing a potential tool for the treatment of stress-induced disorders.

ML218 modulates calcium binding protein, oxidative stress, and inflammation during ischemia-reperfusion brain injury in mice

Cerebral ischemia disrupts calcium homeostasis in the brain causing excitotoxicity, oxidative stress, inflammation, and neuronal cell apoptosis. During ischemic conditions, T-type calcium channel channels contribute to increase in intracellular calcium ions in both neurons and glial cells therefore, the current study hypothesizes the antagonism of these channels using ML218, a novel specific T-Type inhibitor in experimental model of cerebral ischemia-reperfusion (CI/R) brain injury. CI/R injury was induced in Swiss Albino mice by occlusion of common carotid arteries followed by reperfusion. Animals were assessed for learning and memory (MWM), motor coordination (Rota rod), neurological function (neurological deficit score), cerebral infarction, edema, and histopathological alterations. Biochemical assessments were made for calcium binding proteins (Calmodulin- CaM, calcium/calmodulin-dependent protein kinase II-CaMKII, S100B), oxidative stress (4-hydroxy 2-nonenal-4-HNE, glutathione-GSH, inflammation (nuclear factor kappa-light-chain-enhancer of activated B-p65-NF-kB, tumor necrosis factor-TNF-α, interleukin-IL-10) inducible nitric oxide synthase (iNOS) levels, and acetylcholinesterase activity (AChE) in brain supernatants. Furthermore, serum levels of NF-kB, iNOS, and S100B were also assessed. CI/R animals showed impairment in learning, memory, motor coordination, and neurological function along with increase in cerebral infarction, edema, and histopathological alterations. Furthermore, increase in brain calcium binding proteins, oxidative stress, inflammation, and AChE activity along with serum NF-kB, iNOS, and S100B levels were recorded in CI/R animals. Administration of ML218 (5 mg/kg and 10 mg/kg; i.p.) was observed to recuperate CI/R induced impairments in behavioral, biochemical, and histopathological analysis. Hence, it may be concluded that ML218 mediates neuroprotection during CI/R via decreasing brain and serum calcium binding proteins, inflammation, iNOS, and oxidative stress markers.

TRPV1 Channels in the Central Nervous System as Drug Targets

TRPV1 channels are polymodal cation channels located predominantly on primary afferent neurons that are activated by inflammatory mediators, capsaicin (the active component in chili peppers), and noxious heat. TRPV1 channel antagonists are potential new analgesic agents, but their development has been hindered by the finding that they also produce loss of thermal homeostasis and response to noxious heat. Results from recent studies of the TRPV1 channel indicate that it might be possible to develop TRPV1 channel antagonists that inhibit pain without affecting noxious heat sensation. TRPV1 channels are also present in the central nervous system (CNS) and have been implicated in learning, memory, and behaviour. TRPV1 channel modulators have been proposed to have possible therapeutic potential in the treatment of neurological and psychiatric conditions. However, further understanding of the role of TRPV1 channels in the CNS is required before therapeutic advances in the treatment of neuropsychiatric conditions with TRPV1 channel modulators can be made.

Ameliorative effects of vanillin against pentylenetetrazole-induced epilepsy and associated memory loss in mice: The role of Nrf2/HO-1/NQO1 and HMGB1/RAGE/TLR4/NFκB pathways

BACKGROUND

Epilepsy is a severe neurological disorder associated with substantial morbidity and mortality. Vanillin (Van) is a natural phenolic aldehyde with beneficial pharmacological properties. This study investigated the neuroprotective effects of Van in epilepsy and elucidated its mechanism of action.

METHODS

Swiss albino mice were divided into the following five groups: "normal group", 0.9 % saline; "pentylenetetrazole (PTZ) group", intraperitoneal administration of 35 mg/kg PTZ on alternate days up to 42 days; and "PTZ + Van 20", "PTZ + Van 40", and "PTZ + sodium valproate (Val)" groups received PTZ injections in conjunction withVan 20 mg, Van 40 mg/kg, and Val 300 mg/kg, respectively. Behavioural tests and hippocampal histopathological analysis were performed in all groups. The Nrf2/HO-1/NQO1 and HMGB1/RAGE/TLR4/NFκB pathways, oxidative stress, neuro-inflammation, and apoptotic markers were analysed. Furthermore, brain acetylcholinesterase (AChE) activity and levels of dopamine (DA), gamma-aminobutyric acid GABA, and serotonin 5-HT were assessed.

RESULTS

Van prolonged seizure manifestations and improved electroencephalogram (EEG)criteriain conjunction with 100 mg/kg PTZ once daily. Van administration increased Nrf2/HO-1/NQO1 levels, with subsequent attenuation of malondialdehyde (MDA) and nitric oxide (NO) levels with elevated glutathione (GSH) levels and intensified superoxide dismutase (SOD) and catalase activities. Van reduced the gene and protein expression of HMGB1/RAGE/TLR4/NFκB and decreased the levels of inflammatory and apoptotic markers. In addition, Van reduced AChE activity, and elevated glial fibrillary acidic proteins (GFAP) increased neurotransmitter and brain-derived neurotrophic factors (BDNF).

CONCLUSION

By increasing Nrf2/HO-1/NQO1 levels and downregulating the HMGB1/RAGE/TLR4/ NFκB pathway, Van offered protection in PTZ-kindled mice with subsequent attenuation in lipid peroxidation, upregulation in antioxidant enzyme activities, and reduction in inflammation and apoptosis.

Mitochondrial dysfunction and neurological disorders: A narrative review and treatment overview

Mitochondria play a vital role in the nervous system, as they are responsible for generating energy in the form of ATP and regulating cellular processes such as calcium (Ca2+) signaling and apoptosis. However, mitochondrial dysfunction can lead to oxidative stress (OS), inflammation, and cell death, which have been implicated in the pathogenesis of various neurological disorders. In this article, we review the main functions of mitochondria in the nervous system and explore the mechanisms related to mitochondrial dysfunction. We discuss the role of mitochondrial dysfunction in the development and progression of some neurological disorders including Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD), depression, and epilepsy. Finally, we provide an overview of various current treatment strategies that target mitochondrial dysfunction, including pharmacological treatments, phototherapy, gene therapy, and mitotherapy. This review emphasizes the importance of understanding the role of mitochondria in the nervous system and highlights the potential for mitochondrial-targeted therapies in the treatment of neurological disorders. Furthermore, it highlights some limitations and challenges encountered by the current therapeutic strategies and puts them in future perspective.

Overview of the Role of Vanillin in Neurodegenerative Diseases and Neuropathophysiological Conditions

Nowadays, bioactive natural products play key roles in drug development due to their safety profile and strong antioxidant power. Vanillin is a natural phenolic compound found in several vanilla beans and widely used for food, cosmetic, and pharmaceutical products. Besides its industrial applications, vanillin possesses several beneficial effects for human health, such as antioxidant activity in addition to anti-inflammatory, anti-mutagenic, anti-metastatic, and anti-depressant properties. Moreover, vanillin exhibits neuroprotective effects on multiple neurological disorders and neuropathophysiological conditions. This study reviews the mechanisms of action by which vanillin prevents neuroinflammation and neurodegeneration in vitro and in vivo systems, in order to provide the latest views on the beneficial properties of this molecule in chronic neurodegenerative diseases and neuropathophysiological conditions.

Centella asiatica Alleviates AlCl3-induced Cognitive Impairment, Oxidative Stress, and Neurodegeneration by Modulating Cholinergic Activity and Oxidative Burden in Rat Brain

Aluminum (Al) is linked to the development of many neurological disorders such as Alzheimer's disease (AD), Parkinson's disease, and autism. Centella asiatica (CA) is a regenerating herb traditionally used to stimulate memory. This study was designed to assess the neuroprotective role of ethanolic extract of CA (CAE) in AlCl₃-induced neurological conditions in rats. Adult rats were chronically treated with AlCl₃ (100 mg/kg b.w./day) for 60 days to establish the dementia model, and co-administration of CAE was evaluated for its ability to attenuate the toxic effect of AlCl₃. CAE was given orally at a dose of 150 and 300 mg/kg b.w./day, for 60 days. The behavioral performances of rats were tested through Y-maze and open field tests. Lipid peroxidation, superoxide dismutase, and catalase activity were evaluated to measure oxidative stress; and acetylcholinesterase (AChE) activity was assessed to evaluate cholinergic dysfunction in the rat brain. H&E staining was used to assess structural abnormalities in the cortex and hippocampus. The result showed that AlCl₃ induces cognitive dysfunction (impaired learning and memory, anxiety, diminished locomotor activity), oxidative stress, cholinergic impairment, and histopathological alteration in the rat brain. Co-administration of CAE with AlCl₃ markedly protects the brain from AlCl₃-induced cognitive dysfunction, oxidative stress, AChE activity, and cytoarchitectural alterations. Furthermore, 15 days CAE treatment after 45 days AlCl₃ administration markedly ameliorates the AlCl₃-induced neurotoxicity indicating its potential for therapeutic use.

Synaptic Effects of Palmitoylethanolamide in Neurodegenerative Disorders

Increasing evidence strongly supports the key role of neuroinflammation in the pathophysiology of neurodegenerative diseases, such as Alzheimer’s disease, frontotemporal dementia, and amyotrophic lateral sclerosis. Neuroinflammation may alter synaptic transmission contributing to the progression of neurodegeneration, as largely documented in animal models and in patients’ studies. In the last few years, palmitoylethanolamide (PEA), an endogenous lipid mediator, and its new composite, which is a formulation constituted of PEA and the well-recognized antioxidant flavonoid luteolin (Lut) subjected to an ultra-micronization process (co-ultraPEALut), has been identified as a potential therapeutic agent in different disorders by exerting potential beneficial effects on neurodegeneration and neuroinflammation by modulating synaptic transmission. In this review, we will show the potential therapeutic effects of PEA in animal models and in patients affected by neurodegenerative disorders.

Salubrious effects of ulinastatin and quercetin alone or in combination in endothelial dysfunction and vascular dementia

BACKGROUND

Vascular dementia is the second most prevalent form of dementia. Hypertension is the leading risk factor for endothelial dysfunction and the progression of dementia that is of vascular origin. This study investigates the role of ulinastatin (UTI) and quercetin alone as well as in combination in hypertension-induced endothelial dysfunction and vascular dementia (VaD).

METHOD

Two-kidney one-clip (2K1C) renovascular model was set up to induce hypertension in the Albino Wistar rats (males). Rats were assessed for mean arterial blood pressure, behavioral function (Morris water maze, attention set-shifting tests), vascular endothelial function, and biochemical levels (aortic superoxide anion and serum nitrite/nitrate), as well as brains' thiobarbituric acid reactive species-TBARS, reduced glutathione-GSH, interleukin-6, 10, tumor necrosis factor-TNF-α and acetylcholinesterase-AChE). UTI (10,000 U/kg, ip) and quercetin (60 mg/kg) were used alone and in combination for treatment. Donepezil (0.5 mg/kg) was used as a positive control.

RESULTS

2K1C rats showed impairment in learning, memory, executive functioning, and reversal learning. These rats further showed endothelial dysfunction as well as an increase in mean arterial blood pressure, brains' oxidative stress, inflammation, and AChE-activity. Treatment with UTI and quercetin alone as well in combination significantly attenuated the 2K1C model induced impairments in the behavioural, biochemical, and endothelial parameters.

CONCLUSION

2K1C renovascular hypertension-induced impairment in behavioural, biochemical, and endothelial parameters were attenuated by the treatment with UTI and quercetin alone as well as in combination. Therefore, the utility of these agents might be studied further to understand their full potential in hypertension-induced VaD.

The Roles of Transient Receptor Potential Ion Channels in Pathologies of Glaucoma

Transient receptor ion potential (TRP) channels are a cluster of non-selective cation channels present on cell membranes. They are important mediators of sensory signals to regulate cellular functions and signaling pathways. Alterations and dysfunction of these channels could disrupt physiological processes, thus leading to a broad array of disorders, such as cardiovascular, renal and nervous system diseases. These effects position them as potential targets for drug design and treatment. Because TRP channels can mediate processes such as mechanical conduction, osmotic pressure, and oxidative stress, they have been studied in the context of glaucoma. Glaucoma is an irreversible blinding eye disease caused by an intermittent or sustained increase in intraocular pressure (IOP), which results in the apoptosis of retinal ganglion cells (RGCs), optic nerve atrophy and eventually visual field defects. An increasing number of studies have documented that various TRP subfamilies are abundantly expressed in ocular structures, including the cornea, lens, ciliary body (CB), trabecular meshwork (TM) and retina. In alignment with these findings, there is also mounting evidence supporting the potential role of the TRP family in glaucoma progression. Therefore, it is of great interest and clinical significance to gain an increased understanding of these channels, which in turn could shed more light on the identification of new therapeutic targets for glaucoma. Moreover, this role is not understood completely to date, and whether the activation of TRP channels contributes to glaucoma, or instead aggravates progression, needs to be explored. In this manuscript, we aim to provide a comprehensive overview of recent research on TRP channels in glaucoma and to suggest novel targets for future therapeutic interventions in glaucoma.

Functional Importance of Transient Receptor Potential (TRP) Channels in Neurological Disorders

Transient receptor potential (TRP) channels are transmembrane protein complexes that play important roles in the physiology and pathophysiology of both the central nervous system (CNS) and the peripheral nerve system (PNS). TRP channels function as non-selective cation channels that are activated by several chemical, mechanical, and thermal stimuli as well as by pH, osmolarity, and several endogenous or exogenous ligands, second messengers, and signaling molecules. On the pathophysiological side, these channels have been shown to play essential roles in the reproductive system, kidney, pancreas, lung, bone, intestine, as well as in neuropathic pain in both the CNS and PNS. In this context, TRP channels have been implicated in several neurological disorders, including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and epilepsy. Herein, we focus on the latest involvement of TRP channels, with a special emphasis on the recently identified functional roles of TRP channels in neurological disorders related to the disruption in calcium ion homeostasis.

Lowest aqueous picomolar fluoride ions and in vivo aluminum toxicity detection by an aluminum(iii) binding chemosensor

Aluminum toxicity in biological systems is a well-known issue yet remains as a prevalent and unsolvable problem due to the lack of proper molecular tools that can detect free aluminum(iii) or Al(iii) ions in vivo. Herein, we report a water-soluble photo-induced electron transfer (PET)-based turn-ON/OFF fluorometric chemosensor for the dual detection of Al(iii) and fluoride ions in aqueous media with a nanomolar (∼1.7 × 10^-9 M) and picomolar (∼2 × 10^-12 M, lowest ever detection so far) detection limit, respectively. Fluoride ions in sea water could be detected as well as the recognition of non-contamination in drinking water. In addition, using live-cell microscopy, Al(iii) ions were detected in live biological samples in vivo to aid establishing the aluminum-toxicity effect.

Coupled mixed model for joint genetic analysis of complex disorders with two independently collected data sets

BACKGROUND

In the last decade, Genome-wide Association studies (GWASs) have contributed to decoding the human genome by uncovering many genetic variations associated with various diseases. Many follow-up investigations involve joint analysis of multiple independently generated GWAS data sets. While most of the computational approaches developed for joint analysis are based on summary statistics, the joint analysis based on individual-level data with consideration of confounding factors remains to be a challenge.

RESULTS

In this study, we propose a method, called Coupled Mixed Model (CMM), that enables a joint GWAS analysis on two independently collected sets of GWAS data with different phenotypes. The CMM method does not require the data sets to have the same phenotypes as it aims to infer the unknown phenotypes using a set of multivariate sparse mixed models. Moreover, CMM addresses the confounding variables due to population stratification, family structures, and cryptic relatedness, as well as those arising during data collection such as batch effects that frequently appear in joint genetic studies. We evaluate the performance of CMM using simulation experiments. In real data analysis, we illustrate the utility of CMM by an application to evaluating common genetic associations for Alzheimer's disease and substance use disorder using datasets independently collected for the two complex human disorders. Comparison of the results with those from previous experiments and analyses supports the utility of our method and provides new insights into the diseases. The software is available at https://github.com/HaohanWang/CMM .

Effect of Treadmill Exercise and Trans-Cinnamaldehyde against d-Galactose- and Aluminum Chloride-Induced Cognitive Dysfunction in Mice

Mild cognitive impairment (MCI) generally refers to impairment in cognition above that which accompanies the normal age-related cognitive decline and has attracted attention in recent years. Trans-cinnamaldehyde (TCA), which is isolated from cinnamon, has anti-inflammatory and antioxidant properties. Treadmill exercise also has diverse positive effects. The purpose of this study was to investigate the combination effects of TCA and treadmill exercise on learning and memory in a cognitive impairment mouse induced by a combination of d-galactose (d-gal) and aluminum chloride (AlCl₃). We found that exercise and TCA attenuated cognitive impairment in mice with induced MCI. This effect was further increased by costimulation of exercise and TCA. To clarify the mechanisms of the positive effects of TCA and exercise, we analyzed the nuclear factor erythroid 2-related factor (Nrf2) and related signaling pathways. We found that TCA and exercise upregulated Nrf2, NAD(P)H dehydrogenase quinone 1 (NQO-1), heme oxygenase 1 (HO-1), and superoxide dismutase 1 (SOD-1); this suggests that TCA and exercise attenuate cognitive dysfunction by reducing oxidative stress. We also found that Nrf2-related signaling pathways, i.e., the AMP-activated protein kinase (AMPK)/Nrf2 and SIRT1/PGC-1a/Nrf2-ARE pathways, exerted antioxidant effects. Together, these results suggest that costimulation with TCA and exercise may be a therapeutic candidate for mild cognitive impairment.

Amelioration of diabetes-induced cognitive impairment by Transient Receptor Potential Vanilloid 2 (TRPV2) channel inhibitor: Behavioral and mechanistic study

Transient receptor potential (TRP) channels are Ca²⁺ permeable non-selective cation channels which play a pivotal role in diabetes and diabetic complications. Among diabetic complications, diabetes-induced cognitive impairment is a major CNS complication. The role of several TRP channels has been investigated extensively for their diverse Ca²⁺ regulating mechanism, and recently their role has been postulated in the progression of neurodegenerative disorders. However, the role of TRPV2 has not been investigated yet. Therefore, in the present study, the involvement of TRPV2 channels was investigated in diabetes-induced cognitive impairment using TRPV2 inhibitor, tranilast. High glucose exposure in rat C6 glial cells enhances the Ca²⁺-entry through TRPV2 channels. In our in-vivo study, diabetic rats showed increased gene and protein expression of TRPV2 in the hippocampus. Subsequent increase in the acetylcholinesterase activity in the cortex, as well as decrease in the phosphorylation of Ca²⁺/calmodulin-dependent protein kinase II (p-CaMKII-Thr-286), p-GSK-3β (Ser-9), p-CREB (Ser-133) and postsynaptic density protein 95 (PSD-95) in the hippocampus were also observed this led to the impairment in the learning and memory as evident from behavioral parameters such as Morris water maze test, passive avoidance and Y-maze test paradigm. Three-week treatment with tranilast (30 and 100 mg/kg, p.o.) showed improvement in learning and memory associated behaviours (Morris water maze test, passive avoidance, and Y-maze test) by increasing the p-CaMKII (Thr-286), p-GSK-3β (Ser-9), p-CREB (Ser-133) and PSD-95 in the hippocampus. Cortical acetylcholinesterase activity was also reduced by the tranilast. These findings depicted that TRPV2 inhibition may be an effective treatment strategy in diabetes-induced cognitive deficits.

Therapeutic potential of pharmacological agents targeting TRP channels in CNS disorders

Central nervous system (CNS) disorders like Alzheimer's disease (AD), Parkinson disease (PD), stroke, epilepsy, depression, and bipolar disorder have a high impact on both medical and social problems due to the surge in their prevalence. All of these neuronal disorders share some common etiologies including disruption of Ca²⁺ homeostasis and accumulation of misfolded proteins. These misfolded proteins further disrupt the intracellular Ca²⁺ homeostasis by disrupting the activity of several ion channels including transient receptor potential (TRP) channels. TRP channel families include non-selective Ca²⁺ permeable channels, which act as cellular sensors activated by various physio-chemical stimuli, exogenous, and endogenous ligands responsible for maintaining the intracellular Ca²⁺ homeostasis. TRP channels are abundantly expressed in the neuronal cells and disturbance in their activity leads to various neuronal diseases. Under the pathological conditions when the activity of TRP channels is perturbed, there is a disruption of the neuronal homeostasis through increased inflammatory response, generation of reactive oxygen species, and mitochondrial dysfunction. Therefore, there is a potential of pharmacological interventions targeting TRP channels in CNS disorders. This review focuses on the role of TRP channels in neurological diseases; also, we have highlighted the current insights into the pharmacological modulators targeting TRP channels.

History repeats itself: Role of characterizing flavors on nicotine use and abuse

The popularity of e-cigarettes has skyrocketed in recent years, and most vapers use flavored e-cigarette products. Consumption of flavored e-cigarettes exceeds that of combustible cigarettes and other tobacco products among adolescents, who are particularly vulnerable to becoming nicotine dependent. Flavorings have been used by the tobacco industry since the 17th century, but the use of flavors by the e-cigarette industry to create products with "characterizing" flavors (i.e. flavors other than tobacco or menthol) has sparked a public health debate. This review addresses the possibility that characterizing flavors make nicotine more appealing, rewarding and addictive. It also discusses ways in which preclinical and clinical studies could improve our understanding of the mechanisms by which flavors may alter nicotine reward and reinforcement. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

Effects of α-Mangostin Derivatives on the Alzheimer's Disease Model of Rats and Their Mechanism: A Combination of Experimental Study and Computational Systems Pharmacology Analysis

α-Mangostin (α-M) is a natural xanthone from the pericarp of fruit Garcinia mangostana and possesses versatile biological activities. α-M has a therapeutic potential to treat Alzheimer's disease (AD) because of its anti-inflammatory, antioxidative, and neuroprotective activities. However, the use of α-M for AD treatment is limited due to its cytotoxic activities and relatively low potency. Modifications of its chemical structure were needed to reduce its cytotoxicity and improve its therapeutic potential against AD. For this purpose, 16 α-M carbamate derivatives were synthesized. An animal model of AD was established, and the effects of AMG-1 on the spatial learning ability and memory ability were evaluated using behavioral tests. The effect on neuropathology was tested by histopathological evaluation, Nissl staining, and silver staining. Computational systems pharmacology analysis using the chemogenomics knowledgebase was applied for network studies. Compound-target, target-pathway, and target-disease networks were constructed, integrating both in silico analysis and reported experimental data. The results show that AMG-1 can demonstrate its therapeutic effects in a one-molecule, multiple-targets manner to remarkably ameliorate neurological changes and reverse behavioral deficits in AD model rats. The improved cognitive function and alleviated neuronal injury can be observed. The ability of AMG-1 to scavenge β-amyloid in the hippocampus was validated in AD model rats.

TRPV1 Tunes Optic Nerve Axon Excitability in Glaucoma

The transient receptor potential vanilloid member 1 (TRPV1) in the central nervous system may contribute to homeostatic plasticity by regulating intracellular Ca²⁺, which becomes unbalanced in age-related neurodegenerative diseases, including Alzheimer’s and Huntington’s. Glaucomatous optic neuropathy – the world’s leading cause of irreversible blindness – involves progressive degeneration of retinal ganglion cell (RGC) axons in the optic nerve through sensitivity to stress related to intraocular pressure (IOP). In models of glaucoma, genetic deletion of TRPV1 (Trpv1^–/–) accelerates RGC axonopathy in the optic projection, whereas TRPV1 activation modulates RGC membrane polarization. In continuation of these studies, here, we found that Trpv1^–/– increases the compound action potential (CAP) of optic nerves subjected to short-term elevations in IOP. This IOP-induced increase in CAP was not directly due to TRPV1 channels in the optic nerve, because the TRPV1-selective antagonist iodoresiniferatoxin had no effect on the CAP for wild-type optic nerve. Rather, the enhanced CAP in Trpv1^–/– optic nerve was associated with increased expression of the voltage-gated sodium channel subunit 1.6 (NaV1.6) in longer nodes of Ranvier within RGC axons, rendering Trpv1^–/– optic nerve relatively insensitive to NaV1.6 antagonism via 4,9-anhydrotetrodotoxin. These results indicate that with short-term elevations in IOP, Trpv1^–/– increases axon excitability through greater NaV1.6 localization within longer nodes. In neurodegenerative disease, native TRPV1 may tune NaV expression in neurons under stress to match excitability to available metabolic resources.

Shared cerebral metabolic pathology in non-transgenic animal models of Alzheimer's and Parkinson's disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common chronic neurodegenerative disorders, characterized by motoric dysfunction or cognitive decline in the early stage, respectively, but often by both symptoms in the advanced stage. Among underlying molecular pathologies that PD and AD patients have in common, more attention is recently paid to the central metabolic dysfunction presented as insulin resistant brain state (IRBS) and altered cerebral glucose metabolism, both also explored in animal models of these diseases. This review aims to compare IRBS and alterations in cerebral glucose metabolism in representative non-transgenic animal PD and AD models. The comparison is based on the selectivity of the neurotoxins which cause experimental PD and AD, towards the cellular membrane and intracellular molecular targets as well as towards the selective neurons/non-neuronal cells, and the particular brain regions. Mitochondrial damage and co-expression of insulin receptors, glucose transporter-2 and dopamine transporter on the membrane of particular neurons as well as astrocytes seem to be the key points which are further discussed in a context of alterations in insulin signalling in the brain and its interaction with dopaminergic transmission, particularly regarding the time frame of the experimental AD/PD pathology appearance and the correlation with cognitive and motor symptoms. Such a perspective provides evidence on IRBS being a common underlying metabolic pathology and a contributor to neurodegenerative processes in representative non-transgenic animal PD and AD models, instead of being a direct cause of a particular neurodegenerative disorder.

Palmitoylethanolamide (PEA) as a Potential Therapeutic Agent in Alzheimer's Disease

N-Palmitoylethanolamide (PEA) is a non-endocannabinoid lipid mediator belonging to the class of the N-acylethanolamine phospolipids and was firstly isolated from soy lecithin, egg yolk, and peanut meal. Either preclinical or clinical studies indicate that PEA is potentially useful in a wide range of therapeutic areas, including eczema, pain, and neurodegeneration. PEA-containing products are already licensed for use in humans as a nutraceutical, a food supplement, or a food for medical purposes, depending on the country. PEA is especially used in humans for its analgesic and anti-inflammatory properties and has demonstrated high safety and tolerability. Several preclinical in vitro and in vivo studies have proven that PEA can induce its biological effects by acting on several molecular targets in both central and peripheral nervous systems. These multiple mechanisms of action clearly differentiate PEA from classic anti-inflammatory drugs and are attributed to the compound that has quite unique anti(neuro)inflammatory properties. According to this view, preclinical studies indicate that PEA, especially in micronized or ultramicronized forms (i.e., formulations that maximize PEA bioavailability and efficacy), could be a potential therapeutic agent for the effective treatment of different pathologies characterized by neurodegeneration, (neuro)inflammation, and pain. In particular, the potential neuroprotective effects of PEA have been demonstrated in several experimental models of Alzheimer's disease. Interestingly, a single-photon emission computed tomography (SPECT) case study reported that a mild cognitive impairment (MCI) patient, treated for 9 months with ultramicronized-PEA/luteolin, presented an improvement of cognitive performances. In the present review, we summarized the current preclinical and clinical evidence of PEA as a possible therapeutic agent in Alzheimer's disease. The possible PEA neuroprotective mechanism(s) of action is also described.

Capsaicin Attenuates Amyloid-β-Induced Synapse Loss and Cognitive Impairments in Mice

Alzheimer's disease (AD) is the most common cause of progressive cognitive impairment in the aged. The aggregation of the amyloid β-protein (Aβ) is a hallmark of AD and is linked to synapse loss and cognitive impairment. Capsaicin, a specific agonist of the transient receptor potential vanilloid 1 (TRPV1), has been proven to ameliorate stress-induced AD-like pathological and cognitive impairments, but it is unclear whether TRPV1 activation can affect cognitive and synaptic functions in Aβ-induced mouse model of AD. In this study, we investigated the effects of TRPV1 activation on spatial memory and synaptic plasticity in mice treated with Aβ. To induce AD-like pathological and cognitive impairments, adult C57Bl/6 mice were microinjected with Aβ42 (100 μM, 2.5 μl/mouse, i.c.v.). Two weeks after Aβ42 microinjection, spatial learning and memory as well as hippocampal long-term potentiation (LTP) were examined. The results showed that Aβ42 microinjection significantly impaired spatial learning and memory in the Morris water maze and novel object recognition tests compared with controls. These behavioral changes were accompanied by synapse loss and impaired LTP in the CA1 area of hippocampus. More importantly, daily capsaicin (1 mg/kg, i.p.) treatment throughout the experiment dramatically improved spatial learning and memory and synaptic function, as reflected by enhanced hippocampal LTP and reduced synapse loss, whereas the TRPV1 antagonist capsazepine (1 mg/kg, i.p.) treatment had no effects on cognitive and synaptic function in Aβ42-treated mice. These results indicate that TRPV1 activation by capsaicin rescues cognitive deficit in the Aβ42-induced mouse model of AD both structurely and functionally.