UHPLC-MS/MS combined with microdialysis for simultaneous determination of nicotine and neurotransmitter metabolites in the rat hippocampal brain region: application to pharmacokinetic and pharmacodynamic study

Nicotine crosses the blood-brain barrier and interacts with nicotinic acetylcholine receptors, initiating a cascade of neurotransmitter effects with potential therapeutic implications for neurodegenerative conditions such as Alzheimer's and Parkinson's disease. The hippocampus, pivotal for cognitive processes, plays a crucial role in nicotine-mediated cognitive enhancement due to its abundant expression of nicotinic acetylcholine receptors, particularly the α7 subtype, which is heavily implicated in hippocampus-related behavioral functions and dysfunctions. However, the intricate process of nicotine metabolism within the hippocampus remains poorly understood, impeding our comprehension of how nicotine and its metabolites modulate neurotransmitter dynamics. To address this gap, we have developed and validated a novel methodology combining microdialysis with UHPLC-MS/MS, enabling simultaneous detection of 12 neurotransmitters, nicotine, and its seven metabolites within the rat hippocampus. The linearity range of the targeted compounds is satisfactory (R2 > 0.9970), with intra-day and inter-day precision not exceeding 12.7%, and accuracy ranging from -12.4% to 13.7%. Our findings reveal differential pharmacokinetics of nicotine and its metabolites in the α7KO group compared to the control group, characterized by heightened nicotine absorption and slower elimination and distribution in the former. Notably, the pharmacokinetic parameters of cotinine exhibit similarity across both groups. Studies investigating the impact of nicotine on monoamine neurotransmitters have elucidated its capacity to augment the release of dopamine, serotonin, norepinephrine, glutamate, and acetylcholine in the rat hippocampus. This integrated approach facilitates a comprehensive analysis of neurotransmitter alterations within the hippocampal region following nicotine administration, thereby providing robust technical support and scientific rationale for understanding the neurochemical effects of nicotine and its metabolites. Further exploration into the pharmacokinetics and pharmacodynamics of nicotine holds promise for uncovering novel therapeutic avenues in the management of neurodegenerative diseases such as Alzheimer's.

Study on multi-target effects of the novel HDAC6 inhibitor W5 on Aβ/Cu2+-induced Alzheimer's disease model of rats

Histone deacetylase 6 (HDAC6) is a key therapeutic target in neurodegenerative diseases such as Alzheimer's disease (AD), which has been demonstrated to play an essential role in memory function and microtubule-associated tau physiology. In this study, W5 was used to treat AD model rats induced by Aβ/Cu2+ to study the improving effect of W5 on learning and memory impairment in AD rats and its related mechanism, to provide the basis for the subsequent development of W5 as an anti-AD drug. Results showed that W5 could decrease the expression of Aβ, Tau, and p-Tau proteins in the hippocampus of AD rats to inhibit the formation of senile plaques and neurofibrillary tangles, down-regulate the expression of Bax mRNA and Caspase-3 mRNA, and up-regulate the expression of Bcl-2 mRNA to reduce the apoptosis of neuron cells, reverse the expression of TNF-α, IL-1β and IL-6 mRNA to regulate neuroinflammatory response in AD rat brain. W5 also could regulate the oxidative stress state of AD rats, and balance the neurotransmitter disorder in AD rats' brain tissue. Overall, W5 could recover the morphology of hippocampal neurons and improve the learning and memory dysfunction in AD rats by regulating multiple targets in AD rats, providing a promising therapeutic avenue for the treatment of AD.

The underlying roles and neurobiological mechanisms of music-based intervention in Alzheimer's disease: A comprehensive review

Non-pharmacological therapy has gained popularity in the intervention of Alzheimer's disease (AD) due to its apparent therapeutic effectiveness and the limitation of biological drug. A wealth of research indicates that music interventions can enhance cognition, mood and behavior in individuals with AD. Nonetheless, the underlying mechanisms behind these improvements have yet to be fully and systematically delineated. This review aims to holistically review how music-based intervention (MBI) ameliorates abnormal emotion, cognition decline, and behavioral changes in AD patients. We cover several key dimensions: the regulation of MBIs on cerebral blood flow (CBF), their impact on neurotransmission (including GABAergic and monoaminergic transmissions), modulation of synaptic plasticity, and hormonal release. Additionally, we summarize the clinical applications and limitations of active music-based intervention (AMBI), passive music-based intervention (PMBI), and hybrid music-based intervention (HMBI). This thorough analysis enhances our understanding of the role of MBI in AD and supports the development of non-pharmacological therapeutic strategies.

Barbaloin's Chemical Intervention in Aluminum Chloride Induced Cognitive Deficits and Changes in Rats through Modulation of Oxidative Stress, Cytokines, and BDNF Expression

Alzheimer's disease (AD) is a long-term neurodegenerative condition characterized by impaired cognitive functions, particularly in the domains of learning and memory. Finding promising options for AD can be successful with a medication repurposing strategy. The goal of the research was to examine the neuroprotective characteristics of barbaloin in aluminum chloride (AlCl3)-induced cognitive deficits and changes in rats through modulation of oxidative stress, cytokines, and brain-derived neurotrophic factor (BDNF) expression. Thirty male Wistar rats were subjected to AlCl3 at a dosage of 100 mg/kg via the per oral route (p.o.), which induced cognitive decline. Morris water maze (MWM) is used to assess behavioral metrics. Assays for catalase (CAT), malondialdehyde (MDA), reduced glutathione (GSH), acetylcholinesterase (AChE), choline-acetyltransferase (ChAT), interleukins-1β (IL-1β), superoxide dismutase (SOD), tumor necrosis factor-α (TNF-α), nuclear factor kappa-B (NF-κB), interleukins-6 (IL-6), BDNF, and neurotransmitter levels [dopamine (DA), acetylcholine (Ach), and γ-aminobutyric acid (GABA)] were performed. Results: The transfer latency time was notably decreased, and substantial modifications in the concentrations of GSH, MDA, CAT, SOD, AChE, ChAT and observed modulations in the formation of interleukins-6 (IL-6), TNF-α, IL-1β, BDNF, and NF-κB were also evidenced after the treatment of rats with barbaloin in comparison to AlCl3-induced control groups. Significant alterations in neurotransmitter levels (DA, Ach, and GABA) were also seen in barbaloin-treated groups in comparison to AlCl3-induced groups. The current investigation has provided evidence that the administration of barbaloin yielded notable enhancements in cognitive function in rats through the inhibition of MDA, enhancing endogenous antioxidant enzymes, reduction of cytokine levels, and enhancement of neurotransmitter contents in the brain. These effects were observed in comparison to a control group treated with AlCl3 and can be attributable to barbaloin's strong anti-inflammatory and antioxidant properties, and metal chelating properties may contribute to its neuroprotective effects. Barbaloin may also promote neuronal survival and enhance learning and memory by upregulating the expression of BDNF.

Neurotransmitters in Prevention and Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is the most frequent cause of cognitive impairment in middle-aged and older populations. There is a lack of drugs that demonstrate significant efficacy in AD, so the study of the pathogenesis of AD is of great importance. More efficacious interventions are needed, as reflected by our population's fast aging. Synaptic plasticity is the capacity of neurons to adjust their connections, and it is strongly tied to learning and memory, cognitive function, and brain injury recovery. Changes in synaptic strength, such as long-term potentiation (LTP) or inhibition (LTD), are thought to represent the biological foundation of the early stages of learning and memory. The results of numerous studies confirm that neurotransmitters and their receptors play an important role in the regulation of synaptic plasticity. However, so far, there is no definite correlation between the function of neurotransmitters in aberrant neural oscillation and AD-related cognitive impairment. We summarized the AD process to understand the impact of neurotransmitters in the progression and pathogenesis of AD, including the current status of neurotransmitter target drugs, and the latest evidence of neurotransmitters' function and changes in the AD process.

The cognitive dysfunction of claustrum on Alzheimer's disease: A mini-review

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases characterized by cognitive deficits and dementia. AD entails predominant pathological characteristics including amyloid beta (Aβ) plaque formation, neurofibrillary entanglements, and brain atrophy, which gradually result in cognitive dysfunctions. Studies showed that these pathological changes are found in a myriad of brain structures, including the claustrum (CLA), a nucleus that penetrates deeply into the brain and is extensively interconnected to various brain structures. The CLA modulates many aspects of cognitive functions, with attention, executive function, visuospatial ability, language, and memory in particular. It is also implicated in multiple neuropsychiatric disorders, of which one worthy of particular attention is AD-related cognitive impairments. To inspire novel AD treatment strategies, this review has summarized the CLA functionality in discriminative cognitive dysfunctions in AD. And then propose an array of potential mechanisms that might contribute to the cognitive impairments caused by an abnormal CLA physiology. We advocate that the CLA might be a new promising therapeutic target in combination with existing anti-AD drugs and brain stimulation approaches for future AD treatment.

Mahanimbine Improved Aging-Related Memory Deficits in Mice through Enhanced Cholinergic Transmission and Suppressed Oxidative Stress, Amyloid Levels, and Neuroinflammation

Murraya koenigii leaves contain mahanimbine, a carbazole alkaloid, reported with improving cholinergic neuronal transmission and reducing neuroinflammation in the CNS. The current research investigated the effects of mahanimbine on age-related memory deficits, oxidative stress, cholinergic dysfunction, amyloid formation, and neuroinflammation in aged mice (16 months old). Mahanimbine was administered (1 and 2 mg/kg, p.o.) daily to groups of aged mice for 30 days. The Morris water maze (MWM) task was performed to study spatial learning (escape latency (EL) and swimming distance (SD)) and memory (probe test). The levels of malondialdehyde (MDA), glutathione (GSH), acetylcholine (ACh), acetylcholinesterase (AChE), β-amyloid (Aβ1-40 and Aβ1-42), β-secretase (BACE-1), as well as neuroinflammation markers (total cyclooxygenase (COX) and COX-2 expression), were measured from the isolated brain. Mahanimbine reduced the EL time and SD in the MWM test. From the probe trial, the mahanimbine-treated group spent more time in the targeted quadrant related to the age-matched control, which indicated the enhancement of memory retention. From the biochemical tests, the treatment decreased MDA, AChE, Aβ1-40, and Aβ1-42, BACE-1, total COX activity, and COX-2 expression. It also raised the brain GSH and ACh levels in aged mice compared to age-matched control. These results have supported the reversal of memory dysfunctions by mahanimbine in aged mice and hypothesized that it could be a potential target to treat age-related neurodegenerative disease.

Ameliorative effect of myrcene in mouse model of Alzheimer's disease

Myrcene (Myr) has been reported to show neuroprotective effects in cerebral ischemia. In this research work, we investigated the Myr effect on neurobehavioural, and neuropathological alteration in mice induced by Aluminium trichloride (AlCl3) and D - galactose. The administration of AlCl3 (5 mg/kg; p. o.), and D - galactose (60 mg/kg; i. p.) for 90 days in mice resulted in spatial learning and memory deficits, cognitive decline, as well as neurotoxicity. The treatments with Myr low dose (100 mg/kg), Myr high dose (200 mg/kg), donepezil (2 mg/kg), and Myr low dose + donepezil (100 + 2 mg/kg) were administered via intraperitoneal route for 30 days significantly reversed the neurobehavioral, and neuropathological effects of AlCl3 and D - galactose in mice. The results of behavioural tests such as Morris water maze, elevated plus maze, and locomotor; biochemical analysis such as malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), nitrite, and acetylcholinesterase (AChE); and ELISA tests such as mouse β - secretase (BACE), amyloid-beta peptide1-42 (Aβ1 - 42), tumor necrosis factor - α (TNF-α), interleukin - 6 (IL-6), and brain-derived neurotrophic factor (BDNF) demonstrated a significant (p < 0.05) neuroprotective effect of the Myr and donepezil co-treatments. In addition, hematoxylin and eosin staining of the cerebral cortex and hippocampus revealed eosinophilic lesions and hyperchromatic nuclei in Alzheimer's disease mice, but treatments with Myr low dose, Myr high dose, donepezil, and Myr low dose + donepezil reversed these neurodegenerative effects. Myr showed these activities by enhancing synaptic plasticity and cholinergic activity, as well as reducing oxidative damage, neuroinflammation, Aβ1-42 aggregations, and histopathological damage. Myr alone and in combination with donepezil may serve as a potential candidate for the treatment of Alzheimer's disease.

Influence of PICALM and CLU risk variants on beta EEG activity in Alzheimer's disease patients

PICALM and CLU genes have been linked to alterations in brain biochemical processes that may have an impact on Alzheimer’s disease (AD) development and neurophysiological dynamics. The aim of this study is to analyze the relationship between the electroencephalographic (EEG) activity and the PICALM and CLU alleles described as conferring risk or protective effects on AD patients and healthy controls. For this purpose, EEG activity was acquired from: 18 AD patients and 12 controls carrying risk alleles of both PICALM and CLU genes, and 35 AD patients and 12 controls carrying both protective alleles. Relative power (RP) in the conventional EEG frequency bands (delta, theta, alpha, beta, and gamma) was computed to quantify the brain activity at source level. In addition, spatial entropy (SE) was calculated in each band to characterize the regional distribution of the RP values throughout the brain. Statistically significant differences in global RP and SE at beta band (p-values < 0.05, Mann–Whitney U-test) were found between genotypes in the AD group. Furthermore, RP showed statistically significant differences in 58 cortical regions out of the 68 analyzed in AD. No statistically significant differences were found in the control group at any frequency band. Our results suggest that PICALM and CLU AD-inducing genotypes are involved in physiological processes related to disruption in beta power, which may be associated with physiological disturbances such as alterations in beta-amyloid and neurotransmitter metabolism.

Personalized brain models identify neurotransmitter receptor changes in Alzheimer's disease

Alzheimer's disease (AD) involves many neurobiological alterations from molecular to macroscopic spatial scales, but we currently lack integrative, mechanistic brain models characterizing how factors across different biological scales interact to cause clinical deterioration in a way that is subject-specific or personalized. Neurotransmitter receptors, as important signaling molecules and potential drug targets, are key mediators of interactions between many neurobiological processes altered in AD. We present a neurotransmitter receptor-enriched multifactorial brain model, which integrates spatial distribution patterns of 15 neurotransmitter receptors from post-mortem autoradiography with multiple in-vivo neuroimaging modalities (tau, amyloid-β and glucose PET, and structural, functional and arterial spin labeling MRI) in a personalized, generative, whole-brain formulation. Applying this data-driven model to a heterogeneous aged population (N = 423, ADNI data), we observed that personalized receptor-neuroimaging interactions explained about 70% (± 20%) of the across-population variance in longitudinal changes to the six neuroimaging modalities, and up to 39.7% (P < 0.003, FWE-corrected) of inter-individual variability in AD cognitive deterioration via an axis primarily affecting executive function. Notably, based on their contribution to the clinical severity in AD, we found significant functional alterations to glutamatergic interactions affecting tau accumulation and neural activity dysfunction, and GABAergic interactions concurrently affecting neural activity dysfunction, amyloid and tau distributions, as well as significant cholinergic receptor effects on tau accumulation. Overall, GABAergic alterations had the largest effect on cognitive impairment (particularly executive function) in our AD cohort (N = 25). Furthermore, we demonstrate the clinical applicability of this approach by characterizing subjects based on individualized 'fingerprints' of receptor alterations. This study introduces the first robust, data-driven framework for integrating several neurotransmitter receptors, multi-modal neuroimaging and clinical data in a flexible and interpretable brain model. It enables further understanding of the mechanistic neuropathological basis of neurodegenerative progression and heterogeneity, and constitutes a promising step towards implementing personalized, neurotransmitter-based treatments.

An integrated strategy using LC-MS/MS combined with in vivo microdialysis for the simultaneous determination of lignans of Schisandra chinensis (Turcz.) Baill. Fructus and endogenous neurotransmitters: application in pharmacokinetic and pharmacodynamic studies

Schisandra chinensis (Turcz.) Baill Fructus (SCF) is the ripe fruit of Schisandra chinensis (Turcz.) Baill, and is often used as a neuroprotective drink. Modern pharmacological studies have shown that lignans are the main bioactive components responsible for neuroprotection and have potential in the treatment of Alzheimer's disease (AD). However, the mechanism of action of SCF in the treatment of AD from the pharmacokinetics-pharmacodynamics (PK-PD) perspective remains not well established. The purpose of this study is to investigate and compare the pharmacokinetic differences of lignans in normal and AD rats, as well as to investigate their effects on neurotransmitters and their role in the treatment of AD. To achieve this goal, an integrated strategy using LC-MS/MS combined with in vivo microdialysis for the simultaneous determination of lignans of SCF and endogenous neurotransmitters has been developed and validated. The results show that the pharmacokinetic behaviors of ten lignans in the AD group were significantly different from those in the normal group. The AD group had better absorption and slower elimination than the normal group. In addition, the pharmacodynamic results of the Morris water maze (MWM) test, biochemical tests, histopathological examination, as well as immunohistochemistry analysis showed that lignans could improve the learning and memory of AD rats. The oral administration of SCF could restore the levels of the neurotransmitter parameters; seven neurotransmitters showed clockwise or counterclockwise changes with the four lignans in the hippocampal region. Taken together, the PK and PD studies based on in vivo microdialysis sampling might offer novel insights into the mechanisms of action of SCF against AD.

Ginsenoside Rg3 Prevents Cognitive Impairment by Improving Mitochondrial Dysfunction in the Rat Model of Alzheimer's Disease

Ginseng, the roots and rhizomes of Panax ginseng C. A. Meyer, is used not only as a herbal medicine but also as a functional food to support body functions. Ginsenoside Rg3 (GRg3) is a major bioactive component in ginseng. In this study, the beneficial effects of GRg3 on rats with Alzheimer's disease (AD) were evaluated via the behavioral experiment and antioxidant capacity. Moreover, metabolomic analysis based on UPLC-QTOF-MS/MS and apoptosis analysis was used to obtain the change between AD and GRg3-administrated rats to assess the underlying mechanisms on improving mitochondrial dysfunction. Results showed that GRg3 could prevent the cognitive impairment of AD rats by improving the mitochondrial dysfunction. The potential mechanisms were related to regulate the abnormality of energy metabolism, electron transport chain, amino acid metabolism, purine metabolism, and antiapoptosis. These findings support the exploitation of GRg3 as an effective complementary and functional food to prevent and delay AD.

Computational modeling and biomarker studies of pharmacological treatment of Alzheimer's disease (Review)

Alzheimer's disease (AD) is a complex and multifactorial disease. In order to understand the genetic influence in the progression of AD, and to identify novel pharmaceutical agents and their associated targets, the present study discusses computational modeling and biomarker evaluation approaches. Based on mechanistic signaling pathway approaches, various computational models, including biochemical and morphological models, are discussed to explore the strategies that may be used to target AD treatment. Different biomarkers are interpreted on the basis of morphological and functional features of amyloid β plaques and unstable microtubule‑associated tau protein, which is involved in neurodegeneration. Furthermore, imaging and cerebrospinal fluids are also considered to be key methods in the identification of novel markers for AD. In conclusion, the present study reviews various biochemical and morphological computational models and biomarkers to interpret novel targets and agonists for the treatment of AD. This review also highlights several therapeutic targets and their associated signaling pathways in AD, which may have potential to be used in the development of novel pharmacological agents for the treatment of patients with AD. Computational modeling approaches may aid the quest for the development of AD treatments with enhanced therapeutic efficacy and reduced toxicity.

Schisandrin ameliorates cognitive impairment and attenuates Aβ deposition in APP/PS1 transgenic mice: involvement of adjusting neurotransmitters and their metabolite changes in the brain

Neurotransmitters (NTs) in the brain are involved in neurodegenerative diseases, such as Alzheimer's disease (AD). Schisandrin is a major ingredient of Schisandra chinensis (Turcz.) Baill and has been used for the treatment of AD. In this study we examined the therapeutic effects of schisandrin in APP/PS1 transgenic mice, and correlated the beneficial effects on cognitive impairment with the adjustments in NTs and their metabolites in the mouse brains. APP/PS1 mice were treated with schisandrin (2 mg·kg-1·d-1, ip) for 2 weeks. In Morris Water Maze test; untreated APP/PS1 mice displayed significant cognitive impairment compared with normal mice; schisandrin administration ameliorated the cognitive impairment and significantly decreased Aβ deposition in the hippocampus. In order to assess the effects of schisandrin on NTs and their metabolites, we developed a rapid and sensitive UPLC-MS/MS method for simultaneous determination of serotonin, 5-hydroxyindole acetic acid, dopamine, norepinephrine, γ-aminobutyric acid, glutamic acid, homovanillic acid, 3,4-dihydroxyphenylacetic acid and acetylcholine in mouse brains. This method conformed to methodology validation requirements. We found that there were statistically significant differences in these NTs and their metabolites between untreated APP/PS1 mice and normal mice, whereas schisandrin administration restored the abnormal NTs and their metabolites levels. These results suggest that schisandrin could alter the levels of these NTs and their metabolites in the brain, thus ameliorating learning and memory impairments in APP/PS1 mice.

Ginsenosides attenuate d-galactose- and AlCl3-inducedspatial memory impairment by restoring the dysfunction of the neurotransmitter systems in the rat model of Alzheimer's disease

ETHNOPHARMACOLOGICAL RELEVANCE

Panax ginseng C.A.Mey. is a traditional Chinese herbal medicine, which has been used to treat Alzheimer's disease (AD) for thousands of years. Ginsenoside is one of the major compounds found in P. ginseng. This study aimed to explore the attenuation of spatial memory impairment by ginsenosides and its correlation with restoring the dysfunction of the neurotransmitter systems in AD model rats to understand the mechanism underlying the anti-AD effect of P. ginseng.

MATERIALS AND METHODS

In this study, the AD model was established by combining d-galactose (d-gal) with AlCl₃ (Al) for 60 days. From day 30, the ginsenosides group was intragastrically administered with ginsenosides for 30 days. The ethology of rats was tested through the Morris water maze test(MWM). Histopathological changes in the hippocampus of rats were observed through hematoxylin and eosin staining. The expressions of amyloid β peptide (Aβ) and phospho-tau (p-tau) in the hippocampus and cortex of rats were detected by immunohistochemistry. A liquid chromatography-mass spectrometry assay was used to measure neurotransmitter concentrations in the hippocampus, cortex, and blood.

RESULTS

Ginsenosides could significantly decrease the escape latency time and the average latency time in the place navigation test and increase the times of crossing the platform area, the percentage of residence time, and the distance in the original platform quadrant in the spatial probe test. Ginsenosides could repair the damage of the hippocampus and reduce the expressions of Aβ and p-tau. Ginsenosides could also increase γ-aminobutyric acid, acetylcholine, and dopamine levels and decrease glutamate and aspartic acid levels in the hippocampus and cortex and increase glycine and serotonin levels in the blood.

CONCLUSIONS

After effectively administrated, ginsenosides attenuate d-gal- and Al-induced spatial memory impairment. The possible mechanism of the beneficial effect is restoring the dysfunction of various neurotransmitters.

Quantitative-profiling of neurotransmitter abnormalities in the disease progression of experimental diabetic encephalopathy rat

Diabetic encephalopathy (DE) is one of the most prevalent chronic complications of diabetes mellitus (DM), with neither effective prevention nor proven therapeutic regimen. This study aims to uncover the potential dysregulation pattern of the neurotransmitters in a rat model of streptozotocin (STZ)-induced experimental DE. For that purpose, male Sprague–Dawley (SD) rats were treated with a single intraperitoneal injection of STZ. Cognitive performance was detected with the Morris water maze (MWM) test. Serum, cerebrospinal fluid (CSF), and brain tissues were collected to measure the levels of neurotransmitters. Compared with the control rats, the acetylcholine (ACh) levels in serum, CSF, hippocampus, and cortex were all significantly down-regulated as early as 6 weeks in the STZ treatment group. In contrast, the glutamate (Glu) levels were decreased in CSF and the hippocampus, but unaffected in the serum and cortex of STZ-treated rats. As for γ-aminobutyric acid (GABA), it was down-regulated in serum, but up-regulated in CSF, hippocampus, and the cortex in the STZ-treated group. The mRNA expressions of neurotransmitter-related rate limiting enzymes (including AChE, GAD1, and GAD2) and pro-inflammatory cytokines (including IL-1β and TNF-α) were all increased in the DE rats. Our data suggest that DM induces isoform-dependent and tissue-specific neurotransmitter abnormalities, and that neuroinflammation may underlay the nervous system dysfunction observed in the progression of DE.