Effect of anti-dementia drugs on LPS induced neuroinflammation in mice

Sea Cucumber Hydrolysates Alleviate Cognitive Deficits in D-Galactose-Induced C57BL/6J Aging Mice Associated with Modulation of Gut Microbiota

As the global elderly population is rising, concerns about cognitive decline and memory loss are becoming urgent. This study evaluated the potential of sea cucumber hydrolysates (SCH) from Stichopus japonicus in alleviating cognitive deficits using a D-galactose-induced murine aging model. The effects of SCH on behavior, hippocampal morphology, gut microbiota, hippocampal cholinergic system, brain-derived neurotrophic factor (BDNF) signaling, and neuroinflammatory pathways were investigated. Results showed that SCH ameliorated learning and memory deficits and reduced neuronal damage in aging mice. SCH also modulated gut microbiota, along with increased fecal short-chain fatty acids levels. Functional prediction revealed that alterations in gut microbiota were related to signal transduction. Further, SCH enhanced hippocampal cholinergic function through elevating acetylcholine (ACh) levels and inhibiting acetylcholinesterase (AChE) activity and activated BDNF signaling, consistent with predictions of gut microbiota function. Restoration of cholinergic homeostasis and transmission of the BDNF pathway might contribute to the inhibition of hippocampal neuroinflammation via suppressing microglial activation and the nuclear factor kappa-B (NF-κB) pathway. In summary, SCH attenuated cognitive deficits through suppressing neuroinflammation, which might be correlated with the signal transduction caused by regulating gut microbiota. Further validation will be conducted through microbiota depletion and fecal microbiota transplantation. These findings suggest that SCH is a promising functional component for counteracting aging-related cognitive deficits.

The Role of Inflammation in Neurodegenerative Diseases: Parkinson's Disease, Alzheimer's Disease, and Multiple Sclerosis

Neurodegenerative diseases are a group of conditions that have in common the progressive damage and degeneration of neurons in the central nervous system. This group includes Parkinson's disease, Alzheimer's disease, and multiple sclerosis, among others. In recent years, increasing evidence has pointed to the important role of inflammation in the pathogenesis of these conditions. The occurrence of inflammation in the brain, which is often triggered by pro-inflammatory activation of microglia or astrocytes, can consequently lead to a chronic inflammatory response that contributes to the development of neurodegenerative processes. Inflammatory processes themselves, both within the nervous system and throughout the human body, appear to be central to the initiation and progression of neuronal damage. Understanding the role of inflammation in these diseases may open up new perspectives and opportunities in the future in the development of effective therapies to improve patients' quality of life as the vast majority of cases of patients affected by neurodegenerative diseases continue to be treated symptomatically since causal treatments are lacking. In this review, we provide information on the impact of inflammation on the pathogenesis, course, and potential therapeutic options for selected neurodegenerative diseases. In addition, this article provides a general description of neuroinflammation and the involvement and role of specific cells in the central nervous system.

"Lipopolysaccharide-induced animal models for neuroinflammation - An overview."

Neuroinflammation is a pathological mechanism contributing to neurodegenerative diseases. For in-depth studies of neuroinflammation, several animal models reported reproducing behavioral dysfunctions and cellular pathological mechanisms induced by brain inflammation. One of the most popular models of neuroinflammation is the one generated by lipopolysaccharide exposure. Despite its importance, the reported results using this model show high heterogeneity, making it difficult to analyze and compare the outcomes between studies. Therefore, the current review aims to summarize the different experimental paradigms used to reproduce neuroinflammation by lipopolysaccharide exposure and its respective outcomes, helping to choose the model that better suits each specific research aim.

Evaluation of Lentilactobacillus parafarraginis A6-2 strain for aluminum removal and anti-inflammatory effects: implications for alleviating Al toxicity

AIM

To assess the effectiveness of Lentilactobacillus parafarraginis A6-2 cell lysate for the removal of aluminum (Al), which induces neurotoxicity, and its protective effect at cellular level.

METHODS AND RESULTS

The cell lysate of the selected L. parafarraginis A6-2 strain demonstrated superior Al removal compared to live or dead cells. The Al removal efficiency of L. parafarraginis A6-2 cell lysate increased with decreasing pH and increasing temperature, primarily through adsorption onto peptidoglycan. Neurotoxicity mitigation potential of L. parafarraginis A6-2 was evaluated using C6 glioma cells. C6 cells exposed with increasing concentration of Al led to elevated toxicity and inflammation, which were gradually alleviated upon treatment with L. parafarraginis A6-2. Moreover, Al-induced oxidative stress in C6 cells showed a concentration-dependent reduction upon treatment with L. parafarraginis A6-2.

CONCLUSIONS

This study demonstrated that L. parafarraginis A6-2 strain, particularly in its lysate form, exhibited enhanced capability for Al removal. Furthermore, it effectively mitigated Al-induced toxicity, inflammation, and oxidative stress.

Impact of levetiracetam on cognitive impairment, neuroinflammation, oxidative stress, and neuronal apoptosis caused by lipopolysaccharides in rats

Introduction

Neuroinflammation is associated with the elevation of toxic proinflammatory mediators that promote neurodegeneration and subsequently affect cognition. Causes of inflammation in the neuronal cells are believed to initiate various neurodegenerative disorders, mainly Alzheimer's disease. Levetiracetam is a second-generation antiepileptic drug. There is evidence supporting the memory-enhancing effect of levetiracetam from numerous experimental and clinical studies. Therefore, this research focused on finding its protective effects against lipopolysaccharides prompted cognitive impairment and exploring possible mechanisms underlining their neuroprotection.

Methodology

Two doses (100 or 200 mg/kg) of levetiracetam were administrated orally for 30 days. Additionally, four doses (250 µg/kg) of lipopolysaccharide were injected peripherally to induce neurotoxicity. Behavioral tests were carried out using various maze models. At the end of the tests, brain tissues were collected for biochemical evaluations. Cholinergic, neuroinflammatory, apoptosis, and oxidative-related parameters were analyzed in the brain homogenate to explore the possible mechanisms of action of levetiracetam.

Results

In lipopolysaccharide-induced rats, levetiracetam indicated a reduction (p < 0.01) in transfer latency using the elevated plus-maze. An improvement (p < 0.01) in novel and familiar objects exploration time using novel object recognition test. A rise (p < 0.05) in novel arm entries and extended time spent in the novel arm using the Y-maze test. In extension, the levels of acetylcholine (p < 0.001), anti-inflammatory factors (transforming growth factor-β1; p < 0.01 and interleukin-10; p < 0.05), and an antioxidant (catalase; p < 0.01) were elevated in lipopolysaccharide-induced rats after the administration of levetiracetam. In contrast, inflammatory factors (cyclooxygenase-2; p < 0.05, nuclear factor kappa B; p < 0.05, tumor necrosis factor-α; p < 0.01, and interleukin-6 (p < 0.01), apoptosis inducers (BCL2-associated X protein; p < 0.05 and Caspase-3 (p < 0.001), and oxidative stress (malondialdehyde; p < 0.05) were considerably reduced with levetiracetam in lipopolysaccharide-induced rats.

Conclusion

The collective results suggested that levetiracetam may be able to treat neuroinflammatory-related memory loss by enhancing cholinergic activity while reducing neuroinflammation, cellular apoptosis, and oxidative stress.

Blood MAPT expression and methylation status in Alzheimer's disease

Aim

This study aimed to investigate the expression levels and methylation status of microtubule-associated protein tau (MAPT) in the blood of Alzheimer's disease (AD) patients and age- and sex-matched healthy controls.

Methods

Fifty AD outpatients and 50 healthy contorls were enrolled. Blood samples were collected for processing of complementary DNA and genomic DNA. MAPT messenger ribonucleic acid (mRNA) expression was analyzed by real-time quantitative polymerase chain reaction. The methylation rates of four cytosine-phosphate-guanine (CpG) sites in the upstream region of MAPT exon1 were evaluated by the pyrosequencing method.

Results

No significant differences in MAPT mRNA expression levels were found between AD and control subjects (AD 0.97 ± 0.49 vs. control 1.0 ± 0.64, p = 0.62). MAPT mRNA expression levels were not correlated with any other clinical characteristics or results of psychological tests. MAPT mRNA expression levels were significantly higher in AD subjects treated with acetylcholinesterase inhibitors (AchEIs) (n = 25) than in subjects not treated with AChEIs (n = 25) (unmedicated 0.83 ± 0.33 vs. medicated 1.12 ± 0.59, p = 0.049). The AD subjects did not differ from the control subjects in methylation rates at selected CpG sites. MAPT methylation status were not correlated with clinical characteristics, the results of psychological tests, or MAPT mRNA expression.

Conclusion

MAPT mRNA expression levels and methylation status in blood do not appear useful as biomarkers for AD or the examined CpG sites were not genetically significant for MAPT gene expression or AD pathology. However, AChEIs may alter MAPT mRNA expression. Further studies are needed to explore blood biomarkers that can discriminate AD patients from controls.

Lipopolysaccharide-Induced Model of Neuroinflammation: Mechanisms of Action, Research Application and Future Directions for Its Use

Despite advances in antimicrobial and anti-inflammatory therapies, inflammation and its consequences still remain a significant problem in medicine. Acute inflammatory responses are responsible for directly life-threating conditions such as septic shock; on the other hand, chronic inflammation can cause degeneration of body tissues leading to severe impairment of their function. Neuroinflammation is defined as an inflammatory response in the central nervous system involving microglia, astrocytes, and cytokines including chemokines. It is considered an important cause of neurodegerative diseases, such as Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Lipopolysaccharide (LPS) is a strong immunogenic particle present in the outer membrane of Gram-negative bacteria. It is a major triggering factor for the inflammatory cascade in response to a Gram-negative bacteria infection. The use of LPS as a strong pro-inflammatory agent is a well-known model of inflammation applied in both in vivo and in vitro studies. This review offers a summary of the pathogenesis associated with LPS exposure, especially in the field of neuroinflammation. Moreover, we analyzed different in vivo LPS models utilized in the area of neuroscience. This paper presents recent knowledge and is focused on new insights in the LPS experimental model.

Tacrine Derivatives in Neurological Disorders: Focus on Molecular Mechanisms and Neurotherapeutic Potential

Tacrine is a drug used in the treatment of Alzheimer's disease as a cognitive enhancer and inhibitor of the enzyme acetylcholinesterase (AChE). However, its clinical application has been restricted due to its poor therapeutic efficacy and high prevalence of detrimental effects. An attempt was made to understand the molecular mechanisms that underlie tacrine and its analogues influence over neurotherapeutic activity by focusing on modulation of neurogenesis, neuroinflammation, endoplasmic reticulum stress, apoptosis, and regulatory role in gene and protein expression, energy metabolism, Ca2+ homeostasis modulation, and osmotic regulation. Regardless of this, analogues of tacrine are considered as a model inhibitor of cholinesterase in the therapy of Alzheimer's disease. The variety both in structural make-up and biological functions of these substances is the main appeal for researchers' interest in them. A new paradigm for treating neurological diseases is presented in this review, which includes treatment strategies for Alzheimer's disease, as well as other neurological disorders like Parkinson's disease and the synthesis and biological properties of newly identified versatile tacrine analogues and hybrids. We have also shown that these analogues may have therapeutic promise in the treatment of neurological diseases in a variety of experimental systems.

Autonomic and cholinergic mechanisms mediating cardiovascular and temperature effects of donepezil in conscious mice

Donepezil is a centrally acting acetylcholinesterase (AChE) inhibitor with therapeutic potential in inflammatory diseases; however, the underlying autonomic and cholinergic mechanisms remain unclear. Here, we assessed effects of donepezil on mean arterial pressure (MAP), heart rate (HR), HR variability, and body temperature in conscious adult male C57BL/6 mice to investigate the autonomic pathways involved. Central versus peripheral cholinergic effects of donepezil were assessed using pharmacological approaches including comparison with the peripherally acting AChE inhibitor, neostigmine. Drug treatments included donepezil (2.5 or 5 mg/kg sc), neostigmine methyl sulfate (80 or 240 μg/kg ip), atropine sulfate (5 mg/kg ip), atropine methyl bromide (5 mg/kg ip), or saline. Donepezil, at 2.5 and 5 mg/kg, decreased HR by 36 ± 4% and 44 ± 3% compared with saline (n = 10, P < 0.001). Donepezil, at 2.5 and 5 mg/kg, decreased temperature by 13 ± 2% and 22 ± 2% compared with saline (n = 6, P < 0.001). Modest (P < 0.001) increases in MAP were observed with donepezil after peak bradycardia occurred. Atropine sulfate and atropine methyl bromide blocked bradycardic responses to donepezil, but only atropine sulfate attenuated hypothermia. The pressor response to donepezil was similar in mice coadministered atropine sulfate; however, coadministration of atropine methyl bromide potentiated the increase in MAP. Neostigmine did not alter HR or temperature, but did result in early increases in MAP. Despite the marked bradycardia, donepezil did not increase normalized high-frequency HR variability. We conclude that donepezil causes marked bradycardia and hypothermia in conscious mice via the activation of muscarinic receptors while concurrently increasing MAP via autonomic and cholinergic pathways that remain to be elucidated.

Protective effect of Indole-3-carbinol, an NF-κB inhibitor in experimental paradigm of Parkinson's disease: In silico and in vivo studies

Parkinson's disease (PD) is a progressive neurodegenerative disorder, majorly with symptoms of motor dysfunction. Study was performed to explore the effect of nuclear factor κB (NF-κB) inhibitors against neurobehavioral abnormalities and neuroinflammation in PD. Cost effective in silico approaches of docking-based ligand -target complex predictions and optimal physicochemical properties were utilised to identify lead NF-κB inhibitor using database. Our studies revealed the potential hit Indole-3-carbinol (I3C) which was considered for the next phase, pharmacological validations. Intranigral administration of lipopolysaccharide (LPS) in rats is utilized as a neuroinflmmation model of PD. In the present study it caused an impairment in motor functions, its coordination, learning and memory as demonstrated in rotarod apparatus, beam balance test, open field test and Morris water maze test. Chronic administration of I3C for 21 days in intranigral LPS treated rats led to a significant improvement in motor functions, coordination, learning and memory which were associated with a decrease in the activity of inflammatory cytokines such as TNF-α and IL-6. Further, it was found to inhibit NF-κB whose levels increased after LPS administration. Moreover, decreased levels of malondialdehyde and increased levels of reduced glutathione, superoxide dismutase and catalase were observed in cortex and striatum after I3C administration in LPS rats. These results suggest a possible neuroprotective effect of I3C via amelioration of LPS-induced behavioural alterations, oxidative damage and neuroinflammation which in turn is attributed to its potent antioxidant and anti-inflammatory (NF-κB inhibition) property. The effect produced by I3C (50 mg/kg) was found to be comparable with levodopa-carbidopa combination (LD:CD) while, I3C (50 mg/kg) in combination with LD:CD exhibited a potentiating effect in improving motor impairments and cognitive deficit. The results thus depict I3C as a promising agent to delay neurodegeneration of the neurons in PD with improvement in motor functions and cognitive function.

Virgin Coconut Oil-Induced Neuroprotection in Lipopolysaccharide-Challenged Rats is Mediated, in Part, Through Cholinergic, Anti-Oxidative and Anti-Inflammatory Pathways

Neuroinflammation is associated with neuronal cell death and could lead to chronic neurodegeneration. This study investigated the neuroprotective potential of virgin coconut oil (VCO) against lipopolysaccharide (LPS)-induced cytotoxicity of neuroblastoma SK-N-SH cells. The findings were validated using Wistar rats, which were fed with 1-10 g/kg VCO for 31 days, exposed to LPS (0.25 mg/kg) and subjected to the Morris Water Maze Test. Brain homogenate was subjected to biochemical analyses and gene expression studies. α-Tocopherol (α-T; 150 mg/kg) served as the positive control. VCO (100 µg/mL) significantly (p < 0.01) improved SK-N-SH viability (+57%) and inhibited reactive oxygen species (-31%) in the presence of LPS. VCO (especially 10 g/kg) also significantly (p < 0.05) enhanced spatial memory of LPS-challenged rats. Brain homogenate of VCO-fed rats was presented with increased acetylcholine (+33%) and reduced acetylcholinesterase (-43%). The upregulated antioxidants may have reduced neuroinflammation [malondialdehyde (-51%), nitric oxide (-49%), Cox-2 (-64%) and iNos (-63%)] through upregulation of IL-10 (+30%) and downregulation of IL-1β (-65%) and Interferon-γ (-25%). There was also reduced expression of Bace-1 (-77%). VCO-induced neuroprotection, which was comparable to α-T, could be mediated, in part, through inflammatory, cholinergic and amyloidogenic pathways.

Interacting with α 7 nAChR is a new mechanism for AChE to enhance the inflammatory response in macrophages

Acetylcholine (ACh) regulates inflammation via α7 nicotinic acetylcholine receptor (α7 nAChR). Acetylcholinesterase (AChE), an enzyme hydrolyzing ACh, is expressed in immune cells suggesting non-classical function in inflammatory responses. Here, the expression of PRiMA-linked G4 AChE was identified on the surface of macrophages. In lipopolysaccharide-induced inflammatory processes, AChE was upregulated by the binding of NF-κB onto the ACHE promotor. Conversely, the overexpression of G4 AChE inhibited ACh-suppressed cytokine release and cell migration, which was in contrast to that of applied AChE inhibitors. AChEmt, a DNA construct without enzymatic activity, was adopted to identify the protein role of AChE in immune system. Overexpression of G4 AChEmt induced cell migration and inhibited ACh-suppressed cell migration. The co-localization of α7 nAChR and AChE was found in macrophages, suggesting the potential interaction of α7 nAChR and AChE. Besides, immunoprecipitation showed a close association of α7 nAChR and AChE protein in cell membrane. Hence, the novel function of AChE in macrophage by interacting with α7 nAChR was determined. Together with hydrolysis of ACh, AChE plays a direct role in the regulation of inflammatory response. As such, AChE could serve as a novel target to treat age-related diseases by anti-inflammatory responses.

Acotiamide attenuates central urocortin 2-induced intestinal inflammatory responses, and urocortin 2 treatment reduces TNF-α productions in LPS-stimulated macrophage cell lines

BACKGROUND

To determine whether central and in vitro administration of urocortin 2 (Ucn 2) affected intestinal inflammatory responses in LPS-stimulated rat models and macrophage cell lines and acotiamide modified mucosal inflammation in this model.

METHODS

Rats were divided into four groups. LPS-stimulated group (n = 4); LPS- and urocortin 2-treated group (n = 4); LPS- and acotiamide-treated group (n = 4); and LPS-, urocortin 2-, and acotiamide-treated group (n = 4). CD68-, CCR2-, and corticotropin-releasing hormone receptor type 2 (CRHR2)-positive cells were assessed by immunostaining. Myeloperoxidase (MPO) activity was measured. TNF-α, IL-6, and IL-4 levels were measured by ELISA method. Gastric emptying and small intestinal transit time were determined using Evans blue.

KEY RESULTS

Central administration of Ucn 2 significantly aggravated infiltrations of CD68- and CCR2-positive cells in the intestinal mucosa of LPS-stimulated rat models compared to those in LPS treatment alone. Interestingly, acotiamide treatment significantly reduced the migrations of both CD68- and CCR2-positive cells in the jejunum of central Ucn 2-treated LPS-stimulated rat models. Acotiamide significantly reduced the expression levels of IkB-α phosphorylation in LPS- and MCP-1-stimulated NR8383 cells. Central administration of Ucn 2 significantly delayed gastric emptying. In contrast, Ucn 2 stimulation significantly reduced TNF-α and IL-6 productions in LPS-stimulated NR8383 cells and astressin B reversed the inhibition of TNF-α production in stimulated NR8383 cells. Acotiamide (30 μmol/L) significantly reduced TNF-α and IL-6 productions in LPS- and MCP-1-stimulated NR8383 cells.

CONCLUSIONS AND INFERENCES

Central and in vitro treatments of Ucn 2 affected intestinal inflammatory responses, respectively, and acotiamide improved them.

Nootkatone, a neuroprotective agent from Alpiniae Oxyphyllae Fructus, improves cognitive impairment in lipopolysaccharide-induced mouse model of Alzheimer's disease

Neuroinflammatory responses play a crucial role in the pathogenesis of Alzheimer's disease (AD). Our previous study demonstrated that petroleum ether extracts from Alpiniae Oxyphyllae Fructus(AOF) could attenuate lipopolysaccharide (LPS)-induced learning and memory impairment in mice, which could be associated with its inhibitory effect on neuroinflammation. Therefore, our present study is to investigate the potential therapeutic neuroprotective effects of nootkatone (NKT) on an AD mouse model induced by intracerebroventricular injection of LPS. We found that NKT (10 mg/kg) group showed good performance in behavior experiments including Y-maze test and Morris water maze test. The results of histopathological examination and immunohistochemical analysis showed that LPS induced degeneration of neurons and activation of microglia particularly in hippocampus and NKT (10 mg/kg) reversed these changes. Enzyme linked immunosorbent assay and western blot analysis also demonstrated that the model group had increased expression of IL-1β, IL-6, TNF-α, NLRP3 and NF-κB p65, especially in hippocampus relative to sham-operated group, and NKT (10 mg/kg) decreased the high expression of these inflammatory cytokines. Collectively, these data indicated that LPS-induced learning and memory impairments in mice could be improved by NKT, which was associated with attenuating neuroinflammatory responses. Our study indicated that NKT could act as a potential therapeutic agent for the treatment of neuroinflammation and AD.

Effect of acetylcholinesterase inhibitors donepezil and rivastigmine on the activity and expression of cyclooxygenases in a model of the inflammatory action of fluoride on macrophages obtained from THP-1 monocytes

Inflammation is an important factor in the development of many diseases of the central nervous system, including Alzheimer's disease and other types of dementia. ‪Given that acetylcholinesterase inhibitors are also currently believed to have anti-inflammatory properties, the purpose of this study was to investigate the effect of acetylcholinesterase inhibitors (rivastigmine, donepezil) on cyclooxygenase activity and expression using the proinflammatory action of fluoride (F^-) on cultured macrophages obtained from THP-1 monocytes. COX-1 and COX-2 activity was determined through measurement of the products of prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) in cell culture supernatants. Expression of COX-1 and COX-2 proteins was examined immunocytochemically, and mRNA expression was determined by qRT PCR. ‪‪ Our study confirmed the inhibitory effects of donepezil and rivastigmine on the production of PGE2, TXB2, COX-1 and COX-2 mRNA and protein expression in macrophages. We also demonstrated that the pro-inflammatory effect of fluoride may be reduced by the use of both drugs. The additive effect of these drugs cannot be ruled out, and effects other than those observed in the use of one drug should also be taken into account.

LPS and neuroinflammation: a matter of timing

Lipopolysaccharide (LPS) administration has been repeatedly shown to elicit central inflammation, regardless of the route of administration. In a recent study, Tiwari et al. (Inflammopharmacology 10.1007/s10787-016-0274-3 , 2016) dispute the potential of peripheral administration of LPS to induce neuroinflammation. Here, I summarise literature indicating that the neuroinflammatory effects of LPS are time dependent, and suggest that their findings can be explained by the time at which they chose to measure neuroinflammation.

Donepezil, an acetylcholinesterase inhibitor, attenuates LPS-induced inflammatory response in murine macrophage cell line RAW 264.7 through inhibition of nuclear factor kappa B translocation

We have previously demonstrated that the pharmacotherapy with donepezil, an acetylcholinesterase inhibitor, suppresses cardiac remodeling in a mouse model of ischemic heart failure after myocardial infarction (MI). However, the precise mechanisms of the cardioprotective effect of donepezil have not been completely delineated. Because post-ischemic inflammation is a pathological key event in the cardiac remodeling process following MI, we investigated the hypothesis that donepezil acts as an inhibitor of inflammatory mediators. RAW 264.7 murine macrophage cells were pretreated with donepezil (100µM) prior to a pro-inflammatory stimulation by administration of lipopolysaccharide (LPS, 10ng/ml). Donepezil significantly reduced intra- and extracellular levels of various kinds of inflammatory mediators such as TNF-α, IL-1β, IL-2, IL-6 and IL-18 after the LPS stimulation, and attenuated LPS-induced nuclear translocation of nuclear factor-kappa B (NF-κB). These results indicate that donepezil possesses an anti-inflammatory property. However, the inhibitory effect of donepezil on the macrophage inflammatory responses was never reproduced by ACh, nor was disrupted by ACh receptor blockers. Moreover, other kinds of acetylcholinesterase inhibitors failed to inhibit the inflammatory responses in LPS-stimulated macrophage cells. These results suggest that a cholinergic anti-inflammatory pathway would not be involved in the anti-inflammatory effect of donepezil and that the specific characteristics of donepezil in suppressing the LPS-induced cytokine release and the NF-κB activation would be independent of its acetylcholinesterase inhibition. The present study showed that donepezil exerts an anti-inflammatory effect independently of acetylcholinesterase inhibitory action, thereby donepezil may contribute to cardioprotection during cardiac remodeling process in an ischemic heart failure after MI.

Does Anticholinergic Activity Affect Neuropathology? Implication of Neuroinflammation in Alzheimer's Disease

One characteristic neuropathological feature of Alzheimer's disease (AD) is profound neuronal loss in the nucleus basalis of Meynert, the major source of cholinergic innervation of the cerebral cortex. Clinically, anticholinergic activity causes a decline in cognitive function and increases the risk of dementia, thus possibly enhancing AD pathologies and neurodegeneration. Until now there has been insufficient human neuropathological data to support this conclusion. Experimental studies using a tauopathy mouse model demonstrated anticholinergics enhanced tau pathology and neurodegeneration corresponding to central anticholinergic activity. Additionally, donepezil, a cholinesterase inhibitor, ameliorated tau pathology and neurodegeneration in the same mouse model. These results indicate the balance between cholinergic and anticholinergic activities might affect neurodegeneration. Importantly, neurodegeneration observed in the mouse model seemed to correspond to the distribution of microglial activation, and it was reported that neuroinflammation plays an important role in the pathomechanism of AD, while anticholinergic activity augments inflammatory responses. Moreover, some studies indicated β-amyloid itself depletes cholinergic function similarly to anticholinergic activity. Thus, anticholinergic activity might initiate and/or accelerate AD pathology. Limited human data support the conclusion that anticholinergic activity enhances AD-related neuropathology and neurodegeneration. However, experimental data from a tauopathy mouse model indicated anticholinergic activity might enhance neurodegeneration with enhanced neuroinflammation including microglial activation.

Silibinin ameliorates LPS-induced memory deficits in experimental animals

Neuroinflammation is considered as one of the predisposing factor in the etiology of several neurodegenerative disorders. Therefore, the objective of the present study was to evaluate the protective effect of silibinin (SIL) in the lipopolysaccharide (LPS)-induced neuroinflammatory model. The effect of SIL on memory function was also evaluated on normal rats without LPS administration. In the first experiment, male rats were divided into five groups. Except control group animals, all rats received bilateral intracerebroventricular injection of LPS (5 μg/5 μl) into lateral ventricles on the first day of the experimental schedule. Control rats received bilateral intracerebroventricular injection of artificial cerebrospinal fluid into lateral ventricles. SIL in doses of 50, 100 and 200 mg/kg, p.o. was administered 1h before LPS injection and continued for 7 days. On Day-7, SIL attenuated the LPS-induced long-term and working memory loss in elevated plus and Y-maze test respectively. Further, SIL dose-dependently attenuated LPS-induced decrease in acetylcholine level and increase in the acetylcholinestrase activity in hippocampus and pre-frontal cortex. SIL ameliorated LPS-induced decrease in the mitochondrial complex activity (I, IV and V) and integrity, increase in lipid peroxidation and decrease in the activity of superoxide dismutase in both the brain regions. SIL attenuated amyloidogenesis in the hippocampus, while it decreased the LPS-induced increase in the level of NFκB in the pre-frontal cortex. In another study, SIL dose-dependently, enhanced memory functions in the normal rats, indicating its nootropic activity. Hence, SIL could be a potential candidate in the management of neuroinflammation-related memory disorders.

Effects of sub-chronic donepezil on brain Abeta and cognition in a mouse model of Alzheimer's disease

RATIONALE

Acetylcholinesterase inhibitors (AChEIs) are approved to treat the symptoms of mild to moderate Alzheimer's disease by restoring acetylcholine levels at synapses where the neurotransmitter has been depleted due to neurodegeneration. This assumption is challenged by more recent clinical studies suggesting the potential for disease-modifying effects of AChEIs as well as in vitro studies showing neuroprotective effects. However, few preclinical studies have assessed whether the improvement of cognitive symptoms may be mediated by reductions in Abeta or Tau pathology.

OBJECTIVES

The objective of the present study was to determine whether short-duration treatment with donepezil could improve spatial learning and memory in transgenic mice overexpressing mutant human amyloid precursor protein (hAPP) and presenilin 1 (PS1) (Dewachter et al., J Neurosci 20(17):6452-6458, 2000) after amyloid pathology has fully developed, consistent with early stages of Alzheimer'sdisease in humans. In parallel, the effect of donepezil treatment on brain amyloid, Tau, and glial endpoints was measured.

RESULTS

This study showed a significant improvement in reference memory in hAPP/PS1 mice along with dose-dependent reductions in brain amyloid-β (Aβ).

CONCLUSION

These results suggest that the observed cognitive improvement produced by donepezil in Alzheimer's disease may be due, at least in part, to reduction of brain Aβ.

Donepezil inhibits the amyloid-beta oligomer-induced microglial activation in vitro and in vivo

Recent studies on Alzheimer's disease (AD) have focused on soluble oligomeric forms of amyloid-beta (Aβ oligomer, AβO) that are directly associated with AD-related pathologies, such as cognitive decline, neurodegeneration, and neuroinflammation. Donepezil is a well-known anti-dementia agent that increases acetylcholine levels through inhibition of acetylcholinesterase. However, a growing body of experimental and clinical studies indicates that donepezil may also provide neuroprotective and disease-modifying effects in AD. Additionally, donepezil has recently been demonstrated to have anti-inflammatory effects against lipopolysaccharides and tau pathology. However, it remains unknown whether donepezil has anti-inflammatory effects against AβO in cultured microglial cells and the brain in animals. Further, the effects of donepezil against AβO-mediated neuronal death, astrogliosis, and memory impairment have also not yet been investigated. Thus, in the present study, we examined the anti-inflammatory effect of donepezil against AβO and its neuroinflammatory mechanisms. Donepezil significantly attenuated the release of inflammatory mediators (prostaglandin E2, interleukin-1 beta, tumor necrosis factor-α, and nitric oxide) from microglia. Donepezil also decreased AβO-induced up-regulation of inducible nitric oxide synthase and cyclooxygenase-2 protein and phosphorylation of p38 mitogen-activated protein kinase as well as translocation of nuclear factor-kappa B. We next showed that donepezil suppresses activated microglia-mediated toxicity in primary hippocampal cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. In intrahippocampal AβO-injected mice, donepezil significantly inhibited microgliosis and astrogliosis. Furthermore, behavioral tests revealed that donepezil (2 mg/kg/day, 5 days, p.o.) significantly ameliorated AβO-induced memory impairment. These results suggest that donepezil directly inhibits microglial activation induced by AβO through blocking MAPK and NF-κB signaling and, in part, contributing to the amelioration of neurodegeneration and memory impairment.

Chronological changes in inflammatory cytokines immunoreactivities in the mouse hippocampus after systemic administration of high dosage of tetanus toxin

Tetanus toxin (TeT) is an exotoxin and has a capacity for neuronal binding and internalization. In the present study, we compared changes in the immunoreactivities and protein levels of interleukin (IL-) 2 as a pro-inflammatory cytokine and IL-4 as an anti-inflammatory cytokine in the hippocampus proper (HP) and dentate gyrus (DG) after systemic treatment of 10 or 100 ng/kg TeT into mice. In this study, we could not find any neuronal damage or loss in any subregions of the hippocampus after TeT treatment. In the control groups, strong IL-2 immunoreactivity was shown in the stratum pyramidal (SP) of the HP and in the granule cell layer (GCL) of the DG. At 6 h post-treatment, IL-2 immunoreactivity was hardly detected in the SP and GCL; however, strong IL-2 immunoreactivity was shown in the stratum oriens of the HP in both the groups. Thereafter, intermediate IL-2 immunoreactivity was shown in the SP and GCL. On the other hand, intermediate IL-4 immunoreactivity was detected in the SP and GCL of the control groups. At 6 h post-treatment, IL-4 immunoreactivity in the SP and GCL was apparently increased. Thereafter, IL-4 immunoreactivity was lower than that at 6 h post-treatment. In brief, IL-2 and 4 immunoreactivities were easily detected in SP and GCL in the controls and dramatically decreased and increased at 6 h post-treatment, respectively.

Comparison of inflammatory cytokines changes in the hippocampal CA1 region between the young and adult gerbil after transient cerebral ischemia

Young animals appear much less vulnerable to ischemic insults. In present study, we compared neuronal damage and changes in the immunoreactivities and levels of inflammatory cytokine, interleukin (IL-) 2 as a pro-inflammatory cytokine and its receptor (IL-2Rβ), IL-4 and IL-13 as anti-inflammatory cytokines, in the hippocampal CA1 region between adult and young gerbils after 5 min of transient cerebral ischemia. Most (about 89%) of hippocampal CA1 pyramidal neurons showed neuronal damage only in the adult gerbil at 4 days post-ischemia; in the young ischemia-group, about 61% of CA1 pyramidal neurons showed neuronal damage at 7 days post-ischemia. Thereafter, the neuronal damage in the CA1 pyramidal neurons was not significantly changed in both the groups. IL-2 and IL-2Rβ immunoreactivity in the stratum pyramidale (SP) of the CA1 region was similar in both the sham groups. At 4 days post-ischemia, IL-2 and IL-2Rβ immunoreactivity in the adult SP was dramatically decreased; however, in the young SP, they were not changed, and they were decreased at 7 days post-ischemia. IL-4 and IL-13 immunoreactivity in the SP of the young sham-group were much lower than those in the adult group. Four days after ischemia-reperfusion, they were dramatically decreased in the adult ischemia-group; however, at this time, they were markedly increased in the young ischemia-group. In brief, our findings indicate that IL-2, 2Rβ, IL-4 and IL-13 immunoreactivity in young gerbils was similar or low compared to those in the adult, and they were decreased at 4 days post-ischemia in the adult; however, at this time, they were distinctively increased in the young.

Differential levels of apolipoprotein E and butyrylcholinesterase show strong association with pathological signs of Alzheimer's disease in the brain in vivo

Recently, we reported that 3 of the known risk factors of Alzheimer's disease (AD), i.e., advanced age, apolipoprotein E (ApoE) ε4, and female gender, are associated with differential levels of ApoE proteins and butyrylcholinesterase (BuChE) in the cerebrospinal fluid (CSF) of AD patients. The ApoE ε4 allele and certain BuChE polymorphisms synergistically affect the conversion rate of mild cognitive impairment (MCI) to AD. Here, we investigated interrelationships between ApoE and BuChE levels, and pathological markers of AD in vivo. CSF from patients with probable AD, assessed for cerebral glucose metabolism (CMRglc; n = 50) and Pittsburgh compound B (PIB) retention (β-amyloid [Aβ] load, n = 29) by positron emission tomography (PET), was used for measurement of BuChE, ApoE, Aβ, tau, phosphorylated tau (P-tau) and interleukin-1β (IL-1β) levels. Levels of ApoE and BuChE strongly correlated with CMRglc (fluorodeoxyglucose [FDG]-PET, r = 0.54, p < 0.0001, n = 50), cerebral Aβ load (PIB retention, r = 0.73, p < 0.0001, n = 29), and CSF P-tau (r = 0.73, p < 0.0001, n = 33). High ApoE protein was tied to low CMRglc and high PIB retention and P-tau. BuChE levels had opposite relationships. Other CSF covariates were levels of interleukin-1β and Aβ(42) peptide. The pattern of the patients' cognitive Z-scores strongly supported these observations. High ApoE protein was also linked to changes in 3 of the biodynamic properties of BuChE. In vitro analysis indicated that high ApoE protein levels were related to an increased pool of dormant BuChE molecules with an abnormally high intrinsic catalytic rate in CSF, which was "turned on" by excess Aβ peptides. The findings suggest that abnormally high levels of ApoE may play a causative role in the pathological events of AD, particularly those involving the early cholinergic deficit in the AD brain, through modulation of cholinesterases activities, hence disturbing the acetylcholine-dependent activity of neurons and nonexcitable cells such as glial cells.

Microglia signaling as a target of donepezil

Donepezil is a reversible and noncompetitive cholinesterase inhibitor. The drug is considered as a first-line treatment in patients with mild to moderate Alzheimer's disease. Recently, anti-inflammatory and neuroprotective effects of the drug have been reported. "Cholinergic anti-inflammation pathway" has major implications in these effects. Here, we present evidence that donepezil at 5-20 microM directly acts on microglial cells to inhibit their inflammatory activation. Our conclusion is based on the measurement of nitric oxide and proinflammatory mediators using purified microglia cultures and microglia cell lines: donepezil attenuated microglial production of nitric oxide and tumor necrosis factor (TNF)-alpha, and suppressed the gene expression of inducible nitric oxide synthase, interleukin-1 beta, and TNF-alpha. Subsequent studies showed that donepezil inhibited a canonical inflammatory NF-kappaB signaling. Microglia/neuroblastoma coculture and animal experiments supported the anti-inflammatory effects of donepezil. Based on the studies using nicotinic acetylcholine receptor antagonists, the donepezil inhibition of microglial activation was independent of acetylcholine and its receptor. Thus, inflammatory activation signaling of microglia may be one of the direct targets of donepezil in the central nervous system. It should be noted, however, that there is a large gap between the therapeutic dose of the drug used clinically and the concentration of the drug that exerts the direct action on microglial cells.

Cholinergic protection via alpha7 nicotinic acetylcholine receptors and PI3K-Akt pathway in LPS-induced neuroinflammation

The present study was planned to investigate the effect of anti-cholinesterase drugs donepezil and neostigmine on neuroinflammation induced by intracerebroventricular administration of lipopolysaccharide (LPS, 50 microg) in rat. Proinflammatory cytokines (TNF-alpha and IL-1beta), expressions of iNOS and COX-2, acetylcholinesterase activity, malondialdehyde and reduced glutathione were studied in different brain regions at 24h of LPS injection. Donepezil was found to decrease the LPS-induced AChE activity and oxidative stress in all the brain regions. It also inhibited the LPS-induced proinflammatory cytokines and iNOS expression but did not affect the increased COX-2 expression whereas neostigmine treatment had no effect on LPS-induced proinflammatory cytokines. Methyllycaconitine (MLA), a alpha7 nicotinic acetylcholine receptor antagonist, significantly antagonized the donepezil mediated inhibition of LPS-induced proinflammatory cytokines, indicating that alpha7 nicotinic acetylcholine receptor subunit was playing a role in regulation of neuroinflammation. The phosphorylation of Akt, an effector of PI3K, increased with donepezil treatment. These results suggest that increased cholinergic activity in brain by donepezil prevents LPS-induced neuroinflammation via alpha7-nAChRs, followed by the PI3K-Akt pathway and this system may form the basis for the development of novel agents for reversing neuroinflammation or provide new indications for existing drugs.

Inhibitory role of cholinergic system mediated via α7 nicotinic acetylcholine receptor in LPS-induced neuro-inflammation

This study investigated the influence of the cholinergic system on neuro-inflammation using nicotinic and muscarinic receptor agonists and antagonists. Intracerebroventricular (ICV) injection of lipopolysaccharide (LPS, 50 µg) was used to induce neuro-inflammation in rats and estimations of pro-inflammatory cytokines, α7 nicotinic acetylcholine receptor (nAChR) mRNA expression were done in striatum, cerebral cortex, hippocampus and hypothalamus at 24 h after LPS injection. Nicotine (0.2, 0.4 and 0.8 mg/kg, i.p.) or oxotremorine (0.2, 0.4 and 0.8 mg/kg, i.p.) were administered 2 h prior to sacrifice. We found that only nicotine was able to block the proinflammatory cytokines induced by LPS whereas, oxotremorine was found ineffective. Methyllycaconitine (MLA; 1.25, 2.5 and 5 mg/kg, i.p.), an α7 nAChR antagonist or dihydro-β-erythroidine (DHβE; 1.25, 2.5 and 5 mg/kg, i.p.), an α4β2 nAChR antagonist, was given 20 min prior to nicotine in LPS-treated rats. Methyllycaconitine antagonized the anti-inflammatory effect of nicotine whereas DHβE showed no effect demonstrating that α7 nAChR is responsible for attenuation of LPS-induced pro-inflammatory cytokines. This study suggests that the inhibitory role of the central cholinergic system on neuro-inflammation is mediated via α7 nicotinic acetylcholine receptor and muscarinic receptors are not involved.

Cholinergic deficiency involved in vascular dementia: possible mechanism and strategy of treatment

Vascular dementia (VaD) is a progressive neurodegenerative disease with a high prevalence. Several studies have recently reported that VaD patients present cholinergic deficits in the brain and cerebrospinal fluid (CSF) that may be closely related to the pathophysiology of cognitive impairment. Moreover, cholinergic therapies have shown promising effects on cognitive improvement in VaD patients. The precise mechanisms of these cholinergic agents are currently not fully understood; however, accumulating evidence indicates that these drugs may act through the cholinergic anti-inflammatory pathway, in which the efferent vagus nerve signals suppress pro-inflammatory cytokine release and inhibit inflammation, although regulation of oxidative stress and energy metabolism, alleviation of apoptosis may also be involved. In this paper, we provide a brief overview of the cholinergic treatment strategy for VaD and its relevant mechanisms of anti-inflammation.Acta Pharmacologica Sinica (2009) 30: 879-888; doi: 10.1038/aps.2009.82.

Influence of LPS-induced neuroinflammation on acetylcholinesterase activity in rat brain

In the present study, neuroinflammation was induced by bilateral intracerebroventricular (ICV) administration of Lipopolysaccharide (LPS). Proinflammatory cytokines (TNF-alpha and IL-1beta), acetylcholinesterase (AChE) activity, malondialdehyde (MDA) and reduced glutathione (GSH) were studied as markers for neuroinflammation, cholinergic activity and oxidative stress respectively in different brain regions at different time points after LPS injection. LPS produced increase in proinflammatory cytokines, MDA and the decrease in level of GSH at 24 h indicating a state of inflammation in brain regions, which was significantly blocked by Ibuprofen, a non steroidal anti-inflammatory drug. Enhanced AChE activity with these inflammatory markers after LPS administration indicates a possible relationship between neuroinflammation and cholinergic system during the development of neurodegenerative diseases.