Molecular Mechanisms Regulating LPS-Induced Inflammation in the Brain

Huperzine a ameliorates sepsis-induced acute lung injury by suppressing inflammation and oxidative stress via α7 nicotinic acetylcholine receptor

Sepsis, characterized by high mortality rates, causes over 50 % of acute lung injury (ALI) cases, primarily due to the heightened susceptibility of the lungs during this condition. Suppression of the excessive inflammatory response is critical for improving the survival of patients with sepsis; nevertheless, no specific anti-sepsis drugs exist. Huperzine A (HupA) exhibits neuroprotective and anti-inflammatory properties; however, its underlying mechanisms and effects on sepsis-induced ALI have yet to be elucidated. In this study, we demonstrated the potential of HupA for treating sepsis and explored its mechanism of action. To investigate the in vivo impacts of HupA, a murine model of sepsis was induced through cecal ligation and puncture (CLP) in both wild-type (WT) and α7 nicotinic acetylcholine receptor (α7nAChR) knockout mice. Our results showed that HupA ameliorates sepsis-induced acute lung injury by activating the α7nAChR. We used the CLP sepsis model in wild-type and α7nAChR -/- mice and found that HupA significantly increased the survival rate through α7nAChR, reduced the pro-inflammatory cytokine levels and oxidative stress, ameliorated histopathological lung injury, altered the circulating immune cell composition, regulated gut microbiota, and promoted short-chain fatty acid production through α7nAChR in vivo. Additionally, HupA inhibited Toll-like receptor NF-κB signaling by upregulating the α7nAChR/protein kinase B/glycogen synthase kinase-3 pathways. Our data elucidate HupA's mechanism of action and support a "new use for an old drug" in treating sepsis. Our findings serve as a basis for further in vivo studies of this drug, followed by application to humans. Therefore, the findings have the potential to benefit patients with sepsis.

TLR4-mediated chronic neuroinflammation has no effect on tangle pathology in a tauopathy mouse model

Introduction

Alzheimer's disease (AD) is marked by the accumulation of fibrillary aggregates composed of pathological tau protein. Although neuroinflammation is frequently observed in conjunction with tau pathology, current preclinical evidence does not sufficiently establish a direct causal role in tau tangle formation. This study aimed to evaluate whether chronic Toll-like receptor 4 (TLR4) stimulation, induced by a high dose of lipopolysaccharide (LPS, 5 mg/kg), exacerbates neurofibrillary tangle (NFT) pathology in a transgenic mouse model of tauopathy that expresses human truncated 151-391/3R tau, an early feature of sporadic AD.

Methods

We utilized a transgenic mouse model of tauopathy subjected to chronic TLR4 stimulation via weekly intraperitoneal injections of LPS over nine consecutive weeks. Neurofibrillary tangle formation, microglial activation, and tau hyperphosphorylation in the brainstem and hippocampus were assessed through immunohistochemistry, immunofluorescence, and detailed morphometric analysis of microglia.

Results

Chronic LPS treatment led to a significant increase in the number of Iba-1+ microglia in the LPS-treated group compared to the sham group (p < 0.0001). Notably, there was a 1.5- to 1.7-fold increase in microglia per tangle-bearing neuron in the LPS-treated group. These microglia exhibited a reactive yet exhausted phenotype, characterized by a significant reduction in cell area (p < 0.0001) without significant changes in other morphometric parameters, such as perimeter, circumference, solidity, aspect ratio, or arborization degree. Despite extensive microglial activation, there was no observed reduction in tau hyperphosphorylation or a decrease in tangle formation in the brainstem, where pathology predominantly develops in this model.

Discussion

These findings suggest that chronic TLR4 stimulation in tau-transgenic mice results in significant microglial activation but does not influence tau tangle formation. This underscores the complexity of the relationship between neuroinflammation and tau pathology, indicating that additional mechanisms may be required for neuroinflammation to directly contribute to tau tangle formation.

Implications of microbe-derived ɣ-aminobutyric acid (GABA) in gut and brain barrier integrity and GABAergic signaling in Alzheimer's disease

The gut microbial ecosystem communicates bidirectionally with the brain in what is known as the gut-microbiome-brain axis. Bidirectional signaling occurs through several pathways including signaling via the vagus nerve, circulation of microbial metabolites, and immune activation. Alterations in the gut microbiota are implicated in Alzheimer's disease (AD), a progressive neurodegenerative disease. Perturbations in gut microbial communities may affect pathways within the gut-microbiome-brain axis through altered production of microbial metabolites including ɣ-aminobutyric acid (GABA), the primary inhibitory mammalian neurotransmitter. GABA has been shown to act on gut integrity through modulation of gut mucins and tight junction proteins and may be involved in vagus nerve signal inhibition. The GABAergic signaling pathway has been shown to be dysregulated in AD, and may be responsive to interventions. Gut microbial production of GABA is of recent interest in neurological disorders, including AD. Bacteroides and Lactic Acid Bacteria (LAB), including Lactobacillus, are predominant producers of GABA. This review highlights how temporal alterations in gut microbial communities associated with AD may affect the GABAergic signaling pathway, intestinal barrier integrity, and AD-associated inflammation.

Ellagic Acid Prevented Dextran-Sodium-Sulfate-Induced Colitis, Liver, and Brain Injury through Gut Microbiome Changes

Inflammatory bowel disease (IBD) affects millions of people worldwide and is considered a significant risk factor for colorectal cancer. Recent in vivo and in vitro studies reported that ellagic acid (EA) exhibits important antioxidant and anti-inflammatory properties. In this study, we investigated the preventive effects of EA against dextran sulfate sodium (DSS)-induced acute colitis, liver, and brain injury in mice through the gut-liver-brain axis. Acute colitis, liver, and brain injury were induced by treatment with 5% (w/v) DSS in the drinking water for 7 days. Freshly prepared EA (60 mg/kg/day) was orally administered, while control (CON) group mice were treated similarly by daily oral administrations with a vehicle (water). All the mice were euthanized 24 h after the final treatment with EA. The blood, liver, colon, and brain samples were collected for further histological and biochemical analyses. Co-treatment with a physiologically relevant dose (60 mg/kg/day) of EA for 7 days significantly reduced the DSS-induced gut barrier dysfunction; endotoxemia; and inflammatory gut, liver, and brain injury in mice by modulating gut microbiota composition and inhibiting the elevated oxidative and nitrative stress marker proteins. Our results further demonstrated that the preventive effect of EA on the DSS-induced IBD mouse model was mediated by blocking the NF-κB and mitogen-activated protein kinase (MAPK) pathway. Therefore, EA co-treatment significantly attenuated the pro-inflammatory and oxidative stress markers by suppressing the activation of NF-κB/MAPK pathways in gut, liver, and brain injury. These results suggest that EA, effective in attenuating IBD in a mouse model, deserves further consideration as a potential therapeutic for the treatment of inflammatory diseases.

Microfluidic/HPLC combination to study carnosine protective activity on challenged human microglia: Focus on oxidative stress and energy metabolism

Carnosine (β-alanyl-L-histidine) is a naturally occurring endogenous peptide widely distributed in excitable tissues such as the brain. This dipeptide possesses well-demonstrated antioxidant, anti-inflammatory, and anti-aggregation properties, and it may be useful for treatment of pathologies characterized by oxidative stress and energy unbalance such as depression and Alzheimer's disease (AD). Microglia, the brain-resident macrophages, are involved in different physiological brain activities such synaptic plasticity and neurogenesis, but their dysregulation has been linked to the pathogenesis of numerous diseases. In AD brain, the activation of microglia towards a pro-oxidant and pro-inflammatory phenotype has found in an early phase of cognitive decline, reason why new pharmacological targets related to microglia activation are of great importance to develop innovative therapeutic strategies. In particular, microglia represent a common model of lipopolysaccharides (LPS)-induced activation to identify novel pharmacological targets for depression and AD and numerous studies have linked the impairment of energy metabolism, including ATP dyshomeostasis, to the onset of depressive episodes. In the present study, we first investigated the toxic potential of LPS + ATP in the absence or presence of carnosine. Our studies were carried out on human microglia (HMC3 cell line) in which LPS + ATP combination has shown the ability to promote cell death, oxidative stress, and inflammation. Additionally, to shed more light on the molecular mechanisms underlying the protective effect of carnosine, its ability to modulate reactive oxygen species production and the variation of parameters representative of cellular energy metabolism was evaluated by microchip electrophoresis coupled to laser-induced fluorescence and high performance liquid chromatography, respectively. In our experimental conditions, carnosine prevented LPS + ATP-induced cell death and oxidative stress, also completely restoring basal energy metabolism in human HMC3 microglia. Our results suggest a therapeutic potential of carnosine as a new pharmacological tool in the context of multifactorial disorders characterize by neuroinflammatory phenomena including depression and AD.

Transient disruption of functional connectivity and depression of neural fluctuations in a mouse model of acute septic encephalopathy

Septic encephalopathy leads to major and costly burdens for a large percentage of admitted hospital patients. Elderly patients are at an increased risk, especially those with dementia. Current treatments are aimed at sedation to combat mental status changes and are not aimed at the underlying cause of encephalopathy. Indeed, the underlying pathology linking together peripheral infection and altered neural function has not been established, largely because good, acutely accessible readouts of encephalopathy in animal models do not exist. Behavioral testing in animals lasts multiple days, outlasting the time frame of acute encephalopathy. Here, we propose optical fluorescent imaging of neural functional connectivity (FC) as a readout of encephalopathy in a mouse model of acute sepsis. Imaging and basic behavioral assessment were performed at baseline, Hr8, Hr24, and Hr72 following injection of either lipopolysaccharide or phosphate buffered saline. Neural FC strength decreased at Hr8 and returned to baseline by Hr72 in motor, somatosensory, parietal, and visual cortical regions. Additionally, neural fluctuations transiently declined at Hr8 and returned to baseline by Hr72. Both FC strength and fluctuation tone correlated with neuroscore indicating this imaging methodology is a sensitive and acute readout of encephalopathy.

The role of microRNA-485 in neurodegenerative diseases

Neurodegenerative diseases (NDDs) are age-related disorders characterized by progressive neurodegeneration and neuronal cell loss in the central nervous system. Neuropathological conditions such as the accumulation of misfolded proteins can cause neuroinflammation, apoptosis, and synaptic dysfunction in the brain, leading to the development of NDDs including Alzheimer's disease (AD) and Parkinson's disease (PD). MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate gene expression post-transcriptionally via RNA interference. Recently, some studies have reported that some miRNAs play an important role in the development of NDDs by regulating target gene expression. MiRNA-485 (miR-485) is a highly conserved brain-enriched miRNA. Accumulating clinical reports suggest that dysregulated miR-485 may be involved in the pathogenesis of AD and PD. Emerging studies have also shown that miR-485 plays a novel role in the regulation of neuroinflammation, apoptosis, and synaptic function in the pathogenesis of NDDs. In this review, we introduce the biological characteristics of miR-485, provide clinical evidence of the dysregulated miR-485 in NDDs, novel roles of miR-485 in neuropathological events, and discuss the potential of targeting miR-485 as a diagnostic and therapeutic marker for NDDs.

H2S-based fluorescent imaging for pathophysiological processes

Hydrogen sulfide (H2S), as an important endogenous signaling molecule, plays a vital role in many physiological processes. The abnormal behaviors of hydrogen sulfide in organisms may lead to various pathophysiological processes. Monitoring the changes in hydrogen sulfide is helpful for pre-warning and treating these pathophysiological processes. Fluorescence imaging techniques can be used to observe changes in the concentration of analytes in organisms in real-time. Therefore, employing fluorescent probes imaging to investigate the behaviors of hydrogen sulfide in pathophysiological processes is vital. This paper reviews the design strategy and sensing mechanisms of hydrogen sulfide-based fluorescent probes, focusing on imaging applications in various pathophysiological processes, including neurodegenerative diseases, inflammation, apoptosis, oxidative stress, organ injury, and diabetes. This review not only demonstrates the specific value of hydrogen sulfide fluorescent probes in preclinical studies but also illuminates the potential application in clinical diagnostics.

Novel Insight into the Mechanisms of Neurotoxicity Induced by 6:6 PFPiA through Disturbing the Gut-Brain Axis

As alternatives to traditional per- and polyfluoroalkyl substances, perfluoroalkyl phosphonic acids (PFPiAs) are frequently detected in aquatic environments, but the neurotoxic effects and underlying mechanisms remain unclear. In this study, male zebrafish were exposed to 6:6 PFPiA (1 and 10 nM) for 28 days, which exhibited anxiety-like symptoms. Gut microbiome results indicated that 6:6 PFPiA significantly increased the abundance of Gram-negative bacteria, leading to enhanced levels of lipopolysaccharide (LPS) and inflammation in the gut. The LPS was delivered to the brain through the gut-brain axis (GBA), damaged the blood-brain barrier (BBB), stimulated neuroinflammation, and caused apoptosis as well as neural injury in the brain. This mechanism was verified by the fact that antibiotics reduced the LPS levels in the gut and brain, accompanied by reduced inflammatory responses and anxiety-like behavior. The BBB damage also resulted in the enhanced accumulation of 6:6 PFPiA in the brain, where it might bind strongly with and activate aryl hydrocarbon receptor (AhR) to induce brain inflammation directly. Additionally, as the fish received treatment with an inhibitor of AhR, the inflammation response and anxiety-like behavior decreased distinctly. This study sheds light on the new mechanisms of neurotoxicity-induced 6:6 PFPiA due to the interruption on GBA.

Manipulation of the diet-microbiota-brain axis in Alzheimer's disease

Several studies investigating the pathogenesis of Alzheimer's disease have identified various interdependent constituents contributing to the exacerbation of the disease, including Aβ plaque formation, tau protein hyperphosphorylation, neurofibrillary tangle accumulation, glial inflammation, and the eventual loss of proper neural plasticity. Recently, using various models and human patients, another key factor has been established as an influential determinant in brain homeostasis: the gut-brain axis. The implications of a rapidly aging population and the absence of a definitive cure for Alzheimer's disease have prompted a search for non-pharmaceutical tools, of which gut-modulatory therapies targeting the gut-brain axis have shown promise. Yet multiple recent studies examining changes in human gut flora in response to various probiotics and environmental factors are limited and difficult to generalize; whether the state of the gut microbiota in Alzheimer's disease is a cause of the disease, a result of the disease, or both through numerous feedback loops in the gut-brain axis, remains unclear. However, preliminary findings of longitudinal studies conducted over the past decades have highlighted dietary interventions, especially Mediterranean diets, as preventative measures for Alzheimer's disease by reversing neuroinflammation, modifying the intestinal and blood-brain barrier (BBB), and addressing gut dysbiosis. Conversely, the consumption of Western diets intensifies the progression of Alzheimer's disease through genetic alterations, impaired barrier function, and chronic inflammation. This review aims to support the growing body of experimental and clinical data highlighting specific probiotic strains and particular dietary components in preventing Alzheimer's disease via the gut-brain axis.

Age-Dependent and Pathway-Specific Bimodal Action of Nicotine on Synaptic Plasticity in the Hippocampus of Mice Lacking the miR-132/212 Genes

Nicotine addiction develops predominantly during human adolescence through smoking. Self-administration experiments in rodents verify this biological preponderance to adolescence, suggesting evolutionary-conserved and age-defined mechanisms which influence the susceptibility to nicotine addiction. The hippocampus, a brain region linked to drug-related memory storage, undergoes major morpho-functional restructuring during adolescence and is strongly affected by nicotine stimulation. However, the signaling mechanisms shaping the effects of nicotine in young vs. adult brains remain unclear. MicroRNAs (miRNAs) emerged recently as modulators of brain neuroplasticity, learning and memory, and addiction. Nevertheless, the age-dependent interplay between miRNAs regulation and hippocampal nicotinergic signaling remains poorly explored. We here combined biophysical and pharmacological methods to examine the impact of miRNA-132/212 gene-deletion (miRNA-132/212-/-) and nicotine stimulation on synaptic functions in adolescent and mature adult mice at two hippocampal synaptic circuits: the medial perforant pathway (MPP) to dentate yrus (DG) synapses (MPP-DG) and CA3 Schaffer collaterals to CA1 synapses (CA3-CA1). Basal synaptic transmission and short-term (paired-pulse-induced) synaptic plasticity was unaltered in adolescent and adult miRNA-132/212-/- mice hippocampi, compared with wild-type controls. However, nicotine stimulation promoted CA3-CA1 synaptic potentiation in mature adult (not adolescent) wild-type and suppressed MPP-DG synaptic potentiation in miRNA-132/212-/- mice. Altered levels of CREB, Phospho-CREB, and acetylcholinesterase (AChE) expression were further detected in adult miRNA-132/212-/- mice hippocampi. These observations propose miRNAs as age-sensitive bimodal regulators of hippocampal nicotinergic signaling and, given the relevance of the hippocampus for drug-related memory storage, encourage further research on the influence of miRNAs 132 and 212 in nicotine addiction in the young and the adult brain.

Visualization of Acute Inflammation through a Macrophage-Camouflaged Afterglow Nanocomplex

Acute inflammation is a basic innate, immediate, and stereotyped immune response to injury, which is characterized by rapid recruitment of immune cells to the vasculature and extravasation into the damaged parenchyma. Visualization of acute inflammation plays an important role in monitoring the disease course and understanding pathogenesis, which lacks specific targeted and observing tools in vivo. Here, we report a Trojan horse strategy of a macrophage-camouflaged afterglow nanocomplex (UCANPs@RAW) to specifically visualize acute inflammation. Due to the advantages of optical antibackground interference elimination, as well as particular immune homing and long-term tracking capacity, UCANPs@RAW demonstrates an excellent acute inflammatory recognition ability. In an arthritis model, previously intravenously injected UCANPs@RAW could directionally migrate from the liver to the inflammation site as soon as 3 h after the model was induced, which could be continuously lighted for at least 36 h with the highest imaging signal-to-background ratio (SBR) as 382 at the time point of 9 h. Additionally, UCANPs@RAW is observed to penetrate the blood-brain barrier and image the deep brain inflamed region covered by the thick skull in an acute brain inflammation model with an SBR_max of 258, which is based on the strong recruiting ability of macrophages to immune response. In view of this smart nanocomplex, our strategy holds great potential for inflammatory detection and treatments.

Dexmedetomidine Restores Autophagic Flux, Modulates Associated microRNAs and the Cholinergic Anti-inflammatory Pathway upon LPS-Treatment in Rats

Infections and perioperative stress can lead to neuroinflammation, which in turn is linked to cognitive impairments such as postoperative delirium or postoperative cognitive dysfunctions. The α2-adrenoceptor agonist dexmedetomidine (DEX) prevents cognitive impairments and has organo-protective and anti-inflammatory properties. Macroautophagy (autophagy) regulates many biological processes, but its role in DEX-mediated anti-inflammation and the underlying mechanism of DEX remains largely unclear. We were interested how a pretreatment with DEX protects against lipopolysaccharide (LPS)-induced inflammation in adult male Wistar rats. We used Western blot and activity assays to study how DEX modulated autophagy- and apoptosis-associated proteins as well as molecules of the cholinergic anti-inflammatory pathway, and qPCR to analyse the expression of autophagy and inflammation-associated microRNAs (miRNA) in the spleen, cortex and hippocampus at different time points (6 h, 24 h, 7 d). We showed that a DEX pretreatment prevents LPS-induced impairments in autophagic flux and attenuates the LPS-induced increase in the apoptosis-associated protein cleaved poly(ADP-ribose)-polymerase (PARP) in the spleen. Both, DEX and LPS altered miRNA expression and molecules of the cholinergic anti-inflammatory pathway in the spleen and brain. While only a certain set of miRNAs was up- and/or downregulated by LPS in each tissue, which was prevented or attenuated by a DEX pretreatment in the spleen and hippocampus, all miRNAs were up- and/or downregulated by DEX itself - independent of whether or not they were altered by LPS. Our results indicate that the organo-protective effect of DEX may be mediated by autophagy, possibly by acting on associated miRNAs, and the cholinergic anti-inflammatory pathway. Preventive effects of DEX on LPS-induced inflammation. DEX restores the LPS-induced impairments in autophagic flux, attenuates PARP cleavage and alters molecules of the cholinergic system in the spleen. Furthermore, DEX alters and prevents LPS-induced miRNA expression changes in the spleen and brain along with LPS.

Promising tacrine/huperzine A-based dimeric acetylcholinesterase inhibitors for neurodegenerative disorders: From relieving symptoms to modifying diseases through multitarget

Neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, are devastating diseases in the elderly world, which are closely associated with progressive neuronal loss induced by a variety of genetic and/or environmental factors. Unfortunately, currently available treatments for neurodegenerative disorders can only relieve the symptoms but not modify the pathological processes. Over the past decades, our group by collaborating with Profs. Yuan-Ping Pang and Paul R. Carlier has developed three series of homo/hetero dimeric acetylcholinesterase inhibitors derived from tacrine and/or huperzine A. The representative dimers bis(3)-Cognitin (B3C), bis(12)-hupyridone, and tacrine(10)-hupyridone might possess disease-modifying effects through the modulation of N-methyl-d-aspartic acid receptors, the activation of myocyte enhancer factor 2D gene transcription, and the promotion of neurotrophic factor secretion. In this review, we summarize that the representative dimers, such as B3C, provide neuroprotection against a variety of neurotoxins via multiple targets, including the inhibitions of N-methyl-d-aspartic acid receptor with pathological-activated potential, neuronal nitric oxide synthase, and β-amyloid cascades synergistically. More importantly, B3C might offer disease-modifying potentials by activating myocyte enhancer factor 2D transcription, inducing neuritogenesis, and promoting the expressions of neurotrophic factors in vitro and in vivo. Taken together, the novel dimers might offer synergistic disease-modifying effects, proving that dimerization might serve as one of the strategies to develop new generation of therapeutics for neurodegenerative disorders.

Neuroprotective Effect of Taurine against Cell Death, Glial Changes, and Neuronal Loss in the Cerebellum of Rats Exposed to Chronic-Recurrent Neuroinflammation Induced by LPS

The present study investigated the neuroprotective effect of taurine against the deleterious effects of chronic-recurrent neuroinflammation induced by LPS in the cerebellum of rats. Adult male Wistar rats were treated with taurine for 28 days. Taurine was administered at a dose of 30 or 100 mg/kg, by gavage. On days 7, 14, 21, and 28, the animals received LPS (250 μg/kg) intraperitoneally. The vehicle used was saline. The animals were divided into six groups: vehicle, taurine 30 mg/kg, taurine 100 mg/kg, LPS, LPS plus taurine 30 mg/kg, and LPS plus taurine 100 mg/kg. On day 29, the animals were euthanized, and the cerebellum was removed and prepared for immunofluorescence analysis using antibodies of GFAP, NeuN, CD11b, and cleaved caspase-3. LPS group showed a reduction in the immunoreactivity of GFAP in the arbor vitae and medullary center and of NeuN in the granular layer of the cerebellar cortex. LPS increased the immunoreactivity of CD11b in the arbor vitae and in the medullary center. Taurine protected against these effects induced by LPS in immunoreactivity of GFAP, NeuN, and CD11b, with the 100 mg/kg dose being the most effective. LPS induced an increase in the number of positive cleaved caspase-3 cells in the Purkinje cell layers, granular layer, arbor vitae, and medullary center. Taurine showed its antiapoptotic activity by reducing the cleaved caspase-3 cells in relation to the LPS group. Here, a potential neuroprotective role of taurine can be seen since this amino acid was effective in protecting the cerebellum of rats against cell death and changes in glial and neuronal cells in the face of chronic-recurrent neuroinflammation.

Alzheimer's Disease and microRNA-132: A Widespread Pathological Factor and Potential Therapeutic Target

Alzheimer's disease (AD) is a common neurodegenerative disease in the elderly and is the most common type of dementia. AD is mostly gradual onset, and involves slow, progressive mental decline, accompanied by personality changes; the incidence of AD gradually increases with age. The etiology of AD is unknown, although it is currently believed to be related to abnormal deposition of amyloid β-protein (Aβ) in the brain, hyperphosphorylation of microtubule-associated protein tau, and the release of various cytokines, complements, activators and chemokines by cells. MicroRNAs (miRNAs) are a class of highly conserved non-coding RNAs that regulate gene expression at the post-transcriptional level, and manipulate the functions of intracellular proteins and physiological processes. Emerging studies have shown that miRNA plays an important role in regulating AD-related genes. MiR-132 is known as "NeurimmiR" due to its involvement in numerous neurophysiological and pathological processes. Accumulating pre-clinical results suggest that miR-132 may be involved in the progression of Aβ and tau pathology. Moreover, clinical studies have indicated that decreased circulating miR-132 levels could be used a potential diagnostic biomarker in AD. Here, we review the pathogenic role of miR-132 activity in AD, and the potential of targeting miR-132 for developing future therapeutic strategies.

nAChRs gene expression and neuroinflammation in APPswe/PS1dE9 transgenic mouse

An evaluation of the APPswe/PS1dE9 transgenic AD mouse, presenting with the toxic Aβ1-42 deposition found in human AD, allowed us to characterize time-dependent changes in inflammatory and cholinergic markers present in AD. Astrogliosis was observed in cortex and hippocampus, with cellular loss occurring in the same areas in which Aβ plaques were present. In this setting, we found early significantly elevated levels of IL-1β and TNFα gene expression; with the hippocampus showing the highest IL-1β expression. To investigate the cholinergic anti-inflammatory pathway, the expression of nicotinic receptors (nAChRs) and cholinesterase enzymes also was evaluated. The anti-inflammatory nAChRα7, α4, and β2 were particularly increased at 6 months of age in the hippocampus, potentially as a strategy to counteract Aβ deposition and the ensuing inflammatory state. A time-dependent subunit switch to the α3β4 type occurred. Whether α3, β4 subunits have a pro-inflammatory or an inhibitory effect on ACh stimulation remains speculative. Aβ1-42 deposition, neuronal loss and increased astrocytes were detected, and a time-dependent change in components of the cholinergic anti-inflammatory pathway were observed. A greater understanding of time-dependent Aβ/nAChRs interactions may aid in defining new therapeutic strategies and novel molecular targets.

Anti-inflammatory effect of rosmarinic acid isolated from Blechnum brasiliense in adult zebrafish brain

Neuroinflammation has been associated to neurodegenerative disease development, with evidence suggesting that high levels of proinflammatory cytokines promote neuronal dysfunction and death. Therefore, it is necessary to study new compounds that may be used as adjuvant treatments of neurodegenerative diseases by attenuating the inflammatory response in the central nervous system (CNS). The aim of this study was to utilize the lipopolysaccharide (LPS) induction model of neuroinflammation to evaluate the modulation of inflammation by rosmarinic acid (RA) isolated from Blechnum brasiliense in adult zebrafish. First, we investigated the toxicity and antioxidant properties of fractionated B. brasiliense extract (ethyl acetate fraction- EAF) and the isolated RA in zebrafish embryos. Next, we developed a model of neuroinflammation induction by intraperitoneal (i.p.) injection of LPS to observe the RA modulation of proinflammatory cytokines. The median lethal concentration (LC50) calculated was 185.2 ± 1.24 μg/mL for the ethyl acetate fraction (EAF) and 296.0 ± 1.27 μM for RA. The EAF showed free radical inhibition ranging from 23.09% to 63.44% at concentrations of 10-250 μg/mL. The RA presented a concentration-dependent response ranging from 18.24% to 47.63% at 10-250 μM. Furthermore, the RA reduced LPS induction of TNF-α and IL-1β levels, with the greatest effect observed 6 h after LPS administration. Thus, the data suggested an anti-inflammatory effect of RA isolated from B. brasiliense and reinforced the utility of the new model of neuroinflammation to test the possible neuroprotective effects of novel drugs or compounds.

The Functional Roles and Applications of Immunoglobulins in Neurodegenerative Disease

Natural autoantibodies, immunoglobulins (Igs) that target self-proteins, are common in the plasma of healthy individuals; some of the autoantibodies play pathogenic roles in systemic or tissue-specific autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. Recently, the field of autoantibody-associated diseases has expanded to encompass neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), with related studies examining the functions of Igs in the central nervous system (CNS). Recent evidence suggests that Igs have various effects in the CNS; these effects are associated with the prevention of neurodegeneration, as well as induction. Here, we summarize the functional roles of Igs with respect to neurodegenerative disease (AD and PD), focusing on the target antigens and effector cell types. In addition, we review the current knowledge about the roles of these antibodies as diagnostic markers and immunotherapies.

Anti-Inflammatory and Anti-Migratory Activities of Isoquinoline-1-Carboxamide Derivatives in LPS-Treated BV2 Microglial Cells via Inhibition of MAPKs/NF-κB Pathway

Eleven novel isoquinoline-1-carboxamides (HSR1101~1111) were synthesized and evaluated for their effects on lipopolysaccharide (LPS)-induced production of pro-inflammatory mediators and cell migration in BV2 microglial cells. Three compounds (HSR1101~1103) exhibited the most potent suppression of LPS-induced pro-inflammatory mediators, including interleukin (IL)-6, tumor necrosis factor-alpha, and nitric oxide (NO), without significant cytotoxicity. Among them, only N-(2-hydroxyphenyl) isoquinoline-1-carboxamide (HSR1101) was found to reverse LPS-suppressed anti-inflammatory cytokine IL-10, so it was selected for further characterization. HSR1101 attenuated LPS-induced expression of inducible NO synthase and cyclooxygenase-2. Particularly, HSR1101 abated LPS-induced nuclear translocation of NF-κB through inhibition of IκB phosphorylation. Furthermore, HSR1101 inhibited LPS-induced cell migration and phosphorylation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase, and p38 MAPK. The specific MAPK inhibitors, U0126, SP600125, and SB203580, suppressed LPS-stimulated pro-inflammatory mediators, cell migration, and NF-κB nuclear translocation, indicating that MAPKs may be the upstream kinase of NF-κB signaling. Collectively, these results demonstrate that HSR1101 is a potent and promising compound suppressing LPS-induced inflammation and cell migration in BV2 microglial cells, and that inhibition of the MAPKs/NF-κB pathway mediates its anti-inflammatory and anti-migratory effects. Based on our findings, HSR1101 may have beneficial impacts on various neurodegenerative disorders associated with neuroinflammation and microglial activation.

Inhibitory Effects of Raw-Extract Centella asiatica (RECA) on Acetylcholinesterase, Inflammations, and Oxidative Stress Activities via In Vitro and In Vivo

Centella asiatica (C. asiatica) is one of the medicinal plants that has been reported to exert comprehensive neuroprotection in vitro and in vivo. In view of this, the present study was performed to investigate the effect of ethanolic extract of C. asiatica, designated as raw-extract of C. asiatica (RECA) in reducing the acetylcholinesterase (AChE), inflammations, and oxidative stress activities via both in vitro (SH-SY5Y and RAW 264.7 cells) and in vivo (Sprague Dawley rats). Quantitative high-performance liquid chromatography analysis reveals that RECA contains a significantly high proportion of glycosides than the aglycones with madecassoside as the highest component, followed by asiaticoside. Treatment of SH-SY5Y cells with RECA significantly reduced the AChE activity in a concentration-dependent manner with an IC₅₀ value of 31.09 ± 10.07 µg/mL. Furthermore, the anti-inflammatory and antioxidant effects of RECA were evaluated by lipopolysaccharides (LPS)-stimulated RAW 264.7 cells. Our results elucidated that treatment with RECA significantly suppressed the level of pro-inflammatory cytokine/mediators and oxidative stress released in a concentration-dependent manner. Interestingly, these patterns of inhibition were consistent as observed in the LPS-induced neuroinflammation Sprague Dawley rats’ model. The highest concentration used in the two models presented the most significant results. Herein, our findings strongly suggest that RECA may offer therapeutic potential for the treatment of Alzheimer’s disease through inhibiting the AChE, inflammation, and oxidative stress activities.

Inhibition of inflammatory mediators and cell migration by 1,2,3,4-tetrahydroquinoline derivatives in LPS-stimulated BV2 microglial cells via suppression of NF-κB and JNK pathway

Novel 1,2,3,4-tetrahydroquinoline derivatives with N-alkanoyl, N-benzoyl, or chlorobenzoyl substituents were designed and synthesized to inhibit nuclear factor-kappa B (NF-κB) known to be involved in the regulation of many immune and inflammatory responses. These compounds have been previously reported to inhibit NF-κB transcriptional activity in Raw 267.4 macrophage cells and exhibit cytotoxicities to several human cancer cell lines (Jo et al., ACS Med. Chem. Lett. 7 (2016) 385-390). Accumulating evidence indicated that NF-κB is also involved in neuroinflammation implicated in many neurodegenerative diseases. Thus, the present study investigated effects of 1,2,3,4-tetrahydroquinoline derivatives on LPS-stimulated inflammatory mediators and cell migration using BV2 microglial cells as a model. We found that seven compounds tested in this study inhibited LPS-induced pro-inflammatory mediators including interleukin-6, tumor necrosis factor-α, and nitric oxide in concentration-dependent manners. Among these compounds, ELC-D-2 exhibited the most potent inhibition without showing significant cytotoxicity. We also found that ELC-D-2 attenuated levels of LPS-induced inducible nitric oxide synthase and cyclooxygenase-2. Moreover, ELC-D-2 inhibited nuclear translocation of NF-κB by suppressing inhibitor of kappa Bα phosphorylation. Furthermore, ELC-D-2 inhibited LPS-induced activation of c-Jun N-terminal kinase (JNK), which was associated with suppression of inflammatory mediators and migration of LPS-treated BV2 cells. Collectively, our findings demonstrate that ELC-D-2 inhibits LPS-induced pro-inflammatory mediators and cell migration by suppressing NF-κB translocation and JNK phosphorylation in BV2 microglial cells. These results suggest that ELC-D-2 might have a beneficial impact on various brain disorders in which neuroinflammation involving microglial activation plays a crucial role in the pathogenesis of these diseases.

Comparison of the TLR4/NFκB and NLRP3 signalling pathways in major organs of the mouse after intravenous injection of lipopolysaccharide

Context: Lipopolysaccharide (LPS) is often used to induce immunoinflammatory reactions. TLR4/NFκB and NLRP3 signalling are major factors for inflammation. Dexamethasone (DXM) has an anti-immunoinflammatory effect. Objective: To investigate the inflammatory reaction in pathological changes of organs and the expression of inflammatory signalling during LPS infection. Materials and methods: ICR mice were divided into control group (n = 9), LPS group (n = 15) and LPS + DXM group (n = 14). LPS (10 mg/kg) was injected intravenously in LPS group and LPS + DXM group, normal saline was injected to the control group; DXM (0.5 mg/kg) was given by intragastric administration. 12 h after LPS, the blood was collected and the organs were isolated for biochemical analysis, protein expression, and morphological examination. Results: The results showed that BUN, Cre, ALT, AST in the LPS group increased distinctly by 81.42, 67.84, 40.53 and 36.05%, respectively, and CK, ALP, TP and ALB decreased by 71.37, 60.6, 12.57 and 19.73%, respectively, compared with the control group. In the morphologic observation, local necrosis in the liver, arterial vasodilation in the heart and kidney, alveolar secretions and pulmonary interstitial in the lungs, and mucosal shedding in the small and large intestines, the expression of TLR4-NFκB signalling were up-regulated distinctly whereas NLRP3 signalling was less broadly affected. DXM can decrease BUN and Cre, downregulate the expression of TLR4-NFκB signalling, but has no effect on the organ damage based on morphology. Conclusion: Acute injuries induced by LPS are extensive. The inflammatory damage in small and large intestines, liver and kidney was more severe than other organs. TLR4-NFκB signalling was the major response to LPS stress.

Using high-throughput sequencing to explore the anti-inflammatory effects of α-mangostin

Lipopolysaccharide (LPS) causes an inflammatory response, and α-mangostin (α-MG) is an ingredient of a Chinese herbal medicine with anti-inflammatory effects. We investigated the mechanism by which α-MG reduces LPS-stimulated IEC-6 cells inflammation. A genome-wide examination of control, LPS-stimulated, and α-MG-pretreated cells was performed with the Illumina Hiseq sequencing platform, and gene expression was verified with quantitative real-time PCR (qPCR). Among the 37,199 genes profiled, 2014 genes were regulated in the LPS group, and 475 genes were regulated in the α-MG group. GO enrichment and KEGG pathway analyses of the differentially expressed genes (DEGs) showed that they were mainly related to inflammation and oxidative stress. Based on the transcriptomic results, we constructed a rat model of inflammatory bowel disease (IBD) with LPS and investigated the effects of α-MG on NLRP3 inflammasomes. After LPS stimulation, the rat intestinal villi were significantly detached, with congestion and hemorrhage; the intestinal epithelial cell nuclei were deformed; and the mitochondria were swollen. However, after pretreatment with α-MG, the intestinal villus congestion and hemorrhage were reduced, the epithelial nuclei were rounded, and the mitochondrial morphology was intact. qPCR and western blotting were used to detect NLRP3, caspase 1, interleukin (IL)-18, and IL-1β expression at the gene and protein levels. Their expression increased at both the transcript and protein levels after LPS stimulation, whereas it decreased after pretreatment with α-MG. This study provides new methods and ideas for the treatment of inflammation. α-MG may have utility as a drug for intestinal inflammation.

Malva sylvestris extract alleviates the astrogliosis and inflammatory stress in LPS-induced depression mice

Neuro-inflammation is widely regarded as the inflammation occurred in the central nervous system (CNS) tissue, which authentically involved in the pathogenesis such as depression although the underlying mechanism remains to be elucidated. Malva sylvestris (MS), a plant widely used in traditional medicine to mitigate urological, respiratory and oral diseases, exhibits excellent anti-oxidative and anti-inflammatory properties. In the present study, we first used LPS-induced depression-like mice to evaluate the neuro-protective effect of MS extract. We found that, after 7 days' administration of MS extract, the cognitive impairment of LPS-induced depression-like mice was efficiently alleviated, evaluated by behavioral test including the Open field, Morris water maze (MWM), Elevated plus-maze (EPM) and Rota-rod test. Furthermore, we found that MS extract also inhibited the LPS-induced neuron apoptosis and astrogliosis both in the cortex and the CA1 region of hippocampus. Finally, our findings showed that the extract of MS relieved inflammatory stress induced by LPS injury, indicated by the down-regulation of IL-1β/6 and TNF-α, and up-regulation of IL-4 level both in vitro and in vivo. Collectively, MS extract exhibits neuro-protective activity in vivo, and therefore, it may be widely used for food to relieve the symptoms of neuro-inflammation associated disorders such as depression.

microRNA dysregulation in neurodegenerative diseases: A systematic review

While the root causes for individual neurodegenerative diseases are distinct, many shared pathological features and mechanisms contribute to neurodegeneration across diseases. Altered levels of microRNAs, small non-coding RNAs involved in post transcriptional regulation of gene expression, are reported for numerous neurodegenerative diseases. Yet, comparison between diseases to uncover commonly dysregulated microRNAs during neurodegeneration in general is lagging. We performed a systematic review of peer-reviewed publications describing differential microRNA expression in neurodegenerative diseases and related animal models. We compiled the results from studies covering the prevalent neurodegenerative diseases in the literature: Alzheimer's disease, amyotrophic lateral sclerosis, age-related macular degeneration, ataxia, dementia, myotonic dystrophy, epilepsy, glaucoma, Huntington's disease, multiple sclerosis, Parkinson's disease, and prion disorders. MicroRNAs which were dysregulated most often in these diseases and their models included miR-9-5p, miR-21-5p, the miR-29 family, miR-132-3p, miR-124-3p, miR-146a-5p, miR-155-5p, and miR-223-3p. Common pathways targeted by these predominant miRNAs were identified and revealed great functional overlap across diseases. We also identified a strong role for each microRNA in both the neural and immune components of diseases. microRNAs regulate broad networks of genes and identifying microRNAs commonly dysregulated across neurodegenerative diseases could cultivate novel hypotheses related to common molecular mechanisms underlying neurodegeneration.

Phytomedicine-Based Potent Antioxidant, Fisetin Protects CNS-Insult LPS-Induced Oxidative Stress-Mediated Neurodegeneration and Memory Impairment

Phytomedicine based natural flavonoids have potent antioxidant, anti-inflammatory, and neuroprotective activities against neurodegenerative diseases. The aim of the present study is to investigate the potent neuroprotective and antioxidant potential effects of fisetin (natural flavonoid) against central nervous system (CNS)-insult, lipopolysaccharide (LPS)-induced reactive oxygen species (ROS), neuroinflammation, neurodegeneration, and synaptic/memory deficits in adult mice. The mice were injected intraperitoneally (i.p.) with LPS (250 μg/kg/day for 1 week) and a fisetin dosage regimen (20 mg/kg/day i.p. for 2 weeks, 1 week pre-treated to LPS and 1 week co-treated with LPS). Behavioral tests, and biochemical and immunofluorescence assays were applied. Our results revealed that fisetin markedly abrogated the LPS-induced elevated ROS/oxidative stress and activated phosphorylated c-JUN N-terminal Kinase (p-JNK) in the adult mouse hippocampus. Fisetin significantly alleviated LPS-induced activated gliosis. Moreover, fisetin treatment inhibited LPS-induced activation of the inflammatory Toll-like Receptors (TLR4)/cluster of differentiation 14 (CD14)/phospho-nuclear factor kappa (NF-κB) signaling and attenuated other inflammatory mediators (tumor necrosis factor-α (TNF-α), interleukin-1 β (IL1-β), and cyclooxygenase (COX-2). Furthermore, immunoblotting and immunohistochemical results revealed that fisetin significantly reversed LPS-induced apoptotic neurodegeneration. Fisetin improved the hippocampal-dependent synaptic and memory functions in LPS-treated adult mice. In summary, our results strongly recommend that fisetin, a natural potent antioxidant, and neuroprotective phytomedicine, represents a promising, valuable, and therapeutic candidate for the prevention and treatment of neurodegenerative diseases.

Lipopolysaccharide-Induced Neuroinflammation as a Bridge to Understand Neurodegeneration

A large body of experimental evidence suggests that neuroinflammation is a key pathological event triggering and perpetuating the neurodegenerative process associated with many neurological diseases. Therefore, different stimuli, such as lipopolysaccharide (LPS), are used to model neuroinflammation associated with neurodegeneration. By acting at its receptors, LPS activates various intracellular molecules, which alter the expression of a plethora of inflammatory mediators. These factors, in turn, initiate or contribute to the development of neurodegenerative processes. Therefore, LPS is an important tool for the study of neuroinflammation associated with neurodegenerative diseases. However, the serotype, route of administration, and number of injections of this toxin induce varied pathological responses. Thus, here, we review the use of LPS in various models of neurodegeneration as well as discuss the neuroinflammatory mechanisms induced by this toxin that could underpin the pathological events linked to the neurodegenerative process.

Morin decreases cortical pyramidal neuron degeneration via inhibition of neuroinflammation in mouse model of schizophrenia

Neuroinflammation plays a prominent role in the pathophysiology and progression of schizophrenia. Thus, suppression of neuroinflammation may retard the progression of the disease. This study was designed to investigate whether morin, a bioactive compound with antipsychotic-like activity could reduce biomarkers of neuroinflammation and neurodegeneration in lipopolysaccharide (LPS)- and ketamine (KET)-induced schizophrenic-like behavior in mice. Animals were treated once daily intraperitoneally with morin (100 mg/kg), haloperidol (1 mg/kg), risperidone (0.5 mg/kg), or saline (10 mL/kg) in combination with LPS (0.1 mg/kg) for 14 consecutive days. However, from days 8-14, overt schizophrenia-like episode was produced with i.p. injection of KET (20 mg/kg) once daily. Schizophrenic-like behaviors: positive (open-field test), negative (social-interaction and social-memory tests) and cognitive (Y-maze test) symptoms were assessed on day 14. Thereafter, the levels and expressions of biomarkers of neuroinflammation were estimated in the striatum (ST), prefrontal cortex (PFC) and hippocampus (HC) using spectrophotometry, ELISA and immunohistochemistry. The effects of morin on cortical pyramidal neurons were estimated using Golgi-impregnation staining technique. LPS in combination with KET significantly (p < 0.05) induced schizophrenia-like behaviors, which was attenuated by morin. Morin significantly (p < 0.05) decreased tumor necrosis factor-α, interleukine-6 levels and myeloperoxidase activity in the ST, PFC and HC of mice treated with LPS + KET. Moreover, morin reduced regional brain expressions of cyclooxygenase-2, inducible nitric oxide synthase and nuclear factor kappa-B, and also rescued loss of pyramidal neurons in the PFC. Taken together, these findings suggest that morin reduces schizophrenic-like symptoms induced by LPS + KET via mechanisms related to inhibition of the release of pro-inflammatory mediators and suppression of degeneration of cortical pyramidal neurons in mice.

Berberine ameliorates lipopolysaccharide-induced learning and memory deficit in the rat: insights into underlying molecular mechanisms

Systemic lipopolysaccharide (LPS) triggers neuroinflammation with consequent development of behavioral and cognitive deficits. Neuroinflammation plays a crucial role in the pathogenesis of neurodegenerative disorders including Alzheimer's disease (AD). Berberine is an isoquinoline alkaloid in Berberis genus with antioxidant and anti-inflammatory property and protective effects in neurodegenerative disorders. In this research, beneficial effect of this alkaloid against LPS-induced cognitive decline was assessed in the adult male rats. LPS was intraperitoneally administered at a dose of 1 mg/kg to induce neuroinflammation and berberine was given via gavage at doses of 10 or 50 mg/kg, one h after LPS, for 7 days. Treatment of LPS group with berberine at a dose of 50 mg/kg (but not at a dose of 10 mg/kg) improved spatial recognition memory in Y maze, performance in novel object recognition task (NORT), and prevented learning and memory dysfunction in passive avoidance tasks. Furthermore, berberine lowered hippocampal activity of acetylcholinesterase (AChE), malondialdehyde (MDA), protein carbonyl, activity of caspase 3, and DNA fragmentation and improved antioxidant capacity through enhancing glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase, and glutathione (GSH). Besides, berberine attenuated inflammation-related indices, as was evident by lower levels of nuclear factor-kappa B (NF-κB), toll-like receptor 4 (TLR4), tumor necrosis factor α (TNFα), and interleukin 6 (IL-6). Berberine also appropriately restored hippocampal 3-nitrotyrosine (3-NT), cyclooxygenase 2 (Cox 2), glial fibrillary acidic protein (GFAP), sirtuin 1, and mitogen-activated protein kinase (p38 MAPK) with no significant alteration of brain-derived neurotrophic factor (BDNF). In summary, berberine could partially ameliorate LPS-induced cognitive deficits via partial suppression of apoptotic cascade, neuroinflammation, oxido-nitrosative stress, AChE, MAPK, and restoration of sirtuin 1.

Glucocorticoid Induced Leucine Zipper in Lipopolysaccharide Induced Neuroinflammation

Glucocorticoids (GCs) are steroid hormones secreted as the end-product of the neuroendocrine stress cascade. Both absence and elevated GC mediate neurotoxic responses, suggesting that a narrow window ranging from physiological to slightly high GC mediate protective responses. The beneficial effects of GC are attributed to the transactivation of regulatory proteins and inhibition mediated by glucocorticoid receptor (GR) interactions with other co-factors. The glucocorticoid induced leucine zipper (GILZ) is a gene strongly upregulated by GC and mediates many of the anti-inflammatory and anti-proliferative effects of GC. Although GILZ is constitutively expressed in many tissues including the brain, the expression has been shown to occur with varying dynamics suggesting that the local milieu modulates its expression with consequent effects on cellular responses. Here we investigated the expression profile of GILZ in lipopolysaccharide (LPS) mediated neuroinflammation model of Alzheimer's disease (AD). Our data suggest that the GILZ expression is downregulated in neuroinflammation correlating inversely with the pro-inflammatory cytokines and innate immune responses.

Trigonelline mitigates lipopolysaccharide-induced learning and memory impairment in the rat due to its anti-oxidative and anti-inflammatory effect

Brain inflammation is associated with cognitive dysfunction, especially in elderly. Trigonelline is a plant alkaloid and a major component of coffee and fenugreek with anti-diabetic, antioxidant, anti-inflammatory, and neuroprotective effects. In this study, the beneficial effect of trigonelline against lipopolysaccharide (LPS)-induced cognitive decline was assessed in the rat. LPS was injected i.p. at a dose of 500 μg/kg to induce neuroinflammation and trigonelline was administered p.o. at doses of 20, 40, or 80 mg/kg/day 1 h after LPS that continued for one week. Trigonelline-treated LPS-challenged rats showed improved spatial recognition memory in Y maze, discrimination ratio in novel object discrimination test, and retention and recall in passive avoidance paradigm. Additionally, trigonelline lowered hippocampal malondialdehyde (MDA) and acetylcholinesterase (AChE) activity and improved superoxide dismutase (SOD), catalase, and glutathione (GSH). Furthermore, trigonelline depressed hippocampal nuclear factor-kappaB (NF-κB), toll-like receptor 4 (TLR4), and tumor necrosis factor α (TNF α) in LPS-challenged rats. All of the effects of trigonelline followed a dose-dependent pattern and in some aspects, it acted even better than the routinely-used anti-inflammatory drug dexamethasone. Collectively, trigonelline is capable to diminish LPS-induced cognitive decline via suppression of hippocampal oxidative stress and inflammation and appropriate modulation of NF-κB/TLR4 and AChE activity.

Mitochondrial Nicotinic Acetylcholine Receptors Support Liver Cells Viability After Partial Hepatectomy

Nicotinic acetylcholine receptors (nAChRs) expressed on the cell plasma membrane are ligand-gated ion channels mediating fast synaptic transmission, regulating neurotransmitter and cytokine release and supporting the viability of many cell types. The nAChRs expressed in mitochondria regulate the release of pro-apoptotic factors, like cytochrome c, in ion channel-independent manner. Here we show that α3β2, α7β2, and α9α10 nAChR subtypes are up-regulated in rat liver mitochondria 3–6 h after partial hepatectomy resulting in increased sustainability of mitochondria to apoptogenic effects of Ca²⁺ and H₂O₂. In contrast, laparotomy resulted in down-regulation of all nAChR subunits, except α9, and decreased mitochondria sustainability to apoptogenic effects of Ca²⁺ and H₂O₂. Experiments performed in liver mitochondria from α3+/-, α7-/-, β4-/-, α7β2-/-, or wild-type C57Bl/6J mice demonstrated that the decrease of α3 or absence of α7 or α7/β2 subunits in mitochondria is compensated with β4 and α9 subunits, which could be found in α3β4, α4β4, α9β4, and α9α10 combinations. Mitochondria from knockout mice maintained their sustainability to Ca²⁺ but were differently regulated by nAChR subtype-specific ligands: PNU-282987, methyllycaconitine, dihydro-β-erythroidine, α-conotoxin MII, and α-conotoxin PeIA. It is concluded that mitochondrial nAChRs play an important role in supporting the viability of hepatic cells and, therefore, may be a pharmacological target for pro-survival therapy. The concerted action of multiple nAChR subtypes controlling either CaKMII- or Src-dependent signaling pathways in mitochondria ensures a reliable protection against apoptogenic factors of different nature.

Deoxyelephantopin ameliorates lipopolysaccharides (LPS)-induced memory impairments in rats: Evidence for its anti-neuroinflammatory properties

AIM

Neuroinflammation is a critical pathogenic mechanism of most neurodegenerative disorders especially, Alzheimer's disease (AD). Lipopolysaccharides (LPS) are known to induce neuroinflammation which is evident from significant upsurge of pro-inflammatory mediators in in vitro BV-2 microglial cells and in vivo animal models. In present study, we investigated anti-neuroinflammatory properties of deoxyelephantopin (DET) isolated from Elephantopus scaber in LPS-induced neuroinflammatory rat model.

MATERIALS AND METHODS

In this study, DET (0.625. 1.25 and 2.5 mg/kg, i.p.) was administered in rats for 21 days and those animals were challenged with single injection of LPS (250 μg/kg, i.p.) for 7 days. Cognitive and behavioral assessment was carried out for 7 days followed by molecular assessment on brain hippocampus. Statistical significance was analyzed with one-way analysis of variance followed by Dunnett's test to compare the treatment groups with the control group.

KEY FINDINGS

DET ameliorated LPS-induced neuroinflammation by suppressing major pro-inflammatory mediators such as iNOS and COX-2. Furthermore, DET enhanced the anti-inflammatory cytokines and concomitantly suppressed the pro-inflammatory cytokines and chemokine production. DET treatment also reversed LPS-induced behavioral and memory deficits and attenuated LPS-induced elevation of the expression of AD markers. DET improved synaptic-functionality via enhancing the activity of pre- and post-synaptic markers, like PSD-95 and SYP. DET also prevented LPS-induced apoptotic neurodegeneration via inhibition of PARP-1, caspase-3 and cleaved caspase-3.

SIGNIFICANCE

Overall, our studies suggest DET can prevent neuroinflammation-associated memory impairment and neurodegeneration and it could be developed as a therapeutic agent for the treatment of neuroinflammation-mediated and neurodegenerative disorders, such as AD.

Direct and indirect pro-inflammatory cytokine response resulting from TC-83 infection of glial cells

Venezuelan equine encephalitis virus (VEEV) is a neurotropic arbovirus that is highly infectious as an aerosol and can result in an encephalitic phenotype in infected individuals. VEEV infections are known to be associated with robust inflammation that eventually contributes to neurodegenerative phenotypes. In this study, we utilize the TC-83 strain of VEEV, which is known to induce the expression of IL-6, IL-8, and other pro-inflammatory cytokines. We had previously demonstrated that TC-83 infection resulted in changes in mitochondrial function, eventually resulting in mitophagy. In this manuscript, we provide data that links upstream mitochondrial dysfunction with downstream pro-inflammatory cytokine production in the context of microglia and astrocytoma cells. We also provide data on the role of bystander cells, which significantly contribute to the overall inflammatory load. Use of a mitochondrial-targeted antioxidant, mitoquinone mesylate, greatly reduced the inflammatory cytokine load and ameliorated bystander cell inflammatory responses more significantly than a broad-spectrum anti-inflammatory compound (BAY 11-7082). Our data suggest that the inflammatory mediators, especially IL-1β, may prime naïve cells to infection and lead to increased infection rates in microglial and astrocytoma cells. Cumulatively, our data suggest that the interplay between mitochondrial dysfunction and inflammatory events elicited in a neuronal microenvironment during a TC-83 infection may contribute to the spread of infection.

Pharmacologic activation of cholinergic alpha7 nicotinic receptors mitigates depressive-like behavior in a mouse model of chronic stress

Background

It has been shown that chronic stress-induced depression is associated with exaggerated inflammatory response in the brain. Alpha7 nicotinic acetylcholine receptors (α7nAChRs) regulate the cholinergic anti-inflammatory pathway, but the role of cholinergic signaling and α7nAChR in chronic stress has not yet been examined.

Methods

In this study, we used a well-documented model of depression in which mice were exposed to 6 h of restraint stress for 21 consecutive days. Components of cholinergic signaling and TLR4 signaling were analyzed in the hippocampus. The main targets of neuroinflammation and neuronal damage were also evaluated after a series of tests for depression-like behavior.

Results

Chronic restraint stress (CRS) induced alterations in components of central cholinergic signaling in hippocampus, including increases in choline acetyltransferase protein expression and decreases in nuclear STAT3 signaling. CRS also increased TLR4 signaling activity, interleukin-1β, and tumor necrosis factor-α expression, microglial activation, and neuronal morphologic changes. Cholinergic stimulation with the α7nAChR agonist DMXBA significantly alleviated CRS-induced depressive-like behavior, neuroinflammation, and neuronal damage, but these effects were abolished by the selective α7nAChR antagonist α-bungarotoxin. Furthermore, activation of α7nAChRs restored the central cholinergic signaling function, inhibited TLR4-mediated inflammatory signaling and microglial activity, and increased the number of regulatory T cells in the hippocampus.

Conclusions

These findings provide evidence that α7nAChR activation mitigates CRS-induced neuroinflammation and cell death, suggesting that α7nAChRs could be a new therapeutic target for the prevention and treatment of depression.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1007-2) contains supplementary material, which is available to authorized users.

N-Stearoylethanolamine protects the brain and improves memory of mice treated with lipopolysaccharide or immunized with the extracellular domain of α7 nicotinic acetylcholine receptor

Neuroinflammation is an important risk factor for neurodegenerative disorders like Alzheimer's disease. Nicotinic acetylcholine receptors of α7 subtype (α7 nAChRs) regulate inflammatory processes in various tissues, including the brain. N-stearoylethanolamine (NSE) is a biologically active cell membrane component with anti-inflammatory and membrane-protective properties. Previously we found that mice injected with bacterial lipopolysaccharide (LPS) or immunized with recombinant extracellular domain (1-208) of α7 nAChR subunit possessed decreased α7 nAChR levels, accumulated pathogenic amyloid-beta peptide Aβ(1-42) in the brain and demonstrated impaired episodic memory compared to non-treated mice. Here we studied the effect of NSE on behavior and brain components of LPS- treated or α7(1-208)-immunized mice. NSE, given per os, non-significantly decreased LPS-stimulated interleukin-6 elevation in the brain, slowed down the α7(1-208)-specific IgG antibody production and prevented the antibody penetration into the brain of mice. NSE prevented the loss of α7 nAChRs and accumulation of α7-bound Aβ(1-42) in the brain and brain mitochondria of LPS-treated or α7(1-208)-immunized mice and supported mitochondria resistance to apoptosis by attenuating Ca²⁺-stimulated cytochrome c release. Finally, NSE significantly improved episodic memory of mice impaired by either LPS treatment or immunization with α7(1-208). The results of our study demonstrate a therapeutic potential of NSE for prevention of cognitive disfunction caused by neuroinflammation or autoimmune reaction that allows suggesting this drug as a candidate for the treatment or prophylaxis of Alzheimer's pathology.

Microbiome-Derived Lipopolysaccharide Enriched in the Perinuclear Region of Alzheimer's Disease Brain

Abundant clinical, epidemiological, imaging, genetic, molecular, and pathophysiological data together indicate that there occur an unusual inflammatory reaction and a disruption of the innate-immune signaling system in Alzheimer’s disease (AD) brain. Despite many years of intense study, the origin and molecular mechanics of these AD-relevant pathogenic signals are still not well understood. Here, we provide evidence that an intensely pro-inflammatory bacterial lipopolysaccharide (LPS), part of a complex mixture of pro-inflammatory neurotoxins arising from abundant Gram-negative bacilli of the human gastrointestinal (GI) tract, are abundant in AD-affected brain neocortex and hippocampus. For the first time, we provide evidence that LPS immunohistochemical signals appear to aggregate in clumps in the parenchyma in control brains, and in AD, about 75% of anti-LPS signals were clustered around the periphery of DAPI-stained nuclei. As LPS is an abundant secretory product of Gram-negative bacilli resident in the human GI-tract, these observations suggest (i) that a major source of pro-inflammatory signals in AD brain may originate from internally derived noxious exudates of the GI-tract microbiome; (ii) that due to aging, vascular deficits or degenerative disease these neurotoxic molecules may “leak” into the systemic circulation, cerebral vasculature, and on into the brain; and (iii) that this internal source of microbiome-derived neurotoxins may play a particularly strong role in shaping the human immune system and contributing to neural degeneration, particularly in the aging CNS. This “Perspectives” paper will further highlight some very recent developments that implicate GI-tract microbiome-derived LPS as an important contributor to inflammatory-neurodegeneration in the AD brain.

[Choline improves lipopolysaccharide-induced central nervous system inflammatory response and cognitive dysfunction in mice]

OBJECTIVE

To assess the effect of choline in ameliorating lipopolysaccharide (LPS)-induced central nervous system inflammation and cognitive deficits in mice and explore the underlying mechanism.

METHODS

Seventy-two mice were randomized into saline control group, LPS group, choline intervention group and choline control group. In the latter two groups, the mice received pretreatment with intraperitoneal injections of choline (40 mg/kg, 3 times daily for 3 consecutive days) prior to microinjection of LPS into the lateral cerebral ventricle to induce central nervous system inflammation; in saline and LPS groups, the mice were pretreated with saline in the same manner before intraventicular injection of artificial cerebrospinal fluid. Choline treatment was administered in the mice till the end of the experiment. The locomotor activity and spatial learning and memory capacity of the mice were examined. The expressions of Iba1 protein and proinflammatory cytokines (TNF-α and IL-β) I the hippocampal dentate gyrus, and the expressions of α 7nAchR, p38 MAPK and phosphorylated p38 MAPK in the hippocampus of the mice were detected.

RESULTS

Water maze test showed that compared with the saline control group, the mice in LPS group exhibited significantly reduced platform crossings (P<0.05), which was significantly increased by choline pretreatment (P<0.05). The mice pretreated with LPS expressed obviously increased levels of IBA-1 protein, TNF-α, and IL-1β in the hippocampus (P<0.01), and choline pretreatment significantly lowered the expressions of IBA-1 protein and IL-1β (P<0.05). The phosphorylation level of p38 MAPK increased significantly after LPS pretreatment (P<0.05), and was reduced by choline pretreatment (P<0.05); α 7nAchR expression increased significantly in choline intervention group as compared with that in the other 3 groups (P<0.05).

CONCLUSION

Choline can probably antagonize LPS-induced hippocampal p38 MAPK phosphorylation in mice via the α 7nAchR signaling pathway to protective against LPS-induced neuroinflammation and cognitive impairment in mice.

Autophagy Plays an Important Role in Anti-inflammatory Mechanisms Stimulated by Alpha7 Nicotinic Acetylcholine Receptor

Alpha7 nicotinic acetylcholine receptor (α7nAChR) has been reported to alleviate neuroinflammation. Here, we aimed to determine the role of autophagy in α7nAChR-mediated inhibition of neuroinflammation and its underlying mechanism. Experimental autoimmune encephalomyelitis (EAE) mice and lipopolysaccharide-stimulated BV2 microglia were used as in vivo and in vitro models of neuroinflammation, respectively. The severity of EAE was evaluated with neurological scoring. Autophagy-related proteins (Beclin 1, LC3-II/I, p62/SQSTM1) were detected by immunoblot. Autophagosomes were observed using transmission electron microscopy and tandem fluorescent mRFP-GFP-LC3 plasmid was applied to test autophagy flux. The mRNA levels of interleukin-6 (IL-6), IL-1β, IL-18, and tumor necrosis factor-α (TNF-α) were detected by real-time PCR. We used 3-methyladenine (3-MA) and autophagy-related gene 5 small interfering RNA (Atg5 siRNA) to block autophagy in vivo and in vitro, respectively. Activating α7nAChR with PNU282987 ameliorates EAE severity and spinal inflammatory infiltration in EAE mice. PNU282987 treatment also enhanced monocyte/microglia autophagy (Beclin 1, LC3-II/I ratio, p62/SQSTM1, colocalization of CD45- or CD68-positive cells with LC3) both in spinal cord and spleen from EAE mice. The beneficial effects of PNU282987 on EAE mice were partly abolished by 3-MA, an autophagy inhibitor. In vitro, PNU282987 treatment increased autophagy and promoted autophagy flux. Blockade of autophagy by Atg5 siRNA or bafilomycin A1 attenuated the inhibitory effect of PNU282987 on IL-6, IL-1β, IL-18, and TNF-α mRNA. Our results demonstrate for the first time that activating α7nAChR enhances monocyte/microglia autophagy, which suppresses neuroinflammation and thus plays an alleviative role in EAE.

Antisense miR-132 blockade via the AChE-R splice variant mitigates cortical inflammation

MicroRNA (miR)-132 brain-to-body messages suppress inflammation by targeting acetylcholinesterase (AChE), but the target specificity of 3'-AChE splice variants and the signaling pathways involved remain unknown. Using surface plasmon resonance (SPR), we identified preferential miR-132 targeting of soluble AChE-R over synaptic-bound AChE-S, potentiating miR-132-mediated brain and body cholinergic suppression of pro-inflammatory cytokines. Inversely, bacterial lipopolysaccharide (LPS) reduced multiple miR-132 targets, suppressed AChE-S more than AChE-R and elevated inflammatory hallmarks. Furthermore, blockade of peripheral miR-132 by chemically protected AM132 antisense oligonucleotide elevated muscle AChE-R 10-fold over AChE-S, and cortical miRNA-sequencing demonstrated inverse brain changes by AM132 and LPS in immune-related miRs and neurotransmission and cholinergic signaling pathways. In neuromuscular junctions, AM132 co-elevated the nicotinic acetylcholine receptor and AChE, re-balancing neurotransmission and reaching mild muscle incoordination. Our findings demonstrate preferential miR-132-induced modulation of AChE-R which ignites bidirectional brain and body anti-inflammatory regulation, underscoring splice-variant miR-132 specificity as a new complexity level in inflammatory surveillance.

Investigations on 16-Arylideno Steroids as a New Class of Neuroprotective Agents for the Treatment of Alzheimer's and Parkinson's Diseases

Neuroinflammatory mechanisms mediated by activated glial and cytokines (TNF-α, IL-1β) might contribute to neuronal degeneration leading to Alzheimer's (AD) and Parkinson's disease (PD). Lipopolysaccharide (LPS) is an inflammogen derived from the cell wall of Gram-negative bacteria, which promotes neuroinflammation and subsequent neurodegeneration. Dehydroepiandrosterone (DHEA) and testosterone have been reported as neuroprotective steroids useful for the treatment of various neurodegenerative disorders. In the present study, several 16-arylidene steroidal derivatives have been evaluated as neuroprotective agents in LPS-treated animal models. It was observed that 16-arylidene steroidal derivatives 1a-d and 6a-h considerably improve LPS-induced learning, memory, and movement deficits in animal models. Biochemical estimations of brain serum of treated animals revealed suppression of oxidative and nitrosative stress, acetylcholinesterase activity, and reduction in TNF-α levels, which were induced through LPS mediated neuroinflammatory mechanisms leading to neurodegeneration of brain. Of all the steroidal derivatives, 16-(4-pyridylidene) steroid 1c and its 4-aza analogue 6c were found to be the most active neuroprotective agents and produced effects comparable to standard drug celecoxib at a much lower dose and better than dexamethasone at the same dose in terms of behavioral, biochemical, and molecular aspects.