Inflammasomes as therapeutic targets for Alzheimer's disease

Chronic kidney disease leads to microglial potassium efflux and inflammasome activation in the brain

Cognitive impairment is common in extracerebral diseases such as chronic kidney disease (CKD). Kidney transplantation reverses cognitive impairment, indicating that cognitive impairment driven by CKD is therapeutically amendable. However, we lack mechanistic insights allowing development of targeted therapies. Using a combination of mouse models (including mice with neuron-specific IL-1R1 deficiency), single cell analyses (single-nuclei RNA-sequencing and single-cell thallium autometallography), human samples and in vitro experiments we demonstrate that microglia activation impairs neuronal potassium homeostasis and cognition in CKD. CKD disrupts the barrier of brain endothelial cells in vitro and the blood-brain barrier in vivo, establishing that the uremic state modifies vascular permeability in the brain. Exposure to uremic conditions impairs calcium homeostasis in microglia, enhances microglial potassium efflux via the calcium-dependent channel KCa3.1, and induces p38-MAPK associated IL-1β maturation in microglia. Restoring potassium homeostasis in microglia using a KCa3.1-specific inhibitor (TRAM34) improves CKD-triggered cognitive impairment. Likewise, inhibition of the IL-1β receptor 1 (IL-1R1) using anakinra or genetically abolishing neuronal IL-1R1 expression in neurons prevent CKD-mediated reduced neuronal potassium turnover and CKD-induced impaired cognition. Accordingly, in CKD mice, impaired cognition can be ameliorated by either preventing microglia activation or inhibiting IL-1R-signaling in neurons. Thus, our data suggest that potassium efflux from microglia triggers their activation, which promotes microglia IL-1β release and IL-1R1-mediated neuronal dysfunction in CKD. Hence, our study provides new mechanistic insight into cognitive impairment in association with CKD and identifies possible new therapeutic approaches.

Inflammation and DNA methylation in Alzheimer's disease: mechanisms of epigenetic remodelling by immune cell oxidants in the ageing brain

Alzheimer's disease is a neurodegenerative disease involving memory impairment, confusion, and behavioural changes. The disease is characterised by the accumulation of amyloid beta plaques and neurofibrillary tangles in the brain, which disrupt normal neuronal function. There is no known cure for Alzheimer's disease and due to increasing life expectancy, occurrence is projected to rise over the coming decades. The causes of Alzheimer's disease are multifactorial with inflammation, oxidative stress, genetic and epigenetic variation, and cerebrovascular abnormalities among the strongest contributors. We review the current literature surrounding inflammation and epigenetics in Alzheimer's disease, with a focus on how oxidants from infiltrating immune cells have the potential to alter DNA methylation profiles in the ageing brain.

Broad-spectrum inflammasome inhibition by thiomuscimol

Inflammasome formation, arising from pathogen or internal activating signals, is a key step in canonical pyroptosis, a gasdermin-mediated inflammatory cell death. Inhibition of pyroptosis has great clinical relevance due to its involvement in many different disease states. Current inhibitors of pyroptosis either only inhibit the final lytic step, which still allows inflammatory signal release, or only inhibit a single inflammasome, which does not account for inherent redundancy in activation of other inflammatory pathways. Here, we show that thiomuscimol, a structural analog of the lysis inhibitor muscimol, exhibits unique inhibitory activity upstream of plasma membrane rupture. We find that thiomuscimol inhibits inflammasome formation, as well as downstream caspase-1 activation, initiated by multiple pyroptotic signals, regardless of whether NLR recruitment of caspase-1 to the inflammasome relies on the ASC adapter protein. The ability of thiomuscimol to block multiple different inflammasomes opens the door for development of therapeutics with increased applications to broadly inhibit pyroptosis in multiple pathological settings.

NLRP3/1-mediated pyroptosis: beneficial clues for the development of novel therapies for Alzheimer's disease

The inflammasome is a multiprotein complex involved in innate immunity that mediates the inflammatory response leading to pyroptosis, which is a lytic, inflammatory form of cell death. There is accumulating evidence that nucleotide-binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome-mediated microglial pyroptosis and NLRP1 inflammasome-mediated neuronal pyroptosis in the brain are closely associated with the pathogenesis of Alzheimer's disease. In this review, we summarize the possible pathogenic mechanisms of Alzheimer's disease, focusing on neuroinflammation. We also describe the structures of NLRP3 and NLRP1 and the role their activation plays in Alzheimer's disease. Finally, we examine the neuroprotective activity of small-molecule inhibitors, endogenous inhibitor proteins, microRNAs, and natural bioactive molecules that target NLRP3 and NLRP1, based on the rationale that inhibiting NLRP3 and NLRP1 inflammasome-mediated pyroptosis can be an effective therapeutic strategy for Alzheimer's disease.

NLRP3/1-mediated pyroptosis: beneficial clues for the development of novel therapies for Alzheimer's disease

The inflammasome is a multiprotein complex involved in innate immunity that mediates the inflammatory response leading to pyroptosis, which is a lytic, inflammatory form of cell death. There is accumulating evidence that nucleotide-binding domain and leucine-rich repeat pyrin domain containing 3 (NLRP3) inflammasome-mediated microglial pyroptosis and NLRP1 inflammasome-mediated neuronal pyroptosis in the brain are closely associated with the pathogenesis of Alzheimer's disease. In this review, we summarize the possible pathogenic mechanisms of Alzheimer's disease, focusing on neuroinflammation. We also describe the structures of NLRP3 and NLRP1 and the role their activation plays in Alzheimer's disease. Finally, we examine the neuroprotective activity of small-molecule inhibitors, endogenous inhibitor proteins, microRNAs, and natural bioactive molecules that target NLRP3 and NLRP1, based on the rationale that inhibiting NLRP3 and NLRP1 inflammasome-mediated pyroptosis can be an effective therapeutic strategy for Alzheimer's disease.

SARS-CoV-2 spike S1 protein induces microglial NLRP3-dependent neuroinflammation and cognitive impairment in mice

Cognitive impairment is often found at the acute stages and sequelae of coronavirus disease 2019 (COVID-19), and the underlying mechanisms remain unclear. The S1 protein from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might be a cause of cognitive impairment associated with COVID-19. The nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome and neuroinflammation play important roles in Alzheimer's disease (AD) with cognitive impairment. However, their roles remain unknown in COVID-19 with cognitive impairment. We stimulated BV2 cells with S1 protein in vitro and injected the hippocampi of wild-type (WT) mice, NLRP3 knockout (KO), and microglia NLRP3 KO mice in vivo with S1 protein to induce cognitive impairment. We assessed exploratory behavior as associative memory using novel object recognition and Morris water maze tests. Neuroinflammation was analyzed using immunofluorescence and western blotting to detect inflammatory markers. Co-localized NLRP3 and S1 proteins were investigated using confocal microscopy. We found that S1 protein injection led to cognitive impairment, neuronal loss, and neuroinflammation by activating NLRP3 inflammation, and this was reduced by global NLRP3 KO and microglia NLRP3 KO. Furthermore, TAK 242, a specific inhibitor of Toll-like receptor-4, resulted in a significant reduction in NLRP3 and pro-IL-1β in BV2 cells with S1 protein stimulation. These results reveal a distinct mechanism through which the SARS-CoV-2 spike S1 protein promotes NLRP3 inflammasome activation and induces excessive inflammatory responses.

C9orf72 dipeptides activate the NLRP3 inflammasome

Frontotemporal dementia and amyotrophic lateral sclerosis are neurodegenerative diseases with considerable clinical, genetic and pathological overlap. The most common cause of both diseases is a hexanucleotide repeat expansion in C9orf72. The expansion is translated to produce five toxic dipeptides, which aggregate in patient brain. Neuroinflammation is a feature of frontotemporal dementia and amyotrophic lateral sclerosis; however, its causes are unknown. The nod-like receptor family, pyrin domain-containing 3 inflammasome is implicated in several other neurodegenerative diseases as a driver of damaging inflammation. The inflammasome is a multi-protein complex which forms in immune cells in response to tissue damage, pathogens or aggregating proteins. Inflammasome activation is observed in models of other neurodegenerative diseases such as Alzheimer's disease, and inflammasome inhibition rescues cognitive decline in rodent models of Alzheimer's disease. Here, we show that a dipeptide arising from the C9orf72 expansion, poly-glycine-arginine, activated the inflammasome in microglia and macrophages, leading to secretion of the pro-inflammatory cytokine, interleukin-1β. Poly-glycine-arginine also activated the inflammasome in organotypic hippocampal slice cultures, and immunofluorescence imaging demonstrated formation of inflammasome specks in response to poly-glycine-arginine. Several clinically available anti-inflammatory drugs rescued poly-glycine-arginine-induced inflammasome activation. These data suggest that C9orf72 dipeptides contribute to the neuroinflammation observed in patients, and highlight the inflammasome as a potential therapeutic target for frontotemporal dementia and amyotrophic lateral sclerosis.

Dexmedetomidine Alleviates Acute Stress-Induced Acute Kidney Injury by Attenuating Inflammation and Oxidative Stress via Inhibiting the P2X7R/NF-κB/NLRP3 Pathway in Rats

This study aimed to investigate the potential protective effects of Dexmedetomidine (DEX) against acute kidney injury (AKI) induced by acute stress (AS). Wistar rats were divided into five groups: Control, DEX, AS, AS + DEX, and AS + A438079. The results showed that AS led to AKI by increasing inflammatory biomarkers and oxidative stress-related indicators. The acute stress model in rats was successfully established. Renal function, histopathology, oxidative stress, and inflammation were assessed. Localization of P2X7 receptor (P2X7R) was determined by immunofluorescence. Additionally, the key inflammatory proteins of the P2X7R/NF-κB/NLRP3 signaling pathway were measured by Western blotting. DEX significantly improved kidney function, alleviated kidney injury, and reduced oxidative stress and inflammation. DEX inhibited the activation of the P2X7R, decreased the expression of NF-κB, NLRP3 inflammasome, and Caspase-1, and inhibited the expression of interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα). Furthermore, DEX also alleviated AS-induced AKI by inhibiting the excessive production of reactive oxygen species (ROS) and reducing oxidative stress. In conclusion, DEX attenuates AS-induced AKI by mitigating inflammation and oxidative stress through the inhibition of the P2X7R/NF-κB/NLRP3 pathway in rats.

Betanin combined with virgin coconut oil inhibits neuroinflammation in aluminum chloride-induced toxicity in rats by regulating NLRP3 inflammasome

Background and aim

Activating NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) is crucial in the pathogenesis of Alzheimer's disease (AD). A multimodal treatment intervention is the most feasible way to alter the course of AD progression. Hence, the current study was conducted to study the combination of betanin (BET) and virgin coconut oil (VCO) on NLRP3 regulation in aluminum chloride-induced AD in Wistar rats.

Experimental procedure

BET (100,200 mg/kg) and VCO (1, 5 g/kg) alone and in combination (BET 100 mg/kg + VCO 1 g/kg and BET 200 mg/kg + VCO 5 g/kg) were given orally for 42 days. On day 21 and 42nd, the behavioral test was performed to check the animal's cognition. Acetylcholinesterase (AChE) activity, oxidative stress markers, estimation of NLRP3 and IL-1β, and histological examinations were conducted in the hippocampus (H) and cortex (C).

Results and conclusion

Treatment with BET and VCO alone or combined improved behavioral characteristics (MWM and PA p < 0.0001; EPM p = 0.5184), inhibited AChE activity (C, p = 0.0101; H, p < 0.0001), and lowered oxidative stress in the brain. Also, combination treatment restored the levels of NLRP3 (C, p = 0.0062; H, p < 0.0001) and IL1β (C, p = 0.0005; H, p = 0.0098). The combination treatment significantly reduced the degree of neuronal degeneration, amyloid deposition, and necrosis in the brain tissue. The current study revealed that the combination strategy effectively controlled neuroinflammation via modulation of the NLRP3 inflammasome pathway, paving the way for the new treatment.

Huang-Lian-Jie-Du decoction drug-containing serum inhibits IL-1β secretion from D-glucose and PA induced BV2 cells via autophagy/NLRP3 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Huang-Lian-Jie-Du decoction (HLJDD), a famous traditional Chinese medicine prescription with heat-clearing and detoxifying effects, has been widely used to treat diabetes, dementia, stroke, and other diseases. However, the detailed mechanisms of HLJDD against type 2 diabetes associated cognitive dysfunction (DACD) through inhibiting interleukin-1β (IL-1β) mediated neuroinflammation remain to be further elucidated.

AIM OF THE STUDY

The aim of this study was to investigate the effect and potential mechanism of HLJDD on IL-1β secretion in a DACD model of BV2 cells induced by D-glucose and palmitic acid (PA).

MATERIALS AND METHOD

sUltra-performance liquid chromatography-quadrupole/electrostatic field orbital well high-resolution mass spectrometry technology was used to analyze the compounds in HLJDD drug-containing serum. The cytotoxicity was detected by cell counting kit-8. Enzyme-linked immunosorbent assay was used to measure the secretion of IL-1β in BV2 cells. Reactive oxygen species, glutathione, superoxide dismutase, and malondialdehyde kits were used to detect the intracellular oxidative stress levels. The autophagy level was determined by autophagy staining kit and transmission electron microscope. The expression levels of autophagy-related 7 (Atg7), P62, LC3, nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3(NLRP3), Caspase1, and IL-1β were detected by real-time PCR, immunofluorescence, and western blotting. The Atg7siRNA was transfected into BV2 cells to produce autophagy inhibitory effect. Then the effect of HLJDD drug-containing serum on IL-1β secretion in D-glucose and PA induced BV2 cells and the potential mechanism of autophagy-NLRP3 inflammasome activation were further observed.

RESULTS

Eighty-eight compounds were preliminarily identified in HLJDD drug-containing serum, among which geniposide, baicalin, palmatine, berberine, wogonoside, wogonin, and geniposidic acid were identified as the main prototype components of HLJDD into the blood. In this study, the DACD model of BV2 cells induced by high concentrations of glucose and PA was successfully constructed. HLJDD drug-containing serum significantly reduced the secretion of IL-1β and the activity of NLRP3 inflammasome with improving the oxidative stress level. Interestingly, the enhanced autophagy level was also found. After transfection of Atg7siRNA into BV2 cells, the effect of HLJDD drug-containing serum on autophagy promotion was reversed, but the inhibitory effects on IL-1β secretion, NLRP3 inflammasome activation, and oxidative stress were reduced.

CONCLUSIONS

These results indicated that the inhibition of HLJDD drug-containing serum on the IL-1β secretion in D-glucose and PA induced BV2 cells was related to autophagy promotion, the decreased NLRP3 inflammasome activation, and the improved oxidative stress. Moreover, the improvement of HLJDD drug-containing serum on IL-1β secretion, NLRP3 inflammasome activation, and oxidative stress were all closely associated with Atg7 mediated autophagy promotion. Geniposide, baicalin, palmatine, berberine, wogonoside, wogonin, and geniposidic acid may be the potential active ingredients of HLJDD drug-containing serum.

Exercise mimetics: a novel strategy to combat neuroinflammation and Alzheimer's disease

Neuroinflammation is a pathological hallmark of Alzheimer's disease (AD), characterized by the stimulation of resident immune cells of the brain and the penetration of peripheral immune cells. These inflammatory processes facilitate the deposition of amyloid-beta (Aβ) plaques and the abnormal hyperphosphorylation of tau protein. Managing neuroinflammation to restore immune homeostasis and decrease neuronal damage is a therapeutic approach for AD. One way to achieve this is through exercise, which can improve brain function and protect against neuroinflammation, oxidative stress, and synaptic dysfunction in AD models. The neuroprotective impact of exercise is regulated by various molecular factors that can be activated in the same way as exercise by the administration of their mimetics. Recent evidence has proven some exercise mimetics effective in alleviating neuroinflammation and AD, and, additionally, they are a helpful alternative option for patients who are unable to perform regular physical exercise to manage neurodegenerative disorders. This review focuses on the current state of knowledge on exercise mimetics, including their efficacy, regulatory mechanisms, progress, challenges, limitations, and future guidance for their application in AD therapy.

Gardenia jasminoides J. Ellis extract attenuates memory impairment in rats with Alzheimer's disease by suppressing NLRP3 inflammasome

Alzheimer's disease (AD) is characterized by degeneration of the central nervous system. Recently, many studies have emphasized the beneficial role of Gardenia jasminoides J. Ellis extract (GJ-4) in neuroprotection, which is considered a potential drug for treating AD. However, the mechanism underlying its neuroprotective effects is obscure. This research intended to analyze the effectiveness of GJ-4 to induce neuronal protective role on a rat model of neurotoxicity and probe the potential mechanism. An AD model was established by intraperitoneal injection of aluminum chloride (AlCl3). Then, AlCl3-induced rats were administered 25 mg/kg and 50 mg/kg of GJ-4 orally. This study indicated that GJ-4 (25 and 50 mg/kg) mitigated AD-like behaviors, as evidenced by enhanced ambulation frequency, rearing frequency, and time spent in the target quadrant and decreased grooming frequency, defecation frequency, and escape latency in AlCl3-challenged rats. Also, GJ-4 at 25 and 50 mg/kg exerted an anti-apoptosis effect in the hippocampus of AlCl3-treated rats. Furthermore, GJ-4 (25 and 50 mg/kg) exhibited an anti-inflammatory effect in the hippocampus by repressing the activation of NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome, further inhibiting the activation of Caspase 1, ASC, IL-1β, and IL-18 in AD hippocampus. Altogether, GJ-4 mitigated AlCl3-triggered impairment of learning and memory in AD rats via repressing NLRP3 inflammasome.

"Other Than NLRP3" Inflammasomes: Multiple Roles in Brain Disease

Human neuroinflammatory and neurodegenerative diseases, whose prevalence keeps rising, are still unsolved pathobiological/therapeutical problems. Among others, recent etiology hypotheses stressed as their main driver a chronic neuroinflammation, which is mediated by innate immunity-related protein oligomers: the inflammasomes. A panoply of exogenous and/or endogenous harmful agents activates inflammasomes' assembly, signaling, and IL-1β/IL-18 production and neural cells' pyroptotic death. The underlying concept is that inflammasomes' chronic activation advances neurodegeneration while their short-lasting operation restores tissue homeostasis. Hence, from a therapeutic standpoint, it is crucial to understand inflammasomes' regulatory mechanisms. About this, a deluge of recent studies focused on the NLRP3 inflammasome with suggestions that its pharmacologic block would hinder neurodegeneration. Yet hitherto no evidence proves this view. Moreover, known inflammasomes are numerous, and the mechanisms regulating their expression and function may vary with the involved animal species and strains, as well as organs and cells, and the harmful factors triggered as a result. Therefore, while presently leaving out some little-studied inflammasomes, this review focuses on the "other than NLRP3" inflammasomes that participate in neuroinflammation's complex mechanisms: NLRP1, NLRP2, NLRC4, and AIM2. Although human-specific data about them are relatively scant, we stress that only a holistic view including several human brain inflammasomes and other potential pathogenetic drivers will lead to successful therapies for neuroinflammatory and neurodegenerative diseases.

DPA714 PET Imaging Shows That Inflammation of the Choroid Plexus Is Active in Chronic-Phase Intracerebral Hemorrhage

PURPOSE

Our aims were to investigate the presence of choroid plexus (CP) inflammation in chronic-phase intracerebral hemorrhage (ICH) patients and to characterize any inflammatory cells in the CP.

PATIENTS AND METHODS

An in vivo 18 F-DPA714 PET study was undertaken in 22 chronic-phase ICH patients who were admitted to the First Affiliated Hospital of Fujian Medical University or Tianjin Medical University General Hospital from April 2017 to June 2020. Ten control participants with nonhemorrhagic central nervous system diseases were included. Choroid plexus 18 F-DPA714 uptake was calculated as the average SUVR. To aid the interpretation of the 18 F-DPA714 uptake results at the CP level, Cy5-DPA714 in vivo imaging and immunofluorescence staining were used to show the presence of CP inflammation in an ICH mouse model during the chronic phase (14 weeks after ICH). Then immunofluorescence staining against translocator protein and other specific biomarkers was used to characterize the cells present in the inflamed CP of ICH mice in the chronic phase.

RESULTS

PET imaging showed that CP DPA714 SUVRs in chronic-phase ICH patients were higher than in controls (mean CP SUVR ± SD; ICH group: 1.05 ± 0.35; control group: 0.81 ± 0.21; P = 0.006). Immunofluorescence staining of the CP in ICH model mice identified a population of CD45 + immune cells, peripheral monocyte-derived CD14 + cells, CD68 + phagocytes, and CD11b + resident microglia/macrophages expressing translocator protein, possibly contributing to the increased 18 F-DPA714 uptake.

CONCLUSIONS

Our study shows that CP DPA714 uptake in chronic-phase ICH patients was higher than that of participants with nonhemorrhagic central nervous system diseases, which means that CP inflammation is still active in chronic-phase ICH patients.

NLRP3 inflammasome in cognitive impairment and pharmacological properties of its inhibitors

Cognitive impairment is a multifactorial and multi-step pathological process that places a heavy burden on patients and the society. Neuroinflammation is one of the main factors leading to cognitive impairment. The inflammasomes are multi-protein complexes that respond to various microorganisms and endogenous danger signals, helping to initiate innate protective responses in inflammatory diseases. NLRP3 inflammasomes produce proinflammatory cytokines (interleukin IL-1β and IL-18) by activating caspase-1. In this review, we comprehensively describe the structure and functions of the NLRP3 inflammasome. We also explore the intrinsic relationship between the NLRP3 inflammasome and cognitive impairment, which involves immune cell activation, cell apoptosis, oxidative stress, mitochondrial autophagy, and neuroinflammation. Finally, we describe NLRP3 inflammasome antagonists as targeted therapies to improve cognitive impairment.

Antiplatelet drugs: Potential therapeutic options for the management of neurodegenerative diseases

The blood platelet plays an important role but often remains under-recognized in several vascular complications and associated diseases. Surprisingly, platelet hyperactivity and hyperaggregability have often been considered the critical risk factors for developing vascular dysfunctions in several neurodegenerative diseases (NDDs) like Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. In addition, platelet structural and functional impairments promote prothrombotic and proinflammatory environment that can aggravate the progression of several NDDs. These findings provide the rationale for using antiplatelet agents not only to prevent morbidity but also to reduce mortality caused by NDDs. Therefore, we thoroughly review the evidence supporting the potential pleiotropic effects of several novel classes of synthetic antiplatelet drugs, that is, cyclooxygenase inhibitors, adenosine diphosphate receptor antagonists, protease-activated receptor blockers, and glycoprotein IIb/IIIa receptor inhibitors in NDDs. Apart from this, the review also emphasizes the recent developments of selected natural antiplatelet phytochemicals belonging to key classes of plant-based bioactive compounds, including polyphenols, alkaloids, terpenoids, and flavonoids as potential therapeutic candidates in NDDs. We believe that the broad analysis of contemporary strategies and specific approaches for plausible therapeutic treatment for NDDs presented in this review could be helpful for further successful research in this area.

The Dual Nature of Microglia in Alzheimer's Disease: A Microglia-Neuron Crosstalk Perspective

Microglia are critical players in the neuroimmune system, and their involvement in Alzheimer's disease (AD) pathogenesis is increasingly being recognized. However, whether microglia play a positive or negative role in AD remains largely controversial and the precise molecular targets for intervention are not well defined. This partly results from the opposing roles of microglia in AD pathology, and is mainly reflected in the microglia-neuron interaction. Microglia can prune synapses resulting in excessive synapse loss and neuronal dysfunction, but they can also promote synapse formation, enhancing neural network plasticity. Neuroimmune crosstalk accelerates microglial activation, which induces neuron death and enhances the microglial phagocytosis of β-amyloid to protect neurons. Moreover, microglia have dual opposing roles in developing the major pathological features in AD, such as amyloid deposition and blood-brain barrier permeability. This review summarizes the dual opposing role of microglia in AD from the perspective of the interaction between neurons and microglia. Additionally, current AD treatments targeting microglia and the advantages and disadvantages of developing microglia-targeted therapeutic strategies are discussed.

DNA hypomethylation promotes the expression of CASPASE-4 which exacerbates neuroinflammation and amyloid-β deposition in Alzheimer's disease The Ohio State University College of Medicine

Alzheimer's Disease (AD) is the 6th leading cause of death in the US. It is established that neuroinflammation contributes to the synaptic loss, neuronal death, and symptomatic decline of AD patients. Accumulating evidence suggests a critical role for microglia, innate immune phagocytes of the brain. For instance, microglia release proinflammatory products such as IL-1β which is highly implicated in AD pathobiology. The mechanisms underlying the transition of microglia to proinflammatory promoters of AD remain largely unknown. To address this gap, we performed Reduced Representation Bisulfite Sequencing (RRBS) to profile global DNA methylation changes in human AD brains compared to no disease controls. We identified differential DNA methylation of CASPASE-4 (CASP4), which when expressed, can be involved in generation of IL-1β and is predominantly expressed in immune cells. DNA upstream of the CASP4 transcription start site was hypomethylated in human AD brains, which was correlated with increased expression of CASP4. Furthermore, microglia from a mouse model of AD (5xFAD) express increased levels of CASP4 compared to wild-type (WT) mice. To study the role of CASP4 in AD, we developed a novel mouse model of AD lacking the mouse ortholog of CASP4, CASP11, which is encoded by mouse Caspase-4 (5xFAD/Casp4-/-). The expression of CASP11 was associated with increased accumulation of pathologic protein aggregate amyloid-β (Aβ) and increased microglial production of IL-1β in 5xFAD mice. Utilizing RNA sequencing, we determined that CASP11 promotes unique transcriptomic phenotypes in 5xFAD mouse brains, including alterations of neuroinflammatory and chemokine signaling pathways. Notably, in vitro, CASP11 promoted generation of IL-1β from macrophages in response to cytosolic Aβ through cleavage of downstream effector Gasdermin D (G SDMD). We describe a role for CASP11 and GSDMD in the generation of IL-1β in response to Aβ and the progression of pathologic inflammation in AD. Overall, our results demonstrate that overexpression of CASP4 due to differential methylation in AD microglia contributes to the progression of AD pathobiology, thus identifying CASP4 as a potential target for immunotherapies for the treatment of AD.

The emerging role of IL-38 in diseases: A comprehensive review

INTRODUCTION

Interleukin-38 (IL-38) is a new type of anti-inflammatory cytokine, which is mainly expressed in the immunity-related organs and is involved in various diseases including cardiovascular and cerebrovascular diseases, lung diseases, viral infectious diseases and autoimmune diseases.

AIM

This review aims to detail the biological function, receptors and signaling of IL-38, which highlights its therapeutic potential in related diseases.

CONCLUSION

This article provides a comprehensive review of the association between interleukin-38 and related diseases, using interleukin-38 as a keyword and searching the relevant literature through Pubmed and Web of science up to July 2023.

Electroacupuncture at ST 36 ameliorates cognitive impairment and beta-amyloid pathology by inhibiting NLRP3 inflammasome activation in an Alzheimer's disease animal model

Background

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder leading to cognitive impairment in the elderly, and no effective treatment exists. Increasing evidence has demonstrated that physical therapy and electroacupuncture (EA) effectively improve spatial learning and memory abilities. Nevertheless, the mechanism underlying the effects of EA on AD pathology is largely unexplored. Acupuncture at Zusanli (ST 36) has previously been shown to improve cognitive impairment in AD, but the mechanism is unclear. According to recent studies, EA drives the vagal-adrenal axis from the hindlimb ST 36 acupoint but not from the abdominal Tianshu (ST 25) to curb severe inflammation in mice. This study examined whether ST 36 acupuncture improves cognitive dysfunction in AD model mice by improving neuroinflammation and its underlying mechanism.

Methods

Male 5xFAD mice (aged 3, 6, and 9 months) were used as the AD animal model and were randomly divided into three groups: the AD model group (AD group), the electroacupuncture at ST 36 acupoint group (EA-ST 36 group), and the electroacupuncture at ST 25 acupoint group (EA-ST 25 group). Age-matched wild-type mice were used as the normal control (WT) group. EA (10 Hz, 0.5 mA) was applied to the acupoints on both sides for 15 min, 5 times per week for 4 weeks. Motor ability and cognitive ability were assessed by the open field test, the novel object recognition task, and the Morris water maze test. Thioflavin S staining and immunofluorescence were used to mark Aβ plaques and microglia. The levels of NLRP3, caspase-1, ASC, interleukin (IL)-1β, and IL-18 in the hippocampus were assayed by Western blotting or qRT-PCR.

Results

EA at ST 36, but not ST 25, significantly improved motor function and cognitive ability and reduced both Aβ deposition and microglia and NLRP3 inflammasome activation in 5×FAD mice.

Conclusion

EA stimulation at ST 36 effectively improved memory impairment in 5×FAD mice by a mechanism that regulated microglia activation and alleviated neuroinflammation by inhibiting the NLRP3 inflammatory response in the hippocampus. This study shows that ST 36 may be a specific acupoint to improve the condition of AD patients.

Recent Mechanisms of Neurodegeneration and Photobiomodulation in the Context of Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease and the world's primary cause of dementia, a condition characterized by significant progressive declines in memory and intellectual capacities. While dementia is the main symptom of Alzheimer's, the disease presents with many other debilitating symptoms, and currently, there is no known treatment exists to stop its irreversible progression or cure the disease. Photobiomodulation has emerged as a very promising treatment for improving brain function, using light in the range from red to the near-infrared spectrum depending on the application, tissue penetration, and density of the target area. The goal of this comprehensive review is to discuss the most recent achievements in and mechanisms of AD pathogenesis with respect to neurodegeneration. It also provides an overview of the mechanisms of photobiomodulation associated with AD pathology and the benefits of transcranial near-infrared light treatment as a potential therapeutic solution. This review also discusses the older reports and hypotheses associated with the development of AD, as well as some other approved AD drugs.

C4b-binding protein inhibits particulate- and crystalline-induced NLRP3 inflammasome activation

Dysregulated NLRP3 inflammasome activation drives a wide variety of diseases, while endogenous inhibition of this pathway is poorly characterised. The serum protein C4b-binding protein (C4BP) is a well-established inhibitor of complement with emerging functions as an endogenously expressed inhibitor of the NLRP3 inflammasome signalling pathway. Here, we identified that C4BP purified from human plasma is an inhibitor of crystalline- (monosodium urate, MSU) and particulate-induced (silica) NLRP3 inflammasome activation. Using a C4BP mutant panel, we identified that C4BP bound these particles via specific protein domains located on the C4BP α-chain. Plasma-purified C4BP was internalised into MSU- or silica-stimulated human primary macrophages, and inhibited MSU- or silica-induced inflammasome complex assembly and IL-1β cytokine secretion. While internalised C4BP in MSU or silica-stimulated human macrophages was in close proximity to the inflammasome adaptor protein ASC, C4BP had no direct effect on ASC polymerisation in in vitro assays. C4BP was also protective against MSU- and silica-induced lysosomal membrane damage. We further provide evidence for an anti-inflammatory function for C4BP in vivo, as C4bp^-/- mice showed an elevated pro-inflammatory state following intraperitoneal delivery of MSU. Therefore, internalised C4BP is an inhibitor of crystal- or particle-induced inflammasome responses in human primary macrophages, while murine C4BP protects against an enhanced inflammatory state in vivo. Our data suggests C4BP has important functions in retaining tissue homeostasis in both human and mice as an endogenous serum inhibitor of particulate-stimulated inflammasome activation.

Structural-Activity Relationship of Rare Ginsenosides from Red Ginseng in the Treatment of Alzheimer's Disease

Rare ginsenosides are the major components of red ginseng. However, there has been little research into the relationship between the structure of ginsenosides and their anti-inflammatory activity. In this work, BV-2 cells induced by lipopolysaccharide (LPS) or nigericin, the anti-inflammatory activity of eight rare ginsenosides, and the target proteins expression of AD were compared. In addition, the Morris water maze test, HE staining, thioflavins staining, and urine metabonomics were used to evaluate the effect of Rh4 on AD mice. Our results showed that their configuration influences the anti-inflammatory activity of ginsenosides. Ginsenosides Rk1, Rg5, Rk3, and Rh4 have significant anti-inflammatory activity compared to ginsenosides S-Rh1, R-Rh1, S-Rg3, and R-Rg3. Ginsenosides S-Rh1 and S-Rg3 have more pronounced anti-inflammatory activity than ginsenosides R-Rh1 and R-Rg3, respectively. Furthermore, the two pairs of stereoisomeric ginsenosides can significantly reduce the level of NLRP3, caspase-1, and ASC in BV-2 cells. Interestingly, Rh4 can improve the learning ability of AD mice, improve cognitive impairment, reduce hippocampal neuronal apoptosis and Aβ deposition, and regulate AD-related pathways such as the tricarboxylic acid cycle and the sphingolipid metabolism. Our findings conclude that rare ginsenosides with a double bond have more anti-inflammatory activity than those without, and 20(S)-ginsenosides have more excellent anti-inflammatory activity than 20(R)-ginsenosides.

Single-cell analysis reveals inflammatory interactions driving macular degeneration

Due to commonalities in pathophysiology, age-related macular degeneration (AMD) represents a uniquely accessible model to investigate therapies for neurodegenerative diseases, leading us to examine whether pathways of disease progression are shared across neurodegenerative conditions. Here we use single-nucleus RNA sequencing to profile lesions from 11 postmortem human retinas with age-related macular degeneration and 6 control retinas with no history of retinal disease. We create a machine-learning pipeline based on recent advances in data geometry and topology and identify activated glial populations enriched in the early phase of disease. Examining single-cell data from Alzheimer's disease and progressive multiple sclerosis with our pipeline, we find a similar glial activation profile enriched in the early phase of these neurodegenerative diseases. In late-stage age-related macular degeneration, we identify a microglia-to-astrocyte signaling axis mediated by interleukin-1β which drives angiogenesis characteristic of disease pathogenesis. We validated this mechanism using in vitro and in vivo assays in mouse, identifying a possible new therapeutic target for AMD and possibly other neurodegenerative conditions. Thus, due to shared glial states, the retina provides a potential system for investigating therapeutic approaches in neurodegenerative diseases.

Revisiting the intersection of microglial activation and neuroinflammation in Alzheimer's disease from the perspective of ferroptosis

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by chronic neuroinflammation with amyloid beta-protein deposition and hyperphosphorylated tau protein. The typical clinical manifestation of AD is progressive memory impairment, and AD is considered a multifactorial disease with various etiologies (genetic factors, aging, lifestyle, etc.) and complicated pathophysiological processes. Previous research identified that neuroinflammation and typical microglial activation are significant mechanisms underlying AD, resulting in dysfunction of the nervous system and progression of the disease. Ferroptosis is a novel modality involved in this process. As an iron-dependent form of cell death, ferroptosis, characterized by iron accumulation, lipid peroxidation, and irreversible plasma membrane disruption, promotes AD by accelerating neuronal dysfunction and abnormal microglial activation. In this case, disturbances in brain iron homeostasis and neuronal ferroptosis aggravate neuroinflammation and lead to the abnormal activation of microglia. Abnormally activated microglia release various pro-inflammatory factors that aggravate the dysregulation of iron homeostasis and neuroinflammation, forming a vicious cycle. In this review, we first introduce ferroptosis, microglia, AD, and their relationship. Second, we discuss the nonnegligible role of ferroptosis in the abnormal microglial activation involved in the chronic neuroinflammation of AD to provide new ideas for the identification of potential therapeutic targets for AD.

A Brief Overview of Neutrophils in Neurological Diseases

Neutrophils are the most abundant leukocyte in circulation and are the first line of defense after an infection or injury. Neutrophils have a broad spectrum of functions, including phagocytosis of microorganisms, the release of pro-inflammatory cytokines and chemokines, oxidative burst, and the formation of neutrophil extracellular traps. Traditionally, neutrophils were thought to be most important for acute inflammatory responses, with a short half-life and a more static response to infections and injury. However, this view has changed in recent years showing neutrophil heterogeneity and dynamics, indicating a much more regulated and flexible response. Here we will discuss the role of neutrophils in aging and neurological disorders; specifically, we focus on recent data indicating the impact of neutrophils in chronic inflammatory processes and their contribution to neurological diseases. Lastly, we aim to conclude that reactive neutrophils directly contribute to increased vascular inflammation and age-related diseases.

Protective Effects of Cannabis in Neuroinflammation-Mediated Alzheimer's Disease

In recent years, Alzheimer's disease (AD) has been recognized as an age-related neurological disorder wherein neurons degenerate and exhibit abnormal structure and function. Aging is the primary factor in the progression of AD from mild to severe cognitive impairment. No effective targeted therapies are presently available, and treatment is limited to symptomatic management. The neuropathologic hallmarks of the disease include the accumulation of amyloid-beta (Aβ) plaques in brain tissues and the aggregation of hyperphosphorylated-tau proteins (tangles) within neurons. Associated hyperactivation of neuroinflammation results in release of inflammatory molecules from neurons, microglia, and astrocytes, which have been linked with neuronal loss and the worsening neurodegeneration. The anti-inflammatory and neuroprotective properties of cannabis-based medicines may offer benefits in delaying the progression of neurodegenerative diseases including AD. This chapter explores the role of cannabinoids in countering neuroinflammation-mediated AD pathology.

Microglial Activation and Priming in Alzheimer's Disease: State of the Art and Future Perspectives

Alzheimer's Disease (AD) is the most common cause of dementia, having a remarkable social and healthcare burden worldwide. Amyloid β (Aβ) and protein Tau aggregates are disease hallmarks and key players in AD pathogenesis. However, it has been hypothesized that microglia can contribute to AD pathophysiology, as well. Microglia are CNS-resident immune cells belonging to the myeloid lineage of the innate arm of immunity. Under physiological conditions, microglia are in constant motion in order to carry on their housekeeping function, and they maintain an anti-inflammatory, quiescent state, with low expression of cytokines and no phagocytic activity. Upon various stimuli (debris, ATP, misfolded proteins, aggregates and pathogens), microglia acquire a phagocytic function and overexpress cytokine gene modules. This process is generally regarded as microglia activation and implies that the production of pro-inflammatory cytokines is counterbalanced by the synthesis and the release of anti-inflammatory molecules. This mechanism avoids excessive inflammatory response and inappropriate microglial activation, which causes tissue damage and brain homeostasis impairment. Once the pathogenic stimulus has been cleared, activated microglia return to the naïve, anti-inflammatory state. Upon repeated stimuli (as in the case of Aβ deposition in the early stage of AD), activated microglia shift toward a less protective, neurotoxic phenotype, known as "primed" microglia. The main characteristic of primed microglia is their lower capability to turn back toward the naïve, anti-inflammatory state, which makes these cells prone to chronic activation and favours chronic inflammation in the brain. Primed microglia have impaired defence capacity against injury and detrimental effects on the brain microenvironment. Additionally, priming has been associated with AD onset and progression and can represent a promising target for AD treatment strategies. Many factors (genetics, environmental factors, baseline inflammatory status of microglia, ageing) generate an aberrantly activated phenotype that undergoes priming easier and earlier than normally activated microglia do. Novel, promising targets for therapeutic strategies for AD have been sought in the field of microglia activation and, importantly, among those factors influencing the baseline status of these cells. The CX3CL1 pathway could be a valuable target treatment approach in AD, although preliminary findings from the studies in this field are controversial. The current review aims to summarize state of the art on the role of microglia dysfunction in AD pathogenesis and proposes biochemical pathways with possible targets for AD treatment.

The Regulation of Microglial Cell Polarization in the Tumor Microenvironment: A New Potential Strategy for Auxiliary Treatment of Glioma-A Review

Glioma is the most common primary tumor of the central nervous system and normally should be treated by synthetic therapy, mainly with surgical operation assisted by radiotherapy and chemotherapy; however, the therapeutic effect has not been satisfactory, and the 5-year survival rates of anaplastic glioma and glioblastoma are 29.7% and 5.5%, respectively. To identify a more efficient strategy to treat glioma, in recent years, the influence of the inflammatory microenvironment on the progression of glioma has been studied. Various immunophenotypes exist in microglial cells, each of which has a different functional property. In this review, references about the phenotypic conversion of microglial cell polarity in the microenvironment were briefly summarized, and the differences in polarized state and function, their influences on glioma progression under different physiological and pathological conditions, and the interactive effects between the two were mainly discussed. Certain signaling molecules and regulatory pathways involved in the microglial cell polarization process were investigated, and the feasibility of targeted regulation of microglial cell conversion to an antitumor phenotype was analyzed to provide new clues for the efficient auxiliary treatment of neural glioma.

The relationships between neuroglial and neuronal changes in Alzheimer's disease, and the related controversies II:

Since the original description of Alzheimer´s disease (AD), research into this condition has mainly focused on assessing the alterations to neurons associated with dementia, and those to the circuits in which they are involved. In most of the studies on human brains and in many models of AD, the glial cells accompanying these neurons undergo concomitant alterations that aggravate the course of neurodegeneration. As a result, these changes to neuroglial cells are now included in all the "pathogenic cascades" described in AD. Accordingly, astrogliosis and microgliosis, the main components of neuroinflammation, have been integrated into all the pathogenic theories of this disease, as discussed in this part of the two-part monograph that follows an accompanying article on gliopathogenesis and glioprotection. This initial reflection verified the implication of alterations to the neuroglia in AD, suggesting that these cells may also represent therapeutic targets to prevent neurodegeneration. In this second part of the monograph, we will analyze the possibilities of acting on glial cells to prevent or treat the neurodegeneration that is the hallmark of AD and other pathologies. Evidence of the potential of different pharmacological, non-pharmacological, cell and gene therapies (widely treated) to prevent or treat this disease is now forthcoming, in most cases as adjuncts to other therapies. A comprehensive AD multimodal therapy is proposed in which neuronal and neuroglial pharmacological treatments are jointly considered, as well as the use of new cell and gene therapies and non-pharmacological therapies that tend to slow down the progress of dementia.

Apoptosis-associated speck-like protein containing a CARD-mediated release of matrix metalloproteinase 10 stimulates a change in microglia phenotype

Inflammation contributes to amyloid-β and tau pathology in Alzheimer's disease (AD). Microglia facilitate an altered immune response that includes microgliosis, upregulation of inflammasome proteins, and elevation of matrix-metalloproteinases (MMPs). Studies of cerebrospinal fluid (CSF) and blood in dementia patients show upregulation of two potential biomarkers of inflammation at the cellular level, MMP10 and apoptosis-associated speck-like protein containing a CARD (ASC). However, little is known about their relationship in the context of brain inflammation. Therefore, we stimulated microglia cultures with purified insoluble ASC speck aggregates and MMP10 to elucidate their role. We found that ASC specks altered microglia shape and stimulated the release of MMP3 and MMP10. Furthermore, MMP10 stimulated microglia released additional MMP10 along with the inflammatory cytokines, tumor-necrosis factor-α (TNFα), Interleukin 6 (IL-6), and CXCL1 CXC motif chemokine ligand 1 (CXCL1). A broad-spectrum MMP inhibitor, GM6001, prevented TNFα release. With these results, we conclude that MMP10 and ASC specks act on microglial cells to propagate inflammation.

Aerobic exercise alleviates pyroptosis-related diseases by regulating NLRP3 inflammasome

Pyroptosis plays a crucial role in a variety of human diseases, including atherosclerosis, obesity, diabetes, depression, and Alzheimer’s disease, which usually release pyroptosis-related cytokines due to inflammation. Many studies have demonstrated that aerobic exercise is a good option for decreasing the release of pyroptosis-related cytokines. However, the molecular mechanisms of aerobic exercise on pyroptosis-related diseases remain unknown. In this review, the effects of aerobic exercise on pyroptosis in endothelial cells, adipocytes and hippocampal cells, and their potential mechanisms are summarized. In endothelial cells, aerobic exercise could inhibit NOD-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis by improving the endothelial function, while reducing vascular inflammation and oxidative stress. In adipocytes, aerobic exercise has been shown to inhibit pyroptosis by ameliorating inflammation and insulin resistance. Moreover, aerobic exercise could restrict pyroptosis by attenuating microglial activation, neuroinflammation, and amyloid-beta deposition in hippocampal cells. In summary, aerobic exercise alleviates the pyroptosis-related diseases by regulating the NLRP3 inflammation si0067naling.

Trichodimerol inhibits inflammation through suppression of the nuclear transcription factor-kappaB/NOD-like receptor thermal protein domain associated protein 3 signaling pathway

Excessive inflammation causes chronic diseases and tissue damage. Although there has been drug treatment, its side effects are relatively large. Searching for effective anti-inflammatory drugs from natural products has become the focus of attention. First isolated from Trichoderma longibraciatum, trichodimerol is a natural product with TNF inhibition. In this study, lipopolysaccharide (LPS)-induced RAW264.7 macrophages were used as a model to investigate the anti-inflammatory activity of trichodimerol. The results of nitric oxide (NO) detection, enzyme-linked immunosorbent assay (ELISA), and reactive oxygen species (ROS) showed that trichodimerol could reduce the production of NO, ROS, and the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α. Western blotting results showed that trichodimerol could inhibit the production of inflammatory mediators such as cyclooxygenase (COX)-2 and inducible nitric oxide synthase (iNOS) and the protein expression of nuclear transcription factor-kappaB (NF-κB), p-IKK, p-IκB, Toll-like receptor 4 (TLR4), NOD-like receptor thermal protein domain associated protein 3 (NLRP3), cysteinyl aspartate specific proteinase (Caspase)-1, and ASC, which indicated that trichodimerol may inhibit inflammation through the NF-κB and NLRP3 pathways. At the same time, molecular docking showed that trichodimerol can directly combine with the TLR4-MD2 complex. Hence, trichodimerol inhibits inflammation by obstructing the interaction between LPS and the TLR4-MD2 heterodimer and suppressing the downstream NF-κB and NLRP3 pathways.

Benzimidazole Derivatives as New Potential NLRP3 Inflammasome Inhibitors That Provide Neuroprotection in a Rodent Model of Neurodegeneration and Memory Impairment

Objective

The study investigated the effect of newly synthesized benzimidazole derivatives against ethanol-induced neurodegeneration. According to evidence, ethanol consumption may cause a severe insult to the central nervous system (CNS), resulting in mental retardation, neuronal degeneration, and oxidative stress. Targeting neuroinflammation and oxidative stress may be a useful strategy for preventing ethanol-induced neurodegeneration.

Methodology

Firstly, the newly synthesized compounds were subjected to molecular simulation and docking in order to predict ligand binding status. Later, for in vivo observations, adult male Sprague Dawley rats were used for studying behavioral and oxidative stress markers. ELIZA kits were used to analyse tumour necrosis factor-alpha (TNF-), nuclear factor-B (NF-B), interleukin (IL-18), and pyrin domain-containing protein 3 (NLRP3) expression, while Western blotting was used to measure IL-1 and Caspase-1 expression.

Results

Our findings suggested that altered levels of antioxidant enzymes were associated with elevated levels of TNF-α, NF-B, IL-1, IL-18, Caspase-1, and NLRP3 in the ethanol-treated group. Furthermore, ethanol also caused memory impairment in rats, as measured by behavioural tests. Pretreatment using selected benzimidazole significantly increased the combat of the brain against ethanol-induced oxidative stress. The neuroprotective effects of benzimidazole derivatives were promoted by their free radical scavenging activity, augmentation of endogenous antioxidant proteins (GST, GSH), and amelioration of lipid peroxide (LPO) and other pro-inflammatory mediators. Molecular docking and molecular simulation studies further supported our hypothesis that the synthetic compounds Ca and Cb had an excellent binding affinity with proper bond formation with their targets (TNF-α and NLRP3).

Conclusion

It is revealed that these benzimidazole derivatives can reduce ethanol-induced neuronal toxicity by regulating the expression of cytokines, antioxidant enzymes, and the inflammatory cascade.

Huang-Lian-Jie-Du decoction attenuates cognitive dysfunction of rats with type 2 diabetes by regulating autophagy and NLRP3 inflammasome activation

ETHNOPHARMACOLOGICAL RELEVANCE

Huang-Lian-Jie-Du decoction (HLJDD) is a traditional Chinese formula that is efficacious in treating diabetes mellitus, Alzheimer's disease, and diabetic encephalopathy; the underlying mechanisms of HLJDD in diabetes-associated cognitive dysfunction remain unclear.

AIM OF THE STUDY

This study investigated the neuroprotective effects of HLJDD on cognitive function, and the possible underlying mechanisms in type 2 diabetes mellitus (T2DM) in a rat model of cognitive impairment.

MATERIALS AND METHODS

Twelve active ingredients in HLJDD were detected using high-performance liquid chromatography analysis. An animal model of cognitive dysfunction in T2DM was induced via a high-sugar and high-fat diet combined with a low dose of streptozotocin. Sprague-Dawley rats were randomly divided into six groups: control, T2DM, metformin (0.34 g/kg/day), and HLJDD groups (3, 1.5, and 0.75 g/kg/day). All treatments were intragastrically administrated for nine continuous weeks after the development of T2DM. Body weight, food and water intake, fasting blood glucose, insulin sensitivity, and blood lipid levels were measured. Spatial learning and memory of the rats were assessed using the Morris water maze test. Hematoxylin and eosin and Nissl staining were performed to evaluate neuronal morphology and vitality. Glutathione, malondialdehyde, and superoxide dismutase levels were measured to determine the level of oxidative stress in the hippocampus. Transmission electron microscopy was performed to observe the synaptic morphology and structure of hippocampal neurons. IL-1β levels in the hippocampus and cerebrospinal fluid were determined. The protein expression of NLRP3, cleaved caspase-1, mature IL-1β, ATG7, P62, LC3, and brain-derived neurotrophic factor (BDNF) was determined using western blotting and immunofluorescence analysis.

RESULTS

HLJDD attenuated cognitive dysfunction in rats with T2DM as shown by the decreased escape latency, increased times crossing the platform and time spent in the target quadrant in the Morris water maze test (P < 0.05), improvement in hippocampal histopathological changes, and an elevated level of cell vitality. HLJDD treatment also reduced blood glucose and lipid levels, ameliorated oxidative stress, and downregulated IL-1β expression in the hippocampus and cerebrospinal fluid (P < 0.05). Moreover, HLJDD enhanced BDNF, ATG7, and LC3 protein expression and significantly inhibited the expression of P62, NLRP3, cleaved caspase-1, and mature IL-1β in the hippocampal CA1 region (P < 0.05). Immunofluorescence results further confirmed that the fluorescence intensity of NLRP3 and P62 in the hippocampus decreased after HLJDD intervention (P < 0.05).

CONCLUSIONS

HLJDD ameliorated cognitive dysfunction in T2DM rats. The neuroprotective effect is exerted via the modulation of glucose and lipid metabolism, upregulation of autophagy, and inhibition of NLRP3 inflammasome signaling pathway.

Neuroprotective Effects of the Pannexin-1 Channel Inhibitor: Probenecid on Spinal Cord Injury in Rats

Proinflammatory immune cell subsets constitute the majority in the local microenvironment after spinal cord injury (SCI), leading to secondary pathological injury. Previous studies have demonstrated that inflammasomes act as an important part of the inflammatory process after SCI. Probenecid, an inhibitor of the Pannexin-1 channel, can inhibit the activation of inflammasomes. This article focuses on the effects of probenecid on the local immune microenvironment, histopathology, and behavior of SCI. Our data show that probenecid inhibited the expression and activation of nucleotide-binding oligomerization domain receptor pyrindomain-containing 1 (NLRP1), apoptosis-associated speck-like protein containing a CARD (ASC) and caspase-1, interleukin-1β (IL-1β), and caspase-3 proteins associated with inflammasomes, thereby suppressing the proportion of M1 cells. And consequently, probenecid reduced the lesion area and demyelination in SCI. Moreover, the drug increased the survival of motor neurons, which resulted in tissue repair and improved locomotor function in the injured SC. Altogether, existing studies indicated that probenecid can alleviate inflammation by blocking Pannexin-1 channels to inhibit the expression of caspase-1 and IL-1β, which in turn restores the balance of immune cell subsets and exerts neuroprotective effects in rats with SCI.

Microglial activation in Alzheimer's disease: The role of flavonoids and microRNAs

Alzheimer's disease (AD) is the most common form of senile dementia and is characterized by progressive cognitive impairment and neuronal degeneration. Microglial activation is an important pathologic hallmark of AD. During disease progression, microglial cells switch from an alternative or anti-inflammatory and neuroprotective profile (M2) to a classic or proinflammatory and neurotoxic profile (M1). Phenotypically, M1 microglia is characterized by the activation of inflammatory signaling pathways that cause increased expression of proinflammatory genes, including those coding for cytokines and chemokines. This microglia-mediated neuroinflammation contributes to neuronal cell death. Recent studies in microglial cells have shown that a group of plant-derived compounds, known as flavonoids, possess anti-inflammatory properties and therefore exert a neuroprotective effect through regulating microglia activation. Here, we discuss how flavonoids can promote the switch from an inflammatory M1 phenotype to an anti-inflammatory M2 phenotype in microglia and how this represents a valuable opportunity for the development of novel therapeutic strategies to blunt neuroinflammation and boost neuronal recovery in AD. We also review how certain flavonoids can inhibit neuroinflammation through their action on the expression of microglia-specific microRNAs (miRNAs), which also constitute a key therapeutic approach in different neuropathologies involving an inflammatory component, including AD. Finally, we propose novel targets of microglia-specific miRNAs that may be considered for AD treatment.

Current status of sevoflurane anesthesia in association with microglia inflammation and neurodegenerative diseases

Sevoflurane is one of the most commonly used volatile anesthetics in clinical practice and is often used in pediatric anesthesia and intraoperative maintenance. Microglia exist in the central nervous system and are innate immune cells in the central nervous system. Under external stimulation, microglia are divided into two phenotypes: proinflammatory (M1 type) and anti-inflammatory (M2 type), maintaining the stability of the central nervous system through induction, housekeeping, and defense functions. Sevoflurane can activate microglia, increase the expression of inflammatory factors through various inflammatory signaling pathways, release inflammatory mediators to cause oxidative stress, damage nerve tissues, and eventually develop into neurodegenerative diseases. In this article, the relationship between sevoflurane anesthesia and microglia inflammation expression and the occurrence of neurodegenerative diseases is reviewed as follows.

Dementia and COVID-19: A Case Report and Literature Review on Pain Management

The coronavirus disease 2019 (COVID-19) pandemic imposes an unprecedented lifestyle, dominated by social isolation. In this frame, the population to pay the highest price is represented by demented patients. This group faces the highest risk of mortality, in case of severe acute respiratory syndrome coronavirus (SARS-CoV-2) infection, and they experience rapid cognitive deterioration, due to lockdown measures that prevent their disease monitoring. This complex landscape mirrors an enhancement of neuropsychiatric symptoms (NPSs), with agitation, delirium and reduced motor performances, particularly in non-communicative patients. Due to the consistent link between agitation and pain in these patients, the use of antipsychotics, increasing the risk of death during COVID-19, can be avoided or reduced through an adequate pain treatment. The most suitable pain assessment scale, also feasible for e-health implementation, is the Mobilization-Observation-Behaviour-Intensity-Dementia (MOBID-2) pain scale, currently under validation in the Italian real-world context. Here, we report the case of an 85-year-old woman suffering from mild cognitive impairment, subjected to off-label treatment with atypical antipsychotics, in the context of undertreated pain, who died during the pandemic from an extensive brain hemorrhage. This underscores the need for appropriate assessment and treatment of pain in demented patients.

N-acetyldopamine dimer inhibits neuroinflammation through the TLR4/NF-κB and NLRP3/Caspase-1 pathways

Neuroinflammation mediated by microglia is an important pathophysiological mechanism in neurodegenerative diseases. However, there is a lack of effective drugs to treat neuroinflammation. N-acetyldopamine dimer (NADD) is a natural compound from the traditional Chinese medicine Isaria cicada. In our previous study, we found that NADD can attenuate DSS-induced ulcerative colitis by suppressing the NF-κB and MAPK pathways. Does NADD inhibit neuroinflammation, and what is the target of NADD? To answer this question, lipopolysaccharide (LPS)-stimulated BV-2 microglia was used as a cell model to investigate the effect of NADD on neuroinflammation. Nitric oxide (NO) detection, reactive oxygen species (ROS) detection and enzyme-linked immunosorbent assay (ELISA) results show that NADD attenuates inflammatory signals and proinflammatory cytokines in LPS-stimulated BV-2 microglia, including NO, ROS, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and interleukin-6 (IL-6). Western blot analysis show that NADD inhibits the protein levels of Toll-like receptor 4 (TLR4), nuclear factor kappa-B (NF-κB), NOD-like receptor thermal protein domain associated protein 3 (NLRP3), ASC and cysteinyl aspartate specific proteinase (Caspase)-1, indicating that NADD may inhibit neuroinflammation through the TLR4/NF-κB and NLRP3/Caspase-1 signaling pathways. In addition, surface plasmon resonance assays and molecular docking demonstrate that NADD binds with TLR4 directly. Our study reveals a new role of NADD in inhibiting the TLR4/NF-κB and NLRP3/Caspase-1 pathways, and shows that TLR4-MD2 is the direct target of NADD, which may provide a potential therapeutic candidate for the treatment of neuroinflammation.

Neuroinflammation and Oxidative Stress in Alzheimer's Disease; Can Nutraceuticals and Functional Foods Come to the Rescue?

Alzheimer's disease (AD), the most prevalent form of age-related dementia, is typified by progressive memory loss and spatial awareness with personality changes. The increasing socioeconomic burden associated with AD has made it a focus of extensive research. Ample scientific evidence supports the role of neuroinflammation and oxidative stress in AD pathophysiology, and there is increasing research into the possible role of anti-inflammatory and antioxidative agents as disease modifying therapies. While, the result of numerous preclinical studies has demonstrated the benefits of anti-inflammatory agents, these benefits however have not been replicated in clinical trials, necessitating a further search for more promising anti-inflammatory agents. Current understanding highlights the role of diet in the development of neuroinflammation and oxidative stress, as well as the importance of dietary interventions and lifestyle modifications in mitigating them. The current narrative review examines scientific literature for evidence of the roles (if any) of dietary components, nutraceuticals and functional foods in the prevention or management of AD. It also examines how diet/ dietary components could modulate oxidative stress/inflammatory mediators and pathways that are crucial to the pathogenesis and/or progression of AD.

Systemic inflammasome activation and pyroptosis associate with the progression of amnestic mild cognitive impairment and Alzheimer's disease

BACKGROUND

Growing evidence indicates that inflammasome-mediated inflammation plays important roles in the pathophysiology of amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD). Pyroptosis induced by inflammasome, and Gasdermin D (GSDMD) is involved in several neurodegenerative disorders. However, it is not clear whether peripheral inflammasome and pyroptosis are activated in aMCI and AD patients, influencing on neuroinflammation. The aim of this study was to examine the association between systemic inflammasome-induced pyroptosis and clinical features in aMCI and AD.

METHODS

A total of 86 participants, including 33 subjects with aMCI, 33 subjects with AD, and 20 cognitively normal controls, in this study. The Mini Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA) scale were used for cognitive assessment. Levels of inflammasome-related genes/proteins in peripheral blood mononuclear cells (PBMCs) were determined using quantitative polymerase chain reaction and Western blotting. The levels of IL-1β, Aβ1-42, Aβ1-40, p-tau, and t-tau in cerebrospinal fluid (CSF), as well as the plasma IL-1β level, were measured by enzyme-linked immunosorbent assay. Finally, lipopolysaccharides (LPS) were used to investigate the effects of systemic inflammasome-induced pyroptosis in an AD mice model.

RESULTS

Several genes involved in the inflammatory response were enriched in PBMCs of AD patients. The mRNA and protein levels of NLRP3, caspase-1, GSDMD, and IL-1β were increased in PBMCs of aMCI and AD patients. The IL-1β level in plasma and CSF of aMCI and AD patients was significantly higher than that in controls and negatively correlated with the CSF Aβ1-42 level, as well as MMSE and MoCA scores. Furthermore, there was a positive correlation between the IL-1β level in plasma and CSF of aMCI or AD patients. In vivo experiments showed that systemic inflammasome-induced pyroptosis aggravated neuroinflammation in 5 × FAD mice.

CONCLUSIONS

Our findings showed that canonical inflammasome signaling and GSDMD-induced pyroptosis were activated in PBMCs of aMCI and AD patients. In addition, the proinflammatory cytokine IL-1β was strongly associated with the pathophysiology of aMCI and AD. As such, targeting inflammasome-induced pyroptosis may be a new approach to inhibit neuroinflammation in aMCI and AD patients.

Innate immunity receptors in depression and suicide: upregulated NOD-like receptors containing pyrin (NLRPs) and hyperactive inflammasomes in the postmortem brains of people who were depressed and died by suicide

BACKGROUND

Abnormalities of inflammation have been implicated in the pathophysiology of depression and suicide, based on observations of increased levels of proinflammatory cytokines in the serum of people who were depressed and died by suicide. More recently, abnormalities in cytokines and innate immunity receptors such as toll-like receptors have also been observed in the postmortem brains of people who were depressed and died by suicide. In addition to toll-like receptors, another subfamily of innate immunity receptors known as NOD-like receptors containing pyrin (NLRPs) are the most widely present NOD-like receptors in the central nervous system. NLRPs also form inflammasomes that play an important role in brain function. We studied the role of NLRPs in depression and suicide.

METHODS

We determined the protein and mRNA expression of NLRP1, NLRP3 and NLRP6 and the components of their inflammasomes (i.e., adaptor molecule apoptosis-associated speck-like protein [ASC], caspase1, caspase3, interleukin [IL]-1β and IL-18) postmortem in the prefrontal cortex of people who were depressed and died by suicide, and in healthy controls. We determined mRNA levels using quantitative polymerase chain reaction, and we determined protein expression using Western blot immunolabelling.

RESULTS

We found that the protein and mRNA expression levels of NLRP1, NLRP3, NLRP6, caspase3 and ASC were significantly increased in people who were depressed and died by suicide compared to healthy controls.

LIMITATIONS

Some people who were depressed and died by suicide were taking antidepressant medication at the time of their death.

CONCLUSION

Similar to toll-like receptors, NLRP and its inflammasomes were upregulated in people who were depressed and died by suicide compared to healthy controls. Innate immunity receptors in general - and NLRPs and inflammasomes in particular - may play an important role in the pathophysiology of depression and suicide.

NLRP3 Inflammasome-Dependent Increases in High Mobility Group Box 1 Involved in the Cognitive Dysfunction Caused by Tau-Overexpression

Tau hyperphosphorylation is a characteristic alteration present in a range of neurological conditions, such as traumatic brain injury (TBI) and neurodegenerative diseases. Treatments targeting high-mobility group box protein 1 (HMGB1) induce neuroprotective effects in these neuropathologic conditions. However, little is known about the interactions between hyperphosphorylated tau and HMGB1 in neuroinflammation. We established a model of TBI with controlled cortical impacts (CCIs) and a tau hyperphosphorylation model by injecting the virus encoding human P301S tau in mice, and immunofluorescence, western blotting analysis, and behavioral tests were performed to clarify the interaction between phosphorylated tau (p-tau) and HMGB1 levels. We demonstrated that p-tau and HMGB1 were elevated in the spatial memory-related brain regions in mice with TBI and tau-overexpression. Animals with tau-overexpression also had significantly increased nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome activation, which manifested as increases in apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), activating caspase-1 and interleukin 1 beta (IL-1β) levels. In addition, NLRP3^–/– mice and the HMGB1 inhibitor, glycyrrhizin, were used to explore therapeutic strategies for diseases with p-tau overexpression. Compared with wild-type (WT) mice with tau-overexpression, downregulation of p-tau and HMGB1 was observed in NLRP3^–/– mice, indicating that HMGB1 alterations were NLRP3-dependent. Moreover, treatment with glycyrrhizin at a late stage markedly reduced p-tau levels and improved performance in the Y- and T-mazes and the ability of tau-overexpressing mice to build nests, which revealed improvements in spatial memory and advanced hippocampal function. The findings identified that p-tau has a triggering role in the modulation of neuroinflammation and spatial memory in an NLRP3-dependent manner, and suggest that treatment with HMGB1 inhibitors may be a better therapeutic strategy for tauopathies.

Immune modulations and immunotherapies for Alzheimer's disease: a comprehensive review

Alzheimer's disease (AD), the most common cause of dementia, is characterized by progressive cognitive and memory impairment ensued from neuronal dysfunction and eventual death. Intraneuronal deposition of tau proteins and extracellular senile amyloid-β plaques have ruled as the supreme postulations of AD for a relatively long time, and accordingly, a wide range of therapeutics, especially immunotherapies have been implemented. However, none of them resulted in significant positive cognitive outcomes. Especially, the repetitive failure of anti-amyloid therapies proves the inefficiency of the amyloid cascade hypothesis, suggesting that it is time to reconsider this hypothesis. Thus, for the time being, the focus is being shifted to neuroinflammation as a third core pathology in AD. Neuroinflammation was previously considered a result of the two aforementioned phenomena, but new studies suggest that it might play a causal role in the pathogenesis of AD. Neuroinflammation can act as a double-edged sword in the pathogenesis of AD, and the activation of glial cells is indispensable for mediating such attenuating or detrimental effects. The association of immune-related genes polymorphisms with the clinical phenotype of AD as well as the protective effect of anti-inflammatory drugs like nonsteroidal anti-inflammatory drugs supports the possible causal role of neuroinflammation in AD. Here, we comprehensively review immune-based therapeutic approaches toward AD, including monoclonal antibodies and vaccines. We also discuss their efficacy and underlying reasons for shortcomings. Lastly, we highlight the capacity of modulating the neuroimmune interactions and targeting neuroinflammation as a promising opportunity for finding optimal treatments for AD.

Targeting NLRP3 Inflammasome in Translational Treatment of Nervous System Diseases: An Update

Neuroinflammatory response is the immune response mechanism of the innate immune system of the central nervous system. Both primary and secondary injury can activate neuroinflammatory response. Among them, the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome plays a key role in the inflammatory response of the central system. Inflammasome is a type of pattern recognition receptor, a cytoplasmic polyprotein complex composed of members of the Nod-like receptor (NLR) family and members of the pyrin and HIN domain (PYHIN) family, which can be affected by a variety of pathogen-related molecular patterns or damage-related molecular patterns are activated. As one of the research hotspots in the field of medical research in recent years, there are increasing researches on immune function abnormalities in the onset of neurological diseases such as depression, AD, ischemic brain injury and cerebral infarction, the NLRP3 inflammasome causes the activated caspase-1 to cleave pre-interleukin-1β and pre-interleukin-18 into mature interleukin-1β and interleukin-18, in turn, a large number of inflammatory factors are produced, which participate in the occurrence and development of the above-mentioned diseases. Targeted inhibition of the activation of inflammasomes can reduce the inflammatory response, promote the survival of nerve cells, and achieve neuroprotective effects. This article reviews NLRP3 inflammasome's role in neurological diseases and related regulatory mechanisms, which providing references for future research in this field.

Dietary Spray-Dried Porcine Plasma Reduces Neuropathological Alzheimer's Disease Hallmarks in SAMP8 Mice

Alzheimer's disease (AD) is characterized by the aberrant processing of amyloid precursor protein (APP) and the accumulation of hyperphosphorylated tau, both of which are accompanied by neuroinflammation. Dietary supplementation with spray-dried porcine plasma (SDP) has anti-inflammatory effects in inflammation models. We investigated whether dietary supplementation with SDP prevents the neuropathological features of AD. The experiments were performed in 2- and 6-month-old SAMP8 mice fed a control diet, or a diet supplemented with 8% SDP, for 4 months. AD brain molecular markers were determined by Western blot and real-time PCR. Senescent mice showed reduced levels of p-GSK3β (Ser9) and an increase in p-CDK5, p-tau (Ser396), sAPPβ, and the concentration of Aβ40, (all p < 0.05). SDP prevented these effects of aging and reduced Bace1 levels (all p < 0.05). Senescence increased the expression of Mme1 and Ide1 and pro-inflammatory cytokines (Il-17 and Il-18; all p < 0.05); these changes were prevented by SDP supplementation. Moreover, SDP increased Tgf-β expression (p < 0.05). Furthermore, in aged mice, the gene expression levels of the microglial activation markers Trem2, Ym1, and Arg1 were increased, and SDP prevented these increases (all p < 0.05). Thus, dietary SDP might delay AD onset by reducing its hallmarks in senescent mice.