Activation of NLRP3 Inflammasome and Onset of Alzheimer's Disease

Advances in the Understanding of the Correlation Between Neuroinflammation and Microglia in Alzheimer's Disease

Alzheimer's disease (AD) is a fatal neurodegenerative disease with a subtle and progressive onset and is the most common type of dementia. However, its etiology and pathogenesis have not yet been fully elucidated. The common pathological manifestations of AD include extraneuronal β-amyloid deposition (Aβ), intraneuronal tau protein phosphorylation leading to the formation of 'neurofibrillary tangles' (NFTs), neuroinflammation, progressive loss of brain neurons/synapses, and glucose metabolism disorders. Current treatment approaches for AD primarily focus on the 'Aβ cascade hypothesis and abnormal aggregation of hyperphosphorylation of tau proteins', but have shown limited efficacy. Therefore, there is an ongoing need to identify more effective treatment targets for AD. The central nervous system (CNS) inflammatory response plays a key role in the occurrence and development of AD. Neuroinflammation is an immune response activated by glial cells in the CNS that usually occurs in response to stimuli such as nerve injury, infection and toxins or in response to autoimmunity. Neuroinflammation ranks as the third most prominent pathological feature in AD, following Aβ and NFTs. In recent years, the focus on the role of neuroinflammation and microglia in AD has increased due to the advancements in genome-wide association studies (GWAS) and sequencing technology. Furthermore, research has validated the pivotal role of microglia-mediated neuroinflammation in the progression of AD. Therefore, this article reviews the latest research progress on the role of neuroinflammation triggered by microglia in AD in recent years, aiming to provide a new theoretical basis for further exploring the role of neuroinflammation in the process of AD occurrence and development.

Correlation between abnormal cellular immune and changes of magnetic resonance spectroscopy in patients with Alzheimer's disease

BACKGROUND

Evidence from previous studies indicates that neuroinflammation contributes to the onset of Alzheimer's Disease (AD). Moreover, cellular dysfunction is induced by impaired signaling of neurotransmitters. This study aimed to explore the correlation between cellular immune dysfunction and neurotransmitter changes through cranial Magnetic Resonance Spectroscopy (MRS) in AD patients.

METHODS

Here, 32 AD, 40 Vascular Dementia (VD), and 35 Non-Dementia Elderly Control (NDE) cases were enrolled. Flow cytometry was performed to characterize lymphocyte subsets in plasma samples. The IL-1β and Caspase-1 levels were detected by ELISA. The NLRP3 expression level was measured by Western Blot (WB). The equivalence of N-acetylaspartate (NAA), Creatine (Cr), Choline (Cho), and Inositol (MI) in bilateral hippocampi of patients was examined by MRS. The association of NAA/Cr or MI/Cr ratios with the proportion of T lymphocyte subsets or NK cell subsets was determined through single-factor correlation analysis.

RESULTS

The proportion of T lymphocyte subsets was significantly lower in the AD group than in the NDE group (P < 0.01). On the other hand, the Caspase-1, NLRP3, and IL-1β protein expression levels were significantly higher in the AD group than in the other groups. Further analysis showed that the NAA/Cr ratio was lower in the AD group than in the NDE group. Additionally, a significant positive correlation was found between the NAA/Cr ratio and the MMSE score (r = 0.81, P < 0.01). Moreover, a significant positive correlation was observed between the NAA/Cr and T lymphocyte ratios. The NAA/Cr ratio was significantly negatively correlated with the proportion of NK cells in the blood (r = －0.83, P < 0.01). A significant negative correlation was also recorded between the MI/Cr and T cell ratios in blood samples.

CONCLUSIONS

Impaired cellular immune dysfunction in AD patients was significantly correlated with abnormal MRS. Neuroimmune dysfunction may contribute to the pathogenesis of AD and alter the metabolism of neurotransmitters such as aspartic acid and MI in the brains of AD patients.

TRIAL REGISTRATION

Not applicable.

The interplay between mitochondrial dysfunction and NLRP3 inflammasome in multiple sclerosis: Therapeutic implications and animal model studies

Multiple sclerosis (MS) is a complex autoimmune disorder that impacts the central nervous system (CNS), resulting in inflammation, demyelination, and neurodegeneration. The NOD-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome, a multiprotein complex of the innate immune system, serves an essential role in the pathogenesis of MS by regulating the production of pro-inflammatory cytokines (IL-1β & IL-18) and the induction of pyroptotic cell death. Mitochondrial dysfunction is one of the main potential factors that can trigger NLRP3 inflammasome activation and lead to inflammation and axonal damage in MS. This highlights the importance of understanding how mitochondrial dynamics modulate NLRP3 inflammasome activity and contribute to the inflammatory and neurodegenerative features of MS. The lack of a comprehensive understanding of the pathogenesis of MS and the urge for the introduction of new therapeutic strategies led us to review the therapeutic potential of targeting the interplay between mitochondrial dysfunction and the NLRP3 inflammasome in MS. This paper also evaluates the natural and synthetic compounds that can improve mitochondrial function and/or inhibit the NLRP3 inflammasome, thereby providing neuroprotection. Moreover, it summarizes the evidence from animal models of MS that demonstrate the beneficial effects of these compounds on reducing inflammation, demyelination, and neurodegeneration. Finally, this review advocates for a deeper investigation into the molecular crosstalk between mitochondrial dynamics and the NLRP3 inflammasome as a means to refine therapeutic targets for MS.

Targeting lysosomal quality control as a therapeutic strategy against aging and diseases

Previously, lysosomes were primarily referred to as the digestive organelles and recycling centers within cells. Recent discoveries have expanded the lysosomal functional scope and revealed their critical roles in nutrient sensing, epigenetic regulation, plasma membrane repair, lipid transport, ion homeostasis, and cellular stress response. Lysosomal dysfunction is also found to be associated with aging and several diseases. Therefore, function of macroautophagy, a lysosome-dependent intracellular degradation system, has been identified as one of the updated twelve hallmarks of aging. In this review, we begin by introducing the concept of lysosomal quality control (LQC), which is a cellular machinery that maintains the number, morphology, and function of lysosomes through different processes such as lysosomal biogenesis, reformation, fission, fusion, turnover, lysophagy, exocytosis, and membrane permeabilization and repair. Next, we summarize the results from studies reporting the association between LQC dysregulation and aging/various disorders. Subsequently, we explore the emerging therapeutic strategies that target distinct aspects of LQC for treating diseases and combatting aging. Lastly, we underscore the existing knowledge gap and propose potential avenues for future research.

Targeting terminal pathway reduces brain complement activation, amyloid load and synapse loss, and improves cognition in a mouse model of dementia

Complement is dysregulated in the brain in Alzheimer's Disease and in mouse models of Alzheimer's disease. Each of the complement derived effectors, opsonins, anaphylatoxins and membrane attack complex (MAC), have been implicated as drivers of disease but their relative contributions remain unclarified. Here we have focussed on the MAC, a lytic and pro-inflammatory effector, in the AppNL-G-F mouse amyloidopathy model. To test the role of MAC, we back-crossed to generate AppNL-G-F mice deficient in C7, an essential MAC component. C7 deficiency ablated MAC formation, reduced synapse loss and amyloid load and improved cognition compared to complement-sufficient AppNL-G-F mice at 8-10 months age. Adding back C7 caused increased MAC formation in brain and an acute loss of synapses in C7-deficient AppNL-G-F mice. To explore whether C7 was a viable therapeutic target, a C7-blocking monoclonal antibody was administered systemically for one month in AppNL-G-F mice aged 8-9 months. Treatment reduced brain MAC and amyloid deposition, increased synapse density and improved cognitive performance compared to isotype control-treated AppNL-G-F mice. The findings implicate MAC as a driver of pathology and highlight the potential for complement inhibition at the level of MAC as a therapy in Alzheimer's disease.

Integrated Proteomics Characterization of NLRP3 Inflammasome Inhibitor MCC950 in Monocytic Cell Line Confirms Direct MCC950 Engagement with Endogenous NLRP3

Inhibition of the NLRP3 inflammasome is a promising strategy for the development of new treatments for inflammatory diseases. MCC950 is a potent and selective small-molecule inhibitor of the NLRP3 pathway and has been validated in numerous species and disease models. Although the capacity of MCC950 to block NLRP3 signaling is well-established, it is still critical to identify the mechanism of action and molecular targets of MCC950 to inform and derisk drug development. Quantitative proteomics performed in disease-relevant systems provides a powerful method to study both direct and indirect pharmacological responses to small molecules to elucidate the mechanism of action and confirm target engagement. A comprehensive target deconvolution campaign requires the use of complementary chemical biology techniques. Here we applied two orthogonal chemical biology techniques: compressed Cellular Thermal Shift Assay (CETSA) and photoaffinity labeling chemoproteomics, performed under biologically relevant conditions with LPS-primed THP-1 cells, thereby deconvoluting, for the first time, the molecular targets of MCC950 using chemical biology techniques. In-cell chemoproteomics with inlysate CETSA confirmed the suspected mechanism as the disruption of inflammasome formation via NLRP3. Further cCETSA (c indicates compressed) in live cells mapped the stabilization of NLRP3 inflammasome pathway proteins, highlighting modulation of the targeted pathway. This is the first evidence of direct MCC950 engagement with endogenous NLRP3 in a human macrophage cellular system using discovery proteomics chemical biology techniques, providing critical information for inflammasome studies.

Neuroinflammation of Microglial Regulation in Alzheimer's Disease: Therapeutic Approaches

Alzheimer's disease (AD) is a complex degenerative disease of the central nervous system that is clinically characterized by a progressive decline in memory and cognitive function. The pathogenesis of AD is intricate and not yet fully understood. Neuroinflammation, particularly microglial activation-mediated neuroinflammation, is believed to play a crucial role in increasing the risk, triggering the onset, and hastening the progression of AD. Modulating microglial activation and regulating microglial energy metabolic disorder are seen as promising strategies to intervene in AD. The application of anti-inflammatory drugs and the targeting of microglia for the prevention and treatment of AD has emerged as a new area of research interest. This article provides a comprehensive review of the role of neuroinflammation of microglial regulation in the development of AD, exploring the connection between microglial energy metabolic disorder, neuroinflammation, and AD development. Additionally, the advancements in anti-inflammatory and microglia-regulating therapies for AD are discussed.

Gut Microbiota Modulation and Its Implications on Neuropathic Pain: A Comprehensive Literature Review

Neuropathic pain (NP) is a chronic pain disorder arising from somatosensory nervous system impairment. Extensive evidence supports the notion that the gut microbiota (GM) is crucial in maintaining human health by performing vital tasks. At the same time, its disruption has been linked to the emergence and advancement of an expanding range of disorders, including NP, in which GM could play a role in its pathophysiology. The crosstalk between the nervous system and GM happens through immune mediators, metabolites, and nervous structures and involves both central and peripheral nervous systems. This literature review aims to thoroughly investigate the function of modulating GM in the treatment of NP. It will achieve this by integrating existing knowledge, identifying underlying mechanisms, and evaluating the possible clinical consequences of exploiting the gut-brain axis. We will cover the main therapeutic applications of the described GM-modulators, such as probiotics, faecal microbiota transplantation, dietary supplements and emotional support, to the main kinds of NP in which any evidence, even if only pre-clinical, has been unravelled in recent years. The explored NP areas include chemotherapy-induced peripheral neuropathy, diabetic neuropathy, trauma-induced neuropathic pain, trigeminal neuralgia, postherpetic neuralgia and low back pain.

Inflammation, Autoimmunity and Neurodegenerative Diseases, Therapeutics and Beyond

Neurodegenerative disease (ND) incidence has recently increased due to improved life expectancy. Alzheimer's (AD) or Parkinson's disease (PD) are the most prevalent NDs. Both diseases are poly genetic, multifactorial and heterogenous. Preventive medicine, a healthy diet, exercise, and controlling comorbidities may delay the onset. After the diseases are diagnosed, therapy is needed to slow progression. Recent studies show that local, peripheral and age-related inflammation accelerates NDs' onset and progression. Patients with autoimmune disorders like inflammatory bowel disease (IBD) could be at higher risk of developing AD or PD. However, no increase in ND incidence has been reported if the patients are adequately diagnosed and treated. Autoantibodies against abnormal tau, β amyloid and α- synuclein have been encountered in AD and PD and may be protective. This discovery led to the proposal of immune-based therapies for AD and PD involving monoclonal antibodies, immunization/ vaccines, pro-inflammatory cytokine inhibition and anti-inflammatory cytokine addition. All the different approaches have been analysed here. Future perspectives on new therapeutic strategies for both disorders are concisely examined.

TLR4/Rac1/NLRP3 Pathway Mediates Amyloid-β-Induced Neuroinflammation in Alzheimer's Disease

Background

Neuroinflammation plays a crucial part in the initial onset and progression of Alzheimer's disease (AD). NLRP3 inflammasome was demonstrated to get involved in amyloid-β (Aβ)-induced neuroinflammation. However, the mechanism of Aβ-triggered activation of NLRP3 inflammasome remains poorly understood.

Objective

Based on our previous data, the study aimed to identify the downstream signals that bridge the activation of TLR4 and NLRP3 inflammasome associated with Aβ.

Methods

BV-2 cells were transfected with TLR4siRNA or pretreated with a CLI-095 or NSC23766, followed by Aβ1-42 treatment. APP/PS1 mice were injected intraperitoneally with CLI-095 or NSC23766. NLRP3 inflammasome and microglia activation was detected with immunostaining and western blot. G-LISA and Rac1 pull-down activation test were performed to investigate the activation of Rac1. Real-time PCR and ELISA were used to detect the inflammatory cytokines. Aβ plaques were assessed by western blotting and immunofluorescence staining. Morris water maze test was conducted to determine the spatial memory in mice.

Results

Rac1 and NLRP3 inflammasome were activated by Aβ in both in vitro and in vivo experiments. Inhibition of TLR4 reduced the activity of Rac1 and NLRP3 inflammasome induced by Aβ1-42. Furthermore, inhibition of Rac1 blocked NLRP3 inflammasome activation mediated by TLR4. Blocking the pathway by CLI095 or NSC23766 suppressed Aβ1-42-triggered activation of microglia, reduced the expression of pro-inflammatory mediators and ameliorated the cognition deficits in APP/PS1 mice.

Conclusions

Our study demonstrated that TLR4/Rac1/NLRP3 pathway mediated Aβ-induced neuroinflammation, which unveiled a novel pathway and key contributors underlying the pathogenic mechanism of Aβ.

Food-derived peptides as novel therapeutic strategies for NLRP3 inflammasome-related diseases: a systematic review

NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3), a member of the nucleotide-binding domain (NOD) and leucine-rich repeat sequence (LRR) protein (NLR) family, plays an essential role in the inflammation initiation and inflammatory mediator secretion, and thus is also associated with many disease progressions. Food-derived bioactive peptides (FDBP) exhibit excellent anti-inflammatory activity in both in vivo and in vitro models. They are encrypted in plant, meat, and milk proteins and can be released under enzymatic hydrolysis or fermentation conditions, thereby hindering the progression of hyperuricemia, inflammatory bowel disease, chronic liver disease, neurological disorders, lung injury and periodontitis by inactivating the NLRP3. However, there is a lack of systematic review around FDBP, NLRP3, and NLRP3-related diseases. Therefore, this review summarized FDBP that exert inhibiting effects on NLRP3 inflammasome from different protein sources and detailed their preparation and purification methods. Additionally, this paper also compiled the possible inhibitory mechanisms of FDBP on NLRP3 inflammasomes and its regulatory role in NLRP3 inflammasome-related diseases. Finally, the progress of cutting-edge technologies, including nanoparticle, computer-aided screening strategy and recombinant DNA technology, in the acquisition or encapsulation of NLRP3 inhibitory FDBP was discussed. This review provides a scientific basis for understanding the anti-inflammatory mechanism of FDBP through the regulation of the NLRP3 inflammasome and also provides guidance for the development of therapeutic adjuvants or functional foods enriched with these FDBP.

Assess Alzheimer's Disease via Plasma Extracellular Vesicle-derived mRNA

Alzheimer's disease (AD), the most prevalent neurodegenerative disorder globally, has emerged as a significant health concern, particularly due to the increasing aging population. Recently, it has been revealed that extracellular vesicles (EVs) originating from neurons play a critical role in AD pathogenesis and progression. These neuronal EVs can cross the blood-brain barrier and enter peripheral circulation, offering a less invasive means for assessing blood-based AD biomarkers. In this study, we analyzed plasma EV-derived messenger RNA (mRNA) from 82 subjects, including individuals with AD, mild cognitive impairment (MCI), and healthy controls, using next-generation sequencing (NGS) to profile their gene expression for functional enrichment and pathway analysis. Based on the differentially expressed genes identified in both MCI and AD groups, we established a diagnostic model by implementing a machine learning classifier. The refined model demonstrated an average diagnostic accuracy over 98% and showed a strong correlation with different AD stages, suggesting the potential of plasma EV-derived mRNA as a promising non-invasive biomarker for early detection and ongoing monitoring of AD.

Pyroptosis in neurodegenerative diseases: from bench to bedside

The central nervous system regulates all aspects of physiology to some extent. Neurodegenerative diseases (NDDs) lead to the progressive loss and dysfunction of neurons, which are particularly evident in Alzheimer's disease, Parkinson's disease, and many other conditions. NDDs are multifactorial diseases with complex pathogeneses, and there has been a rapid increase in the prevalence of NDDs. However, none of these diseases can be cured, making the development of novel treatment strategies an urgent necessity. Numerous studies have indicated how pyroptosis induces inflammation and affects many aspects of NDD. Therefore, components related to pyroptosis are potential therapeutic candidates and are attracting increasing attention. Here, we review the role of pyroptosis in the pathogenesis of NDDs and potential treatment options. Additionally, several of the current drugs and relevant inhibitors are discussed. Through this article, we provide theoretical support for exploring new therapeutic targets and updating clinical treatment strategies for NDDs. Notably, pyroptosis, a recently widely studied mode of cell death, is still under-researched compared to other traditional forms of cell death. Moreover, the focus of research has been on the onset and progression of NDDs, and the lack of organ-specific target discovery and drug development is a common problem for many basic studies. This urgent problem requires scientists and companies worldwide to collaborate in order to develop more effective drugs against NDDs.

Diallyl disulfide attenuates pyroptosis via NLRP3/Caspase-1/IL-1β signaling pathway to exert a protective effect on hypoxic-ischemic brain damage in neonatal rats

Hypoxic-ischemic encephalopathy (HIE) is a perinatal brain disease caused by hypoxia in neonates. It is one of the leading causes of neonatal death in the perinatal period, as well as disability beyond the neonatal period. Due to the lack of a unified and comprehensive treatment strategy for HIE, research into its pathogenesis is essential. Diallyl disulfide (DADS) is an allicin extract, with detoxifying, antibacterial, and cardiovascular disease protective effects. This study aimed to determine whether DADS can alleviate HIE induced brain damage in rats and oxygen-glucose deprivation (OGD)-induced pyroptosis in PC12 cells, as well as whether it can inhibit pyroptosis via the NLRP3/Caspase-1/IL-1β signaling pathway. In vivo, DADS significantly reduced the cerebral infarction volume, alleviated inflammatory reaction, reduced astrocyte activation, promoted tissue structure recovery, improved pyroptosis caused by HIE and improved the prognosis following HI injury. In vitro findings indicated that DADS increased cell activity, decreased LDH activity and reduced the expression of pyroptosis-related proteins, including IL-1β, IL-18, and certain inflammatory factors in PC12 cells caused by OGD. Mechanistically, DADS inhibited pyroptosis and protected against HIE via the NLRP3/Caspase-1/IL-1β pathway. The specific inhibitor of caspase-1, VX-765, inhibited caspase-1 activation, and IL-1β expression was determined. Additionally, the overexpression of NLRP3 reversed the protective effect of allicin against OGD-induced pyroptosis. In conclusion, these findings demonstrated that DADS inhibits the NLRP3/Caspase-1/IL-1β signaling pathway and decreases HI brain damage.

Role of the NLRP3 inflammasome in gynecological disease

The NLR family pyrin domain containing 3 (NLRP3) inflammasome is involved in the innate immune system and is a three-part macromolecular complex comprising the NLRP3 protein, apoptosis-associated speck-like protein containing a CARD (ASC) and the cysteine protease pro-caspase-1. When the NLRP3 inflammasome is activated, it can produce interleukin (IL)- 1β and IL-18 and eventually lead to inflammatory cell pyroptosis. Related studies have demonstrated that the NLRP3 inflammasome can induce an immune response and is related to the occurrence and development of gynecological diseases, such as endometriosis, polycystic ovary syndrome and breast cancer. NLRP3 inflammasome inhibitors are beneficial for maintaining cellular homeostasis and tissue health and have been found effective in targeting some gynecological diseases. However, excessive inhibitor concentrations have been found to cause adverse effects. Therefore, proper control of NLRP3 inflammasome activity is critical. This paper summarizes the structure and function of the NLRP3 inflammasome and highlights the therapeutic potential of targeting it in gynecological diseases, such as endometriosis, polycystic ovary syndrome and breast cancer The application of NLRP3 inflammasome inhibitors is also discussed.

Effects of Jatrorrhizine on inflammatory response induced by H2O2 in microglia by regulating the MAPK/NF-κB/NLRP3 signaling pathway

Microglia-induced neuroinflammation is a contributing factor to neurodegenerative diseases. Jatrorrhizine (JAT), an alkaloid isolated from Huanglian, has been shown to have neuroprotective effects against various neurodegenerative diseases, but its impact on microglia-induced neuroinflammation remains unclear. In this study, we investigated the role of JAT in MAPK/NF-κB/NLRP3 signaling pathway in an H2O2-induced oxidative stress model using microglia (N9 cells). We divided cells into six groups, including control, JAT, H2O2, H2O2 + 5 μmol/L JAT, H2O2 + 10 μmol/L JAT, and H2O2 + 20 μmol/L minocycline groups. Cell viability was measured using MTT assay and TNF-α levels were detected with an ELISA Kit. Western blot was used to detect NLRP3, HMGB1, NF-κB, p-NF-κB, ERK, p-ERK, p38, p-p38, p-JNK, JNK, IL-1β, and IL-18 expressions. Our results showed that JAT intervention improved H2O2-induced cytotoxicity in N9 cells and reduced the elevated expression of TNF-α, IL-1β, IL-18, p-ERK/ERK, p-p38/p38, p-JNK/JNK, p-p65/p65, NLRP3, and HMGB1 in H2O2 group. Furthermore, treatment with ERK inhibitor SCH772984 specifically blocked ERK phosphorylation, resulting in decreased protein levels of p-NF-κB, NLRP3, IL-1β, and IL-18 in H2O2 group. These results suggest that the MAPK/NF-κB signaling pathway may regulate the protein levels of NLRP3. Overall, our study indicates that JAT may have a protective effect on H2O2-treated microglia via inhibition the MAPK/NF-κB/NLRP3 pathway and could be a potential therapeutic approach for neurodegenerative diseases.

Ghrelin inhibits NLRP3 inflammasome activation by upregulating autophagy to improve Alzheimer's disease

Nod-like receptor protein 3 (NLRP3) inflammasome, autophagy, and the aggregation of β-amyloid (Aβ) are key factors in Alzheimer's disease (AD) development. Ghrelin has shown promise in providing neuroprotection for AD. However, the mechanism underlying ghrelin's ability to improve AD by modulating autophagy and the NLRP3 inflammasome requires further clarification. Primary hippocampus neurons and mice were stimulated with Aβ1-42 to create an in vitro and in vivo AD model, followed by ghrelin administration for intervention. Additionally, we subjected the cells to 3-methyladenine (3-MA) treatment. Neuron morphology, microtubule-associated protein 2 (MAP-2) expression, apoptosis, cytokine levels, and protein expression were measured using various techniques. The escape latency of mice was assessed using the Morris water maze (MWM) test, and histopathology of the hippocampus was determined using hematoxylin-eosin staining. At 1-100 nM, ghrelin increased neuron/synapse numbers and MAP-2 expression dose-dependently while blocking apoptosis in Aβ1-42-treated cells. Moreover, ghrelin reduced the expression of Aβ1-42, p-Tau/Tau, p62, NLRP3, ASC, and cleaved Caspase-1, while increasing the expression of LC3II/LC3I and Beclin1 in AD cells. Furthermore, ghrelin treatment also decreased the levels of Aβ1-42, IL-1β, and IL-18 in the cells. The effects of ghrelin were reversed by 3-MA. Our in vivo experiments provided further confirmation of the above effect of ghrelin on AD. Additionally, the injection of Aβ1-42 induced increased escape latency in mice and histopathological changes in hippocampal neurons. All of these abnormalities were significantly improved following administration of ghrelin. Ghrelin mitigated Aβ1-42-induced neurotoxicity and relieved neuronal damage by upregulating autophagy to inactivate NLRP3, thus showing promising potential in treating AD.

In-silico modeling of the interplay between APOE4, NLRP3, and ACE2-SPIKE complex in neurodegeneration between Alzheimer and SARS-CoV: implications for understanding pathogenesis and developing therapeutic strategies

The multifaceted interplay between neurodegenerative pathologies, including Alzheimer's disease (AD), and the highly virulent severe acute respiratory syndrome coronavirus (SARS-CoV), is implicated in various conditions. AD and SARS-CoV pathogenesis involve the APOE4 allele, NLRP3 inflammasome, and ACE2-SPIKE complex. APOE4, a genetic polymorphism of the APOE gene, is associated with an increased susceptibility to AD. NLRP3, an inflammatory protein of the innate immune system, plays a pivotal role in immune response cascades. In SARS-CoV, the ACE2 receptor serves as the principal portal for cellular entry, while APOE4 intricately interacts with the ACE2-spike protein complex, enhancing viral internalization process. The interaction of NLRP3 with the ACE2-spike protein complex leads to increased inflammatory signaling. The convergence of APOE4/NLRP3 and ACE2-spike protein complex interactions suggests a possible link between SARS and AD. Therefore, the current research centralizes the association between by utilizing SARS-CoV datasets to explore possible mechanisms that account for the pathogenesis of SARS-CoV and AD. The work is further extended to unveil the molecular interactions of APOE4 and NLRP3 with the ACE2-Spike protein complex at the molecular level by employing molecular dynamics simulation techniques. The therapeutic efficacy of Chyawanprash nutraceuticals is evaluated as their inhibitory potential towards APOE4-ACE2-Spike protein and NLRP3-ACE2-Spike protein complexes. Notably, our simulations unequivocally demonstrate the robust and enduring binding capability of the compound Phyllantidine with the target complexes throughout the simulation period. The findings of the studies further corroborate the primary hypothesis of APOE4 and NLRP3 as driver factors in the pathogenesis of both SARS-CoV and AD. Therefore, this research establishes a paradigm for comprehending the complex interaction between AD and SARS-CoV and lays the groundwork for further study in this domain.Communicated by Ramaswamy H. Sarma.

Aging Aggravates Periodontal Inflammatory Responses and Alveolar Bone Resorption by Porphyromonas gingivalis Infection

Periodontitis is a chronic inflammatory disease driven by periodontal pathogens such as Porphyromonas gingivalis (P. gingivalis), and its prevalence increases with age. However, little is known about the effect of immunosenescence on inflammatory response to P. gingivalis infection. In the present study, 16S rDNA sequencing analysis showed the relative abundance of P. gingivalis was significantly higher in periodontitis patients than healthy group, but there was no difference between the young (20 to 40 years old) and old (65 to 86 years old) periodontitis groups. Furthermore, the cytotoxic effect of P. gingivalis was greater on old THP-1 macrophages and on bone mar-row-derived cells (BMDMs) from old mice, and levels of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-12 were higher in old than in young THP-1 macrophages. Furthermore, the activations of inflammasome components for IL-1β production by P. gingivalis infection were greater in old THP-1 macrophages. Finally, bone loss was significantly greater in P. gingivalis-infected aged mice than in young mice. These findings indicate that aging aggravates P. gingivalis-induced inflammatory cytokine secretion and inflammasome activation. The study enhances understanding of the relationship between periodontal immunosenescence and inflammatory response in the elderly.

Common Signaling Pathways Involved in Alzheimer's Disease and Stroke: Two Faces of the Same Coin

Alzheimer's disease (AD) and stroke are two interrelated neurodegenerative disorders which are the leading cause of death and affect the neurons in the brain and central nervous system. Although amyloid-β aggregation, tau hyperphosphorylation, and inflammation are the hallmarks of AD, the exact cause and origin of AD are still undefined. Recent enormous fundamental discoveries suggest that the amyloid hypothesis of AD has not been proven and anti-amyloid therapies that remove amyloid deposition have not yet slowed cognitive decline. However, stroke, mainly ischemic stroke (IS), is caused by an interruption in the cerebral blood flow. Significant features of both disorders are the disruption of neuronal circuitry at different levels of cellular signaling, leading to the death of neurons and glial cells in the brain. Therefore, it is necessary to find out the common molecular mechanisms of these two diseases to understand their etiological connections. Here, we summarized the most common signaling cascades including autotoxicity, ApoE4, insulin signaling, inflammation, mTOR-autophagy, notch signaling, and microbiota-gut-brain axis, present in both AD and IS. These targeted signaling pathways reveal a better understanding of AD and IS and could provide a distinguished platform to develop improved therapeutics for these diseases.

The involvement of NLRP3 inflammasome in CUMS-induced AD-like pathological changes and related cognitive decline in mice

BACKGROUND

Numerous studies have found that inhibiting the expression of NLRP3 inflammasome can significantly improve depressive-like behaviors in mice, but the research on its effect on cognitive decline in depression and its mechanism is still lacking. This study aimed to elucidate the role of NLRP3 inflammasome in cognitive decline in depression and explore the common neuro-immunological mechanisms of depression and Alzheimer's disease (AD).

METHODS

Male C57BL/6 mice were subjected to chronic unpredictable mild stress (CUMS) for 5 weeks, treatment group was administered with the NLRP3 inhibitor MCC950 (10 mg/kg, i.p.), fluoxetine served as positive control. Then, the mice were assessed for cognitive behaviors and depression-like behaviors, and changes of microglia and neurons in hippocampus and levels of Aβ metabolic pathway and tau protein were measured. To explore the mechanism of NLRP3 activation on neurons, we performed in vitro studies using BV2 microglia and mouse primary neurons. Furthermore, we focused on the role of NLRP3 inflammasome in the function of neurons and the expression of AD pathological indicators.

RESULTS

CUMS induced depressive-like behaviors and cognitive decline in mice, which could be reversed by inhibiting NLRP3 inflammasome. MCC950, a specific NLRP3 inhibitor, alleviated CUMS-induced neuron injury and AD-like pathological changes, including the abnormal expression of Aβ metabolic pathway and the hyper-phosphorylation of tau protein. LPS (1 μg/mL) + ATP (1 mM) treatment activated the expression of NLRP3 inflammasome and IL-1β in vitro. In vitro experiment also proved that inhibiting the expression of NLRP3 inflammasome in microglia can restore the Aβ metabolic pathway to normal, decrease neuronal tau protein phosphorylation and protect neurons.

CONCLUSIONS

Inhibition of NLRP3 inflammasome effectively alleviated CUMS-induced depressive-like behaviors and cognitive decline in mice, and inhibited the activation of AD physiological indicators.

Cause or consequence? The role of IL-1 family cytokines and receptors in neuroinflammatory and neurodegenerative diseases

Cytokines and receptors of the IL-1 family are key mediators in innate immune and inflammatory reactions in physiological defensive conditions, but are also significantly involved in immune-mediated inflammatory diseases. Here, we will address the role of cytokines of the IL-1 superfamily and their receptors in neuroinflammatory and neurodegenerative diseases, in particular Multiple Sclerosis and Alzheimer's disease. Notably, several members of the IL-1 family are present in the brain as tissue-specific splice variants. Attention will be devoted to understanding whether these molecules are involved in the disease onset or are effectors of the downstream degenerative events. We will focus on the balance between the inflammatory cytokines IL-1β and IL-18 and inhibitory cytokines and receptors, in view of future therapeutic approaches.

Thymopentin (TP-5) prevents lipopolysaccharide-induced neuroinflammation and dopaminergic neuron injury by inhibiting the NF-κB/NLRP3 signaling pathway

Neuroinflammation plays a pivotal role in neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis and stroke, and is accompanied by excessive release of inflammatory cytokines and mediators by activated microglia. Microglial inflammatory response inhibition may be an effective strategy for preventing inflammatory disorders. However, the reciprocal connections between the central nervous system (CNS) and immune system have not been elucidated. Thus far, these links have been proven to mainly involve immuno- and neuropeptides. The pentapeptide thymopentin (TP-5) exerts a significant immunomodulatory effect; however, its antineuroinflammatory effects and underlying mechanism are still unclear. In this study, lipopolysaccharide (LPS) was used to establish an inflammation model, and the therapeutic effect of TP-5 was evaluated. Behavioral tests showed that TP-5 treatment could improve the performance of LPS-treated mice in the open field and pole test, but not hanging wire test. TP-5 also attenuated neuronal lesions in the brains of LPS-treated mice. TP-5 reduced cytotoxicity and morphological changes in activated microglia. Label-free quantitative analysis indicated that the expression of multiple proteins and the activation of associated signaling pathways were altered by TP-5. Moreover, TP-5 could inhibit LPS-induced neuroinflammation in the brain and BV2 microglia and the expression of major genes in the NF-κB/NLRP3 signaling pathway. Additionally, tyrosine hydroxylase (TH) expression downregulation was rescued in the LPS + TP-5 group compared with the LPS group. We conclude that TP-5 exerts neuroprotection by alleviating LPS-induced inflammatory damage and dopaminergic neurodegeneration. The protective effect of TP-5 may involve the NF-κB/NLRP3 signaling pathway.

Essential oil of Acorus tatarinowii Schott inhibits neuroinflammation by suppressing NLRP3 inflammasome activation in 3 × Tg-AD transgenic mice

BACKGROUND

Shi chang pu (Acorus tatarinowii Schott) is a herbal used in the treatment of Alzheimer's disease (AD) in China. The essential oil of Shi chang pu (SCP-oil) is the main active component. However, its effects on the neuroinflammation of AD have not been well studied.

PURPOSE

Neuroinflammation mediated by the NLRP3 inflammasome plays a crucial role in AD. This study was designed to evaluate the effect of SCP-oil on cognitive impairment of App_Swe/PSEN1_M146V/MAPT_P301L triple transgenic (3 × Tg-AD) mice model and investigate the mechanism underlying its anti-inflammation effects.

METHODS

Thirty-two 3 × Tg-AD mice at 12 months and 8 wild-type B6 mice were used for this experiment. The 3 × Tg-AD mice were administered with SCP-oil or donepezil hydrochloride for 8 weeks. Morris water maze test and step-down test were used to evaluate the cognitive ability of mice. The pathological changes, neuroinflammation, and the NLRP3 inflammasome related-protein of AD mice were detected by histomorphological examination, TUNEL staining, immunofluorescence, immunohistochemistry, qRT-PCR, Elisa, and western blot assays.

RESULTS

SCP-oil treatment attenuated cognitive dysfunction of 3 × Tg-AD mice. Moreover, SCP-oil also ameliorated characteristics pathological of AD, such as pathological changes damage, deposition of Aβ, phosphorylation of Tau, and neuronal loss. Additionally, SCP-oil treatment alleviated the neuroinflammation and inhibited phosphorylation of IKKβ, NF-κB, and NLRP3 inflammasome related-protein NLRP3, ASC, Caspase-1, cleaved-Caspase-1, and GSDMD-N in the hippocampus of 3 × Tg-AD mice.

CONCLUSION

Overall, SCP-oil contributed to neuroprotection in 3 × Tg-AD mice by reduced activation of NLRP3 inflammasome by inhibiting the NF-κB signaling pathway.

Virus-Like Cytosolic and Cell-Free Oxidatively Damaged Nucleic Acids Likely Drive Inflammation, Synapse Degeneration, and Neuron Death in Alzheimer's Disease

Oxidative stress, inflammation, and amyloid-β are Alzheimer's disease (AD) hallmarks that cause each other and other AD hallmarks. Most amyloid-β-lowering, antioxidant, anti-inflammatory, and antimicrobial AD clinical trials failed; none stopped or reversed AD. Although signs suggest an infectious etiology, no pathogen accumulated consistently in AD patients. Neuropathology, neuronal cell culture, rodent, genome-wide association, epidemiological, biomarker, and clinical studies, plus analysis using Hill causality criteria and revised Koch's postulates, indicate that the virus-like oxidative damage-associated molecular-pattern (DAMP) cytosolic and cell-free nucleic acids accumulated in AD patients' brains likely drive neuroinflammation, synaptotoxicity, and neurotoxicity. Cytosolic oxidatively-damaged mitochondrial DNA accumulated outside mitochondria dose-dependently in preclinical AD and AD patients' hippocampal neurons, and in AD patients' neocortical neurons but not cerebellar neurons or glia. In oxidatively-stressed neural cells and rodents' brains, cytosolic oxidatively-damaged mitochondrial DNA accumulated and increased antiviral and inflammatory proteins, including cleaved caspase-1, interleukin-1β, and interferon-β. Cytosolic double-stranded RNA and DNA are DAMPs that induce antiviral interferons and/or inflammatory proteins by oligomerizing with various innate-immune pattern-recognition receptors, e.g., cyclic GMP-AMP synthase and the nucleotide-binding-oligomerization-domain-like-receptor-pyrin-domain-containing-3 inflammasome. In oxidatively-stressed neural cells, cytosolic oxidatively-damaged mitochondrial DNA caused synaptotoxicity and neurotoxicity. Depleting mitochondrial DNA prevented these effects. Additionally, cell-free nucleic acids accumulated in AD patients' blood, extracellular vesicles, and senile plaques. Injecting cell-free nucleic acids bound to albumin oligomers into wild-type mice's hippocampi triggered antiviral interferon-β secretion; interferon-β injection caused synapse degeneration. Deoxyribonuclease-I treatment appeared to improve a severe-AD patient's Mini-Mental Status Exam by 15 points. Preclinical and clinical studies of deoxyribonuclease-I and a ribonuclease for AD should be prioritized.

Acute Pancreatitis and the Risk of Dementia in Diabetes: A Nationwide Cohort Study Using Korean Healthcare Claims Database

BACKGROUND

Diabetes is a major risk factor for the development of dementia, which has been proven to be associated with systemic inflammation. Acute pancreatitis, also a local and systemic inflammatory disease, is the most common gastrointestinal disease requiring acute hospitalization.

OBJECTIVE

The effect of acute pancreatitis on dementia was investigated in type 2 diabetic patients.

METHODS

Data was collected from the Korean National Health Insurance Service. The study sample included type 2 diabetes patients who received general health examination from 2009 to 2012. Cox proportional hazard regression analysis was used to evaluate the association between acute pancreatitis and dementia with adjustment of confounders. Stratified subgroup analysis by age, sex, smoking, alcohol consumption, hypertension, dyslipidemia, and body mass index was conducted.

RESULTS

Among the 2,328,671 participants in total, 4,463 patients had a history of acute pancreatitis before the health examination. During a median follow-up of 8.1 (IQR, 6.7-9.0) years, 194,023 participants (8.3%) developed all-cause dementia. Previous history of acute pancreatitis was a significant risk factor for dementia after adjustment of confounding variables (HR 1.39 [95% CI 1.26-1.53]). In the subgroup analysis, patient characteristics such as age under 65 years, male, current smoker, and alcohol consumption were significant risk factors for dementia in patients with a history of acute pancreatitis.

CONCLUSION

The history of acute pancreatitis was associated with the development of dementia in patients with diabetes. Because the risk of dementia increases with alcohol consumption and smoking in diabetic patients with history of acute pancreatitis, abstinence from alcohol and smoking should be recommended.

Mitochondria in innate immunity signaling and its therapeutic implications in autoimmune diseases

Autoimmune diseases are characterized by vast alterations in immune responses, but the pathogenesis remains sophisticated and yet to be fully elucidated. Multiple mechanisms regulating cell differentiation, maturation, and death are critical, among which mitochondria-related cellular organelle functions have recently gained accumulating attention. Mitochondria, as a highly preserved organelle in eukaryotes, have crucial roles in the cellular response to both exogenous and endogenous stress beyond their fundamental functions in chemical energy conversion. In this review, we aim to summarize recent findings on the function of mitochondria in the innate immune response and its aberrancy in autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, etc., mainly focusing on its direct impact on cellular metabolism and its machinery on regulating immune response signaling pathways. More importantly, we summarize the status quo of potential therapeutic targets found in the mitochondrial regulation in the setting of autoimmune diseases and wish to shed light on future studies.

NLRP3 Inflammasome: An Emerging Therapeutic Target for Alzheimer's Disease

Alzheimer's disease (AD) is currently the most prevalent neurological disease, and no effective and practical treatments and therapies exist. The nucleotide-binding oligomerization domain-, leucine-rich repeat-, and pyrin domain- containing receptor 3 (NLRP3) inflammasome is vital in the human innate immune response. However, when the NLRP3 inflammasome is overactivated by persistent stimulation, several immune-related diseases, including AD, atherosclerosis, and obesity, result. This review will focus on the composition and activation mechanism of the NLRP3 inflammasome, the relevant mechanisms of involvement in the inflammatory response to AD, and AD treatment targeting NLRP3 inflammasome. This review aims to reveal the pathophysiological mechanism of AD from a new perspective and provide the possibility of more effective and novel strategies for preventing and treating AD.

Computational Evaluation of Azadirachta indica-Derived Bioactive Compounds as Potential Inhibitors of NLRP3 in the Treatment of Alzheimer's Disease

BACKGROUND

The development of therapeutic agents against Alzheimer's disease (AD) has stalled recently. Drug candidates targeting amyloid-β (Aβ) deposition have often failed clinical trials at different stages, prompting the search for novel targets for AD therapy. The NLRP3 inflammasome is an integral part of innate immunity, contributing to neuroinflammation and AD pathophysiology. Thus, it has become a promising new target for AD therapy.

OBJECTIVE

The study sought to investigate the potential of bioactive compounds derived from Azadirachta-indica to inhibit the NLRP3 protein implicated in the pathophysiology of AD.

METHODS

Structural bioinformatics via molecular docking and density functional theory (DFT) analysis was utilized for the identification of novel NLRP3 inhibitors from A. indica bioactive compounds. The compounds were further subjected to pharmacokinetic and drug-likeness analysis. Results obtained from the compounds were compared against that of oridonin, a known NLRP3 inhibitor.

RESULTS

The studied compounds optimally saturated the binding site of the NLRP3 NACHT domain, forming principal interactions with the different amino acids at its binding site. The studied compounds also demonstrated better bioactivity and chemical reactivity as ascertained by DFT analysis and all the compounds except 7-desacetyl-7-benzoylazadiradione, which had two violations, conformed to Lipinski's rule of five.

CONCLUSION

In silico studies show that A. indica derived compounds have better inhibitory potential against NLRP3 and better pharmacokinetic profiles when compared with the reference ligand (oridonin). These compounds are thus proposed as novel NLRP3 inhibitors for the treatment of AD. Further wet-lab studies are needed to confirm the potency of the studied compounds.

Interactions between gut microbes and NLRP3 inflammasome in the gut-brain axis

The role of the gut-brain axis in maintaining the brain's and gut's homeostasis has been gradually recognized in recent years. The connection between the gut and the brain takes center stage. In this scenario, the nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome promotes inflammatory cell recruitment. It plays a crucial role in coordinating host physiology and immunity. Recent evidence shows how vital the gut-brain axis is for maintaining brain and gut homeostasis. However, more research is needed to determine the precise causal link between changed gut microbiota structure and NLRP3 activation in pathogenic circumstances. This review examines the connection between gut microbiota and the NLRP3 inflammasome. We describe how both dynamically vary in clinical cases and the external factors affecting both. Finally, we suggest that the crosstalk between the gut microbiota and NLRP3 is involved in signaling in the gut-brain axis, which may be a potential pathological mechanism for CNS diseases and intestinal disorders.

The central role of the gut in intensive care

Critically ill patients undergo early impairment of their gut microbiota (GM) due to routine antibiotic therapies and other environmental factors leading to intestinal dysbiosis. The GM establishes connections with the rest of the human body along several axes representing critical inter-organ crosstalks that, once disrupted, play a major role in the pathophysiology of numerous diseases and their complications. Key players in this communication are GM metabolites such as short-chain fatty acids and bile acids, neurotransmitters, hormones, interleukins, and toxins. Intensivists juggle at the crossroad of multiple connections between the intestine and the rest of the body. Harnessing the GM in ICU could improve the management of several challenges, such as infections, traumatic brain injury, heart failure, kidney injury, and liver dysfunction. The study of molecular pathways affected by the GM in different clinical conditions is still at an early stage, and evidence in critically ill patients is lacking. This review aims to describe dysbiosis in critical illness and provide intensivists with a perspective on the potential as adjuvant strategies (e.g., nutrition, probiotics, prebiotics and synbiotics supplementation, adsorbent charcoal, beta-lactamase, and fecal microbiota transplantation) to modulate the GM in ICU patients and attempt to restore eubiosis.

The role of the NLRP3 inflammasome in chronic inflammation in asthma and chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease (COPD) are lung diseases characterized by airflow limitation and chronic inflammation. More and more studies have shown that the occurrence and development of asthma and COPD are related to abnormal immune responses caused by dysregulation of many genetic and environmental factors. The exact pathogenesis of the disease is still unclear. A large number of studies have shown that the NLRP3 inflammasome is involved in the process of chronic airway inflammation in asthma and COPD. Here, we summarize recent advances in the mechanism of NLRP3 inflammasome activation and regulation and its role in the pathogenesis of inflammatory lung diseases such as asthma and COPD. Meanwhile we propose possible therapeutic targets in asthma and COPD.

Diverse pathways to neuronal necroptosis in Alzheimer's disease

Necroptosis, or programmed necrosis, involves the kinase activity of receptor interacting kinases 1 and 3, the activation of the pseudokinase mixed lineage kinase domain-like and formation of a complex called the necrosome. It is one of the non-apoptotic cell death pathways that has gained interest in the recent years, especially as a neuronal cell death pathway occurring in Alzheimer's disease. In this review, we focus our discussion on the various molecular mechanisms that could trigger neuronal death through necroptosis and have been shown to play a role in Alzheimer's disease pathogenesis and neuroinflammation. We describe how each of these pathways, such as tumour necrosis factor signalling, reactive oxygen species, endosomal sorting complex, post-translational modifications and certain individual molecules, is dysregulated or activated in Alzheimer's disease, and how this dysregulation/activation could trigger necroptosis. At the cellular level, many of these molecular mechanisms and pathways may act in parallel to synergize with each other or inhibit one another, and changes in the balance between them may determine different cellular vulnerabilities at different disease stages. However, from a therapeutic standpoint, it remains unclear how best to target one or more of these pathways, given that such diverse pathways could all contribute to necroptotic cell death in Alzheimer's disease.

The NLR family pyrin domain containing 3 inflammasome in the mechanism of electroacupuncture: Current status and future perspectives

Electroacupuncture, which is the most widely used alternative medicine treatment, has been gradually recognized for its effectiveness; however, its mechanism of action is not fully understood. The NLR family pyrin domain containing 3 (NLRP3) inflammasome is a thoroughly studied inflammasome that is closely associated with Alzheimer’s disease, spinal cord injury, and other diseases and plays an important role in the diagnosis and treatment of human immune system diseases. In recent years, some scholars have found that the NLRP3 inflammasome is a part of the mechanism of action of electroacupuncture, which has attracted further attention. In the current review, using “electroacupuncture” and “NLRP3 inflammasome” as keywords and based on the existing randomized controlled trials or clinical trials, we summarize the mechanisms of electroacupuncture targeting NLRP3 inflammasome in the treatment of different diseases and discuss how to optimize the electroacupuncture protocol to obtain thorough mechanisms of NLRP3 inflammasome in electroacupuncture and improve the level of evidence.

The emerging role of autophagy and mitophagy in tauopathies: From pathogenesis to translational implications in Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease, affecting more than 55 million individuals worldwide in 2021. In addition to the "amyloid hypothesis," an increasing number of studies have demonstrated that phosphorylated tau plays an important role in AD pathogenesis. Both soluble tau oligomers and insoluble tau aggregates in the brain can induce structural and functional neuronal damage through multiple pathways, eventually leading to memory deficits and neurodegeneration. Autophagy is an important cellular response to various stress stimuli and can generally be categorized into non-selective and selective autophagy. Recent studies have indicated that both types of autophagy are involved in AD pathology. Among the several subtypes of selective autophagy, mitophagy, which mediates the selective removal of mitochondria, has attracted increasing attention because dysfunctional mitochondria have been suggested to contribute to tauopathies. In this review, we summarize the latest findings on the bidirectional association between abnormal tau proteins and defective autophagy, as well as mitophagy, which might constitute a vicious cycle in the induction of neurodegeneration. Neuroinflammation, another important feature in the pathogenesis and progression of AD, has been shown to crosstalk with autophagy and mitophagy. Additionally, we comprehensively discuss the relationship between neuroinflammation, autophagy, and mitophagy. By elucidating the underlying molecular mechanisms governing these pathologies, we highlight novel therapeutic strategies targeting autophagy, mitophagy and neuroinflammation, such as those using rapamycin, urolithin, spermidine, curcumin, nicotinamide, and actinonin, for the prevention and treatment of AD.

Symptomatic and Disease-Modifying Therapy Pipeline for Alzheimer’s Disease: Towards a Personalized Polypharmacology Patient-Centered Approach

Since 1906, when Dr. Alois Alzheimer first described in a patient “a peculiar severe disease process of the cerebral cortex”, people suffering from this pathology have been waiting for a breakthrough therapy. Alzheimer’s disease (AD) is an irreversible, progressive neurodegenerative brain disorder and the most common form of dementia in the elderly with a long presymptomatic phase. Worldwide, approximately 50 million people are living with dementia, with AD comprising 60–70% of cases. Pathologically, AD is characterized by the deposition of amyloid β-peptide (Aβ) in the neuropil (neuritic plaques) and blood vessels (amyloid angiopathy), and by the accumulation of hyperphosphorylated tau in neurons (neurofibrillary tangles) in the brain, with associated loss of synapses and neurons, together with glial activation, and neuroinflammation, resulting in cognitive deficits and eventually dementia. The current competitive landscape in AD consists of symptomatic treatments, of which there are currently six approved medications: three AChEIs (donepezil, rivastigmine, and galantamine), one NMDA-R antagonist (memantine), one combination therapy (memantine/donepezil), and GV-971 (sodium oligomannate, a mixture of oligosaccharides derived from algae) only approved in China. Improvements to the approved therapies, such as easier routes of administration and reduced dosing frequencies, along with the developments of new strategies and combined treatments are expected to occur within the next decade and will positively impact the way the disease is managed. Recently, Aducanumab, the first disease-modifying therapy (DMT) has been approved for AD, and several DMTs are in advanced stages of clinical development or regulatory review. Small molecules, mAbs, or multimodal strategies showing promise in animal studies have not confirmed that promise in the clinic (where small to moderate changes in clinical efficacy have been observed), and therefore, there is a significant unmet need for a better understanding of the AD pathogenesis and the exploration of alternative etiologies and therapeutic effective disease-modifying therapies strategies for AD. Therefore, a critical review of the disease-modifying therapy pipeline for Alzheimer’s disease is needed.

Targeting NLRP3-Mediated Neuroinflammation in Alzheimer’s Disease Treatment

Alzheimer’s disease (AD) is the most common cause of dementia in the general population and, to date, constitutes a major therapeutic challenge. In the pathogenesis of AD, aggregates of amyloid β (Aβ) and neurofibrillary tangles (NFTs) containing Tau-microtubule-associated protein (tau) are known to trigger a neuroinflammatory response with subsequent formation of an inflammasome. In particular, the NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is thought to play a crucial role in AD-related pathology. While the mechanisms for NLRP3 activation are not fully understood, it has been demonstrated that, after detection of protein aggregates, NLRP3 induces pro-inflammatory cytokines, such as interleukin 18 (IL-18) or interleukin 1β (IL-1β), that further potentiate AD progression. Specific inhibitors of NLRP3 that exhibit various mechanisms to attenuate the activity of NLRP3 have been tested in in vivo studies and have yielded promising results, as shown by the reduced level of tau and Aβ aggregates and diminished cognitive impairment. Herein, we would like to summarize the current state of knowledge on NLRP3 inflammasome priming, activation, and its actual role in AD pathogenesis, and to characterize the NLRP3 inhibitors that have been studied most and their impact on AD-related pathology.

DMTHB ameliorates memory impairment in Alzheimer's disease mice through regulation of neuroinflammation

BACKGROUND

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative diseases. Growing evidence suggested that AD is associated with neuroinflammation, characterized with the chronic activation of microglial cells and astrocytes along with the subsequent excessive generation of the proinflammatory molecules. This study aimed to investigate the effect and molecular mechanism of Demethylenetetrahydroberberine (DMTHB) on Alzheimer's disease (AD).

METHODS

AD mice model were made by intracranial injection of Aβ_25-35. DMTHB (50 mg/kg or 150 mg/kg) was intragastrically administered every day for three weeks. Morris water maze (MWM) was applied to evaluate the capacity of learning and memory of mice. Pathological change and neuronal death were detected by HE staining Moreover, the expressions of NLRP3, ASC, Caspase 1, IL-6, IL-1β, TNF-α and Tau in the brain tissue were measured by qRT-PCR and western blot.

RESULTS

Our results showed that the cognition of AD mice was significantly improved by DMTHB administration. DMTHB inhibited the activation of the microglia and significantly reduced the expression of Iba-1 in the brains of AD mice. In addition, DMTHB effectively suppressed the activation of NLRP3 inflammasome induced by Aβ_25-35. The results showed that the content of inflammatory cytokine (TNF-α, IL-1β and IL-6) in the brains of AD mice were down-regulated by DMTHB treatment. More importantly, DMTHB treatment significantly alleviated hippocampus neuron deformation and apoptosis.

CONCLUSION

These results indicated that DMTHB could be a potential medicine against AD through regulation of neuroinflammation.

HECTD3 promotes NLRP3 inflammasome and pyroptosis to exacerbate diabetes-related cognitive impairment by stabilising MALT1 to regulate JNK pathway

BACKGROUND

HECTD3 (HECT domain E3 ubiquitin protein ligase 3) exerts biological activities in neuroinflammation of distinct diseases, such as autoimmune encephalomyelitis and donations after heart death. However, the effect of HECTD3 on diabetes-associated cognitive decline (DACD) remains unclear.

METHODS

Wild-type or HECTD3-knockout rats were administered with streptozotocin to establish diabetic model. Pathological changes in the hippocampus were assessed by NISSL and haematoxylin and eosin staining. Morris water maze test was used to assess cognitive function. Neuronal survival and inflammation were investigated by immunofluorescence staining and ELISA assay. NLRP3 inflammasome and pyroptosis were assessed by western blot, immunofluorescence and flow cytometry assays.

RESULTS

HECTD3 was up-regulated in hippocampus of streptozotocin-induced diabetic rats and high glucose-induced PC12 cells. Knockout of HECTD3 increased the number of neurons and improved the learning and memory function. Moreover, knockout of HECTD3 promoted in vivo neuronal survival, and reduced levels of IL-1β, TNF-α, and IL-6 in the hippocampus. Silencing of HECTD3 increased cell viability, and reduced IL-1β, TNF-α, and IL-6 in high glucose-induced PC12 cells. Fluorescence intensities of NLRP3, GSDMD-N and caspase-1 were reduced in HECTD3-knockout diabetic rats, and knockdown of HECTD3 down-regulated protein expression of NLRP3, GSDMD-N, caspase-1, IL-1β, and IL-18 in high glucose-induced PC12 cells to suppress the pyroptosis. HECTD3 promoted the stability of mucosa-associated lymphoid tissue 1 (MALT1) through up-regulation of c-JUN and phospho (p)-JNK in high glucose-induced PC12 cells. Over-expression of MALT1 attenuated neuroprotective effects of HECTD3 silencing on high glucose-induced PC12 cells.

CONCLUSION

HECTD3 silencing exerted neuroprotective effect against DACD through MALT1-mediated JNK signalling.HighlightsHECTD3 was up-regulated in hippocampus of streptozotocin-induced diabetic rats and high glucose-induced PC12.Knockout of HECTD3 promoted in vivo neuronal survival, reduced inflammation and pyroptosis, and improved the learning and memory function in diabetic rats.Knockout of HECTD3 suppressed the activation of NLRP3 inflammasome in diabetic rats.Silencing of HECTD3 exerted neuroprotective effects through MALT1-mediated JNK signalling.

Mechanisms of NLRP3 activation and pathology during neurodegeneration

Inflammasomes are multiprotein complexes that are mainly present in resident and infiltrating immune cells in the central nervous system. Inflammasomes function as intracellular sensors of immunometabolic stress, infection and changes in the local microenvironment. Inflammasome assembly in response to these 'danger signals', triggers recruitment and cluster-dependent activation of caspase-1 and the subsequent proteolytic activation of inflammatory cytokines such as interleukin-1β and interleukin-18. This is typically followed by a form of inflammatory cell death through pyroptosis. Since the discovery of inflammasomes in 2002, they have come to be recognized as central regulators of acute and chronic inflammation, a hallmark of progressive neurological diseases. Indeed, over the last decade, extensive inflammasome activation has been found at the sites of neuropathology in all progressive neurodegenerative diseases. Disease-specific misfolded protein aggregates which accumulate in neurodegenerative diseases, such as alpha synuclein or beta amyloid, have been found to be important triggers of NLRP3 inflammasome activation in the central nervous system. Together, these discoveries have transformed our understanding of how chronic inflammation is triggered and sustained in the central nervous system, and how it can contribute to neuronal death and disease progression in age-related neurodegenerative diseases. Therapeutic strategies around inhibition of NLRP3 activation in the central nervous system are already being evaluated to determine their effectiveness to slow progressive neurodegeneration. This review summarizes current understanding of inflammasomes in the most prevalent neurodegenerative diseases and discusses current knowledge gaps and inflammasome inhibition as a therapeutic strategy.

New Insights into Neuroinflammation Involved in Pathogenic Mechanism of Alzheimer's Disease and Its Potential for Therapeutic Intervention

Alzheimer's disease (AD) is the most common form of dementia, affecting more than 50 million people worldwide with an estimated increase to 139 million people by 2050. The exact pathogenic mechanisms of AD remain elusive, resulting in the fact that the current therapeutics solely focus on symptomatic management instead of preventative or curative strategies. The two most widely accepted pathogenic mechanisms of AD include the amyloid and tau hypotheses. However, it is evident that these hypotheses cannot fully explain neuronal degeneration shown in AD. Substantial evidence is growing for the vital role of neuroinflammation in AD pathology. The neuroinflammatory hypothesis provides a new, exciting lead in uncovering the underlying mechanisms contributing to AD. This review aims to highlight new insights into the role of neuroinflammation in the pathogenesis of AD, mainly including the involvement of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), nucleotide-binding oligomerization domain, leucine-rich repeat-containing protein 3 (NLRP3)/caspase-1 axis, triggering receptor expressed on myeloid cells 2 (TREM2) and cGAS-STING as key influencers in augmenting AD development. The inflammasomes related to the pathways of NF-κB, NLRP3, TREM2, and cGAS-STING as biomarkers of the neuroinflammation associated with AD, as well as an overview of novel AD treatments based on these biomarkers as potential drug targets reported in the literature or under clinical trials, are explored.

A Diagnostic Model for Alzheimer’s Disease Based on Blood Levels of Autophagy-Related Genes

Alzheimer’s disease (AD) is a common neurodegenerative disease. The major problems that exist in the diagnosis of AD include the costly examinations and the high-invasive sampling tissue. Therefore, it would be advantageous to develop blood biomarkers. Because AD’s pathological process is considered tightly related to autophagy; thus, a diagnostic model for AD based on ATGs may have more predictive accuracy than other models. We obtained GSE63060 dataset from the GEO database, ATGs from the HADb and screened 64 differentially expressed autophagy-related genes (DE-ATGs). We then applied them to Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses as well as DisGeNET and PaGenBase enrichment analyses. By using the univariate analysis, least absolute shrinkage and selection operator (LASSO) regression method and the multivariable logistic regression, nine DE-ATGs were identified as biomarkers, which are ATG16L2, BAK1, CAPN10, CASP1, RAB24, RGS19, RPS6KB1, ULK2, and WDFY3. We combined them with sex and age to establish a nomogram model. To evaluate the model’s distinguishability, consistency, and clinical applicability, we applied the receiver operating characteristic (ROC) curve, C-index, calibration curve, and on the validation datasets GSE63061, GSE54536, GSE22255, and GSE151371 from GEO database. The results show that our model demonstrates good prediction performance. This AD diagnosis model may benefit both clinical work and mechanistic research.