Intracerebroventricular infusion of secretoneurin inhibits neuronal NLRP3-Apoptosis pathway and preserves learning and memory after cerebral ischemia

Transient global cerebral ischemia (GCI) results in delayed neuronal death, primarily apoptosis, in the hippocampal CA1 subregion, which leads to severe cognitive deficits. While therapeutic hypothermia is an approved treatment for patients following cardiac arrest, it is associated with various adverse effects. Secretoneurin (SN) is an evolutionarily conserved neuropeptide generated in the brain, adrenal medulla and other endocrine tissues. In this study, SN was infused into the rat brain by intracerebroventricular injection 1 day after GCI, and we demonstrated that SN could significantly preserve spatial learning and memory in the Barnes maze tasks examined on days 14-17 after GCI. To further investigate underlying pathways involved, we demonstrated that, on day 5 after GCI, SN could significantly inhibit GCI-induced expression levels of Apoptosis Inducing Factor (AIF) and cleaved-PARP1, as well as neuronal apoptosis and synaptic loss in the hippocampal CA1 region. Additionally, SN could attenuate GCI-induced activation of both caspase-1 and caspase-3, and the levels of pro-inflammatory cytokines IL-1β and IL-18 in the CA1 region. Mechanically, we observed that treatment with SN effectively inhibited NLRP3 protein elevation and the bindings of NLRP3-ASC and ASC-caspase-1 in hippocampal neurons after GCI. In summary, our data indicate that SN could effectively attenuate NLRP3 inflammasome formation, as well as the activation of caspase-1 and -3, the production of pro-inflammatory cytokines, and ultimately the neuronal apoptotic loss induced by GCI. Potential neuronal pyroptosis, or caspase-1-dependent cell death, could also be involved in ischemic neuronal death, which needs further investigation.

Microglia as a Game Changer in Epilepsy Comorbid Depression

As one of the most common neurological diseases, epilepsy is often accompanied by psychiatric disorders. Depression is the most universal comorbidity of epilepsy, especially in temporal lobe epilepsy (TLE). Therefore, it is urgently needed to figure out potential mechanisms and the optimization of therapeutic strategies. Microglia play a pivotal role in the coexistent relationship between epilepsy and depression. Activated microglia released cytokines like IL-6 and IL-1β, orchestrating neuroinflammation especially in the hippocampus, worsening both depression and epilepsy. The decrease of intracellular K+ is a common part in various molecular changes. The P2X7-NLRP3-IL-1β is a major inflammatory pathway that disrupts brain network. Extra ATP and CX3CL1 also lead to neuronal excitotoxicity and blood-brain barrier (BBB) disruption. Regulating neuroinflammation aiming at microglia-related molecules is capable of suspending the vicious mutual aggravating circle of epilepsy and depression. Other overlaps between epilepsy and depression lie in transcriptomic, neuroimaging, diagnosis and treatment. Hippocampal sclerosis (HS) and amygdala enlargement (AE) may be the underlying macroscopic pathological changes according to current studies. Extant evidence shows that cognitive behavioral therapy (CBT) and antidepressants like selective serotonin-reuptake inhibitors (SSRIs) are safe, but the effect is limited. Improvement in depression is likely to reduce the frequency of seizure. More comprehensive experiments are warranted to better understand the relationship between them.

BPOZ-2-deficient mice exhibit aggravated inflammation-associated tissue damage after acute dextran sodium sulfate or diethylnitrosamine exposure

An excessive inflammatory response plays an important role in pathological tissue damage associated with pathogen infection and tumorigenesis. Blood POZ-containing gene type 2 (BPOZ-2), an adaptor protein for the E3 ubiquitin ligase scaffold protein CUL3, is a negative regulator of the inflammatory response. In this study, we investigated the pathophysiological functions of BPOZ-2 in dextran sodium sulfate (DSS)-induced colon injury and diethylnitrosamine (DEN)-induced liver damage. Our results indicated that BPOZ-2 deficiency increased IL-1β induction after DSS and DEN treatment. In addition, BPOZ-2-deficient mice were more susceptible to DSS-induced colitis. Notably, BPOZ-2 deficiency aggravated DEN-induced acute liver injury. These results revealed that BPOZ-2 protected against pathological tissue damage with a dysregulated inflammatory response.

Irbesartan mitigates the impact of cyclophosphamide-induced acute neurotoxicity in rats: Shedding highlights on NLRP3 inflammasome/CASP-1 pathway-driven immunomodulation

IIrbesartan (IRB), an angiotensin II type 1 receptor (AT1R) antagonist, has been widely employed in the medical field for its effectiveness in managing hypertension. However, there have been no documented investigations regarding the immunostimulatory properties of IRB. To address this gap, this study has been performed to assess the neuroprotective impact of IRB as an immunostimulatory agent in mitigating acute neurotoxicity induced by cyclophosphamide (CYP) in rats. mRNA levels of nuclear factor erythroid 2 (Nrf-2), interleukin (IL)-18, IL-1β, and MMP-1 have been assessed using quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the levels of malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD) has been evaluated to assess the oxidative stress. Additionally, macrophage inflammatory protein 2 (MIP2) has been evaluated using enzyme-linked immunosorbent assay (ELISA). Western blotting has been used to investigate the protein expression of nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) and caspase-1 (CASP-1), along with an assessment of histopathological changes. Administration of IRB protected against oxidative stress by augmenting the levels of GSH and SOD as well as reducing MDA level. Also, administration of IRB led to a diminishment in the brain levels of MIP2 and MMP1. Furthermore, it led to a suppression of IL-1β and IL-18 levels, which are correlated with a reduction in the abundance of NLRP3 and subsequently CASP-1. This study provides new insights into the immunomodulatory effects of IRB in the context of CYP-induced acute neurotoxicity. Specifically, IRB exerts its effects by reducing oxidative stress, neuroinflammation, inhibiting chemokine recruitment, and mitigating neuronal degeneration through the modulation of immune markers. Therefore, it can be inferred that the use of IRB as an immunomodulator has the potential to effectively mitigate immune disorders associated with inflammation.

Involvement of oxidative stress-AMPK-Cx43-NLRP3 pathway in extracellular matrix remodeling of gastric smooth muscle cells in rats with diabetic gastroparesis

This study aimed to investigate the changes in oxidative stress, adenosine monophosphate-activated protein kinase (AMPK), connexin43 (Cx43), nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) expression, and extracellular matrix (ECM) in the gastric smooth muscle tissues of rats with diabetic gastroparesis (DGP) and high glucose-cultured gastric smooth muscle cells, determine the existence of oxidative stress-AMPK-Cx43-NLRP3 pathway under high glucose condition, and the involvement of this pathway in ECM remodeling in DGP rats. The results showed that with increasing duration of diabetes, oxidation stress levels gradually increased, the AMPK activity decreased first and then increased, NLRP3, CX43 expression, and membrane/cytoplasm ratio of Cx43 expression were increased in the gastric smooth muscle tissues of diabetic rats. Changes in ECM of gastric smooth muscle cells were observed in DGP rats. The DGP group showed higher collagen type I content, increased expression of Caspase-1, transforming growth factor-beta 3 (TGF-β3), and matrix metalloproteinase-2 (MMP-2), decreased tissue inhibitor of metalloproteinase-1 (TIMP-1) expression, and higher interleukin-1 beta content when compared with the control group. For gastric smooth muscle cells cultured under higher glucose, the MMP-2 and TGF-β3 expression was decreased, TGF-β1 and TIMP-1 expression was increased, the interleukin-1 beta content was decreased in cells after inhibition of NLRP3 expression; the NLRP3 and Caspase-1 expression was decreased, and adenosine triphosphate content was lower after inhibition of Cx43; the expression of NLRP3, Caspase-1, P2X7, and the membrane/cytoplasm ratio of CX43 expression was decreased in cells after inhibition of AMPK and oxidative stress, the phospho-AMPK expression was also decreased after suppressing oxidative stress. Our findings suggest that high glucose induced the activation of the AMPK-Cx43-NLRP3 pathway through oxidative stress, and this pathway was involved in the ECM remodeling of gastric smooth muscles in DGP rats by regulating the biological functions of TGF-β3, TGF-β1, MMP-2, and TIMP-1.

Long non-coding RNA ENSMUST00000197208 promotes a shift in the Th17/Treg ratio via the P2X7R-NLRP3 inflammasome axis in collagen-induced arthritis

Recently, long non‑coding RNAs (lncRNAs) have been implicated in several human diseases, including arthritis. However, the role of lncRNAs in regulating the Th17/Treg ratio during the progression of collagen-induced arthritis (CIA) is poorly understood. Therefore, the aim of this study was to determine the role of the lncRNA ENSMUST00000197208 and the P2X7R-NLRP3 inflammasome axis in changes in the Th17/Treg ratio in CIA. To achieve this, the distribution of T cell subgroups in the spleen cells of a CIA mouse model and control mice was examined. Additionally, we examined the expression profile of ENSMUST00000197208 in a CIA mouse model and healthy mice. The results showed that ENSMUST00000197208 expression was significantly upregulated in the CIA models compared with the control group. Additionally, the P2X7R-NLRP3 inflammasome axis participated in the pathogenesis of CIA and knockdown of ENSMUST00000197208 inhibited CD4+ T cell differentiation into Th17 cells. Compared with the control group, joint inflammation was less visible in NLRP3 knockout mice. Additionally, the P2X7R-NLRP3 inflammasome axis, which is downstream of ENSMUST00000197208, can be positively targeted and regulated by ENSMUST00000197208 through miR-107. Overall, the findings of this study showed that the "lncRNA ENSMUST00000197208-miR 107-P2X7R/NLRP3" axis plays an important role in CIA and knocking down ENSMUST00000197208 can efficiently inhibit Th17 differentiation by suppressing the P2X7R-NLRP3 inflammasome axis. Therefore, targeting this axis may represent a novel strategy for arthritis treatment.

Advances and Challenges in Sepsis Management: Modern Tools and Future Directions

Sepsis, a critical condition marked by systemic inflammation, profoundly impacts both innate and adaptive immunity, often resulting in lymphopenia. This immune alteration can spare regulatory T cells (Tregs) but significantly affects other lymphocyte subsets, leading to diminished effector functions, altered cytokine profiles, and metabolic changes. The complexity of sepsis stems not only from its pathophysiology but also from the heterogeneity of patient responses, posing significant challenges in developing universally effective therapies. This review emphasizes the importance of phenotyping in sepsis to enhance patient-specific diagnostic and therapeutic strategies. Phenotyping immune cells, which categorizes patients based on clinical and immunological characteristics, is pivotal for tailoring treatment approaches. Flow cytometry emerges as a crucial tool in this endeavor, offering rapid, low cost and detailed analysis of immune cell populations and their functional states. Indeed, this technology facilitates the understanding of immune dysfunctions in sepsis and contributes to the identification of novel biomarkers. Our review underscores the potential of integrating flow cytometry with omics data, machine learning and clinical observations to refine sepsis management, highlighting the shift towards personalized medicine in critical care. This approach could lead to more precise interventions, improving outcomes in this heterogeneously affected patient population.

Reversal of Experimental Autoimmune Diabetes With an sCD39/Anti-CD3 Treatment

Extracellular (e)ATP, a potent proinflammatory molecule, is released by dying/damaged cells at the site of inflammation and is degraded by the membrane ectonucleotidases CD39 and CD73. In this study, we sought to unveil the role of eATP degradation in autoimmune diabetes. We then assessed the effect of soluble CD39 (sCD39) administration in prevention and reversal studies in NOD mice as well as in mechanistic studies. Our data showed that eATP levels were increased in hyperglycemic NOD mice compared with prediabetic NOD mice. CD39 and CD73 were found expressed by both α- and β-cells and by different subsets of T cells. Importantly, prediabetic NOD mice displayed increased frequencies of CD3+CD73+CD39+ cells within their pancreata, pancreatic lymph nodes, and spleens. The administration of sCD39 into prediabetic NOD mice reduced their eATP levels, abrogated the proliferation of CD4+- and CD8+-autoreactive T cells, and increased the frequency of regulatory T cells, while delaying the onset of T1D. Notably, concomitant administration of sCD39 and anti-CD3 showed a strong synergism in restoring normoglycemia in newly hyperglycemic NOD mice compared with monotherapy with anti-CD3 or with sCD39. The eATP/CD39 pathway plays an important role in the onset of T1D, and its targeting might represent a potential therapeutic strategy in T1D.

ARTICLE HIGHLIGHTS

Evaluation of the association of chronic inflammation and cancer: Insights and implications

Among the most extensively researched processes in the development and treatment of cancer is inflammatory condition. Although acute inflammation is essential for the wound healing and reconstruction of tissues that have been damaged, chronic inflammation may contribute to the onset and growth of a number of diseases, including cancer. By disrupting the signaling processes of cells, which result in cancer induction, invasion, and development, a variety of inflammatory molecules are linked to the development of cancer. The microenvironment surrounding the tumor is greatly influenced by inflammatory cells and their subsequent secretions, which also contribute significantly to the tumor's growth, survivability, and potential migration. These inflammatory variables have been mentioned in several publications as prospective diagnostic tools for anticipating the onset of cancer. Targeting inflammation with various therapies can reduce the inflammatory response and potentially limit or block the proliferation of cancer cells. The scientific medical literature from the past three decades has been studied to determine how inflammatory chemicals and cell signaling pathways related to cancer invasion and metastasis are related. The current narrative review updates the relevant literature while highlighting the specifics of inflammatory signaling pathways in cancer and their possible therapeutic possibilities.

Strategy and application of manipulating DCs chemotaxis in disease treatment and vaccine design

As the most versatile antigen-presenting cells (APCs), dendritic cells (DCs) function as the cardinal commanders in orchestrating innate and adaptive immunity for either eliciting protective immune responses against canceration and microbial invasion or maintaining immune homeostasis/tolerance. In fact, in physiological or pathological conditions, the diversified migratory patterns and exquisite chemotaxis of DCs, prominently manipulate their biological activities in both secondary lymphoid organs (SLOs) as well as homeostatic/inflammatory peripheral tissues in vivo. Thus, the inherent mechanisms or regulation strategies to modulate the directional migration of DCs even could be regarded as the crucial cartographers of the immune system. Herein, we systemically reviewed the existing mechanistic understandings and regulation measures of trafficking both endogenous DC subtypes and reinfused DCs vaccines towards either SLOs or inflammatory foci (including neoplastic lesions, infections, acute/chronic tissue inflammations, autoimmune diseases and graft sites). Furthermore, we briefly introduced the DCs-participated prophylactic and therapeutic clinical application against disparate diseases, and also provided insights into the future clinical immunotherapies development as well as the vaccines design associated with modulating DCs mobilization modes.

The Efficacy and Safety of Oral Nutrient Solution Supplementation in Patients with Esophageal Cancer under Nutritional, Psychological, Physical, and Prognostic Survival Differences

Inflammasomes are massive intracellular multiprotein signaling complexes produced in the cytosolic compartment. Tumor etiology involves dysregulation of NLRP3 inflammasome activation. Current studies are being conducted to ascertain the effectiveness and safety of oral nutrient solution supplementation in patients with esophageal cancer based on the current understanding of the role of the NLRP3 inflammasome in possible cancer promotion and therapy. This study examines how oral nutrient solution supplement therapy affects patients receiving radiotherapy and chemotherapy for esophageal cancer in terms of nutrition, physical composition, quality of life, psychology, prognosis, and survival. A total of 120 patients with esophageal cancer admitted to our hospital from March 2020 to January 2021 were selected for the current study. The selected 120 patients are divided into nutritional supplement and traditional groups according to the random number table method, with 60 cases in each group. The nutritional supplement group received an oral nutritional solution, whereas the conventional group received the ordinary dietary intervention. Since radiotherapy can potentially damage healthy tissue with short- and long-term negative effects. Inflammatory reactions are a common component of adverse effects of early and late ionizing radiation. Oral nutrient solution supplement therapy for patients with esophageal cancer after radiotherapy and chemotherapy can significantly improve the levels of blood nutrients, later physical components, and quality of life of patients.

Why Are Some People with Lower Urinary Tract Symptoms (LUTS) Depressed? New Evidence That Peripheral Inflammation in the Bladder Causes Central Inflammation and Mood Disorders

Anecdotal evidence has long suggested that patients with lower urinary tract symptoms (LUTS) develop mood disorders, such as depression and anxiety, at a higher rate than the general population and recent prospective studies have confirmed this link. Breakthroughs in our understanding of the diseases underlying LUTS have shown that many have a substantial inflammatory component and great strides have been made recently in our understanding of how this inflammation is triggered. Meanwhile, studies on mood disorders have found that many are associated with central neuroinflammation, most notably in the hippocampus. Excitingly, work on other diseases characterized by peripheral inflammation has shown that they can trigger central neuroinflammation and mood disorders. In this review, we discuss the current evidence tying LUTS to mood disorders, its possible bidirectionally, and inflammation as a common mechanism. We also review modern theories of inflammation and depression. Finally, we discuss exciting new animal studies that directly tie two bladder conditions characterized by extensive bladder inflammation (cyclophosphamide-induced hemorrhagic cystitis and bladder outlet obstruction) to neuroinflammation and depression. We conclude with a discussion of possible mechanisms by which peripheral inflammation is translated into central neuroinflammation with the resulting psychiatric concerns.

Bacterial strategies for immune systems - Role of the type VI secretion system

The process of host infection by bacteria is complicated. Bacterial infections strongly induce the host immune system, which necessitates a robust clearance of the infection. However, bacteria have over time developed strategies that enable their evasion of attacks by the host immune system. One such strategy is the type VI secretion system (T6SS), a special needle-like secretion system that is widespread in Gram-negative bacteria and is responsible for delivering effector proteins into the external bacterial environment or directly into the host cell cytosol. Bacterial T6SS and its secreted effector proteins play an important role in the interaction between bacteria and host immune system. They also serve as antigens that are employed in the development of vaccines for clinical trials as well as future vaccine candidates. This review focuses mainly on aspects of T6SS effectors that impact the strength of the host immune system, including inflammation, autophagy, and apoptosis (silent programmed cell death). The T6SS-based vaccines are also described.

Molecular Bases of Protein Antigenicity and Determinants of Immunogenicity, Anergy, and Mitogenicity

BACKGROUND

The immune system is able to recognize substances that originate from inside or outside the body and are potentially harmful. Foreign substances that bind to immune system components exhibit antigenicity and are defined as antigens. The antigens exhibiting immunogenicity can induce innate or adaptive immune responses and give rise to humoral or cell-mediated immunity. The antigens exhibiting mitogenicity can cross-link cell membrane receptors on B and T lymphocytes leading to cell proliferation. All antigens vary greatly in physicochemical features such as biochemical nature, structural complexity, molecular size, foreignness, solubility, and so on.

OBJECTIVE

Thus, this review aims to describe the molecular bases of protein-antigenicity and those molecular bases that lead to an immune response, lymphocyte proliferation, or unresponsiveness.

CONCLUSION

The epitopes of an antigen are located in surface areas; they are about 880-3,300 Da in size. They are protein, carbohydrate, or lipid in nature. Soluble antigens are smaller than 1 nm and are endocytosed less efficiently than particulate antigens. The more the structural complexity of an antigen increases, the more the antigenicity increases due to the number and variety of epitopes. The smallest immunogens are about 4,000-10,000 Da in size. The more phylogenetically distant immunogens are from the immunogen-recipient, the more immunogenicity increases. Antigens that are immunogens can trigger an innate or adaptive immune response. The innate response is induced by antigens that are pathogen-associated molecular patterns. Exogenous antigens, T Dependent or T Independent, induce humoral immunogenicity. TD protein-antigens require two epitopes, one sequential and one conformational to induce antibodies, whereas, TI non-protein-antigens require only one conformational epitope to induce low-affinity antibodies. Endogenous protein antigens require only one sequential epitope to induce cell-mediated immunogenicity.

Lutein isolated from Scenedesmus obliquus microalga boosts immunity against cyclophosphamide-induced brain injury in rats

Lutein is a naturally potent antioxidant carotenoid synthesized in green microalgae with a potent ability to prevent different human chronic conditions. To date, there are no reports of the immune-stimulating effect of pure lutein isolated from Scenedesmus obliquus. Thus, we isolated the natural lutein from S. obliquus and evaluated its effectiveness as an immunostimulant against cyclophosphamide-induced brain injury. We purified all-E-(3R, 3'R, 6'R)-Lutein from S. obliquus using prep-HPLC and characterized it by ¹H- and ¹³C-NMR spectroscopy. We assigned rats randomly to four experimental groups: the Control group got a vehicle for lutein dimethyl sulfoxide for ten successive days. The Cyclophosphamide group received a single i.p injection of Cyclophosphamide (200 mg/kg). Lutein groups received 50 and 100 (mg/kg) of lutein one time per day for ten successive days after the cyclophosphamide dose. Lutein administration reduced brain contents of Macrophage inflammatory protein2 (MIP2), cytokine-induced- neutrophil chemoattractant (CINC), and Matrix metalloproteinase 1 (MMP1). Besides, it lowered the contents of interleukin 1 beta (IL-1β) and interleukin 18 (IL-18), associated with low content of NLR pyrin domain protein 3 (NLRP3) and consequently caspase-1 compared to the cyclophosphamide group. In the histomorphometric analysis, lutein groups (50 and 100 mg/Kg) showed mild histopathological alterations as they significantly reduced nuclear pyknosis numbers by 65% and 69% respectively, compared to the cyclophosphamide group. This is the first study that showed the immunomodulatory roles of lutein against cyclophosphamide-induced brain injury via decreasing neuroinflammation, chemokines recruitment, and neuron degeneration with the modulation of immune markers. Hence, lutein can be an effective immunomodulator against inflammation-related immune disorders.

New Insights into the Crosstalk among the Interferon and Inflammatory Signaling Pathways in Response to Viral Infections: Defense or Homeostasis

Innate immunity plays critical roles in eliminating viral infections, healing an injury, and restoring tissue homeostasis. The signaling pathways of innate immunity, including interferons (IFNs), nuclear factor kappa B (NF-κB), and inflammasome responses, are activated upon viral infections. Crosstalk and interplay among signaling pathways are involved in the complex regulation of antiviral activity and homeostasis. To date, accumulating evidence has demonstrated that NF-κB or inflammasome signaling exhibits regulatory effects on IFN signaling. In addition, several adaptors participate in the crosstalk between IFNs and the inflammatory response. Furthermore, the key adaptors in innate immune signaling pathways or the downstream cytokines can modulate the activation of other signaling pathways, leading to excessive inflammatory responses or insufficient antiviral effects, which further results in tissue injury. This review focuses on the crosstalk between IFN and inflammatory signaling to regulate defense and homeostasis. A deeper understanding of the functional aspects of the crosstalk of innate immunity facilitates the development of targeted treatments for imbalanced homeostasis.

Prevotella genus and its related NOD-like receptor signaling pathway in young males with stage III periodontitis

Background

As periodontitis progresses, the oral microbiota community changes dynamically. In this study, we evaluated the dominant bacteria and their roles in the potential pathway in young males with stage III periodontitis.

Methods

16S rRNA sequencing was performed to evaluate variations in the composition of oral bacteria between males with stage I and III periodontitis and identify the dominant bacteria of each group. Function prediction was obtained based on 16S rRNA sequencing data. The inhibitor of the predominant pathway for stage III periodontitis was used to investigate the role of the dominant bacteria in periodontitis in vivo and in vitro.

Results

Chao1 index, Observed Species and Phylogenetic Diversity (PD) whole tree values were significantly higher in the stage III periodontitis group. β-diversity suggested that samples could be divided according to the stages of periodontitis. The dominant bacteria in stage III periodontitis were Prevotella, Prevotella_7, and Dialister, whereas that in stage I periodontitis was Cardiobacterium. KEGG analysis predicted that variations in the oral microbiome may be related to the NOD-like receptor signaling pathway. The inhibitor of this pathway, NOD-IN-1, decreased P. intermedia -induced Tnf-α mRNA expression and increased P. intermedia -induced Il-6 mRNA expression, consistent with the ELISA results. Immunohistochemistry confirmed the down-regulation of TNF-α and IL-6 expressions by NOD-IN-1 in P. intermedia-induced periodontitis.

Conclusion

The composition of the oral bacteria in young males varied according to the stage of periodontitis. The species richness of oral microtia was greater in young males with stage III periodontitis than those with stage I periodontitis. Prevotella was the dominant bacteria in young males with stage III periodontitis, and inhibition of the NOD-like receptor signaling pathway can decrease the periodontal inflammation induced by P. intermedia.

Diabetes causes NLRP3-dependent barrier dysfunction in mice with detrusor overactivity but not underactivity

Approximately half of the patients with diabetes develop diabetic bladder dysfunction (DBD). The initiation and progression of DBD is largely attributed to inflammation due to dysregulated glucose and the production of toxic metabolites that activate the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome. NLRP3 activation leads to the production and release of proinflammatory cytokines and causes urothelial pyroptosis, a form of programmed cell necrosis, which we hypothesize compromises urothelial barrier integrity. Here, we investigated how NLRP3-dependent inflammation impacts barrier function during the progression of diabetes using a type 1 diabetic female Akita mouse model that progresses from an early overactive to a late underactive detrusor phenotype at 15 and 30 wk, respectively. To determine the specific role of NLRP3, Akita mice were crossbred with mice lacking the NLRP3 gene. To determine barrier function, permeability to small molecules was assessed, ex vivo using Evans blue dye and in vivo using sulfo-NHS-biotin. Both ex vivo and in vivo permeabilities were increased in diabetic mice at 15 wk. Expression of uroplakin and tight junction components was also significantly downregulated at 15 wk. Interestingly, diabetic mice lacking the NLRP3 gene showed no evidence of barrier damage or downregulation of barrier genes and proteins. At the 30-wk time point, ex vivo and in vivo barrier damage as well as barrier component downregulation was no longer evident in diabetic mice, suggesting urothelial repair or remodeling occurs between the overactive and underactive stages of DBD. Collectively, these findings demonstrate the role of NLRP3-mediated inflammation in urothelial barrier damage associated with detrusor overactivity but not underactivity.NEW & NOTEWORTHY This is the first study to demonstrate that NLRP3-mediated inflammation is responsible for urothelial barrier damage in type 1 diabetic female Akita mice with an overactive bladder. Eliminating the NLRP3 gene in these diabetic mice prevented barrier damage as a result of diabetes. By the time female Akita mice develop an underactive phenotype, the urothelial barrier has been restored, suggesting that inflammation is a critical causative factor early in the development of diabetic bladder dysfunction.

A pyroptosis-related gene model and its correlation with the microenvironment of lung adenocarcinoma: A bioinformatics analysis and experimental verification

Background: Non-small cell lung cancer, comprising lung adenocarcinoma (LUAD) and lung squamous cell carcinoma, is one of the leading causes of cancer-related mortality. Pyroptosis is a new form of programmed cell death involved in cancer development. The relationship between LUAD and pyroptosis is unclear. This research aims to investigate this relationship and develop a stratified clinical model based on pyroptosis-related genes (PRGs).

Methods: We analyzed the data of LUAD from The Cancer Genome Atlas (TCGA) and evaluated the expression of 48 PRGs to identify the differentially expressed genes. Then, constructing the risk model using the least absolute shrinkage and selection operator and the Cox regression method to find the gene signatures. The functional enrichment, immune cell infiltration, tumor mutational burden (TMB), and expression of immune checkpoints were compared to investigate the potential mechanism. The IC50 of common drugs was evaluated and compared. The inflammasome activation assay and lactate dehydrogenase (LDH) assay of NLR-family CARD-containing protein 4 (NLRC4) were also performed to confirm the role of pyroptosis in LUAD.

Results: The pyroptosis-related model accurately predicted the prognosis of patients with LUAD, with the low-risk group exhibiting a higher survival probability. The risk score was an independent prognostic factor for survival. The stratified patients exhibited distinct tumor microenvironments, TMB, and drug sensitivity. The validation experiments of NLRC4 confirmed its role in inducing pyroptosis via promoting IL-1 maturation.

Conclusion: PRGs regulated the tumor microenvironment and influenced the outcome of LUAD. NLRC4 may function as a hub gene in the process of LUAD.

A Possible Causal Involvement of Neuroinflammatory, Purinergic P2X7 Receptors in Psychiatric Disorders

P2X7 receptors (Rs) are prominent members of the P2XR family, which after binding ATP, open non-selective cationic channels, thereby allowing the transmembrane passage of Na+, Ca²⁺, and K+. Long-lasting and repetitive stimulation of the receptor by its agonist leads to the formation of large membrane pores permeable for organic cations of up to 900 Da molecular size. These pores are believed to play a role in apoptosis and inflammation. P2X7Rs are located primarily at peripheral macrophages and microglial cells, the resident macrophages of the CNS. The coactivation of toll-like receptors 4 (TLR4) by lipopolysaccharide, a constituent of the cell membrane of gram-negative bacteria, and the P2X7R by ATP leads to the generation and release of the proinflammatory cytokines interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α. Together with the microglial release of chemokines, reactive oxygen and nitrogen species, proteases, and excitotoxic glutamate, these cytokines result in neurodegeneration. P2X7Rs were found not only to amplify various neurodegenerative illnesses, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis, but also to participate in a range of psychiatric diseases, such as major depression, bipolar disorder, schizophrenia, and autism spectrum disorder. Based on the prevention/reversal of neuroinflammation, pharmacological antagonists of P2X7Rs and their genetic deletion in animal experiments counteract these deleterious psychiatric conditions. Hence, brain penetrant P2X7R antagonists are potential therapeutics for psychiatric diseases, although the available evidence still needs to be extended and validated by further clinical data.

NF-κB: A Double-Edged Sword Controlling Inflammation

Inflammation, when properly mounted and precisely calibrated, is a beneficial process that enables the rapid removal of invading pathogens and/or cellular corpses and promotes tissue repair/regeneration to restore homeostasis after injury. Being a paradigm of a rapid response transcription factor, the nuclear factor-kappa B (NF-κB) transcription factor family plays a central role in amplifying inflammation by inducing the expression of inflammatory cytokines and chemokines. Additionally, NF-κB also induces the expression of pro-survival and -proliferative genes responsible for promoting tissue repair and regeneration. Paradoxically, recent studies have suggested that the NF-κB pathway can also exert inhibitory effects on pro-inflammatory cytokine production to temper inflammation. Here, we review our current understanding about the pro- and anti-inflammatory roles of NF-κB and discuss the implication of its dichotomous inflammation-modulating activity in the context of inflammasome activation and tumorigenesis.

Inflammasome and Its Therapeutic Targeting in Rheumatoid Arthritis

Inflammasome is a cytoplasmic multiprotein complex that facilitates the clearance of exogenous microorganisms or the recognition of endogenous danger signals, which is critically involved in innate inflammatory response. Excessive or abnormal activation of inflammasomes has been shown to contribute to the development of various diseases including autoimmune diseases, neurodegenerative changes, and cancers. Rheumatoid arthritis (RA) is a chronic and complex autoimmune disease, in which inflammasome activation plays a pivotal role in immune dysregulation and joint inflammation. This review summarizes recent findings on inflammasome activation and its effector mechanisms in the pathogenesis of RA and potential development of therapeutic targeting of inflammasome for the immunotherapy of RA.

Metformin reduces chondrocyte pyroptosis in an osteoarthritis mouse model by inhibiting NLRP3 inflammasome activation

Osteoarthritis (OA) is an age-related degenerative disease, and its incidence is increasing with the ageing of the population. Metformin, as the first-line medication for the treatment of diabetes, has received increasing attention for its role in OA. The purpose of the present study was to confirm the therapeutic effect of metformin in a mouse model of OA and to determine the mechanism underlying the resultant delay in OA progression. The right knees of 8-week-old C57BL/6 male mice were subjected to destabilization of the medial meniscus (DMM). Metformin (200 mg/kg) was then administered daily for 4 or 8 weeks. Safranin O-fast green staining, H&E staining and micro-CT were used to analyse the structure and morphological changes. Immunohistochemical staining was used to detect type II collagen (Col II), matrix metalloproteinase 13 (MMP-13), NOD-like receptor protein 3 (NLRP3), caspase-1, gasdermin D (GSDMD) and IL-1β protein expression. Reverse transcription-quantitative PCR was used to detect the mRNA expression of NLRP3, caspase-1, GSDMD and IL-1β. Histomorphological staining showed that metformin delayed the progression of OA in the DMM model. With respect to cartilage, metformin decreased the Osteoarthritis Research Society International score, increased the thickness of hyaline cartilage and decreased the thickness of calcified cartilage. Regarding the mechanism, in cartilage, metformin increased the expression of Col II and decreased the expression of MMP-13, NLRP3, caspase-1, GSDMD and IL-1β. In addition, in subchondral bone, metformin inhibited osteophyte formation, increased the bone volume fraction (%) and the bone mineral density (g/cm³), decreased the trabecular separation (mm) in early stage of osteoarthritis (4 weeks) but the opposite in an advanced stage of osteoarthritis (8 weeks). Overall, metformin inhibited the activation of NLRP3 inflammasome, decreased cartilage degradation, reversed subchondral bone remodelling and inhibited chondrocyte pyroptosis.

Environmental pollutant N-N'ethylnitrosourea-induced leukemic NLRP3 inflammasome activation and its amelioration by Eclipta prostrata and its active compound wedelolactone

Environmental exposure of N-nitroso compounds (NOCs) from various sources like tobacco smoke, pesticides, smoked meat, and rubber manufacturing industries has been an alarming cause of carcinogenesis. Neonatal exposure to the carcinogenic N-N'ethylnitrosourea (ENU), a NOC has been established to cause leukemogenesis. Our world is constantly battling against cancer with consistent investigations of new anti-cancer therapeutics. Plant derived compounds have grasped worldwide attention of researchers for their promising anti-cancer potentials. Eclipta prostrata is one such ayurvedic herb, renowned for its anti-inflammatory properties. Currently, it has been explored in various cancer cell lines to establish its anti-cancer effect, but rarely in in-vivo cancer models. Wedelolactone (WDL), the major coumestan of E. prostrata is recognized as an inhibitor of IKK, a master regulator of the NF-kB inflammatory pathway. As persistent inflammation and activated inflammasome contribute to leukemogenesis, we tried to observe anti-leukemogenic efficacy of E. prostrata and its active compound WDL on the marrow cells of ENU induced experimental leukemic mice. Treatment groups were administered an oral gavage at a dose of 1200 mg/kg and 50 mg/kg b.w of crude extract and WDL respectively for 4 weeks. Various parameters like hemogram, survivability, cytological and histological investigations, migration assay, cell culture, flowcytometry and confocal microscopy were taken into consideration pre- and post-treatment. Interestingly, the plant concoction portrayed maximum effects in comparison to WDL alone. The study suggests E. prostrata and WDL as vital complementary adjuncts for anti-inflammasome mechanism in ENU-induced leukemia.

P2X7R antagonist protects against renal injury in mice with adriamycin nephropathy

Activation of the purinergic P2X7 receptor (P2X7R) has been associated with the development of experimental nephritis. Therefore, the current study aimed to explore the mechanism of P2X7R in renal injured mice with adriamycin (ADR) nephropathy. The protective effect of a P2X7R antagonist on the kidneys of mice with ADR nephropathy was also evaluated. Nephropathy was induced by a single intravenous injection of ADR (10.5 mg/kg). A total of 6 h before the model was established, the P2X7R antagonist A438079 (100, 200 and 300 µmol/kg) was injected into the mice, which was subsequently administered daily for 1 week by intraperitoneal injection. Subsequently, all mice were sacrificed, after which blood, 24 h-urine and the kidneys were collected. The levels of albumin (ALB) and total cholesterol (TC) in the serum, along with urine protein content at 24 h were determined using an automatic biochemical analyzer. The levels of IL-1β and IL-18 were additionally detected in the renal tissues by ELISA. Moreover, the expression of P2X7R, oxidized (ox)-low density lipoprotein (LDL), C-X-C motif chemokine ligand 16 (CXCL16), Bax, caspase-3 and NLRP3 in renal tissues was detected by immunohistochemistry. Apoptosis in the renal tissues was observed using the TUNEL assay. The results demonstrated that compared with the control group, decreased weight, increased proteinuria, decreased serum ALB and increased serum TC was observed in the ADR group. The expression of IL-1β, IL-18, P2X7R, ox-LDL, CXCL16, Bax, caspase-3 and NLRP3, as well as cellular apoptosis in the renal tissues of the ADR group, was significantly increased in the ADR group compared with the control. However, compared with the ADR group, the changes in all indices in the ADR + A438079 groups were attenuated. Overall, P2X7R, ox-LDL and CXCL16 may be associated with ADR nephropathy, while inhibition of P2X7R may reduce the expression of ox-LDL by downregulating the CXCL16 pathway to alleviate kidney injury in mice with ADR nephropathy. Furthermore, activated P2X7R may promote the release of inflammatory cytokines IL-1β and IL-18 through the downstream P2X7R/NLRP3 pathway and upregulate the expression of Bax and caspase-3 to promote apoptosis, which participates in the process of ADR nephropathy. Inhibiting P2X7R may also reduce the release of IL-1β and IL-18 by downregulating the P2X7R/NLRP3 pathway, downregulating the expression of Bax and caspase-3, and reducing apoptosis, thereby alleviating kidney injury in mice with ADR nephropathy.

Pyroptosis: A New Insight Into Eye Disease Therapy

Pyroptosis is a lytic form of programmed cell death mediated by gasdermins (GSDMs) with pore-forming activity in response to certain exogenous and endogenous stimuli. The inflammasomes are intracellular multiprotein complexes consisting of pattern recognition receptors, an adaptor protein ASC (apoptosis speck-like protein), and caspase-1 and cause autocatalytic activation of caspase-1, which cleaves gasdermin D (GSDMD), inducing pyroptosis accompanied by cytokine release. In recent years, the pathogenic roles of inflammasomes and pyroptosis in multiple eye diseases, including keratitis, dry eyes, cataracts, glaucoma, uveitis, age-related macular degeneration, and diabetic retinopathy, have been continuously confirmed. Inhibiting inflammasome activation and abnormal pyroptosis in eyes generally attenuates inflammation and benefits prognosis. Therefore, insight into the pathogenesis underlying pyroptosis and inflammasome development in various types of eye diseases may provide new therapeutic strategies for ocular disorders. Inhibitors of pyroptosis, such as NLRP3, caspase-1, and GSDMD inhibitors, have been proven to be effective in many eye diseases. The purpose of this article is to illuminate the mechanism underlying inflammasome activation and pyroptosis and emphasize its crucial role in various ocular disorders. In addition, we review the application of pyroptosis modulators in eye diseases.

Strategy and clinical application of up-regulating cross presentation by DCs in anti-tumor therapy

The cross presentation of exogenous antigen (Ag) by dendritic cells (DCs) facilitates a diversified mode of T-cell activation, orchestrates specific humoral and cellular immunity, and contributes to an efficient anti-tumor immune response. DCs-mediated cross presentation is subject to both intrinsic and extrinsic factors, including the homing and phenotype of DCs, the spatiotemporal trafficking and degradation kinetics of Ag, and multiple microenvironmental clues, with many details largely unexplored. Here, we systemically review the current mechanistic understanding and regulation strategies of cross presentation by heterogeneous DC populations. We also provide insights into the future exploitation of DCs cross presentation for a better clinical efficacy in anti-tumor therapy.

Pyroptosis-related gene mediated modification patterns and immune cell infiltration landscapes in cutaneous melanoma to aid immunotherapy

Tumor occurrence, infiltration, and metastasis are significantly affected by the tumor microenvironment (TME). Increasing evidence has elucidated TME's clinical significance in prognostic assessment and immunotherapy efficacy. Nonetheless, no studies have reported the potential pyroptosis-related genes (PRGs) function in TME immune cell infiltration. In this study, we systematically analyzed different PRG modification patterns in 685 cutaneous melanoma (CM) cases. We comprehensively explored the relationship between these PRG modification patterns and TME cell infiltration characteristics. Then, we used principal component analysis to construct a pyroptosis scoring system to quantify the PRG modification patterns in each CM patient. Three different PRG modification patterns were identified. Pyroptosis score was confirmed as an independent prognostic factor for CM patients. High pyroptosis score was characterized by high immunophenscore and more lymphocytes infiltration, such as T, B, and NK cells - indicating a strong ability to monitor and clear tumors, which may be responsible for the advantageous survival. Three independent cohorts that received immunotherapy confirmed the significant therapeutic efficacy and clinical benefit in high pyroptosis scores patients. This study revealed that the PRG modification patterns have a crucial effect on the CM complex and diverse microenvironment. Pyroptosis scores might serve as credible predictors of immunotherapy response and prognostic assessment. This provides a new direction for personalized immunotherapy strategies and appropriate immunotherapy candidates screening.

NOD-like receptors in autoimmune diseases

Autoimmune diseases are chronic immune diseases characterized by dysregulation of immune system, which ultimately results in a disruption in self-antigen tolerance. Cumulative data show that nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) play essential roles in various autoimmune diseases, such as inflammatory bowel disease (IBD), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriasis, multiple sclerosis (MS), etc. NLR proteins, consisting of a C-terminal leucine-rich repeat (LRR), a central nucleotide-binding domain, and an N-terminal effector domain, form a group of pattern recognition receptors (PRRs) that mediate the immune response by specifically recognizing cellular pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and triggering numerous signaling pathways, including RIP2 kinase, caspase-1, nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK) and so on. Based on their N-terminal domain, NLRs are divided into five subfamilies: NLRA, NLRB, NLRC, NLRP, and NLRX1. In this review, we briefly describe the structures and signaling pathways of NLRs, summarize the recent progress on NLR signaling in the occurrence and development of autoimmune diseases, as well as highlight numerous natural products and synthetic compounds targeting NLRs for the treatment of autoimmune diseases.

Highlighting the interplay of microRNAs from Leishmania parasites and infected-host cells

Leishmania parasites, the causative agents of leishmaniasis, are protozoan parasites with the ability to modify the signalling pathway and cell responses of their infected host cells. These parasite strategies alter the host cell environment and conditions favouring their replication, survival and pathogenesis. Since microRNAs (miRNAs) are able to post-transcriptionally regulate gene expression processes, these biomolecules can exert critical roles in controlling Leishmania-host cell interplay. Therefore, the identification of relevant miRNAs differentially expressed in Leishmania parasites as well as in infected cells, which affect the host fitness, could be critical to understand the infection biology, pathogenicity and immune response against these parasites. Accordingly, the current review aims to address the differentially expressed miRNAs in both, the parasite and infected host cells and how these biomolecules change cell signalling and host immune responses during infection. A deep understanding of these processes could provide novel guidelines and therapeutic strategies for managing and treating leishmaniasis.

P2X7 receptor in multifaceted cellular signalling and its relevance as a potential therapeutic target in different diseases

P2X7 receptor, a purinergic receptor family member, is abundantly expressed on many cells, including immune, muscle, bone, neuron, and glia. It acts as an ATP-activated cation channel that permits the influx of Ca²⁺, Na⁺ and efflux of K⁺ ions. The P2X7 receptor plays crucial roles in many physiological processes including cytokine and chemokine secretion, NLRP3 inflammasome activation, cellular growth and differentiation, locomotion, wound healing, transcription factors activation, cell death and T-lymphocyte survival. Past studies have demonstrated the up-regulation and direct association of this receptor in many pathophysiological conditions such as cancer, diabetics, arthritis, tuberculosis (TB) and inflammatory diseases. Hence, targeting this receptor is considered a worthwhile approach to lessen the afflictions associated with the disorders mentioned above by understanding the receptor architecture and downstream signalling processes. Here, in the present review, we have dissected the structural and functional aspects of the P2X7 receptor, emphasizing its role in various diseased conditions. This information will provide in-depth knowledge about the receptor and help to develop apt curative methodologies for the betterment of humanity in the coming years.

Simulated aeromedical evacuation exacerbates burn induced lung injury: targeting mitochondrial DNA for reversal

BACKGROUND

Aeromedical evacuation of patients with burn trauma is an important transport method in times of peace and war, during which patients are exposed to prolonged periods of hypobaric hypoxia; however, the effects of such exposure on burn injuries, particularly on burn-induced lung injuries, are largely unexplored. This study aimed to determine the effects of hypobaric hypoxia on burn-induced lung injuries and to investigate the underlying mechanism using a rat burn model.

METHODS

A total of 40 male Wistar rats were randomly divided into four groups (10 in each group): sham burn (SB) group, burn in normoxia condition (BN) group, burn in hypoxia condition (BH) group, and burn in hypoxia condition with treatment intervention (BHD) group. Rats with 30% total body surface area burns were exposed to hypobaric hypoxia (2000 m altitude simulation) or normoxia conditions for 4 h. Deoxyribonuclease I (DNase I) was administered systemically as a treatment intervention. Systemic inflammatory mediator and mitochondrial deoxyribonucleic acid (mtDNA) levels were determined. A histopathological evaluation was performed and the acute lung injury (ALI) score was determined. Malonaldehyde (MDA) content, myeloperoxidase (MPO) activity, and the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome level were determined in lung tissues. Data among groups were compared using analysis of variance followed by Tukey's test post hoc analysis.

RESULTS

Burns resulted in a remarkably higher level of systemic inflammatory cytokines and mtDNA release, which was further heightened by hypobaric hypoxia exposure (P < 0.01). Moreover, hypobaric hypoxia exposure gave rise to increased NLRP3 inflammasome expression, MDA content, and MPO activity in the lung (P < 0.05 or P < 0.01). Burn-induced lung injuries were exacerbated, as shown by the histopathological evaluation and ALI score (P < 0.01). Administration of DNase I markedly reduced mtDNA release and systemic inflammatory cytokine production. Furthermore, the NLRP3 inflammasome level in lung tissues was decreased and burn-induced lung injury was ameliorated (P < 0.01).

CONCLUSIONS

Our results suggested that simulated aeromedical evacuation further increased burn-induced mtDNA release and exacerbated burn-induced inflammation and lung injury. DNase I reduced the release of mtDNA, limited mtDNA-induced systemic inflammation, and ameliorated burn-induced ALI. The intervening mtDNA level is thus a potential target to protect from burn-induced lung injury during aeromedical conditions and provides safer air evacuations for severely burned patients.

Roles of Inflammasomes in Epstein-Barr Virus-Associated Nasopharyngeal Cancer

Epstein-Barr virus (EBV) infection is recognised as one of the causative agents in most nasopharyngeal carcinoma (NPC) cases. Expression of EBV viral antigens can induce host's antiviral immune response by activating the inflammasomes to produce pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and IL-18. These cytokines are known to be detrimental to a wide range of virus-infected cells, in which they can activate an inflammatory cell death program, called pyroptosis. However, aberrant inflammasome activation and production of its downstream cytokines lead to chronic inflammation that may contribute to various diseases, including NPC. In this review, we summarise the roles of inflammasomes during viral infection, how EBV evades inflammasome-mediated immune response, and progress into tumourigenesis. The contrasting roles of inflammasomes in cancer, as well as the current therapeutic approaches used in targeting inflammasomes, are also discussed in this review. While the inflammasomes appear to have dual roles in carcinogenesis, there are still many questions that remain unanswered. In particular, the exact molecular mechanism responsible for the regulation of the inflammasomes during carcinogenesis of EBV-associated NPC has not been explored thoroughly. Furthermore, the current practical application of inflammasome inhibitors is limited to specific tumour types, hence, further studies are warranted to discover the potential of targeting the inflammasomes for the treatment of NPC.

Inflammasome in ALS Skeletal Muscle: NLRP3 as a Potential Biomarker

Since NLRP3 inflammasome plays a pivotal role in several neurodegenerative disorders, we hypothesized that levels of inflammasome components could help in diagnosis or prognosis of amyotrophic lateral sclerosis (ALS). Gene and protein expression was assayed by RT-PCR and Western blot. Spearman's correlation coefficient was used to determine the linear correlation of transcriptional expression levels with longevity throughout disease progression in mice models. Kaplan-Meier analysis was performed to evaluate MCC950 effects (NLRP3 inhibitor) on lifespan of SOD1G93A mice. The results showed significant alterations in NLRP3 inflammasome gene and protein levels in the skeletal muscle of SOD1G93A mice. Spearman's correlation coefficient revealed a positive association between Nlrp3 transcriptional levels in skeletal muscle and longevity of SOD1G93A mice (r = 0.506; p = 0.027). Accordingly, NLRP3 inactivation with MCC950 decreased the lifespan of mice. Furthermore, NLRP3 mRNA levels were significantly elevated in the blood of ALS patients compared to healthy controls (p = 0.03). In conclusion, NLRP3 could be involved in skeletal muscle pathogenesis of ALS, either through inflammasome or independently, and may play a dual role during disease progression. NLRP3 gene expression levels could be used as a biomarker to improve diagnosis and prognosis in skeletal muscle from animal models and also to support diagnosis in clinical practice with the blood of ALS patients.

The P2X7 Receptor in Osteoarthritis

Osteoarthritis (OA) is the most common joint disease. With the increasing aging population, the associated socio-economic costs are also increasing. Analgesia and surgery are the primary treatment options in late-stage OA, with drug treatment only possible in early prevention to improve patients' quality of life. The most important structural component of the joint is cartilage, consisting solely of chondrocytes. Instability in chondrocyte balance results in phenotypic changes and cell death. Therefore, cartilage degradation is a direct consequence of chondrocyte imbalance, resulting in the degradation of the extracellular matrix and the release of pro-inflammatory factors. These factors affect the occurrence and development of OA. The P2X7 receptor (P2X7R) belongs to the purinergic receptor family and is a non-selective cation channel gated by adenosine triphosphate. It mediates Na⁺, Ca²⁺ influx, and K⁺ efflux, participates in several inflammatory reactions, and plays an important role in the different mechanisms of cell death. However, the relationship between P2X7R-mediated cell death and the progression of OA requires investigation. In this review, we correlate potential links between P2X7R, cartilage degradation, and inflammatory factor release in OA. We specifically focus on inflammation, apoptosis, pyroptosis, and autophagy. Lastly, we discuss the therapeutic potential of P2X7R as a potential drug target for OA.

Mitochondrial P2X7 Receptor Localization Modulates Energy Metabolism Enhancing Physical Performance

Basal expression of the P2X7 receptor (P2X7R) improves mitochondrial metabolism, Adenosine 5'-triphosphate (ATP) synthesis, and overall fitness of immune and non-immune cells. We investigated P2X7R contribution to energy metabolism and subcellular localization in fibroblasts (mouse embryo fibroblasts and HEK293 human fibroblasts), mouse microglia (primary brain microglia, and the N13 microglia cell line), and heart tissue. The P2X7R localizes to mitochondria, and its lack (1) decreases basal respiratory rate, ATP-coupled respiration, maximal uncoupled respiration, resting mitochondrial potential, mitochondrial matrix Ca²⁺ level, (2) modifies expression pattern of oxidative phosphorylation enzymes, and (3) severely affects cardiac performance. Hearts from P2rx7-deleted versus wild-type mice are larger, heart mitochondria smaller, and stroke volume, ejection fraction, fractional shortening, and cardiac output, are significantly decreased. Accordingly, the physical fitness of P2X7R-null mice is severely reduced. Thus, the P2X7R is a key modulator of mitochondrial energy metabolism and a determinant of physical fitness.

Alzheimer's Disease: New Concepts on the Role of Autoimmunity and NLRP3 Inflammasome in the Pathogenesis of the Disease

Alzheimer's disease (AD), recognized as the most common neurodegenerative disorder, is clinically characterized by the presence of extracellular beta-amyloid (Aβ) plaques and by intracellular neurofibrillary tau tangles, accompanied by glial activation and neuroinflammation. Increasing evidence suggests that self-misfolded proteins stimulate an immune response mediated by glial cells, inducing the release of inflammatory mediators and the recruitment of peripheral macrophages into the brain, which in turn aggravate AD pathology. The present review aims to update the current knowledge on the role of autoimmunity and neuroinflammation in the pathogenesis of the disease, indicating a new target for therapeutic intervention. We mainly focused on the NLRP3 microglial inflammasome as a critical factor in stimulating innate immune responses, thus sustaining chronic inflammation. Additionally, we discussed the involvement of the NLRP3 inflammasome in the gut-brain axis. Direct targeting of the NLRP3 inflammasome and the associated receptors could be a potential pharmacological strategy since its inhibition would selectively reduce AD neuroinflammation.

Ellagic Acid Protects Dopamine Neurons via Inhibition of NLRP3 Inflammasome Activation in Microglia

Neuroinflammation plays a crucial role in the pathological process of Parkinson's disease (PD). Nod-like receptor protein 3 (NLRP3) inflammasome was highly located in microglia and involved in the process of neuroinflammation. Activation of the NLRP3 inflammasome has been confirmed to contribute to the progression of PD. Thus, inhibition of NLRP3 inflammasome activation could be an important breakthrough point on PD therapy. Ellagic acid (EA) is a natural polyphenol that has been widely found in soft fruits, nuts, and other plant tissues with anti-inflammatory, antioxidant, and neuroprotective properties. However, the mechanisms underlying EA-mediated anti-inflammation and neuroprotection have not been fully elucidated. In this study, a lipopolysaccharide- (LPS-) induced rat dopamine (DA) neuronal damage model was performed to determine the effects of EA on the protection of DA neurons. In addition, the DA neuronal MN9D cell line and microglial BV-2 cell line were employed to explore whether EA-mediated neuroprotection was through an NLRP3-dependent mechanism. Results indicated that EA ameliorated LPS-induced DA neuronal loss in the rat substantia nigra. Further, inhibition of microglial NLRP3 inflammasome signaling activation was involved in EA-generated neuroprotection, as evidenced by the following observations. First, EA reduced NLRP3 inflammasome signaling activation in microglia and subsequent proinflammatory cytokines' excretion. Second, EA-mediated antineuroinflammation and further DA neuroprotection from LPS-induced neurotoxicity were not shown upon microglial NLRP3 siRNA treatment. In conclusion, this study demonstrated that EA has a profound effect on protecting DA neurons against LPS-induced neurotoxicity via the suppression of microglial NLRP3 inflammasome activation.

Dysregulation of the NLRP3 Inflammasome in Diabetic Retinopathy and Potential Therapeutic Targets

Diabetic Retinopathy (DR) is an insidious neurovascular disorder secondary to chronic glycemic dysregulation in elderly diabetic patients. In the later stages of DR, the disease manifests as fluid infiltrating the macula, culminating in the leading cause of irreversible visual impairment in working age adults. With the current mainstay treatments preoccupied with slowing down the progression of DR, this presents an unsustainable solution from both an economic and quality of life perspective. Although the exact mechanisms by which hyperglycemia leads to retinal tissue insult are unknown, the evidence suggests that chronic low-grade inflammation in diabetic eye is in part driving the constellation of symptoms present in DR. Of the innate immune system within the eye, the NLR Family Pyrin Domain Containing 3 Inflammasome (NLRP3) has been identified in retinal cells as a causal factor in the pathogenesis of DR. Multiple pathways appear to be present in the diabetic eye that instigate prolonged activation of the NLRP3 which subsequently exerts its deleterious effects by upregulating the release of Interleukin-1Beta and Interleukin-18. In this review, we highlight the current understanding of the pathophysiology of DR, the dysregulation of the NLRP3 secondary to hyperglycemic stress in retinal cells, and novel therapeutic targets to alleviate overactivation of the inflammasome.

The Long Non-coding RNAs: Paramount Regulators of the NLRP3 Inflammasome

The NOD LRR pyrin domain containing protein 3 (NLRP3) inflammasome is a cytosolic multi-proteins conglomerate with intrinsic ATPase activity. Their predominant presence in the immune cells emphasizes its significant role in immune response. The downstream effector proteins IL-1β and IL-18 are responsible for the biological functions of the NLRP3 inflammasome upon encountering the alarmins and microbial ligands. Although the NLRP3 inflammasome is essential for host defense during infections, uncontrolled activation and overproduction of IL-1β and IL-18 increase the risk of developing autoimmune and metabolic disorders. Emerging evidences suggest the action of lncRNAs in regulating the activity of NLRP3 inflammasome in various disease conditions. The long non-coding RNA (lncRNA) is an emerging field of study and evidence on their regulatory role in various diseases is grabbing attention. Recent studies emphasize the functions of lncRNAs in the fine control of the NLRP3 inflammasome at nuclear and cytoplasmic levels by interfering in chromatin architecture, gene transcription and translation. Recently, lncRNAs are also found to control the activity of various regulators of NLRP3 inflammasome. Understanding the precise role of lncRNA in controlling the activity of NLRP3 inflammasome helps us to design targeted therapies for multiple inflammatory diseases. The present review is a novel attempt to consolidate the substantial role of lncRNAs in the regulation of the NLRP3 inflammasome. A deeper insight on the NLRP3 inflammasome regulation by lncRNAs will help in developing targeted and beneficial therapeutics in the future.

Energy Provisioning and Inflammasome Activation: The Pivotal Role of AMPK in Sterile Inflammation and Associated Metabolic Disorders

BACKGROUND

Body defenses and metabolic processes probably co-evolved in such a way that rapid, energy-intensive acute inflammatory repair is functionally integrated with energy allocation in a starvation/ infection / injury-prone primitive environment. Disruptive metabolic surplus, aggravated by sedentary lifestyle induces chronic under-activation of AMPK, the master regulator of intracellular energy homeostasis. Sudden increase in chronic, dysregulated 'sterile' inflammatory disorders probably results from a shift towards calorie rich, sanitized, cushioned, injury/ infection free environment, repositioning inflammatory repair pathways towards chronic, non-microbial, 'sterile', 'low grade', and 'parainflammation'. AMPK, (at the helm of energy provisioning) supervises the metabolic regulation of inflammasome activation, a common denominator in lifestyle disorders.

DISCUSSION

In this review, we discuss various pathways linking AMPK under-activation and inflammasome activation. AMPK under-activation, the possible norm in energy-rich sedentary lifestyle, could be the central agency that stimulates inflammasome activation by multiple pathways such as 1: decreasing autophagy, and accumulation of intracellular DAMPs, (particulate crystalline molecules, advanced glycation end-products, oxidized lipids, etc.) 2: stimulating a glycolytic shift (pro-inflammatory) in metabolism, 3: promoting NF-kB activation and decreasing Nrf2 activation, 4: increasing reactive oxygen species (ROS) formation, Unfolded Protein Response (UPR) and Endoplasmic Reticulum (ER) stress.

CONCLUSION

The 'inverse energy crisis' associated with calorie-rich, sedentary lifestyle, advocates dietary and pharmacological interventions for treating chronic metabolic disorders by overcoming / reversing AMPK under-activation.

A rationale for targeting the P2X7 receptor in Coronavirus disease 19

Severe pneumonia which shares several of the features of acute respiratory distress syndrome (ARDS) is the main cause of morbidity and mortality in Coronavirus disease 19 (Covid‐19) for which there is no effective treatment, so far. ARDS is caused and sustained by an uncontrolled inflammatory activation characterized by a massive release of cytokines (cytokine storm), diffuse lung oedema, inflammatory cell infiltration, and disseminated coagulation. Macrophage and T lymphocyte dysfunction plays a central role in this syndrome. In several experimental in vitro and in vivo models, many of these pathophysiological changes are triggered by stimulation of the P2X7 receptor. We hypothesize that this receptor might be an ideal candidate to target in Covid‐19‐associated severe pneumonia.

Linked Articles

This article is part of a themed issue on The Pharmacology of COVID‐19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc

Inflammasome activation and regulation: toward a better understanding of complex mechanisms

Inflammasomes are cytoplasmic multiprotein complexes comprising a sensor protein, inflammatory caspases, and in some but not all cases an adapter protein connecting the two. They can be activated by a repertoire of endogenous and exogenous stimuli, leading to enzymatic activation of canonical caspase-1, noncanonical caspase-11 (or the equivalent caspase-4 and caspase-5 in humans) or caspase-8, resulting in secretion of IL-1β and IL-18, as well as apoptotic and pyroptotic cell death. Appropriate inflammasome activation is vital for the host to cope with foreign pathogens or tissue damage, while aberrant inflammasome activation can cause uncontrolled tissue responses that may contribute to various diseases, including autoinflammatory disorders, cardiometabolic diseases, cancer and neurodegenerative diseases. Therefore, it is imperative to maintain a fine balance between inflammasome activation and inhibition, which requires a fine-tuned regulation of inflammasome assembly and effector function. Recently, a growing body of studies have been focusing on delineating the structural and molecular mechanisms underlying the regulation of inflammasome signaling. In the present review, we summarize the most recent advances and remaining challenges in understanding the ordered inflammasome assembly and activation upon sensing of diverse stimuli, as well as the tight regulations of these processes. Furthermore, we review recent progress and challenges in translating inflammasome research into therapeutic tools, aimed at modifying inflammasome-regulated human diseases.

Moderate Mechanical Stimulation Protects Rats against Osteoarthritis through the Regulation of TRAIL via the NF-κB/NLRP3 Pathway

The aim of this study was to examine exercise-related genes in articular cartilage identified through bioinformatics analysis to dissect the potential signaling pathway involved in mechanical stimulation in osteoarthritis (OA). To this end, we evaluated the GSE74898 dataset from the Gene Expression Omnibus database for exercise-related differentially expressed miRNAs (DE-miRNAs) using the R software package and predicted potential target genes for these miRNAs using miRTarBase. Functional annotation and pathway enrichment analysis were performed for these potential DE-miRNA targets. The effects of mechanical stimulation on the tumor necrosis factor-related apoptosis-induced ligand (TRAIL)/nuclear factor-kappa B (NF-κB)/nucleotide-binding and oligomerization domain-like receptor containing protein 3 (NLRP3) signaling pathway were evaluated in articular cartilage and chondrocytes. A total of 394 DE-miRNAs were identified (103 upregulated miRNAs; 291 downregulated miRNAs) in the cartilage of rats following treadmill exercise compared to the cartilage of unexercised control rats. Thus, mechanical stimulation could modulate the TRAIL/NF-κB/NLRP3 signaling pathway on OA. Histological and protein analysis demonstrated that moderate-intensity treadmill exercise could ameliorate OA through the downregulation of TRAIL. Furthermore, moderate cyclic tensile strain (CTS) could rescue chondrocytes from the effects of TRAIL via the inhibition of the nuclear translocation of NF-κB p65 and formation of NLRP3. Our findings indicate that moderate mechanical stimulation could ameliorate the degeneration of cartilage and chondrocyte damage through the inhibition of the TRAIL/NF-κB/NLRP3 pathway.

Ginsenoside Rg1 attenuates chronic unpredictable mild stress-induced depressive-like effect via regulating NF-κB/NLRP3 pathway in rats

Ginsenoside (GS Rg1), which has neuroprotection and anti-inflammation activities, is the main active ingredient of Radix Ginseng. However, its antidepressant-like effect in rats remains unclear. Our study was conducted to investigate whether GS Rg1 confers an antidepressant effect in rats exposed to a chronic unpredictable mild stress model of depression and to explore its possible mechanisms. Our results revealed that GS Rg1 treatments for 3 weeks alleviated the depression-related behaviors of chronic unpredictable mild stress-exposed rats, as indicated by increasing sucrose preference, improving locomotor activity and shortening immobile time in both the forced swimming tests and tail suspension tests. And these ameliorative effects of GS Rg1 treatment were involved with regulating chronic unpredictable mild stress-induced pro-inflammatory cytokine interleukin beta (IL-1β) related neuro-inflammation. In addition, we further found that GS Rg1 reversed chronic unpredictable mild stress-induced IL-1β elevation, possibly by inhibiting nuclear factor kappa B pathway activation and regulating nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 inflammasome expression. In short, our results suggested that GS Rg1 exerted a potential antidepressant-like effect in chronic unpredictable mild stress rat model of depression, which may provide an insight into the potential of GS Rg1 in therapeutic implications for depression.

Association of Hypomorphic P2X7 Receptor Genotype With Age

One of the main risk factors for brain diseases is aging. Recent studies have shown that aging is a progressive degenerative process associated with chronic low-level inflammation. The ATP-gated P2X7 receptor (P2X7R) plays an important role in inflammation and has been associated with different brain (e.g., Alzheimer’s and Parkinson’s) or other age-related (osteoporosis, arthritis, cancer) diseases. Several single nucleotide polymorphisms (SNPs) in the P2RX7 gene have been identified, including the loss-of-function 1513A>C and 1405A>G SNPs, and the gain-of-function 489C>T and 1068G>A SNPs. We carried out a literature analysis to verify an association between P2RX7 SNPs’ frequency and age. In 34 worldwide eligible studies (11.858 subjects) no correlation between 1513CC genotype frequency and age emerged. On the contrary, analysis of European Caucasian cohorts (7.241 subjects) showed a significant increase in 1513CC frequency with age (P = 0.027). In agreement with these findings, analysis of two publicly available datasets, including USA Caucasian cohorts, unveiled an increased frequency of 1513CC and 489CC genotypes with age (P = 0.0055 and P = 0.0019, respectively). Thus, hypomorphic P2RX7 genotypes may be positively selected with age in European and North American Caucasian populations. We hypothesize that Caucasian individuals bearing an anti-inflammatory P2X7R phenotype and living in high-income countries may have a longer life expectancy.

Loganin ameliorates cartilage degeneration and osteoarthritis development in an osteoarthritis mouse model through inhibition of NF-κB activity and pyroptosis in chondrocytes

ETHNOPHARMACOLOGICAL RELEVANCE

Corni Fructus (CF), the red fruit of Cornus officinalis Siebold & Zucc, has been used both as food and medicinal herb in traditional Chinese medicine (TCM). Loganin is a major iridoid glycoside and one of the quality control indexes of CF. In TCM clinical practice, prescription containing CF is commonly used to treat osteoarthritis (OA), but the underlying mechanisms of loganin are not yet utterly understood.

AIM OF THE STUDY

The aims of the present study are to confirm the therapeutic effects of loganin in an OA mouse model and to determine the mechanisms involved in the OA protective effects.

MATERIALS AND METHODS

The destabilization of the medial meniscus (DMM) procedure was performed on the right knee of 8-week-old C57BL/6 male mice. 30 or 100 μg/ml of loganin was then injected into articular space twice a week for 8 and 12-week. Safranin O/Fast green staining, H&E staining, micro-CT analysis were performed to analyze structural and morphological changes. The protein expression of collagen type II (Col2), metalloproteinase-3 (Mmp3), matrix metalloproteinase 13 (Mmp13) collagen type X (Col10), cryopyrin and caspase-1 were detected by immunochemistry staining. Immuno-fluorescence assay was performed to assess changes in expression of CD31, endomucin, p65 and p-I-κB.

RESULTS

Results of histomorphometry showed that loganin delays the progression of OA in the DMM model. In cartilage, loganin decreased the OARSI score, increasing hyaline cartilage (HC) thickness and decreasing calcified cartilage (CC) thickness. Moreover, loganin inhibited osteophyte formation, reduced the bone volume fraction (BV/TV), lowered trabecular thickness (Tb.Th) and increased trabecular separation (Tb.Sp) in subchondral bone. Mechanistically, loganin increased the expressions of Col2, decreases the expression of Mmp3, Mmp13, Col10, cryopyrin and caspase-1 in cartilage. In parallel, loganin inhibited the expression of CD31 and endomucin in subchondral bone. Furthermore, loganin suppressed nuclear translocation of p65 protein, and decreased the amount of p-I-κB in chondrocytes.

CONCLUSIONS

In summary, these results uncovered that loganin inhibits NF-κB signaling and attenuates cartilage matrix catabolism and pyroptosis of chondrocytes in articular cartilage. Loganin may serve as a potential therapeutic agent for OA treatment.