NLRP3 (NALP3, Cryopyrin) facilitates in vivo caspase-1 activation, necrosis, and HMGB1 release via inflammasome-dependent and -independent pathways

Metabolism-inflammasome crosstalk shapes innate and adaptive immunity

Inflammasomes are a central component of innate immunity and play a vital role in regulating innate immune response. Activation of inflammasomes is also indispensable for adaptive immunity, modulating the development and response of adaptive immunity. Recently, increasing studies have shown that metabolic alterations and adaptations strongly influence and regulate the differentiation and function of the immune system. In this review, we will take a holistic view of how inflammasomes bridge innate and adaptive (especially T cell) immunity and how inflammasomes crosstalk with metabolic signals during the immune responses. And, special attention will be paid to the metabolic control of inflammasome-mediated interactions between innate and adaptive immunity in disease. Understanding the metabolic regulatory functions of inflammasomes would provide new insights into future research directions in this area and may help to identify potential targets for inflammasome-associated diseases and broaden therapeutic avenues.

Melatonin suppresses TLR4-mediated RSV infection in the central nervous cells by inhibiting NLRP3 inflammasome formation and autophagy

Respiratory syncytial virus (RSV) infects neuronal cells in the central nervous system (CNS), resulting in neurological symptoms. In the present study, we intended to explore the mechanism of RSV infection-induced neuroinflammatory injury from the perspective of the immune response and sought to identify effective protective measures against the injury. The findings showed that toll-like receptor 4 (TLR4) was activated after RSV infection in human neuronal SY5Y cells. Furthermore, TLR4 activation induced autophagy and apoptosis in neuronal cells, promoted the formation of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, and increased the secretion of downstream inflammatory cytokines such as interleukin-1β (IL-1β), interleukin-18 (IL-18) and tumour necrosis factor-α (TNF-α). Interestingly, blockade of TLR4 or treatment with exogenous melatonin significantly suppressed TLR4 activation as well as TLR4-mediated apoptosis, autophagy and immune responses. Therefore, we infer that melatonin may act on the TLR4 to ameliorate RSV-induced neuronal injury, which provides a new therapeutic target for RSV infection.

The discovery of NLRP3 and its function in cryopyrin-associated periodic syndromes and innate immunity

From studies of individual families to global collaborative efforts, the NLRP3 inflammasome is now recognized to be a key regulator of innate immunity. Activated by a panoply of pathogen-associated and endogenous triggers, NLRP3 serves as an intracellular sensor that drives carefully coordinated assembly of the inflammasome, and downstream inflammation mediated by IL-1 and IL-18. Initially discovered as the cause of the autoinflammatory spectrum of cryopyrin-associated periodic syndrome (CAPS), NLRP3 is now also known to play a role in more common diseases including cardiovascular disease, gout, and liver disease. We have seen cohesion in results from clinical studies in CAPS patients, ex vivo studies of human cells and murine cells, and in vivo murine models leading to our understanding of the downstream pathways, cytokine secretion, and cell death pathways that has solidified the role of autoinflammation in the pathogenesis of human disease. Recent advances in our understanding of the structure of the inflammasome have provided ways for us to visualize normal and mutant protein function and pharmacologic inhibition. The subsequent development of targeted therapies successfully used in the treatment of patients with CAPS completes the bench to bedside translational loop which has defined the study of this unique protein.

Connecting the Dots: The Cerebral Lymphatic System as a Bridge Between the Central Nervous System and Peripheral System in Health and Disease

As a recently discovered waste removal system in the brain, cerebral lymphatic system is thought to play an important role in regulating the homeostasis of the central nervous system. Currently, more and more attention is being focused on the cerebral lymphatic system. Further understanding of the structural and functional characteristics of cerebral lymphatic system is essential to better understand the pathogenesis of diseases and to explore therapeutic approaches. In this review, we summarize the structural components and functional characteristics of cerebral lymphatic system. More importantly, it is closely associated with peripheral system diseases in the gastrointestinal tract, liver, and kidney. However, there is still a gap in the study of the cerebral lymphatic system. However, we believe that it is a critical mediator of the interactions between the central nervous system and the peripheral system.

Emerging bacterial factors for understanding pathogenesis of endometriosis

The pathogenesis of endometriosis is a complex process, and recent research has introduced novel hypotheses in this field. This review summarizes recent studies on the pathogenesis of endometriosis. We focused on several classical hypotheses, as well as their interactions with the microenvironment of hormonal dependence and immunosuppression. Furthermore, we highlighted the emergence of bacterial factors associated with endometriosis. Recent advances in next-generation sequencing (NGS) have revealed the presence and detailed distribution of these bacteria as well as the involvement of specific bacteria in pathogenesis. These factors alter the microenvironment in the early stages of endometriosis development, leading to lesion formation. Understanding the mechanisms underlying the early development of endometriosis from a new perspective would be helpful for the development of novel therapeutic agents for endometriosis.

Global trends in research on endothelial cells and sepsis between 2002 and 2022: A systematic bibliometric analysis

Sepsis is a systemic syndrome involving physiological, pathological, and biochemical abnormalities precipitated by infection and is a major global public health problem. Endothelial cells (ECs) dysfunction is a major contributor to sepsis-induced multiple organ failure. This bibliometric analysis aimed to identify and characterize the status, evolution of the field, and new research trends of ECs and sepsis over the past 20 years. For this analysis, the Web of Science Core Collection database was searched to identify relevant publications on ECs in sepsis published between January 1, 2002, and December 31, 2022. Microsoft Excel 2021, VOSviewer software, CiteSpace software, and the online analysis platform of literature metrology (http://bibliometric.com) were used to visualize the trends of publications' countries/regions, institutions, authors, journals, and keywords. In total, 4200 articles were identified and screened, primarily originating from 86 countries/regions and 3489 institutions. The USA was the leading contributor to this research field, providing 1501 articles (35.74 %). Harvard University's scientists were the most prolific, with 129 articles. Overall, 21,944 authors were identified, among whom Bae Jong Sup was the most prolific, contributing 129 publications. Additionally, Levi Marcel was the most frequently co-cited author, appearing 538 times. The journals that published the most articles were SHOCK, CRITICAL CARE MEDICINE, and PLOS ONE, accounting for 10.79 % of the total. The current emerging hotspots are concentrated on "endothelial glycocalyx," "NLRP3 inflammasome," "extracellular vesicle," "biomarkers," and "COVID-19," among others. In conclusion, this study provides a comprehensive overview of the scientific productivity and emerging research trends in the field of ECs in sepsis. The evidence supporting the significant role of ECs in both physiological and pathological responses to sepsis is continuously growing. More in-depth studies of the molecular mechanisms underlying sepsis-induced endothelial dysfunction and EC-targeted therapies are warranted in the future.

Cervical carcinoma induces NLRP3 inflammasome activation and IL-1ß release in human peripheral blood monocytes affecting patients' overall survival

PURPOSE

Our group previously demonstrated that genetic variants in inflammasome genes contribute to protection against the establishment of human papilloma virus (HPV)-associated cervical carcinoma (CC). The objective of this study was to better understand the contribution of inflammasome and its cytokines in the CC microenvironment.

METHODS

The inflammasome activation was analyzed in CC tumoral cell lines and healthy donors (HD)' monocytes in co-culture. In vitro results were then compared to CC patients' public databases.

RESULTS

CC cells did not produce IL-1ß or IL-18 themselves, however, when in co-culture with HD monocytes, induced IL-1ß release in those leucocytes. Inflammasome activation appears to be partially dependent on the NLRP3 receptor. Public data analysis revealed that IL1B expression is increased in the CC compared to normal uterine cervix, and that patients with high IL1B expression had a shorter overall survival.

CONCLUSION

CC microenvironment can activate the inflammasome and IL-1ß release in surrounding monocytes, which could be detrimental for CC prognosis.

Functionalized nanomaterials targeting NLRP3 inflammasome driven immunomodulation: Friend or Foe

The advancement in drug delivery systems in recent times has significantly enhanced therapeutic effects by enabling site-specific targeting through nanocarriers. These nanocarriers serve as invaluable tools for pharmacotherapeutic advancements against various disorders that enhance the effectiveness of encapsulated drugs by reducing their toxicity and increasing the efficacy of less potent drugs, thereby improving the therapeutic index. Inflammasomes, protein complexes located in the activated immune cell cytoplasm, regulate the activation of caspases involved in inflammation. However, aberrant activation of inflammasomes can result in uncontrolled tissue responses, contributing to the development of various diseases. Therefore, achieving a precise balance between inflammasome inhibition and activation is crucial for effectively treating inflammatory disorders through targeted functionalized nanocarriers. Despite the wealth of available data on the relevance of functionalized nanocarriers in inflammatory disorders, the nanotechnological potential to modulate inflammasomes has not been adequately explored. In this comprehensive review, we highlight the latest research on the modulation of the inflammasome cascade, both upregulating and downregulating its function, using nanocarriers in the context of inflammatory disorders. The utilization of nanocarriers as a therapeutic strategy holds immense potential for researchers aiming to effectively target and modulate inflammasomes in the treatment of inflammatory disorders, thus improving disease severity outcomes.

Role of toll-like receptors and nod-like receptors in acute lung infection

The respiratory system exposed to microorganisms continuously, and the pathogenicity of these microbes not only contingent on their virulence factors, but also the host's immunity. A multifaceted innate immune mechanism exists in the respiratory tract to cope with microbial infections and to decrease tissue damage. The key cell types of the innate immune response are macrophages, neutrophils, dendritic cells, epithelial cells, and endothelial cells. Both the myeloid and structural cells of the respiratory system sense invading microorganisms through binding or activation of pathogen-associated molecular patterns (PAMPs) to pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and NOD-like receptors (NLRs). The recognition of microbes and subsequent activation of PRRs triggers a signaling cascade that leads to the activation of transcription factors, induction of cytokines/5chemokines, upregulation of cell adhesion molecules, recruitment of immune cells, and subsequent microbe clearance. Since numerous microbes resist antimicrobial agents and escape innate immune defenses, in the future, a comprehensive strategy consisting of newer vaccines and novel antimicrobials will be required to control microbial infections. This review summarizes key findings in the area of innate immune defense in response to acute microbial infections in the lung. Understanding the innate immune mechanisms is critical to design host-targeted immunotherapies to mitigate excessive inflammation while controlling microbial burden in tissues following lung infection.

Klebsiella pneumoniae manipulates human macrophages to acquire iron

Background

Klebsiella pneumoniae (KP) is a major cause of hospital-acquired infections, such as pneumonia. Moreover, it is classified as a pathogen of concern due to sprawling anti-microbial resistance. During infection, the gram-negative pathogen is capable of establishing an intracellular niche in macrophages by altering cellular metabolism. One factor critically affecting the host-pathogen interaction is the availability of essential nutrients, like iron, which is required for KP to proliferate but which also modulates anti-microbial immune effector pathways. We hypothesized, that KP manipulates macrophage iron homeostasis to acquire this crucial nutrient for sustained proliferation.

Methods

We applied an in-vitro infection model, in which human macrophage-like PMA-differentiated THP1 cells were infected with KP (strain ATCC 43816). During a 24-h course of infection, we quantified the number of intracellular bacteria via serial plating of cell lysates and evaluated the effects of different stimuli on intracellular bacterial numbers and iron acquisition. Furthermore, we analyzed host and pathogen specific gene and protein expression of key iron metabolism molecules.

Results

Viable bacteria are recovered from macrophage cell lysates during the course of infection, indicative of persistence of bacteria within host cells and inefficient pathogen clearing by macrophages. Strikingly, following KP infection macrophages strongly induce the expression of the main cellular iron importer transferrin-receptor-1 (TFR1). Accordingly, intracellular KP proliferation is further augmented by the addition of iron loaded transferrin. The induction of TFR1 is mediated via the STAT-6-IL-10 axis, and pharmacological inhibition of this pathway reduces macrophage iron uptake, elicits bacterial iron starvation, and decreases bacterial survival.

Conclusion

Our results suggest, that KP manipulates macrophage iron metabolism to acquire iron once confined inside the host cell and enforces intracellular bacterial persistence. This is facilitated by microbial mediated induction of TFR1 via the STAT-6-IL-10 axis. Mechanistic insights into immune metabolism will provide opportunities for the development of novel antimicrobial therapies.

Air pollution induces pyroptosis of human monocytes through activation of inflammasomes and Caspase-3-dependent pathways

According to the World Health Organization (WHO), air pollution is one of the most serious threats for our planet. Despite a growing public awareness of the harmful effects of air pollution on human health, the specific influence of particulate matter (PM) on human immune cells remains poorly understood. In this study, we investigated the effect of PM on peripheral blood monocytes in vitro. Monocytes from healthy donors (HD) were exposed to two types of PM: NIST (SRM 1648a, standard urban particulate matter from the US National Institute for Standards and Technology) and LAP (SRM 1648a with the organic fraction removed). The exposure to PM-induced mitochondrial ROS production followed by the decrease of mitochondrial membrane potential and activation of apoptotic protease activating factor 1 (Apaf-1), Caspase-9, and Caspase-3, leading to the cleavage of Gasdermin E (GSDME), and initiation of pyroptosis. Further analysis showed a simultaneous PM-dependent activation of inflammasomes, including NLRP3 (nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3) and Caspase-1, followed by cleavage of Gasdermin D (GSDMD) and secretion of IL-1β. These observations suggest that PM-treated monocytes die by pyroptosis activated by two parallel signaling pathways, related to the inorganic and organic PM components. The release of IL-1β and expression of danger-associated molecular patterns (DAMPs) by pyroptotic cells further activated the remnant viable monocytes to produce inflammatory cytokines (TNF-α, IL-6, IL-8) and protected them from death induced by the second challenge with PM.In summary, our report shows that PM exposure significantly impacts monocyte function and induces their death by pyroptosis. Our observations indicate that the composition of PM plays a crucial role in this process-the inorganic fraction of PM is responsible for the induction of the Caspase-3-dependent pyroptotic pathway. At the same time, the canonical inflammasome path is activated by the organic components of PM, including LPS (Lipopolysaccharide/endotoxin). PM-induced pyroptosis of human monocytes. Particulate matter (PM) treatment affects monocytes viability already after 15 min of their exposure to NIST or LAP in vitro. The remnant viable monocytes in response to danger-associated molecular patterns (DAMPs) release pro-inflammatory cytokines and activate Th1 and Th17 cells. The mechanism of PM-induced cell death includes the increase of reactive oxygen species (ROS) production followed by collapse of mitochondrial membrane potential (ΔΨm), activation of Apaf-1, Caspase-9 and Caspase-3, leading to activation of Caspase-3-dependent pyroptotic pathway, where Caspase-3 cleaves Gasdermin E (GSDME) to produce a N-terminal fragment responsible for the switch from apoptosis to pyroptosis. At the same time, PM activates the canonical inflammasome pathway, where activated Caspase-1 cleaves the cytosolic Gasdermin D (GSDMD) to produce N-terminal domain allowing IL-1β secretion. As a result, PM-treated monocytes die by pyroptosis activated by two parallel pathways-Caspase-3-dependent pathway related to the inorganic fraction of PM and the canonical inflammasome pathway dependent on the organic components of PM.

Anti-inflammatory therapies were associated with reduced risk of myocardial infarction in patients with established cardiovascular disease or high cardiovascular risks: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIMS

We aimed to evaluate the association between anti-inflammatory therapies and the incidence of cardiovascular events in patients with established cardiovascular disease (CVD) or high cardiovascular risks.

METHODS

Literature retrieval was conducted in PubMed, Medline, Embase, the Cochrane Central Register of Controlled Trials and Clinicaltrial.gov website from the inception to December 2022. Randomized controlled trials comparing anti-inflammatory therapies with placebo in patients with established CVD or high cardiovascular risks were included. The results of the meta-analysis were computed as the risk ratio (RR) with 95% confidence interval (CI).

RESULTS

Compared with placebo, anti-inflammatory therapies were associated with decreased incidence of myocardial infarction (MI) (RR = 0.93, 95% CI, 0.88 to 0.98), which was mainly driven by therapies targeting central IL-6 signaling pathway (RR = 0.83, 95% CI, 0.74 to 0.93). IL-1 inhibitors treatment was associated with reduced risks of heart failure (RR = 0.38, 95% CI, 0.18 to 0.80) while lower incidence of stroke was observed in patients with colchicine treatment (RR = 0.47, 95% CI, 0.28 to 0.77). MI events were less frequent in patients over 65 years of age (RR = 0.90, 95% CI, 0.83 to 0.98) or with follow-up duration over 1 year (RR = 0.90, 95% CI, 0.85 to 0.96) when comparing anti-inflammatory therapies with placebo.

CONCLUSIONS

Anti-inflammatory therapies, especially those targeting the central IL-6 signaling pathway, may serve as promising treating strategies to ameliorate the risk of MI. IL-1 inhibitor and colchicine were associated with decreased risks of heart failure and stroke, respectively. MI risk reduction by anti-inflammatory therapies seemed to be more prominent in older patients with long follow-up duration.

The Role of Alarmins in Osteoarthritis Pathogenesis: HMGB1, S100B and IL-33

Osteoarthritis (OA) is a multifactorial disease in which genetics, aging, obesity, and trauma are well-known risk factors. It is the most prevalent joint disease and the largest disability problem worldwide. Recent findings have described the role of damage-associated molecular patterns (DAMPs) in the course of the disease. In particular, alarmins such as HMGB1, IL-33, and S100B, appear implicated in enhancing articular inflammation and favouring a catabolic switch in OA chondrocytes. The aims of this review are to clarify the molecular signalling of these three molecules in OA pathogenesis, to identify their possible use as staging biomarkers, and, most importantly, to find out whether they could be possible therapeutic targets. Osteoarthritic cartilage expresses increased levels of all three alarmins. HMGB1, in particular, is the most studied alarmin with increased levels in cartilage, synovium, and synovial fluid of OA patients. High levels of HMGB1 in synovial fluid of OA joints are positively correlated with radiological and clinical severity. Counteracting HMGB1 strategies have revealed improving results in articular cells from OA patients and in OA animal models. Therefore, drugs against this alarmin, such as anti-HMGB1 antibodies, could be new treatment possibilities that can modify the disease course since available medications only alleviate symptoms.

Resistance of hypervirulent Klebsiella pneumoniae to cathepsin B-mediated pyroptosis in murine macrophages

Introduction

Hypervirulent Klebsiella pneumoniae (hvKp) has emerged as a clinically significant global pathogen in the last decade. However, the host immune responses of the macrophages during hvKp infection are largely unknown. In the present study, we aimed to compare the cytotoxic effects of hvKp and classical K. pneumoniae (cKp) in murine macrophages.

Results

We found that the activation of caspase-1 -dependent pyroptosis was higher in cKp-infected macrophages compared with that in hvKp-infected macrophages. In Caspase-1 deficiency macrophages, pyroptosis diminished during infection. Both hvKp and cKp strains led to nucleotide-binding and oligomerization domain-like receptor protein 3 (NLRP3) inflammasome formation and lysosomal cathepsin B activation, thus resulting in pyroptosis. Compared with the cKp strain, the hvKp strain inhibited these phenomena in murine macrophages.

Conclusion

HvKp infection resulted in different levels of pyroptosis via the activation of cathepsin B-NLRP3-caspase-1 in murine macrophages. Therefore, the manipulation of pyroptotic cell death is a potential target for host response during hvKp infection in macrophages.

A positive feedback cycle between the alarmin S100A8/A9 and NLRP3 inflammasome-GSDMD signalling reinforces the innate immune response in Candida albicans keratitis

OBJECTIVE

Fungal keratitis is a severe sight-threatening ocular infection, without effective treatment strategies available now. Calprotectin S100A8/A9 has recently attracted great attention as a critical alarmin modulating the innate immune response against microbial challenges. However, the unique role of S100A8/A9 in fungal keratitis is poorly understood.

METHODS

Experimental fungal keratitis was established in wild-type and gene knockout (TLR4^-/- and GSDMD^-/-) mice by infecting mouse corneas with Candida albicans. The degree of mouse cornea injuries was evaluated by clinical scoring. To interrogate the molecular mechanism in vitro, macrophage RAW264.7 cell line was challenged with Candida albicans or recombinant S100A8/A9 protein. Label-free quantitative proteomics, quantitative real-time PCR, Western blotting, and immunohistochemistry were conducted in this research.

RESULTS

Herein, we characterized the proteome of mouse corneas infected with Candida albicans and found that S100A8/A9 was robustly expressed at the early stage of the disease. S100A8/A9 significantly enhanced disease progression by promoting NLRP3 inflammasome activation and Caspase-1 maturation, accompanied by increased accumulation of macrophages in infected corneas. In response to Candida albicans infection, toll-like receptor 4 (TLR4) sensed extracellular S100A8/A9 and acted as a bridge between S100A8/A9 and NLRP3 inflammasome activation in mouse corneas. Furthermore, the deletion of TLR4 resulted in noticeable improvement in fungal keratitis. Remarkably, NLRP3/GSDMD-mediated macrophage pyroptosis in turn facilitates S100A8/A9 secretion during Candida albicans keratitis, thus forming a positive feedback cycle that amplifies the proinflammatory response in corneas.

CONCLUSIONS

The present study is the first to reveal the critical roles of the alarmin S100A8/A9 in the immunopathology of Candida albicans keratitis, highlighting a promising approach for therapeutic intervention in the future.

Nigericin Boosts Anti-Tumor Immune Response via Inducing Pyroptosis in Triple-Negative Breast Cancer

Although immune checkpoint inhibitors improved the clinical outcomes of advanced triple negative breast cancer (TBNC) patients, the response rate remains relatively low. Nigericin is an antibiotic derived from Streptomyces hydrophobicus. We found that nigericin caused cell death in TNBC cell lines MDA-MB-231 and 4T1 by inducing concurrent pyroptosis and apoptosis. As nigericin facilitated cellular potassium efflux, we discovered that it caused mitochondrial dysfunction, leading to mitochondrial ROS production, as well as activation of Caspase-1/GSDMD-mediated pyroptosis and Caspase-3-mediated apoptosis in TNBC cells. Notably, nigericin-induced pyroptosis could amplify the anti-tumor immune response by enhancing the infiltration and anti-tumor effect of CD4+ and CD8+ T cells. Moreover, nigericin showed a synergistic therapeutic effect when combined with anti-PD-1 antibody in TNBC treatment. Our study reveals that nigericin may be a promising anti-tumor agent, especially in combination with immune checkpoint inhibitors for advanced TNBC treatment.

Disulfiram with Cu2+ alleviates dextran sulfate sodium-induced ulcerative colitis in mice

Background: Disulfiram (DSF), a Food and Drug Administration (FDA)-approved drug for chronic alcohol addiction, has anti-inflammatory effects that help prevent various cancers, and Cu²⁺ can enhance the effects of DSF. Inflammatory bowel diseases (IBD) are characterized by chronic or recurrent relapsing gastrointestinal inflammation. Many drugs targeting the immune responses of IBD have been developed, but their application has many problems, including side effects and high costs. Therefore, there is an urgent need for new drugs. In this study, we investigated the preventive effects of DSF+Cu²⁺ on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) in mice. Methods: The anti-inflammatory effects were investigated using the DSS-induced colitis mouse model and lipopolysaccharide (LPS)-induced macrophages. DSS-induced TCRβ^-/- mice were used to demonstrate the effect of DSF in conjunction with Cu²⁺ on CD4⁺ T cell-secreted interleukin 17 (IL-17). In addition, the effect of DSF+Cu²⁺ on intestinal flora was studied by 16S rRNA microflora sequencing. Results: DSF and Cu²⁺ could significantly reverse the symptom of DSS-induced UC in mice, such as weight loss, disease activity index score, colon length shortening, and reversal of colon pathological changes. DSF and Cu²⁺ could inhibit colonic macrophage activation by blocking the nuclear factor kappa B (NF-κB) pathway, reducing nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3)-inflammasome-derived interleukin 1 beta (IL-1β) secretion and caspase-1 (CASP1) activation, and decreasing IL-17 secretion by CD4⁺ T cells. Moreover, the treatment of DSF and Cu²⁺ could protect the intestinal barrier by reversing the expression of tight junction proteins, zonula occluden-1 (ZO-1), occludin, and mucoprotein-2 (MUC2). Additionally, DSF+Cu²⁺ could reduce the abundance of harmful bacteria and increase beneficial bacteria in the intestinal tract of mice, effectively improving intestinal microecology. Conclusion: Our study evaluated the effect of DSF+Cu²⁺ on the immune system and gut microbiota in colonic inflammation and highlighted its potential to treat UC in the clinic.

HMGB1, angel or devil, in ischemic stroke

INTRODUCTION

High-mobility group box 1 protein (HMGB1) is extensively involved in causing ischemic stroke, pathological damage of ischemic brain injury, and neural tissue repair after ischemic brain injury. However, the precise role of HMGB1 in ischemic stroke remains to be elucidated.

METHODS

Comprehensive literature search and narrative review to summarize the current field of HMGB1 in cerebral ischemic based on the basic structure, structural modification, and functional roles of HMGB1 described in the literature.

RESULTS

Studies have exhibited the crucial roles of HMGB1 in cell death, immunity and inflammation, thrombosis, and remodeling and repair. HMGB1 released after cerebral infarction is extensively involved in the pathological injury process in the early stage of cerebral infarction, whereas it is involved in the promotion of brain tissue repair and remodeling in the late stage of cerebral infarction. HMGB1 plays a neurotrophic role in acute white matter stroke, whereas it causes sustained activation of inflammation and plays a damaging role in chronic white matter ischemia.

CONCLUSIONS

HMGB1 plays a complex role in cerebral infarction, which is related to not only the modification of HMGB1 and bound receptors but also different stages and subtypes of cerebral infarction. future studies on HMGB1 should investigate the spatial and temporal dynamics of HMGB1 after cerebral infarction. Moreover, future studies on HMGB1 should attempt to integrate different stages and infarct subtypes of cerebral infarction.

Protective effects of an anti-4-HNE monoclonal antibody against liver injury and lethality of endotoxemia in mice

4-hydroxy-2-nonenal (4-HNE) is a lipid peroxidation product that is known to be elevated during oxidative stress. During systemic inflammation and endotoxemia, plasma levels of 4-HNE are elevated in response to lipopolysaccharide (LPS) stimulation. 4-HNE is a highly reactive molecule due to its generation of both Schiff bases and Michael adducts with proteins, which may result in modulation of inflammatory signaling pathways. In this study, we report the production of a 4-HNE adduct-specific monoclonal antibody (mAb) and the effectiveness of the intravenous injection of this mAb (1 mg/kg) in ameliorating LPS (10 mg/kg, i.v.)-induced endotoxemia and liver injury in mice. Endotoxic lethality in control mAb-treated group was suppressed by the administration of anti-4-HNE mAb (75 vs. 27%). After LPS injection, we observed a significant increase in the plasma levels of AST, ALT, IL-6, TNF-α and MCP-1, and elevated expressions of IL-6, IL-10 and TNF-α in the liver. All these elevations were inhibited by anti-4-HNE mAb treatment. As to the underlining mechanism, anti-4-HNE mAb inhibited the elevation of plasma high mobility group box-1 (HMGB1) levels, the translocation and release of HMGB1 in the liver and the formation of 4-HNE adducts themselves, suggesting a functional role of extracellular 4-HNE adducts in hypercytokinemia and liver injury associated with HMGB1 mobilization. In summary, this study reveals a novel therapeutic application of anti-4-HNE mAb for endotoxemia.

Tivantinib alleviates inflammatory diseases by directly targeting NLRP3

NLRP3 inflammasome-mediated immune responses are involved in the pathogenesis of multiple inflammatory diseases, but few clinical drugs are identified that directly target the NLRP3 inflammasome to treat these diseases to date. Here, we show that the anticancer agent tivantinib is a selective inhibitor of NLRP3 and has a strong therapeutic effect on inflammasome-driven disease. Tivantinib specifically inhibits canonical and non-canonical NLRP3 inflammasome activation without affecting AIM2 and NLRC4 inflammasome activation. Mechanistically, Tivantinib inhibits NLRP3 inflammasome by directly blocking NLRP3 ATPase activity and subsequent inflammasome complex assembly. In vivo, Tivantinib reduces IL-1β production in mouse models of lipopolysaccharide (LPS)-induced systemic inflammation, monosodium urate (MSU)-induced peritonitis and Con A-induced acute liver injury (ALI), and also has remarkable preventive and therapeutic effects on experimental autoimmune encephalomyelitis (EAE). In conclusion, our study identifies the anticancer drug tivantinib as a specific inhibitor of NLRP3 and provides a promising therapeutic agent for inflammasome-driven disease.

Recombinant human angiotensin-converting enzyme 2 plays a protective role in mice with sepsis-induced cardiac dysfunction through multiple signaling pathways dependent on converting angiotensin II to angiotensin 1-7

Background

Sepsis-induced cardiac dysfunction (SICD) is a common complication of sepsis and contributes to mortality and the complexity of management in patients with sepsis. Recombinant human angiotensin-converting enzyme 2 (rhACE2) has been reported to protect the heart from injury and dysfunction in conditions which involve increased angiotensin II (Ang II). In this study, we aimed to detect the effects of rhACE2 on SICD.

Methods

A SICD model was developed in male C57/B6 mice by lipopolysaccharide (LPS) intraperitoneal injection. When cardiac dysfunction was confirmed by echocardiography 3 hours after LPS administration, mice were treated with either saline, rhACE2, or rhACE2 + A779. All mice received echocardiographic examination at 6 hours after LPS injection and then were sacrificed for serum and myocardial tissues collection. Angiotensin, cardiac troponin I (cTnI), and inflammatory markers in serum were measured. Histopathology features were examined by hematoxylin and eosin (HE) and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining to evaluate structure injury and cell pyroptosis rate in heart tissue respectively. Pyroptosis-related proteins and signaling pathways involved in nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation in heart tissue were investigated by western blot (WB).

Results

RhACE2 relieved myocardial injury and improved cardiac function in mice with SICD accompanied by decrease of Ang II and increase of angiotensin 1-7 (Ang 1-7) in serum. RhACE2 diminished activation of NLRP3 inflammasome, inflammatory response, and cell pyroptosis induced by LPS. In addition, rhACE2 partly inhibited activation of nuclear factor κB (NF-κB), the p38 mitogen-activated protein kinase (MAPK) pathway, and promoted activation of the AMP-activated protein kinase-α1 (AMPK-α1) pathway in heart tissue. Administration of A779 offset the inhibitive effects of rhACE2 on NLRP3 expression and protective role on cardiac injury and dysfunction in mice with SICD.

Conclusions

RhACE2 plays a protective role in SICD, ameliorating cardiac injury and dysfunction through NF-κB, p38 MAPK, and the AMPK-α1/NLRP3 inflammasome pathway dependent on converting Ang II to Ang 1-7.

Neutrophilic Pleuritis Is a Severe Complication of Klebsiella pneumoniae Pneumonia in Old Mice

The pathomechanisms underlying the frequently observed fatal outcome of Klebsiella pneumoniae pneumonia in elderly patients are understudied. In this study, we examined the early antibacterial immune response in young mice (age 2-3 mo) as compared with old mice (age 18-19 mo) postinfection with K. pneumoniae. Old mice exhibited significantly higher bacterial loads in lungs and bacteremia as early as 24 h postinfection compared with young mice, with neutrophilic pleuritis nearly exclusively developing in old but not young mice. Moreover, we observed heavily increased cytokine responses in lungs and pleural spaces along with increased mortality in old mice. Mechanistically, Nlrp3 inflammasome activation and caspase-1-dependent IL-1β secretion contributed to the observed hyperinflammation, which decreased upon caspase-1 inhibitor treatment of K. pneumoniae-infected old mice. Irradiated old mice transplanted with the bone marrow of young mice did not show hyperinflammation or early bacteremia in response to K. pneumoniae. Collectively, the accentuated lung pathology observed in K. pneumoniae-infected old mice appears to be due to regulatory defects of the bone marrow but not the lung, while involving dysregulated activation of the Nlrp3/caspase-1/IL-1β axis.

Bone Marrow Immune Microenvironment in Myelodysplastic Syndromes

The BM, the major hematopoietic organ in humans, consists of a pleiomorphic environment of cellular, extracellular, and bioactive compounds with continuous and complex interactions between them, leading to the formation of mature blood cells found in the peripheral circulation. Systemic and local inflammation in the BM elicit stress hematopoiesis and drive hematopoietic stem cells (HSCs) out of their quiescent state, as part of a protective pathophysiologic process. However, sustained chronic inflammation impairs HSC function, favors mutagenesis, and predisposes the development of hematologic malignancies, such as myelodysplastic syndromes (MDS). Apart from intrinsic cellular mechanisms, various extrinsic factors of the BM immune microenvironment (IME) emerge as potential determinants of disease initiation and evolution. In MDS, the IME is reprogrammed, initially to prevent the development, but ultimately to support and provide a survival advantage to the dysplastic clone. Specific cellular elements, such as myeloid-derived suppressor cells (MDSCs) are recruited to support and enhance clonal expansion. The immune-mediated inhibition of normal hematopoiesis contributes to peripheral cytopenias of MDS patients, while immunosuppression in late-stage MDS enables immune evasion and disease progression towards acute myeloid leukemia (AML). In this review, we aim to elucidate the role of the mediators of immune response in the initial pathogenesis of MDS and the evolution of the disease.

Different modalities of host cell death and their impact on Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) is the pathogen that causes tuberculosis (TB), a leading infectious disease of humans worldwide. One of the main histopathological hallmarks of TB is the formation of granulomas comprised of elaborately organized aggregates of immune cells containing the pathogen. Dissemination of Mtb from infected cells in the granulomas due to host and mycobacterial factors induces multiple cell death modalities in infected cells. Based on molecular mechanism, morphological characteristics, and signal dependency, there are two main categories of cell death: programmed and nonprogrammed. Programmed cell death (PCD), such as apoptosis and autophagy, is associated with a protective response to Mtb by keeping the bacteria encased within dead macrophages that can be readily phagocytosed by arriving in uninfected or neighboring cells. In contrast, non-PCD necrotic cell death favors the pathogen, resulting in bacterial release into the extracellular environment. Multiple types of cell death in the PCD category, including pyroptosis, necroptosis, ferroptosis, ETosis, parthanatos, and PANoptosis, may be involved in Mtb infection. Since PCD pathways are essential for host immunity to Mtb, therapeutic compounds targeting cell death signaling pathways have been experimentally tested for TB treatment. This review summarizes different modalities of Mtb-mediated host cell deaths, the molecular mechanisms underpinning host cell death during Mtb infection, and its potential implications for host immunity. In addition, targeting host cell death pathways as potential therapeutic and preventive approaches against Mtb infection is also discussed.

Exploring the mechanism of action of dapansutrile in the treatment of gouty arthritis based on molecular docking and molecular dynamics

Purpose: Dapansutrile is an orally active β-sulfonyl nitrile compound that selectively inhibits the NLRP3 inflammasome. Clinical studies have shown that dapansutrile is active in vivo and limits the severity of endotoxin-induced inflammation and joint arthritis. However, there is currently a lack of more in-depth research on the effect of dapansutrile on protein targets such as NLRP3 in gouty arthritis. Therefore, we used molecular docking and molecular dynamics to explore the mechanism of dapansutrile on NLRP3 and other related protein targets.

Methods: We use bioinformatics to screen active pharmaceutical ingredients and potential disease targets. The disease-core gene target-drug network was established and molecular docking was used for verification. Molecular dynamics simulations were utilized to verify and analyze the binding stability of small molecule drugs to target proteins. The supercomputer platform was used to measure and analyze the binding free energy, the number of hydrogen bonds, the stability of the protein target at the residue level, the radius of gyration and the solvent accessible surface area.

Results: The protein interaction network screened out the core protein targets (such as: NLRP3, TNF, IL1B) of gouty arthritis. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that gouty arthritis mainly played a vital role by the signaling pathways of inflammation and immune response. Molecular docking showed that dapansutrile play a role in treating gouty arthritis by acting on the related protein targets such as NLRP3, IL1B, IL6, etc. Molecular dynamics was used to prove and analyze the binding stability of active ingredients and protein targets, the simulation results found that dapansutrile forms a very stable complex with IL1B.

Conclusion: We used bioinformatics analysis and computer simulation system to comprehensively explore the mechanism of dapansutrile acting on NLRP3 and other protein targets in gouty arthritis. This study found that dapansutrile may not only directly inhibit NLRP3 to reduce the inflammatory response and pyroptosis, but also hinder the chemotaxis and activation of inflammatory cells by regulating IL1B, IL6, IL17A, IL18, MMP3, CXCL8, and TNF. Therefore, dapansutrile treats gouty arthritis by attenuating inflammatory response, inflammatory cell chemotaxis and extracellular matrix degradation by acting on multiple targets.

Klebsiella pneumoniae hijacks the Toll-IL-1R protein SARM1 in a type I IFN-dependent manner to antagonize host immunity

Many bacterial pathogens antagonize host defense responses by translocating effector proteins into cells. It remains an open question how those pathogens not encoding effectors counteract anti-bacterial immunity. Here, we show that Klebsiella pneumoniae exploits the evolutionary conserved innate protein SARM1 to regulate negatively MyD88- and TRIF-governed inflammation, and the activation of the MAP kinases ERK and JNK. SARM1 is required for Klebsiella induction of interleukin-10 (IL-10) by fine-tuning the p38-type I interferon (IFN) axis. SARM1 inhibits the activation of Klebsiella-induced absent in melanoma 2 inflammasome to limit IL-1β production, suppressing further inflammation. Klebsiella exploits type I IFNs to induce SARM1 in a capsule and lipopolysaccharide O-polysaccharide-dependent manner via the TLR4-TRAM-TRIF-IRF3-IFNAR1 pathway. Absence of SARM1 reduces the intracellular survival of K. pneumoniae in macrophages, whereas sarm1-deficient mice control the infection. Altogether, our results illustrate an anti-immunology strategy deployed by a human pathogen. SARM1 inhibition will show a beneficial effect to treat Klebsiella infections.

Selenium Antagonizes Cadmium-Induced Inflammation and Oxidative Stress via Suppressing the Interplay between NLRP3 Inflammasome and HMGB1/NF-κB Pathway in Duck Hepatocytes

Cadmium (Cd) is a toxic heavy metal that can accumulate in the liver of animals, damaging liver function. Inflammation and oxidative stress are considered primary causes of Cd-induced liver damage. Selenium (Se) is an antioxidant and can resist the detrimental impacts of Cd on the liver. To elucidate the antagonism of Se on Cd against hepatocyte injury and its mechanism, duck embryo hepatocytes were treated with Cd (4 μM) and/or Se (0.4 μM) for 24 h. Then, the hepatocyte viability, oxidative stress and inflammatory status were assessed. The findings manifested that the accumulation of reactive oxygen species (ROS) and the levels of pro-inflammatory factors were elevated in the Cd group. Simultaneously, immunofluorescence staining revealed that the interaction between NOD-like receptor pyran domain containing 3 (NLRP3) and apoptosis-associated speck-like protein (ASC) was enhanced, the movement of high-mobility group box 1 (HMGB1) from nucleus to cytoplasm was increased and the inflammatory response was further amplified. Nevertheless, the addition of Se relieved the above-mentioned effects, thereby alleviating cellular oxidative stress and inflammation. Collectively, the results suggested that Se could mitigate Cd-stimulated oxidative stress and inflammation in hepatocytes, which might be correlated with the NLRP3 inflammasome and HMGB1/nuclear factor-κB (NF-κB) signaling pathway.

Microarray Profiling and Co-Expression Network Analysis of LncRNAs and mRNAs in Acute Respiratory Distress Syndrome Mouse Model

Background: Long noncoding RNAs (LncRNAs) play critical roles in many respiratory diseases. Acute respiratory distress syndrome (ARDS) is a destructive clinical syndrome of respiratory diseases. However, the potential mechanism of LncRNAs on ARDS remains largely unknown. Methods: To identify the profiles of LncRNAs and mRNAs in the LPS-induced ARDS mouse model, the microarray analyses were hired to detect the expression of LncRNAs and mRNAs in present study. Subsequently, microarray data were verified by quantitative qRT-PCR. Functional annotation on DE mRNAs and LncRNAs were carried out by bioinformatics analysis. Furthermore, the role of selected DE LncRNAs on correlated genes was confirmed by si-RNA and Western blot. Results: The expression of 2110 LncRNAs and 2690 mRNAs were significantly changed, which were further confirmed by qRT-PCR. GO and KEGG analysis indicated that the up-regulated mRNAs were mainly related to a defense response and tumor necrosis factor (TNF) signaling pathway, respectively. LncRNA-mRNA co-expression analyses showed that LncRNAs NR_003508, ENSMUST00000131638, ENSMUST00000119467, and ENSMUST00000124853 may correlate to MLKL, RIPK3, RIPK1, Caspase1, and NLRP3, respectively, or cooperatively, which were highly involved in the cell necroptosis process. Furthermore, siRNA for NR_003508 confirmed the co-expression analyses results. Conclusion: To summarize, this study implied that the DE LncRNAs could be potent regulators and target genes of ARDS and will provide a novel insight into the regulation of the pathogenesis of ARDS.

An assessment of vaping-induced inflammation and toxicity: A feasibility study using a 2-stage zebrafish and mouse platform

It is currently understood that tobacco smoking is a major cause of pulmonary disease due to pulmonary/lung inflammation. However, due to a highly dynamic market place and an abundance of diverse products, less is known about the effects of e-cigarette (E-cig) use on the lung. In addition, varieties of E-cig liquids (e-liquids), which deliver nicotine and numerous flavor chemicals into the lungs, now number in the 1000s. Thus, a critical need exists for safety evaluations of these E-cig products. Herein, we employed a "2-stage in vivo screening platform" (zebrafish to mouse) to assess the safety profiles of e-liquids. Using the zebrafish, we collected embryo survival data after e-liquid exposure as well as neutrophil migration data, a key hallmark for a pro-inflammatory response. Our data indicate that certain e-liquids induce an inflammatory response in our zebrafish model and that e-liquid exposure alone results in pro-inflammatory lung responses in our C57BL/6J model, data collected from lung staining and ELISA analysis, respectively, in the mouse. Thus, our platform can be used as an initial assessment to ascertain the safety profiles of e-liquid using acute inflammatory responses (zebrafish, Stage 1) as our initial metric followed by chronic studies (C57BL/6J, Stage 2).

Exploring the Mechanism through which Phyllanthus emblica L. Extract Exerts Protective Effects against Acute Gouty Arthritis: A Network Pharmacology Study and Experimental Validation

Increased uric acid levels and inflammatory reactions are the main factors considered responsible for the development of gouty arthritis. Phyllanthus emblica L. (PEL) has several promising pharmacological properties, including anti-inflammation and antioxidation. However, only a few studies have investigated its use for treating acute gouty arthritis (AGA), and the mechanism of action of PEL has not yet been clarified. The aim of this study was to verify the protective effects of PEL against gout and explore its underlying mechanism through network pharmacology and animal experiments. The main active components of the extract from PEL including mucic acid, mucic acid lactone, gallic acid, ethyl hexyl phthalate, and glucose were identified by UPLC-ESI-qTOF-MS. Network pharmacological analysis results revealed 13 active compounds in PEL and 85 related targets for the treatment of gout. The core mechanism of action of PEL is mainly associated with inflammation-related pathways, including the HIF-1, PI3K-Akt, TNF, and NOD-like receptor signaling pathways. Previous studies revealed that the NOD-like receptor signaling pathway, especially the NLRP3 inflammasome, plays an important role in the pathogenesis of AGA; therefore, we mainly investigated the effect of PEL on the NLRP3/ASC/caspase-1 pathway in gout rats. In the animal experiments, PEL was shown to have a satisfactory antigout effect, as it effectively reduced uric acid (UA) and xanthine oxidase (XOD) levels. In terms of inhibiting AGA-associated inflammatory reactions, our results showed that PEL significantly decreased the expression of NLRP3 and caspase-1 in ankle synoviocytes as well as the levels of downstream inflammatory factors, such as TNF-α, IL-10, and IL-1β in serum. Moreover, the results of our study show that PEL reduced MMP13 expression in the ankle synovium. Overall, the results of this study indicate that PEL exerted a therapeutic effect against AGA. Reducing uric acid levels, inhibiting inflammation, and decreasing the expression of MMP13 may be responsible for the therapeutic effect of PEL, which suggests that PEL can be further developed as a drug for the treatment of gout.

The mechanism of HMGB1 secretion and release

High mobility group box 1 (HMGB1) is a nonhistone nuclear protein that has multiple functions according to its subcellular location. In the nucleus, HMGB1 is a DNA chaperone that maintains the structure and function of chromosomes. In the cytoplasm, HMGB1 can promote autophagy by binding to BECN1 protein. After its active secretion or passive release, extracellular HMGB1 usually acts as a damage-associated molecular pattern (DAMP) molecule, regulating inflammation and immune responses through different receptors or direct uptake. The secretion and release of HMGB1 is fine-tuned by a variety of factors, including its posttranslational modification (e.g., acetylation, ADP-ribosylation, phosphorylation, and methylation) and the molecular machinery of cell death (e.g., apoptosis, pyroptosis, necroptosis, alkaliptosis, and ferroptosis). In this minireview, we introduce the basic structure and function of HMGB1 and focus on the regulatory mechanism of HMGB1 secretion and release. Understanding these topics may help us develop new HMGB1-targeted drugs for various conditions, especially inflammatory diseases and tissue damage.

A nuclear protein that gets released after cell death or is actively secreted by immune cells offers a promising therapeutic target for treating diseases linked to excessive inflammation. Daolin Tang from the University of Texas Southwestern Medical Center in Dallas, USA, and colleagues review how cellular stresses can trigger the accumulation of HMGB1, a type of alarm signal protein that promotes the recruitment and activation of inflammation-promoting immune cells. The researchers discuss various mechanisms that drive both passive and active release of HMGB1 into the space around cells. These processes, which include enzymatic modifications of the HMGB1 protein, cell–cell interactions and molecular pathways of cell death, could be targeted by drugs to lessen tissue damage and inflammatory disease caused by HMGB1-induced immune responses

Biomaterials-Driven Sterile Inflammation

Performance of the biomaterials used for regenerative medicine largely depends on biocompatibility; however, the biological mechanisms underlying biocompatibility of a biomaterial within the host system is poorly understood. In addition to the classical immune response against non-self-entities, the sterile inflammatory response could limit the compatibility of biological scaffolds. Whereas the immediate to short-term host response to a biomaterial implant have been characterized, the long-term progression of host-biomaterial relationship has not been described. This article explores the novel concept of biomaterials-driven sterile inflammation (BSI) in long-term biodegradable implants and throws light for possible explanation for the onset of BSI and the associated damage-associated molecular patterns. The understanding of BSI would advance the current strategies to improve biomaterial-host tissue integration and open novel translational avenues in biomaterials-based tissue regeneration. Impact statement Understanding the novel concept of biomaterials-driven sterile inflammation and associated damage-associated molecular patterns in long-term biodegradable implants would determine their success and improves the tissue engineering and regenerative strategies.

Nrf2 in the Field of Dentistry with Special Attention to NLRP3

The aim of this review article was to summarize the functional implications of the nuclear factor E2-related factor or nuclear factor (erythroid-derived 2)-like 2 (Nrf2), with special attention to the NACHT (nucleotide-binding oligomerization), LRR (leucine-rich repeat), and PYD (pyrin domain) domains-containing protein 3 (NLRP3) inflammasome in the field of dentistry. NLRP3 plays a crucial role in the progression of inflammatory and adaptive immune responses throughout the body. It is already known that this inflammasome is a key regulator of several systemic diseases. The initiation and activation of NLRP3 starts with the oral microbiome and its association with the pathogenesis and progression of several oral diseases, including periodontitis, periapical periodontitis, and oral squamous cell carcinoma (OSCC). The possible role of the inflammasome in oral disease conditions may involve the aberrant regulation of various response mechanisms, not only in the mouth but in the whole body. Understanding the cellular and molecular biology of the NLRP3 inflammasome and its relationship to Nrf2 is necessary for the rationale when suggesting it as a potential therapeutic target for treatment and prevention of oral inflammatory and immunological disorders. In this review, we highlighted the current knowledge about NLRP3, its likely role in the pathogenesis of various inflammatory oral processes, and its crosstalk with Nrf2, which might offer future possibilities for disease prevention and targeted therapy in the field of dentistry and oral health.

An Epigenetic Insight into NLRP3 Inflammasome Activation in Inflammation-Related Processes

Aberrant NLRP3 (NOD-, LRR-, and pyrin domain-containing protein 3) inflammasome activation in innate immune cells, triggered by diverse cellular danger signals, leads to the production of inflammatory cytokines (IL-1β and IL-18) and cell death by pyroptosis. These processes are involved in the pathogenesis of a wide range of diseases such as autoimmune, neurodegenerative, renal, metabolic, vascular diseases and cancer, and during physiological processes such as aging. Epigenetic dynamics mediated by changes in DNA methylation patterns, chromatin assembly and non-coding RNA expression are key regulators of the expression of inflammasome components and its further activation. Here, we review the role of the epigenome in the expression, assembly, and activation of the NLRP3 inflammasome, providing a critical overview of its involvement in the disease and discussing how targeting these mechanisms by epigenetic treatments could be a useful strategy for controlling NLRP3-related inflammatory diseases.

Induction of innate immune responses by KPC-producing Klebsiella pneumoniae of the pandemic sequence type 258-clade I

Klebsiella pneumoniae -carbapenemase-producing K. pneumoniae (KPC) sequence-type 258 (ST258) has emerged as an important human pathogen throughout the world. Although lacking known virulence factors, it is associated with significant morbidity and high mortality rates. The pathogenicity of KPC K. pneumoniae ST258 strains has not been fully elucidated yet. We sought to investigate the interactions of the KPC K. pneumoniae ST258-clade I with different components of innate immunity. Human serum was used to evaluate the serum bactericidal activity and the J774A.1 murine (BALB/c mice) macrophage cell-line was used to examine phagocytosis, mRNA expression and production of the pro-inflammatory cytokines IL-1β, TNF-α and IL-6. L-78, a KPC-producing K. pneumoniae ST258-clade I strain was used as representative of the strains circulating in Greek hospitals. K. pneumoniae ATCC 43816, a virulent K2 strain, was used for comparison. Strain L-78 was susceptible to human serum and rapidly phagocytosed by J774A.1 cells, in contrast to the virulent K2 strain, which was serum-resistant and slowly phagocytosed. Stimulation of the J774A.1 cells with the L-78 strain induced production of IL-1β at concentration levels significantly higher compared to K2, whereas production of TNF-α and IL-6 levels were comparable by the two strains. L-78 was able to induce IL-1β mRNA and NLRP3 mRNA expression. Our findings indicate that K. pneumoniae ST258-clade I is serum sensitive, rapidly phagocytosed and is capable of eliciting adequate innate immune response in terms of production of pro-inflammatory cytokines.

Galacto-oligosaccharides alleviate lung inflammation by inhibiting NLRP3 inflammasome activation in vivo and in vitro

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GOS suppress both local and systemic inflammation in lung infections.

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GOS reduce the M. haemolytica positivity in calves with lung infections.

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GOS inhibit NLRP3 inflammasome activation in vivo and in vitro.

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GOS decrease ATP production in PBECs induced by M. haemolytica.

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Direct anti-oxidative effects of GOS on lung cells are involved.

Introduction

Objectives

Methods

Results

Conclusion

Anthocyanin Extract from Purple Sweet Potato Exacerbate Mitophagy to Ameliorate Pyroptosis in Klebsiella pneumoniae Infection

Given the rise of morbidity and mortality caused by Klebsiella pneumoniae (KP), the increasing number of strains resistant to antibiotics, and the emergence of hypervirulent Klebsiella pneumonia, treatment of KP infection becomes difficult; thus, novel drugs are necessary for treatment. Anthocyanins, or natural flavonoids, have an extensive effect against bacterial infection. However, few studies on anti-KP are identified. Here, we evaluated the therapeutic effect of purple sweet potato anthocyanins (PSPAs) on KP, containing 98.7% delphinidin 3-sambubioside. Results showed that KP-infected mice after PSPAs treatment manifested decreased mortality, weakened lung injury, dampened inflammatory responses, and reduced bacterial systemic dissemination in vivo. In Vitro, PSPAs significantly suppressed pyroptosis and restricted NLRP3 inflammasome activation in alveolar macrophages infected with KP. As for the mechanism, PSPAs promote mitophagy by recruiting Parkin to the mitochondria. PSPAs-conferred mitophagy increased mitochondrial membrane potential and decreased mitochondrial reactive oxygen species and mitochondrial DNA, resulting in impaired NLRP3 inflammasome activation. In addition, the promotion of mitophagy by PSPAs required the Nrf2 signaling pathway. Collectively, these findings suggest that PSPAs are a potential option for the treatment of KP infection.

High Mobility Group Box 1 Protein in Osteoarthritic Knee Tissue and Chondrogenic Progenitor Cells: An Ex Vivo and In Vitro Study

OBJECTIVE

In osteoarthritis (OA), a loss of healthy cartilage extracellular matrix (ECM) results in cartilage degeneration. Attracting chondrogenic progenitor cells (CPCs) to injury sites and stimulating them toward chondrogenic expression profiles is a regenerative approach in OA therapy. High mobility group box 1 protein (HMGB1) is associated with chemoattractant and proinflammatory effects in various pathological processes. Here, we investigate the migratory effects of HMGB1 in knee OA and CPCs for the first time.

DESIGN

Immunohistochemistry, immunoblotting, and immunocytochemistry were performed to identify HMGB1 and its receptors, receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4) in OA knee tissue, chondrocytes, and CPCs. In situ hybridization for HMGB1 mRNA was performed in CPCs ex vivo. The chemoattractant effects of HMGB1 on CPCs were analyzed in cell migration assays.

RESULTS

HMGB1 expression in OA tissue and OA chondrocytes was higher than in healthy specimens and cells. HMGB1, RAGE, and TLR4 were expressed in CPCs and chondrocytes. In situ hybridization revealed HMGB1 mRNA in CPCs after migration into OA knee tissue, and immunohistochemistry confirmed HMGB1 expression at the protein level. Stimulation via HMGB1 significantly increased the migration of CPCs.

CONCLUSIONS

Our results show the chemoattractant role of HMGB1 in knee OA. HMGB1 is released by chondrocytes and has migratory effects on CPCs. These effects might be mediated via RAGE and TLR4. The in vitro and ex vivo results of this study need to be confirmed in vivo.

The Natural Products Targeting on Allergic Rhinitis: From Traditional Medicine to Modern Drug Discovery

More than 500 million people suffer from allergic rhinitis (AR) in the world. Current treatments include oral antihistamines and intranasal corticosteroids; however, they often cause side effects and are unsuitable for long-term exposure. Natural products could work as a feasible alternative, and this study aimed to review the efficacies and mechanisms of natural substances in AR therapies by examining previous literature. Fifty-seven studies were collected and classified into plants, fungi, and minerals decoction; clinical trials were organized separately. The majority of the natural products showed their efficacies by two mechanisms: anti-inflammation regulating diverse mediators and anti-oxidation controlling the activity of nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) pathway stimulated by reactive oxygen species (ROS). The main AR factors modified by natural products included interleukin (IL)-4, IL-5, IL-13, interferon-gamma (IFN-γ), tumor necrosis factor-α (TNF-α), cyclooxygenase 2 (COX-2), and phospho-ERK1/2 (p-ERK1/2). Although further studies are required to verify their efficacies and safeties, natural products can significantly contribute to the treatment of AR.

Overcoming Immunotherapy Resistance by Targeting the Tumor-Intrinsic NLRP3-HSP70 Signaling Axis

Simple Summary

The tumor-intrinsic NLRP3 inflammasome is a newly recognized player in the regulation of tumor-directed immune responses and promises to provide fresh insight into how tumors respond to immunotherapy. This brief review discusses recent data describing how activation of the tumor-intrinsic NLRP3 inflammasome contributes to immune evasion and what this pathway may provide to the field of immuno-oncology both in terms of pharmacologic targets capable of boosting responses to checkpoint inhibitor therapies and predictive biomarkers indicating which tumors may be most susceptible to these new therapeutic strategies.

Abstract

The tumor-intrinsic NOD-like receptor family, pyrin-domain-containing-3 (NLRP3) inflammasome, plays an important role in regulating immunosuppressive myeloid cell populations in the tumor microenvironment (TME). While prior studies have described the activation of this inflammasome in driving pro-tumorigenic mechanisms, emerging data is now revealing the tumor NLRP3 inflammasome and the downstream release of heat shock protein-70 (HSP70) to regulate anti-tumor immunity and contribute to the development of adaptive resistance to anti-PD-1 immunotherapy. Genetic alterations that influence the activity of the NLRP3 signaling axis are likely to impact T cell-mediated tumor cell killing and may indicate which tumors rely on this pathway for immune escape. These studies suggest that the NLRP3 inflammasome and its secreted product, HSP70, represent promising pharmacologic targets for manipulating innate immune cell populations in the TME while enhancing responses to anti-PD-1 immunotherapy. Additional studies are needed to better understand tumor-specific regulatory mechanisms of NLRP3 to enable the development of tumor-selective pharmacologic strategies capable of augmenting responses to checkpoint inhibitor immunotherapy while minimizing unwanted off-target effects. The execution of upcoming clinical trials investigating this strategy to overcome anti-PD-1 resistance promises to provide novel insight into the role of this pathway in immuno-oncology.

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

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

Acute vaping exacerbates microbial pneumonia due to calcium (Ca2+) dysregulation

As electronic cigarette (E-cig) use, also known as "vaping", has rapidly increased in popularity, data regarding potential pathologic effects are recently emerging. Recent associations between vaping and lung pathology have led to an increased need to scrutinize E-cigs for adverse health impacts. Our previous work (and others) has associated vaping with Ca2+-dependent cytotoxicity in cultured human airway epithelial cells. Herein, we develop a vaped e-liquid pulmonary exposure mouse model to evaluate vaping effects in vivo. Using this model, we demonstrate lung pathology through the use of preclinical measures, that is, the lung wet: dry ratio and lung histology/H&E staining. Further, we demonstrate that acute vaping increases macrophage chemotaxis, which was ascertained using flow cytometry-based techniques, and inflammatory cytokine production, via Luminex analysis, through a Ca2+-dependent mechanism. This increase in macrophage activation appears to exacerbate pulmonary pathology resulting from microbial infection. Importantly, modulating Ca2+ signaling may present a therapeutic direction for treatment against vaping-associated pulmonary inflammation.

HMGB1, neuronal excitability and epilepsy

Epilepsy is a common neurological disease caused by synchronous firing of hyperexcitable neurons. Currently, anti-epileptic drugs remain the main choice to control seizure, but 30% of patients are resistant to the drugs, which calls for more research on new promising targets. Neuroinflammation is closely associated with the development of epilepsy. As an important inflammatory factor, high mobility group protein B1 (HMGB1) has shown elevated expression and an increased proportion of translocation from the nucleus to the cytoplasm in patients with epilepsy and in multiple animal models of epilepsy. HMGB1 can act on downstream receptors such as Toll-like receptor 4 and receptor for advanced glycation end products, thereby activating interleukin (IL)-1β and nuclear factor kappa-B (NF-κB), which in turn act with glutamate receptors such as the N-methyl-D-aspartate (NMDA) receptors to aggravate hyperexcitability and epilepsy. The hyperexcitability can in turn stimulate the expression and translocation of HMGB1. Blocking HMGB1 and its downstream signaling pathways may be a direction for antiepileptic drug therapy. Here, we review the changes of HMGB1-related pathway in epileptic brains and its role in the modulation of neuronal excitability and epileptic seizure. Furthermore, we discuss the potentials of HMGB1 as a therapeutic target for epilepsy and provide perspective on future research on the role of HMGB1 signaling in epilepsy.

A gain-of-function NLRP3 3'-UTR polymorphism causes miR-146a-mediated suppression of NLRP3 expression and confers protection against sepsis progression

Nucleotide-binding domain and leucine-rich repeat (LRR)-containing family protein 3 (NLRP3) regulated the maturation of inflammation-related cytokines by forming NLRP3 inflammasome, which plays pivotal roles in sepsis pathogenesis. In this study, we evaluated the genetic association of NLRP3 polymorphisms with sepsis (640 patients and 769 controls) and characterized the impact of NLRP3 polymorphisms on NLRP3 expression and inflammatory responses. No significant differences were observed in genotype/allelic frequencies of NLRP3 29940G>C between sepsis cases and controls. The G allele was significantly overrepresented in patients with septic shock than those in sepsis subgroup, and the GC/GG genetypes were related to the 28-day mortality of sepsis. Lipopolysaccharide challenge to peripheral blood mononuclear cells showed a significant suppression of NLRP3 mRNA expression and release of IL-1β and TNF-α in CC compared with the GC/GG genotype category. Functional experiments with luciferase reporter vectors containing the NLRP3 3′-UTR with the 29940 G-to-C variation in HUVECs and THP-1 cells showed a potential suppressive effect of miR-146a on NLRP3 transcription in the presence of the C allele. Taken together, these results demonstrated that the 29940 G-to-C mutation within the NLRP3 3′-UTR was a gain-of-function alteration that caused the suppression of NLRP3 expression and downstream inflammatory cytokine production via binding with miR-146a, which ultimately protected patients against susceptibility to sepsis progression and poor clinical outcome.

Jiangzhi Ligan Decoction Inhibits GSDMD-Mediated Canonical/Noncanonical Pyroptosis Pathways and Alleviates High-Fat Diet-Induced Nonalcoholic Fatty Liver Disease

Increasing evidence suggests that gasdermin D (GSDMD) mediated pyroptosis signaling pathways play a vital role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Jiangzhi Ligan Decoction (JZLGD) has been verified to prevent NAFLD, but its specific mechanism has not been determined. In this study, an NAFLD model was established in Sprague-Dawley rats by a high-fat diet (HFD). After 12 weeks, JZLGD was orally administered once a day for 6 additional weeks. We investigated the effects of JZLGD on NAFLD rats and determined the GSDMD pathway-associated proteins to explore whether such effects were associated with pyroptosis. Our data show that JZLGD significantly reduced the liver index; improved serum lipid levels, liver function parameters, and lipid droplet content; and relieved NAFLD. We further found that the serum levels of the proinflammatory factors interleukin-1β (IL-1β), IL-18, tumor necrosis factor-α, and IL-6 were obviously decreased in the JZLGD group. HFD rats treated with GSDMD exhibited NLRP3, caspase-1, lipopolysaccharide (LPS), and caspase-11 activation; however, these effects were blunted by JZLGD treatment. Taken together, JZLGD may exert hepatoprotective effects against NAFLD in a rat HFD model by regulating GSDMD-mediated canonical/noncanonical pyroptosis pathways.

Proposal for the use of anakinra in acute respiratory distress secondary to COVID-19

The outcome of the SARS-CoV-2 (COVID-19) infection fundamentally affects the lung field, causing ACUTE RESPIRATORY DISTRESS SYNDROME (ARDS). This process is an inflammatory picture, involving an NLRP3 INFLAMOSOME-triggered cytokine storm, the main player in alveolar destruction. IL-1 beta stands out among the cytokines that are triggered in this picture. ANAKINRA is a potent biological drug, capable of blocking this IL 1 beta. We propose its use in controlling ARDS secondary to COVID-19 infection.

[Proposal for the use of anakinra in acute respiratory distress secondary to COVID-19]

The outcome of the SARS-CoV-2 (COVID-19) infection fundamentally affects the lung field, causing acute respiratory distress syndrome (ARDS). This process is an inflammatory picture, involving an NLRP3 inflamosome-triggered cytokine storm, the main player in alveolar destruction. IL-1 beta stands out among the cytokines that are triggered in this picture. Anakinra is a potent biological drug, capable of blocking this IL-1ß. We propose its use in controlling ARDS secondary to COVID-19 infection.