Extracellular SQSTM1 mediates bacterial septic death in mice through insulin receptor signalling

Extracellular NCOA4 is a mediator of septic death by activating the AGER-NFKB pathway

Sepsis, a life-threatening condition resulting from a dysregulated response to pathogen infection, poses a significant challenge in clinical management. Here, we report a novel role for the autophagy receptor NCOA4 in the pathogenesis of sepsis. Activated macrophages and monocytes secrete NCOA4, which acts as a mediator of septic death in mice. Mechanistically, lipopolysaccharide, a major component of the outer membrane of Gram-negative bacteria, induces NCOA4 secretion through autophagy-dependent lysosomal exocytosis mediated by ATG5 and MCOLN1. Moreover, bacterial infection with E. coli or S. enterica leads to passive release of NCOA4 during GSDMD-mediated pyroptosis. Upon release, extracellular NCOA4 triggers the activation of the proinflammatory transcription factor NFKB/NF-κB by promoting the degradation of NFKBIA/IκB molecules. This process is dependent on the pattern recognition receptor AGER, rather than TLR4. In vivo studies employing endotoxemia and polymicrobial sepsis mouse models reveal that a monoclonal neutralizing antibody targeting NCOA4 or AGER delays animal death, protects against organ damage, and attenuates systemic inflammation. Furthermore, elevated plasma NCOA4 levels in septic patients, particularly in non-survivors, correlate positively with the sequential organ failure assessment score and concentrations of lactate and proinflammatory mediators, such as TNF, IL1B, IL6, and HMGB1. These findings demonstrate a previously unrecognized role of extracellular NCOA4 in inflammation, suggesting it as a potential therapeutic target for severe infectious diseases. Abbreviation: BMDMs: bone marrow-derived macrophages; BUN: blood urea nitrogen; CLP: cecal ligation and puncture; ELISA: enzyme-linked immunosorbent assay; LPS: lipopolysaccharide; NO: nitric oxide; SOFA: sequential organ failure assessment.

PIKfyve, expressed by CD11c-positive cells, controls tumor immunity

Cancer treatment continues to shift from utilizing traditional therapies to targeted ones, such as protein kinase inhibitors and immunotherapy. Mobilizing dendritic cells (DC) and other myeloid cells with antigen presenting and cancer cell killing capacities is an attractive but not fully exploited approach. Here, we show that PIKFYVE is a shared gene target of clinically relevant protein kinase inhibitors and high expression of this gene in DCs is associated with poor patient response to immune checkpoint blockade (ICB) therapy. Genetic and pharmacological studies demonstrate that PIKfyve ablation enhances the function of CD11c+ cells (predominantly dendritic cells) via selectively altering the non-canonical NF-κB pathway. Both loss of Pikfyve in CD11c+ cells and treatment with apilimod, a potent and specific PIKfyve inhibitor, restrained tumor growth, enhanced DC-dependent T cell immunity, and potentiated ICB efficacy in tumor-bearing mouse models. Furthermore, the combination of a vaccine adjuvant and apilimod reduced tumor progression in vivo. Thus, PIKfyve negatively regulates the function of CD11c+ cells, and PIKfyve inhibition has promise for cancer immunotherapy and vaccine treatment strategies.

PET imaging for the early evaluation of ocular inflammation in diabetic rats by using [18F]-DPA-714

Ocular complications of diabetes mellitus (DM) are the leading cause of vision loss. Ocular inflammation often occurs in the early stage of DM; however, there are no proven quantitative methods to evaluate the inflammatory status of eyes in DM. The 18 kDa translocator protein (TSPO) is an evolutionarily conserved cholesterol binding protein localized in the outer mitochondrial membrane. It is a biomarker of activated microglia/macrophages; however, its role in ocular inflammation is unclear. In this study, fluorine-18-DPA-714 ([18F]-DPA-714) was evaluated as a specific TSPO probe by cell uptake, cell binding assays and micro positron emission tomography (microPET) imaging in both in vitro and in vivo models. Primary microglia/macrophages (PMs) extracted from the cornea, retina, choroid or sclera of neonatal rats with or without high glucose (50 mM) treatment were used as the in vitro model. Sprague-Dawley (SD) rats that received an intraperitoneal administration of streptozotocin (STZ, 60 mg/kg once) were used as the in vivo model. Increased cell uptake and high binding affinity of [18F]-DPA-714 were observed in primary PMs under hyperglycemic stress. These findings were consistent with cellular morphological changes, cell activation, and TSPO up-regulation. [18F]-DPA-714 PET imaging and biodistribution in the eyes of DM rats revealed that inflammation initiates in microglia/macrophages in the early stages (3 weeks and 6 weeks), corresponding with up-regulated TSPO levels. Thus, [18F]-DPA-714 microPET imaging may be an effective approach for the early evaluation of ocular inflammation in DM.

Molecular mechanisms of secretory autophagy and its potential role in diseases

Autophagy is a cellular degradation system that recycles or degrades damaged organelles, viral particles, and aggregated proteins through the lysosomal pathway. Autophagy plays an indispensable role in cellular homeostasis and communication processes. An interesting aspect is that autophagy also mediates the secretion of cellular contents, a process known as secretory autophagy. Secretory autophagy differs from macroautophagy, which sequesters recruited proteins, organelles, or viral particles into autophagosomes and degrades these sequesters in lysosomes, while the secretory autophagy pathway participates in the extracellular export of cellular contents sequestered by autophagosomes through autophagy and endosomal modulators. Recent evidence reveals that secretory autophagy is pivotal in the occurrence and progression of diseases. In this review, we summarize the molecular mechanisms of secretory autophagy. Furthermore, we review the impact of secretory autophagy on diseases, including cancer, viral infectious diseases, neurodegenerative diseases, and cardiovascular diseases. Considering the pleiotropic actions of secretory autophagy on diseases, studying the mechanism of secretory autophagy may help to understand the relevant pathophysiological processes.

p62/sequestosome-1 as a severity-reflecting plasma biomarker in Charcot-Marie-Tooth disease type 1A

Autophagy is a self-degradation system for recycling to maintain homeostasis. p62/sequestosome-1 (p62) is an autophagy receptor that accumulates in neuroglia in neurodegenerative diseases. The objective of this study was to determine the elevation of plasma p62 protein levels in patients with Charcot-Marie-Tooth disease 1A (CMT1A) for its clinical usefulness to assess disease severity. We collected blood samples from 69 CMT1A patients and 59 healthy controls. Plasma concentrations of p62 were analyzed by ELISA, and we compared them with Charcot-Marie-Tooth neuropathy score version 2 (CMTNSv2). A mouse CMT1A model (C22) was employed to determine the source and mechanism of plasma p62 elevation. Plasma p62 was detected in healthy controls with median value of 1978 pg/ml, and the levels were significantly higher in CMT1A (2465 pg/ml, p < 0.001). The elevated plasma p62 levels were correlated with CMTNSv2 (r = 0.621, p < 0.0001), motor nerve conduction velocity (r =  - 0.490, p < 0.0001) and disease duration (r = 0.364, p < 0.01). In C22 model, increased p62 expression was observed not only in pathologic Schwann cells but also in plasma. Our findings indicate that plasma p62 measurement could be a valuable tool for evaluating CMT1A severity and Schwann cell pathology.

Caspase-5: Structure, Pro-Inflammatory Activity and Evolution

Caspase-5 is a protease that induces inflammation in response to lipopolysaccharide (LPS), a component of the cell envelope of Gram-negative bacteria. The expression level of the CASP5 gene is very low in the basal state, but strongly increases in the presence of LPS. Intracellular LPS binds to the caspase activation and recruitment domain (CARD) of caspase-5, leading to the formation of a non-canonical inflammasome. Subsequently, the catalytic domain of caspase-5 cleaves gasdermin D and thereby facilitates the formation of cell membrane pores through which pro-inflammatory cytokines of the interleukin-1 family are released. Caspase-4 is also able to form a non-canonical inflammasome upon binding to LPS, but its expression is less dependent on LPS than the expression of caspase-5. Caspase-4 and caspase-5 have evolved via the duplication of a single ancestral gene in a subclade of primates, including humans. Notably, the main biomedical model species, the mouse, has only one ortholog, namely caspase-11. Here, we review the structural features and the mechanisms of regulation that are important for the pro-inflammatory roles of caspase-5. We summarize the interspecies differences and the evolution of pro-inflammatory caspases in mammals and discuss the potential roles of caspase-5 in the defense against Gram-negative bacteria and in sepsis.

Lipopolysaccharide delivery systems in innate immunity

Lipopolysaccharide (LPS), a key component of the outer membrane in Gram-negative bacteria (GNB), is widely recognized for its crucial role in mammalian innate immunity and its link to mortality in intensive care units. While its recognition via the Toll-like receptor (TLR)-4 receptor on cell membranes is well established, the activation of the cytosolic receptor caspase-11 by LPS is now known to lead to inflammasome activation and subsequent induction of pyroptosis. Nevertheless, a fundamental question persists regarding the mechanism by which LPS enters host cells. Recent investigations have identified at least four primary pathways that can facilitate this process: bacterial outer membrane vesicles (OMVs); the spike (S) protein of SARS-CoV-2; host-secreted proteins; and host extracellular vesicles (EVs). These delivery systems provide new avenues for therapeutic interventions against sepsis and infectious diseases.

PIKfyve controls dendritic cell function and tumor immunity

The modern armamentarium for cancer treatment includes immunotherapy and targeted therapy, such as protein kinase inhibitors. However, the mechanisms that allow cancer-targeting drugs to effectively mobilize dendritic cells (DCs) and affect immunotherapy are poorly understood. Here, we report that among shared gene targets of clinically relevant protein kinase inhibitors, high PIKFYVE expression was least predictive of complete response in patients who received immune checkpoint blockade (ICB). In immune cells, high PIKFYVE expression in DCs was associated with worse response to ICB. Genetic and pharmacological studies demonstrated that PIKfyve ablation enhanced DC function via selectively altering the alternate/non-canonical NF-κB pathway. Both loss of Pikfyve in DCs and treatment with apilimod, a potent and specific PIKfyve inhibitor, restrained tumor growth, enhanced DC-dependent T cell immunity, and potentiated ICB efficacy in tumor-bearing mouse models. Furthermore, the combination of a vaccine adjuvant and apilimod reduced tumor progression in vivo. Thus, PIKfyve negatively controls DCs, and PIKfyve inhibition has promise for cancer immunotherapy and vaccine treatment strategies.

The lipid basis of cell death and autophagy

ABBREVIATIONS

ACSL: acyl-CoA synthetase long chain family; DISC: death-inducing signaling complex; DAMPs: danger/damage-associated molecular patterns; Dtgn: dispersed trans-Golgi network; FAR1: fatty acyl-CoA reductase 1; GPX4: glutathione peroxidase 4; LPCAT3: lysophosphatidylcholine acyltransferase 3; LPS: lipopolysaccharide; MUFAs: monounsaturated fatty acids; MOMP: mitochondrial outer membrane permeabilization; MLKL, mixed lineage kinase domain like pseudokinase; oxPAPC: oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine; OxPCs: oxidized phosphatidylcholines; PUFAs: polyunsaturated fatty acids; POR: cytochrome p450 oxidoreductase; PUFAs: polyunsaturated fatty acids; RCD: regulated cell death; RIPK1: receptor interacting serine/threonine kinase 1; SPHK1: sphingosine kinase 1; SOAT1: sterol O-acyltransferase 1; SCP2: sterol carrier protein 2; SFAs: saturated fatty acids; SLC47A1: solute carrier family 47 member 1; SCD: stearoyl-CoA desaturase; VLCFA: very long chain fatty acids.

Hepatic Transcriptome and Its Regulation Following Soluble Epoxide Hydrolase Inhibition in Alcohol-Associated Liver Disease

Alcohol-associated liver disease (ALD) is a serious public health problem with limited pharmacologic options. The goal of the current study was to investigate the efficacy of pharmacologic inhibition of soluble epoxide hydrolase (sEH), an enzyme involved in lipid metabolism, in experimental ALD, and to examine the underlying mechanisms. C57BL/6J male mice were subjected to acute-on-chronic ethanol (EtOH) feeding with or without the sEH inhibitor 4-[[trans-4-[[[[4-trifluoromethoxy phenyl]amino]carbonyl]-amino]cyclohexyl]oxy]-benzoic acid (TUCB). Liver injury was assessed by multiple end points. Liver epoxy fatty acids and dihydroxy fatty acids were measured by targeted metabolomics. Whole-liver RNA sequencing was performed, and free modified RNA bases were measured by mass spectrometry. EtOH-induced liver injury was ameliorated by TUCB treatment as evidenced by reduced plasma alanine aminotransferase levels and was associated with attenuated alcohol-induced endoplasmic reticulum stress, reduced neutrophil infiltration, and increased numbers of hepatic M2 macrophages. TUCB altered liver epoxy and dihydroxy fatty acids and led to a unique hepatic transcriptional profile characterized by decreased expression of genes involved in apoptosis, inflammation, fibrosis, and carcinogenesis. Several modified RNA bases were robustly changed by TUCB, including N6-methyladenosine and 2-methylthio-N6-threonylcarbamoyladenosine. These findings show the beneficial effects of sEH inhibition by TUCB in experimental EtOH-induced liver injury, warranting further mechanistic studies to explore the underlying mechanisms, and highlighting the translational potential of sEH as a drug target for this disease.

Single-cell RNA-seq analyses inform necroptosis-associated myeloid lineages influence the immune landscape of pancreas cancer

Introduction

Tumor-infiltrating myeloid cells (TIMs) are key regulators in tumor progression, but the similarity and distinction of their fundamental properties in pancreatic ductal adenocarcinoma (PDAC) remain elusive.

Method

In this study, we conducted scRNA-seq data analysis of cells from 12 primary tumor (PT) tissues, 4 metastatic (Met) tumor tissues, 3 adjacent normal pancreas tissues (Para), and PBMC samples across 16 PDAC patients, and revealed a heterogeneous TIMs environment in PDAC.

Result

Systematic comparisons between tumor and non-tumor samples of myeloid lineages identified 10 necroptosis-associated genes upregulated in PDAC tumors compared to 5 upregulated in paratumor or healthy peripheral blood. A novel RTM (resident tissue macrophages), GLUL-SQSTM1- RTM, was found to act as a positive regulator of immunity. Additionally, HSP90AA1+HSP90AB1+ mast cells exhibited pro-immune characteristics, and JAK3+TLR4+ CD16 monocytes were found to be anti-immune. The findings were validated through clinical outcomes and cytokines analyses. Lastly, intercellular network reconstruction supported the associations between the identified novel clusters, cancer cells, and immune cell populations.

Conclusion

Our analysis comprehensively characterized major myeloid cell lineages and identified three subsets of myeloid-derived cells associated with necroptosis. These findings not only provide a valuable resource for understanding the multi-dimensional characterization of the tumor microenvironment in PDAC but also offer valuable mechanistic insights that can guide the design of effective immuno-oncology treatment strategies.

The multifunctional protein HMGB1: 50 years of discovery

Fifty years since the initial discovery of HMGB1 in 1973 as a structural protein of chromatin, HMGB1 is now known to regulate diverse biological processes depending on its subcellular or extracellular localization. These functions include promoting DNA damage repair in the nucleus, sensing nucleic acids and inducing innate immune responses and autophagy in the cytosol and binding protein partners in the extracellular environment and stimulating immunoreceptors. In addition, HMGB1 is a broad sensor of cellular stress that balances cell death and survival responses essential for cellular homeostasis and tissue maintenance. HMGB1 is also an important mediator secreted by immune cells that is involved in a range of pathological conditions, including infectious diseases, ischaemia-reperfusion injury, autoimmunity, cardiovascular and neurodegenerative diseases, metabolic disorders and cancer. In this Review, we discuss the signalling mechanisms, cellular functions and clinical relevance of HMGB1 and describe strategies to modify its release and biological activities in the setting of various diseases.

The pathogenesis and potential therapeutic targets in sepsis

Sepsis is defined as "a life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection." At present, sepsis continues to pose a grave healthcare concern worldwide. Despite the use of supportive measures in treating traditional sepsis, such as intravenous fluids, vasoactive substances, and oxygen plus antibiotics to eradicate harmful pathogens, there is an ongoing increase in both the morbidity and mortality associated with sepsis during clinical interventions. Therefore, it is urgent to design specific pharmacologic agents for the treatment of sepsis and convert them into a novel targeted treatment strategy. Herein, we provide an overview of the molecular mechanisms that may be involved in sepsis, such as the inflammatory response, immune dysfunction, complement deactivation, mitochondrial damage, and endoplasmic reticulum stress. Additionally, we highlight important targets involved in sepsis-related regulatory mechanisms, including GSDMD, HMGB1, STING, and SQSTM1, among others. We summarize the latest advancements in potential therapeutic drugs that specifically target these signaling pathways and paramount targets, covering both preclinical studies and clinical trials. In addition, this review provides a detailed description of the crosstalk and function between signaling pathways and vital targets, which provides more opportunities for the clinical development of new treatments for sepsis.

The noncanonical inflammasome-induced pyroptosis and septic shock

Sepsis remains one of the most common and lethal conditions globally. Currently, no proposed target specific to sepsis improves survival in clinical trials. Thus, an in-depth understanding of the pathogenesis of sepsis is needed to propel the discovery of effective treatment. Recently attention to sepsis has intensified because of a growing recognition of a non-canonical inflammasome-triggered lytic mode of cell death termed pyroptosis upon sensing cytosolic lipopolysaccharide (LPS). Although the consequences of activation of the canonical and non-canonical inflammasome are similar, the non-canonical inflammasome formation requires caspase-4/5/11, which enzymatically cleave the pore-forming protein gasdermin D (GSDMD) and thereby cause pyroptosis. The non-canonical inflammasome assembly triggers such inflammatory cell death by itself; or leverages a secondary activation of the canonical NLRP3 inflammasome pathway. Excessive cell death induced by oligomerization of GSDMD and NINJ1 leads to cytokine release and massive tissue damage, facilitating devastating consequences and death. This review summarized the updated mechanisms that initiate and regulate non-canonical inflammasome activation and pyroptosis and highlighted various endogenous or synthetic molecules as potential therapeutic targets for treating sepsis.

Pyroptosis-induced inflammation and tissue damage

Pyroptosis is a programmed necrotic cell death executed by gasdermins, a family of pore-forming proteins. The cleavage of gasdermins by specific proteases enables their pore-forming activity. The activation of the prototype member of the gasdermin family, gasdermin D (GSDMD), is linked to innate immune monitoring by inflammasomes. Additional gasdermins such as GSDMA, GSDMB, GSDMC, and GSDME are activated by inflammasome-independent mechanisms. Pyroptosis is emerging as a key host defense strategy against pathogens. However, excessive pyroptosis causes cytokine storm and detrimental inflammation leading to tissue damage and organ dysfunction. Consequently, dysregulated pyroptotic responses contribute to the pathogenesis of various diseases, including sepsis, atherosclerosis, acute respiratory distress syndrome, and neurodegenerative disorders. This review will discuss the inflammatory consequences of pyroptosis and the mechanisms of pyroptosis-induced tissue damage and disease pathogenesis.

The Redox Protein High-Mobility Group Box 1 in Cell Death and Cancer

Significance: As a redox-sensitive protein, high-mobility group box 1 (HMGB1) is implicated in regulating stress responses to oxidative damage and cell death, which are closely related to the pathology of inflammatory diseases, including cancer. Recent Advances: HMGB1 is a nonhistone nuclear protein that acts as a deoxyribonucleic acid chaperone to control chromosomal structure and function. HMGB1 can also be released into the extracellular space and function as a damage-associated molecular pattern protein during cell death, including during apoptosis, necrosis, necroptosis, pyroptosis, ferroptosis, alkaliptosis, and cuproptosis. Once released, HMGB1 binds to membrane receptors to shape immune and metabolic responses. In addition to subcellular localization, the function and activity of HMGB1 also depend on its redox state and protein posttranslational modifications. Abnormal HMGB1 plays a dual role in tumorigenesis and anticancer therapy (e.g., chemotherapy, radiation therapy, and immunotherapy) depending on the tumor types and stages. Critical Issues: A comprehensive understanding of the role of HMGB1 in cellular redox homeostasis is important for deciphering normal cellular functions and pathological manifestations. In this review, we discuss compartmental-defined roles of HMGB1 in regulating cell death and cancer. Understanding these advances may help us develop potential HMGB1-targeting drugs or approaches to treat oxidative stress-related diseases or pathological conditions. Future Directions: Further studies are required to dissect the mechanism by which HMGB1 maintains redox homeostasis under different stress conditions. A multidisciplinary effort is also required to evaluate the potential applications of precisely targeting the HMGB1 pathway in human health and disease. Antioxid. Redox Signal. 39, 569-590.

SQSTM1 is a therapeutic target for infection and sterile inflammation

Inflammation represents a fundamental immune response triggered by various detrimental stimuli, such as infections, tissue damage, toxins, and foreign substances. Protein degradation plays a crucial role in regulating the inflammatory process at multiple levels. The identification of sequestosome 1 (SQSTM1, also known as p62) protein as a binding partner of lymphocyte-specific protein tyrosine kinase in 1995 marked a significant milestone. Subsequent investigations unveiled the activity of SQSTM1 to interact with diverse unstructured substrates, including proteins, organelles, and pathogens, facilitating their delivery to the lysosome for autophagic degradation. In addition to its well-established intracellular functions, emerging studies have reported the active secretion or passive release of SQSTM1 by immune or non-immune cells, orchestrating the inflammatory responses. These distinct characteristics render SQSTM1 a critical therapeutic target in numerous human diseases, including infectious diseases, rheumatoid arthritis, inflammatory bowel disease, pancreatitis, asthma, chronic obstructive pulmonary disease, and cardiovascular diseases. This review provides a comprehensive overview of the structure and modulation of SQSTM1, discusses its intracellular and extracellular roles in inflammation, and highlights its significance in inflammation-related diseases. Future investigations focusing on elucidating the precise localization, structure, post-translational modifications of SQSTM1, as well as the identification of additional interacting partners, hold promise for unravelling further insights into the multifaceted functions of SQSTM1.

The Dual Role of ACOD1 in Inflammation

Immunometabolism is an interdisciplinary field that focuses on the relationship between metabolic pathways and immune responses. Dysregulated immunometabolism contributes to many pathological settings, such as cytokine storm or immune tolerance. Aconitate decarboxylase 1 (ACOD1, also known as immunoresponsive gene 1), the mitochondrial enzyme responsible for catalyzing itaconate production, was originally identified as a bacterial LPS-inducible gene involved in innate immunity in mouse macrophages. We now know that the upregulation of ACOD1 expression in immune or nonimmune cells plays a context-dependent role in metabolic reprogramming, signal transduction, inflammasome regulation, and protein modification. The emerging function of ACOD1 in inflammation and infection is a double-edged sword. In this review, we discuss how ACOD1 regulates anti-inflammatory or proinflammatory responses in an itaconate-dependent or -independent manner. Further understanding of ACOD1 expression and function may pave the way for the development of precision therapies for inflammatory diseases.

A two-decade journey in identifying high mobility group box 1 (HMGB1) and procathepsin L (pCTS-L) as potential therapeutic targets for sepsis

INTRODUCTION

Microbial infections and resultant sepsis are leading causes of death in hospitals, representing approximately 20% of total deaths worldwide. Despite the difficulties in translating experimental insights into effective therapies for often heterogenous patient populations, an improved understanding of the pathogenic mechanisms underlying experimental sepsis is still urgently needed. Sepsis is partly attributable to dysregulated innate immune responses manifested by hyperinflammation and immunosuppression at different stages of microbial infections.

AREAS COVERED

Here we review our recent progress in searching for late-acting mediators of experimental sepsis and propose high mobility group box 1 (HMGB1) and procathepsin-L (pCTS-L) as potential therapeutic targets for improving outcomes of lethal sepsis and other infectious diseases.

EXPERT OPINION

It will be important to evaluate the efficacy of HMGB1- or pCTS-L-targeting agents for the clinical management of human sepsis and other infectious diseases in future studies.

Extracellular SQSTM1 exacerbates acute pancreatitis by activating autophagy-dependent ferroptosis

ABBREVIATIONS

5-HETE, 5-hydroxyeicosatetraenoic acid; ACSL4, acyl-CoA synthetase long chain family member 4; AP, acute pancreatitis; ATG, autophagy related; AGER, advanced glycosylation end-product specific receptor; DAMPs, danger/damage-associated molecular patterns; FTH1, ferritin heavy chain 1; GPX4, glutathione peroxidase 4; IL, interleukin; INSR, insulin receptor; MAP1LC3B, microtubule associated protein 1 light chain 3 beta; MDA, malondialdehyde; MPO, myeloperoxidase; PRRs, pattern recognition receptors; PUFA, polyunsaturated fatty acid; RNAi, RNA interference; SQSTM1, sequestosome 1; TNF, tumor necrosis factor; TLR, toll like receptor.

Gasdermins assemble; recent developments in bacteriology and pharmacology

The discovery of gasdermin D (GSDMD) as the terminal executioner of pyroptosis provided a large piece of the cell death puzzle, whilst simultaneously and firmly putting the gasdermin family into the limelight. In its purest form, GSDMD provides a connection between the innate alarm systems to an explosive, inflammatory form of cell death to jolt the local environment into immunological action. However, the gasdermin field has moved rapidly and significantly since the original seminal work and novel functions and mechanisms have been recently uncovered, particularly in response to infection. Gasdermins regulate and are regulated by mechanisms such as autophagy, metabolism and NETosis in fighting pathogen and protecting host. Importantly, activators and interactors of the other gasdermins, not just GSDMD, have been recently elucidated and have opened new avenues for gasdermin-based discovery. Key to this is the development of potent and specific tool molecules, so far a challenge for the field. Here we will cover some of these recently discovered areas in relation to bacterial infection before providing an overview of the pharmacological landscape and the challenges associated with targeting gasdermins.

The versatile defender: exploring the multifaceted role of p62 in intracellular bacterial infection

As a highly conserved, multifunctional protein with multiple domains, p62/SQSTM1 plays a crucial role in several essential cellular activities, particularly selective autophagy. Recent research has shown that p62 is crucial in eradicating intracellular bacteria by xenophagy, a selective autophagic process that identifies and eliminates such microorganisms. This review highlights the various roles of p62 in intracellular bacterial infections, including both direct and indirect, antibacterial and infection-promoting aspects, and xenophagy-dependent and independent functions, as documented in published literature. Additionally, the potential applications of synthetic drugs targeting the p62-mediated xenophagy mechanism and unresolved questions about p62's roles in bacterial infections are also discussed.

Autophagy Receptor p62 Regulates SARS-CoV-2-Induced Inflammation in COVID-19

As autophagy can promote or inhibit inflammation, we examined autophagy-inflammation interplay in COVID-19. Autophagy markers in the blood of 19 control subjects and 26 COVID-19 patients at hospital admission and one week later were measured by ELISA, while cytokine levels were examined by flow cytometric bead immunoassay. The antiviral IFN-α and proinflammatory TNF, IL-6, IL-8, IL-17, IL-33, and IFN-γ were elevated in COVID-19 patients at both time points, while IL-10 and IL-1β were increased at admission and one week later, respectively. Autophagy markers LC3 and ATG5 were unaltered in COVID-19. In contrast, the concentration of autophagic cargo receptor p62 was significantly lower and positively correlated with TNF, IL-10, IL-17, and IL-33 at hospital admission, returning to normal levels after one week. The expression of SARS-CoV-2 proteins NSP5 or ORF3a in THP-1 monocytes caused an autophagy-independent decrease or autophagy-inhibition-dependent increase, respectively, of intracellular/secreted p62, as confirmed by immunoblot/ELISA. This was associated with an NSP5-mediated decrease in TNF/IL-10 mRNA and an ORF3a-mediated increase in TNF/IL-1β/IL-6/IL-10/IL-33 mRNA levels. A genetic knockdown of p62 mimicked the immunosuppressive effect of NSP5, and a p62 increase in autophagy-deficient cells mirrored the immunostimulatory action of ORF3a. In conclusion, the proinflammatory autophagy receptor p62 is reduced inacute COVID-19, and the balance between autophagy-independent decrease and autophagy blockade-dependent increase of p62 levels could affect SARS-CoV-induced inflammation.

Endothelial dysfunction and immunothrombosis in sepsis

Sepsis is a life-threatening clinical syndrome characterized by multiorgan dysfunction caused by a dysregulated or over-reactive host response to infection. During sepsis, the coagulation cascade is triggered by activated cells of the innate immune system, such as neutrophils and monocytes, resulting in clot formation mainly in the microcirculation, a process known as immunothrombosis. Although this process aims to protect the host through inhibition of the pathogen’s dissemination and survival, endothelial dysfunction and microthrombotic complications can rapidly lead to multiple organ dysfunction. The development of treatments targeting endothelial innate immune responses and immunothrombosis could be of great significance for reducing morbidity and mortality in patients with sepsis. Medications modifying cell-specific immune responses or inhibiting platelet–endothelial interaction or platelet activation have been proposed. Herein, we discuss the underlying mechanisms of organ-specific endothelial dysfunction and immunothrombosis in sepsis and its complications, while highlighting the recent advances in the development of new therapeutic approaches aiming at improving the short- or long-term prognosis in sepsis.

Identification of procathepsin L (pCTS-L)-neutralizing monoclonal antibodies to treat potentially lethal sepsis

Antibody-based strategies have been attempted to antagonize early cytokines of sepsis, but not yet been tried to target inducible late-acting mediators. Here, we report that the expression and secretion of procathepsin-L (pCTS-L) was induced by serum amyloid A (SAA) in innate immune cells, contributing to its late and systemic accumulation in experimental and clinical sepsis. Recombinant pCTS-L induced interleukin-6 (IL-6), IL-8, GRO-α/KC, GRO-β/MIP-2, and MCP-1 release in innate immune cells and moderately correlated with blood concentrations of these cytokines/chemokines in clinical sepsis. Mechanistically, pCTS-L interacted with Toll-like receptor 4 (TLR4) and the receptor for advanced glycation end products (RAGE) to induce cytokines/chemokines. Pharmacological suppression of pCTS-L with neutralizing polyclonal and monoclonal antibodies attenuated pCTS-L-mediated inflammation by impairing its interaction with TLR4 and RAGE receptors, and consequently rescued animals from lethal sepsis. Our findings have suggested a possibility of developing antibody strategies to prevent dysregulated immune responses mediated by late-acting cytokines.

The redox protein HMGB1 in cell death and cancer

SIGNIFICANCE

As a redox-sensitive protein, high-mobility group box 1 (HMGB1) is implicated in regulating stress responses to oxidative damage and cell death, which are closely related to the pathology of inflammatory diseases, including cancer.

RECENT ADVANCES

HMGB1 is a non-histone nuclear protein that acts as a DNA chaperone to control chromosomal structure and function. HMGB1 can also be released into the extracellular space and function as a damage-associated molecular pattern protein during cell death, including during apoptosis, necrosis, necroptosis, pyroptosis, ferroptosis, alkaliptosis, and cuproptosis. Once released, HMGB1 binds to membrane receptors to shape immune and metabolic responses. In addition to subcellular localization, the function and activity of HMGB1 also depends on its redox state and protein posttranslational modifications. Abnormal HMGB1 plays a dual role in tumorigenesis and anticancer therapy (e.g., chemotherapy, radiation therapy, and immunotherapy) depending on tumor types and stages.

CRITICAL ISSUES

A comprehensive understanding of the role of HMGB1 in cellular redox homeostasis is important for deciphering normal cellular functions and pathological manifestations. In this review, we discuss compartmental-defined roles of HMGB1 in regulating cell death and cancer. Understanding these advances may help us develop potential HMGB1-targeting drugs or approaches to treat oxidative stress-related diseases or pathological conditions.

FUTURE DIRECTIONS

Further studies are required to dissect the mechanism by which HMGB1 maintains redox homeostasis under different stress conditions. A multidisciplinary effort is also required to evaluate the potential applications of precisely targeting the HMGB1 pathway in human health and disease.

Single-Cell Transcriptome Analysis of H5N1-HA-Stimulated Alpaca PBMCs

Avian influenza A virus H5N1 is a highly pathogenic and persistently a major threat to global health. Vaccines and antibodies targeting hemagglutinin (HA) protein are the primary management strategies for the epidemic virus. Although camelids possess unique immunological features, the immune response induced by specific antigens has not yet been thoroughly investigated. Herein, we immunized an alpaca with the HA antigen of the H5N1 virus and performed single-cell transcriptome profiling for analysis of longitudinal peripheral blood mononuclear cell (PBMCs) behavior using single-cell sequencing technology (scRNA-seq). We revealed multiple cellular immunities during the immunization. The monocytes continued to expand after immunization, while the plasma cells reached their peak three days after the second antigen stimulation. Both monocytes and B cells were stimulated by the HA antigen and produced cell-type-specific cytokines to participated in the immune response. To our knowledge, this is the first study to examine the HA-specific immunological dynamics of alpaca PBMCs at the single-cell level, which is beneficial for understanding the anti-viral immune system and facilitating the development of more potent vaccines and antibodies in camelid animals.

Sepsis-induced immunosuppression: mechanisms, diagnosis and current treatment options

Sepsis is a common complication of combat injuries and trauma, and is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. It is also one of the significant causes of death and increased health care costs in modern intensive care units. The use of antibiotics, fluid resuscitation, and organ support therapy have limited prognostic impact in patients with sepsis. Although its pathophysiology remains elusive, immunosuppression is now recognized as one of the major causes of septic death. Sepsis-induced immunosuppression is resulted from disruption of immune homeostasis. It is characterized by the release of anti-inflammatory cytokines, abnormal death of immune effector cells, hyperproliferation of immune suppressor cells, and expression of immune checkpoints. By targeting immunosuppression, especially with immune checkpoint inhibitors, preclinical studies have demonstrated the reversal of immunocyte dysfunctions and established host resistance. Here, we comprehensively discuss recent findings on the mechanisms, regulation and biomarkers of sepsis-induced immunosuppression and highlight their implications for developing effective strategies to treat patients with septic shock.

Aconitate decarboxylase 1 is a mediator of polymicrobial sepsis

Sepsis is a challenging clinical syndrome caused by a dysregulated host response to infection. Here, we identified an unexpected proseptic activity of aconitate decarboxylase 1 (ACOD1) in monocytes and macrophages. Previous studies have suggested that ACOD1, also known as immune-responsive gene 1, is an immunometabolic regulator that favors itaconate production to inhibit bacterial lipopolysaccharide-induced innate immunity. We used next-generation sequencing of lipopolysaccharide-activated THP1 cells to demonstrate that ACOD1 accumulation confers a robust proinflammation response by activating a cytokine storm, predominantly through the tumor necrosis factor signaling pathway. We further revealed that the phosphorylation of cyclin-dependent kinase 2 (CDK2) on threonine-160 mediates the activation of mitogen-activated protein kinase 8 through receptor for activated C kinase 1, leading to JUN-dependent transcription of ACOD1 in human and mouse macrophages or monocytes. Genetic deletion of CDK2 or ACOD1 in myeloid cells, or the administration of the CDK inhibitor dinaciclib, protected mice against polymicrobial sepsis and was associated with improved survival and decreased cytokine storm. The expression of the CDK2-ACOD1 axis also correlated with severity of illness in a cohort of 40 patients with bacterial sepsis. Thus, our findings provide evidence for a previously unrecognized function of ACOD1 in innate immunity and suggest it as a potential therapeutic target for the treatment of sepsis.

Metabolic reprogramming consequences of sepsis: adaptations and contradictions

During sepsis, the importance of alterations in cell metabolism is underappreciated. The cellular metabolism, which has a variable metabolic profile in different cells and disease stages, is largely responsible for the immune imbalance and organ failure associated with sepsis. Metabolic reprogramming, in which glycolysis replaces OXPHOS as the main energy-producing pathway, is both a requirement for immune cell activation and a cause of immunosuppression. Meanwhile, the metabolites produced by OXPHOS and glycolysis can act as signaling molecules to control the immune response during sepsis. Sepsis-induced "energy shortage" leads to stagnated cell function and even organ dysfunction. Metabolic reprogramming can alleviate the energy crisis to some extent, enhance host tolerance to maintain cell survival functions, and ultimately increase the adaptation of cells during sepsis. However, a switch from glycolysis to OXPHOS is essential for restoring cell function. This review summarized the crosstalk between metabolic reprogramming and immune cell activity as well as organ function during sepsis, discussed the benefits and drawbacks of metabolic reprogramming to show the contradictions of metabolic reprogramming during sepsis, and assessed the feasibility of treating sepsis through targeted metabolism. Using metabolic reprogramming to achieve metabolic homeostasis could be a viable therapy option for sepsis.

The STING1-MYD88 complex drives ACOD1/IRG1 expression and function in lethal innate immunity

ACOD1 (also known as IRG1) has emerged as a regulator of immunometabolism that operates by producing metabolite itaconate. Here, we report a key role of STING1 (also known as STING and TMEM173) in mediating ACOD1 expression in myeloid cells in response to toll-like receptor (TLR) signaling. The activation of STING1 through exogenous cyclic dinucleotides (e.g., 3′3′-cGAMP) or endogenous gain-of-function mutation (e.g., V155M) enhances lipopolysaccharide-induced ACOD1 expression and itaconate production in macrophages and monocytes, whereas the deletion of STING1 blocks this process. The adaptor protein MYD88, instead of DNA sensor cyclic GMP-AMP synthase (CGAS), favors STING1-dependent ACOD1 expression. Mechanistically, MYD88 directly blocks autophagic degradation of STING1 and causes subsequent IRF3/JUN-mediated ACOD1 gene transcription. Consequently, the conditional deletion of STING1 in myeloid cells fails to produce ACOD1 and itaconate, thereby protecting mice against endotoxemia and polymicrobial sepsis. Our results, therefore, establish a direct link between TLR4 signaling and ACOD1 expression through the STING1-MYD88 complex during septic shock.

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The MYD88-STING1 protein complex is required for lipopolysaccharide (LPS)-induced ACOD1 expression

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The MYD88-STING1 protein complex prevents autophagic degradation of STING1

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The IRF3-JUN transcription factor complex favors ACOD1 upregulation

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STING1-mediated itaconate production promotes experimental sepsis

HSP90 Mediates IFNγ-Induced Adaptive Resistance to Anti-PD-1 Immunotherapy

SIGNIFICANCE

This study reveals an HSP90-centric, iron-modulated mechanism that confers immunosuppression, offering potential therapeutic targets for interfering with acquired resistance to the most prevalent anticancer immunotherapies.

Immunothrombosis and the molecular control of tissue factor by pyroptosis: prospects for new anticoagulants

The interplay between innate immunity and coagulation after infection or injury, termed immunothrombosis, is the primary cause of disseminated intravascular coagulation (DIC), a condition that occurs in sepsis. Thrombosis associated with DIC is the leading cause of death worldwide. Interest in immunothrombosis has grown because of COVID-19, the respiratory disease caused by SARS-CoV-2, which has been termed a syndrome of dysregulated immunothrombosis. As the relatively new field of immunothrombosis expands at a rapid pace, the focus of academic and pharmacological research has shifted from generating treatments targeted at the traditional 'waterfall' model of coagulation to therapies better directed towards immune components that drive coagulopathies. Immunothrombosis can be initiated in macrophages by cleavage of the non-canonical inflammasome which contains caspase-11. This leads to release of tissue factor (TF), a membrane glycoprotein receptor that forms a high-affinity complex with coagulation factor VII/VIIa to proteolytically activate factors IX to IXa and X to Xa, generating thrombin and leading to fibrin formation and platelet activation. The mechanism involves the post-translational activation of TF, termed decryption, and release of decrypted TF via caspase-11-mediated pyroptosis. During aberrant immunothrombosis, decryption of TF leads to thromboinflammation, sepsis, and DIC. Therefore, developing therapies to target pyroptosis have emerged as an attractive concept to counteract dysregulated immunothrombosis. In this review, we detail the three mechanisms of TF control: concurrent induction of TF, caspase-11, and NLRP3 (signal 1); TF decryption, which increases its procoagulant activity (signal 2); and accelerated release of TF into the intravascular space via pyroptosis (signal 3). In this way, decryption of TF is analogous to the two signals of NLRP3 inflammasome activation, whereby induction of pro-IL-1β and NLRP3 (signal 1) is followed by activation of NLRP3 (signal 2). We describe in detail TF decryption, which involves pathogen-induced alterations in the composition of the plasma membrane and modification of key cysteines on TF, particularly at the location of the critical, allosterically regulated disulfide bond of TF in its 219-residue extracellular domain. In addition, we speculate towards the importance of identifying new therapeutics to block immunothrombotic triggering of TF, which can involve inhibition of pyroptosis to limit TF release, or the direct targeting of TF decryption using cysteine-modifying therapeutics.

Mechanisms and Consequences of Noncanonical Inflammasome-Mediated Pyroptosis

The noncanonical inflammasome, comprising inflammatory caspases 4, 5, or 11, monitors the cytosol for bacterial lipopolysaccharide (LPS). Intracellular LPS-elicited autoproteolysis of these inflammatory caspases leads to the cleavage of the pore-forming protein gasdermin D (GSDMD). GSDMD pore formation induces a lytic form of cell death known as pyroptosis and the release of inflammatory cytokines and DAMPs, thereby promoting inflammation. The noncanonical inflammasome-dependent innate sensing of cytosolic LPS plays important roles in bacterial infections and sepsis pathogenesis. Exciting studies in the recent past have significantly furthered our understanding of the biochemical and structural basis of the caspase-4/11 activation of GSDMD, caspase-4/11's substrate specificity, and the biological consequences of noncanonical inflammasome activation of GSDMD. This review will discuss these recent advances and highlight the remaining gaps in our understanding of the noncanonical inflammasome and pyroptosis.

Mitochondrial ACOD1/IRG1 in infection and sterile inflammation

Immunometabolism is a dynamic process involving the interplay of metabolism and immune response in health and diseases. Increasing evidence suggests that impaired immunometabolism contributes to infectious and inflammatory diseases. In particular, the mitochondrial enzyme aconitate decarboxylase 1 (ACOD1, best known as immunoresponsive gene 1 [IRG1]) is upregulated under various inflammatory conditions and serves as a pivotal regulator of immunometabolism involved in itaconate production, macrophage polarization, inflammasome activation, and oxidative stress. Consequently, the activation of the ACOD1 pathway is implicated in regulating the pathogenic process of sepsis and septic shock, which are part of a clinical syndrome of life-threatening organ failure caused by a dysregulated host response to pathogen infection. In this review, we discuss the latest research advances in ACOD1 expression and function, with particular attention to how the ACOD1-itaconate pathway affects infection and sterile inflammation diseases. These new insights may give us a deeper understanding of the role of immunometabolism in innate immunity.

p62 works as a hub modulation in the ageing process

p62 (also known as SQSTM1) is widely used as a predictor of autophagic flux, a process that allows the degradation of harmful and unnecessary components through lysosomes to maintain protein homeostasis in cells. p62 is also a stress-induced scaffold protein that resists oxidative stress. The multiple domains in its structure allow it to be connected with a variety of vital signalling pathways, autophagy and the ubiquitin proteasome system (UPS), allowing p62 to play important roles in cell proliferation, apoptosis and survival. Recent studies have shown that p62 is also directly or indirectly involved in the ageing process. In this review, we summarize in detail the process by which p62 regulates ageing from multiple ageing-related signs with the aim of providing new insight for the study of p62 in ageing.

STING1 in sepsis: Mechanisms, functions, and implications

Sepsis is a life-threatening clinical syndrome and one of the most challenging health problems in the world. Pathologically, sepsis and septic shock are caused by a dysregulated host immune response to infection, which can eventually lead to multiple organ failure and even death. As an adaptor transporter between the endoplasmic reticulum and Golgi apparatus, stimulator of interferon response cGAMP interactor 1 (STING1, also known as STING or TMEM173) has been found to play a vital role at the intersection of innate immunity, inflammation, autophagy, and cell death in response to invading microbial pathogens or endogenous host damage. There is ample evidence that impaired STING1, through its immune and non-immune functions, is involved in the pathological process of sepsis. In this review, we discuss the regulation and function of the STING1 pathway in sepsis and highlight it as a suitable drug target for the treatment of lethal infection.

Innate Immunity as an Executor of the Programmed Death of Individual Organisms for the Benefit of the Entire Population

In humans, over-activation of innate immunity in response to viral or bacterial infections often causes severe illness and death. Furthermore, similar mechanisms related to innate immunity can cause pathogenesis and death in sepsis, massive trauma (including surgery and burns), ischemia/reperfusion, some toxic lesions, and viral infections including COVID-19. Based on the reviewed observations, we suggest that such severe outcomes may be manifestations of a controlled suicidal strategy protecting the entire population from the spread of pathogens and from dangerous pathologies rather than an aberrant hyperstimulation of defense responses. We argue that innate immunity may be involved in the implementation of an altruistic programmed death of an organism aimed at increasing the well-being of the whole community. We discuss possible ways to suppress this atavistic program by interfering with innate immunity and suggest that combating this program should be a major goal of future medicine.

The multiomics landscape of serum exosomes during the development of sepsis

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The study for the first time describes the profile of molecular dynamics in septic serum exosomes.

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We provide a new direction into proteasome-mediated protein degradation in septic serum exosomes.

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IL-10 delivery by septic exosomes may play a vital role in alleviation of AKI of CLP mice.

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Septic serum exosomes participate in the modulation of sepsis by regulating vitamin metabolism.

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The molecular mechanisms proposed in the study may provide helpful insights for the therapy of sepsis.

Introduction

Sepsis is an infection-induced severe inflammatory disorder leading to multiple organ dysfunction. It remains a highly lethal condition for which early diagnosis and therapy achieve unsatisfactory results. Circulating exosomes containing biomarkers and mediators of sepsis have recently received attention, but the progress has been far from optimal.

Objectives

The present study focuses on the profiles of molecular dynamics in serum exosomes and explores the potential molecular mechanisms on serum exosomes during the process of sepsis.

Methods

We used high-performance liquid chromatography-tandem mass spectrometry and RNA-seq to detect the dynamic profiles of exosome proteins and RNAs (including mRNAs, lncRNAs and miRNAs) in serum exosomes from 3 healthy individuals and 9 septic patients at the different stages. Then integrative multiomics analyses were performed and the results were validated by qRT-PCR, LiquiChip assay and metabolomics analysis on mice subjected to cecal ligation and puncture (CLP) modeling.

Results

A total of 354 proteins, 195 mRNAs, 82 lncRNAs and 55 miRNAs were identified as differentially expressed molecules in serum exosomes from septic patients. Integrative multiomics analysis showed that exosome components were associated with cytokine storm, complement and clotting cascades, the endothelial barrier, 20S proteasome-dependent protein degradation and vitamin metabolism. Importantly, pretreatment with serum exosomes derived from mice subjected to CLP significantly restrained proinflammatory cytokine expression and alleviated tissue injury in septic mice. Further metabolomics analysis demonstrated that pretreatment with septic serum exosomes significantly affected the metabolites associated with vitamin digestion and absorption in CLP mice.

Conclusion

Our study for the first time describes the landscape of the molecular dynamics of serum exosomes during the development of sepsis and proposes some hypothetical molecular mechanisms by integrative multiomics analysis, which may provide helpful diagnostic and therapeutic insights for the ongoing battle against sepsis.

Endogenous Regulation and Pharmacological Modulation of Sepsis-Induced HMGB1 Release and Action: An Updated Review

Sepsis remains a common cause of death in intensive care units, accounting for approximately 20% of total deaths worldwide. Its pathogenesis is partly attributable to dysregulated inflammatory responses to bacterial endotoxins (such as lipopolysaccharide, LPS), which stimulate innate immune cells to sequentially release early cytokines (such as tumor necrosis factor (TNF) and interferons (IFNs)) and late mediators (such as high-mobility group box 1, HMGB1). Despite difficulties in translating mechanistic insights into effective therapies, an improved understanding of the complex mechanisms underlying the pathogenesis of sepsis is still urgently needed. Here, we review recent progress in elucidating the intricate mechanisms underlying the regulation of HMGB1 release and action, and propose a few potential therapeutic candidates for future clinical investigations.

The Pathways Underlying the Multiple Roles of p62 in Inflammation and Cancer

p62 is a highly conserved, multi-domain, and multi-functional adaptor protein critically involved in several important cellular processes. Via its pronounced domain architecture, p62 binds to numerous interaction partners, thereby influencing key pathways that regulate tissue homeostasis, inflammation, and several common diseases including cancer. Via binding of ubiquitin chains, p62 acts in an anti-inflammatory manner as an adaptor for the auto-, xeno-, and mitophagy-dependent degradation of proteins, pathogens, and mitochondria. Furthermore, p62 is a negative regulator of inflammasome complexes. The transcription factor Nrf2 regulates expression of a bundle of ROS detoxifying genes. p62 activates Nrf2 by interaction with and autophagosomal degradation of the Nrf2 inhibitor Keap1. Moreover, p62 activates mTOR, the central kinase of the mTORC1 sensor complex that controls cell proliferation and differentiation. Through different mechanisms, p62 acts as a positive regulator of the transcription factor NF-κB, a central player in inflammation and cancer development. Therefore, p62 represents not only a cargo receptor for autophagy, but also a central signaling hub, linking several important pro- and anti-inflammatory pathways. This review aims to summarize knowledge about the molecular mechanisms underlying the roles of p62 in health and disease. In particular, different types of tumors are characterized by deregulated levels of p62. The elucidation of how p62 contributes to inflammation and cancer progression at the molecular level might promote the development of novel therapeutic strategies.

The STING1 network regulates autophagy and cell death

Cell death and immune response are at the core of life. In past decades, the endoplasmic reticulum (ER) protein STING1 (also known as STING or TMEM173) was found to play a fundamental role in the production of type I interferons (IFNs) and pro-inflammatory cytokines in response to DNA derived from invading microbial pathogens or damaged hosts by activating multiple transcription factors. In addition to this well-known function in infection, inflammation, and immunity, emerging evidence suggests that the STING1-dependent signaling network is implicated in health and disease by regulating autophagic degradation or various cell death modalities (e.g., apoptosis, necroptosis, pyroptosis, ferroptosis, mitotic cell death, and immunogenic cell death [ICD]). Here, we outline the latest advances in our understanding of the regulating mechanisms and signaling pathways of STING1 in autophagy and cell death, which may shed light on new targets for therapeutic interventions.

Emerging mechanisms of immunocoagulation in sepsis and septic shock

Sepsis and septic shock driven by microbial infections are still among the most challenging health problems, causing 11 million deaths worldwide every year. How does the host's response to pathogen infections effectively restore homeostasis instead of precipitating pathogenic and potentially fatal feedforward reactions? Recently, there have been significant new advances in our understanding of the interface between mammalian immunity and coagulation ('immunocoagulation') and its impact on sepsis. In particular, the release and activation of F3 (the main initiator of coagulation) from and on myeloid or epithelial cells is facilitated by activating inflammasomes and consequent gasdermin D (GSDMD)-mediated pyroptosis, coupled to signaling via high mobility group box 1 (HMGB1), stimulator of interferon response CGAMP interactor 1 (STING1), or sequestosome 1 (SQSTM1). Pharmacological modulation of the immunocoagulation pathways emerge as novel and potential therapeutic strategies for sepsis.

Inflammasome-Dependent Coagulation Activation in Sepsis

Sepsis is a potentially life-threatening, pathological condition caused by a dysregulated host response to infection. Pathologically, systemic inflammation can initiate coagulation activation, leading to organ dysfunction, and ultimately to multiple organ failure and septic death. The inflammasomes are cytosolic multiprotein signaling complexes that control the host response to diverse pathogen-associated molecular patterns (PAMPs) from microorganisms as well as damage-associated molecular patterns (DAMPs) from dead or dying host cells. Recent studies highlight that the activation of canonical and non-canonical inflammasomes not only mediate the maturation and secretion of interleukin-1 (IL1) family cytokines, but also trigger the release of coagulation factor III, tissue factor (F3, best known as TF) in activated macrophages and monocytes. These emerging functions of inflammasomes in immunocoagulation are further positively regulated by stimulator of interferon response cGAMP interactor 1 (STING1, also known as STING or TMEM173, a hub of the innate immune signaling network) and high mobility group box 1 (HMGB1, a nuclear DAMP). This mini-review will discuss the regulation and function of inflammasome-dependent coagulation activation in sepsis.

Pharmacological Modulation of BET Family in Sepsis

The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis 3.0) recommended defining sepsis as a life-threatening organ dysfunction caused by the host's uncontrolled response to infection. The bromodomain and extra-terminal (BET) protein family (such as BRD2, BRD3, and BRD4), an epigenetic regulator of gene transcription, has recently been recognized as a significant septic regulator of inflammation and immune response, including cytokine and chemokine production. Mechanistically, the two N-terminal conserved tandem bromodomains (namely the first bromodomain [BD1] and the second bromodomain [BD2]) favor the binding of BETs to acetylated histones or transcription factors, thereby initiating gene transcription machinery after CycT1 and CDK9 (also known as P-TEFb) are recruited to gene promoters to phosphorylate RNA pol II. Notably, BD1 and BD2 are not functionally redundant because they have different target genes in innate immune cells. Small-molecule BET inhibitors (BETis) for different BDs, such as I-BET, JQ1, I-BET151, apabetalone, RVX-297, and dBET1 have shown promising therapeutic effects in experimental sepsis models. This mini-review summarizes the emerging roles of BETs and the applications of BETis in sepsis, discusses the existing shortcomings of BETis, and introduces possible future research directions in this area.

What's new in trauma 2020

Throughout the past 2020, the pandemic COVID-19 has caused a big global shock, meanwhile it brought a great impact on the public health network. Trauma emergency system faced a giant challenge and how to manage trauma under the pandemic of COVID-19 was widely discussed. However, the trauma treatment of special population (geriatric patients and patients taking anticoagulant drugs) has received inadequate attention. Due to the high mortality following severe traumatic hemorrhage, hemostasis and trauma-induced coagulopathy are the important concerns in trauma treatment. Sepsis is another topic should not be ignored when we talking about trauma. COVID-19 itself is a special kind of sepsis, and it may even be called as serious systemic infection syndrome. Sepsis has been become a serious problem waiting to be solved urgently no matter in the fields of trauma, or in intensive care and infection, etc. This article reviewed the research progress in areas including trauma emergency care, trauma bleeding and coagulation, geriatric trauma and basic research of trauma within 2020.

Extracellular SQSTM1 as an inflammatory mediator

Excessive inflammation may lead to irreparable injury and even death, but the key mediators and underlying mechanisms remain unclear. Our recent findings indicate that SQSTM1/p62 (sequestosome 1), a well-known macroautophagy/autophagy receptor, is a lethal inflammatory mediator of sepsis and septic shock. The release of SQSTM1 occurs during tissue damage or microbial invasion through two main ways: one is passive and the other is active. Passive release occurs in the context of GSDMD-mediated pyroptosis. Active SQSTM1 secretion requires two basic steps: the first step is the expression and phosphorylation of SQSTM1 mediated by STING1/STING/TMEM173, and then the unconventional secretion of SQSTM1 by secretory lysosomes. After release, the extracellular SQSTM1 binds to membrane receptor INSR to activate glycolysis, leading to subsequent production of pro-inflammatory cytokines in a transcription factor NFKB-dependent manner. Functionally, genetic deletion or pharmacological inhibition of the SQSTM1-INSR pathway limits tissue damage, systemic inflammation, organ failure, and death in experimental sepsis models in mice. Moreover, the activation of the SQSTM1-INSR pathway is related to the severity of sepsis in patients. These findings highlight a pathological role of extracellular SQSTM1 in infection, inflammation, and immunity.