Cytosolic HMGB1 controls the cellular autophagy/apoptosis checkpoint during inflammation

CAMSAP3-mediated regulation of HMGB1 acetylation and subcellular localization in lung cancer cells: Implications for cell death modulation

BACKGROUND

Deregulation of cell death is a common characteristic of cancer, and resistance to this process often occurs in lung cancer. Understanding the molecular mechanisms underlying an aberrant cell death is important. Recent studies have emphasized the involvement of calmodulin-regulated spectrin-associated protein 3 (CAMSAP3) in lung cancer aggressiveness, its influence on cell death regulation remains largely unexplored.

METHODS

CAMSAP3 was knockout in lung cancer cells using CRISPR-Cas9 system. Cell death and autophagy were evaluated using MTT and autophagic detection assays. Protein interactions were performed by proteomic analysis and immunoprecipitation. Protein expressions and their cytoplasmic localization were analyzed through immunoblotting and immunofluorescence techniques.

RESULTS

This study reveals a significant correlation between low CAMSAP3 expression and poor overall survival rates in lung cancer patients. Proteomic analysis identified high mobility group box 1 (HMGB1) as a candidate interacting protein involved in the regulation of cell death. Treatment with trichostatin A (TSA), an inhibitor of histone deacetylases (HDACs) resulted in increased HMGB1 acetylation and its translocation to the cytoplasm and secretion, thereby inducing autophagic cell death. However, this process was diminished in CAMSAP3 knockout lung cancer cells. Mechanistically, immunoprecipitation indicated an interaction between CAMSAP3 and HMGB1, particularly with its acetylated form, in which this complex was elevated in the presence of TSA.

CONCLUSIONS

CAMSAP3 is prerequisite for TSA-mediated autophagic cell death by interacting with cytoplasmic acetylated HMGB1 and enhancing its release.

SIGNIFICANT

This finding provides molecular insights into the role of CAMSAP3 in regulating cell death, highlighting its potential as a therapeutic target for lung cancer treatment.

Genetically encoded caspase sensor and RFP-LC3 for temporal analysis of apoptosis-autophagy

The balance between pro-death and pro-survival signaling determines the fate of cells under a variety of pathological and physiological conditions. The pro-cell death signaling, apoptosis, and survival singling, autophagy work in an integrated manner for maintaining cell integrity. Their altered balance drives pathological conditions such as cancer, inflammatory disorders, and neurodegenerative diseases. Dissecting complex crosstalk between autophagy and apoptosis requires simultaneous detection of both events at a single cell level with good temporal resolution in real-time. Here, we have used two distinct fluorescent-based probes of caspase activation and autophagy for generating such sensor cells. Cells stably expressing RFP-LC3 as an autophagy marker were further stably expressed with a FRET-based probe for caspase activation with a nuclear localization signal. The functional validation and live-cell imaging of the sensor cells using selected treatments revealed that stress that induces rapid cell death often fails to induce autophagy signaling, and slow cell death induction triggers simultaneous autophagy signaling with caspase activation. The real-time imaging revealed the time-dependent shift of cells towards caspase activation while autophagy is inhibited confirming basal autophagy confers survival against apoptosis under stress conditions. Confocal imaging also revealed that cells under 3D culture condition maintain increased autophagy over monolayer cultures. High-throughput adaptability of the system extends its application for the screening of compounds that cause caspase activation, autophagy, or both demonstrating the potential utility of the sensor probe for diverse biological applications.

Use of Machine Learning for the Identification and Validation of Immunogenic Cell Death Biomarkers and Immunophenotypes in Coronary Artery Disease

Objective

Immunogenic cell death (ICD) is part of the immune system's response to coronary artery disease (CAD). In this study, we bioinformatically evaluated the diagnostic and therapeutic utility of immunogenic cell death-related genes (IRGs) and their relationship with immune infiltration features in CAD.

Methods

We acquired the CAD-related datasets GSE12288, GSE71226, and GSE120521 from the Gene Expression Omnibus (GEO) database and the IRGs from the GeneCards database. After identifying the immune cell death-related differentially expressed genes (IRDEGs), we developed a risk model and detected immune subtypes in CAD. IRDEGs were identified using least absolute shrinkage and selection operator (LASSO) analysis. Using a nomogram, we confirmed that both the LASSO model and ICD signature genes had good diagnostic performance.

Results

There was a high degree of coincidence and immune representativeness between two CAD groups based on characteristic genes and hub genes. Hub genes were associated with the interaction of neuroactive ligands with receptors and cell adhesion receptors. The two groups differed in terms of adipogenesis, allograft rejection, and apoptosis, as well as the ICD signature and hub gene expression levels. The two CAD-ICD subtypes differed in terms of immune infiltration.

Conclusion

Quantitative real-time PCR (qRT-PCR) correlated CAD with the expression of OAS3, ITGAV, and PIBF1. The ICD signature genes are candidate biomarkers and reference standards for immune grouping in CAD and can be beneficial in precise immune-targeted therapy.

Npro of classical swine fever virus enhances HMGB1 acetylation and its degradation by lysosomes to evade from HMGB1-mediated antiviral immunity

Classical swine fever virus (CSFV) can dampen the host innate immunity by destabilizing IRF3 upon its binding with viral Npro. High mobility group box 1 (HMGB1), a non-histone nuclear protein, has diverse functions, including inflammation, innate immunity, etc., which are closely related to its cellular localization. We investigated potential mutual interactions between CSFV and HMGB1 and their effects on virus replication. We found that HMGB1 at the protein level, but not at mRNA level, was markedly reduced in CSFV-infected or Npro-expressing IPEC-J2 cells. HMGB1 in the nuclear compartment is anti-CSFV by promoting IFN-mediated innate immune response, as evidenced by overexpression of nuclear or cytoplasmic dominant HMGB1 mutant in IPEC-J2 cells stimulated with poly(I:C). However, CSFV Npro upregulates HMGB1 acetylation, a modification that promotes HMGB1 translocation into the cytoplasmic compartment where it is degraded by lysosomes. Ethyl pyruvate could downregulate HMGB1 acetylation and prevent Npro-mediated HMGB1 reduction. Inhibition of deacetylase HDAC1 with MS275 or by RNA silencing could promote Npro-mediated HMGB1 degradation. Taken together, our study elucidates the mechanism with which HMGB1 in the nuclei initiates antiviral innate immune response to suppress CSFV replication and elaborates the pathway by which CSFV uses its Npro to evade from HMGB1-mediated antiviral immunity through upregulating HMGB1 acetylation with subsequent translocation into cytoplasm for lysosomal degradation.

Investigating cell death responses associated with histotripsy ablation of canine osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most frequently occurring primary bone tumor in dogs and people and innovative treatment options are profoundly needed. Histotripsy is an emerging tumor ablation modality, and it is essential for the clinical translation of histotripsy to gain knowledge about the outcome of nonablated tumor cells that could remain postablation. The objective of this study was to characterize the cell death genetic signature and proliferation response of canine OS cells post a near complete histotripsy ablation (96% ± 1.5) and to evaluate genetic cell death signatures associated with histotripsy ablation and OS in vivo.

METHODS

In the current study, we ablated three canine OS cell lines with a histotripsy dose that resulted in near complete ablation to allow for a viable tumor cell population for downstream analyses. To assess the in vivo cell death genetic signature, we characterized cell death genetic signature in histotripsy-ablated canine OS tumors collected 24-h postablation.

RESULTS

Differential gene expression changes observed in the 4% viable D17 and D418 cells, and histotripsy-ablated OS tumor samples, but not in Abrams cells, were associated with immunogenic cell death (ICD). The 4% viable OS cells demonstrated significantly reduced proliferation, compared to control OS cells, in vitro.

CONCLUSION

Histotripsy ablation of OS cell lines leads to direct and potentially indirect cell death as evident by, reduced proliferation in remaining viable OS cells and cell death genetic signatures suggestive of ICD both in vitro and in vivo.

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.

Role of HMGB1 and its associated signaling pathways in human malignancies

The High-Mobility Group Box-1 (HMGB1), a non-histone chromatin-associated protein, plays a crucial role in cancer growth and response to therapy as it retains a pivotal role in promoting both cell death and survival. HMGB1 has been reported to regulate several signaling pathways engaged in inflammation, genome stability, immune function, cell proliferation, cell autophagy, metabolism, and apoptosis. However, the association between HMGB1 and cancer is complex and its mechanism in tumorigenesis needs to be further elucidated. This review aims to understand the role of HMGB1 in human malignancies and discuss the signaling pathways linked to this process to provide a comprehensive understanding on the association of HMGB1 with carcinogenesis. Further, we will review the role of HMGB1 as a target/biomarker for cancer therapy, the therapeutic strategies used to target this protein, and its potential role in preventing or treating cancers. In light of the recent growing evidence linking HMGB1 to cancer progression, we think that it may be suggested as a novel and emergent therapeutic target for cancer therapy. Hence, HMGB1 warrants paramount investigation to comprehensively map its role in tumorigenesis.

The role of HMGB1 in digestive cancer

High mobility group box protein B1 (HMGB1) belongs to the HMG family, is widely expressed in the nucleus of digestive mucosal epithelial cells, mesenchymal cells and immune cells, and binds to DNA to participate in genomic structural stability, mismatch repair and transcriptional regulation to maintain normal cellular activities. In the context of digestive inflammation and tumors, HMGB1 readily migrates into the extracellular matrix and binds to immune cell receptors to affect their function and differentiation, further promoting digestive tract tissue injury and tumor development. Notably, HMGB1 can also promote the antitumor immune response. Therefore, these seemingly opposing effects in tumors make targeted HMGB1 therapies important in digestive cancer. This review focuses on the role of HMGB1 in tumors and its effects on key pathways of digestive cancer and aims to provide new possibilities for targeted tumor therapy.

The interaction between autophagy, Helicobacter pylori, and gut microbiota in gastric carcinogenesis

Chronic infection with Helicobacter pylori is the primary risk factor for the development of gastric cancer. Hindering our ability to comprehend the precise role of autophagy during H. pylori infection is the complexity of context-dependent autophagy signaling pathways. Recent and ongoing progress in understanding H. pylori virulence allows new frontiers of research for the crosstalk between autophagy and H. pylori. Novel approaches toward discovering autophagy signaling networks have further revealed their critical influence on the structure of gut microbiota and the metabolome. Here we intend to present a holistic view of the perplexing role of autophagy in H. pylori pathogenesis and carcinogenesis. We also discuss the intermediate role of autophagy in H. pylori-mediated modification of gut inflammatory responses and microbiota structure.

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.

Tim-3 protects against cisplatin nephrotoxicity by inhibiting NF-κB-mediated inflammation

The impact of Tim-3 (T cell immunoglobulin and mucin domain-containing protein 3) on cisplatin-induced acute kidney injury was investigated in this study. Cisplatin-induced Tim-3 expression in mice kidney tissues and proximal tubule-derived BUMPT cells in a time-dependent manner. Compared with wild-type mice, Tim-3 knockout mice have higher levels of serum creatinine and urea nitrogen, enhanced TUNEL staining signals, more severe 8-OHdG (8-hydroxy-2' -deoxyguanosine) accumulation, and increased cleavage of caspase 3. The purified soluble Tim-3 (sTim-3) protein was used to intervene in cisplatin-stimulated BUMPT cells by competitively binding to the Tim-3 ligand. sTim-3 obviously increased the cisplatin-induced cell apoptosis. Under cisplatin treatment conditions, Tim-3 knockout or sTim-3 promoted the expression of TNF-α (tumor necrosis factor-alpha) and IL-1β (Interleukin-1 beta) and inhibited the expression of IL-10 (interleukin-10). NF-κB (nuclear factor kappa light chain enhancer of activated B cells) P65 inhibitor PDTC or TPCA1 lowed the increased levels of creatinine and BUN (blood urea nitrogen) in cisplatin-treated Tim-3 knockout mice serum and the increased cleavage of caspase 3 in sTim-3 and cisplatin-treated BUMPT cells. Moreover, sTim-3 enhanced mitochondrial oxidative stress in cisplatin-induced BUMPT cells, which can be mitigated by PDTC. These data indicate that Tim-3 may protect against renal injury by inhibiting NF-κB-mediated inflammation and oxidative stress.

HMGB1: a potential new target for tendinopathy treatment

Tendinopathy describes a complex pathology of the tendon characterized by abnormalities in the microstructure, composition, and cellularity of the tendon, leading to pain, limitation of activity and reduced function. Nevertheless, the mechanism of tendinopathy has not been fully elucidated, and the treatment of tendinopathy remains a challenge. High mobility group box 1 (HMGB1), a highly conserved and multifaceted nuclear protein, exerts multiple roles and high functional variability and is involved in many biological and pathological processes. In recent years, several studies have suggested that HMGB1 is associated with tendinopathy and may play a key role in the pathogenesis of tendinopathy. Therefore, this review summarizes the expression and distribution of HMGB1 in tendinopathy, focuses on the roles of HMGB1 and HMGB1-based potential mechanisms involved in tendinopathy, and finally summarizes the findings on HMGB1-based therapeutic approaches in tendinopathy, probably providing new insight into the mechanism and further potential therapeutic targets of tendinopathy.

HMGB1 acts as an agent of host defense at the gut mucosal barrier

Mucosal barriers provide the first line of defense between internal body surfaces and microbial threats from the outside world. ¹ In the colon, the barrier consists of two layers of mucus and a single layer of tightly interconnected epithelial cells supported by connective tissue and immune cells. ² Microbes colonize the loose, outer layer of colonic mucus, but are essentially excluded from the tight, epithelial-associated layer by host defenses. ³ The amount and composition of the mucus is calibrated based on microbial signals and loss of even a single component of this mixture can destabilize microbial biogeography and increase the risk of disease. ^4-7 However, the specific components of mucus, their molecular microbial targets, and how they work to contain the gut microbiota are still largely unknown. Here we show that high mobility group box 1 (HMGB1), the prototypical damage-associated molecular pattern molecule (DAMP), acts as an agent of host mucosal defense in the colon. HMGB1 in colonic mucus targets an evolutionarily conserved amino acid sequence found in bacterial adhesins, including the well-characterized Enterobacteriaceae adhesin FimH. HMGB1 aggregates bacteria and blocks adhesin-carbohydrate interactions, inhibiting invasion through colonic mucus and adhesion to host cells. Exposure to HMGB1 also suppresses bacterial expression of FimH. In ulcerative colitis, HMGB1 mucosal defense is compromised, leading to tissue-adherent bacteria expressing FimH. Our results demonstrate a new, physiologic role for extracellular HMGB1 that refines its functions as a DAMP to include direct, virulence limiting effects on bacteria. The amino acid sequence targeted by HMGB1 appears to be broadly utilized by bacterial adhesins, critical for virulence, and differentially expressed by bacteria in commensal versus pathogenic states. These characteristics suggest that this amino acid sequence is a novel microbial virulence determinant and could be used to develop new approaches to diagnosis and treatment of bacterial disease that precisely identify and target virulent microbes.

Nano Delivery of Chemotherapeutic ICD Inducers for Tumor Immunotherapy

Immunogenic cell death (ICD, also known as immunogenic apoptosis) of malignant cells is confirmed to activate the host immune system to prevent, control, and eliminate tumors. Recently, a range of chemotherapeutic drugs have been repurposed as ICD inducers and applied for tumor immunotherapy. However, several hurdles to the widespread application of chemotherapeutic ICD inducers remain, namely poor water solubility, short blood circulation, non-specific tissue distribution, and severe toxicity. Recent advances in nanotechnology and pharmaceutical formulation foster the development of nano drug delivery systems to tackle the aforementioned hurdles and expedite safe, effective, and specific delivery. This review will describe delivery barriers to chemical ICD inducers and highlight recent nanoformulations for these drugs in tumor immunotherapy.

Cytoplasmic HMGB1 induces renal tubular ferroptosis after ischemia/reperfusion

As a damage-associated molecular pattern molecule, high-mobility group box 1 (HMGB1) is well-studied and is released from injured tubular epithelial cells to trigger cell death. However, the role of intracellular HMGB1 induced cell death during acute kidney injury (AKI) is poorly understood. We showed that cytosolic HMGB1 induced ferroptosis by binding to acyl-CoA synthetase long-chain family member 4 (ACSL4), the driver of ferroptosis, following renal ischemia/reperfusion (I/R). Both mouse and human kidneys with acute tubular injury were characterized by nucleocytoplasmic translocation of HMGB1in tubular cells. Pharmacological inhibition of HMGB1 nucleocytoplasmic translocation and deletion of HMGB1 in tubular epithelial cells in mice inhibited I/R-induced AKI, tubular ferroptosis, and inflammation compared to those in controls. Co-immunoprecipitation and serial section staining confirmed the interaction between HMGB1 and ACSL4. Taken together, our results demonstrated that cytoplasmic HMGB1 is essential for exacerbating inflammation-associated cellular injury by activating renal tubular ferroptosis via ACSL4 after I/R injury. These findings indicate that cytoplasmic HMGB1 is a regulator of ferroptosis and a promising therapeutic target for AKI.

Dengue virus induced autophagy is mediated by HMGB1 and promotes viral propagation

Dengue virus (DENV) exploits various cellular pathways including autophagy to assure enhanced virus propagation. The mechanisms of DENV mediated control of autophagy pathway are largely unknown. Our investigations have revealed a novel role for high-mobility group box1 protein (HMGB1) in regulation of cellular autophagy process in DENV-2 infected A549 cell line. While induction of autophagy by rapamycin treatment resulted in enhanced DENV-2 propagation, the blockade of autophagy flux with bafilomycin A1 suppressed viral replication. Furthermore, siRNA-mediated silencing of HMGB1 significantly abrogated dengue induced autophagy, while LPS induced HMGB1 expression counteracted these effects. Interestingly, silencing of HMGB1 showed reduction of BECN1 and stabilization of BCL-2 protein. On the contrary, LPS induction of HMGB1 resulted in enhanced BECN1 and reduction in BCL-2 levels. This study shows that the modulation of autophagy by DENV-2 is HMGB1/BECN1 dependent. In addition, glycyrrhizic acid (GA), a potent HMGB1 inhibitor suppressed autophagy as well as DENV-2 replication. Altogether, our data suggests that HMGB1 induces BECN1 dependent autophagy to promote DENV-2 replication.

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.

HMGB1 mediates lipopolysaccharide-induced macrophage autophagy and pyroptosis

Autophagy and pyroptosis of macrophages play important protective or detrimental roles in sepsis. However, the underlying mechanisms remain unclear. High mobility group box protein 1 (HMGB1) is associated with both pyroptosis and autophagy. lipopolysaccharide (LPS) is an important pathogenic factor involved in sepsis. Lentivirus-mediated HMGB1 shRNA was used to inhibit the expression of HMGB1. Macrophages were treated with acetylation inhibitor (AA) to suppress the translocation of HMGB1 from the nucleus to the cytosol. Autophagy and pyroptosis-related protein expressions were detected by Western blot. The levels of caspase-1 activity were detected and the rate of pyroptotic cells was detected by flow cytometry. LPS induced autophagy and pyroptosis of macrophages at different stages, and HMGB1 downregulation decreased LPS-induced autophagy and pyroptosis. Treatment with acetylation inhibitor (anacardic acid) significantly suppressed LPS-induced autophagy, an effect that was not reversed by exogenous HMGB1, suggesting that cytoplasmic HMGB1 mediates LPS-induced autophagy of macrophages. Anacardic acid or an anti-HMGB1 antibody inhibited LPS-induced pyroptosis of macrophages. HMGB1 alone induced pyroptosis of macrophages and this effect was inhibited by anti-HMGB1 antibody, suggesting that extracellular HMGB1 induces macrophage pyroptosis and mediates LPS-induced pyroptosis. In summary, HMGB1 plays different roles in mediating LPS-induced autophagy and triggering pyroptosis according to subcellular localization.

How autophagy, a potential therapeutic target, regulates intestinal inflammation

Inflammatory bowel disease (IBD) is a group of disorders that cause chronic inflammation in the intestines, with the primary types including ulcerative colitis and Crohn's disease. The link between autophagy, a catabolic mechanism in which cells clear protein aggregates and damaged organelles, and intestinal health has been widely studied. Experimental animal studies and human clinical studies have revealed that autophagy is pivotal for intestinal homeostasis maintenance, gut ecology regulation and other aspects. However, few articles have summarized and discussed the pathways by which autophagy improves or exacerbates IBD. Here, we review how autophagy alleviates IBD through the specific genes (e.g., ATG16L1, IRGM, NOD2 and LRRK2), crosstalk of multiple phenotypes with autophagy (e.g., Interaction of autophagy with endoplasmic reticulum stress, intestinal antimicrobial defense and apoptosis) and autophagy-associated signaling pathways. Moreover, we briefly discuss the role of autophagy in colorectal cancer and current status of autophagy-based drug research for IBD. It should be emphasized that autophagy has cell-specific and environment-specific effects on the gut. One of the problems of IBD research is to understand how autophagy plays a role in intestinal tract under specific environmental factors. A better understanding of the mechanism of autophagy in the occurrence and progression of IBD will provide references for the development of therapeutic drugs and disease management for IBD in the future.

The relationship between HMGB1 and autophagy in the pathogenesis of diabetes and its complications

Diabetes mellitus is a chronic metabolic disorder characterized by elevated blood glucose levels and has become the third leading threat to human health after cancer and cardiovascular disease. Recent studies have shown that autophagy is closely associated with diabetes. Under normal physiological conditions, autophagy promotes cellular homeostasis, reduces damage to healthy tissues and has bidirectional effects on regulating diabetes. However, under pathological conditions, unregulated autophagy activation leads to cell death and may contribute to the progression of diabetes. Therefore, restoring normal autophagy may be a key strategy to treat diabetes. High-mobility group box 1 protein (HMGB1) is a chromatin protein that is mainly present in the nucleus and can be actively secreted or passively released from necrotic, apoptotic, and inflammatory cells. HMGB1 can induce autophagy by activating various pathways. Studies have shown that HMGB1 plays an important role in insulin resistance and diabetes. In this review, we will introduce the biological and structural characteristics of HMGB1 and summarize the existing knowledge on the relationship between HMGB1, autophagy, diabetes, and diabetic complications. We will also summarize potential therapeutic strategies that may be useful for the prevention and treatment of diabetes and its complications.

Gastric alarmin release: A warning signal in the development of gastric mucosal diseases

Alarmins exist outside cells and are early warning signals to the immune system; as such, alarmin receptors are widely distributed on various immune cells. Alarmins, proinflammatory molecular patterns associated with tissue damage, are usually released into the extracellular space, where they induce immune responses and participate in the damage and repair processes of mucosal diseases.In the stomach, gastric alarmin release has been shown to be involved in gastric mucosal inflammation, antibacterial defense, adaptive immunity, and wound healing; moreover, this release causes damage and results in the development of gastric mucosal diseases, including various types of gastritis, ulcers, and gastric cancer. Therefore, it is necessary to understand the role of alarmins in gastric mucosal diseases. This review focuses on the contribution of alarmins, including IL33, HMGB1, defensins and cathelicidins, to the gastric mucosal barrier and their role in gastric mucosal diseases. Here, we offer a new perspective on the prevention and treatment of gastric mucosal diseases.

Interactions of Autophagy and the Immune System in Health and Diseases

Autophagy is a highly conserved process that utilizes lysosomes to selectively degrade a variety of intracellular cargo, thus providing quality control over cellular components and maintaining cellular regulatory functions. Autophagy is triggered by multiple stimuli ranging from nutrient starvation to microbial infection. Autophagy extensively shapes and modulates the inflammatory response, the concerted action of immune cells, and secreted mediators aimed to eradicate a microbial infection or to heal sterile tissue damage. Here, we first review how autophagy affects innate immune signaling, cell-autonomous immune defense, and adaptive immunity. Then, we discuss the role of non-canonical autophagy in microbial infections and inflammation. Finally, we review how crosstalk between autophagy and inflammation influences infectious, metabolic, and autoimmune disorders.

Cytosolic HMGB1 Mediates LPS-Induced Autophagy in Microglia by Interacting with NOD2 and Suppresses Its Proinflammatory Function

The high mobility group box 1 (HMGB1), a well-known danger-associated molecule pattern (DAMP) molecule, is a non-histone chromosomal protein localized in the nucleus under normal physiological conditions. HMGB1 exhibits diverse functions depending on its subcellular location. In the present study, we investigated the role of HMGB1-induced autophagy in the lipopolysaccharide (LPS)-treated BV2 microglial cell line in mediating the transition between the inflammatory and autophagic function of the nucleotide-binding oligomerization domain-containing 2 (NOD2), a cytoplasmic pattern-recognition receptor. The induction of the microtubule-associated protein 1 light chain 3 (LC3), an autophagy biomarker, was detected slowly in BV2 cells after the LPS treatment, and peak induction was detected at 12 h. Under these conditions, NOD2 level was significantly increased and the binding between HMGB1 and NOD2 and between HMGB1 and ATG16L1 was markedly enhanced and the temporal profiles of the LC3II induction and HMGB1-NOD2 and HMGB1-ATG16L1 complex formation coincided with the cytosolic accumulation of HMGB1. The LPS-mediated autophagy induction was significantly suppressed in BV2 cells after HMGB1 or NOD2 knock-down (KD), indicating that HMGB1 contributes to NOD2-mediated autophagy induction in microglia. Moreover, NOD2-RIP2 interaction-mediated pro-inflammatory cytokine induction and NF-κB activity were significantly enhanced in BV2 cells after HMGB1 KD, indicating that HMGB1 plays a critical role in the modulation of NOD2 function between pro-inflammation and pro-autophagy in microglia. The effects of the cell-autonomous pro-autophagic pathway operated by cytoplasmic HMGB1 may be beneficial, whereas those from the paracrine pro-inflammatory pathway executed by extracellularly secreted HMGB1 can be detrimental. Thus, the overall functional significance of HMGB1-induced autophagy is different, depending on its temporal activity.

Inflammatory gene expression during acute high‐altitude exposure

Abstract

The molecular signalling pathways that regulate inflammation and the response to hypoxia share significant crosstalk and appear to play major roles in high‐altitude acclimatization and adaptation. Several studies demonstrate increases in circulating candidate inflammatory markers during acute high‐altitude exposure, but significant gaps remain in our understanding of how inflammation and immune function change at high altitude and whether these responses contribute to high‐altitude pathologies, such as acute mountain sickness. To address this, we took an unbiased transcriptomic approach, including RNA sequencing and direct digital mRNA detection with NanoString, to identify changes in the inflammatory profile of peripheral blood throughout 3 days of high‐altitude acclimatization in healthy sea‐level residents (n = 15; five women). Several inflammation‐related genes were upregulated on the first day of high‐altitude exposure, including a large increase in HMGB1 (high mobility group box 1), a damage‐associated molecular pattern (DAMP) molecule that amplifies immune responses during tissue injury. Differentially expressed genes on the first and third days of acclimatization were enriched for several inflammatory pathways, including nuclear factor‐κB and Toll‐like receptor (TLR) signalling. Indeed, both TLR4 and LY96, which encodes the lipopolysaccharide binding protein (MD‐2), were upregulated at high altitude. Finally, FASLG and SMAD7 were associated with acute mountain sickness scores and peripheral oxygen saturation levels on the first day at high altitude, suggesting a potential role of immune regulation in response to high‐altitude hypoxia. These results indicate that acute high‐altitude exposure upregulates inflammatory signalling pathways and might sensitize the TLR4 signalling pathway to subsequent inflammatory stimuli.

Key points

Inflammation plays a crucial role in the physiological response to hypoxia.

High‐altitude hypoxia exposure causes alterations in the inflammatory profile that might play an adaptive or maladaptive role in acclimatization.

In this study, we characterized changes in the inflammatory profile following acute high‐altitude exposure.

We report upregulation of novel inflammation‐related genes in the first 3 days of high‐altitude exposure, which might play a role in immune system sensitization.

These results provide insight into how hypoxia‐induced inflammation might contribute to high‐altitude pathologies and exacerbate inflammatory responses in critical illnesses associated with hypoxaemia.

RAGE management: ETS1- EGR1 mediated transcriptional networks regulate angiogenic factors in wood frogs

Freeze-tolerant species, such as wood frogs (Rana sylvatica), are susceptible to multiple co-occurring stresses that they must overcome to survive. Freezing is accompanied by mechanical stress and dehydration due to ice crystal formation in the extracellular space, ischemia/anoxia due to interruption in blood flood, and hyperglycemia due to cryoprotective measures. Wood frogs can survive dehydration, anoxia, and high glucose stress independently of freezing, thereby creating a multifactorial model for studying freeze-tolerance. Oxidative stress and high glucose levels favors the production of pro-oxidant molecules and advanced glycation end product (AGE) adducts that could cause substantial cellular damage. In this study, the involvement of the high mobility group box 1 (HMGB1)-AGE/RAGE (receptor for AGE) axis and the regulation of ETS1 and EGR1-mediated angiogenic responses were investigated in liver of wood frogs expose to freeze/thaw, anoxia/reoxygenation and dehydration/rehydration treatments. HMGB1 and not AGE-adducts are likely to induce the activation of ETS1 and EGR1 via the RAGE pathway. The increase in nuclear localization of both ETS1 and EGR1, but not DNA binding activity in response to stress hints to a potential spatial and temporal regulation in inducing angiogenic factors. Freeze/thaw and dehydration/rehydration treatments increase the levels of both pro- and anti-angiogenic factors, perhaps to prepare for the distribution of cryoprotectants or enable the repair of damaged capillaries and wounds when needed. Overall, wood frogs appear to anticipate the need for angiogenesis in response to freezing and dehydration but not anoxic treatments, probably due to mechanical stress associated with the two former conditions.

Molecular insights into the multifaceted functions and therapeutic targeting of high mobility group box 1 in metabolic diseases

HMGB1 is a ubiquitously expressed protein localized in nucleus, cytoplasm, as well as secreted into extracellular space. Nuclear HMGB1 binds to DNAs and RNAs, regulating genomic stability and transcription. Cytoplasmic HMGB1 regulates autophagy through binding to core autophagy regulators. Secreted extracellular HMGB1 functions as a ligand to various receptors (RAGE and TLRs, etc.), regulating multiple signalling pathways, such as MAPK, PI3K and NF-κB signallings. Trafficking and localization of HMGB1 across cellular compartments could be regulated by its posttranslational modifications, which fine-tune its functions in metabolic diseases, inflammation and cancers. The current review examines the up-to-date findings pertaining to the biological functions of HMGB1, with focus on its posttranslational modifications and roles in downstream signalling pathways involved in metabolic diseases. This review also discusses the feasibility of targeting HMGB1 as a potential pharmacological intervention for metabolic diseases.

Decreased HMGB1 expression contributed to cutaneous toxicity caused by lapatinib

The application of lapatinib, a widely used dual inhibitor of human epidermal growth factor receptor 1 (EGFR/ERBB1) and 2 (HER2/ERBB2), has been seriously limited due to cutaneous toxicity. However, the specific mechanism of lapatinib-induced cutaneous toxicity has not been clarified, leading to the lack of an effective strategy to improve clinical safety. Here, we found that lapatinib could induce mitochondrial dysfunction, lead to DNA damage and ultimately cause apoptosis of keratinocytes. In addition, we found that lapatinib could induce an aberrant immune response and promote the release of inflammatory factors in vitro and in vivo. Mechanistically, downregulated expression of the DNA repair protein HMGB1 played a critical role in these toxic reaction processes. Overexpression of HMGB1 inhibited keratinocyte apoptosis and inflammatory reactions. Therefore, restoring HMGB1 expression might be an effective remedy against lapatinib-induced cutaneous toxicity. Finally, we found that saikosaponin A could significantly rescue the reduced HMGB1 transcription, which could alleviate lapatinib-induced DNA damage, inhibit keratinocyte apoptosis and further prevent the toxicity of lapatinib in mice. Collectively, our study might bring new hope to clinicians and tumor patients and shed new light on the prevention of cutaneous adverse drug reactions induced by EGFR inhibitors.

The Role of HMGB1 in Rheumatic Diseases

HMGB1, a highly conserved non-histone nuclear protein, is widely expressed in mammalian cells. HMGB1 in the nucleus binds to the deoxyribonucleic acid (DNA) to regulate the structure of chromosomes and maintain the transcription, replication, DNA repair, and nucleosome assembly. HMGB1 is actively or passively released into the extracellular region during cells activation or necrosis. Extracellular HMGB1 as an alarmin can initiate immune response alone or combined with other substances such as nucleic acid to participate in multiple biological processes. It has been reported that HMGB1 is involved in various inflammatory responses and autoimmunity. This review article summarizes the physiological function of HMGB1, the post-translational modification of HMGB1, its interaction with different receptors, and its recent advances in rheumatic diseases and strategies for targeted therapy.

Cardiovascular Dysfunction in COVID-19: Association Between Endothelial Cell Injury and Lactate

Coronavirus disease 2019 (COVID-19), an infectious respiratory disease propagated by a new virus known as Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), has resulted in global healthcare crises. Emerging evidence from patients with COVID-19 suggests that endothelial cell damage plays a central role in COVID-19 pathogenesis and could be a major contributor to the severity and mortality of COVID-19. Like other infectious diseases, the pathogenesis of COVID-19 is closely associated with metabolic processes. Lactate, a potential biomarker in COVID-19, has recently been shown to mediate endothelial barrier dysfunction. In this review, we provide an overview of cardiovascular injuries and metabolic alterations caused by SARS-CoV-2 infection. We also propose that lactate plays a potential role in COVID-19-driven endothelial cell injury.

Ginseng root extract attenuates inflammation by inhibiting the MAPK/NF-κB signaling pathway and activating autophagy and p62-Nrf2-Keap1 signaling in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Panax ginseng C.A. Meyer is a type of herbal plant that has frequently been used in many Asian countries to treat a variety of diseases. Ginseng is considered to exhibit anti-inflammatory and anti-oxidative pharmacological effects. However, the specific mechanism is still not entirely understood.

AIM OF THE STUDY

In this study, we investigated if ginseng extract could attenuate inflammation and oxidative stress in RAW264.7 cells and in dextran sulfate sodium (DSS)-induced colitis mouse model.

MATERIALS AND METHODS

RAW264.7 cells and LPS were used to develop inflammatory and oxidative cell models. C57/6J male mice and DSS were used to construct the animal models. O2-, mitochondria number, and mitochondrial membrane potential were analyzed using fluorescent probes and fluorescence microscopy. Reactive oxygen species and nitric oxide generation were detected with probes and microplate readers. The secreted amounts of inflammatory cytokines were measured by enzyme-linked immunosorbent assay kits. Protein expression levels in the cytoplasm and nucleus were measured by western blotting analyses. Quantitative real-time PCR (qRT-PCR) was used to determine the changes in mRNA levels. Autophagosome accumulation was analyzed by transmission electron microscopy. A p62-specific siRNA was used to evaluate the effect of p62 on the anti-oxidative function of ginseng root extract (GRE). Asperuloside and SP600125 were used to confirm the involvement of the MAPK/NF-κB signaling pathway.

RESULTS

We performed a systematic analysis of the anti-inflammatory, anti-oxidative, and autophagy regulatory mechanisms of GRE in LPS-treated RAW264.7 cells. GRE considerably reduced the levels of nitric oxide, TNF-α, and IL-6 secreted by LPS-treated cells. GRE treatments dose-dependently upregulated IL-10 mRNA levels and decreased IL-6 and IL-1β mRNA levels in LPS-treated cells. Similar to the NF-κB and JNK inhibitors, GRE treatment significantly inhibited NF-κB activity and phosphorylation of MAPKs (JNK, ERK-1/2, and p38). Additionally, GRE treatment remarkably decreased LPS-triggered reactive oxygen species production and mitochondrial dysfunction by motivating Nrf2 nuclear translocation by enhancing phosphorylated p62. Knockdown of p62 resulted in the loss of GRE anti-oxidative ability. Autophagy was strongly induced by GRE via the Akt-mTOR signaling pathway, relieving excessive oxidation, mitochondrial dysfunction, and inflammation, while enhancing Beclin-1, LC3 II, and Atg7 protein expression. Furthermore, GRE alleviated the degree of injury, inflammatory cytokine production, and regulated the relative signaling pathway in DSS-induced colitis.

CONCLUSIONS

GRE can exert both anti-inflammatory and anti-oxidative functions by targeting the MAPK/NF-κB and p62-Nrf2-Keap1 pathways, as well as autophagy, in vitro and vivo.

miR-505 inhibits replication of Borna disease virus 1 via inhibition of HMGB1-mediated autophagy

Borna disease virus 1 (BoDV-1) is a highly neurotropic RNA virus which was recently demonstrated to cause deadly human encephalitis. Viruses can modulate microRNA expression, in turn modulating cellular immune responses and regulating viral replication. A previous study indicated that BoDV-1 infection down-regulated the expression of miR-505 in rats. However, the underlying mechanism of miR-505 during BoDV-1 infection remains unknown. In this study, we found that miR-505 can inhibit autophagy activation by down-regulating the expression of its target gene HMGB1, and ultimately inhibit the replication of BoDV-1. Specifically, we found that the expression of miR-505 was significantly down-regulated in rat primary neurons stably infected with BoDV-1. Overexpression of miR-505 can inhibit the replication of BoDV-1 in cells. Bioinformatics analysis and dual luciferase reporter gene detection confirmed that during BoDV-1 infection, the high-mobility group protein B1 (HMGB1) that mediates autophagy is the direct target gene of miR-505. The expression of HMGB1 was up-regulated after BoDV-1 infection, and overexpression of miR-505 could inhibit the expression of HMGB1. Autophagy-related detection found that after infection with BoDV-1, the expression of autophagy-related proteins and autophagy-related marker LC3 in neuronal cells was significantly up-regulated. Autophagy flow experiments and transmission electron microscopy also further confirmed that BoDV-1 infection activated HMGB1-mediated autophagy. Further regulating the expression of miR-505 found that overexpression of miR-505 significantly inhibited HMGB1-mediated autophagy. The discovery of this mechanism may provide new ideas and directions for the prevention and treatment of BoDV-1 infection in the future.

How autophagy controls the intestinal epithelial barrier

Macroautophagy/autophagy is a cellular catabolic process that results in lysosome-mediated recycling of organelles and protein aggregates, as well as the destruction of intracellular pathogens. Its role in the maintenance of the intestinal epithelium is of particular interest, as several autophagy-related genes have been associated with intestinal disease. Autophagy and its regulatory mechanisms are involved in both homeostasis and repair of the intestine, supporting intestinal barrier function in response to cellular stress through tight junction regulation and protection from cell death. Furthermore, a clear role has emerged for autophagy not only in secretory cells but also in intestinal stem cells, where it affects their metabolism, as well as their proliferative and regenerative capacity. Here, we review the physiological role of autophagy in the context of intestinal epithelial maintenance and how genetic mutations affecting autophagy contribute to the development of intestinal disease.Abbreviations: AKT1S1: AKT1 substrate 1; AMBRA1: autophagy and beclin 1 regulator 1; AMPK: AMP-activated protein kinase; APC: APC regulator of WNT signaling pathway; ATF6: activating transcription factor 6; ATG: autophagy related; atg16l1[ΔIEC] mice: mice with a specific deletion of Atg16l1 in intestinal epithelial cells; ATP: adenosine triphosphate; BECN1: beclin 1; bsk/Jnk: basket; CADPR: cyclic ADP ribose; CALCOCO2: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CD: Crohn disease; CDH1/E-cadherin: cadherin 1; CF: cystic fibrosis; CFTR: CF transmembrane conductance regulator; CGAS: cyclic GMP-AMP synthase; CLDN2: claudin 2; CoPEC: colibactin-producing E. coli; CRC: colorectal cancer; CYP1A1: cytochrome P450 family 1 subfamily A member 1; DC: dendritic cell; DDIT3: DNA damage inducible transcript 3; DEPTOR: DEP domain containing MTOR interacting protein; DSS: dextran sulfate sodium; EGF: epidermal growth factor; EGFR: epidermal growth factor receptor; EIF2A: eukaryotic translation initiation factor 2A; EIF2AK3: eukaryotic translation initiation factor 2 alpha kinase 3; EIF2AK4/GCN2: eukaryotic translation initiation factor 2 alpha kinase 4; ER: endoplasmic reticulum; ERN1: endoplasmic reticulum to nucleus signaling 1; GABARAP: GABA type A receptor-associated protein; HMGB1: high mobility group box 1; HSPA5/GRP78: heat shock protein family A (Hsp70) member 5; IBD: inflammatory bowel disease; IEC: intestinal epithelial cell; IFN: interferon; IFNG/IFNγ:interferon gamma; IL: interleukin; IRGM: immunity related GTPase M; ISC: intestinal stem cell; LGR5: leucine rich repeat containing G protein-coupled receptor 5; LRRK2: leucine rich repeat kinase 2; MAP1LC3A/LC3: microtubule associated protein 1 light chain 3 alpha; MAPK/JNK: mitogen-activated protein kinase; MAPK14/p38 MAPK: mitogen-activated protein kinase 14; MAPKAP1: MAPK associated protein 1; MAVS: mitochondrial antiviral signaling protein; miRNA: microRNA; MLKL: mixed lineage kinase domain like pseudokinase; MLST8: MTOR associated protein, LST8 homolog; MNV: murine norovirus; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; NLRP: NLR family pyrin domain containing; NOD: nucleotide binding oligomerization domain containing; NRBF2: nuclear receptor binding factor 2; OPTN: optineurin; OXPHOS: oxidative phosphorylation; P: phosphorylation; Patj: PATJ crumbs cell polarity complex component; PE: phosphatidyl-ethanolamine; PI3K: phosphoinositide 3-kinase; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; PIK3R4: phosphoinositide-3-kinase regulatory subunit 4; PPARG: peroxisome proliferator activated receptor gamma; PRR5: proline rich 5; PRR5L: proline rich 5 like; PtdIns3K: phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol 3-phosphate; RB1CC1/FIP200: RB1 inducible coiled-coil 1; RER: rough endoplasmic reticulum; RHEB: Ras homolog, MTORC1 binding; RICTOR: RPTOR independent companion of MTOR complex 2; RIPK1: receptor interacting serine/threonine kinase 1; ROS: reactive oxygen species; RPTOR: regulatory associated protein of MTOR complex 1; RPS6KB1: ribosomal protein S6 kinase B1; SH3GLB1: SH3 domain containing GRB2 like, endophilin B1; SNP: single-nucleotide polymorphism; SQSTM1: sequestosome 1; STAT3: signal transducer and activator of transcription 3; STING1: stimulator of interferon response cGAMP interactor 1; TA: transit-amplifying; TFEB: transcription factor EB; TFE3: transcription factor binding to IGHM enhancer 3; TGM2: transglutaminase 2; TJ: tight junction; TJP1/ZO1: tight junction protein 1; TNBS: 2,4,6-trinitrobenzene sulfonic acid; TNF/TNFα: tumor necrosis factor; Tor: target of rapamycin; TRAF: TNF receptor associated factor; TRIM11: tripartite motif containing 11; TRP53: transformation related protein 53; TSC: TSC complex subunit; Ub: ubiquitin; UC: ulcerative colitis; ULK1: unc-51 like autophagy activating kinase 1; USO1/p115: USO1 vesicle transport factor; UVRAG: UV radiation resistance associated; WIPI: WD repeat domain, phosphoinositide interacting; WNT: WNT family member; XBP1: X-box binding protein 1; ZFYVE1/DFCP1: zinc finger FYVE-type containing 1.

Preventive effect of sanguinarine on intestinal injury in mice exposed to whole abdominal irradiation

Intestinal injury is one of the major side effects that are induced by medical radiation exposure, and has limited effective therapies. In this study, we investigated the beneficial effects of sanguinarine (SAN) on intestinal injury induced by ionizing radiation (IR) both in vitro and in vivo. Mice were exposed to whole abdominal irradiation (WAI) to mimic clinical scenarios. SAN was injected intraperitoneally to mitigate IR-induced injury. Histological examination was performed to assess the tissue injuries of the spleen and small intestine. A small intestinal epithelial cell line-6 (IEC-6) was analyzed for its viability and apoptosis in vitro under different treatments. Inflammation-related pathways and serum inflammatory cytokines were detected via Western blot analysis and ELISA, respectively. High-throughput sequencing was used to characterize the gut microbiota profile. High-performance liquid chromatography was performed to assess short-chain fatty acid contents in the colon. In vitro, SAN pretreatment protected cell viability and reduced apoptosis in IEC-6 cells. In vivo, SAN pretreatment protected immune organs, alleviated intestinal injury, and promoted intestinal recovery. SAN also reduced the levels of inflammatory cytokines, suppressed high mobility group box 1 (HMGB1)/ Toll-like receptor 4 (TLR4) pathway activation, and modulated gut microbiota composition. Our findings demonstrate that the beneficial properties of SAN alleviated intestinal radiation injury. Thus, SAN represents a therapeutic option for protecting against IR-induced intestinal injury in preclinical settings.

Signaling pathways and intervention therapies in sepsis

Sepsis is defined as life-threatening organ dysfunction caused by dysregulated host systemic inflammatory and immune response to infection. Over decades, advanced understanding of host-microorganism interaction has gradually unmasked the genuine nature of sepsis, guiding toward new definition and novel therapeutic approaches. Diverse clinical manifestations and outcomes among infectious patients have suggested the heterogeneity of immunopathology, while systemic inflammatory responses and deteriorating organ function observed in critically ill patients imply the extensively hyperactivated cascades by the host defense system. From focusing on microorganism pathogenicity, research interests have turned toward the molecular basis of host responses. Though progress has been made regarding recognition and management of clinical sepsis, incidence and mortality rate remain high. Furthermore, clinical trials of therapeutics have failed to obtain promising results. As far as we know, there was no systematic review addressing sepsis-related molecular signaling pathways and intervention therapy in literature. Increasing studies have succeeded to confirm novel functions of involved signaling pathways and comment on efficacy of intervention therapies amid sepsis. However, few of these studies attempt to elucidate the underlining mechanism in progression of sepsis, while other failed to integrate preliminary findings and describe in a broader view. This review focuses on the important signaling pathways, potential molecular mechanism, and pathway-associated therapy in sepsis. Host-derived molecules interacting with activated cells possess pivotal role for sepsis pathogenesis by dynamic regulation of signaling pathways. Cross-talk and functions of these molecules are also discussed in detail. Lastly, potential novel therapeutic strategies precisely targeting on signaling pathways and molecules are mentioned.

Anticancer Activity of Biogenic Selenium Nanoparticles: Apoptotic and Immunogenic Cell Death Markers in Colon Cancer Cells

Colorectal cancer is a health problem with high mortality rates and prevalence. Thus, innovative treatment approaches need to be developed. Biogenic nanoparticles are nanomaterials that can be synthesised in biological systems and, compared to chemically synthesised nanoparticles, have better bioavailability while being more cost-effective, eco-friendlier, and less toxic. In our previous studies, the probiotic strain Lactobacillus casei ATCC 393 was used to synthesise selenium nanoparticles (SeNps), which were shown to inhibit colon cancer cell growth in vitro and in vivo. Herein, we have further investigated SeNps' pro-apoptotic activity and their ability to induce immunogenic cell death (ICD) in colon cancer cells. The SeNps' effect on Caco-2 cells growth was examined along with their potential to induce caspase activation. Moreover, the expression of typical pro-apoptotic and ICD markers were examined in SeNps-treated HT29 and CT26 cells by flow cytometry, Western blot, ELISA and fluorescence microscopy. Elevated caspase-3 activation and surface phosphatyldoserine, that subsided upon co-incubation with a pan-caspase inhibitor, were detected in SeNps-treated cells. Furthermore, nanoparticles induced modulation of the expression of various apoptosis-related proteins. We also report the detection of biomarkers involved in ICD, namely the translocation of calreticulin and ERp57, the release of HMGB1 and ATP, and the secretion of pro-inflammatory cytokines from SeNps-treated cells. Moreover, RAW246.7 macrophages exhibited a higher rate of phagocytosis against treated CT26 when compared to control cells. Taken together, our findings indicate that treatment with SeNps might be an efficient strategy to destroy tumour cells by inducing apoptotic cell death and triggering immune responses.

HMGB1 could restrict 1,3-β-glucan induced mice lung inflammation by affecting Beclin1 and Bcl2 interaction and promoting the autophagy of epithelial cells

Fungi were microorganisms that are ubiquitous in a variety of environments. Inhalation of fungi-contaminated organic dust led to hypersensitivity pneumonitis and might eventually cause irreversible pulmonary fibrosis. Studies showed that maintaining the homeostasis of epithelial cells was vital for defending the exogenous fungi invasion. HMGB1-dependent autophagy played a critical role in maintaining cell homeostasis in multiple inflammatory diseases. However, the actual role of HMGB1-dependent autophagy in hypersensitivity pneumonitis was unclear. In our study, mice were exposed to 0.3 mg/50 μL 1,3-β-glucan solution by intratracheal instillation to set up the lung inflammation model. To investigate the role of HMGB1-dependent autophagy in 1,3-β-glucan induced lung inflammation, AAV-sh-HMGB1 was intratracheally injected to silence HMGB1 in the lung. Our finding suggested that silencing HMGB1 could aggravate the 1,3-β-glucan induced lung inflammation by inhibiting the autophagy of epithelial cells. And ubiquitination of Beclin1 contributed to decreasing the interaction of Beclin1 and Bcl2, which might be a key regulatory mechanism of HMGB1 on 1,3-β-glucan induced autophagy.

Calpain-Mediated Mitochondrial Damage: An Emerging Mechanism Contributing to Cardiac Disease

Calpains belong to the family of calcium-dependent cysteine proteases expressed ubiquitously in mammals and many other organisms. Activation of calpain is observed in diseased hearts and is implicated in cardiac cell death, hypertrophy, fibrosis, and inflammation. However, the underlying mechanisms remain incompletely understood. Recent studies have revealed that calpains target and impair mitochondria in cardiac disease. The objective of this review is to discuss the role of calpains in mediating mitochondrial damage and the underlying mechanisms, and to evaluate whether targeted inhibition of mitochondrial calpain is a potential strategy in treating cardiac disease. We expect to describe the wealth of new evidence surrounding calpain-mediated mitochondrial damage to facilitate future mechanistic studies and therapy development for cardiac disease.

Conditional Knock out of High-Mobility Group Box 1 (HMGB1) in Rods Reduces Autophagy Activation after Retinal Detachment

After retinal detachment (RD), the induction of autophagy protects photoreceptors (PR) from apoptotic cell death. The cytoplasmic high-mobility group box 1 (HMGB1) promotes autophagy. We previously demonstrated that the deletion of HMGB1 from rod PRs results in a more rapid death of these cells after RD. In this work, we tested the hypothesis that the lack of HMGB1 accelerates PR death after RD due to the reduced activation of protective autophagy in the retina after RD. The injection of 1% hyaluronic acid into the subretinal space was used to create acute RD in mice with a rhodopsin-Cre-mediated conditional knockout (cKO) of HMGB1 in rods (HMGB1Δrod) and littermate controls. RD sharply increased the number of apoptotic cells in the outer nuclear layer (ONL), and this number was further increased in HMGB1Δrod mouse retinas. The activation of autophagy after RD was reduced in the HMGB1Δrod mouse retinas compared to controls, as evidenced by diminished levels of autophagy regulatory proteins LC3-II, Beclin1, ATG5/12, and phospho-ATG16L1. The cKO of HMGB1 in rods increased the expression of Fas and the Bax/Bcl-2 ratio in detached retinas, promoting apoptotic cell death. In conclusion, endogenous HMGB1 facilitates autophagy activation in PR cells following RD to promote PR cell survival and reduce programmed apoptotic cell death.

Leukocyte-Derived High-Mobility Group Box 1 Governs Hepatic Immune Responses to Listeria monocytogenes

High-mobility group box 1 (HMGB1) is a nucleoprotein with proinflammatory functions following cellular release during tissue damage. Moreover, antibody-mediated HMGB1 neutralization alleviates lipopolysaccharide (LPS)-induced shock, suggesting a role for HMGB1 as a superordinate therapeutic target for inflammatory and infectious diseases. Recent genetic studies have indicated cell-intrinsic functions of HMGB1 in phagocytes as critical elements of immune responses to infections, yet the role of extracellular HMGB1 signaling in this context remains elusive. We performed antibody-mediated and genetic HMGB1 deletion studies accompanied by in vitro experiments to discern context-dependent cellular sources and functions of extracellular HMGB1 during murine bloodstream infection with Listeria monocytogenes. Antibody-mediated neutralization of extracellular HMGB1 favors bacterial dissemination and hepatic inflammation in mice. Hepatocyte HMGB1, a key driver of postnecrotic inflammation in the liver, does not affect Listeria-induced inflammation or mortality. While we confirm that leukocyte HMGB1 deficiency effectuates disseminated listeriosis, we observed no evidence of dysfunctional autophagy, xenophagy, intracellular bacterial degradation, or inflammatory gene induction in primary HMGB1-deficient phagocytes or altered immune responses to LPS administration. Instead, we demonstrate that mice devoid of leukocyte HMGB1 exhibit impaired hepatic recruitment of inflammatory monocytes early during listeriosis, resulting in alterations of the transcriptional hepatic immune response and insufficient control of bacterial dissemination. Bone marrow chimera indicate that HMGB1 from both liver-resident and circulating immune cells contributes to effective pathogen control. Conclusion: Leukocyte-derived extracellular HMGB1 is a critical cofactor in the immunologic control of bloodstream listeriosis. HMGB1 neutralization strategies preclude an efficient host immune response against Listeria.

Neutrophil extracellular traps in inflammatory bowel diseases: Implications in pathogenesis and therapeutic targets

Crohn's disease (CD) and ulcerative colitis (UC) are the two main forms of inflammatory bowel disease (IBD). Among the various immune cells involved in IBD, neutrophils are the first to infiltrate and appear to contribute to the impairment of the epithelial barrier, destruction of tissues by oxidative and proteolytic damage, as well as to the perpetuation of inflammation by the release of cytokines and chemokines associated with pro-inflammatory effects. In addition to basic effector mechanisms, such as phagocytosis and chemotaxis, neutrophils can also form extracellular traps (NETs), which is made up of a mesh-like structure - which contains its chromatin (DNA + histones) together with granules and enzymes, such as myeloperoxidase (MPO) and neutrophilic elastase (NE) - and that acts as a trap that can result in the death of extracellular pathogens and/or can promote tissue damage. Recent evidence indicates that NETs also play an important and significant role in the pathogenesis of IBD. Previous studies have reported increased levels of NETs in tissue and serum samples from patients with IBD, as well as in experimental colitis. In this review, we discuss current knowledge about the formation of NETs and their role in the pathophysiology of IBD, pointing out potential mechanisms by which NETs promote tissue damage, as well as their involvement in complications associated with IBD. In addition, we propose potential targets for therapy to regulate the production of NETs, making it possible to expand the current spectrum of therapies for IBD.

Non-coding RNAs modulate autophagy in myocardial ischemia-reperfusion injury: a systematic review

The myocardial infarction is the main cause of morbidity and mortality in cardiovascular diseases around the world. Although the timely and complete reperfusion via Percutaneous Coronary Intervention (PCI) or thrombolysis have distinctly decreased the mortality of myocardial infarction, reperfusion itself may lead to supererogatory irreversible myocardial injury and heart function disorders, namely ischemia-reperfusion (I/R) injury. Extensive studies have indicated that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), play important roles in the progress of myocardial I/R injury, which is closely correlative with cardiomyocytes autophagy. Moreover, autophagy plays an important role in maintaining homeostasis and protecting cells in the myocardial ischemia reperfusion and cardiomyocyte hypoxia-reoxygenation (H/R) progress. In this review, we first introduced the biogenesis and functions of ncRNAs, and subsequently summarized the roles and relevant molecular mechanisms of ncRNAs regulating autophagy in myocardial I/R injury. We hope that this review in addition to develop a better understanding of the physiological and pathological roles of ncRNAs, can also lay a foundation for the therapies of myocardial I/R injury, and even for other related cardiovascular diseases.

Value of HMGB1 expression for assessing gastric cancer severity: a systematic meta-analysis

OBJECTIVE

To evaluate the clinical value of high mobility group box-1 (HMGB1) expression levels in patients with gastric cancer.

METHODS

Articles published from January 2000 to August 2022 were searched using PubMed, Google Scholar and Science Direct, Springer, Wiley and NIH to evaluate the clinicopathological significance of HMGB1 expression in gastric cancer.

RESULTS

A total of 156 publications were selected, of which six studies, comprising 846 patients, met the criteria for inclusion in this study. Forest plots of clinicopathological characteristics indicated that HMGB1 expression was not associated with age (odds ratio (OR) = 1.07, 95% confidence interval (CI): 0.89-1.28), sex (OR = 0.90, 95% CI: 0.81-1.00), TNM (OR = 1.39, 95% CI: 0.82-2.37), N stage (OR = 1.42, 95% CI: 0.97-2.07), or tumor differentiation (OR = 0.96, 95% CI: 0.71-1.29), but was highly correlated with pT stage (OR = 1.56, 95% CI: 1.17-2.07). Funnel plots showed no significant publication bias in the included studies in terms of age, sex, TNM, pT stage, N stage, or tumor differentiation.

CONCLUSION

HMGB1 expression was significantly correlated with tumor pT stage, but not with age, sex, TNM stage, tumor N stage, tumor differentiation, or lymphatic metastasis in patients with GC.

The Effect and Regulatory Mechanism of High Mobility Group Box-1 Protein on Immune Cells in Inflammatory Diseases

High mobility group box-1 protein (HMGB1), a member of the high mobility group protein superfamily, is an abundant and ubiquitously expressed nuclear protein. Intracellular HMGB1 is released by immune and necrotic cells and secreted HMGB1 activates a range of immune cells, contributing to the excessive release of inflammatory cytokines and promoting processes such as cell migration and adhesion. Moreover, HMGB1 is a typical damage-associated molecular pattern molecule that participates in various inflammatory and immune responses. In these ways, it plays a critical role in the pathophysiology of inflammatory diseases. Herein, we review the effects of HMGB1 on various immune cell types and describe the molecular mechanisms by which it contributes to the development of inflammatory disorders. Finally, we address the therapeutic potential of targeting HMGB1.

Association of High-Mobility Group Box-1 with Inflammationrelated Cytokines in the Aqueous Humor with Acute Primary Angle-Closure Eyes

AIM

The aim of this study was to measure the levels of High-mobility group box-1 (HMGB1) and inflammation-related cytokines in the aqueous humor of patients with acute primary angle-closure glaucoma (APAG) and age-related cataract eyes (ARC).

METHODS

Aqueous humor samples were obtained from 59 eyes of 59 Chinese subjects (APAG, 32 eyes; and ARC, 27eyes). The multiplex bead immunoassay technique was used to measure the levels of HMGB1 and IL-8, IL-6, G-CSF, MCP-3, VEGF, sVEGFR- 1, sVEFGR-2, TNF-α, PDGF, and IL-10 in aqueous. The data of Patients' demographics and preoperative intraocular pressure (IOP) were also collected for detailed analysis.

RESULTS

The APAG group showed significantly elevated concentrations of HMGB1, IL- 8, IL-6, G-CSF, VEGF, sVEGFR-1, and TNF-α than those in the ARC group. Aqueous HMGB1 level correlated significantly with IOP, IL-8, IL-6, G-CSF and sVEGFR-1 levels but not with age, TNF-α, or VEGF levels.

CONCLUSION

The aqueous level of HMGB1 is elevated in APAG and associated with aqueous level of inflammation-related cytokines, suggesting an association between elevated levels of HMGB1, APAC and certain inflammatory modulators which, of course, should lead to further investigations in order to demonstrate the cause and effect.

Metabolic Syndrome and Autophagy: Focus on HMGB1 Protein

Metabolic syndrome (MetS) affects the population worldwide and results from several factors such as genetic background, environment and lifestyle. In recent years, an interplay among autophagy, metabolism, and metabolic disorders has become apparent. Defects in the autophagy machinery are associated with the dysfunction of many tissues/organs regulating metabolism. Metabolic hormones and nutrients regulate, in turn, the autophagy mechanism. Autophagy is a housekeeping stress-induced degradation process that ensures cellular homeostasis. High mobility group box 1 (HMGB1) is a highly conserved nuclear protein with a nuclear and extracellular role that functions as an extracellular signaling molecule under specific conditions. Several studies have shown that HMGB1 is a critical regulator of autophagy. This mini-review focuses on the involvement of HMGB1 protein in the interplay between autophagy and MetS, emphasizing its potential role as a promising biomarker candidate for the early stage of MetS or disease's therapeutic target.

MiR-22-3p suppresses sepsis-induced acute kidney injury by targeting PTEN

Background: Septic acute kidney injury is considered as a severe and frequent complication that occurs during sepsis. The present study was performed to understand the role of miR-22-3p and its underlying mechanism in sepsis-induced acute kidney injury.

Methods: Rats were injected with adenovirus carrying miR-22-3p or miR-NC in the caudal vein before cecal ligation. Meanwhile, HK-2 cells were transfected with the above adenovirus following LPS stimulation. We measured the markers of renal injury (blood urea nitrogen (BUN), serum creatinine (SCR)). Histological changes in kidney tissues were examined by hematoxylin and eosin (H&E), Masson staining, periodic acid Schiff staining and TUNEL staining. The levels of IL-1β, IL-6, TNF-α and NO were determined by ELISA assay. Using TargetScan prediction and luciferase reporter assay, we predicted and validated the association between PTEN and miR-22-3p.

Results: Our data showed that miR-22-3p was significantly down-regulated in a rat model of sepsis-induced acute kidney injury, in vivo and LPS-induced sepsis model in HK-2 cells, in vitro. Overexpression of miR-22-3p remarkably suppressed the inflammatory response and apoptosis via down-regulating HMGB1, p-p65, TLR4 and pro-inflammatory factors (IL-1β, IL-6, TNF-α and NO), both in vivo and in vitro. Moreover, PTEN was identified as a target of miR-22-3p. Furthermore, PTEN knockdown augmented, while overexpression reversed the suppressive role of miR-22-3p in LPS-induced inflammatory response.

Conclusions: Our results showed that miR-22-3p induced protective role in sepsis-induced acute kidney injury may rely on the repression of PTEN.

The Immune Tolerance Role of the HMGB1-RAGE Axis

The disruption of the immune tolerance induces autoimmunity such as systemic lupus erythematosus and vasculitis. A chromatin-binding non-histone protein, high mobility group box 1 (HMGB1), is released from the nucleus to the extracellular milieu in particular environments such as autoimmunity, sepsis and hypoxia. Extracellular HMGB1 engages pattern recognition receptors, including Toll-like receptors (TLRs) and the receptor for advanced glycation endproducts (RAGE). While the HMGB1-RAGE axis drives inflammation in various diseases, recent studies also focus on the anti-inflammatory effects of HMGB1 and RAGE. This review discusses current perspectives on HMGB1 and RAGE’s roles in controlling inflammation and immune tolerance. We also suggest how RAGE heterodimers responding microenvironments functions in immune responses.