HMGB1 and leukocyte migration during trauma and sterile inflammation

May high mobility group box protein-1 be a biomarker for major depressive disorder?

High Mobility Group Box Protein-1 (HMGB1), which has proinflammatory properties, is known to be involved in psychiatric disorders as far as we know, there are only one clinical studies investigating the role of HMGB1 in major depressive disorder (MDD). In this study, we aimed to investigate the role of HMGB1 in the etiopathogenesis of MDD and whether HMGB1 can be used as a biomarker in MDD by measuring the serum HMGB1 levels of depressed patients in the episode and remission periods. This study included 30 patients diagnosed with MDD in episode, 30 patients in remission and 30 healthy controls. Each group comprised 20 female and 10 male participants. In this study, serum HMGB1 levels were found to be lower in the patient group in the episode compared to the patient group in the remission period and the healthy control group. There was no significant difference between the patient group in remission and the healthy control group in terms of serum HMGB1 levels. The fact that serum HMGB1 levels were lower in the patient group in the episode compared to the patient group in the remission period and the control group may be related to the neuroprotective effects of HMGB1. HMGB1 may be used as a biomarker for MDD.

The influence of sex on neuroimmune communication, pain, and physiology

With the National Institutes of Health's mandate to consider sex as a biological variable (SABV), there has been a significant increase of studies utilizing both sexes. Historically, we have known that biological sex and hormones influence immunological processes and now studies focusing on interactions between the immune, endocrine, and nervous systems are revealing sex differences that influence pain behavior and various molecular and biochemical processes. Neuroendocrine-immune interactions represent a key integrative discipline that will reveal critical processes in each field as it pertains to novel mechanisms in sex differences and necessary therapeutics. Here we appraise preclinical and clinical literature to discuss these interactions and key pathways that drive cell- and sex-specific differences in immunity, pain, and physiology.

High mobility group box-1 protein promotes astrocytic CCL5 production through the MAPK/NF-κB pathway following spinal cord injury

Astrocytes act as immune cells that can produce a series of chemokines to attract large numbers of leucocytes to the lesion site, where they contribute to excessive inflammation following spinal cord injury (SCI). However, the relevant regulatory mechanism involved in chemokine production by astrocytes has not been fully elucidated. In the present study, we examined the correlation between C-C motif chemokine ligand 5 (CCL5) and high mobility group box-1 protein (HMGB1) in a T8-T10 spinal cord contusion model. Our results revealed that SCI-induced CCL5 protein levels increased synchronously with the increase in HMGB1. Administration of an HMGB1-neutralizing antibody significantly reduced the protein expression of CCL5 in the context of SCI. An in vitro study revealed that HMGB1 binding with TLR2/4 receptors potently facilitates the production of CCL5 by astrocytes by activating the intracellular ERK/JNK-mediated NF-κB pathway. Furthermore, the HMGB1-induced release of CCL5 from astrocytes is involved in promoting microglia/macrophage accumulation and M1 polarization. The inhibition of HMGB1 activity reduces microglia/macrophage infiltration by decreasing the expression of CCL5 and improves motor functional recovery following SCI. Our results provide insights into the new functions of HMGB1-mediated astrocytic CCL5 production, which elicits inflammatory cell recruitment to the site of injury; this recruitment is associated with excessive inflammation activation. These data may provide a new therapeutic strategy for central nervous system (CNS) inflammation.

Metformin lotion promotes scarless skin tissue formation through AMPK activation, TGF-β1 inhibition, and reduced myofibroblast numbers

Scar tissue formation following skin wound healing is a challenging public health problem. Skin regeneration and preventing the formation of scar tissue by currently available commercial products are largely ineffective. This study aimed to test the efficacy of a novel topical metformin lotion (ML) in inhibiting scar tissue formation during skin wound healing in rats and to determine the mechanisms of action involved. A 6% ML was prepared in our laboratory. A skin wound healing model in rats was used. The wounded rats were divided into two groups and treated daily for 10 days as follows: Group 1 received a daily application of 50 mg of control lotion, or 0% ML (totaling 100 mg of lotion per rat), and Group 2 received a daily application of 50 mg of 6% ML (totaling 100 mg of 6% ML per rat). Blood samples from the heart of each rat were analyzed for inflammatory markers, HMGB1 and IL-1β, using ELISA, and immunological and histological analyses were performed on skin tissue sections. ML decreased levels of inflammatory markers HMGB1 and IL-1β in the serum of rats and inhibited the release of HMGB1 from cell nuclei into the skin tissue matrix. Additionally, ML demonstrated anti-fibrotic properties by enhancing AMPK activity, decreasing the expression of TGF-β1, reducing the number of myofibroblasts, decreasing the production of collagen III, and increasing the expression of collagen I. ML promotes the regeneration of high-quality skin during wound healing by reducing scar tissue formation. This effect is mediated through the activation of AMPK, inhibition of TGF-β1, and a decrease in the number of myofibroblasts.

Alcohol, HMGB1, and Innate Immune Signaling in the Brain

PURPOSE

Binge drinking (i.e., consuming enough alcohol to achieve a blood ethanol concentration of 80 mg/dL, approximately 4-5 drinks within 2 hours), particularly in early adolescence, can promote progressive increases in alcohol drinking and alcohol-related problems that develop into compulsive use in the chronic relapsing disease, alcohol use disorder (AUD). Over the past decade, neuroimmune signaling has been discovered to contribute to alcohol-induced changes in drinking, mood, and neurodegeneration. This review presents a mechanistic hypothesis supporting high mobility group box protein 1 (HMGB1) and Toll-like receptor (TLR) signaling as key elements of alcohol-induced neuroimmune signaling across glia and neurons, which shifts gene transcription and synapses, altering neuronal networks that contribute to the development of AUD. This hypothesis may help guide further research on prevention and treatment.

SEARCH METHODS

The authors used the search terms "HMGB1 protein," "alcohol," and "brain" across PubMed, Scopus, and Embase to find articles published between 1991 and 2023.

SEARCH RESULTS

The database search found 54 references in PubMed, 47 in Scopus, and 105 in Embase. A total of about 100 articles were included.

DISCUSSION AND CONCLUSIONS

In the brain, immune signaling molecules play a role in normal development that differs from their functions in inflammation and the immune response, although cellular receptors and signaling are shared. In adults, pro-inflammatory signals have emerged as contributing to brain adaptation in stress, depression, AUD, and neurodegenerative diseases. HMGB1, a cytokine-like signaling protein released from activated cells, including neurons, is hypothesized to activate pro-inflammatory signals through TLRs that contribute to adaptations to binge and chronic heavy drinking. HMGB1 alone and in heteromers with other molecules activates TLRs and other immune receptors that spread signaling across neurons and glia. Both blood and brain levels of HMGB1 increase with ethanol exposure. In rats, an adolescent intermittent ethanol (AIE) binge drinking model persistently increases brain HMGB1 and its receptors; alters microglia, forebrain cholinergic neurons, and neuronal networks; and increases alcohol drinking and anxiety while disrupting cognition. Studies of human postmortem AUD brain have found elevated levels of HMGB1 and TLRs. These signals reduce cholinergic neurons, whereas microglia, the brain's immune cells, are activated by binge drinking. Microglia regulate synapses through complement proteins that can change networks affected by AIE that increase drinking, contributing to risks for AUD. Anti-inflammatory drugs, exercise, cholinesterase inhibitors, and histone deacetylase epigenetic inhibitors prevent and reverse the AIE-induced pathology. Further, HMGB1 antagonists and other anti-inflammatory treatments may provide new therapies for alcohol misuse and AUD. Collectively, these findings suggest that restoring the innate immune signaling balance is central to recovering from alcohol-related pathology.

Gadolinium-Based NMR Spin Relaxation Measurements of Near-Surface Electrostatic Potentials of Biomolecules

NMR spectroscopy is an important tool for the measurement of the electrostatic properties of biomolecules. To this point, paramagnetic relaxation enhancements (PREs) of 1H nuclei arising from nitroxide cosolutes in biomolecular solutions have been used to measure effective near-surface electrostatic potentials (ϕENS) of proteins and nucleic acids. Here, we present a gadolinium (Gd)-based NMR method, exploiting Gd chelates with different net charges, for measuring ϕENS values and demonstrate its utility through applications to a number of biomolecular systems. The use of Gd-based cosolutes offers several advantages over nitroxides for ϕENS measurements. First, unlike nitroxide compounds, Gd chelates enable electrostatic potential measurements on oxidation-sensitive proteins that require reducing agents. Second, the large electron spin quantum number of Gd (7/2) results in notably larger PREs for Gd chelates when used at the same concentrations as nitroxide radicals. Thus, it is possible to measure ϕENS values exclusively from + and - charged compounds even for highly charged biomolecules, avoiding the use of neutral cosolutes that, as we further establish here, limits the accuracy of the measured electrostatic potentials. In addition, the smaller concentrations of cosolutes required minimize potential binding to sites on macromolecules. Fourth, the closer proximity of the paramagnetic center and charged groups within Gd chelates, in comparison to the corresponding nitroxide compounds, enables more accurate predictions of ϕENS potentials for cross-validation of the experimental results. The Gd-based method described here, thus, broadens the applicability of studies of biomolecular electrostatics using solution NMR spectroscopy.

Phosphorylation by Protein Kinase C Weakens DNA-Binding Affinity and Folding Stability of the HMGB1 Protein

The HMGB1 protein typically serves as a DNA chaperone that assists DNA-repair enzymes and transcription factors but can translocate from the nucleus to the cytoplasm or even to extracellular space upon some cellular stimuli. One of the factors that triggers the translocation of HMGB1 is its phosphorylation near a nuclear localization sequence by protein kinase C (PKC), although the exact modification sites on HMGB1 remain ambiguous. In this study, using spectroscopic methods, we investigated the HMGB1 phosphorylation and its impact on the molecular properties of the HMGB1 protein. Our nuclear magnetic resonance (NMR) data on the full-length HMGB1 protein showed that PKC specifically phosphorylates the A-box domain, one of the DNA binding domains of HMGB1. Phosphorylation of S46 and S53 was particularly efficient. Over a longer reaction time, PKC phosphorylated some additional residues within the HMGB1 A-box domain. Our fluorescence-based binding assays showed that the phosphorylation significantly reduces the binding affinity of HMGB1 for DNA. Based on the crystal structures of HMGB1-DNA complexes, this effect can be ascribed to electrostatic repulsion between the negatively charged phosphate groups at the S46 side chain and DNA backbone. Our data also showed that the phosphorylation destabilizes the folding of the A-box domain. Thus, phosphorylation by PKC weakens the DNA-binding affinity and folding stability of HMGB1.

Epigenetic regulation of microglia and neurons by proinflammatory signaling following adolescent intermittent ethanol (AIE) exposure and in human AUD

Adolescent alcohol drinking is linked to high rates of adult alcohol problems and alcohol use disorder (AUD). The Neurobiology of Alcohol Drinking in Adulthood (NADIA) consortium adolescent intermittent ethanol (AIE) models adolescent binge drinking, followed by abstinent maturation to adulthood to determine the persistent AIE changes in neurobiology and behavior. AIE increases adult alcohol drinking and preference, increases anxiety and reward seeking, and disrupts sleep and cognition, all risks for AUD. In addition, AIE induces changes in neuroimmune gene expression in neurons and glia that alter neurocircuitry and behavior. HMGB1 is a unique neuroimmune signal released from neurons and glia by ethanol that activates multiple proinflammatory receptors, including Toll-like receptors (TLRs), that spread proinflammatory gene induction. HMGB1 expression is increased by AIE in rat brain and in post-mortem human AUD brain, where it correlates with lifetime alcohol consumption. HMGB1 activation of TLR increase TLR expression. Human AUD brain and rat brain following AIE show increases in multiple TLRs. Brain regional differences in neurotransmitters and cell types impact ethanol responses and neuroimmune gene induction. Microglia are monocyte-like cells that provide trophic and synaptic functions, that ethanol proinflammatory signals sensitize or "prime" during repeated drinking cycles, impacting neurocircuitry. Neurocircuits are differently impacted dependent upon neuronal-glial signaling. Acetylcholine is an anti-inflammatory neurotransmitter. AIE increases HMGB1-TLR4 signaling in forebrain, reducing cholinergic neurons by silencing multiple cholinergic defining genes through upregulation of RE-1 silencing factor (REST), a transcription inhibitor known to regulate neuronal differentiation. HMGB1 REST induction reduces cholinergic neurons in basal forebrain and cholinergic innervation of hippocampus. Adult brain hippocampal neurogenesis is regulated by a neurogenic niche formed from multiple cells. In vivo AIE and in vitro studies find ethanol increases HMGB1-TLR4 signaling and other proinflammatory signaling as well as reducing trophic factors, NGF, and BDNF, coincident with loss of the cholinergic synapse marker vChAT. These changes in gene expression-transcriptomes result in reduced adult neurogenesis. Excitingly, HMGB1 antagonists, anti-inflammatories, and epigenetic modifiers like histone deacetylase inhibitors restore trophic the neurogenesis. These findings suggest anti-inflammatory and epigenetic drugs should be considered for AUD therapy and may provide long-lasting reversal of psychopathology.

Downregulation of pattern recognition receptors on macrophages involved in aggravation of endometriosis

PROBLEM

In women of reproductive age, endometriosis may contribute to dysmenorrhea, chronic pelvic pain, dyspareunia, infertility, adenomyosis, and endometrial ovarian cyst (EOC). Recent studies have shown that chronic inflammation occurs in the pelvis of endometriosis patients and that this inflammation is exacerbated by immunosuppression, leading to survival endometrial debris. However, the detailed immunological mechanisms underlying the aggravation of inflammation and immunosuppression in endometriosis patients remain unclear.

METHOD OF STUDY

We investigate the alarmins (high-mobility group box-1, IL-33, IL-1α, and S100B protein), proinflammatory cytokines (IL-6 and IL-1β), and immune cells (CD8+ T cells, CD4+ T cells, natural killer cells, natural killer T cells, dendritic cells, and macrophages) in peritoneal fluid of patients with EOC using enzyme-linked immunosorbent assay, electrochemiluminescence, and flow cytometry. Then, we analyzed the correlation between these factors and the aggravating indicators of endometriosis, tumor size and revised American Society for Reproductive Medicine (r-ASRM) score.

RESULTS

Unexpectedly, there was no correlation between each alarmin level and aggravating indicators. However, the expression of pattern recognition receptors, toll-like receptor 4, and receptor of advanced glycation end-products on macrophages was inversely correlated with aggravating indicators.

CONCLUSIONS

The aggravation of endometriosis is associated with a decrease in alarmin receptors but not alarmin levels. Investigation of innate immune systems, such as alarmins and their receptors, may help elucidate new mechanisms of endometriosis.

Mitigating Scar Tissue Formation in Tendon Injuries: Targeting HMGB1, AMPK Activation, and Myofibroblast Migration All at Once

Tendon injuries, while prevalent, present significant challenges regarding their structural and functional restoration. Utilizing alpha-smooth muscle actin (α-SMA)-Ai9-scleraxis (Scx)-green fluorescent protein (GFP) transgenic mice, which exhibit both Scx (a tendon cell marker) and α-SMA (a myofibroblast marker), we explored the effects of metformin (Met) on tendon healing, repair, and its mechanisms of action. Our findings revealed that intraperitoneal (IP) injections of Met, administered before or after injury, as well as both, effectively prevented the release of HMGB1 into the tendon matrix and reduced circulating levels of HMGB1. Additionally, Met treatment increased and activated AMPK and suppressed TGF-β1 levels within the healing tendon. Tendon healing was also improved by blocking the migration of α-SMA+ myofibroblasts, reducing the prevalence of disorganized collagen fibers and collagen type III. It also enhanced the presence of collagen type I. These outcomes highlight Met's anti-fibrotic properties in acutely injured tendons and suggest its potential for repurposing as a therapeutic agent to minimize scar tissue formation in tendon injuries, which could have profound implications in clinical practice.

Perish in the Attempt: Regulated Cell Death in Regenerative and Nonregenerative Tissue

Significance: A cell plays its roles throughout its life span, even during its demise. Regulated cell death (RCD) is one of the key topics in modern biomedical studies. It is considered the main approach for removing stressed and/or damaged cells. Research during the past two decades revealed more roles of RCD, such as coordinating tissue development and driving compensatory proliferation during tissue repair. Recent Advances: Compensatory proliferation, initially identified in primitive organisms during the regeneration of lost tissue, is an evolutionarily conserved process that also functions in mammals. Among various types of RCD, apoptosis is considered the top candidate to induce compensatory proliferation in damaged tissue. Critical Issues: The roles of apoptosis in the recovery of nonregenerative tissue are still vague. The roles of other types of RCD, such as necroptosis and ferroptosis, have not been well characterized in the context of tissue regeneration. Future Directions: In this review article, we attempt to summarize the recent insights on the role of RCD in tissue repair. We focus on apoptosis, with expansion to ferroptosis and necroptosis, in primitive organisms with significant regenerative capacity as well as common mammalian research models. After gathering hints from regenerative tissue, in the second half of the review, we take a notoriously nonregenerative tissue, the myocardium, as an example to discuss the role of RCD in terminally differentiated quiescent cells. Antioxid. Redox Signal. 39, 1053-1069.

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.

Cisplatin Dependent Secretion of Immunomodulatory High Mobility Group Box 1 (HMGB1) Protein from Lung Cancer Cells

High mobility group box 1 (HMGB1) is secreted from activated immune cells, necrotic cells, and certain cancers. Previous studies have reported that different patterns of post-translational modification, particularly acetylation and oxidation, mediate HMGB1 release and confer distinct extracellular HMGB1 signaling activity. Here we report that cisplatin but not carboplatin induces secretion of HMGB1 from human A549 non-small cell lung cancer (NSCLC) cells. Cisplatin-mediated HMGB1 secretion was dose-dependent and was regulated by nuclear exportin 1 (XPO1) also known as chromosomal maintenance 1 (CRM1) rather than adenosine diphosphate (ADP)-ribosylation, acetylation, or oxidation. HMGB1, as well as lysine acetylation and cysteine disulfide oxidation of secreted HMGB1, were monitored by sensitive and specific assays using immunoprecipitation, stable isotope dilution, differential alkylation, and nano liquid chromatography parallel reaction monitoring/high-resolution mass spectrometry (nano-LC-PRM/HRMS). A major fraction of the HMGB1 secreted by low-dose cisplatin treatment of A549 NSCLC cells was found to be in the fully reduced form. In contrast, mainly oxidized forms of HMGB1 were secreted by dimethyl sulfoxide (DMSO)-mediated apoptosis. These findings suggest that inhibition of XPO1 could potentiate the anti-tumor activity of cisplatin by increasing the nuclear accumulation of HMGB1 protein, an inhibitor of cisplatin DNA-adduct repair. Furthermore, low-dose cisplatin therapy could modulate the immune response in NSCLC through the established chemokine activity of extracellular reduced HMGB1. This could potentially enhance the efficacy of subsequent immunotherapy treatment.

HMGB1: a double-edged sword and therapeutic target in the female reproductive system

HMGB1 that belongs to the High Mobility Group-box superfamily, is a nonhistone chromatin associated transcription factor. It is present in the nucleus of eukaryotes and can be actively secreted or passively released by kinds of cells. HMGB1 is important for maintaining DNA structure by binding to DNA and histones, protecting it from damage. It also regulates the interaction between histones and DNA, affecting chromatin packaging, and can influence gene expression by promoting nucleosome sliding. And as a DAMP, HMGB1 binding to RAGE and TLRs activates NF-κB, which triggers the expression of downstream genes like IL-18, IL-1β, and TNF-α. HMGB1 is known to be involved in numerous physiological and pathological processes. Recent studies have demonstrated the significance of HMGB1 as DAMPs in the female reproductive system. These findings have shed light on the potential role of HMGB1 in the pathogenesis of diseases in female reproductive system and the possibilities of HMGB1-targeted therapies for treating them. Such therapies can help reduce inflammation and metabolic dysfunction and alleviate the symptoms of reproductive system diseases. Overall, the identification of HMGB1 as a key player in disease of the female reproductive system represents a significant breakthrough in our understanding of these conditions and presents exciting opportunities for the development of novel therapies.

PARP1 Inhibition and Effect on Burn Injury-Induced Inflammatory Response and Cardiac Function

BACKGROUND

Burn injury induces multiple signaling pathways leading to a significant inflammatory storm that adversely affects multiple organs, including the heart. Poly (ADP-ribose) polymerase inhibitor 1 (PARP1) inhibition, with specific agents such as N-(5,6-Dihydro-6-oxo-2-phenanthridinyl)-2-acetamide (PJ34), is effective in reducing oxidative stress and cytokine expression in the heart. We hypothesized that PARP1 inhibition would reduce inflammatory signaling and protect against burn injury-induced cardiac dysfunction.

STUDY DESIGN

Male Sprague-Dawley rats (8 weeks old, 300 to 350 g) were randomly assigned to sham injury (Sham), 60% total body surface area burn (24 hours post burn), or 60% total body surface area burn with intraperitoneal administration of PJ34 (20 mg/kg, 24 hours post burn + PJ34) and sacrificed 24 hours after injury. Cardiac function was determined using Vevo 2100 echocardiography. Genetic expression of 84 specific toll-like receptor-mediated signal transduction and innate immunity genes were examined using microarray to evaluate cardiac tissue. Qiagen GeneGlobe Data Analysis Center was used to analyze expression, and genetic clustering was performed using TreeView V2.0.8 software. Real-time quantitative polymerase chain reaction was used to validate identified differentially expressed genes.

RESULTS

Burn injury significantly altered multiple genes in the toll-like receptor signaling, interleukin-17 signaling, tumor necrosis factor signaling, and nuclear factor-κB signaling pathways and led to significant cardiac dysfunction. PARP1 inhibition with PJ34 normalized these signaling pathways to sham levels as well as improved cardiac function to sham levels.

CONCLUSIONS

PARP1 inhibition normalizes multiple inflammatory pathways that are altered after burn injury and improves cardiac dysfunction. PARP1 pathway inhibition may provide a novel methodology to normalize multiple burn injury-induced inflammatory pathways in the heart.

Targeting circulating high mobility group box-1 and histones by extracorporeal blood purification as an immunomodulation strategy against critical illnesses

Both high mobility group box-1 (HMGB1) and histones are major damage-associated molecular patterns (DAPMs) that mediate lethal systemic inflammation, activation of the complement and coagulation system, endothelial injury and multiple organ dysfunction syndrome in critical illnesses. Although accumulating evidence collectively shows that targeting HMGB1 or histones by their specific antibodies or inhibitors could significantly mitigate aberrant immune responses in multiple critically ill animal models, routine clinical use of such agents is still not recommended by any guideline. In contrast, extracorporeal blood purification, which has been widely used to replace dysfunctional organs and remove exogenous or endogenous toxins in intensive care units, may also exert an immunomodulatory effect by eliminating inflammatory mediators such as cytokines, endotoxin, HMGB1 and histones in patients with critical illnesses. In this review, we summarize the multiple immunopathological roles of HMGB1 and histones in mediating inflammation, immune thrombosis and organ dysfunction and discuss the rationale for the removal of these DAMPs using various hemofilters. The latest preclinical and clinical evidence for the use of extracorporeal blood purification to improve the clinical outcome of critically ill patients by targeting circulating HMGB1 and histones is also gathered.

Co-Targeting IL-6 and EGFR signaling for the treatment of schwannomatosis and associated pain

Patients with Schwannomatosis (SWN) overwhelmingly present with intractable, debilitating chronic pain. There are no effective therapies to treat SWN. The drivers of pain response and tumor progression in SWN are not clear. The pain is not proportionally linked to tumor size and is not always relieved by tumor resection, suggesting that mechanisms other than mechanical nerve compression exist to cause pain. SWN research is limited by the lack of clinically-relevant models. Here, we established novel patient-derived xenograft (PDX) models, dorsal root ganglia (DRG) imaging model, and combined with single-cell resolution intravital imaging and RNASeq, we discovered: i) schwannomas on the peripheral nerve cause macrophage influx into the DRG, via secreting HMGB1 to directly stimulate DRG neurons to express CCL2, the key macrophage chemokine, ii) once recruited, macrophages cause pain response via overproduction of IL-6, iii) IL-6 blockade in a therapeutic setting significantly reduces pain but has modest efficacy on tumor growth, iv) EGF signaling is a potential driver of schwannoma growth and escape mechanism from anti-IL6 treatment, and v) combined IL-6 and EGFR blockade simultaneously controlled pain and tumor growth in SWN models. Our findings prompted the initiation of phase II clinical trial ( NCT05684692 ) for pain relief in patients with SWN.

High Mobility Group Box 1 as an Autocrine Chemoattractant for Oligodendrocyte Lineage Cells in White Matter Stroke

BACKGROUND

The migration of oligodendrocyte precursor cells (OPC) is a key process of remyelination, which is essential for the treatment of white matter stroke. This study aimed to investigate the role of HMGB1 (high mobility group box 1), a damage-associated molecular pattern released from dying oligodendrocytes, as an autocrine chemoattractant that promotes OPC migration.

METHODS

The migratory capacity of primary cultured OPCs was measured using the Boyden chamber assay. The downstream pathway of HMGB1-mediated OPC migration was specified by siRNA-induced knockdown or pharmacological blockade of TLR2 (toll-like receptor 2), RAGE (receptor for advanced glycation end product), Src, ERK1/2 (extracellular signal-regulated kinase1/2), and FAK (focal adhesion kinase). Conditioned media were collected from oxygen-glucose deprivation-treated oligodendrocytes, and the impact on OPC migration was assessed. Lesion size and number of intralesional Olig2(+) cells were analyzed in an in vivo model of white matter stroke with N5-(1-iminoethyl)-L-ornithine (L-NIO).

RESULTS

HMGB1 treatment promoted OPC migration. HMGB1 antagonism reversed such effects to untreated levels. Among the candidates for the downstream signal of HMGB1-mediated migration, the knockdown of TLR2 rather than that of RAGE attenuated the migration-promoting effect of HMGB1. Further specification of the HMGB1-TLR2 axis revealed that the phosphorylation of ERK1/2 and its downstream molecule FAK, rather than of Src, was decreased in TLR2-knockdown OPCs, and pharmacological inhibition of ERK1/2 and FAK led to decreased OPC migration. Oxygen-glucose deprivation-conditioned media promoted OPC migration, suggesting the autocrine chemoattractant function of HMGB1. In vivo, TLR2(-/-)-mice showed lesser intralesional Olig2(+) cells compared to wild-type controls in response to L-NIO induced ischemic injury regardless of HMGB1 administration.

CONCLUSIONS

HMGB1, through the TLR2-ERK1/2-FAK axis, functions as an autocrine chemoattractant to promote OPC migration, which is an initial and indispensable step in remyelination. Thus, a novel treatment strategy for white matter stroke based on the HMGB1-TLR2 axis in the oligodendrocyte lineage could be feasible.

BMP-7 Attenuates Sarcopenia and Adverse Muscle Remodeling in Diabetic Mice via Alleviation of Lipids, Inflammation, HMGB1, and Pyroptosis

Diabetic myopathy involves hyperglycemia, oxidative stress, and inflammation. However, the role of hypercholesterolemia-induced inflammation-mediated pathological mechanisms leading to fibrosis, sarcopenia, deterioration of muscle, and muscle dysfunction in diabetes is not well understood. In this study, we investigated the novel role of bone morphogenetic protein-7 (BMP-7) in ameliorating metabolic alterations, inflammation, pyroptosis, TGF-β/SMAD cell signaling mechanisms, and progression of diabetic myopathy. C57BL/6J mice were treated with saline, streptozotocin (STZ), or STZ+BMP-7. Diabetes was confirmed by increased fasting glucose levels and a glucose tolerance test. Gastrocnemius muscle and blood samples were collected for lipid and tissue analysis using various methods. A significant increase in hyperglycemia resulted in an increase in lipid accumulation, monocyte infiltration, and inflammation, as well as an increase in pyroptotic markers and signaling markers in diabetic muscle myocytes. A structural analysis showed significant muscle loss, and increased muscle deterioration and fibrosis leading to muscle dysfunction. BMP-7 attenuated pathological processes that resulted in significantly improved muscle function. We report, for the first time, that increased hyperlipidemia aggravates inflammation-induced pyroptosis, resulting in significant muscle loss, sarcopenia, and adverse skeletal muscle remodeling in diabetic muscle myopathy. Interventional treatment with BMP-7 attenuates hypercholesterolemia-induced inflammation-mediated sarcopenia and adverse muscle remodeling, suggesting BMP-7 could be a potential treatment option for diabetic muscle myopathy.

HMGB1 is a Potential and Challenging Therapeutic Target for Parkinson's Disease

Parkinson's disease (PD) is one of the most common degenerative diseases of the human nervous system and has a wide range of serious impacts on human health and quality of life. Recently, research targeting high mobility group box 1 (HMGB1) in PD has emerged, and a variety of laboratory methods for inhibiting HMGB1 have achieved good results to a certain extent. However, given that HMGB1 undergoes a variety of intracellular modifications and three different forms of extracellular redox, the possible roles of these forms in PD are likely to be different. General inhibition of all forms of HMGB1 is obviously not ideal and has become one of the biggest obstacles in the clinical application of targeting HMGB1. In this review, pure mechanistic research of HMGB1 and in vivo research targeting HMGB1 were combined, the effects of HMGB1 on neurons and immune cell responses in PD are discussed in detail, and the problems that need to be focused on in the future are addressed.

Inflammation in preterm birth: Novel mechanism of preterm birth associated with innate and acquired immunity

Preterm birth (PB) is the most-frequent complication occurring during pregnancy, with a significant impact on neonatal morbidity and mortality. Chorioamnionitis (CAM), the neutrophil infiltration into chorioamniotic membranes, is a major cause of PB. However, several cases of PB have also been reported without apparent pathogenic infection or CAM. Such cases are now attributed to "sterile inflammation." The concept of sterile inflammation has already attracted attention in various diseases, like cardiovascular diseases, diabetes, and autoimmune diseases; recently been discussed for obstetric complications such as miscarriage, PB, gestational hypertension, and gestational diabetes. Sterile inflammation is induced by alarmins, such as high-mobility group box 1 (HMGB1), interleukins (IL-33 and IL-1α), and S100 proteins, that are released by cellular damage without apparent pathogenic infection. These antigens are recognized by pattern-recognition receptors, expressed mainly on antigen-presenting cells of decidua, placenta, amnion, and myometrium, which consequently trigger inflammation. In reproduction, these alarmins are associated with the development of various pregnancy complications, including PB. In this review, we have summarized the development of PB related to acute CAM, chronic CAM, and sterile inflammation as well as proposed a new mechanism for PB that involves innate immunity, acquired immunity, and sterile inflammation.

Cytokine Pathways in Cardiac Dysfunction following Burn Injury and Changes in Genome Expression

In 2016, an estimated 486,000 individuals sustained burn injuries requiring medical attention. Severe burn injuries lead to a persistent, hyperinflammatory response that may last up to 2 years. The persistent release of inflammatory mediators contributes to end-organ dysfunction and changes in genome expression. Burn-induced cardiac dysfunction may lead to heart failure and changes in cardiac remodeling. Cytokines promote the inflammatory cascade and promulgate mechanisms resulting in cardiac dysfunction. Here, we review the mechanisms by which TNFα, IL-1 beta, IL-6, and IL-10 cause cardiac dysfunction in post-burn injuries. We additionally review changes in the cytokine transcriptome caused by inflammation and burn injuries.

The role of HMGB1/RAGE/TLR4 signaling pathways in cigarette smoke-induced inflammation in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common chronic respiratory disease with irreversible and continuous progression. It has become the fifth most burdensome disease and the third most deadly disease globally. Therefore, the prevention and treatment of COPD are urgent, and it is also important to clarify the pathogenesis of it. Smoking is the main and most common risk factor for COPD. Cigarette smoke (CS) can cause lung inflammation and other pathological mechanisms in the airways and lung tissue. Airway inflammation is one of the important mechanisms leading to the pathogenesis of COPD. Recent studies have shown that high mobility group box 1 (HMGB1) is involved in the occurrence and development of respiratory diseases, including COPD. HMGB1 is a typical damage-associated molecular pattern (DAMP) protein, which mainly exerts its activity by binding to the receptor for advanced glycation end products (RAGE) and toll-like receptor 4 (TLR4) and further participate in the process of airway inflammation. Studies have shown that the abnormal expression of HMGB1, RAGE, and TLR4 are related to inflammation in COPD. Herein, we discuss the roles of HMGB1, RAGE, and TLR4 in CS/cigarette smoke extract-induced inflammation in COPD, providing a new target for the diagnosis, treatment and prevention of COPD.

α-Iso-cubebene attenuates neointima formation by inhibiting HMGB1-induced monocyte to macrophage differentiation via suppressing ROS production

α-Iso-cubebene (ICB) is a dibenzocyclooctadiene lignin contained in Schisandra chinensis, a medicinal herb used to improve cardiovascular symptoms. To investigate the mechanisms involved, the effects of ICB on cellular production of reactive oxygen species (ROS) was determined using cultured human THP-1 cells. When THP-1 cells were stimulated with HMGB1, cellular concentration of ROS was increased in dose- and time-dependent manners. These increases were significantly attenuated in cells pretreated with NADPH oxidase inhibitors, diphenyleneiodonium chloride and apocynin, but not by other inhibitors related to ROS generation in monocytes. The expression of constitutively expressed NADPH oxidase (NOX) subunits including NOX1, NOX2, NOX4 and NOX5 was not affected by HMGB1, but HMGB1-induced ROS production was exclusively attenuated in NOX2-deficient cells using siRNA, suggesting an enhanced NOX2 complex assembly. When cells were stimulated with HMGB1, p47phox phosphorylation at ser345, ser359 and ser370 was increased in dose- and time-dependent manners, which were significantly attenuated in ICB (3-10 μg/mL)-pretreated cells. In addition, HMGB1-induced monocyte-macrophage differentiation (MMD) in bone marrow-derived cells isolated from mice were significantly attenuated in cells treated with apocynin and ICB. Also, macrophage infiltration and intimal hyperplasia in the wire-injured femoral artery were significantly attenuated in ICB-treated mice compared to wild-type control mice. The results of this study show that ICB inhibits HMGB1-induced MMD by suppressing ROS production in monocytes, thus suggest that ICB has therapeutic potential for vascular inflammation with subsequent intimal hyperplasia related to vascular injury.

Molecular cloning and functional characterization of HMGB1 and HMGB2 in large yellow croaker Larimichthys crocea

High mobility group box 1 (HMGB1) and HMGB2 have been demonstrated to be key regulators not only in DNA recombination, replication, gene transcription, but also in host inflammation and immune responses. In the present study, orthologs of HMGB1 and HMGB2 named Lc-HMGB1 and Lc-HMGB2 were characterized in large yellow croaker (Larimichthys crocea). The ORFs of Lc-HMGB1 and Lc-HMGB2 are 621 bp and 648 bp, encoding proteins of 206 aa and 215 aa, with the putative Lc-HMGB1 and Lc-HMGB2 proteins both contain two HMG domains, respectively. The genome organizations of Lc-HMGB1 and Lc-HMGB2 are both composed of four exons and three introns, which are conserved in vertebrates. Lc-HMGB1 and Lc-HMGB2 were identified as cell nucleus localized proteins, and were ubiquitously distributed in the examined organs/tissues. Additionally, Lc-HMGB1 was significantly up-regulated under LPS and PGN stimulation, whereas the stimulation of poly I:C, LPS, PGN, and Pseudomonas plecoglossicida infection could significantly induce Lc-HMGB2 expression in vivo. Notably, both Lc-HMGB1 and Lc-HMGB2 overexpression could significantly up-regulated the expression of diverse immune-related genes, including IFN1, IRF3, ISG15, ISG56, RSAD2, g-type lysozyme, and TNF-α. Moreover, overexpression of Lc-HMGB1 could also induce the expression of IRF7 and Mx. These results collectively indicate that Lc-HMGB1 and Lc-HMGB2 play important roles in host immune responses against pathogen infection.

Regulation of Key Immune-Related Genes in the Heart Following Burn Injury

Immune cascade is one of major factors leading to cardiac dysfunction after burn injury. TLRs are a class of pattern-recognition receptors (PRRs) that initiate the innate immune response by sensing conserved molecular patterns for early immune recognition of a pathogen. The Rat Toll-Like Receptor (TLR) Signaling Pathway RT² Profiler PCR Array profiles the expression of 84 genes central to TLR-mediated signal transduction and innate immunity, and is a validated tool for identifying differentially expressed genes (DEGs). We employed the PCR array to identify burn-induced cardiac TLR-signaling-related DEGs. A total of 38 up-regulated DEGs and 19 down-regulated DEGs were identified. Network analysis determined that all DEGS had 10 clusters, while up-regulated DEGs had 6 clusters and down-regulated DEGs had 5 clusters. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were involved in TLR signaling, the RIG-I-Like receptor signaling pathway, the IL-17 signaling pathway, and the NFkB signaling pathway. Function analysis indicated that DEGs were associated with Toll-like receptor 2 binding, Lipopeptide binding, Toll-like receptor binding, and NAD(P)+ nucleosidase activity. The validation of 18 up-regulated DEGs (≥10-fold change) and 6 down-regulated DEGs (≤5-fold change) demonstrated that the PCR array is a trusted method for identifying DEGs. The analysis of validated DEG-derived protein–protein interaction networks will guide our future investigations. In summary, this study not only identified the TLR-signaling-pathway-related DEGs after burn injury, but also confirmed that the burn-induced cardiac cytokine cascade plays an important role in burn-induced heart dysfunction. The results will provide the novel therapeutic targets to protect the heart after burn injury.

The Fatal Circle of NETs and NET-Associated DAMPs Contributing to Organ Dysfunction

The innate immune system is the first line of defense against invading pathogens or sterile injuries. Pattern recognition receptors (PRR) sense molecules released from inflamed or damaged cells, or foreign molecules resulting from invading pathogens. PRRs can in turn induce inflammatory responses, comprising the generation of cytokines or chemokines, which further induce immune cell recruitment. Neutrophils represent an essential factor in the early immune response and fulfill numerous tasks to fight infection or heal injuries. The release of neutrophil extracellular traps (NETs) is part of it and was originally attributed to the capture and elimination of pathogens. In the last decade studies revealed a detrimental role of NETs during several diseases, often correlated with an exaggerated immune response. Overwhelming inflammation in single organs can induce remote organ damage, thereby further perpetuating release of inflammatory molecules. Here, we review recent findings regarding damage-associated molecular patterns (DAMPs) which are able to induce NET formation, as well as NET components known to act as DAMPs, generating a putative fatal circle of inflammation contributing to organ damage and sequentially occurring remote organ injury.

Endothelial Cell Phenotype, a Major Determinant of Venous Thrombo-Inflammation

Reduced blood flow velocity in the vein triggers inflammation and is associated with the release into the extracellular space of alarmins or damage-associated molecular patterns (DAMPs). These molecules include extracellular nucleic acids, extracellular purinergic nucleotides (ATP, ADP), cytokines and extracellular HMGB1. They are recognized as a danger signal by immune cells, platelets and endothelial cells. Hence, endothelial cells are capable of sensing environmental cues through a wide variety of receptors expressed at the plasma membrane. The endothelium is then responding by expressing pro-coagulant proteins, including tissue factor, and inflammatory molecules such as cytokines and chemokines involved in the recruitment and activation of platelets and leukocytes. This ultimately leads to thrombosis, which is an active pro-inflammatory process, tightly regulated, that needs to be properly resolved to avoid further vascular damages. These mechanisms are often dysregulated, which promote fibrinolysis defects, activation of the immune system and irreversible vascular damages further contributing to thrombotic and inflammatory processes. The concept of thrombo-inflammation is now widely used to describe the complex interactions between the coagulation and inflammation in various cardiovascular diseases. In endothelial cells, activating signals converge to multiple intracellular pathways leading to phenotypical changes turning them into inflammatory-like cells. Accumulating evidence suggest that endothelial to mesenchymal transition (EndMT) may be a major mechanism of endothelial dysfunction induced during inflammation and thrombosis. EndMT is a biological process where endothelial cells lose their endothelial characteristics and acquire mesenchymal markers and functions. Endothelial dysfunction might play a central role in orchestrating and amplifying thrombo-inflammation thought induction of EndMT processes. Mechanisms regulating endothelial dysfunction have been only partially uncovered in the context of thrombotic diseases. In the present review, we focus on the importance of the endothelial phenotype and discuss how endothelial plasticity may regulate the interplay between thrombosis and inflammation. We discuss how the endothelial cells are sensing and responding to environmental cues and contribute to thrombo-inflammation with a particular focus on venous thromboembolism (VTE). A better understanding of the precise mechanisms involved and the specific role of endothelial cells is needed to characterize VTE incidence and address the risk of recurrent VTE and its sequelae.

PDGFR-β signaling mediates HMGB1 release in mechanically stressed vascular smooth muscle cells

Mechanically stressed vascular smooth muscle cells (VSMCs) have potential roles in the development of vascular complications. However, the underlying mechanisms are unclear. Using VSMCs cultured from rat thoracic aorta explants, we investigated the effects of mechanical stretch (MS) on the cellular secretion of high mobility group box 1 (HMGB1), a major damage-associated molecular pattern that mediates vascular complications in stressed vasculature. Enzyme-linked immunosorbent assay (ELISA) demonstrated an increase in the secretion of HMGB1 in VSMCs stimulated with MS (0–3% strain, 60 cycles/min), and this secretion was markedly and time-dependently increased at 3% MS. The increased secretion of HMGB1 at 3% MS was accompanied by an increased cytosolic translocation of nuclear HMGB1; the acetylated and phosphorylated forms of this protein were significantly increased. Among various inhibitors of membrane receptors mediating mechanical signals, AG1295 (a platelet-derived growth factor receptor (PDGFR) inhibitor) attenuated MS-induced HMGB1 secretion. Inhibitors of other receptors, including epidermal growth factor, insulin-like growth factor, and fibroblast growth factor receptors, did not inhibit this secretion. Additionally, MS-induced HMGB1 secretion was markedly attenuated in PDGFR-β-deficient cells but not in cells transfected with PDGFR-α siRNA. Likewise, PDGF-DD, but not PDGF-AA, directly increased HMGB1 secretion in VSMCs, indicating a pivotal role of PDGFR-β signaling in the secretion of this protein in VSMCs. Thus, targeting PDGFR-β-mediated secretion of HMGB1 in VSMCs might be a promising therapeutic strategy for vascular complications associated with hypertension.

HMGB1 Inhibition to Ameliorate Organ Failure and Increase Survival in Trauma

Several preclinical and clinical reports have demonstrated that levels of circulating high mobility group box 1 protein (HMGB1) are increased early after trauma and are associated with systemic inflammation and clinical outcomes. However, the mechanisms of the interaction between HMGB1 and inflammatory mediators that lead to the development of remote organ damage after trauma remain obscure. HMGB1 and inflammatory mediators were analyzed in plasma from 54 combat casualties, collected on admission to a military hospital in Iraq, and at 8 and 24 h after admission. In total, 45 (83%) of these patients had traumatic brain injury (TBI). Nine healthy volunteers were enrolled as controls. HMGB1 plasma levels were significantly increased in the first 8 h after admission, and were found to be associated with systemic inflammatory responses, injury severity score, and presence of TBI. These data provided the rationale for designing experiments in rats subjected to blast injury and hemorrhage, to explore the effect of HMGB1 inhibition by CX-01 (2-O, 3-O desulfated heparin). Animals were cannulated, then recovered for 5–7 days before blast injury in a shock tube and volume-controlled hemorrhage. Blast injury and hemorrhage induced an early increase in HMGB1 plasma levels along with severe tissue damage and high mortality. CX-01 inhibited systemic HMGB1 activity, decreased local and systemic inflammatory responses, significantly reduced tissue and organ damage, and tended to increase survival. These data suggest that CX-01 has potential as an adjuvant treatment for traumatic hemorrhage.

Increased Frequency of Circulating Classical Monocytes in Patients with Rosacea

Purpose

Monocyte subsets, including classical, intermediate and non-classical monocytes, are involved in the pathogenesis of inflammatory or autoimmune diseases. The pathogenic role of monocytes in the peripheral blood mononuclear cells (PBMCs) of patients with rosacea remains unclear. This study aimed to assess frequencies of monocyte subsets in PBMCs from rosacea patients before and after clinical treatment.

Patients and Methods

We applied flow cytometry to examine frequencies of monocyte subsets in 116 patients with rosacea, while patients with 26 systemic lupus erythematosus (SLE), 28 acne and 42 normal healthy subjects without skin problems (HC) were recruited as controls. Expression of C–C chemokine receptor 2 (CCR2) on monocytes and plasma levels of CC-chemokine ligand 2 (CCL2), high mobility group box-1 (HMGB-1), interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) were measured in HC and rosacea patients before and after treatment.

Results

The frequency of classical monocytes, but not intermediate or non-classical monocytes, was higher in rosacea as compared with HC, which decreased after treatment. Frequencies of monocyte subsets showed no gender difference, while increased with age in patients but not in HC. Frequencies of classical monocytes in patients with erythematotelangiectatic rosacea (ETR) and ETR-papulopustular rosacea (PPR) overlap were significantly higher than HC or patients with only PPR or phymatous rosacea (PhR). There was a significant higher expression of CCR2 in classical monocytes, with higher plasma levels of CCL2, HMGB-1, IL-1β and TNF-α in patients than in HC, which all significantly decreased after treatment.

Conclusion

Our data indicated a possible association between abnormal classical monocytes frequencies and rosacea.

Damage-Associated Molecular Patterns As Double-Edged Swords in Sepsis

Significance: Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host response to infection. This leads to an uncontrolled inflammatory response at the onset of infection, followed by immunosuppression. The development of a specific treatment modality for sepsis is still challenging, reflecting our inadequate understanding of its pathophysiology. Understanding the mechanism and transition of the early hyperinflammation to late stage of immunosuppression in sepsis is critical for developing sepsis therapeutics. Recent Advances: Damage-associated molecular patterns (DAMPs) are intracellular molecules and released upon tissue injury and cell death in sepsis. DAMPs are recognized by pattern recognition receptors to initiate inflammatory cascades. DAMPs not only elicit an inflammatory response but also they subsequently induce immunosuppression, both are equally important for exacerbating sepsis. Recent advances on a new DAMP, extracellular cold-inducible RNA-binding protein for fueling inflammation and immunosuppression in sepsis, have added a new avenue into the dual functions of DAMPs in sepsis. Critical Issues: The molecular modification of DAMPs and their binding to pattern recognition receptors transit dynamically by the cellular environment in pathophysiologic conditions. Correlation between the dynamic changes of the impacts of DAMPs and the clinical outcomes in sepsis still lacks adequate understanding. Here, we focus on the impacts of DAMPs that cause inflammation as well as induce immunosuppression in sepsis. We further discuss the therapeutic potential by targeting DAMPs to attenuate inflammation and immunosuppression for mitigating sepsis. Future Directions: Uncovering pathways of the transition from inflammation to immunosuppression of DAMPs is a potential therapeutic avenue for mitigating sepsis.

Increased cell-free fetal DNA release after apoptosis and sterile inflammation in human trophoblast cells

PROBLEM

Cell-free fetal DNA (cffDNA) shed from the placenta can be detected in maternal blood and increases incrementally during gestation. Concentrations are further elevated with pregnancy complications. Specific activators of cffDNA release in such complications have not been identified. Here, we use trophoblast cells from early and term placenta to examine cffDNA release following apoptosis, infection, and sterile inflammatory stress.

METHOD OF STUDY

HTR8/SVneo cells were used to model first-trimester trophoblasts, and term cytotrophoblasts (CTBs) were isolated from placentae collected after uncomplicated deliveries. Trophoblasts were treated with varying concentrations of doxorubicin (DOX), lipopolysaccharide (LPS), or high-mobility group box protein 1 (HMGB1) for 18 h. Cells or supernatants were quantified for caspase-3/7 cleavage, pro-inflammatory cytokine secretion, and cffDNA release.

RESULTS

Both HTR8/SVneo and CTBs underwent caspase-3/7 cleavage following DOX treatment, with HTR8/SVneo cells more sensitive to apoptosis than term CTBs. Apoptotic cells released more cffDNA in a dose-dependent manner. Treatment with LPS resulted in an increase in pro-inflammatory IL-6 release, particularly in term CTBs compared to early trophoblasts; however, LPS did not affect cffDNA release. Lastly, while neither cell released more TNF-α following stimulation with HMGB1, both HTR8/SVneo and CTBs released significantly more cffDNA in the presence of HMGB1.

CONCLUSIONS

These data show that apoptosis and sterile inflammation induced by DOX and HMGB1, respectively, cause an increase in cffDNA concentrations in both first-trimester and term trophoblasts. Understanding physiologic release of cffDNA during healthy and complicated pregnancy can identify new targets for the diagnosis and treatment of gestational complications.

Caspase-Dependent HMGB1 Release from Macrophages Participates in Peripheral Neuropathy Caused by Bortezomib, a Proteasome-Inhibiting Chemotherapeutic Agent, in Mice

Given the role of macrophage-derived high mobility group box 1 (HMGB1) in chemotherapy-induced peripheral neuropathy (CIPN) caused by paclitaxel, we analyzed the role of HMGB1 and macrophages in the CIPN caused by bortezomib, a proteasome-inhibiting chemotherapeutic agent used for the treatment of multiple myeloma. Repeated administration of bortezomib caused CIPN accompanied by early-stage macrophage accumulation in the dorsal root ganglion. This CIPN was prevented by an anti-HMGB1-neutralizing antibody, thrombomodulin alfa capable of accelerating thrombin-dependent degradation of HMGB1, antagonists of the receptor for advanced glycation end-products (RAGE) and C-X-C motif chemokine receptor 4 (CXCR4), known as HMGB1-targeted membrane receptors, or macrophage depletion with liposomal clodronate, as reported in a CIPN model caused by paclitaxel. In macrophage-like RAW264.7 cells, bortezomib as well as MG132, a well-known proteasome inhibitor, caused HMGB1 release, an effect inhibited by caspase inhibitors but not inhibitors of NF-κB and p38 MAP kinase, known to mediate paclitaxel-induced HMGB1 release from macrophages. Bortezomib increased cleaved products of caspase-8 and caused nuclear fragmentation or condensation in macrophages. Repeated treatment with the caspase inhibitor prevented CIPN caused by bortezomib in mice. Our findings suggest that bortezomib causes caspase-dependent release of HMGB1 from macrophages, leading to the development of CIPN via activation of RAGE and CXCR4.

Histotripsy Ablation Alters the Tumor Microenvironment and Promotes Immune System Activation in a Subcutaneous Model of Pancreatic Cancer

Pancreatic cancer is a significant cause of cancer-related deaths in the United States with an abysmal five-year overall survival rate that is under 9%. Reasons for this mortality include the lack of late-stage treatment options and the immunosuppressive tumor microenvironment. Histotripsy is an ultrasound-guided, noninvasive, nonthermal tumor ablation therapy that mechanically lyses targeted cells. To study the effects of histotripsy on pancreatic cancer, we utilized an in vitro model of pancreatic adenocarcinoma and compared the release of potential antigens following histotripsy treatment to other ablation modalities. Histotripsy was found to release immune-stimulating molecules at magnitudes similar to other nonthermal ablation modalities and superior to thermal ablation modalities, which corresponded to increased innate immune system activation in vivo. In subsequent in vivo studies, murine Pan02 tumors were grown in mice and treated with histotripsy. Flow cytometry and rtPCR were used to determine changes in the tumor microenvironment over time compared to untreated animals. In mice with pancreatic tumors, we observed significantly increased tumor-progression-free and general survival, with increased activation of the innate immune system 24 h posttreatment and decreased tumor-associated immune cell populations within 14 days of treatment. This study demonstrates the feasibility of using histotripsy for pancreatic cancer ablation and provides mechanistic insight into the initial innate immune system activation following treatment. Further work is needed to establish the mechanisms behind the immunomodulation of the tumor microenvironment and immune effects.

Dexmedetomidine relieved neuropathic pain and inflammation response induced by CCI through HMGB1/TLR4/NF-κB signal pathway

Neuropathic pain is one of the most intractable diseases. The lack of effective therapy measures remains a critical problem due to the poor understanding of the cause of neuropathic pain. The aim of this study was to investigate the effect of dexmedetomidine (Dex) in trigeminal neuropathic pain and the underlying molecular mechanism in order to identify possible therapeutic targets. We used a chronic constriction injury (CCI) model of mice to investigate whether Dex prevents neuropathic pain and the inflammation response. The α 2-adrenoceptors (α2AR) inhibitor BRL44408 and adenovirus for knocking down High mobility group box 1 (HMGB1) was administrated to confirm whether Dex exert its effect through targeting α2AR and HMGB1. The results indicated that Dex significantly inhibited CCI induced neuropathic pain through targeting α2AR and HMGB1. Dex inhibited the inflammatory response through decreasing the release and the mRNA expression of IL-1β, IL-6, and TNF-ɑ while increasing that of IL-10. Moreover, Dex participates in the regulation of HMGB1, Toll-like receptor 4 (TLR4), NFκb (p-65) expression and the phosphorylation of IκB-ɑ. In conclusion, Dex could relieve neuropathic pain through α2AR and HMGB1 and attenuate inflammation response.

Bioinformatics integrated analysis to investigate candidate biomarkers and associated metabolites in osteosarcoma

BACKGROUND

This study hoped to explore the potential biomarkers and associated metabolites during osteosarcoma (OS) progression based on bioinformatics integrated analysis.

METHODS

Gene expression profiles of GSE28424, including 19 human OS cell lines (OS group) and 4 human normal long bone tissue samples (control group), were downloaded. The differentially expressed genes (DEGs) in OS vs. control were investigated. The enrichment investigation was performed based on DEGs, followed by protein-protein interaction network analysis. Then, the feature genes associated with OS were explored, followed by survival analysis to reveal prognostic genes. The qRT-PCR assay was performed to test the expression of these genes. Finally, the OS-associated metabolites and disease-metabolic network were further investigated.

RESULTS

Totally, 357 DEGs were revealed between the OS vs. control groups. These DEGs, such as CXCL12, were mainly involved in functions like leukocyte migration. Then, totally, 38 feature genes were explored, of which 8 genes showed significant associations with the survival of patients. High expression of CXCL12, CEBPA, SPARCL1, CAT, TUBA1A, and ALDH1A1 was associated with longer survival time, while high expression of CFLAR and STC2 was associated with poor survival. Finally, a disease-metabolic network was constructed with 25 nodes including two disease-associated metabolites cyclophosphamide and bisphenol A (BPA). BPA showed interactions with multiple prognosis-related genes, such as CXCL12 and STC2.

CONCLUSION

We identified 8 prognosis-related genes in OS. CXCL12 might participate in OS progression via leukocyte migration function. BPA might be an important metabolite interacting with multiple prognosis-related genes.

HMGB1 promotes CXCL12-dependent egress of murine B cells from Peyer's patches in homeostasis

High mobility group box-1 protein (HMGB1) is an alarmin that, once released, promotes inflammatory responses, alone and as a complex with the chemokine CXCL12. Here, we report that the HMGB1-CXCL12 complex plays an essential role also in homeostasis by controlling the migration of B lymphocytes. We show that extracellular HMGB1 is critical for the CXCL12-dependent egress of B cells from the Peyer's patches (PP). This promigratory function of the complex was restricted to the PPs, since HMGB1 was not required for B-cell migratory processes in other locations. Accordingly, we detected higher constitutive levels of the HMGB1-CXCL12 complex in PPs than in other lymphoid organs. HMGB1-CXCL12 in vivo inhibition was associated with a reduced basal IgA production in the gut. Collectively, our results demonstrate a role for the HMGB1-CXCL12 complex in orchestrating B-cell trafficking in homeostasis, and provide a novel target to control lymphocyte migration in mucosal immunity.

A novel CXCR4 antagonist counteracts paradoxical generation of cisplatin-induced pro-metastatic niches in lung cancer

Platinum-based chemotherapy remains widely used in advanced non-small cell lung cancer (NSCLC) despite experimental evidence of its potential to induce long-term detrimental effects, including the promotion of pro-metastatic microenvironments. In this study, we investigated the interconnected pathways underlying the promotion of cisplatin-induced metastases.

In tumor-free mice, cisplatin treatment resulted in an expansion in the bone marrow of CCR2⁺CXCR4⁺Ly6C^high inflammatory monocytes (IMs) and an increase in lung levels of stromal SDF-1, the CXCR4 ligand. In experimental lung metastasis assays, cisplatin-induced IMs promoted the extravasation of tumor cells and the expansion of CD133⁺CXCR4⁺ metastasis-initiating cells (MICs). Peptide R, a novel CXCR4 inhibitor designed as an SDF-1 mimetic peptide, prevented cisplatin-induced IM expansion, the recruitment of IMs into the lungs, and the promotion of metastasis. At the primary tumor site, cisplatin treatment reduced tumor size while simultaneously inducing tumor release of SDF-1, MIC expansion, and recruitment of pro-invasive CXCR4⁺ macrophages. Co-recruitment of MICs and CCR2⁺CXCR4⁺ IMs to distant SDF-1-enriched sites also promoted spontaneous metastases that were prevented by CXCR4 blockade. In clinical specimens from NSCLC patients SDF-1 levels were found to be higher in platinum-treated samples and related to a worse clinical outcome. Our findings reveal that activation of the CXCR4/SDF-1 axis specifically mediates the pro-metastatic effects of cisplatin and suggest CXCR4 blockade as a possible novel combination strategy to control metastatic disease.

Can the calcium-regulating hormones counteract the detrimental impact of pro-inflammatory damage-associated molecular patterns in the development of heart failure?

Growing evidence suggests an important role of the inflammatory component in heart failure (HF). Recent developments in this field indicate an ambiguous role that innate immunity plays in immune-driven HF. Damaged or stressed cells, cardiomyocytes, in particular, emit damage-associated molecular patterns (DAMPs) including HMGB1, S100 A8/A9, HSP70, and other molecules, unfolding paracrine mechanisms that induce an innate immune response. Designed as an adaptive, regenerative reaction, innate immunity may nevertheless become overactivated and thus contribute to the development of HF by altering the pacemaker rhythm, contraction, and electromechanical coupling, presumably by impairing the calcium homeostasis. The current review will explore a hypothesis of the involvement of the calcium-regulating hormones such as parathyroid hormone and parathyroid hormone–related protein in counteracting the detrimental impact of the excess of DAMPs and therefore improving the functional cardiac characteristics especially in the acute phase of the disease.

Upregulated HMGB1 levels in maternal-fetal interface of patients with unexplained recurrent spontaneous abortion from different sources

OBJECTIVE

To investigate the expression and sources of high mobility group box 1 (HMGB1) protein in the maternal-fetal interface of patients with unexplained recurrent spontaneous abortion (URSA), and further to verify the role of HMGB1 in the etiology of URSA.

METHODS

55 women at early pregnancy with URSA and 55 women undergoing selective termination of normal early pregnancy as control were included. The abortion tissues including villi and decidua were collected. The expression of HMGB1, CD45, CK7, and vimentin in abortion tissues was detected, and the localization and sources of HMGB1 were analyzed.

RESULTS

Infiltrating immune cells and expression of HMGB1 were significantly increased in villi and decidua in URSA group compared with those in the control group. In the URSA group, HMGB1 was colocalized with the CD45-labeled immune cells, and it was more obvious in decidua than in villi; in addition, HMGB1 was colocalized with the vimentin-labeled decidual stromal cells, but not with the CK7- labeled villous epithelial cells.

CONCLUSION

High expression of HMGB1 in the maternal-fetal interface in URSA patients was actively secreted by the infiltrating immune cells, and decidual stromal cells may passively release HMGB1 during necrosis.

Anti-HMGB1 auto-Abs influence fatigue in patients with Crohn's disease

Fatigue is common in all chronic inflammatory and autoimmune diseases. A conceptual model for understanding the biological basis of fatigue describes it as being a part of the sickness behaviour response generated by pro-inflammatory cytokines and other mediators. We hypothesised that the pro-inflammatory high mobility group box 1 (HMGB1) protein is a fatigue-inducing molecule and that auto-Abs against HMGB1 reduce fatigue. We measured Abs against disulphide (ds) HMGB1 and fully reduced (fr) HMGB1 in plasma from 57 patients with Crohn’s disease. Fatigue was rated using the fatigue visual analogue scale (fVAS) and disease activity with faecal calprotectin, C-reactive protein and the Simple Endoscopic Score for Crohn’s disease. Multivariable regression models identified anti-dsHMGB1 and anti-frHMGB1 Abs as the strongest contributing factors for fVAS scores (B = −29.10 (P = 0.01), R² = 0.17, and B = −17.77 (P = 0.01), R² = 0.17, respectively). Results indicate that anti-HMGB1 auto-Abs alleviate fatigue possibly by down-regulating HMGB1-induced sickness behaviour.

Lipopolysaccharides induce a RAGE-mediated sensitization of sensory neurons and fluid hypersecretion in the upper airways

Thoracic dorsal root ganglia (tDRG) contribute to fluid secretion in the upper airways. Inflammation potentiates DRG responses, but the mechanisms remain under investigation. The receptor for advanced glycation end-products (RAGE) underlies potentiation of DRG responses in pain pathologies; however, its role in other sensory modalities is less understood. We hypothesize that RAGE contributes to electrophysiological and biochemical changes in tDRGs during inflammation. We used tDRGs and tracheas from wild types (WT), RAGE knock-out (RAGE-KO), and with the RAGE antagonist FPS-ZM1, and exposed them to lipopolysaccharides (LPS). We studied: capsaicin (CAP)-evoked currents and action potentials (AP), tracheal submucosal gland secretion, RAGE expression and downstream pathways. In WT neurons, LPS increased CAP-evoked currents and AP generation, and it caused submucosal gland hypersecretion in tracheas from WT mice exposed to LPS. In contrast, LPS had no effect on tDRG excitability or gland secretion in RAGE-KO mice or mice treated with FPS-ZM1. LPS upregulated full-length RAGE (encoded by Tv1-RAGE) and downregulated a soluble (sRAGE) splice variant (encoded by MmusRAGEv4) in tDRG neurons. These data suggest that sensitization of tDRG neurons contributes to hypersecretion in the upper airways during inflammation. And at least two RAGE variants may be involved in these effects of LPS.

Amelioration of diabetes-induced inflammation mediated pyroptosis, sarcopenia, and adverse muscle remodelling by bone morphogenetic protein-7

BACKGROUND

Diabetic myopathy involves hyperglycaemia and inflammation that causes skeletal muscle dysfunction; however, the potential cellular mechanisms that occur between hyperglycaemia and inflammation, which induces sarcopenia, and muscle dysfunction remain unknown. In this study, we investigated hyperglycaemia-induced inflammation mediating high-mobility group box 1 activation, which is involved in a novel form of cell death, pyroptosis, diabetic sarcopenia, atrophy, and adverse muscle remodelling. Furthermore, we investigated the therapeutic potential of bone morphogenetic protein-7 (BMP-7), an osteoporosis drug, to treat pyroptosis, and diabetic muscle myopathy.

METHODS

C57BL6 mice were treated with saline (control), streptozotocin (STZ), or STZ + BMP-7 to generate diabetic muscle myopathy. Diabetes was established by determining the increased levels of glucose. Then, muscle function was examined, and animals were sacrificed. Gastrocnemius muscle or blood samples were analysed for inflammation, pyroptosis, weight loss, muscle atrophy, and adverse structural remodelling of gastrocnemius muscle using histology, enzyme-linked immunosorbent assay, immunohistochemistry, western blotting, and reverse transcription polymerase chain reaction.

RESULTS

A significant (P < 0.05) increase in hyperglycaemia leads to an increase in inflammasome (high-mobility group box 1, toll-like receptor-4, and nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing protein 3) formation in diabetic muscle cells. Further analysis showed an up-regulation of the downstream pyroptotic pathway with significant (P < 0.05) number of positive muscle cells expressing pyroptosis-specific markers [caspase-1, interleukin (IL)-1β, IL-18, and gasdermin-D]. Pyroptotic cell death is involved in further increasing inflammation by releasing pro-inflammatory cytokine IL-6. Structural analysis showed the loss of muscle weight, decreased myofibrillar area, and increased fibrosis leading to muscle dysfunction. Consistent with this finding, BMP-7 attenuated hyperglycaemia (~50%), pyroptosis, inflammation, and diabetic adverse structural modifications as well as improved muscle function.

CONCLUSIONS

In conclusion, we report for the first time that increased hyperglycaemia and inflammation involve cellular pyroptosis that induces significant muscle cell loss and adverse remodelling in diabetic myopathy. We also report that targeting pyroptosis with BMP-7 improves diabetic muscle pathophysiology and muscle function. These findings suggest that BMP-7 could be a potential therapeutic option to treat diabetic myopathy.

Inflammation related to high-mobility group box-1 in endometrial ovarian cyst

Endometriosis is a chronic inflammatory disease often associated with dysmenorrhea, infertility, adenomyosis, and endometrial ovarian cyst (EOC). In particular, EOC can sometimes become malignant in a longitudinal follow-up. This study aimed to investigate the involvement of high-mobility group box-1 (HMGB1) in an inflammatory milieu and the characteristics of immune cells in EOC. The samples were obtained from patients who underwent ovarian cystectomy for benign ovarian cyst. The participants were divided into two groups: patients with EOC (EOC group) and those without EOC (nEOC group). We divided a part of the removed ovary into small sections and isolated the tissue cells. Thereafter, the cytoplasmic HMGB1 levels in DCs, macrophages, and non-immune cells were analyzed by flow cytometry. We also evaluated the proportions of immune, T, NK, iNKT, NK, and regulatory T (Treg) cells. Results showed that the DCs, macrophages, and non-immune cells of EOC had significantly higher cytoplasmic HMGB1 levels than those of nEOC. The expression of CD69 and CD107a on CD8⁺ T and CD4⁺ T cells of EOC was also more enhanced than that of nEOC. Furthermore, the M2 macrophages and Tregs highly accumulated in EOC. These results indicate that HMGB1 may aggravate chronic inflammation related to T-cell activation and simultaneously facilitate development of the immunosuppressive milieu in EOCs.

Expatiating the molecular approaches of HMGB1 in diabetes mellitus: Highlighting signalling pathways via RAGE and TLRs

Diabetes mellitus (DM) has become one of the major healthcare challenges worldwide in the recent times and inflammation being one of its key pathogenic process/mechanism affect several body parts including the peripheral and central nervous system. High-mobility group box 1 (HMGB1) is one of the major non-histone proteins that plays a key role in triggering the inflammatory response. Upon its release into the extracellular milieu, HMGB1 acts as an "alarmin" for the immune system to initiate tissue repair as a component of the host defense system. Furthermore, HMGB1 along with its downstream receptors like Toll-like receptors (TLRs) and receptors for advanced glycation end products (RAGE) serve as the suitable target for DM. The forthcoming research in the field of diabetes would potentially focus on the development of alternative approaches to target the centre of inflammation that is primarily mediated by HMGB1 to improve diabetic-related complications. This review covers the therapeutic actions of HMGB1 protein, which acts by activating the RAGE and TLR molecules to constitute a functional tripod system, in turn activating NF-κB pathway that contributes to the production of mediators for pro-inflammatory cytokines associated with DM. The interaction between TLR2 and TLR4 with ligands present in the host and the activation of RAGE stimulates various immune and metabolic responses that contribute to diabetes. This review emphasizes to elucidate the role of HMGB1 in the initiation and progression of DM and control over the inflammatory tripod as a promising therapeutic approach in the management of DM.

Interplay between inflammation and thrombosis in cardiovascular pathology

Thrombosis is the most feared complication of cardiovascular diseases and a main cause of death worldwide, making it a major health-care challenge. Platelets and the coagulation cascade are effectively targeted by antithrombotic approaches, which carry an inherent risk of bleeding. Moreover, antithrombotics cannot completely prevent thrombotic events, implicating a therapeutic gap due to a third, not yet adequately addressed mechanism, namely inflammation. In this Review, we discuss how the synergy between inflammation and thrombosis drives thrombotic diseases. We focus on the huge potential of anti-inflammatory strategies to target cardiovascular pathologies. Findings in the past decade have uncovered a sophisticated connection between innate immunity, platelet activation and coagulation, termed immunothrombosis. Immunothrombosis is an important host defence mechanism to limit systemic spreading of pathogens through the bloodstream. However, the aberrant activation of immunothrombosis in cardiovascular diseases causes myocardial infarction, stroke and venous thromboembolism. The clinical relevance of aberrant immunothrombosis, referred to as thromboinflammation, is supported by the increased risk of cardiovascular events in patients with inflammatory diseases but also during infections, including in COVID-19. Clinical trials in the past 4 years have confirmed the anti-ischaemic effects of anti-inflammatory strategies, backing the concept of a prothrombotic function of inflammation. Targeting inflammation to prevent thrombosis leaves haemostasis mainly unaffected, circumventing the risk of bleeding associated with current approaches. Considering the growing number of anti-inflammatory therapies, it is crucial to appreciate their potential in covering therapeutic gaps in cardiovascular diseases.

Role of HMGB1 in Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN), one of major dose-limiting side effects of first-line chemotherapeutic agents such as paclitaxel, oxaliplatin, vincristine, and bortezomib is resistant to most of existing medicines. The molecular mechanisms of CIPN have not been fully understood. High mobility group box 1 (HMGB1), a nuclear protein, is a damage-associated molecular pattern protein now considered to function as a pro-nociceptive mediator once released to the extracellular space. Most interestingly, HMGB1 plays a key role in the development of CIPN. Soluble thrombomodulin (TMα), known to degrade HMGB1 in a thrombin-dependent manner, prevents CIPN in rodents treated with paclitaxel, oxaliplatin, or vincristine and in patients with colorectal cancer undergoing oxaliplatin-based chemotherapy. In this review, we describe the role of HMGB1 and its upstream/downstream mechanisms in the development of CIPN and show drug candidates that inhibit the HMGB1 pathway, possibly useful for prevention of CIPN.

Effect of metformin on stem cells: Molecular mechanism and clinical prospect

Metformin is a first-line medication for type II diabetes. Numerous studies have shown that metformin not only has hypoglycemic effects, but also modulates many physiological and pathological processes ranging from aging and cancer to fracture healing. During these different physiological activities and pathological changes, stem cells usually play a core role. Thus, many studies have investigated the effects of metformin on stem cells. Metformin affects cell differentiation and has promising applications in stem cell medicine. It exerts anti-aging effects and can be applied to gerontology and regenerative medicine. The potential anti-cancer stem cell effect of metformin indicates that it can be an adjuvant therapy for cancers. Furthermore, metformin has beneficial effects against many other diseases including cardiovascular and autoimmune diseases. In this review, we summarize the effects of metformin on stem cells and provide an overview of its molecular mechanisms and clinical prospects.