Extracellular HMGB1 as a therapeutic target in inflammatory diseases

Correlation of HMGB1, TLR2 and TLR4 with left ventricular diastolic dysfunction in sepsis patients

Left ventricular diastolic dysfunction (LVDD) is a common consequence of sepsis due to dysregulated inflammatory responses. Here we aim to investigate high mobility group box 1 (HMGB1), toll-like receptor 2 (TLR2) and toll-like receptor 4 (TLR4) as serum biomarkers to assess LVDD risk of patients with sepsis. We recruited 120 patients with sepsis, among which 52 had ultrasonically confirmed LVDD and 68 were without LVDD. Blood samples were collected, and enzyme-linked immunosorbent assay (ELISA) was used to analyse levels of HMGB1, TLR2 and TLR4 in serum. Multivariate analysis was performed to assess the odds ratio of the serum biomarkers. Spearman's correlation analysis was conducted to evaluate the correlation between the serum biomarkers to B-type natriuretic peptide (BNP) and cardiac troponin I (cTnl) levels and the ratios of early diastolic mitral inflow velocity to early diastolic mitral annulus velocity (E/e' ratios) in ultrasound. Receiver operating curve was used to measure the sensitivity and specificity of HMGB1, TLR2 and TLR4 individually and in combination as diagnostic markers. Elevated HMGB1, TLR2 and TLR4 had significant values in predicting LVDD suggested by high odds ratio (all P < .05). A significant correlation was found between these values and cTnl, the current gold standard for LVDD analysis. HMGB1, TLR2 and TLR4 also showed a high diagnostic sensitivity and specificity in ROC analysis. HMGB1, TLR2 and TLR4 are potentially valuable in predicting LVDD risk among patients with sepsis, providing additional tools with the capability of potentially assisting the clinical management of patients with sepsis.

Etanercept ameliorates psoriasis progression through regulating high mobility group box 1 pathway

BACKGROUND

As a common skin disease, psoriasis is related to inflammation and immune response. Due to the frequent recurrence of psoriasis, the treatment of psoriasis remains a clinical challenge. As an effective tumor necrosis factor-alpha (TNF-α) inhibitor, etanercept has been used for the treatment of psoriasis. However, some patients with psoriasis have no response to etanercept or discontinue treatment. To improve the therapeutic effect of etanercept, searching the potential biomarkers and investigating the related mechanisms of etanercept in the treatment of psoriasis are vital.

MATERIALS AND METHODS

We stimulated HaCaT cells with lipopolysaccharide (LPS) to generate cellular psoriatic changes and established an imiquimod (IMQ)-induced psoriasis-like mouse model, and then used an etanercept to treat cell and mouse model.

RESULTS

Etanercept alleviated IMQ-induced pathological changes and inflammation, and it also decreased the protein expression of high mobility group box 1 (HMGB1), receptor for advanced glycation end-products, and toll-like receptor 4. Moreover, the results of in vitro experiments showed that etanercept inhibited proliferation and inflammation, and promoted cell cycle arrest and apoptosis in LPS-treated HaCaT cells. Knockdown of HMGB1 further enhanced the inhibitory effects of etanercept on LPS-treated HaCaT cell viability and inflammation, while overexpression of HMGB1 notably reversed the inhibitory effects of etanercept on LPS-induced HaCaT cell viability and inflammation.

CONCLUSION

Etanercept inhibited proliferation and inflammation and promoted cell cycle arrest and apoptosis in LPS-induced HaCaT cells, and etanercept ameliorated inflammation in a psoriasis-like mouse model.

Pyroptosis and airway homeostasis regulation

Pyroptosis is a form of cell death associated with inflammation. In the maintenance of airway homeostasis, pyroptosis goes through activation and assembly of Inflammasome. The pyroptosis pathway is mediated by caspase which activates the pore-forming effect of substrate gasdermin family members. It eventually leads to lysis and release of the cell contents and then induces an inflammatory response. In this process, it participates in airway homeostasis regulation by affecting airway immunity, airway epithelial structure and airway microbiota. Therefore, we discussed the correlation between airway immunity, airway epithelial structure, airway microbiota and the mechanism of pyroptosis to describe the role of pyroptosis in airway homeostasis regulation which is of great significance for understanding the occurrence and treatment of airway inflammatory diseases.

Acupuncture exerts preventive effects in rats of chronic unpredictable mild stress: The involvement of inflammation in amygdala and brain-spleen axis

BACKGROUND

Acupuncture has shown the preventive effects on depression in rats with chronic unpredictable mild stress (CUMS). However, the mechanisms of acupuncture for preventing depression still need to be explored. In the study, acupuncture was applied to a rat depression model of CUMS, high-mobility group box 1(HMGB1)/toll-like receptor 4 (TLR4) and brain-spleen axis were assessed.

METHODS

Male Sprague Dawley (SD) rats were exposed to CUMS with two stressors per day for 28 days. In the meantime, manual acupuncture (at GV16 and GV23 acupoints, once every other day) and fluoxetine gavage (2.1 mg/kg, 0.21 mg/mL) were administered daily post CUMS stressors. Behavioral tests and biological detection methods were conducted in sequence to evaluate depression-like phenotypes in rats.

RESULTS

The results showed CUMS induced depression-like behaviors, hyper-activation of HMGB1/TLR4 signaling pathway, elevated inflammation in amygdala and peripheral blood, and hyperactivation of hypothalamic-pituitary-adrenal (HPA) axis. These changes could be prevented and reversed by acupuncture to varying extents.

CONCLUSION

Acupuncture prevented and ameliorated depression-like symptoms induced by CUMS, possibly via regulating inflammation through brain-spleen axis mediated by HMGB1/TLR4 signaling pathway and HPA axis regulation.

Sulfated Hyperbranched and Linear Polyglycerols Modulate HMGB1 and Morphological Plasticity in Neural Cells

The objective of this study was to establish if polyglycerols with sulfate or sialic acid functional groups interact with high mobility group box 1 (HMGB1), and if so, which polyglycerol could prevent loss of morphological plasticity in excitatory neurons in the hippocampus. Considering that HMGB1 binds to heparan sulfate and that heparan sulfate has structural similarities with dendritic polyglycerol sulfates (dPGS), we performed the experiments to show if polyglycerols can mimic heparin functions by addressing the following questions: (1) do dendritic and linear polyglycerols interact with the alarmin molecule HMGB1? (2) Does dPGS interaction with HMGB1 influence the redox status of HMGB1? (3) Can dPGS prevent the loss of dendritic spines in organotypic cultures challenged with lipopolysaccharide (LPS)? LPS plays a critical role in infections with Gram-negative bacteria and is commonly used to test candidate therapeutic agents for inflammation and endotoxemia. Pathologically high LPS concentrations and other stressful stimuli cause HMGB1 release and post-translational modifications. We hypothesized that (i) electrostatic interactions of hyperbranched and linear polysulfated polyglycerols with HMGB1 will likely involve sites similar to those of heparan sulfate. (ii) dPGS can normalize HMGB1 compartmentalization in microglia exposed to LPS and prevent dendritic spine loss in the excitatory hippocampal neurons. We performed immunocytochemistry and biochemical analyses combined with confocal microscopy to determine cellular and extracellular locations of HMGB1 and morphological plasticity. Our results suggest that dPGS interacts with HMGB1 similarly to heparan sulfate. Hyperbranched dPGS and linear sulfated polymers prevent dendritic spine loss in hippocampal excitatory neurons. MS/MS analyses reveal that dPGS-HMGB1 interactions result in fully oxidized HMGB1 at critical cysteine residues (Cys23, Cys45, and Cys106). Triply oxidized HMGB1 leads to the loss of its pro-inflammatory action and could participate in dPGS-mediated spine loss prevention. LPG-Sia exposure to HMGB1 results in the oxidation of Cys23 and Cys106 but does not normalize spine density.

Heparan sulfates and heparan sulfate binding proteins in sepsis

Heparan sulfates (HSs) are the main components in the glycocalyx which covers endothelial cells and modulates vascular homeostasis through interactions with multiple Heparan sulfate binding proteins (HSBPs). During sepsis, heparanase increases and induces HS shedding. The process causes glycocalyx degradation, exacerbating inflammation and coagulation in sepsis. The circulating heparan sulfate fragments may serve as a host defense system by neutralizing dysregulated Heparan sulfate binding proteins or pro-inflammatory molecules in certain circumstances. Understanding heparan sulfates and heparan sulfate binding proteins in health and sepsis is critical to decipher the dysregulated host response in sepsis and advance drug development. In this review, we will overview the current understanding of HS in glycocalyx under septic condition and the dysfunctional heparan sulfate binding proteins as potential drug targets, particularly, high mobility group box 1 (HMGB1) and histones. Moreover, several drug candidates based on heparan sulfates or related to heparan sulfates, such as heparanase inhibitors or heparin-binding protein (HBP), will be discussed regarding their recent advances. By applying chemical or chemoenzymatic approaches, the structure-function relationship between heparan sulfates and heparan sulfate binding proteins is recently revealed with structurally defined heparan sulfates. Such homogenous heparan sulfates may further facilitate the investigation of the role of heparan sulfates in sepsis and the development of carbohydrate-based therapy.

Lessons from Cardiac and Vascular Biopsies from Patients with and without Inflammatory Rheumatic Diseases

Feiring Heart Biopsy Study enables searching for potential pathogenetic mechanisms, therapeutic targets, and biomarkers through the assessment of clinical data and multiple blood and tissue samples from patients with and without inflammatory rheumatic diseases (IRDs), undergoing coronary artery bypass grafting. Some of our findings, for example, more inflammation (including the presence of immune cells and expression of proinflammatory cytokines) in vessels and the heart, and the presence of certain bacteria and autoantigens in vessels, could contribute to the increased risk of ischemia, aneurysms, and/or cardiac dysfunction in IRDs. Furthermore, some of the detected factors could be involved in the pathomechanisms of these conditions in general.

Genetic factors contributing to a severe course of pneumonia: a systematic review

The article presents a systematic review of publications devoted to the study of genetic markers of severe pneumonia.

The aim of the study was to compile a list of genetic markers that contribute to a severe course of pneumonia on the basis of the published data.

In the current study, we searched for and analyzed articles published between January 2000 and April 2021. Following the search for and subsequent selection of articles, a list of 10 publications was compiled, which demonstrated a clear association of certain gene variants with severe and complicated pneumonia. Finally, we made a list of genetic markers of severe pneumonia consisting of 16 polymorphisms in 12 genes (CD86, IL6, IL10, PAI1, TNFα, HMGB1, ATG16L1, AGTR1, GCLC, CAT, IFNγ, FCGR2A).

These genetic markers of severe and complicated pneumonia are responsible for various innate immune responses. The odds ratio for complicated pneumonia with a risk allele in the polymorphisms in the mentioned genes ranges from 1.39 to 4.28. To understand molecular and genetic mechanisms of severe pneumonia, further investigation of the effect of these genetic factors on the outcomes of pneumonia in different groups of patients with a simultaneous assessment of the cumulative effect of genetic variants and genetic interactions is required.

HMGB1 accumulation in cytoplasm mediates noise-induced cochlear damage

Damage-associated molecular pattern molecules (DAMPs) play a critical role in mediating cochlear cell death, which leads to noise-induced hearing loss (NIHL). High-mobility group box 1 (HMGB1), a prototypical DAMP released from cells, has been extensively studied in the context of various diseases. However, whether extracellular HMGB1 contributes to cochlear pathogenesis in NIHL and the potential signals initiating HMGB1 release from cochlear cells are not well understood. Here, through the transfection of the adeno-associated virus with HMGB1-HA-tag, we first investigated early cytoplasmic accumulation of HMGB1 in cochlear hair cells after noise exposure. We found that the cochlear administration of HMGB1-neutralizing antibody immediately after noise exposure significantly alleviated hearing loss and outer hair cells (OHCs) death induced by noise exposure. In addition, activation of signal transducer and activators of transcription 1 (STAT1) and cellular hyperacetylation were verified as potential canonical initiators of HMGB1 cytoplasmic accumulation. These findings reveal the adverse effects of extracellular HMGB1 on the cochlea and the potential signaling events mediating HMGB1 release in hair cells, indicating multiple potential pharmacotherapeutic targets for NIHL.

Microglia-mediated inflammatory destruction of neuro-cardiovascular dysfunction after stroke

Stroke, a serious systemic inflammatory disease, features neurological deficits and cardiovascular dysfunction. Neuroinflammation is characterized by the activation of microglia after stroke, which disrupts the cardiovascular-related neural network and the blood-brain barrier. Neural networks activate the autonomic nervous system to regulate the cardiac and blood vessels. Increased permeability of the blood-brain barrier and the lymphatic pathways promote the transfer of the central immune components to the peripheral immune organs and the recruitment of specific immune cells or cytokines, produced by the peripheral immune system, and thus modulate microglia in the brain. In addition, the spleen will also be stimulated by central inflammation to further mobilize the peripheral immune system. Both NK cells and Treg cells will be generated to enter the central nervous system to suppress further inflammation, while activated monocytes infiltrate the myocardium and cause cardiovascular dysfunction. In this review, we will focus on microglia-mediated inflammation in neural networks that result in cardiovascular dysfunction. Furthermore, we will discuss neuroimmune regulation in the central-peripheral crosstalk, in which the spleen is a vital part. Hopefully, this will benefit in anchoring another therapeutic target for neuro-cardiovascular dysfunction.

Electroacupuncture Alleviates Neuroinflammation by Inhibiting the HMGB1 Signaling Pathway in Rats with Sepsis-Associated Encephalopathy

Sepsis-Associated Encephalopathy (SAE) is common in sepsis patients, with high mortality rates. It is believed that neuroinflammation is an important mechanism involved in SAE. High mobility group box 1 protein (HMGB1), as a late pro-inflammatory factor, is significantly increased during sepsis in different brain regions, including the hippocampus. HMGB1 causes neuroinflammation and cognitive impairment through direct binding to advanced glycation end products (RAGE) and Toll-like receptor 4 (TLR4). Electroacupuncture (EA) at Baihui (GV20) and Zusanli (ST36) is beneficial for neurological diseases and experimental sepsis. Our study used EA to treat SAE induced by lipopolysaccharide (LPS) in male Sprague-Dawley rats. The Y maze test was performed to assess working memory. Immunofluorescence (IF) and Western blotting (WB) were used to determine neuroinflammation and the HMGB1 signaling pathway. Results showed that EA could improve working memory impairment in rats with SAE. EA alleviated neuroinflammation by downregulating the hippocampus's HMGB1/TLR4 and HMGB1/RAGE signaling, reducing the levels of pro-inflammatory factors, and relieving microglial and astrocyte activation. However, EA did not affect the tight junctions' expression of the blood-brain barrier (BBB) in the hippocampus.

Systematic Review and Meta-Analysis of Damage Associated Molecular Patterns HMGB1 and S100B in Schizophrenia

OBJECTIVE

Immune system dysregulation is hypothesised to be central to the aetiopathogenesis of schizophrenia; however, the role of sterile inflammation remains unclear. Damage associated molecular patterns are key initiators of sterile inflammation and are detectable in peripheral blood.

METHODS

A defined systematic search of the Web of Science, PubMed, and Scopus was performed to identify adult case-control studies published between January 1990 and June 2022. Three studies consisting of 242 cases and 83 controls met inclusion for the systematic review and meta-analysis of HMGB1 while twenty-eight studies consisting of 1,544 cases and 1,248 healthy controls were included for S100B.

RESULTS

A significant standardised mean difference in peripheral S100B and HMGB1 concentrations was detected between cases and controls. S100B subgroup analysis determined the largest significant effect size for unmedicated individuals diagnosed with schizophrenia.

CONCLUSION

This study provides evidence that peripheral S100B and HMGB1 concentrations are elevated in individuals diagnosed with schizophrenia when compared with healthy controls. These results should be interpreted with caution as significant heterogeneity was present during meta-analysis of S100B in the entire sample and in sub-group analysis. The persistence of significant heterogeneity throughout subgroup analysis indicates that the current diagnostic groupings may be a barrier to understanding human behaviours and emotions.

Looking on the horizon; potential and unique approaches to developing radiation countermeasures for deep space travel

Future lunar missions and beyond will require new and innovative approaches to radiation countermeasures. The Translational Research Institute for Space Health (TRISH) is focused on identifying and supporting unique approaches to reduce risks to human health and performance on future missions beyond low Earth orbit. This paper will describe three funded and complementary avenues for reducing the risk to humans from radiation exposure experienced in deep space. The first focus is on identifying new therapeutic targets to reduce the damaging effects of radiation by focusing on high throughput genetic screens in accessible, sometimes called lower, organism models. The second focus is to design innovative approaches for countermeasure development with special attention to nucleotide-based methodologies that may constitute a more agile way to design therapeutics. The final focus is to develop new and innovative ways to test radiation countermeasures in a human model system. While animal studies continue to be beneficial in the study of space radiation, they can have imperfect translation to humans. The use of three-dimensional (3D) complex in vitro models is a promising approach to aid the development of new countermeasures and personalized assessments of radiation risks. These three distinct and unique approaches complement traditional space radiation efforts and should provide future space explorers with more options to safeguard their short and long-term health.

Therapeutic Potential of Targeting the HMGB1/RAGE Axis in Inflammatory Diseases

High mobility group box 1 (HMGB1) is a nuclear protein that can interact with a receptor for advanced glycation end-products (RAGE; a multi-ligand immunoglobulin receptor) and mediates the inflammatory pathways that lead to various pathological conditions, such as cancer, diabetes, neurodegenerative disorders, and cardiovascular diseases. Blocking the HMGB1/RAGE axis could be an effective therapeutic approach to treat these inflammatory conditions, which has been successfully employed by various research groups recently. In this article, we critically review the structural insights and functional mechanism of HMGB1 and RAGE to mediate inflammatory processes. More importantly, current perspectives of recent therapeutic approaches utilized to inhibit the communication between HMGB1 and RAGE using small molecules are also summarized along with their clinical progression to treat various inflammatory disorders. Encouraging results are reported by investigators focusing on HMGB1/RAGE signaling leading to the identification of compounds that could be useful in further clinical studies. We highlight the current gaps in our knowledge and future directions for the therapeutic potential of targeting key molecules in HMGB1/RAGE signaling in the pathophysiology of inflammatory diseases.

Glycyrrhizin through liquorice intake modulates ACE2 and HMGB1 levels-A pilot study in healthy individuals with implications for COVID-19 and ARDS

Background

Glycyrrhizin, an active component of liquorice root extract, exhibits antiviral and immunomodulatory properties by direct inhibition of the pro-inflammatory alarmin HMGB1 (High-mobility group box 1).

Objective

The aim of this study was to explore the role of liquorice intake on the viral entry receptor ACE2 (angiotensin-converting enzyme 2) and the immunoregulatory HMGB1 in healthy individuals and to explore HMGB1 expression in coronavirus disease 2019 (COVID-19) or non-COVID-19 in ARDS (acute respiratory distress syndrome patients).

Material and methods

This study enrolled 43 individuals, including hospitalised patients with i) acute respiratory distress syndrome (ARDS) due to COVID-19 (n = 7) or other underlying causes (n = 12), ii) mild COVID-19 (n = 4) and iii) healthy volunteers (n = 20). Healthy individuals took 50 g of liquorice (containing 3% liquorice root extract) daily for 7 days, while blood samples were collected at baseline and on day 3 and 7. Changes in ACE2 and HMGB1 levels were determined by Western blot analysis and enzyme-linked immunosorbent assay, respectively. Additionally, HMGB1 levels were measured in hospitalised COVID-19 patients with mild disease or COVID-19 associated acute respiratory distress syndrome (ARDS) and compared with a non-COVID-19-ARDS group.

Results

Liquorice intake significantly reduced after 7 days both cellular membranous ACE2 expression (-51% compared to baseline levels, p = 0.008) and plasma HMGB1 levels (-17% compared to baseline levels, p<0.001) in healthy individuals. Half of the individuals had a reduction in ACE2 levels of at least 30%. HMGB1 levels in patients with mild COVID-19 and ARDS patients with and without COVID-19 were significantly higher compared with those of healthy individuals (+317%, p = 0.002), but they were not different between COVID-19 and non-COVID-19 ARDS.

Conclusions

Liquorice intake modulates ACE2 and HMGB1 levels in healthy individuals. HMGB1 is enhanced in mild COVID-19 and in ARDS with and without COVID-19, warranting evaluation of HMGB1 as a potential treatment target and glycyrrhizin, which is an active component of liquorice root extract, as a potential treatment in COVID-19 and non-COVID-19 respiratory disease.

Role of HMGB1 in Vitiligo: Current Perceptions and Future Perspectives

Vitiligo is a chronic depigmenting disorder of the skin and mucosa caused by the destruction of epidermal melanocytes. Although the exact mechanism has not been elucidated, studies have shown that oxidative stress plays an important role in the pathogenesis of vitiligo. High mobility group box protein B1 (HMGB1) is a major nonhistone protein and an extracellular proinflammatory or chemotactic molecule that is actively secreted or passively released by necrotic cells. Recent data showed that HMGB1 is overexpressed in both blood and lesional specimens from vitiligo patients. Moreover, oxidative stress triggers the release of HMGB1 from keratinocytes and melanocytes, indicating that HMGB1 may participate in the pathological process of vitiligo. Overall, this review mainly focuses on the role of HMGB1 in the potential mechanisms underlying vitiligo depigmentation under oxidative stress. In this review, we hope to provide new insights into vitiligo pathogenesis and treatment strategies.

Tea tree oil nanoliposomes: optimization, characterization, and antibacterial activity against Escherichia coli in vitro and in vivo

The purpose of this study was to formulate tee tree oil nanoliposomes (TTONL) and evaluate its characterization and antibacterial activity. TTONL was prepared by thin film hydration and sonication technique, and the preparation conditions were optimized by Box-behnken response surface method. The characterization (morphology, size, zeta potential, and stability) and antibacterial activity of TTONL against Escherichia coli (E. coli) in vitro and in vivo were evaluated. The optimal preparation conditions for TTONL: lecithin to cholesterol mass ratio of 3.7:1, TTO concentration of 0.5%, and pH of the hydration medium of 7.4, which resulted in a TTONL encapsulation rate of 80.31 ± 0.56%. TTONL was nearly spherical in shape and uniform in size, and the average particle size was 227.8 ± 25.3 nm with negative charge. The specific disappearance of the TTO peak in the infrared spectrum suggested the successful preparation of TTONL, which showed high stability at 4°C within 35 d. The result of MIC test found that the nanoliposomes improved antibacterial activity of TTO against various E. coli strains. TTONL exposure in vitro caused different degrees of structural damage to the E. coli. TTONL by oral administration alleviated the clinical symptoms and intestinal lesion of chickens induced with E. coli challenge. Furthermore, TTONL treatment remarkably lowered the mRNA expression of NLRP3 and NF-κB (p65) in the duodenum and cecum of E. coli-infected chickens. In conclusion, the prepared TTONL had good stability and slow-release property with dose-dependent inhibition and killing effects on different strains of E. coli, and exerted a preventive role against chicken colibacillosis through inhibition.

High mobility group box protein 1 (HMGB1) serum and urinary levels and gene polymorphism in Egyptian patients with systemic lupus erythematosus: A possible relation to lupus nephritis

Objective

The aim of this study was to evaluate the effects of the high mobility group box protein 1 (HMGB1) serum and urinary levels and gene polymorphisms on systemic lupus erythematosus (SLE) development and investigate their link to lupus nephritis (LN).

Methods

We enrolled 120 Egyptian SLE patients and 120 healthy controls. Thorough medical and clinical evaluation were carried out, and SLE disease activity index (SLEDAI) was assessed. Lupus patients were divided into two groups according to the presence of LN. Measurement of HMGB1 serum and urinary levels was done using ELISA and genotyping for HMGB1 ( rs1045411) was performed.

Results

There were statistically significantly higher HMGB1 serum and urinary levels in SLE patients ( p < 0.001). There was a marginally significant association between lupus and alleles ( p = 0.059, φ = −0.086). ‘C’ allele was marginally significant risk allele for SLE. After classifying SLE patients based on the presence or absence of LN, there was no significant difference as regard sex ( p = 0.387), age ( p = 0.208) and disease duration ( p = 0.094).However, there was a significant difference between the 2 groups in regard to the frequency of musculoskeletal manifestations ( p = 0.035), SLEDAI score ( p < 0.001), both serum ( p < 0.001) and urinary HMGB1 levels ( p < 0.001) in addition to the frequency of HMGB1 genotypes ( p = 0.003). Lupus patients with C/T-T/T HMGB1 genotypes had 3.5-times higher odds to exhibit LN.

Conclusions

Serum and urine HMGB1 measurements are helpful in the diagnosis of SLE and the prediction of LN. There is a link between HMGB1 gene variations and the risk of SLE, with evidence that the C/T-T/T HMGB1 genotype is linked to a significantly greater risk of LN in the Egyptian population.

High-frequency electrical stimulation attenuates neuronal release of inflammatory mediators and ameliorates neuropathic pain

BACKGROUND

Neuroinflammation is an important driver of acute and chronic pain states. Therefore, targeting molecular mediators of neuroinflammation may present an opportunity for developing novel pain therapies. In preclinical models of neuroinflammatory pain, calcitonin gene-related peptide (CGRP), substance P and high mobility group box 1 protein (HMGB1) are molecules synthesized and released by sensory neurons which activate inflammation and pain. High-frequency electrical nerve stimulation (HFES) has achieved clinical success as an analgesic modality, but the underlying mechanism is unknown. Here, we reasoned that HFES inhibits neuroinflammatory mediator release by sensory neurons to reduce pain.

METHODS

Utilizing in vitro and in vivo assays, we assessed the modulating effects of HFES on neuroinflammatory mediator release by activated sensory neurons. Dorsal root ganglia (DRG) neurons harvested from wildtype or transgenic mice expressing channelrhodopsin-2 (ChR2) were cultured on micro-electrode arrays, and effect of HFES on optogenetic- or capsaicin-induced neuroinflammatory mediator release was determined. Additionally, the effects of HFES on local neuroinflammatory mediator release and hyperalgesia was assessed in vivo using optogenetic paw stimulation and the neuropathic pain model of chronic constriction injury (CCI) of the sciatic nerve.

RESULTS

Light- or capsaicin-evoked neuroinflammatory mediator release from cultured transgenic DRG sensory neurons was significantly reduced by concurrent HFES (10 kHz). In agreement with these findings, elevated levels of neuroinflammatory mediators were detected in the affected paw following optogenetic stimulation or CCI and were significantly attenuated using HFES (20.6 kHz for 10 min) delivered once daily for 3 days.

CONCLUSION

These studies reveal a previously unidentified mechanism for the pain-modulating effect of HFES in the setting of acute and chronic nerve injury. The results support the mechanistic insight that HFES may reset sensory neurons into a less pro-inflammatory state via inhibiting the release of neuroinflammatory mediators resulting in reduced inflammation and pain.

Role of High Mobility Group Box 1 in Cardiovascular Diseases

High Mobility Group Box 1 (HMGB1) is a ubiquitous, highly conserved nuclear and cytosolic protein that has diverse biological roles depending on its cellular location and posttranslational modifications. The HMGB1 is localized in the nucleus but can be translocated to the cytoplasm to modulate the intracellular signaling and eventually secreted outside the cells. It is widely established that HMGB1 plays a key role in inflammation; however, the role of HMGB1 in the cardiovascular diseases is not well understood. In this review, we will discuss the latest reports on the pathophysiological link between HMGB1 and cardiovascular complications, with special emphasis on the inflammation. Thus, the understanding of the role of HMGB1 may provide new insights into developing new HMGB1-based therapies.

Immunopathogenesis of Sjogren's syndrome: Current state of DAMPs

Sjögren's syndrome (SS) is a systemic autoimmune disorder with an estimated global prevalence of 0.3 to 1/1000 persons. This disease has a female predilection and mainly affects salivary and lacrimal glands. The distinctive pathological hallmark of SS is focal lymphocyte infiltration in affected glands, accompanied by the production of autoantibodies and inflammatory cytokines leading to epithelial damage and disease progression. Danger-associated molecular patterns (DAMPs) as alarmins have been demonstrated to promote lymphocyte recruitment in several inflammatory and autoimmune diseases. Here we summarize that the levels of DAMPs were increased in the periphery and affected tissues in SS as the stimulators, DAMPs sensed by pattern recognition receptors (PRRs, the same sensors for PAMPs) initiated the inflammatory and autoimmune response constituting a vicious autoimmunity loop leading to disease exacerbation. Thus, DAMPs are involved in the immunopathogenesis of SS and inhibition of these DAMPs may serve as a novel therapeutic strategy for SS.

Dl-3-n-Butylphthalide (NBP) Mitigates Muscular Injury Induced by Limb Ischemia/Reperfusion in Mice through the HMGB1/TLR4/NF-κB Pathway

Objective

Limb ischemia/reperfusion (I/R) injury is a clinical syndrome associated with severe damages to skeletal muscles and other fatal outcomes. Oxidative stress and inflammatory response play vital roles in the development of limb I/R injury. Existing evidence further indicates that Dl-3-n-butylphthalide (NBP) has anti-inflammatory and antioxidative properties. However, whether NBP can protect skeletal muscles from limb I/R injury and the mechanism in mediating the action of NBP treatment still remain to be investigated, which are the focuses of the current study.

Methods

The model of limb I/R injury was established and H&E staining was adopted to assess the pathological changes in skeletal muscles following limb I/R injury. Additionally, the W/D ratio of muscle tissue was also measured. ELISA and biochemical tests were carried out to measure the levels of inflammatory cytokines and oxidative stress in mouse models of limb I/R injury. Moreover, the levels of the HMGB1/TLR4/NF-κB pathway-related proteins were also determined using immunohistochemistry and immunoblotting.

Results

It was established that NBP treatment alleviated I/R-induced pathological changes in muscular tissue of mice, accompanied by lower W/D ratio of skeletal muscular tissue. Meanwhile, the limb I/R-induced inflammation and oxidative stress in skeletal muscles of mice were also inhibited by NBP. Mechanistic study indicated that the alleviatory effect of NBP was ascribed to inactivation of the HMGB1/TLR4/NF-κB pathway.

Conclusions

Our findings highlighted the potential of NBP as a novel strategy for limb I/R-driven muscle tissue damages by suppressing inflammatory response and oxidative stress via the HMGB1/TLR4/NF-κB pathway.

Melatonin attenuates bone cancer pain via the SIRT1/HMGB1 pathway

Bone cancer pain (BCP), which seriously affects the quality of life of patients, remains a clinically challenging problem. Hence, there is an urgent need to investigate new mechanisms and develop new therapeutics to relieve BCP. In the present study, we investigated the analgesic effect of melatonin on BCP and the underlying mechanisms. Male C57BL/6 mice were used to establish BCP models. We found that the levels of sirtuin 1 (SIRT1) and nucleus-high mobility group box-1 (HMGB1) were decreased, whilst the levels of HMGB1, cytoplasm-HMGB1 and inflammatory cytokines (TNF-α, IL-6, IL-1β) were increased in the spinal cord of BCP mice on days 7, 14 and 21 after implantation compared with the levels in sham mice. Intrathecal administration of melatonin dose-dependently increased values of PWMT and TWL compared with the BCP group. However, intrathecal administration of EX527 (a selective SIRT1 antagonist) reversed the analgesic effect of melatonin. Moreover, mice in the melatonin group exhibited an increase in SIRT1 and nucleus-HMGB1, whilst there was a decrease in HMGB1, cytoplasm-HMGB1, rage, acetyl-HMGB1 and inflammatory cytokines compared with those in BCP mice. EX527 also reversed these changes. Furthermore, SIRT1 physically interacted with HMGB1 in the BCP mice. In conclusion, intrathecal administration of melatonin attenuates BCP through SIRT1-dependent inhibition of HMGB1 translocation and inflammatory cytokines. Melatonin may be a promising drug for the clinical treatment of BCP.

A potential new pathway for heparin treatment of sepsis-induced lung injury: inhibition of pulmonary endothelial cell pyroptosis by blocking hMGB1-LPS-induced caspase-11 activation

Sepsis is a significant cause of mortality in critically ill patients. Acute lung injury (ALI) is a leading cause of death in these patients. Endothelial cells exposed to the bacterial endotoxin lipopolysaccharide (LPS) can progress into pyroptosis, a programmed lysis of cell death triggered by inflammatory caspases. It is characterized by lytic cell death induced by the binding of intracellular LPS to caspases 4/5 in human cells and caspase-11 in mouse cells. In mice,caspase-11-dependent pyroptosis plays an important role in endotoxemia. HMGB1 released into the plasma binds to LPS and is internalized into lysosomes in endothelial cells via the advanced glycation end product receptor. In the acidic lysosomal environment, HMGB1 permeates the phospholipid bilayer, which is followed by the leakage of LPS into the cytoplasm and the activation of caspase-11. Heparin is an anticoagulant widely applied in the treatment of thrombotic disease. Previous studies have found that heparin could block caspase-11-dependent inflammatory reactions, decrease sepsis-related mortality, and reduce ALI, independent of its anticoagulant activity. Heparin or modified heparin with no anticoagulant property could inhibit the alarmin HMGB1-LPS interactions, minimize LPS entry into the cytoplasm, and thus blocking caspase-11 activation. Heparin has been studied in septic ALI, but the regulatory mechanism of pulmonary endothelial cell pyroptosis is still unclear. In this paper, we discuss the potential novel role of heparin in the treatment of septic ALI from the unique mechanism of pulmonary endothelial cell pyroptosis.

Extracellular HMGB1 as Inflammatory Mediator in the Progression of Mycoplasma Gallisepticum Infection

High-mobility group box 1 (HMGB1), a member of damage-associated molecular patterns (DAMPs), is involved in the immune regulation of several infectious diseases. Mycoplasma gallisepticum (MG) infection is proved to cause an abnormal immune response, but the role of HMGB1 in MG-induced chronic respiratory disease (CRD) is unclear. In this study, we found that HMGB1 was released from the nucleus to the extracellular in macrophages upon infection with MG. Extracellular HMGB1 bound to TLR2 activating the NF-κB pathway triggering a severe inflammatory storm and promoting the progression of MG infection. More importantly, TLR4 could be activated by HMGB1 to trigger immune disorders after TLR2 was silenced. This disease process could be interrupted by ethyl pyruvate (EP) inhibition of HMGB1 release or glycyrrhizic acid (GA). Furthermore, treatment of MG-infected chickens with GA significantly alleviated immune organ damage. In conclusion, we demonstrate that HMGB1 is secreted extracellularly to form an inflammatory environment upon MG infection, triggering a further cellular inflammatory storm in a positive feedback approach. Blocking MG-induced HMGB1 release or suppression downstream of the HMGB1-TLR2/TLR4 axis may be a promising novel strategy for the treatment of CRD. Furthermore, this study may provide a theoretical reference for understanding non-LPS-activated TLR4 events.

Therapeutic effects and long-term outcomes of HMGB1-targeted therapy in rats and mice with traumatic spinal cord injury: A systematic review and meta-analysis

Background

To date, the clinical need for therapeutic methods to prevent traumatic spinal cord injury (TSCI) progression and improve functional recovery has not been met. High mobility group box-1 (HMGB1) is released by necrotic neurons or secreted by glial cells after TSCI and plays an important role in pathophysiology.

Objective

The purpose of this study was to evaluate the effects of HMGB1-targeted therapy on locomotor function recovery, inflammation reduction, edema attenuation, and apoptosis reduction in rat and mouse models of TSCI.

Methods

We reviewed the literature on HMGB1-targeted therapy in the treatment and prognosis of TSCI. Twelve articles were identified and analyzed from four online databases (PubMed, Web of Science, Cochrane Library and Embase) based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and strict inclusion criteria.

Results

The methodological quality of the 12 articles was poor. The results of the meta-analysis showed that compared with the SCI group, the treatment group had significantly increased locomotor function scores after SCI [n = 159, standardized mean difference (SMD) = 2.31, 95% confidence interval (CI) (1.52, 3.10), P &lt; 0.00001], and the change in locomotor function scores was significantly increased in both the drug and anti-HMGB1 Ab groups (P &lt; 0.000001 and P &lt; 0.000001). A subgroup analysis showed significant differences (P &gt; 0.05) between the drug group [(SMD) = 1.95, 95% CI (0.95, 2.94), P = 0.0001] and the anti-HMGB1 Ab group [(SMD) = 2.89, 95% CI (1.66, 4.13), P &lt; 0.00001]. Compared with the SCI group, HMGB1 expression was significantly diminished [n = 76, SMD = −2.31, 95% CI (−3.71, −0.91), P = 0.001], TNF-α levels were significantly reduced [n = 76, SMD = −2.52, 95% CI (−3.77, −1.27), P &lt; 0.0001], water content was significantly reduced [n = 44, SMD = −3.94, 95% CI (−6.28, −1.61), P = 0.0009], and the number of apoptotic cells was significantly diminished [n = 36, SMD = −3.31, 95% CI (−6.40, −0.22), P = 0.04] in the spinal cord of the treatment group.

Conclusion

HMGB1-targeted therapy improves locomotor function, reduces inflammation, attenuates edema, and reduces apoptosis in rats and mice with TSCI. Intrathecal injection of anti-HMGB1 Ab 0-3 h after SCI may be the most efficacious treatment.

Systematic review registration

PROSPERO, identifier: CRD42022326114.

Natural Compounds for SIRT1-Mediated Oxidative Stress and Neuroinflammation in Stroke: A Potential Therapeutic Target in the Future

Stroke is a fatal cerebral vascular disease with a high mortality rate and substantial economic and social costs. ROS production and neuroinflammation have been implicated in both hemorrhagic and ischemic stroke and have the most critical effects on subsequent brain injury. SIRT1, a member of the sirtuin family, plays a crucial role in modulating a wide range of physiological processes, including apoptosis, DNA repair, inflammatory response, and oxidative stress. Targeting SIRT1 to reduce ROS and neuroinflammation might represent an emerging therapeutic target for stroke. Therefore, we conducted the present review to summarize the mechanisms of SIRT1-mediated oxidative stress and neuroinflammation in stroke. In addition, we provide a comprehensive introduction to the effect of compounds and natural drugs on SIRT1 signaling related to oxidative stress and neuroinflammation in stroke. We believe that our work will be helpful to further understand the critical role of the SIRT1 signaling pathway and will provide novel therapeutic potential for stroke treatment.

Astrocytic CD24 Protects Neuron from Recombinant High-Mobility Group Box 1 Protein(rHMGB1)-Elicited Neuronal Injury

Endogenous host-derived molecules named damage-associated molecular patterns (DAMPs) can induce excessive non-sterile inflammatory responses on recognition of specific membrane-tethered receptors. Here in this study, we aimed to explore the role of DAMP molecule HMGB1 in astrocyte-mediated sterile neuroinflammation and the resultant influences on neurons. In vitro cultured astrocytes were challenged with rHMGB1 and then harvested at 6 h, 12 h, 24 h, 36 h, and 48 h, respectively. The astrocytic CD24 expression was determined by quantitative real-time polymerase chain reaction (qPCR), Western blot analysis and immunofluorescence, nuclear factor kappa B (NF-κB) binding activity was detected by electrophoretic mobility shift assay (EMSA), and the proinflammatory factors, tumor necrosis factor-α (TNF-α), and interleukin 1β (IL-1β), were measured by qPCR. The neuronal morphology was assessed with phase-contrast microscopy. The results showed that astrocytic mRNA and protein CD24 expression began to rise at 24 h, peaked at 36 h, and remained elevated at 48 h after rHMGB1 stimulation, accompanied with enhanced NF-κB binding activity and augmented expression of TNF-α and IL-1β. Furthermore, rHMGB1 caused cocultured neuron damage and was aggregated upon CD24 knockdown. Taken together, these novel findings suggested that rHMGB1 could promote astrocytic CD24 expression, the inhibition of which could aggregate neuronal damage.

Receptor for Advanced Glycation End Products (RAGE): A Pivotal Hub in Immune Diseases

As a critical molecule in the onset and sustainment of inflammatory response, the receptor for advanced glycation end products (RAGE) has a variety of ligands, such as advanced glycation end products (AGEs), S100/calcium granule protein, and high-mobility group protein 1 (HMGB1). Recently, an increasing number studies have shown that RAGE ligand binding can initiate the intracellular signal cascade, affect intracellular signal transduction, stimulate the release of cytokines, and play a vital role in the occurrence and development of immune-related diseases, such as systemic lupus erythematosus, rheumatoid arthritis, and Alzheimer’s disease. In addition, other RAGE signaling pathways can play crucial roles in life activities, such as inflammation, apoptosis, autophagy, and endoplasmic reticulum stress. Therefore, the strategy of targeted intervention in the RAGE signaling pathway may have significant therapeutic potential, attracting increasing attention. In this paper, through the systematic induction and analysis of RAGE-related signaling pathways and their regulatory mechanisms in immune-related diseases, we provide theoretical clues for the follow-up targeted intervention of RAGE-mediated diseases.

Alarmins in autoimmune diseases

Alarmins are endogenous, constitutively expressed, chemotacting and immune activating proteins or peptides released because of non-programmed cell death (i.e. infections, trauma, etc). They are considered endogenous damage-associated molecular patterns (DAMPs), able to induce a sterile inflammation. In the last years, several studies highlighted a possible role of different alarmins in the pathogenesis of various autoimmune and immune-mediated diseases. We reviewed the relevant literature about this topic, for about 160 articles. Particularly, we focused on systemic autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, idiopathic inflammatory myopathies, ANCA-associated vasculitides, Behçet's disease) and cutaneous organ-specific autoimmune diseases (vitiligo, psoriasis, alopecia, pemphigo). Finally, we discussed about future perspectives and potential therapeutic implications of alarmins in autoimmune diseases. In fact, identification of receptors and downstream signal transducers of alarmins may lead to the identification of antagonistic inhibitors and agonists, with the capacity to modulate alarmins-related pathways and potential therapeutic applicability.

Co-treatment with natural HMGB1 inhibitor Glycyrrhizin exerts neuroprotection and reverses Parkinson's disease like pathology in Zebrafish

ETHNOPHARMACOLOGICAL RELEVANCE

Parkinson's disease (PD) is the second most devastating age-related neurodegenerative diseases after Alzheimer diseases (AD) and is characterized by the loss of dopaminergic (DA) neurons in the substantia nigra (SN) and aggregation of α-synuclein (α-syn). The precise etiology of PD is not yet fully understood and lacks the disease-modifying therapeutic strategies that could reverse the ongoing neurodegeneration. In the quest of exploring novel disease modifying therapeutic strategies, natural compounds from plant sources have gained much attention in recent days. Glycyrrhizin (GL) is the main active ingredient of the roots and rhizomes of licorice (Glycyrrhiza glabra L), which are generally used in the treatment of inflammatory diseases or as a tonifying herbal medicine. In Persia, GL is a conventional neuroprotective agent that are used to treat neurological disorders. The traditional use of GL in Japan is to treat chronic hepatitis B. In addition, GL is a natural inhibitor of high mobility group box 1 (HMGB1) which has exerted neuroprotective effect against several HMGB1 mediated pathological conditions.

AIM OF THE STUDY

The study is aimed to evaluate therapeutic effect of GL against PD in zebrafish.

MATERIAL AND METHODS

PD in zebrafish larvae is induced by administration of neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Apoptosis was assessed with TUNEL assay. Gene expression was performed to assess the modulation in genes related to neuroinflammatory and autophagy.

RESULTS

We observed that GL co-treatment increased the length of DA neurons, decreased the number of apoptotic cells in zebrafish brain, and inhibited the loss of vasculature and disorganized vasculature induced by MPTP. GL co-treatment relieved the MPTP-induced locomotor impairment in zebrafish. GL co-treatment suppressed MPTP-induced upregulated mRNA expression of inflammatory markers such as hmgb1a, tlr4b, nfκb, il1β, and il6. GL co-treatment suppressed the autophagy related genes α-syn and atg5 whereas increased the mRNA expression level of parkin and pink1. In addition, molecular docking study reveals that GL has binding interaction with HMGB1, TLR4, and RAGE.

CONCLUSION

Hence, the effect of GL co-treatment on MPTP-induced PD-like condition in zebrafish is to alleviate apoptosis and autophagy, as well as suppress inflammatory responses.

Remote ischemic preconditioning causes transient cell-cycle arrest and renal protection by a NF-kB-dependent Sema5B pathway

Acute kidney injury increases morbidity and mortality, and previous studies have shown that remote ischemic preconditioning (RIPC) reduces the risk of acute kidney injury after cardiac surgery. RIPC increases urinary high mobility group box protein-1 (HMGB1) levels in patients, and this correlates with kidney protection. Here, we show that RIPC reduces renal ischemia-reperfusion injury and improves kidney function in mice. Mechanistically, RIPC increases HMGB1 levels in the plasma and urine, and HMGB1 binds to TLR4 on renal tubular epithelial cells, inducing transcriptomic modulation of renal tubular epithelial cells and providing renal protection, whereas TLR4 activation on nonrenal cells was shown to contribute to renal injury. This protection is mediated by activation of induction of AMPKα and NF-κB; this induction contributes to the upregulation of Sema5b, which triggers a transient, protective G₁ cell cycle arrest. In cardiac surgery patients at high risk for postoperative acute kidney injury, increased HMGB1 and Sema5b levels after RIPC were associated with renal protection after surgery. The results may help to develop future clinical treatment options for acute kidney injury.

Role of high mobility group box protein 1 in depression: A mechanistic and therapeutic perspective

As a common and serious psychiatric disorder, depression significantly affects psychosocial functioning and quality of life. However, the mechanism of depression is still enigmatic and perplexing, which limits its precise and effective therapeutic methods. Recent studies demonstrated that neuroinflammation activation plays an important role in the pathophysiology of depression. In this respect, high mobility group box 1 (HMGB1) may be a possible signaling inducer of neuroinflammation and can be a potential mechanistic and therapeutic target for depression. Herein, we review recent studies on the mechanistic and therapeutic targets of HMGB1 in depression and propose potential perspectives on this topic.

Toll-like receptors and damage-associated molecular patterns in the pathogenesis of heart transplant rejection

Significant strides have been made in our understanding of the immune system and its role in cardiac transplant rejection. Despite the growing knowledge of immune responses, the mortality rate following cardiac transplantation remains grim. Related to procedural and pathological complications, toll-like receptor (TLR) and damage-associated molecular pattern (DAMP) signaling is the most direct and earliest interface between tissue integration and the innate immune response. This in turn can activate an adaptive immune response that further damages myocardial tissue. Furthermore, relevant literature on the status of DAMPs in the context of heart-transplantation remains limited, warranting further attention in clinical and translational research. This review aims to critically appraise the perspectives, advances, and challenges on DAMP-mediated innate immune response in the immune-mediated rejection of cardiac transplantation. Detailed analysis of the influence of TLR and DAMP signaling in mounting the immune response against the transplanted heart holds promise for improving outcomes through early detection and prevention of varied forms of organ rejection.

Gut Microbes Regulate Innate Immunity and Epilepsy

Epilepsy is a common chronic brain disease. There are many clinical methods to control epileptic seizures, such as anti-seizure medications (ASMs) or surgical removal of epileptogenic lesions. However, the pathophysiology of epilepsy is still unknown, making it difficult to control or prevent it. The host's immune system monitors gut microbes, interacts with microbes through pattern recognition receptors such as Toll-like receptors (TLRs) and NOD-like receptors (NLRs) expressed by innate immune cells, and activates immune responses in the body to kill pathogens and balance the relationship between microbes and host. In addition, inflammatory responses induced by the innate immune system are seen in animal models of epilepsy and temporal lobe epilepsy brain tissue to combat pathogens or injuries. This review summarizes the potential relationship between gut microbes, innate immunity, and epilepsy based on recent research to provide more hints for researchers to explore this field further.

HMGB1-mediated restriction of EPO signaling contributes to anemia of inflammation

Anemia of inflammation, also known as anemia of chronic disease, is refractory to erythropoietin (EPO) treatment, but the mechanisms underlying the EPO refractory state are unclear. Here, we demonstrate that high mobility group box-1 protein (HMGB1), a damage-associated molecular pattern molecule recently implicated in anemia development during sepsis, leads to reduced expansion and increased death of EPO-sensitive erythroid precursors in human models of erythropoiesis. HMGB1 significantly attenuates EPO-mediated phosphorylation of the Janus kinase 2/STAT5 and mTOR signaling pathways. Genetic ablation of receptor for advanced glycation end products, the only known HMGB1 receptor expressed by erythroid precursors, does not rescue the deleterious effects of HMGB1 on EPO signaling, either in human or murine precursors. Furthermore, surface plasmon resonance studies highlight the ability of HMGB1 to interfere with the binding between EPO and the EPOR. Administration of a monoclonal anti-HMGB1 antibody after sepsis onset in mice partially restores EPO signaling in vivo. Thus, HMGB1-mediated restriction of EPO signaling contributes to the chronic phase of anemia of inflammation.

Mechanism Involved in Acute Liver Injury Induced by Intestinal Ischemia-Reperfusion

Intestinal ischemia-reperfusion (I/R) is a common pathophysiological process, which can occur in many conditions such as acute enteric ischemia, severe burns, small intestinal transplantation, etc,. Ischemia-reperfusion of the intestine is often accompanied by distal organ injury, especially liver injury. This paper outlined the signal pathways and cytokines involved in acute liver injury induced by intestinal I/R: the NF-κB Signaling Pathway, the P66shc Signaling Pathway, the HMGB1 Signaling Pathway, the Nrf2-ARE Signaling Pathway, the AMPK-SIRT-1 Signaling Pathway and other cytokines, providing new ideas for the prevention and treatment of liver injury caused by reperfusion after intestinal I/R.

Targeting HMGB1-NFκb Axis and miR-21 by Glycyrrhizin: Role in Amelioration of Corneal Injury in a Mouse Model of Alkali Burn

Corneal neovascularization (CNV) is a sight-threatening condition usually associated with various inflammatory settings including chemical injury. High mobility group box 1 (HMGB1) is identified as an inflammatory alarmin in diverse tissue damage. Here, we evaluate the expression of HMGB1 and the consequences of its inhibition through its selective inhibitor glycyrrhizin (GLY) in alkali burn-induced corneal inflammation and neovascularization. GLY effectively attenuated alkali burn-induced HMGB1 expression at both mRNA and protein levels. Furthermore, slit-lamp analysis, ink perfusion, H&amp;E staining, and CD31 histochemical staining showed that GLY relieved corneal neovascularization, while GLY attenuated VEGF expression via inhibiting HMGB1/NF-κB/HIF-1α signal pathway. In addition, GLY treatment decreased the cytokine expression of CCL2 and CXCL5, accompanied by the reduction of their receptors of CCR2 and CXCR2. GLY diminished the inflammatory cell infiltration of the cornea, as well as reduced the expression of IL-1β, IL-6, and TNF-α. Moreover, treatment with GLY reduced the degree of cornea opacity through inactivating extracellular HMGB1 function, which otherwise induces TGF-β1 release and myofibroblast differentiation. Furthermore, we found that GLY treatment attenuated the upregulation of miR-21 levels in alkali burned cornea; while inhibition of miR-21in keratocytes in vitro, significantly inhibited TGF-β1-induced myofibroblast differentiation. Collectively, our results suggested that targeting HMGB1-NFκb axis and miR-21 by GLY could introduce a therapeutic approach to counter CNV.

Effects of Dexmedetomidine on Immune Cells: A Narrative Review

As we all know, dexmedetomidine (DEX), as a highly selective α₂ adrenergic receptor agonist, exerts sedative, anti-anxiety and hypnotic effects by inhibiting the discharge of norepinephrine neurons in locus coeruleus and GABA-related hypnotic pathways. However, the role of DEX in anti-inflammatory and immune regulation has gradually attracted the attention of researchers in recent years. The α₂ adrenergic receptor is one of the members of the adrenergic receptor family, which is widely present in a variety of immune cells and mediates the biological behavior of the inflammatory immune system. At present, there have been more and more studies on the effects of DEX on immune cells and inflammatory responses, but few studies have systematically explored the anti-inflammatory and immunomodulatory effects of DEX. Here, we comprehensively review the published human and animal studies related to DEX, summarize the effects of DEX on immune cells and its role in related diseases, and propose potential research direction.

Progress in Assays of HMGB1 Levels in Human Plasma-The Potential Prognostic Value in COVID-19

Extracellular HMGB1 protein is known to induce inflammatory responses leading to an inflammatory storm. The outbreak of the Severe Acute Respiratory Syndrome COVID-19 due to the SARS-CoV-2 virus has resulted in a huge health concern worldwide. Recent data revealed that plasma/serum HMGB1 levels of patients suffering from inflammation-mediated disorders-such as COVID-19, cancer, and autoimmune disorders-correlate positively with disease severity and vice versa. A late release of HMGB1 in sepsis suggests the existence of a wide therapeutic window for treating sepsis. Rapid and accurate methods for the detection of HMGB1 levels in plasma/serum are, therefore, of great importance for monitoring the occurrence, treatment success, and survival prediction of patients with inflammation-mediated diseases. In this review, we briefly explain the role of HMGB1 in the cell, and particularly the involvement of extracellular HMGB1 (released from the cells) in inflammation-mediated diseases, with an emphasis on COVID-19. The current assays to measure HMGB1 levels in human plasma-Western blotting, ELISA, EMSA, and a new approach based on electrochemical immunosensors, including some of our preliminary results-are presented and thoroughly discussed.

The roles of HMGB1-produced DNA gaps in DNA protection and aging biomarker reversal

The endogenous DNA damage triggering an aging progression in the elderly is prevented in the youth, probably by naturally occurring DNA gaps. Decreased DNA gaps are found during chronological aging in yeast. So we named the gaps "Youth-DNA-GAPs." The gaps are hidden by histone deacetylation to prevent DNA break response and were also reduced in cells lacking either the high-mobility group box (HMGB) or the NAD-dependent histone deacetylase, SIR2. A reduction in DNA gaps results in shearing DNA strands and decreasing cell viability. Here, we show the roles of DNA gaps in genomic stability and aging prevention in mammals. The number of Youth-DNA-GAPs were low in senescent cells, two aging rat models, and the elderly. Box A domain of HMGB1 acts as molecular scissors in producing DNA gaps. Increased gaps consolidated DNA durability, leading to DNA protection and improved aging features in senescent cells and two aging rat models similar to those of young organisms. Like the naturally occurring Youth-DNA-GAPs, Box A-produced DNA gaps avoided DNA double-strand break response by histone deacetylation and SIRT1, a Sir2 homolog. In conclusion, Youth-DNA-GAPs are a biomarker determining the DNA aging stage (young/old). Box A-produced DNA gaps ultimately reverse aging features. Therefore, DNA gap formation is a potential strategy to monitor and treat aging-associated diseases.

Glycyrrhizin attenuates caspase-11-dependent immune responses and coagulopathy by targeting high mobility group box 1

Caspase-11, a cytosolic endotoxin (lipopolysaccharide: LPS) receptor, mediates pyroptosis, coagulopathy and lethality in endoxemia and bacterial sepsis. The activation of caspase-11 requires high mobility group box 1 (HMGB1)-mediated translocation of LPS from the extracellular space to the cytosol. Here we show that HMGB1-dependent cytosolic delivery of LPS was blocked by glycyrrhizin, a medication to treat liver diseases. Glycyrrhizin competitively bound HMGB1 and thereby inhibiting the physical interaction between HMGB1 and LPS. Treatment of glycyrrhizin significantly attenuated caspase-11-dependent immune responses, coagulopathy, organ injury and lethality in endotoxemia and experimental sepsis. Together, our data suggest that pharmacological inhibition of the cytosolic delivery of LPS by glycyrrhizin might be a potential therapeutic strategy to treat sepsis, which is a leading cause of death in hospitals worldwide.

MicroRNA‑23a‑3p targeting of HMGB1 inhibits LPS‑induced inflammation in murine macrophages in vitro

Inflammatory cytokines, including high mobility group box 1 (HMGB1), play a key role in sepsis via various mechanisms, some of which remain unknown. Sepsis is a common cause of death in patients admitted to the intensive care unit. MicroRNAs (miRs) serve an important role in the inflammatory response. The present study aimed to investigate the role of miR-23a-3p in macrophage inflammation and the targeted regulation of HMGB1 expression. The murine macrophage cell line RAW264.7 was subjected to lipopolysaccharide (LPS) treatment to mimic the inflammation involved in sepsis in vitro. Reverse transcription-quantitative PCR was performed to measure miR-23a-3p expression and mRNA expression. Protein levels were determined using ELISA and western blotting. The target binding relationship between miR-23a-3p and the HMGB1 3'untranslated region was predicted and validated with a dual luciferase reporter assay. HMGB1 expression was increased and miR-23a-3p expression significantly reduced in patients with sepsis and in LPS-treated RAW264.7 cells in comparison with controls. Overexpression of miR-23a-3p reduced interleukin (IL)-6 and tumor necrosis factor (TNF)-α expression in RAW264.7 cells under LPS stimulation, while silencing of miR-23a-3p elevated the expression of IL-6 and TNF-α in comparison with controls. The inhibitory effect of miR-23a-3p on LPS-induced inflammation could be abolished by HMGB1 upregulation in RAW264.7 cells. HMGB1 was targeted by miR-23a-3p. miR-23a-3p is expressed at reduced levels during inflammation in sepsis, and overexpression of miR-23a-3p inhibits LPS-induced inflammation in murine macrophages in vitro by directly downregulating HMGB1. The results of the present study provided a novel insight into the molecular mechanism underlying HMGB1 expression at the post-transcriptional level in sepsis.

HMGB1 augments cognitive impairment in sepsis-associated encephalopathy by binding to MD-2 and promoting NLRP3-induced neuroinflammation

BACKGROUND

Sepsis-associated encephalopathy (SAE) always manifests with severe inflammatory symptoms and cognitive impairment. High mobility group box 1 (HMGB1) is a pro-inflammatory cytokine. In this study we investigated the role of HMGB1 in SAE.

METHODS

An SAE mouse model was established through cecal ligation and puncture surgery and then injected with adenovirus short hairpin RNA (Ad-sh)-HMGB1 or Ad-sh-myeloid differentiation protein (MD-2). The cognitive impairment and pathological injury in mice of different groups were evaluated using the Morris water maze experiment, Y-maze test, tail suspension test, fear conditioning test, and haematoxylin-eosin staining. The expressions of HMGB1 (fully reduced and disulfide (ds)HMGB1), MD-2, and NLRP3 in SAE mice were determined. Then, levels of inflammatory cytokines were measured. The binding relation between HMGB1 and MD-2 was predicted and certified. Additionally, MD-2 was downregulated to verify the role of the binding of HMGB1 and MD-2 in neuroinflammation and cognitive impairment in SAE.

RESULTS

Expressions of HMGB1, MD-2, NLRP3, and inflammatory cytokines were enhanced in the SAE mouse model, which were in parallel with impaired cognitive function. HMGB1 silencing resulted in downregulated NLRP3 expression and alleviated neuroinflammation and cognitive impairment in SAE mice. Mechanically, dsHMGB1 bound to MD-2 to activate NLRP3, thereby exacerbating neuroinflammation and cognitive impairment in SAE mice. The limited binding of HMGB1 and MD-2 downregulated NLRP3 expression to alleviate neuroinflammation and cognitive impairment in SAE mice.

CONCLUSION

HMGB1 was overexpressed in SAE, and dsHMGB1 bound to MD-2 to activate NLRP3 inflammasome, inducing neuroinflammation and cognitive impairment in SAE.

Paracrine signal emanating from stressed cardiomyocytes aggravates inflammatory microenvironment in diabetic cardiomyopathy

Myocardial inflammation contributes to cardiomyopathy in diabetic patients through incompletely defined underlying mechanisms. In both human and time-course experimental samples, diabetic hearts exhibited abnormal ER, with a maladaptive shift over time in rodents. Furthermore, as a cardiac ER dysfunction model, mice with cardiac-specific p21-activated kinase 2 (PAK2) deletion exhibited heightened myocardial inflammatory response in diabetes. Mechanistically, maladaptive ER stress-induced CCAAT/enhancer-binding protein homologous protein (CHOP) is a novel transcriptional regulator of cardiac high-mobility group box-1 (HMGB1). Cardiac stress-induced release of HMGB1 facilitates M1 macrophage polarization, aggravating myocardial inflammation. Therapeutically, sequestering the extracellular HMGB1 using glycyrrhizin conferred cardioprotection through its anti-inflammatory action. Our findings also indicated that an intact cardiac ER function and protective effects of the antidiabetic drug interdependently attenuated the cardiac inflammation-induced dysfunction. Collectively, we introduce an ER stress-mediated cardiomyocyte-macrophage link, altering the macrophage response, thereby providing insight into therapeutic prospects for diabetes-associated cardiac dysfunction.

Molecular hydrogen is a promising therapeutic agent for pulmonary disease

Molecular hydrogen exerts biological effects on nearly all organs. It has anti-oxidative, anti-inflammatory, and anti-aging effects and contributes to the regulation of autophagy and cell death. As the primary organ for gas exchange, the lungs are constantly exposed to various harmful environmental irritants. Short- or long-term exposure to these harmful substances often results in lung injury, causing respiratory and lung diseases. Acute and chronic respiratory diseases have high rates of morbidity and mortality and have become a major public health concern worldwide. For example, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic. An increasing number of studies have revealed that hydrogen may protect the lungs from diverse diseases, including acute lung injury, chronic obstructive pulmonary disease, asthma, lung cancer, pulmonary arterial hypertension, and pulmonary fibrosis. In this review, we highlight the multiple functions of hydrogen and the mechanisms underlying its protective effects in various lung diseases, with a focus on its roles in disease pathogenesis and clinical significance.

Macrophage Polarization and Plasticity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that attacks almost every organ. The condition mostly happens to adults but is also found in children, and the latter have the most severe manifestations. Among adults, females, especially non-Caucasian, are mostly affected. Even if the etiology of SLE remains unclear, studies show a close relation between this disease and both genetics and environment. Despite the large number of published articles about SLE, we still do not have a clear picture of its pathogenesis, and no specific drug has been found to treat this condition effectively. The implication of macrophages in SLE development is gaining ground, and studying it could answer these gaps. Indeed, both in vivo and in vitro studies increasingly report a strong link between this disease and macrophages. Hence, this review aims to explore the role of macrophages polarization and plasticity in SLE development. Understanding this role is of paramount importance because in-depth knowledge of the connection between macrophages and this systemic disease could clarify its pathogenesis and provide a foundation for macrophage-centered therapeutic approaches.

Nanocurcumin alleviates inflammation and oxidative stress in LPS-induced mastitis via activation of Nrf2 and suppressing TLR4-mediated NF-κB and HMGB1 signaling pathways in rats

Coliform mastitis is a worldwide serious disease of the mammary gland. Curcumin is a pleiotropic polyphenol obtained from turmeric, but it is hydrophobic and rapidly eliminated from the body. However, nanoformulation of curcumin significantly improves its pharmacological activity by enhancing its hydrophobicity and oral bioavailability. Our study aimed to investigate the possible antioxidant and anti-inflammatory effects of nanocurcumin as a prophylactic against LPS-induced coliform mastitis in rat model, where LPS was extracted from a field strain of Escherichia coli (bovine mastitis isolate). The study was conducted on twenty lactating Wistar female rats divided into four equal groups, and the mastitis model was initiated by injection of LPS through the duct of the mammary gland. The results showed that nanocurcumin significantly attenuated the lipid peroxidation (MDA), oxidized glutathione, the release of pro-inflammatory cytokines (TNF-α and IL-1β), and the gene expression of TLR4, NF-κB p65, and HMGB1. Meanwhile, it improved the reduced glutathione level and Nrf2 activity and preserved the normal alveolar architecture. These findings suggested that nanocurcumin supplementation can be a promising potential protective approach for coliform mastitis.

Revisiting Excitotoxicity in Traumatic Brain Injury: From Bench to Bedside

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality. Consequences vary from mild cognitive impairment to death and, no matter the severity of subsequent sequelae, it represents a high burden for affected patients and for the health care system. Brain trauma can cause neuronal death through mechanical forces that disrupt cell architecture, and other secondary consequences through mechanisms such as inflammation, oxidative stress, programmed cell death, and, most importantly, excitotoxicity. This review aims to provide a comprehensive understanding of the many classical and novel pathways implicated in tissue damage following TBI. We summarize the preclinical evidence of potential therapeutic interventions and describe the available clinical evaluation of novel drug targets such as vitamin B12 and ifenprodil, among others.