HMGB1 in health and disease

Neuroprotective Effects of Celastrol in Neurodegenerative Diseases-Unscramble Its Major Mechanisms of Action and Targets

There are rarely new therapeutic breakthroughs present for neurodegenerative diseases in the last decades. Thus, new effective drugs are urgently needed for millions of patients with neurodegenerative diseases. Celastrol, a pentacyclic triterpenoid compound, is one of the main active ingredients isolated from Tripterygium wilfordii Hook. f. that has multiple biological activities. Recently, amount evidence indicates that celastrol exerts neuroprotective effects and holds therapeutic potential to serve as a novel agent for neurodegenerative diseases. This review focuses on the therapeutic efficacy and major regulatory mechanisms of celastrol to rescue damaged neurons, restore normal cognitive and sensory motor functions in neurodegenerative diseases. Importantly, we highlight recent progress regarding identification of the drug targets of celastrol by using advanced quantitative chemical proteomics technology. Overall, this review provides novel insights into the pharmacological activities and therapeutic potential of celastrol for incurable neurodegenerative diseases.

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.

HMGB1 mediates invasion and PD-L1 expression through RAGE-PI3K/AKT signaling pathway in MDA-MB-231 breast cancer cells

BACKGROUND

High-mobility group box 1 (HMGB1) is increased in breast cancer cells as the result of exposure to the secreted substances from cancer-associated fibroblasts and plays a crucial role in cancer progression and drug resistance. Its effect, however, on the expression of programmed death ligand 1 (PD-L1) in breast cancer cells has not been investigated. This study aimed to investigate the mechanism of HMGB1 through receptors for advanced glycation end products (RAGE) on cell migration/invasion and PD-L1 expression in breast cancer cells.

METHODS

A 3-dimensional (3-D) migration and invasion assay and Western blotting analysis to evaluate the function and the mechanism under recombinant HMGB1 (rHMGB1) treatment with knockdown of RAGE using shRAGE and PI3K/AKT inhibitors was performed.

RESULTS

The results revealed that rHMGB1 induced MDA-MB-231 cell migration and invasion. The knockdown of RAGE using shRAGE and PI3K/AKT inhibitors attenuated 3-D migration and invasion in response to rHMGB1 compared to mock cells. PD-L1 up-regulation was observed in both parental MDA-MB-231 (P) and MDA-MB-231 metastasis to bone marrow (BM) cells treated with rHMGB1, and these effects were alleviated in RAGE-knock down (KD) breast cancer cells as well as in PI3K/AKT inhibitor-treated cells.

CONCLUSIONS

Collectively, these findings indicate that HMGB1-RAGE through PI3K/AKT signaling promotes not only breast cancer cell invasion but also PD-L1 expression which leads to the destruction of the effector T cells. The attenuating HMGB1-RAGE-PI3K/AKT pathway may help to attenuate breast cancer cell aggressive phenotypes.

Decreased HMGB1 expression contributed to cutaneous toxicity caused by lapatinib

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

The HN1/HMGB1 axis promotes the proliferation and metastasis of hepatocellular carcinoma and attenuates the chemosensitivity to oxaliplatin

Hematological and neurological expressed 1 (HN1) is closely associated with the proliferation and metastasis of various tumors. However, the physiological functions and clinical significance of HN1 in hepatocellular carcinoma (HCC) remain indistinct. In this study, we investigated the role of HN1 in the pathogenesis of HCC and the underlying mechanism using clinical data from HCC patients, in vitro experiments utilizing HCC cell lines and in vivo animal models. We demonstrated that the overexpressed HN1 in HCC was correlated with patients' adverse outcomes. The gain and loss of function experiments indicated that HN1 could promote the proliferation, migration, and invasion of HCC cells in vitro. Furthermore, we found that HN1 knockdown sensitized HCC cells to oxaliplatin. Mechanically, HN1 prevented HMGB1 protein from ubiquitination and degradation via the autophagy-lysosome pathway, which was related to the interaction between HN1 protein and TRIM28 protein. In the nucleus, the downregulation of HMGB1 followed by HN1 knockdown resulted in increased DNA damage and cell death in the oxaliplatin-treated HCC cells. In the cytoplasm, HN1 regulated autophagy via HMGB1. Furthermore, HN1 knockdown in combination with HMGB1 overexpression restored the aggressive phenotypes of HCC cells and the sensitivity of these cells to oxaliplatin. HN1 knockdown inhibited the tumor growth and metastasis, and promoted the anticancer efficiency of oxaliplatin in vivo. In conclusion, our data suggest that the HN1/HMGB1 axis plays an important role in the development/progression and chemotherapy of HCC. Our findings indicate that the HN1/HMGB1 axis may be a promising therapeutic target for HCC treatment.

Analysis of the tumor microenvironment and mutation burden identifies prognostic features in thymic epithelial tumors

Thymic epithelial tumors (TETs) are one of the rarest adult malignancies in the anterior mediastinum. Thymic carcinomas (TCs) are less prevalent among TETs, but they are more clinically aggressive. Immunotherapy has emerged as a promising therapeutic approach for refractory TETs, even though chemotherapy remains the conventional treatment for the advanced disease. However, limited attention has been paid to the features of the tumor microenvironment (TME) which might provide clinically relevant information and guide treatment regimen design. Especially, to date, there have been only a few studies focusing on the differences between the TME and genomic features preserved by TETs and TCs. We analyzed the TME and genomic characteristics of TETs using RNA sequencing and whole-exome sequencing, finding that distinct characteristics of TME in different pathogenic subtypes of TETs. According to those findings, we found that thymic carcinomas had significantly lower expression of HMGB1, a pro-inflammatory cytokine-related gene, than thymomas, and low HMGB1 expression was linked to a poor prognosis. Additionally, higher mutation burdens were significantly associated with the later stage and more advanced pathological types. Thymoma patients with lower mutation burdens tended to relapse within 3 years. In summary, different characteristics of TME and genomic features between thymoma and thymic carcinoma were associated with clinical outcomes of TETs and presented promisingly predictive value for efficacy and toxicity of immunotherapy.

HMGB1: A Potential Target of Nervus Vagus Stimulation in Pediatric SARS-CoV-2-Induced ALI/ARDS

From the start of pandemics, children were described as the ones who were less affected by SARS-Cov-2 or COVID-19, which was mild in most of the cases. However, with the growing vaccination rate of the adult population, children became more exposed to the virus and more cases of severe SARS-CoV-2-induced ARDS are being diagnosed with the disabling consequences or lethal outcomes associated with the cytokine storm. Thus, we do hypothesize that some of the children could benefit from nervus vagus stimulation during COVID-19 ARDS through the inhibition of HMGB1 release and interaction with the receptor, resulting in decreased neutrophil accumulation, oxidative stress, and coagulopathy as well as lung vascular permeability. Moreover, stimulation through alpha-7 nicotinic acetylcholine receptors could boost macrophage phagocytosis and increase the clearance of DAMPs and PAMPs. Further rise of FGF10 could contribute to lung stem cell proliferation and potential regeneration of the injured lung. However, this stimulation should be very specific, timely, and of proper duration, as it could lead to such adverse effects as increased viral spread and systemic infection, especially in small children or infants due to specific pediatric immunity state and anatomical features of the respiratory system.

CgHMGB1 functions as a broad-spectrum recognition molecule to induce the expressions of CgIL17-5 and Cgdefh2 via MAPK or NF-κB signaling pathway in Crassostrea gigas

High-mobility group box 1 (HMGB1), a highly conserved nucleoprotein, functions in immune recognition, inflammation and antibacterial immunization in vertebrates. In the present study, the mediation mechanism of CgHMGB1 in activating MAPK and NF-κB/Rel signaling pathways to induce the expressions of immune effectors was investigated. CgHMGB1 mRNA was detected in all tested developmental stages from fertilized egg to D-larvae, with the higher expressions in 4-cell and 8-cell stages. CgHMGB1 proteins were mainly distributed in haemocyte granulocytes. The expressions of CgHMGB1 mRNA in haemocytes increased significantly after Vibrio splendidus stimulation, and CgHMGB1 protein translocated into the haemocyte cytoplasm and release into cell-free haemolymph. The phosphorylation of CgERK and CgP38 were induced, the nuclear translocation of CgRel were promoted, and the mRNA expressions of CgIL17-5 and Cgdefh2 increased significantly after rCgHMGB1 treatment. Obvious branchial swelling and cilium shedding were observed after rCgHMGB1 treatment. rCgHMGB1 exhibited binding activity to different polysaccharides, bacteria, and fungi. rCgHMGB1 also displayed obvious antibacterial activity to V. splendidus and E. coli. These results indicated that CgHMGB1 functioned as an immune recognition molecule to recognize various PAMPs and bacteria to induce the mRNA expressions of CgIL17-5 and Cgdefh2 via the activation of MAPK and NF-κB signaling pathways in oysters.

Investigation of the relationship between community-acquired respiratory distress syndrome toxin and the high-mobility group box protein 1-toll-like receptors-myeloid differentiation factor 88 signaling pathway in Mycoplasma pneumoniae pneumonia

BACKGROUND

In recent years, reports of refractory Mycoplasma pneumoniae pneumonia (RMPP) have gradually increased, including reports on how these conditions threaten the lives of children. However, the specific mechanism of Mycoplasma pneumoniae pneumonia (MPP) remains unclear. This study aimed to investigate the relationship between community-acquired respiratory distress syndrome toxin (CARDS TX) and High-mobility group box protein 1-Toll-like receptors-Myeloid differentiation factor 88 (HMGB1-TLRs-MyD88) in MPP and to examine the immune pathogenesis of Mycoplasma pneumoniae infection.

METHODS

Children who were diagnosed with MPP and examined by bronchoscopy were included in the MPP group. Additionally, children who underwent bronchoscopy because of bronchial foreign bodies in the same period were included in the control group. Gene expression of CARDS TX, HMGB1, Toll-like receptor 2 (TLR2), Toll-like receptor 4 (TLR4), MyD88, and cluster of differentiation 14 (CD14) in bronchoalveolar lavage fluid (BALF) were detected using real-time reverse transcription-polymerase chain reaction. Correlations between CARDS TX and HMGB1-TLRs-MyD88 were analyzed.

RESULTS

CARDS TX, HMGB1, TLR2, MyD88, and CD14 mRNA expression in BALF in the MPP group was significantly higher than that in the control group (all P < 0.05). CARDS TX mRNA expression was positively correlated with HMGB1, TLR2, MyD88, and CD14 mRNA expression (all P < 0.05). Furthermore, HMGB1 mRNA expression was positively correlated with TLR2, MyD88, and CD14 mRNA expression (all P < 0.05).

CONCLUSIONS

CARDS TX may participate in the immune pathogenesis of MPP through the HMGB1-TLRs/CD14-MyD88 pathway.

The Role of HMGB1 in Rheumatic Diseases

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

Glycyrrhiza uralensis Fisch. and its active components mitigate Semen Strychni-induced neurotoxicity through regulating high mobility group box 1 (HMGB1) translocation

Semen Strychni has long been used for the treatment of rheumatoid arthritis, facioplegia and myasthenia gravis due to its anti-inflammation and anti-nociceptive properties in China. However, the fatal neurotoxicity of Semen Strychni has limited its wider clinical application. To investigate the acute toxicity induced by Semen Strychni and the detoxification of liquorice, we evaluated inflammation, oxidative stress and the translocation of high mobility group box 1 (HMGB1) in rats. As a result, there were obvious oxidative stress and inflammation in hippocampus after the Semen Strychni extracts (STR) treatment in rats. Liquorice extracts (LE) and its three active monomers - glycyrrhizic acid (GA), liquiritigenin (LIQ), isoliquiritigenin (ISL) showed the potential for mitigating STR-induced neurotoxicity. HMGB1 levels in cytoplasm and serum and the levels of two downstream receptors RAGE and TLR4 were significantly increased after STR treatment. Through using LE and the monomers, the nucleocytoplasmic transport and release of HMGB1 were inhibited. In addition, the binding between HMGB1 and TLR4 was weakened in detoxification groups comparing with the STR group. Taken together, these findings indicated that liquorice and its active components alleviated acute neurotoxicity induced by Semen Strychni partly via HMGB1-related pathway.

Involvement of High Mobility Group Box 1 Protein in Optic Nerve Damage in Diabetes

Introduction

Diabetic patients routinely have high levels of high mobility group box 1 (HMGB1) protein in their plasma, vitreous and ocular membranes, which is strongly correlated with subclinical chronic inflammation in the eye. Our previous work has suggested that high HMGB1 in diabetes plays a role in retinal inflammation and angiogenesis, but its role in the optic nerve damage is unclear. Therefore, our goal is to examine the role of HMGB1 in optic nerve damage in diabetes.

Methods

Gene expression of HMGB1 was quantified in the optic nerve from streptozotocin-induced diabetic mice by qRT-PCR, and their protein expressions by Western blot analysis and immunofluorescence staining. Using immunohistochemical technique, expression of reactive astrogliosis (indicator of neuroinflammation) and nerve demyelination/damage were determined by quantifying glial fibrillary acid protein (GFAP) and myelin basic protein (MBP), respectively. The role of HMGB1 in the optic nerve damage and alteration visual pathways was confirmed in mice receiving glycyrrhizin, a HMGB1 inhibitor. Similar parameters were measured in the optic nerve from human donors with diabetes.

Results

Compared to normal mice, diabetic mice exhibited increased levels of HMGB1, higher GFAP expression, and decreased MBP in the optic nerve. Double immunofluorescence microscopy revealed that diabetes induced increased HMGB1 immunoreactivities were significantly colocalized with GFAP in the optic nerve. Glycyrrhizin supplementation effectively reduced HMGB1 and maintained normal axonal myelination and visual conduction. Results from mice optic nerve confirmed the results obtained from human donors with diabetes.

Discussions

Thus, diabetes-induced HMGB1 upregulation promotes optic nerve demyelination and inflammation. The regulation of HMGB1 activation has potential to protect optic nerve damage and the abnormalities of visual pathways in diabetic patients.

Interaction Network of Porcine Circovirus Type 3 and 4 Capsids with Host Proteins

An extensive understanding of the interactions between host cellular and viral proteins provides clues for studying novel antiviral strategies. Porcine circovirus type 3 (PCV3) and type 4 (PCV4) have recently been identified as viruses that can potentially damage the swine industry. Herein, 401 putative PCV3 Cap-binding and 484 putative PCV4 Cap-binding proteins were characterized using co-immunoprecipitation and liquid chromatography-mass spectrometry. Both PCV3 and PCV4 Caps shared 278 identical interacting proteins, but some putative interacting proteins (123 for PCV3 Cap and 206 for PCV4 Cap) differed. A protein-protein interaction network was constructed, and according to gene ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analyses, both PCV3 Cap- and PCV4 Cap-binding proteins participated mainly in ribosome biogenesis, nucleic acid binding, and ATP-dependent RNA helicase activities. Verification assays of eight putative interacting proteins indicated that nucleophosmin-1, nucleolin, DEAD-box RNA helicase 21, heterogeneous nuclear ribonucleoprotein A2/B1, YTH N6-methyladenosine RNA binding protein 1, and Y-box binding protein 1 bound directly to both PCV3 and PCV4 Caps, but ring finger protein 2 and signal transducer and activator of transcription 6 did not. Therefore, the interaction network provided helpful information to support further research into the underlying mechanisms of PCV3 and PCV4 infection.

Complement System and Alarmin HMGB1 Crosstalk: For Better or Worse

Our immune system responds to infectious (PAMPs) and tissue damage (DAMPs) signals. The complement system and alarmin High-Mobility Group Box 1 (HMGB1) are two powerful soluble actors of human host defense and immune surveillance. These systems involve molecular cascades and amplification loops for their signaling or activation. Initially activated as alarm raising systems, their function can be finally switched towards inflammation resolution, where they sustain immune maturation and orchestrate repair mechanisms, opening the way back to homeostasis. However, when getting out of control, these defense systems can become deleterious and trigger serious cellular and tissue damage. Therefore, they can be considered as double-edged swords. The close interaction between the complement and HMGB1 pathways is described here, as well as their traditional and non-canonical roles, their functioning at different locations and their independent and collective impact in different systems both in health and disease. Starting from these systems and interplay at the molecular level (when elucidated), we then provide disease examples to better illustrate the signs and consequences of their roles and interaction, highlighting their importance and possible vicious circles in alarm raising and inflammation, both individually or in combination. Although this integrated view may open new therapeutic strategies, future challenges have to be faced because of the remaining unknowns regarding the molecular mechanisms underlying the fragile molecular balance which can drift towards disease or return to homeostasis, as briefly discussed at the end.

Second-trimester serum high mobility group box-1 and uterine artery Doppler to predict preeclampsia

The objective of this study was to identify the predictive value for preeclampsia of second-trimester serum high mobility group box-1 (HMGB1) and uterine artery Doppler in singleton pregnancies. Between April 2020 and April 2021, a prospective study was conducted on singleton pregnancies with a gestational age of 16–20⁺⁶ weeks at King Chulalongkorn Memorial Hospital, Department of Obstetrics and Gynecology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. Maternal characteristics, uterine artery Doppler, and serum HMGB1 were collected. Serum HMGB1 levels and mean uterine artery pulsatility index (UAPI) were combined to calculate the predictive value for preeclampsia. A total of 393 pregnant women were analyzed, with 25 cases (6.4%) developing preeclampsia and 5 cases (1.3%) developing early-onset preeclampsia. Baseline characteristics of preeclampsia and normal pregnant women were comparable. Preeclamptic pregnant women had significantly higher mean serum HMGB1 levels than normal pregnant women (1112.8 ± 363.1 ng/mL vs 910.8 ± 486.1 ng/mL, p = 0.013). There was no difference in the mean UAPI. Any early-diastolic notching was found more frequently in the preeclampsia group (32.0% vs 12.5%, p = 0.013). The cut-off value for serum HMGB1 levels above 1.04 MoM as abnormal value to predict preeclampsia had sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 88.0%, 53.5%, 11.4% and 98.5%, respectively. When using abnormal serum HMGB1 levels combined with mean UAPI above 95th percentile, the sensitivity, specificity, PPV and NPV to predict preeclampsia were 88.0%, 50.8%, 10.8% and 98.4%, respectively. This study showed that serum HMGB1 at 16–20⁺⁶ weeks of gestation were effective in predicting preeclampsia. The addition of UAPI did not improve the prediction performance.

Serum expression of Vascular Endothelial-Cadherin, CD44, Human High mobility group B1, Kallikrein 6 proteins in different stages of laryngeal intraepithelial lesions and early glottis cancer

Background

The study was designed to evaluate the potential validity and utility of selected molecular markers in serum samples from patients with specific stages of laryngeal intraepithelial lesions that could serve as diagnostic tools in differentiation of benign and dysplastic lesions from invasive pathologies.

Methods

Prospective study included 80 consecutive patients with vocal fold lesions treated at the single otorhinolaryngology centre. All participants had surgical resection of the lesion. Blood samples were collected from each patient before the surgery. Final diagnosis was confirmed on histopathological examination and included 39 (48.75%) non-dysplastic lesions, eight (10%) low-grade dysplasia, six (7.5%) high-grade dysplasia and 27 (33.75%) invasive cancers. The ELISA procedures were performed according to the manufacturer's instruction. Individual serum concentration of selected proteins was reported in ng/ml: Vascular Endothelial-Cadherin Complex (VE-cad), CD44, Human High mobility group protein B1(HMGB1), Kallikrein 6.

Results

The highest mean levels of HMGB1, KLK6 and VE-cad were detected in sera of patients with low-grade dysplasia (81.14, 24.33, 14.17 respectively). Soluble CD44 was the most elevated in patients with non-dysplastic lesions (2.49). The HMGB1, KLK6 and VE-cad serum levels were increasing from non-dysplastic to low-grade dysplasia and followed by the decrease for high-grade dysplasia and invasive cancer, however the differences were not significant (p-values 0.897, 0.354, 0.1 respectively). Patients' serum had the highest CD44 concentration in non-dysplastic and low-grade dysplasia with the following decrease through high-grade dysplasia and invasive cancer. GERD symptomatic patients had higher levels of KLK6 and CD44 than other patients (p-value 0.06 and 0.084 respectively). There were no significant differences of biomarkers levels related to patients' gender (p-value from 0.243 to 1) or smoking status (p-value from 0.22 to 0.706).

Conclusions

VE-cad, HMGB1, CD44 and KLK6 did not prove to be reliable biomarkers implicating malignant potential within vocal fold hypertrophic intraepithelial lesions.

HMGB1 in macrophage nucleus protects against pressure overload induced cardiac remodeling via regulation of macrophage differentiation and inflammatory response

Pressure overload induced cardiac remodeling is associated with a complex spectrum of pathophysiological mechanisms. As inflammatory cells, macrophages maintain a critical position in mechanical stress-induced myocardial remodeling. HMGB1 is a highly conserved, ubiquitous protein in various types of cells whose biological roles are closely dependent on subcellular sites. However, whether HMGB1 expressed in macrophages performs the protective or pathological responses in cardiac remodeling is unknown. In this study, we generated the myeloid-specific HMGB1 knockout mice and detected the effects of macrophage HMGB1 in response to pathophysiological stress. Our data showed HMGB1 in macrophages played a protective role against the pressure overload induced cardiac pathophysiology. The deletion of HMGB1 in macrophages gains more differentiation of M1-type pro-inflammatory macrophage during the mechanical stress-induced myocardial remodeling, thereby aggravating the inflammatory response in whole heart, resulting in accelerated deterioration of cardiac function. Moreover, in vitro data also validated HMGB1 got involved in the process of macrophage polarization. Macrophages without HMGB1 are more inclined to differentiate into M1 during the stretch process. In summary, the present results indicated that loss of HMGB1 in macrophages can exacerbate heart failure through increased differentiation of pro-inflammatory macrophages and enhanced inflammatory response.

Extracellular HMGB1 Impairs Macrophage-Mediated Efferocytosis by Suppressing the Rab43-Controlled Cell Surface Transport of CD91

High-mobility group box 1 (HMGB1) protein can impair phagocyte function by suppressing the macrophage-mediated clearance of apoptotic cells (ACs), thereby delaying inflammation resolution in the lungs and allowing the progression of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, the precise mechanism underlying this HMGB1-mediated inhibition of efferocytosis remains unknown. The aim of this study was to determine the effect of HMGB1 on macrophage-mediated efferocytosis. We discovered that HMGB1 prevented efferocytosis by bone marrow-derived macrophages (BMDMs) and suppressed the expression of Ras-related GTP-binding protein 43 (Rab43), a member of the Ras-associated binding (Rab) family. The downregulation of Rab43 expression resulted in impaired clearance of apoptotic thymocytes by BMDMs. Subsequent analysis of HMGB1-treated and Rab43-deficient BMDMs revealed the inhibited transport of cluster of differentiation 91 (CD91), a phagocyte recognition receptor, from the cytoplasm to the cell surface. Notably, Rab43 directly interacted with CD91 to mediate its intercellular trafficking. Furthermore, Rab43 knockout delayed the inflammation resolution and aggravated the lung tissue damage in mice with ALI. Therefore, our results provide evidence that HMGB1 impairs macrophage-mediated efferocytosis and delays inflammation resolution by suppressing the Rab43-regulated anterograde transport of CD91, suggesting that the restoration of Rab43 levels is a promising strategy for attenuating ALI and ARDS in humans.

Nonoxid-HMGB1 Attenuates Cognitive Impairment After Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is a major global burden of health. As an accepted inflammatory mediator, high mobility group box 1 (HMGB1) is found to be effective in facilitating neurogenesis and axonal regeneration. SH3RF2 (also known as POSHER), an E3 ligase SH3 domain-containing ring finger 2, belongs to the SH3RF family of proteins. Here, we aimed to investigate the role of redox states of HMGB1 on neurite outgrowth and regeneration both in vitro and in vivo. In this study, distinct recombinant HMGB1 redox isoforms were used. Sequencing for RNA-seq and data analysis were performed to find the potential downstream target of nonoxid-HMGB1 (3S-HMGB1). Protein changes and distribution of SH3RF2 were evaluated by western blot assays and immunofluorescence. Lentivirus and adeno-associated virus were used to regulate the expression of genes. Nonoxid-HMGB1-enriched exosomes were constructed and used to treat TBI rats. Neurological function was evaluated by OF test and NOR test. Results demonstrated that nonoxid-HMGB1 and fr-HMGB1, but not ds-HMGB1, promoted neurite outgrowth and axon elongation. RNA-seq and western blot assay indicated a significant increase of SH3RF2 in neurons after treated with nonoxid-HMGB1 or fr-HMGB1. Notably, the beneficial effects of nonoxid-HMGB1 were attenuated by downregulation of SH3RF2. Furthermore, nonoxid-HMGB1 ameliorated cognitive impairment in rats post-TBI via SH3RF2. Altogether, our experimental results suggest that one of the promoting neurite outgrowth and regeneration mechanisms of nonoxid-HMGB1 is mediated through the upregulated expression of SH3RF2. Nonoxid-HMGB1 is an attractive therapeutic candidate for the treatment of TBI.

A Monoclonal Anti-HMGB1 Antibody Attenuates Neurodegeneration in an Experimental Animal Model of Glaucoma

Neuroinflammation is a crucial process for the loss of retinal ganglion cells (RGC), a major characteristic of glaucoma. High expression of high-mobility group box protein 1 (HMGB1) plays a detrimental role in inflammatory processes and is elevated in the retinas of glaucoma patients. Therefore, this study aimed to investigate the effects of the intravitreal injection of an anti-HMGB1 monoclonal antibody (anti-HMGB1 Ab) in an experimental animal model of glaucoma. Two groups of Spraque Dawley rats received episcleral vein occlusion to chronically elevate intraocular pressure (IOP): (1) the IgG group, intravitreal injection of an unspecific IgG as a control, n = 5, and (2) the HMGB1 group, intravitreal injection of an anti-HMGB1 Ab, n = 6. IOP, retinal nerve fiber layer thickness (RNFLT), and the retinal flash response were monitored longitudinally. Post-mortem examinations included immunohistochemistry, microarray, and mass spectrometric analysis. RNFLT was significantly increased in the HMGB1 group compared with the IgG group (p < 0.001). RGC density showed improved neuronal cell survival in the retina in HMGB1 compared with the IgG group (p < 0.01). Mass spectrometric proteomic analysis of retinal tissue showed an increased abundance of RNA metabolism-associated heterogeneous nuclear ribonucleoproteins (hnRNPs), such as hnRNP U, D, and H2, in animals injected with the anti-HMGB1 Ab, indicating that the application of the antibody may cause increased gene expression. Microarray analysis showed a significantly decreased expression of C-X-C motif chemokine ligand 8 (CXCL8, p < 0.05) and connective tissue growth factor (CTGF, p < 0.01) in the HMGB1 group. Thus, these data suggest that intravitreal injection of anti-HMGB1 Ab reduced HMGB1-dependent inflammatory signaling and mediated RGC neuroprotection.

Cell Senescence and Central Regulators of Immune Response

Pathways regulating cell senescence and cell cycle underlie many processes associated with ageing and age-related pathologies, and they also mediate cellular responses to exposure to stressors. Meanwhile, there are central mechanisms of the regulation of stress responses that induce/enhance or weaken the response of the whole organism, such as hormones of the hypothalamic-pituitary-adrenal (HPA) axis, sympathetic and parasympathetic systems, thymic hormones, and the pineal hormone melatonin. Although there are many analyses considering relationships between the HPA axis and organism ageing, we found no systematic analyses of relationships between the neuroendocrine regulators of stress and inflammation and intracellular mechanisms controlling cell cycle, senescence, and apoptosis. Here, we provide a review of the effects of neuroendocrine regulators on these mechanisms. Our analysis allowed us to postulate a multilevel system of central regulators involving neurotransmitters, glucocorticoids, melatonin, and the thymic hormones. This system finely regulates the cell cycle and metabolic/catabolic processes depending on the level of systemic stress, stage of stress response, and energy capabilities of the body, shifting the balance between cell cycle progression, cell cycle stopping, senescence, and apoptosis. These processes and levels of regulation should be considered when studying the mechanisms of ageing and the proliferation on the level of the whole organism.

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.

MicroRNA-541-5p REgulates Type II Alveolar Epithelial Cell Proliferation and Activity by Modulating the HMGB1 Expression

ABSTRACT

Acute lung injury (ALI) is characterized by excessive production of inflammatory factors and alveolar epithelial damage, type II alveolar epithelial (ATII) cells participate in the repairment of the damaged lung tissue in ALI. Recently, microRNAs (miRNAs) have been found to play crucial roles in the amelioration of various inflammation-induced diseases, including ALI. However, the biological function and the mechanisms of action of miRNAs in the regulation of inflammation, and how ATII cells repair damaged lung tissue in ALI remain unknown. In this study, a model of ALI was established using LPS, and ATII cells were isolated and treated with LPS. Hematoxylin and eosin staining revealed the injury to lung tissues. In this study we found that miR-541-5p expression was significantly decreased in ALI tissue and in the LPS-induced ATII cell model. Additionally, the LPS-induced model showed suppression of ATII cell proliferation and activity. Furthermore, overexpression of miR-541-5p was found to promote cell activity and proliferation in the LPS-induced ATII cell model. Moreover, a luciferase assay illustrated that HMGB1 is a target of miR-541-5p, HMGB1 knockdown blocked the inhibitory effect of miR-541-5p on LPS-induced ATII cells. Ultimately, our study demonstrated that expression of p38, JNK, and ERK in LPS-induced ATII cells increased significantly. These results suggest that miR-541-5p is a key effector in ALI tissue, and that LPS-induced ATII cells act by regulating HMGB1 expression. This effect may be related to excessive activation of the JNK/ERK/p38 signaling pathway.

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.

Nuclear HMGB1 protects from nonalcoholic fatty liver disease through negative regulation of liver X receptor

Dysregulations of lipid metabolism in the liver may trigger steatosis progression, leading to potentially severe clinical consequences such as nonalcoholic fatty liver diseases (NAFLDs). Molecular mechanisms underlying liver lipogenesis are very complex and fine-tuned by chromatin dynamics and multiple key transcription factors. Here, we demonstrate that the nuclear factor HMGB1 acts as a strong repressor of liver lipogenesis. Mice with liver-specific Hmgb1 deficiency display exacerbated liver steatosis, while Hmgb1-overexpressing mice exhibited a protection from fatty liver progression when subjected to nutritional stress. Global transcriptome and functional analysis revealed that the deletion of Hmgb1 gene enhances LXRα and PPARγ activity. HMGB1 repression is not mediated through nucleosome landscape reorganization but rather via a preferential DNA occupation in a region carrying genes regulated by LXRα and PPARγ. Together, these findings suggest that hepatocellular HMGB1 protects from liver steatosis development. HMGB1 may constitute a new attractive option to therapeutically target the LXRα-PPARγ axis during NAFLD.

Cyclophosphamide-induced GPX4 degradation triggers parthanatos by activating AIFM1

Cyclophosphamide is an alkylating agent used to treat a variety of cancers, including leukemia. Here, we show a previously unrecognized role of cyclophosphamide in triggering the protein degradation of glutathione peroxidase 4 (GPX4), a phospholipid hydroperoxidase that protects cells from oxidative damage. Mechanistically, we found that the ubiquitin-proteasome system, but not autophagy, mediates cyclophosphamide-induced degradation of GPX4 in human leukemia cell lines. Surprisingly, cyclophosphamide-induced degradation of GPX4 leads to caspase-independent parthanatos, but not lipid peroxidation-mediated ferroptosis, through the nuclear translocation of apoptosis-inducing factor mitochondria-associated 1 (AIFM1). Consequently, the overexpression of GPX4 or the knockdown of AIFM1 limits the anticancer activity of cyclophosphamide in vitro and in xenograft tumor models. These findings establish a new framework for understanding the central role of GPX4 in blocking oxidative cell death.

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.

High Mobility Group Box 1: Biological Functions and Relevance in Oxidative Stress Related Chronic Diseases

In the early 1970s, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and named high-mobility group (HMG) proteins. High-mobility group box 1 (HMGB1) is the most studied HMG protein that detects and coordinates cellular stress response. The biological function of HMGB1 depends on its subcellular localization and expression. It plays a critical role in the nucleus and cytoplasm as DNA chaperone, chromosome gatekeeper, autophagy maintainer, and protector from apoptotic cell death. HMGB1 also functions as an extracellular alarmin acting as a damage-associated molecular pattern molecule (DAMP). Recent findings describe HMGB1 as a sophisticated signal of danger, with a pleiotropic function, which is useful as a clinical biomarker for several disorders. HMGB1 has emerged as a mediator in acute and chronic inflammation. Furthermore, HMGB1 targeting can induce beneficial effects on oxidative stress related diseases. This review focus on HMGB1 redox status, localization, mechanisms of release, binding with receptors, and its activities in different oxidative stress-related chronic diseases. Since a growing number of reports show the key role of HMGB1 in socially relevant pathological conditions, to our knowledge, for the first time, here we analyze the scientific literature, evaluating the number of publications focusing on HMGB1 in humans and animal models, per year, from 2006 to 2021 and the number of records published, yearly, per disease and category (studies on humans and animal models).

Targeting HMGB1 for the treatment of sepsis and sepsis-induced organ injury

High mobility group box 1 (HMGB1) is a ubiquitous nuclear protein that is present in almost all cells and regulates the activity of innate immune responses in both intracellular and extracellular settings. Current evidence suggests that HMGB1 plays a pivotal role in human pathological and pathophysiological processes such as the inflammatory response, immune reactions, cell migration, aging, and cell death. Sepsis is a systemic inflammatory response syndrome (SIRS) that occurs in hosts in response to microbial infections with a proven or suspected infectious etiology and is the leading cause of death in intensive care units worldwide, particularly in the aging population. Dysregulated systemic inflammation is a classic characteristic of sepsis, and suppression of HMGB1 may ameliorate inflammation and improve patient outcomes. Here, we focus on the latest breakthroughs regarding the roles of HMGB1 in sepsis and sepsis-related organ injury, the ways by which HMGB1 are released, and the signaling pathways and therapeutics associated with HMGB1. This review highlights recent advances related to HMGB1: the regulation of HMBG1 might be helpful for both basic research and drug development for the treatment of sepsis and sepsis-related organ injury.

Mitochondrial ACOD1/IRG1 in infection and sterile inflammation

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

Downregulation of LNMAS orchestrates partial EMT and immune escape from macrophage phagocytosis to promote lymph node metastasis of cervical cancer

Epithelial-mesenchymal transition (EMT) is an essential step to drive the metastatic cascade to lymph nodes (LNs) in cervical cancer cells. However, few of them metastasize successfully partially due to increased susceptibility to immunosurveillance conferred by EMT. The precise mechanisms of cancer cells orchestrate EMT and immune evasion remain largely unexplored. In this study, we identified a lncRNA termed lymph node metastasis associated suppressor (LNMAS), which was downregulated in LN-positive cervical cancer patients and correlated with LN metastasis and prognosis. Functionally, LNMAS suppressed cervical cancer cells metastasis in vitro and in vivo. Mechanistically, LNMAS exerts its metastasis suppressive activity by competitively interacting with HMGB1 and abrogating the chromatin accessibility of TWIST1 and STC1, inhibiting TWIST1-mediated partial EMT and STC1-dependent immune escape from macrophage phagocytosis. We further demonstrated that the CpG sites in the promoter region of LNMAS was hypermethylated and contributed to the downregulation of LNMAS. Taken together, our results reveal the essential role of LNMAS in the LN metastasis of cervical cancer and provide mechanistic insights into the regulation of LNMAS in EMT and immune evasion.

Knockout of high-mobility group box 1 in B16F10 melanoma cells induced host immunity-mediated suppression of in vivo tumor growth

High-mobility group box 1 (HMGB1) has been reported as a damage-associated molecular pattern (DAMP) molecule that is released from damaged or dead cells and induces inflammation and subsequent innate immunity. However, the role of HMGB1 in the anti-tumor immunity is unclear since inflammation in the tumor microenvironment also contributes to tumor promotion and progression. In the present study, we established HMGB1-knockout clones from B16F10 and CT26 murine tumors by genome editing using the CRISPR/Cas9 system and investigated the role of HMGB1 in anti-tumor immunity. We found that (1) knockout of HMGB1 in the tumor cells suppressed in vivo, but not in vitro, tumor growth, (2) the suppression of the in vivo tumor growth was mediated by CD8 T cells, and (3) infiltration of CD8 T cells, macrophages and dendritic cells into the tumor tissues was accelerated in HMGB1-knockout tumors. These results demonstrated that knockout of HMGB1 in tumor cells converted tumors from poor infiltration of immune cells called “cold” to “immune-inflamed” or “hot” and inhibited in vivo tumor growth mediated by cytotoxic T lymphocytes. Infiltration of immune cells to the tumor microenvironment is an important step in the series known as the cancer immunity cycle. Thus, manipulation of tumor-derived HMGB1 might be applicable to improve the clinical outcomes of cancer immunotherapies, including immune checkpoint blockades and cancer vaccine therapies.

The mechanism of HMGB1 secretion and release

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

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

Analysis of Early Biomarkers Associated with the Development of Critical Respiratory Failure in Coronavirus Disease 2019 (COVID-19)

Certain biomarkers predict death due to acute respiratory distress syndrome in COVID-19 patients. We retrospectively analyzed biomarkers associated with time to mechanical ventilation for respiratory failure due to COVID-19 (time-to-mechanical ventilation) in 135 consecutive patients in our hospital. We analyzed biomarkers that were elevated immediately (at admission) and later (3 days after admission) using Cox proportional hazards regression analysis. Independent biomarkers of time-to-mechanical ventilation were high C-reactive protein (CRP), interleukin (IL)-6, and Krebs von den Lungen-6 (KL-6) concentrations at admission and elevated CRP, high-mobility group box-1 protein (HMGB-1), and d-dimer levels and low platelets 3 days after admission. Receiver operating characteristic analysis for detecting the association between independent biomarkers associated with time-to-event in multivariate analyses and the start of mechanical ventilation revealed that these biomarkers had area under the curve values higher than 0.700. The present study suggests that CRP was the only biomarker associated with time-to-mechanical ventilation both at admission and 3 days after admission. Moreover, IL-6 (an inflammatory cytokine), HMGB-1 (a late inflammatory mediator), and KL-6 (reflecting injury and/or remodeling of type II pneumocytes) were associated with outcomes in COVID-19 as reported previously. In conclusion, increased CRP, IL-6, KL-6, HMGB-1, and d-dimer levels and decreased platelet counts were associated with the start of mechanical ventilation due to COVID-19.

HMGB1-Mediated Activation of the Inflammatory-Reparative Response Following Myocardial Infarction

Different cell types belonging to the innate and adaptive immune system play mutually non-exclusive roles during the different phases of the inflammatory-reparative response that occurs following myocardial infarction. A timely and finely regulation of their action is fundamental for the process to properly proceed. The high-mobility group box 1 (HMGB1), a highly conserved nuclear protein that in the extracellular space can act as a damage-associated molecular pattern (DAMP) involved in a large variety of different processes, such as inflammation, migration, invasion, proliferation, differentiation, and tissue regeneration, has recently emerged as a possible regulator of the activity of different immune cell types in the distinct phases of the inflammatory reparative process. Moreover, by activating endogenous stem cells, inducing endothelial cells, and by modulating cardiac fibroblast activity, HMGB1 could represent a master regulator of the inflammatory and reparative responses following MI. In this review, we will provide an overview of cellular effectors involved in these processes and how HMGB1 intervenes in regulating each of them. Moreover, we will summarize HMGB1 roles in regulating other cell types that are involved in the different phases of the inflammatory-reparative response, discussing how its redox status could affect its activity.

High Mobility Group Box-1 Protein and Interleukin 33 Expression in Allergic Rhinitis

BACKGROUND

Allergic rhinitis (AR) is characterized by an inflammatory reaction. High mobility group box 1 (HMGB1) protein and interleukin (IL)-33 are damage-associated molecular pattern molecules and have many characteristics similar to pro-inflammatory cytokines. However, the role of IL-33 and HMGB1 in AR remains unclear. The aim of this study is to explore the role of HMGB1 and IL-33 in AR.

METHODS

Twenty patients with AR (AR group) and 10 normal controls (normal group) were enrolled in this study. HMGB1 and IL-33 expression were analyzed by immunohistochemistry in epithelial cells of the inferior turbinate mucosa samples. Then, the human nasal mucosa epithelial cells (HNECs) were cultured in vitro, and the house dust mite allergen (Derp1) was used to stimulate the cells. Quantitative real-time PCR and ELISA assay were performed to detect HMGB1 and IL-33 expression in HNECs.

RESULTS

The expression of HMGB1 and IL-33 in the nasal mucosa was higher in the AR group than in the normal group, with a statistically significant difference (p < 0.05). In HNECs of AR, the expression of both HMGB1 and IL-33 in stimulated groups was higher than that in non-stimulated groups. The differences were statistically significant (p < 0.05). In addition, they increased gradually with the prolonging time and the concentration of the added Derp1.

CONCLUSIONS

The expression of HMGB1 and IL-33 were both increased in AR. HMGB1 and IL-33 may have a close relationship in AR.

The V-ATPases in cancer and cell death

Transmembrane ATPases are membrane-bound enzyme complexes and ion transporters that can be divided into F-, V-, and A-ATPases according to their structure. The V-ATPases, also known as H⁺-ATPases, are large multi-subunit protein complexes composed of a peripheral domain (V1) responsible for the hydrolysis of ATP and a membrane-integrated domain (V0) that transports protons across plasma membrane or organelle membrane. V-ATPases play a fundamental role in maintaining pH homeostasis through lysosomal acidification and are involved in modulating various physiological and pathological processes, such as macropinocytosis, autophagy, cell invasion, and cell death (e.g., apoptosis, anoikis, alkaliptosis, ferroptosis, and lysosome-dependent cell death). In addition to participating in embryonic development, V-ATPase pathways, when dysfunctional, are implicated in human diseases, such as neurodegenerative diseases, osteopetrosis, distal renal tubular acidosis, and cancer. In this review, we summarize the structure and regulation of isoforms of V-ATPase subunits and discuss their context-dependent roles in cancer biology and cell death. Updated knowledge about V-ATPases may enable us to design new anticancer drugs or strategies.

Translocation of High Mobility Group Box 1 From the Nucleus to the Cytoplasm in Depressed Patients With Epilepsy

Depression is a common psychiatric comorbidity in patients with epilepsy, especially those with temporal lobe epilepsy (TLE). The aim of this study was to assess changes in high mobility group box protein 1 (HMGB1) expression in epileptic patients with and without comorbid depression. Sixty patients with drug-resistant TLE who underwent anterior temporal lobectomy were enrolled. Anterior hippocampal samples were collected after surgery and analyzed by immunofluorescence (n = 7/group). We also evaluated the expression of HMGB1 in TLE patients with hippocampal sclerosis and measured the level of plasma HMGB1 by enzyme-linked immunosorbent assay. The results showed that 28.3% of the patients (17/60) had comorbid depression. HMGB1 was ubiquitously expressed in all subregions of the anterior hippocampus. The ratio of HMGB1-immunoreactive neurons and astrocytes was significantly increased in both TLE patients with hippocampal sclerosis and TLE patients with comorbid depression compared to patients with TLE only. The ratio of cytoplasmic to nuclear HMGB1-positive neurons in the hippocampus was higher in depressed patients with TLE than in nondepressed patients, which suggested that more HMGB1 translocated from the nucleus to the cytoplasm in the depressed group. There was no significant difference in the plasma level of HMGB1 among patients with TLE alone, TLE with hippocampal sclerosis, and TLE with comorbid depression. The results of the study revealed that the translocation of HMGB1 from the nucleus to the cytoplasm in hippocampal neurons may play a previously unrecognized role in the initiation and amplification of epilepsy and comorbid depression. The direct targeting of neural HMGB1 is a promising approach for anti-inflammatory therapy.

Circulating HMGB1 is increased in myelodysplastic syndrome but not in other bone marrow failure syndromes: proof-of-concept cross-sectional study

Background

Myelodysplastic syndrome (MDS) is associated with persistent immune activation. High mobility group box-1 (HMGB1) is a ubiquitous, functionally diverse, non-histone intranuclear protein. During acute and chronic inflammatory states, HMGB1 is actively released by inflammatory cells, further amplifying the inflammatory response. A role in MDS and other hypoplastic bone marrow (BM) disorders is incompletely understood.

Objectives

The objective of the study is to evaluate whether circulating HMGB1 is elevated in patients with MDS and other BM failure syndromes [namely, aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH)].

Design

This is a observational, cross-sectional, single-center, exploratory study.

Methods

We evaluated circulating concentrations of HMGB1, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in patients with MDS and age-matched hematologically healthy controls as well as patients with AA and PNH.

Results

We included 66 patients with MDS and 65 age-matched controls as well as 44 patients with other BM failures (AA = 27, PNH = 17). Circulating levels of HMGB1 were higher in patients with MDS [median, 4.9 ng/ml; interquartile range (IQR): 2.3-8.1] than in AA (median, 2.6 ng/ml; IQR: 1.7-3.7), PNH (median, 1.7 ng/ml; IQR: 0.9-2.5), and age-matched healthy individuals (median, 1.9 ng/ml; IQR: 0.9-2.5) (p = 0.0001). We observed higher concentrations of HMGB1 in the very low/low-risk MDS patients than in the intermediate/high/very high-risk ones (p = 0.046). Finally, in comparison with patients with AA, those with hypocellular MDS (h-MDS) had significantly higher levels of circulating HMGB1 (n = 14; median concentration, 5.6 ng/ml, IQR: 2.8-7.3; p = 0.006). We determined a circulating HMGB1 value of 4.095 ng/ml as a diagnostic cutoff differentiator between h-MDS and AA.

Conclusion

These observations indicate that circulating HMGB1 is increased in patients with MDS. HMGB1 (but not IL-1β or TNF-α) differentiated between MDS and other BM failures, suggesting that HMGB1 may be mechanistically involved in MDS and a druggable target to decrease inflammation in MDS.

STING1 in sepsis: Mechanisms, functions, and implications

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

High-mobility group box 1 protein promotes dengue virus replication by interacting with untranslated regions of viral genome

Dengue virus (DENV) is most prevalent arthropod-borne human pathogen belongs to Flaviviridae family causes thousands of deaths annually. HMGB1 is highly conserved, ubiquitously expressed, non-histone nuclear protein which plays important role in diseases like metabolic disorders, cancer, and viral infections. However, the importance of HMGB1 in DENV infection is understudied. In this study, we observed that DENV-2 induces cytoplasmic translocation and secretion of HMGB1. Interestingly, inhibition of HMGB1 secretion by ethyl pyruvate (EP) enhanced viral propagation while silencing of HMGB1 resulted in abrogated viral replication in DENV-2 infected A549 cells. RNA-Electrophoretic mobility shift assay and immunoprecipitation showed that HMGB1 interacts with 5'-3' UTRs of DENV-2 genome. This interaction further stimulates production of proinflammatory cytokines like TNF-α, IL-6 and IL-1β which have been implicated in pathogenesis of severe DENV disease. Together, our finding suggests that DENV-2 modulates HMGB1 translocation and HMGB1-DENV-2 UTRs RNA interaction further induces proinflammatory cytokines production in A549 cells. This study discloses HMGB1 as an important host factor contributing to disease pathogenesis and hence can be targeted as an alternative approach for antiviral development against DENV virus infection.

DCN released from ferroptotic cells ignites AGER-dependent immune responses

Ferroptosis is a form of inflammatory cell death for which key mediators remain obscure. Here, we report that the proteoglycan decorin (DCN) is released by cells that are dying from ferroptosis and then acts as an alarm signal to trigger innate and adaptive immune responses. The early release of DCN during ferroptosis is an active process that involves secretory macroautophagy/autophagy and lysosomal exocytosis. Once released, extracellular DCN binds to the receptor advanced glycosylation end-product-specific receptor (AGER) on macrophages to trigger the production of pro-inflammatory cytokines in an NFKB/NF-κB-dependent manner. Pharmacological and genetic inhibition of the DCN-AGER axis protects against ferroptotic death-related acute pancreatitis and limits the capacity of ferroptotic cancer cells to induce a tumor-protective immune response. Thus, DCN is an essential mediator of the inflammatory and immune consequences of ferroptosis.

Crossed Pathways for Radiation-Induced and Immunotherapy-Related Lung Injury

Radiation-induced lung injury (RILI) is a form of radiation damage to normal lung tissue caused by radiotherapy (RT) for thoracic cancers, which is most commonly comprised of radiation pneumonitis (RP) and radiation pulmonary fibrosis (RPF). Moreover, with the widespread utilization of immunotherapies such as immune checkpoint inhibitors as first- and second-line treatments for various cancers, the incidence of immunotherapy-related lung injury (IRLI), a severe immune-related adverse event (irAE), has rapidly increased. To date, we know relatively little about the underlying mechanisms and signaling pathways of these complications. A better understanding of the signaling pathways may facilitate the prevention of lung injury and exploration of potential therapeutic targets. Therefore, this review provides an overview of the signaling pathways of RILI and IRLI and focuses on their crosstalk in diverse signaling pathways as well as on possible mechanisms of adverse events resulting from combined radiotherapy and immunotherapy. Furthermore, this review proposes potential therapeutic targets and avenues of further research based on signaling pathways. Many new studies on pyroptosis have renewed appreciation for the value and importance of pyroptosis in lung injury. Therefore, the authors posit that pyroptosis may be the common downstream pathway of RILI and IRLI; discussion is also conducted regarding further perspectives on pyroptosis as a crucial signaling pathway in lung injury treatment.

Extracellular HMGB1 interacts with RAGE and promotes chemoresistance in acute leukemia cells

Background

Nowadays, acute leukemia (AL) among children has favorable outcome, yet some of them get refractory or relapse mainly due to drug resistance. High-mobility group box 1 (HMGB1) has been proven to have a important role in drug resistance via upregulation of autophagy after chemotherapy treatment in acute leukemia. However, the mechanism how extracellular HMGB1 acts on AL cells and leads to chemoresistance remains elusive.

Method

CCK8 was used to examine the toxicity of chemotherapeutic drug. Elisa was performed to detect the release of HMGB1. Western blot and mRFP-GFP-LC3 adenoviral particles as well as transmission electron microscopy were used to detect the autophagy flux. Western blot and flow cytometry were applied to evaluate the apoptosis. qPCR and western blot were conducted to detect the expression of drug efflux protein. Lentivirus infection was applied to knock down RAGE. In addition, T-ALL NOD/SCID mice xenograft model was used to observe the effect of inhibiting HMGB1/RAGE axis.

Results

We found that extracellular HMGB1 do upregulate autophagy and in the meantime downregulate apoptosis, primarily through interaction with receptor for advanced glycation end products (RAGE). Suppression of RAGE by RNA interference alleviated the level of autophagy and enhanced apoptosis. What’s more, HMGB1/RAGE induced autophagy was associated with the activation of ERK1/2 and decreased phosphorylation of mammalian target of rapamycin (mTOR), while HMGB1/RAGE limited apoptosis in a Bcl-2-regulated way mediated by P53. On the other hand, we found that HMGB1/RAGE activated the NF-κB pathway and promoted the expression of P-glycation protein (P-gp) as well as multidrug resistance-associated protein (MRP), both are ATP-binding cassette transporters. In vivo experiment, we found that blocking HMGB1/RAGE axis do have a mild pathological condition and a better survival in T-ALL mice.

Conclusion

HMGB1/RAGE have a important role in drug resistance after chemotherapy treatment, mainly by regulating autophagy and apoptosis as well as promoting the expression of drug efflux protein such as P-gp and MRP. HMGB1/RAGE might be a promising target to cure AL, especially for those met with relapse and refractory.

Molecular mechanisms of ferroptosis and their role in inflammation

Ferroptosis is a type of non-apoptotic cell death, which demonstrates a definite iron-dependent expression pattern and is associated with lipid peroxidation. Glutathione peroxidase 4 (GPX4) is a key regulator of ferroptosis. Ferroptosis is involved in the development and progression of various diseases, such as cancer, tissue ischemia-reperfusion injury, neurological diseases, and respiratory diseases. It has been established previously that ferroptotic cells trigger the innate immune system by releasing inflammation-linked damage-related molecules, and immune cells stimulate the inflammatory response by recognizing the operational mechanism of ferroptosis. Some anti-inflammatory drugs have been shown to inhibit ferroptosis in certain cell models. Conversely, some ferroptosis inhibitors also exert anti-inflammatory effects in certain diseases. The present review evaluated the relationship between ferroptosis and inflammation, as well as the underlying internal mechanism, and provided valuable insights into developing novel treatment strategies for inflammatory diseases and cancer.

Increased circulating levels of High Mobility Group Box 1 (HMGB1) in acute-phase Chikungunya virus infection: Potential disease biomarker

BACKGROUND

Chikungunya virus (CHIKV) causes a febrile syndrome with intense and debilitating arthralgia that can persist for several months or years after complete virus clearance. As there is no specific antiviral treatment or vaccine against CHIKV, identification of serological markers that help clinical management of CHIKV patients is urgent. The High Mobility Group Box 1 (HMGB1) protein is secreted to extracellular milieu and triggers an intense inflammatory process by inducing the overexpression of pro-inflammatory cytokines. HMGB1 plays an important role in several virus diseases as well as in rheumatoid arthritis.

OBJECTIVES

This study focus on the investigation of HMGB1 serum levels in a sera panel from CHIKV-infected patients in an attempt to assess its potential as a biomarker for chikungunya clinical management.

STUDY DESIGN

Eighty CHIKV-positive samples and 32 samples from healthy donors were subjected to a quantitative HMGB1 ELISA assay to assess the HMGB1 circulating levels.

RESULTS

HMGB1 levels were significantly higher in CHIKV-positive samples (516.12 ng/mL, SEM ± 48.83 ng/mL) compared to negative control (31.20 ng/mL, SEM ± 3.24 ng/mL, p < 0.0001). Circulating levels of HMGB1 persisted elevated during the whole acute-phase of disease and correlated with virus titer (p < 0.05).

CONCLUSIONS

The present study is the first to describe increased serum levels of HMGB1 in CHIKV infection and its positive correlation with virus titer, suggesting its potential use as a biomarker for diagnosis and treatment of chikungunya fever.

Serpinc1 Acts as a Tumor Suppressor in Hepatocellular Carcinoma Through Inducing Apoptosis and Blocking Macrophage Polarization in an Ubiquitin-Proteasome Manner

Serpinc1 is a serine protease inhibitor in the coagulation cascade, but its role in tumor biology remains obscure. Here, we report an unexpected role of serpinc1 in suppression of hepatocellular carcinoma (HCC). In HCC patients, the mRNA and protein expression of serpinc1 is upregulated, which is negatively correlated with tumor grade, and has a better prognosis than patients with low serpinc1. In addition, patients with high expression of serpinc1 generally have a better tumor immune microenvironment, accompanied by changes in multiple immune cells and mediators. In particular, tumor-promoting M2 macrophages are negatively correlated with serpinc1 expression and the prognosis of HCC patients. In vitro experiments further show that overexpression of serpinc1 inhibits the growth of HCC cells (HepG2 and SMMC7721) by inducing apoptosis. Accordingly, cell co-culture experiments reveal the direct role of serpinc1-overexpressed HCC cells in inhibiting the formation of M2 macrophages. Subsequent unbiased quantitative proteomic and ubiquitinome analyses identify that multiple poly-ubiquitination of proteins involved in signal pathways (such as autophagy, apoptosis, lactate metabolism, and VEGF signaling) are regulated by serpinc1. Overall, these findings establish a serpinc1-dependent ubiquitin-proteasome system to control apoptosis and antitumor immunity.

Antibody and Protein Profiles in Glaucoma: Screening of Biomarkers and Identification of Signaling Pathways

Simple Summary

Glaucoma is a chronic eye disease that is one of the leading causes of blindness worldwide. Currently, the only therapeutic option is to lower intraocular pressure. The onset of the disease is often delayed because patients do not notice visual impairment until very late, which is why glaucoma is also known as “the silent thief of sight”. Therefore, early detection and definition of specific markers, the so-called biomarkers, are immensely important. For the methodical implementation, high-throughput methods and omic-based methods came more and more into focus. Thus, interesting targets for possible biomarkers were already suggested by clinical research and basic research, respectively. This review article aims to join the findings of the two disciplines by collecting overlaps as well as differences in various clinical studies and to shed light on promising candidates concerning findings from basic research, facilitating conclusions on possible therapy options.

Abstract

Glaucoma represents a group of chronic neurodegenerative diseases, constituting the second leading cause of blindness worldwide. To date, chronically elevated intraocular pressure has been identified as the main risk factor and the only treatable symptom. However, there is increasing evidence in the recent literature that IOP-independent molecular mechanisms also play an important role in the progression of the disease. In recent years, it has become increasingly clear that glaucoma has an autoimmune component. The main focus nowadays is elucidating glaucoma pathogenesis, finding early diagnostic options and new therapeutic approaches. This review article summarizes the impact of different antibodies and proteins associated with glaucoma that can be detected for example by microarray and mass spectrometric analyzes, which (i) provide information about expression profiles and associated molecular signaling pathways, (ii) can possibly be used as a diagnostic tool in future and, (iii) can identify possible targets for therapeutic approaches.

A viral histone-like protein exploits antagonism between linker histones and HMGB proteins to obstruct the cell cycle

Virus infection necessarily requires redirecting cellular resources toward viral progeny production. Adenovirus encodes the histone-like protein VII, which causes catastrophic global reorganization of host chromatin to promote virus infection. Protein VII recruits the family of high mobility group box (HMGB) proteins to chromatin along with the histone chaperone SET. As a consequence of this recruitment, we find that protein VII causes chromatin depletion of several linker histone H1 isoforms. The relationship between linker histone H1 and the functionally opposite HMGB proteins is critical for higher-order chromatin structure. However, the physiological consequences of perturbing this relationship are largely unknown. Here, we employ complementary systems in Saccharomyces cerevisiae and human cells to demonstrate that adenovirus protein VII disrupts the H1-HMGB balance to obstruct the cell cycle. We find that protein VII causes an accumulation of G2/M cells both in yeast and human systems, underscoring the high conservation of this chromatin vulnerability. In contrast, adenovirus E1A and E1B proteins are well established to override cell cycle regulation and promote transformation of human cells. Strikingly, we find that protein VII obstructs the cell cycle, even in the presence of E1A and E1B. We further show that, in a protein-VII-deleted infection, several cell cycle markers are regulated differently compared to wild-type infection, supporting our model that protein VII plays an integral role in hijacking cell cycle regulation during infection. Together, our results demonstrate that protein VII targets H1-HMGB1 antagonism to obstruct cell cycle progression, revealing an unexpected chromatin vulnerability exploited for viral benefit.