HMGB1 and repair: focus on the heart

Crosstalk between cancer-associated fibroblasts and regulated cell death in tumors: insights into apoptosis, autophagy, ferroptosis, and pyroptosis

Cancer-associated fibroblasts (CAFs), the main stromal component of the tumor microenvironment (TME), play multifaceted roles in cancer progression through paracrine signaling, exosome transfer, and cell interactions. Attractively, recent evidence indicates that CAFs can modulate various forms of regulated cell death (RCD) in adjacent tumor cells, thus involving cancer proliferation, therapy resistance, and immune exclusion. Here, we present a brief introduction to CAFs and basic knowledge of RCD, including apoptosis, autophagy, ferroptosis, and pyroptosis. In addition, we further summarize the different types of RCD in tumors that are mediated by CAFs, as well as the effects of these modes of RCD on CAFs. This review will deepen our understanding of the interactions between CAFs and RCD and might offer novel therapeutic avenues for future cancer treatments.

Neutrophil extracellular traps mediate cardiomyocyte ferroptosis via the Hippo-Yap pathway to exacerbate doxorubicin-induced cardiotoxicity

Doxorubicin-induced cardiotoxicity (DIC), which is a cardiovascular complication, has become the foremost determinant of decreased quality of life and mortality among survivors of malignant tumors, in addition to recurrence and metastasis. The limited ability to accurately predict the occurrence and severity of doxorubicin-induced injury has greatly hindered the prevention of DIC, but reducing the dose to mitigate side effects may compromise the effective treatment of primary malignancies. This has posed a longstanding clinical challenge for oncologists and cardiologists. Ferroptosis in cardiomyocytes has been shown to be a pivotal mechanism underlying cardiac dysfunction in DIC. Ferroptosis is influenced by multiple factors. The innate immune response, as exemplified by neutrophil extracellular traps (NETs), may play a significant role in the regulation of ferroptosis. Therefore, the objective of this study was to investigate the involvement of NETs in doxorubicin-induced cardiomyocyte ferroptosis and elucidate their regulatory role. This study confirmed the presence of NETs in DIC in vivo. Furthermore, we demonstrated that depleting neutrophils effectively reduced the occurrence of doxorubicin-induced ferroptosis and myocardial injury in DIC. Additionally, our findings showed the pivotal role of high mobility group box 1 (HMGB1) as a critical molecule implicated in DIC and emphasized its involvement in the modulation of ferroptosis subsequent to NETs inhibition. Mechanistically, we obtained preliminary evidence suggesting that doxorubicin-induced NETs could modulate yes-associated protein (YAP) activity by releasing HMGB1, which subsequently bound to toll like receptor 4 (TLR4) on the cardiomyocyte membrane, thereby influencing cardiomyocyte ferroptosis in vitro. Our findings suggest that doxorubicin-induced NETs modulate cardiomyocyte ferroptosis via the HMGB1/TLR4/YAP axis, thereby contributing to myocardial injury. This study offers a novel approach for preventing and alleviating DIC by targeting alterations in the immune microenvironment.

HMGB1/RAGE axis in tumor development: unraveling its significance

High mobility group protein 1 (HMGB1) plays a complex role in tumor biology. When released into the extracellular space, it binds to the receptor for advanced glycation end products (RAGE) located on the cell membrane, playing an important role in tumor development by regulating a number of biological processes and signal pathways. In this review, we outline the multifaceted functions of the HMGB1/RAGE axis, which encompasses tumor cell proliferation, apoptosis, autophagy, metastasis, and angiogenesis. This axis is instrumental in tumor progression, promoting tumor cell proliferation, autophagy, metastasis, and angiogenesis while inhibiting apoptosis, through pivotal signaling pathways, including MAPK, NF-κB, PI3K/AKT, ERK, and STAT3. Notably, small molecules, such as miRNA-218, ethyl pyruvate (EP), and glycyrrhizin exhibit the ability to inhibit the HMGB1/RAGE axis, restraining tumor development. Therefore, a deeper understanding of the mechanisms of the HMGB1/RAGE axis in tumors is of great importance, and the development of inhibitors targeting this axis warrants further exploration.

Serum high mobility group box 1 as a potential biomarker for the progression of kidney disease in patients with type 2 diabetes

Background

As a damage-associated molecular pattern protein, high mobility group box 1 (HMGB1) is associated with kidney and systemic inflammation. The predictive and therapeutic value of HMGB1 as a biomarker has been confirmed in various diseases. However, its value in diabetic kidney disease (DKD) remains unclear. Therefore, this study aimed to investigate the correlation between serum and urine HMGB1 levels and DKD progression.

Methods

We recruited 196 patients with type 2 diabetes mellitus (T2DM), including 109 with DKD and 87 T2DM patients without DKD. Additionally, 60 healthy participants without T2DM were also recruited as controls. Serum and urine samples were collected for HMGB1 analysis. Simultaneously, tumor necrosis factor receptor superfamily member 1A (TNFR-1) in serum and kidney injury molecule (KIM-1) in urine samples were evaluated for comparison.

Results

Serum and urine HMGB1 levels were significantly higher in patients with DKD than in patients with T2DM and healthy controls. Additionally, serum HMGB1 levels significantly and positively correlated with serum TNFR-1 (R 2 = 0.567, p<0.001) and urine KIM-1 levels (R 2 = 0.440, p<0.001), and urine HMGB1 has a similar correlation. In the population with T2DM, the risk of DKD progression increased with an increase in serum HMGB1 levels. Multivariate logistic regression analysis showed that elevated serum HMGB1 level was an independent risk factor for renal function progression in patients with DKD, and regression analysis did not change in the model corrected for multiple variables. The restricted cubic spline depicted a nonlinear relationship between serum HMGB1 and renal function progression in patients with DKD (p-nonlinear=0.007, p<0.001), and this positive effect remained consistent across subgroups.

Conclusion

Serum HMGB1 was significantly correlated with DKD and disease severity. When the HMGB1 level was ≥27 ng/ml, the risk of renal progression increased sharply, indicating that serum HMGB1 can be used as a potential biomarker for the diagnosis of DKD progression.

Glycyrrhizin attenuates myocardial ischemia reperfusion injury by suppressing Inflammation, oxidative stress, and ferroptosis via the HMGB1-TLR4-GPX4 pathway

Ferroptosis, a form of regulated cell death process, play an important role in myocardial ischemia‒reperfusion (I/R) injury. Glycyrrhizin (GL), a natural glycoconjugate triterpene, has the property to improve growth rate, immune regulation, antioxidant, anti-inflammatory. However, whether GL can attenuate myocardial I/R injury by modulating ferroptosis or other mechanisms are still unclear. In this study, SD rats underwent in vivo myocardial ischemia/reperfusion (I/R) surgery, while H9C2 cells were subjected to the hypoxia/reoxygenation (H/R) model for in vitro experiments. In addition, TAK-242, a TLR4-specific antagonist, and GL were also used to evaluate the effect and mechanisms of GL on the cardiac function and expression of ferroptosis-related gene and protein in vivo and vitro. The results show that GL decreased not only the expression of the inflammation-related factors (HMGB1, TNF-α, IL-6, IL-18 and IL-1β), but also reduced the number of TUNEL-positive cardiomyocytes, and mitigated pathological alterations in I/R injury. In addition, GL decreased the levels of MDA, promoted antioxidant capacity such as GSH, CAT, Cu/Zn-SOD, Mn-SOD, and SOD in vivo and vitro. More importantly, GL and TAK-242 regulate ferroptosis-related protein and gene expression in I/R and H/R model. Surprisingly, GL may ameliorate cardiomyocyte ferroptosis and ultimately improves cardiac function induced by H/R via the HMGB1-TLR4-GPX4 axis. Therefore, we have highlighted a novel mechanism by which GL regulates inflammation, oxidative stress, and ferroptosis via the HMGB1-TLR4-GPX4 pathway to prevent myocardial I/R injury. GL appears to be a potentially applicable drug for the treatment of myocardial I/R injury.

HMGB1 in the interplay between autophagy and apoptosis in cancer

Lysosome-mediated autophagy and caspase-dependent apoptosis are dynamic processes that maintain cellular homeostasis, ensuring cell health and functionality. The intricate interplay and reciprocal regulation between autophagy and apoptosis are implicated in various human diseases, including cancer. High-mobility group box 1 (HMGB1), a nonhistone chromosomal protein, plays a pivotal role in coordinating autophagy and apoptosis levels during tumor initiation, progression, and therapy. The regulation of autophagy machinery and the apoptosis pathway by HMGB1 is influenced by various factors, including the protein's subcellular localization, oxidative state, and interactions with binding partners. In this narrative review, we provide a comprehensive overview of the structure and function of HMGB1, with a specific focus on the interplay between autophagic degradation and apoptotic death in tumorigenesis and cancer therapy. Gaining a comprehensive understanding of the significance of HMGB1 as a biomarker and its potential as a therapeutic target in tumor diseases is crucial for advancing our knowledge of cell survival and cell death.

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

Objective

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

Methods

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

Results

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

Conclusion

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

Nanocurcumin attenuates pyroptosis and inflammation through inhibiting NF-κB/GSDMD signal in high altitude-associated acute liver injury

Exposure to a hypobaric hypoxic environment at high altitudes can lead to liver injury, and mounting evidence indicates that pyroptosis and inflammation play important roles in liver injury. Curcumin (Cur) can inhibit pyroptosis and inflammation. Therefore, our purpose here was to clarify the mechanism underlying the protective effect of nanocurcumin (Ncur) and Cur in a rat model of high altitude-associated acute liver injury. Eighty healthy rats were selected and exposed to different altitudes (6000 or 7000 m) for 0, 24, 48, or 72 h. Fifty normal healthy rats were divided into normal control, high-altitude control, salidroside (40 mg/kg [Sal-40]), Cur (200 mg/kg [Cur-200]), and Ncur (25 mg/kg [Ncur-25]) groups and exposed to a high-altitude hypobaric hypoxic environment (48 h, 7000 m). Serum-liver enzyme activities (alanine transaminase, aspartate transaminase, and lactate dehydrogenase were detected and histopathology of liver injury was evaluated by hematoxylin and eosin staining, and inflammatory factors were detected in liver tissues by enzyme-linked immunosorbent assays. Pyroptosis-associated proteins (gasdermin D, gasdermin D N-terminal [GSDMD-N], pro-Caspase-1, and cleaved-Caspase-1 [cleaved-Casp1]) and inflammation-associated proteins (nuclear factor-κB [NF-κB], phospho-NF-κB [P-NF-κB], and high-mobility group protein B1 [HMGB1]) levels were analyzed by immunoblotting. Ncur and Cur inhibited increased serum-liver enzyme activities, alleviated liver injury in rats caused by high-altitude hypobaric hypoxic exposure, and downregulated inflammatory factors, including tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-18, in rat liver tissues. The level of P-NF-κB, GSDMD-N, cleaved-Casp1, and HMGB1 in rat liver tissues increased significantly after high-altitude exposure. Ncur and Cur downregulated P-NF-κB, GSDMD-N, cleaved-Casp-1, and HMGB1. Ncur and Cur may inhibit inflammatory responses and pyroptosis in a rat model of high altitude-associated acute liver injury.

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

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

Serum uric acid and outcome in hospitalized elderly patients with chronic heart failure through the whole spectrum of ejection fraction phenotypes

INTRODUCTION

Elevated serum uric acid (SUA) levels have been associated with poor outcome in patients with heart failure (HF). Uric acid is associated with inflammation and microvascular dysfunction, which may differentially affect left ventricular ejection fraction (EF) phenotypes. We aimed to identify the role of SUA across EF phenotypes in hospitalized elderly patients with chronic HF.

METHODS

We analyzed 1355 elderly patients who were diagnosed with chronic HF. All patients had SUA levels measured within the first 24 h following admission. Patients with left ventricle EF were categorized as having HF with reduced EF (HFrEF, EF < 40%), HF with mid-range EF (HFmrEF, 40%≦LVEF ≦ 49%) or HF with preserved EF (HFpEF, LVEF ≥ 50%). Endpoints were cardiovascular death, HF rehospitalization, and their composite. The median follow-up period was 18 months.

RESULTS

Compared with the lowest SUA quartile, the highest SUA quartile was significantly associated with the endpoints (adjusted HR: 2.404, 95% CI: 1.178-4.906, P = 0.016; HR: 1.418, 95% CI: 1.021-1.971, P = 0.037; HR: 1.439, 95% CI: 1.049-1.972, P = 0.024, respectively). After model adjustment, a significant association of SUA with cardiovascular death and the composite endpoint persisted among HFrEF and HFmrEF patients in the highest SUA quartile (P < 0.05 for all).

CONCLUSIONS

In hospitalized elderly patients with chronic HF, SUA is an independent predictor of adverse outcomes, which can be seen in HFrEF and HFmrEF patients.

Lagopsis supina ameliorates myocardial ischemia injury by regulating angiogenesis, thrombosis, inflammation, and energy metabolism through VEGF, ROS and HMGB1 signaling pathways in rats

BACKGROUND

Lagopsis supina (Steph. ex. Willd.) Ikonn.-Gal. is an important traditional Chinese medicine used to treat various ailments. However, its impact on myocardial ischemia (MI) injury remains unknown.

PURPOSE

This research aimed to reveal the therapeutic effect, potential mechanism, and metabolomics of L. supina against MI injury in rats.

METHODS

The therapeutic effects of the ethanolic extract of L. supina (LS) and its four fractions (LSA∼D) on a left anterior descending (LAD) artery occlusion-induced MI model rat were explored. The pharmacodynamics including myocardial infraction area, myocardial tissue pathology and apoptosis, and serum biochemical parameters (CK, CK-MB, CTn-T, SOD, ET-1, NO, eNOS, VEGF, TXB2, 6-keto-PGF1α, TNF-α, IL-6, and CRP) were evaluated. The 24 related protein expressions were detected using western blotting assay. Simultaneously, the qualitative and quantitative analyses of microporous adsorption resin with 30% (LSC) and 60% (LSD) aqueous ethanol fractions were performed using UHPLC-MS and HPLC. Moreover, the serum metabolomics analysis of rats was profiled using UHPLC-MS.

RESULTS

LS exerted remarkable alleviating effect on MI in rats. Importantly, LSC and LSD, two effective fractions of LS, significantly reduced myocardial infraction area, alleviated myocardial tissue pathology and apoptosis, regulated serum biochemical parameters. Furthermore, LSC and LSD markedly up-regulated the levels of VEGF-A, VEGFR-2, PKC, Bcl-2, Nrf2, HO-1, and thrombin, as well as prominently down-regulated the protein expression of Notch 1, p-PI3K, p-PI3K/PI3K, p-Akt, p-Akt/Akt, Bax, cleaved-caspase-3, cleaved-caspase-3/caspase-3, vWF, p-Erk, p-Erk/Erk, HMGB1, p-p38, p-p38/p38, p-p65, and p-p65/p65. A total of 26 candidate biomarkers were significantly regulated by LSC and LSD and they are mainly involved in amino acid metabolism, glycerophospholipid metabolism, and sphingolipid metabolism. Finally, phenylethanols and flavonoids may be major bio-constituents of LSC and LSD against MI.

CONCLUSIONS

This work, for the first time, demonstrated that L. supina had a significant therapeutic effect on MI in rats. Additionally, LSC and LSD, two bio-fractions from L. supina, exerted their potential to ameliorate MI injury by promoting angiogenesis, inhibiting thrombosis, blocking inflammation, and facilitating energy metabolism through promotion of VEGF pathway, as well as suppression of ROS and HMGB1 pathways in rats. These findings suggest that LSC and LSD hold promise as potential therapeutic agents for MI injury in clinical application.

The role of HMGB1 in digestive cancer

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

Signaling pathways and targeted therapeutic strategies for polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among women of reproductive age. Although promising strides have been made in the field of PCOS over the past decades, the distinct etiologies of this syndrome are not fully elucidated. Prenatal factors, genetic variation, epigenetic mechanisms, unhealthy lifestyles, and environmental toxins all contribute to the development of this intricate and highly heterogeneous metabolic, endocrine, reproductive, and psychological disorder. Moreover, interactions between androgen excess, insulin resistance, disruption to the hypothalamic-pituitary-ovary (HPO) axis, and obesity only make for a more complex picture. In this review, we investigate and summarize the related molecular mechanisms underlying PCOS pathogenesis from the perspective of the level of signaling pathways, including PI3K/Akt, TGF-β/Smads, Wnt/β-catenin, and Hippo/YAP. Additionally, this review provides an overview of prospective therapies, such as exosome therapy, gene therapy, and drugs based on traditional Chinese medicine (TCM) and natural compounds. By targeting these aberrant pathways, these interventions primarily alleviate inflammation, insulin resistance, androgen excess, and ovarian fibrosis, which are typical symptoms of PCOS. Overall, we hope that this paper will pave the way for better understanding and management of PCOS in the future.

Effects of Isoflurane on the Cell Pyroptosis in the Lung Cancer Through the HMGB1/RAGE Pathway

There are many common malignant tumors in clinic. Among them, lung cancer is caused by the failure of suction system, which seriously threatens the life safety of patients. Recent studies have found that anesthetics have achieved certain efficacy in many cancers. Isoflurane, an inhaled anesthetic, is used in this study to explore whether it can prevent the lung cancer development. The A549 and H1299 were purchased. Cell viability was tested by CCK-8 experiment. Cell death and pyroptosis were analyzed by PI staining as well as flow cytometry. HMGB1 as well as RAGE protein levels were tested by Western blot. The same is true of pyroxin-related proteins. The HMGB1 as well as RAGE levels in the lung cancer tissues were determined by Western blot along with immunohistochemistry. Isoflurane treatment can reduce cell viability and promote cell pyroptosis. Additionally, the protein levels of cleaved caspase-1, IL-1β, GSDMD-N, NLRP3, HMGB1, and RAGE were dramatically up-regulated in the lung cancer after isoflurane treatment. Down-regulated proteins in lung cancer tissues include HMGB1 and RAGE proteins. After HMGB1 knockdown or FPS-ZM1 treatment, the role of isoflurane in the lung cancer was neutralized. This study demonstrated that isoflurane induced the cell pyroptosis in the lung cancer through activating the HMGB1/RAGE pathway.

HMGB family proteins: Potential biomarkers and mechanistic factors in cardiovascular diseases

Cardiovascular disease (CVD) is the most fatal disease that causes sudden death, and inflammation contributes substantially to its occurrence and progression. The prevalence of CVD increases as the population ages, and the pathophysiology is complex. Anti-inflammatory and immunological modulation are the potential methods for CVD prevention and treatment. High-Mobility Group (HMG) chromosomal proteins are one of the most abundant nuclear nonhistone proteins which act as inflammatory mediators in DNA replication, transcription, and repair by producing cytokines and serving as damage-associated molecular patterns in inflammatory responses. The most common and well-studied HMG proteins are those with an HMGB domain, which participate in a variety of biological processes. HMGB1 and HMGB2 were the first members of the HMGB family to be identified and are present in all investigated eukaryotes. Our review is primarily concerned with the involvement of HMGB1 and HMGB2 in CVD. The purpose of this review is to provide a theoretical framework for diagnosing and treating CVD by discussing the structure and function of HMGB1 and HMGB2.

Effect of Systemic Inflammation in the CNS: A Silent History of Neuronal Damage

Central nervous system (CNS) infections including meningitis and encephalitis, resulting from the blood-borne spread of specific microorganisms, provoke nervous tissue damage due to the inflammatory process. Moreover, different pathologies such as sepsis can generate systemic inflammation. Bacterial lipopolysaccharide (LPS) induces the release of inflammatory mediators and damage molecules, which are then released into the bloodstream and can interact with structures such as the CNS, thus modifying the blood-brain barrier's (BBB´s) and blood-cerebrospinal fluid barrier´s (BCSFB´s) function and inducing aseptic neuroinflammation. During neuroinflammation, the participation of glial cells (astrocytes, microglia, and oligodendrocytes) plays an important role. They release cytokines, chemokines, reactive oxygen species, nitrogen species, peptides, and even excitatory amino acids that lead to neuronal damage. The neurons undergo morphological and functional changes that could initiate functional alterations to neurodegenerative processes. The present work aims to explain these processes and the pathophysiological interactions involved in CNS damage in the absence of microbes or inflammatory cells.

The role of high mobility group box 1 in neuroinflammatory related diseases

High mobility group box 1 (HMGB1) is a ubiquitous and highly conserved non-histone DNA-binding protein with different biological functions according to its subcellular localization. It is widely believed that HMGB1, which is released into the extracellular space, plays a key role in the inflammatory response. In recent years, numerous studies have shown that the development of various neurological diseases such as epilepsy, Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), cerebrovascular disease and traumatic brain injury (TBI) are inextricably linked to inflammation. We will review the mechanisms of HMGB1 and its receptors in nervous system inflammation to provide a basis for further development of new HMGB1-based therapies.

GAT107-mediated α7 nicotinic acetylcholine receptor signaling attenuates inflammatory lung injury and mortality in a mouse model of ventilator-associated pneumonia by alleviating macrophage mitochondrial oxidative stress via reducing MnSOD-S-glutathionylation

Supraphysiological concentrations of oxygen (hyperoxia) can compromise host defense and increase susceptibility to bacterial and viral infections, causing ventilator-associated pneumonia (VAP). Compromised host defense and inflammatory lung injury are mediated, in part, by high extracellular concentrations of HMGB1, which can be decreased by GTS-21, a partial agonist of α7 nicotinic acetylcholine receptor (α7nAChR). Here, we report that a novel α7nAChR agonistic positive allosteric modulator (ago-PAM), GAT107, at 3.3 mg/kg, i.p., significantly decreased animal mortality and markers of inflammatory injury in mice exposed to hyperoxia and subsequently infected with Pseudomonas aeruginosa. The incubation of macrophages with 3.3 μM of GAT107 significantly decreased hyperoxia-induced extracellular HMGB1 accumulation and HMGB1-induced macrophage phagocytic dysfunction. Hyperoxia-compromised macrophage function was correlated with impaired mitochondrial membrane integrity, increased superoxide levels, and decreased manganese superoxide dismutase (MnSOD) activity. This compromised MnSOD activity is due to a significant increase in its level of glutathionylation. The incubation of hyperoxic macrophages with 3.3 μM of GAT107 significantly decreases the levels of glutathionylated MnSOD, and restores MnSOD activity and mitochondrial membrane integrity. Thus, GAT107 restored hyperoxia-compromised phagocytic functions by decreasing HMGB1 release, most likely via a mitochondrial-directed pathway. Overall, our results suggest that GAT107 may be a potential treatment to decrease acute inflammatory lung injury by increasing host defense in patients with VAP.

Ghost messages: cell death signals spread

Cell death is a mystery in various forms. Whichever type of cell death, this is always accompanied by active or passive molecules release. The recent years marked the renaissance of the study of these molecules showing they can signal to and communicate with recipient cells and regulate physio- or pathological events. This review summarizes the defined forms of messages cells could spread while dying, the effects of these signals on the target tissue/cells, and how these types of communications regulate physio- or pathological processes. By doing so, this review hopes to identify major unresolved questions in the field, formulate new hypothesis worthy of further investigation, and when possible, provide references for the search of novel diagnostic/therapeutics agents. Video abstract.

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

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

Advances in research on the protective mechanisms of traditional Chinese medicine (TCM) in myocardial ischaemia-reperfusion injury

CONTEXT

Developing effective drugs to treat myocardial ischaemia-reperfusion (MI/R) injury is imperative. Traditional Chinese medicines (TCMs) have had considerable success in the treatment of cardiovascular diseases. Elucidating the mechanisms by which TCMs improve MI/R injury can supplement the literature on MI/R prevention and treatment.

OBJECTIVE

To summarise TCMs and their main protective mechanisms against MI/R injury reported over the past 40 years.

METHODS

Relevant literature published between 1980 and 2020 in Chinese and English was retrieved from the Web of Science, PubMed, SpringerLink, PubMed Central, Scopus, and Chinese National Knowledge Infrastructure (CNKI) databases. Search terms included 'medicinal plants', 'myocardial ischaemia reperfusion injury', 'Chinese medicine prescriptions', 'mechanisms', 'prevention', 'treatment' and 'protection'. For inclusion in the analysis, medicinal plants had to be searchable in the China Medical Information Platform and Plant Database.

RESULTS

We found 71 medicinal species (from 40 families) that have been used to prevent MI/R injury, of which Compositae species (8 species) and Leguminosae species (7 species) made up the majority. Most of the effects associated with these plants are described as antioxidant and anti-inflammatory. Furthermore, we summarised 18 kinds of Chinese compound prescriptions, including the compound Danshen tablet and Baoxin pill, which mainly reduce oxidative stress and regulate mitochondrial energy metabolism.

DISCUSSION AND CONCLUSIONS

We summarised TCMs that protect against MI/R injury and their pharmacological mechanisms. This in-depth explanation of the roles of TCMs in MI/R injury protection provides a theoretical basis for the research and development of TCM-based treatment drugs.

The Effect of PD-1 Inhibitor Combined with Irradiation on HMGB1-Associated Inflammatory Cytokines and Myocardial Injury

PURPOSE

To explore the effect of PD-1 inhibitors combined with irradiation on myocardial injury and the changes of HMGB1-associated inflammatory markers.

METHODS

Four groups of five mice were used, each groupformed by randomly dividing 20 mice (group A control; group B PD-1 inhibitors; group C Irradiation; group D PD-1 inhibitors+irradiation; n = 5 for each). The mice were treated with either PD-1 inhibitors or a 15 Gy dose of single heart irradiation, or both. Hematoxylin-eosin staining assessed the morphology and pathology of heart tissue; Masson staining assessed heart fibrosis; Tunel staining evaluated heart apoptosis; flow cytometry detected CD3+, CD4+, and CD8+ T lymphocytes in heart tissues; enzyme linked immunosorbent assay evaluated IL-1β, IL-6, and TNF-ɑ of heart tissue; Western blot and quantitative real-time PCR (qPCR) detected the expression of protein and mRNA of HMGB1, TLR-4, and NF-κB p65 respectively.

RESULTS

The degree of heart injury, collagen volume fraction (CVF) and apoptotic index (AI) in groups B, C, and D were higher than group A, but the differences between the CVF and AI of group A and group B were not statistical significance (P>0.05). Similarly, the absolute counts and relative percentage of CD3+ and CD8+ T lymphocytes and the concentrations of IL-1β, IL-6, and TNF-α in heart tissue with group D were significantly higher than the other groups (P<0.05). In addition, compared with group A, the expression of protein and mRNA of HMGB1 and NF-κB p65 in other groups were higher, and the differences between each group were statistically significant while TLR4 was not. In addition, interaction by PD-1 inhibitors and irradiation was found in inflammatory indicators, especially in the expression of the HMGB1 and CD8+ T lymphocytes.

CONCLUSION

PD-1 inhibitors can increase the expression of HMGB1-associated inflammatory cytokines and aggravate radiation-induced myocardial injury.

Inhibition of inflammatory liver injury by the HMGB1-A box through HMGB1/TLR-4/NF-κB signaling in an acute liver failure mouse model

We aimed to investigate the preventive effect of high mobility group box 1 (HMGB1)-A box and the mechanism by which it alleviates inflammatory injury in acute liver failure (ALF) by inhibiting the extracellular release of HMGB1. BALB/c mice were intraperitoneally (i.p.) administered LPS/D-GalN to establish an ALF mouse model. HMGB1-A box was administered (i.p.) 1 h before establishing the ALF mouse model. The levels of extracellularly released HMGB1, TLR-4/NF-κB signaling molecules, the proinflammatory cytokines TNF-α, IL-1β, and IL-6 and COX-2 were measured in the liver tissue and/or serum by Immunohistochemistry, Western blotting and Enzyme-linked immunosorbent assay (ELISA). The levels of extracellularly released HMGB1, TLR-4/NF-κB signaling molecules and proinflammatory cytokines were measured in Huh7 cells as well as LPS- and/or HMGB1-A box treatment by confocal microscopy, Western blotting and ELISA. In the ALF mouse model, the levels of HMGB1 were significantly increased both in the liver and serum, TLR-4/NF-κB signaling molecules and proinflammatory cytokines also was upregulated. Notably, HMGB1-A box could reverse these changes. HMGB1-A box could also cause these changes in LPS-induced Huh7 cells. HMGB1-A box played a protective role by inhibiting inflammatory liver injury via the regulation of HMGB1/TLR-4/NF-κB signaling in the LPS/D-GaIN-induced ALF mouse model, which may be related to inhibiting the extracellular release of HMGB1.

LRRK2 deficiency protects the heart against myocardial infarction injury in mice via the P53/HMGB1 pathway

LRRK2 is a Ser/Thr kinase with multiple functional domains. Studies have shown that LRRK2 mutations are closely related to hereditary Parkinson's disease. However, its role in cardiovascular disease, especially in myocardial infarction, is unclear. The aim of this study was to explore the functional role of LRRK2 in myocardial infarction. Wild-type and LRRK2-knockout mice were subjected to coronary artery ligation (left anterior descending) to establish a myocardial infarction model. Neonatal rat cardiomyocytes were subjected to hypoxia to induce hypoxic injury in vitro. We found increased LRRK2 expression levels in the infarct periphery in mouse hearts and hypoxic cardiomyocytes. LRRK2-deficient mice exhibited decreased death rates and reduced infarction areas compared to wild-type controls 14 days after infarction. LRRK2-deficient mice showed reduced left ventricular fibrosis and inflammatory responses, as well as improved cardiac function. In the in vitro study, LRRK2 silencing decreased cleaved caspase-3 activity, reduced cardiomyocyte apoptosis, and diminished hypoxia-induced inflammation. However, LRRK2 overexpression enhanced cleaved caspase-3 activity, increased the number of apoptotic cardiomyocytes, and caused remarkable hypoxia-induced inflammation. When examining the underlying mechanisms, we found that hypoxia increased HIFα expression, which enhanced LRRK2 expression. LRRK2 induced high expression of HMGB1 via P53. When HMGB1 was blocked using an anti-HMGB1 antibody, the deleterious effects caused by LRRK2 overexpression following hypoxia were inhibited in cardiomyocytes. In summary, LRRK2 deficiency protects the heart against myocardial infarction injury. The mechanism underlying this effect involves the P53-HMGB1 pathway.

Resveratrol mediates the miR-149/HMGB1 axis and regulates the ferroptosis pathway to protect myocardium in endotoxemia mice

Endotoxemia is a common complication often used to model the acute inflammatory response associated with endotoxemia. Resveratrol has been shown to exert a wide range of therapeutic effects due to its anti-inflammatory and antioxidant properties. This study explored the effect of resveratrol on endotoxemia. Lipopolysaccharide (LPS)-induced endotoxemia mouse model and endotoxemia myocardial injury cell model were established and treated with resveratrol. Cardiomyocyte activity, lactate dehydrogenase (LDH) content in cell supernatant, glutathione (GSH) consumption, lipid reactive oxygen species (ROS) production, and iron accumulation were detected. Cardiac function indexes [left ventricular end-diastolic diameter (LVEDD), left ventricular end-systolic diameter (LVESD), ejection fraction (EF)%, and fractional shortening (FS)%] were measured using echocardiography. The creatine kinase muscle/brain isoenzyme (CK-MB) and CK levels in the serum were detected using an automatic biochemical analyzer. The downstream target of miR-149 was predicted, and the binding relationship between miR-149 and high mobility group box 1 (HMGB1) was verified using a dual-luciferase assay. miR-149 and HMGB1 expressions were detected using RT-qPCR and Western blot. After resveratrol treatment, cardiomyocyte viability and GSH were increased, and LDH secretion, lipid ROS production, lipid peroxidation, and iron accumulation were decreased, and cardiac function and cardiomyocyte injury were improved. Resveratrol improved LPS-induced endotoxemia cardiomyocyte injury by upregulating miR-149 and inhibiting ferroptosis. Resveratrol inhibited HMGB1 expression by upregulating miR-149. HMGB1 upregulation reversed the inhibitory effect of miR-149 on LPS-induced ferroptosis in cardiomyocytes. Resveratrol upregulated miR-149 and downregulated HMGB1 to inhibit ferroptosis and improve myocardial injury in mice with LPS-induced endotoxemia. Collectively, resveratrol upregulated miR-149, downregulated HMGB1, and inhibited the ferroptosis pathway, thus improving cardiomyocyte injury in LPS-induced endotoxemia.NEW & NOTEWORTHY Sepsis is an unusual systemic reaction. Resveratrol is involved in sepsis treatment. This study explored the mechanism of resveratrol in sepsis by regulating the miR-149/HMGB1 axis.

Transcriptomic Profiling Reveals That HMGB1 Induces Macrophage Polarization Different from Classical M1

Macrophages are key inflammatory immune cells that display dynamic phenotypes and functions in response to their local microenvironment. In different conditions, macrophage polarization can be induced by high-mobility group box 1 (HMGB1), a nuclear DNA-binding protein that activates innate immunity via the Toll-like receptor (TLR) 4, the receptor for advanced glycation end products (RAGE), and C-X-C chemokine receptor (CXCR) 4. This study investigated the phenotypes of murine bone-marrow-derived macrophages (BMDMs) stimulated with different HMGB1 redox isoforms using bulk RNA sequencing (RNA-Seq). Disulfide HMGB1 (dsHMGB1)-stimulated BMDMs showed a similar but distinct transcriptomic profile to LPS/IFNγ- and LPS-stimulated BMDMs. Fully reduced HMGB1 (frHMGB1) did not induce any significant transcriptomic change. Interestingly, compared to LPS/IFNγ- and LPS-, dsHMGB1-stimulated BMDMs showed lipid metabolism and foam cell differentiation gene set enrichment, and oil red O staining revealed that both dsHMGB1 and frHMGB1 alleviated oxidized low-density lipoprotein (oxLDL)-induced foam cells formation. Overall, this work, for the first time, used transcriptomic analysis by RNA-Seq to investigate the impact of HMGB1 stimulation on BMDM polarization. Our results demonstrated that dsHMGB1 and frHMGB1 induced distinct BMDM polarization phenotypes compared to LPS/IFNγ- and LPS- induced phenotypes.

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.

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

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

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).

Endothelial cell ferroptosis mediates monocrotaline-induced pulmonary hypertension in rats by modulating NLRP3 inflammasome activation

Inflammation triggers pulmonary vascular remodelling. Ferroptosis, a nonapoptotic form of cell death that is triggered by iron-dependent lipid peroxidation and contributes to the pathogenesis of several inflammation-related diseases, but its role in pulmonary hypertension (PH) has not been studied. We examined endothelial cell ferroptosis in PH and the potential mechanisms. Pulmonary artery endothelial cells (PAECs) and lung tissues from monocrotaline (MCT)-induced PH rats were analysed for ferroptosis markers, including lipid peroxidation, the labile iron pool (LIP) and the protein expression of glutathione peroxidase 4 (GPX4), ferritin heavy chain 1 (FTH1) and NADPH oxidase-4 (NOX4). The effects of the ferroptosis inhibitor ferrostatin-1 (Fer-1) on endothelial cell ferroptosis and pulmonary vascular remodelling in MCT-induced rats were studied in vitro and in vivo. Ferroptosis was observed in PAECs from MCT-induced PH rats in vitro and in vivo and was characterized by a decline in cell viability accompanied by increases in the LIP and lipid peroxidation, the downregulation of GPX4 and FTH1 expression and the upregulation of NOX4 expression. High-mobility group box 1 (HMGB1)/Toll-like receptor 4 (TLR4)/NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome signalling was measured by western blotting. These changes were significantly blocked by Fer-1 administration in vitro and in vivo. These results suggest that Fer-1 plays a role in inhibiting ferroptosis-mediated PAEC loss during the progression of PH. The ferroptosis-induced inflammatory response depended on the activation of HMGB1/TLR4 signalling, which activated the NLRP3 inflammasome in vivo. We are the first to suggest that pulmonary artery endothelial ferroptosis triggers inflammatory responses via the HMGB1/TLR4/NLRP3 inflammasome signalling pathway in MCT-induced rats. Treating PH with a ferroptosis inhibitor and exploring new treatments based on ferroptosis regulation might be promising therapeutic strategies for PH.

HMGB1‐Promoted Neutrophil Extracellular Traps Contribute to Cardiac Diastolic Dysfunction in Mice

Background

Heart failure with preserved ejection fraction (HFpEF) remains an increasing public health problem with substantial morbidity and mortality but with few effective treatments. A novel inflammatory mechanism has been proposed, but the inflammatory signals promoting the development of HFpEF remain greatly unknown.

Methods and Results

Serum of patients with HFpEF was collected for measurement of circulating neutrophils and markers of neutrophil extracellular traps (NETs). To induce HFpEF phenotype, male C57BL/6 mice underwent uninephrectomy, received a continuous infusion of d‐aldosterone for 4 weeks, and maintained on 1.0% sodium chloride drinking water. Heart tissues were harvested, immune cell types determined by flow cytometry, NETs formation by immunofluorescence, and western blotting. Differentiated neutrophils were cultured to investigate the effect of HMGB1 (high mobility group protein B1) and SGLT2 (sodium‐glucose cotransporter‐2) inhibitor on NETs formation in vitro. Circulating neutrophils and NETs markers are elevated in patients with HFpEF, as are cardiac neutrophils and NETs formation in HFpEF mice. NETs inhibition with deoxyribonuclease 1 in experimental HFpEF mice reduces heart macrophages infiltration and inflammation and ameliorates cardiac fibrosis and diastolic function. Damage‐associated molecular pattern HMGB1 expression is elevated in cardiac tissue of HFpEF mice, and HMGB1 inhibition reduces heart neutrophil infiltration and NETs formation and ameliorates diastolic function. Lastly, SGLT2 inhibitor empagliflozin down‐regulates heart HMGB1 expression, attenuates NETs formation and cardiac fibrosis, and improves diastolic function in HFpEF mice.

Conclusions

NETs contribute to the pathogenesis of HFpEF, which can be ameliorated by HMGB1 inhibition and SGLT2 inhibitors. Thus, HMGB1 and NETs may represent novel therapeutic targets for the treatment of HFpEF.

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

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.

Arsenic-induced lung inflammation and fibrosis in a rat model: Contribution of the HMGB1/RAGE, PI3K/AKT, and TGF-β1/SMAD pathways

An increasing number of studies have shown that arsenic exposure increases the risk of lung cancer as well as a variety of non-malignant respiratory diseases, including bronchitis and tracheobronchitis. HMGB1 is widely expressed in a variety of tissues and cells and is involved in the pathological processes of many lung diseases through binding to the corresponding receptors and activating the downstream signaling pathways. However, the exact role of HMGB1/RAGE in arsenic-induced lung injury remains unknown. The aim of this study was to investigate whether HMGB1/RAGE and its activated downstream pathways are involved in the process of arsenic exposure-induced lung injury in rats. In this study, an animal model of oral exposure to arsenic was induced using 2.5, 5 and 10 mg/kg NaAsO2. The results showed that capillary permeability (LDH, TP, ACP, and AKP) was increased in the arsenic exposure groups, resulting in cell damage; this was accompanied by acute inflammation marked by significant neutrophil infiltration. Meanwhile, obvious histopathological damage, including thickening of the lung epithelium, increased infiltration of inflammatory cells, rupture of the alveolar wall, swelling of the mitochondria, and chromatin agglutination was observed by H&E staining and transmission electron microscopy. Furthermore, the results confirmed that the expressions of HMGB1 and RAGE in lung tissue were enhanced, and protein expression of PI3K, p-AKT, IL-1β, IL-18, and MMP-9 was increased in lung homogenates from the arsenic-exposed groups compared to the control group. Finally, Masson's staining results revealed arsenic-induced fibrosis and collagen deposition. Moreover, a significant increase in key fibrosis factors, including TGF-β1, p-SMAD2, p-SMAD3, and SMAD4 was observed in the lung homogenates in arsenic-exposed groups. In conclusion, the current study demonstrates that sub-chronic arsenic exposure triggers the inflammatory response and collagen fiber deposition in rat lung tissue. The potential mechanism may be closely related to activation of the pro-inflammatory-related HMGB1/RAGE pathway and initiation of the PI3K/AKT and TGF-β1/SMAD pathways.

MyD88: At the heart of inflammatory signaling and cardiovascular disease

Cardiovascular disease is a leading cause of death worldwide and is associated with systemic inflammation. In depth study of the cell-specific signaling mechanisms mediating the inflammatory response is vital to improving anti-inflammatory therapies that reduce mortality and morbidity. Cellular damage in the cardiovascular system results in the release of damage associated molecular patterns (DAMPs), also known as "alarmins," which activate myeloid cells through the adaptor protein myeloid differentiation primary response 88 (MyD88). MyD88 is broadly expressed in most cell types of the immune and cardiovascular systems, and its role often differs in a cardiovascular disease context and cell specific manner. Herein we review what is known about MyD88 in the setting of a variety of cardiovascular diseases, discussing cell specific functions and the relative contributions of MyD88-dependent vs. independent alarmin triggered inflammatory signaling. The widespread involvement of these pathways in cardiovascular disease, and their largely unexplored complexity, sets the stage for future in depth mechanistic studies that may place MyD88 in both immune and non-immune cell types as an attractive target for therapeutic intervention in cardiovascular disease.

High mobility group box 1 and homocysteine as preprocedural predictors for contrast-induced acute kidney injury after percutaneous coronary artery intervention

PURPOSE

High mobility group box 1 (HMGB1) and homocysteine (Hcy) play important roles in contrast-induced acute kidney injury (CI-AKI). We compared HMGB1 to Hcy as preprocedural predictors for CI-AKI in coronary artery disease (CAD) patients after percutaneous coronary artery intervention (PCI).

METHODS

We included 257 eligible patients who were categorized into CI-AKI ( +) and CI-AKI ( -) group. The differences in clinical characteristics and biochemical indexes between two groups were analyzed.

RESULTS

We observed that thirty-eight (14.8%) of 257 eligible CAD patients developed CI-AKI. HMGB1 (14.65 [11.13-24.89] vs 10.88 [7.94-13.23], p < 0.001) and Hcy (14.07 [12.07-17.31] vs 12.09 [10.71-13.47], p < 0.001) increased significantly in CI-AKI ( +) group. Both age (r = 0.210, p = 0.001), serum creatinine (r = 0.509, p < 0.001), eGFR (r =  - 0.459, p < 0.001) and Hcy (r = 0.531, p < 0.001) were significantly correlated with HMGB1. Among all patients, HMGB1 (OR 1.181, 95% CI 1.081-1.290, p < 0.001) and Hcy (OR 1.260, 95% CI 1.066-1.489, p = 0.007) were independent predictors for the development of CI-AKI. We built the propensity score matching (PSM) using 38 pairs of patients. After adjustment, HMGB1 (OR 1.169, 95% CI 1.035-1.322, p = 0.012) and Hcy (OR 1.457, 95% CI 1.064-1.997, p = 0.019) were also independent predictors for the development of CI-AKI. Both HMGB1 (AUC: 0.704, 95% CI: 0.588-0.819, p = 0.002) and Hcy (AUC: 0.708, 95% CI: 0.593-0.823, p = 0.002) had predictive values for CI-AKI.

CONCLUSION

There is a significant positive association between HMGB1 and Hcy in CAD patients. Both HMGB1 and Hcy are potential preprocedural predictors of CI-AKI after PCI.

EPHB4 Regulates the Proliferation and Metastasis of Oral Squamous Cell Carcinoma through the HMGB1/NF-κB Signalling Pathway

Background: Malignant proliferation and cervical lymphatic metastasis restrict the prognosis of oral squamous cell carcinoma (OSCC). Erythropoietin-producing human hepatocellular B4 (EPHB4) regulates a series of tumour functions involving tumourigenesis, cancer cell attachment and metastasis. However, the mechanism of EphB4 regulating the malignant progression of OSCC has not been fully elucidated. Methods: EPHB4 expression was analysed in 65 OSCC samples and adjacent noncancerous tissues through immunohistochemistry (IHC). siRNA and overexpression plasmids were transfected into OSCC cells to modify EPHB4 expression, and then, regulatory functions were explored in vitro and in vivo. Co-immunoprecipitation (Co-IP) and mass spectrometry were applied to detect proteins interacting with EPHB4. Subsequently, protein stability assays and NF-κB pathway inhibition assays were used to verify the regulation of EPHB4, high-mobility group box 1 (HMGB1) and nuclear factor-κB (NF-κB) activation. Results: EPHB4 was found to be highly expressed in OSCC tissues, which was related to tumour stage and lymphatic metastasis and resulted in a poor prognosis. Cellular experiments and mouse tongue xenograft models further confirmed that high EPHB4 expression promoted the proliferation and metastasis of OSCC tumours. Mechanistically, co-IP and mass spectrometry studies indicated that EPHB4 could bind to HMGB1 and maintain HMGB1 stability. Downregulation of HMGB1 inhibited the proliferation and metastasis of OSCC cells and inhibited NF-κB phosphorylation activation but did not affect EPHB4 expression. Conclusion: This study revealed the mechanism by which EPHB4 promotes the proliferation and metastasis of OSCC by activating the HMGB1-mediated NF-κB signalling pathway, which can be exploited as a novel marker or therapeutic target to control metastasis and improve the survival rate of OSCC.

Recombinant High-Mobility Group Box 1 (rHMGB1) Promotes NRF2-Independent Mitochondrial Fusion through CXCR4/PSMB5-Mediated Drp1 Degradation in Endothelial Cells

Mitochondrial dynamics plays an important role in maintaining normal endothelial cell function and in the pathogenesis of cardiovascular disease. It is not identified whether high-mobility group box 1 (HMGB1), a representative damage-associated molecular pattern (DAMP) molecule, could influence mitochondrial dynamics in endothelial cells. The objective of this study is to clarify the effect of HMGB1 on mitochondrial dynamics in endothelial cells and the underlying mechanism. EA.hy926 human endothelial cells were incubated with recombinant HMGB1 (rHMGB1); mitochondrial morphology was observed with a confocal microscope and transmission electron microscope (TEM). The expression of dynamin-related protein 1 (Drp1), Mitofusin 1 (Mfn1), Mitofusin 2 (Mfn2), Optic atrophy 1 (Opa1), phosphatase and tensin homolog- (PTEN-) induced kinase 1 (PINK1), NOD-like receptor 3 (NLRP3), caspase 1, cleaved caspase 1, 20S proteasome subunit beta 5 (PSMB5), and antioxidative master nuclear factor E2-related factor 2 (NRF2) and the concentration of interleukin 1β (IL-1β) were determined. Specific inhibitors C29, TAK-242, FPS-ZM1, AMD3100, and epoxomicin were used to block toll-like receptor 2 (TLR2), toll-like receptor 4 (TLR4), receptor for advanced glycation end products (RAGE), C-X-C-chemokine receptor 4 (CXCR4), and PSMB5, respectively. siRNAs were used to silence the expression of NRF2. rHMGB1 promoted mitochondrial fusion in endothelial cells, while no significant proinflammatory effects were found. The expression of mitochondrial fission protein Drp1 and phosphorylated subtypes p-Drp1-S616 and p-Drp1-S637 were all downregulated; no significant expression changes of PINK1 and Mfn1, Mfn2, and Opa1 were found. Inhibition of CXCR4 but not TLR4, RAGE, or TLR2 reversed rHMGB1-induced Drp1 downregulation and mitochondrial fusion. Interestingly, inhibition of TLR4 with TAK-242 promoted Drp1 downregulation and mitochondrial fusion. rHMGB1 increased the expression of NRF2 and PSMB5; inhibition of PSMB5 but not silencing NRF2 abolished rHMGB1-induced Drp1 downregulation and mitochondrial fusion. These results indicate that rHMGB1 promotes NRF2 independent mitochondrial fusion via CXCR4/PSMB5 pathway-mediated Drp1 proteolysis. rHMGB1 may influence mitochondrial and endothelial function through this effect on mitochondrial dynamics.

Genome-Wide Screen and Validation of Microglia Pro-Inflammatory Mediators in Stroke

Stroke activates microglia pro-inflammatory response that not only induces the early neuronal injuries but also causes the secondary brain infarction. Yet, the underlying mechanisms for how microglia become activated in stroke are still unknown. Here, using the next-generation of RNA sequencing we find a total of 778 genes increasingly expressed in brain of stroke mice. Of these, we identified Hmgb2 as a microglia pro-inflammatory mediator by promoting the transcription of Ctss. Inhibition of either Hmgb2 or Ctss blocks microglia pro-inflammatory response and protects against brain damages and improves the neurological functions of stroke mice. This study uncovers Hmgb2 and Ctss as the major microglia inflammatory response mediators in stroke and hence warrants the promising targets for stroke therapies.

Radiotherapy and Cytokine Storm: Risk and Mechanism

Radiotherapy (RT) shows advantages as one of the most important precise therapy strategies for cancer treatment, especially high-dose hypofractionated RT which is widely used in clinical applications due to the protection of local anatomical structure and relatively mild impairment. With the increase of single dose, ranging from 2~20 Gy, and the decrease of fractionation, the question that if there is any uniform standard of dose limits for different therapeutic regimens attracts more and more attention, and the potential adverse effects of higher dose radiation have not been elucidated. In this study, the immunological adverse responses induced by radiation, especially the cytokine storm and the underlying mechanisms such as DAMPs release, pro-inflammatory cytokine secretion and cGAS-STING pathway activation, will be elucidated, which contributes to achieving optimal hypofractionated RT regimen, improving the killing of cancer cells and avoiding the severe side effects.

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSION

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

The Regulatory Role of High-Mobility Group Protein 1 in Sepsis-Related Immunity

High-mobility group box 1 (HMGB1), a prototypical damage-associated molecular pattern (DAMP) molecule, participates in multiple processes of various inflammatory diseases through binding to its corresponding receptors. In the early phase, sepsis is mainly characterized as a multi-bacterial-induced complex, excessive inflammatory response accompanied by the release of pro-inflammatory mediators, which subsequently develops into immune paralysis. A growing number of in vivo and in vitro investigations reveal that HMGB1 plays a pivotal role in the processes of inflammatory response and immunosuppression of sepsis. Therefore, HMGB1 exerts an indispensable role in the immune disorder and life-threatening inflammatory syndrome of sepsis. HMGB1 mainly mediate the release of inflammatory factors via acting on immune cells, pyroptosis pathways and phosphorylating nuclear factor-κB. Moreover HMGB1 is also associated with the process of sepsis-related immunosuppression. Neutrophil dysfunction mediated by HMGB1 is also an aspect of the immunosuppressive mechanism of sepsis. Myeloid-derived suppressor cells (MDSCs), which are also one of the important cells that play an immunosuppressive effect in sepsis, may connect with HMGB1. Thence, further understanding of HMGB1-associated pathogenesis of sepsis may assist in development of promising treatment strategies. This review mainly discusses current perspectives on the roles of HMGB1 in sepsis-related inflammation and immunosuppressive process and its related internal regulatory mechanisms.

HMGB1: A pleiotropic activity

High-mobility group box 1 (HMGB1) is a nuclear protein involved in DNA replication, transcription, recombination, and repair. In the extracellular space, the HMGB1 plays an essential role in the onset and perpetuation of inflammation, belonging to the group of damage-associated molecular pattern (DAMP) molecules, also called alarmins. For this, HMGB1 has been studied in several acute and chronic inflammatory diseases as an early biomarker of inflammation. An increased concentration of HMGB1 has been detected in serum, as the expression of systemic inflammation, and in specific samples (such as stool, synovial fluid, nasal lavage fluid, sputum, and cerebrospinal fluid), as the expression of local production, in several infectious and/or inflammatory diseases. These data are particularly important because they open new futuristic possibilities for target therapies, potentially also for the COVID-19 treatment.

miR-381-3p inhibits high glucose-induced vascular smooth muscle cell proliferation and migration by targeting HMGB1

BACKGROUND

Hyperglycemia increases the risk of many cardiovascular diseases (CVD), and the dysregulation of proliferation and migration in vascular smooth muscle cells (VSMCs) also participates in the pathogenesis of CVD. miR-381-3p is known to suppress the proliferation and migration of multiple human cell types. Nevertheless, the function of miR-381-3p in VSMCs remains largely indistinct.

METHODS

A quantitative real-time polymerase chain reaction (qRT-PCR) was employed to investigate miR-381-3p expression in high-glucose-induced VSMCs. Inflammatory cytokines tumor necrosis factor-α, interleukin-1β and interleukin-6, as well as oxidative stress markers SOD and MDA, were determined by an enzyme-linked immunosorbent assay. Reactive oxygen species generation was examined using a 2,7'-dichlorofluorescein kit. The proliferation, migration and apoptosis of VSMCs were monitored by 3-(4,5-dimethylthiazl2-yl)-2,5-diphenyltetazolium bromide (MTT), transwell and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assays. The TargetScan database (http://www.targetscan.org) was employed to seek the potential target gene of miR-381-3p. Interaction between miR-381-3p and HMGB1 was determined by a qRT-PCR, western blotting and a luciferase reporter assay.

RESULTS

miR-381-3p expression was significantly reduced in a VSMCs dysfunction model induced by high-glucose in a dose- and time-dependent manner. Transfection of miR-381-3p mimics suppressed the inflammation, oxidative stress, proliferation and migration of VSMCs, whereas apoptosis of VSMCs was promoted, and the transfection of miR-381-3p inhibitors had the opposite effect. Mechanistically, HMGB1, an important factor in inflammation response, was confirmed as a target gene of miR-381-3p.

CONCLUSIONS

miR-381-3p targets HMGB1 to suppress the inflammation, oxidative stress, proliferation and migration of high-glucose-induced VSMCs by targeting HMGB1.

Nucleotide-Binding Oligomerization Domain-Like Receptor 3 Deficiency Attenuated Isoproterenol-Induced Cardiac Fibrosis via Reactive Oxygen Species/High Mobility Group Box 1 Protein Axis

Nucleotide-binding oligomerization domain-like receptor 3 (NLRP3) is involved in fibrosis of multiple organs, such as kidney, liver, lung, and the like. However, the role of NLRP3 in cardiac fibrosis is still controversial and remains unclear. The study aims to investigate the role of NLRP3 on cardiac fibrosis induced by isoproterenol (ISO). In vivo, NLRP3 knockout and wild-type mice were subcutaneously injected with ISO to induce the cardiac fibrosis model. The results showed that NLRP3 deficiency alleviated the cardiac fibrosis and inflammation induced by ISO. In vitro, neonatal rat ventricular myocytes (NRVMs) and primary adult mouse cardiac fibroblasts of NLRP3 knockout and wild-type mice were isolated and challenged with ISO. Adenovirus (Ad-) NLRP3 and small interfering RNAs targeting NLRP3 were used to transfect NRVMs to overexpress or knockdown NLRP3. We found that NLRP3 could regulate high-mobility group box 1 protein (HMGB1) secretion via reactive oxygen species production in NRVMs and the HMGB1 secreted by NRVMs promoted the activation and proliferation of cardiac fibroblasts. Thus, we concluded that the NLRP3/reactive oxygen species/HMGB1 pathway could be the underlying mechanism of ISO-induced cardiac fibrosis.

Inflammation in myocardial injury- Stem cells as potential immunomodulators for myocardial regeneration and restoration

The ineffective immunosuppressant's and targeted strategies to neutralize inflammatory mediators have worsened the scenario of heart failure and have opened many questions for debate. Stem cell therapy has proven to be a promising approach for treating heart following myocardial infarction (MI). Adult stem cells, induced pluripotent stem cells and embryonic stem cells are possible cell types and have successfully shown to regenerate damaged myocardial tissue in pre-clinical and clinical studies. Current implications of using mesenchymal stem cells (MSCs) owing to their immunomodulatory functions and paracrine effects could serve as an effective alternative treatment option for rejuvenating the heart post MI. The major setback associated with the use of MSCs is reduced cell retention, engraftment and decreased effectiveness. With a few reports on understanding the role of inflammation and its dual effects on the structure and function of heart, this review focuses on these missing insights and further exemplifies the role of MSCs as an alternative therapy in treating the pathological consequences in myocardial infarction (MI).

Damage-associated molecular patterns in trauma

In 1994, the “danger model” argued that adaptive immune responses are driven rather by molecules released upon tissue damage than by the recognition of “strange” molecules. Thus, an alternative to the “self versus non-self recognition model” has been provided. The model, which suggests that the immune system discriminates dangerous from safe molecules, has established the basis for the future designation of damage-associated molecular patterns (DAMPs), a term that was coined by Walter G. Land, Seong, and Matzinger. The pathological importance of DAMPs is barely somewhere else evident as in the posttraumatic or post-surgical inflammation and regeneration. Since DAMPs have been identified to trigger specific immune responses and inflammation, which is not necessarily detrimental but also regenerative, it still remains difficult to describe their “friend or foe” role in the posttraumatic immunogenicity and healing process. DAMPs can be used as biomarkers to indicate and/or to monitor a disease or injury severity, but they also may serve as clinically applicable parameters for optimized indication of the timing for, i.e., secondary surgeries. While experimental studies allow the detection of these biomarkers on different levels including cellular, tissue, and circulatory milieu, this is not always easily transferable to the human situation. Thus, in this review, we focus on the recent literature dealing with the pathophysiological importance of DAMPs after traumatic injury. Since dysregulated inflammation in traumatized patients always implies disturbed resolution of inflammation, so-called model of suppressing/inhibiting inducible DAMPs (SAMPs) will be very briefly introduced. Thus, an update on this topic in the field of trauma will be provided.