Ethyl pyruvate attenuates myocardial ischemia-reperfusion injury exacerbated by hyperglycemia via retained inhibitory effect on HMGB1

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.

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

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

Inhibition of HMGB1 alleviates myocardial ischemia/reperfusion injury in diabetic mice via suppressing autophagy

BACKGROUND

Diabetes aggravates myocardial ischemia/reperfusion (I/R) injury (MI/RI). The association between high mobility group box 1 protein (HMGB1) and autophagy in diabetic MI/RI remains unknown. Therefore, we investigated whether inhibiting HMGB1 can regulate autophagy in diabetic mice (DM) after I/R injury.

METHODS

I/R models of C57BL/KsJ mice and db/db mice were established. Histological changes, infarct size (IS), HMGB1 protein, and autophagy-related proteins were detected after 24h of reperfusion. In DM treatment groups, anti-HMGB1 antibody (H-Ig) was injected via tail vein after reperfusion for 15min, and the above-mentioned experimental methods were performed at the end of reperfusion.

RESULTS

Compared with the I/R group, the pathological myocardial damage and IS were significantly increased in the I/R (DM) group. Additionally, the levels of HMGB1, Beclin1, and LC3II/LC3I ratio were remarkably higher in the I/R (DM) group than those in the I/R group, while p62 level was lower. In the H-Ig (DM) group, injection of H-Ig significantly reduced the IS, as well as alleviated pathological myocardial damage. Moreover, Beclin1, LC3II/LC3I ratio, and p62 levels were notably reversed after this treatment.

CONCLUSIONS

I/R-induced myocardium was aggravated by diabetes, which may be related to increased release of HMGB1 and activated autophagy. Inhibition of HMGB1 alleviates diabetic MIRI which was associated with reduced autophagy.

Ethyl pyruvate ameliorates heat stroke-induced multiple organ dysfunction and inflammatory responses by induction of stress proteins and activation of autophagy in rats

Objective: Heat stroke (HS) elicits the systemic inflammatory responses that result in multiple organ dysfunction (MOD). Heat shock response and autophagy are activated during heat stress for removal of damaged organelles and proteins, emerging as a major regulator of cellular homeostasis. Ethyl pyruvate (EP) is a derivative of pyruvic acid and possesses antioxidant and anti-inflammatory effects. This study aims to investigate the effects of EP on MOD in HS rats and explore the possible mechanisms.Method: Anesthetized rats were placed in a heating chamber (42 °C) to elevate the core body temperature attaining to 42.9 °C. Rats were then moved to room temperature and monitored for 6 h. EP (60 mg/kg, i.v.) was administered 30 min prior to heat exposure.Results: Results showed that EP significantly reduced HS-induced increases in plasma levels of LDH, CPK, GPT and CK-MB, reversed the decrease of platelet counts, and alleviated intestinal mucosal and pulmonary damage. Moreover, EP reduced pro-inflammatory protein, including TNF-α, IL-6, IL-1β, HMGB1 and iNOS, and induced stress proteins, heme oxygenase-1 (HO-1), heat shock protein (HSP) 70 and HSP90 in the liver of HS rats. The levels of HS-activated autophagy-regulatory proteins were affected by EP, in which the phosphorylated mTOR and AKT were reduced, and the phosphorylated AMPK increased, accompanied with upregulation in ULK1, Atg7, Atg12 and LC3II, and downregulation of p62.Conclusion: In conclusion, EP ameliorated HS-induced inflammatory responses and MOD, and the underlying mechanism is associated with the induction of the stress proteins HO-1 and HSP70 as well as restorage of autophagy.

miR-708 affords protective efficacy in anoxia/reoxygenation-stimulated cardiomyocytes by blocking the TLR4 signaling via targeting HMGB1

Ischemic heart disease is a proverbial and common cardiovascular disease, and constitutes a leading cause of disability and mortality globally. Myocardial ischemic/reperfusion (MI/R) injury is a highly orchestrated phenomenon that involves the excessive activation of high mobility group box 1 (HMGB1) signaling. In the present study, we sought to investigate the function of miR-708 in MI/R injury due to the predicted binding to HMGB1. Intriguingly, down-regulation of miR-708 and up-regulation of HMGB1 were observed in MI/R rat model and H9c2 cardiomyocytes exposed to hypoxia/reoxygenation (H/R) conditions. Dual luciferase reporter assays substantiated that HMGB1 was a direct target of miR-708. Moreover, miR-708 overexpression suppressed the mRNA and protein expression of HMGB1. Noticeably, elevation of miR-708 antagonized H/R-induced inhibition in cell viability; whilst, increased cell apoptosis evoked by H/R was restrained after miR-708 up-regulation. Simultaneously, miR-708 elevation suppressed H/R exposure-increased lactate dehydrogenase (LDH) release and reactive oxygen species (ROS) generation, but elevated the activity of anti-oxidative stress superoxide dismutase (SOD). Additionally, H/R-increased production of pro-inflammatory cytokine TNF-α and IL-6 was offset following miR-708 overexpression. Moreover, enhancement of miR-708 inhibited H/R-evoked activation of the HMGB1-TLR4-NF-κB pathway by inhibiting the protein levels of HMGB1, TLR4 and p-p65 NF-κB. Specially, restoring this pathway offset the protective effects of miR-708 on H/R-induced cardiomyocyte injury. Together, these data indicate that miR-708 may protect against H/R-induced cardiomyocyte damage by directing targeting HMGB1 signaling, implying a promising therapeutic agent against ischemic heart disease including myocardial infarction.

High Mobility Group Box-1 (HMGB1): A Potential Target in Therapeutics

High mobility group box-1 (HMGB1) mainly belongs to the non-histone DNA-binding protein. It has been studied as a nuclear protein that is present in eukaryotic cells. From the HMG family, HMGB1 protein has been focused particularly for its pivotal role in several pathologies. HMGB-1 is considered as an essential facilitator in diseases such as sepsis, collagen disease, atherosclerosis, cancers, arthritis, acute lung injury, epilepsy, myocardial infarction, and local and systemic inflammation. Modulation of HMGB1 levels in the human body provides a way in the management of these diseases. Various strategies, such as HMGB1-receptor antagonists, inhibitors of its signalling pathway, antibodies, RNA inhibitors, vagus nerve stimulation etc. have been used to inhibit expression, release or activity of HMGB1. This review encompasses the role of HMGB1 in various pathologies and discusses its therapeutic potential in these pathologies.

Prognostic role of serum high mobility group box 1 concentration in cardiac surgery

Outcomes of cardiac surgery are influenced by systemic inflammation. High mobility group box 1 (HMGB1), a pivotal inflammatory mediator, plays a potential role as a prognostic biomarker in cardiovascular disease. The aim of this prospective, observational study was to investigate the relationship between serum HMGB1 concentrations and composite of morbidity endpoints in cardiac surgery. Arterial blood samples for HMGB1 measurement were collected from 250 patients after anaesthetic induction (baseline) and 1 h after weaning from cardiopulmonary bypass (post-CPB). The incidence of composite of morbidity endpoints (death, myocardial infarction, stroke, renal failure and prolonged ventilator care) was compared in relation to the tertile distribution of serum HMGB1 concentrations. The incidence of composite of morbidity endpoints was significantly different with respect to the tertile distribution of post-CPB HMGB1 concentrations (p = 0.005) only, and not to the baseline. Multivariable analysis revealed post-CPB HMGB1 concentration (OR, 1.072; p = 0.044), pre-operative creatinine and duration of CPB as independent risk factors of adverse outcome. Accounting for its prominent role in mediating sterile inflammation and its relation to detrimental outcome, HMGB1 measured 1 h after weaning from CPB would serve as a useful biomarker for accurate risk stratification in cardiac surgical patients and may guide tailored anti-inflammatory therapy.

Effect of Simulated Geomagnetic Activity on Myocardial Ischemia/Reperfusion Injury in Rats

Objective

To study the response of myocardial ischemia/reperfusion injury (MI/RI) in rats to simulated geomagnetic activity.

Methods

In a simulated strong geomagnetic outbreak, the MI/RI rat models were radiated, and their area of myocardial infarction, hemodynamic parameters, creatine kinase (CK), lactate dehydrogenase (LDH), melatonin, and troponin I values were measured after a 24-hour intervention.

Results

Our analysis indicates that the concentrations of troponin I in the geomagnetic shielding+operation group were lower than in the radiation+operation group (P<0.05), the concentrations of melatonin in the shielding+operation group and normal+operation group were higher than in the radiation + operation group (P<0.01), and the concentrations of CK in the shielding + operation group were lower than in the radiation + operation group and normal + operation group (P<0.05). Left ventricular developed pressure (LVDP) and ± dP/dtmax in the radiation+operation group were lower than in the shielding + operation group and normal+operation group (P<0.01). Left ventricular end-diastolic pressure (LEVDP) in the shielding + operation group was higher than in the normal + operation group (P<0.05). There was no significant difference in area of myocardial infarction and LDH between the shielding + operation group and the radiation + operation group.

Conclusion

Our data suggest that geomagnetic activity is important in regulating myocardial reperfusion injury. The geomagnetic shielding has a protective effect on myocardial injury, and the geomagnetic radiation is a risk factor for aggravating the cardiovascular and cerebrovascular diseases.

HMGB1-mediated apoptosis and autophagy in ischemic heart diseases

Acute myocardial infarction (MI) and its consequences are the most common and lethal heart syndromes worldwide and represent a significant health problem. Following MI, apoptosis has been generally seen as the major contributor of the cardiomyocyte fate and of the resultant myocardial remodeling. However, in recent years, it has been discovered that, following MI, cardiomyocytes could activate autophagy in an attempt to protect themselves against ischemic stress and to preserve cardiac function. Although initially seen as two completely separate responses, recent works have highlighted the intertwined crosstalk between apoptosis and autophagy. Numerous researches have tried to unveil the mechanisms and the molecular players involved in this phenomenon and have identified in high-mobility group box 1 (HMGB1), a highly conserved non-histone nuclear protein with important roles in the heart, one of the major regulator. Thus, the aim of this mini review is to discuss how HMGB1 regulates these two responses in ischemic heart diseases. Indeed, a detailed understanding of the crosstalk between apoptosis and autophagy in these pathologies and how HMGB1 regulates them would be of tremendous help in developing novel therapeutic approaches aimed to promote cardiomyocyte survival and to diminish tissue injury following MI.

Protective Effect of Ethyl Pyruvate against Myocardial Ischemia Reperfusion Injury through Regulations of ROS-Related NLRP3 Inflammasome Activation

Emerging evidence indicates the pronounced role of inflammasome activation linked to reactive oxygen species (ROS) in the sterile inflammatory response triggered by ischemia/reperfusion (I/R) injury. Ethyl pyruvate (EP) is an antioxidant and conveys myocardial protection against I/R injury, while the exact mechanisms remain elusive. We aimed to investigate the effect of EP on myocardial I/R injury through mechanisms related to ROS and inflammasome regulation. The rats were randomly assigned to four groups: (1) sham, (2) I/R-control (IRC), (3) EP-pretreatment + I/R, and (4) I/R + EP-posttreatment. I/R was induced by a 30 min ligation of the left anterior descending artery followed by 4 h of reperfusion. EP (50 mg/kg) was administered intraperitoneally at 1 h before ischemia (pretreatment) or upon reperfusion (posttreatment). Both pre- and post-EP treatment resulted in significant reductions in myocardial infarct size (by 34% and 31%, respectively) and neutrophil infiltration. I/R-induced myocardial expressions of NADPH oxidase-4, carnitine palmitoyltransferase 1A, and thioredoxin-interacting protein (TXNIP) were mitigated by EP. EP treatment was associated with diminished inflammasome activation (NOD-like receptor 3 (NLRP3), apoptosis-associated speck-like protein, and caspase-1) and interleukin-1β induced by I/R. I/R-induced phosphorylation of ERK and p38 were also mitigated with EP treatments. In H9c2 cells, hypoxia-induced TXNIP and NLRP3 expressions were inhibited by EP and to a lesser degree by U0126 (MEK inhibitor) and SB203580 (p38 inhibitor) as well. EP's downstream protective mechanisms in myocardial I/R injury would include mitigation of ROS-mediated NLRP3 inflammasome upregulation and its associated pathways, partly via inhibition of hypoxia-induced phosphorylation of ERK and p38.

HMGB1 and repair: focus on the heart

High-mobility group box 1 (HMGB1) is one of the most abundant proteins in eukaryotes and the best characterized damage-associated molecular pattern (DAMP). The biological activities of HMGB1 depend on its subcellular location, context and post-translational modifications. Inside the nucleus, HMGB1 is engaged in many DNA events such as DNA repair, transcription regulation and genome stability; in the cytoplasm, its main function is to regulate the autophagic flux while in the extracellular environment, it possesses more complicated functions and it is involved in a large variety of different processes such as inflammation, migration, invasion, proliferation, differentiation and tissue regeneration. Due to this pleiotropy, the role of HMGB1 has been vastly investigated in various pathological diseases and a large number of studies have explored its function in cardiovascular pathologies. However, in this contest, the precise mechanism of action of HMGB1 and its therapeutic potential are still very controversial since is debated whether HMGB1 is involved in tissue damage or plays a role in tissue repair and regeneration. The main focus of this review is to provide an overview of the effects of HMGB1 in different ischemic heart diseases and to discuss its functions in these pathological conditions.

MiR-216a-5p protects 16HBE cells from H2O2-induced oxidative stress through targeting HMGB1/NF-kB pathway

Asthma is a complex, chronic inflammatory disorder of the bronchial tree, and can affect patients of all ages including children. High mobility group box 1 (HMGB1) has been proved as a therapeutic target in children with asthma, and was predicted to be the target gene of microRNA-216a-5p (miR-216a-5p). The present study aimed to investigate the function of miR-216a-5p in asthma by creating a human bronchial epithelial cell (16HBE) injury model using H₂O₂. A significantly elevation of HMGB1 protein expression and a reduction of miR-216a-5p expression were observed in children with asthma as well as in H₂O₂ stimulated 16HBE cells. Dual luciferase reporter assays confirmed the target reaction between HMGB1 and miR-216a-5p. MiR-216a-5p repressed HMGB1 protein expression in H₂O₂ induced 16HBE cells. Moreover, miR-216a-5p inhibited H₂O₂ induced cell injury by elevating cell proliferation and decreasing cell apoptosis in 16HBE cells. Furthermore, miR-216a-5p repressed NF-kB pathway activation in H₂O₂ induced 16HBE cells. In conclusion, these results suggested that miR-216a-5p functions as a negative regulator of H₂O₂ induced 16HBE cell injury through targeting HMGB1/NF-kB pathway, provided a potential therapeutic target for asthma.

Nrf2 activation and down-regulation of HMGB1 and MyD88 expression by amnion membrane extracts in response to the hypoxia-induced injury in cardiac H9c2 cells

BACKGROUND

human Amniotic Membrane (hAM) extracts contain bioactive molecules such as growth factors and cytokines. Studies have confirmed the ability of hAM in reduction of post-operative dysfunction in patients with cardiac surgery. However, the function of Amniotic Membrane Proteins (AMPs), extracted from hAM, against hypoxia-induced H9c2 cells injury have never been investigated. In this study, we aimed to appraise the protective impact of AMPs on H9c2 cells under hypoxia condition.

METHODS

Cardiomyocyte cells were pre-incubated with AMPs and subjected to 24 h hypoxia to elucidate its effects on expression of Nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1(HO-1). Furthermore, the high mobility group box-1 (HMGB1) and Myeloid differentiation primary response 88 (MyD88) expressions were detected by qPCR and western-blotting. The mitochondrial membrane potential (ΔΨm) was estimated by JC-1 using fluorescent microscopy and fluorimetry. Moreover, the cell apoptosis and intracellular calcium levels were measured by flow cytometry.

RESULTS

Pre-treatment of AMPs resulted in significant induction in cell viability and decreased the LDH release under hypoxic condition in H9c2 cells. Accordingly, these protective effects of AMPs were associated with a reduction in apoptosis rates and intracellular Ca2+, meanwhile, ΔΨm was increased. Pre-treatment with AMPs resulted in degradation of HMGB1 and MyD88 levels and depicted pro-survival efficacy of AMPs against hypoxia-induced cell damage through induction of HO-1 and Nrf2.

CONCLUSION

The data indicated that AMPs mediated HO-1 regulation by Nrf2 activation and plays critical protective effects in hypoxia-induced H9c2 injury in vitro by the inhibition of myocardial HMGB1 and MyD88 inflammatory cascade.