High mobility group box-1 protein--one step closer to the clinic?

Protective effects of Hirudin against compartment syndrome in rabbits through the activation of Nrf2/HO-1

Compartment syndrome generates an oxidative condition causing the death of skeletal muscle cells. Hirudin has antioxidant and anti-inflammatory properties. However, its correlation with the pathway of Nrf2/HO-1 for the protection of the skeletal muscle is unknown. We aimed to evaluate the protective efficacy of double-doses of hirudin in compartment syndrome and its association with Nrf2/HO-1 expression. Compartment syndrome was induced in rabbits and double-doses of hirudin (0-8 ATU/kg) were locally administered to select an optimal Hirudin concentration that protects skeletal muscle from damage. The tissue structural changes, W/D ratio, lipid peroxidation level by MDA assay and inflammatory factors were determined in the skeletal muscle. To determine the musculoprotective efficacy of H8 at 72 h timepoint after compartment syndrome, and its association with the Nrf2/HO-1 pathway, the following assays were performed by TUNEL assay and immunofluorescence: necrosis (high-mobility group box-1; HMGB1), Nrf2, and HO-1. In addition, the HO-1 mRNA was evaluated by qPCR. Hirudin in a dose of 8 ATU/kg (H8) presented the lowest levels of histological damage, fibrosis, W/D ratio and oxidative stress in the studied groups. Moreover, treatment with H8 markedly downregulated the level of inflammatory factors including TNF-a, IL-1β and IL-6. H8 showed a protective effect at 72 h timepoint after compartment syndrome, as revealed by a decrease in the levels of all damage markers. Nuclear translocation Nrf2 and HO-1 staining in cytoplasm were increased, and the levels of HO-1 mRNA were also increased. In conclusion, double-doses of H8 alleviate the death of muscle cells induced by oxidative stress 72 h after compartment syndrome in rabbits. This protective effect is associated with the nuclear translocation of Nrf2 and an elevated expression of HO-1.

Heat stroke

Heat stroke is a life-threatening condition clinically diagnosed as a severe elevation in body temperature with central nervous system dysfunction that often includes combativeness, delirium, seizures, and coma. Classic heat stroke primarily occurs in immunocompromised individuals during annual heat waves. Exertional heat stroke is observed in young fit individuals performing strenuous physical activity in hot or temperature environments. Long-term consequences of heat stroke are thought to be due to a systemic inflammatory response syndrome. This article provides a comprehensive review of recent advances in the identification of risk factors that predispose to heat stroke, the role of endotoxin and cytokines in mediation of multi-organ damage, the incidence of hypothermia and fever during heat stroke recovery, clinical biomarkers of organ damage severity, and protective cooling strategies. Risk factors include environmental factors, medications, drug use, compromised health status, and genetic conditions. The role of endotoxin and cytokines is discussed in the framework of research conducted over 30 years ago that requires reassessment to more clearly identify the role of these factors in the systemic inflammatory response syndrome. We challenge the notion that hypothalamic damage is responsible for thermoregulatory disturbances during heat stroke recovery and highlight recent advances in our understanding of the regulated nature of these responses. The need for more sensitive clinical biomarkers of organ damage is examined. Conventional and emerging cooling methods are discussed with reference to protection against peripheral organ damage and selective brain cooling.

Scolopendra subspinipes mutilans protected the cerulein-induced acute pancreatitis by inhibiting high-mobility group box protein-1

AIM: To evaluate the inhibitory effects of Scolopendra subspinipes mutilans (SSM) on cerulein-induced acute pancreatitis (AP) in a mouse model.

METHODS: SSM water extract (0.1, 0.5, or 1 g/kg) was administrated intraperitoneally 1 h prior to the first injection of cerulein. Once AP developed, the stable cholecystokinin analogue, cerulein was injected hourly, over a 6 h period. Blood samples were taken 6 h later to determine serum amylase, lipase, and cytokine levels. The pancreas and lungs were rapidly removed for morphological examination, myeloperoxidase assay, and real-time reverse transcription polymerase chain reaction. To specify the role of SSM in pancreatitis, the pancreatic acinar cells were isolated using collagenase method. Then the cells were pre-treated with SSM, then stimulated with cerulein. The cell viability, cytokine productions and high-mobility group box protein-1 (HMGB-1) were measured. Furthermore, the regulating mechanisms of SSM action were evaluated.

RESULTS: The administration of SSM significantly attenuated the severity of pancreatitis and pancreatitis associated lung injury, as was shown by the reduction in pancreatic edema, neutrophil infiltration, vacuolization and necrosis. SSM treatment also reduced pancreatic weight/body weight ratio, serum amylase, lipase and cytokine levels, and mRNA expression of multiple inflammatory mediators such as tumor necrosis factor-α and interleukin-1β. In addition, treatment with SSM inhibited HMGB-1 expression in the pancreas during AP. In accordance with in vivo data, SSM inhibited the cerulein-induced acinar cell death, cytokine, and HMGB-1 release. SSM also inhibited the activation of c-Jun NH2-terminal kinase, p38 and nuclear factor (NF)-κB.

CONCLUSION: These results suggest that SSM plays a protective role during the development of AP and pancreatitis associated lung injury via deactivating c-Jun NH2-terminal kinase, p38 and NF-κB.

HDAC4/5-HMGB1 signalling mediated by NADPH oxidase activity contributes to cerebral ischaemia/reperfusion injury

Histone deacetylases (HDACs)-mediated epigenetic mechanisms play critical roles in the homeostasis of histone acetylation and gene transcription. HDAC inhibitors have displayed neuroprotective properties in animal models for various neurological diseases including Alzheimer's disease and ischaemic stroke. However, some studies have also reported that HDAC enzymes exert protective effects in several pathological conditions including ischaemic stress. The mixed results indicate the specific roles of each HDAC protein in different diseased states. However, the subtypes of HDACs associated with ischaemic stroke keep unclear. Therefore, in this study, we used an in vivo middle cerebral artery occlusion (MCAO) model and in vitro cell cultures by the model of oxygen glucose deprivation to investigate the expression patterns of HDACs and explore the roles of individual HDACs in ischaemic stroke. Our results showed that inhibition of NADPH oxidase activity ameliorated cerebral ischaemia/reperfusion (I/R) injury and among Zn²⁺-dependent HDACs, HDAC4 and HDAC5 were significantly decreased both in vivo and in vitro, which can be reversed by NADPH oxidase inhibitor apocynin. We further found that both HDAC4 and HDAC5 increased cell viability through inhibition of HMGB1, a central mediator of tissue damage following acute injury, expression and release in PC12 cells. Our results for the first time provide evidence that NADPH oxidase-mediated HDAC4 and HDAC5 expression contributes to cerebral ischaemia injury via HMGB1 signalling pathway, suggesting that it is important to elucidate the role of individual HDACs within the brain, and the development of HDAC inhibitors with improved specificity is required to develop effective therapeutic strategies to treat stroke.

Early elevated HMGB1 level predicting the outcome in exertional heatstroke

BACKGROUND

Heatstroke is generally considered as a syndrome of hyperthermia associated with systemic inflammation leading to multiorgan dysfunction. High mobility group box-1 protein (HMGB1) has recently been identified as a late mediator of systemic inflammation inducing multiorgan dysfunction. Elevation of plasma HMGB1 in heatstroke has been observed in animals, but there is no data available about its changes in heatstroke patients. The objectives of this study are to observe the time course of plasma HMGB1 changes and assess its prognostic value in patients with exertional heatstroke.

METHODS

Blood samples were taken from the patients with exertional heatstroke. Plasma HMGB1 level was detected by the enzyme-linked immunosorbent assay. C-reactive protein level was measured using a fully automated IMMAGE Immunochemistry System. Secreted HMGB1 in the culture supernatant of peripheral blood monocyte was assessed by immunoblotting. Acute Physiology and Chronic Health Evaluation II score was evaluated within 24 hours of admission.

RESULTS

HMGB1 released into circulation at early stage, with peak levels occurring within 6 hours to 13 hours postheatstroke. Plasma HMGB1 levels remained markedly elevated in the following 6 days postheatstroke when compared with healthy volunteers (p<0.005). Positive correlation (r=0.798, p<0.001) was found between Acute Physiology and Chronic Health Evaluation II score and HMGB1 level at admission. HMGB1 levels at admission between survivors and nonsurvivors were significantly different (p<0.001). Receiver operating curve analysis showed that at a level of 47 ng/mL, HMGB1 level at admission indicated lethality with 77.4% sensitivity and 84.2% specificity.

CONCLUSIONS

HMGB1 level at admission is an indicator of the severity of illness and a useful mortality predictor in exertional heatstroke.

Prognostic value of HMGB1 overexpression in resectable gastric adenocarcinomas

INTRODUCTION

HMGB1(High mobility group box 1), originally described as a nuclear protein, is now regarded as a multifunctional protein with a paradoxical dual effect in tumors. In the present study, HMGB1 overexpression and its correlation with the clinicopathologic characteristics and recurrence-free survival were evaluated in gastric adenocarcinomas.

METHODS

76 gastric adenocarcinomas surgically removed entered the study. The immunohistochemical staining was used to assess HMGB1 expression through tissue microarray procedure. The clinicopathologic characteristics of all patients were recorded, and the regular follow-up was made for all patients.

RESULTS

Almost all the gastric adenocarcinomas showed HMGB1 positive staining mainly in the nucleus, and the overexpression of HMGB1 was found in cancerous tissues with higher strong reactivity rate, compared with non-cancerous tissues (total expression score >or= 9, 42.0% vs. 9.0%, P < 0.001). Survival analysis revealed that tumor stage negatively correlated with cancer-free survival (P = 0.022). Furthermore, HMGB1 overexpression positively associated with cancer-free survival of resectable gastric adenocarcinomas (P = 0.023).

CONCLUSIONS

The overexpression of HMGB1 protein indicates that HMGB1 may play a role in the tumorigenesis of gastric adenocarcinomas. And the overexpression of HMGB1 may be a marker of good prognosis of gastric adenocarcinoma given curative resection combined with adjuvant chemotherapy.