Role of neutrophil elastase in lung injury induced by burn-blast combined injury in rats

Tranexamic acid reduces inflammation, edema and burn wound conversion in a rodent model

Burn wound conversion is the observed process where superficial partial thickness burns convert into deep partial or full thickness burn injuries. This conversion process often involves surgical excision to achieve timely wound healing. Unfortunately, the pathophysiology of this phenomenon is multifactorial and poorly understood. Thus, a therapeutic intervention that may prevent secondary progression and cell death in burn-injured tissue is desirable. Recent work by our group and others has established that tranexamic acid (TXA) has significant anti-inflammatory properties in addition to its well-known anti-fibrinolytic effects. This study investigates TXA as a novel therapeutic treatment to mitigate burn wound conversion and reduce systemic inflammation. Sprague-Dawley rats were subjected to a hot comb burn contact injury. A subset of animals underwent a similar comb burn with an adjacent 30%TBSA contact injury. The interspaces represent the ischemic zones simulating the zone of stasis. The treatment group received injections of TXA (100 mg/kg) immediately after injury and once daily until euthanasia. Animals were harvested for analyses at 6 h and 7 days after injury. Full-thickness biopsies from the ischemic zones and lung tissue were assessed with established histological techniques. Plasma was collected for measurement of damage associated molecular patterns (DAMPs), and liver samples were used to study inflammatory cytokines expression. Treatment with TXA was associated with reduced burn wound conversion and decreased burn-induced systemic inflammatory response syndrome (SIRS). Lung inflammation and capillary leak were also significantly reduced in TXA treated animals. Future research will elucidate the underlying anti-inflammatory properties of TXA responsible for these findings.

Effect of Sivelestat in the Treatment of Acute Lung Injury and Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Analysis

Background

The efficacy of neutrophil elastase inhibitor sivelestat in the treatment of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) remains controversial. A systematic review and meta-analysis were performed in accordance with the PRISMA guidelines assess the effect of sivelestat on ALI/ARDS patients, different studies were included.

Methods

Electronic databases, National Knowledge Infrastructure (CNKI), Wan fang data, VIP, PubMed, Embase, Springer, Ovid and the Cochrane Library were searched using the following key words: ("Sivelestat" OR "Elaspol") AND ("ARDS" OR "adult respiratory distress syndrome" OR "acute lung injury"). All databases published from January 2000 to August 2022. The treatment group was treated with sivelestat and the control group was given normal saline. The outcome measurements include the mortality of 28-30 days, mechanical ventilation time, ventilation free days, intensive care unit (ICU) stays, oxygenation index (PaO2/FiO2) on day 3, the incidence of adverse events. The literature search was conducted independently by 2 researchers using standardized methods. We used the Cochrane risk-of-bias tool to assess the quality of the included studies. Mean difference (MD), Standardized mean difference (SMD) and relative risk (RR) were calculated using random effects model or fixed effects model. All statistical analyses were performed using RevMan software 5.4.

Results

A total of 2050 patients were enrolled in 15 studies, including 1069 patients in treatment group and 981 patients in the control group. The results of the meta-analysis showed that: compared with the control group, sivelestat can reduce the mortality of 28-30 days (RR = 0.81, 95% CI = 0.66-0.98, p = 0.03) and the incidence of adverse events (RR = 0.91, 95% CI = 0.85-0.98, p = 0.01), shortened mechanical ventilation time (SMD = - 0.32, 95% CI = - 0.60 to - 0.04, p = 0.02) and ICU stays (SMD = - 0.72, 95% CI = - 0.92 to - 0.52, p < 0.00001), increased the ventilation free days (MD = 3.57, 95% CI = 3.42-3.73, p < 0.00001) and improve oxygenation index (PaO2/FiO2) on day 3 (SMD = 0.88, 95% CI = 0.39-1.36, p = 0.0004).

Conclusions

Sivelestat can not only reduce the mortality of ALI/ARDS patients within 28-30 days and the incidence of adverse events, shorten the mechanical ventilation time and ICU stays, increase ventilation free days, but also improve the oxygenation index of patients on days 3, which has a good effect on the treatment of ALI/ARDS. These findings need to be verified in large-scale trials.

Effect of Hydrogen on AM Pyroptosis Induced by Severe Burns in Rats

Background: Hydrogen has anti-inflammatory and antioxidant effects and is beneficial to multiple organs. However, its effect on alveolar macrophage (AM) pyroptosis induced by burns is still unclear. The purpose of this research was to study the possible positive effects of hydrogen on burn-induced lung injury and the effects of hydrogen on AM pyroptosis during acute lung injury (ALI) induced by burns. Methods: In this study, histological changes in rat lungs in vivo were evaluated by micro-CT, and histological changes in isolated lungs were evaluated by hematoxylin and eosin (HE) staining. The expressions of leucine rich repeat (LRR) and pyrin domain (PYD) containing protein 3 (NLRP3), caspase-1 and Gasdermin-D (GSDMD) were analyzed by Western blotting. The expression of GSDMD was measured by immunofluorescence to evaluate the levels of lung inflammation and pyroptosis. The level of inflammation was assessed by enzyme-linked immunosorbent assay (ELISA). Pyroptosis was observed by transmission electron microscopy. Results: We observed that severe burn resulted in increased IL-1β and IL-18, overexpression of NLRP3 and caspase-1 proteins, and pyroptosis in rat lung tissues, as demonstrated by GSDMD overexpression and electron microscopy of AMs. We also observed that hydrogen treatment partially reversed the increase in lung tissue density and reduced pulmonary inflammation. Moreover, hydrogen reduced the HE pathological injury score in the lung tissues of severely burned rats. Hydrogen treatment significantly reduced the contents of IL-1β and IL-18 in the lung tissues and decreased the expression of NLRP3, caspase-1 and GSDMD proteins compared with the burn group. Transmission electron microscopy results also showed that the number of AM membrane pores was significantly reduced in the hydrogen treatment group. Conclusions: The results of this study suggest that hydrogen may protect against ALI induced by burn injury by inhibiting pyroptosis of macrophages via NLRP3.

Severity of thermal burn injury is associated with systemic neutrophil activation

Burn injuries elicit a unique and dynamic stress response which can lead to burn injury progression. Though neutrophils represent crucial players in the burn-induced immunological events, the dynamic secretion pattern and systemic levels of neutrophil-derived factors have not been investigated in detail so far. Serum levels of neutrophil elastase (NE), myeloperoxidase (MPO), citrullinated histone H3 (CitH3), and complement factor C3a were quantified in burn victims over 4 weeks post injury. Furthermore, the potential association with mortality, degree of burn injury, and inhalation trauma was evaluated. In addition, leukocyte, platelet, neutrophil, and lymphocyte counts were assessed. Lastly, we analyzed the association of neutrophil-derived factors with clinical severity scoring systems. Serum levels of NE, MPO, CitH3, and C3a were remarkably elevated in burn victims compared to healthy controls. Leukocyte and neutrophil counts were significantly increased on admission day and day 1, while relative lymphocytes were decreased in the first 7 days post burn trauma. Though neutrophil-derived factors did not predict mortality, patients suffering from 3rd degree burn injuries displayed increased CitH3 and NE levels. Accordingly, CitH3 and NE were elevated in cases with higher abbreviated burn severity indices (ABSI). Taken together, our data suggest a role for neutrophil activation and NETosis in burn injuries and burn injury progression. Targeting exacerbated neutrophil activation might represent a new therapeutic option for severe cases of burn injury.

Gas explosion-induced acute blast lung injury assessment and biomarker identification by a LC-MS-based serum metabolomics analysis

The objective of this study was to evaluate the histopathological effect of gas explosion on rats, and to explore the metabolic alterations associated with gas explosion-induced acute blast lung injury (ABLI) in real roadway environment using metabolomics analyses. All rats were exposed to the gas explosion source at different distance points (160 m and 240 m) except the control group. Respiratory function indexes were monitored and lung tissue analysis was performed to correlate histopathological effect to serum metabolomics. Their sera samples were collected to measure the metabolic alterations by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). HE staining in lung showed that the gas explosion caused obvious inflammatory pulmonary injury, which was consistent with respiratory function monitoring results and the serum metabolomics analysis results. The metabolomics identified 9 significantly metabolites different between the control- and ABLI rats. 2-aminoadipic acid, L-methionine, L-alanine, L-lysine, L-threonine, cholic acid and L-histidine were significantly increased in the exposed groups. Citric acid and aconitic acid were significantly decreased after exposure. Pathway analyses identified 8 perturbed metabolic pathways, which provided novel potential mechanisms for the gas explosion-induced ABLI. Therefore, metabolomics analysis identified both known and unknown alterations in circulating biomarkers, adding an integral mechanistic insight into the gas explosion-induced ABLI in real roadway environment.

Management of combined massive burn and blast injury: A 20-year experience

INTRODUCTION

Blast injuries are complex types of physical trauma resulting from direct or indirect exposure to an explosion, which can be divided into four classes: primary, secondary, tertiary, and quaternary. Primary blast injury results in damage, principally, in gas-containing organs such as the lungs (blast lung injury, BLI). BLI is defined as radiological and clinical evidence of acute lung injury occurring within 12h of exposure to an explosion and not due to secondary or tertiary injury. BLI often combines with cutaneous thermal injury, a type of quaternary blast injury, either in terrorist bomb attacks or in civilian accidental explosions. This report summarizes our experience in the management of combined massive burn and BLI at a Shanghai Burn Center in China.

METHODS

A retrospective observational analysis of clinical data was performed for massive burn patients with or without BLI during a 20-year interval. Patient characteristics, causes of injury, clinical parameters, management, and outcomes were recorded and evaluated.

RESULTS

A total of 151 patients (120 males and 31 females) with severe burn injury (≥50% TBSA) treated at the Burn Center of Changhai Hospital in Shanghai between July 1997 and June 2017 were enrolled in this study. Their mean age was 38.6±17.8 (3-75) years. Among them, 28 patients had combined BLI and burn injury and 39 patients had no BLI or smoke inhalation injury (non-BLI-SII). No significant difference was observed in the burn area or full-thickness burn area between the two groups. The lowest PaO₂/fraction of inspired oxygen (FiO₂) ratio during the first 24h in BLI patients was significantly lower than that in non-BLI-SII patients. Exudative changes were observed by X-ray radiography in all BLI patients but not in non-BLI-SII patients within 6h after injury. A significantly higher proportion of colloids were used for fluid resuscitation in BLI patients than that in non-BLI-SII patients. A higher proportion and longer time of mechanical ventilation were needed for BLI patients than those for non-BLI-SII patients, and a higher proportion of patients received sedative agents in the BLI group than those in the non-BLI-SII group. The first escharectomy was performed relatively later in BLI patients than in non-BLI-SII patients because of more time taken by BLI patients to recover from lung injury. The length of ICU and hospital stay in BLI patients was significantly longer than that in non-BLI-SII patients. No significant difference in the overall mortality was detected between these two groups.

CONCLUSION

It is a formidable challenge for clinicians to diagnose and manage massive burn patients combined with BLI. A comprehensive treatment approach is strongly recommended, including fluid resuscitation, airway management, mechanical ventilation, and surgical treatment. Given the high mortality of massive burn patients combined with BLI even in a recognized burn center, more prospective studies are encouraged to assess more effective strategies for the treatment of such patients.

Usage of density analysis based on micro-CT for studying lung injury associated with burn-blast combined injury

BACKGROUND

Burn-blast combined injury is a kind of injury caused by heat and blast at the same time. The lung injury after burn-blast combined injuries is of primary importance, and investigation of lung injury is needed in the clinical care of patients. Computed tomography (CT) is one of the standard tools used to observe the anatomical basis and pathophysiology of acute lung injury.

METHODS

We applied a method of fast 3D (three-dimensional) reconstruction to calculate the density value of the lung injury by CT analysis. Blast-injury group (BL group), burn-injury group (B group), burn-blast combined injury group (BBL group), and sham control group (C group) were established. Each group had 16 rats. The three-dimensional images of the lung tissue were obtained at 6h, 24h, and 48h according to the CT value. The average density of the whole lung, left lung, and right lung were measured. The lung tissues were paraffin-embedded and HE stained. Smith scoring was performed according to the pathological findings.

RESULTS

In the BBL group, the density of the lung tissue was higher than those of the BL group and B group (P<0.01). The lung tissue density values at 24h after injury were higher than those at 6h and 48h after injury (P<0.01). Pathological results confirmed the changes of density analysis of the lung tissue.

CONCLUSION

The results have indicated that density analysis through a CT scan can be used as a way to evaluate lung injury in a burn-blast injury.

Neutrophil Phenotype Correlates With Postoperative Inflammatory Outcomes in Infants Undergoing Cardiopulmonary Bypass

OBJECTIVES

Infants with congenital heart disease frequently require cardiopulmonary bypass, which causes systemic inflammation. The goal of this study was to determine if neutrophil phenotype and activation status predicts the development of inflammatory complications following cardiopulmonary bypass.

DESIGN

Prospective cohort study.

SETTING

Tertiary care PICU with postoperative cardiac care.

PATIENTS

Thirty-seven patients 5 days to 10 months old with congenital heart disease requiring cardiopulmonary bypass.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Laboratory and clinical data collected included length of mechanical ventilation, acute kidney injury, and fluid overload. Neutrophils were isolated from whole blood at three time points surrounding cardiopulmonary bypass. Functional analyses included measurement of cell surface protein expression and nicotinamide adenine dinucleotide phosphate oxidase activity. Of all patients studied, 40.5% displayed priming of nicotinamide adenine dinucleotide phosphate oxidase activity in response to N-formyl-Met-Leu-Phe stimulation 24 hours post cardiopulmonary bypass as compared to pre bypass. Neonates who received steroids prior to bypass demonstrated enhanced priming of nicotinamide adenine dinucleotide phosphate oxidase activity at 48 hours. Patients who displayed priming post cardiopulmonary bypass were 8.8 times more likely to develop severe acute kidney injury as compared to nonprimers. Up-regulation of neutrophil surface CD11b levels pre- to postbypass occurred in 51.4% of patients, but this measure of neutrophil priming was not associated with acute kidney injury. Subsequent analyses of the basal neutrophil phenotype revealed that those with higher basal CD11b expression were significantly less likely to develop acute kidney injury.

CONCLUSIONS

Neutrophil priming occurs in a subset of infants undergoing cardiopulmonary bypass. Acute kidney injury was more frequent in those patients who displayed priming of nicotinamide adenine dinucleotide phosphate oxidase activity after cardiopulmonary bypass. This pilot study suggests that neutrophil phenotypic signature could be used to predict inflammatory organ dysfunction.

Effect of sivelestat sodium in patients with acute lung injury or acute respiratory distress syndrome: a meta-analysis of randomized controlled trials

Background

Sivelestat is widely used in treating acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), although the clinical efficacy of sivelestat remains controversial. This study aimed to evaluate the impact of sivelestat in patients with ALI/ARDS.

Methods

Electronic databases, PubMed, Embase, and the Cochrane Library, were searched to identify trials through April 2017. Randomized controlled trials (RCTs) were included irrespective of blinding or language that compared patients with and without sivelestat therapy in ALI/ARDS. A random-effects model was used to process the data, and the relative risk (RR) and standard mean difference (SMD) with corresponding 95% confidence intervals (CIs) were used to evaluate the effect of sivelestat.

Results

Six RCTs reporting data on 804 patients with ALI/ARDS were included. Overall, no significant difference was found between sivelestat and control for the risk of 28–30 days mortality (RR: 0.94; 95% CI: 0.71–1.23; P = 0.718). Sivelestat therapy had no significant effect on ventilation days (SMD: 0.05; 95% CI: −0.27 to 0.38; P = 0.748), arterial oxygen partial pressure (PaO2)/fractional inspired oxygen (FiO2) level (SMD: 0.48; 95% CI: −0.45 to 1.41; P = 0.315), and intensive care unit (ICU) stays (SMD: −9.87; 95% CI: −24.30 to 4.56; P = 0.180). The results of sensitivity analysis indicated that sivelestat therapy might affect the PaO₂/FiO₂ level in patients with ALI/ARDS (SMD: 0.87; 95% CI: 0.39 to 1.35; P < 0.001).

Conclusions

Sivelestat therapy might increase the PaO₂/FiO₂ level, while it had little or no effect on 28–30 days mortality, ventilation days, and ICU stays. These findings need to be verified in large-scale trials.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0498-z) contains supplementary material, which is available to authorized users.

Xuebijing injection treatment inhibits vasopermeability and reduces fluid requirements in a canine burn model

OBJECTIVE

High vasopermeability and excessive inflammation following severe burns may result in tissue edema, organ dysfunction and the loss of circulatory plasma volume, which can influence the doctor to do the prognosis to the patients. The study aims to examine whether Xuebijing injection (XBJ), an extracts of a traditional Chinese medicine used to treat sepsis in clinic, can reduces fluid requirements by inhibiting vasopermeability and tissue edema in a canine model after burn injury.

METHODS

Twenty-four beagle dogs were subjected to 50% TBSA burns, and then were randomly allocated to the following three groups: lactated Ringer's resuscitation (LR) group (n = 8), immediate LR containing Xuebijing injection (LR/XBJ) group (n = 8), and operation control group (n = 8). Hemodynamic variables and net fluid accumulation were measured. Blood samples were collected for measurement of hematocrit and circulatory plasma volume (PV). At 24 h after burn injury, heart, lung, small intestine and kidney were harvested for evaluation of the activities of myeloperoxidase (MPO) and neutrophil elastase (NE), vasopermeability, tissue water content and the amount of neutrophil infiltration.

RESULTS

XBJ treatment significantly reduced net fluid accumulation, and pulmonary vascular permeability index (PVPI), extravascular lung water index (ELWI), and water content of heart, small intestine, kidney and lung compared with LR group. Furthermore, XBJ infusion significantly reduced tissue activities of MPO and NE compared with LR group. The amount of neutrophil infiltration in LR/XBJ group was lower than that in LR group.

CONCLUSIONS

These results indicate that XBJ injection can reduce fluid requirements by inhibition of neutrophil protease-induced high vasopermeability and tissue edema.

Modelling primary blast lung injury: current capability and future direction

Primary blast lung injury frequently complicates military conflict and terrorist attacks on civilian populations. The fact that it occurs in areas of conflict or unpredictable mass casualty events makes clinical study in human casualties implausible. Research in this field is therefore reliant on the use of some form of biological or non-biological surrogate model. This article briefly reviews the modelling work undertaken in this field until now and describes the rationale behind the generation of an in silico physiological model.