Electron paramagnetic resonance analysis of transferrin-bound iron in animal models of blunt trauma

Nebulised recombinant activated factor VII (rFVIIa) does not attenuate the haemorrhagic effects of blast lung injury

Introduction

Primary blast lung injury causes intrapulmonary haemorrhage. A number of case reports have suggested the efficacy of recombinant activated factor VII (rFVIIa) in the treatment of diffuse alveolar haemorrhage from a range of medical causes, but its efficacy in blast lung is unknown. The aim of this study was to investigate whether nebulised rFVIIa attenuates the haemorrhagic effects of blast lung injury in an animal model.

Methods

Terminally anaesthetised rabbits subjected to blast lung injury were randomised to receive either rFVIIa or placebo via a nebuliser. The primary outcome was the level of blood iron–transferrin complex, a marker of the extent of blast lung injury, analysed using low temperature electron paramagnetic resonance spectroscopy.

Results

Blast exposure led to a significant fall in iron-bound transferrin in both groups of animals (p<0.001), which remained depressed during the study. There were no significant differences in iron–transferrin between the rFVIIa and placebo treatment groups over the duration of the study (p=0.081), and there was no trend towards elevated iron–transferrin in the rFVIIa-treated group once drug treatment had started. There was suggestive evidence of systemic absorption of rFVIIa given via the inhaled route.

Conclusion

A single dose of nebulised rFVIIa did not attenuate pulmonary haemorrhage in a rabbit model of blast lung injury. As there was some evidence of systemic absorption, the inhaled route does not avoid the concern about potential thromboembolic complications from administration of rFVIIa.

No effects without causes: the Iron Dysregulation and Dormant Microbes hypothesis for chronic, inflammatory diseases

Since the successful conquest of many acute, communicable (infectious) diseases through the use of vaccines and antibiotics, the currently most prevalent diseases are chronic and progressive in nature, and are all accompanied by inflammation. These diseases include neurodegenerative (e.g. Alzheimer's, Parkinson's), vascular (e.g. atherosclerosis, pre-eclampsia, type 2 diabetes) and autoimmune (e.g. rheumatoid arthritis and multiple sclerosis) diseases that may appear to have little in common. In fact they all share significant features, in particular chronic inflammation and its attendant inflammatory cytokines. Such effects do not happen without underlying and initially 'external' causes, and it is of interest to seek these causes. Taking a systems approach, we argue that these causes include (i) stress-induced iron dysregulation, and (ii) its ability to awaken dormant, non-replicating microbes with which the host has become infected. Other external causes may be dietary. Such microbes are capable of shedding small, but functionally significant amounts of highly inflammagenic molecules such as lipopolysaccharide and lipoteichoic acid. Sequelae include significant coagulopathies, not least the recently discovered amyloidogenic clotting of blood, leading to cell death and the release of further inflammagens. The extensive evidence discussed here implies, as was found with ulcers, that almost all chronic, infectious diseases do in fact harbour a microbial component. What differs is simply the microbes and the anatomical location from and at which they exert damage. This analysis offers novel avenues for diagnosis and treatment.

The role of neutrophil gelatinase-associated lipocalin (NGAL) in the detection of blast lung injury in a military population

PURPOSE

To study the relationship between serum neutrophil gelatinase-associated lipocalin (NGAL) and military blast and gunshot wound (GSW) to establish whether potential exists for NGAL as a biomarker for blast lung injury (BLI).

METHOD

Patients from the intensive care unit (ICU) of the Role 3 Medical Treatment Facility at Camp Bastion, Helmand Province, Afghanistan were studied over a five month period commencing in 2012. Age, mechanism, trauma injury severity score (TRISS) and serum NGAL were recorded on ICU admission (NGAL1). Serum NGAL (NGAL2) and PaO₂/FiO₂ ratio (P/F ratio2) were recorded at 24h.

RESULTS

33 patients were injured by blast and 23 by GSW. NGAL1 inversely correlated with TRISS (p=0.020), pH (p=0.002) and P/F ratio 2 (p=0.009) overall. When data was stratified into blast and GSW, NGAL1 also inversely correlated with P/F ratio 2 in the blast injured group (p=0.008) but not GSW group (p=0.27).

CONCLUSION

Raised NGAL correlated with increased severity of injury (worse survival probability i.e. TRISS and low pH) in both patient groups. There was an inverse correlation between admission NGAL and a marker of blast lung injury (low P/F ratio) at 24h in blast injured group but not GSW group that warrants further investigation.

Steroid-Loaded Hemostatic Nanoparticles Combat Lung Injury after Blast Trauma

In response to the lack of therapeutics for internal bleeding following a traumatic event, we synthesized hemostatic dexamethasone nanoparticles (hDNP) to help alleviate internal hemorrhaging. hDNP consist of a block copolymer, poly(lactic-co-glycolic acid)-poly(l-lysine)-poly(ethylene glycol) conjugated to a peptide, glycine-arginine-glycine-aspartic acid-serine (GRGDS). These particles were evaluated as treatment for primary blast lung injury in a rodent model. Animals were randomly placed into test and control groups, exposed to blast and given immediate injection. Recovery was assessed using physiological parameters and immunohistochemistry. We found that dexamethasone-loaded hemostatic nanoparticles alleviate physiological deprivation caused by blast injury and reduce lung injury damage.

Pulmonary biochemical and histological alterations after repeated low-level blast overpressure exposures

Blast overpressure (BOP), also known as high energy impulse noise, is a damaging outcome of explosive detonations and firing of weapons. Exposure to BOP shock waves alone results in injury predominantly to the hollow organ systems such as auditory, respiratory, and gastrointestinal systems. In recent years, the hazards of BOP that once were confined to military and professional settings have become a global societal problem as terrorist bombings and armed conflicts involving both military and civilian populations increased significantly. We have previously investigated the effects of single BOP exposures at different peak pressures. In this study, we examined the effects of repeated exposure to a low-level BOP and whether the number of exposures or time after exposure would alter the injury outcome. We exposed deeply anesthetized rats to simulated BOP at 62 +/- 2 kPa peak pressure. The lungs were examined immediately after one exposure (1 + 0), or 1 h after one (1 + 1), two (2 + 1), or three (3 + 1) consecutive exposures at 3-min interval. In one group of animals, we examined the effects of repeated exposure on lung weight, methemoglobin, transferrin, antioxidants, and lipid peroxidation. In a second group, the lungs were fixed inflated at 25 cm water, sectioned, and examined histologically after one to three repeated exposures, or after one exposure at 1, 6, and 24 h. We found that single BOP exposure causes notable changes after 1 h, and that repeating BOP exposure did not add markedly to the effect of the first one. However, the effects increased significantly with time from 1 to 24 h. These observations have biological and occupational implications, and emphasize the need for protection from low-level BOP, and for prompt treatment within the first hour following BOP exposure.

Pro-inflammatory alterations and status of blood plasma iron in a model of blast-induced lung trauma

Impact of blast shock waves (SW) with the body wall produces blast lung injuries characterized by bilateral traumatic hemorrhages. Such injuries often have no external signs, are difficult to diagnose, and therefore, are frequently underestimated. Predictive assessment of acute respiratory distress syndrome outcome in SW-related accidents should be based on experimental data from appropriate animal models. Blood plasma transferrin is a major carrier of blood iron essential for proliferative "emergency" response of hematopoietic and immune systems as well as injured tissue in major trauma. Iron-transferrin complexes (Fe3+ TRF) can be quantitatively analyzed in blood and tissue samples with low-temperature EPR techniques. We hypothesized that use of EPR techniques in combination with assays for pro-inflammatory cytokines and granulocytes in the peripheral blood and BAL would reveal a pattern of systemic sequestration of (Fe3+)TRF that could be useful for development of biomarkers of the systemic inflammatory response to lung injury. With this goal we (i) analyzed time-dependent dynamics of (Fe3+)TRF in the peripheral blood of rats after impacts of SW generated in a laboratory shock-tube and (ii) assayed the fluctuation of granulocyte (PMN) counts and expression of CD11b adhesion molecules on the surface of PMNs during the first 24 h after SW induced injury. Sham-treated animals were used as control. Exposure to SW led to a significant decrease in the amount of blood (Fe3+)TRF that correlated with the extent of lung injury and developed gradually during the first 24 h. Thus, sequestration of (Fe3+)TRF occurred as early as 3 h post-exposure. At that time, the steady state concentration of (Fe3+)TRF in blood samples decreased from 19.7+/-0.6 microM in controls to 7.5+/-1.3 microM in exposed animals. The levels of (Fe3+)TRF remained decreased throughout the entire study period. PMN counts increased 5-fold and 3.5-fold over controls respectively, at 3 and 6 h postexposure. These effects were accompanied by an increase in expression of CD11b on the surface membrane of PMNs. Extensive release of cytokines IL-1, IL-6, MCP-1, and MIP-2 was observed in BAL fluid and blood plasma during 24 h postexposure. We conclude that EPR monitoring of blood (Fe3+)TRF can be a useful approach for assessment of systemic pro-inflammatory alterations due to SW-induced lung injury.

Inflammatory leukocytes and iron turnover in experimental hemorrhagic lung trauma

To monitor cascade of events following alveolar extravasation of blood due to exposure to shock wave (SW), we conducted spatiotemporal assessment of myeloperoxidase (MPO), heme oxygenase 1 (HO-1), Cu,Zn superoxide dismutase (SOD-1), transferrin (TRF), 3-nitrotyrosine (3NTyr), alveolar endothelial cadherin (VE-CDH), and the CD11b adhesion molecules on leukocytes using electron microscopy, electron paramagnetic resonance spectroscopy, immunofluorescence imaging, and immunoblotting. Accumulation of HO-1, MPO, 3NTyr, and SOD-1 in HIL at the first 12 h was associated with transmigration of inflammatory leucocytes (ILK) into hemorrhagic lesions (HLs). Biodegradation of extravasated hemoglobin (exvHb) and deposition of iron in alveoli occurred at 3-56 h post-exposure and was preceded by LKC degranulation and accumulation of MPO, HO-1, and SOD-1 in HLs. These alterations were accompanied by appearance of heme and non-heme iron complexes in HLs. A significant increase in TRF-bound [Fe(3+)] (i.e., 14.6 +/- 5.3 microM vs. 4.8 +/- 2.1 microM immediately after exposure) and non-TRF complexes of [Fe(3+)] (i.e., 4.5 +/- 1.8 microM vs. < 0.3 microM immediately after exposure) occurred at 24 h post-exposure. Transmigrations of ILK, nitroxidative stress, and iron deposition in endothelial and epithelial cells were accompanied by destruction of endothelial integrity at 3 h post-exposure, and alveolar capillary network and necrotic changes in the pulmonary epithelial cells at 24-56 h post-exposure.

Assessment of inflammatory response and sequestration of blood iron transferrin complexes in a rat model of lung injury resulting from exposure to low-frequency shock waves

OBJECTIVE

Impact of air blast overpressure waves (OPW), or shock wave, with the body wall or body armor produces two types of energy waves: high-frequency low-amplitude stress waves and long-duration low-frequency share waves. These types of energy waves are characterized by different mechanisms of primary tissue injury that mostly affect lung. Systemic inflammation and resultant acute respiratory distress syndrome are known major secondary causative agents of delayed multiple organ failure and subsequent death after OPW exposure. However, association of each pattern of the blast OPW-produced energy waves with postexposure inflammatory events has not yet been delineated. The objectives of the present research were a) establishment of a rat model for assessment of the inflammatory response following lung injury produced by exposure to medium-amplitude (approximately 120 kPa) low-frequency (260+/-5 Hz) OPWs; and b) assessment of the dynamics of alteration in polymorphonuclear leukocyte counts and expression of CD11b adhesion molecules on the surface of polymorphonuclear leukocytes and status of iron-transferrin complexes in peripheral blood after OPW exposure.

DESIGN

This study focused on the OPW effects at different time periods, using a sequential approach to postexposure events. Lung injury in rat was induced by OPW generated in a laboratory shock tube. Animals were exposed to OPW (at peak overpressure of 118+/-7 kPa) that produced "moderate" lung injury.

SETTING

Military research institute.

SUBJECTS

Twenty-seven CVF Sprague-Dawley rats were subjected to OPW exposures, and 17 sham-treated animals were used as control.

INTERVENTIONS

Lung tissue and blood samples were collected at 1, 3, 6, 12, and 24 hrs following OPW exposures and compared with samples collected from nonexposed animals.

MEASUREMENTS AND MAIN RESULTS

OPW-induced lung injury caused a 2.7-fold increase in the number of circulatory polymorphonuclear leukocytes as early as 1 hr postexposure, which is indicative of mobilization of the pool of marginated polymorphonuclear leukocytes into the free circulation. Polymorphonuclear leukocyte counts increased through the following 3- and 6-hr periods, when they were, respectively, 5-fold and 3.5-fold higher than in controls. These effects were accompanied by a pronounced expression of CD11b in polymorphonuclear leukocytes and tissue sequestration of blood iron-transferrin complexes during the entire 24-hr period of observations. The increase in circulatory polymorphonuclear leukocytes was accompanied by a decrease in iron-transferrin complex concentrations that apparently reflected implication of blood plasma iron in the inflammatory cell response to OPW-induced injury.

CONCLUSIONS

The observed dynamics in polymorphonuclear leukocyte alterations in peripheral blood after OPW exposure were similar to those found recently in clinical observations of nonpenetrating injury and in animal models of infectious insults. Therefore, our data suggest that the main pattern of proinflammatory alterations in the rat model of lung injury induced by exposure to long-duration shock wave is similar to patterns that are characteristic of major trauma. The data further suggest that the expression of polymorphonuclear leukocyte CD11b and the response of iron-transferrin complex can be considered as potential surrogate markers in blood for systemic alterations following OPW-induced injury and, therefore, warrant further investigation in a human pilot study.