The pulmonary and hepatic immune microenvironment and its contribution to the early systemic inflammation following blunt chest trauma

Traumatic inflammatory response: pathophysiological role and clinical value of cytokines

Severe trauma is an intractable problem in healthcare. Patients have a widespread immune system response that is complex and vital to survival. Excessive inflammatory response is the main cause of poor prognosis and poor therapeutic effect of medications in trauma patients. Cytokines are signaling proteins that play critical roles in the body's response to injuries, which could amplify or suppress immune responses. Studies have demonstrated that cytokines are closely related to the severity of injuries and prognosis of trauma patients and help present cytokine-based diagnosis and treatment plans for trauma patients. In this review, we introduce the pathophysiological mechanisms of a traumatic inflammatory response and the role of cytokines in trauma patients. Furthermore, we discuss the potential of cytokine-based diagnosis and therapy for post-traumatic inflammatory response, although further clarification to elucidate the underlying mechanisms of cytokines following trauma is warranted.

Endothelial Protein kinase D1 is a major regulator of post-traumatic hyperinflammation

Trauma is a major cause of death worldwide. The post-traumatic immune response culminates in the release of pro-inflammatory mediators, translating in the infiltration of neutrophils (PMNs) at injury sites. The extent of this inflammation is determined by multiple factors, such as PMN adhesion to the endothelium, transendothelial migration, endothelial barrier integrity as well as PMN swarming, mass infiltration and activation. This process is initiated by secondary lipid mediators, such as leukotriene B₄ (LTB₄). We here provide evidence that Protein kinase D1 (PRKD1) in endothelial cells is implicated in all these processes. Endothelial PRKD1 is activated by pro-inflammatory stimuli and amplifies PMN-mediated inflammation by upregulation of cytokine and chemokines as well as adhesion molecules, such as ICAM-1, VCAM-1 and E-selectin. This induces enhanced PMN adhesion and trans-migration. PRKD1 activation also destabilizes endothelial VE-cadherin adhesion complexes and thus the endothelial barrier, fostering PMN infiltration. We even describe a yet unrecognized PRKD1-dependant mechanism to induce biosynthesis of the PMN-swarming mediator LTB₄ directed via intercellular communication through small extracellular vesicles (sEVs) and enhanced CXCL8 secretion from activated endothelial cells. These endothelial sEVs transfer the LTB₄ biosynthesis enzyme LTA₄ hydrolase (LTA₄H) to prime PMNs, while initiating biosynthesis also requires additional signals, like CXCL8. We further demonstrate the respective LTA₄H-positive sEVs in the serum of polytrauma patients, peaking 12 h post injury. Therefore, PRKD1 is a key regulator in the coordinated communication of the endothelium with PMNs and a vital signaling node during post-traumatic inflammation.

Characteristics of inflammatory response and repair after experimental blast lung injury in rats

BACKGROUND AND OBJECTIVES

Blast-induced lung injury is associated with inflammatory, which are characterised by disruption of the alveolar-capillary barrier, haemorrhage, pulmonary infiltrateration causing oedema formation, pro-inflammatory cytokine and chemokine release, and anti-inflammatory counter-regulation. The objective of the current study was to define sequence of such alterations in with establishing blast-induced lung injury in rats using an advanced blast generator.

METHODS

Rats underwent a standardized blast wave trauma and were euthanised at defined time points. Non-traumatised animals served as sham controls. Obtained samples from bronchoalveolar lavage fluid (BALF) at each time-point were assessed for histology, leukocyte infiltration and cytokine/chemokine profile.

RESULTS

After blast lung injury, significant haemorrhage and neutrophil infiltration were observed. Similarly, protein accumulation, lactate dehydrogenase activity (LDH), alveolar eicosanoid release, matrix metalloproteinase (MMP)-2 and -9, pro-Inflammatory cytokines, including tumour necrosis factor (TNF) and interleukin (IL) -6 raised up. While declining in the level of anti-inflammatory cytokine IL-10 occurred. Ultimately, pulmonary oedema developed that increased to its maximum level within the first 1.5 h, then recovered within 24 h.

CONCLUSION

Using a stablished model, can facilitate the study of inflammatory response to blast lung injury. Following the blast injury, alteration in cytokine/chemokine profile and activity of cells in the alveolar space occurs, which eventuates in alveolar epithelial barrier dysfunction and oedema formation. Most of these parameters exhibit time-dependent return to their basal status that is an indication to resilience of lungs to blast-induced lung injury.

Thoracic trauma promotes alpha-Synuclein oligomerization in murine Parkinson's disease

BACKGROUND

Systemic and neuroinflammatory processes play key roles in neurodegenerative diseases such as Parkinson's disease (PD). Physical trauma which induces considerable systemic inflammatory responses, represents an evident environmental factor in aging. However, little is known about the impact of physical trauma, on the immuno-pathophysiology of PD. Especially blunt chest trauma which is associated with a high morbidity and mortality rate in the elderly population, can induce a strong pulmonary and systemic inflammatory reaction. Hence, we sought out to combine a well-established thoracic trauma mouse model with a well-established PD mouse model to characterize the influence of physical trauma to neurodegenerative processes in PD.

METHODS

To study the influence of peripheral trauma in a PD mouse model we performed a highly standardized blunt thorax trauma in a well-established PD mouse model and determined the subsequent local and systemic response.

RESULTS

We could show that blunt chest trauma leads to a systemic inflammatory response which is quantifiable with increased inflammatory markers in bronchoalveolar fluids (BALF) and plasma regardless of the presence of a PD phenotype. A difference of the local inflammatory response in the brain between the PD group and non-PD group could be detected, as well as an increase in the formation of oligomeric pathological alpha-Synuclein (asyn) suggesting an interplay between peripheral thoracic trauma and asyn pathology in PD.

CONCLUSION

Taken together this study provides evidence that physical trauma is associated with increased asyn oligomerization in a PD mouse model underlining the relevance of PD pathogenesis under traumatic settings.

A Limited Role for AMD3100 Induced Stem Cell Mobilization for Modulation of Thoracic Trauma Outcome

ABSTRACT

Thoracic trauma is a major cause of mortality due to the associated inflammatory acute respiratory distress syndrome and morbidity due to impaired tissue regeneration. Trauma-induced lung inflammation is characterized by the early recruitment of cells with pro- or anti-inflammatory activity to the lung. Therapeutic interventions reducing the level of tissue inflammation may result in decreased tissue damage and improved healing and recovery. Stem cells might be able to improve trauma outcome via immunomodulation or by enhancing tissue regeneration.Here, we describe the migratory dynamics of murine mesenchymal, hematopoietic and endothelial stem and progenitor cells (SPCs) as well as mature inflammatory cells (monocytes, neutrophils, lymphocytes) to peripheral blood (PB) and lung tissue between 0.2 and 48 h post-blunt chest trauma (TXT). We demonstrate that the kinetics of immune cell and SPC distribution upon trauma are both cell-type and tissue-dependent. We identified a transient, early increase in the number of inflammatory cells in PB and lung at 2 h post-TXT and a second wave of infiltrating SPCs in lungs by 48 h after TXT induction, suggesting a role for SPCs in tissue remodeling after the initial inflammatory phase. Cxcl12/Cxcr4 blockade by AMD3100 within the first 6 h after TXT, while inducing a strong and coordinated mobilization of SPCs and leukocytes to PB and lung tissue, did not significantly affect TXT associated inflammation or tissue damage as determined by inflammatory cytokine levels, plasma markers for organ function, lung cell proliferation and survival, and myofibroblast/fibroblast ratio in the lung. Further understanding the dynamics of the distribution of endogenous SPCs and inflammatory cells will therefore be indispensable for stem cell-based or immunomodulation therapies in trauma.

Small Extracellular Vesicles Propagate the Inflammatory Response After Trauma

Trauma is the leading cause of death in individuals under 44 years of age. Thorax trauma (TxT) is strongly associated with trauma-related death, an unbalanced innate immune response, sepsis, acute respiratory distress syndrome, and multiple organ dysfunction. It is shown that different in vivo traumata, such as TxT or an in vitro polytrauma cytokine cocktail trigger secretion of small extracellular nanovesicles (sEVs) from endothelial cells with pro-inflammatory cargo. These sEVs transfer transcripts for ICAM-1, VCAM-1, E-selectin, and cytokines to systemically activate the endothelium, facilitate neutrophil-endothelium interactions, and destabilize barrier integrity. Inhibition of sEV-release after TxT in mice ameliorates local as well as systemic inflammation, neutrophil infiltration, and distant organ damage in kidneys (acute kidney injury, AKI). Vice versa, injection of TxT-plasma-sEVs into healthy animals is sufficient to trigger pulmonary and systemic inflammation as well as AKI. Accordingly, increased sEV concentrations and transfer of similar cargos are observed in polytrauma patients, suggesting a fundamental pathophysiological mechanism.

Selective Inhibition of IL-6 Trans-Signaling Has No Beneficial Effect on the Posttraumatic Cytokine Release after Multiple Trauma in Mice

While improvements in pre-hospital and in-hospital care allow more multiple trauma patients to advance to intensive care, the incidence of posttraumatic multiple organ dysfunction syndrome (MODS) is on the rise. Herein, the influence of a selective IL-6 trans-signaling inhibition on posttraumatic cytokine levels was investigated as an approach to prevent MODS caused by a dysbalanced posttraumatic immune reaction. Therefore, the artificial IL-6 trans-signaling inhibitor sgp130Fc was deployed in a murine multiple trauma model (femoral fracture plus bilateral chest trauma). The traumatized mice were treated with sgp130Fc (FP) and compared to untreated mice (WT) and IL-6 receptor knockout mice (RKO), which received the same traumas. The overall trauma mortality was 4.4%. Microscopic pulmonary changes were apparent after multiple trauma and after isolated bilateral chest trauma. Elevated IL-6, MCP-3 and RANTES plasma levels were measured after trauma, indicating a successful induction of a systemic inflammatory reaction. Significantly reduced IL-6 and RANTES plasma levels were visible in RKO compared to WT. Only a little effect was visible in FP compared to WT. Comparable cytokine levels in WT and FP indicate neither a protective nor an adverse effect of sgp130Fc on the cytokine release after femoral fracture and bilateral chest trauma.

Effect of hesperetin on systemic inflammation and hepatic injury after blunt chest trauma in rats

We investigated the protective effect of hesperetin on hepatic damage after blunt chest trauma in rats using histological and biochemical methods. We used 18 adult male rats in three groups of six: control, chest trauma and chest trauma + hesperetin. Chest trauma was caused by dropping a metal cylinder onto the right hemithorax. Hesperetin, 100 mg/kg, was administered orally for 7 days. At the end of the seventh day, liver tissue samples were obtained. Serum tumor necrosis factor-alpha (TNF-α), interleukin 1-beta (IL-1β), alanine aminotransferase (AST), aspartate transferase (ALT) and lactate dehydrogenase (LDH) enzyme activities were measured in blood samples taken from the heart. The general structure of liver tissue was investigated using hematoxylin and eosin staining. Nuclear factor kappa beta (Nf-κβ) expression in liver tissue was determined by the indirect immunohistochemical method. Apoptosis was determined using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) method. Decreased TNF-α, AST and ALT enzyme activity, fewer histopathological changes and lower Nf-kB expression were observed in the hesperetin treated group compared to the chest trauma group. We also found reduced hepatic apoptosis in the chest trauma + hesperetin group compared to the chest trauma group. Hesperetine inhibits liver damage by reducing proinflammatory cytokines and by suppressing Nf-κβ activity in a blunt chest trauma model in rats.

Shock waves increase pulmonary vascular leakage, inflammation, oxidative stress, and apoptosis in a mouse model

Severe lung damage is a major cause of death in blast victims, but the mechanisms of pulmonary blast injury are not well understood. Therefore, it is important to study the injury mechanism of pulmonary blast injury. A model of lung injury induced by blast exposure was established by using a simulation blast device. The effectiveness and reproducibility of the device were investigated. Eighty mice were randomly divided into eight groups: control group and 3 h, 6 h, 12 h, 24 h, 48 h, 7 days and 14 days post blast. The explosive device induced an explosion injury model of a single lung injury in mice. The success rate of the model was as high as 90%, and the degree of lung injury was basically the same under the same pressure. Under the same conditions, the thickness of the aluminum film can be from 0.8 mm to 1.6 mm, and the peak pressure could be from 95.85 ± 15.61 PSI to 423.32 ± 11.64 PSI. There is no statistical difference in intragroup comparison. A follow-up lung injury experiment using an aluminum film thickness of 1.4 mm showed a pressure of 337.46 ± 18.30 PSI induced a mortality rate of approximately 23.2%. Compared with the control group (372 ± 23 times/min, 85.9 ± 9.4 mmHg, 4.34 ± 0.09), blast exposed mice had decreased heart rate (283 ± 21 times/min) and blood pressure (73.6 ± 3.6 mmHg), and increased lung wet/dry weight ratio(2.67 ± 0.11), marked edematous lung tissue, ruptured blood vessels, infiltrating inflammatory cells, increased NF-κB (4.13 ± 0.01), TNF-α (4.13 ± 0.01), IL-1β (2.43 ± 0.01) and IL-6 (4.65 ± 0.01) mRNA and protein, decreased IL-10(0.18 ± 0.02) mRNA and protein ( P < 0.05). The formation of ROS and the expression of MDA5 (4.46 ± 0.01) and IREα (3.43 ± 0.00) mRNA and protein were increased and the expression of SOD-1 (0.28 ± 0.02) mRNA and protein was decreased ( P < 0.05). Increased expression of Bax (3.54 ± 0.00) and caspase 3 (4.18 ± 0.01) mRNA and protein inhibited the expression of Bcl-2 (0.39 ± 0.02) mRNA and protein. The changes of pulmonary edema, inflammatory cell infiltration, and cell damage factor expression increased gradually with time, and reached the peak at 12-24 h after the outbreak, and returned to normal at 7-14 days. Detonation injury can lead to edema of lung tissue, pulmonary hemorrhage, rupture of pulmonary vessels, induction of early inflammatory responses accompanied by increased oxidative stress in lung tissue cells and increased apoptosis in mice experiencing blast injury. The above results are consistent with those reported in other literatures. It is showed that the mouse lung blast injury model is successfully modeled, and the device can be used for the study of pulmonary blast injury. Impact statement The number of patients with explosive injury has increased year by year, but there is no better treatment. However, the research on detonation injury is difficult to carry out. One of the factors is the difficulty in making the model of blast injury. The laboratory successfully developed and produced a simulation device of explosive knocking through a large amount of literature data and preliminary experiments, and verified the preparation of the simulation device through various experimental techniques. The results showed that the device could simulate the shock wave-induced acute lung injury generated, which was similar to the actual knocking injury. The experimental process was controlled. Under the same condition, there was no statistical difference between the groups. It is possible to realize miniaturization and precision of an explosive knocking simulation device, which is a good experimental tool for further research on the mechanism of organ damage caused by detonation and the development of protective drugs.

Pharmacological inhibition of IL-6 trans-signaling improves compromised fracture healing after severe trauma

Patients with multiple injuries frequently suffer bone fractures and are at high risk to develop fracture healing complications. Because of its key role both in systemic posttraumatic inflammation and fracture healing, the pleiotropic cytokine interleukin-6 (IL-6) may be involved in the pathomechanisms of trauma-induced compromised fracture healing. IL-6 signals are transmitted by two different mechanisms: classic signaling via the membrane-bound receptor (mIL-6R) and trans-signaling via its soluble form (sIL-6R). Herein, we investigated whether IL-6 classic and trans-signaling play different roles in bone regeneration after severe injury. Twelve-week-old C57BL/6J mice underwent combined femur osteotomy and thoracic trauma. To study the function of IL-6, either an anti-IL-6 antibody, which inhibits both IL-6 classic and trans-signaling, or a soluble glycoprotein 130 fusion protein (sgp130Fc), which selectively blocks trans-signaling, were injected 30 min and 48 h after surgery. Bone healing was assessed using cytokine analyses, flow cytometry, histology, micro-computed tomography, and biomechanical testing. Selective inhibition of IL-6 trans-signaling significantly improved the fracture healing outcome after combined injury, as confirmed by accelerated cartilage-to-bone transformation, enhanced bony bridging of the fracture gap and improved mechanical callus properties. In contrast, global IL-6 inhibition did not affect compromised fracture healing. These data suggest that classic signaling may mediate beneficial effects on bone repair after severe injury. Selective inhibition of IL-6 trans-signaling might have therapeutic potential to treat fracture healing complications in patients with concomitant injuries.

A new multiple trauma model of the mouse

Background

Blunt trauma is the most frequent mechanism of injury in multiple trauma, commonly resulting from road traffic collisions or falls. Two of the most frequent injuries in patients with multiple trauma are chest trauma and extremity fracture. Several trauma mouse models combine chest trauma and head injury, but no trauma mouse model to date includes the combination of long bone fractures and chest trauma. Outcome is essentially determined by the combination of these injuries. In this study, we attempted to establish a reproducible novel multiple trauma model in mice that combines blunt trauma, major injuries and simple practicability.

Methods

Ninety-six male C57BL/6 N mice (n = 8/group) were subjected to trauma for isolated femur fracture and a combination of femur fracture and chest injury. Serum samples of mice were obtained by heart puncture at defined time points of 0 h (hour), 6 h, 12 h, 24 h, 3 d (days), and 7 d.

Results

A tendency toward reduced weight and temperature was observed at 24 h after chest trauma and femur fracture. Blood analyses revealed a decrease in hemoglobin during the first 24 h after trauma. Some animals were killed by heart puncture immediately after chest contusion; these animals showed the most severe lung contusion and hemorrhage. The extent of structural lung injury varied in different mice but was evident in all animals. Representative H&E-stained (Haematoxylin and Eosin-stained) paraffin lung sections of mice with multiple trauma revealed hemorrhage and an inflammatory immune response. Plasma samples of mice with chest trauma and femur fracture showed an up-regulation of IL-1β (Interleukin-1β), IL-6, IL-10, IL-12p70 and TNF-α (Tumor necrosis factor- α) compared with the control group. Mice with femur fracture and chest trauma showed a significant up-regulation of IL-6 compared to group with isolated femur fracture.

Conclusions

The multiple trauma mouse model comprising chest trauma and femur fracture enables many analogies to clinical cases of multiple trauma in humans and demonstrates associated characteristic clinical and pathophysiological changes. This model is easy to perform, is economical and can be used for further research examining specific immunological questions.

MDSCs are induced after experimental blunt chest trauma and subsequently alter antigen-specific T cell responses

Severe blunt chest trauma (TxT) induces a strong inflammatory response with posttraumatic immune suppression pointing to an impaired adaptive immune response. Since CD11b⁺Gr-1⁺-expressing myeloid-derived suppressor cells (MDSCs) are induced after inflammation and suppress T cell responses, MDSC induction and their impact on T cell functions was analysed in an experimental TxT model. MDSCs were induced preferentially in the lung until 24 hours after TxT. Although MDSC numbers were only faintly increased in the spleen, splenic MDSCs isolated after TxT strongly inhibited alloantigen-induced T cell proliferation in vitro. Suppressive activity correlated with increased expression of arginase-1 and iNOS. MDSCs also prevented antigen-induced T cell expansion in vivo, since staphylococcus enterotoxin B (SEB)-induced proliferation of vβ8⁺ T cells was impaired in TxT mice in the presence of CD11b⁺Gr-1⁺ cells. Surprisingly, MDSCs were not involved in shifting T cells into Th2 cells, characterized by the secretion of cytokines impairing cell-mediated immunity and promoting immunosuppression. Instead, the presence of CD11b⁺Gr-1⁺ cells was required for efficient IL-2, IFN-γ and TNFα production after antigenic stimulation, indicating, that elevation of MDSCs early after traumatic injuries might contribute to restrict the initial inflammatory response by alleviating T cell expansion, however, without impeding Th1 functions.

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.

CD43Lo classical monocytes participate in the cellular immune response to isolated primary blast lung injury

BACKGROUND

Understanding of the cellular immune response to primary blast lung injury (PBLI) is limited, with only the neutrophil response well documented. Moreover, its impact on the immune response in distal organs remains poorly understood. In this study, a rodent model of isolated primary blast injury was used to investigate the acute cellular immune response to isolated PBLI in the circulation and lung, including the monocyte response, and investigate distal subacute immune effects in the spleen and liver 6 hours after injury.

METHODS

Rats were subjected to a shock wave (~135 kPa overpressure, 2 ms duration) inducing PBLI or sham procedure. Rat physiology was monitored, and at 1, 3, and 6 hours thereafter, blood, lung, and bronchoalveolar lavage fluid (BALF) were collected and analyzed by flow cytometry, enzyme-linked immunosorbent assay, and histologic examination. In addition, at 6 hours, spleen and liver were collected and analyzed by flow cytometry.

RESULTS

Lung histology confirmed pulmonary barotrauma and inflammation. This was associated with rises in CXCL-1, interleukin 6 (IL-6), tumor necrosis factor α and albumin protein in the BALF. Significant acute increases in blood and lung neutrophils and CD43Lo/His48Hi (classical) monocytes/macrophages were detected. No significant changes were seen in blood or lung "nonclassical" monocyte and in natural killler, B, or T cells. In the BALF, significant increases were seen in neutrophils, CD43Lo monocyte-macrophages and monocyte chemoattractant protein-1. Significant increases in CD43Lo and Hi monocyte-macrophages were detected in the spleen at 6 hours.

CONCLUSION

This study reveals a robust and selective response of CD43Lo/His48Hi (classical) monocytes, in addition to neutrophils, in blood and lung tissue following PBLI. An increase in monocyte-macrophages was also observed in the spleen at 6 hours. This profile of immune cells in the blood and BALF could present a new research tool for translational studies seeking to monitor, assess, or attenuate the immune response in blast-injured patients.

Investigation of surfactant protein-D and interleukin-6 levels in patients with blunt chest trauma with multiple rib fractures and pulmonary contusions: a cross-sectional study in Black Sea Region of Turkey

OBJECTIVE

Multiple rib fractures (RFs) and pulmonary contusions (PCs), with resulting systemic lung inflammation, are the most common injuries caused by blunt chest trauma (BCT) in motor vehicle accidents. This study examined levels of the inflammation marker interleukin (IL)-6 and those of the acute-phase reactant surfactant protein (SP)-D in patients with BCT.

DESIGN

Prospective, cross-sectional, observational study.

SETTING

Single-centre, tertiary care hospital in the Black Sea Region of Turkey.

PARTICIPANTS

The study included 60 patients with BCT who were hospitalised in our thoracic surgery department.

PARAMETERS MEASURES

The SP-D and IL-6 serum levels of patients with RFs (two or more RFs) (n=30) and patients with PCs (n=30) were measured after 6 hours, 24 hours and 7 days, and compared with those of age-matched and gender-matched healthy participants.

RESULTS

The 6-hour serum SP-D levels of the RFs (p=0.017) and PCs (p<0.001) groups were significantly higher than those of the healthy controls. The 24-hour and 7-day SP-D levels of both groups were also higher than the control group. The serum IL-6 levels of both groups were significantly higher than those of the control group. We have found Injury Severity Score to be independently related to 6-hour IL-6 (β=1.414, p<0.001) and 24-hour IL-6 levels (β=1.067, p<0.001). The development of complications was independently related to 6-hour SP-D level (β=0.211, p=0.047).

CONCLUSIONS

RFs and PCs after BCT lead to local and systemic inflammation due to lung injury. The levels of the systemic inflammation marker IL-6 and those of the acute-phase reactant SP-D were elevated in the present study. The SP-D level may be used as a marker in the follow-up of BCT-related complications.

Induced hypothermia reduces the hepatic inflammatory response in a swine multiple trauma model

BACKGROUND

Mild therapeutic hypothermia following trauma has been introduced in several studies to reduce the posttraumatic inflammation and organ injury. In this study, we analyzed the effects of induced mild hypothermia (34°C) on the inflammation of the shock organs liver and kidney.

METHODS

In a porcine model of multiple trauma including blunt chest trauma, liver laceration, and hemorrhagic shock followed by fluid resuscitation, the influence of induced hypothermia on hepatic and renal damage and organ-specific inflammation were evaluated. A total of 40 pigs were randomly assigned to four groups, which were sham (anesthesia only) or trauma groups receiving either hypothermia or normothermia. The parameters analyzed were laboratory parameters (aspartate transaminase [AST], lactate dehydrogenase, urea, creatinine) as well as hepatic and renal cytokine expression determined by real-time polymerase chain reaction (interleukin 6 [IL-6], IL-8). Blinded analysis of histologic changes in the liver and kidney was performed.

RESULTS

Fifteen and a half hours following combined trauma, hepatic cytokine expression and liver damage were significantly increased in animals with normothermia compared with the respective sham group. Hypothermia, however, resulted in a fivefold reduced hepatic expression of IL-8 (mean ± SE, 2.4 ± 1.3; p = 0.01) when compared with the normothermic trauma group (IL-8, 12.8 ± 4.7). Accordingly, granulocyte infiltration and a histologic, semiquantitative score for liver injury were significantly higher in the normothermic trauma group. Serum AST levels raised significantly after trauma and normothermia compared with the respective sham group, while AST levels showed no difference from the sham groups in the hypothermic trauma group. In contrast, neither trauma nor hypothermia influenced the expression of IL-6 and IL-8 and tissue injury in the kidney.

CONCLUSION

Therapeutic hypothermia seems to attenuate the hepatic inflammatory response and the associated liver injury after severe trauma. Therefore, induced hypothermia might represent a potential therapeutic strategy to avoid posttraumatic organ dysfunction.

Apoptotic and inflammatory signaling via Fas and tumor necrosis factor receptor I contribute to the development of chest trauma-induced septic acute lung injury

BACKGROUND

Direct acute lung injury (ALI) is still associated with a high mortality, whereas the underlying pathomechanisms are not yet fully understood. In this regard, epithelial cell death in the lungs has been attributed an important role in the pathogenesis of this clinical entity. Based on this background here, we hypothesized that signaling through Fas and tumor necrosis factor receptor 1 (TNFR-1) is involved in mediating apoptosis and inflammation in chest trauma induced septic ALI.

METHODS

Male C57BL/6 mice (wild-type [WT]), male mutant mice expressing nonfunctional Fas receptor (B6.MRL-Faslpr/J [lpr]) (lpr) and male TNFR-1-deficient mice (TNFR-1(-/-)) were subjected to a model of direct ALI consisting of blunt chest trauma followed by cecal ligation and puncture.Cytokine/chemokine concentrations of plasma, bronchoalveolar lavage (BAL) fluids, and lung tissue were investigated as well as BAL protein and lung myeloperoxidase. Lung histology was assessed; lung caspase 3, TUNEL-positive cells, and apoptotic polymorphonuclear neutrophil were measured, followed by a survival study.

RESULTS

Cytokine/chemokine levels in plasma, BAL, and lung tissue were markedly increased in WT animals following ALI, whereas lpr and TNFR-1((-/-) showed significantly decreased levels. BAL protein levels were substantially elevated following ALI, but lpr animals presented markedly diminished protein levels compared with WT and TNFR-1(-/-) animals. Lung myeloperoxidase level was only increased 12 hours after ALI in WT animals, whereas lung myeloperoxidase levels in lpr and TNFR-1(-/-) animals were not increased compared with sham. Lung histology revealed beneficial effects in lpr and TNFR-1(-/-). Lung active caspase 3 after ALI was substantially decreased in lpr and TNFR-1(-/-) mice compared with WT. Interestingly, an early but not persisting survival benefit was observed in lpr and TNFR-1 animals(-/-).

CONCLUSION

Pathomechanistically, Fas and TNFR-1 signaling contributed to the apoptotic and inflammatory response in a clinically relevant double-hit model of trauma-induced septic ALI. Moreover, this was associated with a temporary survival benefit.

Cytokine productive capacity of alveolar macrophages and Kupffer cells after femoral fracture and blunt chest trauma in a murine trauma model

INTRODUCTION

Specific cellular and inflammatory factors that contribute to the severity of pulmonary dysfunction after blunt chest trauma and osteosynthesis of femoral fractures are yet not fully understood. Therefore, we investigated alterations of the cytokine productive capacity of alveolar macrophages (AM) and Kupffer cells (KC) after femoral fracture stabilized with intramedullary pin with or without blunt chest trauma.

MATERIALS AND METHODS

In male C57BL/6N mice an intramedullary pin was implanted in an intact femur as the sham procedure. In trauma groups mice either received an isolated femoral fracture with subsequent fracture stabilization with an intramedullary pin (group Fx) or a combined trauma of blunt chest trauma and femur fracture also stabilized by an intramedullary pin (group TTFx). Animals were sacrificed 0h, 6h, 12h, 24h and 3d after trauma induction. Cytokine concentrations were measured in plasma and supernatant of cultivated AM and KC by FACS analysis. Pulmonary and hepatic infiltration of polymorphonuclear leukocytes (PMN) was determined by Ly6G-staining.

RESULTS

At 6h, isolated femoral fracture with intramedullary stabilization resulted in a significantly increased productive capacity of KC (IL-6, TNF-α, CCL2, CCL3, CCL5 and CCL7) compared to sham animals. Combined trauma additionally resulted in an increased productive capacity of AM (IL-6, TNF-α, CCL2, CCL3, CCL4, CCL5 and CCL7) at 6h and the effect was prolonged up to 3d compared to controls. Combined trauma also led to a significant higher amount of plasma CCL2 at 3d and plasma CCL7 at 6h after the insult compared to group Fx. Compared to shams, pulmonary and hepatic infiltrations of PMNs were increased in group Fx and TTFx after 6h, but in the combined trauma model the effect was prolonged up to 3d.

CONCLUSION

An intramedullary stabilized femur fracture alone results in a significant activation of the immune response. The combination of femoral fracture and blunt chest trauma however, results in an increased and prolonged activation of the inflammatory response. Transferred to the clinical setting, these results emphasize the critical role of severe chest trauma for treatment strategies of femoral fractures in multiple trauma patients.

A new experimental polytrauma model in rats: molecular characterization of the early inflammatory response

BACKGROUND

The molecular mechanisms of the immune response after polytrauma are highly complex and far from fully understood. In this paper, we characterize a new standardized polytrauma model in rats based on the early molecular inflammatory and apoptotic response.

METHODS

Male Wistar rats (250 g, 6-10/group) were anesthetized and exposed to chest trauma (ChT), closed head injury (CHI), or Tib/Fib fracture including a soft tissue trauma (Fx + STT) or to the following combination of injuries: (1) ChT; (2) ChT + Fx + STT; (3) ChT + CHI; (4) CHI; (5) polytrauma (PT = ChT + CHI + Fx + STT). Sham-operated rats served as negative controls. The inflammatory response was quantified at 2 hours and 4 hours after trauma by analysis of "key" inflammatory mediators, including selected cytokines and complement components, in serum and bronchoalveolar (BAL) fluid samples.

RESULTS

Polytraumatized (PT) rats showed a significant systemic and intrapulmonary release of cytokines, chemokines, and complement anaphylatoxins, compared to rats with isolated injuries or selected combinations of injuries.

CONCLUSION

This new rat model appears to closely mimic the early immunological response of polytrauma observed in humans and may provide a valid basis for evaluation of the complex pathophysiology and future therapeutic immune modulatory approaches in experimental polytrauma.

Experimental blunt chest trauma impairs fracture healing in rats

In poly-traumatic patients a blunt chest trauma is an important trigger of the posttraumatic systemic inflammatory response. There is clinical evidence that fracture healing is delayed in such patients, however, experimental data are lacking. Therefore, we investigated the influence of a thoracic trauma on fracture healing in a rat model. Male Wistar rats received either a blunt chest trauma combined with a femur osteotomy or an isolated osteotomy. A more rigid or a more flexible external fixator was used for fracture stabilization to analyze whether the thoracic trauma influences regular healing and mechanically induced delayed bone healing differently. The blunt chest trauma induced a significant increase of IL-6 serum levels after 6 and 24 h, suggesting the induction of a systemic inflammation, whereas the isolated fracture had no effect. Under a more rigid fixation the thoracic trauma considerably impaired fracture healing after 35 days, reflected by a significantly reduced flexural rigidity (three-point-bending test), as well as a significantly diminished callus volume, moment of inertia, and relative bone surface (µCT analysis). In confirming the clinical evidence, this study reports for the first time that a blunt chest trauma considerably impaired bone healing, possibly via the interaction of the induced systemic inflammation with local inflammatory processes.

Blunt chest trauma induces mediator-dependent monocyte migration to the lung

OBJECTIVE

This study was designed to determine whether lung contusion induces an increased pulmonary recruitment of monocytes as a source of alveolar macrophages and which mediators are involved.

SETTING AND DESIGN

Prospective animal study.

SUBJECTS AND INTERVENTIONS

Male Sprague-Dawley rats were subjected to chest trauma by a single blast wave.

MEASUREMENTS

Chemokine concentrations in bronchoalveolar lavage fluids and supernatants of alveolar macrophages, chemokine and chemokine receptor mRNA expressions in monocytes, pulmonary interstitial macrophages, and alveolar macrophages isolated after trauma or sham procedure were evaluated. Immigration of monocytes was determined by staining alveolar macrophages with the fluorescent marker PKH26 before chest trauma. Chemotaxis of naïve monocytes in response to bronchoalveolar lavage or supernatants from alveolar macrophages isolated after trauma or sham procedure and the migratory response of monocytes isolated after trauma/sham to recombinant chemokines were measured.

MAIN RESULTS

Chemokine levels in bronchoalveolar lavage and alveolar macrophage supernatants and the percentage of monocytes migrated to the lungs were increased after chest trauma. Lung contusion enhanced the mRNA expression for CCR2 in monocytes and interstitial macrophages and for monocyte chemotactic protein-1 in alveolar macrophages. Migration of naïve monocytes vs. bronchoalveolar lavage or alveolar macrophage supernatants from traumatized animals was increased when compared with samples from shams. Monocytes isolated 2 hrs after trauma showed a reduced migration to CINC-1 or monocyte chemotactic protein-1 compared with sham.

CONCLUSIONS

Alveolar macrophages seem to contribute to increased chemokine concentrations in alveoli of animals subjected to blunt chest trauma. Mediators released by alveolar macrophage are potent stimuli for monocyte migration. Monocytes alter their chemokine receptor expression and are recruited to the lungs.

Early onset pneumonia in severe chest trauma: a risk factor analysis

BACKGROUND

The development of an early-onset pneumonia (EOP), occurring within the first 72 hours after admission, represents a critical event in severe thoracic trauma population. The aim of this study was to determine risk factors associated with the occurrence of this complication in this specific population.

METHODS

A retrospective review of a prospective implemented trauma registry was conducted during a 4-year period in a Level I trauma center. Over the study period, 223 severely injured patients were admitted with severe thoracic trauma (Injury Severity Score >16 and Thorax Abbreviated Injury Score >2). Multiple logistic regression analysis was used to determine the independent predictors of EOP based on the clinical characteristics and the initial management both in the field and after admission in the trauma center.

RESULTS

Independent predictors of EOP were the necessity of intubation and mechanical ventilation in the field (adjusted odds ratio [OR]: 11.8; 95% confidence interval [CI]: 4.3-32.7), a history of aspiration (OR: 28.6; 95% CI: 4.0-203.5), the presence of pulmonary contusion (OR: 7.0; 95% CI: 2.0-23.9), and the occurrence of a hemothorax (OR: 3.2; 95% CI: 1.4-7.6).

CONCLUSION

These results emphasize the influence of prehospital and early factors in the further occurrence of EOP, which allows the development of early and specific clinical management to prevent it.

Mechanism of the salutary effects of estrogen on kupffer cell phagocytic capacity following trauma-hemorrhage: pivotal role of Akt activation

Kupffer cells are macrophages in the liver whose major role is to clear circulating pathogens. Decreased phagocytic capacity of Kupffer cells may result in severe systemic infection. We tested the hypothesis that the depressed Kupffer cell phagocytic capacity following trauma-hemorrhage is enhanced by estrogen administration and this occurs due to maintenance of Fc receptor expression and cellular ATP content via the activation of Akt. Male C3H/HeN mice were subjected to sham operation or trauma-hemorrhage and sacrificed 2 h thereafter. Estrogen, with or without an estrogen receptor antagonist (ICI 182,780), a PI3K inhibitor (Wortmannin), or vehicle, was injected during resuscitation. Kupffer cell phagocytic capacity was tested in vivo. The expression of Fc receptors, of Akt phosphorylation, of p38 MAPK phosphorylation, of DNA binding activity of NF-kappaB and ATP content of Kupffer cells were also determined. Trauma-hemorrhage suppressed Kupffer cell phagocytosis by decreasing Fc receptor expression and Akt activation; however, it induced p38 MAPK activation and increased NF-kappaB activity. Cellular ATP levels were also decreased following trauma-hemorrhage. Administration of estrogen following trauma-hemorrhage increased phospho-Akt levels and normalized all the parameters described as well as plasma levels of TNF-alpha, IL-6, and IL-10. Coadministration of ICI 182,780 or Wortmannin abolished the beneficial effects of estrogen in improving the phagocytic capacity of Kupffer cells following trauma-hemorrhage. Thus, activation of Akt plays a crucial role in mediating the salutary effect of estrogen in restoring trauma-hemorrhage-induced suppression of Kupffer cell phagocytosis.

Epithelial cell apoptosis and neutrophil recruitment in acute lung injury-a unifying hypothesis? What we have learned from small interfering RNAs

In spite of protective ventilatory strategies, Acute Lung Injury (ALI) remains associated with high morbidity and mortality. One reason for the lack of therapeutic options might be that ALI is a co-morbid event associated with a diverse family of diseases and, thus, may be the result of distinct pathological processes. Among them, activated neutrophil- (PMN-) induced tissue injury and epithelial cell apoptosis mediated lung damage represent two potentially important candidate pathomechanisms that have been put forward. Several approaches have been undertaken to test these hypotheses, with substantial success in the treatment of experimental forms of ALI. With this in mind, we will summarize these two current hypotheses of ALI briefly, emphasizing the role of apoptosis in regulating PMN and/or lung epithelial cell responses. In addition, the contribution that Fas-mediated inflammation may play as a potential biological link between lung cell apoptosis and PMN recruitment will be considered, as well as the in vivo application of small interfering RNA (siRNA) as a novel approach to the inhibition of ALI and its therapeutic implications.

[Significance of liver trauma for the incidence of sepsis, multiple organ failure and lethality of severely injured patients. An organ-specific evaluation of 24,771 patients from the trauma register of the DGU]

BACKGROUND

The prognosis of multiple injured patients is mainly limited by initial severe hemorrhage causing hemorrhagic shock, subsequent sepsis and multiple organ failure (MOF). Although mechanisms of altered microcirculation, cytokine release etc. have been intensively investigated, little is known about the relevance of severe liver trauma as an independent predictive outcome factor in these patients. This study aimed to clarify the impact of severe liver trauma in one of the largest trauma databases.

PATIENTS AND METHODS

The study was based on data from the German trauma register within the German Society for Trauma Surgery (DGU) and 24,711 patients from 113 hospitals were collected for retrospective analysis between 1993 and 2005. Patients with an injury severity score (ISS) >16, no isolated head injury and primary admission to a trauma center were included. Data were allocated according to the injury pattern into I liver group (severe damage of the liver, AIS>3 and AIS abdomen <3), II Abdomen group (severe abdominal trauma AIS>3, AIS liver <3) and III Control group (liver and/or abdominal trauma AIS<3, other trauma AIS>3).

RESULTS

Out of 24,771 multiple injured patients from 113 trauma centers, 321 individuals were identified which matched the criteria of the liver group. Another 574 patients were allocated to the abdomen group while the majority of patients formed the trauma group (9574). Severe injury of the liver is associated with excessive demands for volume resuscitation and induces a significantly increased risk for sepsis and MOF compared to both other groups (sepsis 19.9% vs 11%; MOF 32.7% vs 16.6%). Furthermore, deleterious outcome is more frequent associated with patients with severe liver trauma (lethality 34.9%) compared to severe abdominal trauma (12%) and the control group (19.5%).

CONCLUSIONS

Severe liver trauma is an independent predictor for severe hemorrhage with a substantial increased risk of sepsis, MOF and trauma-related death. While conservative treatment of patients with severe liver trauma but no hemorrhage is effective, patients with hemodynamic instability seem to form a subgroup where contemporary treatment modalities are not yet sufficient.

The role of C5a in the innate immune response after experimental blunt chest trauma

The inflammatory response after severe blunt chest trauma often leads to acute lung injury and acute respiratory distress syndrome which are associated with high mortality rates. Whereas the role of innate immunity in acute lung injury has been broadly investigated, the immune response after blunt chest trauma is still poorly understood. Therefore, the role of complement and neutrophils was determined in bilateral lung injury induced by a single blast wave. The following time-points were investigated posttrauma: sham, 1, 6, 12, and 24 h. There was a time-dependent systemic activation of complement as determined by CH-50 and presence of C5a-dependent chemotactic plasma activity. Moreover, factor H, a complement regulatory protein, was increased systemically and locally after injury. Anti-C5a treatment immediately after trauma ameliorated these peaks. After an initial systemic leukopenic phase, a marked leukocytosis occurred. The latter was normalized by C5a blockade. In parallel, white blood cell count in bronchioalveolar lavage fluids was increased as a function of time and was significantly decreased by anti-C5a treatment. Trauma-induced lung injury was also associated with dramatic changes in neutrophil function, namely early enhanced chemotaxis and phagocytosis, followed by prolonged functional defects-all of which were ameliorated by anti-C5a treatment. Furthermore, blockade of C5a ameliorated the buildup of the proinflammatory cytokine TNF-alpha, diminished the increase of cytokine-induced neutrophil chemoattractant 1, and altered the levels of the anti-inflammatory cytokine IL-10. These data suggest that blunt chest trauma leads to systemic activation of complement and robust C5a generation, which causes perturbations in defensive functions of neutrophils. Thus, C5a might represent a potential target for therapeutic immunomodulation to prevent immune dysfunctions post-trauma and thereby, perhaps, the progression to acute respiratory distress syndrome.