Inflammatory Alterations in a Novel Combination Model of Blunt Chest Trauma and Hemorrhagic Shock

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.

Early local neutralization of CC16 in sepsis‑induced ALI following blunt chest trauma leads to delayed mortality without benefitting overall survival

Blunt thoracic trauma (TxT) is a common injury pattern in polytraumatized patients. When combined with a secondary trigger, TxT often results in acute lung injury (ALI), which negatively affects outcomes. Recent findings suggest that ALI is caused by both local and systemic inflammatory reactions. Club cell protein (CC)16 is an anti‑inflammatory peptide associated with lung injury following TxT. Recently, the anti‑inflammatory properties of endogenous CC16 in a murine model of TxT with subsequent cecal‑ligation and puncture (CLP) as the secondary hit were demonstrated by our group. The present study aimed to determine whether CC16 neutralization improves survival following 'double‑hit'‑induced ALI. For this purpose, a total of 120 C57BL/6N mice were subjected to TxT, followed by CLP after 24 h. Sham‑operated animals underwent anesthesia without the induction of TxT + CLP. CC16 neutralization was performed by providing a CC16 antibody intratracheally following TxT (early) or following CLP (late). Survival was assessed in 48 animals for 6 days after CLP. Sacrifice was performed 6 or 24 h post‑CLP to evaluate the anti‑inflammatory effect of CC16. The results revealed that CC16 neutralization enhanced pro‑inflammatory CXCL1 levels, thereby confirming the anti‑inflammatory characteristics of CC16 in this model. Early CC16 neutralization immediately following TxT significantly prolonged survival within 60 h; however, the survival rate did not change until 6 days post‑trauma. Late CC16 neutralization did not provide any survival benefits. On the whole, the present study demonstrated that neutralizing CC16 confirmed its anti‑inflammatory potential in this double‑hit ALI model. Early CC16 neutralization prolonged survival within 60 h; however, no survival benefits were observed after 6 days post‑CLP in any group.

Dexmedetomidine alleviates blunt chest trauma and hemorrhagic shock‑resuscitation‑induced acute lung injury through inhibiting the NLRP3 inflammasome

Blunt chest trauma with hemorrhagic shock frequently induces pulmonary inflammation that leads to acute lung injury (ALI). The present study aimed to explore the protective effects of dexmedetomidine (Dex) in blunt chest trauma and hemorrhagic shock-resuscitation (THSR)-induced ALI by mediating nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing protein 3 (NLRP3) inflammasome formation in rats. An ALI model in rats induced by THSR was constructed and Dex was administered intraperitoneally (5 µg/kg/h) immediately after blunt chest trauma. Blood samples were collected for the determination of proinflammatory factor levels, and lung tissue specimens were harvested for wet/dry (W/D) weight ratio, hematoxylin and eosin staining, and transmission electron microscopy analyses. Additionally, malondialdehyde (MDA), superoxide dismutase (SOD), lactate dehydrogenase (LDH) and myeloperoxidase (MPO) activity were evaluated, and the expression of protein in lung tissues was examined via western blot analysis. Compared with the sham group, pathological alterations in the ALI group and the W/D ratios were significantly increased. MDA, LDH and MPO activity, and the levels of interleukin (IL)-1β, IL-18, IL-6 and tumor necrosis factor-α were significantly elevated. NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain and caspase-1 expression was significantly increased. Conversely, Dex treatment significantly reversed these changes. The present study demonstrated that by reducing inflammatory responses, Dex exerted protective effects against THSR-ALI in rats, potentially via the inhibition of NLRP3 signaling pathways.

Systemic release of heat-shock protein 27 and 70 following severe trauma

Trauma represents a major cause of morbidity and mortality worldwide. The endogenous inflammatory response to trauma remains not fully elucidated. Pro-inflammation in the early phase is followed by immunosuppression leading to infections, multi-organ failure and mortality. Heat-shock proteins (HSPs) act as intracellular chaperons but exert also extracellular functions. However, their role in acute trauma remains unknown. The aim of this study was to evaluate serum concentrations of HSP 27 and HSP 70 in severely injured patients. We included severely injured patients with an injury severity score of at least 16 and measured serum concentration of both markers at admission and on day two. We found significantly increased serum concentrations of both HSP 27 and HSP 70 in severely injured patients. Concomitant thoracic trauma lead to a further increase of both HSPs. Also, elevated concentrations of HSP 27 and HSP 70 were associated with poor outcome in these patients. Standard laboratory parameters did not correlate with neither HSP 27, nor with HSP 70. Our findings demonstrate involvement of systemic release of HSP 27 and HSP 70 after severe trauma and their potential as biomarker in polytraumatized patients.

Concomitant chest trauma and traumatic brain injury, biomarkers correlate with worse outcomes

BACKGROUND

Clinical data are lacking on the influence of chest trauma on the secondary injury process after traumatic brain injury (TBI), with some data suggesting that multiple trauma may worsens brain injury. Blunt chest trauma and TBI represent the two major single injury entities with the highest risk of complications and are potential biomarker targets.

METHODS

Trauma patients with severe TBI were enrolled. Serum biomarker levels were obtained every 6 hours for 72 hours. Baseline, 6 hours and 24 hours CT head scans were evaluated. Neurologic worsening was defined as increased contusions, ischemia, compression of basal cisterns, and/or midline shift. The TBI patients with chest injury (Abbreviated Injury Scale chest score ≥1) and those without chest injury were compared. Wilcoxon rank sum test, univariate logistic regression and receiver operating characteristic were reported.

RESULTS

Fifty-seven patients. Mean age of 40.5 years. Median motor Glasgow Coma Scale score at admission and 24 hours was 3 (interquartile range, 1-5) and 5 (interquartile range, 3-5). Of the patients enrolled, 12.2% patients underwent craniotomy within 6 hours from the time of admission and 22.8% within 12 hours. Patients with chest trauma, 24.5% had a chest Abbreviated Injury Scale score of 3 or greater, and 73.6% sustained blunt chest trauma. Stratifying TBI patients with and without chest injury revealed higher mean levels of IL-4, IL-5, IL-8, and IL-10 and lower mean IFN-γ and IL-7 levels in patient with chest injury. IL-7 levels adjusted for chest injury predicted neurological worsening with area under the receiver operating characteristic of 0.59 (p value = 0.011). The TBI and chest trauma patients' IL-4 and neuron-specific enolase levels were predictive of mortality (area under the receiver operating characteristic of 0.67 and 0.63, p = 0.0001, 0.003), respectively.

CONCLUSION

Utilizing biomarkers for early identification of patients with TBI and chest trauma has the capability of modifying adverse factors affecting morbidity and mortality in this subset of TBI patients.

LEVEL OF EVIDENCE

Level III.

Alcohol‑induced attenuation of post‑traumatic inflammation is not necessarily liver‑protective following trauma/hemorrhage

Due to their high prevalence, blunt chest trauma (TxT) and hemorrhagic shock have a significant influence on the outcomes of trauma patients, causing severe modulations of the immune system and high mortality rates. Alcohol consumption in trauma patients has a high clinical impact. Studies investigating the timing of alcohol intoxication prior to trauma are limited, although there are two typical scenarios regarding alcohol consumption: Acute ('drink and drive scenario') and sub‑acute ('evening binge drinking'). Therefore, the present study investigated the influence of either an acute or sub‑acute alcohol‑drinking scenario in an in vivo model of TxT and hemorrhagic shock, focusing on liver inflammation and outcomes. At 12 h (sub‑acute) or 2 h (acute) before the experiment, female Lewis rats received a single oral dose of alcohol (ethanol, EtOH) or saline (NaCl, ctrl), followed by TxT, hemorrhagic shock (35±3 mm Hg) and resuscitation (H/R). The animals were either sacrificed 2 h later or their survival was determined for 72 h. The results revealed that EtOH induced significant fatty changes in the liver. TxT + H/R‑induced increases in the gene expression of interleukin (IL)‑6 and intercellular adhesion molecule‑1 and the protein expression of tumor necrosis factor (TNF)‑α and IL‑1β were significantly reduced in both EtOH groups compared with those in the corresponding TxT + H/R ctrl groups. The local presence of IL‑10‑expressing cells in the liver was significantly increased following TxT + H/R in all groups, although the sub‑acute EtOH TxT + H/R group had a significantly higher proportion of IL‑10‑positive cells compared with all other groups. Stimulating peripheral whole blood with lipopolysaccharide led to significantly lower levels of TNF‑α release in the sub‑acute EtOH group compared with the levels in all other groups. Significant TxT + H/R‑induced increases in liver transaminases and liver damage were most prominent in the sub‑acute EtOH group. The TxT + H/R EtOH group exhibited the lowest levels of glucose. There were no significant differences in mortality rate among the TxT + H/R groups. The data obtained indicates that the severity of liver damage following TxT + H/R may depend on the timing of alcohol consumption and severity of trauma, but also on the balance between pro‑ and anti‑inflammatory responses.

Increased serum concentrations of soluble ST2 are associated with pulmonary complications and mortality in polytraumatized patients

BACKGROUND

We sought to evaluate the role of soluble ST2 (suppression of tumorigenicity) serum concentrations in polytraumatized patients and its potential role as biomarker for pulmonary complications.

METHODS

We included severely injured patients (injury severity score≥16) admitted to our level I trauma center and analyzed serum samples obtained on the day of admission and on day 2. Furthermore, patients with isolated thoracic injury and healthy probands were included and served as control groups. Serum samples were analyzed for soluble ST2 concentrations with a commercially available ELISA kit.

RESULTS

A total of 130 patients were included in the present study. Five patients with isolated thoracic injury and eight healthy probands were further included. Serum analyses revealed significantly elevated concentrations of soluble ST2 in polytraumatized patients compared to patients suffering from isolated thoracic trauma and healthy probands. In polytraumatized patients who developed pulmonary complications (acute respiratory distress syndrome and pneumonia) and in patients who died, significantly higher serum concentrations of soluble ST2 were found on day 2 (p<0.001). Serum concentrations of soluble ST2 on day 2 were of prognostic value to predict pulmonary complications in polytraumatized patients (area under the curve=0.720, 95% confidence interval=0.623-0.816). Concomitant thoracic trauma had no further impact on serum concentrations of soluble ST2.

CONCLUSIONS

Serum concentrations of soluble ST2 are upregulated following polytrauma. Increased concentrations were associated with worse outcome.

Monotrauma is associated with enhanced remote inflammatory response and organ damage, while polytrauma intensifies both in porcine trauma model

AIM

Severely injured patients experience substantial immunological stress upon traumatic insult. Next to the direct local tissue injury also other organs, which are not directly injured such as liver and lung, are frequently affected by a so-called remote organ damage (ROD) after trauma. Thus, we studied the inflammatory response of lung and liver either after isolated femur fracture as example for ROD, or after multiple trauma in a porcine polytrauma model.

METHODS

Twenty-four male pigs (Sus scrofa) underwent either isolated standardized femoral fracture (monotrauma, MT, n = 12) or polytrauma (PT, n = 12). PT consisted of a femur fracture, lung contusion, liver laceration, hemorrhagic shock, subsequent resuscitation and surgical fracture fixation. Six animals served as controls (sham). After 72 h inflammatory changes were determined by analyses of the interleukin (IL)-6 gene expression and tissue infiltration of polymorphonuclear leukocyte (PMN, myeloperoxidase staining). ROD in MT, and lung as well as liver damage in PT were assessed histologically by hematoxylin-eosin staining. Expression of phosphorylated p65 NF-κB was evaluated by immunohistology.

RESULTS

IL-6 increased in lungs and liver in both groups MT and PT, respectively, compared to sham. Similarly, PMN infiltration of the lungs and liver increased significantly after both MT and PT compared to sham. Histological evaluation demonstrated tissue damage notably in lungs after MT, while tissue damage after PT was found in both lung and liver after PT. p65 NF-κB tended to an increase upon MT, and was significantly enhanced after PT in both tissues.

CONCLUSION

Our data indicate that remote organ damage after MT notably in lungs was associated with an enhanced inflammatory response. Severe polytrauma substantially intensifies this response and organ damage in the underlying model.

miR-146b overexpression ameliorates lipopolysaccharide-induced acute lung injury in vivo and in vitro

Acute respiratory distress syndrome (ARDS) is a type of acute lung injury (ALI), which causes high morbidity and mortality. So far, effective clinical treatment of ARDS is still limited. Recently, miR-146b has been reported to play a key role in inflammation. In the present study, we evaluated the functional role of miR-146b in ARDS using the murine model of lipopolysaccharide (LPS)-induced ALI. The miR-146b expression could be induced by LPS stimulation, and miR-146b overexpression was required in the maintenance of body weight and survival of ALI mice; after miR-146b overexpression, LPS-induced lung injury, pulmonary inflammation, total cell and neutrophil counts, proinflammatory cytokines, and chemokines in bronchial alveolar lavage (BAL) fluid were significantly reduced. The promotive effect of LPS on lung permeability through increasing total protein, albumin and IgM in BAL fluid could be partially reversed by miR-146b overexpression. Moreover, in murine alveolar macrophages, miR-146b overexpression reduced LPS-induced TNF-α and interleukin (IL)-1β releasing. Taken together, we demonstrated that miR-146b overexpression could effectively improve the LPS-induced ALI; miR-146b is a promising target in ARDS treatment.

Penehyclidine hydrochloride inhibits TLR4 signaling and inflammation, and attenuates blunt chest trauma and hemorrhagic shock-induced acute lung injury in rats

Blunt chest trauma with hemorrhagic shock (THS) frequently induces pulmonary inflammation that leads to acute lung injury (ALI). Penehyclidine hydrochloride (PHC) possesses anti‑inflammatory properties that may attenuate the systemic inflammatory response. The present study aimed to evaluate the molecular mechanism of PHC in modifying THS‑induced ALI in rats. Rats underwent either THS or a sham procedure. At 6 h subsequent to blunt chest trauma, arterial blood was drawn for blood gas and pro‑inflammatory factors analyses, and lung tissue samples were collected to examine pulmonary histopathological alterations, the wet/dry weight ratio, myeloperoxidase activity, and the protein expression levels of Toll-like receptor 4 (TLR4), phosphorylated (p‑)p38 mitogen‑activated protein kinase (MAPK), nuclear factor (NF)‑κB and activator protein‑1 (AP‑1). THS caused significant reductions in heart rate and mean arterial blood pressure, and was associated with significant increases in tumor necrosis factor‑α, interleukin (IL)‑6, IL‑1β, p‑p38MAPK, NF‑κB and AP‑1 activation, in addition to TLR4 expression, in the lung. PHC effectively attenuated THS‑induced ALI, and inhibited TLR4 expression, reduced the activation of p‑p38MAPK, NF‑κB and AP‑1, and downregulated the expression of pro‑inflammatory mediators. In conclusion, the results of the present study demonstrated that PHC may exert an anti‑inflammatory effect and attenuate THS‑induced ALI by inhibiting the TLR4 signaling pathway. These preclinical findings may offer a novel therapeutic strategy to restrict TLR4 overactivation in ALI.

Ethyl pyruvate reduces acute lung damage following trauma and hemorrhagic shock via inhibition of NF-κB and HMGB1

OBJECTIVE

After blunt thoracic trauma (TxT) and hemorrhagic shock with resuscitation (H/R) intense local inflammatory response and cell loss frequently impair the pulmonary function. Ethyl pyruvate (EP) has been reported to improve the pathophysiologic derangements in models of acute inflammation. Here, we studied the effects of EP on inflammation and lung damage after TxT+H/R.

METHODS

Twenty four female Lewis rats (180-240g) were randomly divided into 3 groups: two groups underwent TxT followed by hemorrhagic shock (35±3mmHg) for 60min and resuscitation with either Ringers-Lactat (RL) alone or RL supplemented with EP (EP, 50mg/kg). Sham operated animals underwent surgical procedures. Two hours later bronchoalveolar lavage fluid (BAL), lung tissue and blood were collected for analyses.

RESULTS

EP significantly improved pO₂ levels compared to RL after TxT+H/R. TxT+H/R induced elevated levels of lactate dehydrogenase, total protein concentration in BAL and lung damage as evidenced by lung histology; these effects were significantly reduced by EP. Local inflammatory markers, lung TNF-alpha protein levels and infiltration with polymorphonuclear leukocytes (PMNL) significantly decreased in EP vs. RL group after TxT+H/R. Indicators of apoptosis as reduced BCL-2 and increased FAS gene expression after TxT+H/R were significantly increased or decreased, respectively, by EP after TxT+H/R. EP reduced TxT+H/R-induced p65 phosphorylation, which was concomitant with reduced HMGB1 levels in lung sections.

CONCLUSIONS

Taken together, TxT+H/R induced strong inflammatory response and apoptotic changes as well as lung injury which were markedly diminished by EP. Our results suggest that this might be mediated via NF-κB and/or HMGB1 dependent mechanism.

Acute Alcohol Binge Deteriorates Metabolic and Respiratory Compensation Capability After Blunt Chest Trauma Followed by Hemorrhagic Shock-A New Research Model

BACKGROUND

The clinical relevance of blunt (thoracic) chest trauma (TxT) and hemorrhagic shock is indisputable due to the high prevalence of this injury type, as well as its close association with mortality and/or preventable deaths. Furthermore, there is an ongoing discussion about the influence of alcohol in trauma patients. Thus, we established a model of TxT followed by hemorrhagic shock with resuscitation (H/R) in alcohol-intoxicated rats.

METHODS

Depending on group allocation, 12 (subacute) or 2 (acute) hours before experimentation, the animals received a single oral dose of alcohol (ethanol [EtOH]) or saline (NaCl) followed by TxT, hemorrhagic shock (35 ± 3 mm Hg), and resuscitation (TxT + H/R). Arterial blood gas analyses and continuous monitoring of blood pressure were performed during the experimentation period. Survival during the experimentation procedure was determined.

RESULTS

Subacute and acute EtOH group exhibited lower baseline mean arterial blood pressure values compared with the corresponding NaCl group, respectively. Both EtOH groups showed lower maximal bleed-out volume, which was necessary to induce hemorrhagic shock compared to NaCl groups, and the recovery during the resuscitation period was attenuated. During the experimentation in all groups, a trend to acidic pH was observed. Acute EtOH group showed lowest pH values compared to all other groups. Higher pCO₂ values were observed in both EtOH groups. All groups developed negative base excess and decreasing HCO3- values until the end of hemorrhagic shock and showed increasing base excess and HCO3- values during resuscitation. Significantly higher mortality rate was found in the acute EtOH group.

CONCLUSIONS

This study indicates that alcohol limits the metabolic and respiratory compensation capability, thereby promoting mortality.

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.

Characterization of blunt chest trauma in a long-term porcine model of severe multiple trauma

Chest trauma has a significant relevance on outcome after severe trauma. Clinically, impaired lung function typically occurs within 72 hours after trauma. However, the underlying pathophysiological mechanisms are still not fully elucidated. Therefore, we aimed to establish an experimental long-term model to investigate physiological, morphologic and inflammatory changes, after severe trauma. Male pigs (sus scrofa) sustained severe trauma (including unilateral chest trauma, femur fracture, liver laceration and hemorrhagic shock). Additionally, non-injured animals served as sham controls. Chest trauma resulted in severe lung damage on both CT and histological analyses. Furthermore, severe inflammation with a systemic increase of IL-6 (p = 0.0305) and a local increase of IL-8 in BAL (p = 0.0009) was observed. The pO₂/FiO₂ ratio in trauma animals decreased over the observation period (p < 0.0001) but not in the sham group (p = 0.2967). Electrical Impedance Tomography (EIT) revealed differences between the traumatized and healthy lung (p < 0.0001). In conclusion, a clinically relevant, long-term model of blunt chest trauma with concomitant injuries has been developed. This reproducible model allows to examine local and systemic consequences of trauma and is valid for investigation of potential diagnostic or therapeutic options. In this context, EIT might represent a radiation-free method for bedside diagnostics.

The molecular fingerprint of lung inflammation after blunt chest trauma

Background

After severe blunt chest trauma, the development of an acute lung injury (ALI) is often associated with severe or even lethal complications. Especially in multiple injured patients after blunt chest trauma ALI/ARDS [acute respiratory distress syndrome (ARDS)] is frequent. However, in the initial posttraumatic phase, inflammatory clinical signs are often not apparent and underlying changes in gene-expression profile are unknown.

Methods

Therefore, inflammation in lung tissue following blunt chest trauma was characterized in a well-defined bilateral lung injury model. Using DNA microarrays representing 9240 genes, the temporal sequence of blunt chest trauma-induced gene-expression patterns in lung tissue was examined.

Results

The results suggest an activation of a highly complex transcriptional program in response to chest trauma. Chest trauma led to elevated expression levels of inflammatory and coagulatory proteins (such as TNFα receptor, IL-1α, IL-1β, C3, NF-κB and plasminogen activator). However, upregulation of proteins was found, usually incoherent of exerting effects in blunt thoracic trauma (pendrin, resistin, metallothionein and glucocorticoid-induced leucine zipper). Furthermore, significant downregulation was observed as early as 10 min after trauma for cytokines and complement factors (LCR-1, C4) as well as for intracellular signaling molecules (inhibitory protein phosphatase) and ion-channels (voltage-dependent Ca²⁺ channel).

Conclusions

Taken together, the provided global perspective of the inflammatory response following blunt chest trauma could provide a molecular framework for future research in trauma pathophysiology.

Exposure to 100% Oxygen Abolishes the Impairment of Fracture Healing after Thoracic Trauma

In polytrauma patients a thoracic trauma is one of the most critical injuries and an important trigger of post-traumatic inflammation. About 50% of patients with thoracic trauma are additionally affected by bone fractures. The risk for fracture malunion is considerably increased in such patients, the pathomechanisms being poorly understood. Thoracic trauma causes regional alveolar hypoxia and, subsequently, hypoxemia, which in turn triggers local and systemic inflammation. Therefore, we aimed to unravel the role of oxygen in impaired bone regeneration after thoracic trauma. We hypothesized that short-term breathing of 100% oxygen in the early post-traumatic phase ameliorates inflammation and improves bone regeneration. Mice underwent a femur osteotomy alone or combined with blunt chest trauma 100% oxygen was administered immediately after trauma for two separate 3 hour intervals. Arterial blood gas tensions, microcirculatory perfusion and oxygenation were assessed at 3, 9 and 24 hours after injury. Inflammatory cytokines and markers of oxidative/nitrosative stress were measured in plasma, lung and fracture hematoma. Bone healing was assessed on day 7, 14 and 21. Thoracic trauma induced pulmonary and systemic inflammation and impaired bone healing. Short-term exposure to 100% oxygen in the acute post-traumatic phase significantly attenuated systemic and local inflammatory responses and improved fracture healing without provoking toxic side effects, suggesting that hyperoxia could induce anti-inflammatory and pro-regenerative effects after severe injury. These results suggest that breathing of 100% oxygen in the acute post-traumatic phase might reduce the risk of poorly healing fractures in severely injured patients.

Activation of NF-κB after chronic ethanol intake and haemorrhagic shock/resuscitation in mice

BACKGROUND AND PURPOSE

Chronic ethanol abuse and haemorrhagic shock are major causes of global mortality and, separately, induce profound hepato- and immune-toxic effects via activation of NF-κB. Here, we assessed the effects of chronic ethanol intake upon the pathophysiological derangements after haemorrhagic shock with subsequent resuscitation (H/R), with particular attention to the contribution of NF-κB.

EXPERIMENTAL APPROACH

Transgenic NF-κB(EGFP) mice, expressing the enhanced green fluorescent protein (EGFP) under the transcriptional control of NF-κB cis-elements were fed a Lieber-DeCarli diet containing ethanol (EtOH-diet) or an isocaloric control diet for 4 weeks and were then pairwise subjected to H/R. Liver tissues and peripheral blood were sampled at 2 or 24 h after H/R. Cytokines in blood and tissue and leukocyte activation (as CD11b expression) were measured, along with EGFP as a marker of NF-κB activation.

KEY RESULTS

The EtOH-diet increased mortality at 24 h after H/R and elevated liver injury, associated with an up-regulation of NF-κB-dependent genes and IL-6 release; it also increased production of NF-κB-driven intercellular adhesion molecule 1 (ICAM-1) and EGFP in liver tissue. At 2h after the H/R procedure in ethanol-fed mice we observed the highest proportion of NF-κB activated non-parenchymal cells and an NF-κB-dependent increase in polymorphonuclear leukocyte CD11b expression.

CONCLUSIONS AND IMPLICATIONS

The EtOH-diet exacerbated liver injury after H/R, accompanying an overwhelming hepatic and systemic immune response. Our findings contribute to evidence implicating NF-κB as a key player in the orchestration of the immune response in haemorrhagic shock patients with a history of chronic ethanol abuse.

Hemorrhagic shock and resuscitation are associated with peripheral blood mononuclear cell mitochondrial dysfunction and immunosuppression

BACKGROUND

Trauma and hypovolemic shock are associated with mitochondrial dysfunction and septic complications. We hypothesize that hypovolemic shock and resuscitation results in peripheral blood mononuclear cell (PBMC) mitochondrial dysfunction that is linked to immunosuppression.

METHODS

With the use of a decompensated shock model, Long-Evans rats were bled to a mean arterial pressure of 40 mm Hg until the blood pressure could no longer be maintained without fluid infusion. Shock was sustained by incremental infusion of lactated Ringer's solution until 40% of the shed volume had been returned (severe shock). Animals were resuscitated with four times the shed volume in lactated Ringer's solution over 60 minutes (resuscitation). Control animals underwent line placement but were not hemorrhaged. Animals were randomized to control (n = 5), severe shock (n = 5), or resuscitation (n = 6) groups. At each time point, PBMC were isolated for mitochondrial function analysis using flow cytometry and high-resolution respirometry. Immune function was evaluated by quantifying serum interleukin 6 (IL-6) and tumor necrosis factor (TNF-α) after PBMC stimulation with lipopolysaccharide. The impact of plasma on mitochondrial function was evaluated by incubating PBMCs harvested following severe shock with control plasma. PBMCs from control animals were likewise mixed with plasma collected following resuscitation. Student's t test and Pearson correlations were performed (significance, p < 0.05).

RESULTS

Following resuscitation, PBMCs demonstrated significant bioenergetic failure with a marked decrease in basal, maximal, and adenosine triphosphate-linked respiration. Mitochondrial membrane potential also decreased significantly by 50% following resuscitation. Serum IL-6 increased, while lipopolysaccharide stimulated TNF-α production decreased dramatically following shock and resuscitation. Observed mitochondrial dysfunction correlated significantly with IL-6 and TNF-α levels. PBMCs demonstrated significant mitochondrial recovery when incubated in control serum, whereas control PBMCs developed depressed function when incubated with serum collected following severe shock.

CONCLUSION

Mitochondrial dysfunction following hemorrhagic shock and resuscitation was associated with the inhibition of PBMC response to endotoxin that may lead to an immunosuppressed state.

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.

Mechanical ventilation increases the inflammatory response induced by lung contusion

BACKGROUND

Posttraumatic lung contusion is common after blunt chest trauma, and patients often need ventilatory support. Lung contusion induces an inflammatory response signified by primed polymorph neutrophil granulocytes (PMNs) in blood and tissue. Mechanical ventilation (MV) can also cause an inflammatory response. The aim of this study was to develop an animal model to investigate the effect of high-volume ventilation on the inflammatory response in blunt chest trauma.

MATERIALS AND METHODS

We assigned 23 male Sprague-Dawley rats to either MV or bilateral lung contusion followed by MV. We used three extra rats as controls. Lung contusion was induced by a blast generator, a device releasing a single pressure blast wave centered on the chest. We determined tissue and systemic inflammation by absolute PMN numbers in blood and bronchoalveolar lavage fluid (BALF), myeloperoxidase, interleukin (IL)-6, IL 1β, growth-related oncogene-KC, and IL-10 in both plasma and BALF.

RESULTS

Survival after blunt chest trauma was correlated to the distance to the blast generator. Compared with controls, both MV and blast plus MV rats showed increased systemic and pulmonary inflammation, expressed by higher PMNs, myeloperoxidase levels, and cytokine levels in both blood and BALF. Blast plus MV rats showed a higher systemic and pulmonary inflammatory response than MV rats.

CONCLUSIONS

The blast generator generated reproducible blunt chest trauma in rats. Mechanical ventilation after lung contusion induced a larger overall inflammatory response than MV alone, which indicates that local damage contributes not only to local inflammation, but also to systemic inflammation. This emphasizes the importance of lung protective ventilation strategies after pulmonary contusion.

C5aR-antagonist significantly reduces the deleterious effect of a blunt chest trauma on fracture healing

Confirming clinical evidence, we recently demonstrated that a blunt chest trauma considerably impaired fracture healing in rats, possibly via the interaction of posttraumatic systemic inflammation with local healing processes, the underlying mechanisms being unknown. An important trigger of systemic inflammation is the complement system, with the potent anaphylatoxin C5a. Therefore, we investigated whether the impairment of fracture healing by a severe trauma resulted from systemically activated complement. Rats received a blunt chest trauma and a femur osteotomy stabilized with an external fixator. To inhibit the C5a-dependent posttraumatic systemic inflammation, half of the rats received a C5aR-antagonist intravenously immediately and 12 h after the thoracic trauma. Compared to the controls (control peptide), the treatment with the C5aR-antagonist led to a significantly increased flexural rigidity (three-point-bending test), an improved bony bridging of the fracture gap, and a slightly larger and qualitatively improved callus (µCT, histomorphometry) after 35 days. In conclusion, immunomodulation by a C5aR-antagonist could abolish the deleterious effects of a thoracic trauma on fracture healing, possibly by influencing the function of inflammatory and bone cells locally at the fracture site. C5a could possibly represent a target to prevent delayed bone healing in patients with severe trauma.

The effect of both a thoracic trauma and a soft-tissue trauma on fracture healing in a rat model

BACKGROUND AND PURPOSE

There is some clinical evidence that fracture healing is impaired in multiply injured patients. Nothing is known, however, about the effects of various types of injuries and their contribution to a possible disturbance of the fracture-healing process. We investigated the effect of a thoracic trauma and an additional soft-tissue trauma on fracture healing in a rat tibia model.

METHODS

3 groups of rats were operated: group A with a simple fracture of the tibia and fibula, group B with a fracture and an additional thoracic trauma, and group C with a fracture, thoracic trauma, and an additional soft-tissue trauma. The fracture and the soft-tissue injury were produced by a special guillotine-like device and the thoracic trauma by a blast wave generator. After one day, the serum level of IL-6 was quantified, and at the end of the study (28 days) the mechanical properties and the callus volume of the healed tibia were determined.

RESULTS

Increasing the severity of the injury caused IL-6 levels to more than double 1 day after injury. It halved the load to failure in mechanical tests and led to reduced callus volume after 28 days of healing.

INTERPRETATION

Fracture healing is impaired when additional thoracic trauma and soft tissue trauma occurs.