Increased neutrophil migratory activity after major trauma: a factor in the etiology of acute respiratory distress syndrome?

Fluid resuscitation increases inflammatory gene transcription after traumatic injury

BACKGROUND

The debate continues over type and quantity of fluid to administer for resuscitation after traumatic injury. This study aimed to examine effects of resuscitation with lactated Ringer's (LR) and Hextend (HEX) on the inflammatory response after uncontrolled hemorrhagic shock (UHS).

METHODS

There were 38 swine randomized. Control swine were anesthetized and killed. Sham swine underwent laparotomy, splenectomy, and 2 hours of anesthesia. UHS swine received a grade V liver injury after laparotomy and splenectomy and were randomized to no fluid (NF) resuscitation or to blinded resuscitation 30 minutes after injury with LR or HEX. Fluids were infused as needed to maintain baseline blood pressure for 90 minutes. Lung tissue mRNA levels of interleukin-6 (IL-6), granulocyte colony stimulating factor (G-CSF), and tumor necrosis factor alpha (TNF-alpha) were determined. Lung sections were examined for neutrophils (PMNs) sequestered within alveolar walls.

RESULTS

All UHS animals survived and initial blood loss was similar between groups. Mean arterial pressures (MAPs) were similar for all UHS animals until resuscitation was initiated. MAPs of resuscitated animals remained similar and were significantly higher than MAPs of the NF animals. Sequestered PMNs were equally elevated in all UHS animals. Cytokine analysis showed increased IL-6, G-CSF, and TNF-alpha gene transcription in resuscitated swine compared with NF swine. LR and HEX resuscitated swine tissue mRNA levels showed no differences.

CONCLUSIONS

Fluid resuscitation after solid organ injury and uncontrolled hemorrhage results in greater proinflammatory gene transcription than no resuscitation. LR and HEX resuscitation have equivalent effects on indices of inflammation in the lungs.

Alteration of Polymorphonuclear Neutrophil Surface Receptor Expression and Migratory Activity After Isolation: Comparison of Whole Blood and Isolated PMN Preparations from Normal and Postfracture Trauma Patients

BACKGROUND

Post-traumatic MOF results from local tissue injury because of migration and activation of dysfunctional polymorphonuclear leukocytes (PMN). Although fracture surgery exacerbates the postinjury inflammatory response, it is usually beneficial. This study compared changes in PMN receptor expression and migratory activity, in whole blood and following PMN isolation.

METHODS

IL-8 mediated PMN migration and expression of CXCR-1, CD11b, and CD18 was studied in isolated and whole blood PMN in normal controls. Migration was studied at admission and day 5 after surgery in trauma patients undergoing fracture surgery.

RESULTS

PMN isolation results in increased expression of surface receptors and enhanced migration in normal controls. In trauma patient samples, isolated PMN migration is enhanced after injury, but suppressed when migration from whole blood is studied, both after injury and fracture surgery.

CONCLUSION

PMN isolation results in priming for migration, which has a relatively greater impact upon PMN in trauma patients. The observation that PMN activity may decline but priming potential remains enhanced is novel. Further refinements of whole blood and isolated PMN techniques are clearly warranted. This may help to resolve the mismatch in clinical and scientific experience in those patients with major fractures requiring surgical stabilization.

Neutrophil Priming for Elastase Release in Adult Blunt Trauma Patients

BACKGROUND

Elevated plasma elastase levels have been reported following major trauma and isolated femoral fracture. Reamed femoral nailing has been shown to further increase plasma elastase levels. The aim of this study was to investigate polymorphonuclear neutrophil (PMN) priming for degranulation following major trauma and isolated long-bone/pelvis fracture by assessing the ability of PMN to release elastase in vitro in response to a stimulus.

METHODS

We further analyzed PMN surface expression of the integrins CD11b and CD18 as markers of PMN activation. Ten major trauma (Injury Severity Score>or=18) patients and 12 patients with isolated long-bone/pelvis fracture were included in the study. Patients in the isolated fracture group were further stratified into reamed nail and external-fixation groups following surgery.

RESULTS

A significant increase in the capacity of PMN to release elastase was seen following major trauma, but not in isolated fracture patients. Surgery did not further alter PMN elastase release. CD11b and CD18 expression was essentially unaltered in all groups.

CONCLUSIONS

PMN is primed for increased degranulation following major trauma but not following isolated long-bone/pelvis fracture. Accumulation of primed, hyperactive PMN into tissues can lead to severe tissue damage and thus multiple organ failure.

Matrix metalloproteinase-2 (MMP-2) and MMP-9 in pulmonary pathology

The lung is affected by a variety of disease processes that can lead to considerable morbidity and mortality. As the lung is the only organ for respiration and gas exchange, the structural and functional integrity of the lung is of primary importance. Various pathological processes affect the extracellular matrix (ECM) of the lung in an adverse manner, causing destruction of tissue integrity followed by tissue remodeling, which together impair normal pulmonary function. Matrix metalloproteinases (MMPs) are neutral proteinases that are involved in the breakdown and remodeling of the ECM under a variety of physiological and pathological conditions. MMP-2 and MMP-9, collectively known as the gelatinases, are particularly important in the pathogenesis of inflammatory, infectious, and neoplastic diseases in many organs including the lung. This review examines the expression of MMP-2 and MMP-9 in disease of the lung and discusses the role these gelatinases may play in disease progression.

Enhanced neutrophil migratory activity following major blunt trauma

BACKGROUND

Neutrophil migration into the lung is a critical, but poorly understood step in the pathogenesis of post-traumatic, acute respiratory distress syndrome (ARDS). We investigated changes in interleukin-8 (IL-8) mediated neutrophil migration and associated changes in receptor expression, of the IL-8 receptors CXCR1, the integrins CD11b/CD18 and platelet endothelial cell adhesion molecule-1 (PECAM-1) in patients sustaining major trauma.

METHODS

Eleven patients with major trauma, injury severity score (ISS), median 22 (range 18-41), were followed prospectively. Eleven normal volunteers were used as controls. Blood samples were obtained within 4+/-2 h of injury, at 24 h, day 3 and day 5. Neutrophils migration was assessed by an in vitro IL-8 assay and neutrophil surface receptor expression by FACS analysis.

RESULTS

IL-8 mediated neutrophil migration was significantly increased on admission following major trauma and remained elevated for 3 days (p<0.05). This was associated with up-regulation of CXCR1 (p<0.01) and down-regulation of PECAM-1 (p<0.05). CD11b and CD18 although initially unchanged, became down-regulated on day 3 (p<0.05).

CONCLUSIONS

These data show that major trauma primes circulating neutrophils for increased migration in response to IL-8. This response is sustained for 72 h and is associated with changes in neutrophil surface receptor expression.

Hypotension and acute pulmonary insufficiency following transfusion of autologous red blood cells during surgery: a case report and review of the literature

Transfusion of autologous blood is associated with fewer complications, although all untoward events of transfusion may not be negated with this strategy. We report a case of acute pulmonary insufficiency and hypotension following transfusion of autologous packed red blood cells (PRBCs) in a patient, who was undergoing major surgery. Anti-HLA class-I and class-II and anti-granulocyte antibodies were measured in the unit and in the recipient. Neutrophil (PMN)-priming activity was measured as the augmentation of the formyl-Met-Leu-Phe-activated respiratory burst. No immunoglobulins were identified; however, significant lipid-priming activity was present in the implicated, autologous PRBC unit that primed PMNs from both healthy people and the recipient. In addition, lipids, identical to those that accumulate during PRBC storage, caused significant hypotension when infused into rats at similar concentrations found in stored PRBCs. We conclude that the observed transfusion-related acute lung injury reaction with significant hypotension may be the result of two independent events: the first is related to inherent host factors, in this case major surgery, and the second is the infusion of lipids that accumulate during the routine storage of PRBCs.

The effects of surgical fracture fixation on the systemic inflammatory response to major trauma

Early stabilization of major long bone fractures is beneficial in reducing the incidence of acute respiratory distress syndrome and multiple organ failure, both of which are caused by activation of the systemic inflammatory response. This activation results in tissue recruitment of and injury by circulating polymorphonuclear leukocytes. The reasons for clinical benefits of early fracture stabilization in major trauma are unknown. Published studies indicate that fracture surgery increases the posttraumatic inflammatory response. Major surgery to stabilize fractures carries a higher complication rate when performed on patients whose hypovolemic shock is not fully corrected. Thus, fracture care should be tailored to the patient, not dictated by the injured bone. Understanding the impact of fracture surgery on the systemic inflammatory response to major trauma is necessary to refine treatment and to apply it optimally to all patients.

Chemokines in acute respiratory distress syndrome

A characteristic feature of all inflammatory disorders is the excessive recruitment of leukocytes to the site of inflammation. The loss of control in trafficking these cells contributes to inflammatory diseases. Leukocyte recruitment is a well-orchestrated process that includes several protein families including the large cytokine subfamily of chemotactic cytokines, the chemokines. Chemokines and their receptors are involved in the pathogenesis of several diseases. Acute lung injury that clinically manifests as acute respiratory distress syndrome (ARDS) is caused by an uncontrolled systemic inflammatory response resulting from clinical events including major surgery, trauma, multiple transfusions, severe burns, pancreatitis, and sepsis. Systemic inflammatory response syndrome involves activation of alveolar macrophages and sequestered neutrophils in the lung. The clinical hallmarks of ARDS are severe hypoxemia, diffuse bilateral pulmonary infiltrates, and normal intracardiac filling pressures. The magnitude and duration of the inflammatory process may ultimately determine the outcome in patients with ARDS. Recent evidence shows that activated leukocytes and chemokines play a key role in the pathogenesis of ARDS. The expanding number of antagonists of chemokine receptors for inflammatory disorders may hold promise for new medicines to combat ARDS.

Prospective study of neutrophil chemokine responses in trauma patients at risk for pneumonia

Neutrophil hyperactivity contributes to organ failure, whereas hypofunction permits sepsis. The chemokine receptors CXCR1 and CXCR2 are central to polymorphonuclear neutrophil (PMN) function. We prospectively assessed CXCR function and expression in PMNs from trauma patients at high risk for pneumonia and their matched volunteer controls. CXCR2-specific calcium flux and chemotaxis were desensitized by injury, returning toward normal after 1 week. CXCR1 responses were relatively maintained. These defects appeared to be caused by preferential suppression of CXCR2 surface expression. To evaluate potential mechanisms of in vivo chemokine receptor regulation further we studied cross-desensitization of chemokine receptors in normal PMNs. Susceptibility to desensitization was in the order CXCR2 > CXCR1 > formyl peptide or C5a receptors. Trauma desensitizes CXC receptors, with CXCR2 being especially vulnerable. Desensitization is most marked immediately postinjury, generally resolving by Day 7. High-affinity chemoattractant receptors responsible for PMN chemotaxis from bloodstream to tissue appear to be regulated by injury. Receptors for end-target chemoattractants regulate CXCR1 and CXCR2 but resist suppression themselves and respond normally after injury. CXCR2 desensitization occurs before pneumonia, which developed in 44% of these patients. Suppression of high-affinity PMN receptors, like CXCR2, may predispose to pneumonia after trauma or other inflammatory conditions that lead to systemic inflammatory response syndrome.