Response of circulating immune cells to major gunshot injury, haemorrhage, and acute surgery

Host responses to concurrent combined injuries in non-human primates

Background

Multi-organ failure (MOF) following trauma remains a significant cause of morbidity and mortality related to a poorly understood abnormal inflammatory response. We characterized the inflammatory response in a non-human primate soft tissue injury and closed abdomen hemorrhage and sepsis model developed to assess realistic injury patterns and induce MOF.

Methods

Adult male Mauritan Cynomolgus Macaques underwent laparoscopy to create a cecal perforation and non-anatomic liver resection along with a full-thickness flank soft tissue injury. Treatment consisted of a pre-hospital phase followed by a hospital phase after 120 minutes. Blood counts, chemistries, and cytokines/chemokines were measured throughout the study. Lung tissue inflammation/apoptosis was confirmed by mRNA quantitative real-time PCR (qPCR), H&E, myeloperoxidase (MPO) and TUNEL staining was performed comparing age-matched uninjured controls to experimental animals.

Results

Twenty-one animals underwent the protocol. Mean percent hepatectomy was 64.4 ± 5.6; percent blood loss was 69.0 ± 12.1. Clinical evidence of end-organ damage was reflected by a significant elevation in creatinine (1.1 ± 0.03 vs. 1.9 ± 0.4, p=0.026). Significant increases in systemic levels of IL-10, IL-1ra, IL-6, G-CSF, and MCP-1 occurred (11-2986-fold) by 240 minutes. Excessive pulmonary inflammation was evidenced by alveolar edema, congestion, and wall thickening (H&E staining). Concordantly, amplified accumulation of MPO leukocytes and significant pulmonary inflammation and pneumocyte apoptosis (TUNEL) was confirmed using qRT-PCR.

Conclusion

We created a clinically relevant large animal multi-trauma model using laparoscopy that resulted in a significant systemic inflammatory response and MOF. With this model, we anticipate studying systemic inflammation and testing innovative therapeutic options.

An Evolving Uncontrolled Hemorrhage Model Using Cynomolgus Macaques

BACKGROUND

Trauma-induced hemorrhagic shock produces hemodynamic changes that often result in a systemic inflammatory response that can lead to multiple organ failure and death. In this prospective study, the pathophysiology of a nonhuman primate uncontrolled hemorrhagic shock model is evaluated with the goal of creating an acute systemic inflammatory syndrome response and a reproducible hemorrhage.

METHODS

Nonhuman primates were divided into 2 groups. A laparoscopic left hepatectomy was performed in groups A and B, 60% and 80%, respectively, resulting in uncontrolled hemorrhage. Resuscitation during the prehospital phase lasted 120 min and included a 0.9% saline bolus at 20 mL/kg. The hospital phase involved active warming, laparotomy, hepatorrhaphy for hemostasis, and transfusion of packed red blood cells (10 mL/kg). The animals were recovered and observed over a 14-day survival period with subsequent necropsy for histopathology.

RESULTS

Baseline demographics and clinical parameters of the two groups were similar. Group A (n = 7) underwent a 57.7% ± 2.4% left hepatectomy with a 33.9% ± 4.0% blood loss and 57% survival. Group B (n = 4) underwent an 80.0% ± 6.0% left hepatectomy with 56.0% ± 3.2% blood loss and 75% survival. Group B had significantly lower hematocrit (P < 0.05) for all postinjury time points. Group A had significantly elevated creatinine on postoperative day 1. Nonsurvivors succumbed to an early death, averaging 36 h from the injury. Histopathologic evaluation of nonsurvivors demonstrated kidney tubular degeneration.

CONCLUSIONS

Nonhuman primates displayed the expected physiologic response to hemorrhagic shock due to liver trauma as well as systemic inflammatory response syndrome with resultant multiple organ dysfunction syndrome and either early death or subsequent recovery. Our next step is to establish a clinically applicable nonhuman primate polytrauma model, which reproduces the prolonged maladaptive immunologic reactivity and end-organ dysfunction consistent with multiple organ failure found in the critically injured patient.

Modeling acute traumatic injury

Acute traumatic injury is a complex disease that has remained a leading cause of death, which affects all ages in our society. Direct mechanical insult to tissues may result in physiological and immunologic disturbances brought about by blood loss, coagulopathy, as well as ischemia and reperfusion insults. This inappropriate response leads to an abnormal release of endogenous mediators of inflammation that synergistically contribute to the incidence of morbidity and mortality. This aberrant activation and suppression of the immune system follows a bimodal pattern, wherein activation of the innate immune responses is followed by an anti-inflammatory response with suppression of the adaptive immunity, which can subsequently lead secondary insults and multiple organ dysfunction. Traumatic injury rodent and swine models have been used to describe many of the underlying pathologic mechanisms, which have led to an improved understanding of the morbidity and mortality associated with critically ill trauma patients. The enigmatic immunopathology of the human immunologic response after severe trauma, however, has never more been apparent and there grows a need for a clinically relevant animal model, which mimics this immune physiology to enhance the care of the most severely injured. This has necessitated preclinical studies in a more closely related model system, the nonhuman primate. In this review article, we summarize animal models of trauma that have provided insight into the clinical response and understanding of cellular mechanisms involved in the onset and progression of ischemia-reperfusion injury as well as describe future treatment options using immunomodulation-based strategies.

Kinetics of the innate immune response after trauma: implications for the development of late onset sepsis

BACKGROUND

Severe trauma is characterized by a pronounced immunologic response with both proinflammatory and anti-inflammatory characteristics. The clinical course of trauma patients is often complicated by late-onset (>5 days) sepsis. However, the underlying mechanisms remain poorly defined. Here we studied the kinetics of systemic activation of neutrophils and monocytes following injury in trauma patients in the context of development of sepsis.

METHODS

Thirty-six severely injured patients were included and followed up for 10 days in the intensive care unit. Serial blood samples were taken daily and analyzed ex vivo for activation of PMNs (polymorphonuclear leukocytes, i.e., neutrophils) (expression MAC-1 [macrophage-1 antigen], CXCR-1 [CXC-chemokine receptor 1], FcγRII) and expression of human leukocyte antigen DR (HLA-DR) on monocytes. In addition, the functionality of PMNs was measured by activation of the respiratory burst and responsiveness for the innate immune stimulus N-formyl-methionyl-leucyl-phenylalanine (fMLF).

RESULTS

Ten of 36 patients developed septic shock, invariably 8 to 10 days after admission. CXCR-1 and fMLF-induced active FcγRII showed a gradual decrease in expression before clinical signs of septic shock. Patients who developed septic shock demonstrated a statistically significantly decreased fMLF-induced active FcγRII (P = 0.009) at initial presentation. An immediate decreased percentage of HLA-DR-positive monocytes could be contributed to an increased absolute number of HLA-DR-negative monocytes.

CONCLUSIONS

Phenotyping blood PMNs enables identification of the kinetics and magnitude of the initial systemic inflammatory response after injury. The decreased functionality of PMNs and monocytes reaches its minimum before the development of sepsis and could be an important contributing factor. This could support the early identification of patients at risk.

Severe gunshot injuries in a porcine model: impact on central markers of innate immunity

BACKGROUND

the mechanisms behind lipopolysaccharide (LPS) tolerance remain obscure. LPS signals through Toll-like receptor 4 (TLR4) and severe trauma/haemorrhage may influence binding and signalling through this receptor, e.g. by changing membrane expression or by releasing endogenous ligands like High Mobility Group Box 1 (HMGB1). The aim of this study was to examine these relations further in a porcine model with standardized trauma.

METHODS

nine anaesthetized pigs sustained one gunshot through the femur and one pistol shot through the upper abdomen. Blood was sampled before and 90 min after shooting. The samples were stimulated for 4 h with LPS 10 ng/ml or an equivalent amount of normal saline. The leucocyte response was evaluated by measuring the tumour necrosis factor-α (TNF-α) and CXC ligand 8 (CXCL8) in the supernatant. Flow cytometry was used to measure the surface expression of TLR4 on CD14+ monocytes. HMGB1 concentrations were measured in the plasma.

RESULTS

trauma and treatment caused a significant decline in the LPS-stimulated concentrations of TNF-α [4.53 ± 0.24 pg/ml (ln) at 0 min, 3.54 ± 0.35 pg/ml (ln) at 90 min, P=0.026], but did not modify the release of CXCL8. Monocyte TLR4 expression was unchanged. Plasma HMGB1 increased significantly [<0.92 vs. 3.02 ± 0.19 ng/ml (ln), P<0.001]. The concentrations of TNF-α and CXCL8 did not correlate with TLR4 expression or HMGB1 concentrations.

CONCLUSION

the results suggest that trauma-induced LPS tolerance is not primarily regulated by TLR4 expression on circulating CD14+ monocytes or by the release of HMGB1 from damaged tissues.

Capacity of glycine to modulate early inflammatory disturbances after serious gunshot injuries in the pig

OBJECTIVE

Perturbation of immune homeostasis is an important determinant for organ dysfunction following multiple injuries. The aim of this study was to investigate the ability of glycine to influence the immediate post-traumatic inflammatory environment and altered reactivity of circulating leucocytes.

MATERIAL AND METHODS

Twenty pigs were subjected to two standardized gunshots to the abdomen and thigh. Treatment was started immediately. The animals were randomized to receive either glycine 180 mg/kg i.v. over 30 min (n=10) or normal saline (n=10). Blood samples were drawn at baseline and 75 min after injury. In a follow-up study 12 pigs were exposed to an identical trauma. Blood was drawn at the same time-points and stimulated with lipopolysaccharide (LPS) or LPS plus glycine for 2 h in an ex vivo whole blood model.

RESULTS

Selected physiologic variables and organ injury did not differ between groups 75 min after trauma. Reactive oxygen species decreased to 82.7+/-5.5 % of baseline (p<0.05) in the glycine group (unaltered in the controls). Liver glutathione concentrations decreased in parallel in both groups. In vivo production of TNF-alpha and IL-1-beta increased to the same extent regardless of treatment. Trauma induced a strong LPS tolerance. In whole blood challenged with LPS, glycine inhibited cytokine synthesis, but only in samples drawn at baseline.

CONCLUSIONS

Post-traumatic infusion of glycine only modestly influenced the early post-traumatic inflammatory environment. Our ex vivo results confirm previous reports on the anti-inflammatory potential of glycine, but restricted to pre-trauma conditions.

Early time course of altered leukocyte response to lipopolysaccharide and peptidoglycan in porcine gunshot injury

BACKGROUND

Penetrating injuries are frequently combined with polybacterial soiling. Clearance of the microorganisms depends on the ability to activate immune responses, but post-traumatic hyporeactivity of immune cells is almost universal. The aim of this study was to map the early time course of this altered leukocyte reactivity, and to compare the reactions to subsequent Gram-positive or Gram-negative challenges.

METHODS

Twelve juvenile pigs sustained two standardized rounds, one through the right femur and one through the left upper abdomen. First aid treatment and acute surgery were started immediately. Blood samples were drawn before trauma and after 10, 30, 60, and 90 min, and thereafter stimulated in ex vivo whole blood for 3 h with lipopolysaccharide (LPS, 10 ng/ml), peptidoglycan (PepG, 1 microg/ml), or an equivalent amount of normal saline. The leukocyte response was evaluated by measurement of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, IL-6, IL-8, and IL-10 in the supernatant.

RESULTS

In the post-traumatic in vivo serum, the concentration of TNF-alpha increased steadily (significant after 60 min). A reduced ex vivo reaction to LPS was evident after 10 min, and was statistically significant after 30 min. The lowest levels were reached after 90 min. The ex vivo synthesis of TNF-alpha after stimulation with PepG remained unaltered. A similar development was seen for IL-6. IL-1 beta levels did not change, while IL-8 increased significantly only after 60 and 90 min.

CONCLUSIONS

Trauma almost instantaneously reprogrammed circulating leukocytes. As measured with TNF-alpha, a profound hyporeactivity to LPS, but not to PepG, was induced. In addition, no global down-regulation of leukocyte function was found after stimulation with LPS.

Activation of cytokine synthesis by systemic infusions of lipopolysaccharide and peptidoglycan in a porcine model in vivo and in vitro

BACKGROUND

The incidence of gram-positive and mixed bacterial infections in surgical patients has increased, and there has been an alarming rise in the number of drug-resistant bacteria. Peptidoglycan (PepG) is a cell wall component of gram-positive bacteria that stimulates inflammatory responses both ex vivo and in vivo. The systemic effects of PepG on inflammation have not been studied in a large animal model.

METHODS

Anesthetized pigs were subjected to 8-h continuous intravenous infusions of lipopolysaccharide (LPS) (4 mcg/kg/h), PepG (40 mcg/kg/h), LPS plus PepG, or saline. The concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-8, and IL-10 were measured in the plasma prior to infusion (time 0) and thereafter every second hour until the end of the experiments. Heparinized whole blood samples drawn at time 0 and after a 6-h infusion of LPS or PepG were incubated ex vivo with PepG (10 mcg/mL), LPS (10 ng/mL), or a combination of PepG and LPS to study the immunologic consequences of systemic inflammation. Concentrations of TNF-alpha, IL-8, and IL-1beta were measured in the supernatant liquids.

RESULTS

In vivo, there was transient upregulation of TNF-alpha after infusion of LPS, PepG, or the combination. Interleukin-6 and IL-8 were upregulated by LPS but not by PepG. In vitro studies of whole blood obtained at time 0 revealed a synergistic effect of LPS and PepG on the release of TNF-alpha. Incubation of whole blood obtained after 6 h of infusion of LPS or PepG revealed tolerance and cross-tolerance between the two bacterial components in the induction of TNF-alpha, IL-8, and IL-1beta.

CONCLUSIONS

Peptidoglycan is a potent inducer of TNF-alpha in this large animal model. Peptidoglycan and LPS synergized to increase the formation of the proinflammatory cytokine TNF-alpha. The study demonstrates for the first time the development of tolerance and cross-tolerance between LPS and PepG in a large animal model. These phenomena could be of importance for the signs and symptoms of sepsis.

Late phase TNF-alpha depression in natural orifice translumenal endoscopic surgery (NOTES) peritoneoscopy

BACKGROUND

Natural orifice translumenal endoscopic surgery (NOTES) allows access to the peritoneal cavity without skin incisions. Contamination of the peritoneal cavity by enteric contents may render NOTES more physiologically and immunologically invasive than previously thought. Measurement of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) is a validated method to quantify surgical stress. The physiologic and immunologic impact of NOTES is unknown.

METHODS

A total of 37 swine underwent abdominal exploration via transgastric NOTES peritoneoscopy, laparoscopy (LX), laparotomy (OPEN), or sham surgery (CONTROL) and were allowed to survive. TNF-alpha, IL-1beta, and IL-6 plasma levels were determined at the start and completion of surgery, and at 1 hour, 2 days, and 14 days postoperatively.

RESULTS

At surgical completion, OPEN animals demonstrated higher TNF-alpha levels than all groups. TNF-alpha levels were similar for all groups at 1 hour and 2 days. NOTES animals had significantly reduced plasma levels of TNF-alpha than all other groups on postoperative days 7 and 14. Controlling for baseline cytokine variability, analysis was repeated using normalized data, which confirmed significantly reduced TNF-alpha levels for NOTES compared with all groups at 14 days. Subset analysis excluding LX and OPEN complications revealed lower NOTES TNF-alpha levels at 7 and 14 days compared with all groups. IL-1beta and IL-6 levels were undetectable in 66.8% and 70.5% of samples, respectively, without significant trends.

CONCLUSIONS

Diagnostic NOTES peritoneoscopy demonstrated similar levels of systemic proinflammatory cytokine TNF-alpha compared with diagnostic laparoscopy and exploratory laparotomy in the immediate postoperative period despite gross intraperitoneal contamination. None of the surgical groups, however, produced a measurable, consistent trend in IL-1beta or IL-6. Consistently reduced levels of TNF-alpha in NOTES animals in the late postoperative period indicates an immunomodulatory effect of the NOTES surgical technique not present in laparoscopy or laparotomy.

Aberrant regulation of polymorphonuclear phagocyte responsiveness in multitrauma patients

A systemic inflammatory response often follows severe trauma. Priming (preactivation) of polymorphonuclear phagocytes (PMNs) is an essential first step in the processes that lead to damage caused by the systemic activation of innate immune response. Until recently, priming could only accurately be measured by functional assays, which require isolation of cells, thereby potentially inducing artificial activation. The aim of this study was to identify primed PMNs in response to trauma by using a whole blood analysis with a broad detection range. Twenty-two trauma patients were analyzed for PMN priming with novel developed antibodies recognizing priming epitopes by flow cytometric analysis. Expression of priming epitopes on PMNs was analyzed with respect to time, injury, and disease severity. Expression of priming epitopes in the circulation was compared with expression profiles of PMNs obtained from lung fluid. Fourteen healthy volunteers served as controls. Expression of priming epitopes on peripheral blood PMNs of injured patients was similar, as found in healthy controls, whereas highly primed cells were found in the lung fluid of injured patients (increase of >50 times as compared with peripheral blood cells). In fact, the responsiveness of PMNs toward the bacteria-derived stimulus N-formyl-methionyl-leucyl-phenylalanine was markedly decreased in trauma patients. Lack of expression of priming epitopes and the unresponsiveness to N-formyl-methionyl-leucyl-phenylalanine demonstrates the presence of partially refractory cells in the circulation of trauma patients. An increased expression of epitopes found on pulmonary PMNs suggests that optimal (pre)activation of these cells only occurs in the tissues.

Seven days’ around the clock exhaustive physical exertion combined with energy depletion and sleep deprivation primes circulating leukocytes

Both exhaustive physical exertion and starvation have been reported to induce depression of immune function. The aim of the present study was to investigate the inflammatory environment and state of activation and mediator-producing potential of circulating leukocytes during prolonged physical activity with concomitant energy and sleep deprivation. Eight well-trained males were studied during 7 days of semi-continuous physical activity. Sleep was restricted to about 1 h/24 h, energy intake to 1.5- 3.0 MJ/24 h. Blood was drawn at 07.00 A.M.: on days 0, 2, 4, and 7. Plasma levels of inflammation markers were measured. The response of circulating leukocytes to lipopolysaccharide (LPS; 1 microg mL(-1)), and the effect of added hydrocortisone (10 and 100 nmol L(-1)), were measured in the supernatant after 3 h of incubation in an ex vivo whole blood model. Activation of leukocytes steadily increased as measured by plasma matrix metalloproteinase-9, tumour necrosis factor-alpha, interleukin-1beta, and interleukin-6. Inhibitors of systemic inflammation were either unaltered (tissue inhibitor of matrix metalloproteinase-1) or elevated (plasma interleukin-1 receptor antagonist). Cortisol levels increased on days 2 and 4, but thereafter reverted to baseline values. The leukocytes responded to LPS activation with increasing release of inflammatory cytokines throughout the study period. The anti-inflammatory potency of hydrocortisone decreased. Prolonged multifactorial stress thus activated circulating immune cells and primed them for an increased response to a subsequent microbial challenge.