Patterns of cytokine release and evolution of remote organ dysfunction after bilateral femur fracture

Role of hemorrhage in the induction of systemic inflammation and remote organ damage: analysis of combined pseudo-fracture and hemorrhagic shock

This study was performed to analyze the role of hemorrhage-induced hypotension in the induction of systemic inflammation and remote organ dysfunction. Male C57/BL6 mice (6- to 10-week old and 20-30 g) were used. Animals were either subjected to pseudo-fracture [PF; standardized soft-tissue injury and injection of crushed bone, PF group: n = 9], or PF combined with hemorrhagic shock (HS + PF group: n = 6). Endpoint was 6 h. Systemic inflammation was assessed by IL-6 and IL-10 levels. Myeloperoxidase (MPO) and NF-κB activity in the lung and liver tissue were obtained to assess remote organ damage. The increases of systemic cytokines are similar for animals subjected to PF and PF + HS (IL-6: 189 pg/ml ± 32.5 vs. 160 pg/ml ± 5.3; IL-10: 60.3 pg/ml ± 15.8 vs. 88 pg/ml ± 32.4). Furthermore, the features (ALT; NF-κB) of liver injury are equally elevated in mice subjected to PF (76.9 U/L ± 4.5) and HS + PF (80 U/L ± 5.5). Lung injury, addressed by MPO activity was more severe in group HS + PF (2.95 ng/ml ± 0.32) than in group PF (1.21 ng/ml ± 0.2). Both PF and additional HS cause a systemic inflammatory response. In addition, hemorrhage seems to be associated with remote affects on the lung.

Models of lower extremity damage in mice: time course of organ damage and immune response

BACKGROUND

Post-traumatic inflammatory changes have been identified as major causes of altered organ function and failure. Both hemorrhage and soft tissue damage induce these inflammatory changes. Exposure to heterologous bone in animal models has recently been shown to mimic this inflammatory response in a stable and reproducible fashion. This follow-up study tests the hypothesis that inflammatory responses are comparable between a novel trauma model ("pseudofracture", PFx) and a bilateral femur fracture (BFF) model.

MATERIALS AND METHODS

In C57BL/6 mice, markers for remote organ dysfunction and inflammatory responses were compared in four groups (control/sham/BFF/PFx) at the time points 2, 4, and 6 h.

RESULTS

Hepatocellular damage in BFF and PFx was highly comparable in extent and evolution, as shown by similar levels of NFkappaB activation and plasma ALT. Pulmonary inflammatory responses were also comparably elevated in both trauma models as early as 2 h after trauma as measured by myeloperoxidase activity (MPO). Muscle damage was provoked in both BFF and PFx mice over the time course, although BFF induced significantly higher AST and CK levels. IL-6 levels were also similar with early and sustained increases over time in both trauma models.

CONCLUSIONS

Both BFF and PFx create similar reproducible inflammatory and remote organ responses. PFx will be a useful model to study longer term inflammatory effects that cannot be studied using BFF.

Injury induces localized airway increases in pro-inflammatory cytokines in humans and mice

BACKGROUND

Secretory immunoglobulin A (sIgA) increases in the airways of humans and mice after injury to protect against infection. The pro-inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 are linked molecularly to sIgA production and secretion and are required for sIgA increases in the airway after injury in a mouse model. We investigated the injury effect on airway and serum concentrations to determine the source of the cytokines involved in the airway IgA response.

METHODS

In the first experiment, TNF-α, IL-1β, and IL-6 concentrations in bronchoalveolar lavage (BAL) fluid and serum obtained from 11 ventilated trauma patients within 30 h of admission were compared with those in eight elective surgical patients. In the second experiment, male ICR mice received no injury (n = 7) or injury with sham celiotomy and neck incisions (n = 8) with sacrifice of all animals at 8 h for BAL fluid and serum cytokine measurements by enzyme-linked immunosorbent assay.

RESULTS

Injured patients had significantly higher BAL fluid and serum TNF-α, IL-1β, and IL-6 concentrations, with greater increases in the BAL fluid than in the serum. Injured mice had significantly increased BAL fluid concentrations of TNF-α, IL-1β, and IL-6 without significant changes in serum TNF-α or IL-1β. Serum IL-6 increased significantly.

CONCLUSIONS

Injury significantly increases human and mouse airway TNF-α, IL-1β, and IL-6. Increases are greater in the airway than in serum, implying a local rather than a systemic stress response to injury.

Proinflammatory cytokine surge after injury stimulates an airway immunoglobulin a increase

BACKGROUND

: Injury stimulates an innate airway IgA response in severely injured patients, which also occurs in mice. Tumor necrosis factor (TNF)-α and interleukin (IL)-1β stimulate the production of polymeric immunoglobulin receptor, the protein required to transport immunoglobulin A (IgA) to mucosal surfaces. Blockade of TNF-α and IL-1β eliminates the airway IgA response to injury. IL-6 stimulates differentiation of B cells into IgA-secreting plasma cells at mucosal sites. We investigated the local and systemic kinetics of TNF-α, IL-1β, and IL-6 after injury in mice. We also hypothesized that injection of exogenous TNF-α, IL-1β, and IL-6 would replicate the airway IgA response to injury.

METHODS

: Experiment 1: male Institute of Cancer Research mice were randomized to uninjured controls (n = 8) or to surgical stress with laparotomy and neck incisions, with killing at 1, 2, 3, 5, or 8 hours after injury (n = 8/group). Bronchoalveolar lavage (BAL) and serum levels of TNF-α, IL-1β, and IL-6 were analyzed by enzyme-linked immunosorbent assay. Experiment 2: male Institute of Cancer Research mice were randomized to uninjured controls (n = 6), injury (surgical stress that was similar to experiment 1 except the peritoneum was left intact, n = 6), or cytokine injection with intraperitoneal injection of recombinant TNF-α, IL-1β, and IL-6. Animals were killed at 2 hours after injury, and nasal airway lavage and BAL IgA were analyzed by enzyme-linked immunosorbent assay.

RESULTS

: Experiment 1: BAL TNF-α, IL-1β, and IL-6 levels increased in bimodal pattern after injury at 3 hours and 8 hours versus controls (p < 0.05). Serum IL-6 did not increase at 3 hours, but did show a significant increase by 5 hours versus control (p < 0.05). Serum levels of TNF-α and IL-1β did not change. Experiment 2: both Injury and combination TNF-α, IL-1β, and IL-6 cytokine injection significantly increased IgA levels in airway lavage (BAL + nasal airway lavage) compared with control (p < 0.01 for both).

CONCLUSIONS

: Airway levels of TNF-α, IL-1β, and IL-6 increase in a bimodal pattern after injury with peaks at 3 hours and 8 hours, which do not correspond to serum changes. The peak at 8 hours is consistent with the known increase in airway IgA after injury. Intraperitoneal injection of a combination exogenous TNF-α, IL-1β, and IL-6 replicates the airway IgA increase after injury. This effect is not seen with individual cytokine injections.

Polymorphonuclear cell priming associated with NF-kB activation in patients with severe injury is partially dependent on macrophage migration inhibitory factor

BACKGROUND

Severe trauma may induce alternations of cytokine response and polymorphonuclear cell (PMN) activity in patients. This study investigated the correlation of plasma migration inhibitory factor (MIF) level and PMN activation after severe injury, and their relationship with clinical outcomes.

STUDY DESIGN

A prospective observational study was performed at the emergency department and intensive care unit of a university hospital. Thirty-two severe blunt trauma patients (Injury Severity Score greater than 16) with systemic inflammatory response syndrome (SIRS) were enrolled. Age- and gender-matched healthy persons were the controls. Patient blood samples were obtained within 24 hours of and at 72 hours after injury. PMNs were isolated and measured for NF-kBp65 translocation and respiratory burst. Plasma MIF, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8, and IL-10 concentrations were measured. Control PMNs were incubated with patient plasma preincubated with anti-MIF antibody or anti-IL-6 antibody; cytokine blockade effects were evaluated.

RESULTS

Twelve patients developed organ failure. Compared with patients without organ failure, patients with organ failure had lower blood pressure and a higher base deficit on admission, higher NF-kBp65 translocation and respiratory burst of PMNs, and higher plasma MIF (968 ± 246 pg/mL vs 564 ± 299 pg/mL) and IL-6 (202 ± 91 pg/mL vs 119 ± 84 pg/mL) levels within 24 hours after injury. Plasma MIF had significant positive correlation with NF-kB translocation of PMNs within 24 hours of incurring trauma (R = 0.668). The presence of anti-MIF antibody in patients' plasma obtained within 24 hours, but not at 72 hours, after injury could significantly partially block the NF-kBp65 translocation and respiratory activity of PMNs in the controls.

CONCLUSIONS

An early increase of plasma MIF associates with NF-kB translocation and respiratory burst in PMNs of severe trauma patients and correlates with higher morbidity. MIF is one of the important factors responsible for early PMN activation and may provide a target of immunomodulation after injury.

Is damage control orthopedics essential for the management of bilateral femoral fractures associated or complicated with shock? An animal study

BACKGROUND

The maximum score of a single anatomic system, the Injury Severity Score, may not reflect the overall damage inflicted by bilateral femoral fractures and justify the strategy of damage control orthopedics (DCO). It is necessary to investigate effects of various therapeutic procedures on such fractures with or without shock to facilitate correct decision making on DCO.

METHODS

A model of bilateral femoral fractures was made in 36 of 48 male New Zealand White rabbits. A model of bilateral femoral shaft fractures associated with shock was made. After resuscitation, a reamed intramedullary nailing fixation was performed in the first group (IM group), and an external fixation device applied in the second group (EF group), and the fractures in the third group (control group) were supported with splints only. They were divided into four groups: shock with IM nailing (shock-IM), shock with external fixation (shock-EF), shock with conservative method (shock-Cons), and intramedullary nailing without shock (nonshock-IM). Vital signs and inflammatory reactions were recorded. Thirty-six hours after the therapeutic procedures in four groups, the animals were killed for histologic evaluation.

RESULTS

The changes of vital signs were most significant in shock-IM group (p < 0.05). The exaggerated levels of interleukin-6, Interleukin-10, and tumor necrosis factor alpha concentrations demonstrated a significant difference between all the groups-shock-IM and other groups (p < 0.05). As to histologic appearances, the statistical difference varies from organ to organ. There is highly significant difference when the IM group is compared with the other two groups as far as lungs are concerned. As to the liver, there is only significant difference between the IM group and the control group. In terms of kidney and heart, there is no significant difference cross the groups. As to histologic appearances, there is highly significant difference in lungs between shock-IM group and other three groups. There is significant difference in liver between the shock-IM group and the shock-Cons group (p < 0.05). Kidneys and heart were less affected cross the groups.

CONCLUSIONS

In this study, an early reamed intramedullary nailing fixation procedure resulted in more adverse effects on system stress, inflammatory response, and multiple organs. The injuries also cause histologic damages to lungs and liver. Therefore, early reamed intramedullary nailing fixation may pose a potential risk of developing complications and adopting the DCO strategy may be more preferable. Shock and IM combined cause most severe damages, followed by IM without shock, shock plus EF, and shock plus conservative procedure in that order. If IM must be used for some reasons, it is desirable be delayed until shock has been fully controlled and vasculorespiratory stability restored.

An animal model for open femur fracture and osteomyelitis--Part II: Immunomodulation with systemic IL-12

Infection resulting from open fracture is a common problem in orthopedics. The purpose of this project was to study the effect of Interleukin-12 (IL-12) systemic therapy on a previously established open fracture model. One hundred seven male Sprague-Dawley rats were assigned to five groups: (1) normal (baseline), (2) control (controlled for anesthesia), (3) fracture, (4) staph, and (5) staph and IL-12 (SIL). Each group was divided into four time periods: 6, 10, 14, and 21 days after injury and fixation. The operative groups had a standardized femur fracture and fixation using a Kirschner wire as an intramedullary device. The two infection groups (staph and SIL) were inoculated with Staphylococcus aureus following fracture and fixed with an identical technique. The SIL group was treated with systemic IL-12 for a total of 10 doses over 10 days. Significantly decreased serum IL-12 levels were noted at day 10 in the operative groups compared to the normal and control groups. The SIL group showed significantly higher macrophage activation levels and total platelet counts at day 21 compared to all the other groups. The overall infection rate was not changed by IL-12 supplementation; however, bacterial qualitative growth scores were significantly lower in the SIL group at day 10, which corresponded to the lowest level of systemic IL-12 in the fracture group.

Systems biology and inflammation

Inflammation is a complex, multiscale biological response to threats - both internal and external - to the body, which is also required for proper healing of injured tissue. In turn, damaged or dysfunctional tissue stimulates further inflammation. Despite continued advances in characterizing the cellular and molecular processes involved in the interactions between inflammation and tissue damage, there exists a significant gap between the knowledge of mechanistic pathophysiology and the development of effective therapies for various inflammatory conditions. We have suggested the concept of translational systems biology, defined as a focused application of computational modeling and engineering principles to pathophysiology primarily in order to revise clinical practice. This chapter reviews the existing, translational applications of computational simulations and related approaches as applied to inflammation.

Local exposure of bone components to injured soft tissue induces Toll-like receptor 4-dependent systemic inflammation with acute lung injury

Remote and systemic inflammatory responses after long bone fractures have been well described, but the mechanisms underlying these changes remain unexplained. We hypothesized that bone components locally exposed to injured soft tissue are capable of inducing a systemic inflammatory response associated with acute lung injury, and that this inflammatory cascade requires Toll-like receptor 4 (TLR-4) signaling. Accordingly, male C3H/HeOuJ (TLR-4-competent) and C3H/HeJ (TLR-4-mutant) mice were injected with various bone components (bone marrow cells, bone marrow supernatant, and bone suspension, respectively) in bilaterally injured thigh muscles and euthanized after 6 h. Serum TNF-alpha, IL-6, and IL-10 levels, and pulmonary myeloperoxidase activity was measured using specific enzyme-linked immunosorbent assay kits. Pulmonary permeability changes were assessed with bronchoalveolar lavage. Local exposure of bone components to injured soft tissue induced systemic inflammation and acute lung injury in TLR-4-competent, but not in TLR-4-mutant, animals. These findings suggest that bone components contribute to systemic inflammation and acute lung injury after long bone fractures via TLR-4 signaling and support the notion of a central role for TLR-4 in sensing tissue damage.

The role of estrogen and receptor agonists in maintaining organ function after trauma-hemorrhage

Sex is increasingly recognized as a major factor in the outcome of patients who have trauma and sepsis. Moreover, sex steroids influence chemokine/adhesion molecule expression and neutrophil accumulation. Heat shock proteins, heat shock factor 1, and peroxisome proliferator-activated receptor [gamma] coactivator 1 are regulated by the estrogen receptors and consequently contribute to organ protection after trauma-hemorrhage. Additionally, sex steroids regulate inflammatory cytokines, leading to increased morbidity and mortality. This article deals with trauma-hemorrhage and examines the following: 1) the evidence for sex differences; 2) the mechanisms by which sex hormones affect organ protection; 3) the tissue-specific effect of sex hormone receptors; and 4) the effect of genomic and nongenomic (i.e. membrane-initiated steroid signaling) pathways of sex hormones after trauma. The available information indicates that sex steroids modulate cardiovascular responses after trauma. Thus, alteration or modulation of the prevailing hormone milieu at the time of injury seems to be a novel therapeutic option for improving outcome after injury

Invited review: deterioration of the immune system after trauma: signals and cellular mechanisms

Multiple trauma leads to a deterioration of the immune system. On the one hand, hyperinflammation mediates remote organ damage and may lead to multi-organ failure. On the other hand, immunosuppression develops and promotes an enhanced risk to acquire infectious complications after trauma. The mechanisms that underlie these opposing consequences of trauma are not yet completely understood. There is increasing evidence that endogenous danger signals that derive from destroyed tissues play a role in trauma-induced immune dysfunction. Here, we give an overview on the common animal models that are used to investigate trauma-induced pathology, potential signals and cellular mechanisms that support the imbalance between inflammation and counter-regulation after trauma.

IL-10 deficiency augments acute lung but not liver injury in hemorrhagic shock

In hemorrhagic shock and trauma, patients are prone to develop systemic inflammation with remote organ dysfunction, which is thought to be caused by pro-inflammatory mediators. This study investigates the role of the immuno-modulatory cytokine IL-10 in the development of organ dysfunction following hemorrhagic shock. Male C57/BL6 and IL-10 KO mice were subjected to volume controlled hemorrhagic shock for 3h followed by resuscitation. Animals were either sacrificed 3 or 24h after resuscitation. To assess systemic inflammation, serum IL-6, IL-10, KC, and MCP-1 concentrations were measured with the Luminex multiplexing platform; acute lung injury (ALI) was assessed by pulmonary myeloperoxidase (MPO) activity and lung histology and acute liver injury was assessed by hepatic MPO activity, hepatic IL-6 levels, and serum ALT levels. There was a trend towards increased IL-6 and KC serum levels 3h after resuscitation in IL-10 KO as compared to C57/BL6 mice; however this did not reach statistical significance. Serum MCP-1 levels were significantly increased in IL-10 KO mice 3 and 24 h following resuscitation as compared to C57/BL6 mice. In IL-10 KO mice, pulmonary MPO activity was significantly increased 3 h following resuscitation and after 24 h histological signs of acute lung injury were more apparent than in C57/BL6 mice. In contrast, no significant differences in any liver parameters were detected between IL-10 KO and C57/BL6 mice. Our data indicate that an endogenous IL-10 deficiency augments acute lung but not liver injury following hemorrhagic shock.

Estrogen: a novel therapeutic adjunct for the treatment of trauma-hemorrhage-induced immunological alterations

Trauma-hemorrhage leads to prolonged immune suppression, sepsis, and multiple organ failure. The condition affects all compartments of the immune system, and extensive studies have been carried out elucidating the immunological events following trauma-hemorrhage. The immune alteration observed following trauma-hemorrhage is gender dependent in both animal models and humans, though some studies in humans are contradictory. Within 30 min after trauma-hemorrhage, splenic and peritoneal macrophages, as well as T-cell function, are depressed in male animals, but not in proestrus females. Studies have also shown that the mortality [corrected] rate and the induction of subsequent sepsis following trauma-hemorrhage are significantly higher in males and ovariectomized females compared with proestrus females. These and other investigations show that sex hormones form the basis of this gender dichotomy, and administration of estrogen can ameliorate the immune depression and increase the survival rate after trauma-hemorrhage. This review specifically elaborates the studies carried out thus far demonstrating immunological alteration after trauma-hemorrhage and its modulation by estrogen. Also, estrogen was shown to produce its salutary effects through nuclear as well as extranuclear receptors. Estrogen rapidly activates several protein kinases and phosphatases, as well as the release of calcium in different cell types. The results of the studies exemplify the promise of estrogen as a therapeutic adjunct in treating adverse pathophysiological conditions following trauma-hemorrhage.