Neutrophil apoptosis is delayed by trauma patients' plasma via a mechanism involving proinflammatory phospholipids and protein kinase C

The impact of neutrophil extracellular traps on deep venous thrombosis in patients with traumatic fractures

BACKGROUND

Deep venous thrombosis (DVT) is the most common complication in patients with traumatic fractures. The neutrophil extracellular traps (NETs) can promote thrombus formation. In this prospective study, we investigated the role of NETs in thrombosis in patients with traumatic fractures to evaluate whether the biomarkers of NETs can be used to help predict the risk of thrombosis.

METHODS

Traumatic fracture patients were enrolled in this prospective observational cohort study. Healthy controls (Control); patients with lower extremity fractures who neither present with nor develop DVT (Trauma non-DVT); patients with lower extremity fractures who do not present with DVT but do develop DVT (Trauma DVT); and patients with lower extremity fractures who present with DVT (DVT) were included. NETs biomarker levels of Citrullinated Histone H3 (H3Cit), cell-free DNA (cfDNA) and nucleosomes in the plasma were determined. The D-dimer and fibrin(-ogen) degradation products (FDP) level in plasma was measured. Statistical analysis of the test results was performed to assess changes in NETs biomarker levels during thrombosis in patients with traumatic fractures.

RESULTS

The H3Cit levels in the DVT group were significantly greater than in the Trauma non-DVT group and Trauma DVT group (1.88(1.11, 3.35) ng/ml Vs 0.38(0.10, 1.17) ng/ml, P ≤ 0.05). The level of cfDNA was significantly greater in patients with traumatic fractures and was higher after thrombosis than before. The levels of D-dimer in the DVT, Trauma DVT, and Trauma non-DVT groups were significantly greater than in the Control group (5.11(3.97, 8.11) mg/l; 6.12(2.59, 18.49) mg/l; 2.99(0.99, 9.02) mg/l Vs 0.18(0.08,0.24) mg/l, P < 0.05). The distribution of FDP levels in each group was similar to that of D-dimer. Data are presented as medians (25th percentile, 75th percentile).

CONCLUSIONS

NETs released by neutrophils are involved in the formation of DVTs in patients with traumatic fractures. H3Cit and cfDNA can assist the diagnosis of DVT in patients with traumatic fractures.

Splenectomy is associated with altered leukocyte kinetics after severe trauma

BACKGROUND

Inadequate activation of the innate immune system after trauma can lead to severe complications such as Acute Respiratory Distress Syndrome and Multiple Organ Dysfunction Syndrome. The spleen is thought to modulate the cellular immune system. Furthermore, splenectomy is associated with improved outcome in severely injured trauma patients. We hypothesized that a splenectomy alters the cellular immune response in polytrauma.

METHODS

All adult patients with an ISS ≥ 16 and suffering from splenic or hepatic injuries were selected from our prospective trauma database. Absolute leukocyte numbers in peripheral blood were measured. White blood cell kinetics during the first 14 days were compared between splenectomized patients, patients treated surgically for liver trauma and nonoperatively treated individuals.

RESULTS

A total of 129 patients with a mean ISS of 29 were included. Admission characteristics and leukocyte numbers were similar in all groups, except for slightly impaired hemodynamic status in patients with operatively treated liver injuries. On admission, leukocytosis occurred in all groups. During the first 24 h, leukopenia developed gradually, although significantly faster in the operatively treated patients. Thereafter, leukocyte levels normalized in all nonoperatively treated cases whereas leukocytosis persisted in operatively treated patients. This effect was significantly more prominent in splenectomized patients than all other conditions.

CONCLUSIONS

This study demonstrates that surgery for intra-abdominal injuries is associated with an early drop in leucocyte numbers in peripheral blood. Moreover, splenectomy in severely injured patients is associated with an altered cellular immune response reflected by a persistent state of prominent leukocytosis after trauma.

Multiple Phenotypic Changes Define Neutrophil Priming

Exposure to pro-inflammatory cytokines, chemokines, mitochondrial contents, and bacterial and viral products induces neutrophils to transition from a basal state into a primed one, which is currently defined as an enhanced response to activating stimuli. Although, typically associated with enhanced generation of reactive oxygen species (ROS) by the NADPH oxidase, primed neutrophils show enhanced responsiveness of exocytosis, NET formation, and chemotaxis. Phenotypic changes associated with priming also include activation of a subset of functions, including adhesion, transcription, metabolism, and rate of apoptosis. This review summarizes the breadth of phenotypic changes associated with priming and reviews current knowledge of the molecular mechanisms behind those changes. We conclude that the current definition of priming is too restrictive. Priming represents a combination of enhanced responsiveness and activated functions that regulate both adaptive and innate immune responses.

PRBC-derived plasma induces non-muscle myosin type IIA-mediated neutrophil migration and morphologic change

Context:

Neutrophils are the primary effector cells in the pathogenesis of transfusion-related acute lung injury or multiple organ failure after blood transfusion.

Objective:

We aimed to investigate the effect of fresh (1 day preparation) and aged (42 day preparation) PRBC-derived plasma on neutrophil morphology, migration and phagocytosis.

Materials and methods:

We evaluated the production of reactive oxygen species (ROS) and the expression of non-muscle myosin heavy chain IIA (MYH9) in neutrophils treated with PRBC-derived plasma. We used western blots and antibody arrays to evaluate changes in signal transduction pathways in plasma-treated neutrophils.

Results:

Aged PRBC-derived plasma elicited a stronger oxidative burst in neutrophils when compared with fresh PRBC-derived plasma (p < 0.05). Antibody arrays showed increased phosphorylation of NF-ĸB proteins (p105, p50 and Ikk) in aged PRBC-derived plasma-treated neutrophils. The expression of non-muscle myosin IIA (MYH9), a cytoskeleton protein involved in immune cell migration and morphological change, was also significantly upregulated in neutrophils treated with aged PRBC-derived plasma compared to fresh plasma (p < 0.05). Pretreatment of neutrophils with blebbistatin (a specific type II myosin inhibitor), ascorbic acid (an antioxidant), or staurosporine (a protein tyrosine kinase inhibitor), effectively abrogated the morphological changes, neutrophil migration, and phagocytosis induced by aged PRBC-derived plasma.

Conclusion:

Upregulation of MYH9 in neutrophils treated with aged PRBC-derived plasma and abrogation of neutrophil migration in blebbistatin-treated neutrophils suggested a functional role of MYH9 in the directional migration of immune cells. Our data help elucidate the cellular and molecular mechanisms of transfusion-related injury.

Isolated blunt chest injury leads to transient activation of circulating neutrophils

Introduction

The acute respiratory distress syndrome (ARDS) is a severe and frequently seen complication in multi-trauma patients. ARDS is caused by an excessive innate immune response with a clear role for neutrophils. As ARDS is more frequently seen in trauma patients with chest injury, we investigated the influence of chest injury on the systemic neutrophil response and the development of ARDS.

Materials and methods

Thirteen patients with isolated blunt chest injury [abbreviated injury score (AIS) 2–5] were included. To avoid systemic inflammation caused by tissue damage outside the thorax, injuries to other regions than the chest did not exceed an AIS of 2. At 3, 9 and 24 h after injury, the expression of circulating activating molecules on neutrophils and levels of circulating interleukine (IL)-6 were determined. Blood samples from eight healthy volunteers were used as control.

Results

Blunt chest injury resulted in the activation of circulating neutrophils, as characterized by a decreased expression of l-selectin (CD62L), CXCR2 (CD182b) and C5aR (CD88) compared to control (p < 0.05). Expression of l-selectin, CXCR2 and C5aR was partially restored at 24 h after injury. In addition, the mean expression of FcγRIII (CD16) dropped (p < 0.001), indicating the recruitment of young neutrophils into the circulation. IL-6 levels increased to a maximum mean concentration of 86 ± 31 pg/ml at 24 h postinjury. None of the patients developed ARDS.

Conclusion

Blunt chest trauma caused a systemic inflammatory reaction with transient activation of neutrophils and mobilization of young neutrophils into the circulation. Isolated chest injury, however, was not abundant enough to cause ARDS, so a second hit appears crucial.

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

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

Immunologic responses to critical injury and sepsis

Almost 2 million patients are admitted to hospitals in the United States each year for treatment of traumatic injuries, and these patients are at increased risk of late infections and complications of systemic inflammation as a result of injury. Host response to injury involves a general activation of multiple systems in defending the organism from hemorrhagic or infectious death. Clinicians have the capability to support the critically injured through their traumatic insult with surgery and improved critical care, but the inflammatory response generated by such injuries creates new challenges in the management of these patients. It has long been known that local tissue injury induces systemic changes in the traumatized patient that are often maladaptive. This article reviews the effects of injury on the function of immune system cells and highlights some of the clinical sequelae of this deranged inflammatory-immune interaction.

Clinically relevant hypertonicity prevents stored blood- and lipid-mediated delayed neutrophil apoptosis independent of p38 MAPK or caspase-3 activation

BACKGROUND

Delayed apoptosis of primed neutrophils (PMNs) may facilitate PMN-mediated tissue injury leading to postinjury multiple organ failure. Aged (42-day-old) stored red blood cells (RBC42) delay PMN apoptosis through proinflammatory phospholipids such as platelet-activating factor (PAF) and lyso-phosphatidylcholine (LPC). Hypertonic saline (HTS) attenuates PMN cytotoxic functions. We hypothesized that clinically relevant HTS would provoke PMN apoptosis, as well as prevent stored blood- and lipid-mediated delayed PMN apoptosis through activation of p38 mitogen-activated protein kinase (MAPK) and caspase-3.

METHODS

PMNs harvested from healthy volunteers were incubated (5% CO(2), 37 degrees C, 24 hr) with RBC42 plasma, PAF (20 microM), or LPC (4.5 microM), with or without the p38 MAPK inhibitor SB 203580, the caspase-3 inhibitor zDEVD-fmk (10 micromol/L) or the pan-caspase inhibitor zVAD-fmk (20 micromol/L). Duplicate samples were preincubated in HTS (Na [180 mM]). Apoptotic index (% PMNs undergoing apoptosis) was assessed morphologically. p38 MAPK activation was assessed by Western blotting. Caspase-3 activity was measured colorimetrically.

RESULTS

PAF, LPC, and RBC42 plasma delayed apoptosis; HTS increased apoptosis compared with controls. HTS prevented PAF, LPC, and RBC42-delayed apoptosis. p38 MAPK was not activated by HTS; its inhibition had no effect on the actions of HTS. Caspase inhibition attenuated the ability of HTS to increase apoptosis, but it did not affect the ability of HTS to restore healthy PMN apoptosis in the presence of RBC42.

CONCLUSION

HTS increases PMN apoptosis and prevents stored blood- and lipid-mediated delayed PMN apoptosis. HTS may activate caspase-3, but alternative signaling pathways appear to be involved in modulating the effects of lipids on PMN apoptosis.