Jean Francois Pittet

Critical role of activated protein C in early coagulopathy and later organ failure, infection and death in trauma patients.

Background: Recent studies have identified an acute traumatic coagulopathy that is present on admission to the hospital and is independent of iatrogenic causes. We have previously reported that this coagulopathy is due to the association of severe injury and shock and is characterized by a decrease in plasma protein C (PC) levels. Whether this early coagulopathy and later propensity to infection, multiple organ failure and mortality are associated with the activation of PC pathway has not been demonstrated and constitutes the aim of this study. Methods and Findings: This was a prospective cohort study of 203 major trauma patients. Serial blood samples were drawn on arrival in the emergency department, and at 6, 12, and 24 hours after admission to the hospital. PT, PTT, Va, VIIIa, PC aPC t-PA, and D-dimer levels were assayed. Comprehensive injury, resuscitation, and outcome data were prospectively collected. A total of 203 patients were enrolled. Patients with tissue hypoperfusion and severe traumatic injury showed a strong activation of the PC which was associated with a coagulopathy characterized by inactivation of the coagulation factors V and VIII and a derepression of the fibrinolysis with high plasma levels of plasminogen activator and high D-dimers. Elevated plasma levels of activated PC were significantly associated with increased mortality, organ injury, increased blood transfusion requirements, and reduced ICU ventilator-free days. Finally early depletion of PC after trauma is associated with a propensity to posttraumatic ventilator-associated pneumonia. Conclusions: Acute traumatic coagulopathy occurs in the presence of tissue hypoperfusion and severe traumatic injury and is mediated by activation of the PC pathway. Higher plasma levels of aPC upon admission are predictive of poor clinical outcomes after major trauma. After activation, patients who fail to recover physiologic plasma values of PC have an increased propensity to later nosocomial lung infection.

ANGPT2 Genetic Variant Is Associated with Trauma-associated Acute Lung Injury and Altered Plasma Angiopoietin-2 Isoform Ratio

RATIONALEnAcute lung injury (ALI) acts as a complex genetic trait, yet its genetic risk factors remain incompletely understood. Large-scale genotyping has not previously been reported for ALI.nnnOBJECTIVESnTo identify ALI risk variants after major trauma using a large-scale candidate gene approach.nnnMETHODSnWe performed a two-stage genetic association study. We derived findings in an African American cohort (n = 222) using a cardiopulmonary disease-centric 50K single nucleotide polymorphism (SNP) array. Genotype and haplotype distributions were compared between subjects with ALI and without ALI, with adjustment for clinical factors. Top performing SNPs (P < 10(-4)) were tested in a multicenter European American trauma-associated ALI case-control population (n = 600 ALI; n = 2,266 population-based control subjects) for replication. The ALI-associated genomic region was sequenced, analyzed for in silico prediction of function, and plasma was assayed by ELISA and immunoblot.nnnMEASUREMENTS AND MAIN RESULTSnFive SNPs demonstrated a significant association with ALI after adjustment for covariates in Stage I. Two SNPs in ANGPT2 (rs1868554 and rs2442598) replicated their significant association with ALI in Stage II. rs1868554 was robust to multiple comparison correction: odds ratio 1.22 (1.06-1.40), P = 0.0047. Resequencing identified predicted novel splice sites in linkage disequilibrium with rs1868554, and immunoblots showed higher proportion of variant angiopoietin-2 (ANG2) isoform associated with rs1868554T (0.81 vs. 0.48; P = 0.038).nnnCONCLUSIONSnAn ANGPT2 region is associated with both ALI and variation in plasma angiopoietin-2 isoforms. Characterization of the variant isoform and its genetic regulation may yield important insights about ALI pathogenesis and susceptibility.

The lectin-like domain of tumor necrosis factor improves lung function after rat lung transplantation—Potential role for a reduction in reactive oxygen species generation

Objective:To test the hypothesis that the lectin-like domain of tumor necrosis factor, mimicked by the TIP peptide, can improve lung function after unilateral orthotopic lung isotransplantation. Because of a lack of a specific treatment for ischemia reperfusion-mediated lung injury, accompanied by a disrupted barrier integrity and a dysfunctional alveolar liquid clearance, alternative therapies restoring these parameters after lung transplantation are required. Design:Prospective, randomized laboratory investigation. Setting:University-affiliated laboratory. Subjects:Adult female rats. Interventions:Tuberoinfundibular peptide, mimicking the lectin-like domain of tumor necrosis factor, mutant TIP peptide, N,N′-diacetylchitobiose/TIP peptide, and amiloride/TIP peptide were instilled intratracheally in the left lung immediately before the isotransplantation was performed. An additional group received an intravenous TIP peptide treatment, 1.5 mins before transplantation. Studies using isolated rat type II alveolar epithelial cell monolayers and ovine pulmonary endothelial cells were also performed. Measurements and Main Results:Intratracheal pretreatment of the transplantable left lung with the TIP peptide, but not with an inactive mutant TIP peptide, resulted in significantly improved oxygenation 24 hrs after transplantation. This treatment led to a significantly reduced neutrophil content in the lavage fluid. Both the effects on oxygenation and neutrophil infiltration were inhibited by the epithelial sodium channel blocker amiloride. The TIP peptide blunted reactive oxygen species production in pulmonary artery endothelial cells under hypoxia and reoxygenation and reduced reactive oxygen species content in the transplanted rat lungs in vivo. Ussing chamber experiments using monolayers of primary type II rat pneumocytes indicated that the primary site of action of the peptide was on the apical side of these cells. Conclusions:These data demonstrate that the TIP peptide significantly improves lung function after lung transplantation in the rat, in part, by reducing neutrophil content and reactive oxygen species generation. These studies suggest that the TIP peptide is a potential therapeutic agent against the ischemia reperfusion injury associated with lung transplantation.

Neuropeptides in pulmonary edema fluid of adult respiratory distress syndrome.

A role for peptidergic nerves in the adult respiratory distress syndrome (ARDS) was examined by radioimmunochemically quantifying neuropeptides in pulmonary edema (PE) fluids from seven patients with ARDS and six patients with PE from congestive heart failure (CHF). The PE fluid mean concentrations of substance P (SP) and gastrin-releasing peptide (GRP) were significantly higher in ARDS (0.59 ±0.29SD and 0.10=0.03 nM, respectively,P < 0.001 for both) than in CHF (0.19±0.08 and 0.04±0.01), whereas no difference was detected between the mean levels of vasoacti ve intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) in the two forms of PE. Mean alveolar fluid concentration of SP was 8.7 nM (range 2.1−20.5 nM,N=4) in sheep with acute lung injury from intravenousPseudomonas aeruginosa, but was undetectable in sheep with balloon-induced high left atrial pressure simulating CHF (N=2) or control sheep (N=2). Pulmonary lymphatic clearance of SP, which reflected the rate of generation of SP in the lungs, attained a maximum of 25–95 pmol/h in sheep givenP. aeruginosa intravenously, but was detected in only one of four control sheep at a lower level. Some pulmonary neuropeptides thus are released locally by acute lung injury and may contribute to endothelial and/or epithelial abnormalities underlying the altered capillary-alveolar permeability in ARDS.

Role of Integrin αvβ6 in Acute Lung Injury Induced by Pseudomonas aeruginosa

ABSTRACT Deletion of integrin αvβ6 has been associated with significant protection in experiments where lung injury was induced by bleomycin, lipophilic polysaccharides, and high tidal volume ventilation. This has led to the suggestion that antibody blockade of this integrin is a novel therapy for acute lung injury. We questioned whether β6 gene deletion would also protect against Pseudomonas aeruginosa-induced acute lung injury. Wild-type and littermate β6-null mice, as well as recombinant soluble TGF-β receptor type II-Fc (rsTGF-βRII-Fc) and anti-αvβ6 treated wild-type mice, were instilled with live P. aeruginosa. Four or 8 h after bacterial instillation, the mice were euthanized, and either bronchoalveolar lavage fluid or lung homogenates were obtained. Deletion of the β6 gene resulted in an overall increase in inflammatory cells in the lungs. Bacterial numbers from the lung homogenates of infected β6-null mice were significantly decreased compared to the numbers in the wild-type mice (1.6 × 106 CFU versus 4.2 × 106 CFU [P < 0.01]). There were no significant differences in P. aeruginosa-mediated increases in lung endothelial permeability between wild-type and β6-null mice. Similarly, pretreatment with the αvβ6 antibody or with rsTGF-βRII-Fc did not significantly affect the P. aeruginosa-induced lung injury or rate of survival compared to pretreatment with control immunoglobulin G. We conclude that deletion or inhibition of the integrin αvβ6 did not protect animals from P. aeruginosa-induced lung injury. However, these therapies also did not increase the lung injury, suggesting that host defense was not compromised by this promising new therapy.

Apoptosis in Acute Lung Injury

In 1972, Kerr and Currie described a new type of cell death characterized by morphological changes distinct from the features observed during necrosis (1). The term of “apoptosis” was adopted to describe this highly conserved genetic program leading to regulated cellular self-destruction. Subsequent investigations showed that this programmed cell death is crucial during fetal development and critical for controlling harmful mechanisms triggered by environmental stresses. Recent literature has defined new roles for apoptosis in the normal and injured lung. For example, apoptosis plays an important role in postnatal lung development (2), and it is evident that resolution of lung inflammation after bacterial infection occurs by neutrophil apoptosis (3). While there is an increasing body of evidence supporting a role for apoptosis in the remodeling of the lung after acute lung injury (ALI) (3, 4), the factors that regulate normal and abnormal apoptotic cell death during ALI remain to be fully elucidated.

Early Coagulopathy is Associated with Increased Incidence of Ventilator-Associated Events Among Burn Patients.

Objective: Coagulopathy is known to be associated with burn injury. Our group has shown that, in spinal cord injury patients, coagulopathy is associated with an increase in ventilator-associated pneumonia (VAP). We hypothesized that the same association exists between coagulopathic burn patients and ventilator-associated events. Methods: Patients admitted for burn care between January 1, 2011 and December 31, 2015 who required mechanical ventilation were included in the study. Ventilator-associated events (VAEs) as defined by the Center for Disease Control were categorized as no event, ventilator-associated condition, infection-related ventilator-associated complication, and possible VAP. Demographic, injury characteristics were compared among four international normalized ratio (INR) categories using analysis of variance and chi-square tests. Results: Four hundred four patients were admitted for burn care, of whom 263 met the inclusion criteria. One hundred eleven had normal INR, 59 had a slightly elevated INR (1.2–1.4), 33 had a moderately elevated INR (1.4–1.6), and 60 had a severely elevated INR (>1.6). Those with moderately and severely elevated INR were ventilated for a longer period (Pu200a=u200a0.0034), had more days in the ICU (Pu200a=u200a0.0010), and had longer hospital stay (Pu200a=u200a0.0016). After adjusting for inhalation injury and total body surface area, patients with severely elevated INR were over four times as likely to have any VAE (OR: 4.16, 95% CI: 1.33–13.05) and 4.5 times as likely to develop infection-related ventilator-associated complication or possible ventilator-associated pneumonia combined (OR: 4.59, 1.35–15.67). Conclusions: Early coagulopathy is associated with a significantly increased incidence of VAEs in burn patients. While additional studies need to be conducted to verify these findings, early recognition and treatment could decrease VAEs.

Activation of the Heat Shock Response Attenuates the IL-1β-mediated Inhibition of the Amiloride-Sensitive Alveolar Epithelial Ion Transport

ABSTRACT Acute lung injury (ALI) is a clinical syndrome characterized by hypoxia, which is caused by the breakdown of the alveolar capillary barrier. Interleukin 1&bgr; (IL-1&bgr;), a cytokine released within the airspace in ALI, downregulates the &agr; subunit of the epithelial sodium channel (&agr;ENaC) transcription and protein expression via p38 MAP kinase–dependent signaling. Although induction of the heat shock response can restore alveolar fluid clearance compromised by IL-1&bgr; following the onset of severe hemorrhagic shock in rats, the mechanisms are not fully understood. In this study, we report that the induction of the heat shock response prevents IL-1&bgr;–dependent inhibition of &agr;ENaC mRNA expression and subsequent channel function. Heat shock results in IRAK1 detergent insolubility and a disruption of Hsp90 binding to IRAK1. Likewise, TAK1, another client protein of Hsp90 and signaling component of the IL-1&bgr; pathway, is also detergent insoluble after heat shock. Twenty-four hours after heat shock, both IRAK1 and TAK1 are again detergent soluble, which correlates with the IL-1&bgr;–dependent p38 activation. Remarkably, IL-1&bgr;–dependent p38 activation 24 h after heat shock did not result in an inhibition of &agr;ENaC mRNA expression and channel function. Further analysis demonstrates prolonged preservation of &agr;ENaC expression by the activation of the heat shock response that involves inducible Hsp70. Inhibition of Hsp70 at 24 h after heat shock results in p38-dependent IL-1&bgr; inhibition of &agr;ENaC mRNA expression, whereas overexpression of Hsp70 attenuates the p38-dependent IL-1&bgr; inhibition of &agr;ENaC mRNA expression. These studies demonstrate new mechanisms by which the induction of the heat shock response protects the barrier function of the alveolar epithelium in ALI.