Jérôme Pugin

Cytokine-mediated inflammation in acute lung injury

Clinical acute lung injury (ALI) is a major cause of acute respiratory failure in critically ill patients. There is considerable experimental and clinical evidence that pro- and anti-inflammatory cytokines play a major role in the pathogenesis of inflammatory-induced lung injury from sepsis, pneumonia, aspiration, and shock. A recent multi-center clinical trial found that a lung-protective ventilatory strategy reduces mortality by 22% in patients with ALI. Interestingly, this protective ventilatory strategy was associated with a marked reduction in the number of neutrophils and the concentration of pro-inflammatory cytokines released into the airspaces of the injured lung. Further research is needed to establish the contribution of cytokines to both the pathogenesis and resolution of ALI.

The alveolar space is the site of intense inflammatory and profibrotic reactions in the early phase of acute respiratory distress syndrome.

OBJECTIVES To determine the concentrations of proinflammatory mediators, collagenases, and procollagen type III peptides in undiluted pulmonary edema fluids and in plasma obtained in patients with early acute respiratory distress syndrome (ARDS) and in control patients with hydrostatic lung edema; and to assess the relationship between these inflammatory and profibrotic markers. DESIGN A prospective, clinical study with measurements of inflammatory markers in pulmonary edema fluids and in paired plasma samples. SETTING A medical intensive care unit. PATIENTS Patients intubated with lung permeability (n = 23) and hydrostatic (n = 8) pulmonary edema were prospectively enrolled in the study. The severity of the disease at the time of intubation was assessed, using the Simplified Acute Physiological Score (SAPS) II and the Lung Injury Score (LIS). INTERVENTIONS Plasma and undiluted edema fluids were obtained at the time of intubation with pulmonary edema requiring mechanical ventilation; and in some patients, a second edema fluid sample was collected a few hours later. MEASUREMENTS AND MAIN RESULTS Proinflammatory activity, dependent on the presence of bioactive proinflammatory cytokines, interleukin (IL)-8, and neutrophil matrix metalloproteinase (MMP)-9 were significantly increased in ARDS fluids compared with plasma or control fluids from patients with congestive heart failure. In contrast, MMP-2, originating from lung cells other than phagocytes, was slightly increased in ARDS edema fluids compared with plasma, but similar to levels found in hydrostatic edema fluids. Proinflammatory activity was undetectable in plasma from ARDS patients. Levels of procollagen peptide III, a marker of collagen synthesis, were increased in permeability edema fluids compared with hydrostatic edema fluids or plasma, confirming that alveolar collagen synthesis begins very early and in parallel with acute inflammation in ARDS. Control patients with hydrostatic edema had similar SAPS II and LIS scores compared with ARDS patients. CONCLUSIONS These results strongly support the conclusion that during the early phase of ARDS, the lung is the site of an intense inflammatory process with sequential activation of cytokines, chemokines, and secretion of proteases, as well as concomitant collagen synthesis. The inflammation is mostly limited to the lung, with low levels of inflammatory mediators in the systemic circulation. Unlike clinical scoring systems (SAPS II and LIS), inflammatory markers differentiate patients with permeability and hydrostatic pulmonary edema.

Evaluation of rapid screening and pre-emptive contact isolation for detecting and controlling methicillin-resistant Staphylococcus aureus in critical care: an interventional cohort study

IntroductionRapid diagnostic tests may allow early identification of previously unknown methicillin-resistant Staphylococcus aureus (MRSA) carriers at intensive care unit (ICU) admission. The aim of this study was twofold: first, to assess whether a new molecular MRSA screening test can substantially decrease the time between ICU admission and identification of MRSA carriers; and, second, to examine the combined effect of rapid testing and pre-emptive contact isolation on MRSA infections.MethodSince November 2003, patients admitted for longer than 24 hours to two adult ICUs were screened systematically on admission using quick, multiplex immunocapture-coupled PCR (qMRSA). Median time intervals from admission to notification of test results were calculated for a five-month intervention phase (November 2003–March 2004) and compared with a historical control period (April 2003–October 2003) by nonparametric tests. ICU-acquired MRSA infection rates were determined for an extended surveillance period (January 2003 through August 2005) and analyzed by Poisson regression methods.ResultsDuring the intervention phase, 97% (450/462) of patients admitted to the surgical ICU and 80% (470/591) of patients admitted to the medical ICU were screened. On-admission screening identified the prevalence of MRSA to be 6.7% (71/1053). Without admission screening, 55 previously unknown MRSA carriers would have been missed in both ICUs. Median time from ICU admission to notification of test results decreased from 87 to 21 hours in the surgical ICU (P < 0.001) and from 106 to 23 hours in the medical ICU (P < 0.001). In the surgical ICU, 1,227 pre-emptive isolation days for 245 MRSA-negative patients were saved by using the qMRSA test. After adjusting for colonization pressure, the systematic on-admission screening and pre-emptive isolation policy was associated with a reduction in medical ICU acquired MRSA infections (relative risk 0.3, 95% confidence interval 0.1–0.7) but had no effect in the surgical ICU (relative risk 1.0, 95% confidence interval 0.6–1.7).ConclusionThe qMRSA test decreased median time to notification from four days to one day and helped to identify previously unknown MRSA carriers rapidly. A strategy linking the rapid screening test to pre-emptive isolation and cohorting of MRSA patients substantially reduced MRSA cross-infections in the medical but not in the surgical ICU.

Combination of steroids with infliximab or placebo in severe alcoholic hepatitis: a randomized controlled pilot study☆

BACKGROUND/AIMS The aim of this study is to evaluate the tolerance and effects of infliximab combined with steroids in severe alcoholic hepatitis (AH). METHODS Twenty patients with biopsy-proven severe AH (Maddreys score>32) received prednisone 40 mg/day for 28 days and either infliximab 5mg/kg IV (group A) or placebo (group B) at day 0. Histology, plasma interleukin-6 (IL-6) and interleukin-8 (IL-8) were measured at baseline and at day 10. RESULTS Infliximab was well tolerated. Histology showed no significant changes. At day 28, Maddreys score significantly improved in group A (39 (32-53) to 12 (7-52), P<0.05 vs. baseline) but not in group B (44 (33-50) to 22 (2-59), P=NS). At day 10, IL-6 and IL-8 decreased in group A (25 pg/ml (10-85 pg/ml) to 4.5 pg/ml (2-25 pg/ml); 301 pg/ml (107-1207 pg/ml) to 14 6 pg/ml (25-252 pg/ml), P<0.01, P<0.05 vs. baseline, respectively). In group B, changes were not significant (38 pg/ml (13-116 pg/ml) to 16 pg/ml (4-128); 315 pg/ml (26-1698 pg/ml) to 110 pg/ml (27-492 pg/ml)). CONCLUSIONS In severe AH, infliximab was well tolerated and associated with significant improvement in Maddreys score at day 28. Although the size of this study does not allow comparison between groups, these promising results should encourage larger trials assessing the effects of this therapy on survival.

Oropharyngeal decontamination decreases incidence of ventilator-associated pneumonia

Secondary pneumonia in patients requiring mechanical ventilation has a high morbidity and mortality. Diagnosis is difficult and treatment failure common; therefore, preventive measures are important. In a double-blind, placebo-controlled trial, we evaluated selective decontamination of the oropharynx with polymyxin B sulfate, neomycin sulfate, and vancomycin hydrochloride (PNV) in 52 patients requiring mechanical ventilation during a 3- to 34-day period (mean, 10 days). Either PNV or placebo was administered six times daily in the oropharynx. During the first 12 days of intubation, tracheobronchial colonization by gram-negative bacteria and Staphylococcus aureus, as well as pneumonia, occurred less frequently in the PNV than in the placebo group (16% vs 78%; P less than .0001). Hospital mortality was not different, but systemic antibiotics were prescribed less often in the PNV group and no resistant microorganism emerged. In these critically ill patients, topical oropharyngeal antibiotic application lowered the rate of ventilator-associated pneumonia by a factor of 5, probably by interrupting the stomach-to-trachea route of infection, and decreased the requirement for intravenous antibiotics.

CD14-dependent endotoxin internalization via a macropinocytic pathway.

Gram-negative bacterial endotoxin (a lipopolysaccharide (LPS)) specifically binds to CD14, a glycosylphosphatidyl inositol (GPI)-anchored surface myeloid glycoprotein. This interaction leads to cell activation, but it also promotes LPS internalization and detoxification. In this work, we investigated the route of LPS and CD14 internalization and the relevance of CD14 GPI anchor in the endocytic pathway. In promonocytic THP-1 cells transfected with a GPI or a chimeric integral form of CD14, we showed by differential buoyancy in sucrose density gradients that these two forms of CD14 were sorted to different plasma membrane subdomains. However, both forms of CD14 associated preferentially with the same surface microfilament-enriched microvilli or ruffles. Electron microscopic studies indicated that CD14 internalized via macropinocytosis, a process resembling that of phagocytosis, different from “classical” receptor-mediated endocytic pathways, such as clathrin-coated pits or caveolae. With cell warming, the CD14-enriched ruffles fused and formed large vesicles. Later, these vacuoles made stacks and condensed into phago-lysosomes. CD14 was specifically associated with all of these structures. Radiolabeled LPS internalization paralleled CD14 internalization. Confocal microscopic studies confirmed the co-localization of LPS and CD14 both at the cell surface and in endosomal compartments. The microfilament-disrupting, macropinocytosis blocking agent cytochalasin D inhibited LPS and CD14 internalization but did not prevent LPS-dependent activation, indicating that these two processes are dissociated.

Pulmonary Edema Fluid from Patients with Early Lung Injury Stimulates Fibroblast Proliferation through IL-1β-Induced IL-6 Expression

Although the fibroproliferative response to lung injury occurs with a high frequency in patients with clinical acute lung injury, the mechanisms that initiate this response are largely unknown. This study was undertaken first to identify fibroblast mitogenic factors in pulmonary edema fluid, and second to examine the human lung fibroblast’s gene expression profile in response to pulmonary edema fluid. The edema fluid obtained from patients with early lung injury has an eightfold higher concentration of IL-1β and a twofold greater IL-1β-dependent mitogenic effect than does fluid obtained from control patients with hydrostatic pulmonary edema. Furthermore, fibroblasts responded to acute lung injury patient-derived edema fluid through production of soluble mediators that possess an autocrine mitogenic effect. Gene array analysis reveals that acute lung injury edema fluid induces several inflammation-modulating and proliferation-related genes in fibroblasts, whose inductions are similarly dependent on bioactive IL-1β. Most notably, the 20-fold induction of IL-6 mRNA and protein was completely blocked by IL-1 receptor antagonist. The combined addition of IL-1β and IL-6 was mitogenic, and the proliferative response to conditioned medium from IL-1β-exposed cells was blocked by antagonistically acting Abs to IL-6 or to gp130. These novel findings indicate that soluble IL-1β bioactivity and autocrine IL-1β-dependent IL-6 up-regulation are critical initiators of fibroblast activation and proliferation and that they likely play a role in the fibroproliferative response seen in human acute lung injury.

Molecular mechanisms of lung cell activation induced by cyclic stretch.

ObjectiveTo review molecular mechanisms of lung cell activation by stretch. Data SourcesPublished original and review articles. Data SummaryPositive-pressure mechanical ventilation is associated with both beneficial and harmful effects. Data indicate that mechanical ventilation can induce, or increase, lung inflammation. This effect is clearly linked to the degree of lung cell stretching. By modeling cyclic stretch in cultured cells, it has been possible to investigate the cellular pathways activated by this mechanical strain. Integrin receptors, proteins of the focal adhesion plaque, and the cytoskeleton itself participate in the multiple molecular complex that senses cyclic stretch, transforming a mechanical signal into a biological response. Several intracellular signaling pathways then are activated and eventually result in increased transcription of genes harboring “stretch-response elements” in their promoters. Among these pathways, the mitogen-activated protein kinase signaling cascade appears to be central in mediating the effects of cell stretching. Other posttranscriptional mechanisms, such as messenger RNA stabilization and the secretion of preformed mediators, also may account for the secretion of inflammatory mediators after cyclic stretch. ConclusionIdentification of the relevant molecular mechanisms will help in the development of novel ventilatory and pharmacologic therapeutic strategies aimed at preventing the deleterious effects of mechanical ventilation.

Mechanical ventilation affects lung function and cytokine production in an experimental model of endotoxemia.

Background:Mechanical ventilation using tidal volumes around 10 ml/kg and zero positive end-expiratory pressure is still commonly used in anesthesia. This strategy has been shown to aggravate lung injury and inflammation in preinjured lungs but not in healthy lungs. In this study, the authors investigated whether this strategy would result in lung injury during transient endotoxemia in the lungs of healthy animals. Methods:Volume-controlled ventilation with a tidal volume of 10 ml/kg and zero positive end-expiratory pressure was applied in two groups of anesthetized–paralyzed rabbits receiving either intravenous injection of 5 &mgr;g/kg Escherichia coli lipopolysaccharide (n = 10) or saline (n = 10) 2 h after the start of mechanical ventilation. The third group consisted of 10 spontaneously breathing anesthetized animals receiving lipopolysaccharide. Anesthesia was then continued for 4 h in the three groups while the ventilatory modes were maintained unchanged. Lung injury was studied using blood gases, respiratory physiologic variables, analysis of the bronchoalveolar lavage cell counts, and cytokine concentrations and lung pathologic examination. Results:Significant histologic lung alterations, hypoxemia, and altered lung mechanics were observed in rabbits treated with mechanical ventilation and intravenous lipopolysaccharide but not in the mechanically ventilated animals injected with saline or in spontaneously breathing animals treated with lipopolysaccharide. Endotoxemic ventilated animals also had significantly more lung inflammation as assessed by the alveolar concentration of neutrophils, and the concentrations of the chemokines interleukin 8 and growth-related oncogen &agr;. Conclusions:These results showed that positive-pressure mechanical ventilation using a tidal volume of 10 ml/kg and zero positive end-expiratory pressure was harmful in the setting of endotoxemia, suggesting that the use of this ventilator strategy in the operating room may predispose to lung injury when endotoxemia occurs.

Rapid changes in alcoholic hepatitis histology under steroids: correlation with soluble intercellular adhesion molecule-1 in hepatic venous blood

BACKGROUND/AIMS In alcoholic hepatitis (AH), enhanced expression of intercellular adhesion molecule-1 (ICAM-1) correlates to neutrophil infiltration and histology. In severe AH under steroids, the evolution of the hepatocyte membranous ICAM-1 expression and its soluble form (sICAM-1) is not known. METHODS Twenty-six consecutive patients with biopsy-proven severe AH had liver tissue studies for hepatocyte membranous ICAM-1 expression by immunostaining. Lobular neutrophils (mean per high power field) were counted after chloracetate esterase staining. Histological damage was assessed semiquantitatively. Circulating levels of sICAM-1 and TNFalpha in peripheral and hepatic vein were measured using immunoassays. After 8 days on steroids, 19 patients had repeat biopsy. RESULTS At baseline, hepatocyte membranous ICAM-1 correlated both to histology (r=0.55, P<0.01) and to lobular neutrophils (r=0.56, P<0.01). On steroids, sICAM-1 in hepatic vein and TNFalpha in both vascular beds decreased. Hepatocyte membranous ICAM-1 and hepatocellular damage decreased, but lobular neutrophils increased. Changes in sICAM-1 in hepatic vein correlated to histological changes (r=0.68, P<0.01). CONCLUSIONS In severe AH under steroids, the short term histological improvement was associated with a decrease in circulating TNFalpha, a decrease in ICAM-1 expression, and correlated to hepatic vein sICAM-1 changes.