Infections and the inflammatory response in acute respiratory distress syndrome

Nuclear factor-kappaB- and glucocorticoid receptor alpha- mediated mechanisms in the regulation of systemic and pulmonary inflammation during sepsis and acute respiratory distress syndrome. Evidence for inflammation-induced target tissue resistance to glucocorticoids

To test the hypothesis that the interaction between nuclear factor-kappaB (NF-kappaB) and glucocorticoid receptor alpha (GRalpha) is a key pathogenetic mechanism regulating the progression of systemic and pulmonary inflammation in sepsis and acute respiratory distress syndrome (ARDS), we used an ex vivo model of systemic inflammation. Naïve peripheral blood leukocytes (PBL) were exposed to longitudinal (days 1-10) plasma samples from ARDS patients divided into three groups based on physiological improvement and clinical outcome by days 7-10: improvers, nonimprovers-survivors, and nonimprovers-nonsurvivors. In a separate group of nonimprovers-survivors, we correlated the severity of lung histopathology with the intensity of NF-kappaB and GRalpha nuclear staining in immunohistochemistry analysis of lung tissue obtained by open lung biopsy. We found that exposure of naïve cells to longitudinal plasma samples led to divergent directions in NF-kappaB and GRalpha activation that reflected the severity of systemic inflammation. Plasma samples from improvers with declining cytokine levels over time elicited a progressive increase in all measured aspects of glucocorticoid (GC)-induced GRalpha-mediated activity (p = 0.0001) and a correspondent reduction in NF-kappaB nuclear binding (p = 0.0001) and transcription of TNF-alpha and IL-1beta (regulated, GRalpha-driven response). In contrast, plasma samples from nonimprovers with sustained elevation in cytokine levels over time elicited only a modest longitudinal increase in GC-GRalpha-mediated activity (p = 0.04) and a progressive increase in NF-kappaB nuclear binding over time (p = 0.0001) that was most striking in nonsurvivors (dysregulated, NF-kappaB-driven response). By days 3-5, no overlap was observed between groups for NF-kappaB and GC-GRalpha nuclear binding. In immunohistochemistry analyses, lung tissues of patients with severe versus mild ARDS had a higher intensity of NF-kappaB nuclear staining (13 +/- 1.3 vs. 7 +/- 2.9; p = 0.01) and a lower ratio of GRalpha:NF-kappaB in nuclear staining (0.5 +/- 0.2 vs. 1.5 +/- 0.2; p = 0.007). In conclusion, we demonstrated that the ability of GC-GRalpha to downregulate NF-kappaB activation is critical for the resolution of systemic and pulmonary inflammation in ARDS. The findings provide a rationale for the use of prolonged GC treatment in early ARDS.

Anti-inflammatory response is associated with mortality and severity of infection in sepsis

Using a murine model of sepsis, we found that the balance of tissue pro- to anti-inflammatory cytokines directly correlated with severity of infection and mortality. Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). Liver tissue was analyzed for levels of IL-1beta, IL-1 receptor antagonist (IL-1ra), tumor necrosis factor (TNF)-alpha, and soluble TNF receptor 1 by ELISA. Bacterial DNA was measured using quantitative real-time PCR. After CLP, early predominance of proinflammatory cytokines (6 h) transitioned to anti-inflammatory predominance at 24 h. The elevated anti-inflammatory cytokines were mirrored by increased tissue bacterial levels. The degree of anti-inflammatory response compared with proinflammatory response correlated with the bacterial concentration. To modulate the timing of the anti-inflammatory response, mice were treated with IL-1ra before CLP. This resulted in decreased proinflammatory cytokines, earlier bacterial load, and increased mortality. These studies show that the initial tissue proinflammatory response to sepsis is followed by an anti-inflammatory response. The anti-inflammatory phase is associated with increased bacterial load and mortality. These data suggest that it is the timing and magnitude of the anti-inflammatory response that predicts severity of infection in a murine model of sepsis.

Acute ventilator-induced vascular permeability and cytokine responses in isolated and in situ mouse lungs

To determine the influence of experimental model and strain differences on the relationship of vascular permeability to inflammatory cytokine production after high peak inflation pressure (PIP) ventilation, we used isolated perfused mouse lung and intact mouse preparations of Balb/c and B6/129 mice ventilated at high and low PIP. Filtration coefficients in isolated lungs and bronchoalveolar lavage (BAL) albumin in intact mice increased within 20–30 min after initiation of high PIP in isolated Balb/c lungs and intact Balb/c, B6/129 wild-type, and p55 and p75 tumor necrosis factor (TNF) dual-receptor null mice. In contrast, the cytokine response was delayed and variable compared with the permeability response. In isolated Balb/c lungs ventilated with 25–27 cmH2O PIP, TNF-α, interleukin (IL)-1β, IL-1α, macrophage inflammatory protein (MIP)-2, and IL-6 concentrations in perfusate were markedly increased in perfusate at 2 and 4 h, but only MIP-2 was detectable in intact Balb/c mice using the same PIP. In intact wild-type and TNF dual-receptor null mice with ventilation at 45 cmH2O PIP, the MIP-2 and IL-6 levels in BAL were significantly increased after 2 h in both groups, but there were no differences between groups in the BAL albumin and cytokine concentrations or in lung wet-to-dry weight ratios. TNF-α was not be detected in BAL fluids in any group of intact mice. These results suggest that the alveolar hyperpermeability induced by high PIP ventilation occurs very rapidly and is initially independent of TNF-α participation and unlikely to depend on MIP-2 or IL-6.

Microbiologic findings in feedlot cattle with acute interstitial pneumonia

OBJECTIVE

To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP ANIMALS: 39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens.

PROCEDURES

Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically.

RESULTS

Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem.

Serial monitoring of interleukin-1?, soluble interleukin-2 receptor and lipopolysaccharide binding protein levels after death

We prospectively monitored the postmortem course of interleukin-1beta (IL-1beta), soluble interleukin-2 receptor (sIL-2R) and lipopolysaccharide binding protein (LBP) in septic and non-septic fatalities to evaluate their potential as biochemical postmortem markers of sepsis. Serum concentrations were determined by chemiluminescent immunometric assays. In both the sepsis group and the control group a postmortem increase of IL-1beta levels with the progression of time after death was observed, in both groups mainly starting from the reference concentration of healthy individuals (5 pg/ml) and with no significant differences at later time points postmortem. SIL-2R (reference limit 1,000 U/ml) was highly elevated in all individuals included in the sepsis group at all time points postmortem with statistically significant differences between the sepsis and control groups (p<0.01). An excessive postmortem decrease of sIL-2R serum levels associated with progression of time after death was observed in all cases included in the sepsis group in contrast to just 1 out of 16 control cases. LBP (reference limit <10 g/ml) was elevated in all sepsis cases whereas in the control group LBP levels were below 10 microg/ml in 88%. The postmortem time course of LBP serum concentrations showed a continuous increase in both the sepsis and control groups. We conclude that sIL-2R and LBP seem to represent appropriate diagnostic tools for the postmortem diagnosis of sepsis in forensic autopsy practice. sIL-2R serum levels above 1,000 U/ml and LBP serum levels above 10 microg/ml in peripheral venous blood obtained in the early postmortem interval can be regarded as diagnostic hints for an underlying septic condition in a deceased person.

The clinical significance of serum and bronchoalveolar lavage inflammatory cytokines in patients at risk for Acute Respiratory Distress Syndrome

Background

The predictive role of many cytokines has not been well defined in Acute Respiratory Distress Syndrome (ARDS).

Methods

We measured prospectively IL-4, IL-6, IL-6 receptor, IL-8, and IL-10, in the serum and bronchoalveolar lavage fluid (BALF) in 59 patients who were admitted to ICU in order to identify predictive factors for the course and outcome of ARDS. The patients were divided into three groups: those fulfilling the criteria for ARDS (n = 20, group A), those at risk for ARDS and developed ARDS within 48 hours (n = 12, group B), and those at risk for ARDS but never developed ARDS (n = 27, group C).

Results

An excellent negative predictive value for ARDS development was found for IL-6 in BALF and serum (100% and 95%, respectively). IL-8 in BALF and IL-8 and IL-10 serum levels were higher in non-survivors in all studied groups, and were associated with a high negative predictive value. A significant correlation was found between IL-8 and APACHE score (r = 0.60, p < 0.0001). Similarly, IL-6 and IL-6r were highly correlated with PaO2/FiO2 (r = -0.27, p < 0.05 and r = -0.55, p < 0.0001, respectively).

Conclusions

BALF and serum levels of the studied cytokines on admission may provide valuable information for ARDS development in patients at risk, and outcome in patients either in ARDS or in at risk for ARDS.

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.

Altered p38 Mitogen-Activated Protein Kinase Expression in Different Leukocytes with Increment of Immunosuppressive Mediators in Patients with Severe Acute Respiratory Syndrome

Severe acute respiratory syndrome (SARS) has spread to a global pandemic, especially in Asia. The transmission route of SARS has been clarified, but the immunopathogenesis of SARS is unclear. In an age-matched case-control design, we studied immune parameters in 15 SARS patients who were previously healthy. Plasma was harvested for detection of virus load, cytokines, and nitrite/nitrate levels, and blood leukocytes were subjected to flow cytometric analysis of intracellular mitogen-activated protein kinases (MAPKs) in different leukocytes. Patients with SARS had significantly higher IL-8 levels (p = 0.016) in early stage, and higher IL-2 levels (p = 0.039) in late stage than normal controls. Blood TNF-alpha, IL-6, and IL-10, and nitrite/nitrate levels were not significantly elevated. In contrast, TGF-beta and PGE(2) levels were significantly elevated in SARS patients. Five of the 15 SARS patients had detectable coronaviruses in blood, but patients with detectable and undetectable viremia had no different profiles of immune mediators. Flow cytometric analysis of MAPKs activation by phospho-p38 and phospho-p44/42 (extracellular signal-regulated kinase) expression showed that augmented p38 activation (p = 0.044) of CD14 monocytes associated with suppressed p38 activation (p = 0.033) of CD8 lymphocytes was found in SARS patients. These results suggest that regulation of TGF-beta and PGE(2) production and MAPKs activation in different leukocytes may be considered while developing therapeutics for the SARS treatment.

Systemic Inflammation-Associated Glucocorticoid Resistance and Outcome of ARDS

Dysregulated systemic inflammation with excess activation of pro-inflammatory transcription factor nuclear factor-kappaB (NF-kappaB)-activated by inflammatory signals-compared to the anti-inflammatory transcription factor glucocorticoid receptor-alpha (GRalpha)-activated by endogenous or exogenous glucocorticoids (GCs)-is an important pathogenetic mechanism for pulmonary and extrapulmonary organ dysfunction in patients with acute respiratory distress syndrome (ARDS). Activation of one transcription factor in excess of the binding (inhibitory) capacity of the other shifts cellular responses toward increased (dysregulated) or decreased (regulated) transcription of inflammatory mediators over time. Recent data indicate that failure to improve in ARDS (unresolving ARDS) is frequently associated with failure of the activated GRs to downregulate the transcription of inflammatory cytokines despite elevated levels of circulating cortisol, a condition defined as systemic inflammation-associated acquired GC resistance; it is potentially reversible with prolonged GC supplementation. In the first part of this paper, after a brief description of inflammation in ARDS and our model of translational research, we review the two cellular signaling pathways that are central to the regulation of inflammation-the stimulatory NF-alphaB and the inhibitory GRalpha. In the second part, we review findings of recent studies indicating that excessive inflammatory activity in patients with unresolving ARDS may induce noncompensated GC resistance in target organs. In the third part, we review factors affecting cellular response to GC and potential mechanisms involved in inflammation-associated GC resistance.

Increased IL-6 and TGF-beta1 concentrations in bronchoalveolar lavage fluid associated with thoracic radiotherapy

PURPOSE

To assess, in lung cancer patients, the effects of thoracic radiotherapy (RT) on the concentrations of transforming growth factor-beta(1) (TGF-beta(1)) and interleukin-6 (IL-6) in the bronchoalveolar lavage (BAL) fluid.

METHODS AND MATERIALS

Eleven patients with lung cancer requiring RT as part of their treatment were studied. BAL was performed bilaterally before, during, and 1, 3, and 6 months after RT. Before each BAL session, the patient's status was assessed clinically using pulmonary function tests and an adapted late effects on normal tissue-subjective, objective, management, analytic (LENT-SOMA) scale, including subjective and objective alterations. The National Cancer Institute Common Toxicity Criteria were used to grade pneumonitis. The TGF-beta(1) and IL-6 levels in the BAL fluid were determined using the Easia kit.

RESULTS

The TGF-beta(1) and IL-6 concentrations in the BAL fluid recovered from the irradiated areas were significantly increased by thoracic RT. The increase in TGF-beta(1) levels tended to be greater in the group of patients who developed severe pneumonitis. In the BAL fluid from the nonirradiated areas, the TGF-beta(1) and IL-6 concentrations remained unchanged.

CONCLUSION

The observed increase in TGF-beta(1) and IL-6 concentrations in the BAL fluid recovered from the irradiated lung areas demonstrated that these cytokines may contribute to the process leading to a radiation response in human lung tissue.

Application of Molecular Adsorbents Recirculating System to remove NO and cytokines in severe liver failure patients with multiple organ dysfunction syndrome

BACKGROUND

Molecular Adsorbents Recirculating System (MARS) is a new promising artificial liver support therapy, the aim of this study was to assess the effectiveness of MARS to remove nitrous oxide (NO) and cytokines in severe liver failure patients with multiple organ dysfunction syndrome (MODS).

METHODS

Sixty single MARS treatments were performed with length of 6-24 h on 24 severe liver failure patients (18 males/6 females) with MODS.

RESULTS

The MARS therapy was associated with a significant removal of NO and certain cytokines such as TNF-alpha, IL-6, IL-8, and INF-gamma, together with marked reduction of other non-water-soluble albumin bound toxins and water-soluble toxins, these were associated with a improvement of the patients' clinical conditions including hepatic encephalopathy, deranged hemodynamic situation and as well as renal and respiratory function, thus resulted into marked decrease of Sequential Organ Failure Assessment (SOFA) score and improved outcome: nine patients were able to be discharged from the hospital or bridged to successful liver transplantation, the overall survival of 24 patients was 37.5%.

CONCLUSION

We can confirm the positive therapeutic impact and safety to use MARS on liver failure patients with MODS associated with elevated levels of NO and cytokines.

Inflammatory cytokine profile in children with severe acute respiratory syndrome

OBJECTIVE

To study the inflammatory cytokine profile in children with severe acute respiratory syndrome (SARS) and to investigate whether monoclonal antibody to tumor necrosis factor-alpha (TNF-alpha) could be considered for treatment of these patients.

METHODS

Plasma inflammatory cytokine concentrations (interleukin [IL]-1beta, IL-6, IL-8, IL-10, IL-12p70, and TNF-alpha) were monitored longitudinally on admission, immediately before corticosteroids, and 1 to 2 days and 7 to 10 days after the drug treatment in a cohort of pediatric patients (n = 8) with virologic confirmed SARS-associated coronavirus infection. None of the patients required mechanical ventilation or intensive care treatment. All children except 1 (patient 3) received corticosteroids.

RESULTS

Plasma IL-1beta levels (excluding patient 3) were substantially elevated immediately before (range: 7-721 ng/L) and 7 to 10 days after (range: 7-664 ng/L) corticosteroid treatment. In contrast, the plasma concentrations of other key proinflammatory cytokines, including IL-6 and TNF-alpha, were not overtly increased in any of the patients throughout the course of illness. In addition, plasma IL-10 concentration was significantly lower 1 to 2 days and 7 to 10 days after corticosteroid treatment, compared with the immediate pretreatment level. Similarly, plasma IL-6 and IL-8 concentrations were significantly decreased 7 to 10 days after the drug treatment.

CONCLUSIONS

Pediatric SARS patients have markedly elevated circulating IL-1beta levels, which suggests selective activation of the caspase-1-dependent pathway. Other key proinflammatory cytokines, IL-6 and TNF-alpha, showed only mildly elevated levels at the initial phase of the illness. The current evidence does not support the use of TNF-alpha monoclonal antibody in this group of children.

Fatal systemic inflammatory response syndrome in a ornithine transcarbamylase deficient patient following adenoviral gene transfer

We report the death of an 18-year-old male with partial ornithine transcarbamylase (OTC) deficiency who participated in a pilot (safety) study of gene therapy. The vector used for this trial was based on human adenovirus type 5, deleted in E1 and E4, and contained human OTC cDNA. It was infused into the right hepatic artery at a dose of 6x10(11)particles/kg. Approximately 18 h. following gene transfer the subject was noted to have altered mental status and jaundice--clinical signs not seen in any of the first 17 subjects in this study. Subsequently, his clinical course was marked by systemic inflammatory response syndrome, biochemically detectable disseminated intravascular coagulation, and multiple organ system failure, leading to death 98 h following gene transfer. Post-mortem examination was consistent with the clinical course, and vector DNA sequences were readily detectable in most tissues. The subject had high serum levels of IL-6 and IL-10 but normal TNFalpha immediately after infusion of the vector. This experience points to the limitations of animal studies in predicting human responses, the steep toxicity curve for replication defective adenovirus vectors, substantial subject-to-subject variation in host responses to systemically administered vectors, and the need for further study of the immune response to these vectors.

Case report of the first Severe Acute Respiratory Syndrome patient in China: successful application of extracorporeal liver support MARS therapy in multiorgan failure possibly induced by Severe Acute Respiratory Syndrome

A previously healthy patient was transferred to our infectious department with a 9-day-history of continued fever. The patient was placed on assisted respiration support in addition to anti-viral medication. The diagnosis of SARS (Severe Acute Respiratory Syndrome) was made in view of the severe hypoxemia and the characteristic symptoms exhibited by the patient. Despite the best intensive therapy, he clinically deteriorated into multiorgan dysfunction syndrome (MODS) including additional dysfunction of kidney, liver, and heart. We initiated MARS therapy (extracorporeal liver support utilizing albumin dialysis) with intention to positively influence the organ functions in his MODS on the basis of recently published studies which suggested a positive impact of MARS in multiorgan failure secondary to respiratory illnesses and the possible influence on inflammatory mediators and cytokines. The application of 4 intermittent MARS treatments (8 h each, mean blood flow rate 180 ml/min) on 4 consecutive days resulted in an immediate improvement of clinical conditions within the treatment days. The further improvement of organ functions allowed withdrawing the patient from ventilatory support 13 days after start of MARS, and 44 days after admission he was discharged home with completely resolved organ functions and laboratory abnormalities. SARS is a severe form of the epidemic outbreak of atypical pneumonia which remains poorly defined regarding etiology and special therapy recommendations. However, the development and aggravation of this ARDS-like severe acute respiratory syndrome is pathologically associated with the systemic inflammatory response syndrome (SIRS) which may then mediate or cause MODS. To our knowledge, this is the first report of an application of MARS therapy in MODS which was probably induced by SARS in a patient in China which improved the clinical condition of the patient in multi-organ failure secondary to respiratory failure indicating that MARS might be an additional therapeutic option in multiorgan failure induced by SARS.

Acute respiratory distress syndrome after bacteremic sepsis does not increase mortality

To determine whether acute respiratory distress syndrome (ARDS) complicating bacteremic sepsis independently affects mortality in critically ill patients, we conducted a 3-year retrospective cohort study in a surgical intensive care unit. We included all consecutive patients with blood culture-positive sepsis and measured organ dysfunctions and mortality. Among 4,530 admissions, 196 cases of bacteremic sepsis were recorded. ARDS occurred in 31 (16%) of these patients. The case fatality rate was 58% in patients with ARDS compared with 31% in patients without ARDS. Using Cox proportional hazards regression with time-dependent variables, the unadjusted hazard ratio for death was 1.8 (95% confidence interval [CI], 1.0-3.2). After adjusting for comorbid factors that were present before the onset of sepsis, the hazard ratio was 2.2 (95% CI, 1.2-3.9). After further adjustment was made for nonpulmonary organ dysfunctions and microbiologic factors that were independently associated with mortality, the adjusted hazard ratio for ARDS was 0.6 (95% CI, 0.3-1.2). Among critically ill surgical patients, ARDS complicating bacteremic sepsis remains common, but it is not independently associated with short-term mortality, after adjusting for severity of illness and nonpulmonary organ dysfunctions evolving after the onset of sepsis.

Bronchoalveolar interleukin-1 beta: a marker of bacterial burden in mechanically ventilated patients with community-acquired pneumonia

OBJECTIVE

To assess the relationship between concentrations of bronchoalveolar cytokines and bacterial burden (quantitative bacterial count) in intubated patients with a presumptive diagnosis of community-acquired pneumonia.

DESIGN

A cross-sectional and clinical investigation. SETTING Medical/surgical and respiratory intensive care unit of a tertiary 1,200-bed medical center.

PATIENTS

According to the time course of community-acquired pneumonia at the time of study with bronchoalveolar lavage, 69 mechanically ventilated patients were divided into three subgroups: primary (n = 11), referral (n = 23), and treated (n = 35) community-acquired pneumonia.

INTERVENTIONS

Bronchoalveolar lavage was performed in the most abnormal area on chest radiograph by fiberoptic bronchoscope. Bronchoalveolar lavage fluid was processed for quantitative bacterial culture. The concentrations of bronchoalveolar lavage cytokines (tumor necrosis factor-alpha, interleukin-1 beta, interleukin-6, interleukin-8, and interleukin-10) also were measured.

MEASUREMENTS AND MAIN RESULTS

Thirty-two patients had a positive bacterial culture (bronchoalveolar lavage > or = 10 colony-forming units/mL)., and made up 76% of pathogens recovered at high concentrations. The concentrations of bronchoalveolar lavage interleukin-1 beta were 199.1 +/- 32.1 and 54.9 +/- 13.0 pg/mL (mean +/- se) in the patients with positive and negative bacterial culture, respectively (p < .001). Bronchoalveolar lavage interleukin- 1 beta was significantly higher in the patients with a high bacterial burden (p < .001), with mixed bacterial infection (p < .001), and with pneumonia (p < .001), compared with values in patients without these features. The relationship between bacterial load and concentrations of bronchoalveolar lavage interleukin-1 beta was very strong in the patients with primary and referral community-acquired pneumonia but was borderline in treated community-acquired pneumonia.

CONCLUSIONS

The common pathogens were similar to the core pathogens of hospital-acquired pneumonia, probably due to antibiotic effects, delayed sampling, and superimposed nosocomial infection. Since the concentration of bronchoalveolar lavage interleukin-1 beta was correlated with bacterial burden in the alveoli, it may be a marker for progressive and ongoing inflammation in patients who have not responded to pneumonia therapy and who have persistence of bacteria in the lung.

Heat shock proteins and ventilator-induced lung injury

In this review, we discuss the heat shock response, a specific example of gene expression that has been studied over the past 25 years, and its relevance to acute lung injury and other critical conditions. The heat shock response has been observed in virtually all organisms and involves the rapid induction of a set of highly conserved genes that encode heat shock proteins (HSPs). The HSP70 family represents the most prominent eukaryotic group of HSPs. It has been suggested that members of the HSP70 family act in the protection of cellular damage by binding to denatured or abnormal proteins after heat shock, thereby preventing protein aggregation. The capacity of HSPs to subserve cytoprotection has produced considerable interest from the perspective of elucidating the pathophysiology of organ damage and dysfunction. Several studies support the hypothesis that HSPs are cytoprotective In addition, recent investigations have demonstrated that HSP70 is released into the systemic circulation and is involved in the activation of innate immunity.

Induction of proinflammatory cytokines in human macrophages by influenza A (H5N1) viruses: a mechanism for the unusual severity of human disease?

BACKGROUND

In 1997, the first documented instance of human respiratory disease and death associated with a purely avian H5N1 influenza virus resulted in an overall case-fatality rate of 33%. The biological basis for the severity of human H5N1 disease has remained unclear. We tested the hypothesis that virus-induced cytokine dysregulation has a role.

METHODS

We used cDNA arrays and quantitative RT-PCR to compare the profile of cytokine gene expression induced by viruses A/HK/486/97 and A/HK/483/97 (both H5N1/97) with that of human H3N2 and H1N1 viruses in human primary monocyte-derived macrophages in vitro. Secretion of tumour necrosis factor alpha (TNF alpha) from macrophages infected with the viruses was compared by ELISA. By use of naturally occurring viral reassortants and recombinant viruses generated by reverse genetic techniques, we investigated the viral genes associated with the TNF-alpha response.

FINDINGS

The H5N1/97 viruses induced much higher gene transcription of proinflammatory cytokines than did H3N2 or H1N1 viruses, particularly TNF alpha and interferon beta. The concentration of TNF-alpha protein in culture supernatants of macrophages infected with these viruses was similar to that induced by stimulation with Escherichia coli lipopolysaccharide. The non-structural (NS) gene-segment of H5N1/97 viruses contributed to the increase in TNF alpha induced by the virus.

INTERPRETATION

The H5N1/97 viruses are potent inducers of proinflammatory cytokines in macrophages, the most notable being TNF alpha. This characteristic may contribute to the unusual severity of human H5N1 disease.

Association between increased levels of IL-2 and IL-15 and outcome in patients with early acute respiratory distress syndrome

BACKGROUND

Acute respiratory distress syndrome remains a serious, often fatal, condition, despite progress in modern critical care treatment. Cytokines play an important role in the pathogenesis of the syndrome, although their role in the evolution and outcome has not been clearly elucidated. We explored whether the measurement of serum and bronchoalveolar lavage IL-2 and IL-15 at the time of hospital admission can predict the outcome of this syndrome.

METHODS

Serum and bronchoalveolar lavage levels of IL-2 and IL-15 were measured in eight patients with ARDS (group A) and 26 patients on high risk for ARDS development who never developed ARDS (group B) from samples obtained at the time of admission.

RESULTS

Serum IL-2 (P > 0.05) and IL-15 (P < 0.05) levels were higher in group A than in group B. Serum levels of both cytokines were higher in patients who did not survive in both of the groups A and B compared to those who survived (P < 0.05, and P < 0.0001, respectively). The only significant change in BALF was the higher level of IL-15 in surviving group A patients (P < 0.05) when compared with the non survivors of the same group. For a serum cut-off level of 173 pg mL(-1) for IL-2 and 250 pg mL(-1) for IL-15, they exhibited a very high positive predictive value (PPV), negative predictive value (NPV), sensitivity and specificity for survival (100% in all). A positive correlation was found between serum levels of both cytokines and APACHE II score (IL-2, r = 0.61, and IL-15, r = 0.62, respectively, and P < 0.0001 for both).

CONCLUSION

Determination of serum IL-2 and IL-15 levels may be a valuable and simple aid to improve identification of patients with ARDS or at risk for ARDS who are at high risk of subsequent mortality.

Stress-dose corticosteroid therapy for sepsis and acute lung injury or acute respiratory distress syndrome in critically ill adults

Sepsis and acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) are associated with high mortality rates despite recent therapeutic advances. Both disease states involve uncontrolled host defense responses that lead to inflammation, endothelial damage, enhanced coagulation, diminished fibrinolysis and fibroproliferation to produce microthrombi, and relative adrenal insufficiency. Corticosteroids inhibit the host defense response and may offer an inexpensive therapeutic option. Results of several randomized, double-blind studies demonstrated no survival benefit and higher secondary infection rates when supraphysiologic doses of corticosteroids were administered for less than 24 hours. Recently, the emphasis of research for corticosteroid therapy has involved adrenocortical replacement dosage regimens administered for several days to weeks, with doses corresponding to the stress level of the disease. Stress-dose therapy with hydrocortisone in patients with septic shock who require vasopressor support, especially if adrenal insufficiency is present, accelerates hemodynamic stability and reduces mortality. The frequency of gastrointestinal hemorrhage was higher with corticosteroid therapy than with placebo, but the occurrence of secondary infections was similar to that of placebo. The only randomized, double-blind study that evaluated stress-dose methylprednisolone therapy for ARDS was terminated early after only 24 patients were enrolled because therapy with methylprednisolone was associated with enhanced survival despite higher secondary infection rates. A multicenter study investigating stress-dose methylprednisolone for ARDS is under way and should provide valuable information. Sufficient data support stress-dose hydrocortisone therapy for vasopressor-dependent septic shock. Stress-dose methylprednisolone therapy for ALI-ARDS requires further study but may be warranted in cases of refractory infection-induced ARDS when impending mortality is likely.

Metalloproteinase and growth factor interactions: do they play a role in pulmonary fibrosis?

Chronic lung disease due to interstitial fibrosis can be a consequence of acute lung injury and inflammation. The inflammatory response is mediated through the migration of inflammatory cells, actions of proinflammatory cytokines, and the secretion of matrix-degrading proteinases. After the initial inflammatory insult, successful healing of the lung may occur, or alternatively, dysregulated tissue repair can result in scarring and fibrosis. On the basis of recent insights into the mechanisms underlying acute lung injury and its long-term consequences, data suggest that proteinases, such as the matrix metalloproteinases (MMPs), may not only be involved in the breakdown and remodeling that occurs during the injury but may also cause the release of growth factors and cytokines known to influence growth and differentiation of target cells within the lung. Through the release of and activation of fibrosis-promoting cytokines and growth factors such as transforming growth factor-beta1, tumor necrosis factor-alpha, and insulin-like growth factors by MMPs, we propose that these metalloproteinases may be integral to the initiation and progression of pulmonary fibrosis.

Shock mesenteric lymph-induced rat polymorphonuclear neutrophil activation and endothelial cell injury is mediated by aqueous factors

BACKGROUND

After trauma and hemorrhagic shock (T/HS), mesenteric lymph (ML) activates polymorphonuclear neutrophils (PMNs), injures endothelial cells (ECs), and predisposes to lung injury. The involved mediators, however, are unknown. We studied the ability of aqueous (AQ) and lipid (LIP) extracts of rat T/HS ML to activate PMNs and injure ECs.

METHODS

ML was collected from male rats undergoing trauma (laparotomy) plus hemorrhagic shock (30 mm Hg, 90 minutes) or sham shock. AQ and LIP ML fractions were separated using the Bligh-Dyer technique. Human umbilical vein endothelial cells were incubated 18 hours in 5% LIP or AQ lymph fractions and viability was assessed using the MTT assay. Rat PMNs incubated 5 minutes with 3% LIP or AQ fractions were assessed for respiratory burst (RB) and cytosolic calcium ([Ca(2+)](i)) using dihydrorhodamine 123 and fura-2AM. Human PMN responses to AQ and LIP T/HS lymph were studied similarly.

RESULTS

EC incubated in AQ showed 19 +/- 4% viability as compared with 65 +/- 11% in LIP (p < 0.001). Whole lymph affected ECs comparably to AQ T/HS lymph. Rat PMN basal [Ca(2+)](i) increased after exposure to AQ but not LIP T/HS lymph extracts. AQ T/HS lymph primed [Ca(2+)](i) responses to macrophage inflammatory protein-2 and platelet-activating factor; neither LIP T/HS nor any trauma and sham shock lymph fraction caused PMN priming. Rat PMN RB was elevated after AQ T/HS lymph incubation when compared with buffer (610 +/- 122 U/s vs. 225 +/- 38 U/s, p = 0.01). Rat PMN incubation in LIP T/HS lymph caused minimal activation (289 +/- 28 U/s, p = NS). Conversely, human PMN showed [Ca(2+)](i) and RB priming by rat T/HS LIP and not AQ extracts.

CONCLUSION

T/HS mesenteric lymph contains multiple biologically active mediators. Both AQ and LIP extracts of T/HS lymph are toxic to human umbilical vein endothelial cells, with AQ more active than LIP. Only AQ T/HS lymph activates rat PMNs, although LIP rat lymph extract activates human PMNs. These findings demonstrate the complex nature of gut lymph-derived biologic factors as well as species-specific differences on PMN and EC physiology. Therapies directed at any one specific molecule or mediator are therefore unlikely to be successful.

A prospective study of inflammation markers in patients at risk of indirect acute lung injury

Systemic inflammation triggered by insults like sepsis and acute pancreatitis may play a role in development of indirect acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Because little is known about the course of systemic inflammation on the days preceding diagnosis of ARDS, we prospectively monitored immune inflammatory status in 52 patients at risk and we assessed the presence of ALI and ARDS on day 7 after admission to the intensive care unit. On admission, serum interleukin (IL) 8, IL-6, and soluble IL-2 receptor concentrations were significantly higher in patients with subsequent ALI (n = 18) than in patients without ALI (n = 30). During a 4-day follow-up, IL-8 and IL-6 levels of ALI patients remained high and those of non-ALI patients decreased. None of the markers discriminated ARDS patients (n = 9) from non-ARDS ALI patients (n = 9). Among 11 patients with acute pancreatitis, ALI patients had significantly higher IL-8, IL-6, and phagocyte CD11b expression levels than did non-ALI patients, whereas among 14 patients with massive transfusion, respective findings in ALI and non-ALI patients were comparable. Results give credence to the view that systemic inflammation plays a role in development of ALI triggered by pancreatitis, but not in that by massive transfusion. This finding, if confirmed in studies with sufficient statistical power, suggests that the patients with massive transfusion do not necessarily benefit from novel biotherapies aimed at altering the course of systemic inflammation.

Clinical review: a paradigm shift: the bidirectional effect of inflammation on bacterial growth. Clinical implications for patients with acute respiratory distress syndrome

Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. We hypothesized that cytokines secreted by the host during acute respiratory distress syndrome may indeed favor the growth of bacteria and explain the association between exaggerated and protracted systemic inflammation and the frequent development of nosocomial infections. To test this hypothesis, we conducted in vitro studies evaluating the extracellular and intracellular growth response of three clinically relevant bacteria in response to graded concentrations of pro-inflammatory cytokines tumor necrosis factor-alpha, IL-1beta, and IL-6. In these studies, we identified a U-shaped response of bacterial growth to pro-inflammatory cytokines. When the bacteria were exposed in vitro to a lower concentration of cytokines, extracellular and intracellular bacterial growth was not promoted and human monocytic cells were efficient in killing the ingested bacteria. Conversely, when bacteria were exposed to higher concentrations of pro-inflammatory cytokines, intracellular and extracellular bacterial growth was enhanced in a dose-dependent manner. The bidirectional effects of proinflammatory cytokines on bacterial growth may help to explain the frequent occurrence of nosocomial infections in patients with unresolving acute respiratory distress syndrome.

From bench to bedside: bacterial growth and cytokines

The recognition that neutrophils, macrophages, and other components of the inflammatory cascade participate in the generation and progression of acute lung injury/acute respiratory distress syndrome has resulted in the use of anti-inflammatory agents in an attempt to attenuate this inflammatory response and to prevent further progression of the acute lung injury. The recent finding that cytokines, in part mediators of this 'overwhelming' inflammatory reaction, may also stimulate bacterial growth, impair bacterial clearance, and promote the subsequent development of nosocomial infections may have important implications to the management of the acute lung injury/acute respiratory distress syndrome patient.

Effects of methylprednisolone on intracellular bacterial growth

Clinical studies have shown positive associations among sustained and intense inflammatory responses and the incidence of bacterial infections. Patients presenting with acute respiratory distress syndrome (ARDS) and high levels of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta), and IL-6, have increased risk for developing nosocomial infections attributable to organisms such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter spp., compared to those patients with lower levels. Our previous in vitro studies have demonstrated that these bacterial strains exhibit enhanced growth extracellularly when supplemented with high concentrations of pure recombinant TNF-alpha, IL-1 beta, or IL-6. In addition, we have shown that the intracellular milieu of phagocytic cells that are exposed to supraoptimal concentrations of TNF-alpha, IL-1 beta, and IL-6 or lipopolysaccharide (LPS) favors survival and replication of ingested bacteria. Therefore, we hypothesized that under conditions of intense inflammation the host's micromilieu favors bacterial infections by exposing phagocytic cells to protracted high levels of inflammatory cytokines. Our clinical studies have shown that methylprednisolone is capable of reducing the levels of TNF-alpha, IL-1 beta, and IL-6 in ARDS patients. Hence, we designed a series of in vitro experiments to test whether human monocytic cells (U937 cells) that are activated with high concentrations of LPS, which upregulate the release of proinflammatory cytokines from these phagocytic cells, would effectively kill or restrict bacterial survival and replication after exposure to methylprednisolone. Fresh isolates of S. aureus, P. aeruginosa, and Acinetobacter were used in our studies. Our results indicate that, compared with the control, stimulation of U937 cells with 100-ng/ml, 1.0-microg/ml, 5.0-microg/ml, or 10.0-microg/ml concentrations of LPS enhanced the intracellular survival and replication of all three species of bacteria significantly (for all, P = 0.0001). Stimulation with < or =10.0 ng of LPS generally resulted in efficient killing of the ingested bacteria. Interestingly, when exposed to graded concentrations of methylprednisolone, U937 cells that had been stimulated with 10.0 microg of LPS were able to suppress bacterial replication efficiently in a concentration-dependent manner. Significant reduction in numbers of CFU was observed at > or =150 microg of methylprednisolone per ml (P values were 0.032, 0.008, and 0.009 for S. aureus, P. aeruginosa, and Acinetobacter, respectively). We have also shown that steady-state mRNA levels of TNF-alpha, IL-1 beta, and IL-6 in LPS-activated cells were reduced by treatment of such cells with methylprednisolone, in a concentration-dependent manner. The effective dose of methylprednisolone was 175 mg, a value that appeared to be independent of priming level of LPS and type of mRNA. We therefore postulate that a U-shaped relationship exists between the level of expression of TNF-alpha, IL-1 beta, and IL-6 within the phagocytic cells and their abilities to suppress active survival and replication of phagocytized bacteria.

Regulation of experimental lung inflammation

Acute lung inflammation is an important component of a number of pulmonary diseases, including acute respiratory distress syndrome (ARDS). Much has been learned about the manner in which various insults to lung, such as infection or trauma, bring about recruitment of neutrophils into alveoli and small airways, resulting in parenchymal damage and organ dysfunction. In this brief review, we discuss the endogenous mechanisms in which the lung regulates the acute inflammatory response in rats to intrapulmonary deposition of IgG immune complexes. Emphasis is given to the participation of the transcription factor, NF-kappaB, in the development of lung injury and the endogenous mediators which attempt to control the extent of lung inflammation by modulating the activation of NF-kappaB.

Acute lung injury: cellular mechanisms and derangements

The clinical course of acute lung injury (ALI) is a complex and variable process accompanied by severe lung dysfunction, which persists for a long period of time with variable recovery of pulmonary function. The extent and severity of the lung disease associated with ALI varies with those patients having the most severe manifestations of lung disease being grouped as acute respiratory distress syndrome (ARDS). The pathological injury associated with this disease process, termed diffuse alveolar damage (DAD), has three overlapping phases (exudative, proliferative and fibrotic) which are the consequences of severe injury to the alveolar-capillary unit. There is no uniformity to the progression and length of each stage. This review explores those cellular mechanisms and derangements involved in the progression of ARDS. Those areas that demonstrate the major advances within the field are highlighted because of the diverse and vast nature of the cellular components involved in the process of ALI. We are beginning to identify those processes that contribute to the cellular derangements which are the hallmark of ALI. By expanding our understanding of those factors, we should in the future be able to construct therapeutic interventions that address the aetiology of ALI.

Leucocyte response and anti-inflammatory cytokines in community acquired pneumonia

BACKGROUND

In the host defence of the lung neutrophils (PMN) play a central role. Apart from antimicrobial properties, recent data indicate that PMN also exert anti-inflammatory effects by stimulation and release of cytokine antagonists such as interleukin-1 receptor antagonist (IL-1ra).

METHODS

Cytokine release from lipopolysaccharide stimulated whole blood was studied in 18 patients with community acquired pneumonia (CAP) and severe co-morbidities at admission and after 24 hours. Release of IL-1ra, interleukin-1beta (IL-1beta), tumour necrosis factor alpha (TNFalpha), soluble TNF receptor type I (sTNF-RI), and IL-8 was determined by ELISA.

RESULTS

The mean (SD) leucocyte level at admission was 12.5 (4.1)/nl. There was a significant correlation between the release of anti-inflammatory cytokines such as IL-1ra and sTNF-RI and the leucocyte count at admission and after 24 hours. Additional in vitro experiments showed that co-incubation of peripheral blood mononuclear cells with autologous PMN led to a marked dose dependent increase in IL-1ra and sTNF-RI release.

CONCLUSION

These results indicate that PMN may be responsible for the increase in anti-inflammatory cytokines in CAP. Strategies to increase neutrophil counts may exert beneficial effects, not only by augmenting the antimicrobial activity but also by modulating the inflammatory cytokine response.

Interlobar differences in bronchoalveolar lavage fluid from children with cystic fibrosis

Bronchoalveolar lavage (BAL) performed in specialist centres has improved the understanding of infant cystic fibrosis (CF) lung disease. As most researchers sample from a single lobe, it was determined whether BAL results could be generalized to other lung segments. Thirty-three CF children, aged 1.5-57 months, underwent in random order sequential BAL of their right middle and lingula lobes. Specimens from each lobe had separate quantitative bacteriology, cytology and cytokine analysis. Bacterial counts > or = 1 x 10(5) colony forming units (cfu) x mL(-1) were observed in nine (27%) subjects, including six involving only the right middle lobe. These six children had similar inflammatory indices in their right middle and lingula lobes, and interleukin (IL)-8 concentrations in the latter were significantly higher than that observed within the lingula lobes of the 24 CF children with bacterial counts < 1 x 10(5) cfu x mL(-1). Lingula neutrophil and IL-8 levels correlated best with right middle lobe bacteria numbers. This observational study in cystic fibrosis children suggests that while inflammation is detected in both lungs, bacterial distribution may be more inhomogeneous. Bronchoalveolar lavage microbiological findings from a single lobe may therefore, not be generalized to other lung segments. When performing bronchoalveolar lavage in cystic fibrosis children, it is important to sample from multiple sites.

Interleukin-1 receptor type I gene-deficient mice are less susceptible to Staphylococcus epidermidis biomaterial-associated infection than are wild-type mice

Elevated concentrations of interleukin-1 (IL-1) were found in tissue surrounding biomaterials infected with Staphylococcus epidermidis. To determine the role of IL-1 in biomaterial-associated infection (BAI), IL-1 receptor type I-deficient (IL-1R(-/-)) and wild-type mice received subcutaneous implants of silicon elastomer (SE) or polyvinylpyrrolidone-grafted SE (SEpvp), combined with an injection of 10(6) CFU of S. epidermidis or sterile saline. Neither mouse strain was susceptible to BAI around SE. IL-1R(-/-) mice with SEpvp implants had a no abscess formation and a reduced susceptibility to persistent S. epidermidis infection. The normal foreign body response, characterized by giant-cell formation and encapsulation, was delayed around SEpvp in wild-type mice but not in IL-1R(-/-) mice. This coincided with enhanced local IL-4 production in IL-1R(-/-) mice. These data suggest that inhibition of local IL-1 activity may be beneficial for the outcome of BAI.

Interleukin-2 involvement in early acute respiratory distress syndrome: relationship with polymorphonuclear neutrophil apoptosis and patient survival

OBJECTIVE

To determine blood and lung alveolar concentrations of interleukin (IL)-2 in acute respiratory distress syndrome (ARDS) and their relationship with polymorphonuclear neutrophil (PMN) apoptosis and patient survival.

DESIGN

Prospective cohort study.

SETTING

Medical and surgical intensive care units (ICUs; Canada) and the intensive care department (Belgium).

PATIENTS

Nineteen consecutive patients with ARDS, 14 non-ARDS ICU patients, and 20 healthy volunteers.

INTERVENTIONS

Blood samples and bronchoalveolar lavages (BAL) obtained via venous puncture and by fiberoptic bronchoscopy in the first 72 hrs after the onset of ARDS.

MEASUREMENTS AND MAIN RESULTS

One early point concentration of IL-2 was measured in both blood and BAL fluids of the three groups. In vivo alveolar PMN apoptotic index in BAL fluids and the influence of BAL fluid exposure on normal blood PMN spontaneous apoptosis in vitro were evaluated. Blood IL-2 was significantly lower in patients with ARDS compared with non-ARDS ICU patients and controls. In contrast, IL-2 in BAL fluids of patients with ARDS was dramatically elevated compared with non-ARDS ICU patients and controls. ARDS survivors exhibited lower early IL-2 blood levels than nonsurvivors and generally had a higher IL-2 lung content Lung alveolar PMN apoptosis in vivo was lower in patients with ARDS in comparison with controls. This apoptotic index was correlated with corresponding IL-2 alveolar levels in patients with ARDS. Exposure of normal blood PMN to BAL fluids from patients with ARDS delayed apoptosis in vitro. Immunodepletions of IL-2, granulocyte-macrophage colony stimulating factor, and a combination of both cytokines from BAL fluids of ARDS patients significantly restored PMN apoptosis. The recovery of PMN apoptosis was more effective when IL-2 was depleted in BAL fluids from ARDS survivors compared with nonsurvivors.

CONCLUSIONS

Opposite and disproportional concentrations of IL-2 are observed in blood and lung fluids of patients with early ARDS. IL-2 significantly contributes (with granulocyte-macrophage colony stimulating factor) to the inhibition of PMN apoptosis in BAL fluids of patients with ARDS. Early low blood IL-2 and high IL-2-driven inhibition of PMN apoptosis are beneficial to survivors. Thus, IL-2 is a new candidate for monitoring in early ARDS and an interesting indicator of prognosis.

Acute lung injury and acute respiratory distress syndrome in sepsis and septic shock

Sepsis remains the leading cause of ARDS, and ARDS is still an often fatal condition. With our expanding knowledge of the pathobiologic mechanisms and the relationship between these two entities, early recognition, treatment, and prevention of sepsis may prevent or hasten recovery from ARDS. Understanding the biologic markers involved in the complex inflammatory response of sepsis and acute lung injury offers the possibility of future investigations to target treatment based on these mediators.

Perfluorocarbon blocks tumor necrosis factor-alpha-induced interleukin-8 release from alveolar epithelial cells in vitro

OBJECTIVE

To determine whether tumor necrosis factor (TNF)-alpha-induced interleukin (IL)-8 production by pulmonary alveolar epithelial cells is blocked by perfluorocarbon (PFC).

DESIGN

Controlled, laboratory investigation of IL-8 production by pulmonary alveolar epithelial cells after exposure to PFC in vitro.

SETTING

University research laboratory.

SUBJECT

The human alveolar epithelial cell line with pulmonary type II (A549) cell properties.

INTERVENTIONS

The A549 cells on a polycarbonate porous filter were stimulated either on the apical or the basolateral side with TNF-alpha. To determine TNF-alpha-induced IL-8 production, IL-8 was measured by using a human IL-8 kit in both control and experimental groups.

MEASUREMENTS AND MAIN RESULTS

TNF-alpha stimulation induced a large increase in IL-8. When PFC was added to the medium immediately after TNF-alpha stimulation, PFC separated the medium from the cells and IL-8 production was markedly reduced (TNF-alpha alone, 8342+/-470 pg vs. TNF-alpha followed by PFC, 417+/-88 pg, p < .05). Preincubation of A549 cells with PFC for 24 hrs before stimulation with TNF-alpha followed by removal of PFC did not affect IL-8 production (8834+/-204 vs. 8342+/-470 pg; p = NS). When added to the lower chamber, TNF-alpha also induced IL-8 production unaffected by the addition of PFC to the upper chamber. The decrease in TNF-alpha-induced IL-8 production depended on the time of PFC administration after the initiation of TNF-alpha stimulation. The earlier PFC was added, the more pronounced the diminution was in IL-8.

CONCLUSIONS

PFC appears to function as a physical barrier, thus reducing cytokines produced by alveolar epithelial cells in vitro. This mechanism may partially explain the decreased inflammatory response observed during liquid ventilation in models of acute lung injury.

Enhanced susceptibility to subcutaneous abscess formation and persistent infection around catheters is associated with sustained interleukin-1beta levels

A persistent Staphylococcus epidermidis infection in mice around a subcutaneous polyvinylpyrrolidone-grafted silicon elastomer catheter (SEpvp) but not around a conventional silicon elastomer catheter was observed. With SEpvp pericatheter tissue, protracted and exaggerated interleukin-1beta (IL-1beta) production was found. Apparently, sustained levels of IL-1beta are associated with enhanced susceptibility to biomaterial-associated S. epidermidis infection.

Development of an offline noncompetitive flow immunoassay for the determination of interleukin-8 in cell samples

A noncompetitive flow immunoassay system (FIA) for the analysis of interleukin-8 (IL-8) in cell samples was developed. Affinity interaction assays based on offline incubation of excess labeled antibodies and antigen (IL-8) were carried out. The residual unbound labeled antibody was trapped in an immunoaffinity column with immobilized IL-8 while the immunocomplex, labeled antibody/IL-8, was detected by a fluorescence detector. Two fluorophores, FLUOS and Cy5.5, were conjugated with IL-8 antibody. Optimization and comparison between the two fluorescent labeled antibodies were performed with regard to pH, antibody concentration, flow rate, injection volume, and association time. Additionally, a horseradish peroxidase enzyme label was used for the conjugation to the anti-IL-8. The enzyme substrate reaction was optimized with respect to temperature and length of the substrate reaction coil. The detection limits were found to be 200 amol using the FLUOS-labeled anti-IL-8 and 1 fmol using the Cy5.5 fluorescence label. The developed FIA technique was applied for the analysis of IL-8 in cell samples. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to identify IL-8 in the cell samples.

Hyperoxia synergistically increases TNF-alpha-induced interleukin-8 gene expression in A549 cells

Interleukin (IL)-8 is an important mediator of acute lung injury. Hyperoxia induces IL-8 production in some cell types, but its effect on IL-8 gene expression in respiratory epithelium is not well described. In addition, IL-8 gene expression resulting from the combined effects of hyperoxia and proinflammatory cytokines has not been well characterized. We treated cultured respiratory epithelial-like cells (A549 cells) with hyperoxia alone, tumor necrosis factor (TNF)-alpha alone, or the combination of TNF-alpha and hyperoxia and evaluated IL-8 gene expression. Hyperoxia alone had a minimal effect on IL-8 gene expression, and TNF-alpha alone increased IL-8 gene expression in a time-dependent manner. In contrast, the combination of TNF-alpha and hyperoxia synergistically increased IL-8 gene expression as measured by ELISA (TNF-alpha alone for 24 h = 769 +/- 89 pg/ml vs. hyperoxia + TNF-alpha for 24 h = 1, 189 +/- 89 pg/ml) and Northern blot analyses. Experiments involving IL-8 promoter-reporter assays, electromobility shift assays, and Western blot analyses demonstrated that hyperoxia augmented TNF-alpha-mediated activation of the IL-8 promoter by a nuclear factor (NF)-kappaB-dependent mechanism and increased the duration of NF-kappaB nuclear translocation after concomitant treatment with TNF-alpha. Additional reporter gene assays demonstrated, however, that increased activation of NF-kappaB does not fully account for the synergistic effect of hyperoxia and that the NF-IL-6 site in the IL-8 promoter is also required for the synergistic effect of hyperoxia. We conclude that hyperoxia alone has a minimal effect on IL-8 gene expression but synergistically increases IL-8 gene expression in the presence of TNF-alpha by a mechanism involving cooperative interaction between the transcription factors NF-kappaB and NF-IL-6.

Comparison of systemic cytokine levels in patients with acute respiratory distress syndrome, severe pneumonia, and controls

BACKGROUND

The inflammatory response has been widely investigated in patients with acute respiratory distress syndrome (ARDS) and pneumonia. Studies investigating the diagnostic values of serum cytokine levels have yielded conflicting results and only little information is available for the differential diagnosis between ARDS and pneumonia.

METHODS

Clinical and physiological data, serum concentrations of tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-6, and quantitative cultures of lower respiratory tract specimens were obtained from 46 patients with ARDS and 20 with severe pneumonia within 24 hours of the onset of the disease and from 10 control subjects with no inflammatory lung disease. Cytokine concentrations were compared between groups and determinants in addition to the diagnosis were tested.

RESULTS

Serum TNF-alpha levels were significantly higher in ARDS patients (67 (57) pg/ml) than in patients with severe pneumonia (35 (20) pg/ml; p = 0.031) or controls (17 (8) pg/ml; p = 0.007). For IL-1beta and IL-6 the observed differences were not statistically significant between patients with ARDS (IL-1beta: 34 (65) pg/ml; IL-6: 712 (1058) pg/ml), those with severe pneumonia (IL-1beta: 3 (4) pg/ml, p = 0.071; IL-6: 834 (1165) pg/ml, p = 1.0), and controls (IL-1beta: 6 (11) pg/ml, p = 0.359; IL-6: 94 (110) pg/ml, p = 0.262). TNF-alpha (standardised coefficient beta = 0.410, p<0.001) and IL-1beta (standardised coefficient beta = 0.311, p = 0.006) were most strongly associated with the degree of lung injury, even when the diagnostic group was included in the statistical model.

CONCLUSIONS

Serum TNF-alpha levels were higher in patients with ARDS than in those with severe pneumonia or in control subjects. Multivariate results suggest that the levels of systemic TNF-alpha and IL-1beta reflect the severity of the lung injury rather than the diagnosis.

Immunopathologic alterations in murine models of sepsis of increasing severity

We investigated inflammatory and physiologic parameters in sepsis models of increasing lethality induced by cecal ligation and puncture (CLP). Mice received imipenem for antibiotic therapy, and groups were sacrificed at 2, 4, 8, 12, 16, 20, and 24 h after CLP. The severity of sepsis increased with needle puncture size (lethality with 18-gauge puncture [18G], 100%; 21G, 50%; 25G, 5%; sham treatment, 0%). While the temperature (at 12 h) and the activity and diurnal rhythm (at day 4) of the 25G-treated CLP group recovered to normal, the 21G and 18G treatment groups exhibited severe hypothermia along with decreased activities. A direct correlation was also observed between the severity of sepsis and cytokine (interleukin 1beta [IL-1beta], tumor necrosis factor [TNF], IL-6, and IL-10) concentrations in both the peritoneum and the plasma. There were substantially higher cytokine levels in the more severe CLP models than in the sham-treated one. Peritoneal and plasma TNF levels were always less than 40 pg/ml in all models. None of the cytokines in the septic mice peaked within the first hour, which is in contrast to the results of most endotoxin models. Chemokine (KC and macrophage inflammatory protein 2) profiles also correlated with the severity of sepsis. Except for the chemokines, levels of inflammatory mediators were always higher at the site of inflammation (peritoneum) than in the circulation. Our study demonstrated that sepsis of increasing severity induced increased cytokine levels both within the local environment (peritoneum) and systemically (plasma), which in turn correlated with morbidity and mortality.

New rationale for glucocorticoid treatment in septic shock

Two recent small randomized trials evaluating a 5- to 12-day course of low dose hydrocortisone in patients with septic shock have reported a significant clinical improvement and a reduction in mortality. Recent studies indicate that an overaggressive and unregulated systemic inflammatory response is a major determinant of outcome in sepsis. In septic shock, nonsurvivors as opposed to survivors have over time: (1) significantly higher NF-kB activity in peripheral mononuclear cells, (2) persistent elevation in circulating inflammatory cytokine levels, and (3) elevated ACTH and cortisol levels. Current research recognizes that cytokines can cause a concentration-dependent resistance to endogenous glucocorticoids (GC). It is postulated that an excess of cytokine-induced transcription factors, such as NF-kB, may form complexes with activated glucocorticoid receptors (GCR), preventing GCR interaction with DNA. When T cells are incubated with a combination of cytokines, GC resistance is induced in a cytokine concentration-dependent fashion and reversed by removal of cytokines. Prolonged treatment with physiological doses of exogenous GCs may be necessary to compensate adequately for the inability of target organs to respond to endogenous cortisol and for the inability of the host to produce appropriately elevated levels of GCs. This hypothesis is supported by the laboratory findings of a recent randomized study of patients with unresolving acute respiratory disease.

Estudo de crianças com síndrome do desconforto respiratório agudo: correlação anatomoclínica radiológica

Estudo retrospectivo com revisão dos casos clínicos de Síndrome do Desconforto Respiratório Agudo, realizado no período de out/88 a dez/90 na Unidade de Pacientes Graves do Instituto Fernandes Figueira. Os autores estudaram as características clínicas, radiológicas e histopatológicas de acordo com o estágio evolutivo da doença. Dentre 459 casos estudados, foram selecionados 49 (11%). Onze casos tiveram exame anatomopatologico [biopsia (4), necropsia (8)] e foram classificados de acordo com o estágio evolutivo em: fase exsudativa inicial, fase proliferativa celular e fase proliferativa fibrótica. Houve correlação clínica radiológica e anatomopatológica nos casos confirmados com exame histológico. Os autores consideram importante estudos futuros em que a interação entre a pesquisa clínica e experimental permita o melhor conhecimento desta Síndrome na população pediátrica.

Lung injury and acute respiratory distress syndrome after cardiopulmonary bypass

Cardiopulmonary bypass is often followed by pulmonary dysfunction as assessed by measuring the alveolar-arterial oxygenation gradient, intrapulmonary shunt, degree of pulmonary edema, pulmonary compliance, and pulmonary vascular resistance. It is also regarded as a risk factor for development of acute respiratory distress syndrome. On the other hand, cardiopulmonary bypass is associated with a whole body inflammatory response, which involves activation of complement, leukocytes, and endothelial cells with secretion of cytokines, proteases, arachidonic acid metabolites, and oxygen free radicals. Leukocyte adhesion to microvascular endothelium, leukocyte extravasation, and tissue damage are the final steps. Although the inflammatory response to cardiopulmonary bypass often remains at subclinical levels, it can also lead to major organ dysfunction and multiple organ failure. This review article summarizes the recent literature on the molecular and cellular mechanisms involved in the phenomenon of pulmonary dysfunction after cardiopulmonary bypass. It also summarizes reports on the prevalence and mortality of acute respiratory distress syndrome after cardiac surgery.

Cytokines IL-1beta, IL-6, and TNF-alpha enhance in vitro growth of bacteria

We have previously reported that in acute respiratory distress syndrome (ARDS), nonsurvivors have persistent elevation in pulmonary and circulating proinflammatory cytokine levels over time and a high rate of nosocomial infections antemortem. In these patients, none of the proven or suspected nosocomial infections caused a transient or sustained increase in plasma proinflammatory cytokine levels above preinfection values. We hypothesized that cytokines secreted by the host during ARDS may favor the growth of bacteria. We conducted an in vitro study of the growth of three bacteria clinically relevant in nosocomial infections, evaluating their in vitro response to various concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6. We found that all three bacterial species showed concentration-dependent growth enhancement when incubated with one or more tested cytokines and that blockade by specific neutralizing cytokine MoAb significantly inhibited cytokine-induced growth. When compared with control, the 6-h growth response (cfu/ml) was maximal with IL-1beta at 1,000 pg for Staphylococcus aureus (36 +/- 16 versus 377 +/- 16; p = 0.0001) and Acinetobacter spp. (317 +/- 1,147 versus 1,124 +/- 147; p = 0.002) and with IL-6 at 1,000 pg for Pseudomonas aeruginosa (99 +/- 50 versus 509 +/- 50; p = 0.009). The effects of cytokines were seen only with fresh isolates and were lost with passage in vitro on bacteriologic medium without added cytokines. In this study we provide additional evidence for a newly described pathogenetic mechanism for bacterial proliferation in the presence of exaggerated and protracted inflammation.

Effects of cytokines and endotoxin on the intracellular growth of bacteria

Patients with unresolving acute respiratory distress syndrome (ARDS) have persistently elevated levels of proinflammatory cytokines in the lungs and circulation and increased rates of bacterial infections. Phagocytic cells hyperactivated with lipopolysaccharide (LPS), which induces high levels of proinflammatory cytokines in monocytic cells, are inefficient in killing ingested bacteria despite having intact phagocytic activity. On the other hand, phagocytic cells that are activated with an analogue of LPS that does not induce the expression of proinflammatory cytokines effectively ingest and kill bacteria. We hypothesized that in the presence of high concentrations of proinflammatory cytokines, bacteria may adapt and utilize cytokines to their growth advantage. To test our hypothesis, we primed a human monocytic cell line (U937) with escalating concentrations of the proinflammatory cytokines tumor necrosis factor alpha, interleukin-1beta (IL-1beta), and IL-6 and with LPS. These cells were then exposed to fresh isolates of three common nosocomial pathogens: Staphylococcus aureus, Pseudomonas aeruginosa, and an Acinetobacter sp. In human monocytes primed with lower concentrations of proinflammatory cytokines (10 to 250 pg) or LPS (1 and 10 ng), intracellular bacterial growth decreased. However, when human monocytes were primed with higher concentrations of proinflammatory cytokines (1 to 10 ng) or LPS (1 to 10 micrograms), intracellular growth of the tested bacteria increased significantly (P <0.0001). These results were reproduced with peripheral blood monocytes obtained from normal healthy volunteers. The specificity of the cytokine activity was demonstrated by neutralizing the cytokines with specific antibodies. Our findings provide a possible mechanism to explain the frequent development of bacterial infections in patients with an intense and protracted inflammatory response.

Multicenter randomized controlled trial of the effects of inhaled nitric oxide therapy on gas exchange in children with acute hypoxemic respiratory failure

OBJECTIVES AND BACKGROUND

To determine whether inhaled nitric oxide (iNO) therapy can attenuate the progression of lung disease in acute hypoxemic respiratory failure, we performed a multicenter, randomized, masked, controlled study of the effects of prolonged iNO therapy on oxygenation. We hypothesized that iNO therapy would improve oxygenation in an acute manner, slow the rate of decline in gas exchange, and decrease the number of patients who meet pre-established oxygenation failure criteria.

STUDY DESIGN

A total of 108 children (median age 2.5 years) with severe acute hypoxemic respiratory failure from 7 centers were enrolled. After consent was obtained, patients were randomized to treatment with iNO (10 ppm) or mechanical ventilation alone for at least 72 hours. Patients with an oxygenation index >/=40 for 3 hours or >/=25 for 6 hours were considered treatment failures and exited the study.

RESULTS

Patient age, primary diagnosis, pediatric risk of mortality score, mode of ventilation, and median oxygenation index (35 +/- 22 vs 30 +/- 15; iNO vs control; mean +/- SEM) were not different between groups at study entry. Comparisons of oxygenation indexes during the first 12 hours demonstrated an acute improvement in oxygenation in the iNO group at 4 hours (-10.2 vs -2.7, mean values; P <.014) and at 12 hours (-9.2 vs -2.8; P <.007). At 12 hours 36% of the control group met failure criteria in contrast with 16% in the iNO group (P <.05). During prolonged therapy the failure rate was reduced in the iNO group in patients whose entry oxygenation index was >/=25 (P <.04) and in immunocompromised patients (P <.03).

CONCLUSIONS

We conclude that iNO causes an acute improvement in oxygenation in children with severe AHRF. Two subgroups (immunocompromised and an entry oxygen index >/=25) appear to have a more sustained improvement in oxygenation, and we speculate that these subgroups may benefit from prolonged therapy.

Acute lung injury, acute respiratory distress syndrome and inhalation injury: an overview

Acute Lung Injury (ALI) and the Acute Respiratory Distress Syndrome (ARDS) are severe respiratory diseases that have a very poor prognosis and have numerous causes. Despite a great deal of research and investigation since the initial description of ARDS 30 years ago many questions about the pathogenesis, treatment and outcome of the disease remain unanswered. Although there is evidence to suggest that outcome of ALI and ARDS is improving, the reasons why are unknown and there is not yet a well developed treatment for these diseases. Inhalation injury resulting from exposure to pyrolysis and combustion atmospheres is among the causes of ALI/ARDS. Little is known of the mechanisms of fire related inhalation injury that results in the development of ALI/ARDS. There is a paucity of information about fire atmosphere exposure response relationships for smoke-induced inhalation injury. Although there is considerable information about the pulmonary toxicity of many of the more common constituents of fire atmospheres, little is known about the pulmonary toxicity of mixtures of these constituents. Fire related pulmonary health risks are of particular concern to the Navy due to the limited opportunity to escape the inhalation hazards posed by shipboard fires. Consequently the Naval Medical Research Institute Detachment (Toxicology) has undertaken a research program to develop research models of combustion atmosphere induced ALI/ARDS which can be exploited to systematically address some of the questions surrounding fire related ALI/ARDS. ALI/ARDS has been the topic of a vast amount of research, numerous symposia, working groups and their published proceedings, book chapters, and books. Less information is available regarding experimental models of smoke induced lung damage, however the literature on the subject is extensive. Consequently this article is intended to provide the reader with a primer or cursory "overview" of ALI and ARDS from a toxicological perspective and should not be considered comprehensive.