Plasma levels of tumor necrosis factor in the adult respiratory distress syndrome

Pharmacologic therapies of ARDS: From natural herb to nanomedicine

Acute respiratory distress syndrome (ARDS) is a common critical illness in respiratory care units with a huge public health burden. Despite tremendous advances in the prevention and treatment of ARDS, it remains the main cause of intensive care unit (ICU) management, and the mortality rate of ARDS remains unacceptably high. The poor performance of ARDS is closely related to its heterogeneous clinical syndrome caused by complicated pathophysiology. Based on the different pathophysiology phases, drugs, protective mechanical ventilation, conservative fluid therapy, and other treatment have been developed to serve as the ARDS therapeutic methods. In recent years, there has been a rapid development in nanomedicine, in which nanoparticles as drug delivery vehicles have been extensively studied in the treatment of ARDS. This study provides an overview of pharmacologic therapies for ARDS, including conventional drugs, natural medicine therapy, and nanomedicine. Particularly, we discuss the unique mechanism and strength of nanomedicine which may provide great promises in treating ARDS in the future.

Association between inflammatory biomarkers and acute respiratory distress syndrome or acute lung injury risk : A systematic review and meta-analysis

Background

The relationship between acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) and levels of certain inflammatory factors remains controversial. The purpose of this meta-analysis was to summarize the available studies evaluating the association between levels of inflammatory factors and ARDS/ALI incidence.

Methods

We searched the PubMed, EmBase, and Cochrane databases for studies published up to July 2017. For each inflammatory factor, a random effects model was employed to pool results from different studies.

Results

We identified 63 studies that included 6243 patients in our meta-analysis. Overall, the results indicated that the levels of angiopoietin (ANG)-2 (standard mean difference, SMD: 1.34; P < 0.001), interleukin (IL)-1β (SMD: 0.92; P = 0.012), IL‑6 (SMD: 0.66; P = 0.005), and tumor necrosis factor (TNF)-α (SMD: 0.98; P = 0.001) were significantly higher in patients with ARDS/ALI than in unaffected individuals. No significant differences were observed between patients with ARDS/ALI and unaffected individuals in terms of the levels of IL‑8 (SMD: 0.61; P = 0.159), IL-10 (SMD: 1.10; P = 0.231), and plasminogen activator inhibitor (PAI)-1 (SMD: 0.70; P = 0.060).

Conclusions

ARDS/ALI is associated with a significantly elevated levels of ANG‑2, IL-1β, IL‑6, and TNF‑α, but not with IL‑8, IL-10, and PAI‑1 levels.

Supplementary Information

The online version of this article (10.1007/s00508-021-01971-3) contains supplementary material, which is available to authorized users.

Knockdown of TNF‑α alleviates acute lung injury in rats with intestinal ischemia and reperfusion injury by upregulating IL‑10 expression

Intestinal ischemia and reperfusion (II/R) injury often triggers severe injury in remote organs, with the lungs being considered the main target. Excessive elevation of proinflammatory cytokines is a major contributor in the occurrence and development of II/R-induced acute lung injury (ALI). Therefore, the present study aimed to investigate whether blocking tumor necrosis factor-α (TNF-α) expression could protect the lungs from injury following II/R, and to explore the possible underlying mechanism involving interleukin-10 (IL-10). Briefly, II/R was induced in rats by 40 min occlusion of the superior mesenteric artery and celiac artery, followed by 8, 16 or 24 h of reperfusion. Subsequently, lentiviral vectors containing TNF-α short hairpin (sh)RNA were injected into the right lung tissues, in order to induce TNF-α knockdown. The severity of ALI was determined according to lung injury scores and lung edema (lung wet/dry weight ratio). The expression levels of TNF-α were analyzed by quantitative polymerase chain reaction (qPCR), western blotting and immunofluorescence (IF) staining. IL-10 expression, in response to TNF-α knockdown, was detected in lung tissues by qPCR and IF. The results detected marked inflammatory responses, and increased levels of lung wet/dry weight ratio and TNF-α expression, in the lungs of II/R rats. Conversely, treatment with TNF-α shRNA significantly alleviated the severity of ALI and upregulated the expression levels of IL-10 in lung tissues. These findings suggested that TNF-α RNA interference may exert a protective effect on II/R-induced ALI via the upregulation of IL-10. Therefore, TNF-α knockdown may be considered a potential strategy for the prevention or treatment of ALI induced by II/R in future clinical trials.

Anti-TNFα therapy in inflammatory lung diseases

Increased levels of tumor necrosis factor (TNF) α have been linked to a number of pulmonary inflammatory diseases including asthma, chronic obstructive pulmonary disease (COPD), acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), sarcoidosis, and interstitial pulmonary fibrosis (IPF). TNFα plays multiple roles in disease pathology by inducing an accumulation of inflammatory cells, stimulating the generation of inflammatory mediators, and causing oxidative and nitrosative stress, airway hyperresponsiveness and tissue remodeling. TNFα-targeting biologics, therefore, present a potentially highly efficacious treatment option. This review summarizes current knowledge on the role of TNFα in pulmonary disease pathologies, with a focus on the therapeutic potential of TNFα-targeting agents in treating inflammatory lung diseases.

Paradoxical response with increased tumor necrosis factor-α levels to anti-tuberculosis treatment in a patient with disseminated tuberculosis

It has been reported that tuberculosis (TB) worsens after cessation of tumor necrosis factor-α inhibitors and starting anti-TB treatment. Little is known about the immunological pathogenesis of this paradoxical response (PR). We report the first case of a TB patient in whom PR occurred concurrently with elevation of circulating tumor necrosis factor-α (TNFα) levels. A 75-year-old woman, who had been treated with adalimumab for SAPHO syndrome, developed disseminated TB. Soon after administration of anti-TB treatment (isoniazid, rifampicin, pyrazinamide, and ethambutol), and after discontinuation of adalimumab, a PR occurred. Serial testing of serum cytokine levels revealed a marked increase in TNFα, and a decline in interferon-γ levels. Despite intensive treatment with antibiotics, prednisolone, noradrenaline, and mechanical ventilation, acute respiratory distress syndrome developed and she died. Thus, overproduction of TNFα after cessation of TNFα inhibitors may partially account for the pathogenesis of a PR. This supports preventative or therapeutic reinitiation of TNFα inhibitors when PR occurs. Serial monitoring of circulating inflammatory cytokine levels could lead to earlier identification of a PR.

Effects of Cytokines and Other Inflammatory Mediators on Human Acute Pancreatitis

Most episodes of acute pancreatitis are mild, but severe disease complicated by multiple system organ failure develops in up to 20% of cases. In all patients with pancreatitis, the accumulation of leukocytes in pancreatic and extrapancreatic tissue, and the release of various mediators from them and other sites are important determinants of disease severity. Proinflammatory mediators, whose initial job is to limit the local damage, are released early in the disease. However, these mediators can exacerbate the severity of the pancreatitis when they continue to be elaborated in greater amounts or for longer periods than normal. When their actions are blocked or their release is inhibited, the severity of experimental pancreatitis and its associated mortality rate are less. This suggests the possibility that agents that inhibit the release and/or action of these mediators could be beneficial clinically.

Src Family Kinases Modulate the Loss of Endothelial Barrier Function in Response to TNF-α: Crosstalk with p38 Signaling

Activation of Src Family Kinase (SFK) signaling is required for the increase in endothelial permeability induced by a variety of cytokines and growth factors. However, we previously demonstrated that activation of endogenous SFKs by expression of dominant negative C-terminal Src Kinase (DN-Csk) is not sufficient to decrease endothelial adherens junction integrity. Basal SFK activity has been observed in normal venular endothelia and was not associated with increased basal permeability. The basal SFK activity however was found to contribute to increased sensitivity of the venular endothelium to inflammatory mediator-induced leakage. How SFK activation achieves this is still not well understood. Here, we show that SFK activation renders human dermal microvascular endothelial cells susceptible to low doses of TNF-α. Treatment of DN-Csk-expressing cells with 50 pg/ml TNF-α induced a loss of TEER as well as drastic changes in the actin cytoskeleton and focal adhesion proteins. This synergistic effect was independent of ROCK or NF-κB activity. TNF-α-induced p38 signaling was required for the synergistic effect on barrier function, and activation of the p38 MAPK alone was also able to induce changes in permeability only in monolayers with active SFKs. These results suggest that the activation of endogenous levels of SFK renders the endothelial barrier more susceptible to low, physiologic doses of TNF-α through activation of p38 which leads to a loss of endothelial tight junctions.

Aetiology, outcomes & predictors of mortality in acute respiratory distress syndrome from a tertiary care centre in north India

BACKGROUND & OBJECTIVES

Acute respiratory distress syndrome (ARDS) is a common disorder in critically ill patients and is associated with high mortality. There is a paucity of literature on this condition from developing countries. This prospective observational study was designed to find out the aetiology, outcomes and predictors of mortality in ARDS.

METHODS

Sixty four consecutive patients who satisfied American-European Consensus Conference (AECC) definition of ARDS from medical Intensive Care Unit (ICU) of a tertiary care centre in New Delhi, India, were enrolled in the study. Demographic, biochemical and ventilatory variables were recorded for each patient. Baseline measurements of serum interleukin (IL)-1β, IL-6, tumour necrosis factor-alpha (TNF-α), procalcitonin (PCT) and high sensitivity C-reactive protein (hsCRP) were performed.

RESULTS

Common causes of ARDS included pneumonia [44/64 (68.7%)], malaria [9/64 (14.1%)] and sepsis [8/64 (12.5%]. Eight of the 64 (12.5%) patients had ARDS due to viral pneumonia. The 28-day mortality was 36/64 (56.2%).Independent predictors of mortality included non-pulmonary organ failure, [Hazard ratio (HR) 7.65; 95% CI 0.98-59.7, P=0.05], Simplified Acute Physiology Score (SAPS-II) [HR 2.36; 95% CI 1.14-4.85, P=0.02] and peak pressure (P peak ) [HR 1.13; 95% CI 1.00-1.30, P = 0.04] at admission.

INTERPRETATION & CONCLUSIONS

Bacterial and viral pneumonia, malaria and tuberculosis resulted in ARDS in a considerable number of patients. Independent predictors of mortality included non-pulmonary organ failure, SAPS II score and P peak at baseline. Elevated levels of biomarkers such as TNF-α, PCT and hsCRP at admission might help in identifying patients at a higher risk of mortality.

Inhibition of Acute Lung Injury by TNFR-Fc through Regulation of an Inflammation-Oxidative Stress Pathway

Background

Acute lung injury (ALI), characterized by disruption of the lung alveolar-capillary membrane barrier and resultant pulmonary edema, and associated with a proteinaceous alveolar exudate, is a leading cause of morbidity and mortality. Currently, inflammation-oxidative stress interaction between TNF-α and NF-κB was identified as a key pathway of ALI. We hypothesized that a TNFR-Fc fusion protein would have beneficial effects in experimental ALI, and sought to test this idea in mice by blocking TNF-α.

Methods and Results

Intratracheal instillation of lipopolysaccharide (LPS) into the lungs of ALI mice led to histiocyte apoptosis, and detection of serum and bronchoalveolar lavage fluid (BALF) cytokines, feedback between NF-κB and TNF-α, lung albumin leakage, lung damage, IκB kinase (IKK) and NF-κB activation, I-κB degradation, and oxidative injury. LPS administration raised pulmonary inflammation as reflected by increased inflammatory cytokines, alveoli protein concentration, and ALI scores. IKK is phosphorylated following LPS challenge, leading to I-κB degradation and NF-κB p65 phosphorylation. Furthermore, NF-κB is translocated into the nucleus and up-regulates TNF-α gene transcription. Infusion of TNFR-Fc 24h before LPS challenge significantly abrogated the increase of inflammatory cytokines, especially serum TNF-α concentration, as well as pulmonary alveoli protein levels, and diminished IKK and NF-κB activation and I-κB degradation. The nuclear translocation of NF-κB was inhibited, following by down-regulation of TNF-α gene transcription. In addition, LPS intratracheal instillation induced marked oxidative damage, such as a decrease in total anti-oxidation products and an increase in malondialdehyde (MDA), as well as up-regulation of oxidation enzymes. Histologic analysis and apoptosis scores revealed that the extent of tissue lesions was significantly reduced, but not abrogated, by TNF-α blockade.

Conclusion

Treatment with LPS alone increased inflammation and oxidative stress in ALI mice, while administration of TNFR-Fc 24h before LPS challenge broke the feedback between NF-κB and TNF-α, resulting in decreased pulmonary inflammation/oxidative damage and tissue destruction. These results suggest a potential role for TNF-α therapy to treat clinical ALI.

A Pathophysiologic Approach to Biomarkers in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is an acute-onset hypoxic condition with radiographic bilateral lung infiltration. It is characterized by an acute exudative phase combining diffuse alveolar damage and lung edema followed by a later fibroproliferative phase. Despite an improved understanding of ARDS pathobiology, our ability to predict the development of ARDS and risk-stratify patients with the disease remains limited. Biomarkers may help to identify patients at the highest risk of developing ARDS, assess response to therapy, predict outcome, and optimize enrollment in clinical trials. After a short description of ARDS pathobiology, here, we review the scientific evidence that supports the value of various ARDS biomarkers with regard to their major biological roles in ARDS-associated lung injury and/or repair. Ongoing research aims at identifying and characterizing novel biomarkers, in order to highlight relevant mechanistic explorations of lung injury and repair, and to ultimately develop innovative therapeutic approaches for ARDS patients. This review will focus on the pathophysiologic, diagnostic, and therapeutic implications of biomarkers in ARDS and on their utility to ultimately improve patient care.

Plasma biomarkers for acute respiratory distress syndrome: a systematic review and meta-analysis*

OBJECTIVE

Numerous studies have focused on biomarkers for acute lung injury and acute respiratory distress syndrome. Although several biomarkers have been identified, their relative performance is unclear. We aim to provide a quantitative overview of plasma-derived biomarkers associated with acute respiratory distress syndrome diagnosis or mortality.

DATA SOURCES

MEDLINE (inception to January 2012) and personal databases.

STUDY SELECTION

English-language studies on plasma biomarkers associated with acute respiratory distress syndrome diagnosis or mortality.

DATA EXTRACTION

Demographic variables, plasma levels of biomarker, statistical data, acute respiratory distress syndrome occurrence, and mortality rates were retrieved. The methodological quality was assessed with the Quality Assessment of Diagnostic Accuracy Studies score. Clinical outcomes included 1) diagnosis of acute respiratory distress syndrome in the at-risk population and 2) mortality in acute respiratory distress syndrome patients. For each biomarker, pooled odds ratios for clinical outcome were calculated by meta-analysis, and biomarkers were ranked according to pooled odds ratio.

DATA SYNTHESIS

Fifty-four studies appeared eligible for meta-analysis, together including 3,753 patients. We identified 20 biomarkers for diagnosis of acute respiratory distress syndrome in the at-risk population and 19 biomarkers for mortality of acute respiratory distress syndrome patients. The biomarkers most strongly associated with acute respiratory distress syndrome diagnosis in the at-risk population, when increased, were Krebs von den Lungen-6 (odds ratio [95% CI], 6.1 [3.0-12.1]), lactate dehydrogenase (5.7 [1.7-19.1]), soluble receptor for advanced glycation end products (3.5 [1.7-7.2]), and von Willebrand Factor (3.1 [2.0-5.2]). The biomarkers most strongly associated with acute respiratory distress syndrome mortality, when increased, were interleukin-4 (18.0 [6.0-54.2]), interleukin-2 (11.8 [4.3-32.2]), angiopoietin-2 (6.4 [1.3-30.4]), and Krebs von den Lungen-6 (5.1 [3.0-12.2]). Decreased levels of Protein C were associated with increased odds for acute respiratory distress syndrome diagnosis and mortality.

CONCLUSIONS

This meta-analysis provides a unique ranking of plasma biomarkers according to their strength of association with acute respiratory distress syndrome diagnosis or acute respiratory distress syndrome mortality. The relative performance of biomarkers among studies shown in this ranking may help to improve acute respiratory distress syndrome diagnosis and outcome prediction.

A critical role for phosphatidylinositol (3,4,5)-trisphosphate-dependent Rac exchanger 1 in endothelial junction disruption and vascular hyperpermeability

RATIONALE

The small GTPase Rac is critical to vascular endothelial functions, yet its regulation in endothelial cells remains unclear. Understanding the upstream pathway may delineate Rac activation mechanisms and its role in maintaining vascular endothelial barrier integrity.

OBJECTIVE

By investigating phosphatidylinositol (3,4,5)-trisphosphate-dependent Rac exchanger 1 (P-Rex1), one of the Rac-specific guanine nucleotide exchange factors previously known for G protein-coupled receptor signaling, we sought to determine whether Rac-guanine nucleotide exchange factor is nodal for signal integration and potential target for drug intervention.

METHODS AND RESULTS

Using gene deletion and small interference RNA silencing approach, we investigated the role of P-Rex1 in human lung microvascular endothelial cells. Tumor necrosis factor α (TNF-α) exposure led to disruption of endothelial junctions, and silencing P-Rex1 protected junction integrity. TNF-α stimulated Rac activation and reactive oxygen species production in a P-Rex1-dependent manner. Removal of P-Rex1 significantly reduced intercellular adhesion molecule-1 expression, polymorphonuclear leukocyte transendothelial migration, and leukocyte sequestration in TNF-α-challenged mouse lungs. The P-Rex1 knockout mice were also refractory to lung vascular hyperpermeability and edema in a lipopolysaccharide-induced sepsis model.

CONCLUSIONS

These results demonstrate for the first time that P-Rex1 expressed in endothelial cells is activated downstream of TNF-α, which is not a G protein-coupled receptor agonist. Our data identify P-Rex1 as a critical mediator of vascular barrier disruption. Targeting P-Rex1 may effectively protect against TNF-α- and lipopolysaccharide-induced endothelial junction disruption and vascular hyperpermeability.

Biomarkers in acute lung injury

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) result in high permeability pulmonary edema causing hypoxic respiratory failure with high morbidity and mortality. As the population ages, the incidence of ALI is expected to rise. Over the last decade, several studies have identified biomarkers in plasma and bronchoalveolar lavage fluid providing important insights into the mechanisms involved in the pathophysiology of ALI. Several biomarkers have been validated in subjects from the large, multicenter ARDS clinical trials network. Despite these studies, no single or group of biomarkers has made it into routine clinical practice. New high throughput "omics" techniques promise improved understanding of the biologic processes in the pathogenesis in ALI and possibly new biomarkers that predict disease and outcomes. In this article, we review the current knowledge on biomarkers in ALI.

TNF-alpha increases tyrosine phosphorylation of vascular endothelial cadherin and opens the paracellular pathway through fyn activation in human lung endothelia

Tumor necrosis factor (TNF)-alpha is a key mediator of sepsis-associated multiorgan failure, including the acute respiratory distress syndrome. We examined the role of protein tyrosine phosphorylation in TNF-alpha-induced pulmonary vascular permeability. Postconfluent human lung microvascular and pulmonary artery endothelial cell (EC) monolayers exposed to human recombinant TNF-alpha displayed a dose- and time-dependent increase in transendothelial [(14)C]albumin flux in the absence of EC injury. TNF-alpha also increased tyrosine phosphorylation of EC proteins, and several substrates were identified as the zonula adherens proteins vascular endothelial (VE)-cadherin, and beta-catenin, gamma-catenin, and p120 catenin (p120(ctn)). Prior protein tyrosine kinase (PTK) inhibition protected against the TNF-alpha effect. TNF-alpha activated multiple PTKs, including src family PTKs. Prior PTK inhibition with the src-selective agents PP1 and PP2 each protected against approximately 60% of the TNF-alpha-induced increment in [(14)C]albumin flux. PP2 also blocked TNF-alpha-induced tyrosine phosphorylation of VE-cadherin, gamma-catenin, and p120(ctn). To identify which src family kinase(s) was required for TNF-alpha-induced vascular permeability, small interfering RNA (siRNA) targeting each of the three src family PTKs expressed in human EC, c-src, fyn, and yes, were introduced into the barrier function assay. Only fyn siRNA protected against the TNF-alpha effect, whereas the c-src and yes siRNAs did not. These combined data suggest that TNF-alpha regulates the pulmonary vascular endothelial paracellular pathway, in part, through fyn activation.

Impact of impaired nasal breathing on sleep-disordered breathing

OBJECTIVE

The role of the nose and its importance in the development and severity of sleep-disordered breathing (SDB) is still a matter of discussion. In the first part of this study, often-controversial data and theories about the nose are reviewed concerning its influence on the pathophysiology of SDB and to interpret certain clinical findings connected with impaired nasal breathing. In the second part, the effectiveness of some nonsurgical and surgical therapies is evaluated.

METHOD

A worldwide literature research (Medline) was the basis for this review.

RESULTS

The study of the literature on nasal resistance and clinical findings about the effects of incomplete or complete nasal blockage, particularly in comparison of healthy persons and persons with SDB, allows the assumption of the existence of two different groups of responders: a larger group where the importance of the nose for SDB is negligible and a smaller group where the influence of the nose on SDB is crucial. The same seems to hold true for the responses to nonsurgical and surgical treatments with only a few surgical results available in the literature. While the success rate of nasal surgery for patients with obstructive sleep apnea, for instance, seems to be less than 20%, the normalization of nasal resistance often leads to a positive impact on the well-being and the sleep quality of these patients. However, because criteria to identify responders are lacking, the prediction of success of any treatment for the individual with SDB is not possible.

The role of tumour necrosis factor-alpha in the pathogenesis of complicated falciparum malaria

Plasmodium falciparum malaria is the most important parasitic infection of humans and is one of the most serious health problems facing the inhabitants of developing countries. It is responsible for about 2 million deaths every year. To date there is no specific treatment for the disease apart from anti-malarials. The declining sensitivity to these drugs is a serious therapeutic problem, while no safe and effective vaccine is likely to be available for general use in the near future. There is now abundant laboratory and clinical evidence to suggest that tumour necrosis factor-alpha (TNF-alpha) plays a major role in the pathogenesis of complicated falciparum malaria. Modulation of TNF-alpha response in combination with the current anti-malarial drugs, may represent a novel approach to the treatment of the serious complications associated with the disease.

Acute respiratory distress syndrome. Potential pharmacologic interventions

Remarkable progress has been made in the past 10 years with regard to understanding the interplay of potent physiologic mediators in patients with acute lung injury. Because there are so many mediators and the interaction of these agents is complex, true insight into the process has been slow in coming. Clinical studies in ARDS, as well as sepsis, the leading cause of ARDS, have increased in number, size, and quality over this same period. Although none of these studies has produced an accepted new therapy for ARDS, each has laid the groundwork for more efficient and more elegant studies of the problem. The stage is now set for the real advances to be brought forward and put to rigorous, efficient clinical testing.

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.

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.

The role of complement activation in tumour necrosis factor-induced lethal hepatitis

Injection of tumour necrosis factor (TNF) in animals causes severe liver cell toxicity, especially when D-(+)-galactosamine (GalN) is co-administered. After challenge with TNF/GalN, serum complement activity (CH50 and APCH50) decreased dramatically, suggesting strong activation of both the classical and the alternative pathways. TNF or GalN alone had no such effect. A cleavage product of complement protein C3 [C3(b)] was deposited on the surface of hepatocytes of TNF/GalN-treated mice. Intravenous administration of cobra venom factor (CVF), which depletes complement, inhibited the development of hepatitis. However, CVF pretreatment also protected C3-deficient mice. Pretreatment of mice with a C1q-depleting antibody did not prevent TNF/GalN lethality, although the anti-C1q antibody had depleted plasma C1q. Factor B-deficient and C3-deficient mice, generated by gene targeting, proved to be as sensitive to TNF/GalN as control mice. Furthermore, induction of lethal shock by platelet-activating factor, an important mediator in TNF-induced hepatic failure, was not reduced in C3-deficient mice. These data indicate that complement, although activated, plays no major role in the generation of acute lethal hepatic failure in this model and that CVF-induced protection is independent of complement depletion.

Upregulation of xanthine oxidase by lipopolysaccharide, interleukin-1, and hypoxia. Role in acute lung injury

LPS and selected cytokines upregulate xanthine dehydrogenase/xanthine oxidase (XDH/XO) in cellular systems. However, the effect of these factors on in vivo XDH/XO expression, and their contribution to lung injury, are poorly understood. Rats were exposed to normoxia or hypoxia for 24 h after treatment with LPS (1 mg/kg) and IL-1beta (100 microg/kg) or sterile saline. Lungs were then harvested for measurement of XDH/XO enzymatic activity and gene expression, and pulmonary edema was assessed by measurement of the wet/dry lung weight ratio (W/D). Although treatment with LPS + IL-1beta or hypoxia independently produced a 2-fold elevation (p < 0. 05 versus exposure to normoxia and treatment with saline) in lung XDH/XO activity and mRNA, the combination of LPS + IL-1beta and hypoxia caused a 4- and 3.5-fold increase in these values, respectively. XDH/XO protein expression was increased 2-fold by hypoxia alone and 1.3-fold by treatment with LPS + IL-1beta alone or combination treatment. Compared with normoxic lungs, W/D was significantly increased by exposure to hypoxia, LPS + IL-1beta, or combination treatment. This increase was prevented by treatment of the animals with tungsten, which abrogated lung XDH/XO activity. In conclusion, LPS, IL-1beta, and hypoxia significantly upregulate lung XDH/XO expression in vivo. The present data support a role for this enzyme in the pathogenesis of acute lung injury.

Effect of TNF-alpha antisense oligomers on cytokine production by primary murine alveolar macrophages

Antisense oligomers can inhibit expression of a single gene in a sequence-specific manner. As a result, these sequences are being developed both as powerful experimental tools in the laboratory and as a novel class of therapeutic agents. In this study, we evaluated a panel of morpholino antisense (M-AS) oligomers for their ability to inhibit tumor necrosis factor-alpha (TNF-alpha) production by primary murine alveolar macrophages (AMs) and compared them with the more commonly used phosphorothioate oligonucleotides (S-AS). We found that 25 microM of morpholino oligomers whose sequence spanned the AUG (M-AS 2, M-AS 2me, and M-AS 5) start codon of TNF-alpha significantly inhibited TNF production on stimulation by both lipopolysaccharides (LPS) (36.6 +/- 3.2%, 27.3 +/- 3.0%, and 37.7 +/- 2.0% inhibition, respectively), whereas S-AS targeted toward the same region were ineffective. M-AS 2 and M-AS 2me also significantly inhibited TNF production in AMs stimulated by adherence to a solid substrate (28.7 +/- 2.2% and 29.4 +/- 8.3% inhibition, respectively). Increasing the concentration of M-AS 2 and M-AS 2me to 50 microM improved their efficacy in both LPS-stimulated (42.7 +/- 1.5% and 45.9 +/- 2.1% inhibition, respectively) and adherence-stimulated (52.6 +/- 0.7% and 41.7 +/- 2.9% inhibition, respectively) AMs. In contrast, we showed that neither an antisense sequence targeted to a region upstream of the AUG site (M-AS 4) nor the nonsense control sequences M-NS 1 and M-NS 2 significantly inhibited TNF-alpha production by AMs on exposure to either stimulus. The data indicate that morpholino oligomers inhibit TNF-alpha production by murine AMs in a sequence-dependent and dose-dependent manner.

Suppression of acute lung injury in mice by an inhibitor of phosphodiesterase type 4

The present study has investigated the therapeutic potential of a type 4 phosphodiesterase (PDE) inhibitor, rolipram, in experimental lung injury. Acute lung injury was induced in the mouse by combined treatment with lipopolysaccharide (LPS; 10 mg/kg, i.v.) and zymosan (3 mg/kg, i.v.), and assessed using extravascular albumin accumulation; neutrophil sequestration in pulmonary capillaries was also measured. The results show that pretreatment with rolipram (5 mg/kg, i.p.) was protective against the induction of lung injury by combined LPS and zymosan; extravascular albumin accumulation was reduced by 89% and neutrophil sequestration in lung tissue, as assessed by lung myeloperoxidase (MPO) activity was reduced by 75%. Pretreatment with rolipram also attenuated increases in serum tumor necrosis factor alpha (TNFalpha) levels induced by LPS and zymosan treatment, measured after 2.5 h. The role of endogenous TNFalpha in the induction of lung injury was therefore assessed. Blockade of endogenous TNFalpha by treatment with the soluble receptor p55-IgG fusion protein or an anti-murine TNFalpha monoclonal antibody, TN3. 19.12, had no protective effect against LPS and zymosan-induced lung injury. This suggests that there is a disassociation between TNFalpha production and the induction of injury in this model. Administration of rolipram after LPS and before zymosan treatment obliterated the increase in pulmonary vascular permeability, but its effect on sequestration of neutrophils in pulmonary microvessels, as measured by MPO, was less marked. The results of the present study suggest that use of agents such as rolipram that inhibit PDE4 may have a therapeutic role in treatment of acute lung injury, since we have shown that it is effective in attenuation of neutrophil activation even after sequestration. However, its effect appears to be independent of TNFalpha inhibition.

Effects of a neutrophil elastase inhibitor (ONO-5046) on acute pulmonary injury induced by tumor necrosis factor alpha (TNFalpha) and activated neutrophils in isolated perfused rabbit lungs

The aim of this study was to examine the effect of ONO-5046, a neutrophil elastase (NE) inhibitor, on a model of acute lung injury induced by tumor necrosis factor alpha (TNFalpha) and phorbol myristate acetate (PMA)-activated neutrophils in isolated perfused rabbit lungs. 120 min after TNFalpha (4,000 JRU/ml) was injected into the pulmonary artery (PA), 5 x 10(7) PMA-stimulated neutrophils were infused into the PA together with 1251-rabbit serum albumin (RSA). In the ONO-5046-treated group (ONO), ONO-5046 (20 mg/kg/h) was continuously infused during the experimental period from 30 min prior to neutrophil administration. Saline, the ONO-5046 vehicle, was infused instead of ONO-5046 in the positive control group (ALD) and nonactivated neutrophils were infused without TNFalpha in the negative control group (Cont). PA pressure was monitored over a 240 min period, and bronchoalveolar lavage (BAL) was performed at the end of the experiment. Lung tissues were examined immunohistochemically for the expression of thrombomodulin (TM). The levels of TM in the perfusate were also measured by ELISA and the radioactivities in the BAL fluid, lung tissue and perfusate were determined to calculate the permeability index (PI) as an indicator of alveolar septal or vascular endothelial damage. The rabbit lungs infused with ONO-5046 showed slower and less increases in PA pressure compared with ALD group. The PI was significantly higher in ALD group (PI[BAL] = 0.028 +/- 0.014, PI[LUNG] = 0.04 +/- 0.003) than Cont (PI[BAL] = 0.002 +/- 0.001, PI[LUNG] = 0.015 +/- 0.003) and ONO group (PI[BAL] = 0.004 +/- 0.003, PI[LUNG] = 0.028 +/- 0.003 (p < 0.05). ALD group had higher TM levels in the perfusate and showed decreased expression of TM on the vascular endothelium compared to Cont and ONO group, suggesting that there was shedding of TM on endothelium and ONO-5046 attenuated a shedding of TM. In conclusion, ONO-5046 attenuated acute lung injury by inhibiting the alveolar epithelial and vascular endothelial injury triggered by activated neutrophils. NE appears to play an important role in the neutrophil-induced increase of pulmonary epithelial and microvascular permeability observed in acute lung injury.

Effect of human recombinant tumour necrosis factor-alpha and pentoxifylline on the ultrastructure of type II alveolar epithelial cells in pregnant and non-pregnant rabbits

An ultrastructural study was made of the morphological changes in type II alveolar epithelial cells (epII) of pregnant and non-pregnant rabbits, given human recombinant tumour necrosis factor-alpha (TNF-alpha) to induce experimental shock. TNF-alpha (biological activity 2-4 x 10(7) U/mg of protein) was injected once intraperitoneally, at a dose of 100 micrograms/kg body weight. The moderating effects of pentoxifylline (PTXF), given as four intraperitoneal doses (20 mg/kg) at 12-h intervals before injection of TNF-alpha, were also assessed. In animals treated with PTXF + TNF-alpha and with TNF-alpha only, damage to lung tissue, particularly to epII, was observed. Many epII had empty lamellar bodies. These changes were particularly distinct in the rabbits given TNF-alpha only. PTXF limited the degree of damage to epII, particularly that shown by the lamellar bodies. There were no significant differences in degree of damage to alveolar epithelial cells between pregnant and non-pregnant rabbits. Thus, the increased risk of severe complications due to shock observed in pregnancy may not be associated with changes in the surfactant system. However, further studies, particularly biochemical analysis of the surfactant, are necessary to confirm this.

Taming TNF: strategies to restrain this proinflammatory cytokine

Recent studies have demonstrated the essential role of tumor necrosis factor alpha (TNF-alpha) in rheumatoid arthritis and Crohn's disease. This article discusses agents known to suppress the formation or activity of TNF-alpha, and summarizes clinical studies using anti-TNF-alpha antibodies.

Early detection of type III procollagen peptide in acute lung injury. Pathogenetic and prognostic significance

The fibroproliferative reaction to acute lung injury may limit restoration of normal lung function and increase mortality in patients with acute lung injury. A biologic marker of collagen synthesis in the lung may be useful for studying the pathogenesis of acute lung injury and for identifying patients with acute lung injury who are at high risk for death and might benefit from new therapeutic modalities. Using an immunoassay, type III procollagen NH2 terminal peptide was measured in the pulmonary edema fluid of 44 patients with either acute lung injury or hydrostatic pulmonary edema (control group) within the first 24 h after endotracheal intubation for acute respiratory failure. Patients with acute lung injury (n = 33) or hydrostatic edema (n = 11) had the same degree of lung dysfunction as measured by the severity of oxygenation defect, the level of positive end-expiratory pressure, the decrease in static lung compliance, and the extent of infiltrates on the chest radiograph. However, the median procollagen III level was 5-fold higher in the pulmonary edema fluid of patients with acute lung injury than in the patients with hydrostatic pulmonary edema (p = 0.0001). Of the 33 patients with acute lung injury, 21 patients died and 12 lived. Nonsurvivors had significantly higher procollagen III levels than did survivors (p = 0.05). The positive and negative predictive values for nonsurvival for a procollagen III level > or = 1.75 U/ml were 74 and 83%, respectively. The relative risk of dying in the presence of a procollagen III value > or = 1.75 U/ml was 4.5 (95% CI, 0.7 to 27). Collagen synthesis in the lung, as reflected by elevated levels of procollagen III in pulmonary edema fluid, begins within the first 24 h of acute lung injury concurrent with the acute phase of increased endothelial and epithelial permeability to protein. This evidence suggests that fibrosing alveolitis begins much earlier in the course of clinical acute lung injury than has previously been appreciated. In addition, the presence of an elevated level of procollagen III is an early predictor of poor outcome. Thus, elevation of procollagen III in pulmonary edema fluid may have both pathogenetic and prognostic significance in patients with acute lung injury.

Markers for predicting the development of acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is a relatively common, inflammatory lung disorder that is associated with major morbidity and high mortality. The pathogenesis of ARDS is complex, and unfortunately, the development of ARDS in an individual patient is difficult to anticipate. In this chapter, we outline the rationale for why accurately predicting the development of ARDS would be valuable. We also review the accumulated data on approaches for predicting ARDS and discuss the potential difficulties in establishing predictive markers.

Early detection and markers of sepsis

In vitro and animal models of sepsis have provided a template for studies of the pathogenesis of sepsis in patients at risk for and with the syndrome. Numerous potential markers have been identified in these models and then looked for in patients. No single marker or combination of markers convincingly identifies sepsis, predicts the development of sepsis, predicts the development of complications of sepsis, or predicts mortality. As discussed, the clinical studies have been complicated by many confounding variables, including the lack of adherence to rigorous definitions, differences in assay methods, differences in timing of the studies, and differences in outcome variables analyzed. In spite of the limitations, the studies have been critical in helping determine the pathogenesis of sepsis in humans. As new mediators and modulators of inflammation are identified, it will be important to study their role as markers, individually and in combination, in human disease.

Plasma concentrations of cytokines, their soluble receptors, and antioxidant vitamins can predict the development of multiple organ failure in patients at risk

OBJECTIVES

The aims of this study were: a) to evaluate plasma concentrations of cytokines and their soluble receptors, as well as antioxidant substances in patients at high risk of developing multiple organ failure; b) to investigate early change: and c) to examine the possible prognostic value of these elements.

DESIGN

Prospective analysis.

SETTING

Surgical intensive care unit (ICU) of a university hospital.

PATIENTS

sixteen patients at risk for multiple organ failure.

MEASUREMENTS AND MAIN RESULTS

Ten patients developed multiple organ failure and five of them died. Whereas tumor necrosis factor-alpha (TNF-alpha) plasma concentrations were only borderline higher in patients developing multiple organ failure, TNF-soluble receptors 55 and 75 were significantly increased during all ICU days compared with patients not going into organ failure. Interleukin-6 plasma concentrations were higher in patients developing multiple organ failure during the first 2 days after ICU admission. The antioxidant vitamin C was significantly decreased in patients going into multiple organ failure during all ICU days. Other biochemical markers of antioxidant activity, such as vitamin E, copper, and zinc plasma concentrations, did not differ between the two groups.

CONCLUSIONS

Our data suggest that there is a marked increase in anti-TNF activity and a decrease of antioxidant defense in patients at risk of developing multiple organ failure. The predictive value of plasma concentrations of circulating TNF-soluble receptors and vitamin C in this type of patient needs further evaluation.

Acute respiratory distress syndrome: diagnosis and management

This review will attempt to put together the voluminous studies and concepts that have been published during the past 25 years following the description of the acute respiratory distress syndrome (ARDS) regarding diagnosis and management. The initial discussion will focus on how to clinically diagnose ARDS based recommendations. This also gives the current definition of acute lung injury and when to call it ARDS. The radiographic and hemodynamic characteristics are discussed including oxygenation parameters. The management outlines the conventional as well as new therapies intended to improve survival of this devastating disease.

Persistent elevation of inflammatory cytokines predicts a poor outcome in ARDS. Plasma IL-1 beta and IL-6 levels are consistent and efficient predictors of outcome over time

BACKGROUND

Inflammatory cytokines have been related to the development of adult respiratory distress syndrome (ARDS), shock, and multiple organ dysfunction syndrome (MODS). We tested the hypothesis that unfavorable outcome in patients with ARDS is related to the presence of a persistent inflammatory response. For this purpose, we evaluated the behavior of inflammatory cytokines during progression of ARDS and the relationship of plasma inflammatory cytokines with clinical variables and outcome.

METHODS

We prospectively studied 27 consecutive patients with severe medical ARDS. Plasma levels of tumor necrosis factor alpha (TNF-alpha) and interleukins (ILs) 1 beta, 2, 4, 6, and 8 were measured (enzyme-linked immunosorbent assay [ELISA] method) on days 1, 2, 3, 5, 7, 10, and 12 of ARDS and every third day thereafter while patients were receiving mechanical ventilation. Subgroups of patients were identified based on outcome, cause of ARDS, presence or absence of sepsis, shock, and MODS at the time ARDS developed. Subgroups were compared for levels of plasma inflammatory cytokines on day 1 of ARDS and over time.

RESULTS

Of the 27 patients, 13 survived ICU admission and 14 died (a mortality rate of 52%). Overall mortality was higher in patients with sepsis (86 vs 38%, p < 0.02). The mean initial plasma levels of TNF-alpha, IL-1 beta, IL-6, and IL-8 were significantly higher in nonsurvivors (p < 0.0001) and in those patients with sepsis (p < 0.0001). Plasma levels of IL-1 beta (p < 0.01) and IL-6 (p = 0.03) were more strongly associated with patient outcome than cause of ARDS (p = 0.8), lung injury score (LIS), APACHE II score, sepsis (p = 0.16), shock, or MODS score. Plasma levels of TNF-alpha, IL-1 beta, IL-6, and IL-8 remained significantly elevated over time (p < 0.0001) in those who died. Although it was the best early predictor of death (p < 0.001), plasma IL-2 > 200 pg/mL lost its usefulness after the first 48 h. A plasma IL-1 beta or IL-6 level > 400 pg/mL on any day in the first week of ARDS was associated with a low likelihood of survival.

CONCLUSIONS

Our findings indicate that unfavorable outcome in acute lung injury is related to the degree of inflammatory response at the onset and during the course of ARDS. Patients with higher plasma levels of TNF-alpha, IL-1 beta, IL-6, and IL-8 on day 1 of ARDS had persistent elevation of these inflammatory cytokines over time and died. Survivors had lesser elevations of plasma inflammatory cytokines on day 1 of ARDS and a rapid reduction over time. Plasma IL-1 beta and IL-6 levels were consistent and efficient predictors of outcome.

Tumor necrosis factor-alpha and embryonic mouse lung morphogenesis

The ontogeny of the embryonic and fetal lung involves complex interactions between epithelial and mesenchymal primordia which require a specific program of gene regulation and signal transduction. Past studies in our laboratory using congenic mouse strains indicate that one or more genes which map to the H-2 region of chromosome 17 regulate the rate of lung morphogenesis, defined in this context as differentiative heterochrony among strains. Since hormones and growth factors are the messengers of morphogenesis, it was logical to propose that tumor necrosis factor-alpha (TNF-alpha), a well-characterized cytokine whose gene maps to the D-region of the H-2 complex, is a putative mediator of lung morphogenesis. We investigated this proposition using immunochemical methods and a serumless, chemically defined in vitro model system. Our results demonstrate that: (1) TNF-alpha has a specific spatiotemporal localization, in vivo and in vitro; (2) TNF-alpha receptor, in vivo and in vitro, is localized throughout the embryonic lung; (3) TNF-alpha supplementation in vitro of embryonic lung primordia has a marked dose-dependent, stimulatory effect on branching morphogenesis and surfactant-associated protein (SP-A) expression; (4) multiple immunoreactive proteins, including 17, 26, and 68 kDa species, are expressed during development in vivo, and a subset of these are expressed in vitro; and (5) both time- and glucocorticoid-dependent changes occur in the in vivo expression pattern of TNF-alpha immunoreactive proteins after 4 and 7 days in vitro, including the up-regulation of a novel 40 kDa protein. Given that glucocorticoids (CORT) regulate TNF-alpha expression and TNF-alpha's ability to stimulate pulmonary morphodifferentiation and histodifferentiation, we conclude that TNF-alpha is an autocrine/paracrine pulmonary cytokine, probably a component of the lung morphogenesis pathway regulated by CORT.

Phagocyte function and cytokine production in community acquired pneumonia

BACKGROUND

It is possible that many deaths from pneumonia may involve the generation of inflammatory mediators and tissue damage by activated phagocytes. To test this hypothesis phagocyte function, plasma levels of interleukin 6 (IL-6), tumour necrosis factor alpha (TNF alpha), and soluble interleukin 2 receptor (IL-2R), disease severity, and outcome have been examined in 46 patients with community acquired pneumonia.

METHODS

Polymorphonuclear leucocyte (PMNL) and monocyte function were measured daily by chemiluminescence in these patients during the first week of admission, and cytokine levels were subsequently determined by ELISA. A series of 61 healthy individuals were used as a control group for the chemiluminescence results.

RESULTS

There was evidence of phagocyte, particularly PMNL, activation on admission in 76% of the patients. Most patients (86%) also had raised IL-2R levels on admission. IL-6 and unbound TNF alpha were present in 23% and 41% of patients at varying times during the course of the disease. There was little correlation between measurements of cytokine or phagocyte levels and outcome or indicators of disease severity, although this may be because of the small number of patients included in this preliminary study.

CONCLUSIONS

These results are consistent with the hypothesis that activated phagocyte function and raised levels of circulating cytokines may contribute to the pathogenesis of community acquired pneumonia. There are striking similarities in this respect between pneumonia, adult respiratory distress syndrome, and sepsis.

Biochemical and morphological alterations in xylazine-induced pulmonary edema

Sprague-Dawley rats were given 42 mg/kg xylazine intramuscularly, and lungs were lavaged with phosphate-buffered saline 3, 6, and 12 hr later. Total protein, lactate dehydrogenase (LDH), xanthine oxidase (XO), tumor necrosis factor (TNF), and interleukin 1 (IL-1) were measured in bronchoalveolar lavage fluid (BALF). Protein concentration, LDH, XO, and TNF levels were increased (p < 0.05) in the BALF from xylazine-treated rats as compared to controls. IL-1 level was unchanged at 3 and 6 hr and was reduced (p < 0.05) at 12 hr. Another group of rats was given 42 mg/kg xylazine intramuscularly, and lungs were fixed 0.5 and 12 hr later. Histologically, severe pulmonary edema (PE) involving the alveoli and perivascular stroma was observed. Fibrin, increased numbers of eosinophils, and macrophages with foamy cytoplasm were present in the alveoli of all treated animals. Ultrastructurally, endothelial damage, characterized by thinning, detachment from basement membranes, or bleb formation, was observed. The lesions were similar in both xylazine groups, differing mainly in severity with the 12-hr group having more severe lesions than the 0.5-hr group. To determine whether endothelial injury is caused by direct toxicity of xylazine, bovine pulmonary artery endothelial cells (BPAECs) were incubated with xylazine (0.3, 3, and 30 micrograms) for 0.5 or 3 hr. Xylazine did not have any effects on BPAECs, as indicated by phase-contrast microscopy and dye-exclusion viability assay. These results indicate that xylazine-induced PE is due to increased permeability resulting from endothelial injury, which is not caused by direct effect of xylazine on pulmonary endothelium. While oxygen radicals and TNF are possibly involved, IL-1 does not appear to play a role in xylazine-induced PE.

Interleukin 8 (IL-8) in the bronchoalveolar lavage fluid from patients with the adult respiratory distress syndrome (ARDS) and patients at risk for ARDS

A sensitive and specific radioimmunoassay was used to measure interleukin 8 (IL-8) in bronchoalveolar lavage fluids from control subjects, patients with the adult respiratory distress syndrome (ARDS) and patients undergoing coronary bypass surgery, a risk factor for developing ARDS. Concentrations of IL-8, albumin, total protein and numbers of neutrophils were higher in both patient groups than in controls. Levels of IL-8 were significantly correlated with the influx of neutrophils, plasma protein extravasation and with the PaO2/FiO2 ratio. These data suggest that IL-8 may mediate the recruitment of neutrophils from the vascular compartment into the alveolar space and may therefore be an important determinant in neutrophil-mediated lung injury. Since increased levels of IL-8 were also found in BAL fluid from patients at risk in whom ARDS did not develop, other factors are likely to be involved and IL-8, as well as other markers of inflammation, are of little prognostic use.

Subpopulation of hyperresponsive polymorphonuclear neutrophils in patients with adult respiratory distress syndrome. Role of cytokine production

To gain further insight into the pathogenesis of the adult respiratory distress syndrome (ARDS), we studied possible relationships among the activation status of circulating polymorphonuclear neutrophils (PMN), cytokine levels, and the severity of lung injury in 31 patients: 15 with ARDS, nine with severe pneumonia uncomplicated by ARDS, and seven mechanically ventilated with neither ARDS nor pneumonia. Nine healthy subjects served as controls. Using flow cytometry, we identified a subpopulation of PMN with an increased capacity to generate hydrogen peroxide after stimulation ex vivo in all three patient groups; significantly higher values were found in those with ARDS. The PMN stimulation index, a reflection of the degree of hyperresponsiveness, correlated with elevated levels of tumor necrosis factor-alpha (TNF alpha) in plasma, and both spontaneous and lipopolysaccharide-induced TNF alpha production by cultured monocytes. These biologic expressions of PMN activation and cytokine generation both correlated with indices of the severity of lung injury, but not with the overall clinical severity. In contrast, IL-6 and IL-1 beta showed little or no relationship with either the degree of lung injury or PMN hyperresponsiveness. We conclude that TNF-alpha-primed PMN may play a major role in the pathogenesis of ARDS-associated lung injury.

Studies on the role of tumor necrosis factor in adult respiratory distress syndrome

Tumor necrosis factor (TNF), rapidly becoming recognized as a mediator of inflammation, may be important in the pathogenesis of acute lung injury. Its role in the development of the adult respiratory distress syndrome (ARDS) in humans, however, has been difficult to clarify. To determine if TNF could be important early in the development of acute lung injury from multiple causes, we enrolled 103 patients within 8 h of meeting the criteria for an at-risk illness (sepsis, aspiration of gastric contents, severe pancreatitis, hypertransfusion, abdominal trauma, chest trauma, multiple fractures) and obtained multiple frequent blood samples for TNF measurements. Using five methods of TNF analysis, we were unable to find an association between TNF and the development of ARDS. However, we found significant differences in TNF measurements depending on the methods of analysis used, which could, at least in part, account for the inconsistencies in the published literature regarding the relationship between TNF and disease processes.

The cytokine network in the critically ill

There is increasing experimental and clinical evidence that a number of cytokines play a major role in the response to injury and infection and in the development of organ damage in critically ill patients. Tumour necrosis factor (TNF) is now proposed to be a key mediator of organ injury during sepsis. It is elevated early in the course of septic shock and high levels correlate with unfavourable outcome. In animals it can produce the effects of endotoxin. The prophylactic administration of anti-TNF antisera protects mice and rabbits from lethal effects of lipopolysaccharide. Interleukin-1 (IL-1) is an endogenous pyrogen which induces leukocytosis and muscle catabolism. It causes hypotension and tachycardia by reducing smooth muscle contractility. IL-1 receptor blockers have been shown to diminish mortality in experimental endotoxic shock. Interleukin-6 (IL-6) is a pyrogen and lymphocyte activator. It is the major stimulus to acute phase protein production by the liver. A recently described neutrophil-activating peptide (Interleukin-8; IL-8) may be involved in the pathogenesis of ARDS. High blood levels of IL-8 have been found in patients with septic shock. Platelet-derived growth factor (PDGF) has been shown to stimulate TNF production, leukocyte chemotaxis and pulmonary vasoconstriction in response to endotoxin. Other cytokines and growth factors have not yet been studied in critical illness. The cytokine network can be either protective or damaging. Its activation during critical illness triggers complex and still poorly understood interactions. A better comprehension of its role in protection from infection and in the pathogenesis of multiple organ failure may allow therapeutic manipulations aimed at minimising adverse effects while retaining immunological protection.

High bronchoalveolar levels of tumor necrosis factor and its inhibitors, interleukin-1, interferon, and elastase, in patients with adult respiratory distress syndrome after trauma, shock, or sepsis

Intrapulmonary activation of leukocytes and release of cellular mediators and enzymes are involved in the pathophysiology of the adult respiratory distress syndrome (ARDS). To investigate a possible role of local cytokines, we measured bronchoalveolar fluid (BALF) and plasma levels of tumor necrosis factor alpha (TNF-alpha) and its soluble inhibitors (sTNF-RI + RII), interleukin-1 beta (IL-1 beta), interferon-alpha (IFN-alpha), and granulocyte elastase in 14 patients at risk for ARDS and in 35 patients developing ARDS after trauma, sepsis, or shock. During clinical development of severe ARDS, BALF cytokines increased markedly: TNF-alpha from 116 +/- 36 to 10,731 +/- 5,048 pg/ml (mean +/- SEM), p = 0.001; sTNF-RI + RII from 3.7 +/- 1.4 to 24.6 +/- 2.6 ng/ml, p less than 0.05; and IL-1 beta from 7,746 +/- 5,551 to 42,255 +/- 19,176 pg/ml, p = 0.01. Plasma cytokines were not increased in most patients, nor were they correlated with the development or severity of ARDS. BALF elastase was higher in patients developing ARDS than in those at risk but not going into pulmonary failure (0.97 +/- 0.26 versus 0.28 +/- 0.13 U/ml, p = 0.026), and the highest values were observed in the early stages of severe ARDS (1.85 +/- 0.39 U/ml). BALF elastase levels correlated with IFN-alpha (r = 0.72, p less than 0.001). In conclusion, local release of TNF-alpha and IL-1 beta, possibly by pulmonary macrophages or other cells, and/or accumulation in the lung is associated with the development of ARDS.(ABSTRACT TRUNCATED AT 250 WORDS)