The inflammatory response

Pathophysiology of asthma

Further insight into the inflammatory process of asthma has accumulated during the past few years. New inhalational anaesthetics seem to have a better bronchorelaxant effect, and prophylactic treatment with beta2-agonists and local anaesthetics may also be an alternative. Bronchospasm during anaesthesia appears to be less common now, but persons with asthma should still be considered to be at an increased risk of severe morbidity.

Polymorphisms in interleukin 8 and its receptors (IL8, IL8RA and IL8RB) and association of common IL8 receptor variants with peripheral blood eosinophil counts

Airway inflammation is a major factor in the pathogenesis of asthma. Interleukin 8 (IL8) is a potent proinflammatory cytokine that interacts with its receptors, IL8RA and IL8RB. We investigated the genetic polymorphisms in IL8, IL8RA, and IL8RB for any association with risk of asthma and peripheral blood eosinophil counts in a Korean population. By carrying out direct sequencing in 24 individuals, we identified 20 sequence variants within exons and their flanking regions, including the 1.5 kb promoter regions of IL8, IL8RA, and IL8RB. Among them, seven common single-nucleotide polymorphisms (SNPs) were selected for genotyping in our asthma cohort (n = 1,439). Two common haplotypes in IL8 and three in IL8RA and IL8RB (defined as one block) were identified. Although none of the polymorphisms showed a significant association with risk of asthma, IL8RA-B ht2 showed a significant association with the peripheral blood eosinophil counts (%) among asthma patients, e.g., lower eosinophil levels among individuals with the homozygous IL8RA-B ht2 (3.55 +/- 3.39%) than among other asthmatic patients (5.52 +/- 5.55%; P (corr) = 0.018). Our findings suggest that polymorphisms and haplotypes in IL8RA and IL8RB might be among the genetic factors underlying production of peripheral blood eosinophil.

[Acute viral respiratory tract infections and childhood asthma]

Les infections virales respiratoires sont de très importants facteurs déclenchants des crises d'asthme. Chez l'enfant les études épidémiologiques les plus récentes, utilisant la PCR, leur attribuent le déclenchement de 80 à 85 % des crises, aussi bien pour les crises modérées que les crises nécessitant une hospitalisation. Le virus respiratoire syncytial et les virus parainfluenzae prédominent chez le nourrisson, les rhinovirus et le mycoplasme chez l'enfant plus grand. Les mécanismes précis de l'induction des crises d'asthme par les virus restent mal compris, toutefois de récentes études montrent une augmentation de l'activation des cellules inflammatoires dans le lavage alvéolaire. Les sujets atopiques, en dehors des périodes d'allergie, ne semblent pas avoir plus de manifestations respiratoires viro-induites que les non-atopiques. En revanche, chez le sujet asthmatique, l'infection virale aggrave les réactions immédiate et retardée de l'hypersensibilité immédiate après test de provocation allergénique, en augmentant la libération des médiateurs mastocytaires et le recrutement des éosinophiles dans les voies aériennes inférieures. Les études chez l'homme et l'animal suggèrent que la production locale de cytokines (IL4, IL8, RANTES, MIP-1a...) et l'expression accrue chez l'asthmatique de la molécule d'adhésion ICAM1 aient un rôle important pour le recrutement et l'activation des cellules de l'inflammation dans les voies aériennes. Une hypothèse, qui reste à démontrer serait que dans des situations où, comme dans l'asthme, les lymphocytes Th2 prédominent, un excès d'Il4 pourrait inhiber les CD8 cytotoxiques, les cellules NK et les Th1 et ainsi entraîner une diminution des défenses antivirales et une réaction inflammatoire broncho-pulmonaire plus sévère que chez le non-asthmatique.

Procollagen types I and III aminoterminal propeptide levels during acute respiratory distress syndrome and in response to methylprednisolone treatment

Ineffective lung repair in patients with unresolving acute respiratory distress syndrome (ARDS) is accompanied by progressive fibroproliferation, inability to improve lung injury score (LIS), progressive multiple organ dysfunction syndrome (MODS), and an unfavorable outcome. Our aim was to investigate the relationship between fibrogenesis, pulmonary and extrapulmonary organ dysfunction, and outcome during the natural course of ARDS and in response to prolonged methylprednisolone treatment. We investigated 29 patients with ARDS. We obtained serial measurements of plasma and BAL procollagen aminoterminal propeptide type I (PINP) and type III (PIIINP) levels and components of the lung injury score (LIS) and MODS score. A reduction in LIS greater than one point from day 1 to day 7 of ARDS divided patients in improvers (group 1, n = 7) and nonimprovers (n = 22). Nonimprovers included those who were recruited (day 9 +/- 3 of ARDS) into a prospective, randomized, double-blind, placebo-controlled trial investigating prolonged methylprednisolone therapy in unresolving ARDS (group 2, n = 17), and those who died (all by day 10 of ARDS) prior to meeting eligibility criteria for the randomized trial (group 3, n = 5). On day 1 of ARDS, plasma PINP or PIIINP levels were elevated in all patients. By day 7 of ARDS, mean plasma PINP or PIIINP levels were unchanged in group 1 but increased significantly in group 2 (p = 0. 0002) and group 3 (p = 0.03). On day 7, patients with plasma PINP levels less than 100 ng/ml were 2.5 times more likely to survive (95% CI: 0.855-7.314), and patients with plasma PIIINP levels greater than 25 ng/ml were nine times more likely to die (95% CI: 1. 418-55.556). In group 2, patients taking placebo (n = 6) had no change in plasma PINP or PIIINP levels over time, while patients treated with methylprednisolone (n = 11) had a rapid and sustained reduction in mean plasma and bronchoalveolar lavage (BAL) PINP and PIIINP levels. By day 3 of treatment, mean plasma PINP and PIIINP levels (ng/ml) decreased from 100 +/- 9 to 45 +/- 8 (p = 0.0001) and 31 +/- 3 to 12 +/- 3 (p = 0.0008), respectively. After 8 to 15 d of methylprednisolone, mean BAL PINP and PIIINP levels (ng/ml) decreased from 63 +/- 25 to 6 +/- 23 (p = 0.002) and 42 +/- 5 to 10 +/- 3 (p = 0.003), respectively. Estimated partial correlation coefficients indicated that as plasma PINP and PIIINP levels decreased over the first 7 d of methylprednisolone treatment, positive end-expiratory pressure, creatinine, bilirubin, and temperature also decreased, while PaO2:FIO2 increased. In early ARDS, plasma PINP and PIIINP levels are elevated and continue to increase over time in those not improving. Among nonimprovers, those randomized to prolonged methylprednisolone treatment had a rapid and significant reduction in plasma and BAL aminoterminal propeptide levels and similar changes in lung injury and MODS scores. These findings provide additional evidence of an association between biological efficacy and physiologic response during prolonged methylprednisolone treatment of unresolving ARDS.

The American-European Consensus Conference on ARDS, part 2: Ventilatory, pharmacologic, supportive therapy, study design strategies, and issues related to recovery and remodeling. Acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) continues as a contributor to the morbidity and mortality of patients in intensive care units throughout the world, imparting tremendous human and financial costs. During the last 10 years there has been a decline in ARDS mortality without a clear explanation. The American-European Consensus Committee on ARDS was formed to re-evaluate the standards for the ICU care of patients with acute lung injury (ALI), with regard to ventilatory strategies, the more promising pharmacologic agents, and the definition and quantification of pathologic features of ALI that require resolution. It was felt that the definition of strategies for the clinical design and coordination of studies between centers and continents was becoming increasingly important to facilitate the study of various new therapies for ARDS.

The American-European Consensus Conference on ARDS, part 2. Ventilatory, pharmacologic, supportive therapy, study design strategies and issues related to recovery and remodeling

The acute respiratory distress syndrome (ARDS) continues as a contributor to the morbidity and mortality of patients in intensive care units throughout the world, imparting tremendous human and financial costs. During the last ten years there has been a decline in ARDS mortality without a clear explanation. The American-European Consensus Committee on ARDS was formed to re-evaluate the standards for the ICU care of patients with acute lung injury (ALI), with regard to ventilatory strategies, the more promising pharmacologic agents, and the definition and quantification of pathological features of ALI that require resolution. It was felt that the definition of strategies for the clinical design and coordination of studies between centers and continents was becoming increasingly important to facilitate the study of various new therapies for ARDS.

Development of bone marrow eosinophilia in mice induced by Aspergillus fumigatus antigens

A model of allergic bronchopulmonary aspergillosis (ABPA) developed by exposing mice to Aspergillus fumigatus antigen (Af) exhibits peripheral blood (PB), lung, and bone marrow (BM) eosinophilia. Because the BM is a site of eosinophilopoiesis, we have investigated the role of Af in the induction of this process in the BM. Groups of mice were exposed intranasally (i.n.) or intraperitoneally (i.p.) to Af. BM cells from mice were cultured with either Af or allogenic spleen cell supernatant stimulated with Af. Eosinophil counts in different lymphoid compartments, eosinophil peroxidase (EPO), and mRNA for cytokines and IgE in BM cells were studied. Results indicate that the eosinophil numbers were significantly elevated in PB and BM of all Af-exposed mice. Lung lavage eosinophils increased only in the i.n. group. Af induced EPO activity only in BM cultures from Af-exposed mice. The EPO activity was further enhanced by supernatants from spleen cells from Af-exposed mice. mRNA transcription of IL-3 and IL-5 were measurable in BM cells of the ip exposed mice. These findings suggest that Af mediates eosinophil development in BM of mice and this process is promoted by hematopoietic factors generated within the BM and in other lymphoid tissue such as the spleen.

Inhibition of CD18 or CD11b attenuates acute lung injury after acid instillation in rabbits

Acid-induced lung injury is mediated primarily by activated neutrophils. Although a prior study demonstrated that acid-induced neutrophil influx into the air spaces was not CD18 dependent, we hypothesized that either a neutralizing anti-CD18 monoclonal antibody (MHM23) or a neutrophil inhibitory factor (NIF), NIF (CD11b,18), might attenuate acid-induced lung injury in rabbits by interfering with neutrophil activation. This hypothesis derived from in vitro stu ies that reported that anti-CD18 therapy prevented tumor necrosis factor-alpha-induced neutrophil activation. Hydrochloric acid (pH = 1.5 in one-third normal saline) or one-third normal saline (4 ml/kg) was instilled into the lungs of ventilated, anesthetized rabbits. The rabbits were studied for 6 h. In acid-instilled rabbits without the anti-CD18 monoclonal antibody or NIF (CD11b,18), severe lung injury developed. In acid-instilled rabbits, pretreatment (5 min before acid) with the anti-CD18 monoclonal antibody (2 mg/kg i.v.) or pretreatment with the NIF (anti-CD11b,18, 10 mg/kg i.v.) prevented 50-70% of acid-induced abnormalities in oxygenation, the increase in extravascular lung water, and extravascular protein accumulation. The anti-CD18 monoclonal antibody was associated with a significant increase in air space neutrophils by bronchoalveolar lavage, suggesting that the neutrophils respond normally to chemotactic stimuli but that the neutrophils did not injure the lung even though they accumulated in the air spaces. In summary, neutralization of CD18 attenuates the acute lung injury after acid instillation without reducing the number of neutrophils in the air spaces, suggesting that anti-CD18 therapy may be beneficial because of its capacity to reduce neutrophil activation.

Asthma: a dynamic disease of inflammation and repair

It is now widely accepted that asthma in its varied forms is an inflammatory disorder of the airways in which mediator release from activated mast cells and eosinophils plays a major role. T lymphocytes take a primary role in orchestrating these processes through their capacity to generate a range of cytokines of the interleukin 4 gene cluster encoded on the long arm of chromosome 5. Additional cytokines derived from mast cells and eosinophils also play a key role, especially tumour necrosis factor alpha, which is responsible for initiating the up-regulation of vascular adhesion molecules involved in the recruitment of eosinophils and other inflammatory cells from the circulation. The importance of C-X-C and C-C chemokines as local chemoattractants and activating stimuli is also recognized. In addition to releasing an array of pharmacologically active autacoids, the inflammatory response in asthma results in the generation of proteolytic activities from mast cells (tryptase, chymase), eosinophils (MMP-9) and the epithelium itself (MMP-2, MMP-9), which exert tissue-destructive and cell-signalling effects. The epithelium is also highly activated, as evidenced by the up-regulation of cytokine production, inducible enzymes and soluble mediators. Increased surface expression of the epithelial isoform of CD44 (9v) and subepithelial proliferation of myofibroblasts are indicative of a simultaneous active repair process and the laying down of new interstitial collagens. Together, inflammatory and repair processes create the complex phenotype that characterizes asthma and its progression.