Study On The Role Of Interleukin-18 In The Pathogenesis Of Chronic Obstructive Pulmonary Disease

PART ONEIncreased expression of interleukin-18 and its receptor in peripheral blood of patients with chronic obstructive pulmonary diseaseObjective:Chronic obstructive pulmonary disease (COPD) is a complex systemic disorder characterized by both local pulmonary and systemic inflammation. Many studies suggested that activation of circulating inflammatory cells and increased circulating levels of inflammatory cytokines occur in COPD. Interleukin (IL)-18 is a unique proinflammatory cytokine that mediates its effects by binding to the IL-18 receptor (IL-18R). In the present study, the expression of IL-18 in serum and IL-18R on peripheral blood T lymphocytes were analyzed.Methods:Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of IL-18 and interferon (IFN)-γ, and high sensitivity C-reactive protein (hsCRP) were measured by chemiluminiscent immunoassay. Expression of IL-18R was examined using a three-color flow cytometry method.Results:In total,120 subjects were recruited including 32 nonsmokers,30 current smokers and 58 stable COPD patients. Serum levels of IL-18 and hsCRP were significantly higher in stable COPD patients than those in nonsmokers and current smokers. A significant negative correlation existed between pulmonary function and serum level of IL-18 rather than hsCRP in stable COPD patients. The proportions of IL-18Ra-expressing T lymphocytes and CD8+ T lymphocytes were significantly higher in stable COPD patients than in nonsmokers and current smokers.Conclusions:The current study extended prior analyses by examining IL-18R expression in peripheral blood. The results suggested that IL-18/IL-18R system was active in peripheral blood of COPD patients. PART TWOExpression of interleukin-18 in rats with passive smoking induced chronic obstructive pulmonary diseaseObjective:To study the expression of interleukin-18 (IL-18) in rats with passive smoking induced chronic obstructive pulmonary disease (COPD).Methods:Twenty rats were randomly divided into a normal control group and a COPD model group. Rat COPD model was established by passive smoking for 6 months. The levels of IL-18 in serum and bronchoalveolar lavage fluid (BALF) were measured by ELISA. The levels of IL-18 mRNA in BALF were determined by real time RT-PCR. The lung tissue pathology was observed with HE staining. Immunohistochemical staining was used to investigate the expression of IL-18 in pulmonary tissues.Results:The levels of IL-18 in serum and BALF in COPD group were significantly higher than those in control group (P<0.01). The levels of IL-18 mRNA in BALF were significantly higher in COPD group than in control group (P<0.01). The expressions of IL-18 in pulmonary tissues were significantly higher in COPD group compared with control group (P<0.01).Conclusions:The expression of IL-18 significantly increased in peripheral blood and lung of rats with passive smoking induced COPD. Theses results suggest that IL-18 may be implicated in the pathogenesis of COPD caused by smoking. PART THREEAssociation of interleukin-18 promoter polymorphisms with chronic obstructive pulmonary disease in male smokersObjective:Chronic obstructive pulmonary disease (COPD) is considered a complex genetic disorder and it is expected that many genes play a role in the pathogenesis of this disease. Previous studies have reported that several variations within the interleukin (IL)-18 gene promoter region have been associated with different inflammatory diseases such as asthma. However, the association of IL-18 promoter polymorphisms with COPD has not been studied yet. We then performed a prospective case-control study to explore this association in male smoker of Chinese Han people.Methods:Our study recruited 112 COPD cases and 105 healthy controls matched for age. Pulmonary function tests were performed in all subjects. Genomic DNA was extracted from whole blood using a DNA blood kit. The genotyping of IL-18 promoter polymorphisms (-607 C/A and-137 G/C) was performed using TaqMan SNP Genotyping Assays. The frequencies of the alleles and genotypes in patients and controls were compared.Results:The frequency of IL-18 -607 allele C was significantly increased in COPD patients compared with healthy smokers (odds ratio (OR)=1.48,95% confidence interval (CI)=1.01-2.15, P=0.04). The -607 C/C genotype frequency was significantly higher in the GOLD 3-4 group compared with the GOLD 1-2 group (OR=4.31,95% CI=1.39-13.4, P=0.01). The frequency of allele C was also significantly higher in the GOLD 3-4 group compared with the GOLD 1-2 group (OR=2.06,95% CI=1.21-3.51, P=0.01). There were no significant differences in the frequencies of the alleles and genotypes of IL-18 -137 G/C polymorphism between COPD patients and healthy smokers or between GOLD 3-4 group and GOLD 1-2 group.Conclusions:Our study revealed that the IL-18 -607 C/A polymorphism was associated with COPD susceptibility and severity of airflow limitation in male smokers of Chinese Han people, and there was no such an association in the IL-18-137 G/C polymorphism. PART FOURComparison of tiotropium plus formoterol to tiotropium alone in stable chronic obstructive pulmonary diseaseObjective:It is not convincing that combination therapy of tiotropium plus formoterol improves efficacy without increasing the burden of adverse events compared with tiotropium alone. This meta-analysis was performed to evaluate the difference of efficacy and adverse events of the combination therapy compared with tiotropium alone in patients with stable chronic obstructive pulmonary disease (COPD).Methods:MEDLINE, EMBASE, CINAHL and the Cochrane trials database were searched for the review. Randomized controlled trials of greater than or equal to 2 weeks'treatment duration comparing tiotropium plus formoterol or arformoterol with tiotropium alone were reviewed. Studies were pooled to yield odds ratios (OR) or weighted mean differences (WMD) with 95% confidence intervals (CI).Results:Eight trials (1868 randomized patients) met the inclusion criteria. Tiotropium plus formoterol significantly improved the average FEV1 (WMD,105ml; 95% CI 69 to 142), average FVC (WMD,135ml; 95% CI 96 to 174) and trough FEV1(WMD,53ml; 95% CI 30 to 76) compared with tiotropium alone, though the difference was not statistically significant in trough FVC. The mean change in TDI was markedly larger with tiotropium plus formoterol (WMD,1.50; 95% CI 1.01 to 1.99) than with tiotropium alone, and a similar result was observed for the proportion with a clinically significant change in TDI (OR,2.34; 95% CI 1.58 to 3.46). Tiotropium plus formoterol had a tendency to reduce adverse events and COPD exacerbations compared with tiotropium alone, but the differences were not statistically significant.Conclusions:Tiotropium plus formoterol significantly improved lung function and symptom scales compared with tiotropium alone. There was a trend toward reduction instead of increase in adverse events, although the difference was not statistically significant. Long term trials are necessary to evaluate the effects of tiotropium plus formoterol and to clarify their role compared with tiotropium alone. PART FIVEEffect of long-acting beta-agonists on the frequency of COPD exacerbationsObjective:Inhaled long-acting beta-agonists have been licensed for the treatment of chronic obstructive pulmonary disease (COPD) since the late 1990s, and they improve lung function and symptoms of dyspnea. However the evidence that long-acting beta-agonists alone can reduce the rate of COPD exacerbations is not conclusive. This meta-analysis was performed to evaluate their effect on the frequency of exacerbations.Methods:MEDLINE, EMBASE, CINAHL and the Cochrane trials database were searched for the review. Randomized controlled trials of greater than or equal to 24 weeks'treatment duration comparing LAB As with placebo were reviewed. Studies were pooled to yield odds ratios (ORs) with 95% confidence intervals (CIs).Results:Seventeen randomized controlled trials (11871 randomized subjects) met the inclusion criteria and were selected for analysis. Salmeterol, formoterol and indacaterol significantly reduced COPD exacerbations compared with placebo. Salmeterol significantly reduced COPD exacerbations with both study arms exposed or not exposed to inhaled corticosteroids (ICS). The summary ORs were 0.79 (95% CI 0.67 to 0.92; P<0.01) and 0.80 (95% CI 0.65 to 0.99; P=0.04), respectively. However, when both arms were not exposed to ICS, there was no significant reduction in exacerbations with formoterol compared to placebo. The summary OR was 0.93 (95% CI 0.75 to 1.15; P=0.50).Conclusions:Long-acting beta-agonists reduce the frequency of COPD exacerbations. Salmeterol, formoterol and indacaterol significantly reduced COPD exacerbations compared with placebo. Salmeterol but not formoterol decreased exacerbations significantly in the absence of ICS.