Serum IgG Levels and Risk of COPD Hospitalization: A Pooled Meta-analysis

BACKGROUND

Hypogammaglobulinemia (serum IgG levels < 7.0 g/L) has been associated with increased risk of COPD exacerbations but has not yet been shown to predict hospitalizations.

RESEARCH QUESTION

To determine the relationship between hypogammaglobulinemia and the risk of hospitalization in patients with COPD.

STUDY DESIGN AND METHODS

Serum IgG levels were measured on baseline samples from four COPD cohorts (n = 2,259): Azithromycin for Prevention of AECOPD (MACRO, n = 976); Simvastatin in the Prevention of AECOPD (STATCOPE, n = 653), Long-Term Oxygen Treatment Trial (LOTT, n = 354), and COPD Activity: Serotonin Transporter, Cytokines and Depression (CASCADE, n = 276). IgG levels were determined by immunonephelometry (MACRO; STATCOPE) or mass spectrometry (LOTT; CASCADE). The effect of hypogammaglobulinemia on COPD hospitalization risk was evaluated using cumulative incidence functions for this outcome and deaths (competing risk). Fine-Gray models were performed to obtain adjusted subdistribution hazard ratios (SHR) related to IgG levels for each study and then combined using a meta-analysis. Rates of COPD hospitalizations per person-year were compared according to IgG status.

RESULTS

The overall frequency of hypogammaglobulinemia was 28.4%. Higher incidence estimates of COPD hospitalizations were observed among participants with low IgG levels compared with those with normal levels (Gray's test, P < .001); pooled SHR (meta-analysis) was 1.29 (95% CI, 1.06-1.56, P = .01). Among patients with prior COPD admissions (n = 757), the pooled SHR increased to 1.58 (95% CI, 1.20-2.07, P < .01). The risk of COPD admissions, however, was similar between IgG groups in patients with no prior hospitalizations: pooled SHR = 1.15 (95% CI, 0.86-1.52, P =.34). The hypogammaglobulinemia group also showed significantly higher rates of COPD hospitalizations per person-year: 0.48 ± 2.01 vs 0.29 ± 0.83, P < .001.

INTERPRETATION

Hypogammaglobulinemia is associated with a higher risk of COPD hospital admissions.

Independent association of subclinical coronary artery disease and emphysema in HIV-infected patients

OBJECTIVES

Chronic obstructive pulmonary disease (COPD) and coronary artery disease are inflammatory states with a significant clinical impact. The relationship between them has not been investigated in patients with HIV infection. We assessed the presence of subclinical emphysema and coronary artery disease using chest computed tomography (CT) imaging in a cohort of HIV-infected patients receiving antiretroviral therapy.

METHODS

Gated chest CT scans were performed in 1446 consecutive patients to assess the presence and severity of coronary artery calcium (CAC) (classified as a score of 0, 1-100 or > 100) and emphysema (classified using a visual semiquantitative scale: 0, absent; 1-4, mild to moderate; > 4, severe). Univariable and multivariable logistic regression analyses were performed to identify factors independently associated with CAC and emphysema.

RESULTS

The emphysema score was significantly higher in patients with CAC scores of 1-100 and > 100 compared with those with a CAC score of 0. After adjustments for age, sex, smoking status, pack-years of smoking, visceral adiposity and duration of HIV infection, the presence of any emphysema was significantly associated with a CAC score > 0 [odds ratio (OR) 1.43; 95% confidence interval (CI) 1.08-1.88; P = 0.012]. The association persisted after adjustment for the Framingham risk score (OR 1.52; 95% CI 1.16-1.99; P = 0.002). There was a dose-dependent effect in the association between emphysema score and CAC score.

CONCLUSIONS

In this cross-sectional study of HIV-infected patients, there was an independent association between emphysema and CAC, after adjustment for traditional cardiovascular risk factors, suggesting a common pathogenesis of these chronic inflammatory conditions in a chronic inflammatory disease such as HIV infection.

Estradiol increases mucus synthesis in bronchial epithelial cells

Airway epithelial mucus hypersecretion and mucus plugging are prominent pathologic features of chronic inflammatory conditions of the airway (e.g. asthma and cystic fibrosis) and in most of these conditions, women have worse prognosis compared with male patients. We thus investigated the effects of estradiol on mucus expression in primary normal human bronchial epithelial cells from female donors grown at an air liquid interface (ALI). Treatment with estradiol in physiological ranges for 2 weeks caused a concentration-dependent increase in the number of PAS-positive cells (confirmed to be goblet cells by MUC5AC immunostaining) in ALI cultures, and this action was attenuated by estrogen receptor beta (ER-β) antagonist. Protein microarray data showed that nuclear factor of activated T-cell (NFAT) in the nuclear fraction of NHBE cells was increased with estradiol treatment. Estradiol increased NFATc1 mRNA and protein in ALI cultures. In a human airway epithelial (1HAE₀) cell line, NFATc1 was required for the regulation of MUC5AC mRNA and protein. Estradiol also induced post-translational modification of mucins by increasing total fucose residues and fucosyltransferase (FUT-4, -5, -6) mRNA expression. Together, these data indicate a novel mechanism by which estradiol increases mucus synthesis in the human bronchial epithelium.

Associations of IL6 polymorphisms with lung function decline and COPD

BACKGROUND

Interleukin-6 (IL6) is a pleiotropic pro-inflammatory and immunomodulatory cytokine which probably plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD). There is a functional single nucleotide polymorphism (SNP), -174G/C, in the promoter region of IL6. It was hypothesised that IL6 SNPs influence susceptibility for impaired lung function and COPD in smokers.

METHODS

Seven and five SNPs in IL6 were genotyped in two nested case-control samples derived from the Lung Health Study (LHS) based on phenotypes of rate of decline of forced expiratory volume in 1 s (FEV(1)) over 5 years and baseline FEV(1) at the beginning of the LHS. Serum IL6 concentrations were measured for all subjects. A partially overlapping panel of nine IL6 SNPs was genotyped in 389 cases of COPD from the National Emphysema Treatment Trial (NETT) and 420 controls from the Normative Aging Study (NAS).

RESULTS

In the LHS, three IL6 SNPs were associated with decline in FEV(1) (0.023< or =p< or =0.041 in additive models). Among them, the IL6_-174C allele was associated with a rapid decline in lung function. The association was more significant in a genotype-based analysis (p = 0.006). In the NETT-NAS study, IL6_-174G/C and four other IL6 SNPs, all of which are in linkage disequilibrium with IL6_-174G/C, were associated with susceptibility to COPD (0.01< or =p< or =0.04 in additive genetic models).

CONCLUSION

The results suggest that the IL6_-174G/C SNP is associated with a rapid decline in FEV(1) and susceptibility to COPD in smokers.

The natural history of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality in the USA, and it remains one of the few diseases that continues to increase its numbers. The development and progression of COPD can vary dramatically between individuals. A low level of lung function remains the cornerstone of COPD diagnosis and is a key predictor of prognosis. Lung function, however, is not the only factor in determining morbidity and mortality related to COPD, with factors such as body mass index, exercise capability and comorbid disease being important predictors of poor outcomes. Exacerbations of COPD are additional important indicators of both quality of life and outcomes in COPD patients. Definitions of exacerbations can vary, ranging from an increase in symptoms to COPD-related hospitalisations and death. COPD exacerbations are more common in patients with lower levels of lung function and may lead to more rapid declines in lung function. Better understanding of the natural history of COPD may lead to better definitions of specific COPD phenotypes, better interventions and improved outcomes.

C-reactive protein and mortality in mild to moderate chronic obstructive pulmonary disease

BACKGROUND

Although C-reactive protein (CRP) levels are increased in chronic obstructive pulmonary disease (COPD), it is not certain whether they are associated with adverse clinical outcomes.

METHODS

Serum CRP levels were measured in 4803 participants in the Lung Health Study with mild to moderate COPD. The risk of all-cause and disease specific causes of mortality was determined as well as cardiovascular event rates, adjusting for important covariates such as age, sex, cigarette smoking, and lung function. Cardiovascular events were defined as death from coronary heart disease or stroke, or non-fatal myocardial infarction or stroke requiring admission to hospital.

RESULTS

CRP levels were associated with all-cause, cardiovascular, and cancer specific causes of mortality. Individuals in the highest quintile of CRP had a relative risk (RR) for all-cause mortality of 1.79 (95% confidence interval (CI) 1.25 to 2.56) compared with those in the lowest quintile of CRP. For cardiovascular events and cancer deaths the corresponding RRs were 1.51 (95% CI 1.20 to 1.90) and 1.85 (95% CI 1.10 to 3.13), respectively. CRP levels were also associated with an accelerated decline in forced expiratory volume in 1 second (p < 0.001). The discriminative property of CRP was greatest during the first year of measurement and decayed over time. Comparing the highest and lowest CRP quintiles, the RR was 4.03 (95% CI 1.23 to 13.21) for 1 year mortality, 3.30 (95% CI 1.38 to 7.86) for 2 year mortality, and 1.82 (95% CI 1.22 to 2.68) for > or =5 year mortality.

CONCLUSIONS

CRP measurements provide incremental prognostic information beyond that achieved by traditional markers of prognosis in patients with mild to moderate COPD, and may enable more accurate detection of patients at a high risk of mortality.

Relationship between reduced forced expiratory volume in one second and the risk of lung cancer: a systematic review and meta-analysis

BACKGROUND

Individuals with severely impaired lung function have an increased risk of lung cancer. Whether milder reductions in forced expiratory volume in 1 second (FEV(1)) also increase the risk of lung cancer is controversial. Moreover, there is little consensus on whether men and women have similar risks for lung cancer for similar decreases in FEV(1).

METHODS

A search was conducted of PubMed and EMBASE from January 1966 to January 2005 and studies that examined the relationship between FEV1 and lung cancer were identified. The search was limited to studies that were population based, employed a prospective design, were large in size (> or = 5000 participants), and adjusted for cigarette smoking status.

RESULTS

Twenty eight abstracts were identified, six of which did not report FEV1 and eight did not adjust for smoking. Included in this report are four studies that reported FEV1 in quintiles. The risk of lung cancer increased with decreasing FEV1. Compared with the highest quintile of FEV1 (> 100% of predicted), the lowest quintile of FEV1 (< approximately 70% of predicted) was associated with a 2.23 fold (95% confidence interval (CI) 1.73 to 2.86) increase in the risk for lung cancer in men and a 3.97 fold increase in women (95% CI 1.93 to 8.25). Even relatively small decrements in FEV1 ( approximately 90% of predicted) increased the risk for lung cancer by 30% in men (95% CI 1.05 to 1.62) and 2.64 fold in women (95% CI 1.30 to 5.31).

CONCLUSION

Reduced FEV1 is strongly associated with lung cancer. Even a relatively modest reduction in FEV1 is a significant predictor of lung cancer, especially among women.

Steroid naive eosinophilic asthma: anti-inflammatory effects of fluticasone and montelukast

BACKGROUND

Inhaled corticosteroids and leukotriene receptor antagonists reduce airway eosinophilia and have been used as first line anti-inflammatory therapy for mild persistent asthma.

METHODS

A multicentre, randomised, placebo controlled, parallel group study was performed to compare the anti-inflammatory effects of fluticasone propionate and montelukast as measured by sputum eosinophils in 50 adults with symptomatic steroid naive asthma and sputum eosinophilia of > or =3.5%.

RESULTS

Eighteen patients received low dose fluticasone (250 mug/day), 19 received montelukast (10 mg/day), and 13 were given placebo for 8 weeks. Fluticasone treatment resulted in a greater reduction in sputum eosinophils (geometric mean (SD) 11.9 (2.3)% to 1.7 (5.1)%) than montelukast (10.7 (2.3)% to 6.9 (3.8)%; p = 0.04) or placebo (15.4 (2.4)% to 7.8 (4.2)%; p = 0.002), and improvement in FEV(1) (mean (SD) 2.6 (0.9) l to 3.0 (0.9) l) than montelukast (2.8 (0.7) l to 2.8 (0.9) l; p = 0.02) or placebo (2.4 (0.8) l to 2.4 (0.9) l; p = 0.01). Treatment with fluticasone suppressed sputum eosinophilia within a week while montelukast only attenuated it. The effect of montelukast was maximal at 1 week and was maintained over 4 weeks. The effect of fluticasone was maintained over 8 weeks while that of montelukast was not.

CONCLUSIONS

Montelukast is not as effective as low dose fluticasone in reducing or maintaining an anti-inflammatory effect in steroid naive eosinophilic asthma.

Association between chronic obstructive pulmonary disease and systemic inflammation: a systematic review and a meta-analysis

BACKGROUND

Individuals with chronic obstructive pulmonary disease (COPD) are at increased risk of cardiovascular diseases, osteoporosis, and muscle wasting. Systemic inflammation may be involved in the pathogenesis of these disorders. A study was undertaken to determine whether systemic inflammation is present in stable COPD.

METHODS

A systematic review was conducted of studies which reported on the relationship between COPD, forced expiratory volume in 1 second (FEV(1)) or forced vital capacity (FVC), and levels of various systemic inflammatory markers: C-reactive protein (CRP), fibrinogen, leucocytes, tumour necrosis factor-alpha (TNF-alpha), and interleukins 6 and 8. Where possible the results were pooled together to produce a summary estimate using a random or fixed effects model.

RESULTS

Fourteen original studies were identified. Overall, the standardised mean difference in the CRP level between COPD and control subjects was 0.53 units (95% confidence interval (CI) 0.34 to 0.72). The standardised mean difference in the fibrinogen level was 0.47 units (95% CI 0.29 to 0.65). Circulating leucocytes were also higher in COPD than in control subjects (standardised mean difference 0.44 units (95% CI 0.20 to 0.67)), as were serum TNF-alpha levels (standardised mean difference 0.59 units (95% CI 0.29 to 0.89)).

CONCLUSIONS

Reduced lung function is associated with increased levels of systemic inflammatory markers which may have important pathophysiological and therapeutic implications for subjects with stable COPD.

Impaired lung function and serum leptin in men and women with normal body weight: a population based study

BACKGROUND

Impaired lung function is a risk factor for cardiovascular morbidity. Whether circulating factors are responsible for this association is unknown. A study was undertaken to determine whether leptin, a hormone that can promote atherothrombosis, is raised in individuals with impaired lung function.

METHODS

Data from non-obese participants in the Third National Health, Nutrition, and Examination Survey (n=2808) were analysed to determine the relationship between circulating leptin levels and forced expiratory volume in 1 second (FEV(1)) values divided into quintiles (quintile 1, FEV(1) predicted < or =85.2%; quintile 2, 85.3-94.3%; quintile 3, 94.4-101.4%; quintile 4, 101.5-110.0%; and quintile 5, > or =110.1%).

RESULTS

Serum leptin levels changed along the FEV(1) gradient. The highest leptin levels were found in quintile 1 (geometric mean (GM) 5.42; interquartile range (IQR) 3.00-9.60 fg/l) and the lowest in quintile 5 (GM 4.94; IQR 2.80-9.10 fg/l). Adjustments for age, body mass index, and other confounders strengthened this relationship. Compared with quintile 5, the odds of having an increased serum leptin level in quintiles 1, 2, 3, and 4 were 2.26 (95% confidence interval (CI) 1.54 to 3.31), 2.20 (95% CI 1.52 to 3.17), 1.46 (95% CI 1.01 to 2.09), and 1.28 (95% CI 0.90 to 1.83), respectively.

CONCLUSION

Individuals with impaired lung function have raised serum leptin levels. Leptin may play a role in the pathogenesis of cardiovascular morbidity and mortality related to impaired lung function.

Coupling of CFTR-mediated anion secretion to nucleoside transporters and adenosine homeostasis in Calu-3 cells

The purpose of this study was to characterize the role of adenosine-dependent regulation of anion secretion in Calu-3 cells. RT-PCR studies showed that Calu-3 cells expressed mRNA for A2A and A2B but not A1 or A3 receptors, and for hENT1, hENT2 and hCNT3 but not hCNT1 or hCNT2 nucleoside transporters. Short-circuit current measurements indicated that A2B receptors were present in both apical and basolateral membranes, whereas A2A receptors were detected only in basolateral membranes. Uptake studies demonstrated that the majority of adenosine transport was mediated by hENT1, which was localized to both apical and basolateral membranes, with a smaller hENT2-mediated component in basolateral membranes. Whole-cell current measurements showed that application of extracellular nitrobenzylmercaptopurine ribonucleoside (NBMPR), a selective inhibitor of hENT1-mediated transport, had similar effects on whole-cell currents as the application of exogenous adenosine. Inhibitors of adenosine kinase and 5'-nucleotidase increased and decreased, respectively, whole-cell currents, whereas inhibition of adenosine deaminase had no effect. Single-channel studies showed that NBMPR and adenosine kinase inhibitors activated CFTR Cl- channels. These results suggested that the equilibrative nucleoside transporters (hENT1, hENT2) together with adenosine kinase and 5'-nucleotidase play a crucial role in the regulation of CFTR through an adenosine-dependent pathway in human airway epithelia.

Inhaled corticosteroids and survival in chronic obstructive pulmonary disease: does the dose matter?

Recent data suggest that inhaled corticosteroids reduce the number of clinical exacerbations in chronic obstructive pulmonary disease (COPD). It remains unknown whether a dose/response relationship exists. The present study was conducted to evaluate the long-term impact of varying doses of inhaled corticosteroids on COPD mortality. Hospital discharge data were used to identify all patients aged > or = 65 yrs recently hospitalised due to COPD in Alberta, Canada (n = 6,740). The relative risk (RR) for all-cause mortality was compared across different dose categories of inhaled corticosteroids (none and low, medium and high doses) following hospital discharge. Inhaled corticosteroid therapy after discharge was associated with a 25% relative reduction in risk for all-cause mortality (RR 0.75, 95% confidence interval (CI) 0.68-0.82). Patients on medium- or high-dose therapy showed lower risks for mortality than those on low doses (RR 0.77, 95% CI 0.69-0.86 for low dose; RR 0.48, 95% CI 0.37-0.63 for medium dose; and RR 0.55, 95% CI 0.44-0.69 for high dose). Use of inhaled corticosteroids following hospital discharge for chronic obstructive pulmonary disease was associated with a significant reduction in the overall mortality rate. Low- was inferior to medium- or high-dose therapy in protecting against mortality in chronic obstructive pulmonary disease.

Inhibition of matrix metalloproteinase MMP-2 activates chloride current in human airway epithelial cells

Matrix metalloproteinases (MMPs) are involved in the remodeling and degradation of the extracellular matrix. Recently, it has been found that MMPs also contribute to processes not directly related to tissue remodeling, such as platelet aggregation or degranulation of airway gland cells. Since mucus secretion is closely related to ion channel function, we investigated whether MMPs could also be involved in the regulation of ion channels. We used human airway submucosal cell line Calu-3 to study the effects of MMPs on whole-cell current and transepithelial short-circuit current (Isc). Phenanthroline, a specific inhibitor of MMPs, increased whole-cell current with the half-maximally effective dose of 5.2 µM, and reversibly activated Isc in transepithelial measurements. Current stimulated by phenanthroline displayed linear current-voltage relationships and had inhibitor pharmacology and ion selectivity consistent with cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel activity. Zymography and Western blot showed significant expression of MMP-2 in Calu-3 cells. Moreover, anti-MMP-2 antibodies (1 µg/mL) increased whole-cell current and Isc, whereas human recombinant MMP-2 (10 ng/mL) reduced it. We also studied the expression of MMPs and the effects of phenanthroline on whole-cell current in A549 cells, which are derived from airway surface epithelium and do not express CFTR Cl- channels. While these cells also showed significant expression of MMP-2, inhibition of this enzyme with phenanthroline exerted no significant effect on whole-cell current. It is concluded that MMP-2 is involved in the regulation of CFTR Cl- channels in human airways.Key words: matrix metalloproteinases, Cl- current, Calu-3 cells, zymography, phenanthroline.