The relationship between chronic hypoxemia and activation of the tumor necrosis factor-alpha system in patients with chronic obstructive pulmonary disease

The value of C-reactive protein as a marker of systemic inflammation in stable chronic obstructive pulmonary disease

BACKGROUND

Systemic aspects of chronic obstructive pulmonary disease (COPD) include oxidative stress and altered circulating levels of inflammatory mediators and acute-phase proteins. C-reactive protein (CRP) reflects total systemic burden of inflammation in several disorders and has been shown to upregulate the production of proinflammatory cytokines. The aim of this study was to evaluate circulating CRP levels to determine the value of CRP as a biomarker of systemic inflammation and as an indicator of malnutrition or severity of COPD in stable COPD patients in comparison to the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6).

METHODS

Thirty-five male patients with stable COPD and 30 age- and sex-matched subjects with normal pulmonary function were admitted to the study. Serum CRP levels were measured using a commercially available kit with the turbidimetric method. Serum TNF-alpha and IL-6 concentrations were measured with ELISA kits.

RESULTS

Sixty percent of the patients had severe or very severe and 40% moderate COPD. Serum CRP was significantly higher in stable COPD patients than in control subjects (p<0.001), while TNF-alpha and IL-6 concentrations were not statistically different. Serum TNF-alpha was higher in severe or very severe COPD patients (p=0.046). When the COPD patients with a low BMI were compared to those with a normal-to-high BMI, there was a significant difference in CRP (p=0.034) and TNF-alpha (p=0.037).

CONCLUSION

The present study confirms that circulating CRP levels are higher in stable COPD patients and may thus be regarded as a valid biomarker of low-grade systemic inflammation. In addition, CRP is significantly higher in COPD patients with a low BMI and thus, together with TNF-alpha, may be considered an indicator of malnutrition in COPD patients.

Coexistent chronic obstructive pulmonary disease and heart failure in the elderly

The prevalence of chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) increases substantially with age. The coexistence of COPD and CHF is common but often unrecognized in elderly patients. To avoid overlooking COPD in elderly patients with known CHF pulmonary function tests should be routinely obtained. Likewise, to avoid overlooking CHF in elderly patients with known COPD left ventricular (LV) function should be routinely assessed. Plasma brain natriuretic peptide levels are useful to differentiate COPD exacerbation from CHF decompensation in patients presenting with acute dyspnea. Aging exacerbates skeletal muscle alterations that occur in patients with CHF and COPD. Skeletal muscle metabolic alterations and atrophy and the resulting deterioration of functional capacity progress rapidly in elderly patients with COPD and CHF. Physical conditioning reverses rapidly progressing skeletal muscle metabolic alterations and atrophy and promotes independence and life quality in the elderly. Physical conditioning is clearly an essential component of the management of elderly patients with COPD and CHF. The pharmacological management of patients with coexistent COPD and CHF should focus on not depriving these patients from long-term beta adrenergic blockade. Long-term beta adrenergic blockade has been repeatedly shown to improve survival in elderly patients with CHF due to LV systolic dysfunction and, contrary to conventional belief, is well tolerated by patients with COPD.

C-reactive protein correlates with tissue oxygen availability in patients with stable COPD

BACKGROUND

Arterial oxygen tension, oxygen delivery to tissue, and systemic inflammation are recognized as pivotal factors in the progression of chronic obstructive pulmonary disease (COPD). However, interconnections between systemic inflammation and tissue oxygen availability are scantly investigated. Tissue oxygen availability depends on arterial PaO2, oxygen concentration, hemoglobin oxygen affinity (P50), and hemoglobin oxygen binding capacity (ceHb). As the integrated changes of those indices are summarized by oxygen extraction tension (PaO2x), the objective of this study was to explore the association between C-reactive protein (CRP) blood levels and either PaO2x or each of its determinants, in stable COPD.

MATERIALS AND METHODS

Blood CRP and oxygen status of arterial blood were measured at rest while breathing room air in 44 moderate to severe stable COPD patients. PaO2x was calculated along the shape of oxygen binding curve as the oxygen tension resulting from removal of 2.3 mmol of oxygen per liter of blood. Multiple linear regression analysis was performed with PaO2, ceHb, and P50 as independent variables, and CRP as the dependent variable, adjusting for age and sex. The analysis was repeated using PaO2x as a sole independent variable.

RESULTS

Multiple linear regression analysis indicated that ceHb, PaO2, and P50, were significant and independent predictors of CRP (R2 = 0.52, p < 0.0001). PaO2x alone was an even stronger predictor of CRP (R2 = 0.62, p < 0.0001).

CONCLUSIONS

These findings indicate that physiological determinants of tissue oxygen availability are independently associated with CRP blood levels. Thus, improvement of tissue oxygen availability is a central therapeutic option to modulate the severity of systemic inflammatory processes in patients with COPD.

Targeting lung inflammation: novel therapies for the treatment of COPD

Chronic obstructive pulmonary disease (COPD) is a global health problem. As understanding of pathology of COPD has increased it has been established that COPD is associated with the progressive pulmonary inflammation and destruction of lung parenchyma (emphysema) that relate to disease severity. Therefore, it is anticipated that drugs that reduce pulmonary inflammation will provide effective, disease modifying therapy for COPD. Several specific therapies are directed against the influx of inflammatory cells into the airways and lung parenchyma that occurs in COPD; these include agents directed against cytokines and chemokines. Broad-range anti-inflammatory drugs are now in phase III development for COPD; they include inhibitors of phosphodiesterase 4 (PDE4). Other drugs that inhibit cell signaling include inhibitors of p38 mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB), and phosphoinositide-3-kinase (PI3K). There is also a search for inhibitors of proteinases and matrix metalloproteinases (MMPs) to prevent lung destruction and the development of emphysema. This review highlights studies on novel or potential anti-inflammatory agents that might be considered in the development of new future therapies for COPD.

Management of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major cause of mortality and morbidity throughout the world. It is the only cause of death among the top 10 causes that is increasing and is expected to become the third leading cause of death in the world by 2020. A diagnosis of COPD should be considered in any patient with previous exposure to risk factors for the disease and/or the presence of chronic cough, sputum production, or dyspnea. Patients with COPD are categorized into five stages based on their pulmonary function tests and symptoms. Smoking cessation is the single most effective way to halt the progression of COPD and prolong life. Pharmacological management of stable COPD includes the use of bronchodilators (beta2 agonists, anticholinergics and methylxanthines) and inhaled corticosteroids. Other adjunctive measures include vaccination, oxygen therapy, pulmonary rehabilitation, and certain surgical measures like bullectomy and lung transplantation. Management of acute exacerbations includes the use of systemic steroids, antibiotics, bronchodilators, and oxygen therapy. During very severe exacerbations, patients may need ventilatory support.

Effects of TNF-alpha and leptin on weight loss in patients with stable chronic obstructive pulmonary disease

BACKGROUND

Weight loss is common in patients with chronic obstructive pulmonary disease (COPD). However, the mechanisms of this weight loss are still unclear.

METHODS

Sixty male patients with stable COPD and 45 healthy male controls participated in this study. The COPD patients were divided into two groups, that is, the emphysema and chronic bronchitis groups, by the transfer coefficient of carbon monoxide. The body composition, resting energy expenditure (REE), plasma leptin levels and serum tumor necrosis factor-alpha (TNF-alpha) were measured in all the study participants. The difference and correlation of these parameters were investigated between the two groups.

RESULTS

Emphysematous patients were characterized by a lower body mass index (BMI) and fat-mass (FM) compared with the chronic bronchitis patients (p < 0.001). The plasma leptin levels, as corrected for the FM, were not different between the COPD patients and healthy controls (78.3 +/- 30.9 pg/mL/kg vs. 70.9 +/- 17.3 pg/mL/kg, respectively), and the plasma leptin levels, as adjusted for the FM, were also not different between the two groups of COPD patients. In the chronic bronchitis patients, the plasma leptin concentration was correlated with the BMI (r = 0.866, p < 0.001) but it was not correlated with the BMI in the emphysema patients. The serum TNF-alpha levels were higher in the stable COPD patients than those in the controls, but there was no statistical difference (10.7 +/- 18.6 pg/mL vs. 7.2 x 3.5 pg/mL, respectively, p0.05). The leptin concentration was well correlated with the BMI and %FM in the patients with chronic bronchitis and the leptin concentration was only correlated with the %FM (r = 0.450, p = 0.027) in emphysema patients. There was no correlation between the plasma leptin concentration, as adjusted for the fat mass, and the activity of the TNF-alpha system.

CONCLUSION

The interaction of leptin and the activity of the TNF-alpha system in the pathogenesis of tissue depletion may not play an important role in chronic stable COPD patients.

Systemic Inflammation and Skeletal Muscle Dysfunction in Chronic Obstructive Pulmonary Disease: State of the Art and Novel Insights in Regulation of Muscle Plasticity

Systemic inflammation is a recognized hallmark of chronic obstructive pulmonary disease pathogenesis. Although the origin and mechanisms responsible for the persistent chronic inflammatory process remain to be elucidated, it is recognized that it plays an important role in skeletal muscle pathology as observed in chronic obstructive pulmonary disease and several other chronic inflammatory disorders. This article describes state-of-the-art knowledge and novel insights in the role of inflammatory processes on several aspects of inflammation-related skeletal muscle pathology and offers new insights in therapeutic perspectives.

Aspects on pathophysiological mechanisms in COPD

Chronic obstructive pulmonary disease (COPD) is a condition which is characterized by irreversible airway obstruction due to narrowing of small airways, bronchiolitis, and destruction of the lung parenchyma, emphysema. It is the fourth most common cause of mortality in the world and is expected to be the third most common cause of death by 2020. The main cause of COPD is smoking but other exposures may be of importance. Exposure leads to airway inflammation in which a variety of cells are involved. Besides neutrophil granulocytes, macrophages and lymphocytes, airway epithelial cells are also of particular importance in the inflammatory process and in the development of emphysema. Cell trafficking orchestrated by chemokines and other chamoattractants, the proteinase-antiproteinase system, oxidative stress and airway remodelling are central processes associated with the development of COPD. Recently systemic effects of COPD have attracted attention and the importance of systemic inflammation has been recognized. This seems to have direct therapeutic implications as treatment with inhaled glucocorticosteroids has been shown to influence mortality. The increasing body of knowledge regarding the inflammatory mechanism in COPD will most likely have implications for future therapy and new drugs, specifically aimed at interaction with the inflammatory processes, are currently being developed.

Longitudinal follow-up of systemic inflammation after acute exacerbations of COPD

BACKGROUND

Acute exacerbations are important in the clinical course of COPD, yet the underlying mechanisms are poorly understood. Systemic inflammation is now considered as an important component in the disease process. In this study we evaluated longitudinally the systemic inflammation during hospital treatment for acute exacerbation and after clinical recovery.

METHODS

Blood was collected on day 0, 1, 4 and 8 in 21 patients admitted for an acute exacerbation of COPD and at 1 month, 3 months and 6 months after discharge. Systemic inflammation was determined by measurement of the pro-inflammatory markers interleukin (IL)-6, soluble tumor necrosis factor (TNF) receptors sTNFR55 and sTNFR75, the anti-inflammatory mediator sIL-1RII, and bactericidal permeability increasing protein (BPI) as a marker of neutrophil activation. In addition, plasma level of Trolox antioxidant capacity (TEAC) was determined. Healthy age-matched controls were measured for the same markers at one time-point.

RESULTS

All inflammatory markers analyzed were elevated on first day of admission for exacerbation of COPD, as compared to healthy controls. During treatment, levels of IL-6, and sTNFR75 rapidly decreased, whereas sTNFR55 and BPI remained elevated. Moreover, sIL-1RII and TEAC increased during first 8 days of treatment. In the stable condition all inflammatory markers returned to values comparable to healthy controls, with the exception of BPI, which remained persistently elevated compared to healthy controls.

CONCLUSION

This study clearly demonstrates upregulation of systemic inflammation in acute exacerbations of COPD. Attenuation of systemic inflammation may offer new perspectives in the management of COPD patients to reduce the burden of exacerbations.

Correlates of erectile dysfunction in moderate-to-severe chronic obstructive pulmonary disease patients

OBJECTIVE AND BACKGROUND

Erectile dysfunction (ED) has important negative effects on male quality of life and self-esteem. The aim of this study was to acquire an insight into the sexual status of COPD patients.

METHODS

Ninety-five male patients aged 48-75 years, with moderate-to-severe stable COPD, and 30 age-matched subjects with normal pulmonary function were included. After clinical evaluation and measurement of serum sex hormones and TNF-alpha concentration, subjects were asked to answer the International Index of Erectile Function (IIEF) questionnaire as a method to diagnose and classify ED.

RESULTS

Varying degrees of ED were detected in 87% of COPD patients and 83% of controls. Although the total percentages of subjects with various severities of ED seemed similar, moderate and severe ED was 57% in COPD group and 20% in control subjects, suggesting a more severe course of ED in COPD patients. ED score of COPD patients was not correlated with age, smoking burden, duration of COPD, FEV1%, PaO2, PaCO2, serum dehydroepiandrosterone-sulphate, testosterone or estradiol levels. When patients were subgrouped according to severity of ED, serum TNF-alpha concentration, used as a marker of systemic inflammatory status in COPD, was significantly higher in patients with moderate-to-severe ED compared with mild-moderate ED.

CONCLUSION

The present study showed that ED is frequent and more severe in COPD patients than age-matched controls. Chronic systemic inflammation is likely to play a role in ED in COPD; the role of TNF-alpha should be evaluated further. Patients with COPD need comprehensive management including a detailed sexual evaluation.

Arterial stiffness and osteoporosis in chronic obstructive pulmonary disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is associated with an increased risk of cardiovascular events and osteoporosis. Increased arterial stiffness is an independent predictor of cardiovascular disease.

OBJECTIVES

We tested the hypothesis that patients with COPD would have increased arterial stiffness, which would be associated with osteoporosis and systemic inflammation.

METHODS

We studied 75 clinically stable patients with a range of severity of airway obstruction and 42 healthy smoker or ex-smoker control subjects, free of cardiovascular disease. All subjects underwent spirometry, measurement of aortic pulse wave velocity (PWV) and augmentation index, dual-energy X-ray absorptiometry, and blood sampling for inflammatory mediators.

MEASUREMENTS AND MAIN RESULTS

Mean (SD) aortic PWV was greater in patients, 11.4 (2.7) m/s, than in control subjects, 8.95 (1.7) m/s, p < 0.0001. Inflammatory mediators and augmentation index were also greater in patients. Patients with osteoporosis at the hip had a greater aortic PWV, 13.1 (1.8) m/s, than those without, 11.2 (2.7) m/s, p < 0.05. In patients, aortic PWV was related to age (r = 0.63, p < 0.0001) and log(10) IL-6 (r = 0.31, p < 0.01), and inversely to FEV(1) (r = -0.34, p < 0.01). The strongest predictors of aortic PWV in all subjects were age (p < 0.0001), percent predicted FEV(1) (p < 0.05), mean arterial pressure (p < 0.05), and log(10) IL-6 (p < 0.05).

CONCLUSIONS

Increased arterial stiffness was related to the severity of airflow obstruction and may be a factor in the excess risk for cardiovascular disease in COPD. The increased aortic PWV in patients with osteoporosis and the association with systemic inflammation suggest that age-related bone and vascular changes occur prematurely in COPD.

Systemic inflammation in COPD: is genetic susceptibility a key factor?

COPD is a multicomponent disease characterized by abnormal inflammatory response of the lungs to noxious particles that is accompanied by systemic effects like weight loss, muscle wasting, reduced functional capacity and impaired health status. A persistent low-grade systemic inflammatory response reflected by enhanced levels of acute phase proteins like C-reactive protein (CRP) and pro-inflammatory cytokines such as tumor necrosis factor (TNF)-alpha, is present in part of the COPD population. The production of inflammatory proteins is partly genetically determined. Several studies have shown that polymorphisms within genes coding for these inflammatory mediators may modulate systemic inflammatory responses. Among all of these genes, the TNF family (TNF-alpha, lymphotoxin (LT)-alph and their receptors TNF-R55 and TNF-R75), interleukin (IL)-6 and CRP gene polymorphisms are the most prominent candidates. However, large carefully designed studies in well-characterized COPD cohorts are required to unravel the exact role of genetic background in the systemic component of this disease.

Thioredoxin-1 suppresses systemic inflammatory responses against cigarette smoking

Thioredoxin-1 (TRX) is a small redox-active protein with antioxidative effects and redox-regulating functions. Cigarette smoking is a major etiological factor in the pathogenesis of a variety of diseases and recruits systemic immune and inflammatory responses. This report demonstrates that TRX attenuates the systemic inflammatory responses induced by cigarette smoking. The mRNA expressions of tumor necrosis factor alpha (TNF-alpha) and macrophage migration inhibitory factor (MIF) were suppressed in the spleen of TRX overexpressing transgenic mice (TRX-tg) exposed to cigarette smoking, compared with control C57BL/6 mice. In addition, protein carbonylation, a marker of cellular protein oxidation, was enhanced by cigarette smoking in the tissues of heart and liver in control mice more than in TRX-tg mice. These findings suggest that TRX may suppress the systemic inflammatory responses against cigarette smoking.

A single nucleotide polymorphism in the CCL1 gene predicts acute exacerbations in chronic obstructive pulmonary disease

RATIONALE

Acute exacerbations (AEs) in chronic obstructive pulmonary disease (COPD) are a major cause of morbidity and mortality in COPD.

OBJECTIVES

The marked heterogeneity in the host defense mechanisms may be attributed to single nucleotide polymorphisms (SNPs) in the inflammatory chemokines that show enhanced expression in the airway of patients with COPD who experience AEs.

METHODS

We investigated four SNPs of the CCL11, CCL1, and CCL5 genes in relation to the frequency and severity of AEs in retrospective and prospective studies of a cohort of 276 male patients with COPD.

MEASUREMENTS AND MAIN RESULTS

In the 2-yr retrospective study , one SNP (National Center for Biotechnology Information SNP reference: rs2282691) in the predicted enhancer region of the CCL1 gene, encoding a chemotactic factor for a series of leukocytes, was significantly associated with the frequency of AEs in a dominant model (Fisher's exact test: odds ratio [OR], 2.70; 95% confidence interval [CI], 1.36-5.36; p=0.004; logistic regression: OR, 3.06; 95% CI, 1.46-6.41; p=0.003; and Kruskal-Wallis test: p=0.003). In the 30-mo prospective study, the "A" allele was a significant risk allele for the severity of AEs, with a gene-dosage effect (Kaplan-Meier method with log-rank test: AA vs. TT; log-rank statistic: 7.67, p=0.006; Cox proportional hazards regression method: OR, 5.93; 95% CI, 1.28-27.48; p=0.023). The electromobility shift assay showed that C/EBPbeta, a key transcriptional factor in response to pulmonary infections, binds to the "T" allele, but not to the "A" allele.

CONCLUSIONS

Variants in the CCL1 gene are associated with susceptibility to AEs through their potential implication in the host defense mechanisms against AEs.

Muscle wasting and impaired muscle regeneration in a murine model of chronic pulmonary inflammation

Muscle wasting and increased circulating levels of inflammatory cytokines, including TNF-alpha, are common features of chronic obstructive pulmonary disease. To investigate whether inflammation of the lung is responsible for systemic inflammation and muscle wasting, we adopted a mouse model of pulmonary inflammation resulting from directed overexpression of a TNF-alpha transgene controlled by the surfactant protein C (SP-C) promoter. Compared with wild-type mice, SP-C/TNF-alpha mice exhibited increased levels of TNF-alpha in the circulation and increased endogenous TNF-alpha expression in skeletal muscle, potentially reflecting an amplificatory response to circulating TNF-alpha. Decreased muscle and body weights observed in SP-C/TNF-alpha mice were indicative of muscle wasting. Further evaluation of the SP-C/TNF-alpha mouse musculature revealed a decreased muscle regenerative capacity, shown by attenuated myoblast proliferation and differentiation in response to reloading of disuse-atrophied muscle, which may contribute to skeletal muscle wasting. Importantly, incubation of cultured myoblasts with TNF-alpha also resulted in elevated TNF-alpha mRNA levels and inhibition of myoblast differentiation. Collectively, our results demonstrate that chronic pulmonary inflammation results in muscle wasting and impaired muscle regeneration in SP-C/TNF-alpha mice, possibly as a consequence of an amplificatory TNF-alpha expression circuit extending from the lung to skeletal muscle.

Chronic Obstructive Pulmonary Disease, inflammation and co-morbidity--a common inflammatory phenotype?

Chronic Obstructive Pulmonary Disease (COPD) is and will remain a major cause of morbidity and mortality worldwide. The severity of airflow obstruction is known to relate to overall health status and mortality. However, even allowing for common aetiological factors, a link has been identified between COPD and other systemic diseases such as cardiovascular disease, diabetes and osteoporosis.

COPD is known to be an inflammatory condition and neutrophil elastase has long been considered a significant mediator of the disease. Pro-inflammatory cytokines, in particular TNF-α (Tumour Necrosis Factor alpha), may be the driving force behind the disease process. However, the roles of inflammation and these pro-inflammatory cytokines may extend beyond the lungs and play a part in the systemic effects of the disease and associated co-morbidities. This article describes the mechanisms involved and proposes a common inflammatory TNF-α phenotype that may, in part, account for the associations.

Greater whole-body myofibrillar protein breakdown in cachectic patients with chronic obstructive pulmonary disease

BACKGROUND

Experimental studies indicate that greater skeletal muscle protein breakdown is a trigger for the cachexia that often is prevalent in chronic obstructive pulmonary disease (COPD).

OBJECTIVE

We compared myofibrillar protein breakdown (MPB) with whole-body (WB) protein breakdown (PB) in 9 cachectic COPD patients [x +/- SEM forced expiratory volume in 1 s (FEV(1)): 48 +/- 4% of predicted], 7 noncachectic COPD patients (FEV(1): 53 +/- 5% of predicted), and 7 age-matched healthy control subjects, who were matched by body mass index with the noncachectic patients.

DESIGN

After the subjects fasted overnight (10 h) and discontinued the maintenance medication, a primed constant and continuous infusion protocol was used to infuse L-[ring-(2)H(5)]-phenylalanine and L-[ring-(2)H(2)]-tyrosine to measure WB protein turnover and L-[(2)H(3)]-3-methylhistidine to measure WB MPB. Three arterialized venous blood samples were taken between 80 and 90 min of infusion to measure amino acid concentrations and tracer enrichments.

RESULTS

Body composition, WB protein turnover, and WB MPB did not differ significantly between the noncachectic COPD and control subjects. Cachectic COPD patients had lower fat mass and fat-free mass values (both: P < 0.01) than did the noncachectic COPD patients. WB MPB was significantly (P < 0.05) higher in the cachectic COPD group (18 +/- 3 nmol . kg(-1) . min(-1)) than in the combined control and noncachectic COPD groups (10 +/- 1 nmol . kg(-1) . min(-1)), but WB protein turnover did not differ significantly between the groups. Correlations with fat-free mass were significant (P < 0.05) for plasma glutamate and branched-chain amino acids, and that for WB MPB trended toward significance (P = 0.07).

CONCLUSION

Cachexia in clinically stable patients with moderate COPD is characterized by increased WB MPB, which indicates that myofibrillar protein wasting is an important target for nutritional and pharmacologic modulation.

Manifestações sistêmicas na doença pulmonar obstrutiva crônica

A doença pulmonar obstrutiva crônica é progressiva e está relacionada a uma resposta inflamatória anormal dos pulmões à inalação de partículas e/ou gases tóxicos, sobretudo a fumaça de cigarro. Embora acometa primariamente os pulmões, diversas manifestações extrapulmonares relacionadas a esta enfermidade têm sido descritas. O aumento do número de células inflamatórias, que resulta em produção anormal de citocinas pró-inflamatórias, e o desequilíbrio entre a formação de radicais livres e a capacidade antioxidante, resultando em sobrecarga oxidativa, provavelmente são mecanismos envolvidos na inflamação local e sistêmica. Além disso, a diminuição do condicionamento físico secundária às limitações ventilatórias pode estar envolvida no desenvolvimento de alterações musculares. A doença pulmonar obstrutiva crônica apresenta diversas manifestações sistêmicas que incluem a depleção nutricional, a disfunção dos músculos esqueléticos, que contribui para a intolerância ao exercício, e as manifestações relacionadas a co-morbidades comumente observadas nestes pacientes. Essas manifestações têm sido relacionadas à sobrevida e ao estado geral de saúde dos pacientes. Nesse sentido, esta revisão tem como objetivo discutir os achados da literatura relacionados às manifestações sistêmicas da doença pulmonar obstrutiva crônica, ressaltando o papel da inflação sistêmica, e algumas perspectivas de tratamento.

Inflammatory markers are associated with ventilatory limitation and muscle dysfunction in obstructive lung disease in well functioning elderly subjects

BACKGROUND

Inflammatory markers are increased in chronic obstructive pulmonary disease (COPD) and are hypothesised to play an important part in muscle dysfunction and exercise intolerance.

METHODS

The Health Aging and Body Composition (Health ABC) study is a prospective observational cohort of well functioning individuals aged 70-79 years. A cross sectional analysis of the baseline data was conducted to examine the association between inflammatory markers and ventilatory limitation, muscle strength, and exercise capacity. These associations were compared in participants with and without obstructive lung disease (OLD).

RESULTS

Of the 3075 participants enrolled in the Health ABC cohort, OLD was identified by spirometric testing in 268 participants and 2005 participants had normal spirometric results. Of the participants with OLD, 35%, 38%, and 27% participants had mild, moderate, and severe OLD, respectively. Participants with OLD had lower quadriceps strength (102.5 Nm v 108.9 Nm, p = 0.02), lower maximum inspiratory pressure (64.7 cm H(2)O v 74.2 cm H(2)O, p<0.0001), higher systemic interleukin (IL)-6 levels (2.6 pg/ml v 2.2 pg/ml, p<0.0001), and higher C-reactive protein (CRP) levels (3.5 mg/l v 2.5 mg/l, p<0.0001) than those with normal spirometry. In participants with OLD and those with normal spirometry, forced expiratory volume in 1 second (FEV(1)) was associated with IL-6 (adjusted regression coefficients (beta) = -5.3 (95% CI -9.1 to-1.5) and -3.1 (95% CI -4.3 to -1.9), respectively). IL-6 and TNF were also associated with quadriceps strength among participants with OLD and those with normal spirometry (beta = -6.4 (95% CI -12.8 to -0.03) and -3.4 (95% CI -5.4 to -1.3), respectively, for IL-6 and beta = -10.1 (95% CI -18.7 to -1.5) and -3.8 (95% CI -7 to -0.6), respectively, for TNF). IL-6, quadriceps strength, and maximum inspiratory pressures were independent predictors of reduced exercise capacity in both groups.

CONCLUSIONS

In well functioning elderly subjects with or without OLD, IL-6 is associated with reduced FEV(1), quadriceps strength, and exercise capacity.

Association between cytokines in induced sputum and severity of chronic obstructive pulmonary disease

Cytokines are known to be increased in induced sputum in chronic obstructive pulmonary disease (COPD). In this study, the relationship between the levels of interleukin-6 (IL-6), interleukin-8 (IL-8), and tumour necrosis factor-alpha (TNF-alpha) in induced sputum of patients with exacerbation of COPD, and the severity of the disease, pulmonary function tests (PFT), arterial blood gases (ABG) were studied. Twenty-four patients with exacerbation of COPD were included in the study. The patients were grouped according to their PFT into two as: Group 1 (FEV1 below 50% of the predicted value, severe-very severe COPD, n=12) and, Group 2 (FEV1 above 50% of the predicted value, mild-moderate COPD, n=12). The levels of IL-6, IL-8 and TNF-alpha in induced sputum of the subjects were measured. The mean levels of IL-6, IL-8 and TNF-alpha in induced sputum were found to be higher in Group 1 (severe-very severe COPD) than in Group 2 (mild-moderate COPD). The differences in IL-6 and IL-8 levels between groups were statistically significant (P<0.05). A significant correlation was observed between the IL-6 value and FEV(1) (r=-0.435, P=0.034), FEV1/FVC (r=-0.446, P=0.029), PaO2 (r=-0.711, P=0.000), SaO2 (r=-0.444, P=0.030) and disease duration (r=0.427, P=0.037), respectively. Also, the level of IL-8 in induced sputum was inversely correlated with FEV1 (r=-0.562, P=0.004), PaO2 (r=-0.540, P=0.006) and SaO2 (r=-0.435, P=0.034). However, all three cytokines were positively correlated with the smoking load (r=0.653, P=0.001; r=0.439, P=0.032; r=0.649, P=0.001). We conclude, therefore, that in exacerbated COPD cases with greater degrees of obstruction of the airways have higher levels of cytokines in induced sputum. This can be interpreted to mean that these cytokines are related to the clinical parameters like the ABG and PFT and seem to be the determinant of the severity of the disease.

Apoptosis of peripheral blood neutrophils in COPD exacerbation does not correlate with serum cytokines

The study investigated the relationship between apoptosis of peripheral blood neutrophils during exacerbation of chronic obstructive pulmonary disease (COPD) and the inflammatory response that characterises this condition. Twenty-six hospitalised patients with COPD exacerbation and 13 controls were included. Three sequential blood and sputum samples were obtained from patients at admission, after 3 days and at discharge. Blood apoptotic neutrophils were measured by flow-cytometry and light microscopy. Serum and sputum levels of IL-6, IL-8 and TNF-alpha were determined by an immunoassay technique. We found a significantly reduced percentage of apoptotic neutrophils at the onset of COPD exacerbation which increased over time (1.1+/-0.4% at admission vs. 2.4+/-0.4% at discharge, P<0.0001). Patients presented no changes in serum cytokines neither during exacerbation nor in comparison to controls. In contrast, sputum levels of cytokines were significantly increased compared to serum levels. There was no significant correlation between the apoptotic neutrophils and the cytokine concentrations in serum or sputum. None of the clinical parameters, such as smoking, microbial infection, corticosteroids or hypoxemia showed a correlation with neutrophil apoptosis. No relationship could be found between the reduced percentage of apoptotic neutrophils in blood and serum concentration of IL-6, IL-8 and TNF-alpha or other clinical parameters in patients with COPD exacerbation.

Systemic inflammation in COPD visualised by gene profiling in peripheral blood neutrophils

BACKGROUND

The inflammatory process in chronic obstructive pulmonary disease (COPD) is characterised by the presence of neutrophils in the lung that are able to synthesise de novo several inflammatory mediators. The local chronic persistent inflammatory response is accompanied by systemic effects such as cytokine induced priming of peripheral leucocytes and muscle wasting. The preactivation or priming of peripheral blood neutrophils was used to gain more insight into the mechanisms of this systemic inflammatory response.

METHODS

Gene arrays were performed on peripheral blood neutrophils obtained from healthy donors after stimulation in vitro with tumour necrosis factor (TNF)-alpha, granulocyte-macrophage colony stimulating factor (GM-CSF), or both. The expression of many inflammatory genes was regulated in these cells following stimulation. The expression of inflammatory genes in peripheral blood neutrophils in healthy subjects and those with COPD was measured by real time RT-PCR after stimulation with TNFalpha, GM-CSF, interleukin (IL)-8, fMLP, TNFalpha + GM-CSF, and lipopolysaccharide (LPS).

RESULTS

The genes regulated in the gene array with TNFalpha/GM-CSF stimulated neutrophils included cytokines (such as IL-1beta), chemokines (such as IL-8), and adhesion molecules (such as ICAM-1). Disease severity as measured by forced expiratory volume in 1 second (FEV(1)) in COPD patients correlated with expression of several of these genes including IL-1beta (r = -0.540; p = 0.008), MIP-1beta (r = -0.583; p = 0.003), CD83 (r = -0.514; p = 0.012), IL-1 receptor 2 (r = -0.546; p = 0.007), and IL-1 receptor antagonist (r = -0.612; p = 0.002).

CONCLUSIONS

These data are consistent with the hypothesis that progression of COPD is associated with the activation of neutrophils in the systemic compartment. De novo expression of inflammatory mediators by peripheral blood neutrophils suggests a pro-inflammatory role for these cells in the pathogenesis of COPD.

The relationship between reduced lung function and cardiovascular mortality: a population-based study and a systematic review of the literature

STUDY OBJECTIVES

Conditions that give rise to reduced lung function are frequently associated with low-grade systemic inflammation, which may lead to poor cardiovascular outcomes. We sought to determine the relationship between reduced FEV1 and cardiovascular mortality, independent of smoking.

DESIGN

Longitudinal population-based study and a meta-analysis of literature.

SETTING

Representative sample of the general population.

PARTICIPANTS

Participants of the first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study who were 40 to 60 years of age at baseline assessment (n = 1,861).

MEASUREMENTS AND RESULTS

We compared the risk of cardiovascular mortality across quintiles of FEV1. Individuals in the lowest FEV1 quintile had the highest risk of cardiovascular mortality (relative risk [RR], 3.36; 95% confidence interval [CI], 1.54 to 7.34). Compared to FEV1 quintile 1, individuals in quintile 5 had a fivefold increase in the risk of death from ischemic heart disease (RR, 5.65; 95% CI, 2.26 to 14.13). We also performed a systematic review of large cohort studies (> 500 participants) that reported on the relationship between FEV1 and cardiovascular mortality (12 studies; n = 83,880 participants). Compared to participants in the highest FEV1 category, those with reduced FEV1 had a higher risk of cardiovascular mortality (pooled RR, 1.77; 95% CI, 1.56 to 1.97).

CONCLUSIONS

There is strong epidemiologic evidence to indicate that reduced FEV1 is a marker for cardiovascular mortality independent of age, gender, and smoking history.

A novel polymorphism in secretory phospholipase A2-IID is associated with body weight loss in chronic obstructive pulmonary disease

RATIONALE

Chronic and systemic inflammation, a potential cause of body weight loss in patients with chronic obstructive pulmonary disease (COPD), may be associated with the proinflammatory properties of secretory phospholipases A2 (sPLA2s), especially the group II subfamily sPLA2s.

OBJECTIVES

We tested our hypothesis that the individual susceptibility to body weight loss in patients with COPD is attributed to the genetic variances of this sPLA2 gene region.

METHODS

A total of 12 single nucleotide polymorphisms (SNPs) encompassing the sPLA2 gene region were determined in 276 male patients with COPD.

MEASUREMENTS AND MAIN RESULTS

We first analyzed our patients whose body mass index (BMI) was at the bottom 100 (BMI, 17.13 +/- 1.29 kg/m2) and at the top 100 (23.83 +/- 1.98) in relation to SNPs. Both the Fisher's exact test (odds ratio, 2.36; 95% confidence interval, 1.34-4.18; p = 0.004) and logistic regression analysis (odds ratio, 2.10; 95% confidence interval, 1.13-3.90; p = 0.019) showed statistical significance between one SNP (National Center for Biotechnology Information SNP reference: rs584367) and the reduction of BMI in the recessive model in patients with COPD. Using all the patients, a significant difference between the values of BMI (log transformed) of the mutant group (CT + TT) and that of the nonmutant group (CC) of this SNP (mean [SE], 1.293 [0.005] vs. 1.317 [0.006]; p = 0.003) was found after adjustment for age, smoking habit, and pulmonary function (analysis of covariance). Importantly, this SNP caused a change in amino acids in sPLA2-IID protein (Gly80Ser).

CONCLUSIONS

These results suggest that sPLA2-IID may be one of the susceptibility genes that contribute to body weight loss in patients with COPD.

Hypoxaemia enhances peripheral muscle oxidative stress in chronic obstructive pulmonary disease

BACKGROUND

Because oxidative stress affects muscle function, the underlying mechanism to explain exercise induced peripheral muscle oxidative stress in patients with chronic obstructive pulmonary disease (COPD) is clinically relevant. This study investigated whether chronic hypoxaemia in COPD worsens peripheral muscle oxidative stress and whether an abnormal muscle inflammatory process is associated with it.

METHODS

Nine chronically hypoxaemic and nine non-hypoxaemic patients performed repeated knee extensions until exhaustion. Biopsy specimens were taken from the vastus lateralis muscle before and 48 hours after exercise. Muscle oxidative stress was evaluated by lipid peroxidation (lipofuscin and thiobarbituric acid reactive substances (TBARs)) and oxidised proteins. Inflammation was evaluated by quantifying muscle neutrophil and tumour necrosis factor (TNF)-alpha levels.

RESULTS

When both groups were taken together, arterial oxygen pressure was positively correlated with quadriceps endurance time (n = 18, r = 0.57; p < 0.05). At rest, quadriceps lipofuscin inclusions were significantly greater in hypoxaemic patients than in non-hypoxaemic patients (2.9 (0.2) v 2.0 (0.3) inclusions/fibre; p < 0.05). Exercise induced a greater increase in muscle TBARs and oxidised proteins in hypoxaemic patients than in non-hypoxaemic patients (40.6 (9.1)% v 10.1 (5.8)% and 51.2 (11.9)% v 3.7 (12.2)%, respectively, both p = 0.01). Neutrophil levels were significantly higher in hypoxaemic patients than in non-hypoxaemic patients (53.1 (11.6) v 21.5 (11.2) counts per fibre x 10(-3); p < 0.05). Exercise did not alter muscle neutrophil levels in either group. Muscle TNF-alpha was not detected at baseline or after exercise.

CONCLUSION

Chronic hypoxaemia was associated with lower quadriceps endurance time and worsened muscle oxidative stress at rest and after exercise. Increased muscle neutrophil levels could be a source of the increased baseline oxidative damage. The involvement of a muscle inflammatory process in the exercise induced oxidative stress of patients with COPD remains to be shown.

Impaired systemic cell-mediated immunity and increased susceptibility to acute respiratory tract infections in patients with COPD

Although it has been reported that chronic obstructive pulmonary disease (COPD) is frequently associated with systemic immune disturbances, negative impact of these disturbances on the increased prevalence of acute respiratory tract infections (aRTIs) has remained unclear. We evaluated circulating levels of interferon-gamma (IFN-gamma), soluble interleukin-2 receptor (sIL-2R), neopterin, and soluble intercellular adhesion molecule-1 (sICAM-1) in 35 clinically stable patients with COPD and in 22 age-matched healthy controls, since these molecules are considered to reflect the in vivo status of systemic cell-mediated immunity (CMI). We found that circulating levels of sIL-2R (1.52+/-1.25 vs. 0.97+/-0.48 ng/ml; P<0.05), neopterin (7.23+/-4.24 vs. 4.95+/-1.52 nmol/l; P<0.05), and sICAM-1 (665+/-302 vs. 328+/-164 ng/ml; P<0.0001), but not IFN-gamma (7.55+/-4.72 vs. 6.65+/-1.13 pg/ml; P=NS) were significantly higher in patients with COPD than in the controls. Importantly, follow-up study for 12 months demonstrated that patients in subgroup with relatively higher circulating levels of sIL-2R (2.20+/-1.44 ng/ml, n=18) had significantly higher risk of developing aRTIs (P=0.0204) than those in subgroup with relatively lower circulating levels of sIL-2R (0.80+/-0.23 ng/ml, n=17). These results may suggest that impaired systemic CMI observed in COPD patients is associated with the increased susceptibility to aRTIs in these patients.

Possible pathomechanisms of sudden infant death syndrome: key role of chronic hypoxia, infection/inflammation states, cytokine irregularities, and metabolic trauma in genetically predisposed infants

Chronic hypoxia, viral infections/bacterial toxins, inflammation states, biochemical disorders, and genetic abnormalities are the most likely trigger of sudden infant death syndrome (SIDS). Autopsy studies have shown increased pulmonary density of macrophages and markedly more eosinophils in the lungs accompanied by increased T and B lymphocytes. The elevated levels of immunoglobulins, about 20% more muscle in the pulmonary arteries, increased airway smooth muscle cells, and increased fetal hemoglobin and erythropoietin are evidence of chronic hypoxia before death. Other abnormal findings included mucosal immune stimulation of the tracheal wall, duodenal mucosa, and palatine tonsils, and circulating interferon. Low normal or higher blood levels of cortisol often with petechiae on intrathoracic organs, depleted maternal IgG antibodies to endotoxin core (EndoCAb) and early IgM EndoCAb triggered, partial deletions of the C4 gene, and frequent IL-10-592*A polymorphism in SIDS victims as well as possible hypoxia-induced decreased production of antiinflammatory, antiimmune, and antifibrotic cytokine IL-10, may be responsible for the excessive reactions to otherwise harmless infections. In SIDS infants, during chronic hypoxia and times of infection/inflammation, several proinflammatory cytokines are released in large quantities, sometimes also representing a potential source of tissue damage if their production is not sufficiently well controlled, eg, by pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP). These proinflammatory cytokines down-regulate gene expression of major cytochrome P-450 and/or other enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity, thus affecting metabolism of several endogenous lipophilic substances, such as steroids, lipid-soluble vitamins, prostaglandins, leukotrienes, thromboxanes, and exogenous substances. In SIDS victims, chronic hypoxia, TNF-alpha and other inflammatory cytokines, and arachidonic acid (AA) as well as n-3 polyunsaturated fatty acids (FA), stimulated and/or augmented superoxide generation by polymorphonuclear leukocytes, which contributed to tissue damage. Chronic hypoxia, increased amounts of nonheme iron in the liver and adrenals of these infants, enhanced activity of CYP2C9 regarded as the functional source of reactive oxygen species (ROS) in some endothelial cells, and nicotine accumulation in tissues also intensified production of ROS. These increased quantities of proinflammatory cytokines, ROS, AA, and nitric oxide (NO) also resulted in suppression of many CYP450 and other enzymes, eg, phosphoenolpyruvate carboxykinase (PEPCK), an enzyme important in the metabolism of FA during gluconeogenesis and glyceroneogenesis. PEPCK deficit found in SIDS infants (caused also by vitamin A deficiency) and eventually enhanced by PACAP lipolysis of adipocyte triglycerides resulted in an increased FA level in blood because of their impaired reesterification to triacylglycerol in adipocytes. In turn, the overproduction and release of FA into the blood of SIDS victims could lead to the metabolic syndrome and an early phase of type 2 diabetes. This is probably the reason for the secondary overexpression of the hepatic CYP2C8/9 content and activity reported in SIDS infants, which intensified AA metabolism. Pulmonary edema and petechial hemorrhages often present in SIDS victims may be the result of the vascular leak syndrome caused by IL-2 and IFN-alpha. Chronic hypoxia with the release of proinflammatory mediators IL-1alpha, IL-1beta and IL-6, and overloading of the cardiovascular and respiratory systems due to the narrowing airways and small pulmonary arteries of these children could also contribute to the development of these abnormalities. Moreover, chronic hypoxia of SIDS infants induced also production of hypoxia-inducible factor 1alpha (HIF-1alpha), which stimulated synthesis and release of different growth factors by vascular endothelial cells and intensified subclinical inflammatory reactions in the central nervous system, perhaps potentiated also by PACAP and VIP gene mutations. These processes could lead to the development of brainstem gliosis and disorders in the release of neuromediators important for physiologic sleep regulation. All these changes as well as eventual PACAP abnormalities could result in disturbed homeostatic control of the cardiovascular and respiratory responses of SIDS victims, which, combined with the nicotine effects and metabolic trauma, finally lead to death in these often genetically predisposed children.

Chronic obstructive pulmonary disease, asthma, and risk of type 2 diabetes in women

OBJECTIVE

Inflammation plays a key role in chronic obstructive pulmonary disease (COPD) and asthma. Increasing evidence points toward a role of inflammation in the pathogenesis of type 2 diabetes. We wanted to determine the relation of COPD and asthma with the development of type 2 diabetes.

RESEARCH DESIGN AND METHODS

The Nurses' Health Study is a prospective cohort study. From 1988-1996, 103,614 female nurses were asked biennially about a physician diagnosis of emphysema, chronic bronchitis, asthma, and diabetes.

RESULTS

During 8 years of follow-up, we documented a total of 2,959 new cases of type 2 diabetes. The risk of type 2 diabetes was significantly higher for patients with COPD than those without (multivariate relative risk 1.8, 95% CI 1.1-2.8). By contrast, the risk of type 2 diabetes among asthmatic patients was not increased (1.0, 0.8-1.2). The asthma results remained nonsignificant even when we evaluated diabetes risk by duration of asthma exposure.

CONCLUSIONS

Our findings suggest that COPD may be a risk factor for developing type 2 diabetes. Differences in the inflammation and cytokine profile between COPD and asthma might explain why COPD, but not asthma, is associated with increased risk of type 2 diabetes.

Hypoxia-induced dysfunction of rat diaphragm: role of peroxynitrite

Oxidants may play a role in hypoxia-induced respiratory muscle dysfunction. In the present study we hypothesized that hypoxia-induced impairment in diaphragm contractility is associated with elevated peroxynitrite generation. In addition, we hypothesized that strenuous contractility of the diaphragm increases peroxynitrite formation. In vitro force-frequency relationship, isotonic fatigability, and nitrotyrosine levels were assessed under hypoxic (Po(2) approximately 6.5 kPa) and hyperoxic (Po(2) approximately 88.2 kPa) control conditions and also in the presence of authentic peroxynitrite (60 min), ebselen (60 min), and the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine acetate (L-NMMA) (90 min). A hypoxia-induced downward shift of the force-frequency relationship was associated with elevated nitrotyrosine level in the diaphragm. During hypoxia, both ebselen and L-NMMA decreased nitrotyrosine levels but did not affect force generation. Strenuous contractions impaired force generation but did not affect nitrotyrosine levels in the diaphragm during hypoxia. But under hyperoxic conditions, fatiguing contractions were associated with elevated diaphragm nitrotyrosine levels. Under hyperoxic conditions exogenous peroxynitrite impaired force generation and increased nitrotyrosine level. These studies show that hypoxia-induced impairment in diaphragm contractility is associated with increased diaphragm protein nitration, but no causal relationship was found between diaphragm nitrotyrosine formation and in vitro force generation.

Recognizing and treating glucocorticoid-induced osteoporosis in patients with pulmonary diseases

Glucocorticoids are frequently used to treat patients with pulmonary diseases, but continuous long-term use of glucocorticoids may lead to significant bone loss and an increased risk of fragility fractures. Patients with certain lung diseases, regardless of pharmacotherapy-particularly COPD and cystic fibrosis-and patients waiting for lung transplantation are also at increased risk of osteoporosis. Fragility fractures, especially of the hip, will have substantial effects on the health and well-being of older patients. Vertebral collapse and kyphosis secondary to glucocorticoid-induced osteoporosis (GIO) may affect lung function. Identification of patients with osteopenia, osteoporosis, or fragility fractures related to osteoporosis is strongly recommended and should lead to appropriate treatment. Prevention of GIO in patients receiving continuous oral glucocorticoids is also recommended. In patients receiving either high-dose inhaled glucocorticoids or low- to medium-dose inhaled glucocorticoids with frequent courses of oral glucocorticoids, bone mineral density measurements should be performed to screen for osteopenia and osteoporosis. A bisphosphonate (risedronate or alendronate), calcium and vitamin D supplementation, and lifestyle modifications are recommended for the prevention and treatment of GIO.

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.

Chronic hypoxia: common traits between chronic obstructive pulmonary disease and altitude

PURPOSE OF REVIEW

Loss of body mass and exercise intolerance are common findings in chronic obstructive pulmonary disease and are often difficult to reverse despite optimal nutritional intake. Similar findings have been reported in healthy individuals during high-altitude exposure. The role of hypoxia in modulating metabolism has been largely investigated in vitro and in animal studies. More fragmentary is the knowledge regarding hypoxia effects on in-vivo human metabolism. This paper reviews recent literature regarding the effects of chronic exposure to hypoxia on metabolism, particularly comparing chronic obstructive pulmonary disease patients with humans exposed to high altitude.

RECENT FINDINGS

Hypoxia has important metabolic effects. Many oxygen-sensitive regulatory mechanisms work through hypoxia inducible factor 1, and recent literature regarding the hypoxic stimulus and its pathological implications deals largely with hypoxia inducible factor 1-related findings. Hypoxia inducible factor 1 is pivotal in the adaptation to chronic hypoxia: it induces gene expression for fructose-2-6-biphosphatase, an enzyme switching glucose metabolism towards glycolysis, allowing energy production in anaerobic conditions. Hypoxia inducible factor 1 is also involved in the development of anorexia because it induces the promoter of the leptin gene. Particularly important for future therapeutic implications are findings related to hypoxia inducible factor 1 polymorphism and interaction with other molecules, especially estrogens, in the clinical evolution of disease.

SUMMARY

Malnutrition is a worsening factor in chronic obstructive pulmonary disease. Similarities between chronic obstructive pulmonary disease and altitude exposure point to the importance of hypoxia in this regard. A better understanding of the underlying mechanisms will help to find alternative therapeutic approaches.

Determinants of BMI in patients with COPD

OBJECTIVE

COPD is characterized by significant chronic inflammation that is evident not only in the pulmonary compartment but also in the circulation. Peripheral blood features of COPD include markers of oxidative stress and altered circulating levels of inflammatory mediators and acute-phase proteins. The presence of a systemic inflammatory response may influence quality of life by giving rise to weight loss, muscle wasting and tissue depletion. The aim of the present study was to evaluate the determinants of body mass and the value of serum tumour necrosis factor alpha (TNF-alpha) as a marker of weight loss in COPD patients, and to correlate this with the burden of oxidative stress as measured by serum malonyldialdehyde (MDA) levels.

METHODOLOGY

Fifty-two male COPD patients (mean age 62.55 +/- 6.81 years) were studied. After anthropometric measurements and standard spirometry, serum TNF-alpha concentration was measured by enzyme-linked immunosorbent assay using an hTNF-alpha kit, and MDA was studied spectrophotometrically using the Yoshioka-Kawada method.

RESULTS

The mean BMI was 24.82 +/- 3.46. BMI was lower than normal (< 19) in six patients. Mean serum TNF-alpha concentration was 14.99 +/- 8.98 pg/mL and MDA was 0.93 +/- 0.13 nmol/L. There was no significant correlation between serum MDA and TNF concentrations (P = 0.140). Serum TNF-alpha and MDA concentrations were not correlated with severity of airflow obstruction or degree of hypoxaemia (P > 0.05 for all). BMI was negatively correlated with burden of smoking (pack-years) (r = -0.392, P= 0.004); but not with pulmonary function, degree of hypoxaemia, serum TNF-alpha or MDA levels. BMI was significantly lower in current smokers than ex-smokers (P = 0.041); however, serum MDA and TNF levels were similar in both groups.

CONCLUSION

The results of this study indicate that body mass is related to smoking status (both pack-years and continuance of smoking) in COPD; however, serum TNF-alpha concentration does not seem to be a good marker of weight loss in these patients.

Limitations in the Clinical Usefulness of Single-Dose Pharmacokinetic Studies of Drugs and a Bayesian Approach for the Estimation of Kinetic Parameters

This review presents several clinical examples indicating that physiological changes in the body dependent and/or independent of developmental age, genetic polymorphisms, different disease states, acute and/or chronic inflammations, and physicochemical properties of drugs as well as some environmental factors, such as viral infections, may exert a significant effect on the first-time assessment of kinetic parameters of drug absorption, disposition, metabolism, and excretion after a single-dose administration in children and adults. The available pharmacokinetic data in the literature suggest that one must be cautious in interpretation and practical use of pharmacokinetic variables derived from either single-dose studies or bayesian methods, especially in a pediatric population.

Reversal of Chronic Obstructive Pulmonary Disease-Associated Weight Loss

Poor nutritional status is associated with an increased incidence of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD). While a number of factors have been shown to produce tissue catabolism, no single mechanism has been clearly identified as a primary cause for weight loss in patients with severe COPD. Without a clear understanding of the aetiology of weight loss, therapeutic strategies to reverse this process have historically been unsuccessful. A review of recent studies allows consideration of a model of mechanisms of weight loss. This model includes multiple pathways that may be activated singly or simultaneously to cause loss of weight, specifically lean body mass. These include energy imbalances, elevated levels of cytokines, tissue hypoxia and the effects of cocorticosteroid therapy. To date, interventional studies that have looked at newer pharmacotherapies such as growth hormone and anabolic steroids in patients with COPD who are losing weight have not demonstrated reversal of weight loss or improvement in nutritional status. Currently, early identification of patients at risk for weight loss and aggressive nutritional supplementation coupled with an exercise programme has demonstrated the greatest benefit. However, with increasing understanding of the mechanisms that may be implicated, new targets for therapies are being identified. Of particular research interest are molecules such as leukotrienes, hormones, tumour necrosis factor-alpha and acute-phase proteins, which are noted to be elevated in some patients with COPD-associated weight loss. Currently, inhibitors to some of these inflammatory substances are used therapeutically in other chronic illnesses such as rheumatoid arthritis and cancer cachexia. Future research may investigate their usefulness in COPD and direct new therapies that target the processes contributing to weight loss in these patients.

Plasma cytokine levels in patients with obstructive sleep apnea syndrome: a preliminary study

The levels of some pro- and anti-inflammatory cytokines [interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, IL-6, IL-10, and transforming growth factor (TGF)-beta], were measured by enzyme-linked immunosorbent assay (ELISA) method in the plasma of patients affected by obstructive sleep apnea syndrome (OSAS) at 22:00 hours before polysomnographic recording and immediately after the first obstructive apnea causing an SaO2 below 85%. Significantly higher levels of TNF-alpha were found in OSAS patients assessed before polysomnography compared with the control group (P < 0.01). A slight but significant increase in the plasma levels of IL-6 was also present (P < 0.05). Conversely, a significant decrease in the plasma levels of IL-10 was evident at baseline in OSAS patients (P < 0.04). No significant difference emerged between the mean values of IL-1alpha and TGF-beta between OSAS patients and controls. The present data support a prevailing activation of the Th1-type cytokine pattern in OSAS patients, which is not associated with the severity and duration of OSAS. This can have important consequences for the outcome of OSAS patients, especially with regard to the increased risk for developing atherosclerosis and cardiovascular and cerebrovascular diseases. Immediately after the first obstructive apnea causing an SaO2 <85%, a significant variation was observed in the plasma levels of TNF-alpha in OSAS patients compared with those measured before the beginning of polysomnographic recording (P < 0.001). The role played by this further increase in TNF-alpha levels after the obstructive apnea in OSAS patients remains to be established in the light of the pathogenic mechanisms of this sleep disorder.

Matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1: expression in the lung of fetal rats with nitrofen-induced diaphragmatic hernia

The surrounding extracellular matrix of airway wall tissues changes in response to mechanical stresses and hypoxia. The presence of matrix metalloproteinase-9 (MMP-9) and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), is correlated with collagen degradation and tissue repair in lung disorders. The aim of this study was to evaluate the expression of MMP-9 and TIMP-1 in the lung of fetal rats with nitrofen-induced congenital diaphragmatic hernia (CDH). Administering 100 mg of nitrofen dissolved in 1 ml olive oil to pregnant Wistar rats on day 9 of gestation induced left-sided CDH in fetal rats. In control animals, the same dose of olive oil was given without nitrofen. Cesarean section was performed on day 21 of gestation. The fetuses were divided into two groups: normal controls (n = 10) and nitrofen-induced left-sided CDH (n = 10). Immunoreactivity of the staining for MMP-9 and TIMP-1 in the lung tissues was semiquantitatively analyzed using the staining scores. The relative amount of MMP-9 or TIMP-1 divided by the amount of beta-actin for each lung sample was measured by using the real-time reverse-transcriptase polymerase chain reaction. The immunoreactivity of MMP-9 was significantly increased in the CDH group (n = 5) compared with the control group (n = 5) (p = 0.031). On the other hand, the immunoreactivity of TIMP-1 in the two groups was not significantly different (n = 0.134). The relative amount of MMP-9 (or TIMP-1) in the CDH group (n = 5) does not differ significantly from that in the control group (n = 5) (p = 0.059, 0.596, respectively), but the relative amount of MMP-9 is higher in the CDH group, although it is not significantly higher. On the other hand, the ratios of MMP-9 to TIMP-1 were significantly higher in the CDH group (p = 0.028). In conclusion, fetal rats with nitrofen-induced CDH, a model of respiratory disorders, manifested the excess of MMP-9 activity due to the absence of TIMP-1 that would suggest a trend toward disruption of the extracellular matrix in the CDH lung tissues.

Why are patients with chronic obstructive pulmonary disease at increased risk of cardiovascular diseases? The potential role of systemic inflammation in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) increases the risk of cardiovascular disease 2- to 3-fold. The factors responsible for this association remain largely unknown.

METHODS AND RESULTS

We analyzed data from participants, > or =50 years of age, of the Third National Health and Nutrition Examination Survey (n=6629) to determine whether C-reactive protein (CRP) and other systemic inflammatory markers are present in participants with chronic airflow obstruction and are associated with cardiac injury. Participants with severe airflow obstruction had circulating leukocyte, platelet, and fibrinogen levels that were 460/ microL (95% confidence interval [CI], 30 to 890/ microL), 39 510/ microL (95% CI, 21 730 to 57 290/ microL), and 41.63 mg/dL (95% CI, 19.87 to 63.39 mg/dL) higher, respectively, than in those without airflow obstruction. They were also 2.18 times (95% CI, 1.46 to 3.27) more likely to have an elevated circulating CRP level. Moderate airflow obstruction was associated with smaller but still significant increases in these levels. Moderate and severe airflow obstruction was associated with increased occurrence of ischemic changes on electrocardiograms of participants. In the presence of both highly elevated CRP and moderate or severe airflow obstruction, the Cardiac Infarction Injury Score was 2.68 and 5.88 U higher, respectively, than in those without airflow obstruction and with low CRP, which suggests an additive effect of CRP and COPD on the risk of cardiac injury.

CONCLUSION

Low-grade systemic inflammation was present in participants with moderate to severe airflow obstruction and was associated with increased risk of cardiac injury. This may in part explain the high rates of cardiovascular complications in COPD.

Impaired pulmonary inflammatory responses are a prominent feature of streptococcal pneumonia in mice with experimental emphysema

Little is known about why patients with chronic obstructive pulmonary disease are susceptible to bacterial infections. Using an animal model of pulmonary emphysema, we investigated the inflammatory responses to bacterial infection. After intratracheal infection with Streptococcus pneumoniae (10(3)-10(7) cfu/mouse), the control mice did not die. However, the mice with emphysema died in a dose-dependent manner. Bronchoalveolar lavage fluid, examined 24 hours after infection showed that the numbers of total cells and neutrophils, in addition to murine tumor necrosis factor-alpha and macrophage inflammatory protein-2 concentrations, were significantly less in the mice with emphysema compared with the control mice. Histopathologic findings revealed that the alveoli were filled with inflammatory cells and exudate in the control mice but not in the mice with emphysema. Seventy-two hours after infection, serum cytokine levels were significantly higher in the mice with emphysema, and significant numbers of S. pneumoniae were detected in both the whole lung tissues and the blood of mice with emphysema. These findings suggest that the inflammatory response in mice with emphysema was impaired at the site of bacterial infection despite the bacteremia, which accelerated severe systemic inflammatory responses. Accordingly, intra-alveolar but not systemic immune responses to bacterial infection were impaired in the presence of experimental emphysema.

Strenuous resistive breathing induces plasma cytokines: role of antioxidants and monocytes

Inspiratory resistive breathing increases plasma cytokines, yet the stimulus (or stimuli) and source(s) remain unknown. We tested the role of reactive oxygen species as stimuli and of monocytes as sources of resistive breathing-induced cytokines. Six healthy subjects performed two resistive breathing sessions at 75% of maximum inspiratory pressure before and after a combination of antioxidants (vitamin E 200 mg, vitamin A 50,000 IU, and vitamin C 1,000 mg per day for 60 days, allopurinol 600 mg/day for 15 days, and N-acetylcysteine 2 g/day for 3 days before the second session). Blood was drawn before, at the end, and at 30 and 120 minutes after resistive breathing. Before antioxidants, plasma cytokine levels (determined by enzyme-linked immunosorbent assay) increased secondary to resistive breathing (tumor necrosis factor-alpha and interleukin [IL]-6 by twofold and IL-1beta by threefold). After antioxidants, plasma IL-1beta became undetectable. The tumor necrosis factor-alpha response to resistive breathing was abolished, and the IL-6 response was significantly blunted. Intracellular cytokine detection (by flow cytometry) showed no change in either the percentage of monocytes producing the cytokines or their mean fluorescence intensity both before and after antioxidants. We conclude that oxidative stress is a major stimulus for the resistive breathing-induced cytokine production and that monocytes play no role in this process.

A comparison of bone mineral density in elderly female patients with COPD and bronchial asthma

BACKGROUND

A recent study has shown that osteoporosis and vertebral fractures are quite common in patients with advanced COPD and showed a significant relationship to the mortality of these patients. These results suggested that management of osteoporosis in advanced COPD is an important intervention. But whether patients with COPD who had never received chronic systemic corticosteroids have a high incidence of osteoporosis and whether these patients require treatment strategies to decrease osteoporotic fracture is not yet known. Furthermore, it is unclear whether there are differences in terms of the degree of osteoporosis between patients with COPD and patients with bronchial asthma.

OBJECTIVES

To compare the degree of osteoporosis and bone metabolism markers between elderly women with COPD and those with bronchial asthma who had never received chronic systemic corticosteroids, and to determine the factors influencing bone metabolism in these patients.

DESIGN

Cross-sectional medical survey.

PATIENTS

A total of 44 elderly female patients with COPD (n = 20) or bronchial asthma (n = 24) who had not received chronic systemic corticosteroids were enrolled (mean +/- SEM age, 74.6 +/- 1.0 years).

MEASUREMENTS

Total body and lumbar bone mineral density (BMD) were measured by dual-energy x-ray absorptiometry, and the data were compared between the two groups. In addition, the association between bone mass and clinical variables was determined.

RESULTS

When lumbar BMD was expressed as a Z score, the Z scores of patients with COPD were significantly lower than those of patients with bronchial asthma (p < 0.01). The prevalence of osteoporosis was also significantly higher in patients with COPD (50% vs 21%, p < 0.05). In patients with COPD, body mass index was positively correlated with BMD in the lumbar spine (r = 0.55, p = 0.02) and total body (r = 0.49, p = 0.03). Other clinical, biochemical, and anthropometric variables were not correlated with BMD.

CONCLUSIONS

In elderly female patients, osteoporosis is more common in cases of COPD than in bronchial asthma, even if these patients had not received long-term systemic corticosteroids. The explanation for the higher prevalence of osteoporosis in COPD is still not known, but preventive strategies to decrease osteoporotic fractures should be added to the management of elderly patients with COPD.

Tumor necrosis factor-alpha +489G/A gene polymorphism is associated with chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized by a chronic inflammatory process, in which the pro-inflammatory cytokine Tumor Necrosis Factor (TNF)-alpha is considered to play a role. In the present study the putative involvement of TNF-alpha gene polymorphisms in pathogenesis of COPD was studied by analysis of four TNF-alpha gene polymorphisms in a Caucasian COPD population.

METHODS

TNF-alpha gene polymorphisms at positions -376G/A, -308G/A, -238G/A, and +489G/A were examined in 169 Dutch COPD patients, who had a mean forced expiratory volume in one second (FEV1) of 37 +/- 13%, and compared with a Dutch population control group of 358 subjects.

RESULTS

The data showed that the TNF-alpha +489G/A genotype frequency tended to be different in COPD patients as compared to population controls, which was due to an enhanced frequency of the GA genotype. In line herewith, carriership of the minor allele was associated with enhanced risk of development of COPD (odds ratio = 1.9, p = 0.009). The other TNF-alpha gene polymorphisms studied revealed no discrimination between patients and controls. No differences in the examined four TNF-alpha polymorphisms were found between subtypes of COPD, which were stratified for the presence of radiological emphysema. However, comparison of the COPD subtypes with controls showed a significant difference in the TNF-alpha +489G/A genotype in patients without radiological emphysema (chi2-test: p < 0.025 [Bonferroni adjusted]), while no differences between COPD patients with radiological emphysema and controls were observed.

CONCLUSION

Based on the reported data, it is concluded that COPD, and especially a subgroup of COPD patients without radiological emphysema, is associated with TNF-alpha +489G/A gene polymorphism.

Local and systemic inflammation in patients with chronic obstructive pulmonary disease: soluble tumor necrosis factor receptors are increased in sputum

Chronic obstructive pulmonary disease (COPD) is characterized by significant chronic inflammation in the pulmonary compartment as well as in the circulation. This study aimed to elucidate the relationship between local and systemic inflammation in smoking-induced COPD by assessing levels of soluble (s) tumor necrosis factor (TNF) receptors, TNF-alpha, and interleukin-8 (IL-8) in induced sputum and in plasma. Sputum induction was performed in 18 subjects with COPD (FEV(1) 56% predicted) and 17 healthy smokers (FEV(1) 99% predicted). Patients with COPD showed significantly higher percentages of neutrophils and levels of sTNF-R55 and IL-8 in sputum as compared with control subjects, whereas sputum sTNF-R75 levels tended to be higher in COPD. Sputum TNF-alpha levels were similar in both groups. When comparing sTNF receptors in sputum and plasma, no direct correlations were found despite elevation of circulating sTNF-R75 levels in patients with COPD. In addition, sputum sTNF receptors were inversely related to the FEV(1) in patients with COPD, whereas circulating sTNF receptors were not, suggesting different regulation of inflammation in the pulmonary and systemic compartment. When subjects were divided according to their current smoking status, levels of sTNF-R55, sTNF-R75, and IL-8 in sputum were significantly elevated in ex-smoking versus currently smoking patients with COPD, suggesting ongoing inflammation in airways and circulation of patients with COPD after smoking cessation.

Hypoxia-induced down-regulation of CYP1A1/1A2 and up-regulation of CYP3A6 involves serum mediators

1. Acute moderate hypoxia modifies the catalytic activity and expression of certain isoenzymes of hepatic cytochrome P450 (P450). The aim of this study was to document whether hypoxia affects hepatic P450 directly or through the release of serum mediators. 2. Rabbits were subjected to a FiO(2) of 8% for 48 h, sacrificed, and serum and hepatocytes were isolated; hepatocytes from control and rabbits with hypoxia were incubated with serum from control and hypoxic rabbits for 4 and 24 h, and total P450 content, CYP1A1, 1A2 and 3A6 activities and expressions were assessed. Sera were fractionated by size exclusion chromatography and fractions tested for their ability to modify activity and amount of P450, and serum mediators were identified through neutralization experiments. 3. Total serum and fractions with proteins of 15-23 and 65-94 kDa of M(r) reduced P450 content and expression of CYP1A1, 1A2 and 3A6, as well as CYP1A1, 1A2 and 3A6 mRNA. Total serum and the fraction with 32-44 kDa proteins increased CYP3A6 activity and protein and mRNA. The serum mediators implicated in the decrease in activity and expression of CYP1A1, 1A2 and 3A6 were interferon-gamma (IFN-gamma), interleukin-1beta (IL-1beta) and IL-2. Erythropoietin (Epo) was partly responsible for the increase in P450 content and CYP3A6 expression. 4. In conclusion, acute moderate hypoxia diminishes the activity and expression of CYP1A1, 1A2 and CYP1A1, 1A2 mRNA, and increases CYP3A6 protein, activity and CYP3A6 mRNA. Several mechanisms contribute to these changes in P450, among them the release of cytokines acting as serum mediators.

Tumor necrosis factor-alpha is central to acute cigarette smoke-induced inflammation and connective tissue breakdown

The role of tumor necrosis factor-alpha (TNF-alpha) as a mediator of cigarette smoke-induced disease is controversial. We exposed mice with knocked-out p55/p75 TNF-alpha receptors (TNF-alpha-RKO mice) to cigarette smoke and compared them with control mice. Two hours after smoke exposure, increases in gene expression of TNF-alpha, neutrophil chemoattractant, macrophage inflammatory protein-2, and macrophage chemoattractant, protein-1 were seen in control mice. By 6 hours, TNF-alpha, macrophage inflammatory protein-2, and macrophage chemoattractant protein-1 gene expression levels had returned to control values in control mice and stayed at control values through 24 hours. In TNF-alpha-RKO mice, no changes in gene expression of these mediators were seen at any time. At 24 hours, control mice demonstrated increases in lavage neutrophils, macrophages, desmosine (a measure of elastin breakdown), and hydroxyproline (a measure of collagen breakdown), whereas TNF-alpha-RKO mice did not. In separate experiments, pure strain 129 mice, which produce low levels of TNF-alpha, showed no inflammatory response to smoke at 24 hours or 7 days. We conclude that TNF-alpha is central to acute smoke-induced inflammation and resulting connective tissue breakdown, the precursor of emphysema. The findings support the idea that TNF-alpha promoter polymorphisms may be of importance in determining who develops smoke-induced chronic obstructive pulmonary disease.