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

Cytokines, apoptosis and cachexia: the potential for TNF antagonism

The cachexia syndrome is characterised by progressive weight loss and depletion of lean body mass and has long been recognised as a poor prognostic sign. Whilst the clinical features of the wasting process are readily apparent, its pathogenesis is complex and poorly understood. There is increasing evidence that the immune system, in particular inflammatory cytokines, may play an important role in the development of cachexia. The cytokine considered to be the most relevant to this process is tumor necrosis factor alpha (TNF), although other mediators such as interleukin (IL) 1, IL-6 and interferon gamma have also been implicated. Apoptosis represents a potential pathway by which wasting can occur in chronic diseases. Cytokines and their corresponding receptors are known to be important regulators of cell death. Apoptosis has been demonstrated in the skeletal muscle of patients with chronic heart failure (CHF) and is thought to be partly responsible for the significant impairment of functional work capacity associated with this condition. An understanding of the mechanisms that regulate muscle protein breakdown is essential for the development of strategies for treating or even preventing muscle cachexia in patients. It is the aim of this article to review the role of inflammatory cytokines, particularly TNF, in the pathogenesis of wasting and also the potential for anti-cytokine therapy. Although this review will concentrate predominantly on the syndrome of CHF, other chronic illnesses such as liver disease, cancer, and sepsis will also be discussed.

Effect of theophylline on induced sputum inflammatory indices and neutrophil chemotaxis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by a neutrophilic airway inflammation that can be demonstrated by examination of induced sputum. Theophylline has antiinflammatory effects in asthma, and in the present study we investigated whether a similar effect occurs in COPD patients treated with low doses of theophylline. Twenty-five patients with COPD were treated with theophylline (plasma level of 9-11 mg/L) for 4 weeks in a placebo-controlled, randomized, double-blind crossover study. Theophylline was well tolerated. Induced sputum inflammatory cells, neutrophils, interleukin-8, myeloperoxidase, and lactoferrin were all significantly reduced by about 22% by theophylline. Neutrophils from subjects treated with theophylline showed reduced chemotaxis to N-formyl-met-leu-phe (approximately 28%) and interleukin-8 (approximately 60%). Neutrophils from a healthy donor showed reduced chemotaxis (approximately 30%) to induced sputum samples obtained during theophylline treatment. These results suggest that theophylline has antiinflammatory properties that may be useful in the long-term treatment of COPD.

Systemic anti-inflammatory mediators in COPD: increase in soluble interleukin 1 receptor II during treatment of exacerbations

BACKGROUND

The aim of this study was to test the hypothesis that the chronic inflammatory process present in chronic obstructive pulmonary disease (COPD) is due to a defective endogenous anti-inflammatory mechanism.

METHODS

Systemic levels of the anti-inflammatory mediators soluble interleukin 1 receptor II (sIL-1RII), soluble tumour necrosis factor receptor p55 (sTNF-R55) and sTNF-R75, and of C reactive protein (CRP) and lipopolysaccharide binding protein (LBP) were analysed in 55 patients with stable COPD (median forced expiratory volume in one second (FEV1) 34% predicted (range 15–78)) and compared with levels in 23 control subjects. In addition, changes in these mediators were studied in 13 patients with COPD (median FEV1 34% predicted (range 19–51)) during the first 7 days in hospital with an exacerbation of the disease.

RESULTS

Patients with stable COPD were characterised by a systemic inflammatory process indicated by an increased leucocyte count (7.2 (4.7–16.4)v 4.8 (3.5–8.3) × 109/l), raised levels of CRP (11.8 (1.1–75.0) v 4.1 (0.6–75.0) μg/ml) and LBP (45.6 (8.1–200.0)v 27.9 (14.1–71.5) μg/ml), and moderate increases in both sTNF-Rs. In contrast, the sIL-1RII level did not differ between patients and controls (4.53 (2.09–7.60)v 4.63 (3.80–5.93) ng/ml). During treatment of disease exacerbations, systemic levels of both CRP (at day 3) and LBP (at day 7) were significantly reduced compared with day 1, whereas sIL-1RII levels increased.

CONCLUSIONS

These data suggest an imbalance in systemic levels of pro- and anti-inflammatory mediators in patients with stable COPD. The increase in the anti-inflammatory mediator sIL-1RII during treatment of exacerbations may contribute to the clinical improvement.

Systemic anti-inflammatory mediators in COPD: increase in soluble interleukin 1 receptor II during treatment of exacerbations

BACKGROUND

The aim of this study was to test the hypothesis that the chronic inflammatory process present in chronic obstructive pulmonary disease (COPD) is due to a defective endogenous anti-inflammatory mechanism.

METHODS

Systemic levels of the anti-inflammatory mediators soluble interleukin 1 receptor II (sIL-1RII), soluble tumour necrosis factor receptor p55 (sTNF-R55) and sTNF-R75, and of C reactive protein (CRP) and lipopolysaccharide binding protein (LBP) were analysed in 55 patients with stable COPD (median forced expiratory volume in one second (FEV(1)) 34% predicted (range 15-78)) and compared with levels in 23 control subjects. In addition, changes in these mediators were studied in 13 patients with COPD (median FEV(1) 34% predicted (range 19-51)) during the first 7 days in hospital with an exacerbation of the disease.

RESULTS

Patients with stable COPD were characterised by a systemic inflammatory process indicated by an increased leucocyte count (7.2 (4.7-16.4) v 4.8 (3.5-8.3) x 10(9)/l), raised levels of CRP (11.8 (1.1-75.0) v 4.1 (0.6-75.0) microg/ml) and LBP (45.6 (8.1-200.0) v 27.9 (14.1-71.5) microg/ml), and moderate increases in both sTNF-Rs. In contrast, the sIL-1RII level did not differ between patients and controls (4.53 (2.09-7.60) v 4.63 (3.80-5.93) ng/ml). During treatment of disease exacerbations, systemic levels of both CRP (at day 3) and LBP (at day 7) were significantly reduced compared with day 1, whereas sIL-1RII levels increased.

CONCLUSIONS

These data suggest an imbalance in systemic levels of pro- and anti-inflammatory mediators in patients with stable COPD. The increase in the anti-inflammatory mediator sIL-1RII during treatment of exacerbations may contribute to the clinical improvement.

A novel pathophysiologic phenomenon in cachexic patients with chronic obstructive pulmonary disease: the relationship between the circadian rhythm of circulating leptin and the very low-frequency component of heart rate variability

Cachexic patients with chronic obstructive pulmonary disease (COPD) show abnormalities of the autonomic nervous system (ANS), neuroendocrine function, and energy expenditure. Leptin has been implicated in the regulation of ANS, neuroendocine function, and thermogenesis in humans. We assessed the physiologic significance of the circadian rhythm of circulating leptin using power spectrum analysis of heart rate variability (HRV) in nine cachexic male patients with COPD, eight noncachexic patients with COPD, and seven healthy control subjects. A diurnal pattern of 24-h leptin levels was present in both the control subjects (analysis of variance [ANOVA]; F = 7.80, p < 0.0001) and noncachexic COPD patients (F = 9.29, p < 0.0001), but was strikingly absent in the cachexic COPD patients (F = 2.09, p = NS). Analysis of HRV demonstrated that the diurnal rhythm of 24-h very low frequency (VLF; 0.003 to 0.04 Hz) showed significantly identical fluctuations with those of 24-h leptin levels, in all of the three groups (r = 0.388, p < 0.0001). Because VLF has been considered to reflect neuroendocrine and thermoregulatory influences, these data may suggest that the loss of circadian rhythm of circulating leptin has clinical importance in the pathophysiologic features in cachexic patients with COPD.

Circulating levels of soluble Fas ligand and soluble Fas in patients with chronic obstructive pulmonary disease

Fas- and tumour necrosis factor (TNF) receptor-mediated apoptosis are known to be two principal apoptotic mechanisms in humans. Although there are several distinctions between these two systems, in vitro studies have demonstrated similar hypoxic activation and a functional relationship. Since patients with chronic obstructive pulmonary disease (COPD) show chronic hypoxaemia and the activation of the TNF-alpha system, we investigated whether these pathophysiological changes influence the Fas-Fas ligand system. We measured the circulating soluble Fas ligand (sFas-L) level, an inducer of apoptosis, and the soluble Fas receptor (sFas) level, an inhibitor of apoptosis, in 34 COPD patients and 35 age-matched healthy controls. In addition, we investigated the relationships between the levels of sFas-L or sFas and clinical variables including the TNF-alpha system; circulating TNF-alpha and soluble TNF-receptor (sTNF-Rs: sTNF-R55 and R75) levels, in the COPD patients. Although circulating TNF-alpha, sTNF-R55 and R75 levels were significantly higher in the COPD patients than in the healthy controls, serum level of sFas-L (Fisher's exact probability test; P = 0.26) and plasma level of sFas [COPD patients vs. controls; mean (SD); 3.74 (0.63) vs. 3.67 (0.48) ng/ml; P = 0.89) were not increased in the COPD patients. There was no significant correlation between the levels of sFas-L or sFas and clinical variables in COPD patients. These results suggest that the Fas-Fas ligand system does not independently play an important role in the pathophysiology of patients with COPD.