Local and systemic inflammation in chronic obstructive pulmonary disease

There is growing evidence for systemic inflammation in chronic obstructive pulmonary disease (COPD). Increased circulating levels of inflammatory cytokines and acute phase proteins occur in stable disease, and COPD exacerbations are notably associated with pulmonary and systemic inflammation. Although the course of inflammation is determined by the balance between pro- and antiinflammatory mediators, in COPD most attention has focused on the former. During exacerbation, however, upregulation of antiinflammatory markers occurs. The main causes of systemic inflammation in COPD remain to be elucidated, although systemic hypoxia is a candidate factor. Although a relationship between lung and systemic inflammation has been suggested, experimental evidence indicates no direct correlations in the regulation of inflammation in the pulmonary and systemic compartments. Longitudinal studies are needed to unravel the role of systemic inflammation in the course of COPD, to analyze the role of acute exacerbations on the chronicity of inflammation, and to evaluate the response of systemic inflammation to different interventions. Emphasis should be placed on the identification of signaling pathways induced and/or altered in skeletal muscle by inflammation, as muscle wasting is a prominent feature of chronic inflammatory disease conditions and contributes significantly to impaired physical functioning and health status in COPD.