COPD as a disease of accelerated lung aging.

There is increasing evidence for a close relationship between aging and chronic inflammatory diseases. COPD is a chronic inflammatory disease of the lungs, which progresses very slowly and the majority of patients are therefore elderly. We here review the evidence that accelerating aging of lung in response to oxidative stress is involved in the pathogenesis and progression of COPD, particularly emphysema. Aging is defined as the progressive decline of homeostasis that occurs after the reproductive phase of life is complete, leading to an increasing risk of disease or death. This results from a failure of organs to repair DNA damage by oxidative stress (nonprogrammed aging) and from telomere shortening as a result of repeated cell division (programmed aging). During aging, pulmonary function progressively deteriorates and pulmonary inflammation increases, accompanied by structural changes, which are described as senile emphysema. Environmental gases, such as cigarette smoke or other pollutants, may accelerate the aging of lung or worsen aging-related events in lung by defective resolution of inflammation, for example, by reducing antiaging molecules, such as histone deacetylases and sirtuins, and this consequently induces accelerated progression of COPD. Recent studies of the signal transduction mechanisms, such as protein acetylation pathways involved in aging, have identified novel antiaging molecules that may provide a new therapeutic approach to COPD.