Antimicrobial peptides in COPD--basic biology and therapeutic applications

A large number of studies have implicated activation of innate immune mechanisms in the pathogenesis of chronic obstructive pulmonary disease (COPD). Accumulation of inflammatory cells, chemokines and pro-inflammatory cytokines is a hallmark of activation of these mechanisms, but only a few studies have focussed on antimicrobial peptides in COPD. These peptides are a central component of innate immunity, and airway epithelial cells and neutrophils in the lung are the main cellular sources. In addition to their direct antimicrobial action, antimicrobial peptides have been shown to display a variety of activities that may implicate them in the pathogenesis of COPD. This is based on the observation that they not only contribute to defense against respiratory pathogens that have been associated with COPD, but may also contribute to the influx of inflammatory cells, activation of adaptive immunity and epithelial remodeling. The aim of this review is to provide an update on the basic biology of antimicrobial peptides in the lung, with a focus on their putative role in COPD. In addition, the implication of this knowledge for future treatment of COPD is discussed.