Preferential binding of lysozyme to elastic fibres in pulmonary emphysema

Abstract

Background-Lysozyme is increased in inflammatory reactions and is a component of the extracellular matrix, but its possible role in lung diseases such as emphysema and interstitial fibrosis has not been investigated. Methods-To characterise differences in lysozyme content among normal, emphysematous, and fibrotic human lungs, tissue sections obtained from necropsy specimens were immunostained with rabbit polyclonal anti-human lysozyme antibody using the labelled streptavidin-biotin peroxidase method. The immunostained sections were evaluated semi-quantitatively (grading the degree of immunostaining on a scale of 0-4). To determine if degradation of the extracellular matrix affects lysozyme binding, hyaluronidase-treated normal lung tissues were incubated with egg white lysozyme, immunostained with the lysozyme antibody, which crossreacts with egg white lysozyme, and evaluated for degree of staining. Results-Lysozyme immunostaining was significantly increased in lungs with pulmonary emphysema compared with normal or fibrotic tissues (3.4 versus 1.6 and 1.9, respectively; p<0.05) and was preferentially associated with interstitial elastic fibres. Hyaluronidase-treated lung tissues incubated with lysozyme showed increased immunostaining for this protein compared with untreated controls (1.9 versus 1.2; p<0.05). Conclusions-The results suggest that damage to elastic fibres and/or the surrounding extracellular matrix increases lysozyme binding. It is hypothesised that attachment of lysozyme to elastic fibres may interfere with their repair and possibly enhance the progression of pulmonary emphysema.