MMP-9 as a marker of inflammation in tracheal epithelial lining fluid (TELF) and in bronchoalveolar fluid (BALF) of COPD horses

Gelatinolytic activity was analysed to study whether elevated activity prev iously found at the tracheal level of the respiratory tract of horses with chronic obstructive pulmonary disease (COPD) could also be found at the low er part of the respiratory tract. Furthermore, presence and significance of the gelatinolytic matrix metalloproteinases (MMPs) MMP-2 and MMP-9 in resp iratory secretions of healthy and COED horses were determined. Elevated gel atinolytic matrix metalloproteinases were detected in bronchoalveolar and t racheobronchial secretions from COPD horses. The main pathologically elevat ed MMP was characterised to be MMP-9, Significantly increased MMP-9 activit ies as measured by gelatin zymography and Western blotting were found in al l the respiratory samples from COPD horses compared to healthy horses. Elev ation of active MMP-9 paralleled with increased gelatinase-associated lipoc alin levels. Bronchoalveolar lavage fluid (BALF) epithelial cells, macropha ges, neutrophils and lymphocytes expressed MMP-9 immunoreactivity demonstra ted by immunocytochemistry and MMP-9 mRNA was expressed by bronchial epithe lial cells of lung tissue section shown by in sitar hybridisation, MMP-2 se ems not to play a major role in chronic lung inflammation. No clear differe nces in MMP-2 or MMP-14 (a potent MMP-2 activator) levels were found when c omparing the samples from COPD or healthy horses, These results suggests th at MMP-9 could serve as a potential diagnostic marker for the active ongoin g tissue remodelling in the acute phase of equine COPD, Increased gelatinol ytic activity could be found at both tested respiratory tract levels, There fore, tracheal epithelial lining fluid (TELF) samples can usefully serve as diagnostic material for detection of increased levels of the main gelatino lytic MMP, MMP-9, representing the entire diseased lung.