AEROSOLIZED HYALURONIC-ACID DECREASES ALVEOLAR INJURY-INDUCED BY HUMAN NEUTROPHIL ELASTASE

This laboratory has previously shown that an intratracheally instilled solution of hyaluronic acid (HA) protects the lung from elastase-indu ced airspace enlargement. In those studies, fluorescein-labeled HA was found to bind preferentially to lung elastic fibers, suggesting a mec hanism for the protective effect. The current investigation extends th ese findings by examining the capacity of an aerosol preparation of HA to similarly inhibit elastase-induced lung injury. Syrian hamsters we re exposed to aerosolized bovine tracheal HA (0.1% solution in water) for either 25 or 50 min, then immediately instilled intratracheally wi th 80 units of human neutrophil elastase. One week later the lungs wer e examined for airspace enlargement, using the mean linear intercept m ethod, Animals exposed to HA for 50 min showed a significant decrease in airspace enlargement compared to controls exposed to aerosolized wa ter alone (68.2 mu m vs 85.9 mu m; P < 0.05). The 25-min exposure to t he HA aerosol also reduced the mean linear intercept compared to contr ols (73.7 mu m vs 85.9 mu m), but this decrease was not statistically significant. With regard to possible inflammatory effects of HA, there was no difference in the percentage of lavaged neutrophils between HA -treated and control lungs at 24 hr (1.4% vs 1.8%, respectively). As w ith earlier experiments using intratracheally instilled HA, aerosolize d fluorescein-labeled HA was found to bind to lung elastic fibers. The se results suggest that aerosolized HA may prevent elastase-mediated i njury in pulmonary emphysema.