Effect of Ozone on Concentrations of Lysozyme in Phagocytizing Alveolar

Demonstration of lysozyme by the immunoperoxidase method was used to determine whether ozone-induced defects in phagocytic killing of inhaled Staphylococcus aureus by rat alveolar macrophageswereassociatedwith absenceof this important bactericidal enzyme. Rats were infected with aerosols of S. aureus and then exposed for 5 hr to 2.5 ppm of ozone. Left lungs were cultured for staphylococci; right lungs were stained for lysozyme and bacteria. Compared with control animals, rats exposed to ozone showed diminished rates of bacterial killing; a larger percentage of extracellular, uningested bacteria; an increased number of intracellular staphylococcal clumps; and absence of lysozyme in macrophages permitting staphylococcal proliferation. These results, in which absence of enzymeactivityoccurred in macrophagessubjected to the dual insults of ozone exposure and ingested bacteria, provide an explanation for the inability of phagocytes to kill ingested bacteria after exposure to ozone. The enhanced susceptibility to pulmonary infec-tion that follows exposure to ozone is due primari-ly to impairment of intracellular killing of bacteria by pulmonary macrophages [1-3]. Recent studies have correlated reductions in intracellular concen-trations of acid phosphatase and fJ-glucuronidase with defects in bactericidal function [4]. Although these lysosomal enzymes are not known to be bactericidal, their absence suggests that the mech-anism of the ozone-induced impairment of bac-tericidal function involves injury to lysosomal enzymes. The present studies extend these observa-tions by demonstrating reduced concentrations of lysozyme, a lysosomal enzyme of proven bacteri-cidal capability [5-9], in macrophages with im-paired microbicidal activity consequent to ozone exposure. Materials and Methods The methods used for the in vivo assessment of Received for publication June 23, 1980, and in revised for