Surfactant protein A (SP-A) plays an important role in innate immunity. The sex-dependent survival of infected SP-A knockout (KO) mice has been observed. Our goal was to study the impact of ozone (O3) and sex, as well as gonadal hormones, on the bronchoalveolar lavage (BAL) readouts and survival, respectively, of Klebsiella pneumoniae-infected SP-A KO mice. Male and female SP-A KO mice were exposed to O3 or filtered air and infected with K. pneumoniae. We studied markers of inflammation and tissue damage at 4, 24, and 48 h, as well as the survival over 14 days, of gonadectomized (Gx) mice implanted with control pellets (CoP) or hormone (5α-dihydrotestosterone (DHT) in female gonadectomized mice (GxF) or 17β-estradiol (E2) in male gonadectomized mice (GxM)). We observed: (1) an increase in neutrophil and macrophage inflammatory protein-2 levels as time progressed post-infection, and O3 exposure appeared to increase this response; (2) an increase in lactate dehydrogenase, total protein, oxidized protein, and phospholipids in response to O3 with no consistent sex differences in studied parameters; and (3) a reduction in survival of the GxM and CoP mice, the GxM and E2 mice, and the GxF and DHT mice but not for the GxF and CoP mice after O3. Without SP-A, (a) sex was found to have a minimal impact on BAL cellular composition and tissue damage markers, and (b) the impact of gonadal hormones on survival was found to involve different mechanisms than in the presence of SP-A.
Keywords: innate immunity; oxidative stress; pneumonia; sex differences; surfactant protein-A.