FIG. 6.

Estrogen alleviates mortality and bacterial clearance in male and oophorectomized female mice after post-traumatic brain injury (TBI) bacterial pneumonia. For all in vivo experiments, mice received TBI according to protocol. Twenty-four hours later, Pseudomonas aeruginosa K-strain (PAK) was instilled intratracheally and either mortality or bacterial clearance was measured. Estrogen or vehicle was administered at the indicated doses. (A) P. aeruginosa pneumonia leads to decreased mortality after TBI in male mice that received 100 μg/kg estrogen (pink line, n = 10) compared with male mice that received 50 μg/kg estrogen (purple line, n = 6) or vehicle (blue line, n = 4), p < 0.05; *represents a significant difference compared with 50 μg/kg estrogen or vehicle. (B) P. aeruginosa pneumonia leads to decreased mortality after TBI in oophorectomized female mice that received 100 μg/kg estrogen (pink line, n = 10) compared with oophorectomized female mice that received vehicle (blue line, n = 9), p < 0.05; *represents a significant difference compared with vehicle. (C, D) Lungs from wild-type male mice that received 100 μg/kg estrogen or vehicle or oophorectomized female mice that received 100 μg/kg estrogen or vehicle were isolated 6 h after PAK instillation, and colony-forming units/mL were measured. For (C), wild-type male mice that received 100 μg/kg estrogen (pink diamonds) had improved bacterial clearance compared with those that received vehicle (blue circles); n = 4 for each group, p < 0.05; *represents a significant difference compared with vehicle. For (D), oophorectomized female mice that received 100 μg/kg estrogen (pink diamonds) had improved bacterial clearance compared with those that received vehicle (blue circles); n = 4 for each group, p < 0.05; *represents a significant difference compared with vehicle. (E) Male (blue circles) and female (pink diamonds) alveolar macrophages were pre-treated with 10 nM estradiol (or vehicle) for 30 min before exposure to PAK. Tumor nephrosis factor (TNF)-α was 6 h after exposure to PAK, n = 3 for all conditions assayed, TNF-α was measured in duplicate, p < 0.05; both * and ** represent a significant difference compared with male cells treated with vehicle and PAK. (F) Male (blue circles) and female (pink diamonds) alveolar macrophages were pre-treated with 10 nM estradiol (or vehicle) for 30 min before exposure to PAK and measurement of phagocytosis. All groups examined phagocytose bacteria; n = 3 per group.