FIG. 9.

Polymyxin B inhibits LOS-mediated apoptosis of bovine endothelial cells. Bovine pulmonary artery endothelial cells (5 × 10⁴) were incubated with 500 ng of H. somnus LOS/ml with (□) or without (■) 10 μg polymyxin B (PMB)/ml for 22 h at 37°C with 5% CO₂. Controls consisted of endothelial cells incubated in medium alone (UT), 10 μg of polymyxin B/ml, or staurosporine (200 nM; Stauro). Apoptosis was detected by Hoechst 33342 staining. The data illustrate the mean ± SEM of three separate experiments. Statistical analysis was performed by ANOVA followed by the Tukey-Kramer significant difference test. There was a significant reduction in the level of apoptosis (∗, P < 0.005) when endothelial cells were treated with polymyxin B and LOS compared to that of LOS-treated endothelial cells.