Pertussis toxin (PTX) attenuates HDL-induced HUVEC COX-2 expression and PGI-2 release. Cells were preincubated with PTX (2 ng/ml) for 24 hours. Cells were further incubated with 30 μg/ml of N-HDL or D-HDL for 6 hours. The expression of COX-2 was measured by Western blotting (A, B) and the PGI-2 release was determined by the competitive ELISA (C). In all experiments above, PBS was used as vehicle control. Data are expressed as the means ± SEM of three independent experiments. Student’s t test. ** p < 0.01, *** p < 0.001.