PTGS2 and Hermansky-Pudlak syndrome: Liu et al. found the COX-2/PGE2 signaling pathway to be activated in common bile duct ligation rat lung in vivo (an animal model of HPS) and PMVEC in vitro, which resulted in the accumulation of macrophages via an imbalance in the ratio of secreted bone morphogeneticprotein-2 (BMP-2) to crossveinless-2 (CV-2) [203].