Identification of Emetine as a Therapeutic Agent for Pulmonary Arterial Hypertension: Novel Effects of an Old Drug

OBJECTIVE: Excessive proliferation and apoptosis resistance are special characteristics of pulmonary artery smooth muscle cells (PASMCs) in pulmonary arterial hypertension (PAH). However, the drugs in clinical use for PAH target vascular dilatation, which do not exert adequate effects in patients with advanced PAH. Here, we report a novel therapeutic effect of emetine, a principal alkaloid extracted from the root of ipecac clinically used as an emetic and antiprotozoal drug. Approach and Results: We performed stepwise screenings for 5562 compounds from original library. First, we performed high-throughput screening with PASMCs from patients with PAH (PAH-PASMCs) and found 80 compounds that effectively inhibited proliferation. Second, we performed the repeatability and counter assay. Finally, we performed a concentration-dependent assay and found that emetine inhibits PAH-PASMC proliferation. Interestingly, emetine significantly reduced protein levels of HIFs (hypoxia-inducible factors; HIF-1α and HIF-2α) and downstream PDK1 (pyruvate dehydrogenase kinase 1). Moreover, emetine significantly reduced the protein levels of RhoA (Ras homolog gene family, member A), Rho-kinases (ROCK1 and ROCK2 [rho-associated coiled-coil containing protein kinases 1 and 2]), and their downstream CyPA (cyclophilin A), and Bsg (basigin) in PAH-PASMCs. Consistently, emetine treatment significantly reduced the secretion of cytokines/chemokines and growth factors from PAH-PASMCs. Interestingly, emetine reduced protein levels of BRD4 (bromodomain-containing protein 4) and downstream survivin, both of which are involved in many cellular functions, such as cell cycle, apoptosis, and inflammation. Finally, emetine treatment ameliorated pulmonary hypertension in 2 experimental rat models, accompanied by reduced inflammatory changes in the lungs and recovered right ventricular functions. CONCLUSIONS: Emetine is an old but novel drug for PAH that reduces excessive proliferation of PAH-PASMCs and improves right ventricular functions.