Serotonin Transporter Inhibition Prevents and Reverses Monocrotaline-Induced Pulmonary Hypertension in Rats (original) (raw)

Background-Progression of pulmonary hypertension (PH) is associated with increased lung expression of the serotonin transporter (5-HTT), which leads to hyperplasia of the pulmonary artery smooth muscle cells (PA-SMCs). Given the postulated causal relation between 5-HTT overexpression and PH, we herein investigated whether the highly selective 5-HTT inhibitor fluoxetine prevented and/or reversed PH induced by monocrotaline (MCT) in rats. Selective 5-HT 1B/1D , 5-HT 2A , and 5-HT 2B receptor antagonists were used for comparative testing. Methods and Results-MCT injection (60 mg/kg SC) was followed by an early peak in lung 5-HTT expression on day 1, which preceded the onset of PH. Established PH on day 15 was associated with a sustained 5-HTT increase. Continued fluoxetine treatment completely prevented PA-SMC proliferation and PH development and also suppressed the late 5-HTT increase, without affecting the early peak. The 5-HT receptor antagonists did not affect PH. Fluoxetine (10 mg · kg Ϫ1 · d Ϫ1 PO) started 3 weeks after MCT injection completely reversed established PH, normalizing PA pressure and structure. MCT-induced PH was also associated with increased expression of various cytokines, but only interleukin-1␤ and monocyte chemotactic protein-1 increased at the early phase and stimulated 5-HTT expression by cultured PA-SMCs.