Induction of Serotonin Transporter by Hypoxia in Pulmonary Vascular Smooth Muscle Cells

Abstract

-The increased delivery of serotonin (5-hydroxytryptamine, 5-HT) to the lung aggravates the development of hypoxia-induced pulmonary hypertension in rats, possibly through stimulation of the proliferation of pulmonary artery smooth muscle cells (PA-SMCs). In cultured rat PA-SMCs, 5-HT (10(-8) to 10(-6) mol/L) induced DNA synthesis and potentiated the mitogenic effect of platelet-derived growth factor-BB (10 ng/mL). This effect was dependent on the 5-HT transporter (5-HTT), since it was prevented by the 5-HTT inhibitors fluoxetine (10(-6) mol/L) and paroxetine (10(-7) mol/L), but it was unaltered by ketanserin (10(-6) mol/L), a 5-HT2A receptor antagonist. In PA-SMCs exposed to hypoxia, the levels of 5-HTT mRNA (measured by competitive reverse transcriptase-polymerase chain reaction) increased by 240% within 2 hours, followed by a 3-fold increase in the uptake of [3H]5-HT at 24 hours. Cotransfection of the cells with a construct of human 5-HTT promoter-luciferase gene reporter and of pCMV-beta-galactosidase gene allowed the demonstration that exposure of cells to hypoxia produced a 5.5-fold increase in luciferase activity, with no change in beta-galactosidase activity. The increased expression of 5-HTT in hypoxic cells was associated with a greater mitogenic response to 5-HT (10(-8) to 10(-6) mol/L) in the absence as well as in the presence of platelet-derived growth factor-BB. 5-HTT expression assessed by quantitative reverse transcriptase-polymerase chain reaction and in situ hybridization in the lungs was found to predominate in the media of pulmonary artery, in which a marked increase was noted in rats that had been exposed to hypoxia for 15 days. These data show that in vitro and in vivo exposure to hypoxia induces, via a transcriptional mechanism, 5-HTT expression in PA-SMCs, and that this effect contributes to the stimulatory action of 5-HT on PA-SMC proliferation. In vivo expression of 5-HTT by PA-SMC may play a key role in serotonin-mediated pulmonary vascular remodeling.

Polymorphism of the Serotonin Transporter Gene and Pulmonary Hypertension in Chronic Obstructive Pulmonary Disease

“…ine. 12,14,16 The ability of 5-HTT to cause PA-SMC proliferation is directly related to the level of 5-HTT gene expression, which is controlled by environmental and genetic factors. Hypoxia is a strong inducer of 5-HTT expression in vitro and in vivo.…”

“…13 Conversely, hypoxia is a strong inducer of 5-HTT gene expression. 14 We therefore hypothesized that 5-HTT gene polymorphism, in combination with hypoxia, may determine the extent of pulmonary vascular remodeling and, consequently, the severity of PH in patients with advanced hypoxemic COPD.…”

Hipertensão arterial pulmonar: fisiopatologia, aspectos genéticos e resposta ao uso crônico do sildenafil

“…In the periphery, also for interfering with the transporter, fenfluramine is able to inhibits serotonin reuptake in platelets and pulmonary endothelial cells. The conse-quences are the increase of free serotonin, in a similar way to what happens in platelet storage pool disease, and pulmonary vasoconstriction 19,46 . Not every oral fenfluramine user develops PAH, which suggests that disorders in serotonin metabolism and in its transporter functioning are facilitating events that need predisposing factors for the development of the disease.…”

“…On the other hand, diacylglycerol generation is implied in the induction of proteinkinase C mitogenic pathway. Serotonin connection to 5-HTT starts intracellular events, involving the formation of oxygen reactive species and the activation of MAPP kinase pathway, resulting in the expression of genes involved with hypertrophy and cellular proliferation 46 . Many studies suggest that serotonin has a role in PAH pathogenesis, including the idiopathic form.…”

Beneficial effect of dehydroepiandrosterone on pulmonary hypertension in a rodent model of pulmonary hypertension in infants

“…We then studied the effect of DHEA on in vitro proliferation of pulmonary artery smooth muscle cells (PASMCs) induced by three different mitogens: fetal calf serum (FCS), serotonin (5-HT) (a well-known mitogenic agent in PASMCs) (12)(13)(14), and hypoxia. Dose-dependent proliferation induced by FCS was inhibited by DHEA (50 µmol/l, Figure 3a).…”