PRX-08066

Serotonin [5-hydroxytryptamine (5-HT)] is associated with several chronic pulmonary diseases, recognizing 5-HT₂ receptor antagonists as potential inhibitors of tissue remodeling. However, the effects of 5-HT₂ receptors, especially 5-HT_2B receptors on airway function and remodeling, are unclear. We investigated the role of 5-HT_2B receptors on airway smooth muscle contractility and remodeling processes. Murine precision-cut lung slices were pretreated with 5-HT_2B receptor antagonists (EXT5, EXT9, RS 127445, and PRX 08066), as well as ketanserin (5-HT_2A/2C receptor antagonist) (1, 10 μmol/L), before addition of cumulative concentrations of 5-HT to induce bronchoconstriction. Remodeling effects after treatment with 10 μmol/L 5-HT and 5-HT₂ receptor antagonists were further studied in distal lung tissue by examining release of profibrotic transforming growth factor (TGF)-β1 and proliferation of human bronchial smooth muscle cells (HBSMCs). 5-HT-induced bronchoconstriction was significantly reduced by EXT5, EXT9, and ketanserin, but not by RS 127445 or PRX 08066. The 5-HT_2B receptor antagonists significantly reduced TGF-β1 release. 5-HT, in combination with TGF-β1, increased proliferation of HBSMCs, a process reduced by EXT5 and EXT9. Our results indicate that EXT5 and EXT9 may relieve bronchoconstriction in murine airways and serve as an add-on effect in attenuating pulmonary remodeling by improving airway function. The antiproliferative effect on HBSMCs and the inhibition of TGF-β1 release further support a role of 5-HT_2B receptors in pathologic remodeling processes.

Uveal melanoma (UM) is the most common primary tumor in the adult, and disseminates to the liver in half of patients. A 15-gene expression profile prognostic assay allows to determine the likelihood of metastasis in patients using their ocular tumor DNA, but a cure still remains to be discovered. The serotonin receptor 2B represents the discriminant gene of this molecular signature with the greatest impact on the prognosis of UM. However, its contribution to the metastatic potential of UM remains unexplored. The purpose of this study was to investigate the effects of a selective serotonin receptor 2B antagonist on cellular and molecular behaviours of UM cells. UM cell lines expressing high level of serotonin receptor 2B proteins were selected by Western blotting. The selective serotonin receptor 2B antagonist PRX-08066 was evaluated for its impact on UM cells using viability assays, phosphorylated histone H3 immunostainings, clonogenic assays, migration assays, invasion assays and membrane-based protein kinase phosphorylation antibody arrays. The pharmacological inhibition of the serotonin receptor 2B reduced the viability of UM cells and the population in mitosis, and impaired their clonogenicity and potential of migration. It also decreased the phosphorylation of kinases from signaling pathways classically activated by the serotonin receptor 2B, as well as kinases β-catenin, Proline-rich tyrosine kinase 2, and Signal transducer and activator of transcription 5. Our findings support a role for the serotonin receptor 2B in the proliferation and migration of UM cells, through activation of many signaling pathways such as WNT, Focal adhesion kinase and Janus kinase/STAT.