Proceedings of The Physiological Society

Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, PCB373

Poster Communications

The Gq protein inhibitor FR900359 induces strong vasodilation in pulmonary arteries

A. Seidinger1, G. König2, E. Kostenis2, B. K. Fleischmann1, D. Wenzel1

1. Physiology I, University of Bonn, Bonn, Germany. 2. Pharmaceutical Biology, University of Bonn, Bonn, Germany.

Gq proteins are of high relevance in the pulmonary vasculature, since they determine tone regulation in health and disease. Previously, we have identified the depsipeptide FR900359 (FR) as a strong and specific pharmacological pan-Gq inhibitor. In the current study we have investigated the effect of FR on pulmonary arterial tone regulation in mouse ex and in vivo, as well as on human pulmonary artery smooth muscle cell (hPASMC) growth in vitro. The effect of FR was examined in isometric force measurements of murine pulmonary arteries in a wire-myograph, in precision cut lung slices and in the isolated perfused lung model of mouse. Additionally, cell growth was investigated in hPASMCs with and without FR treatment. The effect of FR on pulmonary blood pressure in vivo was determined in healthy CD1 WT mice and animals after induction of hypoxia-induced PH by exposure to hypoxia (10 % O2) for 3 weeks. One hour after intratracheal application of FR (2.5 µg per mouse, 5 % isoflurane) right ventricular systolic pressure was recorded under ketamine (50mg/kg)/xylazine (5 mg/kg) and 1.5 % isoflurane anesthesia. Our results show that a single dose application of FR (1 µM) induced a pronounced pulmonary arterial vasorelaxation after pre-treatment with different Gq-dependent vasoconstrictors in the wire-myograph. After endothelin induced pre-constriction FR caused a dose-dependent (1 nM - 10 µM) pulmonary vasorelaxation reaching 74 ± 2.8 % (n=7) at the highest dose. In contrast, drugs currently used for PH in humans were less effective at 10 µM (bosentan: 8.8 ± 2.9 %, n=5; iloprost: 27.5 ± 3.9 %, n=7; sildenafil 34.6 ± 3.5 % vasorelaxation, n=6, p<0.001 vs FR). Maximal vasorelaxation in these experiments could be strongly enhanced by the additional application of 1 µM FR (bosentan + FR: 70.4 ± 2.3 %, n=5; iloprost + FR: 68.2 ± 4.4 %, n=7; sildenafil + FR 73.4 ± 3.9 %, n=6). FR (1 µM) also induced strong vasorelaxation after serotonin-mediated pre-constriction in lung slices (FR: 93 ± 1.2 %, n=7) as well as a pronounced decrease of the pulmonary arterial pressure in the isolated perfused lung model of mouse (FR: 101.1 ± 4.5 %, n=3). In a cell growth assay FR (1 µM) reduced hPASMC numbers to 76.8 ± 2.1 % (n=3, p<0.01) compared to vehicle controls. A similar reduction of hPASMC growth was found after bosentan and iloprost treatment, but not after exposure to sildenafil. Right ventricular catheter measurements showed that FR can reduce pulmonary blood pressure in hypoxia-induced PH mice (n=8) in vivo. Thus, we show that the pharmacological Gq inhibitor FR is a strong pulmonary vasorelaxant under (patho)physiological conditions in mice ex and in vivo. Moreover, FR limits hPASMC growth in vitro. When comparing the action and efficacy of FR with currently applied drugs for the treatment of PH, FR appears superior, as it can reduce both vascular tone and hPASMC growth.

Where applicable, experiments conform with Society ethical requirements