Silencing Gq Proteins Prevents and Reverses Pulmonary Hypertension

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Abstract Gq proteins (e.g. Gαq and Gα11) are central signaling hubs in the regulation of pulmonary vascular tone, since many disease-related vasoconstrictors act via Gq proteins. Additionally, Gq signaling is discussed to play an essential role in vascular remodeling. Both, vasoconstriction and vascular remodeling, are major hallmarks of pulmonary hypertension (PH). Therefore, we analyzed the potential of the specific pan-Gq inhibitor FR900359 (FR) to modulate pulmonary vascular tone and remodeling; in addition, we evaluated the contribution of Gαq and Gα11 to the pathophysiology of PH using the respective knockout (KO) mice. The effect of FR on pulmonary arterial tone was determined by isometric force measurements in a wire-myograph or in precision-cut lung slices from mice, pigs and humans ex vivo. Cell growth and migration were assessed in vitro in murine pulmonary artery smooth muscle cells (mPASMCs) and knockdown of Gαq and Gα11 was achieved by lentiviral transduction with specific sh-RNA. The effect of FR on pulmonary hemodynamics was determined by pressure catheter measurements in mouse in vivo. The Sugen5416/hypoxia-induced mouse model of PH was applied to test the preventive and therapeutic potential of FR. To discriminate between the different Gq family members Gα11-KO animals or the conditional smooth muscle specific Gαq-KO were used. Isometric force measurements in pulmonary arteries (PAs) from wildtype mice revealed that FR completely prevented dose-dependent serotonin (5-HT)-induced constriction, whereas constriction was only minimally attenuated in PAs from Gαq-KO or Gα11-KO animals. Gq inhibition by FR also prevented Gq-related endothelin 1 (ET-1)-induced constriction in pigs and mice. After ET-1 pre-constriction in mouse PAs, the vasodilatory effect of FR was superior to the relaxation in response to currently used drugs such as the ET-1 receptor antagonist bosentan, the prostacyclin analog iloprost or the phosphodiesterase 5 inhibitor sildenafil. Furthermore, FR strongly reversed ET-1 constriction in mouse and human pulmonary resistance arteries using precision-cut lung slices. Gq inhibition by FR reduced cell growth and migration of mPASMCs after stimulation with a combination of PDGF and 5-HT, which could be attributed to Gαq. Furthermore, in in vivo experiments in mice, FR treatment or Gαq deletion prevented the development of PH. In a therapeutic approach, pharmacological Gq inhibition by FR reversed PH without obvious side effects. Thus, we show that the pharmacological Gq inhibitor FR counteracts the main hallmarks of PH and that these are predominantly Gαq-driven. Therefore, Gq proteins, especially Gαq, could be a promising therapeutic target for PH in the future.

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