Sildenafil alters calcium signaling and vascular tone in pulmonary arteries from chronically hypoxic rats

Abstract

Pauvert, Olivier, Sébastien Bonnet, Eric Rousseau, Roger Marthan, and Jean-Pierre Savineau. Sildenafil alters calcium signaling and vascular tone in pulmonary arteries from chronically hypoxic rats. Am J Physiol Lung Cell Mol Physiol 287: L577-L583, 2004. First published May 21, 2004 10.1152/ajplung.00449.2003.-Sildenafil, a potent type 5 nucleotide-dependent phosphodiesterase (PDE) inhibitor, has been recently proposed as a therapeutic tool to treat or prevent pulmonary artery hypertension (PAHT). We thus studied the effect of sildenafil on both the calcium signaling of isolated pulmonary artery smooth muscle cells (PASMCs) and the reactivity of pulmonary artery (PA) obtained from chronic hypoxia (CH)-induced pulmonary hypertensive rats compared with control (normoxic) rats. CH rats were maintained in an hypobaric chamber (50.5 kPa) for 3 wk leading to full development of PAHT. Intracellular calcium concentration ([Ca 2ϩ ]i) was measured in PASMCs loaded with the calcium fluorophore indo 1. Unlike in control rats, sildenafil (10 -100 nM) decreased the resting [Ca 2ϩ ]i value in PASMCs obtained from CH rats. In PASMCs from both control and CH rats, sildenafil concentration dependently inhibited the [Ca 2ϩ ]i response induced by G-coupled membrane receptor agonists such as angiotensin II and phenylephrine but had no effect on the amplitude of the [Ca 2ϩ ]i response induced by caffeine. Sildenafil (0.1 nM-1 M) concentration dependently reduced basal PA tone that is present in CH rats and relaxed PA rings precontracted with phenylephrine in both control and CH rats. These data show that sildenafil is a potent pulmonary artery relaxant in CH rats and that it normalizes CH-induced increases in resting [Ca 2ϩ ]i and basal tone. Consequently, pharmacological inhibition of sildenafil-sensitive PDE5 downregulates the Ca 2ϩ signaling pathway involved in this model of pulmonary hypertension. pulmonary hypertension; vascular smooth muscle; phosphodiesterase 5; pulmonary vasodilator INTRACELLULAR CYCLIC NUCLEOTIDE [cAMP and guanosine 3Ј,5Ј-cyclic monophosphate (cGMP)] concentration is implicated in the control of the vascular smooth muscle tone including in the pulmonary artery (PA) (3, 9). Agents elevating cAMP or cGMP concentration relax precontracted PA (35,36,38). For instance, the endothelium-derived factor nitric oxide (NO) induces a dose-dependent increase in cGMP concentration and a step-wise relaxation of PA (30,45). In smooth muscle cells, concentration of cGMP is mainly dependent on the balance between the production by guanylate cyclase and the degradation by phosphodiesterases (PDEs), which represent the unique degradation pathway for these intracellular compounds (34, 44). As a consequence, PDE activity is also implicated in the control of smooth muscle tone, and PDE inhibition relaxes smooth muscle (21,41,46). In PA from rats and humans, four types of PDE (PDE1, 3, 4, and 5) have been identified (23,31,34,36). Hence, the pharmacological modulation of PDE activity (e.g., using selective PDE inhibitor...

Sildenafil Inhibits Human Pulmonary Artery Smooth Muscle Cell Proliferation by Decreasing Capacitative Ca2+ Entry

“…The relaxant effect of sildenafil appears mainly related to action on calcium signaling via the IP3-dependent calcium release pathway and calcium reuptake mechanisms (7,8). However, the mechanism of its antiproliferative effect in PASMCs has not been studied.…”

Effects of ω-hydroxylase product on distal human pulmonary arteries

“…Although arachidonic acid-induced relaxation in human pulmonary arteries (HPAs) involves cytochrome P-450-dependent metabolites and potassium channels (9), the precise molecular mode of action of 20-HETE remains to be ascertained. Since 20-HETE may be of putative clinical interest for PAH (11,24,25), we have focused the present study on the alternative mechanisms involved in the 20-HETE-induced relaxation in HPAs.The aim of the present work was to assess the physiological effects of 20-HETE on resistance vessels. Complementary approaches used include 1) tension measurements of relaxation on human arterial rings; 2) analyses of the effects of 20-HETE on the Ca 2ϩ sensitivity of the mechanical apparatus; and 3) evaluation of the status and expression of the PKC-potentiated inhibitory protein CPI-17 and p116 Rip proteins, which are involved in the control of the Ca 2ϩ sensitivity in vascular smooth muscle (VSM) cells (17,30).…”

“…In that respect, vasodilators have some beneficial effects on PAH. Among various existing pulmonary arterial vasodilators, such as NO, sildenafil, and cGMP (24,25), 20-hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P-450 4A metabolite of arachidonic acid, consistently dilates pulmonary arteries in several species, including humans (2). 20-HETE induces a relaxation in bovine pulmonary arteries, whereas it induces a contraction in bovine renal arteries (12,15), suggesting a specific mode of action of 20-HETE according to vascular beds.…”

“…Although arachidonic acid-induced relaxation in human pulmonary arteries (HPAs) involves cytochrome P-450-dependent metabolites and potassium channels (9), the precise molecular mode of action of 20-HETE remains to be ascertained. Since 20-HETE may be of putative clinical interest for PAH (11,24,25), we have focused the present study on the alternative mechanisms involved in the 20-HETE-induced relaxation in HPAs.…”

ω3 and ω6 CYP450 Eicosanoid Derivatives: Key Lipid Mediators in the Regulation of Pulmonary Hypertension

“…Hence, the potential clinical benefit of phosphodiesterase type-5 inhibitors has been investigated in PAH (Pauvert et al, 2004). In addition, phosphodiesterase type-5 inhibitors exert anti-proliferative effects (Galie et al, 2009b).…”