Effects of ω-hydroxylase product on distal human pulmonary arteries

Abstract

Morin C, Guibert C, Sirois M, Echave V, Gomes MM, Rousseau E. Effects of -hydroxylase product on distal human pulmonary arteries. Am J Physiol Heart Circ Physiol 294: H1435-H1443, 2008. First published January 18, 2008 doi:10.1152/ajpheart.01115.2007The aim of the present study was to provide a mechanistic insight into how 20-hydroxyeicosatetraenoic acid (20-HETE) relaxes distal human pulmonary arteries (HPAs). This compound is produced by -hydroxylase from free arachidonic acid. Tension measurements, performed on either fresh or 1 day-cultured pulmonary arteries, revealed that the contractile responses to 1 M 5-hydroxytryptamine were largely relaxed by 20-HETE in a concentration-dependent manner (0.01-10 M). Iberiotoxin pretreatments (10 nM) partially decreased 20-HETE-induced relaxations. However, 10 M indomethacin and 3 M SC-560 pretreatments significantly reduced the relaxations to 20-HETE in these tissues. The relaxing responses induced by the eicosanoid were likely related to a reduced Ca 2ϩ sensitivity of the myofilaments since free Ca 2ϩ concentration ([Ca 2ϩ ])-response curves performed on ␤-escin-permeabilized cultured explants were shifted toward higher [Ca 2ϩ ]. 20-HETE also abolished the tonic responses induced by phorbol-ester-dibutyrate (a PKC-sensitizing agent). Western blot analyses, using two specific primary antibodies against the PKC-potentiated inhibitory protein CPI-17 and its PKC-dependent phosphorylated isoform pCPI-17, confirmed that 20-HETE interferes with this intracellular process. We also investigated the effect of 20-HETE on the activation of Rho-kinase pathway-induced Ca 2ϩ sensitivity. The data demonstrated that 20-HETE decreased U-46619-induced Ca 2ϩ sensitivity on arteries. Hence, this observation was correlated with an increased staining of p116 Rip , a RhoA-binding protein. Together, these results strongly suggest that the 20-hydroxyarachidonic acid derivative is a potent modulator of tone in HPAs in vitro. 20-hydroxyeicosatetraenoic acid; calcium sensitivity; tension measurement PULMONARY ARTERY VASOCONSTRICTION and vascular remodeling greatly contribute to a sustained elevation of pulmonary vascular resistance and pulmonary arterial pressure in patients with pulmonary arterial hypertension (PAH), an often fatal hemodynamic abnormality (11). Pulmonary vasoconstriction is believed to be an early component of the pulmonary hypertensive process and has been attributed to an impaired production of vasodilators [nitric oxide (NO) and prostacyclin] and an increased production of vasoconstrictors (endothelin-1 and serotonin) (11). 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 arte...

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

“…To perform these experiments, human lung tissues from patients undergoing surgery for lung carcinoma and distant from the malignant lesion were obtained. Pulmonary arteries of similar weight and length (inner diameter of 0.5 -0.8 mm) were micro-dissected and placed in culture for 24 hours in a humidified incubator at 37C under 5% CO 2 as previously reported (Guibert et al, 2005, Morin et al, 2008. Resulting data demonstrated that 20-HETE acts as a potent vasodilator on HPA pre-contracted with 5-HT and phenylephrine (PE) (Figure 2A, Morin C et al, 2008).…”

“…However, 20-HETE has been shown to be an eicosanoid product of human lung tissue that acts as a potent vasodilator of isolated pressurized pulmonary arteries (Birks et al, 1997, Morin et al, 2008. Furthermore, cytochrome P-450 4A (CYP4A) protein is expressed in the pulmonary vasculature, a finding based on Western blots of PA microsomes (Zhu et al, 1998), the conversion of arachidonic acid into 20-HETE by dispersed vascular smooth muscle cells (Zhu et al, 1998), and immunohistochemistry localizing CYP4A to rabbit pulmonary capillary endothelium (Roman et al, 1993).…”

“…Pulmonary arteries of similar weight and length (inner diameter of 0.5 -0.8 mm) were micro-dissected and placed in culture for 24 hours in a humidified incubator at 37C under 5% CO 2 as previously reported (Guibert et al, 2005, Morin et al, 2008. Resulting data demonstrated that 20-HETE acts as a potent vasodilator on HPA pre-contracted with 5-HT and phenylephrine (PE) (Figure 2A, Morin C et al, 2008). 20-HETE displayed potent relaxing effects on HPA, with IC 50 values in the sub-micromolar range ( 0.3 µM) on both resting and active tone.…”

“…20-HETE displayed potent relaxing effects on HPA, with IC 50 values in the sub-micromolar range ( 0.3 µM) on both resting and active tone. In HPA, the relaxing effect induced by 20-HETE was partially abolished by 30 % in the presence of iberiotoxin (IbTx) (Morin et al, 2008), suggesting that the eicosanoid activates large conducting Ca 2+ -activated potassium (BK Ca ) channels which usually results in membrane hyperpolarisation. Indeed, microelectrode measurements demonstrated that 20-HETE hyperpolarizes human ASM cells, an effect abolished by 10 nM IbTx (Morin et al, 2007b).…”

“…The role of various ion channels in acute and chronic hypoxia in pulmonary vasculature has already been described as well (Weir et al, 2006, Guibert et al, 2007. Hence, from a physiological standpoint, it is noteworthy to emphasize the relaxing effects displayed by 20-HETE on both HPA and airway smooth muscle (Birks et al, 1997, Jacobs et al, 1999, Morin et al, 2008.…”