5-6-epoxy-8-11-14-eicosatrienoic-acid and Hypoxia

The aim of the study was to investigate the role of cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) in sustained hypoxic pulmonary vasoconstriction (HPV).. Vasomotor responses of isolated mouse intrapulmonary arteries (IPAs) were assessed using wire myography. Key findings were verified by haemodynamic measurements in isolated perfused and ventilated mouse lungs.. Pharmacological inhibition of EET synthesis with MS-PPOH, application of the EET antagonist 14,15-EEZE or deficiency of CYP2J isoforms suppressed sustained HPV. In contrast, knockdown of EET-degrading soluble epoxide hydrolase or its inhibition with TPPU augmented sustained HPV almost twofold. All EET regioisomers elicited relaxation in IPAs pre-contracted with thromboxane mimetic U46619. However, in the presence of KCl-induced depolarization, 5,6-EET caused biphasic contraction in IPAs and elevation of pulmonary vascular tone in isolated lungs, whereas other regioisomers had no effect. In patch-clamp experiments, hypoxia elicited depolarization in pulmonary artery smooth muscle cells (PASMCs), and 5,6-EET evoked inward whole cell currents in PASMCs depolarized to the hypoxic level, but not at their resting membrane potential.. The EET pathway substantially contributes to sustained HPV in mouse pulmonary arteries. 5,6-EET specifically appears to be involved in HPV, as it is the only EET regioisomer able to elicit not only relaxation, but also sustained contraction in these vessels. 5,6-EET-induced pulmonary vasoconstriction is enabled by PASMC depolarization, which occurs in hypoxia. The discovery of the dual role of 5,6-EET in the regulation of pulmonary vascular tone may provide a basis for the development of novel therapeutic strategies for treatment of HPV-related diseases.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cytochrome P-450 Enzyme System; Hypoxia; Lung; Mice; Pulmonary Artery; Vasoconstriction; Vasodilation

The biological role of epoxyeicosatrienoic acids (EETs) in the regulation of pulmonary circulation is currently under debate. We hypothesized that EETs initiate increases in right ventricular systolic pressure (RVSP) via perhaps, pulmonary vasoconstriction.. Mice were anesthetized with isoflurane. Three catheters, inserted into the left jugular vein, the left carotid artery, and the right jugular vein, were used for infusing EETs, monitoring blood pressure (BP), and RVSP respectively. BP and RVSP were continuously recorded at basal conditions, in response to administration of 4 regioisomeric EETs (5,6-EET; 8,9-EET; 11,12-EET, and 14,15-EET; 1, 2, 5 and 10 ng/g body weight (BW) for each EET), and during exposure of mice to hypoxia.. All 4 EETs initiated dose-dependent increases in RVSP, though reduced BP. 11,12-EET elicited the greatest increment in RVSP among all EET isoforms. To clarify the direct elevation of RVSP in a systemic BP-independent manner, equivalent amounts of 14,15-EET were injected over 1 and 2 minutes respectively. One-minute injection of 14,15-EET elicited significantly faster and greater increases in RVSP than the 2-minute injection, whereas their BP changes were comparable. Additionally, direct injection of low doses of 14,15-EET (0.1, 0.2, 0.5, and 1 ng/g BW) into the right ventricle caused significant increases in RVSP without effects on BP, confirming that systemic vasodilation-induced increases in venous return are not the main cause for the increased RVSP. Acute exposure of mice to hypoxia significantly elevated RVSP, as well as 14,15-EET-induced increases in RVSP.. EETs directly elevate RVSP, a response that may play an important role in the development of hypoxia-induced pulmonary hypertension (PH).

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arterial Pressure; Disease Models, Animal; Dose-Response Relationship, Drug; Hypertension, Pulmonary; Hypoxia; Infusions, Intravenous; Male; Mice, Inbred C57BL; Pulmonary Artery; Time Factors; Ventricular Function, Right; Ventricular Pressure

The intravenous administration of ethchlorvynol (ECV), in dogs, resulted in an acute lung injury (ALI) characterized by a 200 +/- 80% increase in venous admixture and a 142 +/- 30% increase in extravascular lung water (EVLW). Pretreatment with the cytochrome P-450 inhibitor 8-methoxypsoralen prevented the ECV-induced increase in venous admixture but not the increased EVLW. These findings parallel those reported for cyclooxygenase inhibition in ECV-induced ALI and suggest that an arachidonic acid (AA) metabolite of pulmonary cytochrome P-450 activity may mediate the increase in venous admixture of ALI. We demonstrate that canine pulmonary microsomes metabolize [1-(14)C]AA to a variety of products, including the cytochrome P-450 metabolites 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET). In prostaglandin F2 alpha-contracted, isolated pulmonary venous rings, 5,6-EET induced relaxation in a concentration-dependent manner. This action of 5,6-EET was prevented by indomethacin (10(-5) M). These results suggest that may serve as the cyclooxygenase-dependent endogenous pulmonary vasodilator responsible for the increase in venous admixture of ECV-induced ALI.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Cytochrome P-450 Enzyme Inhibitors; Dinoprost; Dogs; Ethchlorvynol; Hypoxia; Lung; Lung Injury; Male; Methoxsalen; Microsomes; Pharmaceutical Vehicles; Vasoconstriction