EET-dependent potentiation of pulmonary arterial pressure: sex-different regulation of soluble epoxide hydrolase

Abstract

We tested the hypothesis that suppression of epoxyeicosatrienoic acid (EET) metabolism via genetic knockout of the gene for soluble epoxide hydrolase (sEH-KO), or female-specific downregulation of sEH expression, plays a role in the potentiation of pulmonary hypertension. We used male (M) and female (F) wild-type (WT) and sEH-KO mice; the latter have high pulmonary EETs. Right ventricular systolic pressure (RVSP) and mean arterial blood pressure (MABP) in control and in response to in vivo administration of U46619 (thromboxane analog), 14,15-EET, and 14,15-EEZE [14,15-epoxyeicosa-5(z)-enoic acid; antagonist of EETs] were recorded. Basal RVSP was comparable among all groups of mice, whereas MABP was significantly lower in F-WT than M-WT mice and further reduced predominantly in F-KO compared with M-KO mice. U46619 dose dependently increased RVSP and MABP in all groups of mice. The increase in RVSP was significantly greater and coincided with smaller increases in MABP in M-KO and F-WT mice compared with M-WT mice. In F-KO mice, the elevation of RVSP by U46619 was even higher than in M-KO and F-WT mice, associated with the least increase in MABP. 14,15-EEZE prevented the augmentation of U46619-induced elevation of RVSP in sEH-KO mice, whereas 14,15-EET-induced pulmonary vasoconstriction was comparable in all groups of mice. sEH expression in the lungs was reduced, paralleled with higher levels of EETs in F-WT compared with M-WT mice. In summary, EETs initiate pulmonary vasoconstriction but act as vasodilators systemically. High pulmonary EETs, as a function of downregulation or deletion of sEH, potentiate U46619-induced increases in RVSP in a female-susceptible manner. pulmonary hypertension; soluble epoxide hydrolase; epoxyeicosatrienoic acids; right ventricular systolic pressure; sex difference PULMONARY ARTERIAL HYPERTENSION (PAH) is a progressive disease with different etiologies that primarily affects small pulmonary arteries (28) and is associated with elevated pulmonary vasoconstriction, smooth muscle proliferation, endothelial dysfunction, and pulmonary remodeling (32). The two major factors that specifically contribute to the increase in pulmonary vascular resistance are vasoconstriction and vascular remodeling (9). Acute vasodilation resulting from the inhibition of Rho-kinase, an enzyme that causes sustained pulmonary vasoconstriction to generate pulmonary hypertension (33), significantly ameliorates pulmonary arterial pressure in patients with severe pulmonary hypertension (PH) (14, 17). Based on this evidence, recent studies arose to address the concern that specific roles of vasoconstriction in late stages of PH was underappreciated (39). The findings address an important issue that pulmonary artery tone and consequentially pulmonary resistance are controlled by factors released from the pulmonary vasculature. In this regard, any lung-sourced vasoconstrictors merit consideration as an endogenous trigger for PAH. For instance, endothelium-derived metabolites of arachidonic acid (AA) by lipoxygenase to ...

Estrogen-dependent epigenetic regulation of soluble epoxide hydrolase via DNA methylation

“…Consequentially, the suppression of Ephx2 mRNA is concomitantly associated with the same reduction in sEH protein levels ( Fig. 1 B and D), as we reported previously (9)(10)(11)(12)(13)20), demonstrating that regulation of sEH by estrogen is at the transcriptional level. We then indicated that DNA methylation is a crucial step in the estrogen/ER-governed regulatory process for Ephx2 expression.…”

“…Indeed, findings of estrogen-dependent suppression of sEH to increase tissue EETs in the cerebral circulation provide mechanistically based evidence for a female-favorable protection from cerebral ischemic damages (7,8). We have also provided evidence indicating that female-specific down-regulation of sEH protein expression in cardiac, pulmonary, and vascular tissues favors a greater contribution of EETs in females than males and initiates the same cardiovascular responses as those observed in male sEH-KO mice, or male mice treated with sEHIs (9)(10)(11)(12). Particularly in the microcirculation, a genetic deficiency in the Ephx2 gene or down-regulation of sEH expression elicits significantly enhanced flow/shear stress-induced vasodilation and attenuated pressure-induced vasoconstriction via an EET-dependent mechanism in the mesenteric, coronary, and skeletal muscle arterioles (9,11,13).…”

“…During this process, specific TFs interface with both methylation-direct and -indirect procedures to collectively constitute the main component of estrogen-mediated signaling through combinatorial and coordinated actions, leading to estrogen-specific physiological down-regulation of Ephx2 gene/sEH expression. Our findings uncover the molecular mechanism that provides explanations for the sexual dimorphism of sEH expression (3,19) and all of the consequences arising there, defined as a female-favorable protection against cardiac and cerebral ischemia (7)(8)(9)(10)(11)(12).…”

Female-favorable attenuation of coronary myogenic constriction via reciprocal activations of epoxyeicosatrienoic acids and nitric oxide

“…During these processes, an EETdependent modulation of pressure-sensitive behavior was indicated for the first time that elucidates, at least in part, the mechanistic insights for EET-exerted cardioprotective properties in terms of an improvement in myocardial perfusion through a significant reduction in coronary resistance (26). Moreover, consistent with our previous findings showing a female-specific downregulation of sEH in arteries of skeletal muscle and mesentery (29), as well as in the pulmonary circulation (22) to potentiate the bioactivity of EETs, the present study indicates a female-favorable attenuation of myogenic constriction, as a function of suppression of sEH expression in the coronary circulation revealing, from a physiological point of view, the female-specific regulation that possesses universally based characteristics.…”

Estradiol Metabolism: Crossroads in Pulmonary Arterial Hypertension

“…Moreover, E2 inhibits the expression/activity of soluble epoxide hydrolase (sEH), a key enzyme in EET metabolism [144]. Several studies linked low sEH activity to the pathophysiology of PAH: (1) E2-, genetic-, and pharmacologically-induced downregulation of sEH (and increased pulmonary EET) potentiates hypoxic pulmonary vasoconstriction [145][146][147]; (2) lungs from PH patients express no/little sEH; (3) hypoxia decreases the expression of sEH; and (4) when exposed to hypoxia, sEH KO mice exhibit exacerbated pulmonary vascular remodeling [147]. It seems that E2 plays a role in female-specific (physiological) downregulation of sEH, as suggested by the much higher sEH activity in male and OVX mice compared to intact female mice [148,149].…”