SOX17 Deficiency Mediates Pulmonary Hypertension: At the Crossroads of Sex, Metabolism, and Genetics.

Genetic studies suggest that SOX17 (SRY-related HMG-box 17) deficiency increases pulmonary arterial hypertension (PAH) risk. On the basis of pathological roles of estrogen and HIF2α (hypoxia-inducible factor 2α) signaling in pulmonary artery endothelial cells (PAECs), we hypothesized that SOX17 is a target of estrogen signaling that promotes mitochondrial function and attenuates PAH development via HIF2α inhibition. We used metabolic (Seahorse) and promoter luciferase assays in PAECs together with the chronic hypoxia murine model to test the hypothesis.

Penetrance of Severe Pulmonary Arterial Hypertension in Response to Vascular Endothelial Growth Factor Receptor 2 Blockade in a Genetically Prone Rat Model Is Reduced by Female Sex.

Background We have previously reported important strain differences in response to SU5416 (SU, a vascular endothelial growth factor receptor 2 inhibitor) in rats and have identified a specific colony of Sprague-Dawley rats that are hyperresponsive (SD) to SU alone and develop severe pulmonary arterial hypertension (PAH) with a single injection of SU, even in the absence of hypoxia. Interestingly, SD rats exhibit incomplete penetrance of the severe PAH phenotype with an "all-or-none" response to SU alone, which provides a unique opportunity to assess the influence of female sex and sex hormones on susceptibility to PAH after endothelial injury in a genetically prone model. Methods and Results SD rats were injected with SU (20 mg/kg SC) and, in the absence of hypoxia, 72% of male but only 27% of female rats developed severe PAH at 7 weeks, which was associated with persistent endothelial cell apoptosis.

Optimizing imaging of the rat pulmonary microvasculature by micro-computed tomography.

Micro-computed tomography (micro-CT) is used in pre-clinical research to generate high-resolution three-dimensional (3D) images of organs and tissues. When combined with intravascular contrast agents, micro-CT can provide 3D visualization and quantification of vascular networks in many different organs. However, the lungs present a particular challenge for contrast perfusion due to the complexity and fragile nature of the lung microcirculation.

Medical Therapy for Heart Failure Associated With Pulmonary Hypertension.

The past 2 decades have witnessed a >40% improvement in mortality for patients with heart failure and left ventricular systolic dysfunction. This success has coincided with the stepwise availability of drugs that target neurohormonal activation: β-adrenergic receptor blockers (β-blockers), ACE (angiotensin-converting enzyme) inhibitors and ANG (angiotensin) II blockers, neprilysin inhibitors, and aldosterone antagonists. Our understanding of right heart failure (RHF) has lagged behind and many proven targeted therapies for left heart failure do not appear to provide similar benefits for RHF.

Fischer rats exhibit maladaptive structural and molecular right ventricular remodelling in severe pulmonary hypertension: a genetically prone model for right heart failure.

Aims: The ability of the right ventricle (RV) to adapt to increased afterload is the major determinant of survival in patients with pulmonary hypertension (PH). In this study, we explored the effect of genetic background on RV adaptation and survival in a rat model of severe pulmonary arterial hypertension (PAH).

Methods And Results: PH was induced by a single injection of SU5416 (SU) in age-matched Sprague Dawley (SD) or Fischer rats, followed by a 3-week exposure to chronic hypoxia (SUHx).

Efficacy of treprostinil in the SU5416-hypoxia model of severe pulmonary arterial hypertension: haemodynamic benefits are not associated with improvements in arterial remodelling.

Background And Purpose: Pulmonary arterial hypertension (PAH) is a life-threatening disease that leads to progressive pulmonary hypertension, right heart failure and death. Parenteral prostaglandins (PGs), including treprostinil, a prostacyclin analogue, represent the most effective medical treatment for severe PAH. We investigated the effect of treprostinil on established severe PAH and underlying mechanisms using the rat SU5416 (SU, a VEGF receptor-2 inhibitor)-chronic hypoxia (Hx) model of PAH.

Marked Strain-Specific Differences in the SU5416 Rat Model of Severe Pulmonary Arterial Hypertension.

We assessed the pulmonary hemodynamic response to vascular endothelial growth factor receptor, type 2, inhibition using SU5416 (SU) with and without chronic hypoxia (CH) in different background strains and colonies of rats. A single subcutaneous injection of SU (20 mg/kg) or vehicle was administered to different substrains of Sprague-Dawley (SD) rats, and they were compared with Lewis and Fischer rats, with and without exposure to CH (10% O2 for 3 wk). Remarkably, a unique colony of SD rats from Charles River Laboratories, termed the SD-hyperresponsive type, exhibited severe pulmonary arterial hypertension (PAH) with SU alone, characterized by increased right ventricular systolic pressure, right ventricular/left ventricular plus septal weight ratio, and arteriolar occlusive lesions at 7-8 weeks (all P < 0.

Effect of ischemia reperfusion injury and epoxyeicosatrienoic acids on caveolin expression in mouse myocardium.

Background: Caveolins (Cav) are structural proteins that insert into the plasma membrane to form caveolae that can bind molecules important in cardiac signal transduction and function. Cytochrome P450 epoxygenases can metabolize arachidonic acid to epoxyeicosatrienoic acids (EETs) which have known cardioprotective effects. Subsequent metabolism of EETs by soluble epoxide hydrolase reduces the protective effect.

Differential effects of soluble epoxide hydrolase inhibition and CYP2J2 overexpression on postischemic cardiac function in aged mice.

Cardioprotective effects of epoxyeicosatrienoic acids (EETs) have been demonstrated in models of young mice with either the cardiomyocyte specific over-expression of cytochrome P450 2J2 (CYP2J2 Tr) or deletion of soluble epoxide hydrolase (sEH null). In this study we examined differences in EET-induced cardioprotection in young (2 months) and aged (12 months) CYP2J2 Tr and sEHnull mice using Langendorff isolated perfused heart model. Improved postischemic functional recovery was observed in both young and aged sEH null mice compared to age matched WT.

Mitochondria and the aging heart.

The average human life span has markedly increased in modern society largely attributed to advances in medical and therapeutic sciences that have successfully reduced important health risks. However, advanced age results in numerous alterations to cellular and subcellular components that can impact the overall health and function of an individual. Not surprisingly, advanced age is a major risk factor for the development of heart disease in which elderly populations observe increased morbidity and mortality.

Novel soluble epoxide hydrolase inhibitor protects mitochondrial function following stress.

Epoxyeicosatrienoic acids (EETs) are active metabolites of arachidonic acid that are inactivated by soluble epoxide hydrolase enzyme (sEH) to dihydroxyeicosatrienoic acid. EETs are known to render cardioprotection against ischemia reperfusion (IR) injury by maintaining mitochondrial function. We investigated the effect of a novel sEH inhibitor (sEHi) in limiting IR injury.

Role of PI3Kα and sarcolemmal ATP-sensitive potassium channels in epoxyeicosatrienoic acid mediated cardioprotection.

Aims: Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase metabolites of arachidonic acid that have known cardioprotective properties. While the mechanism(s) remains unknown, evidence suggests that phosphoinositide 3-kinase (PI3K) and sarcolemmal ATP-sensitive potassium channels (pmK(ATP)) are important. However the role of specific PI3K isoforms and corresponding intracellular mechanisms remains unknown.

Inhibition of soluble epoxide hydrolase by trans-4- [4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid is protective against ischemia-reperfusion injury.

Arachidonic acid, a polyunsaturated fatty acid, can be metabolized to cardioprotective epoxyeicosatrienoic acids (EETs) by cytochrome P450 epoxygenases, which are subsequently hydrolyzed to less bioactive dihydroxyeicosatrienoic acids by soluble epoxide hydrolase (sEH). To study the effects of pharmacological inhibitor of sEH (sEHi), C57BL6 mice hearts were perfused in Langendorff mode for 40 minutes of baseline and subjected to 30 minutes of global no-flow ischemia followed by 40 minutes of reperfusion. Hearts were perfused with the sEHi, trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (t-AUCB; 0.

Cytochrome P450 enzymes and the heart.

The cytochrome P450 monooxygenase system (CYP) is a multigene superfamily of heme-thiolate enzymes, which are important in the metabolism of foreign and endogenous compounds. Genetic variations, drug interactions, or pathophysiological factors can lead to reduced, absent, or increased enzymatic activity. This altered CYP activity greatly influences an individual's response to therapeutic treatment.

Overexpression of CYP2J2 provides protection against doxorubicin-induced cardiotoxicity.

Human cytochrome P-450 (CYP)2J2 is abundant in heart and active in biosynthesis of epoxyeicosatrienoic acids (EETs). Recently, we demonstrated that these eicosanoid products protect myocardium from ischemia-reperfusion injury. The present study utilized transgenic (Tr) mice with cardiomyocyte-specific overexpression of human CYP2J2 to investigate protection toward toxicity resulting from acute (0, 5, or 15 mg/kg daily for 3 days, followed by 24-h recovery) or chronic (0, 1.

Role of B-type natriuretic peptide in epoxyeicosatrienoic acid-mediated improved post-ischaemic recovery of heart contractile function.

Aims: This study examined the functional role of B-type natriuretic peptide (BNP) in epoxyeicosatrienoic acid (EET)-mediated cardioprotection in mice with targeted disruption of the sEH or Ephx2 gene (sEH null).

Methods And Results: Isolated mouse hearts were perfused in the Langendorff mode and subjected to global no-flow ischaemia followed by reperfusion. Hearts were analysed for recovery of left ventricular developed pressure (LVDP), mRNA levels, and protein expression.