Mutagenesis on a complex mouse genetic background by site-specific nucleases.

Mouse models with complex genetic backgrounds are increasingly used in preclinical research to accurately model human disease and to enable temporal and cell-specific evaluation of genetic manipulations. Backcrossing mice onto these complex genetic backgrounds takes time and leads to significant wastage of animals. In this study, we aimed to evaluate whether site-specific nucleases could be used to generate additional genetic mutations in a complex genetic background, using the REVERSA mouse model of atherosclerosis, a model harbouring four genetically altered alleles. The model is comprised of a functional null mutation in the Ldlr gene in combination with a ApoB100 allele, which, after high-fat diet, leads to the rapid development of atherosclerosis. The regression of the pathology is achieved by inducible knock-out of the Mttp gene. Here we report an investigation to establish if microinjection of site-specific nucleases directly into zygotes prepared from the REVERSA could be used to investigate the role of the ATP binding cassette transporter G1 (ABCG1) in atherosclerosis regression. We show that using this approach we could successfully generate two independent knockout lines on the REVERSA background, both of which exhibited the expected phenotype of a significant reduction in cholesterol efflux to HDL in bone marrow-derived macrophages. However, loss of Abcg1 did not impact atherosclerosis regression in either the aortic root or in aortic arch, demonstrating no important role for this transporter subtype. We have demonstrated that site-specific nucleases can be used to create genetic modifications directly onto complex disease backgrounds and can be used to explore gene function without the need for laborious backcrossing of independent strains, conveying a significant 3Rs advantage.

Endothelial cell-specific roles for tetrahydrobiopterin in myocardial function, cardiac hypertrophy, and response to myocardial ischemia-reperfusion injury.

The cofactor tetrahydrobiopterin (BH4) is a critical regulator of nitric oxide synthase (NOS) function and redox signaling, with reduced BH4 implicated in multiple cardiovascular disease states. In the myocardium, augmentation of BH4 levels can impact on cardiomyocyte function, preventing hypertrophy and heart failure. However, the specific role of endothelial cell BH4 biosynthesis in the coronary circulation and its role in cardiac function and the response to ischemia has yet to be elucidated. Endothelial cell-specific Gch1 knockout mice were generated by crossing Gch1fl/fl with Tie2cre mice, generating Gch1fl/flTie2cre mice and littermate controls. GTP cyclohydrolase protein and BH4 levels were reduced in heart tissues from Gch1fl/flTie2cre mice, localized to endothelial cells, with normal cardiomyocyte BH4. Deficiency in coronary endothelial cell BH4 led to NOS uncoupling, decreased NO bioactivity, and increased superoxide and hydrogen peroxide productions in the hearts of Gch1fl/flTie2cre mice. Under physiological conditions, loss of endothelial cell-specific BH4 led to mild cardiac hypertrophy in Gch1fl/flTie2cre hearts. Endothelial cell BH4 loss was also associated with increased neuronal NOS protein, loss of endothelial NOS protein, and increased phospholamban phosphorylation at serine-17 in cardiomyocytes. Loss of cardiac endothelial cell BH4 led to coronary vascular dysfunction, reduced functional recovery, and increased myocardial infarct size following ischemia-reperfusion injury. Taken together, these studies reveal a specific role for endothelial cell Gch1/BH4 biosynthesis in cardiac function and the response to cardiac ischemia-reperfusion injury. Targeting endothelial cell Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of cardiac dysfunction and ischemia-reperfusion injury.NEW & NOTEWORTHY We demonstrate a critical role for endothelial cell Gch1/BH4 biosynthesis in coronary vascular function and cardiac function. Loss of cardiac endothelial cell BH4 leads to coronary vascular dysfunction, reduced functional recovery, and increased myocardial infarct size following ischemia/reperfusion injury. Targeting endothelial cell Gch1 and BH4 biosynthesis may provide a novel therapeutic target for the prevention and treatment of cardiac dysfunction, ischemia injury, and heart failure.

Cardiomyocyte tetrahydrobiopterin synthesis regulates fatty acid metabolism and susceptibility to ischaemia-reperfusion injury.

NEW FINDINGS: What is the central question of this study? What are the physiological roles of cardiomyocyte-derived tetrahydrobiopterin (BH4) in cardiac metabolism and stress response? What is the main finding and its importance? Cardiomyocyte BH4 has a physiological role in cardiac metabolism. There was a shift of substrate preference from fatty acid to glucose in hearts with targeted deletion of BH4 synthesis. The changes in fatty-acid metabolic profile were associated with a protective effect in response to ischaemia-reperfusion (IR) injury, and reduced infarct size. Manipulating fatty acid metabolism via BH4 availability could play a therapeutic role in limiting IR injury. ABSTRACT: Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide (NO) synthases in which its production of NO is crucial for cardiac function. However, non-canonical roles of BH4 have been discovered recently and the cell-specific role of cardiomyocyte BH4 in cardiac function and metabolism remains to be elucidated. Therefore, we developed a novel mouse model of cardiomyocyte BH4 deficiency, by cardiomyocyte-specific deletion of Gch1, which encodes guanosine triphosphate cyclohydrolase I, a required enzyme for de novo BH4 synthesis. Cardiomyocyte (cm)Gch1 mRNA expression and BH4 levels from cmGch1 KO mice were significantly reduced compared to Gch1flox/flox (WT) littermates. Transcriptomic analyses and protein assays revealed downregulation of genes involved in fatty acid oxidation in cmGch1 KO hearts compared with WT, accompanied by increased triacylglycerol concentration within the myocardium. Deletion of cardiomyocyte BH4 did not alter basal cardiac function. However, the recovery of left ventricle function was improved in cmGch1 KO hearts when subjected to ex vivo ischaemia-reperfusion (IR) injury, with reduced infarct size compared to WT hearts. Metabolomic analyses of cardiac tissue after IR revealed that long-chain fatty acids were increased in cmGch1 KO hearts compared to WT, whereas at 5 min reperfusion (post-35 min ischaemia) fatty acid metabolite levels were higher in WT compared to cmGch1 KO hearts. These results indicate a new role for BH4 in cardiomyocyte fatty acid metabolism, such that reduction of cardiomyocyte BH4 confers a protective effect in response to cardiac IR injury. Manipulating cardiac metabolism via BH4 could play a therapeutic role in limiting IR injury.

Promoting safer sex in the context of heterosexual anal intercourse: A scoping review.

AIMS AND OBJECTIVES: To locate and summarise existing literature regarding safer sex practices specific to heterosexual anal intercourse and identify promising health promotion strategies. BACKGROUND: Much of the literature regarding anal intercourse and safer sex is related to men who have sex with men. However, some studies suggest there are more women than men engaging in unprotected receptive anal intercourse. The risks associated with this sexual practice have been well documented, although many healthcare providers fail to ask about anal intercourse while addressing safer sex in the heterosexual population. DESIGN: The study was based on Arksey and O'Malley's 2005 five-step methodology. METHODS: A search was conducted of MEDLINE; CINAHL; PsycInfo; Cochrane; and PubMed. Databases were searched from 1990-2020. The 72 studies selected were classified according to their main area of focus. A grey literature search was also included. This scientific submission has been assessed for accuracy and completeness using the PRISMA-ScR guideline criteria (File S1). RESULTS: The literature in this area is heterogeneous in terms of method and topic. Prevalence and incidence (n = 26) in addition to sexually transmitted infection risks (n = 26) related to heterosexual anal intercourse are well understood. However, there is limited information on condom use (n = 6), factors that influence heterosexual anal intercourse (n = 10) and health promotion strategies for this population and practice (n = 4). Two websites that mentioned heterosexual anal intercourse risk reduction activities were included. CONCLUSIONS: Although heterosexual anal intercourse appears to be an increasingly common sexual practice, very little is known about health promotion strategies nurses might use for encouraging safer sex in this population. RELEVANCE TO CLINICAL PRACTICE: Increased awareness of the prevalence and risks of heterosexual anal intercourse could enhance nurses' harm reduction strategies. Screening for sexually transmitted infections may be based on incorrect assumptions about sexual practices or due to stigma linked with anal intercourse. Reducing unprotected heterosexual anal intercourse will reduce sexually transmitted infections and their long-term sequelae.

JCAD, a Gene at the 10p11 Coronary Artery Disease Locus, Regulates Hippo Signaling in Endothelial Cells.

Objective- A large number of genetic loci have been associated with risk of coronary artery disease (CAD) through genome-wide association studies, however, for most loci the underlying biological mechanism is unknown. Determining the molecular pathways and cellular processes affected by these loci will provide new insights into CAD pathophysiology and may lead to new therapies. The CAD-associated variants at 10p11.23 fall in JCAD, which encodes an endothelial junction protein, however, its molecular function in endothelial cells is not known. In this study, we characterize the molecular role of JCAD (junctional cadherin 5 associated) in endothelial cells. Approach and Results- We show that JCAD knockdown in endothelial cells affects key phenotypes related to atherosclerosis including proliferation, migration, apoptosis, tube formation, and monocyte binding. We demonstrate that JCAD interacts with LATS2 (large tumor suppressor kinase 2) and negatively regulates Hippo signaling leading to increased activity of YAP (yes-associated protein), the transcriptional effector of the pathway. We also show by double siRNA knockdown that the phenotypes caused by JCAD knockdown require LATS2 and that JCAD is involved in transmission of RhoA-mediated signals into the Hippo pathway. In human tissues, we find that the CAD-associated lead variant, rs2487928, is associated with expression of JCAD in arteries, including atherosclerotic arteries. Gene co-expression analyses across disease-relevant tissues corroborate our phenotypic findings and support the link between JCAD and Hippo signaling. Conclusions- Our results show that JCAD negatively regulates Hippo signaling in endothelial cells and we suggest that JCAD contributes to atherosclerosis by mediating YAP activity and contributing to endothelial dysfunction.

A Genomic DNA Reporter Screen Identifies Squalene Synthase Inhibitors That Act Cooperatively with Statins to Upregulate the Low-Density Lipoprotein Receptor.

Hypercholesterolemia remains one of the leading risk factors for the development of cardiovascular disease. Many large double-blind studies have demonstrated that lowering low-density lipoprotein (LDL) cholesterol using a statin can reduce the risk of having a cardiovascular event by approximately 30%. However, despite the success of statins, some patient populations are unable to lower their LDL cholesterol to meet the targeted lipid levels, due to compliance or potency issues. This is especially true for patients with heterozygous familial hypercholesterolemia who may require additional upregulation of the low-density lipoprotein receptor (LDLR) to reduce LDL cholesterol levels below those achievable with maximal dosing of statins. Here we identify a series of small molecules from a genomic DNA reporter screen that upregulate the LDLR in mouse and human liver cell lines at nanomolar potencies (EC50 = 39 nM). Structure-activity relationship studies carried out on the lead compound, OX03771 [(E)-N,N-dimethyl-3-(4-styrylphenoxy)propan-1-amine], led to the identification of compound OX03050 [(E)-3-(4-styrylphenoxy)propan-1-ol], which had similar potency (EC50 = 26 nM) but a much-improved pharmacokinetic profile and showed in vivo efficacy. Compounds OX03050 and OX03771 were found to inhibit squalene synthase, the first committed step in cholesterol biosynthesis. These squalene synthase inhibitors were shown to act cooperatively with statins to increase LDLR expression in vitro. Overall, we demonstrated here a novel series of small molecules with the potential to be further developed to treat patients either alone or in combination with statins.

A requirement for Gch1 and tetrahydrobiopterin in embryonic development.

INTRODUCTION: GTP cyclohydrolase I (GTPCH) catalyses the first and rate-limiting reaction in the synthesis of the enzymatic cofactor, tetrahydrobiopterin (BH4). Loss of function mutations in the GCH1 gene lead to congenital neurological diseases such as DOPA-responsive dystonia and hyperphenylalaninemia. However, little is known about how GTPCH and BH4 affects embryonic development in utero, and in particular whether metabolic replacement or supplementation in pregnancy is sufficient to rescue genetic GTPCH deficiency in the developing embryo. METHODS AND RESULTS: Gch1 deficient mice were generated by the insertion of loxP sites flanking exons 2-3 of the Gch1 gene. Gch1(fl/fl) mice were bred with Sox2cre mice to generate mice with global Gch1 deficiency. Genetic ablation of Gch1 caused embryonic lethality by E13.5. Despite loss of Gch1 mRNA and GTPCH enzymatic activity, whole embryo BH4 levels were maintained until E11.5, indicating sufficient maternal transfer of BH4 to reach this stage of development. After E11.5, Gch1(-/-) embryos were deficient in BH4, but an unbiased metabolomic screen indicated that the lethality was not due to a gross disturbance in metabolic profile. Embryonic lethality in Gch1(-/-) embryos was not caused by structural abnormalities, but was associated with significant bradycardia at E11.5. Embryonic lethality was not rescued by maternal supplementation of BH4, but was partially rescued, up to E15.5, by maternal supplementation of BH4 and l-DOPA. CONCLUSION: These findings demonstrate a requirement for Gch1 in embryonic development and have important implications for the understanding of pathogenesis and treatment of genetic BH4 deficiencies, as well as the identification of new potential roles for BH4.

Regulation of ventilatory sensitivity and carotid body proliferation in hypoxia by the PHD2/HIF-2 pathway.

Ventilatory sensitivity to hypoxia increases in response to continued hypoxic exposure as part of acute acclimatisation. Although this process is incompletely understood, insights have been gained through studies of the hypoxia-inducible factor (HIF) hydroxylase system. Genetic studies implicate these pathways widely in the integrated physiology of hypoxia, through effects on developmental or adaptive processes. In keeping with this, mice that are heterozygous for the principal HIF prolyl hydroxylase, PHD2, show enhanced ventilatory sensitivity to hypoxia and carotid body hyperplasia. Here we have sought to understand this process better through comparative analysis of inducible and constitutive inactivation of PHD2 and its principal targets HIF-1α and HIF-2α. We demonstrate that general inducible inactivation of PHD2 in tamoxifen-treated Phd2(f/f);Rosa26(+/CreERT2) mice, like constitutive, heterozygous PHD2 deficiency, enhances hypoxic ventilatory responses (HVRs: 7.2 ± 0.6 vs. 4.4 ± 0.4 ml min(-1) g(-1) in controls, P < 0.01). The ventilatory phenotypes associated with both inducible and constitutive inactivation of PHD2 were strongly compensated for by concomitant inactivation of HIF-2α, but not HIF-1α. Furthermore, inducible inactivation of HIF-2α strikingly impaired ventilatory acclimatisation to chronic hypoxia (HVRs: 4.1 ± 0.5 vs. 8.6 ± 0.5 ml min(-1) g(-1) in controls, P < 0.0001), as well as carotid body cell proliferation (400 ± 81 vs. 2630 ± 390 bromodeoxyuridine-positive cells mm(-2) in controls, P < 0.0001). The findings demonstrate the importance of the PHD2/HIF-2α enzyme-substrate couple in modulating ventilatory sensitivity to hypoxia.

Endothelial cell-specific reactive oxygen species production increases susceptibility to aortic dissection.

BACKGROUND: Increased production of reactive oxygen species (ROS) throughout the vascular wall is a feature of cardiovascular disease states, but therapeutic strategies remain limited by our incomplete understanding of the role and contribution of specific vascular cell ROS to disease pathogenesis. To investigate the specific role of endothelial cell (EC) ROS in the development of structural vascular disease, we generated a mouse model of endothelium-specific Nox2 overexpression and tested the susceptibility to aortic dissection after angiotensin II (Ang II) infusion. METHODS AND RESULTS: A specific increase in endothelial ROS production in Nox2 transgenic mice was sufficient to cause Ang II-mediated aortic dissection, which was never observed in wild-type mice. Nox2 transgenic aortas had increased endothelial ROS production, endothelial vascular cell adhesion molecule-1 expression, matrix metalloproteinase activity, and CD45(+) inflammatory cell infiltration. Conditioned media from Nox2 transgenic ECs induced greater Erk1/2 phosphorylation in vascular smooth muscle cells compared with wild-type controls through secreted cyclophilin A (CypA). Nox2 transgenic ECs (but not vascular smooth muscle cells) and aortas had greater secretion of CypA both at baseline and in response to Ang II stimulation. Knockdown of CypA in ECs abolished the increase in vascular smooth muscle cell Erk1/2 phosphorylation conferred by EC conditioned media, and preincubation with CypA augmented Ang II-induced vascular smooth muscle cell ROS production. CONCLUSIONS: These findings demonstrate a pivotal role for EC-derived ROS in the determination of the susceptibility of the aortic wall to Ang II-mediated aortic dissection. ROS-dependent CypA secretion by ECs is an important signaling mechanism through which EC ROS regulate susceptibility of structural components of the aortic wall to aortic dissection.

Cardiac dysfunction and peri-weaning mortality in malonyl-coenzyme A decarboxylase (MCD) knockout mice as a consequence of restricting substrate plasticity.

UNLABELLED: Inhibition of malonyl-coenzyme A decarboxylase (MCD) shifts metabolism from fatty acid towards glucose oxidation, which has therapeutic potential for obesity and myocardial ischemic injury. However, ~40% of patients with MCD deficiency are diagnosed with cardiomyopathy during infancy. AIM: To clarify the link between MCD deficiency and cardiac dysfunction in early life and to determine the contributing systemic and cardiac metabolic perturbations. METHODS AND RESULTS: MCD knockout mice ((-/-)) exhibited non-Mendelian genotype ratios (31% fewer MCD(-/-)) with deaths clustered around weaning. Immediately prior to weaning (18days) MCD(-/-) mice had lower body weights, elevated body fat, hepatic steatosis and glycogen depletion compared to wild-type littermates. MCD(-/-) plasma was hyperketonemic, hyperlipidemic, had 60% lower lactate levels and markers of cellular damage were elevated. MCD(-/-) hearts exhibited hypertrophy, impaired ejection fraction and were energetically compromised (32% lower total adenine nucleotide pool). However differences between WT and MCD(-/-) converged with age, suggesting that, in surviving MCD(-/-) mice, early cardiac dysfunction resolves over time. These observations were corroborated by in silico modelling of cardiomyocyte metabolism, which indicated improvement of the MCD(-/-) metabolic phenotype and improved cardiac efficiency when switched from a high-fat diet (representative of suckling) to a standard post-weaning diet, independent of any developmental changes. CONCLUSIONS: MCD(-/-) mice consistently exhibited cardiac dysfunction and severe metabolic perturbations while on a high-fat, low carbohydrate diet of maternal milk and these gradually resolved post-weaning. This suggests that dysfunction is a common feature of MCD deficiency during early development, but that severity is dependent on composition of dietary substrates.

Tetrahydrobiopterin determines vascular remodeling through enhanced endothelial cell survival and regeneration.

BACKGROUND: Endothelial cell (EC) survival and regeneration are important determinants of the response to vascular injury that leads to neointimal hyperplasia and accelerated atherosclerosis. Nitric oxide (NO) is a key regulator of EC and endothelial progenitor cell function, but the pathophysiological mechanisms that regulate endothelial NO synthase in endothelial regeneration remain unclear. METHODS AND RESULTS: Endothelium-targeted overexpression of GTP cyclohydrolase (GCH) I increased levels of the endothelial NO synthase cofactor, tetrahydrobiopterin, in an EC-specific manner and reduced neointimal hyperplasia in experimental vein grafts in GCH/apolipoprotein E-knockout mice. These effects were mediated through enhanced donor-derived survival and recipient-derived repopulation of GCH transgenic ECs, revealed by tracking studies in Tie2-LacZ/GCH-Tg/apolipoprotein E-knockout recipient mice or donor grafts, respectively. Endothelial GCH overexpression increased endothelial NO synthase coupling and enhanced the proliferative capacity of ECs and circulating endothelial progenitor cell numbers after vascular injury. CONCLUSIONS: These observations indicate that endothelial tetrahydrobiopterin availability modulates neointimal hyperplasia after vascular injury via accelerated EC repopulation and growth. Targeting tetrahydrobiopterin-dependent endothelial NO synthase regulation in the endothelium is a rational therapeutic target to enhance endothelial regeneration and reduce neointimal hyperplasia in vascular injury states.

Endothelial cell repopulation after stenting determines in-stent neointima formation: effects of bare-metal vs. drug-eluting stents and genetic endothelial cell modification.

AIMS: Understanding endothelial cell repopulation post-stenting and how this modulates in-stent restenosis is critical to improving arterial healing post-stenting. We used a novel murine stent model to investigate endothelial cell repopulation post-stenting, comparing the response of drug-eluting stents with a primary genetic modification to improve endothelial cell function. METHODS AND RESULTS: Endothelial cell repopulation was assessed en face in stented arteries in ApoE(-/-) mice with endothelial-specific LacZ expression. Stent deployment resulted in near-complete denudation of endothelium, but was followed by endothelial cell repopulation, by cells originating from both bone marrow-derived endothelial progenitor cells and from the adjacent vasculature. Paclitaxel-eluting stents reduced neointima formation (0.423 ± 0.065 vs. 0.240 ± 0.040 mm(2), P = 0.038), but decreased endothelial cell repopulation (238 ± 17 vs. 154 ± 22 nuclei/mm(2), P = 0.018), despite complete strut coverage. To test the effects of selectively improving endothelial cell function, we used transgenic mice with endothelial-specific overexpression of GTP-cyclohydrolase 1 (GCH-Tg) as a model of enhanced endothelial cell function and increased NO production. GCH-Tg ApoE(-/-) mice had less neointima formation compared with ApoE(-/-) littermates (0.52 ± 0.08 vs. 0.26 ± 0.09 mm(2), P = 0.039). In contrast to paclitaxel-eluting stents, reduced neointima formation in GCH-Tg mice was accompanied by increased endothelial cell coverage (156 ± 17 vs. 209 ± 23 nuclei/mm(2), P = 0.043). CONCLUSION: Drug-eluting stents reduce not only neointima formation but also endothelial cell repopulation, independent of strut coverage. In contrast, selective targeting of endothelial cell function is sufficient to improve endothelial cell repopulation and reduce neointima formation. Targeting endothelial cell function is a rational therapeutic strategy to improve vascular healing and decrease neointima formation after stenting.

Novel Role of 5-Methyl-(6S)-Tetrahydrofolate in Mediating Endothelial Cell Tetrahydrobiopterin in Pregnancy and Implications for Gestational Hypertension.

BACKGROUND: Folate intake during pregnancy is essential for fetal development and maternal health. However, the specific effects of folic acid (FA) and 5-methyl-(6S)-tetrahydrofolate (5-MTHF) on the prevention and treatment of hypertensive disorders of pregnancy remain unclear. We investigated whether FA and 5-MTHF have different effects on endothelial cell tetrahydrobiopterin (BH4) metabolism in pregnancy and the possible consequences for endothelial NO generation, maternal blood pressure, and fetal growth. METHODS: We analyzed the maternal blood pressure in pregnant wild-type (Gch1fl/fl) and Gch1fl/fl Tie2cre mice treated with either FA or 5-MTHF starting before pregnancy, mid-pregnancy or late pregnancy. BH4, superoxide, and NO bioavailability were determined in mouse and human models of endothelial cell BH4 deficiency by high-performance liquid chromatography. RESULTS: In vitro studies in mouse and human endothelial cells showed that treatment with 5-MTHF, but not FA, elevated BH4 levels, reduced superoxide production, and increased NO synthase activity. In primary endothelial cells isolated from women with hypertensive pregnancies, exposure to 5-MTHF, but not FA, restored the reduction in BH4 levels and NO synthase activity. In vivo studies in mice revealed that oral treatment with 5-MTHF, but not FA, prevented and treated hypertension in pregnancy when administered either before or during pregnancy, respectively, and normalized placental and fetal growth restriction if administered from mid-gestation onward. CONCLUSIONS: Collectively, these studies identify a critical role for 5-MTHF in endothelial cell function in pregnancy, related to endothelial cell BH4 availability and NO synthase activity. Thus, 5-MTHF represents a novel therapeutic agent that may potentially improve endothelial function in hypertensive disorders of pregnancy by targeting endothelial cell BH4.

Hif-2α programs oxygen chemosensitivity in chromaffin cells.

The study of transcription factors that determine specialized neuronal functions has provided invaluable insights into the physiology of the nervous system. Peripheral chemoreceptors are neurone-like electrophysiologically excitable cells that link the oxygen concentration of arterial blood to the neuronal control of breathing. In the adult, this oxygen chemosensitivity is exemplified by type I cells of the carotid body, and recent work has revealed one isoform of the hypoxia-inducible transcription factor (HIF), HIF-2α, as having a nonredundant role in the development and function of that organ. Here, we show that activation of HIF-2α, including isolated overexpression of HIF-2α but not HIF-1α, is sufficient to induce oxygen chemosensitivity in adult adrenal medulla. This phenotypic change in the adrenal medulla was associated with retention of extra-adrenal paraganglioma-like tissues resembling the fetal organ of Zuckerkandl, which also manifests oxygen chemosensitivity. Acquisition of chemosensitivity was associated with changes in the adrenal medullary expression of gene classes that are ordinarily characteristic of the carotid body, including G protein regulators and atypical subunits of mitochondrial cytochrome oxidase. Overall, the findings suggest that, at least in certain tissues, HIF-2α acts as a phenotypic driver for cells that display oxygen chemosensitivity, thus linking 2 major oxygen-sensing systems.

Carotid body hyperplasia and enhanced ventilatory responses to hypoxia in mice with heterozygous deficiency of PHD2.

Oxygen-dependent prolyl hydroxylation of hypoxia-inducible factor (HIF) by a set of closely related prolyl hydroxylase domain enzymes (PHD1, 2 and 3) regulates a range of transcriptional responses to hypoxia. This raises important questions about the role of these oxygen-sensing enzymes in integrative physiology. We investigated the effect of both genetic deficiency and pharmacological inhibition on the change in ventilation in response to acute hypoxic stimulation in mice. Mice exposed to chronic hypoxia for 7 days manifest an exaggerated hypoxic ventilatory response (HVR) (10.8 ± 0.3 versus 4.1 ± 0.7 ml min(-1) g(-1) in controls; P < 0.01). HVR was similarly exaggerated in PHD2(+/-) animals compared to littermate controls (8.4 ± 0.7 versus 5.0 ± 0.8 ml min(-1) g(-1); P < 0.01). Carotid body volume increased (0.0025 ± 0.00017 in PHD2(+/-) animals versus 0.0015 ± 0.00019 mm(3) in controls; P < 0.01). In contrast, HVR in PHD1(-/-) and PHD3(-/-) mice was similar to littermate controls. Acute exposure to a small molecule PHD inhibitor (PHI) (2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetic acid) did not mimic the ventilatory response to hypoxia. Further, 7 day administration of the PHI induced only modest increases in HVR and carotid body cell proliferation, despite marked stimulation of erythropoiesis. This was in contrast with chronic hypoxia, which elicited both exaggerated HVR and cellular proliferation. The findings demonstrate that PHD enzymes modulate ventilatory sensitivity to hypoxia and identify PHD2 as the most important enzyme in this response. They also reveal differences between genetic inactivation of PHDs, responses to hypoxia and responses to a pharmacological inhibitor, demonstrating the need for caution in predicting the effects of therapeutic modulation of the HIF hydroxylase system on different physiological responses.

Mood symptoms in cervical dystonia: Relationship with motor symptoms and quality of life.

Background: Cervical dystonia (CD) has a high prevalence of anxiety and depression. The relationship between motor severity, mood symptoms and QoL is unclear and how to adequately assess these is also unknown. Instruments like the BAI, BDI and HADS are often used but items within these relating to somatic symptoms might influence the results. Methods: Patients with idiopathic cervical dystonia (CD) were included. The BAI, BDI, HADS, CIDP58 and TWSTRS2- severity score were used for assessment of motor, mood and QoL symptoms. Pearson's correlations between motor and non-motor symptom scores were assessed. The psychometric properties of the psychiatric tools were measured and principal component analysis performed after identifying items that could correspond to somatic symptoms. Results: 201 participants were included. 42% of participants had either significant depression or anxiety symptoms or both when measured by BAI and BDI and 51% of patients met criteria on HADS. HADS-A and HADS-D, BAI and BDI were poorly correlated with TWSTRS2-S. The HADS-A and HADS-D both showed strong correlation with the sleep subdomain of CDIP58. Psychometric and principal component analysis on 149/201 participants did not reveal factor loadings consistent with the a priori somatic groupings. However mean scores were higher for somatic items. Conclusion: A good score on the CDIP58, a commonly used tool, does not indicate mild disease severity or minimal mood symptoms. Minimal motor symptoms, similarly, also does not imply a positive QoL. Clinicians should be mindful on ideal methods for performing a holistic assessment of CD patients. This likely warrants a combination of motor, QoL and mood assessment tools.

Endothelial cell vasodilator dysfunction mediates progressive pregnancy-induced hypertension in endothelial cell tetrahydrobiopterin deficient mice.

BACKGROUND AND PURPOSE: Pregnancy-associated vascular remodelling is essential for both maternal and fetal health. We have previously shown that maternal endothelial cell tetrahydrobiopterin (BH4) deficiency causes poor pregnancy outcomes. Here, we investigated the role and mechanisms of endothelial cell-mediated vasorelaxation function in these outcomes. EXPERIMENTAL APPROACH: The vascular reactivity of mouse aortas and uterine arteries from non-pregnant and pregnant endothelial cell-specific BH4 deficient mice (Gch1fl/flTie2cre mice) was assessed by wire myography. Systolic blood pressure was assessed by tail cuff plethysmography. KEY RESULTS: In late pregnancy, systolic blood pressure was significantly higher (∼24 mmHg) in Gch1fl/flTie2cre mice compared with wild-type littermates. This was accompanied by enhanced vasoconstriction and reduced endothelial-dependent vasodilation in both aorta and uterine arteries from pregnant Gch1fl/flTie2cre mice. In uterine arteries loss of eNOS-derived vasodilators was partially compensated by upregulation of intermediate and large-conductance Ca2+-activated K+ channels. In rescue experiments, oral BH4 supplementation alone did not rescue vascular dysfunction and pregnancy-induced hypertension in Gch1fl/flTie2cre mice. However, combination with the fully reduced folate, 5-methyltetrahydrofolate (5-MTHF), restored endothelial cell vasodilator function and blood pressure. CONCLUSIONS AND IMPLICATIONS: We identify a critical requirement for maternal endothelial cell Gch1/BH4 biosynthesis in endothelial cell vasodilator function in pregnancy. Targeting vascular Gch1 and BH4 biosynthesis with reduced folates may provide a novel therapeutic target for the prevention and treatment of pregnancy-related hypertension.

Role of Human Epicardial Adipose Tissue-Derived miR-92a-3p in Myocardial Redox State.

BACKGROUND: Visceral obesity is directly linked to increased cardiovascular risk, including heart failure. OBJECTIVES: This study explored the ability of human epicardial adipose tissue (EAT)-derived microRNAs (miRNAs) to regulate the myocardial redox state and clinical outcomes. METHODS: This study screened for miRNAs expressed and released from human EAT and tested for correlations with the redox state in the adjacent myocardium in paired EAT/atrial biopsy specimens from patients undergoing cardiac surgery. Three miRNAs were then tested for causality in an in vitro model of cardiomyocytes. At a clinical level, causality/directionality were tested using genome-wide association screening, and the underlying mechanisms were explored using human biopsy specimens, as well as overexpression of the candidate miRNAs and their targets in vitro and in vivo using a transgenic mouse model. The final prognostic value of the discovered targets was tested in patients undergoing cardiac surgery, followed up for a median of 8 years. RESULTS: EAT miR-92a-3p was related to lower oxidative stress in human myocardium, a finding confirmed by using genetic regulators of miR-92a-3p in the human heart and EAT. miR-92a-3p reduced nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase-derived superoxide (O2.-) by targeting myocardial expression of WNT5A, which regulated Rac1-dependent activation of NADPH oxidases. Finally, high miR-92a-3p levels in EAT were independently related with lower risk of adverse cardiovascular events. CONCLUSIONS: EAT-derived miRNAs exert paracrine effects on the human heart. Indeed miR-92a-3p suppresses the wingless-type MMTV integration site family, member 5a/Rac1/NADPH oxidase axis and improves the myocardial redox state. EAT-derived miR-92a-3p is related to improved clinical outcomes and is a rational therapeutic target for the prevention and treatment of obesity-related heart disease.

Insights into the Role of a Cardiomyopathy-Causing Genetic Variant in ACTN2.

Pathogenic variants in ACTN2, coding for alpha-actinin 2, are known to be rare causes of Hypertrophic Cardiomyopathy. However, little is known about the underlying disease mechanisms. Adult heterozygous mice carrying the Actn2 p.Met228Thr variant were phenotyped by echocardiography. For homozygous mice, viable E15.5 embryonic hearts were analysed by High Resolution Episcopic Microscopy and wholemount staining, complemented by unbiased proteomics, qPCR and Western blotting. Heterozygous Actn2 p.Met228Thr mice have no overt phenotype. Only mature males show molecular parameters indicative of cardiomyopathy. By contrast, the variant is embryonically lethal in the homozygous setting and E15.5 hearts show multiple morphological abnormalities. Molecular analyses, including unbiased proteomics, identified quantitative abnormalities in sarcomeric parameters, cell-cycle defects and mitochondrial dysfunction. The mutant alpha-actinin protein is found to be destabilised, associated with increased activity of the ubiquitin-proteasomal system. This missense variant in alpha-actinin renders the protein less stable. In response, the ubiquitin-proteasomal system is activated; a mechanism that has been implicated in cardiomyopathies previously. In parallel, a lack of functional alpha-actinin is thought to cause energetic defects through mitochondrial dysfunction. This seems, together with cell-cycle defects, the likely cause of the death of the embryos. The defects also have wide-ranging morphological consequences.

PHACTR1 modulates vascular compliance but not endothelial function: a translational study.

AIMS: The non-coding locus at 6p24 located in Intron 3 of PHACTR1 has consistently been implicated as a risk allele in myocardial infarction and multiple other vascular diseases. Recent murine studies have identified a role for Phactr1 in the development of atherosclerosis. However, the role of PHACTR1 in vascular tone and in vivo vascular remodelling has yet to be established. The aim of this study was to investigate the role of PHACTR1 in vascular function. METHODS AND RESULTS: Prospectively recruited coronary artery disease (CAD) patients undergoing bypass surgery and retrospectively recruited spontaneous coronary artery dissection (SCAD) patients and matched healthy volunteers were genotyped at the PHACTR1 rs9349379 locus. We observed a significant association between the PHACTR1 loci and changes in distensibility in both the ascending aorta (AA = 0.0053 ± 0.0004, AG = 0.0041 ± 0.003, GG = 0.0034 ± 0.0009, P < 0.05, n = 58, 54, and 7, respectively) and carotid artery (AA = 12.83 ± 0.51, AG = 11.14 ± 0.38, GG = 11.69 ± 0.66, P < 0.05, n = 70, 65, and 18, respectively). This association was not observed in the descending aorta or in SCAD patients. In contrast, the PHACTR1 locus was not associated with changes in endothelial cell function with no association between the rs9349379 locus and in vivo or ex vivo vascular function observed in CAD patients. This finding was confirmed in our murine model where the loss of Phactr1 on the pro-atherosclerosis ApoE-/- background did not alter ex vivo vascular function. CONCLUSION: In conclusion, we have shown a role for PHACTR1 in arterial compliance across multiple vascular beds. Our study suggests that PHACTR1 has a key structural role within the vasculature.