Impaired Endothelium-dependent Vasodilation Research Articles

Admission heart failure and coronary perfusion in ST-elevation myocardial infarction patients undergoing primary percutaneous coronary intervention

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Studies demonstrated a link between the presence of HF on the admission of ACS patients and increased in-hospital morbidity and mortality. However, the literature did not establish the connection between the admission HF and the angiographic burden and the coronary vessel perfusion post-PPCI. Purpose To establish the correlation between acute HF on admission of STEMI patients, the coronary thrombus burden and the final coronary perfusion post PPCI. Methods We retrospectively studied 210 STEMI patients who presented to a single PPCI centre. We excluded post-fibrinolysis patients, patients with old stents and those who presented more than 24 hours after the onset of pain. We divided the studied cohort into two subgroups based on the presence of HF on presentation to the emergency department. We obtained Informed consent from all patients, and all procedures were done in compliance with the Helsinki declaration for research on human beings. Two blinded interventional cardiology consultants assessed the thrombus burden and coronary flow using TIMI grades of both variables. Results 20 patients (10%) of the studied group had HF on admission. There was no significant difference between the two subgroups regarding other cardiovascular risk factors (figure 1). The coronary thrombus burden did not differ significantly between the HF and no HF subgroups (50% vs 43.16%, respectively, p=0.557). However, the incidence of impaired coronary flow post-PPCI was significantly higher in the HF group (25% vs 8.4%, p=0.019) (figure 2). Multivariate logistic regression analysis showed that admission HF is an independent predictor of impaired perfusion post-PPCI ( OR= 5.49, 95% CI=1.54-19.49, p=0.01). Our study demonstrates the association between admission HF in STEMI patients undergoing PPCI and increased incidence of impaired coronary flow after PPCI. This finding was independent of the heavy coronary thrombus burden on angiography. Animal studies have demonstrated impaired coronary flow even in HF secondary to non-ischaemic causes.1,2 Possible mechanisms include impaired nitric oxide-mediated endothelium-dependent vasodilatation and enhanced vasoconstriction to mediators of neurohumoral activation.3 These mechanisms can explain our study's impaired coronary flow in HF patients. Conclusion Admission HF is an independent predictor of reduced coronary blood flow after PPCI. Timely treatment of STEMI patients can prevent HF development and improve their prognosis.

The Use of L-Arginine in Hypertension: An Educational Article and Expert Opinion

Background: Impairment of endothelium-dependent vasodilation has been increasingly recognized as an important contributor for the development of essential hypertension’s-arginine is an amino acid that is considered the biological precursor of nitric oxide which is an important contributor to microvascular vasodilation and to the reduction atherosclerosis. L-arginine has been recognized as safe (GRAS-status) when taken in an oral dose of up to 20 g daily. Patients and Methods: A 49-year male patient was recently found to be hypertensive on a routine check, and was advised to take an antihypertensive medication, but he requested treatment with health supplement initially to avoid the development of impotence attributed to antihypertensive medications. Results: The patient was recently found to be hypertensive on a routine check (Blood pressure: 160/110 mmHg), and was advised to take an antihypertensive medication, but he requested treatment with health supplement initially to avoid the development of impotence attributed to antihypertensive medications. The patient was treated with a unique approach under close supervision to avoid the development of hypertensive complication. He received oral l-arginine 3g daily before breakfast taken with lemon juice for its antioxidant vitamin C content. Within less than one week, his blood pressure normalized (Blood pressure: 135/85 mmHg). Conclusion: Oral L-arginine has been emerging as a new effective approach of reducing blood through improving endothelial function in hypertensive patients. This paper reports the successful treatment of hypertension with L-arginine.

Creating the Phenotype of Preeclamptic Endothelial Dysfunction in Placental Vessels

Objective: To determine if placental vessel endothelial dysfunction can be produced in control vessels by exposure to preeclamptic plasma, establishing a model to further explore the mechanisms of dysfunction and therapeutics to restore function in preeclampsia. Hypothesis: Preeclamptic plasma administered to unaffected vessels induces endothelial dysfunction. Methods: Placental microvessels were dissected from the maternal side of placentas from patients consented to the Medical College of Wisconsin Maternal Research Placenta and Cord Blood Bank. Control vessels were treated with 10% healthy maternal plasma or 10% preeclamptic (PreE) maternal plasma within the vessel lumen for 12-16 hours[MJ1]. PreE vessels were not treated with plasma. Microvessels were then cannulated on glass micropipettes, pressurized to 60mmHg and constricted with 0.1-1.0 nM Endothelin-1 (ET-1). A 1-100cm H2O pressure gradient was applied and the inner diameter of the vessel was measured by video microscopy. The change in diameter was calculated as a % of maximum diameter as assessed by exposure to 100μM papaverine. Flow mediated dilation (FMD) was evaluated by a two-way ANOVA test with Dunnett’s multiple comparisons. The maximum dilation values were evaluated by a Kruskal-Wallis test with Dunn’s multiple comparative test or t-test as appropriate. FMD is evaluated as mean +/- SEM. Data: Control vessels at maximum flow dilated to 81.1 % ± 7.1 % (n=5), whereas vessel from PreE placentas dilated to 36.9 % ± 8.6% (n=3,). Incubation of control vessels with normal plasma resulted in maximal dilation of 80.6% ± 3.3%, n=3. Control vessels incubated with plasma from PreE patients dilated to 44.7% ± 4.7%. n=3). Summary of Results: Control vessels dilated significantly more than PreE vessels when evaluated by t-test (p=0.05). Incubation of control vessels with normal plasma did not change maximal dilation (p>0.99). Control vessels incubated with PreE plasma demonstrated a near significant drop in dilatory capacity (p=0.05). PreE plasma exposed vessels compared to untreated PreE vessels showed no significant difference (p=0.46[DDG2] ).When comparing overall flow mediated dilatory responses in these vessels there is a significant difference observed between control vessels, control vessels treated with PreE plasma, and PreE vessels at 50cm H2O (p<0.05). This difference is even more significant (p<0.01) at the maximum pressure gradient when analyzed by two-way ANOVA. There is no significant difference at any point between control vessels and control vessels treated with normal plasma as evaluated by two-way ANOVA (p>0.99). Conclusions: The addition of PreE plasma to control vessels demonstrates similar impairment in endothelium-dependent vasodilation as seen in untreated PreE vessels. Future directions will include evaluation of the mechanisms of vasodilation and therapeutic options that could restore endothelial function in PreE vessels. NHLBI 1K08HL150340-01 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The role of ADAM17 in cerebrovascular and cognitive function in the APP/PS1 mouse model of Alzheimer's disease.

The disintegrin and metalloproteinase 17 (ADAM17) exhibits α-secretase activity, whereby it can prevent the production of neurotoxic amyloid precursor protein-α (APP). ADAM17 is abundantly expressed in vascular endothelial cells and may act to regulate vascular homeostatic responses, including vasomotor function, vascular wall morphology, and formation of new blood vessels. The role of vascular ADAM17 in neurodegenerative diseases remains poorly understood. Here, we hypothesized that cerebrovascular ADAM17 plays a role in the pathogenesis of Alzheimer's disease (AD). We found that 9-10 months old APP/PS1 mice with b-amyloid accumulation and short-term memory and cognitive deficits display a markedly reduced expression of ADAM17 in cerebral microvessels. Systemic delivery and adeno-associated virus (AAV)-mediated re-expression of ADAM17 in APP/PS1 mice improved cognitive functioning, without affecting b-amyloid plaque density. In isolated and pressurized cerebral arteries of APP/PS1 mice the endothelium-dependent dilation to acetylcholine was significantly reduced, whereas the vascular smooth muscle-dependent dilation to the nitric oxide donor, sodium nitroprusside was maintained when compared to WT mice. The impaired endothelium-dependent vasodilation of cerebral arteries in APP/PS1 mice was restored to normal level by ADAM17 re-expression. The cerebral artery biomechanical properties (wall stress and elasticity) and microvascular network density was not affected by ADAM17 re-expression in the APP/PS1 mice. Additionally, proteomic analysis identified several differentially expressed molecules involved in AD neurodegeneration and neuronal repair mechanisms that were reversed by ADAM17 re-expression. Thus, we propose that a reduced ADAM17 expression in cerebral microvessels impairs vasodilator function, which may contribute to the development of cognitive dysfunction in APP/PS1 mice, and that ADAM17 can potentially be targeted for therapeutic intervention in AD.

Hypoglycaemia aggravates impaired endothelial-dependent vasodilation in diabetes by suppressing endothelial nitric oxide synthase activity and stimulating inducible nitric oxide synthase expression.

Diabetes exacerbates vascular injury by triggering endothelial dysfunction. Endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) both play major roles in endothelial dysfunction. However, effects of hypoglycaemia, the main complication of the insulin therapy to the glycemic control in diabetes, on eNOS activity and iNOS expression, and underlying mechanisms in diabetes remain unknown. Hence, we aimed to determine the effects of hypoglycaemia on eNOS activity and iNOS expression in different arterial beds of diabetic rats. Sprague-Dawley rats were subjected to Streptozotocin (STZ) combined with high fat diet (HFD) to induce diabetes and then received insulin injection to attain acute and recurrent hypoglycaemia. Immunoblotting was used to analyse the phosphorylation and O-glycosylation status of eNOS and iNOS level from thoracic aorta and mesenteric artery tissue. Indicators of oxidative stress from plasm were determined, and endothelial-dependent vasodilation was detected via wire myograph system. Hypoglycaemia was associated with a marked increase in eNOS O-GlcNAcylation and decrease in Serine (Ser)-1177 phosphorylation from thoracic aortas and mesenteric arteries. Moreover, hypoglycaemia resulted in elevated phosphorylation of eNOS at Threonine (Thr)-495 site in mesenteric arteries. Besides, changes in these post-translational modifications were associated with increased O-GlcNAc transferase (OGT), decreased phosphorylation of Akt at Ser-473, and increased protein kinase C α subunit (PKCα). iNOS expression was induced in hypoglycaemia. Furthermore, endothelial-dependent vasodilation was impaired under insulin-induced hypoglycaemia, and further in recurrent hypoglycaemia. Conclusively, these findings strongly indicate that hypoglycaemia-dependent vascular dysfunction in diabetes is mediated through altered eNOS activity and iNOS expression. Therefore, this implies that therapeutic modulation of eNOS activity and iNOS expression in diabetics under intensive glucose control may prevent and treat adverse cardiovascular events.

Asprosin aggravates vascular endothelial dysfunction via disturbing mitochondrial dynamics in obesity models.

The aim of the study was to investigate the contribution of asprosin (ASP), a fasting-induced hormone involved in metabolic disorders, to vascular endothelial dysfunction in obesity models. Primary rat thoracic aortic endothelial cells treated with palmitic acid and mice fed with a high-fat diet (HFD) were used as the obesity models. The role and mechanism of ASP in endothelial dysfunction were investigated by the means of morphologic, functional, and genetic analysis. ASP aggravated the endothelial dysfunction induced by either palmitic acidin vitro or an HFD in vivo, characterized as the impairment of endothelium-dependent vasodilation, reduction of nitric oxide levels, elevation of malondialdehyde levels, and inhibition of phosphoinositide 3-kinase-AKT-endothelial nitric oxide synthase signaling. However, adipose conditional knockout of ASP or ASP neutralization significantly alleviated the endothelial dysfunction induced by an HFD. Mechanistically, ASP enhanced mitochondrial fission, and inhibition of the fission through knockdown of dynamin-related protein 1 (a fission-hallmark factor) rescued the endothelial dysfunction and the disturbance to mitochondrial dynamics induced by ASP. The findings demonstrate that ASP causes and even exacerbates vascular endothelial dysfunction through promoting mitochondrial fission in obesity, suggesting that ASP can act as an early predictive marker of blood vessel dysfunction and become a novel potential therapeutic target for obesity-related cardiovascular diseases.

PS-BPB01-1: SPARC IS INDUCED AT THE EARLY STAGE OF VASCULAR ENDOTHELIAL DYSFUNCTION TO COMPENSATE INFLAMMATION IN DOCA-SALT HYPERTENSIVE RATS

Objective: Extracellular matrix (ECM) regulates various cellular functions as well as provides structural support. SPARC (secreted protein acidic and rich in cysteine) is one of the ECM components, which participates in various cellular functions, especially during morphogenesis and tissue remodeling. We have reported that 1) SPARC, which increases in accordance with renal injury, causes collagen deposition through ADAMTS1 (a disintegrin and metalloproteinase with thrombospondin type 1 motif) production, and 2) renin-angiotensin system is placed in the upstream of SPARC overexpression in the hypertensive rat kidney. The present study investigated the roles for SPARC in vascular endothelial cell dysfunction and inflammation in the setting of hypertension. Design and method: Rats were treated with deoxycorticosterone acetate (DOCA) and 1% salt water for 0, 1, 2 or 3 weeks. Blood pressure was measured by tail-cuff methods, and thoracic aorta was isolated to examine acetylcholine-induced vasodilatory response, macrophage infiltration by immunohistochemistry, and protein expression of SPARC and ADAMTS1 by Western blotting. In the separate experiment, angiotensin II (10–7mol/L, 6hr) or SPARC recombinant protein (100nmol/L, 24hr) was treated to cultured rat aortic endothelial cells (RAECs) with/without siRNA targeting SPARC and ADAMTS1. MCP-1 and LOX-1 mRNA levels were measured by real-time RT-PCR. Result: DOCA-salt caused time-dependent increases in systolic blood pressure, impairment of endothelium-dependent vasodilation, and macrophage infiltration into the adventitial area of the aorta. The expression of SPARC in the DOCA-salt rat aorta was enhanced at week1 and week2 compared to week0. ADAMTS1 expression tended to increase from week1 and showed significant increases at week3. In RAECs, SPARC and ADAMTS1 gene knockdown aggravated angiotensin II-induced overexpression of LOX-1 and MCP-1 mRNA, indicating anti-inflammatory effects of SPARC. On the other hand, SPARC recombinant protein treatment induced the upregulation of LOX-1 and MCP-1. Conclusions: SPARC may be induced at the early stage of vascular injury to compensate inflammation under the existence of angiotensin II. We need further investigation into the diverse effects of SPARC and the relationship between SPARC and ADAMTS1.

The Long-Term Effects of Prenatal Hypoxia on Coronary Artery Function of the Male and Female Offspring.

Prenatal hypoxia predisposes the offspring to the development of cardiovascular (CV) dysfunction in adult life. Using a rat model, we assessed the effect of prenatal hypoxia on vasoconstrictive and vasodilative mechanisms in left anterior descending coronary arteries of 4- and 9.5-month-old offspring. Endothelium-dependent relaxation to methylcholine and vasoconstriction responses to endothelin-1 (ET-1) were assessed by wire myography. Prenatal hypoxia impaired endothelium-dependent vasodilation in 4- and 9.5-month-old offspring. Inhibition of nitric oxide (NO) synthase prevented coronary artery relaxation in all groups. Inhibition of prostaglandin H synthase (PGHS) improved relaxation in prenatally hypoxic males and tended to improve vasorelaxation in females, suggesting that impaired vasodilation was mediated via increased PGHS-dependent vasoconstriction. An enhanced contribution of endothelium-dependent hyperpolarization to coronary artery vasodilation was observed in prenatally hypoxic males and females. No changes in endothelial NO synthase (eNOS) and PGHS-1 expressions were observed, while PGHS-2 expression was decreased in only prenatally hypoxic males. At 4 months, ET-1 responses were similar between groups, while ETB inhibition (with BQ788) tended to decrease ET-1-mediated responses in only prenatally hypoxic females. At 9.5 months, ET-1-mediated responses were decreased in only prenatally hypoxic females. Our data suggest that prenatal hypoxia has long-term similar effects on the mechanisms of impaired endothelium-dependent vasodilation in coronary arteries from adult male and female offspring; however, coronary artery contractile capacity is impaired only in prenatally hypoxic females. Understanding the mechanistic pathways involved in the programming of CV disease may allow for the development of therapeutic interventions.

Abstract 15365: The Regulatory Role of Sirtuin 6 in Diabetic Cardiomyopathy

Introduction: DCM is a complex disease with many possible causes and multifactorial pathophysiology, but its underlying mechanisms are poorly understood, and no specific therapeutic guideline has yet been established. Increasing evidence suggests that coronary microvascular dysfunction (CMD) might be one of the primary mechanisms in DCM development. CMD is characterized by impaired endothelial-dependent vasodilation, but detailed mechanisms have yet to be elucidated. Sirtuin 6 (Sirt6) has been implicated in obesity, insulin resistance, type 2 diabetes mellitus, and cardiovascular diseases. Sirt6 protects EC from premature senescence, oxidative stress, and atherosclerosis by sustaining high eNOS levels and preserving cell replication. How Sirt6 regulates coronary microvascular function remains to be determined. Methods: Inducible Sirt6 global knockout, endothelial-specific knockout, and wild-type (WT) mice were fed a diet high in fat and sugar (HFHS), and blood lipid and glucose were measured. Coronary arteries were isolated, and endothelial-dependent vasodilation (EDD) was assessed using myography (DMT). Echocardiography and treadmill exercise exertion tests were performed to evaluate cardiac function. Myocardial blood flow (MBF) was measured by doppler. Cardiac fibrosis was detected using trichrome staining, and molecular pathways were elucidated via gene and protein analysis. Results: Our preliminary data show that Sirt6 was downregulated in diabetes. The EDD of coronary arterioles Sirt6 global knockout and endothelial-specific knockout treated with HFHS was impaired, and the mediator of coronary vasodilation switched from NO to H 2 O 2 in the Sirt6 knockout mice. Compared to the WT mice, myocardial blood flow was decreased, ejection fraction (EF) was not changed, the running distance was reduced, and E/E’ ratio was increased in Sirt6 knockout mice. The Sirt6 targeted proteins were identified. Conclusions: Our suggest Sirt6 regulated coronary microvascular function through endothelial cells, and ablation of Sirt6 in endothelial cells caused CMD and diastolic dysfunction. Further genetic profiling will elucidate the pathways and mechanisms converging with Sirt6 to regulate microvascular function.

Interaction of FOXO1 and SUMOylated PPARγ1 induced by hyperlipidemia and hyperglycemia favors vascular endothelial insulin resistance and dysfunction

PPARγ1 and FOXO1 are the key transcription factors that regulate insulin sensitivity. We previously found that a small ubiquitin-related modifier of PPARγ1 at K77 (SUMOylation) favored endothelial insulin resistance (IR) induced by high fat/high glucose (HF/HG) administration. However, whether and how the crosstalk between SUMOylated PPARγ1 and FOXO1 would mediate the development of the endothelial IR and dysfunction remains unclear. Here, we emphasize how PPARγ1-K77 SUMOylation would interact with FOXO1 and participate in the development of the endothelial IR and dysfunction. Our results show that the combination of HF/HG and PPARγ1-K77 SUMOylation exhibits a synergistic deteriorative effect on the endothelial IR and dysfunction, presenting decreased NO levels and elevated ET-1 levels, weakened PI3K/Akt/eNOS signaling, and impaired endothelium-dependent vasodilation function. The further researches reveal that PPARγ1-K77 SUMOylation readily interacts with FOXO1, and FOXO1 occupies the PPAR response element (PPRE) which is supposed to be occupied by PPARγ, thus resulting in the decrease of PPARγ1 transcription activity and the mitigation of the PI3K/Akt signaling. Moreover, the mitigation of the PI3K/Akt signaling promotes in turn the accumulation of FOXO1 in the nucleus where FOXO1 interacts with the SUMOylated PPARγ1, thus exerting a positive feedback effect on IR pathogenesis. The findings uncover a novel association between PPARγ1-K77 SUMOylation and FOXO1, which contributes to our understanding of the pathogenesis of endothelial IR and dysfunction and provides novel pharmacological targets for diabetic angiopathy.

Abstract P210: Mir-204 In Endothelial Cells Contributes To The Development Of Hypertension

Global knockout of microRNA miR-204 leads to significant attenuation of hypertension in mice treated with uninephrectomy, angiotensin II (AngII), and a high-salt diet. We hypothesize that miR-204 in endothelial cells (EC) contributes to hypertension. We developed Mir204 fl/fl mice and crossed them with VE-Cadherin-Cre mice. The loss of miR-204 was confirmed in isolated endothelial cells (1 ± 0.15, 0.41 and 0.13 ± 0.05, fold in EC- Mir204 +/+ , EC- Mir204 +/- , and EC- Mir204 -/- mice, respectively; n=4, 1, and 4). AngII and 4% NaCl diet increased systolic blood pressure (SBP) by up to 40-50 mmHg in both male and female EC- Mir204 +/- and WT littermates (n=11 and 17). The SBP was significantly decreased by 20-30 mmHg in EC- Mir204 -/- mice (P < 0.05, n=10). Vascular function was assessed by pressure myograph in basilar artery following the Ang II and 4% NaCl diet treatment. In EC- Mir204 -/- male mice, the wall thickness (21.5 ± 0.1 vs 30 ± 3.1μm, n=7 and 2) and media/lumen ratio (0.2 ± 0.01 vs 0.51 ± 0.09, n=7 and 2) was significantly reduced compared with EC- Mir204 +/+ mice. Endothelial-dependent vasodilation (response to Ach) was lost in EC- Mir204 +/+ mice but largely preserved in EC- Mir204 -/- mice (P= 0.007). Renal interstitial fibrosis was not influenced by the miR-204 KO in endothelial cells (Cortex: 0.27 ± 0.04, 0.18 ± 0.01 %; Outer medulla: 0.18 ± 0.05, 0.19 ± 0.05 % in EC- Mir204 +/+ and EC- Mir204 -/- male mice, respectively; n=3 and 2). Urinary albumin excretion was increased during the two-week treatment. However, the albuminuria was not significantly affected by the knockout of miR-204 in endothelial cells (2.65 ± 1.13, 3.41 ± 0.86, and 2.86 ± 0.85 mg/24h in EC- Mir204 +/+ , EC- Mir204 +/- , and EC- Mir204 -/- mice, respectively; n=9, 11 and 6). Glomerular filtration rate did not differ among the three groups at baseline or study termination (Baseline: 188.3 ± 30.1, 223.1 ± 34.9, and 185.3 ± 21.3 μl/min, n=4, 2 and 5; Termination: 203.8 ± 22.1, 150.7 ± 30.3, and 193.9 ± 42.5 μl/min, n=6, 2 and 5 in EC- Mir204 +/+ , EC- Mir204 +/- , and EC- Mir204 -/- mice, respectively). The findings suggest that miR-204 in endothelial cells plays an important role in the development of hypertension associated with impaired endothelial-dependent vasodilation and vascular remodeling.

SOLUBLE GUANYLYL CYCLASE ACTIVATION RESCUES HYPEROXIA-INDUCED DYSFUNCTION OF VASCULAR RELAXATION.

Introduction: Perioperative alterations in perfusion lead to ischemia and reperfusion injury, and supplemental oxygen is administered during surgery to limit hypoxic injury but can lead to hyperoxia. We hypothesized that hyperoxia impairs endothelium-dependent and endothelium-independent vasodilation but not the vasodilatory response to heme-independent soluble guanylyl cyclase activation. Methods: We measured the effect of oxygen on vascular reactivity in mouse aortas. Mice were ventilated with 21% (normoxia), 60% (moderate hyperoxia), or 100% (severe hyperoxia) oxygen during 30 minutes of renal ischemia and 30 minutes of reperfusion. After sacrifice, the thoracic aorta was isolated, and segments mounted on a wire myograph. We measured endothelium-dependent and endothelium-independent vasodilation with escalating concentrations of acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, and we measured the response to heme-independent soluble guanylyl cyclase activation with cinaciguat. Vasodilator responses to each agonist were quantified as the maximal theoretical response ( Emax ) and the effective concentration to elicit 50% relaxation (EC 50 ) using a sigmoid model and nonlinear mixed-effects regression. Aortic superoxide was measured with dihydroethidium probe and high-performance liquid chromatography quantification of the specific superoxide product 2-hydroxyethidium. Results: Hyperoxia impaired endothelium-dependent (ACh) and endothelium-independent (SNP) vasodilation compared with normoxia and had no effect on cinaciguat-induced vasodilation. The median ACh Emax was 76.4% (95% confidence interval = 69.6 to 83.3) in the normoxia group, 53.5% (46.7 to 60.3) in the moderate hyperoxia group, and 53.1% (46.3 to 60.0) in the severe hyperoxia group ( P < 0.001, effect across groups), while the ACh EC 50 was not different among groups. The SNP Emax was 133.1% (122.9 to 143.3) in normoxia, 128.3% (118.1 to 138.6) in moderate hyperoxia, and 114.8% (104.6 to 125.0) in severe hyperoxia ( P < 0.001, effect across groups), and the SNP EC 50 was 0.38 log M greater in moderate hyperoxia than in normoxia (95% confidence interval = 0.18 to 0.58, P < 0.001). Cinaciguat Emax and EC 50 were not different among oxygen treatment groups (median range Emax = 78.0% to 79.4% and EC 50 = -18.0 to -18.2 log M across oxygen groups). Aorta 2-hydroxyethidium was 1419 pmol/mg of protein (25th-75th percentile = 1178-1513) in normoxia, 1993 (1831-2473) in moderate hyperoxia, and 2078 (1936-2922) in severe hyperoxia ( P = 0.008, effect across groups). Conclusions: Hyperoxia, compared with normoxia, impaired endothelium-dependent and endothelium-independent vasodilation but not the response to heme-independent soluble guanylyl cyclase activation, and hyperoxia increased vascular superoxide production. Results from this study could have important implications for patients receiving high concentrations of oxygen and at risk for ischemia reperfusion-mediated organ injury.

Abstract P3138: The Regulatory Role Of Sirtuin 6 In Coronary Microvascular Dysfunction

Introduction: Coronary microvascular dysfunction (CMD) is characterized by impaired endothelial-dependent vasodilation. These impairments are seen in diabetic cardiomyopathy, ischemia with no obstructive coronary artery disease, and heart failure with preserved ejection fraction (HFpEF), but detailed mechanisms have yet to be elucidated. Sirtuin 6 (Sirt6), an important member of the Sirtuin family, has been implicated in obesity, insulin resistance, type 2 diabetes mellitus (T2DM), and cardiovascular diseases. Sirt6 protects EC from premature senescence, oxidative stress, and atherosclerosis by sustaining high eNOS levels and preserving cell replication. Sirt6 was reported to regulate endothelial dilation in atherosclerosis in Sirt6 heterozygous mice, but how Sirt6 regulates coronary microvascular function remains to be determined. Methods: Sirt6 knockout and wild-type (WT) mice were fed a diet high in fat and sugar (HFHS) for six months, and blood lipid and glucose were measured. Coronary arteries were isolated, and endothelial-dependent vasodilation (EDD) was assessed using myography (DMT). Echocardiography and treadmill exercise exertion tests were performed to evaluate cardiac function. Myocardial blood flow (MBF) was measured by doppler. Cardiac fibrosis was detected using trichrome staining, and molecular pathways were elucidated via gene and protein analysis. Results: Our preliminary data show that Sirt6 was downregulated in diabetes. The EDD of coronary arterioles was impaired, and the mediator of coronary vasodilation switched from NO to H 2 O 2 in the Sirt6 knockout mice. Compared to the WT mice, myocardial blood flow is decreased, ejection fraction (EF) was not changed, the running distance was reduced, and E/E’ ratio was increased in Sirt6 knockout mice. The Sirt6 targeted proteins were identified. Conclusions: Sirt6 regulated coronary microvascular function, and ablation of Sirt6 caused CMD and diastolic dysfunction. Further genetic profiling will elucidate the pathways and mechanisms converging with Sirt6 to regulate microvascular function.

Abstract P3023: The Regulatory Role Of Mir-21 In Heart Failure With Preserved Ejection Fraction (hfpef)

Introduction: Coronary microvascular dysfunction (CMD) is characterized by impaired endothelial-dependent vasodilation. These impairments are seen in diabetic cardiomyopathy, ischemia with no obstructive coronary artery disease, and heart failure with preserved ejection fraction (HFpEF), but detailed mechanisms have yet to be elucidated. Moreover, how microRNA (miR-21) regulates CMD in HFpEF is not entirely understood. Methods: miR-21 knockout and wild-type (WT) mice were fed a diet high in fat and sugar (HFHS) for 6 months and blood lipid and glucose were measured. Echocardiography and treadmill exercise exertion tests were performed to assess cardiac function. Myocardial blood flow (MBF) under stress was measured by contrast echocardiography or doppler after the treatment with different dosages of norepinephrine and mean arterial blood pressure was measured simultaneously by femoral pressure catheter. Cardiac fibrosis was detected using trichrome staining and molecular pathways were elucidated via gene and protein analysis. Results: Our preliminary data show decreased MBF during stress in WT mice fed a HFHS diet. While ejection fraction was not changed, cardiac index, stroke volume, and running distance were decreased. Furthermore, E/E’ ratio was increased in WT mice fed HFHS diet compared to the WT mice fed a chow diet, suggesting heart failure and impaired diastolic function with normal systolic function. Moreover, perivascular fibrosis was increased in the WT mice fed a HFHS diet compared to WT mice fed a chow diet. However, the ablation of miR-21 reversed all these changes in the mice fed a HFHS diet. Conclusions: miR-21 regulates CMD and ameliorated HFpEF. Further investigation will elucidate the pathways and mechanisms converging with miR-21 to regulate HFpEF.

MTOR contributes to endothelium-dependent vasorelaxation by promoting eNOS expression and preventing eNOS uncoupling

Clinically used inhibitors of mammalian target of rapamycin (mTOR) negatively impacts endothelial-dependent vasodilatation (EDD) through unidentified mechanisms. Here we show that either the endothelium-specific deletion of Mtor to inhibit both mTOR complexes, or depletion of Raptor or Rictor to disrupt mTORC1 or mTORC2, causes impaired EDD, accompanied by reduced NO in the serum of mice. Consistently, inhibition of mTOR decreases NO production by human and mouse EC. Specifically, inhibition of mTORC1 suppresses eNOS gene expression, due to impairment in p70S6K-mediated posttranscriptional regulation of the transcription factor KLF2 expression. In contrast to mTORC1 inhibition, a positive-feedback between MAPK (p38 and JNK) activation and Nox2 upregulation contributes to the excessive generation of reactive oxygen species (ROS), which causes eNOS uncoupling and decreased NO bioavailability in mTORC2-inhibited EC. Adeno-associated virus-mediated EC-specific overexpression of KLF2 or suppression of Nox2 restores EDD function in endothelial mTORC1- or mTORC2-inhibited mice.

Maternal perfluorooctane sulfonic acid exposure during rat pregnancy causes hypersensitivity to angiotensin II and attenuation of endothelium-dependent vasodilation in the uterine arteries †.

Epidemiological studies show a strong association between environmental exposure to perfluorooctane sulfonic acid (PFOS) and preeclampsia and fetal growth restriction; however, the underlying mechanisms are unclear. We tested the hypothesis that gestational PFOS exposure leads to pregnancy complications via alterations in uterine vascular endothelium-independent angiotensin II-related mechanisms and endothelium-derived factors such as nitric oxide. Pregnant Sprague-Dawley rats were exposed to PFOS 0.005, 0.05, 0.5, 5, 10, and 50μg/mL through drinking water from gestational day 4 to 20, and dams with PFOS 50μg/mL were used to assess mechanisms. PFOS exposure dose dependently increased maternal blood pressure but decreased fetal weights. Uterine artery blood flow was lower and resistance index was higher in the PFOS dams. In PFOS dams, uterine artery contractile responses to angiotensin II were significantly greater, whereas contractile responses to K+ depolarization and phenylephrine were unaffected. Plasma angiotensin II levels were not significantly different between control and PFOS dams; however, PFOS exposure significantly increased Angiotensin II type 1 receptor (AGTR1) and decreased AGTR2 protein levels in uterine arteries. Endothelium-dependent relaxation response to acetylcholine was significantly reduced with decreased endothelial nitric oxide synthase expression in the uterine arteries of PFOS dams. Left ventricular hypertrophy and fibrosis were observed, along with increased ejection fraction and fractional shortening in PFOS dams. These results suggest that elevated maternal PFOS levels decrease uterine blood flow and increase vascular resistance via heightened angiotensin II-mediated vasoconstriction and impaired endothelium-dependent vasodilation, which provides a molecular mechanism linking elevated maternal PFOS levels with gestational hypertension and fetal growth restriction.

Th17 cell-linked mechanisms mediate vascular dysfunction induced by testosterone in a mouse model of gender-affirming hormone therapy.

Clinical data point to adverse cardiovascular events elicited by testosterone replacement therapy. Testosterone is the main hormone used in gender-affirming hormone therapy (GAHT) by transmasculine people. However, the cardiovascular impact of testosterone in experimental models of GAHT remains unknown. Sex hormones modulate T-cell activation, and immune mechanisms contribute to cardiovascular risk. The present study evaluated whether testosterone negatively impacts female cardiovascular function by enhancing Th17 cell-linked effector mechanisms. Female (8 wk old) C57BL/6J mice received testosterone (48 mg/kg/wk) for 8 wk. Male mice were used for phenotypical comparisons. The hormone treatment in female mice increased circulating testosterone to levels observed in male mice. Testosterone increased lean body mass and body mass index, and decreased perigonadal fat mass, mimicking clinical findings. After 8 wk, testosterone decreased endothelium-dependent vasodilation and increased peripheral Th17 cells. After 24 wk, testosterone increased blood pressure in female mice. Ovariectomy did not intensify phenotypical or cardiovascular effects by testosterone. Female mice lacking T and B cells [Rag1 knockout (-/-)], as well as female mice lacking IL-17 receptor (IL-17Ra-/-), did not exhibit vascular dysfunction induced by testosterone. Testosterone impaired endothelium-dependent vasodilation in female mice lacking γδ T cells, similarly to the observed in wild-type female mice. Adoptive transfer of CD4+ T cells restored testosterone-induced vascular dysfunction in Rag1-/- female mice. Together, these data suggest that CD4+ T cells, most likely Th17 cells, are central to vascular dysfunction induced by testosterone in female mice, indicating that changes in immune-cell balance are important in the GAHT in transmasculine people.NEW & NOTEWORTHY Sex hormone-induced cardiovascular events are important undesirable effects in transgender people under GAHT. Studies addressing the cardiovascular impact of GAHT will certainly contribute to improve healthcare services offered to this population. Our study showing that vascular dysfunction, via Th17 cell-related mechanisms, precedes increased blood pressure induced by testosterone in a GAHT mouse model, reveals potential mechanisms involved in GAHT-related cardiovascular events and may provide new markers/targets for clinical practices in transmasculine people.

The Regulatory Role of miR‐21 in Coronary Microcirculation

IntroductionCoronary microvascular dysfunction is characterized by impaired endothelial‐dependent vasodilation. These impairments are seen in diabetic cardiomyopathy (DCM), coronary artery disease (CAD) and ischemia with non‐obstructive coronary artery (INOCA), Takotsubo cardiomyopathy, myocardial infarction with non‐obstructive coronary artery disease (MINOCA), and heart failure with preserved ejection fraction (HFpEF), but detailed mechanisms have yet to be elucidated.MethodsmicroRNA‐21 (miR‐21) global and conditional knockout mice were used to study how miR‐21 regulates coronary microcirculation in pathological conditions like DCM. Both genetic (db/db) and diet‐induced diabetic models were used. Coronary arteries were isolated, and endothelial‐dependent vasodilation was assessed using myography (DMT). In vivo myocardial blood flow (MBF) under stress was measured by contrast echocardiography or doppler after the treatment with different dosages of norepinephrine. Quantitative polymerase chain reaction (qPCR) was performed for gene expression analysis. Trichrome staining and histology were performed for structural changes of the hearts.ResultsOur preliminary data show that miR‐21 is upregulated in DCM and the deficiency of miR‐21 restores the endothelial‐dependent vasodilation in isolated diabetic coronary arterioles and coronary blood flow under stress in DCM through the mechanism that miR‐21 prevents the mediator of coronary vasodilation switching from NO to H2O2 in diabetes.ConclusionsmiR‐21 regulates microvascular dysfunction in DCM. Further genetic profiling will elucidate the pathways and mechanisms converging with miR‐21 to regulate microvascular function.

Sex Difference in Renal Artery Contractility in a Novel CRISPR/Cas9‐Generated P2X7 Knockout Rat

Purinergic signaling regulates numerous physiological processes, including renal hemodynamics. The P2X7 receptor (P2X7) is a non‐selective cation channel activated by extra‐cellular adenosine triphosphate (ATP) which plays an important role in immune cell response and inflammation. P2X7 is also expressed in endothelial cells. In the kidney, acute pharmacological blockade of P2X7 increases renal perfusion in healthy rats (Kidney Int. 88(5): 1079–1087, 2015). Here, we generated a novel P2X7 knockout (KO) rat and examined ex vivo contractility of the renal artery in male and female rats.A P2rx7 global KO rat was generated on a F344 IcoCrl background using CRISPR/Cas9 technology. KO was achieved via a two‐adenine insertion predicted to introduce a premature stop codon in exon 2. RNA and protein were extracted from KO and wild‐type (WT) kidneys to detect P2X7 by RTqPCR (n=4‐5/group) and western blotting (n=2/group). Bone marrow‐derived macrophages (BMDM) from KO and WT rats were used to assess P2X7 function by measuring interleukin (IL)‐1β release (ELISA) after stimulation with lipopolysaccharide (LPS) (1μg/mL, 4h) and ATP (3mM, 1h) (n=5‐6/group). RNA from BMDM was extracted after LPS to detect P2rx7, Il1b, Tnf and Il6 mRNA by RTqPCR (n=3/group), and Griess reaction was used to assess BMDM nitric oxide (NO) production (n=5‐6/group). One main renal artery from 2.5‐to‐4.5‐month‐old male and female KO and WT rats (n=8‐11/group) was mounted on a wire myograph to assess the response to 125 mM potassium physiological solution (KPSS) and to cumulative doses (1 nM‐30 μM) of phenylephrine (PE), acetylcholine (ACh) and sodium nitroprusside (SNP).The P2rx7 mutation in exon 2 was confirmed by genome sequencing (Sanger). P2rx7 mRNA abundance was decreased by ~60% in kidney and ~53% in BMDM from KO vs WT. P2X7 protein was detected in kidneys from WT but not from KO rats. P2X7 KO did not alter BMDM polarization after LPS stimulation. The induction of NO production was not different between genotypes (2.14±0.26 vs 2.31±0.43 μM, NS) and mRNA expression of M1 markers Il1b, Tnf and Il6 was similarly increased. In BMDM from male WT rats, ATP stimulation induced IL‐1β release; this response was markedly suppressed in KO BMDM (2577±70 vs 413±19 pg/mL, p<0.0001). In the renal artery, the constriction induced by KPSS depolarization or by PE was not different between genotypes for either sex. In male rats, the maximum vasodilation induced by ACh was significantly decreased in KO compared to WT (IC50=0.25 vs 0.20 μM, NS; %Imax= 24±3 vs 10±2%, p=0.0015); this was not observed in females (IC50=0.11 vs 8.28 μM, NS; %Imax= 19±4 vs 12±4%, NS). The dilation induced by the direct NO donor, SNP was not affected by either genotype or sex.Global genetic deletion of P2X7 impaired endothelial‐dependent vasodilation in the renal artery of male rats that may reflect diminished NO production in response to ACh. Thus, the increased renal perfusion induced by P2X7 inhibitor may arise from off‐target effects. The potential sexual dimorphism in vascular expression and/or function of P2X7 requires further investigation.

NADPH oxidase 4 contributes to TRPV4-mediated endothelium-dependent vasodilation in human arterioles by regulating protein phosphorylation of TRPV4 channels.

Impaired endothelium-dependent vasodilation has been suggested to be a key component of coronary microvascular dysfunction (CMD). A better understanding of endothelial pathways involved in vasodilation in human arterioles may provide new insight into the mechanisms of CMD. The goal of this study is to investigate the role of TRPV4, NOX4, and their interaction in human arterioles and examine the underlying mechanisms. Arterioles were freshly isolated from adipose and heart tissues obtained from 71 patients without coronary artery disease, and vascular reactivity was studied by videomicroscopy. In human adipose arterioles (HAA), ACh-induced dilation was significantly reduced by TRPV4 inhibitor HC067047 and by NOX 1/4 inhibitor GKT137831, but GKT137831 did not further affect the dilation in the presence of TRPV4 inhibitors. GKT137831 also inhibited TRPV4 agonist GSK1016790A-induced dilation in HAA and human coronary arterioles (HCA). NOX4 transcripts and proteins were detected in endothelial cells of HAA and HCA. Using fura-2 imaging, GKT137831 significantly reduced GSK1016790A-induced Ca2+ influx in the primary culture of endothelial cells and TRPV4-WT-overexpressing human coronary artery endothelial cells (HCAEC). However, GKT137831 did not affect TRPV4-mediated Ca2+ influx in non-phosphorylatable TRPV4-S823A/S824A-overexpressing HCAEC. In addition, treatment of HCAEC with GKT137831 decreased the phosphorylation level of Ser824 in TRPV4. Finally, proximity ligation assay (PLA) revealed co-localization of NOX4 and TRPV4 proteins. In conclusion, both TRPV4 and NOX4 contribute to ACh-induced dilation in human arterioles from patients without coronary artery disease. NOX4 increases TRPV4 phosphorylation in endothelial cells, which in turn enhances TRPV4-mediated Ca2+ entry and subsequent endothelium-dependent dilation in human arterioles.