Vasoconstrictor Responses Research Articles

Noninvasive identification of ANOCA endotypes by stepwise, multi-stress, multi-marker stress echocardiography

Abstract Background Angina with non-obstructive coronary artery disease (ANOCA) is increasingly recognized in clinical practice, but effective therapy is difficult due to the heterogenity of pathophysiological substrates: organic coronary microvascular dysfunction (CMD), functional (vasospastic) CMD, epicardial artery vasospasm, non-cardiac chest pain. Current guidelines recommend invasive coronary function testing with the inherent cost of catheterization time, radiation exposure, iodinated contrast effects and risks of invasive procedures. Objective To evaluate the feasibility of a step-wise, multi-marker, multi-stress assessment of ANOCA patients by stress echocardiography (SE). Methods In a prospective study design, we enrolled 54 ANOCA patients (age =54±14 years, 14 men, 25 %), without significant coronary artery disease (CAD) on invasive or noninvasive angiography. In all patients hyperventilation (HYPER) test (30 deep breaths/min for 5 min) was performed, followed by semi-supine exercise (EX) if negative. All patients underwent adenosine (ADO) test with coronary flow velocity reserve (CFVR) measurement in the mid-distal left anterior descending artery (LAD). Positivity criteria were a coronary flow velocity (CFV) decrease during HYPER despite the increase in the double product (DP) indicating functional CMD i.e. vasoconstriction); the presence of inducible regional wall motion abnormality (RWMA) with HYPER-EX (microvascular/epicardial spasm), and CFVR ≤2.0 with ADO hyperemia (organic CMD). Results Fifty one pts (94%) had normal increase in CFV at ADO: CFV rest 0.264±0.078 vs ADO 0.608±0.133, p<0.001, while 3pts (5%) showed decrease in CFV at ADO suggesting organic CMD. Double product (DP) increased during HYPER (rest 10061 ±2406 vs. HYPER 13580 ±3356, p<0.001). Twenty-nine pts (53%) showed a paradoxical vasoconstrictor response during HYPER despite the increase in DP (CFV decreased during HYPER: CFV rest 0.261±0.059 vs HYP 0.216±0.057, p<0.001). With HYPER-EX, RWMA was induced in 15 patients (27%), while 7 patients had also RWMA during HYPER. Conclusion In patients with ANOCA, a stepwise multi-marker (CFVR and RWMA) and multi-stress (ADO, HYPER and EX) SE identifies CMD phenotypes and actionable therapeutic targets. According to our results functional vasospastic CMD (paradoxical decrease of CFV with HYPER), is more frequent than organic CMD (reduced CFVR with ADO) in patients with ANOCA. Inducible RWMA with HYPER-EX indicate severe vasoconstrictor response.

Aerobic exercise training-induced bone and vascular adaptations in mice lacking adiponectin

Adiponectin regulates lipid and glucose metabolism, and insulin sensitivity in various target organs; however, the effects of adiponectin on bone health remain controversial. Exercise training can enhance bone density, bone microarchitecture, and blood flow. This study aimed to elucidate the role of adiponectin in adaptations of bone microarchitecture and bone vasculature in response to aerobic exercise training.Adult male C57BL/6 wild-type (WT) and homozygous adiponectin knockout (AdipoKO) mice were either treadmill exercise trained or remained sedentary for 8–10 weeks. The trabecular structures of the distal femoral metaphysis, a weight-bearing bone, and the mandible, a non-weight-bearing bone, were examined using microcomputed tomography. The femoral principal nutrient arteries were isolated to assess vasoreactivity (vasodilation and vasoconstriction) and structural remodeling.At the femoral metaphysis, impaired trabecular bone structures, including reduced connectivity density and increased trabecular spacing, were observed in AdipoKO mice compared to WT mice. In addition, nitric oxide-mediated, endothelium-dependent vasodilation was substantially reduced, and wall-to-lumen ratio was significantly increased in the femoral principal nutrient artery of AdipoKO mice. Interestingly, although exercise training-induced enhancements in trabecular connectivity density were observed at the femoral metaphysis of both WT and AdipoKO, increased vasoconstrictor responses were only observed in the femoral principal nutrient artery of WT mice, not in the AdipoKO mice. In mandibular trabecular bone, exercise training increased trabecular bone volume fraction (BV/TV, %) and intersection surface in the mandible of both WT and AdipoKO mice.These findings indicate that adiponectin is crucial for maintaining normal bone microarchitecture and vasculature. Although the absence of adiponectin compromises bone vascular adaptation to exercise training in mice, some exercise training-induced alterations in bone microarchitecture occurred in the absence of adiponectin, suggesting contribution of compensatory mechanisms during exercise training.

Dysregulated Mitochondrial Calcium Causes Spiral Artery Remodeling Failure in Preeclampsia.

Calcium deficiency in women is strongly linked to an increased risk of developing preeclampsia. Mitochondrial calcium ([Ca2+]m) homeostasis is essential to regulate vascular smooth muscle cell (VSMC) function. However, the role of [Ca2+]m in preeclampsia development remains largely unknown. To investigate this, human spiral arteries obtained from normotensive and preeclamptic women were collected for vascular function, RNA sequencing, and VSMC studies. N(ω)-nitro-L-arginine methyl ester-induced preeclampsia animal experiments were established to investigate the effects of intervening in [Ca2+]m to improve the outcome for preeclamptic mothers or their infants. Our initial findings revealed compromised vessel function in spiral arteries derived from patients with preeclampsia, as evidenced by diminished vasoconstriction and vasodilation responses to angiotensin II and sodium nitroprusside, respectively. Moreover, the spiral artery VSMCs from patients with preeclampsia exhibited phenotypic transformation and proliferation associated with the disrupted regulatory mechanisms of [Ca2+]m uptake. Subsequent in vitro experiments employing gain- and loss-of-function approaches demonstrated that the mitochondrial Na+/Ca2+ exchanger played a role in promoting phenotypic switching and impaired mitochondrial functions in VSMCs. Furthermore, mtNCLX (mitochondrial Na+/Ca2+ exchanger) inhibitor CGP37157 significantly improved VSMC phenotypic changes and restored mitochondrial function in both patients with preeclampsia-derived VSMCs and the preeclampsia rat model. This study provides comprehensive evidence supporting the disrupted regulatory mechanisms of [Ca2+]m uptake in VSMCs of spiral arteries of patients with preeclampsia and further elucidates its correlation with VSMC phenotypic switching and defective spiral artery remodeling. The findings suggest that targeting mtNCLX holds promise as a novel therapeutic approach for managing preeclampsia.

A Skeletal Muscle-Mediated Anticontractile Response on Vascular Tone: Unraveling the Lactate-AMPK-NOS1 Pathway in Femoral Arteries.

The regulation of vascular tone by perivascular tissues is a complex interplay of various paracrine factors. Here, we investigate the anti-contractile effect of skeletal muscle surrounding the femoral and carotid arteries and its underlying mechanisms. Using male and female Wistar rats, we demonstrated that serotonin, phenylephrine, and U-46619 induced a concentration-dependent vasoconstrictor response in femoral artery rings. Interestingly, this response was diminished in the presence of surrounding femoral skeletal muscle, irrespective of sex. No anti-contractile effect was observed when the carotid artery was exposed to its surrounding skeletal muscle. The observed effect in the femoral artery persisted even in the absence of endothelium and when the muscle was detached from the artery. Furthermore, the skeletal muscle surrounding the femoral artery was able to promote an anti-contractile effect in three other vascular beds (basilar, mesenteric, and carotid arteries). Using inhibitors of lactate dehydrogenase and the 1/4 monocarboxylate transporter, we confirmed the involvement of lactate, as both inhibitors were able to abolish the anti-contractile effect. However, lactate did not directly promote vasodilation; rather, it exerted its effect by activating 5' AMP-activated protein kinase (AMPK) and neuronal nitric oxide synthase (NOS1) in the skeletal muscle. Accordingly, Nω-propyl L-arginine, a specific inhibitor of NOS1, prevented the anti-contractile effect, as well as lactate-induced phosphorylation of NOS1 at the stimulatory serine site (1417) in primary skeletal muscle cells. Phosphorylation of NOS1 was reduced in the presence of Bay-3827, a selective AMPK inhibitor. In conclusion, femoral artery-associated skeletal muscle is a potent paracrine and endocrine organ that influences vascular tone in both sexes. Mechanistically, the anti-contractile effect involves muscle fiber type and/or its anatomical location but not the type of artery or its related vascular endothelium. Finally, the femoral artery anti-contractile effect is mediated by the lactate-AMPK-phospho-NOS1Ser1417-NO signaling axis.

Impaired Peripheral Vascular Function Following Ischemic Stroke in Mice: Potential Insights into Blood Pressure Variations in the Post-Stroke Patient.

High systolic blood pressure and increased blood pressure variability after the onset of ischemic stroke are associated with poor clinical outcomes. One of the key determinants of blood pressure is arteriolar size, determined by vascular smooth muscle tone and vasodilatory and vasoconstrictor substances that are released by the endothelium. The aim of this study is to outline alterations in vasomotor function in isolated peripheral arteries following ischemic stroke. The reactivity of thoracic aortic segments from male C57BL/6 mice to dilators and constrictors was quantified using wire myography. Acetylcholine-induced endothelium-dependent vasodilation was impaired after ischemic stroke (LogIC50 Sham = -7.499, LogIC50 Stroke = -7.350, p = 0.0132, n = 19, 31 respectively). The vasodilatory responses to SNP were identical in the isolated aortas in the sham and stroke groups. Phenylephrine-induced vasoconstriction was impaired in the aortas isolated from the stroke animals in comparison to their sham treatment counterparts (Sham LogEC50= -6.652 vs. Stroke LogEC50 = -6.475, p < 0.001). Our study demonstrates that 24 h post-ischemic stroke, peripheral vascular responses are impaired in remote arteries. The aortas from the stroke animals exhibited reduced vasoconstrictor and endothelium-dependent vasodilator responses, while the endothelium-independent vasodilatory responses were preserved. Since both the vasodilatory and vasoconstrictor responses of peripheral arteries are impaired following ischemic stroke, our findings might explain increased blood pressure variability following ischemic stroke.

Abstract MP35: Angiotensin II-induced vascular response is enhanced by Extracellular Vesicles

Intro: The exact effects of extracellular vesicles (EVs) on renal hemodynamics and blood pressure remain to be determined. In this study, we examined the effect of EVs from hypertensive mice and humans on Angiotensin II (ANG II)-induced vascular response in an ex vivo model of isolated and perfused renal afferent arterioles (Af-Arts) and also assessed their effect on renal blood flow (RBF) and systolic blood pressure (SBP) in normotensive mice in vivo. Method: Circulating EVs were collected from mice with ANG II-induced hypertension (n=5) and hypertensive humans (n=2). Differential centrifugation (DCF) (5000G x 30min, followed by 17.000G for 30 minutes) was applied to generate an EV pellet (p20) which was subsequently run through size exclusion chromatography (SEC). EV size and concentration was determined by nanoparticle tracking analysis and spectral flow cytometry. Basic EV characterization was performed with cryo electron microscopy and western blotting of EV and non EV proteins. Following a 30-minute perfusion with EVs (p20 EV pellet (10 10 /ml) or fraction 1-3 or 4-6 of SEC (doses 1-9 7/ml )), dose-response curves to ANG II (10 -12 to 10 -6 mol/l) were measured in Af-Arts of C57BL/6 mice. Similar doses of EVs were infused into the penile vein of C57BL/6 mice and RBF and SBP were measured. As EVs might deliver AT1R we explored the final common pathway in vasoconstriction in vessels treated with EVs from hypertensive animals vs controls by performing immunoblotting of myosin light chain II S19 phosphorylation. Results: EVs deriving from ANG II-treated mice and hypertensive humans, but not those from normotensive control mice and humans, significantly enhanced the vasoconstrictor response to ANG II in Af-Arts of C57BL/6 mice. The same vasoconstrictor response was observed when Af-Arts were perfused with combined EV preps from DCF and SEC (fraction 1-3 vs fraction 1-6) from hypertensive animals. In vivo injection of EVs from ANG II-treated hypertensive mice reduced RBF and increased SBP in C57BL/6 mice compared to EVs from normotensive control mice. Immunoblotting of myosin light chain II S19 phosphorylation was inconclusive. Conclusion: These data suggest that EVs from hypertensive animals and humans directly affect ANG II response, renal hemodynamic and blood pressure regulation. Further work is needed to identify the EV effector candidate for enhanced ANG II response and possible effect on ART1 activation.

Abstract 46: Reduced Angiotensin II Type 2 Receptor-Mediated Responses Contribute to Increased Angiotensin II Vasoconstrictor Sensitivity in Otherwise Healthy Women With a History Of Preeclampsia

Women with a history of preeclampsia (hxPE) have a ≥4-fold risk for developing cardiovascular disease compared to matched women who had a healthy pregnancy (hxHC). Angiotensin (ang) II-mediated vasoconstriction contributes to the persistently reduced microvascular function in the years after preeclampsia. Excessive activation of ang II type 1 receptors (AT 1 R) is one putative mechanism underlying increased ang II constrictor sensitivity. This may be countered by ang II type 2 receptor (AT 2 R) activation; however, the extent that reductions in AT 2 R-mediated responses contribute to increased ang II sensitivity after preeclampsia is unknown. Using the cutaneous microcirculation as a model, we hypothesized that 1) AT 2 R-mediated dilation is attenuated in hxPE compared with hxHC, 2) AT 1 R inhibition improves reduced AT 2 R-mediated dilation in hxPE, and 3) AT 2 R inhibition would increase ang II-mediated constriction in hxHC but have no effect in hxPE. Nine hxPE (37±5 years) and 9 matched hxHC (34±5 years) within 5 years postpartum had 4 intradermal microdialysis fibers placed in the ventral forearm for the local delivery of pharmacological agents. Two fibers received graded infusions of compound 21 (AT 2 R agonist; 10 -14 -10 -8 mol/L) alone or co-perfused with losartan (AT 1 R antagonist; 43µmol/L) for the assessment of AT 2 R-mediated dilation. The remaining 2 sites received graded infusions of ang II (10 −20 –10 −4 mol/L) alone or co-perfused with PD-123319 (AT 2 R antagonist; 1µmol/L) to assess the role of AT 2 R in vasoconstrictor sensitivity to ang II. Red blood cell flux was measured directly over each fiber and cutaneous vascular conductance was calculated (CVC=flux/MAP) and expressed as a % maximum (43°C + 28mM SNP) or % baseline. Those with hxPE had attenuated AT 2 R-mediated dilation (hxPE: 15±5 vs hxHC: 27±9%max; P=0.01) that was improved with AT 1 R inhibition (losartan: 22±7 vs control: 15±5%max; P=0.003). Vasoconstrictor sensitivity to ang II was greater in hxPE compared with hxHC (hxPE: 39±14 vs hxHC: 55±6%baseline; P&lt;0.001). AT 2 R inhibition increased the vasoconstrictor response to ang II in hxHC (PD-123319: 39±12 vs control: 55±65%baseline; P&lt;0.001) but had no effect in hxPE (PD-123319: 39±13 vs control: 39±14%baseline; P=0.29). These data suggest that women with a history of preeclampsia have reductions in AT 2 R-mediated dilation that contributes to increased ang II vasoconstrictor sensitivity and sustained microvascular dysfunction after preeclampsia.

Is there a role for biogenic amine receptors in mediating β-phenylethylamine and RO5256390-induced vascular contraction?

BackgroundSubstantial evidence indicates trace amines can induce vasoconstriction independently of noradrenaline release. However, the mechanism underlying noradrenaline-independent vasoconstrictor responses to trace amines has not yet been established. This study evaluates the role of trace amine-associated receptor 1 (TAAR1) and other biogenic amine receptors in mediating β-phenylethylamine and the TAAR-1 selective agonist RO5256390-induced vasoconstriction. MethodsVasoconstrictor responses to β-PEA and the TAAR1-selective agonist, RO5256390 were assessed in vitro in endothelium-denuded aortic rings and third-order mesenteric arteries of male Sprague Dawley rats. Resultsβ-PEA and RO5256390 induced concentration-dependent vasoconstriction of aortic rings but not third-order mesenteric arteries. Vasoconstrictor responses in aortic rings were insensitive to antagonists of 5-HT. The murine-selective TAAR1 antagonist, EPPTB, had no effect on either β-PEA or RO5256390-induced vasoconstriction. The α1-adrenoceptor antagonist, prazosin, and the α2-adrenoceptor antagonist, yohimbine, induced a shift of the β-PEA concentration response curve too small to be ascribed to antagonism of α1-or α2-adrenoceptors, respectively. The α2-adrenoceptor antagonist atipamezole had no effect on β-PEA or RO5256390-induced vasoconstriction. ConclusionVasoconstrictor responses to trace amines are not mediated by classical biogenic amine neurotransmitter receptors. Insensitivity of β-PEA vasoconstrictor responses to EPPTB, may be explained by its low affinity for rat rather than murine TAAR1. Therefore, TAAR1 remains the most likely candidate receptor mediating vasoconstrictor responses to trace amines and that prazosin and yohimbine have low affinity for TAAR1.

Effect of Vitamin K2 on Blood Rheology and Vascular Responses in Diabetic Rats

Background/aim: Diabetes is manifested by endothelial dysfunction and an imbalance between vasoconstriction and vasodilation. The aim of our study is to examine the effect of vitK2 application on vascular and rheological parameters in a rat diabetes model. Materials and methods: A total of 60 male Wistar Albino rats were used to examine vascular responses and hemorheological parameters. A total of 6 groups were: control (C), control+vehicle (Cv), control+vitK2 administered (C + K2), diabetes (D), diabetes+vehicle (Dv), and diabetes+vitK2 (D + K2) group. After the animals were sacrificed, blood and vascular samples were taken and the contraction and relaxation responses of the aorta and erythrocyte deformability and aggregation were examined. Results: When KCl dose-response curves are evaluated; Increased vasoconstriction response was found in the Dv group compared to the Cv group. The increase in vasoconstriction observed in the Dv group decreased with the application of vit K2. D+vitK2 group thoracic aorta contraction responses returned to Cv group levels. In response to increasing cumulative doses of Phe, a significant increase in vasoconstriction response was observed in the Dv group compared to the Cv group. VitK2 application reduced the Phe-mediated contractile response, which was increased in the Dv group, and returned the contraction response to Cv conditions except for two intermediate Phe doses. In the Dv + K2 group, a significant decrease was observed in the aggregation index, which was tended to increase. Conclusion: Considering the cardiovascular complications frequently observed in diabetes, it can be suggested that vitK2 therapy may yield positive outcomes in diabetes.

Mitochondrial Ca2+-coupled generation of reactive oxygen species, peroxynitrite formation, and endothelial dysfunction in Cantú syndrome.

Cantú syndrome is a multisystem disorder caused by gain-of-function (GOF) mutations in KCNJ8 and ABCC9, the genes encoding the pore-forming inward rectifier Kir6.1 and regulatory sulfonylurea receptor SUR2B subunits, respectively, of vascular ATP-sensitive K+ (KATP) channels. In this study, we investigated changes in the vascular endothelium in mice in which Cantú syndrome-associated Kcnj8 or Abcc9 mutations were knocked in to the endogenous loci. We found that endothelium-dependent dilation was impaired in small mesenteric arteries from Cantú mice. Loss of endothelium-dependent vasodilation led to increased vasoconstriction in response to intraluminal pressure or treatment with the adrenergic receptor agonist phenylephrine. We also found that either KATP GOF or acute activation of KATP channels with pinacidil increased the amplitude and frequency of wave-like Ca2+ events generated in the endothelium in response to the vasodilator agonist carbachol. Increased cytosolic Ca2+ signaling activity in arterial endothelial cells from Cantú mice was associated with elevated mitochondrial [Ca2+] and enhanced reactive oxygen species (ROS) and peroxynitrite levels. Scavenging intracellular or mitochondrial ROS restored endothelium-dependent vasodilation in the arteries of mice with KATP GOF mutations. We conclude that mitochondrial Ca2+ overload and ROS generation, which subsequently leads to nitric oxide consumption and peroxynitrite formation, cause endothelial dysfunction in mice with Cantú syndrome.

The Effect of Angiotensin II Type 1 Receptor Antagonist on Age-Related Differences in Renal Vascular Responses to Angiotensin II in Male and Female Rats.

Advancing age could influence renin angiotensin system components, especially angiotensin type 1 receptor (AT1R). This study examined the effect of AT1R antagonist, losartan, on age-related differences in renal vascular responses to angiotensin II in male and female rats. Forty-eight anesthetized male and female rats (8-12 and 24-28 weeks age ranges) were subjected to catheterize. Then, the responses of mean arterial pressure (MAP), renal perfusion pressure (RPP), renal blood flow (RBF), and renal vascular resistance (RVR) to angiotensin II with or without losartan were determined and evaluated. There were not significant differences in the basal values of MAP, RPP, RBF, and RVR in males. However, it was observed significant difference in RVR in females (P < 0.05). The blockade of AT1R attenuated basal MAP and RPP in all the groups (P < 0.05). The infusion of losartan altered basal RVR and RBF values in female groups (P < 0.05). Moreover, losartan eliminated vasoconstrictor responses to angiotensin II in female groups (P < 0.05). Also, losartan induced significant vascular responses to angiotensin II in male groups (P < 0.05). Losartan could maintain RBF changes in response to angiotensin II in both 8-12- and 24-28-week females. Losartan enhanced the RBF response to angiotensin II in 8-12-week males, but not in 24-28-week males. It seems that females (not males) in various age ranges are resistance against RBF changes by acutely increased angiotensin II.

Vasoconstrictor Effects of Trace Amine Associated Receptor Agonists in the Isolated Perfused Rat Kidney.

Endogenous trace amines such as tryptamine and 3-iodothyronamine (T1AM) are present in mammalian tissues at very low concentrations. They produce their actions by activating surface G protein-coupled receptors known as trace amine-associated receptors (TAARs). The study was designed to investigate the possible vasoconstrictor effects of tryptamine, T1AM, and the selective TAAR1 agonist RO5263397 in isolated perfused rat kidney. Renal vascular reactivity experiment using Male Wistar Kyoto (WKY, n = 82) and Spontaneously Hypertensive Rats (SHR, n = 89) were used in this study. Tryptamine, T1AM, and RO5263397 increased perfusion pressure in preparations from WKY rats and SHRs in a dose-dependent manner, with no significant difference between the agonist's pD2 values (P &gt; 0.05). EPPTB, a selective TAAR1 antagonist (1ηM), significantly (P &lt; 0.05) reduced agonist-induced increase in perfusion pressure in both WKY and SHRs, suggesting a role for TAAR1 activation in these responses. The vasoconstrictor responses in both groups were significantly reduced by L-type dihydropyridine calcium channel blocker, Rho-kinase, and PKC inhibitors suggesting the involvement of extracellular calcium and enhanced calcium sensitization. Reactive oxygen species (ROS) scavenger significantly inhibited the agonist-induced increase in perfusion pressure in preparations from SHRs but not WKY. The agonist-induced increase in perfusion pressure in the kidney involves the influx of extracellular calcium, increased calcium sensitization, and ROS in SHRs only.

Downregulation of stromal interaction molecule-1 is implicated in the age-associated vasoconstriction dysfunction of aorta, intrarenal, and coronary arteries

The contractile function of vascular smooth muscle cells (VSMCs) typically undergoes significant changes with advancing age, leading to severe vascular aging-related diseases. The precise role and mechanism of stromal interaction molecule-1 (STIM1) in age-mediated Ca2+ signaling and vasocontraction remain unclear. The connection between STIM1 and age-related vascular dysfunction was investigated using a multi-myograph system, immunohistochemical analysis, protein blotting, and SA-β-gal staining. Results showed that vasoconstrictor responses in the thoracic aorta, intrarenal artery, and coronary artery decreased with age. STIM1 knockdown in the intrarenal and coronary arteries reduced vascular tone in young mice, while no change was observed in the thoracic aorta. A significant reduction in vascular tone occurred in the STIM1 knockout group with nifedipine. In the thoracic aorta, vasoconstriction significantly decreased with age following the use of nifedipine and thapsigargin and almost disappeared after STIM1 knockdown. The proportion of senescent VSMCs increased significantly in aged mice and further increased in sm-STIM1 KO aged mice. Moreover, the expression of senescence markers p21, p16, and IL-6 significantly increased with age, with p21 expression further increased in the STIM1 knockdown aged group, but not p16 or IL-6. These findings indicate that different arteries exhibit distinct organ-specific features and that STIM1 downregulation may contribute to age-related vasoconstrictive dysfunction through activation of the p21 pathway.

Retinal vascular reactivity in carriers of X-linked inherited retinal disease - a study using optical coherence tomography angiography.

Female carriers of X-linked inherited retinal diseases (IRDs) can show highly variable phenotypes and disease progression. Vascular reactivity, a potential disease biomarker, has not been investigated in female IRD carriers. In this study, functional optical coherence tomography angiography (OCT-A) was used to dynamically assess the retinal microvasculature of X-linked IRD carriers. Genetically confirmed female carriers of IRDs (choroideremia or X-linked retinitis pigmentosa), and healthy women were recruited. Macular angiograms (3x3mm, Zeiss Plex Elite 9000) were obtained in 36 eyes of 15 X-linked IRD female carriers and 21 age-matched control women. Two tests were applied to test vascular reactivity: (i) mild hypoxia and (ii) handgrip test, to induce a vasodilatory or vasoconstrictive response, respectively. Changes to vessel density (VD) and vessel length density (VLD) were independently evaluated during each of the tests for both the superficial and deep capillary plexuses. In the control group, the superficial and deep VD decreased during the handgrip test (p<0.001 and p=0.037, respectively). Mean superficial VLD also decreased during the handgrip test (p=0.025), while the deep plexus did not change significantly (p=0.108). During hypoxia, VD and VLD increased in the deep plexus (p=0.027 and p=0.052, respectively) but not in the superficial plexus. In carriers, the physiologic vascular responses seen in controls were not observed in either plexus during either test, with no difference in VD or VLD noted (all p>0.05). Functional OCT-A is a useful tool to assess dynamic retinal microvascular changes. Subclinical impairment of the physiological vascular responses seen in carriers of X-linked IRDs may serve as a valuable clinical biomarker.

Pulmonary Vascular Responses to Chronic Intermittent Hypoxia in a Guinea Pig Model of Obstructive Sleep Apnea.

Experimental evidence suggests that chronic intermittent hypoxia (CIH), a major hallmark of obstructive sleep apnea (OSA), boosts carotid body (CB) responsiveness, thereby causing increased sympathetic activity, arterial and pulmonary hypertension, and cardiovascular disease. An enhanced circulatory chemoreflex, oxidative stress, and NO signaling appear to play important roles in these responses to CIH in rodents. Since the guinea pig has a hypofunctional CB (i.e., it is a natural CB knockout), in this study we used it as a model to investigate the CB dependence of the effects of CIH on pulmonary vascular responses, including those mediated by NO, by comparing them with those previously described in the rat. We have analyzed pulmonary artery pressure (PAP), the hypoxic pulmonary vasoconstriction (HPV) response, endothelial function both in vivo and in vitro, and vascular remodeling (intima-media thickness, collagen fiber content, and vessel lumen area). We demonstrate that 30 days of the exposure of guinea pigs to CIH (FiO2, 5% for 40 s, 30 cycles/h) induces pulmonary artery remodeling but does not alter endothelial function or the contractile response to phenylephrine (PE) in these arteries. In contrast, CIH exposure increased the systemic arterial pressure and enhanced the contractile response to PE while decreasing endothelium-dependent vasorelaxation to carbachol in the aorta without causing its remodeling. We conclude that since all of these effects are independent of CB sensitization, there must be other oxygen sensors, beyond the CB, with the capacity to alter the autonomic control of the heart and vascular function and structure in CIH.

Sex-specific differences in the mechanisms for enhanced thromboxane A2-mediated vasoconstriction in adult offspring exposed to prenatal hypoxia

BackgroundPrenatal hypoxia, a common pregnancy complication, leads to impaired cardiovascular outcomes in the adult offspring. It results in impaired vasodilation in coronary and mesenteric arteries of the adult offspring, due to reduced nitric oxide (NO). Thromboxane A2 (TxA2) is a potent vasoconstrictor increased in cardiovascular diseases, but its role in the impact of prenatal hypoxia is unknown. To prevent the risk of cardiovascular disease by prenatal hypoxia, we have tested a maternal treatment using a nanoparticle-encapsulated mitochondrial antioxidant (nMitoQ). We hypothesized that prenatal hypoxia enhances vascular TxA2 responses in the adult offspring, due to decreased NO modulation, and that this might be prevented by maternal nMitoQ treatment.MethodsPregnant Sprague–Dawley rats received a single intravenous injection (100 µL) of vehicle (saline) or nMitoQ (125 µmol/L) on gestational day (GD)15 and were exposed to normoxia (21% O2) or hypoxia (11% O2) from GD15 to GD21 (term = 22 days). Coronary and mesenteric arteries were isolated from the 4-month-old female and male offspring, and vasoconstriction responses to U46619 (TxA2 analog) were evaluated using wire myography. In mesenteric arteries, L-NAME (pan-NO synthase (NOS) inhibitor) was used to assess NO modulation. Mesenteric artery endothelial (e)NOS, and TxA2 receptor expression, superoxide, and 3-nitrotyrosine levels were assessed by immunofluorescence.ResultsPrenatal hypoxia resulted in increased U46619 responsiveness in coronary and mesenteric arteries of the female offspring, and to a lesser extent in the male offspring, which was prevented by nMitoQ. In females, there was a reduced impact of L-NAME in mesenteric arteries of the prenatal hypoxia saline-treated females, and reduced 3-nitrotyrosine levels. In males, L-NAME increased U46619 responses in mesenteric artery to a similar extent, but TxA2 receptor expression was increased by prenatal hypoxia. There were no changes in eNOS or superoxide levels.ConclusionsPrenatal hypoxia increased TxA2 vasoconstrictor capacity in the adult offspring in a sex-specific manner, via reduced NO modulation in females and increased TP expression in males. Maternal placental antioxidant treatment prevented the impact of prenatal hypoxia. These findings increase our understanding of how complicated pregnancies can lead to a sex difference in the programming of cardiovascular disease in the adult offspring.Graphical

Stronger vasoconstriction and weaker vasodilation in mesenteric arteries of Ossabaw than Göttingen minipigs before manifestation of metabolic syndrome

The metabolic syndrome predisposes and contributes to the development and progression of atherosclerosis. The minipig strain “Ossabaw” is characterized by a polygenic predisposition to develop metabolic syndrome and diffuse atherosclerosis in response to a hypercaloric atherogenic diet. The aim of this study was to investigate whether Ossabaw minipigs exhibit an altered vasomotor function even before they develop their diseased phenotype. Mesenteric arteries of adult Ossabaw (n=30) and Göttingen minipigs (n=40), a pig strain without genetic predisposition to a metabolic syndrome, were harvested postmortem, dissected, and mounted on a myograph for isometric force measurements. Maximal vasoconstriction to smooth muscle cell depolarization with potassium chloride (KClmax) was repeatedly induced (twice 0.6×10−1 mol/L and twice 1.2×10−1 mol/L). Cumulative concentration-response curves were determined in response to 1×10−9 -1×10−4 mol/L norepinephrine. Endothelium-dependent and -independent vasodilation were analyzed in response to carbachol and nitroprusside, respectively (1×10−9 - 1×10−4 mol/L, each) after pre-constriction by norepinephrine. The baseline diameter of mesenteric arteries from Ossabaw minipigs was smaller than that from Göttingen minipigs (329±20 vs. 435±11 μm), and mesenteric arteries of Ossabaw minipigs developed a higher baseline force of contraction than mesenteric arteries of Göttingen minipigs (6.2±0.7 vs. 3.6±0.3 mN). The maximal vasoconstrictor response to KCl was comparable between the minipig strains. Vasoconstriction in response to norepinephrine was more pronounced in Ossabaw than in Göttingen minipigs (143±9 vs. 108±6% KClmax). Endothelium-dependent vasodilation (46.4±5.5 vs. 16.0±3.0% of norepinephrine-induced preconstriction) and -independent vasodilation (36.7±4.9 vs. 2.3±0.6% of norepinephrine-induced preconstriction) were less pronounced in Ossabaw than in Göttingen minipigs. Neither the differences in baseline diameter nor in baseline developed force of contraction had any effect on the above data, as analyzed in retrospectively matched subsets of mesenteric arteries with a comparable baseline diameter or a comparable baseline developed force of contraction, respectively. Even before the development of metabolic syndrome, vasomotor function is shifted to more vasoconstriction and less vasodilation in Ossabaw minipigs, suggesting a genetic predisposition for the early development of vascular dysfunction. Thus, Ossabaw minipigs may be a suitable model to reflect the human situation of a heterogeneous, genetically determined primordial risk constellation for vascular dysfunction. This work was supported by the German Research Foundation [SFB 1116 B08 to G.H. and P.K.] and the European COST ACTION in CARDIOPROTECTION [CA16225 to G.H. and IG16225 to G.H. and P.K.]. This is the full abstract presented at the American Physiology Summit 2024 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.

Mitochondrial Ca2+-coupled generation of reactive oxygen species causes endothelial dysfunction in Cantú syndrome

Cantú syndrome is a multisystem disorder caused by gain-of-function (GOF) mutations in KCNJ8 and ABCC9, the genes encoding the pore-forming inward rectifier Kir6.1 and regulatory sulfonylurea receptor SUR2B subunits of vascular ATP-sensitive K+ channels (KATP). In this study, we investigated the effects of Cantú syndrome on the vascular endothelium using mutant mice that model the disease. We found that endothelium-dependent dilation was impaired in small mesenteric arteries from Cantú mice. Loss of endothelium-dependent vasodilation led to increased vasoconstriction in response to intraluminal pressure and to the adrenergic receptor agonist phenylephrine. We also found that KATP GOF and acute activation of KATP channels with pinacidil increased the amplitude and frequency of wave-like Ca2+ events that were generated in the endothelium in response to the vasodilator agonist carbachol (CCh). Elevated cytosolic Ca2+ signaling activity in arterial endothelial cells from Cantú mice was associated with high mitochondrial [Ca2+], reactive oxygen species (ROS) generation, and peroxynitrite levels. Scavenging intracellular and mitochondrial ROS restored endothelium-dependent vasodilation in the arteries of mice with KATP GOF mutations. We conclude that mitochondrial Ca2+ overload and ROS generation cause endothelial dysfunction in mice with Cantú syndrome. This study was supported by grants from NHLBI (R35HL155008) and NIGMS (P20GM130459) to S.E., and NIH (R35HL140024) to C.G.N., and NIH (R00HL150277) to C.M. The Transgenic Genotyping and Phenotyping Core and the High Spatial and Temporal Resolution Imaging Core at the COBRE Center for Molecular and Cellular Signaling in the Cardiovascular System, University of Nevada, Reno is maintained by grants from NIH/NIGMS (P20GM130459). This is the full abstract presented at the American Physiology Summit 2024 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.

Effects of aging on vasoconstrictor responses of diaphragm arterioles

Introduction: In health, the diaphragm is the most important inspiratory muscle and the only skeletal muscle that is continuously recruited throughout life. Because of the diaphragm’s importance to generating the exercise hyperpnea and wealth of evidence that diaphragm fatigue and exhaustion can impair exercise tolerance, we were interested in whether the exercise intolerance that attends older populations might be associated with altered diaphragm vasomotor control. While it is known that aging compromises peripheral skeletal muscle vasomotor control, it is not known if similar impairments are present in the respiratory muscle vasculature, namely the diaphragm. Therefore, we tested the hypothesis that advanced age decreases diaphragm arteriole contractile responses to alpha-adrenergic agonists. Methods: 4–5 month old Fischer rats and 22–24 month old Fischer rats were divided by age into two groups: young (Y) and old (O). In Y and O, diaphragm first order (1A) arterioles (~200μm diameter, ~2μm in length) were isolated, cannulated, and pressurized to develop spontaneous tone. Following this, contractile responses to cumulative doses of norepinephrine (NE) and phenylephrine (PE) (10−9 to 10−4M) were determined. Results and Conclusion: The physical characteristics of the two groups differed as O were heavier than Y. However, with respect to the diaphragm 1A arterioles, there were no differences in spontaneous tone development (%) or maximal diameter (μm) between Y (38 ± 4%; 132 ± 19μm) and O (37 ± 4%; 157 ± 14 μm; both P &gt;0.05). In diaphragm 1A arterioles, the maximal vasoconstrictor response to NE was also not different between O and Y animals (O: 37 ± 8% vs. Y: 45 ± 1%; p &gt; 0.05). However, the maximal vasoconstrictor response to PE was greater in Y compared to O (O: 29 ± 3% vs. Y: 39 ± 5%; p ≤ 0.05). These data support that aging may reduce a1 adrenergic receptor mediated vascular control, altering the vasoconstrictive responsiveness of diaphragm resistance vessels. We are increasing our group sizes to test the robustness of this conclusion. This work was supported by the Sustained Momentum for Investigators with Laboratories Established (SMILE) Grants awarded to T.I.M and D.C.P. by Kansas State University College of Veterinary Medicine and the National Institute on Aging 1R15AG078060 awarded to B.J.B and D.C.P. A.G.H and K.M.S. were financially supported by Ruth L. Kirschstein National Research Service Awards 1F31HL167618-01 and 1F31HL170643-01, respectively. This is the full abstract presented at the American Physiology Summit 2024 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.

Excessive Hypercholesterolemia in Pregnancy Impairs Later-life Maternal Vascular Function in Rats

Background: Preeclampsia is a significant risk factor for the development of later-life cardiovascular disease; however, the underlying molecular mechanisms are not fully understood. Studies have shown that excessive hypercholesteremia occurring during pregnancy increases the risk of vascular pregnancy complications, such as preeclampsia. Bioavailability of nitric oxide (NO), a critical endothelium-derived vasodilator in pregnancy, is reduced in both hypercholesteremia and preeclampsia. However, the later-life vascular impact of excessive pregnancy-specific hypercholesteremia is not known. Hypothesis: Excessive hypercholesteremia in pregnancy impairs later-life maternal vascular function by reducing NO availability. Methods: Sprague-Dawley rats were fed a control diet (CD) or high cholesterol diet (HCD; 2% cholesterol + 0.5% cholic acid) from gestational day 6 to 20 (term=22 days; n=10-12). After pregnancy, all dams received a CD. Three months after pregnancy (equal to ~10 years in humans), mesenteric (systemic resistance arteries) and carotid (vascular bed that supplies blood to the cerebral vasculature) arteries were isolated, and endothelium-dependent (to methacholine, MCh) and -independent (to sodium nitroprusside, SNP) vasodilation, plus vasoconstriction responses (to phenylephrine, PE) were assessed using wire myography. NO contribution was assessed using a pan-NO synthase inhibitor (L-NAME; 100 μmol). Data were summarized as maximum responses (Emax), sensitivity (pEC50), or delta Emax (control vs. L-NAME). The statistical tests applied were a Student’s t-test or two-way ANOVA with Sidak’s post-hoc test (significance: p&lt;0.05). Results: In mesenteric arteries, vasodilation to MCh or SNP was not different between the CD and HCD groups three months after the insult. However, L-NAME reduced maximum vasodilation to MCh in the HCD group (p=0.0433) but not in CD animals. Similarly, vasoconstriction to PE was not different between groups, but L-NAME increased the PE sensitivity in the HCD group (p=0.0423), without effects in the CD animals. In carotid arteries, a HCD during pregnancy reduced vasodilation to MCh (p=0.0345), and while L-NAME prevented vasodilation to MCh in both groups (p&lt;0.0001), this effect was more pronounced in the HCD compared to CD group (delta Emax, p=0.0422). Vasodilation to SNP was similar between groups. Vasoconstriction responses to PE were increased in carotid arteries of HCD compared to CD animals (p=0.0357). L-NAME increased PE-mediated vasoconstriction in both groups (CD: 4.32-fold and HCD: 2.71-fold), but this NO modulation was significantly less in the HCD group compared to CD (delta Emax, p=0.0337). Conclusion: Exposure to a HCD, during pregnancy only, impaired later-life maternal vascular function in carotid, but not mesenteric arteries, suggesting vascular-bed specific effects in animals with a history of preeclampsia. Moreover, a HCD during pregnancy altered the NO pathway in both vascular beds, indicating that long-term alterations in NO were established during pregnancy. In summary, excessive pregnancy-specific hypercholesterolemia contributes to later-life maternal vascular dysfunction via modulation of the NO pathway, which may help explain the increased cardiovascular risk after preeclampsia. This work was supported by a foundation grant from the Canadian Institutes of Health Research (CIHR FS154313) and by the Women and Children’s Health Research Institute (WCHRI) through the generosity of the Stollery Children’s Hospital Foundation and the Alberta Women’s Health Foundation. A.A.O. is supported by a WCHRI postdoctoral fellowship through the generosity of the Stollery Children’s Hospital Foundation and the Alberta Women’s Health Foundation. E.E. was supported by a summer research studentship from Alberta Innovates. This is the full abstract presented at the American Physiology Summit 2024 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.