Arterial Response Research Articles

Maternal use of electronic cigarettes and impact on offspring: a double-hit model.

Endothelial dysfunction is a predictor for cardiovascular disease. Preclinical data suggest longstanding cardiovascular and cerebrovascular dysfunction occurs in offspring with perinatal electronic cigarette (Ecig) exposure. Furthermore, direct use of Ecigs increases reactive oxygen species and impairs cerebrovascular function, but the combined effect of direct use in offspring with a history of perinatal exposure (i.e. double-hit condition) is not known. We tested the hypothesis that offspring with double-hit Ecig exposure will lead to greater cerebrovascular and neurocognitive dysfunction compared with in utero exposure only. Male and female offspring were obtained from time-mated Sprague Dawley female rats exposed to air (n = 5 dams) or Ecig exposed (n = 5 dams) and studied at either 3 or 6 mo after birth. Ecig exposure for double-hit offspring began at 1-mo before the timepoints and lasted 4 wk (5 days/wk with 90-min exposure/day). We found double-hit offspring (Ecig:Ecig = exposure dam:offspring) sustained further blunted middle cerebral artery (MCA) reactivity, increased severity of neuronal damage, and increased interactions of astrocytes and endothelial cells compared with offspring with maternal (Ecig:Air) or direct (Air:Ecig) exposure only. Circulating extracellular vesicles (EVs) were increased, whereas sirtuin 1 (SIRT1) was decreased, in all Ecig-exposed groups compared with controls (Air:Air), with Ecig:Ecig group showing the greatest respective change for each. Electron paramagnetic resonance (EPR) spectroscopy revealed oxidative stress was the highest in the plasma of Ecig:Ecig group (P < 0.05) than the other groups. These data show that a double-hit exposure in adolescent or adult offspring results in a greater decline in cerebrovascular function, biomarkers of neuronal dysfunction, and increased circulation of EVs compared with a single-hit exposure.NEW & NOTEWORTHY These data add to the growing body of literature demonstrating that electronic cigarette (Ecig) use during pregnancy (even without nicotine) is not safe, and primes offspring to have worse cardiovascular health outcomes in early and adult life. A key finding from this work is that a second insult from direct vaping in offspring with prior in utero exposure induces greater vascular dysfunction, increased oxidative stress, and shows evidence of neuronal dysfunction compared with either direct- or maternal-only exposure.

Abstract P351: Obesity in Early Life Leads to Endothelial and Erectile Dysfunction in Young Adult Rats.

Background: Erectile dysfunction (ED) is largely associated with obesity, however, the consequences of early life obesity for ED in young adulthood are unknown. We hypothesize that obesity induced by preweaning overfeeding impairs vascular and erectile function and affects blood pressure in young adult male rats (5-month-old). Methods: At postnatal day (PND) 1, Wistar rats were divided into a normal litter (NL, 5 female + 5 male pups/dam) or small litter (SL, 2 male + 1 female pup/dam) during lactation. After weaning, SL pups had increased body weight. Next, rats from both groups returned to normal size colonies (4-5 rats per cage) and were fed standard chow. At PND160, we evaluated body weight and fat pad deposition, mean arterial pressure (MAP) by tail-cuff, and pudendal artery (PA) and corpus cavernosum (CC) reactivity. Concentration-response curves to phenylephrine (PE) or acetylcholine (ACh) were performed in both preparations. In the CC, contraction and relaxation to electrical field stimulation (EFS) were obtained. Concentration-response curves were analyzed using non-linear regression analysis. RNA sequencing (RNAseq) analyses were performed in both PA and CC. Data were analyzed by Student’s t-test and presented as mean ± S.E.M. Statistical significance was set at p&lt;0.05. Results: At PND160 no differences in body weight were observed in SL (594±14g) compared to NL (559±13g), however, there was an increase in fat deposition in SL (retroperitoneal fat: NL 7.47±0.69g vs SL 11.25±1.23g; perigonadal fat: NL 10.05±0.55g vs SL 13.24±1.16g). MAP was higher in SL (120.5±1.20 mmHg vs 114.9±0.58 NL). In the PA, ACh-induced relaxation was reduced in SL (Emax: 28±6%) vs NL (Emax: 68±5.5%), with no changes in the contraction to PE. In the CC, EFS-induced relaxation was significantly decreased in SL rats compared to NL rats (16 Hz: NL 3.06 ± 0.28% vs SL 2.39 ± 0.53%). RNAseq revealed that, in PA from SL rats, 289 and 224 genes were down and upregulated, respectively, while in the CC from SL rats, 115 genes were downregulated, and 110 genes were upregulated. Among them, hcn2 gene (which encodes HCN2, the hyperpolarization-activated cyclic nucleotide-gated potassium and sodium channel 2) was strongly downregulated in both PA and CC, and this may affect mechanotransduction. Conclusion: Our data shows that early-life obesity causes long-lasting vascular and cavernous damage that might be associated with endothelial and erectile dysfunction in young adulthood.

Intrauterine Growth Restriction Does not Change the Regulation of Arterial Contractile Responses in Rats during Early Postnatal Period

Intrauterine Growth Restriction Does not Change the Regulation of Arterial Contractile Responses in Rats during Early Postnatal Period

Acute partial sleep restriction does not impact arterial function in young and healthy humans.

Habitual short sleep durations are associated with several cardiovascular diseases. Experimental research generally supports these findings as metrics of arterial function are impaired after complete deprivation of sleep and after longer periods of partial sleep restriction. The acute influence of a single instance of partial sleep restriction (PSR), however, has not been defined. We evaluated arterial structure and function among 32 university-aged participants on two occasions: once after normal habitual sleep (NS), and again the morning after an acute partial sleep restriction (PSR) intervention involving only 3h of sleep for a single night. Endothelial function was measured using ultrasonography at the brachial artery via flow-mediated dilatation (FMD), and a ramp peak oxygen uptake test was used to evaluate cardiorespiratory fitness. Blood samples were collected from a subset of participants to investigate the influence of circulatory factors on cellular mechanisms implicated in endothelial function. Sleep duration was lower after a night of PSR compared to NS (P<0.001); however, there were no appreciable differences in any haemodynamic outcome between conditions. FMD was not different between NS and PSR (NS: 6.5±2.9%; PSR: 6.3±2.9%; P=0.668), and cardiorespiratory fitness did not moderate the haemodynamic response to PSR (all P>0.05). Ex vivo cell culture results aligned with in vivo data, showing that acute PSR does not alter intracellular processes involved in endothelial function. No differences in arterial structure or function were observed between NS and acute PSR in healthy and young participants, and cardiorespiratory fitness does not modulate the arterial response to acute sleep restriction.

Activation of nociception-sensitive ionotropic glutamate receptor-expressing rostroventrolateral medulla neurons by stimulation of cardiac afferents in rats.

Myocardial ischemia causes the release of bradykinin, which activates afferent nerve endings in the ventricular epicardium. This elicits a sympathetically mediated increase in arterial pressure and heart rate, referred to as the cardiogenic sympathetic afferent reflex. The rostroventrolateral medulla (RVLM) is a key sympathetic brain stem site for regulating cardiovascular activity. This study aimed to determine the importance of non-barosensitive nociception sympathetic activity and the role of glutamate receptor activation of RVLM neurons in the cardiogenic sympathetic afferent reflex. We tested the hypothesis that inhibition of barosensitive sympathetic activity attenuates but does not abolish the reflex response to cardiac visceral afferents. Renal sympathetic nerve activity (RSNA), arterial pressure, and heart rate responses to epicardial bradykinin application were recorded in anesthetized rats before and after bilateral RVLM microinjection of either GABAA agonist muscimol, ionotropic glutamate receptor antagonist kynurenic acid, N-methyl-d-aspartate (NMDA) receptor antagonist 2-amino-5- phosphonopentanoic acid (AP5), or non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Baroreceptor loading-induced inhibition of barosensitive activity attenuated the bradykinin-induced RSNA response (93 ± 14% increase) and tachycardia (18 ± 3 bpm). While RVLM muscimol microinjection abolished the RSNA response (1.6 ± 4.2% from baseline, 0.49 ± 0.38 μV*s), surprisingly, it did not abolish the tachycardia (27 ± 4 bpm). Kynurenic acid microinjection blocked the arterial pressure and RSNA responses, while AP5 or CNQX only attenuated the responses. These data suggest that nociception-sensitive sympathetic activity that does not appear to be barosensitive is also involved in the cardiogenic sympathetic afferent reflex. Importantly, while muscimol and kynurenic acid abolished the arterial pressure and RSNA response, neither affected the tachycardia, suggesting an alternate cardiac pathway independent of RVLM.

Impaired vascular function among young users of anabolic–androgenic steroids

Supraphysiological doses of anabolic–androgenic steroids (AAS) is popular among recreational weightlifters and bodybuilders due to the performance-enhancing properties but is also associated with adverse cardiovascular effects. The knowledge about how AAS affect the vasculature is limited, although results from previous studies suggest alterations in vasoreactivity and morphology. In the present study we investigate the association between long-term use of AAS and vascular function. Hundred and twenty-three males were included in the study, 56 of them current AAS users and 67 weightlifting controls. Vascular function was evaluated by carotid artery reactivity and flow-mediated dilation. AAS users had significantly reduced carotid artery reactivity (p < 0.001) and flow-mediated dilation (p < 0.001) compared to weightlifting controls. Results from the present study indicate that long-term use of AAS affect the cardiovascular system negatively, measured as reduced carotid artery reactivity and flow-mediated dilation. These findings could partly explain sudden cardiovascular events among young long-term users of AAS.

Targeting endothelial KCa channels in vivo restores arterial and endothelial function in type 2 diabetic rats

ObjectiveThis study tested the hypothesis that administration of the KCa channel activator SKA-31 restores endothelium-dependent vasodilation in vivo in Type 2 Diabetic (T2D) rats. BackgroundAcute treatment of isolated resistance arteries from T2D rats and humans with SKA-31 significantly improved endothelium-dependent vasodilation. However, it is unknown whether these in situ actions translate to intact vascular beds in vivo. MethodsMale Sprague Dawley (SD) and T2D Goto-Kakizaki (GK) rats (26–32 weeks of age) were injected intraperitoneally with either drug vehicle or 10 mg/kg SKA-31. Doppler ultrasound imaging was used to record reactive hyperemia/flow-mediated dilation (FMD) in the femoral artery following release of an occlusion cuff on the distal hind limb, along with diameter changes in the left main coronary artery in response to inhaled isoflurane (2 % → 5 %). ResultsVehicle treated SD rats exhibited a robust and reversible FMD response, the magnitude and time course of which did not differ in SD rats treated with SKA-31. In contrast, only a weak FMD response was observed in vehicle-treated T2D GK rats, whereas prior SKA-31 administration restored FMD to the level observed in control SD rats. Exposure of SD rats to 5 % isoflurane caused robust coronary artery dilation, which was not altered by prior treatment with SKA-31. In T2D GK rats, 5 % isoflurane inhalation alone did not increase coronary artery diameter, however, a strong vasodilatory response was observed following SKA-31 treatment. SKA-31 administration did not modify intrinsic heart rate responses in either protocol. ConclusionsEnhancement of KCa channel activity in vivo restores endothelium-dependent vasodilation in T2D rats that exhibit peripheral endothelial dysfunction.

Perinatal hypoxia augments contractile impact of NADPH oxidase-derived ROS in early postnatal rat arteries.

Reactive oxygen species (ROS), including those produced by NADPH oxidase (NOX), play an important vasomotor role, especially at early postnatal period. Mechanisms for regulating vascular tone can change significantly due to neonatal asphyxia and accompanying hypoxia. We tested the hypothesis that normobaric hypoxia (8% O2) for 2 h at the second day of life changes the functional contribution of NOX-derived ROS to the regulation of agonist-induced contraction in early postnatal rats. We studied saphenous arteries from 11- to 14-day-old male offspring using isometric myography and Western blotting and assessed the content of biochemical parameters in blood serum. The values of main biochemical parameters in blood serum and the protein content of NOXs and superoxide dismutases in arterial tissue did not differ between "Control" and "Hypoxia" pups. The NOX inhibitor VAS2870 equally reduced the contractile responses of arteries to α1-adrenoceptor agonist methoxamine in "Control" and "Hypoxia" pups, but its effect was more pronounced in the arteries from "Hypoxia" pups when vasocontraction was evoked by the agonist of thromboxane A2 receptors U46619. Perinatal hypoxia at the second day of life increases procontractile influence of NOX-derived ROS to the regulation of U46619-induced vasocontraction in the systemic arteries at early postnatal ontogenesis. Nothing is known about programming effects of perinatal hypoxia, including birth asphyxia, on the ROS-mediated regulation of contraction in systemic arteries of early postnatal organism. 2-h normobaric hypoxia (8% O2) in rats at the second day of life increases the procontractile contribution of NOX-produced ROS to the regulation of U46619-induced vasocontraction in the systemic arteries at early postnatal ontogenesis. This fact may serve as a risk factor for the development of various disorders at later developmental stages and should be considered regarding the therapy for newborns who have suffered neonatal asphyxia.

Unravelling the impact of active and passive contributors to arterial stiffness in male mice and their role in vascular aging

Arterial stiffness, a key indicator of vascular health, encompassing active (vascular tone) and passive (extracellular matrix) components. This study aims to address how these different components affect arterial stiffness along the aorta and the influence of aging. Aortic segments of 12 week and 24 month old (both n = 6) male C57BL/6J mice were mounted in a Rodent Oscillatory Set-up to study Arterial Compliance, in order to measure arterial stiffness and vascular reactivity. Regional variations in arterial stiffness were evident, with abdominal infrarenal aorta (AIA) exhibiting highest stiffness and smallest diameters. AIA displayed both the highest amount of collagen and collagen:elastin ratio. Regional ex vivo vascular reactivity revealed heightened AIA contractions and lowered NO availability. Aging is a significant factor contributing towards vessel remodelling and arterial stiffness. Aging increased arterial stiffness, aortic diameters, collagen content, and reduced VSMC contraction. The results of this study could identify specific regions or mechanisms to target in the development of innovative therapeutic interventions aimed at enhancing overall vascular health.

Influence of gestational window on offspring vascular health in rodents with in utero exposure to electronic cigarettes.

Studies have shown cerebrovascular dysfunction in offspring with full-gestational electronic cigarette (Ecig) exposure, but little is known about how individual trimester exposure impacts offspring health. This study aimed to determine if there is a critical window during gestation that contributes to vascular and anxiety-like behavioural changes seen with full-term exposure. To test this, rats were time-mated, and the pregnant dams were randomly assigned to Ecig exposure during first trimester (gestational day, GD2-7), second trimester (GD8-14), third trimester (GD15-21) or full-term gestation (GD2-21). We also assessed the effect of maternal preconception exposure. Both male and female offspring from all maternal exposure conditions were compared to offspring from dams under ambient air (control) conditions. Ecig exposure consisted of 60-puffs/day (5days/week) using either 5 or 30watts for each respective exposure group. We found that maternal exposure to Ecig in the second and third trimesters resulted in a decrease (23-38%) in vascular reactivity of the middle cerebral artery (MCA) reactivity in 3- and 6-month-old offspring compared to Air offspring. Further, the severity of impairment was comparable to the full-term exposure (31-46%). Offspring also displayed changes in body composition, body mass, anxiety-like behaviour and locomotor activity, indicating that Ecigs influence neurodevelopment and metabolism. Maternal preconception exposure showed no impact on offspring body mass, anxiety-like behaviour, or vascular function. Thus, the critical exposure window where Ecig affects vascular development in offspring occurs during mid- to late-gestation in pregnancy, and both 5W and 30W exposure produce significant vascular dysfunction compared to Air. KEY POINTS: Exposure to electronic cigarettes (Ecigs) is known to increase risk factors for cardiovascular disease in both animals and humans. Maternal Ecig use during pregnancy in rodents is found to impair the vascular health of adolescent and adult offspring, but the critical gestation window for Ecig-induced vascular impairment is not known. This study demonstrates Ecig exposure during mid- and late-gestation (i.e. second or third trimester) results in impaired endothelial cell-mediated dilatation (i.e. middle cerebral artery reactivity) and alters anxiety-like behaviour in offspring. Maternal exposure prior to conception did not impact offspring's vascular or anxiety-like behavioural outcomes. Rodent models have been a reliable and useful predictor of inhalation-induced harm to humans. These data indicate maternal use of Ecigs during pregnancy should not be considered safe, and begin to inform clinicians and women about potential long-term harm to their offspring.

Hif1α-dependent mitochondrial acute O2 sensing and signaling to myocyte Ca2+ channels mediate arterial hypoxic vasodilation

Vasodilation in response to low oxygen (O2) tension (hypoxic vasodilation) is an essential homeostatic response of systemic arteries that facilitates O2 supply to tissues according to demand. However, how blood vessels react to O2 deficiency is not well understood. A common belief is that arterial myocytes are O2-sensitive. Supporting this concept, it has been shown that the activity of myocyte L-type Ca2+channels, the main ion channels responsible for vascular contractility, is reversibly inhibited by hypoxia, although the underlying molecular mechanisms have remained elusive. Here, we show that genetic or pharmacological disruption of mitochondrial electron transport selectively abolishes O2 modulation of Ca2+ channels and hypoxic vasodilation. Mitochondria function as O2 sensors and effectors that signal myocyte Ca2+ channels due to constitutive Hif1α-mediated expression of specific electron transport subunit isoforms. These findings reveal the acute O2-sensing mechanisms of vascular cells and may guide new developments in vascular pharmacology.

Does dexamethasone therapy affect intimal hyperplasia after injury in rat abdominal aorta models?

Intimal hyperplasia is a normal adaptive feature of arteries in response to injuries, which include invasive vascular interventions. Its development limits the long-term success of bypass grafts. Various pharmacological agents have been successfully employed in experimental models to reduce the degree of intimal hyperplasia. In our study, we investigated the efficacy of dexamethasone in reducing intimal hyperplasia in rat abdominal aortas after partial transection and primary repair. In this study, 20 Wistar Albino rats were randomly selected and divided into four groups to compare the effects of low- and high-dose dexamethasone on intima and media thickness compared to the control. Group A (n=5) was the control group, where only skin incision and laparotomy were performed. For Group B (n=5), a median laparotomy was performed, the abdominal aorta was partially transected, and repaired with an 8.0 prolene suture. Doses of 0.1 mg/kg and 0.2 mg/kg dexamethasone were administered in Group C (n=5) and Group D (n=5), respectively. After two weeks, all rats were euthanized, and the repaired abdominal aortas were excised and examined histopathologically. Intima and media thicknesses were measured using the 'Olympus AnalySIS 5' program (Olympus Corporation, Japan) after digital photos were taken. Based on the measurements, we demonstrated that after transection and repair of the abdominal aorta, the intima/media ratio was not significantly different between the low-dose dexamethasone and non-dexamethasone groups. The intima/media ratio was significantly lower in the high-dose dexamethasone group than in the non-dexamethasone and low-dose dexamethasone groups. After vascular interventions, dexamethasone treatment may reduce intimal hyperplasia and increase patency by providing vascular remodeling.

Heterogeneous and overlapping mechanisms of ischemia and nonobstructive coronary arteries: in-hospital results of the MOSAIC-COR registry.

Ischemia and nonobstructive coronary arteries (INOCA) remains a significant clinical issue. Recent guidelines underscore the importance of comprehensive coronary physiology assessment to make specific diagnoses and implement tailored treatment strategies. Our primary objective was to implement comprehensive invasive diagnostics. The secondary objective was to determine the pathomechanism of INOCA in consecutive adult patients with symptomatic chronic coronary syndrome, noninvasive evidence of myocardial ischemia, and nonobstructive coronary artery disease included in the prospective MOSAIC‑COR registry, and therefore, to define new INOCA subgroups. All patients underwent comprehensive coronary physiological assessment, including resting full‑cycle ratio, fractional flow reserve, index of microcirculatory resistance, and coronary flow reserve using a pressure wire and the thermodilution method. Coronary artery reactivity was assessed with acetylcholine in a provocative test. A total of 173 patients were enrolled (median [interquartile range] age, 66 [58-71] years; 66% women). A high prevalence of typical cardiovascular risk factors was registered. According to physiological assessment, the patients were divided into the following subgroups: epicardial vasospastic angina (EVSA; 19%), microvascular vasospastic angina (MVSA; 19%), coronary microcirculatory disease (CMD; 11%), EVSA+CMD (21%), MVSA+CMD (18%), and noncoronary disorders (12%). The diagnosis of MVSA and MVSA+CMD was more frequent in women (94% vs 76%, respectively). The patients diagnosed with INOCA in the MOSAIC‑COR registry exhibit significant symptomatology and a high prevalence of typical cardiovascular risk factors. Myocardial ischemia in this population may be generated by various pathomechanisms that may overlap.

Respiratory modulation of sympathetic transduction to blood pressure in health and type 2 diabetes.

Type 2 diabetes (T2D) is often accompanied by hypertension, exaggerated blood pressure (BP) responses to sympatho-excitatory stressors, and raised cardiovascular disease risk. Appropriate respiratory-sympathetic coupling and sympathetic transduction to BP are important for short- and longer-term BP control. We tested the hypotheses that respiratory modulation of muscle sympathetic nerve activity (MSNA) and its transduction to BP would be impaired in T2D and associated with higher BP and respiratory-coupled BP variability. Resting MSNA, respiration and beat-to-beat BP were recorded in 20 T2D (49.1 ± 7.4 years; mean ± SD) and 13 healthy control (46.3 ± 9.4 years) participants. MSNA and the transduction of sympathetic bursts (signal-averaging) to mean arterial pressure (MAP) were compared at low and high lung volume phases. The peak MAP response following a sympathetic burst was lower during the high lung volume than low lung volume phase in controls (P = 0.005), whereas it was unchanged with phase in T2D participants (P = 0.522). Respiratory modulation of MSNA was impaired in T2D participants, who had an attenuated reduction in burst incidence from low to the high lung volume phase, versus controls (27.8 ± 38.4% vs. 49.4 ± 24.6%, respectively; P = 0.043). The T2D participants were grouped into unimpaired respiratory modulators (burst incidence modulation median or above) or impaired respiratory modulators (below median). Impaired modulators had higher systolic BP (133 ± 14 vs. 121 ± 11mmHg, P = 0.046), greater Traube-Hering wave amplitudes (6.3 ± 2.4 vs. 4.6 ± 1.1mmHg; P = 0.028) and higher BP variability (MAP average real variability, 2.0 ± 0.7 vs. 1.4 ± 0.3, P = 0.033). Respiratory modulation of MSNA and sympathetic transduction to BP are altered in T2D patients and may contribute to their increased hypertension and cardiovascular risk. KEY POINTS: Respiratory-sympathetic coupling and sympathetic transduction to blood pressure (BP) contribute to short- and longer-term BP control. Our understanding of these processes in health and type 2 diabetes (T2D), a condition with high prevalence of hypertension and cardiovascular risk, is incomplete. We found that respiration and sympathetic transduction to BP are coupled in healthy individuals. The mean arterial pressure response to a sympathetic burst was reduced during the high lung volume compared to the low lung volume phase. This coupling was absent in T2D. Respiratory modulation of muscle sympathetic nerve activity (MSNA) is impaired in T2D, with a blunted reduction of MSNA observed during the high lung volume phase. T2D patients with impaired respiratory MSNA modulation had augmented systolic BP, respiratory-related BP excursions (Traube-Hering waves) and BP variability. Abnormal respiratory modulation of MSNA and sympathetic transduction to BP in T2D may contribute to altered blood pressure control and cardiovascular risk in this population.

Mild hyperbaric oxygen exposure protects heart during ischemia/reperfusion and affects vascular relaxation.

Mild hyperbaric oxygen therapy (mHBOT) is an adjuvant therapy used in conditions where tissue oxygenation is reduced and is implemented using pressures less than 1.5 ATA and 100% O2 (instead of the classical HBOT at 1.9-3 ATA) which results in cheaper, easier to implement, and equally effective. mHBOT is offered for wellness and beauty and as an anti-aging strategy, in spite of the absence of studies on the cardiovascular system. Consequently, we investigated the impact of mHBOT on the cardiovascular system. Mechanical and energetic parameters of isolated heart submitted to ischemia/reperfusion injury and arterial contractile response from mHBOT-exposed rats were evaluated. In the heart, mHBOT increased pre-ischemic velocity of contraction and ischemic end-diastolic pressure and developed pressure and contractile economy during reperfusion. mHBOT decreased infarct size and increased the plasma nitrite levels. In the artery, mHBOT increased acetylcholine sensitivity. mHBOT protects the heart during ischemia/reperfusion and affects vascular relaxation.

NONO2P, a novel nitric oxide donor, causes vasorelaxation through NO/sGC/PKG pathway, K+ channels opening and SERCA activation

Background & aimsThe treatment of cardiovascular diseases (CVD) could greatly benefit from using nitric oxide (NO) donors. This study aimed to investigate the mechanisms of action of NONO2P that contribute to the observed responses in the mesenteric artery. The hypothesis was that NONO2P would have similar pharmacological actions to sodium nitroprusside (SNP) and NO. MethodsMale Wistar rats were euthanized to isolate the superior mesenteric artery for isometric tension recordings. NO levels were measured using the DAF-FM/DA dye, and cyclic guanosine monophosphate (cGMP) levels were determined using a cGMP-ELISA Kit. ResultsNONO2P presented a similar maximum efficacy to SNP. The free radical of NO (NO•) scavengers (PTIO; 100 μM and hydroxocobalamin; 30 μM) and nitroxyl anion (NO−) scavenger (L-cysteine; 3 mM) decreased relaxations promoted by NONO2P. The presence of the specific soluble guanylyl cyclase (sGC) inhibitor (ODQ; 10 μM) nearly abolished the vasorelaxation. The cGMP-dependent protein kinase (PKG) inhibition (KT5823; 1 μM) attenuated the NONO2P relaxant effect. The vasorelaxant response was significantly attenuated by blocking inward rectifying K+ channels (Kir), voltage-operated K+ channels (KV), and large conductance Ca2+-activated K+ channels (BKCa). NONO2P-induced relaxation was attenuated by cyclopiazonic acid (10 μM), indicating that sarcoplasmic reticulum Ca2+-ATPase (SERCA) activation is involved in this relaxation. Moreover, NONO2P increased NO levels in endothelial cells and cGMP production. ConclusionsNONO2P induces vasorelaxation with the same magnitude as SNP, releasing NO• and NO−. Its vasorelaxant effect involves sGC, PKG, K+ channels opening, and SERCA activation, suggesting its potential as a therapeutic option for CVD.

Effect of zamicastat on blood pressure and heart rate response to cold pressor test: A double-blind, randomized, placebo-controlled study in healthy subjects.

Dopamine beta-hydroxylase (DβH) inhibitors, like zamicastat, hold promise for treating pulmonary arterial hypertension. This study aimed to validate the mechanism of action of zamicastat by studying its effect on the overdrive of the sympathetic nervous system (SNS). A single-centre, prospective, double-blind, randomized, placebo-controlled, crossover study evaluated the effect of 400 mg zamicastat in 22 healthy male subjects. Cold pressor test (CPT) was performed at screening and each treatment period on Days -1 and 10. Plasma and 24 h-urine levels of dopamine (DA), epinephrine (EPI) and norepinephrine (NE), and plasma DβH activity, were measured. Compared to placebo, zamicastat showed a - 4.62 mmHg decrease in systolic blood pressure during the cold stimulus vs. rest phases on Day 10 of CPT (P = .020). Zamicastat decreased mean arterial pressure response to cold stimulus during CPT (-2.62 mmHg; P = .025). At Day 10, zamicastat significantly increased plasma DA, before CPT (12.63 ng/L; P = .040) and after CPT (19.22 ng/L; P = .001) as well as the estimated plasma EPI change from baseline after CPT (P = .040). Inhibition of plasma DβH activity ranged from 19.8% to 25.0%. At Day 10, significant reductions in 24-h urinary excretion of EPI (P = .002) and NE (P = .001) were observed. Zamicastat Cτ geometric mean ± GSD ranged from 45.86 ± 1.46 ng/mL on Day 3 to 58.64 ± 1.52 ng/mL on Day 10, with moderate inter-individual variability (CV: 32.6%-36.6%). Steady state was already achieved on Day 6. Our results demonstrated the effect of zamicastat on the overdrive sympathetic response to cold stimulus, confirming its potential as SNS modulator.

P-321 Uterine fibroids secrete vasodilatory factors that induce their response via the opioid pathway

Abstract Study question Do uterine fibroids produce vasoactive factors that could affect vasculature and induce fibroid associated symptoms? Summary answer Ex vivo secretions from uterine fibroids induce a vasodilatory response in rat mesenteric arteries that is mediated via the opioid receptor pathway. What is known already Uterine fibroids (leiomyoma) are a common but clinically neglected gynaecological condition, where benign smooth muscle tumours arise from the myometrium and cause heavy menstrual bleeding (HMB), pain and infertility. Fibroids affect up to one in two women of reproductive age and are the main reason for failure of both medical and surgical treatments in women with HMB. Fibroids are proposed to affect the systemic vasculature system, with angiogenic growth factors and abnormal vasculature implicated in fibroid pathophysiology. However, the precise mechanism of fibroid induced HMB has yet to be fully elucidated. Study design, size, duration Fibroid and myometrium biopsies were prospectively collected from 13 patients undergoing MyoSure, myomectomy or hysterectomy for the treatment of HMB associated with fibroids at Liverpool Women’s Hospital, a tertiary referral centre. The collection and use of human tissue was ethically approved, and all participants gave informed written consent. Tissue biopsies were incubated in a basal medium for 24 hours. Conditioned medium was collected and used for wire myography assays to examine vascular reactivity. Participants/materials, setting, methods Second order mesenteric arteries from female Wistar rats were mounted on a wire myograph system and toned with uridine triphosphate (UTP) before being exposed to control (non-conditioned), normal myometrium (n = 4) or fibroid (n = 9) conditioned medium. Vascular activity was measured relative to UTP induced vasoconstriction. To determine the mediatory factors of observed vasoreactivity, inhibitors of well characterised pathways were systematically tested in the presence of conditioned medium. Main results and the role of chance Fibroid conditioned medium caused a marked dilation of UTP induced vasoconstriction in rat mesenteric arteries, which was significantly greater than that induced by non-conditioned, or control myometrium conditioned medium. Blockage of ATP-sensitive potassium (KATP) channels with PNU37883A completely inhibited fibroid induced vasodilation. However, blockage of other potassium channels did not inhibit dilation, suggesting that a KATP-mediated PKA-dependent pathway is being stimulated. To test the potential involvement of endothelial-derived nitric oxide synthase in vasodilation, vessels were treated with the inhibitor L-NAME, which partially blocked fibroid induced vasodilation. The specificity of nitric oxide synthase inhibition was confirmed by treating vessels with acetylcholine or carbachol, which induced vasodilation via activation of nitric oxide synthase. In the presence of L-NAME, the vasodilatory effects of acetylcholine and carbachol were blocked, thus confirming inhibitor specificity. An adenosine receptor inhibitor, theophylline, had no effect on fibroid induced vasodilation, thus ruling out the adenosine pathway. Blockage of bradykinin and adrenergic receptors also failed to prevent fibroid induced dilation in mesenteric arteries. However, blocking opioid receptors with naloxone completely inhibited vasodilation in the presence of fibroid conditioned medium. These findings suggest that fibroid induced vasodilation is mediated via endothelial nitric oxide synthase and an unknown opioid compound. Limitations, reasons for caution This study was performed using excised tissue in an ex vivo environment, which may not fully simulate the fibroid secretome in vivo. Although rat mesenteric arteries are a well-established model, human uterine arteries may be more appropriate to study fibroid induced vasoreactivity. Wider implications of the findings Fibroids are responsible for up to half of all hysterectomies and healthcare costs run into the billions globally. This study demonstrates that fibroid secreted factors can impact vasoreactivity, which has important connotations for disease pathophysiology regarding HMB. Targeting vasoactive compounds produced by fibroids may be a future novel treatment option. Trial registration number NA

Real-time closed-loop brainstem stimulation modality for enhancing temporal blood pressure reduction

BackgroundTraditional pharmacological interventions are well tolerated in the management of elevated blood pressure (BP) for individuals with resistant hypertension. Although neuromodulation has been investigated as an alternative solution, its open-loop (OL) modality cannot follow the patient's physiological state. In fact, neuromodulation for controlling highly fluctuating BP necessitates a closed-loop (CL) stimulation modality based on biomarkers to monitor the patient's continuously varying physiological state. ObjectiveBy leveraging its intuitive linkage with BP responses in ongoing efforts aimed at developing a CL system to enhance temporal BP reduction effect, this study proposes a CL neuromodulation modality that controls nucleus tractus solitarius (NTS) activity to effectively reduce BP, thus reflecting continuously varying physiological states. MethodWhile performing neurostimulation targeting the NTS in the rat model, the arterial BP response and neural activity of the NTS were simultaneously measured. To evaluate the temporal BP response effect of CL neurostimulation, OL (constant parameter; 20 Hz, 200 μA) and CL (Initial parameter; 11 Hz, 112 μA) stimulation protocols were performed with stimulation 180 s and rest 600 s, respectively, and examined NTS activity and BP response to the protocols. ResultsIn-vivo experiments for OL versus CL protocol for direct NTS stimulation in rats demonstrated an enhancement in temporal BP reduction via the CL modulation of NTS activity. ConclusionThis study proposes a CL stimulation modality that enhances the effectiveness of BP control using a feedback control algorithm based on neural signals, thereby suggesting a new approach to antihypertensive neuromodulation.

Nfluence of extracellular acidosis on the functional contribution of KATP and TASK-1 potassium channels to the regulation of vascular tone in early postnatal ontogenesis

The activity of many proteins and, as a result, of the mechanisms of vascular tone regulation depends on pH. A decrease of pH (uncompensated acidosis), usually causes relaxation of blood vessels, which has been studied in sufficient detail for an adult, matured organism. However, the effect of acidosis on the mechanisms of vascular tone regulation in the early postnatal period remains almost completely unexplored. The aim of this work was to study the effect of extracellular metabolic acidosis on the functional contribution of KATP and TASK-1 potassium channels to the regulation of vascular tone in early postnatal period. We modeled extracellular metabolic acidosis (pH 6.8, equimolar replacement of NaHCO3 with NaCl in solution) and studied isometric contractile responses of the saphenous artery in rats aged 3–4 months and rat pups aged 12–15 days. Arterial contraction to the α1-adrenergic agonist methoxamine at pH 6.8 was reduced compared to normal pH 7.4 in both 3–4-month-old and 12–15-day-old rats. The KATP channel blocker glibenclamide did not change the arterial responses to methoxamine, neither at pH 7.4 nor at pH 6.8 in any of the age groups. The TASK-1 channel blocker AVE1231 did not alter arterial contractile responses at any pH in 3–4-month-old rats. However, in 12–15-day-old rat pups, the increase in contractile responses to methoxamine under the influence of AVE1231 was less at pH 6.8 than at pH 7.4. Thus, the results of this work demonstrate that acidosis reduces the contractile activity of the arteries of 3–4-month-old animals and animals during early postnatal ontogenesis, while in the latter, the anticontractile role of TASK-1 channels decreases, and KATP channels do not affect the regulation of vascular tone, either under normal, or at acidic pH in any of the age groups.