Contribution of sensory nerves to cutaneous reactive hyperaemia in non-Hispanic Black and White young adults.

NEW FINDINGS: What is the central question of this study? Does cutaneous sensory nerve-mediated vasodilatation differ between non-Hispanic Black and White young adults? What is the main finding and its importance? The magnitude of cutaneous reactive hyperaemia is lower in non-Hispanic Black relative to non-Hispanic White young adults, but the overall sensory nerve contribution is the same, suggesting that sensory nerve function is similar in both non-Hispanic Black and White young adults. ABSTRACT: The aim of this study was to assess cutaneous sensory nerve function, independent of nitric oxide, in non-Hispanic Black and White young adults. We tested the hypothesis that cutaneous reactive hyperaemia and sensory nerve-mediated vasodilatation would be lower in non-Hispanic Black young adults relative to non-Hispanic White young adults. Twenty-four participants who self-identified as non-Hispanic Black (n = 12) or non-Hispanic White (n = 12) were recruited. All participants underwent three bouts of reactive hyperaemia. An index of skin blood flow was measured continuously using laser-Doppler flowmetry at a control site and at a site treated with topical 4% lignocaine to inhibit sensory nerve function. Peak reactive hyperaemia was lower in non-Hispanic Black relative to non-Hispanic White participants (P < 0.001). Total reactive hyperaemia was lower in non-Hispanic Black [mean (SD); control, 4085 (955)%CVCmax  s; lignocaine, 2127 (639) percent maximal cutaneous vascular conductance * seconds, %CVCmax  s] relative to non-Hispanic White [control: 6820 (1179)%CVCmax  s; lignocaine, 3573 (712)%CVCmax  s] participants (P < 0.001 for both sites). There was no difference between groups for the calculated contribution of sensory nerves to either the peak [non-Hispanic Black, 25 (14)%; non-Hispanic White, 19 (13)%] or total reactive hyperaemic response [non-Hispanic Black, 48 (10)%; non-Hispanic White, 47 (10)%]. These data suggest that cutaneous reactive hyperaemia is lower in non-Hispanic Black young adults, but the sensory nerve contribution is similar in non-Hispanic Black and White young adults.

Microvascular endothelial function following cessation of long-term oral contraceptive pill use: A case report.

NEW FINDINGS: What is the main observation in this case? The main observation of this case report is substantial improvement in cutaneous microvascular endothelial function after cessation of long-term use of a fourth-generation oral contraceptive pill. This improvement appears independent of relative changes in the contribution of nitric oxide. What insights does it reveal? Our findings suggest that cessation of long-term, fourth-generation oral contraceptive pill use improves endothelial function within 20 months of cessation. ABSTRACT: The purpose of this case report was to evaluate in vivo endothelial function and nitric oxide (NO)-dependent vasodilatation before and after the cessation of long-term (11-12 years) fourth-generation oral contraceptive pill (OCP) use in one young, healthy and premenopausal woman. This retrospective analysis includes data from six experimental visits: three visits during months 133-144 of fourth-generation OCP use and three visits 19-22 months after OCP cessation. Endothelium-dependent and NO-dependent vasodilatation were assessed in the cutaneous microvasculature using laser-Doppler flowmetry, a rapid local heating protocol (39°C, 0.1°C/s) and pharmacological perfusion through intradermal microdialysis fibres. The participant had consistent medical history and lifestyle behaviours throughout both hormonal exposures. Data are presented as the mean (SD). Endothelium-dependent vasodilatation was 42 (10)% of site-specific maximal cutaneous vascular conductance (CVCmax ) during OCP use and 63 (10)%CVCmax after OCP cessation (49% increase). Nitric oxide-dependent vasodilatation was 70 (5)% contribution of NO during OCP use and 60 (15)%NO after OCP cessation (15% reduction). Baseline blood flow was greater after OCP cessation, but maximal blood flow was reduced. Data from this case report support a substantial increase in cutaneous microvascular endothelial function assessed via local heating after cessation of long-term use of a fourth-generation OCP, which does not appear to be attributable to increased NO bioavailability. Overall, these data suggest an improvement in endothelial and microvascular function after the cessation of long-term use of a fourth-generation OCP.

Inhibition of iNOS augments cutaneous endothelial NO-dependent vasodilation in prehypertensive non-Hispanic Whites and in non-Hispanic Blacks.

We tested the hypothesis that inducible nitric oxide synthase (iNOS) contributes to reduced nitric oxide (NO)-dependent vasodilation in non-Hispanic Blacks and prehypertensive non-Hispanic Whites. Twenty Black and twenty White participants (10 normotensive, 10 prehypertensive per group; n = 40 total) participated in this study. Participants were instrumented with two microdialysis fibers, and each site was randomized as control (lactated Ringer) or iNOS inhibition (0.1 mM 1400W). Laser-Doppler flow probes and local heaters were used to measure skin blood flow and heat the skin to induce vasodilation, respectively. Each site was heated from 33°C to 39°C (rate: 0.1°C/s). Once a plateau was established, 20 mM nitro-l-arginine methyl ester (l-NAME), a nonspecific NOS inhibitor, was infused at each site to quantify NO-dependent vasodilation. At control sites, %NO-dependent vasodilation was reduced in prehypertensive Whites (47 ± 10%NO) and in both normotensive and prehypertensive Blacks (39 ± 9%NO and 28 ± 5%NO, respectively) relative to normotensive Whites (73 ± 8%NO; P < 0.0001 for all comparisons). Compared with respective control sites, iNOS inhibition increased NO-dependent vasodilation in prehypertensive Whites (68 ± 8%NO) and in both normotensive and prehypertensive Blacks (78 ± 8%NO and 55 ± 6%NO, respectively; P < 0.0001 for all comparisons). We failed to find an effect for normotensive Whites (77 ± 7%NO). After iNOS inhibition, %NO-dependent vasodilation was similar between normotensive Whites, prehypertensive Whites, and normotensive Blacks. Inhibition of iNOS increased NO-dependent vasodilation to a lesser extent in prehypertensive Blacks. These data suggest that iNOS contributes to reduced NO-dependent vasodilation in prehypertension and in Black participants.NEW & NOTEWORTHY Inducible nitric oxide synthase (iNOS) is typically upregulated in conditions of increased oxidative stress and may have detrimental effects on the vasculature. Endothelial nitric oxide (NO), which is cardioprotective, is reduced in prehypertensive non-Hispanic Whites and in non-Hispanic Blacks. We found that inhibition of iNOS can increase endothelial NO-dependent vasodilation in prehypertensive White participants and in both normotensive and prehypertensive Black participants.Inducible nitric oxide (NO) synthase (iNOS) can be upregulated under conditions of increased oxidative stress and may have detrimental effects on the vasculature. Endothelial NO, which is cardioprotective, is reduced in prehypertensive non-Hispanic Whites and in non-Hispanic Blacks. We found that inhibition of iNOS can increase endothelial NO-dependent vasodilation in prehypertensive White participants and in both normotensive and prehypertensive Black participants.

Berries and Their Polyphenols as a Potential Therapy for Coronary Microvascular Dysfunction: A Mini-Review.

Ischemia with no obstructive coronary artery disease (INOCA) is a common diagnosis with a higher prevalence in women compared to men. Despite the absence of obstructive coronary artery disease and no structural heart disease, INOCA is associated with major adverse cardiovascular outcomes as well a significant contributor to angina and related disability. A major feature of INOCA is coronary microvascular dysfunction (CMD), which can be detected by non-invasive imaging and invasive coronary physiology assessments in humans. CMD is associated with epicardial endothelial-dependent and -independent dysfunction, diffuse atherosclerosis, and left-ventricular hypertrophy, all of which lead to insufficient blood flow to the myocardium. Inflammatory and oxidative stress signaling, upregulation of the renin-angiotensin-aldosterone system and adrenergic receptor signaling are major drivers of CMD. Treatment of CMD centers around addressing cardiovascular risk factors; however, there are limited treatment options for those who do not respond to traditional anti-anginal therapies. In this review, we highlight the ability of berry-derived polyphenols to modulate those pathways. The evidence supports the need for future clinical trials to investigate the effectiveness of berries and their polyphenols in the treatment of CMD in INOCA patients.

Sensory nerve-mediated and nitric oxide-dependent cutaneous vasodilation in normotensive and prehypertensive non-Hispanic blacks and whites.

The purpose of this study was to investigate the effect of race and subclinical elevations in blood pressure (i.e., prehypertension) on cutaneous sensory nerve-mediated and nitric oxide (NO)-dependent vasodilation. We recruited participants who self-identified as either non-Hispanic black (n = 16) or non-Hispanic white (n = 16). Within each group, participants were subdivided as either normotensive (n = 8 per group) or prehypertensive (n = 8 per group). Each participant was instrumented with four intradermal microdialysis fibers: 1) control (lactated Ringer's), 2) 5% lidocaine (sensory nerve inhibition), 3) 20 mM Nω-nitro-l-arginine methyl ester (l-NAME) (NO synthase inhibition), and 4) lidocaine + l-NAME. Skin blood flow was assessed via laser-Doppler flowmetry, and each site underwent local heating from 33°C to 39°C. At the plateau, 20 mM l-NAME were infused at control and lidocaine sites to quantify NO-dependent vasodilation. Maximal vasodilation was induced via 54 mM sodium nitroprusside and local heating to 43°C. Data are means ± SD. Sensory nerve-mediated cutaneous vasodilation was reduced in prehypertensive non-Hispanic white (34 ± 7%) and both non-Hispanic black groups (normotensive, 20 ± 9%, prehypertensive, 24 ± 15%) relative to normotensive non-Hispanic whites (54 ± 12%). NO-dependent vasodilation was also reduced in prehypertensive non-Hispanic white (41 ± 7%) and both non-Hispanic black groups (normotensive, 44 ± 7%, prehypertensive, 19 ± 7%) relative to normotensive non-Hispanic whites (60 ± 11%). The decrease in NO-dependent vasodilation in prehypertensive non-Hispanic blacks was further reduced relative to all other groups. These data suggest subclinical increases in blood pressure adversely affect sensory-mediated and NO-dependent vasodilation in both non-Hispanic blacks and whites.NEW & NOTEWORTHY Overt hypertension is known to reduce cutaneous sensory nerve-mediated and nitric oxide (NO)-dependent vasodilation, but the effect of subclinical increases in blood pressure (i.e., prehypertension) is unknown. The combined effect of race and prehypertension is also unknown. In this study, we found that prehypertension reduces cutaneous sensory nerve-mediated and NO-dependent vasodilation in both non-Hispanic white and black populations, with the greatest reductions observed in prehypertensive non-Hispanic blacks.

Thermotherapy reduces blood pressure and circulating endothelin-1 concentration and enhances leg blood flow in patients with symptomatic peripheral artery disease.

Leg thermotherapy (TT) application reduces blood pressure (BP) and increases both limb blood flow and circulating levels of anti-inflammatory mediators in healthy, young humans and animals. The purpose of the present study was to determine the impact of TT application using a water-circulating garment on leg and systemic hemodynamics and on the concentrations of circulating cytokines and vasoactive mediators in patients with symptomatic peripheral artery disease (PAD). Sixteen patients with PAD and intermittent claudication (age: 63 ± 9 yr) completed three experimental sessions in a randomized order: TT, control intervention, and one exercise testing session. The garment was perfused with 48°C water for 90 min in the TT session and with 33°C water in the control intervention. A subset of 10 patients also underwent a protocol for the measurement of blood flow in the popliteal artery during 90 min of TT using phase-contrast MRI. Compared with the control intervention, TT promoted a significant reduction in systolic (∼11 mmHg) and diastolic (∼6 mmHg) BP (P < 0.05) that persisted for nearly 2 h after the end of the treatment. The serum concentration of endothelin-1 (ET-1) was significantly lower 30 min after exposure to TT (Control: 2.3 ± 0.1 vs. TT: 1.9 ± 0.09 pg/ml, P = 0.026). In addition, TT induced a marked increase in peak blood flow velocity (∼68%), average velocity (∼76%), and average blood flow (∼102%) in the popliteal artery (P < 0.01). These findings indicate that TT is a practical and effective strategy to reduce BP and circulating ET-1 concentration and enhance leg blood flow in patients with PAD.

Heat therapy promotes the expression of angiogenic regulators in human skeletal muscle.

Heat therapy has been shown to promote capillary growth in skeletal muscle and in the heart in several animal models, but the effects of this therapy on angiogenic signaling in humans are unknown. We evaluated the acute effect of lower body heating (LBH) and unilateral thigh heating (TH) on the expression of angiogenic regulators and heat shock proteins (HSPs) in healthy young individuals. Exposure to LBH (n = 18) increased core temperature (Tc) from 36.9 ± 0.1 to 37.4 ± 0.1°C (P < 0.01) and average leg skin temperature (Tleg) from 33.1 ± 0.1 to 39.6 ± 0.1°C (P < 0.01), but did not alter the levels of circulating angiogenic cytokines and bone marrow-derived proangiogenic cells (CD34(+)CD133(+)). In skeletal muscle, the change in mRNA expression from baseline of vascular endothelial growth factor (VEGF), angiopoietin 2 (ANGPT2), chemokines CCL2 and CX3CL1, platelet factor-4 (PF4), and several members of the HSP family was higher 30 min after the intervention in the individuals exposed to LBH (n = 11) compared with the control group (n = 12). LBH also reduced the expression of transcription factor FOXO1 (P = 0.03). Exposure to TH (n = 14) increased Tleg from 32.8 ± 0.2 to 40.3 ± 0.1°C (P < 0.05) but Tc remained unaltered (36.8 ± 0.1°C at baseline and 36.9 ± 0.1°C at 90 min). This intervention upregulated the expression of VEGF, ANGPT1, ANGPT2, CCL2, and HSPs in skeletal muscle but did not affect the levels of CX3CL1, FOXO-1, and PF4. These findings suggest that both LBH and TH increase the expression of factors associated with capillary growth in human skeletal muscle.

Short-term dietary nitrate supplementation augments cutaneous vasodilatation and reduces mean arterial pressure in healthy humans.

Nitrate supplementation in the form of beetroot juice has been shown to increase nitric oxide (NO) where nitrate can be reduced to nitrite and, subsequently, to NO through both nitric oxide synthase (NOS)-dependent and -independent pathways. We tested the hypothesis that nitrate supplementation would augment the NO component of the cutaneous vasodilatation to local skin heating in young, healthy humans. Participants reported to the lab for pre- and post-supplement local heating protocols. Nitrate supplementation consisted of one shot (70 ml) of beetroot juice (0.45 g nitrate; 5mM) for three days. Six participants were equipped with two microdialysis fibers on the ventral forearm and randomly assigned to lactated Ringer's (control) or continuous infusion of 20mM l-NAME (NOS inhibitor). The control site was subsequently perfused with l-NAME once a plateau in skin blood flow was achieved to quantify NOS-dependent cutaneous vasodilatation. Skin blood flow via laser-Doppler flowmetry (LDF) and mean arterial pressure (MAP) were measured; cutaneous vascular conductance (CVC) was calculated as LDF/MAP and normalized to %CVCmax. Beetroot juice reduced MAP (Pre: 90 ± 1 mmHg vs. Post: 83 ± 1 mmHg) and DBP (Pre: 74 ± 2 mmHg vs. Post: 62 ± 3 mmHg) (P<0.05). The plateau phase of the local heating response at control sites was augmented post-beetroot juice (91 ± 5%CVCmax) compared to pre-beetroot juice (79 ± 2%CVCmax) (P<0.05). There was no difference in the %NOS-dependent vasodilatation from pre- to post-beetroot juice. These data suggest that nitrate supplementation via beetroot juice can reduce MAP and DBP as well as augment NOS-independent vasodilatation to local heating in the cutaneous vasculature of healthy humans.

Augmented reflex cutaneous vasodilatation following short-term dietary nitrate supplementation in humans.

NEW FINDINGS: What is the central question of this study? Nitrate supplementation via beetroot juice has been shown to have several benefits in healthy humans, including reduced blood pressure and increased blood flow to exercising muscle. Whether nitrate supplementation can improve blood flow to the skin in heat-stressed humans has not been investigated. What is the main finding and its importance? Similar to previous studies, we found that nitrate supplementation reduces blood pressure. Nitrate supplementation increased vasodilatation in the skin of heat-stressed humans but did not directly increase skin blood flow. Nitrate supplementation has been shown to increase NO-dependent vasodilatation through both NO synthase (NOS)-dependent and NOS-independent pathways. We hypothesized that nitrate supplementation would augment reflex cutaneous active vasodilatation. Subjects were equipped with two microdialysis fibres on the forearm randomly assigned as control (Ringer solution) or NOS inhibition (20 mm l-NAME). Whole-body heating was performed to raise core temperature by 0.8°C above baseline core temperature. Maximal cutaneous vasodilatation was achieved via 54 mm sodium nitroprusside and local heating to 43°C. Skin blood flow (measured by laser-Doppler flowmetry) and blood pressure were measured. Cutaneous vascular conductance (CVC) was calculated as skin blood flow divided by mean arterial pressure (MAP) and expressed as a percentage of maximal CVC (%CVCmax ). Subjects underwent heat stress before and after nitrate supplementation (3 days of beetroot juice; 5 mm, 0.45 g nitrates per day). During heat stress, MAP was reduced following nitrate supplementation compared with the control conditions (before 88 ± 3 mmHg versus after 78 ± 2 mmHg; P < 0.05); however, resting MAP was not different between conditions (before 88 ± 3 mmHg versus after 83 ± 2 mmHg; P = 0.117). Nitrate supplementation increased plateau CVC at control sites (before 67 ± 2%CVCmax  versus after 80 ± 5%CVCmax ; P = 0.01) but not at l-NAME-treated sites (before 45 ± 4%CVCmax  versus after 40 ± 5%CVCmax ; P = 0.617). There was no change in the calculated percentage of NOS-dependent vasodilatation before and after supplementation (before 59 ± 4% versus after 64 ± 6%; P = 0.577). These data suggest that nitrate supplementation augments CVC and reduces MAP during heat stress.

Endothelial nitric oxide synthase mediates the nitric oxide component of reflex cutaneous vasodilatation during dynamic exercise in humans.

Recent data suggests neuronal nitric oxide synthase (nNOS) mediates the NO component of reflex cutaneous vasodilatation with passive heat stress. We tested the hypothesis that nNOS inhibition would attenuate reflex cutaneous vasodilatation during sustained dynamic exercise in young healthy humans. All subjects first performed an incremental V̇O2, peak test to exhaustion on a custom-built supine cycle ergometer. On a separate day, subjects were instrumented with four intradermal microdialysis fibres on the forearm and each randomly assigned as: (1) lactated Ringer's (control); (2) 20 mm Nω-nitro-l-arginine methyl ester hydrochloride (non-selective NOS inhibitor); (3) 5 mm N-propyl-l-arginine (nNOS inhibitor); and (4) 10 mm N(5)-(1-iminoethyl)-l-ornithine dihydrochloride [endothelial NOS (eNOS) inhibitor]. Following microdialysis placement, subjects performed supine cycling with the experimental arm at heart level at 60% V̇O2, peak for a period sufficient to raise core temperature 0.8°C. At the end of cycling, all microdialysis sites were locally heated to 43°C and sodium nitroprusside was perfused to elicit maximal vasodilatation. Mean arterial pressure, skin blood flow via laser-Doppler flowmetry and core temperature via ingestible telemetric pill were measured continuously; cutaneous vascular conductance (CVC) was calculated as laser-Doppler flowmetry/mean arterial pressure and normalized to maximum. There was no significant difference between control (58 ± 2%CVCmax) and nNOS-inhibited (56 ± 3%CVCmax) sites in response to exercise-induced hyperthermia. The increase in CVC at eNOS-inhibited (41 ± 3%CVCmax) and non-selective NOS-inhibited (40 ± 4%CVCmax) sites were significantly attenuated compared to control and nNOS-inhibited (P < 0.001 all conditions) but there was no difference between eNOS-inhibited and non-selective NOS-inhibited sites. These data suggest eNOS, not nNOS, mediate NO synthesis during reflex cutaneous vasodilatation with sustained dynamic exercise.

Influence of exercise intensity on respiratory muscle fatigue and brachial artery blood flow during cycling exercise.

PURPOSE: During high intensity exercise, both respiratory muscle fatigue and cardiovascular reflexes occur; however, it is not known how inactive limb blood flow is influenced. The purpose of this study was to determine the influence of moderate and high exercise intensity on respiratory muscle fatigue and inactive limb muscle and cutaneous blood flow during exercise. METHODS: Twelve men cycled at 70 and 85 % [Formula: see text] for 20 min. Subjects also performed a second 85 % [Formula: see text] test after ingesting 1,800 mg of N-acetylcysteine (NAC), which has been shown to reduce respiratory muscle fatigue (RMF). Maximum inspiratory pressures (P Imax), brachial artery blood flow (BABF), cutaneous vascular conductance (CVC), and mean arterial pressure were measured at rest and during exercise. RESULTS: Significant RMF occurred with 85 % [Formula: see text] (P Imax, -12.8 ± 9.8 %), but not with 70 % [Formula: see text] (P Imax, -5.0 ± 5.9 %). BABF and BA vascular conductance were significantly lower at end exercise of the 85 % [Formula: see text] test compared to the 70 % [Formula: see text] test. CVC during exercise was not different (p > 0.05) between trials. With NAC, RMF was reduced (p < 0.05) and BABF was significantly higher (~30 %) compared to 85 % [Formula: see text] (p < 0.05). CONCLUSIONS: These data suggest that heavy whole-body exercise at 85 % [Formula: see text] leads to RMF, decreases in inactive arm blood flow, and vascular conductance, but not cutaneous blood flow.

The effect of endothelin a receptor inhibition and biological sex on cutaneous microvascular function in non-Hispanic Black and White young adults.

The purpose of this study was to investigate whether endothelin-A receptor (ETAR) inhibition in non-Hispanic Black (NHB) and White (NHW) young adults depends on biological sex. We recruited females during low hormone (n = 22) and high hormone (n = 22) phases, and males (n = 22). Participants self-identified as NHB (n = 33) or NHW (n = 33). Participants were instrumented with two microdialysis fibers: (1) lactated Ringer's (control) and (2) 500 nM BQ-123 (ETAR antagonist). Local heating was used to elicit cutaneous vasodilation, and an infusion of 20 mM L-NAME to quantify NO-dependent vasodilation. At control sites, NO-dependent vasodilation was lowest in NHB males (46 ± 13 %NO) and NHB females during low hormone phases (47 ± 12 %NO) compared to all NHW groups. Inhibition of ETAR increased NO-dependent vasodilation in NHB males (66 ± 13 %NO), in both groups of females during low hormone phases (NHW, control: 64 ± 12 %NO, BQ-123: 85 ± 11 %NO; NHB, BQ-123: 68 ± 13 %NO), and in NHB females during high hormone phases (control: 61 ± 11 %NO, BQ-123: 83 ± 9 %NO). There was no effect for ETAR inhibition in NHW males or females during high hormone phases. These data suggest the effect of ETAR inhibition on NO-dependent vasodilation is influenced by biological sex and racial identity.

Inhibition of superoxide and iNOS augment cutaneous nitric oxide-dependent vasodilation in non-Hispanic black young adults.

We assessed the combined effect of superoxide and iNOS inhibition on microvascular function in non-Hispanic Black and non-Hispanic White participants (n = 15 per group). Participants were instrumented with four microdialysis fibers: (1) lactated Ringer's (control), (2) 10 µM tempol (superoxide inhibition), (3) 0.1 mM 1400 W (iNOS inhibition), (4) tempol + 1400 W. Cutaneous vasodilation was induced via local heating and NO-dependent vasodilation was quantified. At control sites, NO-dependent vasodilation was lower in non-Hispanic Black (45 ± 9% NO) relative to non-Hispanic White (79 ± 9% NO; p < 0.01; effect size, d = 3.78) participants. Tempol (62 ± 16% NO), 1400 W (78 ± 12% NO) and tempol +1400 W (80 ± 13% NO) increased NO-dependent vasodilation in non-Hispanic Black participants relative to control sites (all p < 0.01; d = 1.22, 3.05, 3.03, respectively). The effect of 1400 W (p = 0.04, d = 1.11) and tempol +1400 W (p = 0.03, d = 1.22) was greater than tempol in non-Hispanic Black participants. There was no difference between non-Hispanic Black and non-Hispanic White participants at 1400 W or tempol + 1400 W sites. These data suggest iNOS has a greater effect on NO-dependent vasodilation than superoxide in non-Hispanic Black participants.

Sensory nerves and nitric oxide contribute to reflex cutaneous vasodilation in humans.

We tested the hypothesis that inhibition of cutaneous sensory nerves would attenuate reflex cutaneous vasodilation in response to an increase in core temperature. Nine subjects were equipped with four microdialysis fibers on the forearm. Two sites were treated with topical anesthetic EMLA cream for 120 min. Sensory nerve inhibition was verified by lack of sensation to a pinprick. Microdialysis fibers were randomly assigned as 1) lactated Ringer (control); 2) 10 mM nitro-L-arginine methyl ester (L-NAME) to inhibit nitric oxide synthase; 3) EMLA + lactated Ringer; and 4) EMLA + L-NAME. Laser-Doppler flowmetry was used as an index of skin blood flow, and blood pressure was measured via brachial auscultation. Subjects wore a water-perfused suit, and oral temperature was monitored as an index of core temperature. The suit was perfused with 50°C water to initiate whole body heat stress to raise oral temperature 0.8°C above baseline. Cutaneous vascular conductance (CVC) was calculated and normalized to maximal vasodilation (%CVC(max)). There was no difference in CVC between control and EMLA sites (67 ± 5 vs. 69 ± 6% CVC(max)), but the onset of vasodilation was delayed at EMLA compared with control sites. The L-NAME site was significantly attenuated compared with control and EMLA sites (45 ± 5% CVC(max); P < 0.01). Combined EMLA + L-NAME site (25 ± 6% CVC(max)) was attenuated compared with control and EMLA (P < 0.001) and L-NAME only (P < 0.01). These data suggest cutaneous sensory nerves contribute to reflex cutaneous vasodilation during the early, but not latter, stages of heat stress, and full expression of reflex cutaneous vasodilation requires functional sensory nerves and NOS.

Effects of biological sex and oral contraceptive pill use on cutaneous microvascular endothelial function and nitric oxide-dependent vasodilation in humans.

The purpose of this study was to evaluate in vivo endothelial function and nitric oxide (NO)-dependent vasodilation between women in either menstrual or placebo pill phases of their respective hormonal exposure [either naturally cycling (NC) or using oral contraceptive pills (OCPs)] and men. A planned subgroup analysis was then completed to assess endothelial function and NO-dependent vasodilation between NC women, women using OCP, and men. Endothelium-dependent and NO-dependent vasodilation were assessed in the cutaneous microvasculature using laser-Doppler flowmetry, a rapid local heating protocol (39°C, 0.1 °C/s), and pharmacological perfusion through intradermal microdialysis fibers. Data are represented as means ± standard deviation. Men displayed greater endothelium-dependent vasodilation (plateau, men: 71 ± 16 vs. women: 52 ± 20%CVCmax, P < 0.01), but lower NO-dependent vasodilation (men: 52 ± 11 vs. women: 63 ± 17%NO, P = 0.05) compared with all women. Subgroup analysis revealed NC women had lower endothelium-dependent vasodilation (plateau, NC women: 48 ± 21%CVCmax, P = 0.01) but similar NO-dependent vasodilation (NC women: 52 ± 14%NO, P > 0.99), compared with men. Endothelium-dependent vasodilation did not differ between women using OCP and men (P = 0.12) or NC women (P = 0.64), but NO-dependent vasodilation was significantly greater in women using OCP (74 ± 11%NO) than both NC women and men (P < 0.01 for both). This study highlights the importance of directly quantifying NO-dependent vasodilation in cutaneous microvascular studies. This study also provides important implications for experimental design and data interpretation.NEW & NOTEWORTHY This study supports differences in microvascular endothelial function and nitric oxide (NO)-dependent vasodilation between women in low hormone phases of two hormonal exposures and men. However, when separated into subgroups of hormonal exposure, women during placebo pills of oral contraceptive pill (OCP) use have greater NO-dependent vasodilation than naturally cycling women in their menstrual phase and men. These data improve knowledge of sex differences and the effect of OCP use on microvascular endothelial function.

Endothelin A receptor inhibition increases nitric oxide-dependent vasodilation independent of superoxide in non-Hispanic Black young adults.

Young non-Hispanic Black adults have reduced microvascular endothelial function compared with non-Hispanic White counterparts, but the mechanisms are not fully elucidated. The purpose of this study was to investigate the effect of endothelin-1 A receptor (ETAR) and superoxide on cutaneous microvascular function in young non-Hispanic Black (n = 10) and White (n = 10) adults. Participants were instrumented with four intradermal microdialysis fibers: 1) lactated Ringer's (control), 2) 500 nM BQ-123 (ETAR antagonist), 3) 10 µM tempol (superoxide dismutase mimetic), and 4) BQ-123 + tempol. Skin blood flow was assessed via laser-Doppler flowmetry (LDF), and each site underwent rapid local heating from 33°C to 39°C. At the plateau of local heating, 20 mM l-NAME [nitric oxide (NO) synthase inhibitor] was infused to quantify NO-dependent vasodilation. Data are means ± standard deviation. NO-dependent vasodilation was decreased in non-Hispanic Black compared with non-Hispanic White young adults (P < 0.01). NO-dependent vasodilation was increased at BQ-123 sites (73 ± 10% NO) and at BQ-123 + tempol sites (71 ± 10%NO) in non-Hispanic Black young adults compared with control (53 ± 13%NO, P = 0.01). Tempol alone had no effect on NO-dependent vasodilation in non-Hispanic Black young adults (63 ± 14%NO, P = 0.18). NO-dependent vasodilation at BQ-123 sites was not statistically different between non-Hispanic Black and White (80 ± 7%NO) young adults (P = 0.15). ETAR contributes to reduced NO-dependent vasodilation in non-Hispanic Black young adults independent of superoxide, suggesting a greater effect on NO synthesis rather than NO scavenging via superoxide.NEW & NOTEWORTHY Endothelin-1 A receptors (ETARs) have been shown to reduce endothelial function independently and through increased production of superoxide. We show that independent ETAR inhibition increases microvascular endothelial function in non-Hispanic Black young adults. However, administration of a superoxide dismutase mimetic alone and in combination with ETAR inhibition had no effect on microvascular endothelial function suggesting that, in the cutaneous microvasculature, the negative effects of ETAR in non-Hispanic Black young adults are independent of superoxide production.

Tissue Derivation and Biological Sex Uniquely Mediate Endothelial Cell Protein Expression, Redox Status, and Nitric Oxide Synthesis.

Human endothelial cells are routinely utilized in cardiovascular research to provide a translational foundation for understanding how the vascular endothelium functions in vivo. However, little attention has been given to whether there are sex specific responses in vitro. Similarly, it is unclear whether endothelial cells derived from distinct tissues behave in a homogenous manner. Herein, we demonstrate that marked sex differences exist within, and between, commonly utilized human primary endothelial cells from healthy donors, with respect to redox status, nitric oxide synthesis, and associated proteins that can mediate their expression. Further, we demonstrate that endothelial cells respond uniquely to inflammatory insult in a sex- and tissue origin-dependent manner. Our findings suggest sex and tissue derivation may need to be considered when studying endothelial cells in vitro as cells derived from distinct tissue and sexes may not behave interchangeably.