Cutaneous Microvascular Function Research Articles

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.

Effect of home-based heat therapy on 24-h blood pressure and cutaneous microvascular function in post-menopausal women with hypertension

Hypertension is a leading risk factor for cardiovascular morbidity and mortality and is often accompanied by microvascular dysfunction. Despite a clear effcacy in men, standard antihypertensive medications are less effective in post-menopausal women. Consequently, adjuvant therapies are needed to improve blood pressure control and microvascular function in post-menopausal women. Heat therapy may fill this therapeutic gap as it has been shown to reduce blood pressure and improve microvascular function in healthy and certain clinical populations. Therefore, the purpose of this study was to test the hypothesis that 8 weeks of home-based heat therapy would improve 24-h blood pressure and cutaneous nitric oxide-dependent vasodilation in post-menopausal women with hypertension. Post-menopausal women (69 ± 5 y) with hypertension were randomized to 8 weeks of sham ( N = 15) or heat therapy ( N = 13). Participants immersed their lower legs ~33 cm into a circulated and temperature-controlled (sham: 35 °C; heat therapy: 42 °C) water bath 4 days per week, and 45 min per session. Blood pressure and cutaneous microvascular function and were assessed before (pre) and after (post) the 8-week intervention. Mean arterial blood pressure was measured across 24-h using an ambulatory monitor. To assess microvascular function, an intradermal microdialysis probe was inserted in the anterior aspect of the lower leg at a site directly exposed to water (immersed) and at another site not directly exposed (non-immersed). Red blood cell flux was measured (laser doppler flowmetry) during cutaneous hyperemia induced by 39 °C local heating. N(G)-nitro-L-arginine methyl ester (L-NAME; 20mM) was then infused in each probe until a nadir in red blood cell flux was achieved. Cutaneous vascular conductance was calculated as red blood cell flux divided by mean arterial pressure and normalized to maximal vasodilation (42 °C heating + 56 mM sodium nitroprusside; CVC%max). Nitric oxide-dependent dilation was calculated as the difference between CVC%max measured during the 39 °C plateau and the L-NAME nadir. Mean arterial blood pressure did not differ across time or between groups (sham: pre, 96 ± 5 mmHg vs. post, 96 ± 6 mmHg; heat therapy: pre, 97 ± 4 mmHg vs. 99 ± 7 mmHg; P = 0.5 for interaction). Cutaneous vasodilation induced by local heating did not differ across time for either group (sham: pre, 60 ± 19 CVC%max vs. post, 64 ± 12 CVC%max; heat therapy: pre, 68 ± 15 CVC%max vs. post, 63 ± 13 CVC%max) or between immersed and non-immersed sites ( P = 0.9 for interaction). Similarly, nitric oxide-dependent vasodilation did not differ across time or between sites for either group ( P = 1.0 for interaction). Taken together, 8 weeks of home-based heat therapy does not improve blood pressure or cutaneous microvascular function in post-menopausal women with hypertension. This work was supported by grants from the National Institutes of Health (T32 AG020494; R01AG059314; F32HL167556) and the American Heart Association (TPA958179). 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.

Inhibition of NF-κB Activation Improves Non-Nitric Oxide-Mediated Cutaneous Microvascular Function in Reproductive-Aged Healthy Women

PURPOSE: The human cutaneous circulation is used as an in vivo bioassay to examine mechanisms of systemic vascular function and dysfunction in health and disease. In cohorts of patients with accelerated cardiovascular disease risk, systemic interventions to investigate inflammatory mechanisms [e.g., oral salsalate; nuclear factor kappa-B (NF-κB) inhibitor] have been used to elucidate mechanisms underlying microvascular dysfunction. In healthy control subjects, inhibition of inflammatory mechanisms modestly reduces microvascular function. We hypothesize that inhibition of NF-κB activation may impair nitric oxide (NO)-mediated cutaneous microvascular function in reproductive-aged healthy women. METHODS: In a randomized, single-blind, placebo-controlled design, oral salsalate (1500mg/b.i.d./5 days) was used to assess the impact of systemic inflammation on cutaneous microvascular function. Two intradermal microdialysis fibers were placed into the ventral forearm skin of eleven healthy women [Mean (SEM): 34 (2) yrs]. Laser-Doppler flowmetry was used to measure cutaneous blood flow while increasing concentrations of acetylcholine (10−10 to 10−1 M; endothelium-dependent vasodilator) were perfused with a control (lactated Ringer’s) or a NO synthase inhibitor (15 mM NG-nitro-L-arginine methyl ester). Following the dose-response protocol, maximal cutaneous vasodilation was induced by increasing local skin temperature to 43°C and perfusing 28 mM sodium nitroprusside. Cutaneous vascular conductance (CVC) was calculated as the quotient of red blood cell flux over mean arterial pressure and normalized as a percentage of the site-specific maximum (%CVCmax). The NO-dependent contribution was calculated as the difference between the area under the dose-response curve (AUC) of the control and the NO synthase-inhibited sites. RESULTS: There was an overall main effect of salsalate treatment ( p < 0.001). Both the control and NO synthase-inhibited sites shifted upwards following salsalate treatment (Placebo - Control: 45.78 (8.81)% vs NO synthase inhibited: 33.62 (8.10)%; Salsalate - Control: 56.30 (8.48)% vs NO synthase inhibited: 41.57 (7.85)%; both p < 0.05). There was no change in the NO-dependent contribution between treatments (Placebo: 164.30 (35.40) AU vs Salsalate: 180.30 (51.17) AU; p=0.7028).CONCLUSION: Inhibition of NF-κB activation improved cutaneous microvascular function in reproductive-aged healthy women. This improvement was mediated via non-nitric oxide-dependent mechanisms. Supported by NIH Grant R01 HL161000 (LMA) and Diversity Supplement R01 HL161000-02S2 (VGC). 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.

BRACHIAL, FEMORAL, AND SKIN HAEMODYNAMIC RESPONSES TO WALKING IN HOT CONDITIONS: COMPARISON BETWEEN MALES AND FEMALES

INTRODUCTION & AIMS Heat exposure induces acute changes in arterial function, but sex differences have not been fully addressed. METHODS Participants walked (5km/h; 2% incline) in a climate chamber (42°C;50%RH) for 120mins. Cutaneous microvascular function (laser doppler flowmetry), conduit artery haemodynamics (Doppler ultrasound) and core temperature were measured at baseline, and every 30min. RESULTS 14♂ and 15♀ completed 120min. At baseline, differences in core temperature (Tc) between males and females were not significant (37.2±0.1 vs 37.0±0.1°C; P=0.06). Across all 5 timepoints, females exhibited larger Tc than males (P=0.019). At baseline, males had larger brachial (3.89±0.11 vs 3.13±0.09mm, P<0.001) and femoral (6.22±0.16 vs 5.29±0.14mm, P=0.001) diameters than females. A significant interaction (P=0.047) indicated that brachial diameter increased more in response to heat exertion than in males, whereas no sex difference was apparent in femoral diameter change. Males and females had similar baseline brachial flows (♂80.1±11.2 vs ♀57.0±7.09ml/min, P=0.087), but males had larger baseline femoral flows (♂263.0±23.9 vs ♀151.5±18.6 ml/min, P=0.010). No sex differences were apparent in the terms of the increases in brachial or femoral flows. Finally, at baseline males and females had similar skin blood flux (♂22.6±2.7 vs ♀18.3±2.9PU), but males demonstrated larger increases during heat exertion (P=0.029). CONCLUSIONS Males exhibit larger baseline artery diameters and flows in vessel beds feeding active (femoral) and inactive (brachial) limbs. In response to heat exertion, men and women exhibit similar increases in conduit diameter and flow to active muscle beds (femoral responses). In the inactive forearms, which reflect thermoregulatory responses, females had larger brachial artery diameter changes, but blood flow responses were similar between the sexes and men demonstrated larger increases in skin perfusion. These data indicate that responses to heat exertion differ in the upper and lower limbs, with sex-differences apparent in each of these territories, and at distinct levels of the arterial hierarchy.

Divergent Vasodilator Mechanisms to Endothelial-Dependent Agonists with Advancing Age

Introduction: Microvascular function is maintained by a number of vasodilating factors, with nitric oxide (NO) and endothelial hyperpolarizing factors (EDHF) predominating. Advancing age is an independent risk factor in the development of cardiovascular disease, and NO-mediated vasodilation declines, or is unchanged, depending on the vascular bed examined, number of cardiovascular risk factors, or specific endothelial-dependent agonist used. Mechanisms contributing to cutaneous microvascular dysfunction with age have been attributed largely to reductions in NO signaling, but the role of EDHF-mediated dilation, particularly to acetylcholine (ACh), remains unclear. The purpose of this study was to determine the endothelial mechanisms contributing to age-induced cutaneous microvascular function and compare cutaneous microvascular function responses to those from isolated adipose arteriole preparations. We hypothesized that cutaneous microvascular vasodilation to ACh in older adults will be mediated primarily by EDHFs relative to young adults and that isolated adipose arteriole preparations will corroborate these findings. Methods: Four intradermal microdialysis fibers were placed in the skin of the ventral forearm of 9 young (3F/6M; 29±7 yrs) and 3 older adults (3F/0M; 59±11 yrs) for infusion of Ringer’s solution; L-NAME (10 mM), an NO synthase inhibitor; tetraethylammonium chloride (TEA; 50 mM), a non-specific K+ channel inhibitor; and a combination of L-NAME and TEA. Laser Doppler flowmetry and brachial mean arterial pressure were measured during infusion of ACh (10 mM and 100 mM) and in response to local heating to 39°C. Maximal vasodilation was assessed with heating to 43°C and infusion of sodium nitroprusside (28 mM). Adipose resistance arterioles for pressure myography were obtained from a gluteal biopsy or from surgical discard tissue, which were pre-constricted (ET-1), and ACh responses (10−9–10−4 M) were assessed in the presence of the above inhibitors. Cutaneous vascular conductance (CVC) and isolated arteriole responses are presented as % maximum vasodilation. Results: In response to local heating in young adults, L-NAME reduced vasodilator magnitude (Ringers 69.0±18.1% vs. L-NAME 30.3±12.1%; p< 0.05) while TEA did not have any effect (69±18% vs. 49±28%; p=0.20). Combined L-NAME and TEA reduced vasodilation (69±18% vs. 19±6%; p<0.05). Conversely, vasodilator magnitude to ACh was not different across the Ringers, L-NAME, or TEA sites (p=0.93-0.94), while combined inhibition of NOS and K+ channels with L-NAME and TEA, respectively, reduced vasodilator responsiveness (p<0.05). In isolated resistance arterioles, there were no differences in %max dilation to ACh across inhibitor sites (p=0.19) in young adults. In older adults, neither independent nor combined inhibition of NOS or K+ channels impacted vasodilator responses to local heating, while vasodilator magnitude to ACh was most impacted by combined inhibition with L-NAME and TEA (83±14% vs. 32±15%; p<0.05). Conclusion: Our data demonstrate that vasodilator plasticity in response to local heating is divergent with advancing age, relying on non-NO or K+ mechanisms relative to young adults, while NO and K+ mechanisms are suffcient to maintain ACh-mediated vasodilation. These findings further support the concept of diversity in vasodilator mechanisms within the microvasculature. NHLBI K99-HL161491 (WEH), K08-HL150340 (JJM), R01-HL160752 (JKF), R01-HL133029 (AB), and NICHD R01-HD099340 (MJD). 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.

Nitric oxide‐mediated cutaneous microvascular function is not altered in middle‐aged‐to‐older adults following mild SARS‐CoV‐2 infection: A pilot study

We tested the hypothesis that post-COVID-19 adults (PC) would have impaired cutaneous nitric oxide (NO)-mediated vasodilation compared to controls (CON). We performed a cross-sectional study including 10 (10 F/0 M, 69 ± 7 years) CON and 7 (2 F/5 M, 66 ± 8 years) PC (223 ± 154 days post-diagnosis). COVID-19 symptoms severity (survey) was assessed (0-100 scale for 18 common symptoms). NO-dependent cutaneous vasodilation was induced by a standardized 42°C local heating protocol and quantified via perfusion of 15 mM NG-nitro-L-arginine methyl ester during the plateau of the heating response (intradermal microdialysis). Red blood cell flux was measured with laser-Doppler flowmetry. Cutaneous vascular conductance (CVC = flux/mm Hg) was presented as a percentage of maximum (28 mM sodium nitroprusside +43°C). All data are means ± SD. The local heating plateau (CON: 71 ± 23% CVCmax vs. PC: 81 ± 16% CVCmax , p = 0.77) and NO-dependent vasodilation (CON: 56 ± 23% vs. PC: 60 ± 22%, p = 0.77) were not different between groups. In the PC group neither time since diagnosis nor peak symptom severity (46 ± 18 AU) correlated with NO-dependent vasodilation (r < 0.01, p = 0.99 and r = 0.42, p = 0.35, respectively). In conclusion, middle-aged and older adults who have had COVID-19 did not have impaired NO-dependent cutaneous vasodilation. Additionally, in this cohort of PC, neither time since diagnosis nor symptomology were related to microvascular function.

Within-limb variation in skin pigmentation does not influence cutaneous vasodilation.

Ultraviolet radiation (UVR) exposure acutely reduces nitric oxide (NO)-dependent cutaneous vasodilation. In addition, increased constitutive skin melanin is associated with attenuated NO-dependent cutaneous vasodilation. However, the impact of within-limb variation in skin melanization, associated with seasonal UVR exposure, on NO-dependent cutaneous vasodilation is unknown. We investigated the effect of within-limb variation in skin melanin on NO-dependent cutaneous vasodilation. Intradermal microdialysis fibers were placed in the inner-upper arm, ventral forearm, and dorsal forearm of seven adults (33 ± 14 yr; 4 M/3 F) with constitutively light skin pigmentation. Melanin-index (M-index; an index of skin pigmentation), measured via reflectance spectrophotometry, confirmed differences in sun exposure among sites. A standardized local heating (42°C) protocol induced cutaneous vasodilation. After attaining a stable elevated blood flow plateau, 15 mM NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibitor) was infused to quantify the NO contribution. Laser-Doppler flowmetry (LDF) measured red cell flux and cutaneous vascular conductance (CVC = LDF/mean arterial pressure) and was normalized to maximal (%CVCmax; 28 mM sodium nitroprusside + 43°C local heating). Dorsal forearm M-index was higher [50.5 ± 11.8 au (arbitrary units)] compared with the ventral forearm (37.5 ± 7.4 au; P ≤ 0.03) and upper arm (30.0 ± 4.0 au; P ≤ 0.001) M-index. Cutaneous vasodilation responses to local heating were not different among sites (P ≥ 0.12). Importantly, neither the magnitude of the local heating plateau (dorsal: 85 ± 21%; ventral: 70 ± 21%; upper: 87 ± 15%; P ≥ 0.16) nor the NO-mediated component of that response (dorsal: 59 ± 15%; ventral: 54 ± 13%; upper: 55 ± 11%; P ≥ 0.79) was different among sites. These data suggest that within-limb differences in skin pigmentation secondary to seasonal UVR exposure do not alter NO-dependent cutaneous vasodilation.NEW & NOTEWORTHY Locally derived endothelial nitric oxide (NO) contributes to the full expression of cutaneous vasodilation responses. Acute ultraviolet radiation (UVR) exposure attenuates NO-mediated vasodilation of the cutaneous microvasculature. Our findings suggest that in constitutively lightly pigmented skin, variation in skin melanin due to seasonal exposure to UVR does not alter the NO contribution to cutaneous vasodilation. Seasonal UVR exposure does not impact the NO-mediated cutaneous microvascular function.

Elevations in sweat sodium concentration following ischemia-reperfusion injury during passive heat stress.

Renal ischemia-reperfusion (I/R) injury results in damage to the renal tubules and causes impairments in sodium [Na+] reabsorption. Given the inability to conduct mechanistic renal I/R injury studies in vivo in humans, eccrine sweat glands have been proposed as a surrogate model given the anatomical and physiological similarities. We tested the hypothesis that sweat Na+ concentration is elevated following I/R injury during passive heat stress. We also tested the hypothesis that I/R injury during heat stress will impair cutaneous microvascular function. Fifteen young healthy adults completed ∼160 min of passive heat stress using a water-perfused suit (50°C). At 60 min of whole body heating, one upper arm was occluded for 20 min followed by a 20-min reperfusion. Sweat was collected from each forearm via an absorbent patch pre- and post-I/R. Following the 20-min reperfusion, cutaneous microvascular function was measured via local heating protocol. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux/mean arterial pressure and normalized to CVC during local heating to 44°C. Na+ concentration was log-transformed and data were reported as a mean change from pre-I/R (95% confidence interval). Changes in sweat sodium concentration from pre-I/R differed between arms post-I/R (experimental arm: +0.97 [+0.67 - 1.27] [LOG] Na+; control arm: +0.68 [+0.38 - 0.99] [LOG] Na+; P < 0.01). However, CVC during the local heating was not different between the experimental (80 ± 10%max) and control arms (78 ± 10%max; P = 0.59). In support of our hypothesis, Na+ concentration was elevated following I/R injury, but likely not accompanied by alterations in cutaneous microvascular function.NEW & NOTEWORTHY In the present study, we have demonstrated that sweat sodium concentration is elevated following ischemia-reperfusion injury during passive heat stress. This does not appear to be mediated by reductions in cutaneous microvascular function or active sweat glands, but may be related to alterations in local sweating responses during heat stress. This study demonstrates a potential use of eccrine sweat glands to understand sodium handling following ischemia-reperfusion injury, particularly given the challenges of in vivo studies of renal ischemia-reperfusion injury in humans.

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.

Acute impact of aerobic exercise on local cutaneous thermal hyperaemia.

Little is known about the acute changes in cutaneous microvascular function that occur in response to exercise, the accumulation of which may provide the basis for beneficial chronic cutaneous vascular adaptations. Therefore, we examined the effects of acute exercise on cutaneous thermal hyperaemia. Twelve healthy, recreationally active participants (11 male, 1 female) performed 30-minute cycling at 50% (low-intensity exercise, LOW) or 75% (high-intensity exercise, HIGH) maximum heart rate. Laser Doppler flowmetry (LDF) and rapid local skin heating were used to quantify cutaneous thermal hyperaemia before (PRE), immediately following (IMM) and 1-h (1HR) after exercise. Baseline, axon reflex peak, axon reflex nadir, plateau, maximum skin blood flow responses to rapid local heating (42°C for 30-min followed by 44°C for 15-min) at each stage were assessed and indexed as cutaneous vascular conductance [CVC=flux/mean arterial blood pressure (MAP), PU·mmHg-1], and expressed as a percentage of maximum (%CVCmax). Exercise increased heart rate (HR), MAP and skin blood flow (all P<0.001), and to a greater extent during HIGH (all P<0.001). The axon reflex peak and nadir were increased immediately and 1-h after exercise (all comparisons P<0.01 vs. PRE), which did not differ between intensities (peak: P=0.34, axon reflex nadir: P=0.91). The endothelium-dependent plateau response was slightly elevated after exercise (P=0.06), with no effect of intensity (P=0.58) nor any interaction effect (P=0.55). CONCLUSION: Exercise increases cutaneous microvascular axonal responses to local heating for up to 1-h, suggesting an augmented sensory afferent function post-exercise. Acute exercise may only modestly affect endothelial function in cutaneous microcirculation.

Seven days of statin treatment improves nitric-oxide mediated endothelial-dependent cutaneous microvascular function in women with endometriosis.

Endometriosis is associated with systemic inflammation and increased risk of cardiovascular disease (CVD). Endothelial dysfunction is one of the first manifestations of CVD but is unexplored in women with endometriosis. HMG-CoA-reductase inhibitors (statins) exert potent anti-inflammatory effects, and have been proposed as an adjunctive therapy in women with endometriosis. We hypothesized that microvascular endothelial function would be impaired in otherwise healthy women with endometriosis mediated by reduced nitric oxide (NO)-dependent dilation and that short term statin administration would improve endothelial function. In 8 healthy control (HC: 33±9yr) and 8 women with endometriosis (EN: 34±9yr), laser-Doppler flux (LDF) was measured continuously during graded intradermal microdialysis perfusion of the endothelium-dependent agonist acetylcholine (Ach: 10-10-10-1M) alone and in combination with the NO synthase inhibitor (L-NAME: 0.015M). 6 EN repeated the microdialysis experiment following 7days of oral atorvastatin treatment (10mg). Cutaneous vascular conductance was calculated (CVC=LDF*mmHg-1) and normalized to site-specific maximum (28mM sodium nitroprusside, 43°C). The NO-dependent dilation was calculated as the difference between the areas under the dose response curves. Ach-induced vasodilation was blunted in women with endometriosis (main effect p<0.01), indicating impaired endothelial function. NO-dependent vasodilation was also reduced in women with endometriosis (HC: 217±120.3 AUC vs. EN: 88±97 AUC, p=0.03). Oral atorvastatin improved Ach-induced (main effect p<0.01) and NO-dependent (295±153 AUC; p=0.05) vasodilation in women with endometriosis. Microcirculatory endothelium-dependent vasodilation is impaired in women with endometriosis, mediated in part by reductions in NO. Short-term oral atorvastatin improved endothelium-dependent vasodilation, suggesting that statin therapy may be a viable intervention strategy to mitigate accelerated CVD risk in women with endometriosis.

Cutaneous Microvascular Function Following Ischemia-reperfusion Injury During Passive Heat Stress

Increased kidney injury risk during heat stress is mediated, in part, by renal ischemia-reperfusion (IR) injury. However, in vivo studies are not possible in humans. Eccrine sweat glands and the cutaneous circulation have been proposed as a model of the nephron given the physiological similarities (e.g., sodium reabsorption). We previously reported impairments in sweat gland sodium reabsorption following IR injury during passive heat stress, which could be contributed to by alterations in cutaneous microvascular function (i.e., oxygen supply). PURPOSE: Test the hypothesis that forearm cutaneous microvascular function is impaired following IR injury during passive heat stress. METHODS: Fifteen healthy subjects (10 women; age: 25 ± 3 y; body mass index: 23.7 ± 3.5 kg·m2) completed a cross-body design experiment consisting of ~160 min of passive heat stress (core body temperature: +1.5 ± 0.2 °C) utilizing a suit perfused with 50 °C water. At 60 min of whole-body heating, one forearm arm (randomized) was occluded (220 mmHg) for 20 min followed by reperfusion. Local thermal hyperemia tests were performed 20 min following reperfusion using a standard local heating protocol (39 °C for 40 min + 44 °C for 20 min). Forearm skin blood flow was measured continuously at two sites (one heated, one control) on each forearm using laser-Doppler flowmetry. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux/mean arterial pressure (PU/mmHg) and normalized to maximal CVC during local heating to 44 °C. Data are presented as mean ± SD. RESULTS: Maximal CVC was not different between IR and control arms (3.2 ± 0.7 vs. 3.4 ± 0.8 PU/mmHg, respectively; p = 0.48). Approximately 60 min after reperfusion, CVC at the control sites were not different between IR and control arms (78 ± 11 vs. 76 ± 11%, respectively; p = 0.65). Following 40 min of local heating (39 °C), CVC was not different between IR and control arms (80 ± 10 vs. 78 ± 10%, respectively; p = 0.59). CONCLUSION: Cutaneous microvascular function was maintained following IR during passive heat stress indicating that impaired sodium reabsorption is not mediated by reductions in oxygen supply necessary for active transport of sodium. Rather, a disruption in sodium transporter activity may mediate increased sodium excretion, but this remains unknown.

Skin pigmentation is negatively associated with circulating vitamin D concentration and cutaneous microvascular endothelial function.

Darkly pigmented individuals are at the greatest risk of hypovitaminosis D, which may result in microvascular endothelial dysfunction via reduced nitric oxide (NO) bioavailability and/or increased oxidative stress and inflammation. We investigated the associations among skin pigmentation (M-index; skin reflectance spectrophotometry), serum vitamin D concentration [25(OH)D], circulating inflammatory cytokine (TNF-α, IL-6, and IL-10) concentrations, and the NO contribution to local heating-induced cutaneous vasodilation (%NO-mediated vasodilation) in a diversely pigmented cohort of young adults. An intradermal microdialysis fiber was placed in the forearms of 33 healthy adults (14 men/19 women; 18-27 yr; M-index, 30-81 AU) for local delivery of pharmacological agents. Lactated Ringer's solution was perfused through the fiber during local heating-induced (39°C) cutaneous vasodilation. After attaining stable elevated blood flow, 15 mM NG-nitro-l-arginine methyl ester (l-NAME; NO synthase inhibiter) was infused to quantify %NO-mediated vasodilation. Red cell flux was measured (laser-Doppler flowmetry; LDF) and cutaneous vascular conductance (CVC = LDF/MAP) was normalized to maximal (%CVCmax; 28 mM sodium nitroprusside + 43°C). Serum [25(OH)D] and circulating cytokines were analyzed by ELISA and multiplex assay, respectively. M-index was negatively associated with [25(OH)D] (r = -0.57, P < 0.0001) and %NO-mediated vasodilation (r = -0.42, P = 0.02). Serum[25(OH)D] was positively related to %NO (r = 0.41, P = 0.02). Controlling for [25(OH)D] weakened the association between M-index and %NO-mediated dilation (P = 0.16, r = -0.26). There was a negative curvilinear relation between [25(OH)D] and circulating IL-6 (r = -0.56, P < 0.001), but not TNF-α or IL-10 (P ≥ 0.14). IL-6 was not associated with %NO-mediated vasodilation (P = 0.44). These data suggest that vitamin D insufficiency/deficiency may contribute to reduced microvascular endothelial function in healthy, darkly pigmented young adults.NEW & NOTEWORTHY Endothelial dysfunction, an antecedent to hypertension and overt CVD, is commonly observed in otherwise healthy Black adults, although the underlying causes remain unclear. We show that reduced vitamin D availability with increasing degrees of skin pigmentation is associated with reduced microvascular endothelial function, independent of race or ethnicity, in healthy young adults. Greater prevalence of vitamin D deficiency in more darkly pigmented individuals may predispose them to increased risk of endothelial dysfunction.

Effect of Oral Contraceptive Phase on Mechanisms of Cutaneous Microvascular Function

While the effect of oral contraceptive (OC) use on endothelial function has been previously studied, precise mechanisms of endothelial function in this group of women remains unclear. The purpose of this study was to investigate the contribution of cyclooxygenase (COX), endothelial‐derived hyperpolarizing factors (EDHF), and nitric oxide (NO) to cutaneous microvascular function in women during the low hormone (LH) and high hormone (HH) phases of OC. Five young, healthy women taking monophasic, combined OC of any generation visited the lab twice: once during the LH (d 1‐2 of placebo pills) and once during the HH phase (d 3‐6+ of active pills). Participants were instrumented with three microdialysis fibers, and each site was randomized as control (lactated Ringer's), COX inhibition (10 mM ketorolac), or EDHF inhibition (50 mM tetraethylammonium, TEA). Laser‐Doppler flowmetry and local heaters were used to measure skin blood flow and induce local thermal hyperemia, respectively. Each site was heated from 33°C to 39°C at a rate of 0.1°C/sec. Once a plateau to local heating was established, 20 mM L‐NAME, a NO synthase inhibitor, was infused at each site to quantify NO‐dependent vasodilation. Maximal vasodilation was induced by heating the skin to 43°C and infusing 28 mM sodium nitroprusside. Data are mean ± SD. For baseline, there was a main effect of OC phase (p = 0.03) and treatment (p &lt; 0.001) but no interaction effect (p = 0.21) such that baseline was increased at COX‐inhibited sites (23 ± 3 %CVCmax) compared with control (14 ± 6 %CVCmax; p = 0.03) during the HH phase. For initial peak, there was a main effect of treatment (p &lt; 0.001) but no effect of OC phase (p = 0.99) or interaction effect (p = 0.59) such that initial peak was decreased at EDHF‐inhibited sites during the HH phase (17 ± 6 %CVCmax) compared with control (51 ± 23 %CVCmax; p = 0.02). For local heating plateau, there was a main effect of treatment (p &lt; 0.001) but no effect of OC phase (p = 0.28) or interaction effect (p = 0.21) such that plateau was decreased at EDHF‐inhibited sites during both phases (LH: 18 ± 12 %CVCmax; HH: 20 ± 9 %CVCmax) compared with respective control (LH: 63 ± 13 %CVCmax; HH: 67 ± 23 %CVCmax) and ketorolac sites (LH: 58 ± 21 %CVCmax; HH: 71 ± 12 %CVCmax; all comparisons: p &lt; 0.01). For %NO, there was no observed effect of OC phase (p = 0.77), treatment (p = 0.21), or interaction (p = 0.09). While not statistically significant, there was a large effect size for %NO between LH and HH phases at control sites (LH: 72 ± 15 %NO; HH: 50 ± 23 %NO; Cohen’s d = 1.05). During the LH phase, large effect sizes were observed between control and TEA (48 ± 14 %NO; d = 1.65) sites and control and ketorolac (54 ± 22 %NO; d = 0.96) sites. During the HH phase, a large effect size was observed between control and ketorolac (69 ± 17 %NO; d = 0.94) sites. These preliminary data suggest mechanisms underlying endothelial function vary across OC phase in women. While overall endothelial function (i.e., magnitude of local heating plateau) is similar between OC phases, there may be basal constriction (i.e., increased baseline with COX inhibition) and reduced NO‐dependent dilation during the HH phase. This shift in mechanisms underlying endothelial function in women using OC may contribute to cardiovascular health outcomes.

Cutaneous Microvascular Endothelial Function: Effects of Sex and Menopause Stage

BackgroundEndothelial dysfunction and increased arterial stiffness are both associated with increased risk of cardiovascular events and mortality.Vascular aging has been characterized by deteriorating endothelial function accompanied by increasing vascular stiffness that occurs with increasing chronological age, with the onset of these changes varying by sex. Deteriorating large artery vascular function has been reported across the menopause transition in women, but it is unclear if this relationship extends to the cutaneous microvasculature, which may have critical implications for both thermal regulation and general cardiovascular health.Purpose &amp; HypothesisThe primary purpose of this study was to determine the impact of sex and menopausal stage on cutaneous endothelial dependent (EDD) vasodilation. We hypothesized that cutaneous EDD vasodilation would decrease in women in a graded manner across the transition from pre, to peri, to postmenopause with differences compared to age matched men. Secondly, we hypothesized that there would be no differences in cutaneous EDD vasodilation between natural and surgical (i.e., hysterectomy) menopause.MethodsPremenopausal, (n=8, 44±5y), perimenopausal (n=6, 51±2y), and postmenopausal women (n=9, 60±7y) as well as men age matched to the postmenopausal group (n=6, 59±7y) volunteered for this study. Cutaneous EDD vasodilation was measured by local iontophoresis of Acetylcholine (Ach) administration into the forearm vasculature. Red blood cell flux was determined by laser Doppler flowmetry at baseline and after 200µL of Ach. CVC was calculated as the quotient of red blood cell flux and mean arterial pressure and expressed as the percentage increased from baseline (CVC%). Differences were determined using a 1‐way ANOVA. Data are presented as mean ± standard error.ResultsForearm microvascular CVC% was significantly different among groups (P=0.01) after Ach administration. Post hoc analyses revealed an attenuated CVC% response in postmenopausal women (691±150%; P=0.02) and men (733±127%; P=0.05) compared to premenopausal women (1398±247%). There were no differences detected between peri‐ and premenopausal women (1290±140% vs. 1398±247%; P=0.95). Further, we performed a subanalysis in our postmenopausal group which included surgical (n=3) and natural (n=8) postmenopausal women. No differences were present between surgical and natural postmenopausal women (P=0.87), while both the surgical (646±163%; P=0.08) and natural (713±221%; P=0.05) postmenopausal women appeared to have decreased CVC responses compared to premenopausal women (1398±247%).ConclusionsOur findings indicate that cutaneous EDD vasodilation decreases from pre‐ to postmenopause in healthy women. Our data suggests that decreases in microvascular function agrees with reported decrements in large vessel vascular function associated with the menopause transition.

Delayed Cutaneous Microvascular Responses With Non-consecutive 3 Days of Remote Ischemic Preconditioning.

The optimal frequency and duration of remote ischemic preconditioning (RIPC) that augments microvascular function is unknown. A single bout of RIPC increases cutaneous endothelial function for ∼48 h, whereas 1 week of daily RIPC bouts improves more sustained endothelium-independent function. We hypothesized that 3 days of RIPC separated by rest days (3QOD RIPC) would result in sustained increases in both endothelium-dependent and endothelium-independent functions. Cutaneous microvascular function was assessed in 13 healthy young participants (aged 20.5 ± 3.9 years; 5 males, 8 females) before 3QOD and then 24, 48, and 72 h and a week after 3QOD. RIPC consisted of four repetitions of 5 min of blood flow occlusion separated by 5 min of reperfusion. Skin blood flow responses to local heating (Tloc = 42°C), acetylcholine (Ach), and sodium nitroprusside (SNP) were measured using laser speckle contrast imaging and expressed as cutaneous vascular conductance (CVC = PU⋅mmHg–1). Local heating-mediated vasodilation was increased 72 h after 3QOD and the increased responsivity persisted a week later (1.08 ± 0.24 vs. 1.34 ± 0.46, 1.21 ± 0.36 PU⋅mmHg–1; ΔCVC, pre-RIPC vs. 72 h, a week after 3QOD; P = 0.054). Ach-induced cutaneous vasodilation increased a week after 3QOD (0.73 ± 0.41 vs. 0.95 ± 0.49 PU⋅mmHg–1; ΔCVC, pre-RIPC vs. a week after 3QOD; P < 0.05). SNP-induced cutaneous vasodilation increased 24 h after 3QOD (0.47 ± 0.28 vs. 0.63 ± 0.35 PU⋅mmHg–1; ΔCVC, pre-RIPC vs. 24 h; P < 0.05), but this change did not persist thereafter. Thus, 3QOD induced sustained improvement in endothelium-dependent vasodilation but was not sufficient to sustain increases in endothelium-independent vasodilation.

Sex features of cutaneous microvasculature in healthy working-age people

Aim. To study sex characteristics of cutaneous microvascular structure and function in a cohort of healthy working-age people without cardiovascular diseases.Material and methods. The study included 35 healthy men (42±4 years) and 34 women (41 ±5 years). The cardiovascular system was assessed in all patients. The microcirculatory bed of the skin was investigated by the following non-invasive methods: 1) computerized video capillaroscopy; 2) laser Doppler flowmetry; 3) photoplethysmography.Results. According to computerized video capillaroscopy in men, compared with women, there was a smaller number of both functioning capillaries (78 vs 86 capillaries/mm2, respectively (p&lt;0,05)) and their total number (100 vs 120 capillaries/mm2, respectively (p&lt;0,001)). Against the background of a decrease in capillary density in men, there was a higher skin interstitial hydration — 113 vs 96 gm (p&lt;0,005) in men than in women. At the level of precapillary arterioles, where humoral tone regulation prevails. Laser Doppler flowmetry revealed lower pulse amplitude in men than in women — 0,87 vs 1,02 pf, respectively (p&lt;0,05), which indicates a lower arterial blood inflow to exchange microvessels. Against this background, the constrictor response of precapillary arterioles to a sympathetic nervous system stimulation in men is higher than in women — 45% vs 40%, respectively (p&lt;0,05). At the level of large arterioles, where neural tone regulation prevails, photoplethysmography revealed lower augmentation index standardized at a heart rate in men (-4,6 vs 1,7%, respectively, p&lt;0,05), which indicates lower rigidity of muscular vessels in men.Conclusion. In working-age healthy people, sex differences are noted at all cutaneous microvascular levels, which must be taken into account when planning studies.

Nitric oxide-mediated cutaneous microvascular function is not altered in young adults following mild-to-moderate SARS CoV-2 infection.

Vascular dysfunction has been reported in adults who have recovered from COVID-19. To date, no studies have investigated the underlying mechanisms of persistent COVID-19-associated vascular dysfunction. Our purpose was to quantify nitric oxide (NO)-mediated vasodilation in healthy adults who have recovered from SARS-CoV-2 infection. We hypothesized that COVID-19-recovered adults would have impaired NO-mediated vasodilation compared with adults who have not had COVID-19. In methods, we performed a cross-sectional study including 10 (5 men/5 women, 24 ± 4 yr) healthy control (HC) adults who were unvaccinated for COVID-19, 11 (4 men/7 women, 25 ± 6 yr) healthy vaccinated (HV) adults, and 12 (5 men/7 women, 22 ± 3 yr) post-COVID-19 (PC, 19 ± 14 wk) adults. COVID-19 symptoms severity (survey) was assessed. A standardized 39°C local heating protocol was used to assess NO-dependent vasodilation via perfusion (intradermal microdialysis) of 15 mM NG-nitro-l-arginine methyl ester during the plateau of the heating response. Red blood cell flux was measured (laser-Doppler flowmetry) and cutaneous vascular conductance (CVC = flux/mmHg) was expressed as a percentage of maximum (28 mM sodium nitroprusside + 43°C). In results, the local heating plateau (HC: 61 ± 20%, HV: 60 ± 19%, PC: 67 ± 19%, P = 0.80) and NO-dependent vasodilation (HC: 77 ± 9%, HV: 71 ± 7%, PC: 70 ± 10%, P = 0.36) were not different among groups. Neither symptom severity (25 ± 12 AU) nor time since diagnosis correlated with the NO-dependent vasodilation (r = 0.46, P = 0.13; r = 0.41, P = 0.19, respectively). In conclusion, healthy adults who have had mild-to-moderate COVID-19 do not have altered NO-mediated cutaneous microvascular function.NEW & NOTEWORTHY Healthy young adults who have had mild-to-moderate COVID-19 do not display alterations in nitric oxide-mediated cutaneous microvascular function. In addition, healthy young adults who have COVID-19 antibodies from the COVID-19 vaccinations do not display alterations in nitric oxide-mediated cutaneous microvascular function.

Contributions of endothelin-1 and l-arginine to blunted cutaneous microvascular function in young, black women.

Non-Hispanic black (BL) individuals have the greatest prevalence of cardiovascular disease (CVD), relative to other racial/ethnic groups (e.g., non-Hispanic white population; WH), which may be secondary to blunted vascular function. Although women typically present with reduced CVD relative to men of the same racial/ethnic group, the prevalence is similar between BL women and men though the mechanisms differ. This study hypothesized that reduced microvascular function in young, BL women is associated with endothelin-1 (ET-1) overactivity or insufficient l-arginine bioavailability. Nine BL and nine WH women participated (age: 20 ± 2 vs. 22 ± 2 yr). Cutaneous microvascular function was assessed during 39°C local heating, whereas lactated Ringer's (control), BQ-123 (ET-1 receptor type A antagonist), BQ-788 (ET-1 receptor type B antagonist), or l-arginine were infused via intradermal microdialysis to modify cutaneous vascular conductance (CVC). Subsequent infusion of Nω-nitro-l-arginine methyl ester allowed for quantification of the nitric oxide (NO) contribution to vasodilation, whereas combined sodium nitroprusside and 43°C heating allowed for normalization to maximal CVC (%CVCmax). BL women had blunted %CVCmax and NO contribution to dilation during the 39°C plateau (P < 0.027 for both). BQ-123 improved this response through augmented NO-mediated dilation (P < 0.048 for both). BQ-788 and l-arginine did not alter the CVC responses (P > 0.835 for both) or the NO contribution (P > 0.371 for both). Cutaneous microvascular function is reduced in BL women, and ET-1 receptor type A may contribute to this reduced function. Further research is needed to better characterize these mechanisms in young, BL women.NEW & NOTEWORTHY Cardiovascular disease remains a burden in the United States non-Hispanic black (BL) population, although its manifestation through blunted vasodilation in this population is different between men and women. Accordingly, this study determined that reduced microvascular function in young, BL women may be partially controlled by endothelin-1 (ET-1) type A receptors, although neither type B receptors nor insufficient l-arginine bioavailability seems to contribute to this response. Accordingly, further research is needed to better characterize these ET-1 related mechanisms and illuminate other pathways that may contribute to this disparate vascular function in young, BL women.

Abstract 13944: Young, Non-Hispanic Black Males and Females Exhibit Divergent Peripheral and Cerebral Vascular Reactivity

Introduction: In the U.S., cardiovascular and cerebrovascular diseases (CVD) remain more prominent in non-Hispanic black individuals than in other populations. Across most racial/ethnic groups, total CVD prevalence is ~10% lower in females; however, total CVD prevalence in black females (BF) is similar to that of black males (BM). Conversely, BM have ~23% higher age-adjusted stroke mortality compared to BF, a pattern not seen in other groups. While the mechanisms behind these race-by-sex differences are multifactorial, vascular dysfunction likely contributes. Our group and others have demonstrated reduced brachial artery and cerebrovascular vasodilation in black versus white individuals, though much of this work did not specifically address sex differences. To this end, we have recently investigated and reported divergent mechanisms of reduced cutaneous microvascular function in BM and BF; however, more work is needed to better understand whether such findings extend to other vascular regions. Hypothesis: We tested the hypothesis that BF and BM would have divergent degrees of reduced peripheral and cerebral vasodilator responsiveness. Methods: Eleven BF and 15 BM (22 ± 4 vs. 23 ± 3 yrs) underwent testing for brachial artery flow-mediated dilation (FMD; conduit artery function) and post-occlusive reactive hyperemia (PORH; microvascular function), along with cerebrovascular reactivity (CVR) to rebreathing-induced hypercapnia. Results: FMD was greater in BF versus BM (9.10 ± 3.49 vs. 5.84 ± 2.78%; P = 0.02), even when normalized to baseline diameter or shear rate ( P &lt; 0.05 for both). BF had similar PORH when assessed as peak blood velocity (77.1 ± 19.9 vs. 79.4 ± 19.6 cm • s -1 ; P &gt; 0.05) but lower peak blood flow (343.6 ± 169.8 vs. 495.4 ± 196.9 mL/min; P &lt; 0.05) and blood flow AUC (133.6 ± 61.1 vs. 220.3 ± 130.7 mL; P = 0.04) relative to BM. CVR was greater in BF versus BM (0.024 ± 0.010 vs. 0.012 ± 0.006 cm • s -1 • mmHg -1 • mmHg -1 ; P &lt; 0.01). Conclusion: These data suggest that young, BM have lower vascular reactivity than BF during some, but not all, tests of vascular function. More work in this area is needed to better understand the potential biological and social mechanisms influencing sex differences in vascular function and CVD risk in black individuals.