Cutaneous Vascular Function Research Articles

High antioxidant load impairs cutaneous microvascular function in healthy women

PURPOSE: Human cutaneous circulation is used as an in vivo bioassay to examine mechanisms of systemic vascular dysfunction in cohorts of patients with accelerated cardiovascular disease risk. Local drug infusions, including atorvastatin (statin; LOX inhibitor) and systemic interventions to investigate anti-inflammatory mechanisms (e.g., oral salsalate) have been used to elucidate mechanisms underlying microvascular dysfunction. However, in healthy cohorts, high antioxidant load can attenuate total vasodilation and nitric oxide (NO)-dependent vasodilation. Thus, we aimed to examine endothelial function during high antioxidant load from these localized and systemic treatments in healthy control groups. We hypothesized that combined localized and systemic treatments will attenuate endothelial function in healthy women. METHODS: In a randomized placebo control design, oral salsalate (1500mg/twice daily/5 days) was used to assess the impact of systemic inflammation on cutaneous vascular function. Four intradermal microdialysis fibers were placed into the intradermal space of the ventral forearm of six healthy women (32±7 years). Laser-Doppler flowmeter probes, used to measure cutaneous blood flow, were placed in local heating units set to 33°C. Increasing concentrations of acetylcholine (ACh; endothelium-dependent vasodilator) from 10 -10 to 10 -1 M were co-perfused with one of the following: Lactated Ringer’s (control), 0.02 mM statin, 15 mM N G -nitro-L-arginine methyl ester (L-NAME; nitric oxide synthase inhibitor), and statin + L-NAME (COMBO) sequentially for 5 min each. 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 and mean arterial pressure and normalized as a percentage of the site-specific maximum (%CVC max ). Data at each intervention were compared with control using a two-way (dose x site) analysis of variance. Responses at each dosage were compared using paired t-tests and corrected for multiple comparisons. RESULTS: Following oral salsalate, there was no difference in the %CVC max response to ACh with local L-NAME (p=0.896) or COMBO interventions (p=0.617) as compared to the placebo. However, following oral salsalate, there was a significant reduction in %CVC max in the statin treated site at higher ACh concentrations (10 -5 M, 10 -4 M, 10 -3 M; all p<0.01). CONCLUSION: Endothelial function was attenuated when subjects were introduced to a combination of oral salsalate and statin localized treatments. Five-day oral salsalate intake and local statin may result in high antioxidant load in healthy women creating a shift in redox balance, thus leading to impaired endothelial function. Supported by NIH Grant R01 HL161000 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Does aging alter skin vascular function in humans when spatial variation is considered?

Reports evaluating age-related impairments in cutaneous vascular function assessed by either the venoarteriolar reflex (VAR) induced by venous congestion, or post-occlusive reactive hyperemia (PORH) activated by arterial occlusion, have yielded mixed findings. This may be due to region-specific variability that occurs when assessing local cutaneous vascular responses. We evaluated the hypothesis that aging attenuates VAR and PORH responses in forearm skin assessed across four adjacent sites, each separated by ~4cm to account for inter-site variability. In twenty young (24±4years, 10 females) and twenty older (60±7years, 9 females) adults, VAR and PORH were achieved by a 3-min venous occlusion and 5-min arterial occlusion, each induced by inflating a pressure cuff to 45 and 240mmHg, respectively. Cutaneous blood flow at all skin sites was measured by laser-Doppler flowmetry with the average response from all sites used for between-group comparisons. VAR and PORH responses were similar between groups with the exception that the time required to achieve peak PORH was delayed in older adults (mean difference of 5.5±4.4s, p=0.003, Cohen's d=0.812). We showed that aging had a negligible influence on VAR and PORH responses in forearm skin even when controlling for region-specific variability.

Na+-K+-ATPase plays a major role in mediating cutaneous thermal hyperemia achieved by local skin heating to 39°C.

Na+-K+-ATPase is integrally involved in mediating cutaneous vasodilation during an exercise-heat stress, which includes an interactive role with nitric oxide synthase (NOS). Here, we assessed if Na+-K+-ATPase also contributes to cutaneous thermal hyperemia induced by local skin heating, which is commonly used to assess cutaneous endothelium-dependent vasodilation. Furthermore, we assessed the extent to which NOS contributes to this response. Cutaneous vascular conductance (CVC) was measured continuously at four forearm skin sites in 11 young adults (4 women). After baseline measurement, local skin temperature was increased from 33°C to 39°C to induce cutaneous thermal hyperemia. Once a plateau in CVC was achieved, each skin site was continuously perfused via intradermal microdialysis with either: 1) lactated Ringer solution (control), 2) 6 mM ouabain, a Na+-K+-ATPase inhibitor, 3) 20 mM l-NAME, a NOS inhibitor, or 4) a combination of both. Relative to the control site, CVC during the plateau phase of cutaneous thermal hyperemia (∼50% max) was reduced by the lone inhibition of Na+-K+-ATPase (-19 ± 8% max, P = 0.038) and NOS (-32 ± 4% max, P < 0.001), as well as the combined inhibition of both (-37 ± 9% max, P < 0.001). The magnitude of reduction was similar between NOS inhibition alone and combined inhibition (P = 1.000). The administration of both Na+-K+-ATPase and NOS inhibitors fully abolished the plateau of CVC with values returning to preheating baseline values (P = 0.439). We show that Na+-K+-ATPase contributes to cutaneous thermal hyperemia during local skin heating to 39°C, and this response is partially mediated by NOS.NEW & NOTEWORTHY Cutaneous thermal hyperemia during local skin heating to 39°C, which is highly dependent on nitric oxide synthase (NOS), is frequently used to assess endothelium-dependent cutaneous vasodilation. We showed that Na+-K+-ATPase mediates the regulation of cutaneous thermal hyperemia partly via NOS-dependent mechanisms although a component of the Na+-K+-ATPase modulation of cutaneous thermal hyperemia is NOS independent. Thus, as with NOS, Na+-K+-ATPase may be important in the regulation of cutaneous endothelial vascular function.

Clinical relevance of combining Thermography with Nailfold Capillaroscopy to improve differentiation between primary and secondary Raynaud’s Phenomenon

Objectives: Early microvascular damage and dysfunction are clinically mirrored in Raynaud’s phenomenon (RP). Currently, nailfold capillaroscopy (NC) is applied to differentiate between primary RP (PRP) and secondary RP (PRP), associated with connective tissue disease. However, abnormal morphology can also be caused due to age-related changes and cardiovascular disease. Thermography (TG) is a non-invasive technique which enables quantification of cutaneous vascular function. An approach using both NC and TG could improve the differentiation between PRP and SRP. Methods: Thirty RP patients (PRP, n = 21; SRP, n = 9) underwent nailfold capillaroscopy and thermography. Morphologic features were scored and patients were categorized according to the guidelines of EULAR Study group on Microcirculation in Rheumatic Diseases. TG of the hand was performed before, directly and ten minutes after a cold challenge test. Baseline images and rewarming curves were analyzed. Results: Capillary abnormalities with NC were found in all SRP patients (9/9) and in 48% (10/21) of PRP patients. Out of 10 PRP patients with altered capillary morphology, 9 (90%) had a cardiovascular disease. For all patients mean temperature was significantly higher 10 minutes after cold induction than before (p &lt; 0,01). The gradient of the rewarming curve was significantly lower in patients with SRP compared to PRP patients (p = 0.015). Conclusions: Nailfold capillaroscopy and thermography can reliably be used to measure microvascular damage and dysfunction. Additional thermography can assist in differentiating between PRP and SRP, especially in elderly patients or in presence of a cardiovascular disease. Keywords: Raynaud’s phenomenon; Nailfold capillaroscopy; Thermography

Tissue Optical Clearing for Biomedical Imaging: From In Vitro to In Vivo.

Tissue optical clearing technique provides a prospective solution for the application of advanced optical methods in life sciences. This chapter firstly gives a brief introduction to mechanisms of tissue optical clearing techniques, from the physical mechanism to chemical mechanism, which is the most important foundation to develop tissue optical clearing methods. During the past years, in vitro and in vivo tissue optical clearing methods were developed. In vitro tissue optical clearing techniques, including the solvent-based clearing methods and the hydrophilic reagents-based clearing methods, combined with labeling technique and advanced microscopy, can be applied to image 3D microstructure of tissue blocks or whole organs such as brain and spinal cord with high resolution. In vivo skin or skull optical clearing, promise various optical imaging techniques to detect cutaneous or cortical cell and vascular structure and function without surgical window.

Heat therapy reduces blood pressure and circulating endothelin‐1 levels, but does not improve walking performance or vascular function in patients with symptomatic peripheral artery disease

INTRODUCTIONPatients with peripheral artery disease (PAD) are at a heightened risk of cardiovascular events and have markedly reduced vascular function and exercise tolerance. Heat therapy (HT) has emerged as a practical treatment to improve cardiovascular health in young individuals as well in patients with overt cardiovascular disease. We recently reported that a single 90 min session of HT applied to the legs of patients with PAD using water‐circulating trousers increases popliteal artery blood flow and reduces blood pressure and the circulating levels of the potent endogenous vasoconstrictor endothelin‐1 (ET‐1). The objective of the present study was to test the hypothesis that the repeated exposure to leg HT would lower blood pressure and ET‐1 levels and improve walking performance and conduit artery and cutaneous vascular function in patients with symptomatic PAD.METHODSThirty‐two patients with symptomatic PAD (Age: 68± 8 years; Ankle‐brachial index: 0.67 ± 0.1) were assigned using a balanced randomized design to undergo 90 min of HT (48°C) or a thermoneutral treatment (33°C) 3 times per week for 6 consecutive weeks. The following outcomes were assessed at baseline and 3 and 6 weeks after the intervention: 1) resting ankle‐brachial index, 2) post‐occlusive reactive hyperemia in the popliteal artery (phase contrast magnetic resonance imaging), 3) leg cutaneous thermal hyperemia (laser Doppler flowmetry), 4) resting blood pressure every 5 min for 70 min, 5) 6‐min walk distance and 6) serum levels of ET‐1 and total nitrate (NOx).RESULTSParticipants completed 17.7 ± 0.6 treatment sessions, resulting in a compliance rate of 98.7%. In the group exposed to HT, systolic blood pressure (SBP) decreased from baseline by ~3 mmHg at 6 weeks, while in the control group SBP increased by ~1 mmHg. A significant group by time interaction was observed for the changes in SBP from baseline to 6 weeks (p=0.0049) with significant group differences at 20 min (Change in SBP: Control: 6.27 ± 15.5 vs. HT: −7.60 ± 13.6 mmHg, p=0.015) and 60 min (Change in SBP: Control: 4.13 ± 15.1 vs. HT: −7.33 ± 13.7 mmHg, p=0.0386). Similarly, serum ET‐1 levels decreased by ~15% from baseline to week 6 following exposure to HT, while a ~6% increase in this parameter occurred in the control group (Change in ET‐1: Control: 0.16 ± 0.6 vs. HT: −0.30 ± 0.4 pg/mL, p=0.035 – one outlier removed). Resting ABI, diastolic BP, 6MWT distance, hyperemic peak flow and cutaneous thermal hyperemia were not different between groups.CONCLUSIONExposure to repeated HT reduces systolic blood pressure and ET‐1 levels in patients with symptomatic PAD. These findings indicate that HT may be a practical and accessible nonpharmacological tool to reduce cardiovascular risk in PAD patients.Support or Funding InformationAmerican Heart Association Scientist Development grant (16SDG27600003).

Effect of Physical Activity on Oxidative Stress and Endothelial‐Dependent Cutaneous Microvascular Function in Non‐Hispanic Blacks: A Pilot Study

Cardiovascular disease is a dominant cause of morbidity and mortality in non‐Hispanic Blacks (NHB). This may be due, in part, to vascular endothelial dysfunction which causes reduced nitric oxide (NO) bioavailability and increased oxidative stress. Conversely, physical activity has been shown to attenuate and treat symptoms of cardiovascular disease, endothelial dysfunction, and oxidative stress. It remains unknown whether physical activity reduces oxidative stress and enhances endothelial‐dependent vascular function in NHB. The purpose of this study was to examine the extent to which physical fitness influences oxidative stress and nitric oxide‐dependent cutaneous vascular function in NHB. On the first visit, young, healthy NHB participants (n = 3 regularly active; n=2 inactive) completed a graded exercise test on a cycle ergometer to determine V̇O2max to confirm self‐reported physical activity status. On the second visit, participants were instrumented with 4 microdialysis fibers for infusion of 1) lactated Ringer’s (control), 2) 0.1 mM 1400W (iNOS inhibitor), 3) 0.1 mM tempol to inhibit oxidative stress, 4) and combined tempol + 1400W, respectively. Following infusion of experimental drugs, local skin temperature was increased via rapid local heating to 39°C at a rate of 0.1°C/sec. Once skin blood flow plateaued, 20 mM L‐NAME was infused to quantify NO‐dependent vasodilation. Following L‐NAME infusion, the local heaters were increased to 43°C and 54mM of sodium nitroprusside was infused to elicit maximal endothelium‐independent cutaneous vasodilation. Skin blood flow was measured via laser‐doppler flowmetry (LDF) throughout the local heating protocol. Cutaneous vascular conductance (CVC) was calculated as LDF divided by mean arterial pressure and normalized to maximum (%CVCmax). iNOS inhibition increased %NO‐dependent vasodilation in both active (67 ± 10% vs. 54 ± 7%) and inactive (69 ± 4% vs. 56 ± 10%) groups compared to control. Combined inhibition of iNOS and oxidative stress increased %NO‐dependent vasodilation in both active (72 ± 9%) and inactive (71 ± 13%) NHB compared to control but these were not different compared to inhibition of iNOS or oxidative stress alone. Interestingly, inhibition of oxidative stress significantly increased %NO‐dependent vasodilation in only the active group compared to control (74 ± 8%). Taken together these data indicate that inhibition of iNOS with 1400W increases endothelial‐dependent cutaneous vasodilation in active and inactive NHB while inhibition of oxidative stress increases endothelial‐dependent cutaneous vasodilation in active NHB.

Comparison of cerebral and cutaneous microvascular dysfunction with the development of type 1 diabetes.

Rationale: Diabetes can lead to cerebral and cutaneous vascular dysfunction. However, it is still unclear how vascular function changes with the development of diabetes and what differences exist between cerebral and cutaneous vascular dysfunction. Thus, it is very important to monitor changes in cerebral and cutaneous vascular function responses in vivo and study their differences during diabetes development.Methods: With the assistance of newly developed skull and skin optical clearing techniques, we monitored the responses of sodium nitroprusside (SNP)- and acetyl choline (ACh)-induced cerebral and cutaneous vascular blood flow and blood oxygen in diabetic mice in vivo during the development of type 1 diabetes (T1D) by combining laser speckle contrast imaging with hyperspectral imaging. We then compared the differences between cerebral and cutaneous vascular responses and explored the reasons for abnormal changes induced in response to different vascular beds.Results: In the early stage of diabetes (T1D-1 week), there were abnormal changes in the cerebral vascular blood flow and blood oxygen responses to SNP and ACh as well as cutaneous vascular blood oxygen. The cutaneous vascular blood flow response also became abnormal from T1D-3 weeks. Additionally, the T1D-induced abnormal blood flow response was associated with changes in vascular myosin light chain phosphorylation and muscarinic acetylcholine receptor M3 levels, and the aberrant blood oxygen response was related to an increase in glycated hemoglobin levels.Conclusion: These results suggest that the abnormal cutaneous vascular blood oxygen response occurred earlier than the blood flow response and therefore has the potential to serve as a good assessment indicator for revealing cerebrovascular dysfunction in the early stage of diabetes.

Effects of vehicle microdialysis solutions on cutaneous vascular responses to local heating.

Microdialysis is a minimally invasive technique often paired with laser Doppler flowmetry to examine cutaneous microvascular function, yet presents with several challenges, including incompatibility with perfusion of highly lipophilic compounds. The present study addresses this methodological concern, with an emphasis on the independent effects of commonly used vehicle dialysis solutions to improve solubility of pharmacological agents with otherwise low aqueous solubility. Four microdialysis fibers were placed in the ventral forearm of eight subjects (4 men, 4 women; 25 ± 1 yr) with sites randomized to serve as 1) control (lactated Ringer's), 2) Sodium carbonate-bicarbonate buffer administered at physiological pH [SCB-HCl; pH 7.4, achieved via addition of hydrochloric acid (HCl)], 3) 0.02% ethanol, and 4) 2% dimethyl sulfoxide (DMSO). After baseline (34°C), vehicle solutions were administered throughout a standardized local heating protocol to 42°C. Laser Doppler flowmetry provided an index of blood flow. Cutaneous vascular conductance was calculated and normalized to maximum (%CVCmax, sodium nitroprusside and 43°C local heat). The SCB-HCl solution increased baseline %CVCmax (control: 9.7 ± 0.8; SCB-HCl: 21.5 ± 3.5%CVCmax; P = 0.03), but no effects were observed during heating or maximal vasodilation. There were no differences with perfusion of ethanol or DMSO at any stage of the protocol ( P > 0.05). These data demonstrate the potential confounding effects of some vehicle dialysis solutions on cutaneous vascular function. Notably, this study provides evidence that 2% DMSO and 0.02% ethanol are acceptable vehicles with no confounding local vascular effects to a standardized local heating protocol at the concentrations presented. NEW & NOTEWORTHY This study examined the independent effects of common vehicle solutions on cutaneous vascular responses. A basic buffer (SCB-HCl) caused baseline vasodilation; 2% DMSO and 0.02% ethanol had no effects. This highlights the need for considering potential confounding effects of solubilizing solutions when combined with low aqueous soluble pharmacological agents. Importantly, DMSO and ethanol do not appear to influence cutaneous vascular function during baseline or local heating at the concentrations studied, allowing their use without confounding effects.

Ten days of repeated local forearm heating does not affect cutaneous vascular function.

The aim of the present study was to determine whether 10 days of repeated local heating could induce peripheral adaptations in the cutaneous vasculature and to investigate potential mechanisms of adaptation. We also assessed maximal forearm blood flow to determine whether repeated local heating affects maximal dilator capacity. Before and after 10 days of heat training consisting of 1-h exposures of the forearm to 42°C water or 32°C water (control) in the contralateral arm (randomized and counterbalanced), we assessed hyperemia to rapid local heating of the skin (n = 14 recreationally active young subjects). In addition, sequential doses of acetylcholine (ACh, 1 and 10 mM) were infused in a subset of subjects (n = 7) via microdialysis to study potential nonthermal microvascular adaptations following 10 days of repeated forearm heat training. Skin blood flow was assessed using laser-Doppler flowmetry, and cutaneous vascular conductance (CVC) was calculated as laser-Doppler red blood cell flux divided by mean arterial pressure. Maximal cutaneous vasodilation was achieved by heating the arm in a water-spray device for 45 min and assessed using venous occlusion plethysmography. Forearm vascular conductance (FVC) was calculated as forearm blood flow divided by mean arterial pressure. Repeated forearm heating did not increase plateau percent maximal CVC (CVCmax) responses to local heating (89 ± 3 vs. 89 ± 2% CVCmax, P = 0.19), 1 mM ACh (43 ± 9 vs. 53 ± 7% CVCmax, P = 0.76), or 10 mM ACh (61 ± 9 vs. 85 ± 7% CVCmax, P = 0.37, by 2-way repeated-measures ANOVA). There was a main effect of time at 10 mM ACh (P = 0.03). Maximal FVC remained unchanged (0.12 ± 0.02 vs. 0.14 ± 0.02 FVC, P = 0.30). No differences were observed in the control arm. Ten days of repeated forearm heating in recreationally active young adults did not improve the microvascular responsiveness to ACh or local heating.NEW & NOTEWORTHY We show for the first time that 10 days of repeated forearm heating is not sufficient to improve cutaneous vascular responsiveness in recreationally active young adults. In addition, this is the first study to investigate cutaneous cholinergic sensitivity and forearm blood flow following repeated local heat exposure. Our data add to the limited studies regarding repeated local heating of the cutaneous vasculature.

Does Type 2 Diabetes Modulate Peripheral Cutaneous Vascular Function?

Aging is associated with impairments in cutaneous vasodilation during heat stress (Holowatz et al. Am J Physiol, 284:1662, 2003) which is exacerbated in individuals with type 2 diabetes mellitus (Charkoudian. Mayo Clin Proc, 78:603, 2003). This diabetes‐related modulation of cutaneous vasodilation may be due to attenuated peripheral sensitivity of skin vessels to receptor activation, though this has never been directly investigated. Thus, in this preliminary study, we aimed to evaluate the influence of type 2 diabetes mellitus on the modulation of cutaneous vasodilation in response to activation of the following receptors: cholinergic, purinergic, nicotinic and β‐adrenergic. In this preliminary study, seven older adults (59±9 years) with well‐controlled T2D (hemoglobin A1c, 7.5% ± 1.0, duration 8±5 years) and seven age‐matched counterparts without T2D (Controls) (61±8 years) participated in the study. Subjects were placed in a semi‐recumbent position in a thermoneutral room (~23 °C) during which time four intradermal microdialysis fibers were implanted on the dorsal side of the left forearm within the dermal layer of the skin. Approximately 90 min after the completion of the fiber insertion, cutaneous vascular conductance (CVC, measured as laser‐doppler flowmetry/mean arterial pressure) was then continuously monitored at the four forearm skin sites perfused via intradermal microdialysis with the following receptor agonists in a dose dependent manner: 1) methacholine (cholinergic receptor agonist, 5 doses: 0.0125, 0.25, 5, 100, 2000 mM), 2) ATP (purinergic receptor agonist, 5 doses: 0.03, 0.3, 3, 30, 300 mM), 3) nicotine (nicotinic receptor agonist, 5 doses: 1.2, 3.6, 11, 33, 100 mM), and 4) isoproterenol (β‐adrenergic receptor agonist, 3 doses: 1, 10, 100 μM). Increased CVC in response to all doses of methacholine administration were similar between groups (all P ≥ 0.15). Further, observed increases in CVC resulting from the five dose dependent infusion of ATP were similar in both Controls and T2D (all P ≥ 0.51), as was the case in all five doses of nicotine infusion (all P ≥ 0.32). Finally, similar increases in CVC were observed in both groups following the infusion of all three doses of isoproterenol (all P ≥ 0.20). Our preliminary findings show no attenuations in the sensitivity of the examined cholinergic and non‐cholinergic receptors in older adults with well‐controlled type 2 diabetes.Support or Funding InformationFunding support provided by the Canadian Institutes of Health Research (grant no. 286363, funds held by Dr. Glen P. Kenny).

Ingestion of Coffee Polyphenols Improves a Scaly Skin Surface and the Recovery Rate of Skin Temperature after Cold Stress: A Randomized, Controlled Trial.

Coffee polyphenols (CPPs) derived from coffee beans have beneficial effects on blood pressure and vascular endothelial function. In addition, CPPs suppress ultraviolet light induced erythema. However, the effects of CPPs on dry skin and cutaneous vascular function have not been clarified. We investigated the effects of CPPs on dry skin and the recovery rate (RR) of skin temperature after a cold-stress test as a measure of vascular function in subjects with visible scaliness in a double-blind, placebo-controlled, randomized study. The subjects were divided into two groups, the CPP group and the Placebo group. In the CPP group, the subjects ingested a beverage containing 297.8 mg CPPs every day for 4 wk. The degree of skin dryness was assessed quantitatively using a Visioscan to evaluate skin scaliness and smoothness. A subjective evaluation using a visual analog scale (VAS) of skin smoothness was also used. As a result, the scaliness and smoothness of cheek skin was significantly improved after 4 wk in the CPP group compared to the Placebo group. The improvements of the VAS score on 'skin smoothness' and the RR were also observed in the CPP group but the difference was not statistically significant. However, when the CPP group was divided into subgroups of high RR and low RR, the improvement of the RR was significant in the low RR subgroup. In conclusion, our results suggest that CPPs improve skin scaliness and play a role in cutaneous blood flow regulation after cold stress.

Acute black tea consumption improves cutaneous vascular function in healthy middle-aged humans

Dietary flavonoids, such as those present in black tea, are associated with reduced risk of cardiovascular disease (CVD), possibly through improving nitric oxide (NO) mediated vascular function. The aim of this study was to examine the effect of acute black tea ingestion on cutaneous microvascular function. Twenty healthy participants (58±5y, 9 men) attended two experimental trials (tea, placebo), 7-days apart in a randomised, controlled, double-blind, cross-over design. Participants ingested a single dose of 200ml black tea or placebo, followed by assessment of forearm cutaneous perfusion using laser-Doppler flowmetry (LDF) using three distinct heating protocols, enabling us to distinguish between axon- and endothelium-dependent vasodilation: 1. rapid 42°C, 2. rapid 39°C and 3. gradual 42°C. On the contralateral arm, full-field laser perfusion imaging (FLPI) was used to assess forearm perfusion during gradual 42°C. Data were presented as cutaneous vascular conductance (CVC; flux/mean arterial pressure, MAP) and CVC expressed as a percentage of maximal CVC (%CVCmax). Rapid local heating to 39°C or 42°C demonstrated no effect of tea for flux, CVC or %CVCmax (all P>0.05). Gradual local heating to 42°C, however, produced a higher skin blood flow following black tea ingestion for absolute CVC (P=0.04) when measured by LDF, and higher absolute flux (P<0.001) and CVC (P<0.001) measured with FLPI. No effect of tea was found for %CVCmax when assessed by either LDF or FLPI. Acute tea ingestion enhanced cutaneous vascular responses to gradual local heating to 42°C in healthy, middle-aged participants, possibly through a mechanism related to activation of endothelium-derived chemical mediators, such as NO. These improvements may contribute to the cardiovascular health benefits of regular tea ingestion.

Microvascular Dysfunction is Evident in the Cutaneous Circulation of Psoriatic Patients

Vascular dysfunction in conduit and resistance vessels is evident in adults with plaque psoriasis, a chronic systemic inflammatory disease. However, potential impairments of cutaneous microvascular function in psoriatic patients remain incompletely understood. We hypothesized that microvascular function would be impaired in the cutaneous circulation (non‐lesional) of psoriatic patients. One intradermal microdialysis fiber was placed in the forearm skin of 5 healthy adults (NP: 1M, 4F; 49 ± 1 yr) and 5 adults with moderate (&gt;5% body surface area affected) plaque psoriasis (P: 1M, 4F; 48 ± 1 yr). The site was perfused with lactated Ringer's while red blood cell flux was measured using laser‐Doppler flowmetry during standardized local heating (42°C) to elicit eNOS‐dependent vasodilation. NO‐dependent vasodilation was further quantified after the perfusion of 20 mM L‐NAME (nonspecific NO‐synthase inhibitor). Data were expressed as a percentage of maximum cutaneous vascular conductance (%CVCmax; 28 mM SNP). The local heating‐induced plateau was attenuated in psoriatic patients (NP: 99 ± 1 %CVCmax vs. P: 75 ± 9 %CVCmax; p&lt;0.05). Quantified eNOS‐dependent vasodilation appears to be reduced in the psoriatic group (NP: 57 ± 8 %CVCmax vs. P: 41 ± 8 %CVCmax; p=0.15). These preliminary results suggest that microvascular dysfunction is evident in psoriatic patients and may be mediated by reduced NO bioavailability. Further, the assessment of cutaneous vascular function has particular relevance for this clinical population because the skin‐related symptomology represents the outward manifestation of this systemic inflammatory disease process.FUNDING: Penn State College of HHD Grant

Tempol improves cutaneous thermal hyperemia through increasing nitric oxide bioavailability in young smokers

We recently found that young cigarette smokers display cutaneous vascular dysfunction relative to nonsmokers, which is partially due to reduced nitric oxide (NO) synthase (NOS)-dependent vasodilation. In this study, we tested the hypothesis that reducing oxidative stress improves NO bioavailability, enhancing cutaneous vascular function in young smokers. Ten healthy young male smokers, who had smoked for 6.3 ± 0.7 yr with an average daily consumption of 9.1 ± 0.7 cigarettes, were tested. Cutaneous vascular conductance (CVC) during local heating to 42°C at a rate of 0.1°C/s was evaluated as laser-Doppler flux divided by mean arterial blood pressure and normalized to maximal CVC, induced by local heating to 44°C plus sodium nitroprusside administration. We evaluated plateau CVC during local heating, which is known to be highly dependent on NO, at four intradermal microdialysis sites with 1) Ringer solution (control); 2) 10 μM 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol), a superoxide dismutase mimetic; 3) 10 mM N(ω)-nitro-l-arginine (l-NNA), a nonspecific NOS inhibitor; and 4) a combination of 10 μM tempol and 10 mM l-NNA. Tempol increased plateau CVC compared with the Ringer solution site (90.0 ± 2.3 vs. 77.6 ± 3.9%maximum, P = 0.028). Plateau CVC at the combination site (56.8 ± 4.5%maximum) was lower than the Ringer solution site (P < 0.001) and was not different from the l-NNA site (55.1 ± 4.6%maximum, P = 0.978), indicating the tempol effect was exclusively NO dependent. These data suggest that in young smokers, reducing oxidative stress improves cutaneous thermal hyperemia to local heating by enhancing NO production.

Comparative study of the upper and lower limb skin blood flow control mechanisms in patients with essential hypertension

To investigate limb specific differences in cutaneous vascular function in patients (n=33) with essential hypertension (EHT). In this observational cross-sectional study, baseline skin blood flow and the response to local heating were measured with a laser Doppler flowmeter (LDF) from the volar region of the forearm and the gaiter area of the foot at supine rest. The fractal analysis, detrended fluctuation analysis (DFA), was used to calculate the correlation properties of skin blood flow, LDF signal. The paired t-test and repeated measures ANOVA were used to determine the response to local heating and compare the scaling exponents of different anatomical locations respectively. We found three linear scaling regions that describe the fractal behavior of LDF signal with their slopes, scaling exponents. For cardiac (α(C)) and cardio-respiratory (α(CR)) scaling exponents, thermal hyperemia (T) induced greater change in the leg (α(C)=1.49 ± 0.26; α(CT)=1.62 ± 0.20 p<0.01 and α(CR)=0.84 ± 0.29 α(CRT)=0.42 ± 0.28 p<0.001) than in forearm (α(C)=1.28 ± 0.13; α(CT)=1.33 ± 0.13 p>0.05 and α(CR)=0.73 ± 0.15; α(CRT)=0.65 ± 0.018 p<0.05). Local scaling exponents (α(L) ≈ α(LT) ~ 1) were not significantly different (p>0.05) and, local lines did not shift in parallel with local heating in both extremities. The results of the present study suggest that skin microvascular function is impaired in both extremities in EHT patients. However, myogenic response is not uniform in both extremities and pronounced response to local thermal hyperemia has been observed in the gaiter area compared with the volar region. Further studies are needed to determine if these limb specific microvascular differences is the result of posture-induced structural and functional adaptation.

The regional differences in the contribution of nitric oxide synthase to skin blood flow at forearm and lower leg sites in response to local skin warming

We investigated the role of nitric oxide synthase (NOS) on regional cutaneous vascular function at rest (thermoneutral conditions) and during the vasodilator response to increased local skin temperature (Tloc). Dorsal forearm and lateral leg sites were instrumented with microdialysis fibers, local heaters, and laser-Doppler probes. All sites were heated from 33°C to 42°C. Each limb had 1 skin site treated with l-NAME to inhibit NOS, and 1 site infused with lactated Ringer's to serve as a control. Basal cutaneous vascular conductance (CVC) was measured at 33°C, forearm sites averaged 14±1%max and 17±1%max at l-NAME and control sites, respectively (P=0.26). CVC sites in the leg were different between l-NAME (17±1%max) and control (27±2%max) (P=0.04). CVC between the forearm and the leg across control sites differed (P<0.05). In contrast, at l-NAME treated sites, there was no difference between the forearm and leg sites (P=0.23). When Tloc was increased to 42°C, CVC at the control sites differed between the forearm 93±1%max and leg 98±1%max (P=0.02). There were no differences between the arm and leg at l-NAME treated sites at 42°C (P=0.45). The findings of the current study were that the contribution of nitric oxide (NO) to the vasodilator response to an elevated Tloc is consistent between the arm and the leg, and, under thermoneutral conditions (33°C), NO plays a larger role in the basal vascular function in the legs than that of the forearm. Accordingly, these data suggest, in part, that the differences in basal CVC between the forearm and leg are due to NOS activity.

Knockdown of paraoxonase 1 expression influences the ageing of human dermal microvascular endothelial cells

Skin is one of the most commonly studied tissues for microcirculation research owing to its close correlation of cutaneous vascular function, ageing and age-related cardiovascular events. To elucidate proteins that determine this correlation between endothelial cell function and ageing in the vascular environment of the skin, we performed a proteomic analysis of plasma samples from six donors in their 20s (young) and six donors in their 60s (old). Among identified proteins, paraoxonase 1 (PON1) was selected in this study. To elucidate the role of PON1 on skin ageing and determine how it controls cellular senescence, the characteristics of PON1 in human dermal microvascular endothelial cells (HDMECs) were determined. When the expression of endogenous PON1 was knocked-down by small interfering RNA (siRNA) targeting PON1, HDMECs showed characteristic features of cellular senescence such as increases in senescence-associated β-galactosidase stained cells and enlarged and flattened cell morphology. At 48h post-transfection, the protein expression of p16 in PON1 siRNA-treated HDMECs was higher than that in scrambled siRNA-treated HDMECs. In addition, the expressions of moesin and rho GTP dissociation inhibitor, additional age-related candidate biomarkers, were decreased by PON1 knock-down in HDMECs. In conclusion, these results suggest that PON1 functions as an ageing-related protein and plays an important role in the cellular senescence of HDMECs.

Acetylcholine chloride as a potential source of variability in the study of cutaneous vascular function in man

Introduction Laser-Doppler flowmetry (LDF) coupled with acetylcholine chloride (ACh) iontophoresis is increasingly recognized as a reliable non-invasive method to study the endothelial function. However, ACh-vasodilation measurement appears highly variable possibly due to the ACh pharmacological properties itself. These problems may be partially overcome by using methacholine chloride (MCh), a more stable synthetic agonist of muscarinic receptors, instead of ACh. Therefore, we first studied the correlation between the two drugs and then the effects of (1) spatial variability (inter-site measurements), (2) temporal variability (inter-day measurements), (3) intra-day variability (morning versus evening), and (4) age on the variability of both ACh-vasodilation and MCh-vasodilation. Methods The endothelium-dependent vasodilation response to simultaneous iontophoretic applications (4 doses of 10 s at 0.1 mA with 2 min of current-free interval) of ACh (11 mM) or MCh (10 mM) was studied on the forearm of 40 healthy subjects (36 males, median 28 yr, range 21–59 yr). The percent change in perfusion (CVCpeak) from baseline and the area under the curve (CVC AUC) during iontophoresis were assessed. Inter-site, inter-day and intra-day coefficients of variation (CV) were studied for each drug as well as correlations between drugs and age. Results A linear relationship was found between ACh- and MCh-CVCpeak (r² = 0.75, p = 0.01) and between ACh- and MCh-CVC AUC (r² = 0.55, p = 0.02). MCh inter-site CV for both CVCpeak (12.2%) and CVC AUC (13.8%) was significantly lower than ACh inter-site CV for CVCpeak (15.5%) and CVC AUC (15.3%), respectively. MCh inter-day CV for CVCpeak (17.2%) and CVC AUC (14.6%) was significantly lower than ACh inter-day CV for CVCpeak (19.7%) and ACh CVC AUC (21.2%). For ACh and MCh, the CVCpeak and CVC AUC were higher at 16:00 pm than at 11:00 am (p < 0.05 for all). Finally, both ACh- and MCh-CVCpeak exhibited a logarithmic decrease with age (r² = 0.61, p < 0.01 and r² = 0.58, p < 0.01). Conclusion Although both drugs exhibited circadian and age variability, MCh exhibited less inter-site and interday variabilities than did ACh for the evaluation of cutaneous endothelium-dependent vasodilation. These findings should be taken into account in studies of cutaneous vascular function by iontophoresis coupled with laser Doppler flowmetry.

Dual-mode Imaging of Cutaneous Tissue Oxygenation and Vascular Function

Accurate assessment of cutaneous tissue oxygenation and vascular function is important for appropriate detection, staging, and treatment of many health disorders such as chronic wounds. We report the development of a dual-mode imaging system for non-invasive and non-contact imaging of cutaneous tissue oxygenation and vascular function. The imaging system integrated an infrared camera, a CCD camera, a liquid crystal tunable filter and a high intensity fiber light source. A Labview interface was programmed for equipment control, synchronization, image acquisition, processing, and visualization. Multispectral images captured by the CCD camera were used to reconstruct the tissue oxygenation map. Dynamic thermographic images captured by the infrared camera were used to reconstruct the vascular function map. Cutaneous tissue oxygenation and vascular function images were co-registered through fiduciary markers. The performance characteristics of the dual-mode image system were tested in humans.