Dermal Blood Flow Response Research Articles

Trigeminovascular effects of propranolol in men and women, role for sex steroids

ObjectiveAssess whether propranolol modulates the trigeminovascular system in both men and women.MethodsWe investigated the effect of propranolol (80 mg, 90 min after oral administration, corresponding to T max) on the increase in dermal blood flow of the forehead skin (innervated by the trigeminal nerve) by capsaicin application (0.6 mg/mL) and electrical stimulation (0.2–1.0 mA) before and after placebo (grapefruit juice) or propranolol (oral solution diluted in grapefruit juice) in a randomized, double‐blind, placebo‐controlled cross‐over study, including healthy males (n = 10) and females on contraceptives (n = 11). Additionally, we compared our results with data from the Dutch IADB.nl prescription database by analyzing the change in triptan use after propranolol prescription in a population similar to our dermal blood flow study subjects (males and females, 20–39 years old).ResultsDermal blood flow responses to capsaicin were significantly attenuated after propranolol, but not after placebo. When stratifying by sex, no significant changes in the capsaicin‐induced dermal blood flow were observed in females after propranolol, whereas they remained significant in males. Dermal blood flow responses to electrical stimulation were not modified in any case. In our prescription database study, after propranolol, a more pronounced decrease in triptan use was observed in male patients than in female patients.InterpretationPropranolol (80 mg) inhibits capsaicin‐induced increases in dermal blood flow in a sex‐dependent manner. In patients, a more pronounced decrease in triptan use is observed in males when compared with females, suggesting an interaction between propranolol and sex steroids in the modulation of the trigeminovascular system.

RVCL-S and CADASIL display distinct impaired vascular function.

We aimed to evaluate the role of endothelial-dependent and endothelial-independent vascular reactivity in retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), both cerebral small vessel diseases are considered models for stroke, vascular dementia, and migraine. RVCL-S (n = 18) and CADASIL (n = 23) participants with TREX1 and NOTCH3 mutations, respectively, were compared with controls matched for age, body mass index, and sex (n = 26). Endothelial function was evaluated by flow-mediated vasodilatation, and endothelial-independent vascular reactivity (i.e., vascular smooth muscle cell function) was assessed by dermal blood flow response to capsaicin application. Flow-mediated vasodilatation was decreased in participants with RVCL-S compared with controls (2.32% ± 3.83% vs 5.76% ± 3.07% change in diameter, p = 0.023) but normal in participants with CADASIL. Vascular smooth muscle cell function was reduced in participants with CADASIL compared with controls (maximal dermal blood flow increase at 40 minutes after capsaicin: 1.38 ± 0.88 vs 2.22 ± 1.20 arbitrary units, p = 0.010) but normal in participants with RVCL-S. We identified endothelial dysfunction in RVCL-S and confirmed impaired vascular smooth muscle cell relaxation in CADASIL. Our findings may prove to be biomarkers for disease progression in both monogenic cerebral small vessel diseases and improve mechanistic insight in their pathophysiology. This may help in understanding common neurovascular disorders, including stroke, dementia, and migraine.

PP.20.01] REPRODUCIBILITY OF DIFFERENT MEASURES OF ENDOTHELIAL FUNCTION

Objective: Brachial artery flow-mediated dilatation (FMD) to determine endothelial function is an investigator-demanding method. Impaired endothelial function as measured by FMD is known to be associated with cardiovascular risk factors. Local thermal hyperaemia (LTH) of the skin measured with a laser Doppler flow imager is less demanding and may serve as an alternative. We investigated the reproducibility of LTH and its correlation with FMD. In addition, the association of FMD with post-occlusive dermal hyperaemia (PORH), a widely used measure of microvascular function, was assessed. Design and method: FMD, LTH and PORH were measured in 27 healthy men (8 smokers) on two occasions, one week apart, at the same time of the day. FMD, measured with ultra-sound, was expressed as the maximal percentage increase in brachial artery diameter during reactive hyperaemia. LTH peak was defined as the maximal dermal blood flow (DBF) response within the first ten minutes and LTH plateau as the average DBF response during the last five minutes of 35 heating in arbitrary units (a.u.), measured with a laser Doppler flow imager. PORH Peak and AUC were measured at the volar site of the left forearm just under the pressure cuff, using a laser speckle imager. Results: Coefficients of variation (n = 27) of the LTH peak and plateau response were 18% and 21%, of the PORH peak and area under the curve (AUC) response both 13% and of the FMD response 21%. The LTH peak and plateau response and FMD response were not correlated, whereas the PORH AUC was correlated with FMD (r = 0.46, p < 0.05) and PORH Peak correlated with LTH Plateau (r = 0.58, p < 0.05). Conclusions: The reproducibility of the LTH plateau response and FMD response were almost equal in this study. In addition, as LTH and FMD did not correlate, these responses appear to provide different information. PORH, however, correlated partly with both LTH and FMD and should be further investigated as a possible alternative for FMD in long-term outcome studies.

Activation of PAC1 by maxadilan: a new human target engagement biomarker

Event Abstract Back to Event Activation of PAC1 by maxadilan: a new human target engagement biomarker Linde Buntinx1*, Marleen Depre1, Els Ampe1, Anne Vanhecken1 and Jan De Hoon1 1 Center for Clinical Pharmacology, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Belgium Background: Maxadilan, isolated from the sand fly Lutzomyia longipalpis, is a potent vasodilator peptide activating the mammalian PAC1 receptor, a promising target for migraine therapy (1). Therefore, maxadilan is suggested as a target-engagement tool to study PAC1 antagonists. Objectives: (1) To determine, as a first in human study, the dose response, safety and time course of the dermal blood flow (DBF) after intradermal (ID) injections of maxadilan in the human forearm and (2) to assess the inter-arm and inter-period reproducibility of this response, as measured with Laser Doppler Imaging (LDI). Results: Maxadilan was found to be safe based on AE reporting, ECG, vital signs, physical examination and safety laboratory assessments. ID maxadilan (0.9, 3 and 10ng) produced a robust increase in DBF compared to baseline and placebo. Forearm DBF response to 0.9ng ID injections of maxadilan in healthy male volunteers was reproducible between periods (Concordance correlation coefficient (CCC)>0.7) and between arms (CCC>0.7) when data were calculated as AUC0-180min (perfusion units*min). An increase in DBF was observed already 5 minutes after maxadilan injection and reached a plateau-phase after 60 minutes lasting until 72 hours, with an unexpected peak at 24 hours, compared to baseline and placebo. Sample size calculations show that samples of approximately 10 subjects are sufficient to detect a 50% difference between 2 independent groups with 80% power. Conclusion: As intradermal injections of maxadilan induce reproducible changes in dermal blood flow, it is an appealing new target-engagement biomarker for the study of PAC1 receptor antagonists in early clinical development studies.

Development of an in vivo target-engagement biomarker for TRPA1 antagonists in humans.

To develop a non-invasive, safe and reproducible target-engagement biomarker for future TRPA1 antagonists in healthy volunteers. Dose finding (n=11): 3%, 10%, and 30% cinnamaldehyde (CA) and placebo (= vehicle) was topically applied on the right forearm. One-way ANOVA with post-hoc Bonferroni was used to compare between doses. Reproducibility: 10% CA doses were topically applied during one visit on both arms (n=10) or during two visits (n=23) separated by a washout period of 7 days. CA-induced dermal blood flow (DBF) was assessed by laser Doppler imaging (LDI) at baseline and at 10, 20, 30, 40 and 50min post-CA. Paired t-test was used to compare between arms or visits. Concordance correlation coefficient (CCC) was calculated to assess reproducibility. Data are expressed as percent change from baseline (mean ± 95% CI). All three doses increased DBF compared to vehicle at all time-points, with the maximum response at 10-20min post-CA. Dose response was found when comparing AUC0-50min of 30% CA (51 364 ± 8475%*min) with 10% CA (32 239 ± 8034%*min, P=0.03) and 3% CA (30 226 ± 11 958%*min, P=0.015). 10% CA was chosen as an effective and safe dose. DBF response to 10% CA was found to be reproducible between arms (AUC0-50min , CCC = 0.91) and visits (AUC0-50min , CCC = 0.83). Based on sample size calculations, this model allows a change in CA-induced DBF of 30-50% to be detected between two independent groups of maximum 10-15 subjects with 80% power. Evaluation of CA-induced changes in DBF offers a safe, non-invasive and reproducible target-engagement biomarker in vivo in humans to evaluate TRPA1 antagonists.

A human trigeminovascular biomarker for antimigraine drugs: A randomised, double-blind, placebo-controlled, crossover trial with sumatriptan.

Current antimigraine drugs are believed, besides their direct vasoconstrictive effect, to inhibit calcitonin gene-related peptide (CGRP) release from trigeminal nerve endings during migraine. Objective The objective of this report is to establish a biomarker for the CGRP-interfering effect of antimigraine drugs. Methods We quantified the effect of sumatriptan on the trigeminal nerve-mediated rise in forehead dermal blood flow (DBF), induced by capsaicin application (0.6 mg/ml) and electrical stimulation (0.2-1.0 mA), in a randomised, double-blind, placebo-controlled, crossover study in healthy male ( n = 11, age ± SD: 29 ± 8 years) and female ( n = 11, 32 ± 7 years) individuals. Results DBF responses to capsaicin were attenuated by sumatriptan (ΔDBF, mean ± SEM: 82 ± 18 AU, p = 0.0002), but not by placebo (ΔDBF: 21 ± 12 AU, p = 0.1026). Conclusion We demonstrated that sumatriptan inhibits increases in DBF, induced by the release of, most likely, CGRP. Thus, our model may be used as a biomarker to establish the trigeminovascular effects of (potential) antimigraine drugs, such as CGRP receptor antagonists or antibodies directed against CGRP or its receptor.

The influence of migraine and female hormones on capsaicin-induced dermal blood flow.

Background Migraine is much more common in females than in males, and occurrence is associated with changes in female sex hormones. Calcitonin gene-related peptide (CGRP) plays a key role in migraine, and variations in female sex hormones may affect CGRP sensitivity and/or production. Objectives Investigate repeatability, gender differences, influence of the menstrual cycle and of migraine on CGRP-dependent changes in dermal blood flow (DBF). Methods CGRP-dependent increases in DBF were assessed using laser Doppler perfusion imaging after topical application of 300 or 1000 µg capsaicin on the forearm of healthy subjects and migraine patients. Results In healthy males, DBF response did not vary over time and was comparable with DBF in male migraineurs. In healthy females, capsaicin-induced DBF responses to both doses of capsaicin were higher during menstruation compared to the late-secretory phase (p < 0.05); this menstrual cycle dependence was absent in female migraine patients. Compared to healthy subjects, female migraineurs displayed a higher DBF response both during menstruation and during the late-secretory phase (p < 0.05). Conclusions An increased capsaicin-induced, CGRP-mediated DBF response was observed during menstruation in healthy women, but in female migraine patients this increased response was not affected by the menstrual cycle.

Development of an experimental model to study trigeminal nerve-mediated vasodilation on the human forehead

During migraine, trigeminal sensory nerve terminals release calcitonin gene-related peptide (CGRP), inducing nociception and vasodilation. Applied on the skin, capsaicin activates the transient receptor potential vanilloid type 1 (TRPV1) channel and releases CGRP from sensory nerve terminals, thus increasing dermal blood flow (DBF). Using capsaicin application and electrical stimulation of the forehead skin, a trigeminal nerve-innervated dermatome, we aimed to develop a model to measure trigeminal nerve-mediated vasodilation in humans. Using laser Doppler imaging, forehead DBF responses to application of capsaicin (0.06 mg/ml and 6.0 mg/ml) and saline, with and without iontophoresis, were studied in healthy subjects. The within-subject coefficient of variation (WCV) of repeated DBF measurements was calculated to assess reproducibility. Maximal DBF responses to 6.0 mg/ml capsaicin with and without iontophoresis did not differ (Emax 459 ± 32 and 424 ± 32 arbitrary units (a.u.), WCV 6 ± 4%). In contrast, DBF responses to 0.06 mg/ml capsaicin were significantly larger with than without iontophoresis (Emax 307 ± 60 versus 187 ± 21 a.u., WCV 21 ± 13%). Saline with iontophoresis significantly increased DBF (Emax: 245 ± 26 a.u, WCV 11 ± 8%), while saline application without iontophoresis did not affect DBF. Topical application of capsaicin and electrical stimulation induce reproducible forehead DBF increases and therefore are suitable to study trigeminal nerve-mediated vasodilation in humans.

Influence of varying estrogen levels on trigeminal CGRP release in healthy women

Migraine is 2-3 times more prevalent in women than in men, with frequent perimenstrual attacks. TRPV1 receptors on sensory nerve endings of the trigeminal track are important in mediating migraine attacks by releasing the vasodilator calcitonin gene-related peptide (CGRP). Variation in estrogen levels during the menstrual cycle may have an influence on the sensitivity of the TRPV1 receptor or on the amount of CGRP in perivascular nerve terminals and hence on CGRP release. Capsaicin, the active ingredient of hot chili peppers, stimulates the TRPV1 receptor and causes CGRP-dependent vasodilatation [1]. We set up a model to study trigeminal CGRP release in humans. We compared the vasodilator effects of capsaicin application and electrical stimulation on the forehead skin. Healthy women, not using hormonal contraceptives (age: 18-45, n=14), were studied with a Laser Doppler Imager on day 19-21 of their menstrual cycle and on day 1-2 of their menstruation. A 0.2 mM and a 20 mM capsaicin solution were applied to the skin. In addition, iontophoresis of saline was performed as a TRPV1-independent stimulus. Increases in dermal blood-flow (DBF) were measured. Blood samples were collected to measure estrogen levels. We measured higher DBF responses to application of 0.2 mM capsaicin (Max:226±34 a.u.) and 20 mM capsaicin (Max:507±39 a.u.) during day 1-2 (low estrogen levels: 15±2 pg/ml) of the menstruation, than during day 19-21 (high estrogen levels: 67±9 pg/ml) of the menstrual cycle (Max:176±34 a.u. and 432±33 a.u. for 0.2 mM and 20 mM, respectively, P<0.05). There was no difference in DBF responses to electrical stimulation of the forehead skin, suggesting that the observed changes are related to the sensitivity of the TRPV1 receptor. Our results indicate an influence of variation in estrogen levels on trigeminal CGRP release, with the highest reactivity observed around the menstruation when estrogen levels are low. This mechanism may, at least partly, explain the high incidence of migraine attacks during the perimenstrual period.

Calcitonin Gene-Related Peptide8-37 Antagonizes Capsaicin-Induced Vasodilation in the Skin: Evaluation of a Human in Vivo Pharmacodynamic Model

The purpose of this study was to identify the mediators involved in capsaicin-induced vasodilation in the human skin and to evaluate a pharmacodynamic model for the early clinical evaluation of calcitonin gene-related peptide (CGRP) receptor antagonists. Dermal blood flow (DBF) response of the forearm skin to topically applied capsaicin was measured using laser Doppler perfusion imaging in 22 subjects. The effect of intra-arterially administered CGRP(8-37) (1200 ng . min(-1) . dl(-1) forearm), indomethacin (5 mug . min(-1) . dl(-1) forearm), and N(G)-monomethyl-l-arginine (l-NMMA; 0.2 mg . min(-1) dl(-1) forearm), and orally administered aprepitant (375 mg) on capsaicin-induced dermal vasodilation was assessed. Furthermore, the diurnal variation of the DBF response to capsaicin was studied. CGRP(8-37) inhibited the capsaicin-induced DBF increase: 217(145, 290)% in infused versus 370 (254, 486)% in the noninfused arm [mean (95% CI); p = 0.004]. In contrast, indomethacin, l-NMMA, aprepitant, and the time of assessment did not affect the DBF response to capsaicin. Thus, capsaicin-induced vasodilation in the human forearm skin is largely mediated by CGRP, but not by vasodilating prostaglandins, nitric oxide, or substance P. The response to capsaicin does not display a circadian rhythm. A pharmacodynamic model is proposed to evaluate CGRP receptor antagonists in humans in vivo.

Reduced Vascular Endothelial Growth Factor Expression and Intra-Epidermal Nerve Fiber Loss in Human Diabetic Neuropathy

To assess the relevance of vascular endothelial growth factor (VEGF) in the maintenance of peripheral nerve integrity in diabetic neuropathy we have assessed the expression of VEGF and intra-epidermal nerve fiber density (IENFD) in skin biopsy samples from diabetic patients. Fifty-three diabetic patients and 12 nondiabetic control subjects underwent neurological evaluation, electrophysiology, quantitative sensory, and autonomic function testing. Dermal blood flow responses were evaluated with laser Doppler flowmetry. Skin biopsies were performed on the dorsum of the foot, and IENFD was quantified and compared with the expression of vascular endothelial growth factor A (VEGF-A), its receptor vascular endothelial growth factor receptor 2 (VEGFR-2), hypoxia-inducible factor 1alpha (HIF-1alpha), and microvessel density. IENFD decreased progressively with increasing severity of diabetic neuropathy (P < 0.001). The dermal blood flow response to acetylcholine was reduced in diabetic patients with mild and moderate neuropathy (P < 0.01), and the intensity of staining for epidermal VEGF-A was significantly reduced in diabetic patients compared with control subjects (P < 0.01). Epidermal HIF-1alpha and VEGFR-2 expression did not differ between groups. Progressive endothelial dysfunction, a reduction in VEGF expression, and loss of intra-epidermal nerve fibers occurs in the foot skin of diabetic patients with increasing neuropathic severity.

Reproducibility of the capsaicin‐induced dermal blood flow response as assessed by laser Doppler perfusion imaging

Part I: to establish the dose and appropriate application site of capsaicin on the human forearm in order to produce a robust and reproducible dermal blood flow (DBF) response. Part II: to evaluate the within-subject arm-to-arm and period-to-period reproducibility. Both parts consisted of two study visits. In part I, placebo and 100, 300 and 1000 microg capsaicin were applied at four predefined sites on the volar surface of both forearms. Placebo and capsaicin doses were randomized and balanced by site between subjects. Changes in DBF were assessed by laser Doppler perfusion imaging up to 60 min after capsaicin application. In part II, only 1000 microg capsaicin was applied on the proximal forearm and changes in DBF assessed up to 30 min (t(30)). DBF response was expressed as percent change from baseline +/- SD and the corresponding AUC(0-30). Reproducibility assessment included calculation of the concordance correlation coefficient (CCC). Part I (n = 12 subjects): compared with placebo, 300 and 1000 microg capsaicin increased DBF (P < 0.05) at all time points except at 10 min. This increase was reproducible at the two most proximal sites from the 30-min time point onwards when compared between arms (CCC >or= 0.8, i.e. substantial to almost perfect reproducibility). In part II (n = 11), t(30) averaged 390 +/- 120% and arm-to-arm reproducibility was almost perfect (CCC = 0.91) for AUC(0-30). Capsaicin induces a reproducible within-subject arm-to-arm increase in DBF. We provide a non-invasive pharmacodynamic model in humans to test antagonists of mediators involved in capsaicin-induced dermal vasodilation, including calcitonin gene-related peptide antagonists.

Dermal Blood Flow Response to Constant Pressure in Healthy Older and Younger Subjects

This study compared the dermal blood flow response to low levels of compressive pressure in healthy older and younger subjects. Dermal blood flow was measured over the left trochanter of 19 younger (21-45 yrs) and 22 older (> or = 60 yrs) subjects using a laser-Doppler velocitometer. Interface pressure, baseline flow, and flow during 60 minutes of left-side lying on an air mattress were measured. Baseline dermal blood flow did not differ significantly between the older and younger groups. Both groups showed a significant increase in blood flow over time during the 60 minutes of compression. The change in dermal blood flow over time was not significantly different between the two groups. This study demonstrated that healthy persons, regardless of their age, exhibited an increase in dermal blood flow over time at low levels of compressive pressure.