Functional Analysis of TRPA1, TRPM3, and TRPV1 Channels in Human Dermal Arteries and Their Role in Vascular Modulation.

Transient receptor potential (TRP) channels are pivotal in modulating vascular functions. In fact, topical application of cinnamaldehyde or capsaicin (TRPA1 and TRPV1 channel agonists, respectively) induces "local" changes in blood flow by releasing vasodilator neuropeptides. We investigated TRP channels' contributions and the pharmacological mechanisms driving vasodilation in human isolated dermal arteries. Ex vivo studies assessed the vascular function of artery segments and analyzed the effects of different compounds. Concentration-response curves to cinnamaldehyde, pregnenolone sulfate (PregS, TRPM3 agonist), and capsaicin were constructed to evaluate the effect of the antagonists HC030031 (TRPA1); isosakuranetin (TRPM3); and capsazepine (TRPV1). Additionally, the antagonists/inhibitors olcegepant (CGRP receptor); L-NAME (nitric oxide synthase); indomethacin (cyclooxygenase); TRAM-34 plus apamin (K+ channels); and MK-801 (NMDA receptors, only for PregS) were used. Moreover, CGRP release was assessed in the organ bath fluid post-agonist-exposure. In dermal arteries, cinnamaldehyde- and capsaicin-induced relaxation remained unchanged after the aforementioned antagonists, while PregS-induced relaxation was significantly inhibited by isosakuranetin, L-NAME and MK-801. Furthermore, there was a significant increase in CGRP levels post-agonist-exposure. In our experimental model, TRPA1 and TRPV1 channels seem not to be involved in cinnamaldehyde- or capsaicin-induced relaxation, respectively, whereas TRPM3 channels contribute to PregS-induced relaxation, possibly via CGRP-independent mechanisms.

Vascular read-out for TRP channel functionality on distal peripheral nerve endings in healthy men.

BACKGROUND: Quantification of the vasodilation after topical application of capsaicin or cinnamaldehyde is often implemented to indirectly assess Transient Receptor Potential (TRP) Vanilloid 1 (TRPV1) or Ankyrin 1 (TRPA1) functionality respectively. This method has been well-established on the human forearm. However, to enable TRP functionality assessments in distal peripheral neuropathy, the vascular response upon TRP activation on dorsal finger skin was characterized. METHODS: Two doses of cinnamaldehyde (3 % and 10 % v/v) and capsaicin (300 µg and 1000 µg) were topically applied (20 µL) on the skin of the mid three proximal phalanges in 17 healthy men. The dose-response, and inter-hand and inter-period reproducibility of the dermal blood flow (DBF) increase was assessed using Laser Speckle Contrast Imaging (LSCI) during 60 min post-application. Linear mixed models explored dose-driven differences, whereas the intra-class correlation coefficient (ICC) estimated the reproducibility of the vascular response. RESULTS: Both doses of cinnamaldehyde and capsaicin induced a robust, dose-dependent increase in DBF. The vascular response to cinnamaldehyde 10 % on finger skin, expressed as area under the curve, correlated well over time (ICC = 0.66) and excellently between hands (ICC = 0.87). Similarly, the response to capsaicin 1000 µg correlated moderately over time (ICC = 0.50) and well between hands (ICC = 0.73). CONCLUSION: The vascular response upon topical cinnamaldehyde and capsaicin application on finger skin is an alternative approach for measurements on forearm skin. Thereby, it is a promising vascular read-out to investigate the pathophysiology, and TRP involvement in particular, of specific peripheral neuropathic pain syndromes.

TRPA1 Antagonist LY3526318 Inhibits the Cinnamaldehyde-Evoked Dermal Blood Flow Increase: Translational Proof of Pharmacology.

Transient receptor potential Ankyrin 1 (TRPA1) is an ion channel expressed by sensory neurons, where it mediates pain signaling. Consequently, it has emerged as a promising target for novel analgesics, yet, to date, no TRPA1 antagonists have been approved for clinical use. In the present translational study, we utilized dermal blood flow changes evoked by TRPA1 agonist cinnamaldehyde as a target engagement biomarker to investigate the in vivo pharmacology of LY3526318, a novel TRPA1 antagonist. In rats, LY3526318 (1, 3, and 10 mg/kg, p.o.) dose-dependently reduced the cutaneous vasodilation typically observed following topical application of 10% v/v cinnamaldehyde. The inhibition was significant at the site of cinnamaldehyde application and also when including an adjacent area of skin. Similarly, in a cohort of 16 healthy human volunteers, LY3526318 administration (10, 30, and 100 mg, p.o.) dose-dependently reduced the elevated blood flow surrounding the site of 10% v/v cinnamaldehyde application, with a trend toward inhibition at the site of application. Comparisons between both species reveal that the effects of LY3526318 on the cinnamaldehyde-induced dermal blood flow are greater in rats relative to humans, even when adjusting for cross-species differences in potency of the compound at TRPA1. Exposure-response relationships suggest that a greater magnitude response may be observed in humans if higher antagonist concentrations could be achieved. Taken together, these results demonstrate that cinnamaldehyde-evoked changes in dermal blood flow can be utilized as a target engagement biomarker for TRPA1 activity and that LY3526318 antagonizes the ion channel both in rats and humans.

Does etodolac affect TRPA1 functionality in vivo in human?

OBJECTIVES: In preclinical research, etodolac, a non-steroidal anti-inflammatory drug, affected transient receptor potential ankyrin 1 (TRPA1) activation. Yet, whether the in vitro interaction between etodolac and TRPA1 translates to altered TRPA1 functionality in vivo in human remains to be investigated. METHODS: A randomized, double-blinded, celecoxib-controlled study was conducted to assess the effect of etodolac on TRPA1-mediated dermal blood flow (DBF) changes on the forearm of 15 healthy, male volunteers aged between 18 and 45 years. Over four study visits, separated by at least five days wash-out, a single or four-fold dose of etodolac 200 mg or celecoxib 200 mg was administered orally. Two hours post-dose, TRPA1 functionality was evaluated by assessing cinnamaldehyde-induced DBF changes. DBF changes were quantified and expressed in Perfusion Units (PUs) using laser Doppler imaging during 60 min post-cinnamaldehyde application. The corresponding area under the curve (AUC0-60min) was calculated as summary measure. Statistical analysis was performed using Linear mixed models with post-hoc Dunnett. RESULTS: Neither the single dose of etodolac nor celecoxib inhibited the cinnamaldehyde-induced DBF changes compared to no treatment (AUC0-60min ± SEM of 17,751 ± 1,514 PUs*min and 17,532 ± 1,706 PUs*min vs. 19,274 ± 1,031 PUs*min, respectively, both p=1.00). Similarly, also a four-fold dose of both compounds failed to inhibit the cinnamaldehyde-induced DBF changes (19,235 ± 1,260 PUs*min and 19,367 ± 1,085 PUs*min vs. 19,274 ± 1,031 PUs*min, respectively, both p=1.00). CONCLUSIONS: Etodolac did not affect the cinnamaldehyde-induced DBF changes, suggesting that it does not alter TRPA1 functionality in vivo in human.

Co-creation with research participants to inform the design of electronic informed consent.

Objective: This study aimed to provide recommendations for a personalized electronic informed consent interface that is adapted to research participants' needs and could enable a longitudinal interaction between the participants and the research team. Methods: The co-creation process consisted of three co-creation workshops, one focus group discussion, and four semi-structured interviews. In total, 24 participants, who had taken part in four disparate clinical studies in Belgium, were involved. Descriptive statistics and qualitative content analysis were applied to analyze the survey data and audio recordings. Results: Varying perceptions on the type and amount of information described in an informed consent form were reported. Other findings were related to the structure and presentation of information, setting preferences for data sharing, and electronically signing new informed consent versions. Regarding the long-term interaction, most of the participants wanted to receive progress updates, including the results, of the study in which they had taken part. They proposed to receive a notification, preferably via email, in case new information is made available on the electronic informed consent interface. Conclusions: To optimally support the design of an electronic informed consent interface, it is key to understand the research participants' needs. Study findings suggest that an electronic informed consent interface may be a promising technological application to interactively provide study-related information and to keep participants informed during and after the clinical study.

First-in-human development of a pharmacodynamic biomarker for PAC1 receptor antagonists using intradermal injections of maxadilan.

Maxadilan, a potent vasodilator peptide, selectively activates the PAC1 receptor, a promising target for migraine therapy. Therefore, maxadilan has been suggested as a tool to study the pharmacodynamics (PDs) of PAC1 receptor antagonists. The objectives of this first-in-human study were to: (1) determine the safety, tolerability, dose response, and time course of the dermal blood flow (DBF) changes after intradermal (i.d.) injections of maxadilan in the human forearm, and (2) assess the inter-arm and inter-period reproducibility of this response. This was a single-center, open-label study in healthy subjects, comprising three parts: (1) dose-response (n = 25), (2) response duration (n = 10), and (3) reproducibility (n = 15). DBF measurements were performed using laser Doppler imaging (LDI) up to 60 min postinjection, or up to 5 days for the response duration assessments. To assess reproducibility, the intraclass correlation coefficient (ICC) and sample sizes were calculated. The i.d. maxadilan (0.001, 0.01, 0.1, 0.9, 3, and 10 ng) produced a well-tolerated, dose-dependent increase in DBF, with a half-maximal effective concentration fitted at 0.0098 ng. The DBF response to 0.9 ng maxadilan was quantifiable with LDI up to 72 h postinjection. The inter-period reproducibility of the DBF response was better upon 0.9 ng (ICC > 0.6) compared to 0.01 ng (ICC < 0.4) maxadilan. However, irrespective of the study design or maxadilan dose, a sample size of 11 subjects is sufficient to detect a 30% difference in DBF response with 80% power. In conclusion, intradermal maxadilan provides a safe, well-tolerated, and reproducible PD biomarker for PAC1 receptor antagonists in vivo in humans.

Doppler ultrasound to assess the pharmacodynamic effects of splanchnic vasoactive compounds.

AIMS: In search of noninvasive biomarkers to assess the pharmacodynamic effects of portal pressure-lowering drugs, the reproducibility of flow measurements in the superior mesenteric artery was evaluated using Doppler ultrasound. METHODS: A reproducibility study was conducted in 15 healthy male volunteers (18-50 y). Eight ultrasound measurements were performed for each subject: 2 observers each conducted 2 measurements during 2 separate visits. The following flow parameters were captured: peak systolic velocity (PSV), end diastolic velocity (EDV), pulsatility index (PI), volume flow (VF) and vessel diameter. Reproducibility was assessed by the intraclass correlation coefficient. RESULTS: Results are presented as intraclass correlation coefficient [95% confidence interval]. The flow parameters PSV, EDV, PI and VF correlated excellently within observer during visit 1 (0.888 [0.748-0.953], 0.910 [0.793-0.962], 0.844 [0.656-0.933] and 0.916 [0.857-0.951], respectively) and visit 2 (0.925 [0.829-0.968], 0.942 [0.863-0.976], 0.883 [0.719-0.954] and 0.915 [0.855-0.951], respectively). Measurements conducted during 2 separate visits by 1 observer correlated well to excellently for PSV, EDV, PI and VF (0.756 [0.552-0.875], 0.836 [0.694-0.916], 0.807 [0.631-0.904] and 0.839 [0.783-0.882], respectively). Measurements conducted by 2 distinct observers correlated well to excellently for PSV, EDV and VF during visit 1 (0.813 [0.584-0.922], 0.884 [0.597-0.945] and 0.786 [0.575-0.899], respectively) and visit 2 (0.779 [0.498-0.912], 0.861 [0.672-0.945], 0.810 [0.553-0.926], respectively). Vessel diameter measurements were poorly reproducible. CONCLUSION: Doppler ultrasound is a reproducible method for flow measurements in the superior mesenteric artery in a standardized group of healthy volunteers. Therefore, it is a promising technique to assess pharmacodynamic effects of splanchnic vasoactive compounds in early clinical drug development.

Pharmacokinetics during therapeutic hypothermia for neonatal hypoxic ischaemic encephalopathy: a literature review.

BACKGROUND: Neonatal hypoxic ischaemic encephalopathy due to perinatal asphyxia, can result in severe neurodevelopmental disability or mortality. Hypothermia is at present the only proven neuroprotective intervention. During hypothermia, the neonate may need a variety of drugs with their specific pharmacokinetic profile. The aim of this paper is to determine the effect that hypothermia for neonates suffering from hypoxic ischaemic encephalopathy has on the pharmacokinetics and to what extent dosing regimens need adjustments. METHOD: A systematic search was performed on PubMed, Embase and Cochrane Library of literature (2000-2020) using a combination of the following search terms: therapeutic hypothermia, neonate, hypoxic ischemic encephalopathy and pharmacokinetics. Titles and abstracts were screened, and inclusion/exclusion criteria were applied. Finally, relevant full texts were read, and secondary inclusion was applied on the identified articles. RESULTS: A total of 380 articles were retrieved, and 34 articles included after application of inclusion/exclusion criteria and duplicate removal, two additional papers were included as suggested by the reviewers. Twelve out of 36 studies on 15 compounds demonstrated a significant decrease in clearance, be it that the extent differs between routes of elimination and compounds, most pronounced for renal elimination (phenobarbital no difference, midazolam metabolite -21%, lidocaine -24%; morphine -21% to -47%, gentamicin -25% to -35%, amikacin -40%) during hypothermia. The data as retrieved in literature were subsequent compared with the dosing regimen as stated in the Dutch paediatric formulary. CONCLUSION: Depending on the drug-specific disposition characteristics, therapeutic hypothermia in neonates with hypoxic ischaemic encephalopathy affects pharmacokinetics.