A capsaicinoid-based soft drug, AG1529, for attenuating TRPV1-mediated histaminergic and inflammatory sensory neuron excitability

Abstract

TRPV1, a member of the transient receptor potential (TRP) family, is a nonselective calcium permeable ion channel gated by physical and chemical stimuli. In the skin, TRPV1 plays an important role in neurogenic inflammation, pain and pruritus associated to many dermatological diseases. Consequently, TRPV1 modulators could represent pharmacological tools to respond to important patient needs that still represent an unmet medical demand. Previously, we reported the design of capsaicinoid-based molecules that undergo dermal deactivation (soft drugs), thus preventing their long-term dermal accumulation. Here, we investigated the pharmacological properties of the lead antagonist, 2-((4-hydroxy-2-iodo-5-methoxybenzyl) amino)-2-oxoethyl dodecanoate (AG1529), on heterologously expressed human TRPV1 (hTRPV1), on nociceptor excitability and on an in vivo model of acute pruritus. We report that AG1529 competitively blocked capsaicin-evoked activation of hTRPV1 with micromolar potency, moderately affected pH-induced gating, and did not alter voltage- and heat-mediated responses. AG1529 displays modest receptor selectivity as it mildly blocked recombinant hTRPA1 and hTRPM8 channels. In primary cultures of rat dorsal root ganglion (DRG) neurons, AG1529 potently reduced capsaicin-evoked neuronal firing. AG1529 exhibited lower potency on pH-evoked TRPV1 firing, and TRPA1-elicited nociceptor excitability. Furthermore, AG1529 abolished histaminergic and inflammation mediated TRPV1 sensitization in primary cultures of DRG neurons. Noteworthy, dermal wiping of AG1529, either in an acetone-based formulation or in an anhydrous ointment, dose-dependently attenuated acute histaminergic itch in a rodent model. This cutaneous anti-pruritic effect was devoid of the normal nocifensive action evoked by the burning sensation of capsaicin. Taken together, these preclinical results unveil the mode of action of AG1529 on TRPV1 channels and substantiate the tenet that this capsaicinoid-based soft drug is a promising candidate for drug development as a topical anti-pruritic and anti-inflammatory medication.

β–Lactam TRPM8 Antagonist RGM8-51 Displays Antinociceptive Activity in Different Animal Models

“…All cell culture procedures were performed in a laminar flow cabinet (Model Telstar AV-100, Institut Català de Nanociència i Nanotecnologia, Bellaterra, Spain). Experiments were performed 24-48 h after cell seeding [ 63 ].…”

Synthesis of 6- Tert -Octyl and 6,8-Di Tert -Butyl Coumarins, Two Coumarins of Biological Interest

“…The mixture of products is purified by a rapid method of silica gel chromatography column 60 G (2% ethyl acetate in n-hexane), being obtained a white solid (yield: 19.0 g, 63%): Pf = 38°C. Rf = 0.86 (20% ethyl acetate/n-hexane); 1…”

“…The reaction products are separated on a chromatographic column using Silicagel G and as eluent a solution of increasing concentration of ethyl acetate in n-hexane. After purification 210 mg of the compound is obtained (yield 75%): Pf = 41-43 ºC, Rf = 0.48(20% Ethyl Acetate/n-hexane); 1 Procedure: 3.15 mmol (585 mg) of 2-hydroxy-3,5-diterbutyl benzaldehyde and 3.77 mmol of methyl malonate (0.498 mg, 0.4 mL) are added to a roundbottomed flask containing absolute alcohol (25 mL), and piperidine drops as catalyst. The temperature is raised to reflux and kept under stirring for 3 h. The progress of the reaction was followed visually by thin layer silica gel chromatography, with fluorescence indicator and UV lamp.…”

“…The past ten years have seen the emergence of specific small molecule antagonists targeting receptors on sensory neurons that detect painful stimuli. 1 Among these new therapeutic targets, TRPV1 has attracted the most attention. 2 TRPV1 (formerly known as the vanilloid receptor VR1) is probably still best recognized as the receptor for capsaicin (Figure 1, I), which is responsible for the piquancy of hot chili peppers.…”

“…Figure 3. Structure of 6-tert-octyl-2-oxo-2H-chromene-3-methylcarboxylate.The coumarin 6,8-ditert-butyl-2-oxo-2H-chromene-3-methylcarboxylate (Figure4) presents in the FTIR the signals of both carbonyls at 1.742,7 and 1.760,2 cm -1 (carbonyl ester and lactone, respectively) 1. H-NMR spectrum shows the H4 hydrogen signal of the lactone ring at  (ppm) 8.58 (1H4, s) and the aromatic ring at (ppm) 7.72 (1H5, d, J=1.4 Hz) and (ppm) 7.50 (1H7, d, J=1.4 Hz).…”