Tricyclic Spirolactones as Modular TRPV1 Synthetic Agonists

In Silico-Guided Rational Drug Design and Synthesis of Novel 4-(Thiophen-2-yl)butanamides as Potent and Selective TRPV1 Agonists

We describe an in silico-guided rational drug design and the synthesis of the suggested ligands, aimed at improving the TRPV1-ligand binding properties and the potency of N-(4-hydroxy-3-methoxybenzyl)-4-(thiophen-2-yl) butanamide I, a previously identified TRPV1 agonist. The docking experiments followed by molecular dynamics simulations and thermodynamic analysis led the drug design toward both the introduction of a lipophilic iodine and a flat pyridine/benzene at position 5 of the thiophene nucleus. Most of the synthesized compounds showed high TRPV1 efficacy and potency as well as selectivity. The molecular modeling analysis highlighted crucial hydrophobic interactions between Leu547 and the iodo-thiophene nucleus, as in amide 2a, or between Phe543 and the pyridinyl moiety, as in 3a. In the biological evaluation, both compounds showed protective properties against oxidative stress-induced ROS formation in human keratinocytes. Additionally, while 2a showed neuroprotective effects in both neurons and rat brain slices, 3a exhibited potent antinociceptive effect in vivo..

Agonistic/antagonistic properties of lactones in food flavors on the sensory ion channels TRPV1 and TRPA1

Flavor compounds provide aroma and sensations in the oral cavity. They are not present alone in the oral cavity, but rather in combination with several other food ingredients. This study aimed to clarify the relationship between the mixing of pungent flavor compounds and the response of pungent receptors, TRPV1 and TRPA1 channels. We focused on lactones that activate TRPV1 despite their presence in bland foods, such as dairy products and fruits, and analyzed their interaction with receptors using TRPV1- and TRPA1-expressing HEK293 cells. We found that γ-octalactone, γ-nonalactone, and δ-nonalactone activated TRPA1. When mixed with pungent components, some γ- and δ-lactones inhibited capsaicin-mediated TRPV1 responses, and δ-dodecalactone inhibited allyl isothiocyanate-mediated TRPA1 responses. Furthermore, the dose-response relationship of capsaicin and γ-nonalactone to TRPV1 suggests that γ-nonalactone acts as an agonist or antagonist of TRPV1, depending on its concentration. Conversely, γ-nonalactone and δ-dodecalactone were found to act only as agonists and antagonists, respectively, against TRPA1. These results suggest that lactones in foods may not only endow food with aroma, but also play a role in modulating food pungency by acting on TRPV1 and TRPA1. The dose-response relationships of a mixture of flavor compounds with TRPV1 and TRPA1 provide insights into the molecular physiological basis of pungency that may be the cornerstone for developing new spice mix recipes.

TRPV1-Targeted Drugs in Development for Human Pain Conditions

The transient receptor potential vanilloid-1 (TRPV1) is a non-specific cation channel known for its sensitivity to pungent vanilloid compound (i.e. capsaicin) and noxious stimuli, including heat, low pH or inflammatory mediators. TRPV1 is found in the somatosensory system, particularly primary afferent neurons that respond to damaging or potentially damaging stimuli (nociceptors). Stimulation of TRPV1 evokes a burning sensation, reflecting a central role of the channel in pain. Pharmacological and genetic studies have validated TRPV1 as a therapeutic target in several preclinical models of chronic pain, including cancer, neuropathic, postoperative and musculoskeletal pain. While antagonists of TRPV1 were found to be a valuable addition to the pain therapeutic toolbox, their clinical use has been limited by detrimental side effects, such as hyperthermia. In contrast, capsaicin induces a prolonged defunctionalisation of nociceptors and thus opened the door to the development of a new class of therapeutics with long-lasting pain-relieving effects. Here we review the list of TRPV1 agonists undergoing clinical trials for chronic pain management, and discuss new indications, formulations or combination therapies being explored for capsaicin. While the analgesic pharmacopeia for chronic pain patients is ancient and poorly effective, modern TRPV1-targeted drugs could rapidly become available as the next generation of analgesics for a broad spectrum of pain conditions.