Inhibition of Ligand-Gated TRPA1 by General Anesthetics

Inhaled Volatile Molecules-Responsive TRP Channels as Non-Olfactory Receptors

Generally, odorant molecules are detected by olfactory receptors, which are specialized chemoreceptors expressed in olfactory neurons. Besides odorant molecules, certain volatile molecules can be inhaled through the respiratory tract, often leading to pathophysiological changes in the body. These inhaled molecules mediate cellular signaling through the activation of the Ca2+-permeable transient receptor potential (TRP) channels in peripheral tissues. This review provides a comprehensive overview of TRP channels that are involved in the detection and response to volatile molecules, including hazardous substances, anesthetics, plant-derived compounds, and pheromones. The review aims to shed light on the biological mechanisms underlying the sensing of inhaled volatile molecules. Therefore, this review will contribute to a better understanding of the roles of TRP channels in the response to inhaled molecules, providing insights into their implications for human health and disease.

CYP1B1-derived epoxides modulate the TRPA1 channel in chronic pain

Pain is often debilitating, and current treatments are neither universally efficacious nor without risks. Transient receptor potential (TRP) ion channels offer alternative targets for pain relief, but little is known about the regulation or identities of endogenous TRP ligands that affect inflammation and pain. Here, transcriptomic and targeted lipidomic analysis of damaged tissue from the mouse spinal nerve ligation (SNL)-induced chronic pain model revealed a time-dependent increase in Cyp1b1 mRNA and a concurrent accumulation of 8,9-epoxyeicosatrienoic acid (EET) and 19,20-EpDPA post injury. Production of 8,9-EET and 19,20-EpDPA by human/mouse CYP1B1 was confirmed in vitro, and 8,9-EET and 19,20-EpDPA selectively and dose-dependently sensitized and activated TRPA1 in overexpressing HEK-293 cells and Trpa1-expressing/AITC-responsive cultured mouse peptidergic dorsal root ganglia (DRG) neurons. TRPA1 activation by 8,9-EET and 19,20-EpDPA was attenuated by the antagonist A967079, and mouse TRPA1 was more responsive to 8,9-EET and 19,20-EpDPA than human TRPA1. This latter effect mapped to residues Y933, G939, and S921 of TRPA1. Intra-plantar injection of 19,20-EpDPA induced acute mechanical, but not thermal hypersensitivity in mice, which was also blocked by A967079. Similarly, Cyp1b1-knockout mice displayed a reduced chronic pain phenotype following SNL injury. These data suggest that manipulation of the CYP1B1-oxylipin-TRPA1 axis might have therapeutic benefit.

TRPA1 Polymorphisms Modify the Hypotensive Responses to Propofol with No Change in Nitrite or Nitrate Levels

Anesthesia with propofol is frequently associated with hypotension. The TRPA1 gene contributes to the vasodilator effect of propofol. Hypotension is crucial for anesthesiologists because it is deleterious in the perioperative period. We tested whether the TRPA1 gene polymorphisms or haplotypes interfere with the hypotensive responses to propofol. PCR-determined genotypes and haplotype frequencies were estimated. Nitrite, nitrates, and NOx levels were measured. Propofol induced a more expressive lowering of the blood pressure (BP) without changing nitrite or nitrate levels in patients carrying CG+GG genotypes for the rs16937976 TRPA1 polymorphism and AG+AA genotypes for the rs13218757 TRPA1 polymorphism. The CGA haplotype presented the most remarkable drop in BP. Heart rate values were not impacted. The present exploratory analysis suggests that TRPA1 genotypes and haplotypes influence the hypotensive responses to propofol. The mechanisms involved are probably other than those related to NO bioavailability. With better genetic knowledge, planning anesthesia with fewer side effects may be possible.

Transient receptor potential Ankyrin 1: structure, function and ligands

Introduction: Transient receptor potential ankyrin 1 (TRPA1) is a protein expressed in many living organisms. During the study of TRPA1, its unique biological role as a universal and polymodal sensor of various altering agents was found. The aim of this study is to search and generalize information about structural features and molecular determinants, mechanisms of activation, action and modulation of TRPA1 as a universal pain and inflammation sensor, as well as the nature of activators and antagonists of this target and their therapeutic potential.

Materials and methods: This article presents an overview of the results of scientific research of TRPA1, its modulators, as well as an overview of their pharmacological potential over the period from the discovery of these channels to the present, with an emphasis on the last decade.

Results and discussion: The main collected data on expression, structural features and molecular determinants, mechanisms of activation and action of TRPA1 indicate its role as a universal and labile element of the primary response of the body to adverse exogenous and endogenous factors. Regardless of the nature of the stimulus, hyperstimulation of TRPA1 channels can lead to such phenomena as pain, inflammation, itching, edema and other manifestations of alteration, and therefore TRPA1 blockade can be used in the treatment of various diseases accompanied by these pathological conditions. Currently, TRPA1 antagonists are being actively searched for and studied, as evidenced by a high patent activity over the past 14 years; however, the molecular mechanisms of action and pharmacological properties of TRPA1 blockers remain understudied.

Conclusion: Acquire of new information about TRPA1 will help in the development of its modulators, which can become promising analgesics, anti-inflammatory drugs, bronchodilators, and agents for the treatment of cardiovascular diseases of new generations.

Atomistic mechanisms of human TRPA1 activation by electrophile irritants through molecular dynamics simulation and mutual information analysis

The ion channel TRPA1 is a promiscuous chemosensor, with reported response to a wide spectrum of noxious electrophilic irritants, as well as cold, heat, and mechanosensation. It is also implicated in the inception of itch and pain and has hence been investigated as a drug target for novel analgesics. The mechanism of electrophilic activation for TRPA1 is therefore of broad interest. TRPA1 structures with the pore in both open and closed states have recently been published as well as covalent binding modes for electrophile agonists. However, the detailed mechanism of coupling between electrophile binding sites and the pore remains speculative. In addition, while two different cysteine residues (C621 and C665) have been identified as critical for electrophile bonding and activation, the bound geometry has only been resolved at C621. Here, we use molecular dynamics simulations of TRPA1 in both pore-open and pore-closed states to explore the allosteric link between the electrophile binding sites and pore stability. Our simulations reveal that an open pore is structurally stable in the presence of open ‘pockets’ in the C621/C665 region, but rapidly collapses and closes when these pockets are shut. Binding of electrophiles at either C621 or C665 provides stabilisation of the pore-open state, but molecules bound at C665 are shown to be able to rotate in and out of the pocket, allowing for immediate stabilisation of transient open states. Finally, mutual information analysis of trajectories reveals an informational path linking the electrophile binding site pocket to the pore via the voltage-sensing-like domain, giving a detailed insight into the how the pore is stabilized in the open state.

Efficient and flexible synthesis of new photoactivatable propofol analogs

Propofol is a widely used general anesthetic, which acts by binding to and modulating several neuronal ion channels. We describe the synthesis of photoactivatable propofol analogs functionalized with an alkyne handle for bioorthogonal chemistry. Such tools are useful for detecting and isolating photolabeled proteins. We designed expedient and flexible synthetic routes to three new diazirine-based crosslinkable propofol derivatives, two of which have alkyne handles. As a proof of principle, we show that these compounds activate heterologously expressed Transient Receptor Potential Ankyrin 1 (TRPA1), a key ion channel of the pain pathway, with a similar potency as propofol in fluorescence-based functional assays. This work demonstrates that installation of the crosslinkable and clickable group on a short nonpolar spacer at the para position of propofol does not affect TRPA1 activation, supporting the utility of these chemical tools in identifying and characterizing potentially druggable binding sites in propofol-interacting proteins.