Vanilloid receptor subunit 1 (VR1) appears to play a critical role in the transduction of noxious chemical and thermal stimuli by sensory nerve endings in peripheral tissues. Thus, VR1 antagonists are useful compounds to unravel the contribution of this receptor to pain perception, as well as to induce analgesia. We have used a combinatorial approach to identify new, nonpeptidic channel blockers of VR1. Screening of a library of trimers of N -alkylglycines resulted in the identification of two molecules referred to as DD161515 { N -[2-(2-( N -methylpyrrolidinyl)ethyl]glycyl]-[ N -[2,4-dichlorophenethyl]glycyl]- N -(2,4-dichlorophenethyl)glycinamide} and DD191515 {[ N -[3-( N , N -diethylamino)propyl]glycyl]-[ N -[2,4-dichlorophenethyl]glycyl]- N -(2,4-dichlorophenethyl)glycinamide} that selectively block VR1 channel activity with micromolar efficacy, rivaling that characteristic of vanilloid-related inhibitors. These compounds appear to be noncompetitive VR1 antagonists that recognize a receptor site distinct from that of capsaicin. Intraperitoneal administration of both trialkylglycines into mice significantly attenuated thermal nociception as measured in the hot plate test. It is noteworthy that these compounds eliminated pain and neurogenic inflammation evoked by intradermal injection of capsaicin into the animal hindpaw, as well as the thermal hyperalgesia induced by tissue irritation with nitrogen mustard. In contrast, responses to mechanical stimuli were not modified by either compound. Modulation of sensory nerve fibers excitability appears to underlie the peptoid analgesic activity. Collectively, these results indicate that blockade of VR1 activity attenuates chemical and thermal nociception and hyperalgesia, supporting the tenet that this ionotropic receptor contributes to chemical and thermal sensitivity and pain perception in vivo . These trialkylglycine-based, noncompetitive VR1 antagonists may likely be developed into analgesics to treat inflammatory pain.

The rapid advances of 3D techniques for the structural determination of proteins and the development of numerous computational methods and strategies have led to identifying highly active compounds in computer drug design. Molecular docking is a method widely used in high-throughput virtual screening campaigns to filter potential ligands targeted to proteins. A great variety of docking programs are currently available, which differ in the algorithms and approaches used to predict the binding mode and the affinity of the ligand. All programs heavily rely on scoring functions to accurately predict ligand binding affinity, and despite differences in performance, none of these docking programs is preferable to the others. To overcome this problem, consensus scoring methods improve the outcome of virtual screening by averaging the rank or score of individual molecules obtained from different docking programs. The successful application of consensus docking in high-throughput virtual screening highlights the need to optimize the predictive power of molecular docking methods.

ThermoTRP channels (thermoTRPs) define a subfamily of the transient receptor potential (TRP) channels that are activated by changes in the environmental temperature, from noxious cold to injurious heat. Acting as integrators of several stimuli and signalling pathways, dysfunction of these channels contributes to several pathological states. The surface expression of thermoTRPs is controlled by both, the constitutive and regulated vesicular trafficking. Modulation of receptor surface density during pathological processes is nowadays considered as an interesting therapeutic approach for management of diseases, such as chronic pain, in which an increased trafficking is associated with the pathological state. This review will focus on the recent advances trafficking of the thermoTRP channels, TRPV1, TRPV2, TRPV4, TRPM3, TRPM8 and TRPA1, into/from the plasma membrane. Particularly, regulated membrane insertion of thermoTRPs channels contributes to a fine tuning of final channel activity, and indeed, it has resulted in the development of novel therapeutic approaches with successful clinical results such as disruption of SNARE-dependent exocytosis by botulinum toxin or botulinomimetic peptides.

Potentiation of the pain‐integrator ion channel transient receptor potential vanilloid type 1 (TRPV1) underlies thermal hyperalgesia mediated by a variety of proinflammatory factors. Two complemen‐ tary mechanisms of TRPV1 inflammatory sensitization have been proposed, namely a decrease of its activation threshold and an increment of its surface expression in nociceptors. Here we investigated the involvement of regulated exocytosis to the inflammatory sensitization of TRPV1 in rat neonatal dorsal root ganglion neurons by proalgesic agents. The contribution of soluble N‐ ethylmaleimide‐sensitive factor attachment protein re‐ ceptor (SNARE)‐dependent exocytosis was evaluated using a small peptide patterned after the synaptosomal‐ associated protein of 25 kDa (SNAP‐25) protein that acts as a specific and potent inhibitor of neuronal exocytosis. We found that TRPV1 sensitization medi‐ ated by nerve growth factor, ATP, and IGF‐I was accompanied by a higher channel expression in the neuronal plasma membrane, which was prevented by blockade of regulated exocytosis. In contrast, TRPV1 sensitization caused by bradykinin, IL‐1β, and artemin was insensitive to inhibition of SNARE‐dependent ve‐ sicular fusion and was not due to an increase in TRPV1 surface expression. Therefore, it appears that some, but not all, proinflammatory agents sensitize rat noci‐ ceptors by promoting the recruitment of TRPV1 chan‐ nels to the neuronal surface. These findings support the tenet that SNARE complex‐mediated exocytosis of TRPV1 may be a valid therapeutic target to treat inflammatory pain.—Camprubi‐Robles, M., Planells‐ Cases, R., Ferrer‐Montiel, A. Differential contribution of SNARE‐dependent exocytosis to inflammatory po‐ tentiation of TRPV1 in nociceptors. FASEB J. 23, 3722‐3733 (2009). www.fasebj.org