Cannabinoid and terpene regulation of nocioception and peripheral sensitization through ionotropic receptors

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Cannabis-derived therapeutics promise utility in pain management. Their low side effect profile and low addictive potential add value to this proposition, and in addition, they have been shown to be `opioid-sparing'. However, current medical marijuana patients are limited to native plant mixtures obtained licitly or illicitly from an inconsistent supply chain that is subject to issues of contamination and undefined relationships between formulations (plant chemovars) and efficacy. Popular chemovars have been selected over several decades for ever-increasing THC levels, which is both medically undesirable due to the psychoactivity of THC and may be medically unnecessary if THC is actually dispensable for some indications. These central safety and efficacy problems reinforce the need for rational design of therapies that represent the minimal essential and efficacious set of compounds needed to achieve analgesia. The overall goal of this pre-clinical proposal is to establish efficacy and mechanism of action for cannabinoids (excluding THC), terpenes and rationally-designed cannabinoid/terpene mixtures such that they can be rapidly translated for clinical evaluation in nocioceptive pain and peripheral sensitization. The central premise of the proposed work is that ionotropic cannabinoid receptors (Transient Receptor Potential (TRP) nocioceptive ion channels) are the most important targets for therapeutic desensitization by cannabinoids and terpenes present in Cannabis. The proposal is innovative in that it focuses on ionotropic receptors that are actual nocioceptors rather than CB1 and CB2 GPCR, it excludes THC and focuses on other cannabinoids and terpenes, it embraces the idea of building synthetic mixtures that improve upon the natural plant for efficacy and safety and excludes plant extracts, and it proposes an approach to simultaneously addressing both nocioception and peripheral sensitization. The project is supported by preliminary data that: (a) establish differential activity of CB and TP at nocioceptive TRPs, defining which TRPs are targeted by each compound and identifying novel TRP ligands, (b) describe complex kinetics and desensitization of TRP nocioceptors in response to CB/TP, offering the potential for therapeutic desensitization and tuning of nocioceptive TRP responses; (c) demonstrate a Cannabis component improving upon an established pain therapeutic targeting a TRP channel, and (d) demonstrate interactions of components of complex CB/TP mixtures, informing rational mixture design. The proposed Specific Aims are: Aim 1. Test cannabinoid and terpene regulation of nocioceptive TRP channels. We hypothesize that CB and TP, singly or in mixtures, selectively ligate and desensitize TRPs to promote analgesia. Aim 2. Determine GPCR dependencies and relationships in analgesic effects of cannabinoids and terpenes. We hypothesize that CB and TP target multiple TRPs independently of CB1 and CB2 GPCR, and CB, TP and mixtures that target TRPV1 will influence opioid exposure outcomes. Aim 3. Evaluate CB and TP for their potential to suppress sensitizing mediator release in a model of peripheral sensitization (PS). We hypothesize that CB and TP, singly or in mixtures, will inhibit release of sensitizing mediators from sensory neuron associated mast cells (MC) and basophils. The impact of this work will be to provide concrete, mechanistically-based pre-clinical rationales for the adoption or rejection of Cannabis compounds as pain therapies, elevating the field above its current reliance on anecdotal and incomplete data. In the context of a STEM-focused Native Hawaiian serving undergraduate institution with a strong track record in undergraduate research, this AREA R15 project will provide meaningful undergraduate research opportunities to a largely indigenous student body with a keen cultural and scientific interest in natural products and plant-derived medicine approaches.