<p>CBD Effects on TRPV1 Signaling Pathways in Cultured DRG Neurons</p>

Abstract

Introduction Cannabidiol (CBD) is reported to produce pain relief, but the clinically relevant cellular and molecular mechanisms remain uncertain. The TRPV1 receptor integrates noxious stimuli and plays a key role in pain signaling. Hence, we conducted in vitro studies, to elucidate the efficacy and mechanisms of CBD for inhibiting neuronal hypersensitivity in cultured rat sensory neurons, following activation of TRPV1. Methods Adult rat dorsal root ganglion (DRG) neurons were cultured and supplemented with the neurotrophic factors NGF and GDNF, in an established model of neuronal hypersensitivity. Neurons were stimulated with CBD (Adven 150, EMMAC Life Sciences) at 1, 10, 100 nMol/L and 1, 10 and 50 µMol/L, 48 h after plating. In separate experiments, DRG neurons were also stimulated with capsaicin with or without CBD (1 nMol/L to10 µMol/L), in a functional calcium imaging assay. The effects of the adenylyl cyclase activator forskolin and the calcineurin inhibitor cyclosporin were determined. We also measured forskolin-stimulated cAMP levels, without and after treatment with CBD, using a homogenous time-resolved fluorescence (HTRF) assay. The results were analysed using Mann-Whitney test. Results DRG neurons treated with 10 and 50 µMol/L CBD showed calcium influx, but not at lower doses. Neurons treated with capsaicin demonstrated robust calcium influx, which was dose-dependently reduced in the presence of low dose CBD (IC 50 = 100 nMol/L). The inhibition or desensitization by CBD was reversed in the presence of forskolin and cyclosporin. Forskolin-stimulated cAMP levels were significantly reduced in CBD treated neurons. Conclusion CBD at low doses corresponding to plasma concentrations observed physiologically inhibits or desensitizes neuronal TRPV1 signalling by inhibiting the adenylyl cyclase – cAMP pathway, which is essential for maintaining TRPV1 phosphorylation and sensitization. CBD also facilitated calcineurin-mediated TRPV1 inhibition. These mechanisms may underlie nociceptor desensitization and the therapeutic effect of CBD in animal models and patients with acute and chronic pain.

The Heat Sensing Trpv1 Receptor Is Not a Viable Anticonvulsant Drug Target in the Scn1a+/− Mouse Model of Dravet Syndrome

“…Accordingly, the anticonvulsant effects of CBD were reversed by a Trpv1 antagonist in the PTZ model (Vilela et al, 2017) and reduced in Trpv1 −/− mice compared to wildtype mice in the MES model (Gray et al, 2020). These results are consistent with cellular studies which show that CBD activates and subsequently desensitizes Trpv1 receptors (De Petrocellis et al, 2011;Iannotti et al, 2014;Anand et al, 2020).…”

Dose-Related Inhibition of Capsaicin Responses by Cannabinoids CBG, CBD, THC and their Combination in Cultured Sensory Neurons

“…A recent study, examining the effects of CBD on capsaicin response in rat DRG neurons, found that administration of 10 μM and 50 μM CBD caused significant calcium influx, but lower concentrations did not. 36 In this study, 50 μM CBD was the most effective concentration, in a similar range to CBG (30 μM). Various other receptor targets for CBD have been identified, such as the orphan G-protein coupled receptor GPR18, GPR55, PPARs, 5-HT1a and the α3 and α1 glycine receptors.…”

“…Cannabinoid agonists were previously reported to stimulate TRPV1 and TRPA1 in sensory neurons, leading to calcium influx and desensitization. 35 We have recently reported CBD inhibition of TRPV1 in DRG neurons at low physiological doses that did not stimulate calcium influx, 36 similar to inhibition of TRPV1 and TRPM8 in transfected HEK cells. 27 However, as higher concentrations of cannabinoids induce calcium influx, it is likely that these doses of CBG, CBD and THC would lead to desensitization of TRPV1 in DRG neurons, similar to capsaicin-mediated effects.…”

Sperm Cholesterol Content Modifies Sperm Function and TRPV1-Mediated Sperm Migration

“…From a mechanistic point of view, it should be noted that acrosome reaction in mammals is strictly dependent on the upstream activation of the cAMP/PKA system [ 40 ]. On the other hand, the cAMP/PKA system has recently been involved in the upstream phosphorylation of TRPV1, which is associated with the sensitization of the receptor to activation stimuli [ 41 ]. Our results are consistent with this sequential order of cell events and allow us to tentatively exclude a major role of sperm capacitation on the effect exerted by Chol loss on TRPV1-mediated function.…”