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

Cannabidiol and pain

Chronic pain presents significant personal, psychological, and socioeconomic hurdles, impacting over 30% of adults worldwide and substantially contributing to disability. Unfortunately, current pharmacotherapy often proves inadequate, leaving fewer than 70% of patients with relief. This shortfall has sparked a drive to seek alternative treatments offering superior safety and efficacy profiles. Cannabinoid-based pharmaceuticals, notably cannabidiol (CBD), hold promise in pain management, driven by their natural origins, versatility, and reduced risk of addiction. As we navigate the opioid crisis, ongoing research plunges into CBD's therapeutic potential, buoyed by animal studies revealing its pain-relieving prowess through various system tweaks. However, the efficacy of cannabis in chronic pain management remains a contentious and stigmatized issue. The International Association for the Study of Pain (IASP) presently refrains from endorsing cannabinoid use for pain relief. Nevertheless, evidence indicates their potential in alleviating cancer-related, neuropathic, arthritis, and musculoskeletal pain, necessitating further investigation. Crucially, our comprehension of CBD's role in pain management is a journey still unfolding, with animal studies illustrating its analgesic effects through interactions with the endocannabinoid, inflammatory, and nociceptive systems. As the plot thickens, it's clear: the saga of chronic pain and CBD's potential offers a compelling narrative ripe for further exploration and understanding.

Effect of Cannabidiol on Cyclooxygenase Type 1 and 2 Expression and Function in Human Neutrophils

Introduction: In this study, the effects of the cannabinoid CBD were assessed on cyclooxygenase (COX)-1 and COX-2 expression and activity in resting and activated human neutrophils (polymorphonuclear [PMN] leukocytes). Methods: COX expression was measured at the mRNA levels, whereas COX activity was assessed by enzyme-linked immunosorbent assay measurement of prostaglandin (PG)E2. In vitro experiments in a standard commercial acellular assay of COX-1/COX-2 activity completed the study. Results: Results show that CBD profoundly inhibits expression of COX-1 and COX-2 mRNA in activated PMN, however, without any significant consequences for PGE2 production. CBD, however, was able to induce a slight but significant direct inhibition of COX-2 in the acellular model. Conclusion: The effects of CBD occur in the μM concentration range, which is attained in humans with therapeutic doses of the drug, suggesting the clinical relevance of these findings.

Terpenes in Cannabis sativa Inhibit Capsaicin Responses in Rat DRG Neurons via Na+/K+ ATPase Activation

Terpenes in Cannabis sativa exert analgesic effects, but the mechanisms are uncertain. We examined the effects of 10 terpenes on capsaicin responses in an established model of neuronal hypersensitivity. Adult rat DRG neurons cultured with neurotrophic factors NGF and GDNF were loaded with Fura2AM for calcium imaging, and treated with individual terpenes or vehicle for 5 min, followed by 1 µMol capsaicin. In vehicle treated control experiments, capsaicin elicited immediate and sustained calcium influx. Most neurons treated with terpenes responded to capsaicin after 6-8 min. Few neurons showed immediate capsaicin responses that were transient or normal. The delayed responses were found to be due to calcium released from the endoplasmic reticulum, as they were maintained in calcium/magnesium free media, but not after thapsigargin pre-treatment. Terpene inhibition of calcium influx was reversed after washout of medium, in the absence of terpenes, and in the presence of the Na+/K+ ATPase inhibitor ouabain, but not CB1 or CB2 receptor antagonists. Thus, terpenes inhibit capsaicin evoked calcium influx by Na+/K+ ATPase activation. Immunofluorescence showed TRPV1 co-expression with α1β1 Na+/K+ ATPase in most neurons while others were either TRPV1 or α1β1 Na+/K+ ATPase positive.

A type II cannabis extract and a 1:1 blend of Δ(9)-tetrahydrocannabinol and cannabidiol display distinct antinociceptive profiles and engage different endocannabinoid targets when administered into the subarachnoid space

Introduction: Cannabis extracts are being increasingly used to mitigate chronic pain. Current guidelines for their prescription rely on Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) content as well as the ratio of these major cannabinoids present in the blend. Here we assessed whether these descriptors were representative of product effectiveness to produce a desired outcome such as analgesia. Methods: In this study, we used a rat model of diabetic neuropathy and assessed the reduction in mechanical allodynia following intrathecal injection of pure THC, pure CBD, a 1:1 mix of these compounds and a "balanced" chemotype II cannabis extract. Engagement of endocannabinoid targets by different treatments was investigated using CB1 (AM251) and CB2 (AM630) receptor antagonists as well as a TRPV1 channel blocker (capsazepine). Results: Antinociceptive responses induced by an equivalent amount of THC administered in its pure form, as a THC:CBD mix or as a "balanced" extract were distinct. Furthermore, the 1:1 THC:CBD mix and the balanced extract had not only different response profiles but their relative engagement of CB1, CB2 receptors and TRPV1 channels was distinct. Discussion: These findings indicate that antinociceptive responses and targets engaged by blended cannabinoids are composition-specific, and cannot be simply inferred from THC and CBD contents. This information may have implications in relation to the way medicinal cannabis products are prescribed.

The effect of medical cannabis in inflammatory bowel disease: analysis from the UK Medical Cannabis Registry

OBJECTIVES

Cannabis-based medicinal products (CBMPs) have shown promising preclinical activity in inflammatory bowel disease (IBD). However, clinical trials have not demonstrated effects on inflammation. This study aims to analyze changes in health-related quality of life (HRQoL) and adverse events in IBD patients prescribed CBMPs.

METHODS

A case series from the UK Medical Cannabis Registry was performed. Primary outcomes included changes from baseline in the Short Inflammatory Bowel Disease Questionnaire (SIBDQ), Generalized Anxiety Disorder-7 (GAD-7), Single-Item Sleep Quality Scale (SQS), and EQ-5D-5L Index score at 1 and 3 months. Statistical significance was defined using p < 0.050.

RESULTS

Seventy-six patients with Crohn's disease (n = 51; 67.11%) and ulcerative colitis (n = 25; 32.89%) were included. The median baseline SIBDQ score improved at 1 and 3 months. EQ-5D-5L index values, GAD-7, and SQS also improved after 3 months (p < 0.050). Sixteen (21.05%) patients reported adverse events with the majority being classified as mild to moderate in severity.

CONCLUSION

Patients treated with CBMPs for refractory symptoms of Crohn's disease and ulcerative colitis demonstrated a short-term improvement in IBD-specific and general HRQoL. Prior cannabis consumers reported greater improvement compared to cannabis-naïve individuals.

The Endocannabinoid Analgesic Entourage Effect: Investigations in Cultured DRG Neurons

BACKGROUND

The endocannabinoid 2-Arachidonyl glycerol (2-AG) exerts dose-related anti-nociceptive effects, which are potentiated by the related but inactive 2-palmitoyl glycerol (2-PG) and 2-linoleoyl glycerol (2-LG). This potentiation of analgesia and other in vivo measures was described as the "entourage effect". We investigated this effect on TRPV1 signalling in cultured dorsal root ganglion (DRG) nociceptors.

METHODS

Adult rat DRG neurons were cultured in medium containing NGF and GDNF at 37°C. 48 h later cultures were loaded with 2 µM Fura2AM for calcium imaging, and treated with 2-AG, 2-PG and 2-LG, individually or combined, for 5 min, followed by 1 µMol capsaicin. The amplitude and latency of capsaicin responses were measured (N=3-7 rats, controls N=16), and analysed.

RESULTS

In controls, 1 µMol capsaicin elicited immediate calcium influx in a subset of neurons, with average latency of 1.27 ± 0.2 s and amplitude of 0.15 ± 0.01 Units. 2-AG (10-100 µMol) elicited calcium influx in some neurons. In the presence of 2-AG (0.001-100 µMol), capsaicin responses were markedly delayed in 64% neurons by up to 320 s (P<0.001). 2-PG increased capsaicin response latency at 0.1 nMol-100 µMol (P<0.001), in 60% neurons, as did 2-LG at 0.1-100 µMol (P<0.001), in 76% neurons. Increased capsaicin response latency due to 2-AG and 2-PG was sensitive to the CB2 but not to the CB1 receptor antagonist. Combined application of 1 µMol 2-AG, 5 µMol 2-PG and 10 µMol 2-LG, also resulted in significantly increased capsaicin response latency up to 281.5 ± 41.5 s (P<0.001), in 96% neurons, that was partially restored by the CB2, but not the CB1 antagonist.

CONCLUSION

2-AG, 2-LG and 2-PG significantly delayed TRPV1 signalling in the majority of capsaicin-sensitive DRG neurons, that was markedly increased following combined application. Further studies of these endocannabinoids are required to identify the underlying mechanisms.

Oral cannabidiol for prevention of acute and transient chemotherapy-induced peripheral neuropathy

PURPOSE

To assess the safety, dosing, and preventive effects of cannabidiol (CBD) on chemotherapy-induced peripheral neuropathy (CIPN) in patients receiving oxaliplatin- or paclitaxel-based chemotherapy.

METHODS

Patients with cancer scheduled to undergo treatment with carboplatin and paclitaxel (Carbo-Tax) or capecitabine and oxaliplatin (CAPOX) received 150 mg CBD oil twice daily (300 mg/daily) for 8 days beginning 1 day before initiation of chemotherapy. Ten CIPN-specific patient-reported outcome (PRO) measures were captured at baseline and each day after the first cycle of chemotherapy for 8 days. Multi-frequency vibrometry (MF-V) was captured at baseline and day 4 ± 1 after initiation of chemotherapy. Controls were obtained from a similar patient cohort that did not receive CBD. Adverse events were captured using the CTCAE ver. 4.03.

RESULTS

From March to December 2021, 54 patients were recruited. CBD-treated patients were significantly older (p = 0.013/0.037, CAPOX/Carbo-Tax) compared to controls. Patients receiving CBD and CAPOX or Carbo-Tax showed significantly lower (better) change in Z-scores in high-frequency MF-V (125 and 250 Hz) compared to controls. This difference was most pronounced for patients receiving Carbo-Tax (- 1.76, CI-95 = [- 2.52; - 1.02] at 250 Hz). CAPOX patients treated with CBD had significantly lower peak baseline-adjusted difference in three PRO items on cold sensitivity to touch, discomfort swallowing cold liquids, and throat discomfort (- 2.08, - 2.06, and - 1.81, CI-95 = [- 3.89; - 0.12], NRS 0-10). No significant differences in PRO items were found for patients receiving Carbo-Tax. Possible side effects included stomach pain (grades 1-2) for patients receiving CAPOX.

CONCLUSION

CBD attenuated early symptoms of CIPN with no major safety concerns. Long-term follow-up is ongoing. Results should be confirmed in a larger, randomized study.

TRIAL REGISTRATION NUMBER

NCT 04,167,319 (U.S National Library of Medicine; ClinicalTrials.gov). Date of registration: November 18, 2019.