Cannabidiol Reduces Acute and Chronic Hyperalgesia in Humanized Sickle Mice

Cannabidiol (CBD), one of the 2 major active components of cannabis, has been shown to have beneficial effects on pain, anxiety, cognition, inflammation, oxidative stress and ischemia/reperfusion injury. Unlike tetrahydrocannabinol (THC) containing preparations, CBD does not induce psychoactive effects or catalepsy. THC leads to increased anxiety, dysphoria, and physical and mental sedation in patients when compared to CBD.The lack of psychoactive and sensorimotor effects of CBD make it a desirable therapeutic candidate with potential for pain therapy. Many unregulated over the counter preparations of CBD are available, but their purity and reliability are unknown. Epidiolex, a 99% pure extract of CBD, is approved by the FDA for treatment of seizures associated with Lennox-Gastaut syndrome (LGS) and Dravet syndrome (DS). It remains to be known whether CBD also has therapeutic potential in the treatment of sickle cell disease (SCD) which is characterized by acute and chronic pain as well as severe inflammation, oxidative stress, and organ damage. Thus, we performed a randomized double-blind placebo-controlled trial using Epidiolex to examine the effect of CBD on acute and chronic pain in homozygous HbSS BERK (sickle) and HbAA BERK (control) mice, expressing >99% human sickle hemoglobin and normal human hemoglobin A, respectively.

For acute pain assessment, 2.2 month old male and female mice were treated daily with 100 mg/kg of Epidiolex via gavage for 19 days and underwent hypoxia/reoxygenation (H/R) treatment to simulate acute pain due to VOC on days 6, 7, and 13. Sickle mice at 2.2 months do not show increased hyperalgesia compared to control mice. Mechanical-, cold-, and musculoskeletal/deep hyperalgesia were assessed at baseline (before treatment) and one hour post-gavage on days 1, 4, 6, 7, 13, and 19, as well as post H/R treatment on days 6, 7, and 13. For assessment of chronic pain, ~ 6 month-old male mice were treated daily with 100 mg/kg of Epidiolex via gavage for 9 days, and mechanical-, thermal- (heat and cold), and deep hyperalgesia were assessed at baseline (before treatment) and 1-hour post-gavage on days 1, 4, 6, and 9. A 2-way repeated measures ANOVA with Tukey's correction was used for comparisons between time points and treatments.

For acute pain, we observed an increase in mechanical hyperalgesia in male sickle mice compared to baseline following the first H/R on day 6 which was maintained through the third H/R on day 13 and continued to increase until day 19 (last period of observation), suggesting that repeated episodes of VOC may lead to sustained chronic pain. Continued treatment with Epidiolex, however, led to a decrease in mechanical hyperalgesia back to baseline levels, which was significantly lower compared to vehicle treated mice (P < 0.05). We also observed a decrease in cold hyperalgesia at day 19 compared to baseline in male sickle mice, which was not statistically significant. No changes were observed with Epidiolex treatment for deep hyperalgesia in males, or for mechanical-, cold-, or deep-hyperalgesia in female sickle mice. Our data demonstrate that repeated episodes of acute pain lead to transition to chronic pain and that Epidiolex has a preventive effect in the transition from acute to chronic pain in male sickle mice. It is likely that a higher dose of Epidiolex may be required for acute pain in females, which may also be influenced by disturbed estrus cycle.

Since male mice showed responsiveness to Epidiolex in acute pain, we also examined its effect on chronic pain in males. Epidiolex significantly reduced, [a] mechanical hyperalgesia starting at day 4, which was maintained through day 9 (P < 0.01 compared to baseline), [b] cold hyperalgesia starting at day 1 and maintained through day 9 (P < 0.01 compared to baseline), [c] heat hyperalgesia at day 9 of treatment (P < 0.05 compared to baseline). These results suggest that Epidiolex has a sustained time-dependent analgesic effect on different characteristics of chronic hyperalgesia without causing tolerance in sickle mice.

Our findings demonstrate therapeutic potential of pure and reliable CBD preparations for treating and potentially preventing chronic pain in SCD. We speculate high translational potential for CBD for treating pain in SCD following clinical trials.