Peripherally injected canabidiol reduces neuropathic pain in mice: Role of the 5-HT1A and TRPV1 receptors

Cannabidiol reduces neuropathic pain and cognitive impairments through activation of spinal PPARγ

The purpose of this study was to evaluate the participation of spinal peroxisome proliferator-activated receptor gamma (PPARγ) in the antiallodynic effect of cannabidiol, the expression of PPARγ in sites relevant to the spinal nociceptive processing, and the effect of this cannabinoid on cognitive deficits induced by neuropathic pain in female mice. Either acute or repeated treatment with cannabidiol reduced tactile allodynia and spontaneous pain (flinching) in female neuropathic mice. Cannabidiol induced a greater effect in female mice. Pioglitazone partially reduced tactile allodynia, and this effect was fully blocked by the PPARγ antagonist GW9662. Likewise, intrathecal injection of cannabidiol reduced tactile allodynia, while PPARγ antagonist GW9662 or 5-HT1A receptor antagonist WAY-100635, but not the PPARα antagonist GW6479, partially prevented this effect. GW9662 and WAY-100635 administrated per se did not modify tactile allodynia in neuropathic female mice. Co-administration of GW9662 and WAY-100635 fully prevented the antiallodynic effect of cannabidiol in mice. Nerve injury up-regulated PPARγ expression at the spinal cord and dorsal root ganglia, while cannabidiol further enhanced nerve injury-induced up-regulation of PPARγ expression in both tissues. Repeated intrathecal injection of cannabidiol reduced tactile allodynia and several pain makers (ERK, p-ERK, p38MAPK and p-p38MAPK). In addition, this treatment restored nerve injury-induced interleukin-10 down-regulation and increased PPARγ expression at the spinal cord. Repeated treatment with cannabidiol also improved nerve injury-induced cognitive impairment in mice. These results provide compelling evidence for the involvement of PPARγ in the antiallodynic effect of cannabidiol in mice and highlight its multifaceted therapeutic potential in neuropathic pain management and its comorbidities. PERSPECTIVE: The present study reveals cannabidiol's dual effects in female mice by reducing neuropathic pain through spinal PPARγ and 5-HT1A receptor activation and ameliorating nerve injury-induced cognitive impairment. These findings may assist clinicians seeking new therapeutic approaches for managing neuropathic pain and its associated cognitive deficits.

Impact of an acute 1-month cannabidiol treatment on pain and inflammation after a long bone fracture: a triple-blind randomised, placebo-controlled, clinical trial protocol

INTRODUCTION

Acute pain levels following orthopaedic injury (eg, fracture) are a predictor of the onset of chronic pain, which affects nearly 50% of fracture patients and impairs functional recovery. Among current pharmacological treatments for acute pain, non-steroidal anti-inflammatory drugs have been associated with delayed bone healing, while opioids inhibit effective bone remodelling, increase the risk of pseudarthrosis and carry a high risk of addiction. In light of this, the development of new pain treatments is essential. Cannabidiol (CBD), a non-addictive and non-psychotropic cannabis component stands out as a potential therapeutic agent, given its analgesic and anti-inflammatory properties as well as its potential benefits for bone healing. This randomised controlled trial aims to investigate the effect of acute CBD treatment, compared with placebo, on patients' self-reported pain, inflammation and well-being following a fracture injury.

METHODS AND ANALYSIS

This is a triple-blind, randomised, placebo-controlled clinical trial. A total of 225 adults aged 18-70 years, who have suffered a long bone fracture and were treated at the Hôpital du Sacré-Coeur de Montréal, will be randomly assigned within 1 week to one of three treatment arms (25 mg or 50 mg of CBD or placebo) for 1 month. The primary outcome will be the difference in the pain score between groups at 1-month follow-up. Secondary outcomes will include measures of persistent pain, inflammation, opioid usage, quality of life, sleep quality, depression, anxiety, cognition and orthopaedic function. Data will be collected at baseline, 1-month and 3-month follow-ups.

ETHICS AND DISSEMINATION

This study obtained a Health Canada licence for use of cannabis products. It has also been approved by Health Canada and the Research Ethics Board of the CIUSSS du Nord-de-l'Île-de-Montréal (Project ID 2025-2105). The findings will be published in a peer-reviewed journal and presented at local, national and international conferences. The trial's results will be made publicly available on the ClinicalTrials.gov database.

TRIAL REGISTRATION NUMBER

NCT06448923.

Enhanced brain-targeting and efficacy of cannabidiol via RVG-Exo/CBD nanodelivery system

This study introduces an innovative brain-targeted drug delivery system, RVG-Exo/CBD, utilizing rabies virus glycoprotein (RVG)-engineered exosomes for encapsulating cannabidiol (CBD). The novel delivery system was meticulously characterized, confirming the maintenance of exosomal integrity, size, and successful drug encapsulation with a high drug loading rate of 83.0 %. Evaluation of the RVG-Exo/CBD's brain-targeting capability demonstrated superior distribution and retention in brain tissue compared to unmodified exosomes, primarily validated through in vivo fluorescence imaging. The efficacy of this delivery system was assessed using a behavioral sensitization model in mice, where RVG-Exo/CBD notably suppressed methamphetamine-induced hyperactivity more effectively than CBD alone, indicating a reduction in effective dose and enhanced bioavailability. Overall, the RVG-Exo/CBD system emerges as a promising strategy for enhancing the therapeutic efficacy and safety of CBD, particularly for neurological applications, highlighting its potential for addressing the limitations associated with traditional CBD administration in clinical settings.

Silencing of FTO inhibits oxidative stress to relieve neuropathic pain by m6A modification of GPR177

BACKGROUND

Neuropathic pain (NP) is a challenging health condition owing to its complex nature and associated multiple etiologies. The occurrence of NP involves the abnormal activity of neurons mediated by oxidative stress (OS). Previous research has demonstrated that m6A methylation plays a role in the regulatory pathway of NP. This study aimed to investigate the specific molecular pathways through which m6A methylation modifiers alleviate NP.

METHODS

For this purpose, an NO rat model was developed via spared nerve injury (SNI), followed by quantifying the animal's pain assessment via paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). The OS in SNI rats was evaluated by measuring reactive oxygen species, superoxide dismutase, and catalase (CAT) in spinal cord tissues. Moreover, quantitative-real-time polymerase chain reaction and western blot analysis were employed for detecting fat mass and obesity-associated (FTO) and GPR177 levels, while m6A levels of GPR117 were analyzed via MeRIP.

RESULTS

The results indicated an enhanced OS with highly expressed FTO in spinal cord tissue samples, where knocking down Fto effectively relieved NP and OS in SNI rats. Mechanistic investigations revealed that Fto-mediated reduction of Grp177 m6A modification was involved in the WNT5a/TRPV1 axis-mediated OS remission of NP. Moreover, in vitro experiment results indicated that YTHDF2 was an important m6A methylated reading protein for this process.

CONCLUSIONS

Fto silencing leads to increased m6A methylation of Grp177 through a YTHDF2-dependent mechanism, resulting in decreased Grp177 stability and ultimately reducing NP in rats by OS suppression.

Antinociceptive action of cannabidiol on thermal sensitivity and post-operative pain in male and female rats

This study investigated the antinociceptive potential of cannabidiol (CBD) in male and female Wistar rats. The assessment and analysis included tail withdrawal to thermal stimulation (tail flick test) and mechanical allodynia induced by plantar incision injury (von Frey test). CBD reduced acute thermal sensitivity in uninjured animals and post-operative mechanical allodynia in males and females. In the tail flick test, CBD 30 mg/kg i.p. was required to induce antinociception in males. During the proestrus phase, females did not show a statistically significant antinociceptive response to CBD treatment despite a noticeable trend. In contrast, in a separate group of rats tested during the late diestrus phase, antinociception varied with CBD dosage and time. In the post-operative pain model, CBD at 3 mg/kg decreased mechanical allodynia in males. Similarly, this dose reduced allodynia in females during proestrus. However, in females during late diestrus, the lower dose of CBD (0.3 mg/kg) reduced mechanical allodynia, although the latency to onset of the effect was slower (90 min). The effectiveness of a 10-fold lower dose of CBD during the late diestrus stage in females suggests that ovarian hormones can influence the action of CBD. While CBD has potential for alleviating pain in humans, personalized dosing regimens may need to be developed to treat pain in women.

IUPHAR review- Preclinical models of neuropathic pain: Evaluating multifunctional properties of natural cannabinoid receptors ligands

Neuropathic pain remains prevalent and challenging to manage and is often comorbid with depression and anxiety. The new approach that simultaneously targets neuropathic pain and the associated comorbidities, such as depression and anxiety, is timely and critical, given the high prevalence and severity of neuropathic pain and the lack of effective analgesics. In this review, we focus on the animal models of neuropathic pain that researchers have used to investigate the analgesic effects of cannabidiol (CBD) and Beta-Caryophyllene (BCP) individually and in combination while addressing the impact of these compounds on the major comorbidity (e.g., depression, anxiety) associated with neuropathic pain. We also addressed the potential targets/mechanisms by which CBD and BCP produce analgesic effects in neuropathic pain models. The preclinical studies examined in this review support CBD and BCP individually and combined as potential alternative analgesics for neuropathic pain while showing beneficial effects on depression and anxiety.

Ion Channel Genes in Painful Neuropathies

Neuropathic pain (NP) is a typical symptom of peripheral nerve disorders, including painful neuropathy. The biological mechanisms that control ion channels are important for many cell activities and are also therapeutic targets. Disruption of the cellular mechanisms that govern ion channel activity can contribute to pain pathophysiology. The voltage-gated sodium channel (VGSC) is the most researched ion channel in terms of NP; however, VGSC impairment is detected in only <20% of painful neuropathy patients. Here, we discuss the potential role of the other peripheral ion channels involved in sensory signaling (transient receptor potential cation channels), neuronal excitation regulation (potassium channels), involuntary action potential generation (hyperpolarization-activated cyclic nucleotide-gated channels), thermal pain (anoctamins), pH modulation (acid sensing ion channels), and neurotransmitter release (calcium channels) related to pain and their prospective role as therapeutic targets for painful neuropathy.