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

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.