9: CB13-mediated peripheral cannabinoid receptor activation attenuates frostbite-induced chronic pain.

Topic: Basic Science
Subtopic: Pain category (ICD-11), Chronic neuropathic pain, , , , , , , , , , Pharmacological interventions, Drug development

Background and Aims: Frostbite-associated chronic pain is a severe and persistent complication of cold injury, characterized by long-lasting mechanical and cold hypersensitivity particularly among military personnel driven by sustained neuroimmune and excitatory signaling. Current therapeutic options remain largely symptomatic and fail to target underlying pathophysiological mechanisms. Emerging evidence highlights peripheral cannabinoid receptors as critical regulators of nociceptive transmission, inflammatory cascades, and neuronal sensitization. This study investigated the therapeutic potential of CB13, a peripherally restricted CB1/CB2 receptor agonist, in mitigating frostbite-induced chronic pain, aiming to establish peripheral cannabinoid receptor activation as a novel, mechanism-based, non-central analgesic strategy

Methods: A validated rat model of frostbite-induced chronic pain was used to evaluate the therapeutic efficacy of CB13. Following hind paw frostbite induction and establishment of chronic hypersensitivity, CB13 was administered locally at graded doses, with ibuprofen as a standard. Mechanical, thermal, and cold hypersensitivity, along with spontaneous ongoing pain, were systematically assessed. Locomotor and motor coordination tests were performed to exclude central adverse effects. Molecular analyses of dorsal root ganglia and spinal cord tissues were conducted using RT-PCR, Western blotting, and immunohistochemistry to quantify TRPV1, TRPA1, TRPM8, NF-κB, c-Fos and proinflammatory cytokines expression.

Results: In vivo administration of CB13 significantly reduced mechanical and cold allodynia without affecting locomotor activity, while ibuprofen produced only short-lived analgesia. CB13 did not alter spontaneous ongoing pain, indicating selective modulation of evoked hypersensitivity. Mechanistically, CB13 downregulated TRPV1, TRPA1, TRPM8, and TRPV4 channels and decreased NR2B and c-Fos expression, reflecting attenuation of peripheral and central sensitization. It suppressed NF-κB signaling, reduced TNF-α, IL-1β, and IL-6 levels, and inhibited NLRP3 inflammasome activation. Additionally, CB13 decreased IBA1 expression, restored Beclin-1–mediated autophagy, and normalized oxidative stress markers (↓MDA, ↓nitrite, ↑GSH), demonstrating potent neuroimmune and cellular homeostatic regulation.

Conclusions: This study demonstrates that peripheral cannabinoid receptor activation via CB13 effectively alleviates frostbite-induced chronic pain by targeting nociceptor hyperexcitability, spinal neuronal activation, neuroinflammation, inflammasome signaling, and impaired autophagy. CB13 reversed behavioural hypersensitivity and key molecular alterations without inducing central nervous system side effects, supporting its safety profile. These findings highlight peripheral cannabinoid receptor modulation as a novel and translationally relevant therapeutic strategy for managing chronic pain following cold-induced tissue injury.

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Presenting Author: Dr. Vinod Tiwari
Submitting Author: Vinod Tiwari

Senior Author: Dr. Vinod Tiwari

IASP 2026 Global Year theme of Neuropathic Pain: Yes