Targeting Cannabinoid 1 and Delta Opioid Receptor Heteromers Alleviates Chemotherapy-Induced Neuropathic Pain.

Cannabinoid 1 (CBR) and delta opioid receptors (DOR) associate to form heteromers that exhibit distinct pharmacological properties. Not much is known about CBR-DOR heteromer location or signaling along the pain circuit in either animal models or patients with chemotherapy-induced peripheral neuropathy (CIPN). Here, we use paclitaxel to induce CIPN in mice and confirm the development of mechanical allodynia. Under these conditions, we find significant increases in CBR-DOR heteromers in the dorsal spinal cord of mice with CIPN as well as in postmortem spinal cords from human subjects with CIPN compared to controls. Next, we investigated receptor signaling in spinal cords of mice with CIPN and found that treatment with a combination of low signaling doses of CBR and DOR ligands leads to significant enhancement in G-protein activity that could be selectively blocked by the CBR-DOR antibody. Consistent with this, administration of subthreshold doses of a combination of ligands (CBR agonist, Hu-210, and DOR agonist, SNC80) leads to significant attenuation of allodynia in mice with CIPN that is not seen with the administration of individual ligands, and this could be blocked by the CBR-DOR antibody. Together, these results imply that CBR-DOR heteromers upregulated during CIPN-associated mechanical allodynia could serve as a potential target for treatment of neuropathic pain including CIPN.