The neuroimmune system is known to be pathologically activated after nerve injury and prolonged exposure to opioids. Whereas previous studies have predominantly focused on the involvement of individual chemokine receptors in this phenomenon, dual CCR2/CCR5 blockade with cenicriviroc represents a novel therapeutic strategy towards greater efficacy in alleviating hypersensitivity. In this study, the expression of opioid (MOR, DOR) and chemokine (CCR2, CCR5) receptors in the spinal cord was assessed by immunohistochemistry after chronic constriction injury (CCI) of the sciatic nerve. Analgesic effects of cenicriviroc were evaluated following intraperitoneal administration of cenicriviroc in behavioral tests (von Frey, cold plate) after single (both sexes) and repeated treatment (alone or with morphine in males). Motor coordination and spontaneous locomotor activity were also tested. Spinal protein levels (p-MORS363, p-DORS363, CCR2, CCR5, IBA1, GFAP) were analyzed by Western blot. Immunostaining showed that CCR5 and MOR were expressed exclusively by neurons, whereas CCR2 colocalized with neurons, astrocytes, microglia, and/or macrophages, and DOR with neurons and astrocytes. A single intraperitoneal cenicriviroc administration alleviated hypersensitivity in CCI-subjected mice. Unlike morphine, cenicriviroc did not induce tolerance over 16 days of repeated treatment. Moreover, cenicriviroc attenuated nerve injury-induced upregulation of IBA1 at all examined time points and reduced GFAP expression at day 16, which was accompanied by a decrease in CCR2 levels. Cenicriviroc exerts sustained analgesia by simultaneously blocking CCR2 and CCR5 - particularly CCR2 signaling in neurons and glia - which appears to be key to its efficacy. These findings highlight cenicriviroc as a promising, translational candidate for neuropathic pain therapy.
Piotrowska et al. (Fri,) studied this question.