CCR4 antagonist (C021) influences the level of nociceptive factors and enhances the analgesic potency of morphine in a rat model of neuropathic pain.

Neuropathic pain is a chronic condition which significantly reduces the quality of life and serious clinical issue that is in general resistant to available therapies. Therefore looking for new analgesics is still critical issue. Recent, studies have indicated that chemokine signaling pathways are crucial for the development of neuropathy; however, the role of CC chemokine receptor 4 (CCR4) in this process has not yet been studied. Therefore, the aim of our research was to investigate the influence of C021 (a CCR4 antagonist) and CCR4 CC chemokine ligands 17 and 22 (CCL17 and CCL22) on the development of hypersensitivity and the effectiveness of morphine induced analgesia in naive animals and/or animals exposed to chronic constriction injury (CCI) of the sciatic nerve. Firstly, we demonstrated that the intrathecal administration of CCL17 and CCL22 induced pain-related behavior in naive mice. Secondly, we revealed that the intrathecal injection of C021 significantly reduced CCI-induced hypersensitivity after nerve injury. In parallel, C021 reduced microglia/macrophages activation and the level of some pronociceptive interleukins (IL-1beta; IL-18) in the spinal cord 8 days after CCI. Moreover, C021 not only attenuated mechanical and thermal hypersensitivity but also enhanced the analgesic properties of morphine. Our research indicates that CCR4 ligands might be important factors in the early stages of neuropathy, when we observe intense microglia/macrophages activation. Moreover, pharmacological blockade of CCR4 may serve as a potential new target for better understanding the mechanisms of neuropathic pain development.