Targeting pain mediators induced by injured nerve-derived COX2 and PGE2 to treat neuropathic pain.

INTRODUCTION: Neuropathic pain (NeP) is an intractable chronic pain condition which severely deteriorates the quality of life of 6% of the population. Caused by direct physical damage or diseases of the nervous system responsible for pain generation and transmission, NeP is manifested as spontaneous pain, hyperalgesia and allodynia. Its treatment is a challenging and unmet medical need. It is generally accepted that inflammatory mediators over-produced in injured nerves play a crucial role in the initiation and maintenance of NeP. AREAS COVERED: Among numerous inflammatory mediators, cyclooxygenase 2 (COX2) and its end product prostaglandin E2 (PGE2) are persistently up-regulated in infiltrating macrophages and Schwann cells in injured nerves and contribute to the development of NeP. In a NeP rat model and an ex vivo model of sensory ganglion explant culture, injured nerve-derived COX2 and PGE2 facilitate the synthesis of pain mediators including neuropeptides, ion channels, cytokines and neurotrophins in primary sensory neurons. EXPERT OPINION: Stimulating the synthesis of pain mediators in primary sensory neurons is a novel mechanism underlying the contribution of injured nerve-derived COX2 and PGE2 to the genesis of NeP. Targeting COX2/PGE2/EP signaling in injured nerves through local administration could open a novel therapeutic avenue to treat this debilitating disease.