DHA and DHA-derived SPMs in the prevention and treatment of postoperative pain
Chronic postsurgical pain often develops after major surgery. Orthopaedic injuries and subsequent surgery produce postoperative pain that lasts for weeks; this pain is related to nerve injury and is reflected in central and peripheral neuroinflammation. In the last three decades, much progress has been made in understanding the underlying mechanisms of the pathogenesis of pain after inflammation and nerve injury. Pathological pain is generally thought to be caused by neural plasticity in primary sensory neurons (peripheral sensitivity), the spinal dorsal horn and cerebral neurons (central sensitivity). Gliopathy also contributes to the pathogenesis of pain, partly promoting neuroinflammation. However, despite this understanding of the mechanisms that produce the perception of pain, failure to resolve acute pain can lead to develop into chronic states.
There is increasing evidence to suggest that specialised pro-resolving mediators (SPMs) derived from docosahexaenoic acid (DHA) favour the resolution of inflammation and potentially inhibit inflammatory and neuropathic pain. A recently published study analysed the analgesic effect of DHA and DHA-derived SPMs in a mouse model of postoperative pain induced by tibia fracture. The results suggest that: 1) intravenous perioperative treatment with DHA is effective in the prevention and development of postoperative pain; and 2) intrathecal postoperative treatment with some SPMs (protectin D1, maresin 1, resolvin D1 and resolvin D5) could alleviate established pain. DHA and DHA-derived SPMs have different effects at different times.
Notably, effective doses of SPMs are 1,000 times lower than their precursor. Furthermore, the therapeutic effect of DHA could be associated with its conversion to SPM.
DHA and SPM derivatives have powerful, although differeing, analgesic actions in the prevention and treatment of postoperative pain.