Epoxyeicosatrienoic acids: Emerging therapeutic agents for central post-stroke pain

Central post-stroke pain (CPSP) is chronic neuropathic pain due to a lesion or dysfunction of the central nervous system following cerebrovascular insult. This syndrome is characterized by chronic somatosensory abnormalities including spontaneous pain, hyperalgesia and allodynia, which localize to body areas corresponding to the injured brain region. However, despite its potential to impair activities of daily life and cause mood disorders after stroke, it is probably the least recognized complication of stroke. All currently approved treatments for CPSP have limited efficacy but troublesome side effects. The detailed mechanism underlying CPSP is still under investigation; however, its diverse clinical features indicate excessive central neuronal excitability, which is attributed to loss of inhibition and excessive neuroinflammation. Recently, exogenous epoxyeicosatrienoic acids (EETs) have been used to attenuate the mechanical allodynia in CPSP rats and proven to provide a quicker onset and superior pain relief compared to the current first line drug gabapentin. This anti-nociceptive effect is mediated by reserving the normal thalamic inhibition state through neurosteroid-GABA signaling. Moreover, mounting evidence has revealed that EETs exert anti-inflammatory effects by inhibiting the expression of vascular adhesion molecules, activating NFκB, inflammatory cytokines secretion and COX-2 gene induction. The present review focuses on the extensive evidence supporting the potential of EETs to be a multi-functional therapeutic approach for CPSP. Additionally, the role of EETs in the crosstalk between anti-CPSP and the comorbid mood disorder is reviewed herein.