Sub-anaesthetic dose of propofol attenuates mechanical allodynia in chronic post-ischaemic pain via regulation of PTEN/PI3K/IL-6 signalling

Background: Propofol is an intravenous anaesthetic drug that has been shown to reduce inflammatory pain. Complex regional pain syndrome (CRPS) type I is a pain condition characterized by autonomic, motor and sensory disturbance. The chronic post-ischaemic pain (CPIP) model is a well-established model to recapture CRPS-I syndromes pre-clinically by non-invasive ischaemic-reperfusion (IR) injury. In this study, we investigated the analgesic effects of propofol and underlying mechanisms in mitigating CRPS pain using the CPIP model. Methods: Sub-anaesthetic dose of propofol (25 mg/kg) was intravenously delivered to the CPIP model and sham control. Nociceptive behavioural changes were assayed by the von Frey test. Molecular assays were used to investigate expression changes of PTEN, PI3K, AKT and IL-6 underlying propofol-mediated analgesic effects. Pharmacological inhibition was applied for PTEN/PI3K/AKT pathway manipulation. Results: Both pre- and post-operative administration of propofol attenuated mechanical allodynia induced by CPIP. Propofol could modulate PTEN/PI3K/AKT signalling pathway by increasing active PTEN and reducing phosphorylated PI3K, phosphorylated AKT and IL-6 expression in the spinal dorsal horn, which promoted pain relief in the CPIP model. Inhibition of PTEN with bpV abolished the analgesic effects produced by propofol in CPIP mice. Conclusion: Sub-anaesthetic dose of propofol administration resulted in the activation of PTEN, inhibition of both PI3K/AKT signalling and IL-6 production in the spinal cord, which dramatically reduced CPIP-induced pain. Our findings lay the foundation in using propofol for the treatment of CRPS with great therapeutic implications.