The analgesic effect of propofol associated with the inhibition of hypoxia inducible factor and inflammasome in complex regional pain syndrome.

Complex regional pain syndrome (CRPS) is related to microcirculation impairment caused by tissue hypoxia and peripheral cytokine overproduction in the affected human limb and chronic post-ischemic pain (CPIP) is considered as an animal model for this intractable disease. Previous studies suggest that the pathogenesis of CPIP involves the hypoxia inducible factor-1α (HIF-1α) and an exaggerated regional inflammatory and free radical response. The inhibition of HIF-1α is known to relieve CPIP. So, propofol, as a free radical scavenger, is very likely to be beneficial in terms of relieving CPIP.We set up a CPIP model using the hindpaw of mice. We administered propofol (10 mg/kg) just after the reperfusion period (early stage) and also on the second day (late stage), as treatment. The analysis evaluated the expression of HIF-1α, free radicals, and inflammasome.Propofol administration produced obvious analgesia in both mechanical and thermal evaluation in the early stage of CPIP (2 h after reperfusion). Only a mild analgesic effect was found in the late stage (48 h later after reperfusion). In the early stage, the expression of HIF-1α and the inflammasome marker (NALP1) along with caspase-1 were suppressed by propofol. The free radical level also decreased in the propofol group. But those molecular changes were not founded in the late stage of CPIP.Our data demonstrated that propofol produces mice analgesia in the early stage of CPIP and this effect is associated with inhibition of free radical, hypoxia inducible factor and inflammasome.