Postconditioning with D-limonene exerts neuroprotection in rats via enhancing mitochondrial activity

Abstract Objectives The key component of neuroprotection after cerebral ischemia–reperfusion (I–R) injury is mitochondrial improvement. By focusing on the function of mitochondrial biogenesis and ATP-sensitive potassium (mK–ATP) channels and inflammatory responses, the current study assessed the neuroprotective potentials of lemon essential oil, D-limonene (LIM), in rats with cerebral I–R injury. Methods In order to simulate cerebral I–R injury, Sprague Dawley rats (n=72) were subjected to a two h local ischemia induced by middle cerebral artery blockage, followed by a 24 h reperfusion period. Five minutes before starting reperfusion, rats were intraperitoneally given LIM at doses of 10 or 100 mg/kg. Cerebral infarct volume was assessed by triphenyl-tetrazolium chloride staining, brain activity by behavioral tests and mitochondrial function/biogenesis, as well as proinflammatory cytokines by fluorometry, immunoblotting and other related techniques. Results When compared to the untreated control group, the administration of LIM substantially and dose-dependently decreased cerebral infarct volumes and neurological deficits (p<0.01). I–R injury-induced alterations in mitochondrial membrane depolarization, mitochondrial reactive oxygen species (mitoROS), and superoxide dismutase (mnSOD), as well as inflammatory cytokines TNF-α, IL-6 and IL-1β, were all significantly reversed after treatment with LIM 100 mg/kg (p<0.01). Additionally, this dose of LIM increased the expression of mitochondrial biogenesis proteins PGC-1α, TFAM, and NRF1. Interestingly, blockage of mK–ATP channels by 5-hydoxydecanoate diminished the effects of LIM on cerebral positive endpoints, cytokines production, and mitochondrial function/biogenesis. Conclusions Thus, the strong neuroprotective effects of LIM-postconditioning were mediated by an increase in mK–ATP channel activity, which improved mitochondrial biogenesis and suppressed inflammatory responses.