Co-administration of apocynin with lipoic acid enhances neuroprotection in a rat model of ischemia/reperfusion

► Low doses of lipoic acid or apocynin do not result in neuroprotection. ► Co-administration of lipoic acid and apocynin together enhances neuroprotection. ► Combining these two antioxidants at low doses results in greater neuroprotection. Apocynin is a well-known NADPH-oxidase inhibitor currently being investigated for its potential therapeutic use in patients with cardiovascular disease, such as occlusive stroke. However, the use of apocynin as a potential neuroprotective agent has come under criticism due to a narrow experimental therapeutic dose range and possible pro-oxidant effects at high doses. Lipoic acid is a powerful antioxidant due to its ability to scavenge free radicals at very low doses and has been demonstrated to enhance the therapeutic value of several other classes of drugs. Therefore, the present study was designed to determine if co-administration of previously determined non-neuroprotective doses of lipoic acid and apocynin in combination could enhance their neuroprotective ability thus extending the therapeutic dose range. We tested the hypothesis in a rat model of stroke and reperfusion injury. The middle cerebral artery (MCA) in male Sprague-Dawley rats was occluded for 30 min followed by 5.5 h of reperfusion. Pre-treatment with several doses of apocynin (0.05, 0.1 and 1.0 mg/kg) in combination with a single dose of lipoic acid (0.005 mg/kg) resulted in a dose-dependent reduction in infarct volume up to ∼50%. These results demonstrate that a non-effective dose of lipoic acid can enhance the neuroprotective ability of apocynin at doses which were previously demonstrated to be non-neuroprotective. Co-administration of apocynin with lipoic acid may overcome the criticisms of the use of apocynin as a neuroprotectant and provide an effective therapy in the prevention of cell death following stroke.