Combination of NAD⁺ and NADPH Offers Greater Neuroprotection in Ischemic Stroke Models by Relieving Metabolic Stress

Both reduced nicotinamide adenine dinucleotide phosphate (NADPH) and β-nicotinamide adenine dinucleotide hydrate (NAD⁺) have been reported to have potent neuroprotective effects against ischemic neuronal injury. Both NADPH and NAD⁺ are essential cofactors for anti-oxidation and cellular energy metabolism. We investigated if combined NADPH and NAD⁺ could offer better neuroprotective effects on cellular and animal models of ischemic stroke. In vitro studies with primary cultured neurons demonstrated that NAD⁺ was effective in protecting neurons against oxygen–glucose deprivation/reoxygenation (OGD/R) injury when given during the early time period of reoxygenation. In vivo studies in mice also suggested that NAD⁺ was effective for ameliorating ischemic brain damage when administered within 2 h after reperfusion. The combination of NADPH and NAD⁺ provided not only greater beneficial effects but also larger therapeutic window in both cellular and animal models of stroke. The combination of NADPH and NAD⁺ significantly increased the levels of adenosine triphosphate (ATP) and reduced the levels of reactive oxygen species (ROS) and oxidative damage of macromolecules. Furthermore, the combined medication significantly reduced long-term mortality, improved the functional recovery, and inhibited signaling pathways involved in apoptosis and necroptosis after ischemic stroke. The present study indicates that the combination of NAD⁺ and NADPH can produce greater therapeutic effects with smaller dose of NADPH; on the other hand, NADPH can significantly prolong the therapeutic window of NAD⁺. The current results suggest that the combination of NADPH and NAD⁺ may provide a novel effective therapy for ischemic stroke.