Complexin 2 contributes to the protective effect of NAD⁺ on neuronal survival following neonatal hypoxia-ischemia

Nicotinamide adenine dinucleotide (NAD) is a key coenzyme involved in cell metabolism associated with aging, cancer, neurodegenerative diseases and metabolic disorders. We recently showed that NAD⁺ therapy significantly improved neurobehavioral outcomes in neonatal mice after hypoxia-ischemia (HI), and bioinformatics analysis revealed that the expression of complexin 2 (CPLX2) in the injured cerebral cortex was significantly decreased 24 h after HI injury but could be reversed by NAD⁺ intervention. In this study we explored the role of CPLX2 in the survival and function of neonatal hypoxic-ischemic cortical neurons. HI models were established by permanent ligation of the left common carotid artery in mice. CPLX2-knockdown lentiviral vector was injected intraventricularly on postnatal day 1 (P1); CPLX2 knockout mice were also used. NAD⁺ (5 mg·kg⁻¹·d⁻¹, i.p.) was administered before HI surgery, thereafter once a day until sampling. We showed that NAD⁺ administration significantly ameliorated the morphological damages and neurobehavioral defects, and elevated the seizure thresholds in HI mice. All the beneficial effects of NAD⁺ were abolished by CPLX2 knockdown or knockout. In HT22 neuronal cells subjected to OGD/R, pretreated with NAD⁺ (100 μM) for 12 h significantly increased the cell viability, decreased the LDH levels, and inhibited the ferroptosis evidenced by the changes in redox-related parameters including concentrations of Fe²⁺, GSH, MDA, H₂O₂ as well as the expression of GPX4 and SLC7A11. CPLX2 knockdown in HT22 neuronal cells blocked the protective effects of NAD⁺ as in HI mice, whereas CPLX2 overexpression enhanced the inhibitory effects of NAD⁺ on ferroptosis in HT22 neuronal cells.