Norcepharadione B attenuates H2O2-induced neuronal injury by upregulating cellular antioxidants and inhibiting volume-sensitive Cl- channel

Oxidative stress acts as an essential culprit factor in the development of stroke and Alzheimer’s disease. Norcepharadione B possesses various pharmacologic features as an extract obtained from Houttuynia cordata. Nevertheless, the anti-apoptotic and neuroprotective characteristics of norcepharadione B remain unclear. In this study, the neuronal protection effect provided by norcepharadione B against injury caused by hydrogen peroxide (H₂O₂) in HT22 cell as well as the fundamental mechanism was systematically explored. The neurotoxicity assays of hippocampal cells, which were co-cultured with H₂O₂, showed that norcepharadione B had the ability to insulate the toxicity induced by H₂O₂ with significant reduced cell Apoptosis. Besides, norcepharadione B potentiated the activity of superoxide dismutase (SOD), increased the level of glutathione (GSH), and decreased malondialdehyde content. The H₂O₂-induced apoptotic protein Bax was suppressed, and the anti-apoptotic protein Bcl-2 was boosted by norcepharadione B. Norcepharadione B promoted Akt phosphorylation and further upregulated heme oxygenase (HO-1) in cells exposed to oxidative stress. However, the inductive effect of HO-1 by norcepharadione B was shut off via the PI3K/Akt Inhibitor LY294002. Furthermore, 2-h incubation with H₂O₂ substantially increased cell volume in HT22 cells, while norcepharadione B effectively alleviated such effect by interrupting the activation of VSOR Cl⁻ channel. Collectively, our data revealed protective properties of norcepharadione B in resisting oxidative stress induced by H₂O₂ through elevation of HO-1 in the dependence of PI3K/Akt and in inhibiting H₂O₂-induced cell swelling by VSOR Cl⁻ channel obstruction in HT22 cells.

Impact statement: Norcepharadione B is an aporphine alkaloid compound extracted from Chinese herb Houttuynia cordata. It was well known for its anti-inflammatory, anti-cancer, and anti-platelet aggregation outcomes. Our study demonstrated that Norcepharadione B protected hippocampal neurons against oxidative stress and the resultant cell Apoptosis upon H₂O₂ exposure. Meanwhile, Norcepharadione B also substantially reduced cell swelling induced by H₂O₂ via inhibiting VSOR Cl⁻ channel in neurons. These findings uncovered the potential mechanisms of Norcepharadione B in protecting neuron Apoptosis under oxidative stress and propose that Norcepharadione B may serve as a favorable herb medicine for restoring neuronal injury in the pathogenesis of stroke together with other neurodegenerative diseases.