Dihydromyricetin confers cerebroprotection against subarachnoid hemorrhage via the Nrf2-dependent Prx2 signaling cascade

Several clinical and experimental studies have shown that therapeutic strategies targeting oxidative damage are beneficial for subarachnoid hemorrhage (SAH). A brain-permeable flavonoid, dihydromyricetin (DHM), can modulate redox/oxidative stress and has cerebroprotective effects in several neurological disorders. The effects of DHM on post-SAH early brain injury (EBI) and the underlying mechanism have yet to be clarified. This work investigated a potential role for DHM in SAH, together with the underlying mechanisms. Cerebroprotection by DHM was studied using a SAH rat model and primary cortical neurons. Atorvastatin (Ato) was a positive control drug in this investigation. The effects of DHM on behavior after SAH were evaluated by performing the neurological rotarod and Morris water maze tests, as well as by examining its effects on brain morphology and on the molecular and functional phenotypes of primary cortical neurons using dichlorodihydrofluorescein diacetate (DCFH-DA), immunofluorescent staining, biochemical analysis, and Western blot. DHM was found to significantly reduce the amount of reactive oxygen species (ROS), suppress mitochondrial disruption, and increase intrinsic antioxidant enzymatic activity following SAH. DHM also significantly reduced neuronal apoptosis in SAH rats and improved short- and long-term neurological functions. DHM induced significant increases in peroxiredoxin 2 (Prx2) and nuclear factor erythroid 2-related factor 2 (Nrf2) expression, while decreasing phosphorylation of p38 and apoptotic signal-regulated kinase 1 (ASK1). In contrast, reduction of Prx2 expression using small interfering ribonucleic acid or by inhibiting Nrf2 with ML385 attenuated the neuroprotective effect of DHM against SAH. Moreover, DHM dose-dependently inhibited oxidative damage, decreased neuronal apoptosis, and increased the viability of primary cultured neurons in vitro. These positive effects were associated with Nrf2 activation and stimulation of Prx2 signaling, whereas ML385 attenuated the beneficial effects. These results reveal that DHM protects against SAH primarily by modulating the Prx2 signaling cascade through the Nrf2-dependent pathway. Hence, DHM could be a valuable therapeutic candidate for SAH treatment.