Astragaloside IV reduces neuronal apoptosis and parthanatos in ischemic injury by preserving mitochondrial hexokinase-II

Cerebral ischemia induces neuronal cell death in different ways and mitochondrial dysfunction is an important cause. Astragaloside IV (AIV) is a natural saponin abandent in Astragalus membranaceus and this study aims to find if AIV protects neuronal survival via preserving mitochondrial hexokinase-II (HK-II). Glutamate stimulation induced HK-II dissociation from mitochondria and impaired mitochondrial function, indicated by the opening of the mitochondrial permeability transition pore, the collapse of mitochondrial membrane potential and reduced mitochondrial oxygen consumption ratio in neurons. Accompanied with apoptosis, oxidative DNA damage, PAR formation and nuclear translocation of apoptosis inducing factor (AIF) indicated the presence of parthanatos. AIV activated Akt and protected mitochondrial HK-II via promoting the binding of Akt to HK-II and protected hexokinase activity with improved glycolysis. As a consequence of preserved mitochondrial HK-II, AIV reduced the release of pro-apoptotic proteins and AIF, resultantly protected neurons from apoptosis and parthanatos. Moreover, the neuroprotective effects of AIV were also reproduced in mice subjected to middle cerebral artery occlusion to support the findings in vitro. Together, these results showed that glutamate excitotoxicity impaired mitochondrial HK-II and simultaneously induced apoptosis and parthanatos owing to mitochondrial dysfunction. AIV activated Akt to promote HK-II binding to mitochondria, and the structural and functional integrity of mitochondria contributed to protecting neurons from apoptosis and DNA damage. These findings address the important role of mitochondrial HK-II in neuronal protection.