Autophagy has evolved as a conserved process for the bulk degradation and recycling of cytosolic components, such as long-lived proteins and organelles. In neurons, autophagy is important for homeostasis and protein quality control and is maintained at relatively low levels under normal conditions, while it is upregulated in response to pathophysiological conditions, such as cerebral ischemic injury. However, the role of autophagy is more complex. It depends on age or brain maturity, region, severity of insult, and the stage of ischemia. Whether autophagy plays a beneficial or a detrimental role in cerebral ischemia depends on various pathological conditions. In this review, we elucidate the role of neuronal autophagy in cerebral ischemia.
In previous studies,we showed that TP53-induced glycolysis and apoptosis regulator（TIGAR） protects neurons against ischemic brain injury.In the present study,we investigated the developmental changes of TIGAR level in mouse brain and the correlation of TIGAR expression with the vulnerability of neurons to ischemic injury.We found that the TIGAR level was high in the embryonic stage,dropped at birth,partially recovered in the early postnatal period,and then continued to decline to a lower level in early adult and aged mice.The TIGAR expression was higher after ischemia/reperfusion in mouse brain 8and 12 weeks after birth.Four-week-old mice had smaller infarct volumes,lower neurological scores,and lower mortality rates after ischemia than 8- and12-week-old mice.TIGAR expression also increased in response to oxygen glucose deprivation（OGD）/reoxygenation insult or H_2O_2 treatment in cultured primary neurons from different embryonic stages（E16 and E20）.The neurons cultured from the early embryonic period had a greater resistance to OGD and oxidative insult.Higher TIGAR levels correlated with higher pentose phosphate pathway activity and less oxidative stress.Older mice and more mature neurons had more severe DNA and mitochondrial damage than younger mice and less mature neurons in response to ischemia/reperfusion or OGD/reoxygenation insult.Supplementation of cultured neurons with nicotinamide adenine dinuclectide phosphate（NADPH） significantly reduced ischemic injury.These results suggest that TIGAR expression changes during development and its expression level may be correlated with the vulnerability of neurons to ischemic injury.
