Inhibition of autophagy prevents hippocampal pyramidal neuron death after hypoxic-ischemic injury.

Neonatal hypoxic/ischemic (H/I) brain injury causes neurological impairment, including cognitive and motor dysfunction as well as seizures. However, the molecular mechanisms regulating neuron death after H/I injury are poorly defined and remain controversial. Here we show that Atg7, a gene essential for autophagy induction, is a critical mediator of H/I-induced neuron death. Neonatal mice subjected to H/I injury show dramatically increased autophagosome formation and extensive hippocampal neuron death that is regulated by both caspase-3-dependent and -independent execution. Mice deficient in Atg7 show nearly complete protection from both H/I-induced caspase-3 activation and neuron death indicating that Atg7 is critically positioned upstream of multiple neuronal death executioner pathways. Adult H/I brain injury also produces a significant increase in autophagy, but unlike neonatal H/I, neuron death is almost exclusively caspase-3-independent. These data suggest that autophagy plays an essential role in triggering neuronal death execution after H/I injury and Atg7 represents an attractive therapeutic target for minimizing the neurological deficits associated with H/I brain injury.