Neurobiology of Disease (Oct 2004)
Neonatal mice lacking functional Fas death receptors are resistant to hypoxic–ischemic brain injury
Abstract
Neonatal hypoxia–ischemia (HI) upregulates Fas death receptor expression in the brain, and alterations in expression and activity of Fas signaling intermediates occur in neonatal brain injury. B6.MRL-Tnfrsf6lpr mice lacking functional Fas death receptors are protected from HI brain damage in cortex, striatum, and thalamus compared to wild-type mice. Expression of Fas death receptor and active caspases increase in the cortex after HI. In wild-type mice, the hippocampus is most severely injured, and the hippocampus is the only region not protected in the B6.MRL-Tnfrsf6lpr mice. The selective vulnerability of the hippocampus to injury correlates with (1) lower basal expression of [Fas-associated death-domain-like IL-1β-converting enzyme]-inhibitory protein (FLIP), (2) increased degradation of spectrin to its 145 or 150 kDa breakdown product, and (3) a higher percentage of non-apoptotic cell death following neonatal HI. We conclude that Fas signaling via both extrinsic and intrinsic caspase cascades causes brain injury following neonatal HI in a region-dependent manner. Basal levels of endogenous decoy proteins may modulate the response to Fas death receptor signaling and provide a novel approach to understanding mechanisms of neonatal brain injury.