Stroke is the third leading cause of death in the United States, yet no
neuroprotective agents for treatment are clinically available. There is a pressing need to understand the signaling molecules that mediate ischemic cell death and identify novel neuroprotective targets.
Cyclopentenone isoprostanes (IsoPs), formed after
free radical-mediated peroxidation of
arachidonic acid, are used as markers of stress, but their bioactivity is poorly understood. We have recently shown that
15-A(2t)-IsoP is a potent
neurotoxin in vitro and increases the
free radical burden in neurons. In this work, we demonstrate that
15-A(2t)-IsoP is abundantly produced in
stroke-infarcted human cortical tissue. Using primary neuronal cultures we found that minimally toxic exposure to
15-A(2t)-IsoP does not alter
ATP content, but in combination with
oxygen glucose deprivation resulted in a significant hyperpolarization of the mitochondrial membrane and dramatically increased neuronal cell death. In the presence of Ca(2+),
15-A(2t)-IsoP led to a rapid induction of the permeability transition pore and release of
cytochrome c. Taken with our previous work, these data support a model in which
ischemia causes generation of
reactive oxygen species,
calcium influx, lipid peroxidation, and
15-A(2t)-IsoP formation. These factors combine to enhance opening of the permeability transition pore leading to cell death subsequent to mitochondrial
cytochrome c release. These data are the first documentation of significant
15-A(2t)-IsoP formation after
acute ischemic stroke and suggest that the addition of
15-A(2t)-IsoP to in vitro models of
ischemia may help to more fully recapitulate
stroke injury.