Transferring exogenous mitochondria has therapeutic effects on damaged heart, liver, and lung tissues. Whether this protective effect requires the symbiosis of exogenous mitochondria in host cells remains unknown. Here xenogenic mitochondria derived from a hamster cell line were applied to ischemic rat brains and rat primary cortical neurons. Isolated hamster mitochondria, either through local intracerebral or systemic intra-arterial injection, significantly restored the motor performance of brain-ischemic rats. The brain infarct area and neuronal cell death were both attenuated by the exogenous mitochondria. Although internalized mitochondria could be observed in neurons and astrocytes, the low efficacy of mitochondrial internalization could not completely account for the high rate of rescue of the treated neural cells. We further illustrated that disrupting electron transport or ATPase synthase in mitochondria significantly attenuated the protective effect, suggesting that intact respiratory activity is essential for the mitochondrial potency on neural protection. These results emphasize that nonsymbiotic extracellular mitochondria can provide an effective cell defense against acute injurious ischemic stress in the central nervous system.

Astaxanthin (ATX) is a dietary carotenoid of crustaceans and fish that contributes to their coloration. Dietary ATX is important for development and survival of salmonids and crustaceans and has been shown to reduce cardiac ischemic injury in rodents. The purpose of this study was to examine whether ATX can protect against ischemic injury in the mammalian brain. Adult rats were injected intracerebroventricularly with ATX or vehicle prior to a 60-min middle cerebral artery occlusion (MCAo). ATX was present in the infarction area at 70-75 min after onset of MCAo. Treatment with ATX, compared to vehicle, increased locomotor activity in stroke rats and reduced cerebral infarction at 2 d after MCAo. To evaluate the protective mechanisms of ATX against stroke, brain tissues were assayed for free radical damage, apoptosis, and excitoxicity. ATX antagonized ischemia-mediated loss of aconitase activity and reduced glutamate release, lipid peroxidation, translocation of cytochrome c, and TUNEL labeling in the ischemic cortex. ATX did not alter physiological parameters, such as body temperature, brain temperature, cerebral blood flow, blood gases, blood pressure, and pH. Collectively, our data suggest that ATX can reduce ischemia-related injury in brain tissue through the inhibition of oxidative stress, reduction of glutamate release, and antiapoptosis. ATX may be clinically useful for patients vulnerable or prone to ischemic events.