Ischemic stroke is the leading cause of disability and death worldwide. Currently, the only proven treatment for ischemic stroke is restoring the cerebral blood supply. In addition, some of the tissue is damaged during the subsequent reperfusion because of the overproduction of reactive oxygen species (ROS). Furthermore, antioxidant therapies have shown promise in preclinical studies for the treatment of ischemia-reperfusion injury. However, their therapeutic efficacy has been limited because of their low bioavailability in brain. To resolve this issue, we synthesized ROS-responsive, fan-shaped dendrimer nanoparticles (NPs) and conjugated them with a blood-brain barrier (BBB)-targeting peptide, COG1410, and salvianic acid A (SA), which is an effective antioxidant in ischemic stroke. The BBB targeting peptide acts as a ligand of the nanocarrier system and penetrates the BBB through the endocytosis of the ligand receptor. The results showed that T-SA-NPs not only target and accumulate in the infarct area, they also reduce over 2 times of the infarct area and reverse the behavioral deficits in MCAO mice, which illustrates that these NPs have an effective therapeutic effect on the ischemic stroke. In addition, these NPs had no toxicity in any organs of the body. Importantly, the present study provides an alternative strategy for delivering antioxidants to the brain and achieving targeted therapy of ischemic stroke.

Cerebral ischemia triggers a cascade of events that contribute to ischemic brain damages. Zinc release and accumulation has been shown to lead to brain cell death following cerebral ischemia. However, the mechanism underlying remains to be elucidated. Our recently published work showed that suppression of mitochondrial-derived reactive oxygen species (ROS) production significantly reduced ischemic stroke related brain damage within 6 h. Herein, we investigated the relationship between zinc accumulation and mitochondrial-derived ROS production in astrocytes after 3-h hypoxia. We found that inhibition of mitochondrial-derived ROS significantly decreased total amount of ROS generation and cell death in primary astrocytes during hypoxia when zinc was overload. In contrast, the inhibition of NADPH oxidase-derived ROS had less of an effect. Our results also showed that zinc and mitochondria were colocalized in hypoxic astrocytes. Moreover, extracellular zinc addition caused zinc accumulation in the mitochondria and decreased mitochondrial membrane potential, leading to mitochondria dysfunction. These findings provide a novel mechanism that zinc accumulation contributes to hypoxia-induced astrocytes death by disrupting mitochondria function, following cerebral ischemia.