Intervening to treat stroke in acute and chronic phases: From gene therapy to neurogenesis.

摘要

Preclinical studies of the pathological mechanisms of cerebral ischemic damage have convinced researchers that interventions may be devised to protect the brain from stroke or aid in its repair. The experiments reported here were designed to test the efficacy of two broad forms of intervention for cerebral ischemia; those that target events that occur early after ischemia (e.g., excitotoxicity/oxidative stress and inflammation) and those that target later events (e.g., alterations in neurogenesis).; First, we demonstrated that enhancing neuronal expression of neuroprotective genes, increases the cell's resistance to hostile environmental changes caused by experimental ischemia. Neurons were protected if expression of heat shock protein 70 (HSP70) or glutathione peroxidase (Gpx) was enhanced prior to or within a limited window after ischemia. We also observed that Gpx overexpression decreased expression of the regulators of cell death, cytochrome c, BAX, and caspase-3, while enhancing Bcl-2, a positive regulator of cell survival. Infarct size was not altered by these treatments due to the limited number of cells transfected (300-500 cells). Thus, we sought to enhance the level of transfection by focusing on inflammation as a possible reason for low transfection. Reducing inflammation by pre-treating animals with the non-steroidal anti-inflammatory drug (NSAID) minocycline increased transfection rate by 90%, which has the potential of enhancing the therapeutic effects of neuroprotective gene transfer.; In the later stages of cerebral ischemia inflammation plays a larger role in disturbing the environment. Therefore, we tested the hypothesis that reducing inflammation will enhance the survival of endogenous precursors, perhaps allowing them to participate in neurorestoration. We administered the NSAID indomethacin to rats subjected to experimental stroke and found not only did it increase overall cell survival, but also enhanced the expression of neuronal phenotypes. Further analysis showed this outcome was correlated with reductions in COX2 protein, immune cell activation, and peripheral leukocyte infiltration.; In summary, we have demonstrated that it is possible to increase neuronal survival in the acute phase of ischemia via gene therapy to better withstand the hostile ischemic environment, or in the chronic phase by making the environment less hostile.