Abstract: Objective To investigate the neuroprotective effects of neurotrophin-3 (NT-3) expression controlled by five copies of the hypoxia-responsive elements after focal cerebral ischemia. Methods Three groups of rats received RV-5H-NT3, RV-5H-EGFP or saline injection. Three days after gene transfer, the rats underwent 90 min of transient middle cerebral artery occlusion (tMCAO), followed by 1–28 days of reperfusion. Immunohistostaining and western blotting were performed to detect ischemia/hypoxia-regulated expression of NT-3 controlled by HRE. The volume of brain infarction and the apoptosis were analysised by TTC and TUNEL staining. The neurological scoring was determined by neurological behavior tests. Results Three days after tMCAO, brain NT-3 expression was significantly increased in the RV-5HNT3-transduced animals compared with the RV-5H-EGFP or saline group (P<0.05), and brain infarct volume was smaller in the RV-5H-NT3-transduced group than the RV-5H-EGFP or saline group (P<0.05). The percentage of TUNEL-positive cells was reduced in RV-5H-NT3-transduced brains compared with the RV-5HEGFP or saline group 3 and 7 days after tMCAO (P<0.05). Furthermore, the neurological status of RV-5H-NT3-transduced rats was better than that of RV-5H-EGFP- or saline-transduced animals from 1 day to 4 weeks after tMCAO (P<0.05). Conclusion Our results demonstrated that HRE could modulate NT-3 expression in the ischemic brain environment and that the up-regulated NT-3 could effectively improve neurological status following tMCAO due to decreased initial damage.

Key words: hypoxia-inducible gene expression, neuroprotection, ischemic stroke, gene therapy