Delivery of heme oxygenase-1 gene using dexamethasone conjugated polyethylenimine for brain protection against ischemic stroke

Abstract

Dexamethasone is one of anti-inflammatory glucocorticoid steroids. In this research, dexamethasone was conjugated low molecular weight polyethyleneimne (2,000 Da, PEI2k). PEI has been investigated as a gene carrier for gene therapy. Therefore, dexamethasone conjugated PEI (PEI-Dexa) may have dual functions as an anti-inflammatory reagent and a gene carrier. Heme oxygenase-1 (HO-1) is an anti-apoptotic protein, which can protect cell from apoptosis under hypoxia. In this study, HO-1 gene was delivered to focal ischemic brain of stroke animal model using PEI-Dexa as a gene carrier. In divided groups of rats (n=5), empty plasmid pNull/PEI-Dexa, pNull/PEI and pSV-HO-1/PEI-Dexa complexes were injected directly into the cortex 1 hr prior to middle cerebral artery occlusion (MCAO) except control group. MCAO was performed for 50 min by 4-0 nylon filament suture into internal carotid artery via the external carotid artery in male Sprague Dawley (SD) rats (280-320g). Also, cortical blood flow was continuously monitored by Laser Doppler Flowmetry. At 24 hrs after MCAO, infarct size was evaluated by 2% 2,3,5-triphenyltetrazolium hydrochloride (TTC) staining. The level of cytokine such as TNF-α was measured in the infarcted area. The results showed that injection of pNull/PEI-Dexa reduced infarct size significantly compared with the control and pNull/PEI groups. This suggests that PEI-Dexa protects the brain cells under ischemia-reperfusion condition. The infarct size was further reduced in the group of the pSV-HO-1/PEI-Dexa group, which suggests that HO-1 has synergistic effect with PEI-Dexa in reducing inflammatory response in ischemic brain. Therefore, pSV-HO-1/PEI-Dexa complex is a potential candidate for therapeutic gene delivery to ischemic brain.