Dexamethasone conjugated polyethylenimine as a carrier of plasmid encoding heme oxygenase-1 for stroke gene therapy

Abstract

Dexamethasone is one of the anti-inflammatory glucocorticoid steroids. Previously, we synthesized dexamethasone conjugated polyethylenimine (PEI-Dexa) as a gene carrier with anti-inflammatory effect. In this study, HO-1 gene was delivered to focal ischemic brain of stroke animal model using PEI-Dexa as a gene carrier. Heme oxygenase-1 (HO-1) is an anti-apoptotic protein, which can protect cell from apoptosis under hypoxia. In divided groups of rats (n=9), pCI/PEI, pCI/PEI-Dexa and pEpo-SV-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 60 min 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 cytokines such as TNF-α, IL-1β were measured by ELISA in the infarcted area. ELISA for the HO-1 protein was also performed. The results showed that the injection of pCI/PEI-Dexa complex reduced infarct size significantly, compared with the control and pCI/PEI injection groups. This suggests that dexamethsone segment of PEI-Dexa protects the brain cells under ischemia-reperfusion condition. Also, HO-1 expression was induced in the pEpo-SV-HO-1/PEI-Dexa injection group. The infarct size of the pEpo-SV-HO-1/PEI-Dexa injection group was further reduced compared with the pCI/PEI-Dexa injection group, suggesting that HO-1 has synergistic effect with PEI-Dexa in reducing inflammatory response in ischemic brain. Therefore, pEpo-SV-HO-1/PEI-Dexa complex is a potential candidate for therapeutic gene delivery to ischemic brain.