Development of targeted delivery systems for early detection and genetically therapeutic intervention of cardiovascular disease

Kang, Zhili (2003) Development of targeted delivery systems for early detection and genetically therapeutic intervention of cardiovascular disease. Masters thesis, Memorial University of Newfoundland.

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Abstract

Atherosclerosis is a primary cause of heart disease and stroke. It is known that early detection of atherosclerotic lesions would significantly reduce the risk. One of the objectives in this thesis is to evaluate a noninvasive radioimaging method for detecting early atherosclerotic plaques. A novel polyiodinated cholesterol analog, cholesteryl 1,3-diiopanoate glyceryl ether (C21), radiolabeled with ¹²⁵I, was incorporated into acetylated low density lipoprotein (AcLDL) which is considered as an atherosclerotic plaque seeking carrier. ¹²⁵I-C21 was also prepared as a chylomicron-like emulsion. ¹²⁵I-C21/AcLDL or ¹²⁵I-C21 emulsion was intravenously injected into apoE/LDL receptor (LDLR) double knockout mice that serve as an atherosclerosis animal model. The ex vivo images of radioactivity accumulated in the aortas 24 hours postinjection were compared to the atherosclerotic lesions revealed by histological studies. It was found that both ¹²⁵I-C21/ AcLDL and ¹²⁵I-C21 emulsion resulted in accumulation of radioactivity at the site of early atherosclerotic lesions, and therefore may be useful for early detection of atherosclerosis. -- Treatments for atherosclerosis include general lipid-lowering strategies and approaches toward etiology. Among the multiple risk factors associated with atherosclerosis, familial hypercholesterolemia (FH) is the first genetic disorder recognized to cause severe premature atherosclerosis. Ultimate treatment for FH depends on gene therapy which can correct its WLR deficiency. The second part of this thesis focused on the development of a liver-targeting liposome vector for systemic gene therapy, with the objective of delivering mouse LDLR gene to the liver of the LDLR- knockout mouse, an animal model closely resembling human FH conditions. A peptide from the circumsporozoite protein (CS) of malaria parasites was chosen as the liver-targeting ligand. Cationic liposome/protamine/DNA (LPD) complex conjugated with the malaria peptide was prepared by different protocols and primarily investigated in vitro to transfect cultured cells with a reporter gene, either the chloramphenicol acetyltransferase (CAT) gene or the enhanced green fluorescent protein (EGFP) gene. Peptide-LPD complex showed higher CATIEGFP expression in HepG2 cells (human hepatoma cell line) than LPD itself, whereas no significant difference was observed in Hela cells (human cervical cancer cell line, control). However, these results were still preliminary and somewhat inconsistent. Further studies are needed. -- Finally, chapter 4 summarized other work using LDL as a potential targeting carrier for lipophilic antitumor drugs. A prodrug, dipalmitoyl-5-fluorodeoxyuridine (dpFUdR), was synthesized and incorporated into LDL. The antiproliferative effect of the resultant LDL-dpFUdR was investigated in human cervical cancer cells.

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