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KMID : 0617320020110010272
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Journal of Pharmacetical Sceiences Ewha Womans University
2002 Volume.11 No. 1 p.272 ~ p.280
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Imaging Gene Expression in the Brain In Vivo in a Transgenic Mouse Model of Huntington´s Disease with an Antisense Radiopharmaceutical and Drug-Targeting Technology
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Lee, Hwa Jeong
Boado, Ruben J./Brassch, Dwaine A./Corey, David R./Pardridge, William M.
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Abstract
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Disease-specific genes of unknown function can be imaged invivo with antisense radiopharmaceuticals, providing the trans-cellular transport of these molecules is enabled with drug-tar-geting technology. The current studies describe the productionof 16-mer peptide nucleic acid (PNA) that is antisense aroundthe methionine initiation codon of the huntingtin gene of Hun-tington´s disease (HD). Methods: The PNA is biotinylated,which allows for rapid capture by a conjugate of streptavidinand the rat 8D3 monoclonal antibody (mAb) to the mouse trans-ferrin receptor (TfR), and contains a tyrosine residue, whichenables radiolabeling with ^125I. The reformulated PNA antisenseradiopharmaceutical that is conjugated to the 8D3 mAb is des-ignated ^125I-PNA/8D3, This form of the PNA is able to accessendogenous transferrin transport pathways at both the blood-brain barrier and the brain cell membrane and undergoes bothimport from the blood to the brain and export from the brain tothe blood through the TfR. Results: The ability of the PNA tohybridize to the target huntingtin RNA, despite conjugation tothe mAb, was shown both with cell-free translation assays andwith ribonuclease protection assays. The ^123I-PNA/8D3 conju-gate was administered intravenously to either littermate controlmice or to R6/2 transgenic mice, which express the exon 1 ofthe human HD gene. The mice were sacrificed 6 h later forfrozen sectioning of the brain and quantitative autoradiography.The studies showed a 3-fold increase in sequestration of the^125I-PNA/8D3 antisense radiopharmaceutical in the brains of theHD transgenic mice in vivo, consistent with the selective ex-pression of the HD exon-1 messenger RNA in these animals.Conclusion: These results support the hypothesis that geneexpression in vivo can be quantitated with antisense radiophar-maceuticals, providing these molecules are reformulated withdrug-targeting technology. Drug targeting enables access of theantisense agent to endogenous transport pathways, which per-mits passage across the cellular barriers that separate bloodand intracellular compartments of target tissues.
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