Efficient In Vivo Delivery of siRNA to the Liver by Conjugation of α-Tocopherol

Abstract

RNA interference is a powerful tool for target-specific knockdown of gene expression. However, efficient and safe in vivo delivery of short interfering RNA (siRNA) to the target organ, which is essential for therapeutic applications, has not been established. In this study we used alpha-tocopherol (vitamin E), which has its own physiological transport pathway to most of the organs, as a carrier molecule of siRNA in vivo. The alpha-tocopherol was covalently bound to the antisense strand of 27/29-mer siRNA at the 5'-end (Toc-siRNA). The 27/29-mer Toc-siRNA was designed to be cleaved by Dicer, producing a mature form of 21/21-mer siRNA after releasing alpha-tocopherol. The C6 hydroxyl group of alpha-tocopherol, associated with antioxidant activity, was abolished. Using this new vector, intravenous injection of 2 mg/kg of Toc-siRNA, targeting apolipoprotein B (apoB), achieved efficient reduction of endogenous apoB messenger RNA (mRNA) in the liver. The downregulation of apoB mRNA was confirmed by the accumulation of lipid droplets in the liver as a phenotype. Neither induction of interferons (IFNs) nor other overt side effects were revealed by biochemical and pathological analyses. These findings indicate that Toc-siRNA is effective and safe for RNA interference-mediated gene silencing in vivo.

Exploring Chemical Modifications for siRNA Therapeutics: A Structural and Functional Outlook

“…[215] Other lipophilic species studied for siRNA conjugation are vitamins E and A. [216,217] A vitamin E-siRNA conjugate was systemically delivered to the liver and showed efficient delivery into the target tissues without any interferon response. [216] An aptamer-based approach works along similar lines.…”

“…[216,217] A vitamin E-siRNA conjugate was systemically delivered to the liver and showed efficient delivery into the target tissues without any interferon response. [216] An aptamer-based approach works along similar lines. [195,218] The siRNA was conjugated to an aptamer that targets prostrate-specific membrane antigen (PSMA), which is abundant on prostrate cancer cells; the package efficiently delivered siRNAs into the tumor cells, leading to desirable silencing.…”

Tumor-Suppressing Effect of MiR-4458 on Human Hepatocellular Carcinoma

“…Tumor inhibition effect of miR-4458 showed in our data indicated the therapy drug possibility of miR-4458. Also, viral and nonviral vectors are being developed by delivery of synthetic RNA to liver [46,47,48]. Hence, restoration of miR-4458 should have a considerable potential for HCC molecular therapy.…”

Efficient reduction of serum cholesterol by combining a liver-targeted gene delivery system with chemically modified apolipoprotein B siRNA

“…Several liver-targeted delivery methods for Apo B siRNA have been reported such as direct conjugation of Apo B siRNA to lipophilic molecules (e.g., cholesterol and α-tocopherol) [20,43] or to carriers containing liver-targeted ligands (e.g., N-acetylgalactosamine) [44].…”