Molecular intervention with antisense oligodeoxynucleotides (ODNs) in nephrology.

Abstract

Manipulation of the expression of a specific gene may the encoded protein. The concentration of RNase H in the nucleus is thought to be higher than that in the shed light on the function of the encoded protein under physiological and pathophysiological conditions as cytoplasm because the enzyme participates in DNA replication. Therefore, intranuclear delivery of antiwell as may form the basis for fundamental therapy of genetic disorders. Among various strategies for gene sense ODNs is important for effective inhibition of protein synthesis. modulation, antisense oligodeoxynucleotides (ODNs) complementary to a target mRNA represent a new For translation arrest, antisense ODNs have been designed to bind to the translational initiation codon. paradigm for drug discovery [1–3]. Thus, antisense ODNs containing 15–30 residues offer the potential to However, targeting the initiation codon does not always result in maximal inhibition of gene expression; block the expression of the corresponding gene. Although unmodified phosphodiester ODNs are antisense ODNs specific for the 3∞ non-coding region of mRNAs often provide the greatest inhibition of rapidly degraded by nucleases, chemical modification can increase their stability and potency. The most protein synthesis [5 ]. However, non-specific effects of ODNs should be widely used analogues to date are the phosphorothioate ODNs (S-oligo), in which one of the non-bridging taken into consideration. A sequence-specific action of antisense ODNs can be inferred from the selective oxygen atoms in the phosphodiester backbone is replaced with a sulphur [4]. depletion of the target mRNA and protein. ODNs containing four contiguous guanosine residues occasionally inhibit cell proliferation [6 ], whereas phosoMechanism of inhibition of protein synthesis by phorothioate ODNs have been shown to activate the SP1 transcription factor [7]. ODNs containing CG antisense ODNs motifs with appropriate flanking sequences stimulate the immune system by inducing the production of Various processes on the pathway to protein synthesis interferon [8]. A selective decrease in the abundance are inhibited by antisense ODNs [1]. Thus, such ODNs of the target mRNA and protein should not accomcan induce transcriptional arrest, inhibition of RNA pany such non-specific effects of antisense ODNs. processing, disruption of mRNA structure, or direct inhibition of translation. The formation of a triplestrand structure by double-stranded DNA and antiTargeting of ODNs to glomerular cells sense ODNs in the promoter region may result in transcriptional inhibition. Triplex-forming ODNs Transfer of ODNs to glomerular cells is difficult with binds to the purine-rich strand of double-stranded conventional methods such as based on cationic lipoDNA via Hoogsteen hydrogen bonds, with base triplet somes. Instead, gene transfer mediated by haemagglutistabilized by two such bonds between the ODNs and nating virus of Japan (HVJ )-liposome method appears its complement. to be a feasible technique with which we could target The activation of RNase H is thought to be a major glomerular cells [9 ]. HVJ-liposome method is modified mechanism of action of antisense ODNs at least in fusogenic liposomes that contain the F glycoprotein cell-free systems and in Xenopus oocytes. The hybridon its envelope. HVJ belongs to the paramyxovirus ization of antisense ODNs to complementary mRNA family and can fuse with most cells except lymphocytes result in RNase H-mediated degradation of the hybridvia the F glycoprotein. ODNs are encapsulated in the ized mRNA, and consequent inhibition of synthesis of liposome by vortex mixing, and are then fused with HVJ that has been inactivated by ultraviolet irradiCorrespondence and offprint requests to: Enyu Imai MD, Chief, ation. Transfer of ODNs by this approach results in Division of Nephrology, The First Department of Medicine, Osaka long-term retention and stability of DNA in the nucleus University School of Medicine, 2-2 Yamadaoka, Suita, 565 Osaka, Japan. by an unknown mechanism. Injection of HVJ liposome