Enteral siRNA delivery technique for therapeutic gene silencing in the liver via the lymphatic route

Short DNA/RNA heteroduplex oligonucleotide interacting proteins are key regulators of target gene silencing

Antisense oligonucleotide (ASO)-based therapy is one of the next-generation therapy, especially targeting neurological disorders. Many cases of ASO-dependent gene expression suppression have been reported. Recently, we developed a tocopherol conjugated DNA/RNA heteroduplex oligonucleotide (Toc-HDO) as a new type of drug. Toc-HDO is more potent, stable, and efficiently taken up by the target tissues compared to the parental ASO. However, the detailed mechanisms of Toc-HDO, including its binding proteins, are unknown. Here, we developed native gel shift assays with fluorescence-labeled nucleic acids samples extracted from mice livers. These assays revealed two Toc-HDO binding proteins, annexin A5 (ANXA5) and carbonic anhydrase 8 (CA8). Later, we identified two more proteins, apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1) and flap structure-specific endonuclease 1 (FEN1) by data mining. shRNA knockdown studies demonstrated that all four proteins regulated Toc-HDO activity in Hepa1-6, mouse hepatocellular cells. In vitro binding assays and fluorescence polarization assays with purified recombinant proteins characterized the identified proteins and pull-down assays with cell lysates demonstrated the protein binding to the Toc-HDO and ASO in a biological environment. Taken together, our findings provide a brand new molecular biological insight as well as future directions for HDO-based disease therapy.

Quantum Dot Nanomedicine Formulations Dramatically Improve Pharmacological Properties and Alter Uptake Pathways of Metformin and Nicotinamide Mononucleotide in Aging Mice

Orally administered Ag₂S quantum dots (QDs) rapidly cross the small intestine and are taken up by the liver. Metformin and nicotinamide mononucleotide (NMN) target metabolic and aging processes within the liver. This study examined the pharmacology and toxicology of QD-based nanomedicines as carriers of metformin and NMN in young and old mice, determining if their therapeutic potency and reduced effects associated with aging could be improved. Pharmacokinetic studies demonstrated that QD-conjugated metformin and NMN have greater bioavailability, with selective accumulation in the liver following oral administration compared to unconjugated formulations. Pharmacodynamic data showed that the QD-conjugated medicines had increased physiological, metabolic, and cellular potency compared to unconjugated formulations (25× metformin; 100× NMN) and highlighted a shift in the peak induction of, and greater metabolic response to, glucose tolerance testing. Two weeks of treatment with low-dose QD-NMN (0.8 mg/kg/day) improved glucose tolerance tests in young (3 months) mice, whereas old (18 and 24 months) mice demonstrated improved fasting and fed insulin levels and insulin resistance. High-dose unconjugated NMN (80 mg/kg/day) demonstrated improvements in young mice but not in old mice. After 100 days of QD (320 μg/kg/day) treatment, there was no evidence of cellular necrosis, fibrosis, inflammation, or accumulation. Ag₂S QD nanomedicines improved the pharmacokinetic and pharmacodynamic properties of metformin and NMN by increasing their therapeutic potency, bypassing classical cellular uptake pathways, and demonstrated efficacy when drug alone was ineffective in aging mice.

Opportunities and challenges for the clinical translation of structured DNA assemblies as gene therapeutic delivery and vaccine vectors

Gene therapeutics including siRNAs, anti-sense oligos, messenger RNAs, and CRISPR ribonucleoprotein complexes offer unmet potential to treat over 7,000 known genetic diseases, as well as cancer, through targeted in vivo modulation of aberrant gene expression and immune cell activation. Compared with viral vectors, nonviral delivery vectors offer controlled immunogenicity and low manufacturing cost, yet suffer from limitations in toxicity, targeting, and transduction efficiency. Structured DNA assemblies fabricated using the principle of scaffolded DNA origami offer a new nonviral delivery vector with intrinsic, yet controllable immunostimulatory properties and virus-like spatial presentation of ligands and immunogens for cell-specific targeting, activation, and control over intracellular trafficking, in addition to low manufacturing cost. However, the relative utilities and limitations of these vectors must clearly be demonstrated in preclinical studies for their clinical potential to be realized. Here, we review the major capabilities, opportunities, and challenges we foresee in translating these next-generation delivery and vaccine vectors to the clinic. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Nucleic Acid-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Lipoprotein-based drug delivery

Lipoproteins (LPs) are circulating heterogeneous nanoparticles produced by the liver and intestines. LPs play a major role in the transport of dietary and endogenous lipids to target cells through cell membrane receptors or cell surface-bound lipoprotein lipase. The stability, biocompatibility, and selective transport of LPs make them promising delivery vehicles for various therapeutic and imaging agents. This review discusses isolation, manufacturing, and drug loading techniques used for LP-based drug delivery, as well as recent applications for diagnosis and treatment of cancer, atherosclerosis, and other life-threatening diseases.

Janus microspheres for enhanced enteral drug delivery: Preparation and orientated attachment to a Caco-2 monolayer

Conventional oral preparations generally release incorporated drugs omnidirectionally, including into the lumen, leading to a low bioavailability of drugs that are unstable in the gastrointestinal tract. Here, we designed Janus microspheres for efficient mucosal drug delivery as single-sided-release microspheres with the oriented attachment to mucus and evaluated their attachment to and orientation on a Caco-2 (human Caucasian colon adenocarcinoma cell line) monolayer. The microspheres comprised a mucus-oriented hemisphere of an ammonioalkyl methacrylate copolymer and a protective hemisphere of a hard fat. Fluorescein isothiocyanate-dextran with an average molecular weight of 3,000-5,000 Da (FD4) was used as a model hydrophilic drug. A water-in-oil emulsion-type solvent evaporation method was employed for fabrication of the Janus microspheres. The yield of Janus microspheres was found to be dependent on the polymer-to-hard fat ratio, with a maximum yield of over 90% being obtained at a ratio of 1:2, whereas lower and higher ratios resulted in monolithic or star-shaped microspheres. FD4 was specifically localized in the polymeric hemisphere. A cell culture study revealed that the Janus microspheres attached to a Caco-2 monolayer via their polymeric hemispheres with the hard fat hemisphere providing a protective sealing. This may lead to the development of an effective enteral drug delivery system for biomedicines, such as polypeptides and nucleic acids.

Intestinal lymphatic vessels and their role in chylomicron absorption and lipid homeostasis

PURPOSE OF REVIEW

In this review, we describe novel findings related to intestinal lipid transport in lymphatic vessels.

RECENT FINDINGS

Studies have shown that chylomicron entry to lacteals and lymph movement in intestinal lymphatic capillaries is an active process. Regulators of this intestinal chylomicron transport include among others the autonomous nervous system, transcription factors like PLAGL2, and molecular regulators, such as VEGF-A/Nrp1/VEGFR1, VEGF-C/VEGFR3, DLL4, CALCRL and GLP-2. Chylomicron transport in intestinal lymphatics is now emerging not only as an option for drug delivery but also as a new candidate for drug targeting in lipid-related disorders.

SUMMARY

Dysfunctions of lymphatic lipid transport can result in conditions such as dyslipidaemia. Intestinal lymphatics also provide several potential therapeutic possibilities: molecular regulation of lacteal cell-to-cell junctioning and lymph flow could provide new ways of treating conditions like hyperlipidaemia and associated diseases, such as atherosclerosis and other cardiovascular diseases, obesity, diabetes and fatty-liver disease. The intestinal lymphatic system can also be employed to deliver lipid nanoparticles as drug carriers to the venous circulation for improved treatment outcome. These findings highlight the importance and need for research on the different players of intestinal lymphatics in dietary lipid handling and therapeutic applications.

Hydrophobicity drives the systemic distribution of lipid-conjugated siRNAs via lipid transport pathways

Efficient delivery of therapeutic RNA beyond the liver is the fundamental obstacle preventing its clinical utility. Lipid conjugation increases plasma half-life and enhances tissue accumulation and cellular uptake of small interfering RNAs (siRNAs). However, the mechanism relating lipid hydrophobicity, structure, and siRNA pharmacokinetics is unclear. Here, using a diverse panel of biologically occurring lipids, we show that lipid conjugation directly modulates siRNA hydrophobicity. When administered in vivo, highly hydrophobic lipid-siRNAs preferentially and spontaneously associate with circulating low-density lipoprotein (LDL), while less lipophilic lipid-siRNAs bind to high-density lipoprotein (HDL). Lipid-siRNAs are targeted to lipoprotein receptor-enriched tissues, eliciting significant mRNA silencing in liver (65%), adrenal gland (37%), ovary (35%), and kidney (78%). Interestingly, siRNA internalization may not be completely driven by lipoprotein endocytosis, but the extent of siRNA phosphorothioate modifications may also be a factor. Although biomimetic lipoprotein nanoparticles have been explored for the enhancement of siRNA delivery, our findings suggest that hydrophobic modifications can be leveraged to incorporate therapeutic siRNA into endogenous lipid transport pathways without the requirement for synthetic formulation.

A Therapeutic Silencing RNA Targeting Hepatocyte TAZ Prevents and Reverses Fibrosis in Nonalcoholic Steatohepatitis in Mice

Nonalcoholic steatohepatitis (NASH) is emerging as a major public health issue and is associated with significant liver-related morbidity and mortality. At present, there are no approved drug therapies for NASH. The transcriptional coactivator with PDZ-binding motif (TAZ; encoded by WW domain-containing transcription regulator 1 [WWTR1]) is up-regulated in hepatocytes in NASH liver from humans and has been shown to causally promote inflammation and fibrosis in mouse models of NASH. As a preclinical test of targeting hepatocyte TAZ to treat NASH, we injected stabilized TAZ small interfering RNA (siRNA) bearing the hepatocyte-specific ligand N-acetylgalactosamine (GalNAc-siTAZ) into mice with dietary-induced NASH. As a preventative regimen, GalNAc-siTAZ inhibited inflammation, hepatocellular injury, and the expression of profibrogenic mediators, accompanied by decreased progression from steatosis to NASH. When administered to mice with established NASH, GalNAc-siTAZ partially reversed hepatic inflammation, injury, and fibrosis. Conclusion: Hepatocyte-targeted siTAZ is potentially a novel and clinically feasible treatment for NASH.

Improved systemic delivery of insulin by condensed drug loading in a dimpled suppository

The development of peptide therapeutics owing to the advances in biotechnology has overcome some unmet medical needs; however, the route of administration is still limited to injections. Systemic delivery of insulin via an enteral route remains a great challenge due to its instability and low mucosal permeability. In this study, we investigated the effect of drug condensation in a suppository on the efficacy of insulin after rectal administration. Suppositories with dimples are prepared by a mold method using a hard fat (Suppocire^® AM). Insulin or fluorescein isothiocyanate-dextran (molecular weight: 3,000-5,000) (FD4) as a model of a hydrophilic macromolecule was loaded in the dimples, and sealed with other lipids with different melting points. The in vitro release test showed that the time to 50% drug release depends on the melting point of the lipid for sealing but not on the number of dimples. The suppositories with one-, or three-dimple containing insulin and caprylocaproyl macrogol-8 glyceride (Labrasol^®) were administered to rats at 0.5 U/head. The reduction in plasma glucose level was more significant for the one-dimple-type suppository than for the three-dimple-type although the one-dimple-type suppository contained less amount of Labrasol by one-third compared to the three-dimple-type. These results suggest that condensation of an insulin dose in a limited surface area of a suppository improves systemic availability via the rectal route with a reduced amount of an absorption enhancer.

Oral delivery of non-viral nucleic acid-based therapeutics - do we have the guts for this?

Gene therapy with RNA and pDNA-based drugs is limited by poor enzymatic stability and poor cellular permeation. The delivery of nucleic acids, in particular by the oral route, remains a major hurdle. This review will focus on the barriers to the oral delivery of nucleic acids and the strategies, in particular formulation strategies, which have been developed to overcome these barriers. Due to their very low oral bioavailability, the most obvious and most investigated biomedical applications for their oral delivery are related to the local treatment of inflammatory bowel diseases and colorectal cancers. Preclinical data but not yet clinical studies support the potential use of the oral route for the local delivery of formulated nucleic acid-based drugs.

Layer-by-layer siRNA/poly(L-lysine) Multilayers on Polydopamine-coated Surface for Efficient Cell Adhesion and Gene Silencing

For tissue engineering applications, small interfering RNA (siRNA) is an attractive agent for controlling cellular functions and differentiation. Although polyionic condensation of nucleic acids with polycations has been widely used for gene delivery, siRNA is not strongly associated with cationic carriers due to its low charge density and rigid molecular structures. The use of an excess amount of cationic carriers is often used for siRNA condensation, though they can induce severe cytotoxicity. Here we introduce the self-assembly of siRNA with mild polyelectrolytes into multilayers for efficient gene silencing during cell proliferation. The multilayers were prepared through the sequential layer-by-layer deposition of siRNA and poly-L-lysine (PLL) on a polydopamine-coated substrate. The cells, grown on the siRNA/PLL multilayers, exhibited a remarkable inhibition of the expression of target genes as compared to the use of scrambled siRNA. The gene silencing efficiency depends on the number of siRNA layers within a multilayer. This result indicates that siRNA/PLL multilayers can be potentially utilized for efficient surface-mediated siRNA delivery.

Hydrophobicity of Lipid-Conjugated siRNAs Predicts Productive Loading to Small Extracellular Vesicles

Small extracellular vesicles (sEVs) show promise as natural nano-devices for delivery of therapeutic RNA, but efficient loading of therapeutic RNA remains a challenge. We have recently shown that the attachment of cholesterol to small interfering RNAs (siRNAs) enables efficient and productive loading into sEVs. Here, we systematically explore the ability of lipid conjugates-fatty acids, sterols, and vitamins-to load siRNAs into sEVs and support gene silencing in primary neurons. Hydrophobicity of the conjugated siRNAs defined loading efficiency and the silencing activity of siRNA-sEVs complexes. Vitamin-E-conjugated siRNA supported the best loading into sEVs and productive RNA delivery to neurons.

Covalent Strategies for Targeting Messenger and Non-Coding RNAs: An Updated Review on siRNA, miRNA and antimiR Conjugates

Oligonucleotide-based therapy has become an alternative to classical approaches in the search of novel therapeutics involving gene-related diseases. Several mechanisms have been described in which demonstrate the pivotal role of oligonucleotide for modulating gene expression. Antisense oligonucleotides (ASOs) and more recently siRNAs and miRNAs have made important contributions either in reducing aberrant protein levels by sequence-specific targeting messenger RNAs (mRNAs) or restoring the anomalous levels of non-coding RNAs (ncRNAs) that are involved in a good number of diseases including cancer. In addition to formulation approaches which have contributed to accelerate the presence of ASOs, siRNAs and miRNAs in clinical trials; the covalent linkage between non-viral vectors and nucleic acids has also added value and opened new perspectives to the development of promising nucleic acid-based therapeutics. This review article is mainly focused on the strategies carried out for covalently modifying siRNA and miRNA molecules. Examples involving cell-penetrating peptides (CPPs), carbohydrates, polymers, lipids and aptamers are discussed for the synthesis of siRNA conjugates whereas in the case of miRNA-based drugs, this review article makes special emphasis in using antagomiRs, locked nucleic acids (LNAs), peptide nucleic acids (PNAs) as well as nanoparticles. The biomedical applications of siRNA and miRNA conjugates are also discussed.

Drug delivery system of therapeutic oligonucleotides

Therapeutic oligonucleotides are promising technologies. Nevertheless, improvement of their efficacy is an important issue. Introducing this drug delivery system (DDS) makes for a great enhancement for delivery of oligonucleotides to targeted tissue or cells. The strategy of DDS for therapeutic oligonucleotides is divided into four categories, A) single piece of oligonucleotide, B) oligonucleotide-ligand conjugate, C) oligonucleotide-polymer conjugate, and D) nanoparticle. In this review we will describe those basic concepts, especially for the technology of conjugating ligand. In addition, we developed a new technology, heteroduplex oligonucleotide (HDO), binding ligand-molecule to antisense oligonucleotide indirectly. We also outline α-tocopherol (a natural isomer of vitamin E) conjugated HDO.

Can colorectal delivery technology provide a platform for enteral oligonucleotide-based therapeutics?

Nucleic acid-based therapeutics including antisense and siRNA oligonucleotides has been expected as an innovative treatment for intractable diseases. Oral drug delivery is the most patient-friendly route of administration but developing an effective delivery system for oligonucleotides remains a major challenge. In this commentary, we discuss the potential benefits of the colorectal route as another platform for the development of oral oligonucleotide therapeutics. The importance of the targeting or the availability of oligonucleotides in targeted tissue is highlighted in contrast to systemic availability, while the liver-targeted enteral siRNA delivery technology that we recently developed is introduced.

Therapeutic oligonucleotides and delivery technologies: Research topics in Japan

Oligonucleotides have been gaining considerable attention as promising and effective candidate therapeutics against various diseases. This special issue is aimed at providing a better understanding of the recent progress in the development of oligonucleotide-based therapeutics to encourage further research and innovation in this field to achieve these advancements. Several Japanese scientists have been invited to contribute to this issue by describing their recent findings, overviews, insights, or commentaries on rational designing of therapeutic oligonucleotide molecules and their novel delivery technologies, especially nanocarrier systems.

Liposomal delivery systems for intestinal lymphatic drug transport

Intestinal lymphatic drug delivery has been widely studied because drugs can bypass the first-pass metabolism in the liver via the lymphatic route, which increases oral bioavailability. Various lipid-based nanoparticles have been used to deliver hydrophobic drugs to the lymphatic pathway. This review focuses on the liposomal delivery systems used for intestinal lymphatic drug transport. Liposomal formulations have attracted particular attention because they can stimulate the production of chylomicrons and the incorporated drugs readily associate with enterocyte-derived chylomicrons, enhancing lymphatic drug transport. We believe that a full understanding of their contribution to intestinal drug translocation will lead to effective oral delivery with liposomal formulations.

Delivery of siRNA Using Lipid Nanoparticles Modified with Cell Penetrating Peptide

Clinical development of siRNA has been hindered by the lack of an effective delivery system. Here, we report the construction of a novel siRNA delivery system, sTOLP, which is based on cell penetrating peptide oleoyl-octaarginine (OA-R8) modified multifunctional lipid nanoparticles. sTOLP nanoparticles are composed of a protamine complexed siRNA core, OA-R8, cationic and PEGylated lipids, and transferrin as a targeting ligand. sTOLP formulation was optimized and characterized in vitro and showed excellent gene silencing activity. In vivo, siRNA encapsulated in sTOLP exhibited potent tumor inhibition (61.7%) and was preferentially taken up by hepatocytes and tumor cells in HepG2-bearing nude mice without inducing immunogenicity or hepatic or renal toxicity. Furthermore, sTOLP-loaded siRNA had stability in circulation greater than that of free siRNA. These data demonstrated potential utility of sTOLP-mediated siRNA delivery in cancer therapy.

Carrier-free Gene Silencing by Amphiphilic Nucleic Acid Conjugates in Differentiated Intestinal Cells

Nucleic acid therapy can be beneficial for the local treatment of gastrointestinal diseases that currently lack appropriate treatments. Indeed, several oligonucleotides (ONs) are currently progressing through clinical trials as potential treatments for inflammatory bowel diseases. However, due to low uptake of carrier-free ONs by mucosal cells, strategies aimed at increasing the potency of orally administered ONs would be highly desirable. In this work, we explored the silencing properties of chemically modified and highly resistant ONs derivatized with hydrophobic alkyl chain on intestinal epithelial cells. We screened a set of lipid-ON conjugates for the silencing of model Bcl-2 mRNA and selected 2'-deoxy-2'-fluoro-arabinonucleic acid modified ON bearing docosanoyl moiety (L-FANA) as the most potent candidate with lowest toxicity. The efficacy of L-FANA conjugate was preserved in simulated intestinal fluids and in the inverted transfection setup. Importantly, L-FANA conjugate was able to downregulate target gene expression at both mRNA and protein levels in a difficult-to-transfect polarized epithelial cell monolayer in the absence of delivery devices and membrane disturbing agents. These findings indicate that lipid-ON conjugates could be promising therapeutics for the treatment of intestinal diseases as well as a valuable tool for the discovery of new therapeutic targets.

The delivery of therapeutic oligonucleotides

The oligonucleotide therapeutics field has seen remarkable progress over the last few years with the approval of the first antisense drug and with promising developments in late stage clinical trials using siRNA or splice switching oligonucleotides. However, effective delivery of oligonucleotides to their intracellular sites of action remains a major issue. This review will describe the biological basis of oligonucleotide delivery including the nature of various tissue barriers and the mechanisms of cellular uptake and intracellular trafficking of oligonucleotides. It will then examine a variety of current approaches for enhancing the delivery of oligonucleotides. This includes molecular scale targeted ligand-oligonucleotide conjugates, lipid- and polymer-based nanoparticles, antibody conjugates and small molecules that improve oligonucleotide delivery. The merits and liabilities of these approaches will be discussed in the context of the underlying basic biology.