Antisense gene silencing: therapy for neurodegenerative disorders?

Synthesis and Validation of TRIFAPYs as a Family of Transfection Agents for Therapeutic Oligonucleotides

Transfection agents play a crucial role in facilitating the uptake of nucleic acids into eukaryotic cells offering potential therapeutic solutions for genetic disorders. However, progress in this field needs the development of improved systems that guarantee efficient transfection. Here, we describe the synthesis of a set of chemical delivery agents (TRIFAPYs) containing alkyl chains of different lengths based on the 1,3,5-tris[(4-alkyloxy-1pyridinio)methyl]benzene tribromide structure. Their delivery properties for therapeutic oligonucleotides were evaluated using PolyPurine Reverse Hoogsteen hairpins (PPRHs) as a silencing tool. The binding of liposomes to PPRHs was evaluated by retardation assays in agarose gels. The complexes had a size of 125 nm as determined by DLS, forming well-defined concentrical vesicles as visualized by Cryo-TEM. The prostate cancer cell line PC-3 was used to study the internalization of the nanoparticles by fluorescence microscopy and flow cytometry. The mechanism of entrance involved in the cellular uptake was mainly by clathrin-mediated endocytosis. Cytotoxicity analyses determined the intrinsic toxicity caused by each TRIFAPY and the effect on cell viability upon transfection of a specific PPRH (HpsPr-C) directed against the antiapoptotic target survivin. TRIFAPYs C12-C18 were selected to expand these studies in the breast cancer cell line SKBR-3 opening the usage of TRIFAPYs for both sexes and, in the hCMEC/D3 cell line, as a model for the blood-brain barrier. The mRNA levels of survivin decreased, while apoptosis levels increased upon the transfection of HpsPr-C with these TRIFAPYs in PC-3 cells. Therefore, TRIFAPYs can be considered novel lipid-based vehicles for the delivery of therapeutic oligonucleotides.

Trioleyl Pyridinium, a Cationic Transfection Agent for the Lipofection of Therapeutic Oligonucleotides into Mammalian Cells

BACKGROUND

One of the most significant limitations that therapeutic oligonucleotides present is the development of specific and efficient delivery vectors for the internalization of nucleic acids into cells. Therefore, there is a need for the development of new transfection agents that ensure a proper and efficient delivery into mammalian cells.

METHODS

We describe the synthesis of 1,3,5-tris[(4-oelyl-1-pyridinio)methyl]benzene tribromide (TROPY) and proceeded to the validation of its binding capacity toward oligonucleotides, the internalization of DNA into the cells, the effect on cell viability, apoptosis, and its capability to transfect plasmid DNA.

RESULTS

The synthesis and chemical characterization of TROPY, which can bind DNA and transfect oligonucleotides into mammalian cells through clathrin and caveolin-mediated endocytosis, are described. Using a PPRH against the antiapoptotic survivin gene as a model, we validated that the complex TROPY-PPRH decreased cell viability in human cancer cells, increased apoptosis, and reduced survivin mRNA and protein levels. TROPY was also able to stably transfect plasmid DNA, as demonstrated by the formation of viable colonies upon the transfection of a dhfr minigene into dhfr-negative cells and the subsequent metabolic selection.

CONCLUSIONS

TROPY is an efficient transfecting agent that allows the delivery of therapeutic oligonucleotides, such as PPRHs and plasmid DNA, inside mammalian cells.

Further Studies on Cationic Gemini Amphiphiles as Carriers for Gene Delivery-The Effect of Linkers in the Structure and Other Factors Affecting the Transfection Efficacy of These Amphiphiles

Gene therapy has the therapeutic potential to address a multitude of health problems, and it also has utility in different domains of science. However, its applications are plagued due to the absence of a suitable, safe, efficient, selective, and universal vector, which could help in delivering the desired nucleic acid cargo to the site of action. Though viral vectors are efficient, they pose various health risks. Different types of synthetic agents have been tried as nucleic acid vectors by researchers but with limited success. Gemini amphiphiles (GAs) are a class of synthetic surfactants having biscationic heads with attached hydrophilic and lipophilic groups. Herein, we synthesized two classes of GAs differing in the chemical nature and length of the linkers, head groups, and lipophilic chains. The resulting compounds were evaluated for their efficiency to transfect A549 and HeLa cell lines with a β-galactosidase reporter plasmid. A 3-oxypentyl linker, a monohydroxyethyl head group, and a tetradecyl moiety as the lipophilic chain offered the best transfection efficiency (compound 10BIII). Dioleoylphosphatidylethanolamine (DOPE) as the helper lipid improved the transfection efficacy of the GAs in the absence of serum. In the presence of serum, DOPE and cholesterol, as the helper lipids, improved the transfection efficacy of the resulting formulations. The synthesized GAs showed concentration-dependent toxicity in the MTT assay. Biodistribution studies using 99mTc-labeled lipoplexes indicated that the lipoplexes got concentrated in some vital organs such as the spleen, liver, and lungs.

PolyPurine Reverse Hoogsteen Hairpins Work as RNA Species for Gene Silencing

PolyPurine Reverse Hoogsteen Hairpins (PPRHs) are gene-silencing DNA-oligonucleotides developed in our laboratory that are formed by two antiparallel polypurine mirror repeat domains bound intramolecularly by Hoogsteen bonds. The aim of this work was to explore the feasibility of using viral vectors to deliver PPRHs as a gene therapy tool. After treatment with synthetic RNA, plasmid transfection, or viral infection targeting the survivin gene, viability was determined by the MTT assay, mRNA was determined by RT-qPCR, and protein levels were determined by Western blot. We showed that the RNA-PPRH induced a decrease in cell viability in a dose-dependent manner and an increase in apoptosis in PC-3 and HeLa cells. Both synthetic RNA-PPRH and RNA-PPRH intracellularly generated upon the transfection of a plasmid vector were able to reduce survivin mRNA and protein levels in PC-3 cells. An adenovirus type-5 vector encoding the PPRH against survivin was also able to decrease survivin mRNA and protein levels, leading to a reduction in HeLa cell viability. In this work, we demonstrated that PPRHs can also work as RNA species, either chemically synthesized, transcribed from a plasmid construct, or transcribed from viral vectors. Therefore, all these results are the proof of principle that viral vectors could be considered as a delivery system for PPRHs.

Synthesis and validation of DOPY: A new gemini dioleylbispyridinium based amphiphile for nucleic acid transfection

Nucleic acids therapeutics provide a selective and promising alternative to traditional treatments for multiple genetic diseases. A major obstacle is the development of safe and efficient delivery systems. Here, we report the synthesis of the new cationic gemini amphiphile 1,3-bis[(4-oleyl-1-pyridinio)methyl]benzene dibromide (DOPY). Its transfection efficiency was evaluated using PolyPurine Reverse Hoogsteen hairpins (PPRHs), a nucleic acid tool for gene silencing and gene repair developed in our laboratory. The interaction of DOPY with PPRHs was confirmed by gel retardation assays, and it forms complexes of 155 nm. We also demonstrated the prominent internalization of PPRHs using DOPY compared to other chemical vehicles in SH-SY5Y, PC-3 and DF42 cells. Regarding gene silencing, a specific PPRH against the survivin gene delivered with DOPY decreased survivin protein levels and cell viability more effectively than with N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP) in both SH-SY5Y and PC-3 cells. We also validated the applicability of DOPY in gene repair approaches by correcting a point mutation in the endogenous locus of the dhfr gene in DF42 cells using repair-PPRHs. All these results indicate both an efficient entry and release of PPRHs at the intracellular level. Therefore, DOPY can be considered as a new lipid-based vehicle for the delivery of therapeutic oligonucleotides.

Prion-Like Mechanisms in Parkinson's Disease

Formation and aggregation of misfolded proteins in the central nervous system (CNS) is a key hallmark of several age-related neurodegenerative diseases, including Parkinson’s disease (PD), Alzheimer’s disease (AD), and amyotrophic lateral sclerosis (ALS). These diseases share key biophysical and biochemical characteristics with prion diseases. It is believed that PD is characterized by abnormal protein aggregation, mainly that of α-synuclein (α-syn). Of particular importance, there is growing evidence indicating that abnormal α-syn can spread to neighboring brain regions and cause aggregation of endogenous α-syn in these regions as seeds, in a “prion-like” manner. Abundant studies in vitro and in vivo have shown that α-syn goes through a templated conformational change, propagates from the original region to neighboring regions, and eventually cause neuron degeneration in the substantia nigra and striatum. The objective of this review is to summarize the mechanisms involved in the aggregation of abnormal intracellular α-syn and its subsequent cell-to-cell transmission. According to these findings, we look forward to effective therapeutic perspectives that can block the progression of neurodegenerative diseases.

Immunotherapeutic Approaches Targeting Amyloid-β, α-Synuclein, and Tau for the Treatment of Neurodegenerative Disorders

Disease-modifying alternatives are sorely needed for the treatment of neurodegenerative disorders, a group of diseases that afflict approximately 50 million Americans annually. Immunotherapy is one of the most developed approaches in this direction. Vaccination against amyloid-β, α-synuclein, or tau has been extensively explored, specially as the discovery that these proteins may propagate cell-to-cell and be accessible to antibodies when embedded into the plasma membrane or in the extracellular space. Likewise, the use of passive immunization approaches with specific antibodies against abnormal conformations of these proteins has also yielded promising results. The clinical development of immunotherapies for Alzheimer’s disease, Parkinson’s disease, frontotemporal dementia, dementia with Lewy bodies, and other neurodegenerative disorders is a field in constant evolution. Results to date suggest that immunotherapy is a promising therapeutic approach for neurodegenerative diseases that progress with the accumulation and prion-like propagation of toxic protein aggregates. Here we provide an overview of the most novel and relevant immunotherapeutic advances targeting amyloid-β in Alzheimer’s disease, α-synuclein in Alzheimer’s disease and Parkinson’s disease, and tau in Alzheimer’s disease and frontotemporal dementia.

Application of CPPs for Brain Delivery

Cell-penetrating peptides provide a promising strategy for delivery of drugs across the blood-brain barrier. Here, we present an overview of CPP and peptide-mediated delivery to the central nervous system as well as a Transwell in vitro model to evaluate passage across an endothelial cell layer mimic of the blood-brain barrier.