Highly efficient transfection of rat cortical neurons using carbosilane dendrimers unveils a neuroprotective role for HIF-1alpha in early chemical hypoxia-mediated neurotoxicity

Synthesis and biophysical evaluation of carbosilane dendrimers as therapeutic siRNA carriers

Gene therapy presents an innovative approach to the treatment of previously incurable diseases. The advancement of research in the field of nanotechnology has the potential to overcome the current limitations and challenges of conventional therapy methods, and therefore to unlocking the full potential of dendrimers for use in the gene therapy of neurodegenerative disorders. The blood-brain barrier (BBB) poses a significant challenge when delivering therapeutic agents to the central nervous system. In this study, we investigated the biophysical properties of dendrimers and their complexes with siRNA directed against the apolipoprotein E (APOE) gene to identify an appropriate nanocarrier capable of safely delivering the cargo across the BBB. Our study yielded valuable insights into the complexation process, stability over time, the mechanisms of interaction, the influence of dendrimers on the oligonucleotide's spatial structure, and the potential cytotoxic effects on human cerebral microvascular endothelium cells. Based on our findings, we identified that the dendrimer G3Si PEG6000 was an optimal candidate for further research, potentially serving as a nanocarrier capable of safely delivering therapeutic agents across the BBB for the treatment of neurodegenerative disorders.

Potent and Selective Benzothiazole-Based Antimitotics with Improved Water Solubility: Design, Synthesis, and Evaluation as Novel Anticancer Agents

The design of colchicine site ligands on tubulin has proven to be a successful strategy to develop potent antiproliferative drugs against cancer cells. However, the structural requirements of the binding site endow the ligands with low aqueous solubility. In this work, the benzothiazole scaffold is used to design, synthesize, and evaluate a new family of colchicine site ligands exhibiting high water solubility. The compounds exerted antiproliferative activity against several human cancer cell lines, due to tubulin polymerization inhibition, showing high selectivity toward cancer cells in comparison with non-tumoral HEK-293 cells, as evidenced by MTT and LDH assays. The most potent derivatives, containing a pyridine moiety and ethylurea or formamide functionalities, displayed IC₅₀ values in the nanomolar range even in the difficult-to-treat glioblastoma cells. Flow cytometry experiments on HeLa, MCF7, and U87MG cells showed that they arrest the cell cycle at the G2/M phases at an early time point (24 h), followed by apoptotic cell death 72 h after the treatment. Tubulin binding was confirmed by microtubule network disruption observed via confocal microscopy. Docking studies support favorable interaction of the synthesized ligands at the colchicine binding site. These results validate the proposed strategy to develop potent anticancer colchicine ligands with improved water solubility.

Screening Libraries to Discover Molecular Design Principles for the Targeted Delivery of mRNA with One-Component Ionizable Amphiphilic Janus Dendrimers Derived from Plant Phenolic Acids

Viral and synthetic vectors to deliver nucleic acids were key to the rapid development of extraordinarily efficient COVID-19 vaccines. The four-component lipid nanoparticles (LNPs), containing phospholipids, PEG-conjugated lipids, cholesterol, and ionizable lipids, co-assembled with mRNA via a microfluidic technology, are the leading nonviral delivery vector used by BioNTech/Pfizer and Moderna to access COVID-19 mRNA vaccines. LNPs exhibit a statistical distribution of their four components when delivering mRNA. Here, we report a methodology that involves screening libraries to discover the molecular design principles required to realize organ-targeted mRNA delivery and mediate activity with a one-component ionizable multifunctional amphiphilic Janus dendrimer (IAJD) derived from plant phenolic acids. IAJDs co-assemble with mRNA into monodisperse dendrimersome nanoparticles (DNPs) with predictable dimensions, via the simple injection of their ethanol solution in a buffer. The precise location of the functional groups in one-component IAJDs demonstrated that the targeted organs, including the liver, spleen, lymph nodes, and lung, are selected based on the hydrophilic region, while activity is associated with the hydrophobic domain of IAJDs. These principles, and a mechanistic hypothesis to explain activity, simplify the synthesis of IAJDs, the assembly of DNPs, handling, and storage of vaccines, and reduce price, despite employing renewable plant starting materials. Using simple molecular design principles will lead to increased accessibility to a large diversity of mRNA-based vaccines and nanotherapeutics.

Effects of Dendrimer-microRNA Nanoformulations against Glioblastoma Stem Cells

Glioblastoma is a rapidly progressing tumor quite resistant to conventional treatment. These features are currently assigned to a self-sustaining population of glioblastoma stem cells. Anti-tumor stem cell therapy calls for a new means of treatment. In particular, microRNA-based treatment is a solution, which in turn requires specific carriers for intracellular delivery of functional oligonucleotides. Herein, we report a preclinical in vitro validation of antitumor activity of nanoformulations containing antitumor microRNA miR-34a and microRNA-21 synthetic inhibitor and polycationic phosphorus and carbosilane dendrimers. The testing was carried out in a panel of glioblastoma and glioma cell lines, glioblastoma stem-like cells and induced pluripotent stem cells. We have shown dendrimer-microRNA nanoformulations to induce cell death in a controllable manner, with cytotoxic effects being more pronounced in tumor cells than in non-tumor stem cells. Furthermore, nanoformulations affected the expression of proteins responsible for interactions between the tumor and its immune microenvironment: surface markers (PD-L1, TIM3, CD47) and IL-10. Our findings evidence the potential of dendrimer-based therapeutic constructions for the anti-tumor stem cell therapy worth further investigation.

Dendrimer Technology in Glioma: Functional Design and Potential Applications

Novel therapeutic and diagnostic methods are sorely needed for gliomas, which contribute yearly to hundreds of thousands of cancer deaths worldwide. Despite the outpouring of research efforts and funding aimed at improving clinical outcomes for patients with glioma, the prognosis for high-grade glioma, and especially glioblastoma, remains dire. One of the greatest obstacles to improving treatment efficacy and destroying cancer cells is the safe delivery of chemotherapeutic drugs and biologics to the tumor site at a high enough dose to be effective. Over the past few decades, a burst of research has leveraged nanotechnology to overcome this obstacle. There has been a renewed interest in adapting previously understudied dendrimer nanocarriers for this task. Dendrimers are small, highly modifiable, branched structures featuring binding sites for a variety of drugs and ligands. Recent studies have demonstrated the potential for dendrimers and dendrimer conjugates to effectively shuttle therapeutic cargo to the correct tumor location, permeate the tumor, and promote apoptosis of tumor cells while minimizing systemic toxicity and damage to surrounding healthy brain tissue. This review provides a primer on the properties of dendrimers; outlines the mechanisms by which they can target delivery of substances to the site of brain pathology; and delves into current trends in the application of dendrimers to drug and gene delivery, and diagnostic imaging, in glioma. Finally, future directions for translating these in vitro and in vivo findings to the clinic are discussed.

Effects of Cationic Dendrimers and Their Complexes with microRNAs on Immunocompetent Cells

Short regulatory oligonucleotides are considered prospective tools for immunotherapy. However, they require an adequate carrier to deliver potential therapeutics into immune cells. Herein, we explore the potential of polycationic dendrimers as carriers for microRNAs in peripheral blood mononuclear cells of healthy donors. As an oligonucleotide cargo, we use a synthetic mimic and an inhibitor of miR-155, an important factor in the development and functioning of immunocompetent cells. Dendrimers bind microRNAs into low-cytotoxic polyelectrolyte complexes that are efficiently uptaken by immunocompetent cells. We have shown these complexes to affect the number of T-regulatory cells, CD14⁺ and CD19⁺ cell subpopulations in non-activated mononuclear cells. The treatment affected the expression of HLA-DR on T-cells and PD-1 expression on T- and B-lymphocytes. It also affected the production of IL-4 and IL-10, but not the perforin and granzyme B production. Our findings suggest the potential of dendrimer-mediated microRNA-155 treatment for immunotherapy, though the activity of microRNA-dendrimer constructions on distinct immune cell subsets can be further improved.

Cationic Carbosilane Dendrimers Prevent Abnormal α-Synuclein Accumulation in Parkinson's Disease Patient-Specific Dopamine Neurons

Accumulation of misfolded α-synuclein (α-syn) is a hallmark of Parkinson’s disease (PD) thought to play important roles in the pathophysiology of the disease. Dendritic systems, able to modulate the folding of proteins, have emerged as promising new therapeutic strategies for PD treatment. Dendrimers have been shown to be effective at inhibiting α-syn aggregation in cell-free systems and in cell lines. Here, we set out to investigate the effects of dendrimers on endogenous α-syn accumulation in disease-relevant cell types from PD patients. For this purpose, we chose cationic carbosilane dendrimers of bow-tie topology based on their performance at inhibiting α-syn aggregation in vitro. Dopamine neurons were differentiated from induced pluripotent stem cell (iPSC) lines generated from PD patients carrying the LRRK2^G2019S mutation, which reportedly display abnormal accumulation of α-syn, and from healthy individuals as controls. Treatment of PD dopamine neurons with non-cytotoxic concentrations of dendrimers was effective at preventing abnormal accumulation and aggregation of α-syn. Our results in a genuinely human experimental model of PD highlight the therapeutic potential of dendritic systems and open the way to developing safe and efficient therapies for delaying or even halting PD progression.

Interaction of Cationic Carbosilane Dendrimers and Their siRNA Complexes with MCF-7 Cells

The application of siRNA in gene therapy is mainly limited because of the problems with its transport into cells. Utilization of cationic dendrimers as siRNA carriers seems to be a promising solution in overcoming these issues, due to their positive charge and ability to penetrate cell membranes. The following two types of carbosilane dendrimers were examined: CBD-1 and CBD-2. Dendrimers were complexed with pro-apoptotic siRNA (Mcl-1 and Bcl-2) and the complexes were characterized by measuring their zeta potential, circular dichroism and fluorescence of ethidium bromide associated with dendrimers. CBD-2/siRNA complexes were also examined by agarose gel electrophoresis. Both dendrimers form complexes with siRNA. Moreover, the cellular uptake and influence on the cell viability of the dendrimers and dendriplexes were evaluated using microscopic methods and XTT assay on MCF-7 cells. Microscopy showed that both dendrimers can transport siRNA into cells; however, a cytotoxicity assay showed differences in the toxicity of these dendrimers.

Breaking Barriers: Bioinspired Strategies for Targeted Neuronal Delivery to the Central Nervous System

Central nervous system (CNS) disorders encompass a vast spectrum of pathological conditions and represent a growing concern worldwide. Despite the high social and clinical interest in trying to solve these pathologies, there are many challenges to bridge in order to achieve an effective therapy. One of the main obstacles to advancements in this field that has hampered many of the therapeutic strategies proposed to date is the presence of the CNS barriers that restrict the access to the brain. However, adequate brain biodistribution and neuronal cells specific accumulation in the targeted site also represent major hurdles to the attainment of a successful CNS treatment. Over the last few years, nanotechnology has taken a step forward towards the development of therapeutics in neurologic diseases and different approaches have been developed to surpass these obstacles. The versatility of the designed nanocarriers in terms of physical and chemical properties, and the possibility to functionalize them with specific moieties, have resulted in improved neurotargeted delivery profiles. With the concomitant progress in biology research, many of these strategies have been inspired by nature and have taken advantage of physiological processes to achieve brain delivery. Here, the different nanosystems and targeting moieties used to achieve a neuronal delivery reported in the open literature are comprehensively reviewed and critically discussed, with emphasis on the most recent bioinspired advances in the field. Finally, we express our view on the paramount challenges in targeted neuronal delivery that need to be overcome for these promising therapeutics to move from the bench to the bedside.

Complexes of Pro-Apoptotic siRNAs and Carbosilane Dendrimers: Formation and Effect on Cancer Cells

This paper examines the complexation of anti-cancer small interfering RNAs (siRNAs) by cationic carbosilane dendrimers, and the interaction of the formed complexes with HeLa and HL-60 cancer cells. Stepwise formation of the complexes accompanied by the evolution of their properties has been observed through the increase of the charge ratio (dendrimer/siRNA). The complexes decrease the viability of both “easy-to-transfect” cells (HeLa) and “hard-to transfect” ones (HL-60), indicating a high potential of the cationic carbosilane dendrimers for siRNA delivery into tumor cells.

Evaluation of Amino-Functional Polyester Dendrimers Based on Bis-MPA as Nonviral Vectors for siRNA Delivery

Herein, we present the first evaluation of cationic dendrimers based on 2,2-bis(methylol)propionic acid (bis-MPA) as nonviral vectors for transfection of short interfering RNA (siRNA) in cell cultures. The study encompassed dendrimers of generation one to four (G1⁻G4), modified to bear 6⁻48 amino end-groups, where the G2⁻G4 proved to be capable of siRNA complexation and protection against RNase-mediated degradation. The dendrimers were nontoxic to astrocytes, glioma (C6), and glioblastoma (U87), while G3 and G4 exhibited concentration dependent toxicity towards primary neurons. The G2 showed no toxicity to primary neurons at any of the tested concentrations. Fluorescence microscopy experiments suggested that the dendrimers are highly efficient at endo-lysosomal escape since fluorescently labeled dendrimers were localized specifically in mitochondria, and diffuse cytosolic distribution of fluorescent siRNA complexed by dendrimers was observed. This is a desired feature for intracellular drug delivery, since the endocytic pathway otherwise transfers the drugs into lysosomes where they can be degraded without reaching their intended target. siRNA-transfection was successful in C6 and U87 cell lines using the G3 and G4 dendrimers followed by a decrease of approximately 20% of target protein p42-MAPK expression.

Dendrimers Show Promise for siRNA and microRNA Therapeutics

The lack of an appropriate intracellular delivery system for therapeutic nucleic acids (TNAs) is a major problem in molecular biology, biotechnology, and medicine. A relatively new class of highly symmetrical hyperbranched polymers, called dendrimers, shows promise for transporting small TNAs into both cells and target tissues. Dendrimers have intrinsic advantages for this purpose: their physico-chemical and biological properties can be controlled during synthesis, and they are able to transport large numbers of TNA molecules that can specifically suppress the expression of single or multiple targeted genes. Numerous chemical modifications of dendrimers extend the biocompatibility of synthetic materials and allow targeted vectors to be designed for particular therapeutic purposes. This review summarizes the latest experimental data and trends in the medical application of various types of dendrimers and dendrimer-based nanoconstructions as delivery systems for short small interfering RNAs (siRNAs) and microRNAs at the cell and organism levels. It provides an overview of the structural features of dendrimers, indicating their advantages over other types of TNA transporters.

Brain Delivery of Multifunctional Dendrimer Protein Bioconjugates

Neurological disorders are undoubtedly among the most alarming diseases humans might face. In treatment of neurological disorders, the blood-brain barrier (BBB) is a challenging obstacle preventing drug penetration into the brain. Advances in dendrimer chemistry for central nervous system (CNS) treatments are presented here. A poly(amido)amine (PAMAM) dendrimer bioconjugate with a streptavidin adapter for the attachment of dendrons or any biotinylated drug is constructed. In vitro studies on porcine or murine models and in vivo mouse studies are performed and reveal the permeation of dendronized streptavidin (DSA) into the CNS. The bioconjugate is taken up mainly by the caveolae pathway and transported across the BBB via transcytosis escaping from lysosomes. After transcytosis DSA are delivered to astrocytes and neurons. Furthermore, DSA offer high biocompatibility in vitro and in vivo. In summary, a new strategy for implementing therapeutic PAMAM function as well as drug delivery in neuropathology is presented here.

Docetaxel-Loaded Nanoparticles Assembled from β-Cyclodextrin/Calixarene Giant Surfactants: Physicochemical Properties and Cytotoxic Effect in Prostate Cancer and Glioblastoma Cells

Giant amphiphiles encompassing a hydrophilic β-cyclodextrin (βCD) component and a hydrophobic calix[4]arene (CA₄) module undergo self-assembly in aqueous media to afford core-shell nanospheres or nanocapsules, depending on the nanoprecipitation protocol, with high docetaxel (DTX) loading capacity. The blank and loaded nanoparticles have been fully characterized by dynamic light scattering (DLS), ζ-potential measurements and cryo-transmission electron microscopy (cryo-TEM). The data are compatible with the distribution of the drug between the nanoparticle core and the shell, where it is probably anchored by inclusion of the DTX aromatic moieties in βCD cavities. Indeed, the release kinetics profiles evidenced an initial fast release of the drug, which likely accounts for the fraction hosted on the surface, followed by a slow and sustained release rate, corresponding to diffusion of DTX in the core, which can be finely tuned by modification of the giant amphiphile chemical structure. The ability of the docetaxel-loaded nanoparticles to induce cellular death in different prostate (human LnCap and PC3) and glioblastoma (human U87 and rat C6) cells was also explored. Giant amphiphile-based DTX formulations surpassing or matching the antitumoral activity of the free DTX formulation were identified in all cases with no need to employ any organic co-solvent, thus overcoming the DTX water solubility problems. Moreover, the presence of the βCD shell at the surface of the assemblies is intended to impart stealth properties against serum proteins while permitting nanoparticle surface decoration by supramolecular approaches, paving the way for a new generation of molecularly well-defined antitumoral drug delivery systems with improved specificity and efficiency. Altogether, the results provide a proof of concept of the suitability of the approach based on βCD-CA₄ giant amphiphiles to access DTX carriers with tunable properties.

Brain-Targeted Polymers for Gene Delivery in the Treatment of Brain Diseases

Gene therapies have become a promising strategy for treating neurological disorders, such as brain cancer and neurodegenerative diseases, with the help of molecular biology interpreting the underlying pathological mechanisms. Successful cellular manipulation against these diseases requires efficient delivery of nucleic acids into brain and further into specific neurons or cancer cells. Compared with viral vectors, non-viral polymeric carriers provide a safer and more flexible way of gene delivery, although suffering from significantly lower transfection efficiency. Researchers have been devoted to solving this defect, which is attributed to the multiple barriers existing for gene therapeutics in vivo, such as systemic degradation, blood-brain barrier, and endosome trapping. This review will be mainly focused on systemically administrated brain-targeted polymers developed so far, including PEI, dendrimers, and synthetic polymers with various functions. We will discuss in detail how they are designed to overcome these barriers and how they efficiently deliver therapeutic nucleic acids into targeted cells.

Methods for the In Vitro Characterization of Nanomedicines-Biological Component Interaction

The design of colloidal nanosystems intended for biomedical applications, specifically in the field of personalized medicine, has increased notably in the last years. Consequently, a variety of characterization techniques devoted to studying nanomedicine interactions with proteins and cells have been developed, since a deep characterization of nanosystems is required before starting preclinical and clinical studies. In this context, this review aims to summarize the main techniques used to assess the interaction of nanomedicines with biological systems, highlighting their advantages and disadvantages. Testing designed nanomaterials with these techniques is required in order to have more information about their behavior on a physiological environment. Moreover, techniques used to study the interaction of nanomedicines with proteins, such as albumin and fibrinogen, are summarized. These interactions are not desired, since they usually are the first signal to the body for the activation of the immune system, which leads to the clearance of the exogenous components. On the other hand, techniques for studying the cell toxicity of nanosystems are also summarized, since this information is required before starting preclinical steps. The translation of knowledge from novel designed nanosystems at a research laboratory scale to real human therapies is usually a limiting or even a final point due to the lack of systematic studies regarding these two aspects: nanoparticle interaction with biological components and nanoparticle cytotoxicity. In conclusion, this review will be a useful support for those scientists aiming to develop nanosystems for nanomedicine purposes.

Second Generation Amphiphilic Poly-Lysine Dendrons Inhibit Glioblastoma Cell Proliferation without Toxicity for Neurons or Astrocytes

Glioblastomas are the most common malignant primary brain tumours in adults and one of the most aggressive and difficult-to-treat cancers. No effective treatment exits actually for this tumour and new therapeutic approaches are needed for this disease. One possible innovative approach involves the nanoparticle-mediated specific delivery of drugs and/or genetic material to glioblastoma cells where they can provide therapeutic benefits. In the present work, we have synthesised and characterised several second generation amphiphilic polylysine dendrons to be used as siRNA carriers. We have found that, in addition to their siRNA binding properties, these new compounds inhibit the proliferation of two glioblastoma cell lines while being nontoxic for non-tumoural central nervous system cells like neurons and glia, cell types that share the anatomical space with glioblastoma cells during the course of the disease. The selective toxicity of these nanoparticles to glioblastoma cells, as compared to neurons and glial cells, involves mitochondrial depolarisation and reactive oxygen species production. This selective toxicity, together with the ability to complex and release siRNA, suggests that these new polylysine dendrons might offer a scaffold in the development of future nanoparticles designed to restrict the proliferation of glioblastoma cells.

Dendrimers as nonviral vectors in dendritic cell-based immunotherapies against human immunodeficiency virus: steps toward their clinical evaluation

Although the antiretroviral therapy has led to a long-term control of HIV-1, it does not cure the disease. Therefore, several strategies are being explored to develop an effective HIV vaccine, such as the use of dendritic cells (DCs). DC-based immunotherapies bear different limitations, but one of the most critical point is the antigen loading into DCs. Nanotechnology offers new tools to overcome these constraints. Dendrimers have been proposed as carriers for targeted delivery of HIV antigens in DCs. These nanosystems can release the antigens in a controlled manner leading to a more potent specific immune response. This review focuses on the first steps for clinical development of dendrimers to assess their safety and potential use in DC-based immunotherapies against HIV.

The endoplasmic reticulum stress and the HIF-1 signalling pathways are involved in the neuronal damage caused by chemical hypoxia

BACKGROUND AND PURPOSE

Hypoxia inducible factor-1 (HIF-1) promotes transitory neuronal survival suggesting that additional mechanisms such as the endoplasmic reticulum (ER) stress might be involved in determining neuronal survival or death. Here, we examined the involvement of ER stress in hypoxia-induced neuronal death and analysed the relationship between ER stress and the HIF-1 pathways.

EXPERIMENTAL APPROACH

Cultures of rat cortical neurons were exposed to chemical hypoxia induced by 200 μM CoCl2 , and its effect on neuronal viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and counting apoptotic nuclei. Protein levels were determined by Western blot analysis. RT-PCR was performed to analyse the content and the t1/2 of HIF-1α mRNA.

KEY RESULTS

Chemical hypoxia induced neuronal apoptosis in a time-dependent manner and activated the ER stress PRK-like endoplasmic reticulum kinase (PERK)-dependent pathway. At later stages, chemical hypoxia increased the expression of the C/EBP homologous protein (CHOP) and caspase 12 activity. CoCl2 reduced HIF-1α mRNA t1/2 leading to a decrease in HIF-1α mRNA and protein content, simultaneously activating the ER stress PERK-dependent pathway. Salubrinal, a selective inhibitor of phospho-eIF2α phosphatase, protected neurons from chemical hypoxia by reducing CHOP levels and caspase 12 activity, and increasing the t1/2 of HIF-1α mRNA and the levels of HIF-1α protein. Knocking down HIF-1α blocked the neuroprotective effects of salubrinal.

CONCLUSIONS AND IMPLICATIONS

Neuronal apoptosis induced by chemical hypoxia is a process regulated by HIF-1α stabilization early on and by ER stress activation at later stages. Our data also suggested that HIF-1α levels were regulated by ER stress.

Synthesis, characterization and biological properties of new hybrid carbosilane–viologen–phosphorus dendrimers

Hybrid carbosilane–viologen–phosphorus dendrimers were prepared, as an example of the synthetic “onion peel” approach, on the search of new physical–chemical and biological properties, respecting traditional dendritic architectures.

Dendrimers as carriers for siRNA delivery and gene silencing: a review

RNA interference (RNAi) was first literaturally reported in 1998 and has become rapidly a promising tool for therapeutic applications in gene therapy. In a typical RNAi process, small interfering RNAs (siRNA) are used to specifically downregulate the expression of the targeted gene, known as the term "gene silencing." One key point for successful gene silencing is to employ a safe and efficient siRNA delivery system. In this context, dendrimers are emerging as potential nonviral vectors to deliver siRNA for RNAi purpose. Dendrimers have attracted intense interest since their emanating research in the 1980s and are extensively studied as efficient DNA delivery vectors in gene transfer applications, due to their unique features based on the well-defined and multivalent structures. Knowing that DNA and RNA possess a similar structure in terms of nucleic acid framework and the electronegative nature, one can also use the excellent DNA delivery properties of dendrimers to develop effective siRNA delivery systems. In this review, the development of dendrimer-based siRNA delivery vectors is summarized, focusing on the vector features (siRNA delivery efficiency, cytotoxicity, etc.) of different types of dendrimers and the related investigations on structure-activity relationship to promote safe and efficient siRNA delivery system.

Knocking down HMGB1 using dendrimer-delivered siRNA unveils its key role in NMDA-induced autophagy in rat cortical neurons

PURPOSE

To explore the role of the High Mobility Group Box 1 (HMGB1) protein in NMDA-mediated excitotoxicity in rat cortical neurons.

METHODS

We knocked down HMGB1 using small-interfering RNA (siRNA) delivered into neurons by means of a dendrimer. We determined autophagy activation by measuring the ratio of light chain 3 protein isoforms (LC3B-I)/LC3B-II and by determining autophagolysosome labeling using the specific marker monodansyl cadaverine. Neuronal toxicity was induced by exposing the neurons to N-methyl-D-aspartate (NMDA) and it was determined by measuring Lactate dehydrogenase and MTT reduction.

RESULTS

We found that NMDA receptor stimulation induced both neuronal death and autophagy in rat cortical neurons. In addition, NMDA also caused HMGB1 translocation from the neuronal nucleus to the cytoplasm where it formed a complex with Beclin1. HMGB1 was efficiently knocked down using a specific siRNA causing a blockade of NMDA-induced autophagy and potentiating NMDA-induced neuronal death.

CONCLUSIONS

Our study demonstrates that HMGB1 plays a relevant role in neuronal autophagy regulation and suggest a protective role of autophagy during excitotoxicity. In addition, the dendrimer that we have used here is a good vector for siRNA delivery to neurons allowing lack-of-function studies.

Synthesis, structure and molecular modelling of anionic carbosilane dendrimers

Anionic carbosilane dendrimers of generations 1-3 have been synthesized containing carboxylate G(n)X(C(2)H(4)CO(2)Na)(m) and sulfonate G(n)X(C(2)H(4)SO(3)Na)(m) peripheral groups and derived from two different cores, 1,3,5-(HO)(3)C(6)H(3) (X = O(3)) and Si(C(3)H(5))(4) (X = Si). The peripheral anionic groups make these dendrimers water soluble, despite their highly hydrophobic framework. These dendrimers present a net negative charge in water, which was influenced by the pH of the medium. This characteristic was studied by pH titration. Also molecular modeling calculations have been performed to study differences in an aqueous medium between carboxylate and sulfonate dendrimers of different cores. The results obtained were also compared with those obtained from DOSY NMR experiments and zeta-potential measurements.

Dendrimers for siRNA Delivery

Since the discovery of the “starburst polymer”, later renamed as dendrimer, this class of polymers has gained considerable attention for numerous biomedical applications, due mainly to the unique characteristics of this macromolecule, including its monodispersity, uniformity, and the presence of numerous functionalizable terminal groups. In recent years, dendrimers have been studied extensively for their potential application as carriers for nucleic acid therapeutics, which utilize the cationic charge of the dendrimers for effective dendrimer-nucleic acid condensation. siRNA is considered a promising, versatile tool among various RNAi-based therapeutics, which can effectively regulate gene expression if delivered successfully inside the cells. This review reports on the advancements in the development of dendrimers as siRNA carriers.

Acetaminophen induces human neuroblastoma cell death through NFKB activation

Neuroblastoma resistance to apoptosis may contribute to the aggressive behavior of this tumor. Therefore, it would be relevant to activate endogenous cellular death mechanisms as a way to improve neuroblastoma therapy. We used the neuroblastoma SH-SY5Y cell line as a model to study the mechanisms involved in acetaminophen (AAP)-mediated toxicity by measuring CYP2E1 enzymatic activity, NFkB p65 subunit activation and translocation to the nucleus, Bax accumulation into the mitochondria, cytochrome c release and caspase activation. AAP activates the intrinsic death pathway in the SH-SY5Y human neuroblastoma cell line. AAP metabolism is partially responsible for this activation, because blockade of the cytochrome CYP2E1 significantly reduced but did not totally prevent, AAP-induced SH-SY5Y cell death. AAP also induced NFkB p65 activation by phosphorylation and its translocation to the nucleus, where NFkB p65 increased IL-1β production. This increase contributed to neuroblastoma cell death through a mechanism involving Bax accumulation into the mitochondria, cytochrome c release and caspase3 activation. Blockade of NFkB translocation to the nucleus by the peptide SN50 prevented AAP-mediated cell death and IL-1β production. Moreover, overexpression of the antiapoptotic protein Bcl-x_L did not decrease AAP-mediated IL-1β production, but prevented both AAP and IL-1β-mediated cell death. We also confirmed the AAP toxic actions on SK-N-MC neuroepithelioma and U87MG glioblastoma cell lines. The results presented here suggest that AAP activates the intrinsic death pathway in neuroblastoma cells through a mechanism involving NFkB and IL-1β.

Enhanced docetaxel-mediated cytotoxicity in human prostate cancer cells through knockdown of cofilin-1 by carbon nanohorn delivered siRNA

We synthesized a non-viral delivery system (f-CNH3) for small interfering RNA (siRNA) by anchoring a fourth-generation polyamidoamine dendrimer (G4-PAMAM) to carbon nanohorns (CNHs). Using this new compound, we delivered a specific siRNA designed to knockdown cofilin-1, a key protein in the regulation of cellular cytoskeleton, to human prostate cancer (PCa) cells. The carbon nanohorn (CNH) derivative was able to bind siRNA and release it in the presence of an excess of the polyanion heparin. Moreover, this hybrid nanomaterial protected the siRNA from RNAse-mediated degradation. Synthetic siRNA delivered to PCa cells by f-CNH3 decreased the cofilin-1 mRNA and protein levels to about 20% of control values. Docetaxel, the drug of choice for the treatment of PCa, produced a concentration-dependent activation of caspase-3, an increase in cell death assessed by lactate dehydrogenase release to the culture medium, cell cycle arrest and inhibition of tumor cell proliferation. All of these toxic effects were potentiated when cofilin-1 was down regulated in these cells by a siRNA delivered by the nanoparticle. This suggests that knocking down certain proteins involved in cancer cell survival and/or proliferation may potentiate the cytotoxic actions of anticancer drugs and it might be a new therapeutic approach to treat tumors.

HIF-1α is neuroprotective during the early phases of mild hypoxia in rat cortical neurons

Hypoxia-inducible factor 1α (HIF-1α) is a transcription factor that plays a key role in regulating the adaptive response to hypoxia. HIF-1α is stabilised during hypoxia and, after dimerisation with hypoxia-inducible factor 1β (HIF-1β), triggers the expression of various genes involved in cell cycle control and energy metabolism associated with cell survival. However, HIF-1α also regulates the expression of proapoptotic genes. The aim of this study was to ascertain the influence of HIF-1α on neurotoxicity evoked by hypoxia in rat cortical neurons. We found that mild hypoxia induces time-dependent neuronal death involving free radical production, mitochondrial depolarisation, cytochrome c release and caspase-3 activation. Lentivirus-mediated HIF-1α knockdown markedly strengthened all of these effects during the initial 24h of hypoxia, which suggests that HIF-1α plays a neuroprotective role in hypoxia-mediated neuronal death. After this initial period, the protective actions of HIF-1α disappeared over the course of the hypoxia-mediated HIF-1α stabilisation. Moreover, lentiviral-mediated overexpression of HIF-1α increased lactate dehydrogenase (LDH) A, one of the target genes for HIF-1α, but did not show protective actions on hypoxia-mediated neuronal death, indicating that the level of endogenous HIF-1α stabilisation achieved during hypoxia was already the maximum required for HIF-1α transcription activities. These results indicate that HIF-1α is neuroprotective in the early phases of hypoxia.

Dendrimer-mediated siRNA delivery knocks down Beclin 1 and potentiates NMDA-mediated toxicity in rat cortical neurons

Autophagy is an important process which plays a key role in cellular homeostasis by degrading cytoplasmic components in the lysosomes, which facilitates recycling. Alterations to normal autophagy have been linked to excitotoxicity, but the mechanisms governing its signal transduction remain unclear. The aim of this study was to explore the role of autophagy in neuronal excitotoxic death by delivering small interfering RNA (siRNA) to rat cortical neurons, using a dendrimer to silence the autophagy-related gene 6 (beclin 1) and to determine the role of autophagy in excitotoxicity. We have found that the dendrimer is very efficient to deliver siRNA to rat cortical neurons, leading to almost complete removal of the target protein Beclin 1. In addition, NMDA increases autophagy markers, such as the protein levels of Beclin 1, the microtubule-associated light chain 3 (LC3) B-II/LC3B-I ratio, and monodansylcadaverine (MDC) labeling in rat cortical neurons. Moreover, NMDA also increases the formation of autophagosomes observed under a transmission electron microscope. Silencing beclin 1 expression blocked NMDA-induced autophagy. Moreover, Beclin 1 removal potentiated NMDA-induced neuronal death indicating that autophagy plays a protective role during excitotoxicity and suggesting that targeting autophagy might be a helpful therapeutic strategy in neurodegenerative diseases.

Carbosilane dendrimer 2G-NN16 represses Tc17 differentiation in primary T CD8+ lymphocytes

We studied changes in gene expression induced by the carbosilane dendrimer 2G-NN16 to evaluate their potential as a vehicle for gene therapy and as medication. Global gene expression profiles on CD8+ T lymphocytes reveal that ribosomal proteins are induced in the presence of 2G-NN16. IL17A and IL17F, the principal interleukins secreted by Tc17 cells, a subset of CD8+ T lymphocytes, were down-regulated when cultured in the presence of this dendrimer. Microarray results were confirmed by real time quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). 2G-NN16 also showed a high potential for in vitro inhibition of Tc17 differentiation of CD8+ T lymphocytes in the presence of the Tc17 differentiation molecules IL6 and TGF-B1. These findings suggest that 2G-NN16 could facilitate drug delivery and may be used to treat inflammatory processes driven by Tc17 cells.

Inhibition of p42 MAPK using a nonviral vector-delivered siRNA potentiates the anti-tumor effect of metformin in prostate cancer cells

AIMS

The aim of this work was to study if a G1-polyamidoamine dendrimer/siRNA dendriplex can remove the p42 MAPK protein in prostate cancer cells and to potentiate the anti-tumoral effect of the antidiabetic drug metformin and taxane docetaxel.

MATERIAL & METHODS

The dendriplex uptake was studied using flow cytometry analysis. Transfection efficiency was determined by measuring p42 MAPK mRNA and protein levels. Anti-tumoral effects were determined by measuring cellular proliferation and damage.

RESULTS

The dendriplex siRNA/G1-polyamidoamine dendrimer decreased both p42 MAPK mRNA and protein levels by more than 80%, which potentiates the anti-tumoral effects of metformin.

CONCLUSION

Blockade of the MAPK pathway using a dendrimer-vehiculized siRNA to block the MAPK signaling pathway in prostate cancer cells can potentiate the anti-tumoral activity of anticancer drugs, indicating that the combination of siRNA-mediated blockade of survival signals plus anti-tumoral therapy might be a useful approach for cancer therapy.

Recent advances of siRNA delivery by nanoparticles

INTRODUCTION

The field of RNA interference technology has been researched extensively in recent years. However, the development of clinically suitable, safe and effective drug delivery vehicles is still required.

AREAS COVERED

This paper reviews the recent advances of non-viral delivery of small interfering RNA (siRNA) by nanoparticles, including biodegradable nanoparticles, liposomes, polyplex, lipoplex and dendrimers. The characteristics, composition, preparation, applications and advantages of different nanoparticle delivery strategies are also discussed in detail, along with the recent progress of non-viral nanoparticle carrier systems for siRNA delivery in preclinical and clinical studies.

EXPERT OPINION

Non-viral carrier systems, especially nanoparticles, have been investigated extensively for siRNA delivery, and may be utilized in clinical applications in the future. So far, a few preliminary clinical trials of nanoparticles have produced promising results. However, further research is still required to pave the way to successful clinical applications. The most important issues that need to be focused on include encapsulation efficiency, formulation stability of siRNA, degradation in circulation, endosomal escape and delivery efficiency, targeting, toxicity and off-target effects. Pharmacology and pharmacokinetic studies also present another great challenge for nanoparticle delivery systems, owing to the unique nature of siRNA oligonucleotides compared with small molecules.

Barriers to non-viral vector-mediated gene delivery in the nervous system

Efficient methods for cell line transfection are well described, but, for primary neurons, a high-yield method different from those relying on viral vectors is lacking. Viral transfection has several drawbacks, such as the complexity of vector preparation, safety concerns, and the generation of immune and inflammatory responses when used in vivo. However, one of the main problems for the use of non-viral gene vectors for neuronal transfection is their low efficiency when compared with viral vectors. Transgene expression, or siRNA delivery mediated by non-viral vectors, is the result of multiple processes related to cellular membrane crossing, intracellular traffic, and/or nuclear delivery of the genetic material cargo. This review will deal with the barriers that different nanoparticles (cationic lipids, polyethyleneimine, dendrimers and carbon nanotubes) must overcome to efficiently deliver their cargo to central nervous system cells, including internalization into the neurons, interaction with intracellular organelles such as lysosomes, and transport across the nuclear membrane of the neuron in the case of DNA transfection. Furthermore, when used in vivo, the nanoparticles should efficiently cross the blood-brain barrier to reach the target cells in the brain.

Acetaminophen induces apoptosis in rat cortical neurons

Background

Acetaminophen (AAP) is widely prescribed for treatment of mild pain and fever in western countries. It is generally considered a safe drug and the most frequently reported adverse effect associated with acetaminophen is hepatotoxicity, which generally occurs after acute overdose. During AAP overdose, encephalopathy might develop and contribute to morbidity and mortality. Our hypothesis is that AAP causes direct neuronal toxicity contributing to the general AAP toxicity syndrome.

Methodology/Principal Findings

We report that AAP causes direct toxicity on rat cortical neurons both in vitro and in vivo as measured by LDH release. We have found that AAP causes concentration-dependent neuronal death in vitro at concentrations (1 and 2 mM) that are reached in human plasma during AAP overdose, and that are also reached in the cerebrospinal fluid of rats for 3 hours following i.p injection of AAP doses (250 and 500 mg/Kg) that are below those required to induce acute hepatic failure in rats. AAP also increases both neuronal cytochrome P450 isoform CYP2E1 enzymatic activity and protein levels as determined by Western blot, leading to neuronal death through mitochondrial–mediated mechanisms that involve cytochrome c release and caspase 3 activation. In addition, in vivo experiments show that i.p. AAP (250 and 500 mg/Kg) injection induces neuronal death in the rat cortex as measured by TUNEL, validating the in vitro data.

Conclusions/Significance

The data presented here establish, for the first time, a direct neurotoxic action by AAP both in vivo and in vitro in rats at doses below those required to produce hepatotoxicity and suggest that this neurotoxicity might be involved in the general toxic syndrome observed during patient APP overdose and, possibly, also when AAP doses in the upper dosing schedule are used, especially if other risk factors (moderate drinking, fasting, nutritional impairment) are present.

Triazine dendrimers as nonviral vectors for in vitro and in vivo RNAi: the effects of peripheral groups and core structure on biological activity

A family of triazine dendrimers, differing in their core flexibility, generation number, and surface functionality, was prepared and evaluated for its ability to accomplish RNAi. The dendriplexes were analyzed with respect to their physicochemical and biological properties, including condensation of siRNA, complex size, surface charge, cellular uptake and subcellular distribution, their potential for reporter gene knockdown in HeLa/Luc cells, and ultimately their stability, biodistribution, pharmacokinetics and intracellular uptake in mice after intravenous (iv) administration. The structure of the backbone was found to significantly influence siRNA transfection efficiency, with rigid, second generation dendrimers displaying higher gene knockdown than the flexible analogues while maintaining less off-target effects than Lipofectamine. Additionally, among the rigid, second generation dendrimers, those with either arginine-like exteriors or peripheries containing hydrophobic functionalities mediated the most effective gene knockdown, thus showing that dendrimer surface groups also affect transfection efficiency. Moreover, these two most effective dendriplexes were stable in circulation upon intravenous administration and showed passive targeting to the lung. Both dendriplex formulations were taken up into the alveolar epithelium, making them promising candidates for RNAi in the lung. The ability to correlate the effects of triazine dendrimer core scaffolds, generation number, and surface functionality with siRNA transfection efficiency yields valuable information for further modifying this nonviral delivery system and stresses the importance of only loosely correlating effective gene delivery vectors with siRNA transfection agents.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.