Investigation of the performance of PEG-PEI/ROCK-II-siRNA complexes for Alzheimer's disease in vitro

Design, current states, and challenges of nanomaterials in anti-neuroinflammation: A perspective on Alzheimer's disease

Alzheimer's disease (AD), an age-related neurodegenerative disease, brings huge damage to the society, to the whole family and even to the patient himself. However, until now, the etiological factor of AD is still unknown and there is no effective treatment for it. Massive deposition of amyloid-beta peptide(Aβ) and hyperphosphorylation of Tau proteins are acknowledged pathological features of AD. Recent studies have revealed that neuroinflammation plays a pivotal role in the pathology of AD. With the rise of nanomaterials in the biomedical field, researchers are exploring how the unique properties of these materials can be leveraged to develop effective treatments for AD. This article has summarized the influence of neuroinflammation in AD, the design of nanoplatforms, and the current research status and inadequacy of nanomaterials in improving neuroinflammation in AD.

Nanotechnology used for siRNA delivery for the treatment of neurodegenerative diseases: Focusing on Alzheimer's disease and Parkinson's disease

Neurodegenerative diseases (ND) are often accompanied by dementia, motor dysfunction, or disability. Caring for these patients imposes a significant psychological and financial burden on families. Until now, there are no effective methods for the treatment of NDs. Among them, Alzheimer's disease (AD) and Parkinson's disease (PD) are the two most common. Recently, studies have revealed that the overexpression of certain genes may be linked to the occurrence of AD and PD. Small interfering RNAs (siRNAs) are a powerful tool for gene silencing because they can specifically bind to and cleave target mRNA. However, the intrinsic properties of naked siRNA and various physiological barriers limit the application of siRNA in the brain. Nanotechnology is a promising option for addressing these issues. Nanoparticles are not only able to protect siRNA from degradation but also have the advantage of crossing various physiological barriers to reach the brain target of siRNA. In this review, we aim to introduce diverse nanotechnology used for delivering siRNA to treat AD and PD. Finally, we will briefly discuss our perspectives on this promising field.

In vivo and ex vivo gene therapy for neurodegenerative diseases: a promise for disease modification

Neurodegenerative diseases (NDDs), including AD, PD, HD, and ALS, represent a growing public health concern linked to aging and lifestyle factors, characterized by progressive nervous system damage leading to motor and cognitive deficits. Current therapeutics offer only symptomatic management, highlighting the urgent need for disease-modifying treatments. Gene therapy has emerged as a promising approach, targeting the underlying pathology of diseases with diverse strategies including gene replacement, gene silencing, and gene editing. This innovative therapeutic approach involves introducing functional genetic material to combat disease mechanisms, potentially offering long-term efficacy and disease modification. With advancements in genomics, structural biology, and gene editing tools such as CRISPR/Cas9, gene therapy holds significant promise for addressing the root causes of NDDs. Significant progress in preclinical and clinical studies has demonstrated the potential of in vivo and ex vivo gene therapy to treat various NDDs, offering a versatile and precise approach in comparison to conventional treatments. The current review describes various gene therapy approaches employed in preclinical and clinical studies for the treatment of NDDs, including AD, PD, HD, and ALS, and addresses some of the key translational challenges in this therapeutic approach.

Gene therapy for CNS disorders: modalities, delivery and translational challenges

Gene therapy is emerging as a powerful tool to modulate abnormal gene expression, a hallmark of most CNS disorders. The transformative potentials of recently approved gene therapies for the treatment of spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS) and active cerebral adrenoleukodystrophy are encouraging further development of this approach. However, most attempts to translate gene therapy to the clinic have failed to make it to market. There is an urgent need not only to tailor the genes that are targeted to the pathology of interest but to also address delivery challenges and thereby maximize the utility of genetic tools. In this Review, we provide an overview of gene therapy modalities for CNS diseases, emphasizing the interconnectedness of different delivery strategies and routes of administration. Important gaps in understanding that could accelerate the clinical translatability of CNS genetic interventions are addressed, and we present lessons learned from failed clinical trials that may guide the future development of gene therapies for the treatment and management of CNS disorders.

Lipid nanoparticle mediated small interfering RNA delivery as a potential therapy for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative condition that exhibits a gradual decline in cognitive function and is prevalent among a significant number of individuals globally. The use of small interfering RNA (siRNA) molecules in RNA interference (RNAi) presents a promising therapeutic strategy for AD. Lipid nanoparticles (LNPs) have been developed as a delivery vehicle for siRNA, which can selectively suppress target genes, by enhancing cellular uptake and safeguarding siRNA from degradation. Numerous research studies have exhibited the effectiveness of LNP-mediated siRNA delivery in reducing amyloid beta (Aβ) levels and enhancing cognitive function in animal models of AD. The feasibility of employing LNP-mediated siRNA delivery as a therapeutic approach for AD is emphasized by the encouraging outcomes reported in clinical studies for other medical conditions. The use of LNP-mediated siRNA delivery has emerged as a promising strategy to slow down or even reverse the progression of AD by targeting the synthesis of tau phosphorylation and other genes linked to the condition. Improvement of the delivery mechanism and determination of the most suitable siRNA targets are crucial for the efficacious management of AD. This review focuses on the delivery of siRNA through LNPs as a promising therapeutic strategy for AD, based on the available literature.

Nanotechnology in the diagnostic and therapy for Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disorder primarily characterized by β-amyloid plaque, intraneuronal tangles, significant neuronal loss and cognitive deficit. Treatment in the early stages of the disease is crucial for preventing or perhaps reversing the neurodegeneration in the AD cases. However, none of the current diagnostic procedures are capable of early diagnosis of AD. Further, the available treatments merely provide symptomatic alleviation in AD and do not address the underlying illness. Therefore, there is no permanent cure for AD currently. Better therapeutic outcomes need the optimum drug concentration in the central nervous system (CNS) by traversing blood-brain-barrier (BBB). Nanotechnology offers enormous promise to transform the treatment and diagnostics of neurodegenerative diseases. Nanotechnology based diagnostic tools, drug delivery systems and theragnostic are capable of highly sensitive molecular detection, effective drug targeting and their combination. Significant work has been done in this area over the last decade and prospective results have been obtained in AD therapy. This review explores the various applications of nanotechnology in addressing the varied facets of AD, ranging from early detection to therapeutic interventions. This review also looks at how nanotechnology can help with the development of disease-modifying medicines, such as the delivery of anti-amyloid, anti-tau, cholinesterase inhibitors, antioxidants and hormonal drugs. In conclusion, this paper discusses the role of nanotechnology in the early detection of AD, effective drug targeting to the CNS and theragnostic applications in the management of AD.

Cationic amino-acid functionalized polymethacrylamide vectors for siRNA transfection based on modification of poly(2-isopropenyl-2-oxazoline)

Poly(2-isopropenyl-2-oxazoline) (PiPOx) is a functional polymer showing great potential for the development of smart biomaterials. The straightforward synthesis and post-polymerization functionalization of PiPOx offers many opportunities for tailoring the properties of the polymer towards biomaterials. In this study we report for the first time PiPOx-based cationic charged polymethacrylamides with amino acid side chains that can complex siRNA and promote transfection in vitro. Therefore, PiPOx was fully modified via ring opening addition reactions with the carboxylic acid groups of a series of N-Boc-L-amino acids and their reaction kinetics were investigated. Based on the determined kinetic constants, another series of PiPOx-based copolymers with balanced hydrophilic/hydrophobic content of N-Boc-L-amino acids were obtained via one-pot modification reaction with two different N-Boc-L-amino acids. The N-Boc protected homopolymers and related copolymers were deprotected to obtain (co)polymers with the targeted side chain cationic charged units. The (co)polymers' structures were fully investigated via FT-IR and 1H NMR spectroscopy, size exclusion chromatography (SEC), and TGA-DSC-MS analysis. The polarimetry measurements revealed that the homopolymers retain their chiroptical properties after post-modification, and a sign inversion is noticed from (L) N-Boc-protected analogues to (D) for the TFA cationic charged homopolymers. Generally, cationically charged homopolymers with hydrophilic amino acids on the side chain showed efficient complexation of siRNA, but poor transfection while cationic copolymers having both tryptophan and valine or proline side chains revealed moderate siRNA binding, high transfection efficiency (> 90% of the cells) and potent gene silencing with IC50 values down to 5.5 nM. Particularly, these cationic copolymers showed higher gene silencing potency as compared to the commercial JetPRIME® reference, without reducing cell viability in the concentration range used for transfection, making this a very interesting system for in vitro siRNA transfection.

siRNA drug delivery across the blood-brain barrier in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease with a few FDA-approved drugs that provide modest symptomatic benefits and only two FDA-approved disease-modifying treatments for AD. The advancements in understanding the causative genes and non-coding sequences at the molecular level of the pathophysiology of AD have resulted in several exciting research papers that employed small interfering RNA (siRNA)-based therapy. Although siRNA is being sought by academia and biopharma industries, several challenges still need to be addressed. We comprehensively report the latest advances in AD pathophysiology, druggable targets, ongoing clinical trials, and the siRNA-based approaches across the blood-brain barrier for addressing AD. This review describes the latest delivery systems employed to address this barrier. Critical insights and future perspectives on siRNA therapy for AD are also provided.

Advanced molecular therapies for neurological diseases: focus on stroke, alzheimer's disease, and parkinson's disease

Neurological diseases (NDs) are one of the leading causes of disability and the second leading cause of death globally. Among these stroke, Alzheimer's disease (AD), and Parkinson's disease (PD) are the most common NDs. A rise in the absolute number of individuals affected with these diseases indicates that the current treatment strategies in management and prevention of these debilitating diseases are not effective sufficiently. Therefore, novel treatment strategies are being explored to cure these diseases by addressing the causative mechanisms at the molecular level. Advanced therapies like gene therapy (gene editing and gene silencing) and stem cell therapies aim to cure diseases by gene editing, gene silencing and tissue regeneration, respectively. Gene editing results in the deletion of the aberrant gene or insertion of the corrected gene which can be executed using the CRISPR/Cas gene editing tool a promising treatment strategy being explored for many other prevalent diseases. Gene silencing using siRNA silences the gene by inhibiting protein translation, thereby silencing its expression. Stem cell therapy aims to regenerate damaged cells or tissues because of their ability to divide into any type of cell in the human body. Among these approaches, gene editing and gene silencing have currently been applied in vitro and to animal models, while stem cell therapy has reached the clinical trial stage for the treatment of NDs. The current status of these strategies suggests a promising outcome in their clinical translation.

Role of siRNA-based nanocarriers for the treatment of neurodegenerative diseases

Neurodegenerative disorders (NDs) lead to the progressive degeneration of the structural and physiological functions of the central and peripheral nervous systems, resulting in lifelong cognitive and motor dysfunction. Although comprehensive treatment of NDs is lacking, small interfering (si)RNA has shown therapeutic utility in the form of cellular nuclease-driven downregulation of mRNA levels. Various nanotechnologies have been used to modulate crucial physicochemical and biopharmaceutical properties of siRNA to provide protection and to enhance biomembrane interactions, residence times, tissue absorption, and cellular internalization for improved cytoplasm and/or nucleus interactions. In this review, we highlight advances in, and the role of, siRNA-based nanocarriers for the treatment of various NDs.

PEG-PEI/siROCK2 inhibits Aβ42-induced microglial inflammation via NLRP3/caspase 1 pathway

OBJECTIVES

There is an urgent need to develop therapeutic strategies to improve the treatment outcome of Alzheimer's disease. The treatment strategy of gene therapy mediated by nanocarrier systems brings new hope for the treatment of Alzheimer's disease. ROCK2 is involved in various pathological processes of Alzheimer's disease and may be a potential target for the treatment of Alzheimer's disease. Our previous study indicated that PEG-PEI/siROCK2 [polyethyleneglycol-polyethyleneimine deliver ROCK2-siRNA, (PPSR)] prevented Aβ42-induced neurotoxicity and showed a promising prospect for the treatment of Alzheimer's disease. However, whether PPSR has an effect on the microglial inflammation in Alzheimer's disease is still unclear.

MATERIALS AND METHODS

3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay was used to detect the cytotoxicity of PEG-PEI and PPSR in primary microglial cells. Real-time PCR and western blotting were used to assess the expression of ROCK2 and nucleotide oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3)/caspase 1 pathway in primary microglial cells. ELISA assay was used to measure the effect of PPSR on attenuating the lipopolysaccharide (LPS) + Aβ-induced increase in IL-1β.

RESULTS

PEG-PEI concentration less than 20 μg/ml and the N/P (molar ratio of PEG-PEI amino/siRNA phosphate) ratio of PPSR less than 50 showed no significant cytotoxicity in primary microglia cells. PPSR could effectively inhibit the expression of ROCK2 in primary microglial cells. A further study revealed that PPSR attenuates the LPS+Aβ-induced increase in IL-1β without affecting cell viability. In addition, we found that PPSR suppressed the Aβ-induced NLRP3/caspase 1 pathway in primary microglial cells.

CONCLUSION

PPSR inhibits Aβ42-induced microglial inflammation via NLRP3/caspase 1 pathway.

Alzheimer's disease and its treatment by different approaches: A review

Alzheimer's disease (AD) is a neurodegenerative disorder that impairs mental ability development and interrupts neurocognitive function. This neuropathological condition is depicted by neurodegeneration, neural loss, and development of neurofibrillary tangles and Aβ plaques. There is also a greater risk of developing AD at a later age for people with cardiovascular diseases, hypertension and diabetes. In the biomedical sciences, effective treatment for Alzheimer's disease is a severe obstacle. There is no such treatment to cure Alzheimer's disease. The drug present in the market show only symptomatic relief. The cause of Alzheimer's disease is not fully understood and the blood-brain barrier restricts drug efficacy are two main factors that hamper research. Stem cell-based therapy has been seen as an effective, secure, and creative therapeutic solution to overcoming AD because of AD's multifactorial nature and inadequate care. Current developments in nanotechnology often offer possibilities for the delivery of active drug candidates to address certain limitations. The key nanoformulations being tested against AD include polymeric nanoparticles (NP), inorganic NPs and lipid-based NPs. Nano drug delivery systems are promising vehicles for targeting several therapeutic moieties by easing drug molecules' penetration across the CNS and improving their bioavailability. In this review, we focus on the causes of the AD and their treatment by different approaches.

siRNA Therapeutics: Future Promise for Neurodegenerative Diseases

Neurodegenerative diseases (ND), as a group of central nervous system (CNS) disorders, are among the most prominent medical problems of the 21st century. They are often associated with considerable disability, motor dysfunction and dementia and are more common in the aged population. ND imposes a psychologic, economic and social burden on the patients and their families. Currently, there is no effective treatment for ND. Since many ND result from the gain of function of a mutant allele, small interference RNA (siRNA) can be a potential therapeutic agent for ND management. Based on the RNA interference (RNAi) approach, siRNA is a powerful tool for modulating gene expression through gene silencing. However, there are some obstacles in the clinical application of siRNA, including unfavorable immune response, off-target effects, instability of naked siRNA, nuclease susceptibility and a need to develop a suitable delivery system. Since there are some issues related to siRNA delivery routes, in this review, we focus on the application of siRNA in the management of ND treatment from 2000 to 2020.

Nano-Graphene Oxide-supported APTES-Spermine, as Gene Delivery System, for Transfection of pEGFP-p53 into Breast Cancer Cell Lines

PURPOSE

Genetic diseases can be the result of genetic dysfunctions that happen due to some inhibitory and/or environmental risk factors, which are mostly called mutations. One of the most promising treatments for these diseases is correcting the faulty gene. Gene delivery systems are an important issue in improving the gene therapy efficiency. Therefore, the main purpose of this study was modifying graphene oxide nanoparticles by spermine in order to optimize the gene delivery system.

METHODS

Graphene oxide/APTES was modified by spermine (GOAS) and characterized by FT-IR, DLS, SEM and AFM techniques. Then pEGFP-p53 was loaded on GOAS, transfected into cells and evaluated by fluorescent microscopy and gene expression techniques.

RESULTS

FT-IR data approved the GOAS sheet formation. Ninety percent of the particles were less than 56 nm based on DLS analysis. SEM analysis indicated that the sheets were dispersed with no aggregation. AFM results confirmed the dispersed structures with thickness of 1.25±0.87 nm. STA analysis showed that GOAS started to decompose from 400°C and was very unstable during the heating process. The first weight loss up to 200°C was due to the evaporation of absorbed water, the second one observed in the range of 200-550°C was assigned to the decomposition of labile oxygen- and nitrogen-containing functional groups, and the third one above 550°C was attributed to the removal of oxygen functionalities. In vitro release of DNA demonstrated the efficient activity of the new synthesized system. Ninety percent of the cells were transfected and showed the GFP under fluorescence microscopy, and TP53 gene was expressed 51-fold in BT-20 cells compared to β-actin as the reference gene. Flow cytometry analysis confirmed the apoptosis of the cells rather than necrosis.

CONCLUSION

It could be concluded that the new synthesized structure could transfer a high amount of the therapeutic agent into cells with best activity.

Receptor specific, stimuli responsive and subcellular targeted approaches for effective therapy of Alzheimer: Role of surface engineered nanocarriers

The present review deals in-depth with the current application of nanotechnology in targeting the major pathological hallmarks of Alzheimer's disease. This review further focuses on the surface modification of the nanocarriers using antibody, aptamers, proteins and peptides for specific targeting in the brain by overcoming the biological barriers such as blood brain barrier. The stimuli responsive/pulsatile drug delivery nanoplatforms using stimuli such as pH, temperature, photo-thermal, reactive oxygen species, ultrasonic stimulation and electrical stimulation, which help to create a micro-environment to either trigger the site-specific drug release from the nanoplatform or to reduce the disease burden in the brain, have been discussed. The targeting of nanoplatforms to sub-cellular compartments such as mitochondria, nuclei, endoplasmic reticulum, golgi apparatus and lysosomes along with receptor specific interactions such as such folate, lactoferrin, transferrin, insulin and low-density lipoprotein (LDL) receptors has been included to give reader an idea about strategies to enhance cellular co-localization and receptor based targeting of nanoparticles to enhance efficacy of delivery platform. This article describes the various type of nanoplatforms which include lipidic nanoplatforms, polymeric nanoplatforms, inorganic nanoplatforms (metallic nanocarriers, quantum dots, ceramic based nanocarriers), carbon based nanocarriers and cell derived or biomimetic (exosomes and virus based) nanoplatforms, to either deliver the active ingredient or to themselves target the Alzheimer's disease pathology. Thus the review gives a detailed insight of all the recent research studies carried out using nanotechnology in the field of Alzheimer's disease.

The Rho kinase inhibitor fasudil attenuates Aβ1-42-induced apoptosis via the ASK1/JNK signal pathway in primary cultures of hippocampal neurons

Alzheimer's disease (AD), a chronic, progressive, neurodegenerative disorder, is the most common type of dementia. Beta amyloid (Aβ) peptide aggregation and phosphorylated tau protein accumulation are considered as one of the causes for AD. Our previous studies have demonstrated the neuroprotective effect of the Rho kinase inhibitor fasudil, but the mechanism remains elucidated. In the present study, we examined the effects of fasudil on Aβ_1-42 aggregation and apoptosis and identified the intracellular signaling pathways involved in these actions in primary cultures of mouse hippocampal neurons. The results showed that fasudil increased neurite outgrowth (52.84%), decreased Aβ burden (46.65%), Tau phosphorylation (96.84%), and ROCK-II expression. In addition, fasudil reversed Aβ_1-42-induced decreased expression of Bcl-2 and increases in caspase-3, cleaved-PARP, phospho-JNK(Thr183/Tyr185), and phospho-ASK1(Ser966). Further, fasudil decreased mitochondrial membrane potential and intracellular calcium overload in the neurons treated with Aβ_1-42. These results suggest that inhibition of Rho kinase by fasudil reverses Aβ_1-42-induced neuronal apoptosis via the ASK1/JNK signal pathway, calcium ions, and mitochondrial membrane potential. Fasudil could be a drug of choice for treatment of Alzheimer's disease.

Polymeric siRNA gene delivery - transfection efficiency versus cytotoxicity

Within the field of gene therapy, there is a considerable need for the development of non-viral vectors that are able to compete with the efficiency obtained by viral vectors, while maintaining a good toxicity profile and not inducing an immune response within the body. While there have been many reports of possible polymeric delivery systems, few of these systems have been successful in the clinical setting due to toxicity, systemic instability or gene regulation inefficiency, predominantly due to poor endosomal escape and cytoplasmic release. The objective of this review is to provide an overview of previously published polymeric non-coding RNA and, to a lesser degree, oligo-DNA delivery systems with emphasis on their positive and negative attributes, in order to provide insight in the numerous hurdles that still limit the success of gene therapy.

Nanomedicine in Alzheimer's disease: Amyloid beta targeting strategy

The treatment of Alzheimer's disease (AD) is up to today one of the most unsuccessful examples of biomedical science. Despite the high number of literature evidences detailing the multifactorial and complex etiopathology of AD, no cure is yet present on the market and the available treatments are only symptomatic. The reasons could be ascribed on two main factors: (i) lack of ability of the majority of drugs to cross the blood-brain barrier (BBB), thus excluding the brain for any successful therapy; (ii) lack of selectivity and specificity of drugs, decreasing the efficacy of even potent anti-AD drugs. The exploitation of specifically engineered nanomedicines planned to cross the BBB and to target the most "hot" site of action (i.e., β-amyloid) is one of the most interesting innovations in drug delivery and could reasonably represent an promising choice for possible treatments and even early-diagnosis of AD. In this chapter, we therefore outline the most talented approaches in AD treatment with a specific focus on the main advantages/drawbacks and future possible translation to clinic application.

The therapeutic potential of RNA regulation in neurological disorders

INTRODUCTION

Gene regulation is the term used to describe the mechanisms by which a cell increases or decreases the amount of a gene product (RNA or protein). In complex organs such as the brain, gene regulation is of the utmost importance; aberrations in the regulation of specific genes can lead to neurological disorders. Understanding these mechanisms can create new strategies for targeting these disorders and progress is being made. Two drugs that function at the RNA level (nusinersen and eteplirsen) have now been approved by the FDA for the treatment of Spinomuscular atrophy and Duchenne muscular dystrophy, respectively; several other compounds for neurological disease are currently being investigated in preclinical studies and clinical trials. Areas covered: We highlight how gene regulation at the level of RNA molecules can be used as a therapeutic strategy to treat neurological disorders. We provide examples of how such an approach is being studied or used and discuss the current hurdles. Expert opinion: Targeting gene expression at the RNA level is a promising strategy to treat genetic neurological disorders. Safe administration, long-term efficacy, and potential side effects, however, still need careful evaluation before RNA therapeutics can be applied on a larger scale.

Nanomaterial-involved neural stem cell research: Disease treatment, cell labeling, and growth regulation

Neural stem cells (NSCs) have been widely investigated for their potential in the treatment of various diseases and transplantation therapy. However, NSC growth regulation, labeling, and its application to disease diagnosis and treatment are outstanding challenges. Recently, nanomaterials have shown promise for various applications including genetic modification, imaging, and controlled drug release. Here we summarize the recent progress in the use of nanomaterials in combination with NSCs for disease treatment and diagnosis, cell labeling, and NSC growth regulation. The toxicity of nanomaterials to NSCs is also discussed.

Polymer nanoassemblies with hydrophobic pendant groups in the core induce false positive siRNA transfection in luciferase reporter assays

Poly(ethylene glycol)-conjugated polyethylenimine (PEG-PEI) is a widely studied cationic polymer used to develop non-viral vectors for siRNA therapy of genetic disorders including cancer. Cell lines stably expressing luciferase reporter protein typically evaluate the transfection efficacy of siRNA/PEG-PEI complexes, however recent findings revealed that PEG-PEI can reduce luciferase expression independent of siRNA. This study elucidates a cause of the false positive effect in luciferase assays by using polymer nanoassemblies (PNAs) made from PEG, PEI, poly-(l-lysine) (PLL), palmitate (PAL), and deoxycholate (DOC): PEG-PEI (2P), PEG-PEI-PAL (3P), PEG-PLL (2P'), PEG-PLL-PAL (3P'), and PEG-PEI-DOC (2PD). In vitro transfection and western blot assays of luciferase using a colorectal cancer cell line expressing luciferase (HT29/LUC) concluded that 2P and 2P' caused no luciferase expression reduction while hydrophobically modified PNAs induced a 35-50% reduction (3P'<2PD<3P). Although cell viability remained stagnant, 3P triggered cellular stress responses including increased membrane porosity and decreased ATP and cellular protein concentrations. Raman spectroscopy suggested that hydrophobic groups influence PNA conformation changes, which may have caused over-ubiquitination and degradation of luciferase in the cells. These results indicate that hydrophobically modified PEG-PEI induces cellular distress causing over-ubiquitination of the luciferase protein, producing false positive siRNA transfection in the luciferase assay.

Destination Brain: the Past, Present, and Future of Therapeutic Gene Delivery

Neurological diseases and disorders (NDDs) present a significant societal burden and currently available drug- and biological-based therapeutic strategies have proven inadequate to alleviate it. Gene therapy is a suitable alternative to treat NDDs compared to conventional systems since it can be tailored to specifically alter select gene expression, reverse disease phenotype and restore normal function. The scope of gene therapy has broadened over the years with the advent of RNA interference and genome editing technologies. Consequently, encouraging results from central nervous system (CNS)-targeted gene delivery studies have led to their transition from preclinical to clinical trials. As we shift to an exciting gene therapy era, a retrospective of available literature on CNS-associated gene delivery is in order. This review is timely in this regard, since it analyzes key challenges and major findings from the last two decades and evaluates future prospects of brain gene delivery. We emphasize major areas consisting of physiological and pharmacological challenges in gene therapy, function-based selection of a ideal cellular target(s), available therapy modalities, and diversity of viral vectors and nanoparticles as vehicle systems. Further, we present plausible answers to key questions such as strategies to circumvent low blood-brain barrier permeability and most suitable CNS cell types for targeting. We compare and contrast pros and cons of the tested viral vectors in the context of delivery systems used in past and current clinical trials. Gene vector design challenges are also evaluated in the context of cell-specific promoters. Key challenges and findings reported for recent gene therapy clinical trials, assessing viral vectors and nanoparticles are discussed from the perspective of bench to bedside gene therapy translation. We conclude this review by tying together gene delivery challenges, available vehicle systems and comprehensive analyses of neuropathogenesis to outline future prospects of CNS-targeted gene therapies.

PEG-PEI/siROCK2 Protects Against Aβ42-Induced Neurotoxicity in Primary Neuron Cells for Alzheimer Disease

Gene therapy that targets the ROCK2 gene has yielded promising results in the treatment of AD. Our previous study indicated that PEG-PEI/siROCK2 could effectively suppress ROCK2 mRNA expression and showed a promising prospect for the treatment of Alzheimer's disease. However, the ability of PEG-PEI/siROCK2 to reduce Aβ-induced cytotoxicity is unknown. To investigate the effect of PEG-PEI/siROCK2 against Aβ42-induced neurotoxicity, primary cultured cortical neurons were pretreated with PEG-PEI/siROCK2 for 24 h and then treated with 5 μM Aβ42 for 24 h. We found that PEG-PEI/siROCK2 increased the cell viability and reduced the number of apoptotic cells induced by Aβ42, as measured using an MTT assay and Annexin V/PI staining. A further study revealed that PEG-PEI/siROCK2 can activate p-Akt, and treatment with the PI3K inhibitor LY294002 attenuated the neuroprotective effects. These results suggest that PEG-PEI/siROCK2 prevents Aβ42-induced neurotoxicity and that the activation of PI3K/Akt pathway is involved in neuroprotection. Taken together, these findings shed light on the role of PEG-PEI/siROCK2 as a potential therapeutic agent for AD.

Micellar carriers for the delivery of multiple therapeutic agents

Multi-drug therapy is described as a simultaneous or sequential administration of two or more drugs with similar or different mechanisms of action and is recognized as a more efficient solution to combat successfully, various ailments. Polymeric micelles (PMs) are self-assemblies of block copolymers providing numerous opportunities for drug delivery. To date various micellar formulations were studied for delivery of drugs, nutraceuticals and genes; a few of them are in clinical trials. It was observed that there is an immense need for the development of PMs embedding multiple therapeutic agents to combat various ailments, including cancers, HIV/AIDS, malaria, multiple sclerosis, hypertension, infectious diseases, cardiovascular and metabolic diseases, immune disorders and many psychiatric disorders. Several combinations of drug-drug, drug-nutraceutical, drug-gene and drug-siRNA explored to date are detailed in this review, with a special emphasis on their potential and future perspectives. A summary of various preparation methods, characterization techniques and applications of PMs are also provided. This review presents a holistic approach on multi-drug delivery using micellar carriers and emphasizes on the development of therapeutic hybrids embedding novel combinations for safer and effective therapy.

Nanotherapeutic strategies for the treatment of Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is now representing one of the largest unmet medical needs. However, no effective treatment is now available to impede the progression of AD or delay its onset. There are two major challenges for the development of effective therapy for AD. First, the exact cause for AD onset is still unknown. Second, brain drug delivery is significantly hindered by the blood-brain barrier (BBB). In this review, we will summarize the pathological understanding about AD and the related treatments, compare BBB and its effect on brain drug delivery under normal and AD conditions and review the nanotherapeutic strategies that have been developed for AD therapy in recent years.

siRNA as a tool to improve the treatment of brain diseases: Mechanism, targets and delivery

As the population ages, brain pathologies such as neurodegenerative diseases and brain cancer increase their incidence, being the need to find successful treatments of upmost importance. Drug delivery to the central nervous system (CNS) is required in order to reach diseases causes and treat them. However, biological barriers, mainly blood-brain barrier (BBB), are the key obstacles that prevent the effectiveness of possible treatments due to their ability to strongly limit the perfusion of compounds into the brain. Over the past decades, new approaches towards overcoming BBB and its efflux transporters had been proposed. One of these approaches here reviewed is through small interfering RNA (siRNA), which is capable to specifically target one gene and silence it in a post-transcriptional way. There are different possible functional proteins at the BBB, as the ones responsible for transport or just for its tightness, which could be a siRNA target. As important as the effective silence is the way to delivery siRNA to its anatomical site of action. This is where nanotechnology-based systems may help, by protecting siRNA circulation and providing cell/tissue-targeting and intracellular siRNA delivery. After an initial overview on incidence of brain diseases and basic features of the CNS, BBB and its efflux pumps, this review focuses on recent strategies to reach brain based on siRNA, and how to specifically target these approaches in order to treat brain diseases.

Nanomedicine for the treatment of Alzheimer's disease

Alzheimer's disease affects more than 35 million people worldwide and this number is presumed to double by the year 2050. Currently, there is no efficient therapy for this disorder but a promising approach is represented by nanotechnology, easily multifunctionalizable devices with size in the order of billionth of meter. This review provides a concise survey on the nano-based strategies for Alzheimer's disease treatment, aiming at carrying drugs across the blood–brain barrier, in particular to target the metabolism of β-amyloid peptide, a pivotal player in this pathology.

Downregulation of ROCK2 through nanocomplex sensitizes the cytotoxic effect of temozolomide in U251 glioma cells

OBJECTIVE

Rho-associated coiled-coil kinase 2 (ROCK2) is an attractive therapeutic target because it is overexpressed in many malignancies, including glioma. Therefore, we designed the current study to determine whether the downregulation of ROCK2 would sensitize the cytotoxic effect of temozolomide (TMZ) in U251 cells.

METHODS

Glycol-polyethyleneimine (PEG-PEI) was used to deliver siROCK2 to U251 cells, and the physical characteristics of the PEG-PEI/siROCK2 complex (referred to as the siROCK2 complex) were investigated. The transfection efficiency and cell uptake were determined by flow cytometry (FCM) and confocal laser microscopy (CLSM), respectively. U251 cells were then treated with 100 μM TMZ, siROCK2 complexes or their combination. The apoptosis rate and cell migration were measured by FCM and wound-healing assay, respectively. The levels of Bax, Bcl-2, cleaved caspase-3, MMP-2, and MMP-9 were detected to analyze the degrees of apoptosis and migration.

RESULTS

Our results revealed that the characteristics of the siROCK2 complexes depended closely on the N/P ratios. PEG-PEI served as a good vector for siROCK2 and exhibited low cytotoxicity toward U251 cells. The CLSM assay showed that the siROCK2 complexes were successfully uptaken and that both the protein and mRNA levels of ROCK2 were significantly suppressed. Furthermore, the combination treatment induced a higher apoptosis rate and markedly increased the gap distance of U251 cells in the wound-healing assay. Levels of the proapoptotic proteins Bax and cleaved caspase-3 were significantly increased, whereas levels of the antiapoptotic protein Bcl-2 and the migration-related proteins MMP-2 and MMP-9 were significantly reduced by the combination treatment compared with either treatment alone.

CONCLUSIONS

In conclusion, our results demonstrate that the combination of TMZ and siROCK2 effectively induces apoptosis and inhibits the migration of U251 cells. Therefore, the combination of TMZ and siROCK2 complex is a potential therapeutic approach for human glioma.

Intracranial injection of PEG-PEI/ROCK II-siRNA improves cognitive impairment in a mouse model of Alzheimer's disease

PURPOSE

A plenty of studies have demonstrated that the Rho/ROCK pathway is involved in the neuronal loss and inhibition of axonal regeneration observed in Alzheimer's disease (AD). Therefore, we conducted this study to evaluate whether intracranial injection of PEG-PEI/ROCK II siRNA (PPRS) would improve the cognitive impairments in a senescence-accelerated mouse (SAM) model of AD.

MATERIALS AND METHODS

Five male senescence-resistant inbred strain (SAMR1) mice and 15 male senescence-accelerated mouse prone-8 (SAMP8) strain mice were divided into the following three groups:PPRS group, PEG-PEI/ ROCK II-Scramble (PPRScr) siRNA group, and normal group (SAMR1). Total volumes of 2.3 μl of nanoparticles or saline were intracranially injected under the guidance of a stereotaxic apparatus. The injections were performed every three days and lasted for two weeks. Four weeks after injection, the Morris water maze (MWM) was used to evaluate the spatial learning and memory functions of the mice. Choline acetyltransferase (ChAT) activity was detected by immunohistochemistry.

RESULTS

Mice in the PPRS-treated group exhibited decreases in escape latencies over the three successive days of navigating the test and crossing the target quadrant during the spatial probe test more frequently than did the mice in the PPRScr-treated group. Analyses of ChAT activity revealed that greater numbers of ChAT-positive cells were present in the hippocampal regions of the PPRS-treated mice than in the PPRScr group.

CONCLUSIONS

Intracranial injection of PPRS improved the cognitive impairments of SAM mice, and this improvement may have been mediated by enhancement of ChAT activity in the hippocampus.

Characterization of polyethylene glycol-polyethyleneimine as a vector for alpha-synuclein siRNA delivery to PC12 cells for Parkinson's disease

AIMS

Gene therapy targeting the SNCA gene yields promising results in the treatment of Parkinson's disease (PD). The most challenging issue of the RNAi gene therapy strategy is maintaining efficient delivery without inducing significant toxicity and other adverse effects. This study aimed to characterize polyethylene glycol-polyethyleneimine as a vector for alpha-synuclein siRNA delivery to PC12 cells for Parkinson's disease.

METHODS

The characteristics of PEG-PEI/siSNCA were analyzed via gel retardation assay and assessments of particle size and zeta potential. MTT cytotoxicity assay and flow cytometry were used to detect cytotoxicity and transfection efficiency in PC12 cells. Confocal laser scanning microscopy was employed to examine the intracellular distribution of PEG-PEI/FITC-siSNCA after cellular uptake. RT-PCR and western blotting were used to measure SNCA expression. The MTT cytotoxicity assay was used to study the effect of PEG-PEI/siSNCA on cell viability. The protective effect of PEG-PEI/siSNCA on MPP+-induced apoptosis in PC12 cells was examined via flow cytometry and Hoechst staining.

RESULTS

PEG-PEI/siSNCA complexes were well-developed; they exhibited appropriate particle sizes and zeta potentials at a mass ratio of 5:1. In vitro, PEG-PEI/siSNCA was associated with low cytotoxicity and high transfection efficiency. Complexes were capable of successfully delivering siSNCA into PC12 cells and releasing it from the endosome. Furthermore, PEG-PEI/siSNCA could effectively suppress SNCA mRNA expression and protected cells from death via apoptosis induced by MPP(+) .

CONCLUSIONS

Our results demonstrate that PEG-PEI performs well as a vector for alpha-synuclein siRNA delivery into PC12 cells. Additionally, PEG-PEI/siSNCA complexes were suggested to be able to protect cells from death via apoptosis induced by MPP(+) . These findings suggest that PEG-PEI/siSNCA nanoparticles exhibit remarkable potential as a gene delivery system for Parkinson's disease.