An intranasally delivered peptide drug ameliorates cognitive decline in Alzheimer transgenic mice

Bio-Nano Toolbox for Precision Alzheimer's Disease Gene Therapy

Alzheimer's disease (AD) is the most burdensome aging-associated neurodegenerative disorder, and its treatment encounters numerous failures during drug development. Although there are newly approved in-market β-amyloid targeting antibody solutions, pathological heterogeneity among patient populations still challenges the treatment outcome. Emerging advances in gene therapies offer opportunities for more precise personalized medicine; while, major obstacles including the pathological heterogeneity among patient populations, the puzzled mechanism for druggable target development, and the precision delivery of functional therapeutic elements across the blood-brain barrier remain and limit the use of gene therapy for central neuronal diseases. Aiming for "precision delivery" challenges, nanomedicine provides versatile platforms that may overcome the targeted delivery challenges for AD gene therapy. In this perspective, to picture a toolbox for AD gene therapy strategy development, the most recent advances from benchtop to clinics are highlighted, possibly available gene therapy targets, tools, and delivery platforms are outlined, their challenges as well as rational design elements are addressed, and perspectives in this promising research field are discussed.

Passive immunotherapy for Alzheimer's disease: challenges & future directions

Passive immunotherapy with specific antibodies targeting Amyloid β (Aβ) peptide or tubulin-associated unit (tau) protein has emerged as a promising therapeutic approach in Alzheimer's disease (AD). However, in a recent phase III clinical study, Sperling et al. (N Engl J Med 10.1056/NEJMoa2305032, 2023) reported that solanezumab, a monoclonal antibody targeting Aβ peptide, failed to slow cognitive decline in AD patients. Previously, three other anti-Aβ antibodies, bapineuzumab, crenezumab, and gantenerumab, have also failed to show similar beneficial effects. In addition, three humanized antibodies targeting tau protein failed in their phase II trials. However, other anti-Aβ antibodies, such as lecanemab (a humanized mAb binds to soluble Aβ protofibrils), donanemab (a humanized mAb binds to insoluble, N-terminal truncated form of Aβ peptides) and aducanumab (a human mAb binds to the aggregated form of Aβ), have been shown to slow the decline of cognitive functions in early stage AD patients. The specific targets used in passive immunotherapy in these clinical trials may explain the divergent clinical outcomes. There are several challenges and limitations of passive immunotherapy using anti-Aβ antibodies and long term longitudinal studies are needed to assess their efficacy, side effects and cost effectiveness in a wider spectrum of subjects, from pre-dementia to more advanced dementia. A combination therapeutic approach using both anti-Aβ antibodies and other pharmaceutical agents should also be explored.

Recent trends in treatment strategies for Alzheimer's disease and the challenges: A topical advancement

Alzheimer's Disease (AD) is an irreversible and progressive neurological disease that has affected at least 50 million people around the globe. Considering the severity of the disease and the continuous increase in the number of patients, the development of new effective drugs or intervention strategies for AD has become urgent. AD is caused by a combination of genetic, environmental, and lifestyle factors, but its exact cause has not yet been clarified. Given the current challenges being faced in the clinical treatment of AD, such as complex AD pathological network and insufficient early diagnosis, herein, we have focused on the three core pathological features of AD, including amyloid-β (Aβ) aggregation, tau phosphorylation and tangles, and activation of inflammatory factors. In this review, we have briefly underscored the primary evidence supporting each pathology and discuss AD pathological network among Aβ, tau, and inflammation. We have also comprehensively summarized the most instructive drugs and their treatment strategies against Aβ, tau, or neuroinflammation used in basic research and clinical trials. Finally, we have discussed and outlined the pros and cons of each pathological approach and looked forward to potential personalized diagnosis and treatment strategies that are beneficial to AD patients.

Identification of new pentapeptides as potential inhibitors of amyloid-β42 aggregation using virtual screening and molecular dynamics simulations

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease mainly characterized by extracellular accumulation of amyloid-β (Aβ) peptide. Previous studies reported pentapeptide RIIGL as an effective inhibitor of Aβ aggregation and neurotoxicity induced by Aβ aggregates. In this work, a library of 912 pentapeptides based on RIIGL has been designed and assessed for their efficacy to inhibit Aβ42 aggregation using computational techniques. The top hit pentapeptides revealed by molecular docking were further assessed for their binding affinity with Aβ42 monomer using MM-PBSA (molecular mechanics Poisson-Boltzmann surface area) method. The MM-PBSA analysis identified RLAPV, RVVPI, and RIAPA, which bind to Aβ42 monomer with a higher binding affinity -55.80, -46.32, and -44.26 kcal/mol, respectively, as compared to RIIGL (ΔGbinding = -41.29 kcal/mol). The residue-wise binding free energy predicted hydrophobic contacts between Aβ42 monomer and pentapeptides. The secondary structure analysis of the conformational ensembles generated by molecular dynamics (MD) depicted remarkably enhanced sampling of helical and no β-sheet conformations in Aβ42 monomer on the incorporation of RVVPI and RIAPA. Notably, RVVPI and RIAPA destabilized the D23-K28 salt bridge in Aβ42 monomer, which plays a crucial role in Aβ42 oligomer stability and fibril formation. The MD simulations highlighted that the incorporation of proline and arginine in pentapeptides contributed to their strong binding with Aβ42 monomer. Furthermore, RVVPI and RIAPA prevented conformational conversion of Aβ42 monomer to aggregation-prone structures, which, in turn, resulted in a lower aggregation tendency of Aβ42 monomer.

Neurobiochemical characteristics of arginine-rich peptides explain their potential therapeutic efficacy in neurodegenerative diseases

Neurodegenerative diseases, including Alzheimer̕ s disease (AD), Parkinson̕ s disease (PD), Huntington̕ s disease (HD), and Amyotrophic Lateral Sclerosis (ALS) require special attention to find new potential treatment methods. This review aims to summarize the current knowledge of the relationship between the biochemical properties of arginine-rich peptides (ARPs) and their neuroprotective effects to deal with the harmful effects of risk factors. It seems that ARPs have portrayed a promising and fantastic landscape for treating neurodegeneration-associated disorders. With multimodal mechanisms of action, ARPs play various unprecedented roles, including as the novel delivery platforms for entering the central nervous system (CNS), the potent antagonists for calcium influx, the invader molecules for targeting mitochondria, and the protein stabilizers. Interestingly, these peptides inhibit the proteolytic enzymes and block protein aggregation to induce pro-survival signaling pathways. ARPs also serve as the scavengers of toxic molecules and the reducers of oxidative stress agents. They also have anti-inflammatory, antimicrobial, and anti-cancer properties. Moreover, by providing an efficient nucleic acid delivery system, ARPs can play an essential role in developing various fields, including gene vaccines, gene therapy, gene editing, and imaging. ARP agents and ARP/cargo therapeutics can be raised as an emergent class of neurotherapeutics for neurodegeneration. Part of the aim of this review is to present recent advances in treating neurodegenerative diseases using ARPs as an emerging and powerful therapeutic tool. The applications and progress of ARPs-based nucleic acid delivery systems have also been discussed to highlight their usefulness as a broad-acting class of drugs.

A peptide rich in glycine-serine-alanine repeats ameliorates Alzheimer-type neurodegeneration

BACKGROUND AND PURPOSE

Repeated amino acid sequences in proteins are widely found, and the glycine-serine-alanine repeat is an element with a general propensity to form β-sheet aggregates as found in key pathological factors, in several neurodegenerative diseases. Such properties of this repeat may guide development of disease-modifying therapies for neurodegenerative disease. However, details of its role and underlying mechanism(s) remain largely unknown.

EXPERIMENTAL APPROACH

Actions of specific glycine-serine-alanine repeat peptides (SNPs), especially SNP-9, on Alzheimer's disease (AD)-like abnormalities were evaluated in transgenic mice and Caenorhabditis elegans, and in rat and cell models. Entry of SNPs into the brain, SNP activity in neuronal cells and peptide entry into cells were analysed in vivo and in vitro. Cell-free systems and the yeast two-hybrid system were also used to explore possible targets of SNP-9, and interactions of potential targets with SNP-9 were confirmed in cell-based systems.

KEY RESULTS

We first identified SNP-9 as a potent neuroprotective peptide with the activity to decrease oligomeric amyloid β (Aβ) via co-assembling with the toxic Aβ oligomer to form hetero-oligomers. Also, calcyclin-binding protein was found to act as a SNP-9-binding protein, by screening of a human brain cDNA library. Such binding showed that SNP-9 could regulate the abnormal hyperphosphorylation of tau via calcyclin-binding protein.

CONCLUSION AND IMPLICATIONS

Our study provides a foundation for development of SNPs, especially SNP-9, as potential therapeutic interventions for AD. We propose SNP-9 as a potential therapeutic agent for the treatment of AD.

Diagonal Interactions between Glutamate and Arginine Analogs with Varying Side-Chain Lengths in a β-Hairpin

Cross-strand interactions are important for the stability of β-sheet structures. Accordingly, cross-strand diagonal interactions between glutamate and arginine analogs with varying side-chain lengths were studied in a series of β-hairpin peptides. The peptides were analyzed by homonuclear two-dimensional nuclear magnetic resonance methods. The fraction folded population and folding free energy of the peptides were derived from the chemical shift data. The fraction folded population trends could be rationalized using the strand propensity of the constituting residues, which was not the case for the peptides with lysine analogs, highlighting the difference between the arginine analogs and lysine analogs. Double-mutant cycle analysis was used to derive the diagonal ion-pairing interaction energetics. The most stabilizing diagonal cross-strand interaction was between the shortest residues (i.e., Asp2-Agp9), most likely due to the least side-chain conformational penalty for ion-pair formation. The diagonal interaction energetics in this study involving the arginine analogs appears to be consistent with and extend beyond our understanding of diagonal ion-pairing interactions involving lysine analogs. The results should be useful for designing β-strand-containing molecules to affect biological processes such as amyloid formation and protein-protein interactions.

Applications of Nanoparticles in Alzheimer's Disease

With the rapid aging of the global population, the prevalence of neurodegenerative diseases has become a significant concern, with Alzheimer's disease (AD) being the most common. However, the clinical trials of many drugs targeting AD have failed due to the challenges posed by the blood-brain barrier (BBB), which makes intracerebral administration of drugs difficult. However, nanoparticles (NPs) may aid in the delivery of such drugs. NPs are materials with sizes between 1-100 nm that offer several advantages, such as improving biocompatibility, prolonging half-life, transporting large molecules, crossing the BBB to deliver to the central nervous system, and exhibiting good targeting ability. In addition to drug delivery, NPs also have excellent diagnostic potential, and multifunctional NPs can integrate the advantages of diagnosis, targeting, and treatment. This mini-review article provides an overview of NPs, including the composition of the carrier, strategies for crossing the BBB, and different targets of AD pathology, with the aim of providing guidance for the development prospects of NPs.

Recent Advances of Studies on Cell-Penetrating Peptides Based on Molecular Dynamics Simulations

With the ability to transport cargo molecules across cell membranes with low toxicity, cell-penetrating peptides (CPPs) have become promising candidates for next generation peptide-based drug delivery vectors. Over the past three decades since the first CPP was discovered, a great deal of work has been done on the cellular uptake mechanisms and the applications for the delivery of therapeutic molecules, and significant advances have been made. But so far, we still do not have a precise and unified understanding of the structure-activity relationship of the CPPs. Molecular dynamics (MD) simulations provide a method to reveal peptide-membrane interactions at the atomistic level and have become an effective complement to experiments. In this paper, we review the progress of the MD simulations on CPP-membrane interactions, including the computational methods and technical improvements in the MD simulations, the research achievements in the CPP internalization mechanism, CPP decoration and coupling, and the peptide-induced membrane reactions during the penetration process, as well as the comparison of simulated and experimental results.

Nose-to-Brain Delivery of Therapeutic Peptides as Nasal Aerosols

Central nervous system (CNS) disorders, such as psychiatric disorders, neurodegeneration, chronic pain, stroke, brain tumor, spinal cord injury, and many other CNS diseases, would hugely benefit from specific and potent peptide pharmaceuticals and their low inherent toxicity. The delivery of peptides to the brain is challenging due to their low metabolic stability, which decreases their duration of action, poor penetration of the blood-brain barrier (BBB), and their incompatibility with oral administration, typically resulting in the need for parenteral administration. These challenges limit peptides’ clinical application and explain the interest in alternative routes of peptide administration, particularly nose-to-brain (N-to-B) delivery, which allows protein and peptide drugs to reach the brain noninvasively. N-to-B delivery can be a convenient method for rapidly targeting the CNS, bypassing the BBB, and minimizing systemic exposure; the olfactory and trigeminal nerves provide a unique pathway to the brain and the external environment. This review highlights the intranasal delivery of drugs, focusing on peptide delivery, illustrating various clinical applications, nasal delivery devices, and the scope and limitations of this approach.

Biopolymer Nanoparticles for Nose-to-Brain Drug Delivery: A New Promising Approach for the Treatment of Neurological Diseases

Diseases affecting the central nervous system (CNS) are among the most disabling and the most difficult to cure due to the presence of the blood–brain barrier (BBB) which represents an impediment from a therapeutic and diagnostic point of view as it limits the entry of most drugs. The use of biocompatible polymer nanoparticles (NPs) as vehicles for targeted drug delivery to the brain arouses increasing interest. However, the route of administration of these vectors remains critical as the drug must be delivered without being degraded to achieve a therapeutic effect. An innovative approach for the administration of drugs to the brain using polymeric carriers is represented by the nose-to-brain (NtB) route which involves the administration of the therapeutic molecule through the neuro-olfactory epithelium of the nasal mucosa. Nasal administration is a non-invasive approach that allows the rapid transport of the drug directly to the brain and minimizes its systemic exposure. To date, many studies involve the use of polymer NPs for the NtB transport of drugs to the brain for the treatment of a whole series of disabling neurological diseases for which, as of today, there is no cure. In this review, various types of biodegradable polymer NPs for drug delivery to the brain through the NtB route are discussed and particular attention is devoted to the treatment of neurological diseases such as Glioblastoma and neurodegenerative diseases.

Sirolimus treatment induces dose-dependent involution of the thymus with elevated cellular respiration in BALB/c mice

Several in vitro and in vivo studies have shown that the mammalian target of rapamycin (mTOR) inhibitor sirolimus (rapamycin) suppresses thymus cellular respiration. The objective of this study is to investigate the chronic dose-dependent effects of sirolimus in the thymus. This was monitored using body weight, histomorphology, caspase-3 expression, cytochrome C immunohistochemistry, and cellular bioenergetics as surrogate biomarkers. BALB/c mice received intraperitoneal injections of either sirolimus (2.5, 5, or 10 µg/g) or dimethyl sulfoxide (0.1 µL/g) as a control for 4 weeks. At the end of the treatment, fragments were collected from the thymus, small intestine, adrenal gland, and kidney. They were processed for assessing histologic changes, measuring cellular respiration and ATP levels. Immunohistochemical stain of caspase-3 and cytochrome C was performed on paraffin-embedded tissue. The treated animals exhibited a dose-dependent reduction in weight gain despite adequate food intake. Sirolimus produced significant thymic derangements, manifested by dose-dependent tissue involution, increased cortical apoptotic bodies, increased caspase-3-positive lymphocytes, and increased rate of cellular respiration without a concomitant increase in cellular ATP. There were no similar changes in cellular ATP in the other assessed organs. The effects on thymic cellular bioenergetics suggest mitochondrial derangements, uncoupling of oxidative phosphorylation, and induction of apoptosis.

The Effects of Charged Amino Acid Side-Chain Length on Diagonal Cross-Strand Interactions between Carboxylate- and Ammonium-Containing Residues in a β-Hairpin

The β-sheet is one of the common protein secondary structures, and the aberrant aggregation of β-sheets is implicated in various neurodegenerative diseases. Cross-strand interactions are an important determinant of β-sheet stability. Accordingly, both diagonal and lateral cross-strand interactions have been studied. Surprisingly, diagonal cross-strand ion-pairing interactions have yet to be investigated. Herein, we present a systematic study on the effects of charged amino acid side-chain length on a diagonal ion-pairing interaction between carboxylate- and ammonium-containing residues in a β-hairpin. To this end, 2D-NMR was used to investigate the conformation of the peptides. The fraction folded population and the folding free energy were derived from the chemical shift data. The fraction folded population for these peptides with potential diagonal ion pairs was mostly lower compared to the corresponding peptide with a potential lateral ion pair. The diagonal ion-pairing interaction energy was derived using double mutant cycle analysis. The Asp2-Dab9 (Asp: one methylene; Dab: two methylenes) interaction was the most stabilizing (−0.79 ± 0.14 kcal/mol), most likely representing an optimal balance between the entropic penalty to enable the ion-pairing interaction and the number of side-chain conformations that can accommodate the interaction. These results should be useful for designing β-sheet containing molecular entities for various applications.

Vascular Endothelial Growth Factor-Capturing Aligned Electrospun Polycaprolactone/Gelatin Nanofibers Promote Patellar Ligament Regeneration

Ligament injuries are common in sports and other rigorous activities. It is a great challenge to achieve ligament regeneration after an injury due the avascular structure and low self-renewal capability. Herein, we developed vascular endothelial growth factor (VEGF)-binding aligned electrospun poly(caprolactone)/gelatin (PCL/Gel) scaffolds by incorporating prominin-1-binding peptide (BP) sequence and exploited them for patellar ligament regeneration. The adsorption of BP onto scaffolds was discerned by various techniques, such as Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and confocal laser scanning microscope. The accumulation of VEGF onto scaffolds correlated with the concentration of the peptide in vitro. BP-anchored PCL/Gel scaffolds (BP@PCL/Gel) promoted the tubular formation of human umbilical vein endothelial cells (HUVECs) and wound healing in vitro. Besides, BP containing scaffolds exhibited higher content of CD31⁺ cells than that of the control scaffolds at 1 week after implantation in vivo. Moreover, BP containing scaffolds improved biomechanical properties and facilitated the regeneration of matured collagen in patellar ligament 4 weeks after implantation in mice. Overall, this strategy of peptide-mediated orchestration of VEGF provides an enticing platform for the ligament regeneration, which may also have broad implications for tissue repair applications. STATEMENT OF SIGNIFICANCE: Ligament injuries are central to sports and other rigorous activities. Given to the avascular nature and poor self-healing capability of injured ligament tissues, it is a burgeoning challenge to fabricate tissue-engineered scaffolds for ligament reconstruction. Vascular endothelial growth factor (VEGF) is pivotal to the neo-vessel formation. However, the high molecular weight of VEGF as well as its short half-life in vitro and in vivo limits its therapeutic potential. To circumvent these limitations, herein, we functionalized aligned electrospun polycaprolactone/gelatin (PCL/Gel)-based scaffolds with VEGF-binding peptide (BP) and assessed their biocompatibility and performance in vitro and in vivo. BP-modified scaffolds accumulated VEGF, improved tube formation of HUVECs, and induced wound healing in vitro, which may have broad implications for regenerative medicine and tissue engineering.

Review of Current Strategies for Delivering Alzheimer's Disease Drugs Across the Blood-Brain Barrier

(Appeared originally in the International Journal of Molecular Sciences 2019; 20:381) Reprinted under Creative Commons CC-BY license.

Quantitative Brain Positron Emission Tomography in Female 5XFAD Alzheimer Mice: Pathological Features and Sex-Specific Alterations

Successful back-translating clinical biomarkers and molecular imaging methods of Alzheimer's disease (AD), including positron emission tomography (PET), are very valuable for the evaluation of new therapeutic strategies and increase the quality of preclinical studies. ¹⁸F-Fluorodeoxyglucose (FDG)–PET and ¹⁸F-Florbetaben–PET are clinically established biomarkers capturing two key pathological features of AD. However, the suitability of ¹⁸F-FDG– and amyloid–PET in the widely used 5XFAD mouse model of AD is still unclear. Furthermore, only data on male 5XFAD mice have been published so far, whereas studies in female mice and possible sex differences in ¹⁸F-FDG and ¹⁸F-Florbetaben uptake are missing. The aim of this study was to evaluate the suitability of ¹⁸F-FDG– and ¹⁸F-Florbetaben–PET in 7-month-old female 5XFAD and to assess possible sex differences between male and female 5XFAD mice. We could demonstrate that female 5XFAD mice showed a significant reduction in brain glucose metabolism and increased cerebral amyloid deposition compared with wild type animals, in accordance with the pathology seen in AD patients. Furthermore, we showed for the first time that the hypometabolism in 5XFAD mice is gender-dependent and more pronounced in female mice. Therefore, these results support the feasibility of small animal PET imaging with ¹⁸F-FDG- and ¹⁸F-Florbetaben in 5XFAD mice in both, male and female animals. Moreover, our findings highlight the need to account for sex differences in studies working with 5XFAD mice.

Arginine and Arginine-Rich Peptides as Modulators of Protein Aggregation and Cytotoxicity Associated With Alzheimer's Disease

A substantial body of evidence indicates cationic, arginine-rich peptides (CARPs) are effective therapeutic compounds for a range of neurodegenerative pathologies, with beneficial effects including the reduction of excitotoxic cell death and mitochondrial dysfunction. CARPs, therefore, represent an emergent class of promising neurotherapeutics with multimodal mechanisms of action. Arginine itself is a known chaotrope, able to prevent misfolding and aggregation of proteins. The putative role of proteopathies in chronic neurodegenerative diseases such as Alzheimer's disease (AD) warrants investigation into whether CARPs could also prevent the aggregation and cytotoxicity of amyloidogenic proteins, particularly amyloid-beta and tau. While monomeric arginine is well-established as an inhibitor of protein aggregation in solution, no studies have comprehensively discussed the anti-aggregatory properties of arginine and CARPs on proteins associated with neurodegenerative disease. Here, we review the structural, physicochemical, and self-associative properties of arginine and the guanidinium moiety, to explore the mechanisms underlying the modulation of protein aggregation by monomeric and multimeric arginine molecules. Arginine-rich peptide-based inhibitors of amyloid-beta and tau aggregation are discussed, as well as further modulatory roles which could reduce proteopathic cytotoxicity, in the context of therapeutic development for AD.

The State of The Art on Acetylcholinesterase Inhibitors in the Treatment of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic disabling disease that affects the central nervous system. The main consequences of AD include the decline of cognitive functions and language disorders. One of the causes leading to AD is the decrease of neurotransmitter acetylcholine (ACh) levels in the brain, in part due to a higher activity of acetylcholinesterase (AChE), the enzyme responsible for its degradation. Many acetylcholinesterase inhibitors (AChEIs), both natural and synthetic, have been developed and used through the years to counteract the progression of the disease. The first of such drugs approved for a therapeutic use was tacrine, that binds through a reversible bond to the enzyme. However, tacrine has since been withdrawn because of its adverse effects. Currently, donepezil and galantamine are very promising AChEIs with clinical benefits. Moreover, rivastigmine is considered a pseudo-irreversible compound with anti-AChE action, providing similar effects at the clinical level. The purpose of this review is to provide an overview of what has been published over the last decade on the effectiveness of AChEIs in AD, analysing the most relevant issues under the clinical and methodological profiles and the consequent possible welfare effects for the whole world. Furthermore, novel drugs and possible therapeutic approaches are also discussed.

Brain Targeting and Aβ Binding Bifunctional Nanoparticles Inhibit Amyloid Protein Aggregation in APP/PS1 Transgenic Mice

Alzheimer's disease (AD) is an insidious and progressive neurodegenerative disease with few disease-modifying treatments. A variety of peptide/protein drugs have neuroprotective effects, which brings new hope for the treatment of AD. However, the application of these drugs is limited because of their low specificity and difficulty in crossing the blood-brain barrier. Herein, using the phage display technology, we identified the Aβ oligomer binding peptide (KH) and the brain targeting peptide (IS). We combined these peptides to develop a bifunctional nanoparticle (IS@NP/KH) for the delivery of Aβ_1-42 oligomer binding peptide into the brain. Intranasal administration of IS@NP/KH significantly attenuated the cognitive and behavioral deficits and reduced the Aβ deposition in the brain of an AD animal model (APPswe/PS 1d9 double-transgenic mice). Our results suggest that intranasal IS@NP/KH administration could be a novel therapeutic strategy for the treatment of AD.

Swapping the Positions in a Cross-Strand Lateral Ion-Pairing Interaction between Ammonium- and Carboxylate-Containing Residues in a β-Hairpin

Cross-strand lateral ion-pairing interactions are important for antiparallel β-sheet stability. Statistical studies suggested that swapping the position of cross-strand lateral residues should not significantly affect the interaction. Herein, we swapped the position of ammonium- and carboxylate-containing residues with different side-chain lengths in a cross-strand lateral ion-pairing interaction in a β-hairpin. The peptides were analyzed by 2D-NMR. The fraction folded population and folding free energy were derived from the chemical shift data. The ion-pairing interaction energy was derived using double mutant cycle analysis. The general trends for the fraction folded population and interaction energetics remained similar upon swapping the position of the interacting charged residues. The most stabilizing cross-strand interactions were between short residues, similar to the unswapped study. However, the fraction folded populations for most of the swapped peptides were higher compared to the corresponding unswapped peptides. Furthermore, subtle differences in the ion-pairing interaction energy upon swapping were observed, most likely due to the “unleveled” relative positioning of the interacting residues created by the inherent right-handed twist of the structure. These results should be useful for developing functional peptides that rely on lateral ion-pairing interactions across antiparallel β-strands.

Intranasal drug delivery for treatment of Alzheimer's disease

The Alzheimer's disease is a neurodegenerative condition with severe consequences interfering with patient quality of life. It is characterized as a progressive and irreversible brain disorder hampering memory and thinking, affecting the capacity to perform daily tasks leading to physical and cognitive incapacitation. The conventional treatment occurs by the oral route, but it presents relevant drawbacks such as low bioavailability, fast metabolism, limited brain exposure, and undesirable side effects. The intranasal route has been proposed as a promising alternative to deliver drugs and improve the Alzheimer's disease treatment. Still, there is not a clear alternative delivery system available in the market with advantageous bioavailability and safety. The aim of this review is to perform an overview on the strategies for drug intranasal delivery for Alzheimer's disease treatment. The advantages and disadvantages of this delivery route and the delivery systems developed so far are discussed. A special focus is given on the use of permeation enhancers, the types of intranasal drug delivery devices, as well as possible toxicity concerns.

New approaches to symptomatic treatments for Alzheimer's disease

BACKGROUND

Successful development of agents that improve cognition and behavior in Alzheimer's disease (AD) is critical to improving the lives of patients manifesting the symptoms of this progressive disorder.

DISCUSSION

There have been no recent approvals of cognitive enhancing agents for AD. There are currently 6 cognitive enhancers in Phase 2 trials and 4 in phase 3. They represent a variety of novel mechanisms. There has been progress in developing new treatments for neuropsychiatric symptoms in AD with advances in treatment of insomnia, psychosis, apathy, and agitation in AD. There are currently 4 AD-related psychotropic agents in Phase 2 trials and 7 in Phase 3 trials. Many novel mechanisms are being explored for the treatment of cognitive and behavioral targets. Progress in trial designs, outcomes measures, and population definitions are improving trial conduct for symptomatic treatment of AD.

CONCLUSIONS

Advances in developing new agents for cognitive and behavioral symptoms of AD combined with enhanced trial methods promise to address the unmet needs of patients with AD for improved cognition and amelioration of neuropsychiatric symptoms.

Ophthalmic Administration of a DNA Plasmid Harboring the Murine Tph2 Gene: Evidence of Recombinant Tph2-FLAG in Brain Structures

Tryptophan hydroxylase-type 2 (Tph2) is the first rate-limiting step in the biosynthesis of serotonin (5-HT) in the brain. The ophthalmic administration (Op-Ad) is a non-invasive method that allows delivering genetic vehicles through the eye and reaches the brain. Here, the murine Tph2 gene was cloned in a non-viral vector (pIRES-hrGFP-1a), generating pIRES-hrGFP-1a-Tph2, plus the FLAG-tag. Recombinant Tph2-FLAG was detected and tested in vitro and in vivo, where 25 μg of pIRES-hrGFP-1a-Tph2-FLAG was Op-Ad to mice. The construct was capable of expressing and producing the recombinant Tph2-FLAG in vitro and in vivo. The in vivo assays showed that the construct efficiently crossed the Hemato-Ocular Barrier and the Blood-Brain Barrier, reached brain cells, passed the optical nerves, and transcribed mRNA-Tph2-FLAG in different brain areas. The recombinant Tph2-FLAG was observed in amygdala and brainstem, mainly in raphe dorsal and medial. Relative Tph2 expression of threefold over basal level was recorded three days after Op-Ad. These results demonstrated that pIRES-hrGFP-Tph2-FLAG, administrated through the eyes was capable of reaching the brain, transcribing, and translating Tph2. In conclusion, this study showed the feasibility of delivering therapeutic genes, such as the Tph2, the first enzyme, rate-limiting step in the 5-HT biosynthesis.

RP1, a RAGE antagonist peptide, can improve memory impairment and reduce Aβ plaque load in the APP/PS1 mouse model of Alzheimer's disease

Amyloid-β (Aβ) accumulation is a pathological hallmark of Alzheimer's disease (AD). The receptor for advanced glycation end products (RAGE) is involved in the production and accumulation of Aβ. RP1, a peptide antagonist of RAGE, was screened by phage display technology in our previous studies, and its neuroprotective effects on an AD cell model have been confirmed. However, its efficacy in vivo remains unclear. Here, the intranasal delivery of RP1 to APPSwe/PS1dE9 (APP/PS1) mice significantly improved memory impairment and relieved the Aβ burden by decreasing the expression of amyloid precursor protein and β-secretase. RNA-sequencing (RNA-seq) was utilized to identify differentially expressed genes (DEGs) in APP/PS1 mice after RP1 administration. Several DEGs in RAGE downstream signalling pathways were downregulated. Some transcription factors (such as Fos) and the pathways enriched in the remarkable modules may also be related to the efficacy of RP1. In conclusion, RP1 significantly improves the AD symptoms of APP/PS1 mice, and the RNA-seq results provide new ideas for elucidating the possible mechanisms of RP1 treatment.

Overcoming the blood-brain barrier in neurodegenerative disorders and brain tumours

Drug delivery is one of the major challenges in the treatment of central nervous system disorders. The brain needs to be protected from harmful agents, which are done by the capillary network, the so-called blood-brain barrier (BBB). This protective guard also prevents the delivery of therapeutic agents to the brain and limits the effectiveness of treatment. For this reason, various strategies have been explored by scientists for overcoming the BBB from disruption of the BBB to targeted delivery of nanoparticles (NPs) and cells and immunotherapy. In this review, different promising brain drug delivery strategies including disruption of tight junctions in the BBB, enhanced transcellular transport by peptide-based delivery, local delivery strategies, NP delivery, and cell-based delivery have been fully discussed.

Cationic Arginine-Rich Peptides (CARPs): A Novel Class of Neuroprotective Agents With a Multimodal Mechanism of Action

There are virtually no clinically available neuroprotective drugs for the treatment of acute and chronic neurological disorders, hence there is an urgent need for the development of new neuroprotective molecules. Cationic arginine-rich peptides (CARPs) are an expanding and relatively novel class of compounds, which possess intrinsic neuroprotective properties. Intriguingly, CARPs possess a combination of biological properties unprecedented for a neuroprotective agent including the ability to traverse cell membranes and enter the CNS, antagonize calcium influx, target mitochondria, stabilize proteins, inhibit proteolytic enzymes, induce pro-survival signaling, scavenge toxic molecules, and reduce oxidative stress as well as, having a range of anti-inflammatory, analgesic, anti-microbial, and anti-cancer actions. CARPs have also been used as carrier molecules for the delivery of other putative neuroprotective agents across the blood-brain barrier and blood-spinal cord barrier. However, there is increasing evidence that the neuroprotective efficacy of many, if not all these other agents delivered using a cationic arginine-rich cell-penetrating peptide (CCPPs) carrier (e.g., TAT) may actually be mediated largely by the properties of the carrier molecule, with overall efficacy further enhanced according to the amino acid composition of the cargo peptide, in particular its arginine content. Therefore, in reviewing the neuroprotective mechanisms of action of CARPs we also consider studies using CCPPs fused to a putative neuroprotective peptide. We review the history of CARPs in neuroprotection and discuss in detail the intrinsic biological properties that may contribute to their cytoprotective effects and their usefulness as a broad-acting class of neuroprotective drugs.

Nanoscopic Insights of Amphiphilic Peptide against the Oligomer Assembly Process to Treat Huntington's Disease

Finding an effective therapeutic regimen is an urgent demand for various neurodegenerative disorders including Huntington's disease (HD). For the difficulties in observing the dynamic aggregation and oligomerization process of mutant Huntingtin (mHtt) in vivo, the evaluation of potential drugs at the molecular protein level is usually restricted. By combing lifetime-based fluorescence microscopies and biophysical tools, it is showcased that a designed amphiphilic peptide, which targets the mHtt at an early stage, can perturb the oligomer assembly process nanoscopically, suppress the amyloid property of mHtt, conformationally transform the oligomers and/or aggregates of mHtt, and ameliorate mHtt-induced neurological damage and aggregation in cell and HD mouse models. It is also found that this amphiphilic peptide is able to transport to the brain and rescue the memory deficit through intranasal administration, indicating its targeting specificity in vivo. In summary, a biophotonic platform is provided to investigate the oligomerization/aggregation process in detail that offers insight into the design and effect of a targeted therapeutic agent for Huntington's disease.

Alleviation of symptoms of Alzheimer's disease by diminishing Aβ neurotoxicity and neuroinflammation

Alzheimer's disease (AD) is one of the most prevailing neurodegenerative illnesses in the elderly. Accumulation of amyloid-β peptide (Aβ) and inflammation play critical roles in the pathogenesis and development of AD. Multi-target drugs may interdict the progress of AD through a synergistic mechanism. A neuromodulator, 2-((1H-benzo[d]imidazole-2-yl)methoxy)benzoic acid (BIBA), consisting of an Aβ-targeting group and a derivative of anti-inflammatory aspirin was designed as a potential anti-AD agent. BIBA exhibits a remarkable inhibitory effect on the self- and metal-induced Aβ aggregations and shows outstanding anti-inflammatory activity simultaneously. The neurotoxicity of Aβ aggregates is attenuated, and the production of pro-inflammatory cytokines (PICs), such as IL-6, IL-1β and TNF-α, in microglia stimulated by lipopolysaccharide (LPS) or Aβ is reduced. Owing to the synergy between the inhibition of Aβ oligomerization and downregulation of PICs, BIBA markedly prolongs the lifespan and relieves the Aβ-induced paralysis of Aβ-transgenic Caenorhabditis elegans, thus showing the potential to ameliorate the symptoms of AD through inhibiting Aβ neurotoxicity and deactivating microglia. These findings demonstrate that both Aβ aggregation and neuroinflammation are therapeutic targets for anti-AD drugs, and dual-functional agents that integrate anti-Aβ and anti-inflammatory capabilities have great advantages over the traditional single-target agents for AD treatment.

Early-Onset Molecular Derangements in the Olfactory Bulb of Tg2576 Mice: Novel Insights Into the Stress-Responsive Olfactory Kinase Dynamics in Alzheimer's Disease

The olfactory bulb (OB) is the first processing station in the olfactory pathway. Despite smell impairment, which is considered an early event in Alzheimer’s disease (AD), little is known about the initial molecular disturbances that accompany the AD development at olfactory level. We have interrogated the time-dependent OB molecular landscape in Tg2576 AD mice prior to the appearance of neuropathological amyloid plaques (2-, and 6-month-old), using combinatorial omics analysis. The metabolic modulation induced by overproduction of human mutated amyloid precursor protein (APP) clearly differs between both time points. Besides the progressive perturbation of the APP interactome, functional network analysis unveiled an inverse regulation of downstream extracellular signal-regulated kinase (ERK1/2), and p38 mitogen-activated protein kinase (MAPK) routes in 2-month-old Tg2576 mice with respect to wild-type (WT) mice. In contrast, Akt and MAPK kinase 4 (SEK1)/ stress-activated protein kinase (SAPK) axis were parallel activated in the OB of 6-months-old-Tg2576 mice. Furthermore, a survival kinome profiling performed during the aging process (2-, 6-, and 18-month-old) revealed that olfactory APP overexpression leads to changes in the activation dynamics of protein kinase A (PKA), and SEK1/MKK4-SAPK/JNK between 6 and 18 months of age, when memory deficits appear and AD pathology is well established in transgenic mice. Interestingly, both olfactory pathways were differentially activated in a stage-dependent manner in human sporadic AD subjects with different neuropathological grading. Taken together, our data reflect the early impact of mutated APP on the OB molecular homeostasis, highlighting the progressive modulation of specific signaling pathways during the olfactory amyloidogenic pathology.

An Engineered Variant of the B1 Domain of Protein G Suppresses the Aggregation and Toxicity of Intra- and Extracellular Aβ42

Intra- and extraneuronal deposition of amyloid β (Aβ) peptides have been linked to Alzheimer's disease (AD). While both intra- and extraneuronal Aβ deposits affect neuronal cell viability, the molecular mechanism by which these Aβ structures, especially when intraneuronal, do so is still not entirely understood. This makes the development of inhibitors challenging. To prevent the formation of toxic Aβ structural assemblies so as to prevent neuronal cell death associated with AD, we used a combination of computational and combinatorial-directed evolution approaches to develop a variant of the HTB1 protein (HTB1_M2). HTB1_M2 inhibits in vitro self-assembly of Aβ42 peptide and shifts the Aβ42 aggregation pathway to the formation of oligomers that are nontoxic to neuroblastoma SH-SY5Y cells overexpressing or treated with Aβ42 peptide. This makes HTB1_M2 a potential therapeutic lead in the development of AD-targeted drugs and a tool for elucidating conformational changes in the Aβ42 peptide.

Microenvironment Remodeling Micelles for Alzheimer's Disease Therapy by Early Modulation of Activated Microglia

Current strategies for Alzheimer's disease (AD) treatments focus on pathologies in the late stage of the disease progression. Poor clinical outcomes are displayed due to the irreversible damages caused by early microglia abnormality which triggers disease development before identical symptoms emerge. Based on the crosstalk between microglia and brain microenvironment, a reactive oxygen species (ROS)-responsive polymeric micelle system (Ab-PEG-LysB/curcumin (APLB/CUR)) is reported to normalize the oxidative and inflammatory microenvironment and reeducate microglia from an early phase of AD. Through an β-amyloid (Aβ) transportation-mimicked pathway, the micelles can accumulate into the diseased regions and exert synergistic effects of polymer-based ROS scavenging and cargo-based Aβ inhibition upon microenvironment stimuli. This multitarget strategy exhibits gradual correction of the brain microenvironment, efficient neuroprotection, and microglia modulation, leading to decreased Aβ plaque burdens and consequently enhanced cognitive functions in APPswe/PSEN1dE9 model mice. The results indicate that microglia can be exploited as an early target for AD treatment and their states can be controlled via microenvironment modulation.

Review of Current Strategies for Delivering Alzheimer's Disease Drugs across the Blood-Brain Barrier

Effective therapy for Alzheimer’s disease is a major challenge in the pharmaceutical sciences. There are six FDA approved drugs (e.g., donepezil, memantine) that show some effectiveness; however, they only relieve symptoms. Two factors hamper research. First, the cause of Alzheimer’s disease is not fully understood. Second, the blood-brain barrier restricts drug efficacy. This review summarized current knowledge relevant to both of these factors. First, we reviewed the pathophysiology of Alzheimer’s disease. Next, we reviewed the structural and biological properties of the blood-brain barrier. We then described the most promising drug delivery systems that have been developed in recent years; these include polymeric nanoparticles, liposomes, metallic nanoparticles and cyclodextrins. Overall, we aim to provide ideas and clues to design effective drug delivery systems for penetrating the blood-brain barrier to treat Alzheimer’s disease.

PR1P ameliorates neurodegeneration through activation of VEGF signaling pathway and remodeling of the extracellular environment

Neurodegenerative diseases affect millions of people worldwide. Optic neuropathies are the most commonly occurring neurodegenerative diseases, characterized by progressive retinal ganglion cell (RGC) degeneration. We recently reported that Prominin-1, a protein found on the surface of stem cells, interacts with VEGF and enhances its activity. VEGF is known to have various protective roles in the nervous system. Subsequently, we have developed a 12-mer peptide derived from Prominin-1, named PR1P, and investigated its effects on neuronal survival of damaged RGCs in a rat model of optic nerve crush (ONC). PR1P prevented RGC apoptosis resulting in improvement of retinal function in the rat ONC model. PR1P treatment significantly increased phosphorylation of ERK and AKT and expression its downstream proteins c-fos and Egr-1 in the retina. Additionally, PR1P beneficially increased the MMP-9/TIMP-1 ratio and promoted glial activation in the retina of ONC rats. Thus, PR1P displayed neuroprotective effects through enhanced VEGF-driven neuronal survival and reconstruction of the extracellular environment in ONC model. Our data indicate that PR1P may be a promising new clinical candidate for the treatment of neurodegenerative diseases.

Membrane Active Peptides and Their Biophysical Characterization

In the last 20 years, an increasing number of studies have been reported on membrane active peptides. These peptides exert their biological activity by interacting with the cell membrane, either to disrupt it and lead to cell lysis or to translocate through it to deliver cargos into the cell and reach their target. Membrane active peptides are attractive alternatives to currently used pharmaceuticals and the number of antimicrobial peptides (AMPs) and peptides designed for drug and gene delivery in the drug pipeline is increasing. Here, we focus on two most prominent classes of membrane active peptides; AMPs and cell-penetrating peptides (CPPs). Antimicrobial peptides are a group of membrane active peptides that disrupt the membrane integrity or inhibit the cellular functions of bacteria, virus, and fungi. Cell penetrating peptides are another group of membrane active peptides that mainly function as cargo-carriers even though they may also show antimicrobial activity. Biophysical techniques shed light on peptide–membrane interactions at higher resolution due to the advances in optics, image processing, and computational resources. Structural investigation of membrane active peptides in the presence of the membrane provides important clues on the effect of the membrane environment on peptide conformations. Live imaging techniques allow examination of peptide action at a single cell or single molecule level. In addition to these experimental biophysical techniques, molecular dynamics simulations provide clues on the peptide–lipid interactions and dynamics of the cell entry process at atomic detail. In this review, we summarize the recent advances in experimental and computational investigation of membrane active peptides with particular emphasis on two amphipathic membrane active peptides, the AMP melittin and the CPP pVEC.

Intranasal Administration of a Naked Plasmid Reached Brain Cells and Expressed Green Fluorescent Protein, a Candidate for Future Gene Therapy Studies

BACKGROUND

Intranasal administration (Int adm) has been well-studied and offers the possibility to deliver larger molecular weight biologics, such as proteins, viral vectors, nanoparticles, and naked plasmids to the brain and treat a variety of diseases in the central nervous system. The predominant challenge in this field is finding efficient vectors that are capable of crossing the blood-brain barrier (BBB).

OBJECTIVES

Here, we investigated whether a naked plasmid (pIRES-hrGFP-1a), could cross the BBB, reach brain cells and express green fluorescent protein (GFP) after int-adm and propose it as candidate for future gene therapy studies.

MATERIAL AND METHODS

Thirty-six mice were divided into 2 groups. Eighteen animals were assigned to each cluster. Mice from experimental groups received 25 μg of pIRES-hrGFP-1a. The control groups received 25 μl of PBS. Plasmids were given intranasally by applying little drops in both nostrils. Twenty-four hours later, the mice were sacrificed, and their brains were removed. Later, PCR, RT-PCR, and immunohistochemical techniques were performed.

RESULTS

pIRES-hrGFP-1a crossed the BBB and was mainly detected in the olfactory nerves (20%) and hypothalamus (16%). In contrast, GFP/18S-expressing mRNAs were detected mostly in the olfactory bulbs (95%), frontal cortex (71%) and amygdala (60%). GFP was detected in the olfactory bulb, hippocampus, frontal cortex and brainstem at 24 h.

CONCLUSIONS

pIRES-hrGFP-1a could be considered a good candidate for gene therapy studies. In the future could be cloned some therapeutic genes in the pIRES-hrGFP-1a and could transcribe and translates deficient proteins that are required to restore a function.

Use of Peptides for the Management of Alzheimer's Disease: Diagnosis and Inhibition

Alzheimer's disease (AD) is a form of dementia and the most common progressive neurodegenerative disease (ND). The targeting of amyloid-beta (Aβ) aggregation is one of the most widely used strategies to manage AD, and efforts are being made globally to develop peptide-based compounds for the early diagnosis and treatment of AD. Here, we briefly discuss the use of peptide-based compounds for the early diagnosis and treatment of AD and the use of peptide-based inhibitors targeting various Aβ aggregation checkpoints. In addition, we briefly discuss recent applications of peptide-based inhibitors against various AD targets including amyloid beta, β-site amyloid precursor protein cleaving enzyme 1 (BACE1), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), tyrosine phosphatase (TP) and potassium channel KV1.3.

Peptides as Potential Therapeutics for Alzheimer's Disease

Intracellular synthesis, folding, trafficking and degradation of proteins are controlled and integrated by proteostasis. The frequency of protein misfolding disorders in the human population, e.g., in Alzheimer's disease (AD), is increasing due to the aging population. AD treatment options are limited to symptomatic interventions that at best slow-down disease progression. The key biochemical change in AD is the excessive accumulation of per-se non-toxic and soluble amyloid peptides (Aβ(1-37/44), in the intracellular and extracellular space, that alters proteostasis and triggers Aβ modification (e.g., by reactive oxygen species (ROS)) into toxic intermediate, misfolded soluble Aβ peptides, Aβ dimers and Aβ oligomers. The toxic intermediate Aβ products aggregate into progressively less toxic and less soluble protofibrils, fibrils and senile plaques. This review focuses on peptides that inhibit toxic Aβ oligomerization, Aβ aggregation into fibrils, or stabilize Aβ peptides in non-toxic oligomers, and discusses their potential for AD treatment.

An intranasally delivered peptide drug ameliorates cognitive decline in Alzheimer transgenic mice

Alzheimer's disease (AD) is the most common neurodegenerative disease. Imbalance between the production and clearance of amyloid β (Aβ) peptides is considered to be the primary mechanism of AD pathogenesis. This amyloid hypothesis is supported by the recent success of the human anti‐amyloid antibody aducanumab, in clearing plaque and slowing clinical impairment in prodromal or mild patients in a phase Ib trial. Here, a peptide combining polyarginines (polyR) (for charge repulsion) and a segment derived from the core region of Aβ amyloid (for sequence recognition) was designed. The efficacy of the designed peptide, R₈‐Aβ(25–35), on amyloid reduction and the improvement of cognitive functions were evaluated using APP/PS1 double transgenic mice. Daily intranasal administration of PEI‐conjugated R₈‐Aβ(25–35) peptide significantly reduced Aβ amyloid accumulation and ameliorated the memory deficits of the transgenic mice. Intranasal administration is a feasible route for peptide delivery. The modular design combining polyR and aggregate‐forming segments produced a desirable therapeutic effect and could be easily adopted to design therapeutic peptides for other proteinaceous aggregate‐associated diseases.

Nose-to-brain peptide delivery - The potential of nanotechnology

Nose-to-brain (N-to-B) delivery offers to protein and peptide drugs the possibility to reach the brain in a non-invasive way. This article is a comprehensive review of the state-of-the-art of this emerging peptide delivery route, as well as of the challenges associated to it. Emphasis is given on the potential of nanosized drug delivery carriers to enhance the direct N-to-B transport of protein or peptide drugs. In particular, polymer- and lipid- based nanocarriers are comparatively analyzed in terms of the influence of their physicochemical characteristics and composition on their in vivo fate and efficacy. The use of biorecognitive ligands and permeation enhancers in order to enhance their brain targeting efficiency is also discussed. The article concludes highlighting the early stage of this research field and its still unveiled potential. The final message is that more explicatory PK/PD studies are required in order to achieve the translation from preclinical to the clinical development phase.