The therapeutic potential of the neuroactive peptides of soluble amyloid precursor protein-alpha in Alzheimer's disease and related neurological disorders

sAPPα Peptide Promotes Damaged Microglia to Clear Alzheimer's Amyloid-β via Restoring Mitochondrial Function

Alzheimer's disease (AD) is an age-related neurodegenerative disease with amyloid-β (Aβ) deposition as the main pathological feature. It's an important challenge to find new ways to clear Aβ from the brain. The soluble amyloid precursor protein α (sAPPα) is a neuroprotective protein and can attenuate neuronal damage, including toxic Aβ. However, the regulatory role of sAPPα in non-neuronal cells, such as microglia, is less reported and controversial. Here, we showed that sAPPα promoted the phagocytosis and degradation of Aβ in both normal and damaged microglia. Moreover, the function of damaged microglia was improved by the sAPPα through normalizing mitochondrial function. Furthermore, the results of molecular docking simulation showed that sAPPα had a good affinity with Aβ. We preliminarily reveal that sAPPα is similar to antibodies and can participate in the regulation of microglia phagocytosis and degradation of Aβ after binding to Aβ. sAPPα is expected to be a mild and safe peptide drug or drug carrier for AD.

Macrophage Membrane-Modified MoS2 Quantum Dots as a Nanodrug for Combined Multi-Targeting of Alzheimer's Disease

The complex pathological mechanism of Alzheimer's disease (AD) limits the efficacy of simple drug therapy, and drugs are difficult to penetrate the blood-brain barrier (BBB). Therefore, it is a breakthrough to enhance the therapeutic effect of AD by rationally using multiple therapeutic strategies to inhibit multiple pathological targets. In this study, macrophage membrane (MM) with active targeting inflammation function is used to functionalize molybdenum disulfide quantum dots (MoS2 QDs) with the properties of elimination of reactive oxygen species (ROS) and anti-Aβ1-42 deposition to form the nano drug (MoS2 QDs/MM), and play the role of multi-target combined therapy with NIR. The results show that MoS2 QDs/MM has a targeted therapeutic effect on ROS elimination and anti-deposition of Aβ1-42 . In addition, the combined therapy group effectively reduced Aβ1-42 mediated cytotoxicity. The modification of MM could effectively target the brain, and NIR irradiation could actively increase the cross of BBB of materials. In vivo behavioral study also show that APP/PS1 mice in the combined treatment group showed the similar exploration desire and learning ability to mice in the group of WT. MoS2 QDs/MM is an excellent nano drug with multiple effects, which has advantages in the field of neurological diseases with crisscross pathogenesis.

Metallic Nanocarriers for Therapeutic Peptides: Emerging Solutions Addressing the Delivery Challenges in Brain Ailments

Peptides and proteins have recently emerged as efficient therapeutic alternatives to conventional therapies. Although they emerged a few decades back, extensive exploration of various ailments or disorders began recently. The drawbacks of current chemotherapies and irradiation treatments, such as drug resistance and damage to healthy tissues, have enabled the rise of peptides in the quest for better prospects. The chemical tunability and smaller size make them easy to design selectively for target tissues. Other remarkable properties include antifungal, antiviral, anti-inflammatory, protection from hemorrhage stroke, and as therapeutic agents for gastric disorders and Alzheimer and Parkinson diseases. Despite these unmatched properties, their practical applicability is often hindered due to their weak susceptibility to enzymatic digestion, serum degradation, liver metabolism, kidney clearance, and immunogenic reactions. Several methods are adapted to increase the half-life of peptides, such as chemical modifications, fusing with Fc fragment, change in amino acid composition, and carrier-based delivery. Among these, nanocarrier-mediated encapsulation not only increases the half-life of the peptides in vivo but also aids in the targeted delivery. Despite its structural complexity, they also efficiently deliver therapeutic molecules across the blood-brain barrier. Here, in this review, we tried to emphasize the possible potentiality of metallic nanoparticles to be used as an efficient peptide delivery system against brain tumors and neurodegenerative disorders. SIGNIFICANCE STATEMENT: In this review, we have emphasized the various therapeutic applications of peptides/proteins, including antimicrobial, anticancer, anti-inflammatory, and neurodegenerative diseases. We also focused on these peptides' challenges under physiological conditions after administration. We highlighted the importance and potentiality of metallic nanocarriers in the ability to cross the blood-brain barrier, increasing the stability and half-life of peptides, their efficiency in targeting the delivery, and their diagnostic applications.

The Labyrinthine Landscape of APP Processing: State of the Art and Possible Novel Soluble APP-Related Molecular Players in Traumatic Brain Injury and Neurodegeneration

Amyloid Precursor Protein (APP) and its cleavage processes have been widely investigated in the past, in particular in the context of Alzheimer’s Disease (AD). Evidence of an increased expression of APP and its amyloidogenic-related cleavage enzymes, β-secretase 1 (BACE1) and γ-secretase, at the hit axon terminals following Traumatic Brain Injury (TBI), firstly suggested a correlation between TBI and AD. Indeed, mild and severe TBI have been recognised as influential risk factors for different neurodegenerative diseases, including AD. In the present work, we describe the state of the art of APP proteolytic processing, underlining the different roles of its cleavage fragments in both physiological and pathological contexts. Considering the neuroprotective role of the soluble APP alpha (sAPPα) fragment, we hypothesised that sAPPα could modulate the expression of genes of interest for AD and TBI. Hence, we present preliminary experiments addressing sAPPα-mediated regulation of BACE1, Isthmin 2 (ISM2), Tetraspanin-3 (TSPAN3) and the Vascular Endothelial Growth Factor (VEGFA), each discussed from a biological and pharmacological point of view in AD and TBI. We finally propose a neuroprotective interaction network, in which the Receptor for Activated C Kinase 1 (RACK1) and the signalling cascade of PKCβII/nELAV/VEGF play hub roles, suggesting that vasculogenic-targeting therapies could be a feasible approach for vascular-related brain injuries typical of AD and TBI.