Cortistatin deficiency reveals a dysfunctional brain endothelium with impaired gene pathways, exacerbated immune activation, and disrupted barrier integrity.

BACKGROUND: Brain activity governing cognition and behaviour depends on the fine-tuned microenvironment provided by a tightly controlled blood-brain barrier (BBB). Brain endothelium dysfunction is a hallmark of BBB breakdown in most neurodegenerative/neuroinflammatory disorders. Therefore, the identification of new endogenous molecules involved in endothelial cell disruption is essential to better understand BBB dynamics. Cortistatin is a neuroimmune mediator with anti-inflammatory and neuroprotective properties that exerts beneficial effects on the peripheral endothelium. However, its role in the healthy and injured brain endothelium remains to be evaluated. Herein, this study aimed to investigate the potential function of endogenous and therapeutic cortistatin in regulating brain endothelium dysfunction in a neuroinflammatory/neurodegenerative environment. METHODS: Wild-type and cortistatin-deficient murine brain endothelium and human cells were used for an in vitro barrier model, where a simulated ischemia-like environment was mimicked. Endothelial permeability, junction integrity, and immune response in the presence and absence of cortistatin were evaluated using different size tracers, immunofluorescence labelling, qPCR, and ELISA. Cortistatin molecular mechanisms underlying brain endothelium dynamics were assessed by RNA-sequencing analysis. Cortistatin role in BBB leakage was evaluated in adult mice injected with LPS. RESULTS: The endogenous lack of cortistatin predisposes endothelium weakening with increased permeability, tight-junctions breakdown, and dysregulated immune activity. We demonstrated that both damaged and uninjured brain endothelial cells isolated from cortistatin-deficient mice, present a dysregulated and/or deactivated genetic programming. These pathways, related to basic physiology but also crucial for the repair after damage (e.g., extracellular matrix remodelling, angiogenesis, response to oxygen, signalling, and metabolites transport), are dysfunctional and make brain endothelial barrier lacking cortistatin non-responsive to any further injury. Treatment with cortistatin reversed in vitro hyperpermeability, tight-junctions disruption, inflammatory response, and reduced in vivo BBB leakage. CONCLUSIONS: The neuropeptide cortistatin has a key role in the physiology of the cerebral microvasculature and its presence is crucial to develop a canonical balanced response to damage. The reparative effects of cortistatin in the brain endothelium were accompanied by the modulation of the immune function and the rescue of barrier integrity. Cortistatin-based therapies could emerge as a novel pleiotropic strategy to ameliorate neuroinflammatory/neurodegenerative disorders with disrupted BBB.

A glutamine-based single α-helix scaffold to target globular proteins.

The binding of intrinsically disordered proteins to globular ones can require the folding of motifs into α-helices. These interactions offer opportunities for therapeutic intervention but their modulation with small molecules is challenging because they bury large surfaces. Linear peptides that display the residues that are key for binding can be targeted to globular proteins when they form stable helices, which in most cases requires their chemical modification. Here we present rules to design peptides that fold into single α-helices by instead concatenating glutamine side chain to main chain hydrogen bonds recently discovered in polyglutamine helices. The resulting peptides are uncharged, contain only natural amino acids, and their sequences can be optimized to interact with specific targets. Our results provide design rules to obtain single α-helices for a wide range of applications in protein engineering and drug design.

Peptide Shuttles for Blood-Brain Barrier Drug Delivery.

The blood-brain barrier (BBB) limits the delivery of therapeutics to the brain but also represents the main gate for nutrient entrance. Targeting the natural transport mechanisms of the BBB offers an attractive route for brain drug delivery. Peptide shuttles are able to use these mechanisms to increase the transport of compounds that cannot cross the BBB unaided. As peptides are a group of biomolecules with unique physicochemical and structural properties, the field of peptide shuttles has substantially evolved in the last few years. In this review, we analyze the main classifications of BBB-peptide shuttles and the leading sources used to discover them.

Anti-EGF nanobodies enhance the antitumoral effect of osimertinib and overcome resistance in non-small cell lung cancer (NSCLC) cellular models.

Osimertinib is a third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) that is effective against the EGFR T790M mutation in patients with advanced non-small-cell lung cancer (NSCLC). However, acquired resistance appears invariably due to several mechanisms. The strategy of using EGF-targeted nanobodies (Nbs) to block the initial step of the EGFR pathway constitutes a new research area. Nbs offer several advantages compared to traditional mAbs, such as their reduced size, increased stability, and tissue penetration, which provide key advantages for targeting soluble tumoral growth factors. In this study we investigated the efficacy of anti-EGF Nbs to reduce Osimertinib resistance. Two anti-EGF Nbs, generated in our laboratory, were shown to inhibit cell viability and colony formation in PC9 and PC9-derived osimertinib-resistant cell lines. The combination of these Nbs with osimertinib improved the antitumor efficacy of this EGFR-TKI in cell viability and colony formation experiments. In a mechanistic study of the EGFR pathway, the combination treatment dampened the activation of downstream proteins such as Akt and Erk1/2 MAP kinases. In addition, it increased cellular apoptosis and decreased the expression of Hes1, a cancer stem cell marker involved in metastasis and osimertinib resistance. We conclude that the addition of anti-EGF nanobodies enhances the antitumor properties of osimertinib, thus representing a potentially effective strategy for NSCLC patients.

NIR and glutathione trigger the surface release of methotrexate linked by Diels-Alder adducts to anisotropic gold nanoparticles.

The administration and controlled release of drugs over time remains one of the greatest challenges of science today. In the nanomaterials field, anisotropic gold nanoparticles (AuNPs) with plasmon bands centered at the near-infrared region (NIR), such as gold nanorods (AuNRs) and gold nanoprisms (AuNPrs), under laser irradiation, locally increase the temperature, allowing the release of drugs. In this sense, temporally controlled drug delivery could be promoted by external stimuli using thermo-reversible chemical reactions, such as Diels-Alder cycloadditions from a diene and a dienophile fragment (compound a). In this study, an antitumor drug (methotrexate, MTX) was linked to plasmonic AuNPs by a Diels-Alder adduct (compound c), which after NIR suffers a retro-Diels-Alder reaction, producing release of the drug (compound b). We obtained two nanosystems based on AuNRs and AuNPrs. Both nanoconstructs were coated with BSA-r8 (Bovine Serum Albumin functionalized with Arg8, all-D octa arginine) in order to increase the colloidal stability and promote internalization of the nanosystems on HeLa and SK-BR-3 cells. In addition, the presence of BSA allows protecting the cargo from being released on the extracellular environment and promotes the photothermal release of the drug in the presence of glutathione (GSH). The nanosystems' drug release profile was evaluated after NIR irradiation in the presence and absence of glutathione (GSH), showing a considerable increase of drug release when NIR light and glutathione were combined. This work broadens the range of possibilities of using two complementary strategies for the controlled release of an antitumor drug from AuNRs and AuNPrs: the photothermal cleavage of a thermolabile adduct controlled by an external stimulus (laser irradiation), complemented with the use of the intracellular metabolite GSH.

Oligoarginine Peptide Conjugated to BSA Improves Cell Penetration of Gold Nanorods and Nanoprisms for Biomedical Applications.

Gold nanoparticles (AuNPs) have been shown to be outstanding tools for drug delivery and biomedical applications, mainly owing to their colloidal stability, surface chemistry, and photothermal properties. The biocompatibility and stability of nanoparticles can be improved by capping the nanoparticles with endogenous proteins, such as albumin. Notably, protein coating of nanoparticles can interfere with and decrease their cell penetration. Therefore, in the present study, we functionalized albumin with the r8 peptide (All-D, octaarginine) and used it for coating NIR-plasmonic anisotropic gold nanoparticles. Gold nanoprisms (AuNPrs) and gold nanorods (AuNRs) were coated with bovine serum albumin (BSA) previously functionalized using a cell penetrating peptide (CPP) with the r8 sequence (BSA-r8). The effect of the coated and r8-functionalized AuNPs on HeLa cell viability was assessed by the MTS assay, showing a low effect on cell viability after BSA coating. Moreover, the internalization of the nanostructures into HeLa cells was assessed by confocal microscopy and transmission electron microscopy (TEM). As a result, both nanoconstructs showed an improved internalization level after being capped with BSA-r8, in contrast to the BSA-functionalized control, suggesting the predominant role of CPP functionalization in cell internalization. Thus, our results validate both novel nanoconstructs as potential candidates to be coated by endogenous proteins and functionalized with a CPP to optimize cell internalization. In a further approach, coating AuNPs with CPP-functionalized BSA can broaden the possibilities for biomedical applications by combining their optical properties, biocompatibility, and cell-penetration abilities.

Target-templated de novo design of macrocyclic d-/l-peptides: discovery of drug-like inhibitors of PD-1.

Peptides are a rapidly growing class of therapeutics with various advantages over traditional small molecules, especially for targeting difficult protein-protein interactions. However, current structure-based methods are largely limited to natural peptides and are not suitable for designing bioactive cyclic topologies that go beyond natural l-amino acids. Here, we report a generalizable framework that exploits the computational power of Rosetta, in terms of large-scale backbone sampling, side-chain composition and energy scoring, to design heterochiral cyclic peptides that bind to a protein surface of interest. To showcase the applicability of our approach, we developed two new inhibitors (PD-i3 and PD-i6) of programmed cell death 1 (PD-1), a key immune checkpoint in oncology. A comprehensive biophysical evaluation was performed to assess their binding to PD-1 as well as their blocking effect on the endogenous PD-1/PD-L1 interaction. Finally, NMR elucidation of their in-solution structures confirmed our de novo design approach.

In vivo micro computed tomography detection and decrease in amyloid load by using multifunctionalized gold nanorods: a neurotheranostic platform for Alzheimer's disease.

The development and use of nanosystems is an emerging strategy for the diagnosis and treatment of a broad number of diseases, such as Alzheimer's disease (AD). Here, we developed a neurotheranostic nanosystem based on gold nanorods (GNRs) that works as a therapeutic peptide delivery system and can be detected in vivo for microcomputed tomography (micro-CT), being a diagnostic tool. GNRs functionalized with the peptides Ang2 (a shuttle to the Central Nervous System) and D1 (that binds to the Aß peptide, also inhibiting its aggregation) allowed detecting differences in vivo between wild type and AD mice (APPswe/PSEN1dE9) 15 minutes after a single dose by micro-CT. Moreover, after a recurrent treatment for one month with GNRs-D1/Ang2, we observed a diminution of amyloid load and inflammatory markers in the brain. Thus, this new designed nanosystem exhibits promising properties for neurotheranostics of AD.

Advances in peptide-mediated cytosolic delivery of proteins.

The number of protein-based drugs is exponentially increasing. However, development of protein therapeutics against intracellular targets is hampered by the lack of efficient cytosolic delivery strategies. In recent years, the use of cell-penetrating peptides has been proposed as a strategy to promote protein internalization. In this article, we provide the reader with a succinct update on the strategies exploited to enable peptide-mediated cytosolic delivery of proteins. First, we analyse the various methods available for delivery. We then describe the most popular and the in vitro assays designed to assess the intracellular distribution of protein cargo.

The Combined Use of Gold Nanoparticles and Infrared Radiation Enables Cytosolic Protein Delivery.

Cytosolic protein delivery remains elusive. The inability of most proteins to cross the cellular membrane is a huge hurdle. Here we explore the unique photothermal properties of gold nanorods (AuNRs) to trigger cytosolic delivery of proteins. Both partners, protein and AuNRs, are modified with a protease-resistant cell-penetrating peptide with nuclear targeting properties to induce internalization. Once internalized, spatiotemporal control of protein release is achieved by near-infrared laser irradiation in the safe second biological window. Importantly, catalytic amounts of AuNRs are sufficient to trigger cytosolic protein delivery. To the best of our knowledge, this is the first time that AuNRs with their maximum of absorption in the second biological window are used to deliver proteins into the intracellular space. This strategy represents a powerful tool for the cytosolic delivery of virtually any class of protein.

Peptide Shuttle-Mediated Delivery for Brain Gene Therapies.

The manipulation of an individual's genetic information to treat a disease has revolutionized the biomedicine field. Despite the promise of gene therapy, this treatment can have long-term sideeffects. Efforts in the field and recent discoveries have already led to several improvements, including efficient gene delivery and transfer, as well as inpatient safety. Several studies to treat a wide range of pathologies-such as cancer or monogenic diseases- are currently being conducted. Here we provide a broad overview of methodologies available for gene therapy, placing a strong emphasis on treatments for central nervous system diseases. Finally, we give a perspective on current delivery strategies to treat such diseases, with a special focus on systems that use peptides as delivery vectors.

A Third Shot at EGFR: New Opportunities in Cancer Therapy.

Epidermal growth factor receptor (EGFR) inhibitors were among the first type of targeted agents discovered in cancer and currently constitute the standard of care for a wide range of lung and colon malignancies. However, the therapeutic progress achieved with these drugs has been accompanied by the identification of an ever-increasing number of acquired resistance mechanisms that inevitably appear in nearly all patients. Increased knowledge on EGFR biochemistry, cellular crosstalk, and resistance pathways provides an opportunity to establish effective combination therapies and discover novel-acting inhibitors that prevent or overcome therapeutic resistance. One such strategy is the selective blockade of circulating growth factors such as EGF. In this review, we address the uses and limitations of approved EGFR inhibitors and explore the potential of drug combinations and new third avenues to block the activation of the EGFR.

Protein Chemical Synthesis Combined with Mirror-Image Phage Display Yields d-Peptide EGF Ligands that Block the EGF-EGFR Interaction.

The epidermal growth factor (EGF) pathway, being overactive in a number of cancers, is a good target for clinical therapy. Although several drugs targeting the EGF receptor (EGFR) are on the market, tumours acquire resistance very rapidly. As an alternative, small molecules and peptides targeting EGF have been developed, although with moderate success. Herein, we report the use of mirror-image phage display technology to discover protease-resistant peptides with the capacity to inhibit the EGF-EGFR interaction. After the chemical synthesis of the enantiomeric protein d-EGF, two phage-display peptide libraries were used to select binding sequences. The d versions of these peptides bound to natural EGF, as confirmed by surface acoustic waves (SAWs). High-field NMR spectroscopy showed that the best EGF binder, d-PI_4, interacts preferentially with an EGF region that partially overlaps with the receptor binding interface. Importantly, we also show that d-PI_4 efficiently disrupts the EGF-EGFR interaction. This methodology represents a straightforward approach to find new protease-resistant peptides with potential applications in cancer therapy.

Expanding the MiniAp-4 BBB-shuttle family: Evaluation of proline cis-trans ratio as tool to fine-tune transport.

Venoms have recently emerged as a promising field in drug discovery due to their good selectivity and affinity for a wide range of biological targets. Among their multiple potential applications, venoms are a rich source of blood-brain barrier (BBB) peptide shuttles. We previously described a short nontoxic derivative of apamin, MiniAp-4, which can transport a wide range of cargoes across the BBB. Here, we have studied the conformation of the proline residue of a range of MiniAp-4 analogues by high-field NMR techniques, with the aim to identify whether there is a direct relation between the cis/trans population and a range of features, such as the capacity to transport molecules across a human-based cellular model and stability in various media. The most promising candidate showed improved transport properties for a relevant small fluorophore.

Branched BBB-shuttle peptides: chemoselective modification of proteins to enhance blood-brain barrier transport.

The blood-brain barrier (BBB) hampers the delivery of therapeutic proteins into the brain. BBB-shuttle peptides have been conjugated to therapeutic payloads to increase the permeability of these molecules. However, most BBB-shuttles have several limitations, such as a lack of resistance to proteases and low effectiveness in transporting large biomolecules. We have previously reported on the THRre peptide as a protease-resistant BBB-shuttle that is able to increase the transport of fluorophores and quantum dots in vivo. In this work, we have evaluated the capacity of linear and branched THRre to increase the permeability of proteins in cellular models of the BBB. With this purpose, we have covalently attached peptides with one or two copies of the BBB-shuttle to proteins in order to develop chemically well-defined peptide-protein conjugates. While THRre does not enhance the uptake and transport of a model protein in BBB cellular models, branched THRre peptides displaying two copies of the BBB-shuttle result in a 2.6-fold increase.

From venoms to BBB-shuttles. MiniCTX3: a molecular vector derived from scorpion venom.

The present study aims to develop chlorotoxin (CTX), from Giant Yellow Israeli scorpion venom, as a new BBB-shuttle. Minimised versions of CTX were prepared to reduce its complexity while enhancing its BBB-shuttle capacity and preserving its protease-resistance. MiniCTX3, a monocyclic lactam-bridge peptidomimetic, was capable of transporting nanoparticles across endothelial cell monolayers. Our results reveal animal venoms as an outstanding source of new families of BBB-shuttles.

d-Polyarginine Lipopeptides as Intestinal Permeation Enhancers.

An estimated 285 million people were living with diabetes in 2010, and this number is expected to reach 440 million by 2030. Current treatment of this disease involves the intradermal injection of insulin analogues. Many alternative administration routes have been proposed, the oral route being the most widely studied. One of the most interesting approaches for insulin delivery is the use of permeation enhancers to increase its transport across the gastrointestinal tract (GIT). Cell-penetrating peptides (CPPs) are a remarkable example of this family of compounds. Another alternative is the use of medium-chain fatty acids (MCFAs) to temporally disrupt the tight junctions of the GIT, thereby allowing greater drug transport. A combination of both strategies can provide a synergistic way to increase drug transport through the GIT. In this study we evaluated the complexation of insulin glulisine, an insulin analogue administered subcutaneously or intravenously in clinical practice, with a well-known CPP modified with the MCFA lauric acid. We prepared several formulations, examined their stability, and tested the best candidates in an intestinal cell-based model. In particular, two compounds (C12 -r4 and C12 -r6 ) were found to significantly increase the transport of insulin, and therefore show promise as a new delivery system worthy of further evaluation.

Blocking EGFR Activation with Anti-EGF Nanobodies via Two Distinct Molecular Recognition Mechanisms.

One of the hallmarks of cancer is the overproduction of growth factors such as EGF. Despite the clinical success achieved by EGFR-targeted therapies, their long-term efficacy is compromised by the onset of drug-resistant mutations. To address this issue, a family of camelid-derived single-domain antibodies (Nbs) were generated, obtaining the first direct EGF inhibitors that prevent EGFR phosphorylation and pathway activation through this new mechanism of action. The two best Nbs were subjected to a detailed investigation of their interaction mechanism that revealed important differences in their binding kinetics and equilibrium thermodynamics. These distinct behaviors at the biophysical level translate into an equally efficient inhibition of the cellular EGFR phosphorylation, thus proving the efficacy of these Nbs to turn off the initiation of this key oncogenic pathway in cancer cells.

Indoloazepinone-Constrained Oligomers as Cell-Penetrating and Blood-Brain-Barrier-Permeating Compounds.

Non-cationic and amphipathic indoloazepinone-constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l-Aia-Xxx]n oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc-[l-Aia-Gly]2,4 -OBn oligomers 12 and 13 and Boc-[l-Aia-ß3 -h-l-Ala]2,4 -OBn oligomers 16 and 17 were totally or partially disordered, Boc-[l-Aia-l-Ala]2 -OBn (14) induced a typical turn stabilized by C5 - and C7 -membered H-bond pseudo-cycles and aromatic interactions. Boc-[l-Aia-l-Ala]4 -OBn (15) exhibited a unique structure with remarkable T-shaped π-stacking interactions involving the indole rings of the four l-Aia residues forming a dense hydrophobic cluster. All of the proposed FITC-6-Ahx-[l-Aia-Xxx]4 -NH2 oligomers 19-23, with the exception of FITC-6-Ahx-[l-Aia-Gly]4 -NH2 (18), were internalized by MDA-MB-231 cells with higher efficiency than the positive references penetratin and Arg8 . In parallel, the compounds of this series were successfully explored in an in vitro blood-brain barrier (BBB) permeation assay. Although no passive diffusion permeability was observed for any of the tested Ac-[l-Aia-Xxx]4 -NH2 oligomers in the PAMPA model, Ac-[l-Aia-l-Arg]4 -NH2 (26) showed significant permeation in the in vitro cell-based human model of the BBB, suggesting an active mechanism of cell penetration.

Peptide Mediated Brain Delivery of Nano- and Submicroparticles: A Synergistic Approach.

The brain is a complex, regulated organ with a highly controlled access mechanism: The Blood-Brain Barrier (BBB). The selectivity of this barrier is a double-edged sword, being both its greatest strength and weakness. This weakness is evident when trying to target therapeutics against diseases within the brain. Diseases such as metastatic brain cancer have extremely poor prognosis due to the poor permeability of many therapeutics across the BBB. Peptides can be designed to target BBB receptors and gain access to the brain by transcytosis. These peptides (known as BBB-shuttles) can carry compounds, usually excluded from the brain, across the BBB. BBB-shuttles are limited by poor loading of therapeutics and degradation of the peptide and cargo. Likewise, nano- submicro- and microparticles can be fine-tuned to limit their degradation and with high loading of therapeutics. However, most nano- and microparticles' core materials completely lack efficient targeting, with a few selected materials able to cross the BBB passively. Combining the selectivity of peptides with the high loading potential of nano-, microparticles offers an exciting strategy to develop novel, targeted therapeutics towards many brain disorders and diseases. Nevertheless, at present the field is diverse, in both scope and nomenclature, often with competing or contradictory names. In this review, we will try to address some of these issues and evaluate the current state of peptide mediated nano,-microparticle transport to the brain, analyzing delivery vehicle type and peptide design, the two key components that must act synergistically for optimal therapeutic impact.