Neutralizing SARS-CoV-2 by dimeric side chain-to-side chain cross-linked ACE2 peptide mimetics.

We present the finding of a dimeric ACE2 peptide mimetic designed through side chain cross-linking and covalent dimerization. It has a binding affinity of 16 nM for the SARS-CoV-2 spike RBD, and effectively inhibits the SARS-CoV-2 pseudovirus in Huh7-hACE2 cells with an IC50 of 190 nM and neutralizes the authentic SARS-CoV-2 in Caco2 cells with an IC50 of 2.4 µM. Our study should provide a new insight for the optimization of peptide-based anti-SARS-CoV-2 inhibitors.

Computational study, synthesis and evaluation of active peptides derived from Parasporin-2 and spike protein from Alphacoronavirus against colorectal cancer cells.

Parasporin-2Aa1 (PS2Aa1) is a toxic protein of 37 KDa (30 kDa, activated form produced by proteolysis) that was shown to be cytotoxic against specific human cancer cells, although its mechanism of action has not been elucidated yet. In order to study the role of some native peptide fragments of proteins on anticancer activity, here we investigated the cytotoxic effect of peptide fragments from domain-1 of PS2Aa1 and one of the loops present in the binding region of the virus spike protein from Alphacoronavirus (HCoV-229E), the latter according to scientific reports, who showed interaction with the human APN (h-APN) receptor, evidence corroborated through computational simulations, and thus being possible active against colon cancer cells. Peptides namely P264-G274, Loop1-PS2Aa, and Loop2-PS2Aa were synthesized using the Fmoc solid-phase synthesis and characterized by mass spectrometry (MS). Additionally, one region from loop 1 of HCoV-229E, Loop1-HCoV-229E, was also synthesized and characterized. The A4W-GGN5 anticancer peptide and 5-fluorouracil (5-FU) were taken as a control in all experiments. Circular dichroism revealed an α-helix structure for the peptides derived from PS2Aa1 (P264-G274, Loop1-PS2Aa, and Loop2-PS2Aa) and ß-laminar structure for the peptide derived from Alphacoronavirus spike protein Loop1-HCoV-229E. Peptides showed a hemolysis percentage of less than 20% at 100 µM concentration. Besides, peptides exhibited stronger anticancer activity against SW480 and SW620 cells after exposure for 48 h. Likewise, these compounds showed significantly lower toxicity against normal cells CHO-K1. The results suggest that native peptide fragments from Ps2Aa1 may be optimized as a novel potential cancer-therapeutic agents.

O-Glycosylation Induces Amyloid-ß To Form New Fibril Polymorphs Vulnerable for Degradation.

Brain accumulation of amyloid-ß (Aß) peptides (resulting from a disrupted balance between biosynthesis and clearance) occurs during the progression of Alzheimer's disease (AD). Aß peptides have diverse posttranslational modifications (PTMs) that variously modulate Aß aggregation into fibrils, but understanding the mechanistic roles of PTMs in these processes remains a challenge. Here, we chemically synthesized three homogeneously modified isoforms of Aß (1-42) peptides bearing Tyr10 O-glycosylation, an unusual PTM initially identified from the cerebrospinal fluid samples of AD patients. We discovered that O-glycans significantly affect both the aggregation and degradation of Aß42. By combining cryo-EM and various biochemical assays, we demonstrate that a Galß1-3GalNAc modification redirects Aß42 to form a new fibril polymorphic structure that is less stable and more vulnerable to Aß-degrading enzymes (e.g., insulin-degrading enzyme). Thus, beyond showing how particular O-glycosylation modifications affect Aß42 aggregation at the molecular level, our study provides powerful experimental tools to support further investigations about how PTMs affect Aß42 fibril aggregation and AD-related neurotoxicity.

Inhibition of huntingtin aggregation by its N-terminal 17-residue peptide and its analogs.

The N-terminal 17-residue stretch of huntingtin (httN17) folds into an amphipathic α-helix. The httN17-harboring polyQ peptides form oligomers that are mediated via the assembly of the httN17 α-helices. The oligomerization results in higher local concentration of the polyglutamine (polyQ) region, thereby facilitating amyloid formation. The httN17 co-assembles with the httN17-harbouring polyQ peptides, thereby reducing the local polyQ concentration, and consequently inhibiting aggregation. This study presents the aggregation inhibition of the exon I region of pathogenic huntingtin by httN17 and its analogs. The C-terminal amidation of httN17 is found to be essential for activity. The httN17 peptides with free amino terminus and the acetylated amino terminus possess comparable activity. The httN17 analog, wherein the Leu7 and Ala10 are substituted with 2-aminoisobutyric acid residues, exhibits significantly higher activity than the native httN17.

Synthesis and In Vitro Characterization of Glycopeptide Drug Candidates Related to PACAP1-23.

The search for efficacious treatment of neurodegenerative and progressive neuroinflammatory diseases continues, as current therapies are unable to halt or reverse disease progression. PACAP represents one potential therapeutic that provides neuroprotection effects on neurons, and also modulates inflammatory responses and circulation within the brain. However, PACAP is a relatively long peptide hormone that is not trivial to synthesize. Based on previous observations that the shortened isoform PACAP1-23 is capable of inducing neuroprotection in vitro, we were inspired to synthesize shortened glycopeptide analogues of PACAP1-23. Herein, we report the synthesis and in vitro characterization of glycosylated PACAP1-23 analogues that interact strongly with the PAC1 and VPAC1 receptors, while showing reduced activity at the VPAC2 receptor.

Dissection of phospholipases A2 reveals multifaceted peptides targeting cancer cells, Leishmania and bacteria.

Cationic peptides bio-inspired by natural toxins have been recognized as an efficient strategy for the treatment of different health problems. Due to the specific interaction with substrates from biological membranes, snake venom phospholipases (PLA2s) represent valuable scaffolds for the research and development of short peptides targeting parasites, bacteria, and cancer cells. Considering this, we evaluated the in vitro therapeutic potential of three biomimetic peptides (pCergo, pBmTxJ and pBmje) based on three different amino acid sequences from Asp49 PLA2s. First, short amino acid sequences (12-17 in length) derived from these membranolytic toxins were selected using a combination of bioinformatics tools, including AntiCP, AMPA, PepDraw, ToxinPred, and HemoPI. The peptide, from each polypeptide sequence, with the greatest average antimicrobial index, no toxicity, and no hemolysis predicted was synthesized, purified, and characterized. According to in vitro assays performed, pBmje showed moderate cytotoxicity specifically against MCF-7 (breast cancer cells) with an EC50 of 464.85 µM, whereas pBmTxJ showed an antimicrobial effect against Staphylococcus aureus (ATCC 25923) with an MIC of 37.5 µM, and pCergo against E. coli (ATCC 25922) with an MIC of 75 µM. In addition, pCergo showed antileishmanial activity with an EC50 of 93.69 µM and 110.40 µM against promastigotes of Leishmania braziliensis and L. amazonensis, respectively. Altogether, these results confirmed the versatility of PLA2-derived synthetic peptides, highlighting the relevance of the use of these membrane-interacting toxins as specific archetypes for drug design focused on public health problems.

Intestinal guard: Human CXCL17 modulates protective response against mycotoxins and CXCL17-mimetic peptides development.

Mycotoxin contamination is an ongoing and growing issue that can create health risks and even cause death. Unfortunately, there is currently a lack of specific therapy against mycotoxins with few side effects. On the other hand, the strategic expression of CXCL17 in mucosal tissues suggests that it may be involved in immune response when exposed to mycotoxins, but the exact role of CXCL17 remains largely unknown. Using Caco-2 as a cell model of the intestinal epithelial barrier (the first line of defense against mycotoxins), we showed that a strong production of ROS-dependent CXCL17 was triggered by mycotoxins via p38 and JNK pathways. Under the mycotoxins stress, CXCL17 modulated enhanced immuno-protective response with a remission of inflammation and apoptosis through PI3K/AKT/mTOR. Based on our observed feedback of CXCL17 to the mycotoxins, we developed the CXCL17-mimetic peptides in silico (CX1 and CX2) that possessed the safety and the capability to ameliorate mycotoxins-inducible inflammation and apoptosis. In this study, the identification of detoxifying feature of CXCL17 is a prominent addition to the chemokine field, pointing out a new direction for curing the mycotoxins-caused damage.

Characterization of ACE Inhibitory Peptides Prepared from Pyropia pseudolinearis Protein.

More than 7000 red algae species have been classified. Although most of them are underused, they are a protein-rich marine resource. The hydrolysates of red algal proteins are good candidates for the inhibition of the angiotensin-I-converting enzyme (ACE). The ACE is one of the key factors for cardiovascular disease, and the inhibition of ACE activity is related to the prevention of high blood pressure. To better understand the relationship between the hydrolysates of red algal proteins and the inhibition of ACE activity, we attempted to identify novel ACE inhibitory peptides from Pyropia pseudolinearis. We prepared water soluble proteins (WSP) containing phycoerythrin, phycocyanin, allophycocyanin, and ribulose 1,5-bisphosphate carboxylase/oxygenase. In vitro analysis showed that the thermolysin hydrolysate of the WSP had high ACE inhibitory activity compared to that of WSP. We then identified 42 peptides in the hydrolysate by high-performance liquid chromatography and mass spectrometry. Among 42 peptides, 23 peptides were found in chloroplast proteins. We then synthesized the uncharacterized peptides ARY, YLR, and LRM and measured the ACE inhibitory activity. LRM showed a low IC50 value (0.15 µmol) compared to ARY and YLR (1.3 and 5.8 µmol). In silico analysis revealed that the LRM sequence was conserved in cpcA from Bangiales and Florideophyceae, indicating that the novel ACE inhibitory peptide LRM was highly conserved in red algae.

Improved pharmacokinetics and bone tissue accumulation of Angiotensin-(1-7) peptide through bisphosphonate conjugation.

The renin-angiotensin system (RAS) has a central role in renal and cardiovascular homeostasis. Angiotensin-(1-7) (Ang1-7), one of the RAS active peptides, exerts beneficial effects through different mechanisms. These biological actions suggest that Ang1-7 is an effective therapeutic agent for treating various diseases associated with activated RAS. However, its short half-life and poor pharmacokinetics restrict its therapeutic utility. Our laboratory has successfully synthesized and characterized an Ang1-7 conjugate (Ang Conj.) with a prolonged half-life and improved pharmacokinetics profile. The Ang Conj. has been prepared by PEGylation of Ang1-7 and conjugation with a bisphosphonate using solid-phase peptide synthesis and characterized by HPLC and mass spectrometer. The compound's stability has been tested in different storage conditions. The bone binding capacity was evaluated using a hydroxyapatite assay. Pharmacokinetic and tissue distribution studies were performed using iodinated peptides in rats. Ang Conj. was synthesized with > 90% purity. Bone mineral affinity testing showed Ang Conj. exhibited significantly higher bone mineral affinity than Ang1-7. The Ang Conj. remained stable for more than a month using all tested storage conditions. The Ang Conj. demonstrated higher affinity to bone, a longer half-life, and better bioavailability when compared with the native peptide. These results support that conjugation of Ang1-7 with bisphosphonate enables it to utilize bone as a reservoir for the sustained delivery of Ang1-7 to maintain therapeutic plasma levels. High chemical stability and about five to tenfold prolongation of Ang Conj. plasma half-life after administrations into rats proves the effectiveness of our approach.

Design, Synthesis, and Structural Characterization of Lysine Covalent BH3 Peptides Targeting Mcl-1.

Modulating disease-relevant protein-protein interactions (PPIs) using pharmacological tools is a critical step toward the design of novel therapeutic strategies. Over the years, however, targeting PPIs has proven a very challenging task owing to the large interfacial areas. Our recent efforts identified possible novel routes for the design of potent and selective inhibitors of PPIs using a structure-based design of covalent inhibitors targeting Lys residues. In this present study, we report on the design, synthesis, and characterizations of the first Lys-covalent BH3 peptide that has a remarkable affinity and selectivity for hMcl-1 over the closely related hBfl-1 protein. Our structural studies, aided by X-ray crystallography, provide atomic-level details of the inhibitor interactions that can be used to further translate these discoveries into novel generation, Lys-covalent pro-apoptotic agents.

A double-network polysaccharide-based composite hydrogel for skin wound healing.

Effective wound dressings are of great significance in preventing infections and promoting wound healing. However, most existing hydrogel dressings have an inadequacy in either mechanical performance, biological activities, or versatilities. Here we presented a double-network cross-linked polysaccharide-based hydrogel composed of collagen peptide-functionalized carboxymethyl chitosan (CS) and oxidized methacrylate sodium alginate (SA). The hydrogel possessed interconnected porous morphologies, suitable swelling ratios, excellent mechanical properties, and favorable biocompatibility. Meanwhile, the in vivo studies using a mouse full-thickness skin defect model showed that the double-network CS/SA hydrogel significantly accelerated wound healing by regulating the inflammatory process, promoting collagen deposition, and improving vascularization. Therefore, the functionalized double-network hydrogel should be a potential candidate as wound dressings.

Design, Structural Optimization, and Characterization of the First Selective Macrocyclic Neurotensin Receptor Type 2 Non-opioid Analgesic.

Neurotensin (NT) receptor type 2 (NTS2) represents an attractive target for the development of new NT-based analgesics. Here, we report the synthesis and functional in vivo characterization of the first constrained NTS2-selective macrocyclic NT analog. While most chemical optimization studies rely on the NT(8-13) fragment, we focused on NT(7-12) as a scaffold to design NTS2-selective macrocyclic peptides. Replacement of Ile12 by Leu, and Pro7/Pro10 by allylglycine residues followed by cyclization via ring-closing metathesis led to macrocycle 4, which exhibits good affinity for NTS2 (50 nM), high selectivity over NTS1 (>100 µM), and improved stability compared to NT(8-13). In vivo profiling in rats reveals that macrocycle 4 produces potent analgesia in three distinct rodent pain models, without causing the undesired effects associated with NTS1 activation. We further provide evidence of its non-opioid antinociceptive activity, therefore highlighting the strong therapeutic potential of NTS2-selective analogs for the management of acute and chronic pain.

The Design of a GLP-1/PYY Dual Acting Agonist.

The two gut hormones GLP-1 and PYY3-36 , which are both secreted from the L-cells upon food stimuli, have a stronger inhibitory effect on food intake when they are combined, compared to their individual effects as single agonists. Although they are not homologous and share no sequence similarity, we show that a GLP-1 analogue can be designed to exhibit potent activity on both the Y2 and GLP-1 receptors. Dual acting hybrid analogues were realized by designing truncated and potent Y2 receptor PYY analogues, followed by integrating the critical residues into GLP-1. In this study, we show that one of these dual acting agonists acutely reduces food intake significantly more than the respective mono-agonist counterparts.

Structural and mechanistic insights into the inhibition of amyloid-ß aggregation by Aß39-42 fragment derived synthetic peptides.

The inhibition of amyloid-ß (Aß) aggregation is a promising approach towards therapeutic intervention for Alzheimer's disease (AD). Thirty eight tetrapeptides based upon Aß39-42C-terminus fragment of the parent Aß peptide were synthesized. The sequential replacement/modification employing unnatural amino acids imparted scaffold diversity, augmented activity, enhanced blood brain barrier permeability and offered proteolytic stability to the synthetic peptides. Several peptides exhibited promising protection against Aß aggregation-mediated-neurotoxicity in PC-12 cells at doses ranged between 10 µM and 0.1 µM, further confirmed by the thioflavin-T fluorescence assay. CD study illustrate that these peptides restrict the ß-sheet formation, and the non-appearance of Aß42 fibrillar structures in the electron microscopy confirm the inhibition of Aß42 aggregation. HRMS and ANS fluorescence spectroscopic analysis provided additional mechanistic insights. Two selected lead peptides 5 and 16 depicted enhanced blood-brain penetration and stability against serum and proteolytic enzyme. Structural insights into ligand-Aß interactions on the monomeric and proto-fibrillar units of Aß were computationally studied. Promising inhibitory potential and short sequence of the lead peptides offers new avenues for the advancement of peptide-derived therapeutics for AD.

Designing Novel Teduglutide Analogues with Improved Binding Affinity: An In Silico Peptide Engineering Approach.

INTRODUCTION: Short bowel syndrome (SBS) is a disabling condition that occurs following the loss of substantial portions of the intestine, leading to inadequate absorption of nutrients and fluids. Teduglutide is the only drug that has been FDA-approved for long-term treatment of SBS. This medicine exerts its biological effects through binding to the GLP-2 receptor. METHODS: The current study aimed to use computational mutagenesis approaches to design novel potent analogues of teduglutide. To this end, the constructed teduglutide-GLP2R 3D model was subjected to the alanine scanning mutagenesis where ARG20, PHE22, ILE23, LEU26, ILE27 and LYS30 were identified as the key amino acids involved in ligand-receptor interaction. In order to design potent teduglutide analogues, using MAESTROweb machine learning method, the residues of teduglutide were virtually mutated into all naturally occurring amino acids and the affinity improving mutations were selected for further analysis using PDBePISA methodology which interactively investigates the interactions established at the interfaces of macromolecules. RESULTS: The calculations resulted in D15I, D15L, D15M and N24M mutations, which can improve the binding ability of the ligand to the receptor. The final evaluation of identified mutations was performed by molecular dynamics simulations, indicating that D15I and D15M are the most reliable mutations to increase teduglutide affinity towards its receptor. CONCLUSION: The findings in the current study may facilitate designing more potent teduglutide analogues leading to the development of novel treatments in short bowel syndrome.

Structural, functional, and mechanistic insights uncover the fundamental role of orphan connexin-62 in platelets.

Connexins oligomerise to form hexameric hemichannels in the plasma membrane that can further dock together on adjacent cells to form gap junctions and facilitate intercellular trafficking of molecules. In this study, we report the expression and function of an orphan connexin, connexin-62 (Cx62), in human and mouse (Cx57, mouse homolog) platelets. A novel mimetic peptide (62Gap27) was developed to target the second extracellular loop of Cx62, and 3-dimensional structural models predicted its interference with gap junction and hemichannel function. The ability of 62Gap27 to regulate both gap junction and hemichannel-mediated intercellular communication was observed using fluorescence recovery after photobleaching analysis and flow cytometry. Cx62 inhibition by 62Gap27 suppressed a range of agonist-stimulated platelet functions and impaired thrombosis and hemostasis. This was associated with elevated protein kinase A-dependent signaling in a cyclic adenosine monophosphate-independent manner and was not observed in Cx57-deficient mouse platelets (in which the selectivity of 62Gap27 for this connexin was also confirmed). Notably, Cx62 hemichannels were observed to function independently of Cx37 and Cx40 hemichannels. Together, our data reveal a fundamental role for a hitherto uncharacterized connexin in regulating the function of circulating cells.

Designing Chimeric Peptides: A Powerful Tool for Enhancing Antibacterial Activity.

Chimeric peptides containing short sequences derived from bovine Lactoferricin (LfcinB) and Buforin II (BFII) were synthetized using solid-phase peptide synthesis (SPPS) and characterized via reversed-phase liquid chromatography and mass spectrometry. The chimeras were obtained with high purity, demonstrating their synthetic viability. The chimeras' antibacterial activity against Gram-positive and Gram-negative strains was evaluated. Our results showed that all the chimeras exhibited greater antibacterial activity against the evaluated strains than the individual sequences, suggesting that chemical binding of short sequences derived from AMPs significantly increased the antibacterial activity. For each strain, the chimera with the best antibacterial activity exerted a bacteriostatic and/or bactericidal effect, which was dependent on the concentration. It was found that: (i) the antibacterial activity of a chimera is mainly influenced by the linked sequences, the palindromic motif RLLRRLLR being the most relevant one; (ii) the inclusion of a spacer between the short sequences did not significantly affect the chimera's synthesis process; however, it enhanced its antibacterial activity against Gram-negative and Gram-positive strains; on the other hand, (iii) the replacement of Arg with Lys in the LfcinB or BFII sequences improved the chimeras' synthesis process without significantly affecting their antibacterial activity. These results illustrate the great importance of the synthesis of chimeric peptides for the generation of promising antibacterial peptides.

Synthetic peptides against Trichophyton mentagrophytes and T. rubrum: Mechanisms of action and efficiency compared to griseofulvin and itraconazole.

AIMS: According to the WHO, 20-25% of people worldwide are affected by skin infections caused by dermatophytes, such as those of the Trichophyton genus. Additionally, several dermatophytes have developed resistance to drugs such as griseofulvin and itraconazole. This study tested 2S albumins-derived antimicrobial peptides (AMPs) as alternative antidermatophytic molecules. MAIN METHODS: Membrane pore formation assays, tests to detect overproduction of ROS, scanning electron microscopy (SEM) and fluorescence microscopy (FM) were carried out to provide insight into the mechanisms of antidermatophytic action. KEY FINDINGS: All AMPs (at 50 µg mL-1) tested reduced the mycelial growth of T. mentagrophytes and T. rubrum by up to 95%. In contrast, using a concentration 20-fold higher, griseofulvin only inhibited T. mentagrophytes by 35%, while itraconazole was not active against both dermatophytes. Scanning electron and fluorescence microscopies revealed that the six AMPs caused severe damage to hyphal morphology by inducing cell wall rupture, hyphal content leakage, and death. Peptides also induced membrane pore formation and oxidative stress by overproduction of ROS. Based on the stronger activity of peptides than the commercial drugs and the mechanism of action, all six peptides have the potential to be either employed as models to develop new antidermatophytic drugs or as adjuvants to existing ones. SIGNIFICANCE: The synthetic peptides are more efficient than conventional drug to treat infection caused by dermatophytes being potential molecules to develop new drugs.

Current Synthetic Routes to Peptidyl Mono-Fluoromethyl Ketones (FMKs) and Their Applications.

Peptidyl mono-fluoromethyl ketones (FMKs) are a class of biologically active molecules that show potential as both protease inhibitors for the treatment of a range of diseases and as chemical probes for the interrogation of cellular processes. This review describes the current solid- and solution-phase routes employed for the synthesis of peptidyl mono-FMKs. In addition, it provides a brief overview of some of the key applications of FMKs in the fields of chemical biology and medicinal chemistry.

Blockade of Glial Connexin 43 Hemichannels Reduces Food Intake.

The metabolic syndrome, which comprises obesity and diabetes, is a major public health problem and the awareness of energy homeostasis control remains an important worldwide issue. The energy balance is finely regulated by the central nervous system (CNS), notably through neuronal networks, located in the hypothalamus and the dorsal vagal complex (DVC), which integrate nutritional, humoral and nervous information from the periphery. The glial cells' contribution to these processes emerged few year ago. However, its underlying mechanism remains unclear. Glial connexin 43 hemichannels (Cx43 HCs) enable direct exchange with the extracellular space and can regulate neuronal network activity. In the present study, we sought to determine the possible involvement of glial Cx43 HCs in energy balance regulation. We here show that Cx43 is strongly expressed in the hypothalamus and DVC and is associated with glial cells. Remarkably, we observed a close apposition of Cx43 with synaptic elements in both the hypothalamus and DVC. Moreover, the expression of hypothalamic Cx43 mRNA and protein is modulated in response to fasting and diet-induced obesity. Functionally, we found that Cx43 HCs are largely open in the arcuate nucleus (ARC) from acute mice hypothalamic slices under basal condition, and significantly inhibited by TAT-GAP19, a mimetic peptide that specifically blocks Cx43 HCs activity. Moreover, intracerebroventricular (i.c.v.) TAT-GAP19 injection strongly decreased food intake, without further alteration of glycaemia, energy expenditures or locomotor activity. Using the immediate early gene c-Fos expression, we found that i.c.v. TAT-GAP19 injection induced neuronal activation in hypothalamic and brainstem nuclei dedicated to food intake regulation. Altogether, these results suggest a tonic delivery of orexigenic molecules associated with glial Cx43 HCs activity and a possible modulation of this tonus during fasting and obesity.