(S)-3-(3,4-Dihydroxybenzyl) piperazine-2,5-dione (cyclo-Gly-L-DOPA or CG-Nio-CGLD) peptide loaded in Chitosan Glutamate-Coated Niosomes as anti-Colorectal cancer activity.

BACKGROUND: Colorectal cancer (CRC), now the second most prevalent malignant tumor worldwide, is more prevalent in young adults. In recent decades, there has been progress in creating anti-colorectal cancer medications, including cytotoxic compounds. OBJECTIVES: Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of novel formulations in preventing colorectal cancer. METHODS: During this study, we assessed a new kind of niosome called cyclo-Gly-L-DOPA (CG-Nio-CGLD) made from chitosan glutamate. We evaluated the anti-colorectal cancer properties of CG-Nio-CGLD utilizing CCK-8, invasion assay, MTT assay, flow cytometry, and cell cycle analysis. The transcription of genes associated with apoptosis was analyzed using quantitative real-time PCR. At the same time, the cytotoxicity of nanomaterials on both cancer and normal cell lines was assessed using MTT assays. Novel anticancer drugs are needed to surmount existing obstacles. A recent study investigated the effectiveness of newly developed formulations in preventing colorectal cancer. RESULTS: The Nio-CGLD and CG-Nio-CGLD were spherical mean diameters of 169.12 ± 1.87 and 179.26 ± 2.17 nm, respectively. Entrapment efficiency (EE%) measurements of the Nio-CGLD and CG-Nio-CGLD were 63.12 ± 0.51 and 76.43 ± 0.34%, respectively. In the CG-Nio-CGLD group, the percentages of early, late, necrotic, and viable CL40 cells were 341.93%, 23.27%, 9.32%, and 25.48%. The transcription of the genes PP53, cas3, and cas8 was noticeably higher in the treatment group compared to the control group (P > 0.001). Additionally, the treatment group had lower BCL2 and survivin gene expression levels than the control group (P < 0.01). Additionally, CG-Nio-CGLD formulations demonstrated a biocompatible nanoscale delivery mechanism and displayed little cytotoxicity toward the CCD 841 CoN reference cell line. CONCLUSION: These findings indicate that chitosan-based noisome encapsulation may enhance the effectiveness of CG-Nio-CGLD formulations in fighting cancer.

CXCR4-Targeted 68 Ga-Pentixafor PET/CT Imaging in Inflammatory Bowel Disease.

PURPOSE: To investigate the role of CXCR4-targeted 68 Ga-pentixafor PET/CT imaging in inflammatory bowel disease (IBD). METHODS: Five IBD patients and 12 control subjects performing 68 Ga-pentixafor PET/CT examinations were included. 68 Ga-pentixafor PET/CT imaging and endoscopic findings were recorded and compared. The semiquantitative parameters of 68 Ga-pentixafor uptake by the lesion segments in IBD patients and the normal intestines in the control were investigated. RESULTS: Among these 5 IBD patients, endoscopy successfully examined a total of 26 intestinal segments, with 13 segments showing endoscopic lesions. 68 Ga-pentixafor PET/CT was positive in all endoscopy-proven lesions (13/13). Additionally, 68 Ga-pentixafor PET/CT revealed the lesions in small intestines and colons that cannot be reached by endoscopy due to severe stenosis, and mesenteric lymphadenitis accompanied IBD. The SUV max of the lesion segments in IBD patients was significantly higher than that of the normal intestines in the control group (median, 3.15 [range, 1.61-6.26] vs 1.67 [1.18-2.29], P < 0.001). Moreover, the SUV max ratios of the lesion segments/liver or blood pool were higher when compared with the control (2.20 [1.13-3.26] vs 0.85 [0.54-1.20]; 1.66 [0.94-2.95] vs 0.67 [0.52-1.04]; P ≤ 0.001). CONCLUSIONS: 68 Ga-pentixafor PET/CT can be a potentially valuable tool to assess the active intestinal lesions of IBD with high sensitivity. Moreover, this noninvasive approach does not require fasting or bowel preparation, offering good tolerance and safety.

Oxidation-guided and collision-induced linearization assists de novo sequencing of thioether macrocyclic peptides.

Oxidation of a thioether linkage in thioether-closed macrocyclic peptides led to collision-induced site-selective linearization of the peptides. This method has allowed for de novo sequencing of thioether macrocyclic peptides. The utility of the sequencing method was demonstrated by identifying the correct peptide sequences from a virtually randomized thioether macrocyclic peptide library.

Targeting the hydrophobic region of pyroglutamate-modified amyloid-ß by tyrocidine A prevents its nucleation-aggregation process and its "catalytic effect" on the Aßs aggregation.

Pyroglutamate (pE)-modified amyloid-ß (Aß) peptides play a crucial role in the development of Alzheimer's disease. pEAß3-42 can rapidly form oligomers that gradually elongate hydrophobic segments to form ß-sheet-rich amyloid intermediates, ultimately resulting in the formation of mature amyloid fibrils. pEAß3-42 can also catalyze the aggregation of Aß species and subsequently accelerate the formation of amyloid senile plaques. Considering the recent clinical success of the pEAß3-42-targeting antibody donanemab, molecules that strongly bind pEAß3-42 and prevent its aggregation and catalytic effect on Aßs may also provide potential therapeutic options for Alzheimer's disease. Here, we demonstrate that the natural antibiotic cyclopeptide tyrocidine A (TA) not only strongly inhibits the aggregation of Aß1-42 as previously reported, but also interacts with the hydrophobic C-terminus and middle domain of pEAß3-42 to maintain an unordered conformation, effectively impeding the formation of initial oligomers and subsequently halting the aggregation of pEAß3-42. Furthermore, TA can disrupt the "catalytic effect" of pEAß3-42 on amyloid aggregates, effectively suppressing Aß aggregation and ultimately preventing the pathological events induced by Aßs.

Somatostatin analogues as a treatment option for cystoid maculopathy in retinitis pigmentosa.

AIMS: This study aimed to evaluate the effectiveness of somatostatin analogues (SA) for cystoid maculopathy (CM) in retinitis pigmentosa (RP) patients. MATERIALS AND METHODS: In this retrospective case series, clinical and imaging characteristics of 28 RP patients with CM, unresponsive to carbonic anhydrase inhibitors, were collected from medical charts. All patients received SA treatment as an alternative (octreotide long-acting release at 20 mg/month or 30 mg/month, or lanreotide at 90 mg/month or 120 mg/month). Outcome measures were mean reduction in foveal thickness (FT) and foveal volume (FV) and mean increase in best-corrected visual acuity at 3, 6 and 12 months of treatment initiation. Linear mixed models were used to calculate the effectiveness over time. RESULTS: 52 eyes of 28 RP patients were included; 39% were male. The median age at the start of treatment was 39 years (IQR 30-53). Median follow-up was 12 months (range 6-12). From baseline to 12 months, the mean FT decreased from 409±136 µm to 334±119 µm and the mean FV decreased from 0.31±0.10 mm3 to 0.25±0.04 mm3. Linear mixed model analyses showed a significant decrease in log FT and log FV at 3, 6 and 12 months after the start of treatment compared with baseline measurements (p<0.001, p<0.001, p<0.001). Mean best-corrected visual acuity did not increase significantly (0.46±0.35 logMAR to 0.45±0.38 logMAR after 12 months). DISCUSSION: SA may be an effective alternative treatment to reduce CM in RP patients.

CREMP: Conformer-rotamer ensembles of macrocyclic peptides for machine learning.

Computational and machine learning approaches to model the conformational landscape of macrocyclic peptides have the potential to enable rational design and optimization. However, accurate, fast, and scalable methods for modeling macrocycle geometries remain elusive. Recent deep learning approaches have significantly accelerated protein structure prediction and the generation of small-molecule conformational ensembles, yet similar progress has not been made for macrocyclic peptides due to their unique properties. Here, we introduce CREMP, a resource generated for the rapid development and evaluation of machine learning models for macrocyclic peptides. CREMP contains 36,198 unique macrocyclic peptides and their high-quality structural ensembles generated using the Conformer-Rotamer Ensemble Sampling Tool (CREST). Altogether, this new dataset contains nearly 31.3 million unique macrocycle geometries, each annotated with energies derived from semi-empirical extended tight-binding (xTB) DFT calculations. Additionally, we include 3,258 macrocycles with reported passive permeability data to couple conformational ensembles to experiment. We anticipate that this dataset will enable the development of machine learning models that can improve peptide design and optimization for novel therapeutics.

Insights into the antifungal mechanism of Bacillus subtilis cyclic lipopeptide iturin A mediated by potassium ion channel.

Fungal infections pose severe and potentially lethal threats to plant, animal, and human health. Ergosterol has served as the primary target for developing antifungal medications. However, many antifungal drugs remain highly toxic to humans due to similarity in cell membrane composition between fungal and animal cells. Iturin A, lipopeptide produced by Bacillus subtilis, efficiently inhibit various fungi, but demonstrated safety in oral administration, indicating the existence of targets different from ergosterol. To pinpoint the exact antifungal target of iturin A, we used homologous recombination to knock out and overexpress erg3, a key gene in ergosterol synthesis. Saccharomyces cerevisiae and Aspergillus carbonarius were transformed using the LiAc/SS-DNNPEG and Agrobacterium-mediated transformation (AMT), respectively. Surprisingly, increasing ergosterol content did not augment antifungal activity. Furthermore, iturin A's antifungal activity against S. cerevisiae was reduced while it pre-incubation with voltage-gated potassium (Kv) channel inhibitor, indicating that Kv activation was responsible for cell death. Iturin A was found to activate the Kv protein, stimulating K+ efflux from cell. In vitro tests confirmed interaction between iturin A and Kv protein. This study highlights Kv as one of the precise targets of iturin A in its antifungal activity, offering a novel target for the development of antifungal medications.

An N-ortho-nitrobenzylated benzanilide amino acid enables control of the conformation and membrane permeability of cyclic peptides.

We designed and synthesized an N-ortho-nitrobenzylated benzanilide-based amino acid having a cis-amide structure that facilitates cyclization of peptides containing it. Photo-induced removal of the nitrobenzyl group from this residue in the resulting cyclized peptides dramatically alters their conformation and passive membrane permeability via complete cis-amide to trans-amide conversion.

Targeted Inhibition of Lymphovascular Invasion Formation with CREKA Peptide-Modified Silicasomes to Boost Chemotherapy in Bladder Cancer.

Despite its significant clinical efficacy as a first-line treatment for advanced bladder cancer, cisplatin-based chemotherapy provides a limited benefit for patients with lymphovascular invasion (LVI), which is characterized by the presence of tumor emboli within blood vessels and associated with enhanced cisplatin resistance and metastatic potential. Notably, platelets, a critical component of LVI, hinder the delivery of chemotherapeutic agents to tumors and facilitate metastasis. Consequently, platelet function inhibition holds the potential to disrupt LVI formation, as well as augment the antitumor activity of cisplatin. Herein, we developed a tumor microenvironment-targeted nanodrug with lipid-coated mesoporous silica nanoparticles (silicasomes) that synergistically combines cisplatin with an antiplatelet agent, tirofiban, for bladder cancer treatment. The customized nanodrug can concurrently prevent LVI formation and enhance the chemotherapeutic efficacy without significant adverse effects. This study supports the integration of chemotherapy and antiplatelet therapy via a silicasome-based nanosystem as a highly promising strategy for bladder cancer management.

Proximity-driven site-specific cyclization of phage-displayed peptides.

Cyclization provides a general strategy for improving the proteolytic stability, cell membrane permeability and target binding affinity of peptides. Insertion of a stable, non-reducible linker into a disulphide bond is a commonly used approach for cyclizing phage-displayed peptides. However, among the vast collection of cysteine reactive linkers available, few provide the selectivity required to target specific cysteine residues within the peptide in the phage display system, whilst sparing those on the phage capsid. Here, we report the development of a cyclopropenone-based proximity-driven chemical linker that can efficiently cyclize synthetic peptides and peptides fused to a phage-coat protein, and cyclize phage-displayed peptides in a site-specific manner, with no disruption to phage infectivity. Our cyclization strategy enables the construction of stable, highly diverse phage display libraries. These libraries can be used for the selection of high-affinity cyclic peptide binders, as exemplified through model selections on streptavidin and the therapeutic target αvß3.

A short-lived peptide signal regulates cell-to-cell communication in Listeria monocytogenes.

Quorum sensing (QS) is a mechanism that regulates group behavior in bacteria, and in Gram-positive bacteria, the communication molecules are often cyclic peptides, called autoinducing peptides (AIPs). We recently showed that pentameric thiolactone-containing AIPs from Listeria monocytogenes, and from other species, spontaneously undergo rapid rearrangement to homodetic cyclopeptides, which hampers our ability to study the activity of these short-lived compounds. Here, we developed chemically modified analogues that closely mimic the native AIPs while remaining structurally intact, by introducing N-methylation or thioester-to-thioether substitutions. The stabilized AIP analogues exhibit strong QS agonism in L. monocytogenes and allow structure-activity relationships to be studied. Our data provide evidence to suggest that the most potent AIP is in fact the very short-lived thiolactone-containing pentamer. Further, we find that the QS system in L. monocytogenes is more promiscuous with respect to the structural diversity allowed for agonistic AIPs than reported for the more extensively studied QS systems in Staphylococcus aureus and Staphylococcus epidermidis. The developed compounds will be important for uncovering the biology of L. monocytogenes, and the design principles should be broadly applicable to the study of AIPs in other species.

Cyclo(l-Pro-l-Tyr) Isolated from the Human Skin Commensal Corynebacterium tuberculostearicum Inhibits Tyrosinase.

Melanin is produced by melanocytes to protect human skin from harmful ultraviolet radiation. During skin cell renewal, melanin and dead skin cells are disposed of. However, prolonged exposure to ultraviolet rays or aging can disturb this cycle, leading to skin hyperpigmentation due to melanin accumulation. Tyrosinase is a crucial enzyme involved in melanin biosynthesis. Although various compounds, including tyrosine inhibitors, that counteract melanin accumulation have been reported, some, such as hydroquinone, are toxic and can cause vitiligo. Meanwhile, the skin is the largest organ and the outermost layer of the immune system, containing a diverse range of bacteria that produce low-toxicity compounds. In the current study, we aim to identify metabolites produced by skin microbiota that inhibit tyrosinase. Specifically, mushroom tyrosinase served as the study model. Following commensal skin bacteria screening, Corynebacterium tuberculostearicum was found to inhibit tyrosinase activity. The active compound was cyclo(l-Pro-l-Tyr); commercially available cyclo(l-Pro-l-Tyr) also exhibited inhibitory activity. Docking simulations suggested that cyclo(l-Pro-l-Tyr) binds to the substrate-binding site of mushroom tyrosinase, obstructing the substrate pocket and preventing its activity. Hence, cyclo(l-Pro-l-Tyr) might have potential applications as a cosmetic agent and food additive.

Permutational Encoding Strategy Accelerates HIT Validation from Single-Stranded DNA-Encoded Libraries.

DNA-Encoded Libraries (DELs) allow the parallel screening of millions of compounds for various applications, including de novo discovery or affinity maturation campaigns. However, library construction and HIT resynthesis can be cumbersome, especially when library members present an unknown stereochemistry. We introduce a permutational encoding strategy suitable for the construction of highly pure single-stranded single-pharmacophore DELs, designed to distinguish isomers at the sequencing level (e.g., stereoisomers, regio-isomers, and peptide sequences). This approach was validated by synthesizing a mock 921,600-member 4-amino-proline single-stranded DEL ("DEL1"). While screening DEL1 against different targets, high-throughput sequencing results showed selective enrichment of the most potent stereoisomers, with enrichment factors that outperform conventional encoding strategies. The versatility of our methodology was additionally validated by encoding 24 scaffolds derived from different permutations of the amino acid sequence of a previously described cyclic peptide targeting Fibroblast Activation Protein (FAP-2286). The resulting library ("DEL2") was interrogated against human FAP, showing selective enrichment of five cyclic peptides. We observed a direct correlation between enrichment factors and on-DNA binding affinities. The presented encoding methodology accelerates drug discovery by facilitating library synthesis and streamlining HIT resynthesis while enhancing enrichment factors at the DEL sequencing level. This facilitates the identification of HIT candidates prior to medicinal chemistry and affinity maturation campaigns.

Exploring the Potential of Cyclic Peptidyl Antitumor Agents Derived from Natural Macrocyclic Peptide Phakellistatin 13.

The exploration of novel anticancer compounds based on natural cyclopeptides has emerged as a pivotal paradigm in the contemporary advancement of macrocyclic pharmaceuticals. Phakellistatin 13 is a cycloheptapeptide derived from the brown snubby sponge and exhibits remarkable antitumor activity. In this study, we have designed and synthesized a series of chiral cyclopeptides incorporating the rigid isoindolinone moiety at various sites within the natural cycloheptapeptide Phakellistatin 13, with the aim of investigating conformationally constrained cyclopeptides as potential antitumor agents. Cyclopeptide 3, comprising alternating l-/d-amino acid residues, exhibited promising antihepatocellular carcinoma effects. Detailed biological experiments have revealed that Phakellistatin 13 analogs effectively inhibit the proliferation of tumor cells and induce apoptosis and autophagy, while also causing cell cycle arrest through the modulation of the p53 and mitogen-activated protein kinase (MAPK) signaling pathway. This study not only provides valuable insights into chemical structural modifications but also contributes to a deeper understanding of the biological mechanisms underlying the development of natural cyclopeptide-based drugs.

Discovery of Novel Peptide Antagonists Targeting GPR55 for Liver Inflammation and Fibrosis.

Liver fibrosis is a condition characterized by aberrant proliferation of connective tissue in the liver resulting from diverse etiological factors. G protein-coupled receptor GPR55 has recently been identified as a regulator of liver diseases. Herein, we report the discovery of a cyclic peptide P1-1 that antagonizes GPR55 and suppresses collagen secretion in hepatic stellate cells. The alanine scanning and docking study was carried out to predict the binding mode and allowed for further structural optimization of peptide antagonists for GPR55. The subsequent in vivo study demonstrated that P1-1 ameliorates CCl4-induce and MCD-diet-induce acute liver inflammation and fibrosis. Further study indicates that P1-1 reduces reactive oxygen species (ROS) production, attenuates ER stress, and inhibits mitochondria-associated hepatocyte apoptosis. In this work, we provided the first successful example of antagonizing GPR55 for liver inflammation and fibrosis, which validates GPR55 as a promising target for the treatment of liver fibrosis and affords a high-potent GPR55 antagonist P1-1 as a potential therapeutic candidate.

The effect of endothelin a receptor inhibition and biological sex on cutaneous microvascular function in non-Hispanic Black and White young adults.

The purpose of this study was to investigate whether endothelin-A receptor (ETAR) inhibition in non-Hispanic Black (NHB) and White (NHW) young adults depends on biological sex. We recruited females during low hormone (n = 22) and high hormone (n = 22) phases, and males (n = 22). Participants self-identified as NHB (n = 33) or NHW (n = 33). Participants were instrumented with two microdialysis fibers: (1) lactated Ringer's (control) and (2) 500 nM BQ-123 (ETAR antagonist). Local heating was used to elicit cutaneous vasodilation, and an infusion of 20 mM L-NAME to quantify NO-dependent vasodilation. At control sites, NO-dependent vasodilation was lowest in NHB males (46 ± 13 %NO) and NHB females during low hormone phases (47 ± 12 %NO) compared to all NHW groups. Inhibition of ETAR increased NO-dependent vasodilation in NHB males (66 ± 13 %NO), in both groups of females during low hormone phases (NHW, control: 64 ± 12 %NO, BQ-123: 85 ± 11 %NO; NHB, BQ-123: 68 ± 13 %NO), and in NHB females during high hormone phases (control: 61 ± 11 %NO, BQ-123: 83 ± 9 %NO). There was no effect for ETAR inhibition in NHW males or females during high hormone phases. These data suggest the effect of ETAR inhibition on NO-dependent vasodilation is influenced by biological sex and racial identity.

Accessing diverse bicyclic peptide conformations using 1,2,3-TBMB as a linker.

Bicyclic peptides are a powerful modality for engaging challenging drug targets such as protein-protein interactions. Here, we use 1,2,3-tris(bromomethyl)benzene (1,2,3-TBMB) to access bicyclic peptides with diverse conformations that differ from conventional bicyclisation products formed with 1,3,5-TBMB. Bicyclisation at cysteine residues under aqueous buffer conditions proceeds efficiently, with broad substrate scope, compatibility with high-throughput screening, and clean conversion (>90%) for 96 of the 115 peptides tested. We envisage that the 1,2,3-TBMB linker will be applicable to a variety of peptide screening techniques in drug discovery.

Crafting Unnatural Peptide Macrocycles via Rh(III)-Catalyzed Carboamidation.

Contemporary developments in the field of peptide macrocyclization methodology are imperative for enabling the advance of drug design in medicinal chemistry. This report discloses a Rh(III)-catalyzed macrocyclization via carboamidation, reacting acryloyl-peptide-dioxazolone precursors and arylboronic acids to form complex cyclic peptides with concomitant incorporation of noncanonical α-amino acids. The diverse and modular technology allows for expedient access to a wide variety of cyclic peptides from 4 to 15 amino acids in size and features simultaneous formation of unnatural phenylalanine and tyrosine derivatives with up to >20:1 diastereoselectivity. The reaction showcases an expansive substrate scope with 45 examples and is compatible with the majority of standard protected amino acids used in Fmoc-solid phase peptide synthesis. The methodology is applied to the synthesis of multiple peptidomimetic macrocyclic analogs, including derivatives of cyclosomatostatin and gramicidin S.

Isolation and Total Synthesis of PM170453, a New Cyclic Depsipeptide Isolated from Lyngbya sp.

In our continuing search for biologically active new chemical entities from marine organisms, we have isolated a new cyclic depsipeptide, PM170453 (1), from a cyanobacterium of the genus Lyngbya sp., collected in the Indo-Pacific Ocean. Structure elucidation of the isolated compound was determined by spectroscopic methods including MS, 1H, 13C and 2D-NMR. To solve the supply problem for 1 and progress pharmaceutical development, the total synthesis of 1 that involves a total of 20 chemical steps in a convergent process was carried out. Its in vitro cytotoxic activity against four human tumor cell lines, as well as the inhibition of the interaction between the programmed cell death protein 1 PD-1 and its ligand PD-L1 were also evaluated.

Targeted Delivery of Quinoxaline-Based Semiconducting Polymers for Tumor Photothermal Therapy.

Photothermal therapy (PTT) holds great potential in the field of cancer treatment due to its high specificity and low invasiveness. However, the low conversion efficiency, inadequate tumor accumulation, and limited cellular uptake continue to impede PTT effectiveness in treating tumors. The present study focuses on the utilization of quinoxaline and its nanoparticles to develop an organic semiconducting photothermal agent (PAQI-BDTT) for tumor photothermal therapy. To achieve this, PAQI-BDTT was encapsulated within liposomes modified with cyclic Arg-Gly-Asp (cRGD) peptide targeting tumors (named T-BDTT-Lipo). Notably, T-BDTT-Lipo demonstrated a positive photothermal conversion efficiency of 74% when exposed to an 808 nm laser, along with NIR-II fluorescence imaging capabilities. The efficacy of T-BDTT-Lipo in tumor tissue accumulation and precise targeting of malignant cells has been confirmed through both in vitro and in vivo experiments guided by fluorescence imaging. Under single dose and 808 nm light irradiation, T-BDTT-Lipo generated local intracellular hyperthermia at the tumor site. The elevated temperature additionally exerted a significant inhibitory effect on tumor growth and recurrence, thereby extending the survival duration of mice harboring tumors. The therapeutic nanosystem (T-BDTT-Lipo) proposed in this work demonstrates the enormous potential of semiconducting photothermal agents in photothermal therapy, laying the foundation for the next clinical application.