Quantitative Proteomic Profiling of Tachyplesin I Targets in U251 Gliomaspheres

Current developments and prospects of the antibiotic delivery systems

Antibiotics have remained the cornerstone for the treatment of bacterial infections ever since their discovery in the twentieth century. The uproar over antibiotic resistance among bacteria arising from genome plasticity and biofilm development has rendered current antibiotic therapies ineffective, urging the development of innovative therapeutic approaches. The development of antibiotic resistance among bacteria has further heightened the clinical failure of antibiotic therapy, which is often linked to its low bioavailability, side effects, and poor penetration and accumulation at the site of infection. In this review, we highlight the potential use of siderophores, antibodies, cell-penetrating peptides, antimicrobial peptides, bacteriophages, and nanoparticles to smuggle antibiotics across impermeable biological membranes to achieve therapeutically relevant concentrations of antibiotics and combat antimicrobial resistance (AMR). We will discuss the general mechanisms via which each delivery system functions and how it can be tailored to deliver antibiotics against the paradigm of mechanisms underlying antibiotic resistance.

Natural Anticancer Peptides from Marine Animal Species: Evidence from In Vitro Cell Model Systems

Anticancer peptides are short and structurally heterogeneous aminoacidic chains, which display selective cytotoxicity mostly against tumor cells, but not healthy cells, based on their different cell surface properties. Their anti-tumoral activity is carried out through interference with intracellular homeostasis, such as plasmalemma integrity, cell cycle control, enzymatic activities and mitochondrial functions, ultimately acting as angiogenesis-, drug resistance- and metastasis-inhibiting agents, immune stimulators, differentiation inducers and necrosis or extrinsic/intrinsic apoptosis promoters. The marine environment features an ever-growing level of biodiversity, and seas and oceans are poorly exploited mines in terms of natural products of biomedical interest. Adaptation processes to extreme and competitive environmental conditions led marine species to produce unique metabolites as a chemical strategy to allow inter-individual signalization and ensure survival against predators, infectious agents or UV radiation. These natural metabolites have found broad use in various applications in healthcare management, due to their anticancer, anti-angiogenic, anti-inflammatory and regeneration abilities. The aim of this review is to pick selected studies that report on the isolation of marine animal-derived peptides and the identification of their anticancer activity in in vitro cultures of cancer cells, and list them with respect to the taxonomical hierarchy of the source organism.

The role of lysosomal peptidases in glioma immune escape: underlying mechanisms and therapeutic strategies

Glioblastoma is the most common primary malignant tumor of the central nervous system, which has the characteristics of strong invasion, frequent recurrence, and rapid progression. These characteristics are inseparable from the evasion of glioma cells from immune killing, which makes immune escape a great obstacle to the treatment of glioma, and studies have confirmed that glioma patients with immune escape tend to have poor prognosis. The lysosomal peptidase lysosome family plays an important role in the immune escape process of glioma, which mainly includes aspartic acid cathepsin, serine cathepsin, asparagine endopeptidases, and cysteine cathepsins. Among them, the cysteine cathepsin family plays a prominent role in the immune escape of glioma. Numerous studies have confirmed that glioma immune escape mediated by lysosomal peptidases has something to do with autophagy, cell signaling pathways, immune cells, cytokines, and other mechanisms, especially lysosome organization. The relationship between protease and autophagy is more complicated, and the current research is neither complete nor in-depth. Therefore, this article reviews how lysosomal peptidases mediate the immune escape of glioma through the above mechanisms and explores the possibility of lysosomal peptidases as a target of glioma immunotherapy.

Tachyplesin I and its derivatives: A pharmaco-chemical perspective on their antimicrobial and antitumor potential

INTRODUCTION

Increasing evidence suggests that intratumor microbiota are an intrinsic component in the tumor microenvironment across multiple cancer types, and that there is a close relationship between microbiota and tumor progression. Therefore, how to address the interaction between bacteria and malignances has become a growing concern. Tachyplesin I (TPI), a peptide with dual antimicrobial and antitumor effects, holds great promise as a therapeutic alternative for the aforementioned diseases, with the advantage of broad-spectrum activities, quick killing efficacy, and a low tendency to induce resistance.

AREAS COVERED

This review comprehensively summarizes the pharmacological mechanisms of TPI with an emphasis on its antimicrobial and antitumor potential. Furthermore, it presents advances in TPI derivatives and gives a perspective on their future development. The article is based on literature searches using PubMed and SciFinder to retrieve the most up-to-date information of TPI.

EXPERT OPINION

Bacterial infections and cancer both pose a serious threat to health due to their symbiotic interactions and drug resistance. TPI is anticipated to be a novel agent to control pathogenic bacteria and various tumors through multiple mechanisms of action. Indeed, the continuous advancements in chemical modification and innovative applications of TPI give hope for future improvements in therapeutic efficacy.

Innate Immunity Mechanisms in Marine Multicellular Organisms

The innate immune system provides an adequate response to stress factors and pathogens through pattern recognition receptors (PRRs), located on the surface of cell membranes and in the cytoplasm. Generally, the structures of PRRs are formed by several domains that are evolutionarily conserved, with a fairly high degree of homology in representatives of different species. The orthologs of TLRs, NLRs, RLRs and CLRs are widely represented, not only in marine chordates, but also in invertebrates. Study of the interactions of the most ancient marine multicellular organisms with microorganisms gives us an idea of the evolution of molecular mechanisms of protection against pathogens and reveals new functions of already known proteins in ensuring the body’s homeostasis. The review discusses innate immunity mechanisms of protection of marine invertebrate organisms against infections, using the examples of ancient multicellular hydroids, tunicates, echinoderms, and marine worms in the context of searching for analogies with vertebrate innate immunity. Due to the fact that mucous membranes first arose in marine invertebrates that have existed for several hundred million years, study of their innate immune system is both of fundamental importance in terms of understanding molecular mechanisms of host defense, and of practical application, including the search of new antimicrobial agents for subsequent use in medicine, veterinary and biotechnology.

Marine Invertebrate Peptides: Antimicrobial Peptides

Antimicrobial peptides are an important component of many organisms’ innate immune system, with a good inhibitory or killing effect against the invading pathogens. As a type of biological polypeptide with natural immune activities, antimicrobial peptides have a broad spectrum of antibacterial, antiviral, and antitumor activities. Nevertheless, these peptides cause no harm to the organisms themselves. Compared with traditional antibiotics, antimicrobial peptides have the advantage of not producing drug resistance and have a unique antibacterial mechanism, which has attracted widespread attention. In this study, marine invertebrates were classified into arthropods, annelids, mollusks, cnidarians, and tunicata. We then analyzed the types, sources and antimicrobial activities of the antimicrobial peptides in each group. We also reviewed the immune mechanism from three aspects: membrane-targeted direct killing effects, non-membrane targeting effects and immunomodulatory effects. Finally, we discussed their applications and the existing problems facing antimicrobial peptides in actual production. The results are expected to provide theoretical support for future research and applications of antimicrobial peptides in marine invertebrates.

A proteomic view on lysosomes

Lysosomes are the main degradative organelles of almost all eukaryotic cells. They fulfil a crucial function in cellular homeostasis, and impairments in lysosomal function are connected to a continuously increasing number of pathological conditions. In recent years, lysosomes are furthermore emerging as control centers of cellular metabolism, and major regulators of cellular signaling were shown to be activated at the lysosomal surface. To date, >300 proteins were demonstrated to be located in/at the lysosome, and the lysosomal proteome and interactome is constantly growing. For the identification of these proteins, and their involvement in cellular mechanisms or disease progression, mass spectrometry (MS)-based proteomics has proven its worth in a large number of studies. In this review, we are recapitulating the application of MS-based approaches for the investigation of the lysosomal proteome, and their application to a diverse set of research questions. Numerous strategies were applied for the enrichment of lysosomes or lysosomal proteins and their identification by MS-based methods. This allowed for the characterization of the lysosomal proteome, the investigation of lysosome-related disorders, the utilization of lysosomal proteins as biomarkers for diseases, and the characterization of lysosome-related cellular mechanisms. While these >60 studies provide a comprehensive picture of the lysosomal proteome across several model organisms and pathological conditions, various proteomics approaches have not been applied to lysosomes yet, and a large number of questions are still left unanswered.

Bioactive Compounds with Antiglioma Activity from Marine Species

The search for new chemical compounds with antitumor pharmacological activity is a necessary process for creating more effective drugs for each specific malignancy type. This review presents the outcomes of screening studies of natural compounds with high anti-glioma activity. Despite significant advances in cancer therapy, there are still some tumors currently considered completely incurable including brain gliomas. This review covers the main problems of the glioma chemotherapy including drug resistance, side effects of common anti-glioma drugs, and genetic diversity of brain tumors. The main emphasis is made on the characterization of natural compounds isolated from marine organisms because taxonomic diversity of organisms in seawaters significantly exceeds that of terrestrial species. Thus, we should expect greater chemical diversity of marine compounds and greater likelihood of finding effective molecules with antiglioma activity. The review covers at least 15 classes of organic compounds with their chemical formulas provided as well as semi-inhibitory concentrations, mechanisms of action, and pharmacokinetic profiles. In conclusion, the analysis of the taxonomic diversity of marine species containing bioactives with antiglioma activity is performed noting cytotoxicity indicators and to the tumor cells in comparison with similar indicators of antitumor agents approved for clinical use as antiglioblastoma chemotherapeutics.

Transcriptome Analysis Reveals the Resistance Mechanism of Pseudomonas aeruginosa to Tachyplesin I

Background

Tachyplesin I is a cationic antimicrobial peptide with a typical cyclic antiparallel β-sheet structure. We previously demonstrated that long-term continuous exposure to increased concentration of tachyplesin I can induce resistant Gram-negative bacteria. However, no significant information is available about the resistance mechanism of Pseudomonas aeruginosa (P. aeruginosa) to tachyplesin I.

Materials and Methods

In this study, the global gene expression profiling of P. aeruginosa strain PA-99 and P. aeruginosa CGMCC1.2620 (PA1.2620) was conducted using transcriptome sequencing. For this purpose, outer membrane permeability and outer membrane proteins (OMPs) were further analyzed.

Results

Transcriptome sequencing detected 672 upregulated and 787 downregulated genes, covering Clusters of Orthologous Groups (COGs) of P. aeruginosa strain PA-99 compared with PA1.2620. Totally, 749 differentially expressed genes (DEGs) were assigned to 98 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and among them, a two-component regulatory system, a beta-lactam resistance system, etc. were involved in some known genes resistant to drugs. Additionally, we further attempted to indicate whether the resistance mechanism of P. aeruginosa to tachyplesin I was associated with the changes of outer membrane permeability and OMPs.

Conclusion

Our results indicated that P. aeruginosa resistant to tachyplesin I was mainly related to reduced entry of tachyplesin I into the bacterial cell due to overexpression of efflux pump, in addition to a decrease of outer membrane permeability. Our findings were also validated by pathway enrichment analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR). This study may provide a promising guidance for understanding the resistance mechanism of P. aeruginosa to tachyplesin I.

Cyclic Analogues of Horseshoe Crab Peptide Tachyplesin I with Anticancer and Cell Penetrating Properties

Tachyplesin-I (TI) is a host defense peptide from the horseshoe crab Tachypleus tridentatus that has outstanding potential as an anticancer therapeutic lead. Backbone cyclized TI (cTI) has similar anticancer properties to TI but has higher stability and lower hemolytic activity. We designed and synthesized cTI analogues to further improve anticancer potential and investigated structure-activity relationships based on peptide-membrane interactions, cellular uptake, and anticancer activity. The membrane-binding affinity and cytotoxic activity of cTI were found to be highly dependent on peptide hydrophobicity and charge. We describe two analogues with increased selectivity toward melanoma cells and one analogue with the ability to enter cells with high efficacy and low toxicity. Overall, the structure-activity relationship study shows that cTI can be developed as a membrane-active antimelanoma lead, or be employed as a cell penetrating peptide scaffold that can target and enter cells without damaging their integrity.

Characterization of Tachyplesin Peptides and Their Cyclized Analogues to Improve Antimicrobial and Anticancer Properties

Tachyplesin I, II and III are host defense peptides from horseshoe crab species with antimicrobial and anticancer activities. They have an amphipathic β-hairpin structure, are highly positively-charged and differ by only one or two amino acid residues. In this study, we compared the structure and activity of the three tachyplesin peptides alongside their backbone cyclized analogues. We assessed the peptide structures using nuclear magnetic resonance (NMR) spectroscopy, then compared the activity against bacteria (both in the planktonic and biofilm forms) and a panel of cancerous cells. The importance of peptide-lipid interactions was examined using surface plasmon resonance and fluorescence spectroscopy methodologies. Our studies showed that tachyplesin peptides and their cyclic analogues were most potent against Gram-negative bacteria and melanoma cell lines, and showed a preference for binding to negatively-charged lipid membranes. Backbone cyclization did not improve potency, but improved peptide stability in human serum and reduced toxicity toward human red blood cells. Peptide-lipid binding affinity, orientation within the membrane, and ability to disrupt lipid bilayers differed between the cyclized peptide and the parent counterpart. We show that tachyplesin peptides and cyclized analogues have similarly potent antimicrobial and anticancer properties, but that backbone cyclization improves their stability and therapeutic potential.

Microarray gene profiling analysis of glioblastoma cell line U87 reveals suppression of the FANCD2/Fanconi anemia pathway by the combination of Y15 and temozolomide

INTRODUCTION

A recent study showed that a combination of Y15 (a FAK autophosphorylation inhibitor) with temozolomide (TMZ) treatment was effective in glioblastoma (GBM) therapy. In this study, we further investigated the pathways and genes that are differentially expressed in Y15 and TMZ treated U87 cells via bioinformatics analysis.

MATERIAL AND METHODS

The microarray gene profiling analysis screened out genes with differential expression in U87 cells treated with TMZ and Y15. Gene set enrichment analysis (GSEA) identified the key GO terms and KEGG pathways in TMZ + Y15 treated U87 cells. The functional partner genes of TMZ were predicted by the STICH database. FANCD2 expression in U87 cells was detected by qRT-PCR. MTT assay and colony formation assay were conducted for cell viability detection, and flow cytometry was performed for cell apoptosis detection. Western blot was conducted to determine the expression levels of the downstream proteins of the Fanconi anemia (FA) pathway, FAN1 and BRCA2.

RESULTS

The FA pathway was suppressed in U87 cells after treatment with TMZ and Y15. Genes involved in this pathway, including FANCD2, were also down-regulated. FANCD2 knockdown could restrain viability and promote apoptosis of U87 cells, as well as enhancing the inhibitory effect of TMZ + Y15 treatment. FANCD2 could regulate the FA pathway as the protein expression levels of FAN1 and BRCA2 were modulated by FANCD2.

CONCLUSIONS

The FA pathway and FANCD2 are down-regulated in U87 cells treated with TMZ and Y15. FANCD2 down-regulation by TMZ + Y15 treatment suppressed growth of U87 cells through inhibiting the FA pathway.

Radiosynthesis and evaluation of [11C]CMP, a high affinity GSK3 ligand

Dysfunction of GSK3 is implicated in the etiology of many brain, inflammatory, cardiac diseases, and cancer. PET imaging would enable in vivo detection and quantification of GSK3 and can impact the choice of therapy, allow non-invasive monitoring of disease progression and treatment effects. In this report, the synthesis and evaluation of a high affinity GSK3 ligand, [¹¹C]2-(cyclopropanecarboxamido)-N-(4-methoxypyridin-3-yl)isonicotinamide, ([¹¹C]CMP, (3), (IC₅₀ = 3.4 nM, LogP = 1.1) is described. [¹¹C]CMP was synthesized in 25 ± 5% yield by radiomethylating the corresponding phenolate using [¹¹C]CH₃I. The radioligand exhibited modest uptake in U251 human glioblastoma cell lines with ∼50% specific binding. MicroPET studies in rats indicated negligible blood-brain barrier (BBB) penetration of [¹¹C]CMP, despite its high affinity and suitable logP value for BBB penetration. However, administration of cyclosporine prior to [¹¹C]CMP injection showed significant improvement in brain radioactivity uptake and the tracer binding. This finding indicates that [¹¹C]CMP might be a P-gp efflux substrate and therefore has some limitations for routine in vivo PET evaluations in brain.

Tachyplesin Causes Membrane Instability That Kills Multidrug-Resistant Bacteria by Inhibiting the 3-Ketoacyl Carrier Protein Reductase FabG

Tachyplesin is a type of cationic β-hairpin antimicrobial peptide discovered in horseshoe crab approximately 30 years ago that is well known for both its potential antimicrobial activities against multidrug-resistant bacteria and its cytotoxicity to mammalian cells. Though its physical interactions with artificial membranes have been well studied, details of its physiological mechanism of action the physiological consequences of its action remain limited. By using the DNA-binding fluorescent dye propidium iodide to monitor membrane integrity, confocal microscopy to assess the intracellular location of FITC-tagged tachyplesin, and RNA sequencing of the differentially expressed genes in four Gram-negative bacteria (Escherichia coli, Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa) treated with lethal or sublethal concentrations of tachyplesin, we found that compared with levofloxacin-treated bacteria, tachyplesin-treated bacteria showed significant effects on the pathways underlying unsaturated fatty acid biosynthesis. Notably, RNA levels of the conserved and essential 3-ketoacyl carrier protein reductase in this pathway (gene FabG) were elevated in all of the four bacteria after tachyplesin treatment. In vitro tests including surface plasmon resonance and enzyme activity assays showed that tachyplesin could bind and inhibit 3-ketoacyl carrier protein reductase, which was consistent with molecular docking prediction results. As unsaturated fatty acids are important for membrane fluidity, our results provided one possible mechanism to explain how tachyplesin kills bacteria and causes cytotoxicity by targeting membranes, which may be helpful for designing more specific and safer antibiotics based on the function of tachyplesin.