Genotoxicity and cellular uptake of cyclotides: Evidence for multiple modes of action

Integrative effects based on behavior, physiology and gene expression of tritiated water on zebrafish

Tritium is a water-soluble hydrogen isotope that releases beta rays during decay. In nature, tritium primarily exists as tritiated water (HTO), and its main source is nuclear power/processing plants. In recent decades, with the development of nuclear power industry, it is necessary to evaluate the impact of tritium on organisms. In this study, fertilized zebrafish embryos are treated with different HTO concentrations (3.7 × 10³ Bq/ml, 3.7 × 10⁴ Bq/ml, 3.7 × 10⁵ Bq/ml). After treatment with HTO, the zebrafish embryos developed without evident morphological changes. Nevertheless, the heart rate increased and locomotor activity decreased significantly. In addition, RNA-sequencing shows that HTO can affect gene expressions. The differentially expressed genes are enriched through many physiological processes and intracellular signaling pathways, including cardiac, cardiovascular, and nervous system development and the metabolism of xenobiotics by cytochrome P450. Moreover, the concentrations of thyroid hormones in the zebrafish decrease and the expression of thyroid hormone-related genes is disordered after HTO treatment. Our results suggest that exposure to HTO may affect the physiology and behaviors of zebrafish through physiological processes and intracellular signaling pathways and provide a theoretical basis for ecological risk assessment of tritium.

A Critical Review on Phytochemistry, Pharmacology of Viola odorata L. and Related Multipotential Products in Traditional Persian Medicine

Common violet (Viola odorata L., Violaceae) has shown various medical applications. Current study aimed to compile a review over chemical composition and medicinal properties of this plant in modern phytotherapy and its related multipotential products from traditional Persian medicine (TPM). Medicinal applications of V. odorata and respective products were derived from credible pharmaceutical textbooks of TPM (10th-18th century AD). In parallel, electronic databases including PubMed, Scopus, and ScienceDirect were explored for targeted purposes. Management of cough, fever, common cold, headache, insomnia, epilepsy, constipation, palpitation, dyspnea, dysuria, and skin diseases is of most applications of V. odorata, reported in TPM. On the other side, this herb plant has exerted antiinflammatory, analgesic, antioxidant, diuretic, antihypertensive, and antibacterial activities in modern phytotherapy. Violet TPM therapeutic preparations are including violet oil in the form of nasal or topical application for neurologic and skin disorders as well as pill, decoction, sweet syrup, and confection or semisolid oral preparations for skin, respiratory, gastrointestinal, and urinary ailments. Flavonoids, saponins, and alkaloids are responsible for pharmacological activities. Some medical applications of V. odorata in TPM have been proven by recent studies. However, more studies are needed to confirm these medicinal properties. Copyright © 2017 John Wiley & Sons, Ltd.

Resistance to the Cyclotide Cycloviolacin O2 in Salmonella enterica Caused by Different Mutations That Often Confer Cross-Resistance or Collateral Sensitivity to Other Antimicrobial Peptides

Antimicrobial peptides (AMPs) are essential components of innate immunity in all living organisms, and these potent broad-spectrum antimicrobials have inspired several antibacterial development programs in the past 2 decades. In this study, the development of resistance to the Gram-negative bacterium-specific peptide cycloviolacin O2 (cyO2), a member of the cyclotide family of plant miniproteins, was characterized in Salmonella enterica serovar Typhimurium LT2. Mutants isolated from serial passaging experiments in increasing concentrations of cyO2 were characterized by whole-genome sequencing. The identified mutations were genetically reconstituted in a wild-type background. The additive effect of mutations was studied in double mutants. Fitness costs, levels of resistance, and cross-resistance to another cyclotide, other peptide and nonpeptide antibiotics, and AMPs were determined. A variety of resistance mutations were identified. Some of these reduced fitness and others had no effect on fitness in vitro, in the absence of cyO2. In mouse competition experiments, four of the cyO2-resistant mutants showed a significant fitness advantage, whereas the effects of the mutations in the others appeared to be neutral. The level of resistance was increased by combining several individual resistance mutations. Several cases of cross-resistance and collateral sensitivity between cyclotides, other AMPs, and antibiotics were identified. These results show that resistance to cyclotides can evolve via several different types of mutations with only minor fitness costs and that these mutations often affect resistance to other AMPs.

The increasing role of phosphatidylethanolamine as a lipid receptor in the action of host defence peptides

Host defence peptides (HDPs) are antimicrobial agents produced by organisms across the prokaryotic and eukaryotic kingdoms. Many prokaryotes produce HDPs, which utilise lipid and protein receptors in the membranes of bacterial competitors to facilitate their antibacterial action and thereby survive in their niche environment. As a major example, it is well established that cinnamycin and duramycins from Streptomyces have a high affinity for phosphatidylethanolamine (PE) and exhibit activity against other Gram-positive organisms, such as Bacillus. In contrast, although eukaryotic HDPs utilise membrane interactive mechanisms to facilitate their antimicrobial activity, the prevailing view has long been that these mechanisms do not involve membrane receptors. However, this view has been recently challenged by reports that a number of eukaryotic HDPs such as plant cyclotides also use PE as a receptor to promote their antimicrobial activities. Here, we review current understanding of the mechanisms that underpin the use of PE as a receptor in the antimicrobial and other biological actions of HDPs and describe medical and biotechnical uses of these peptides, which range from tumour imaging and detection to inclusion in topical microbicidal gels to prevent the sexual transmission of HIV.

Chemistry and biology of cyclotides: circular plant peptides outside the box

Cyclotides stand out as the largest family of circular proteins of plant origin hitherto known, with more than 280 sequences isolated at peptide level and many more predicted from gene sequences. Their unusual stability resulting from the signature cyclic cystine knot (CCK) motif has triggered a broad interest in these molecules for potential therapeutic and agricultural applications. Since the time of the first cyclotide discovery, our laboratory in Uppsala has been engaged in cyclotide discovery as well as the development of protocols to isolate and characterize these seamless peptides. We have also developed methods to chemically synthesize cyclotides by Fmoc-SPPS, which are useful in protein grafting applications. In this review, experience in cyclotide research over two decades and the recent literature related to their structures, synthesis, and folding as well the recent proof-of-concept findings on their use as "epitope" stabilizing scaffolds are summarized.

Bioassays in natural product research - strategies and methods in the search for anti-inflammatory and antimicrobial activity

INTRODUCTION

Identifying bioactive molecules from complex biomasses requires careful selection and execution of relevant bioassays in the various stages of the discovery process of potential leads and targets.

OBJECTIVE

The aim of this review is to share our long-term experience in bioassay-guided isolation, and mechanistic studies, of bioactive compounds from different organisms in nature with emphasis on anti-inflammatory and antimicrobial activity.

METHODS

In the search for anti-inflammatory activity, in vivo and in vitro model combinations with enzymes and cells involved in the inflammatory process have been used, such as cyclooxygenases, human neutrophils and human cancer cell lines. Methods concerning adsorption and perforation of bacteria, fungi, human cells and model membranes, have been developed and optimised, with emphasis on antimicrobial peptides and their interaction with the membrane target, in particular their ability to distinguish host from pathogen.

RESULTS

A long-term research has provided experience of selection and combination of bioassay models, which has led to an increased understanding of ethnopharmacological and ecological observations, together with in-depth knowledge of mode of action of isolated compounds.

CONCLUSION

A more multidisciplinary approach and a higher degree of fundamental research in development of bioassays are often necessary to identify and to fully understand the mode of action of bioactive molecules with novel structure-activity relationships from natural sources.