Metergoline-induced cell death in Candida krusei

Biofungicides Based on Plant Extracts: On the Road to Organic Farming

Phytopathogenic fungi are responsible for diseases in commercially important crops and cause major supply problems in the global food chain. Plants were able to protect themselves from disease before humans played an active role in protecting plants. They are known to synthesize a variety of secondary metabolites (SMs), such as terpenes, alkaloids, and phenolic compounds, which can be extracted using conventional and unconventional techniques to formulate biofungicides; plant extracts have antifungal activity and various mechanisms of action against these organisms. In addition, they are considered non-phytotoxic and potentially effective in disease control. They are a sustainable and economically viable alternative for use in agriculture, which is why biofungicides are increasingly recognized as an attractive option to solve the problems caused by synthetic fungicides. Currently, organic farming continues to grow, highlighting the importance of developing environmentally friendly alternatives for crop production. This review provides a compilation of the literature on biosynthesis, mechanisms of action of secondary metabolites against phytopathogens, extraction techniques and formulation of biofungicides, biological activity of plant extracts on phytopathogenic fungi, regulation, advantages, disadvantages and an overview of the current use of biofungicides in agriculture.

Antibacterial Activity of Metergoline Analogues: Revisiting the Ergot Alkaloid Scaffold for Antibiotic Discovery

Metergoline is a semisynthetic ergot alkaloid identified recently as an inhibitor of the Gram-negative intracellular pathogen Salmonella Typhimurium (S. Tm). With the previously unknown antibacterial activity of metergoline, we explored structure-activity relationships (SARs) with a series of carbamate, urea, sulfonamide, amine, and amide analogues. Cinnamide and arylacrylamide derivatives show improved potency relative to metergoline against Gram-positive bacteria, and pyridine derivative 38 is also effective against methicillin-resistant Staphylococcus aureus (MRSA) in a murine skin infection model. Arylacrylamide analogues of metergoline show modest activity against wild-type (WT) Gram-negative bacteria but are more active against strains of efflux-deficient S. Tm and hyperpermeable Escherichia coli. The potencies against WT strains of E. coli, Acinetobacter baumannii, and Burkholderia cenocepacia are also improved considerably (up to >128-fold) with the outer-membrane permeabilizer SPR741, suggesting that the ergot scaffold represents a new lead for the development of new antibiotics.

A macrophage-based screen identifies antibacterial compounds selective for intracellular Salmonella Typhimurium

Salmonella Typhimurium (S. Tm) establishes systemic infection in susceptible hosts by evading the innate immune response and replicating within host phagocytes. Here, we sought to identify inhibitors of intracellular S. Tm replication by conducting parallel chemical screens against S. Tm growing in macrophage-mimicking media and within macrophages. We identify several compounds that inhibit Salmonella growth in the intracellular environment and in acidic, ion-limited media. We report on the antimicrobial activity of the psychoactive drug metergoline, which is specific against intracellular S. Tm. Screening an S. Tm deletion library in the presence of metergoline reveals hypersensitization of outer membrane mutants to metergoline activity. Metergoline disrupts the proton motive force at the bacterial cytoplasmic membrane and extends animal survival during a systemic S. Tm infection. This work highlights the predictive nature of intracellular screens for in vivo efficacy, and identifies metergoline as a novel antimicrobial active against Salmonella.

(3R)-5,6,7-trihydroxy-3-isopropyl-3-methylisochroman-1-one ameliorates retinal degeneration in Pde6brd10 mice

As a severe photoreceptor-degenerative disease, retinitis pigmentosa (RP) is currently incurable and eventually leads to partial or complete blindness. (3R)-5,6,7-trihydroxy-3-isopropyl-3-methylisochroman-1-one (TIM) is a novel antioxidant isolated from the plant of Alpinia katsumadai Hayata, with protective effects on photoreceptor cells against lipoteichoic acid-induced damage through inhibiting oxidative stress. The present study was to further demonstrate whether TIM could ameliorate retinal degeneration of Pde6b^rd10 (rd10) mice, a mouse model of RP. rd10 mice were treated with TIM by intraperitoneal injection daily from postnatal Day 10 (P10) to P26. Retinal function was tested by electroretinography. Histology was evaluated by toluidine blue staining and TUNEL assay. Oxidative stress markers were measured by ELISA. Immunohistochemistry, real-time PCR, and western blotting were applied to explore the protective mechanism. Results showed TIM significantly improved the retinal function and decreased photoreceptor cell apoptosis in rd10 mice through reducing oxidative stress. For the first time, this study demonstrated the protective effects of TIM against retinal degeneration in rd10 mice, providing scientific rationale to use TIM treating the RP.

Guidelines and recommendations on yeast cell death nomenclature

Elucidating the biology of yeast in its full complexity has major implications for science, medicine and industry. One of the most critical processes determining yeast life and physiology is cel-lular demise. However, the investigation of yeast cell death is a relatively young field, and a widely accepted set of concepts and terms is still missing. Here, we propose unified criteria for the defi-nition of accidental, regulated, and programmed forms of cell death in yeast based on a series of morphological and biochemical criteria. Specifically, we provide consensus guidelines on the differ-ential definition of terms including apoptosis, regulated necrosis, and autophagic cell death, as we refer to additional cell death rou-tines that are relevant for the biology of (at least some species of) yeast. As this area of investigation advances rapidly, changes and extensions to this set of recommendations will be implemented in the years to come. Nonetheless, we strongly encourage the au-thors, reviewers and editors of scientific articles to adopt these collective standards in order to establish an accurate framework for yeast cell death research and, ultimately, to accelerate the pro-gress of this vibrant field of research.

Phenoptosis in yeasts

The current view on phenoptosis and apoptosis as genetic programs aimed at eliminating potentially dangerous organisms and cells, respectively, is given. Special emphasis is placed on apoptosis (phenoptosis) in yeasts: intracellular defects and a plethora of external stimuli inducing apoptosis in yeasts; distinctive morphological and biochemical hallmarks accompanying apoptosis in yeasts; pro- and antiapoptotic factors involved in yeast apoptosis signaling; consecutive stages of apoptosis from external stimulus to the cell death; a prominent role of mitochondria and other organelles in yeast apoptosis; possible pathways for release of apoptotic factors from the intermembrane mitochondrial space into the cytosol are described. Using some concrete examples, the obvious physiological importance and expediency of altruistic death of yeast cells is shown. Poorly known aspects of yeast apoptosis and prospects for yeast apoptosis study are defined.

Synthesis of metergoline analogues and their evaluation as antiplasmodial agents

A series of metergoline analogues were synthesized and evaluatedin vitrofor antiplasmodial activity and cytotoxicity towards a mammalian cell line. Some of the compounds exhibited promising selective antiplasmodial activity along with a high selectivity index relative to metergoline.

Reactive oxygen species-inducing antifungal agents and their activity against fungal biofilms

Invasive fungal infections are associated with very high mortality rates ranging from 20–90% for opportunistic fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus. Fungal resistance to antimycotic treatment can be genotypic (due to resistant strains) as well as phenotypic (due to more resistant fungal lifestyles, such as biofilms). With regard to the latter, biofilms are considered to be critical in the development of invasive fungal infections. However, there are only very few antimycotics, such as miconazole (azoles), echinocandins and liposomal formulations of amphotericin B (polyenes), which are also effective against fungal biofilms. Interestingly, these antimycotics all induce reactive oxygen species (ROS) in fungal (biofilm) cells. This review provides an overview of the different classes of antimycotics and novel antifungal compounds that induce ROS in fungal planktonic and biofilm cells. Moreover, different strategies to further enhance the antibiofilm activity of such ROS-inducing antimycotics will be discussed.

Purpurin triggers caspase-independent apoptosis in Candida dubliniensis biofilms

Candida dubliniensis is an important human fungal pathogen that causes oral infections in patients with AIDS and diabetes mellitus. However, C. Dubliniensis has been frequently reported in bloodstream infections in clinical settings. Like its phylogenetically related virulent species C. albicans, C. Dubliniensis is able to grow and switch between yeast form and filamentous form (hyphae) and develops biofilms on both abiotic and biotic surfaces. Biofilms are recalcitrant to antifungal therapies and C. Dubliniensis readily turns drug resistant upon repeated exposure. More than 80% of infections are associated with biofilms. Suppression of fungal biofilms may therefore represent a viable antifungal strategy with clinical relevance. Here, we report that C. dubliniensis biofilms were inhibited by purpurin, a natural anthraquinone pigment isolated from madder root. Purpurin inhibited C. dubliniensis biofilm formation in a concentration-dependent manner; while mature biofilms were less susceptible to purpurin. Scanning electron microscopy (SEM) analysis revealed scanty structure consisting of yeast cells in purpurin-treated C. dubliniensis biofilms. We sought to delineate the mechanisms of the anti-biofilm activity of purpurin on C. Dubliniensis. Intracellular ROS levels were significantly elevated in fungal biofilms and depolarization of MMP was evident upon purpurin treatment in a concentration-dependent manner. DNA degradation was evident. However, no activated metacaspase could be detected. Together, purpurin triggered metacaspase-independent apoptosis in C. dubliniensis biofilms.