Effects of citrinin on iron-redox cycle

Action of the fungal compound citrinin, a bioherbicide candidate, on photosystem II

BACKGROUND

Bioherbicides are becoming more attractive as safe weed control tools towards sustainable agriculture. Natural products constitute an important source chemicals and chemical leads for discovery and development of novel pesticide target sites. Citrinin is a bioactive compound produced by fungi of the genera Penicillium and Aspergillus. However, its physiological-biochemical mechanism as a phytotoxin remains unclear.

RESULTS

Citrinin causes visible leaf lesions on Ageratina adenophora similar to those produced by the commercial herbicide bromoxynil. Phytotoxicity bioassay tests using 24 plant species confirmed that citrinin has a broad activity spectrum and therefore has potential as a bioherbicide. Based on chlorophyll fluorescence studies, citrinin mainly blocks PSII electron flow beyond plastoquinone QA at the acceptor side, resulting in the inactivation of PSII reaction centers. Furthermore, molecular modeling of citrinin docking to the A. adenophora D1 protein suggests that it binds to the plastoquinone QB site by a hydrogen bond between the O1 hydroxy oxygen atom of citrinin and the histidine 215 of the D1 protein, the same way as classical phenolic PSII herbicides do. Finally, 32 new citrinin derivatives were designed and sorted according to free energies on the basis of the molecular model of an interaction between the citrinin molecule and the D1 protein. Five of the modeled compounds had much higher ligand binding affinity within the D1 protein compared with lead compound citrinin.

CONCLUSION

Citrinin is a novel natural PSII inhibitor that has the potential to be developed into a bioherbicide or utilized as a lead compound for discovery of new derivatives with high herbicidal potency. © 2023 Society of Chemical Industry.

Citrinin as a potential anti-cancer therapy: A comprehensive review

Citrinin (CIT) is a polyketide-derived mycotoxin, which is produced by many fungal strains belonging to the gerena Monascus, Aspergillus, and Penicillium. It has been postulated that mycotoxins have several toxic mechanisms and are potentially used as antineoplastic agents. Therefore, the present study carried out a systematic review, including articles from 1978 to 2022, by collecting evidence in experimental studies of CIT antiplorifactive activity in cancer. The Data indicate that CIT intervenes in important mediators and cell signaling pathways, including MAPKs, ERK1/2, JNK, Bcl-2, BAX, caspases 3,6,7 and 9, p53, p21, PARP cleavage, MDA, reactive oxygen species (ROS) and antioxidant defenses (SOD, CAT, GST and GPX). These factors demonstrate the potential antitumor drug CIT in inducing cell death, reducing DNA repair capacity and inducing cytotoxic and genotoxic effects in cancer cells.

Monascin and ankaflavin-Biosynthesis from Monascus purpureus, production methods, pharmacological properties: A review

Monascus purpureus copiously yields beneficial secondary metabolites , including Monascus pigments, which are broadly used as food additives, as a nitrite substitute in meat products, and as a colorant in the food industry. Monascus yellow pigments (monascin and ankaflavin) have shown potential antidiabetic, antibacterial, anti-inflammatory, antidepressant, antibiotic, anticancer, and antiobesity activities. Cosmetic and textile industries are other areas where it has established its potential as a dye. This paper reviews the production methods of Monascus yellow pigments, biosynthesis of Monascus pigments from M. purpureus, factors affecting yellow pigment production during fermentation, and the pharmacological properties of monascin and ankaflavin.

The role of ER stress and ATP/AMPK in oxidative stress meditated hepatotoxicity induced by citrinin

Citrinin, a secondary metabolite, can pose serious risks to the environment and organisms, but its hepatotoxic mechanisms are still unclear. Histopathological and ultrastructural results showed that citrinin-induced liver injury in Kunming mice, and the mechanism of citrinin-induced hepatotoxicity was studied in L02 cells. Firstly, citrinin mades L02 cell cycle arrest in G2/M phase by inhibition of cyclin B1, cyclin D1, cyclin-dependent kinases 2 (CDK2), and CDK4 expression. Secondly, citrinin inhibits proliferation and promotes apoptosis of L02 cells via disruption of mitochondria membrane potential, increase Bax/Bcl-2 ration, activation of caspase-3, 9, and enhance lactate dehydrogenase (LDH) release. Then, citrinin inhibits superoxide dismutase (SOD) activity and increases the accumulation of malondialdehyde (MDA) and reactive oxygen species (ROS), resulting oxidative damage in L02 cells; upregulates the protein expression of binding immunoglobulin protein (Bip), C/EBP homologous protein (CHOP), PKR-like ER kinase (PERK) and activating transcription factor6 (ATF6), inducing ER stress in L02 cells; increases the phosphorylation of AMP-activated protein kinase (AMPK) and decreases the content of adenosine-triphosphate (ATP), activating AMPK pathway in L02 cells. Eventually, pretreatment with NAC, an ROS inhibitor, alleviates citrinin-induced cell cycle G2/M arrest and apoptosis by inhibiting ROS-mediated ER stress; pretreatment with 4-PBA, an ER stress inhibitor, reversed ER stress and p-AMPK; pretreatment with dorsomorphin, an AMPK inhibitor, decreases citrinin-induced cell cycle G2/M arrest and apoptosis. In summary, citrinin induces cell cycle arrest and apoptosis to aggravate liver injury by activating ROS-ER stress-AMPK signaling pathway.

Chemical and Reactive Transport Processes Associated with Hydraulic Fracturing of Unconventional Oil/Gas Shales

Hydraulic fracturing of unconventional oil/gas shales has changed the energy landscape of the U.S. Recovery of hydrocarbons from tight, hydraulically fractured shales is a highly inefficient process, with estimated recoveries of <25% for natural gas and <5% for oil. This review focuses on the complex chemical interactions of additives in hydraulic fracturing fluid (HFF) with minerals and organic matter in oil/gas shales. These interactions are intended to increase hydrocarbon recovery by increasing porosities and permeabilities of tight shales. However, fluid-shale interactions result in the dissolution of shale minerals and the release and transport of chemical components. They also result in mineral precipitation in the shale matrix, which can reduce permeability, porosity, and hydrocarbon recovery. Competition between mineral dissolution and mineral precipitation processes influences the amounts of oil and gas recovered. We review the temporal/spatial origins and distribution of unconventional oil/gas shales from mudstones and shales, followed by discussion of their global and U.S. distributions and compositional differences from different U.S. sedimentary basins. We discuss the major types of chemical additives in HFF with their intended purposes, including drilling muds. Fracture distribution, porosity, permeability, and the identity and molecular-level speciation of minerals and organic matter in oil/gas shales throughout the hydraulic fracturing process are discussed. Also discussed are analysis methods used in characterizing oil/gas shales before and after hydraulic fracturing, including permeametry and porosimetry measurements, X-ray diffraction/Rietveld refinement, X-ray computed tomography, scanning/transmission electron microscopy, and laboratory- and synchrotron-based imaging/spectroscopic methods. Reactive transport and spatial scaling are discussed in some detail in order to relate fundamental molecular-scale processes to fluid transport. Our review concludes with a discussion of potential environmental impacts of hydraulic fracturing and important knowledge gaps that must be bridged to achieve improved mechanistic understanding of fluid transport in oil/gas shales.

Discovery of Cymopolyphenols A-F From a Marine Mesophotic Zone Aaptos Sponge-Associated Fungus Cymostachys sp. NBUF082

Mesophotic coral ecosystems (MCEs) have complex but understudied biodiversity, especially for natural products discovery. Untargeted metabolomics research on 80 extracts prepared from marine sponge-associated fungi, half from shallow reefs (<30 m) and half from MCEs (30–150 m), facilitated prioritization for further study a Cymostachys fungus from a 103 m deep Aaptos sponge. LC-MS target-directed isolation yielded a series of new compounds, cymopolyphenols A−F (1–6), and two known phenylspirodrimanes, F1839-I (7) and stachybotrylactone (8). This is the first report of natural products from the recently described genus, Cymostachys. Compounds 1–6 and 8 contain a dihydroisobenzofuran moiety, and 4–6 are low-order polymers of 1 with novel scaffolds. The structures of the compounds were established by spectroscopic and spectrometric data interpretation, with further support from X-ray crystallography studies of 3 and 4. Compound 3 undergoes facile racemization in solution and was found to crystalize as a racemic mixture. Compound 5 was also obtained in racemic form, and after chiral chromatography, both separated enantiomers racemized in solution by a presumed keto-enol tautomerization. Compounds 1 and 3–6 were found to be weakly antimicrobial (MIC 16–64 μg/ml) in vitro against several Gram-positive and Gram-negative human or aquatic pathogens, compound 5 was shown to chelate iron in vitro at 10 μM, and 8 activated plant disease resistance in vivo in a transgenic model organism.

Flavin Reductase Contributes to Pneumococcal Virulence by Protecting from Oxidative Stress and Mediating Adhesion and Elicits Protection Against Pneumococcal Challenge

Pneumococcal flavin reductase (FlaR) is known to be cell-wall associated and possess age dependent antigenicity in children. This study aimed at characterizing FlaR and elucidating its involvement in pneumococcal physiology and virulence. Bioinformatic analysis of FlaR sequence identified three-conserved cysteine residues, suggesting a transition metal-binding capacity. Recombinant FlaR (rFlaR) bound Fe²⁺ and exhibited FAD-dependent NADP-reductase activity, which increased in the presence of cysteine or excess Fe²⁺ and inhibited by divalent-chelating agents. flaR mutant was highly susceptible to H₂O₂ compared to its wild type (WT) and complemented strains, suggesting a role for FlaR in pneumococcal oxidative stress resistance. Additionally, flaR mutant demonstrated significantly decreased mice mortality following intraperitoneal infection. Interestingly, lack of FlaR did not affect the extent of phagocytosis by primary mouse peritoneal macrophages but reduced adhesion to A549 cells compared to the WT and complemented strains. Noteworthy are the findings that immunization with rFlaR elicited protection in mice against intraperitoneal lethal challenge and anti-FlaR antisera neutralized bacterial virulence. Taken together, FlaR's roles in pneumococcal physiology and virulence, combined with its lack of significant homology to human proteins, point towards rFlaR as a vaccine candidate.

A comprehensive review on biological properties of citrinin

Citrinin (CIT) is a mycotoxin which causes contamination in the food and is associated with different toxic effects. A web search on CIT has been conducted covering the timespan since 1946. The accumulated data indicate that CIT is produced by several fungal strains belonging to Penicillium, Aspergillus and Monascus genera, and is usually found together with another nephrotoxic mycotoxin, ochratoxin A. Although, it is evident that CIT exposure can exert toxic effects on the heart, liver, kidney, as well as reproductive system, the mechanism of CIT-induced toxicity remains largely elusive. It is still controversial what are the genotoxic and mutagenic effects of CIT. Until now, its toxic effect has been linked to the CIT-mediated oxidative stress and mitochondrial dysfunction in biological systems. However, the toxicity strongly depends on its concentration, route, frequency and time of exposure, as well as from the used test systems. Besides the toxic effects, CIT is also reported to possess a broad spectrum of bioactivities, including antibacterial, antifungal, and potential anticancer and neuro-protective effects in vitro. This systematic review presents the current state of CIT research with emphasis on its bioactivity profile.

Identification of Multiple Phytotoxins Produced by Fusarium virguliforme Including a Phytotoxic Effector (FvNIS1) Associated With Sudden Death Syndrome Foliar Symptoms

Sudden death syndrome (SDS) of soybean is caused by a soilborne pathogen, Fusarium virguliforme. Phytotoxins produced by F. virguliforme are translocated from infected roots to leaves, in which they cause SDS foliar symptoms. In this study, additional putative phytotoxins of F. virguliforme were identified, including three secondary metabolites and 11 effectors. While citrinin, fusaric acid, and radicicol induced foliar chlorosis and wilting, Soybean mosaic virus (SMV)-mediated overexpression of F. virguliforme necrosis-inducing secreted protein 1 (FvNIS1) induced SDS foliar symptoms that mimicked the development of foliar symptoms in the field. The expression level of fvnis1 remained steady over time, although foliar symptoms were delayed compared with the expression levels. SMV::FvNIS1 also displayed genotype-specific toxicity to which 75 of 80 soybean cultivars were susceptible. Genome-wide association mapping further identified three single nucleotide polymorphisms at two loci, where three leucine-rich repeat receptor-like protein kinase (LRR-RLK) genes were found. Culture filtrates of fvnis1 knockout mutants displayed a mild reduction in phytotoxicity, indicating that FvNIS1 is one of the phytotoxins responsible for SDS foliar symptoms and may contribute to the quantitative susceptibility of soybean by interacting with the LRR-RLK genes.

Oxidative stress induces the biosynthesis of citrinin by Penicillium verrucosum at the expense of ochratoxin

Penicillium verrucosum is a fungus that can produce ochratoxin A and citrinin, two structurally related nephrotoxic mycotoxins. P. verrucosum usually occurs on wheat but can occasionally also be found in NaCl rich habitats such as salted cheeses or olives, indicating that this fungus can adapt to different environments. The ratio of ochratoxin A to citrinin produced by P. verrucosum is shifted to one of either mycotoxin at the expense of the other dependent on the environmental conditions. High NaCl concentrations shift secondary metabolite biosynthesis towards ochratoxin A production. P. verrucosum copes with NaCl stress by increased ochratoxin A biosynthesis, ensuring chloride homeostasis. Ochratoxin A carries chlorine in its molecule and can excrete chlorine from the cell. It was further shown that the regulation of ochratoxin A by high NaCl conditions is mediated by the HOG MAP kinase signal transduction pathway. Here it is shown that high oxidative stress conditions, evoked for example by increasing concentrations of Cu(2+) cations in the growth medium, shift secondary metabolite biosynthesis of P. verrucosum from ochratoxin A to citrinin. The production of citrinin normalizes the oxidative status of the fungal cell under oxidative stress conditions leading to an adaptation to these environmental conditions and protects against increased oxidative stress caused by increased Cu(2+) concentrations. Moreover citrinin also protects against light of short wavelength, which may also increase the oxidative status of the environment. The biosynthesis of citrinin is apparently regulated by a cAMP/PKA signaling pathway, because increasing amounts of external cAMP reduce citrinin biosynthesis in a concentration dependent manner. These conditions lead to the cross-regulation of the ochratoxin A/citrinin secondary metabolite pair and support the adaptation of P. verrucosum to different environments.

Citrinin, a mycotoxin from Penicillium citrinum, plays a role in inducing motility of Paenibacillus polymyxa

Paenibacillus polymyxa, a Gram-positive low-G+C spore-forming soil bacterium, belongs to the plant growth-promoting rhizobacteria. The swarming motility of P. polymyxa strain E681 was greatly induced by a secondary metabolite, citrinin, produced by Penicillium citrinum KCTC6549 in a dose-dependent manner at concentrations of 2.5-15.0 microg mL(-1) on tryptic soy agar plates containing 1.0% (w/v) agar. Flagellum staining showed that citrinin activated the production of flagella by P. polymyxa. This result was supported by reverse transcriptase-PCR analysis of gene expression, which showed increased transcriptional levels of sigD and hag homologues of P. polymyxa E681 in the presence of citrinin. The results presented here show that a mycotoxin, citrinin, has a newly identified function of inducing bacterial motility by transcriptional activation of related genes. This finding contributes to our understanding of the interactions between bacteria and fungal strains in nature.