Influence of Environmental Factors on the Production of Penitrems A-F by Penicillium crustosum

[Mycotoxin intoxication in 54 dogs after ingestion of walnuts]

OBJECTIVE

The aim of this retrospective study was to decribe the intoxication with tremorgenic mycotoxins subsequent to the ingestion of walnuts in a large population of dogs and the evaluation of the development of the clinical signs under the initiated treatment.

MATERIAL AND METHODS

The study included 54 dogs exhibiting signs of tremor, hyperesthesia, hyperthermia and ataxia, in particular a few hours following observed ingestion of walnuts or its justified suspicion.

RESULTS

The patients were presented to the clinic mostly during winter and spring. Fifty-three of 54 dogs were hospitalized for symptomatic, decontaminating and eliminating therapy (98%). Symptomatic treatment comprised of anticonvulsant therapy in 14 dogs (26%) and an antiemetic therapy in for half of the patients (n=27; 50%). A forced emesis for decontamination was undertaken in only 6 patients due to the severity of their neurological symptoms (11%). For further decontamination, an oral administration of activated charcoal after improvement of clinical signs (n=39; 72%). The majority of dogs (n=45; 83%) additionally received an intravenous lipid therapy for toxin elimination and isotonic crystalloid solution to compensate fluid losses. There were no side effects observed following the administration of intravenous lipid therapy. The majority of dogs were hospitalized for a duration of 2 days (n=44; 81%). In most dogs, examination was unremarkable on the day of their release (n=39; 72%). Potential long-term sequelae of the intoxication were not recorded in any patient.

CONCLUSION

Due to the lipophilic nature of mycotoxins, the use of intravenous lipid therapy may considered for toxin elimination purposes. The prognosis of mycotoxin intoxication following walnut ingestion is good with decontamination and elimination measures.

CLINICAL RELEVANCE

In the case of unspecific neurological signs such as tremor, ataxia and hyperesthesia as well as a corresponding preliminary report, an intoxication with mycotoxin-containing walnuts should be considered.

Construction of an expression platform for fungal secondary metabolite biosynthesis in Penicillium crustosum

Filamentous fungi are prolific producers of bioactive natural products and play a vital role in drug discovery. Yet, their potential cannot be fully exploited since many biosynthetic genes are silent or cryptic under laboratory culture conditions. Several strategies have been applied to activate these genes, with heterologous expression as one of the most promising approaches. However, successful expression and identification of new products are often hindered by host-dependent factors, such as low gene targeting efficiencies, a high metabolite background, or a lack of selection markers. To overcome these challenges, we have constructed a Penicillium crustosum expression host in a pyrG deficient strain by combining the split-marker strategy and CRISPR-Cas9 technology. Deletion of ligD and pcribo improved gene targeting efficiencies and enabled the use of an additional selection marker in P. crustosum. Furthermore, we reduced the secondary metabolite background by inactivation of two highly expressed gene clusters and abolished the formation of the reactive ortho-quinone methide. Finally, we replaced the P. crustosum pigment gene pcr4401 with the commonly used Aspergillus nidulans wA expression site for convenient use of constructs originally designed for A. nidulans in our P. crustosum host strain. As proof of concept, we successfully expressed a single polyketide synthase gene and an entire gene cluster at the P. crustosum wA locus. Resulting transformants were easily detected by their albino phenotype. With this study, we provide a highly efficient platform for heterologous expression of fungal genes. KEY POINTS: Construction of a highly efficient Penicillium crustosum heterologous expression host Reduction of secondary metabolite background by genetic dereplication strategy Integration of wA site to provide an alternative host besides Aspergillus nidulans.

Production and immobilization of pectinases from Penicillium crustosum in magnetic core-shell nanostructures for juice clarification

Global market of food enzymes is held by pectinases, mostly sourced from filamentous fungi via submerged fermentation. Given the one-time use nature of enzymes to clarify juices and wines, there is a crucial need to explore alternatives for enzyme immobilization, enabling their reuse in food applications. In this research, an isolated fungal strain (Penicillium crustosum OR889307) was evaluated as a new potential pectinase producer in submerged fermentation. Additionally, the enzyme was immobilized in magnetic core-shell nanostructures for juice clarification. Findings revealed that Penicillium crustosum exhibited enzymatic activities higher than other Penicillium species, and pectinase production was enhanced with lemon peel as a cosubstrate in submerged fermentation. The enzyme production (548.93 U/mL) was optimized by response surface methodology, determining the optimal conditions at 35 °C and pH 6.0. Subsequently, the enzyme was covalently immobilized on synthesized magnetic core-shell nanoparticles. The immobilized enzyme exhibited superior stability at higher temperatures (50 °C) and acidic conditions (pH 4.5). Finally, the immobilized pectinases decreased 30 % the orange juice turbidity and maintained 84 % of the enzymatic activity after five consecutive cycles. In conclusion, Penicillium crustosum is a proven pectinase producer and these enzymes immobilized on functionalized nanoparticles improve the stability and reusability of pectinase for juice clarification.

Individual and combined effect of acrylamide, fumitremorgin C and penitrem A on human neuroblastoma SH-SY5Y cells

Acrylamide (AA) is a chemical compound that can be formed in certain foods during high-temperature cooking processes such as frying, baking, and roasting. Exposure to AA has been linked to several neurological effects, including peripheral neuropathy, ataxia, and impaired cognitive function. Penitrem A (PEN A) and Fumitremorgin C (FTC) are toxic mycotoxins produced by certain species of fungi, such as Penicillium Crustosum, Aspergillus Fumigatus and Neosartorya Fischeri. Both mycotoxins are commonly found in contaminated foods and animal feeds and have been linked to several adverse health effects in humans and animals, including the ability to disrupt normal functioning of the nervous system, tremors, seizures, muscle spasms, and convulsions. AA, PEN A, and FTC are all chemical contaminants. Understanding their toxicity and how they may affect human cells can help food safety authorities to establish safe exposure levels for these compounds through food and develop strategies to reduce their presence. The aim of this study was to explore the combined in vitro toxicological effects of AA, PEN A and FTC in SH-SY5Y cells. For this purpose, cells were treated with AA, FTC, and PEN A as an individual and combined treatment. The types of interactions were assessed by the isobologram analysis. The cell cycle was performed by flow cytometry. Additive effect in binary and tertiary combinations was the major effect according to isobologram graphics. Our results demonstrate that PEN A possessed the highest potential in disturbing cell cycle progression by disrupting cell density in G0/G1 phase.

Molecular regulation of fungal secondary metabolism

Many bioactive secondary metabolites synthesized by fungi have important applications in many fields, such as agriculture, food, medical and others. The biosynthesis of secondary metabolites is a complex process involving a variety of enzymes and transcription factors, which are regulated at different levels. In this review, we describe our current understanding on molecular regulation of fungal secondary metabolite biosynthesis, such as environmental signal regulation, transcriptional regulation and epigenetic regulation. The effects of transcription factors on the secondary metabolites produced by fungi were mainly introduced. It was also discussed that new secondary metabolites could be found in fungi and the production of secondary metabolites could be improved. We also highlight the importance of understanding the molecular regulation mechanisms to activate silent secondary metabolites and uncover their physiological and ecological functions. By comprehensively understanding the regulatory mechanisms involved in secondary metabolite biosynthesis, we can develop strategies to improve the production of these compounds and maximize their potential benefits.

The hidden power of secondary metabolites in plant-fungi interactions and sustainable phytoremediation

The global environment is dominated by various small exotic substances, known as secondary metabolites, produced by plants and microorganisms. Plants and fungi are particularly plentiful sources of these molecules, whose physiological functions, in many cases, remain a mystery. Fungal secondary metabolites (SM) are a diverse group of substances that exhibit a wide range of chemical properties and generally fall into one of four main family groups: Terpenoids, polyketides, non-ribosomal peptides, or a combination of the latter two. They are incredibly varied in their functions and are often related to the increased fitness of the respective fungus in its environment, often competing with other microbes or interacting with plant species. Several of these metabolites have essential roles in the biological control of plant diseases by various beneficial microorganisms used for crop protection and biofertilization worldwide. Besides direct toxic effects against phytopathogens, natural metabolites can promote root and shoot development and/or disease resistance by activating host systemic defenses. The ability of these microorganisms to synthesize and store biologically active metabolites that are a potent source of novel natural compounds beneficial for agriculture is becoming a top priority for SM fungi research. In this review, we will discuss fungal-plant secondary metabolites with antifungal properties and the role of signaling molecules in induced and acquired systemic resistance activities. Additionally, fungal secondary metabolites mimic plant promotion molecules such as auxins, gibberellins, and abscisic acid, which modulate plant growth under biotic stress. Moreover, we will present a new trend regarding phytoremediation applications using fungal secondary metabolites to achieve sustainable food production and microbial diversity in an eco-friendly environment.

Detection of Mycotoxins in Highly Matrix-Loaded House-Dust Samples by QTOF-HRMS, IM-QTOF-HRMS, and TQMS: Advantages and Disadvantages

The analysis of (trace) contaminants in environmental samples represents an important tool for exposure assessment and for the evaluation of potential risks to human health. Currently, mass spectrometric detection using triple quadrupole (TQMS) systems is the established method of choice. However, screening methods using high resolution mass spectrometry (HRMS) find increasing application as they provide advantages such as enhanced selectivity. A complex composition of environmental samples is known to have enormous effects on mass analyzers. The present work therefore compares the impact of a highly matrix-loaded sample material like house-dust on the performance of mass spectrometric detection of the emerging indoor contaminant group of mycotoxins by quadrupole time-of-flight (QTOF) and TQMS after ultrahigh-performance liquid chromatographic separation. Furthermore, the role of ionization efficiencies of different ion sources in instrument sensitivity was compared using an electrospray ionization source and a newly developed heated electrospray ion source (Bruker VIP-HESI) during QTOF experiments. Finally, it was evaluated whether an additional dimension of separation enables increased sensitivity in QTOF-HRMS detection by applying mycotoxins in house-dust to an (trapped) ion mobility spectrometry instrument. The sensitivity of the QTOF detection was positively influenced by the application of the VIP-HESI ion source, and overall HRMS instruments provided enhanced selectivity resulting in simplified data evaluation compared to the TQMS. However, all performed experiments revealed strong signal suppression due to matrix components. QTOF results showed more severe effects, enabling a more sensitive detection of mycotoxins in house-dust by applying TQMS detection.

Mycopharmaceuticals and Nutraceuticals: Promising Agents to Improve Human Well-Being and Life Quality

Fungi, especially edible mushrooms, are considered as high-quality food with nutritive and functional values. They are of considerable interest and have been used in the synthesis of nutraceutical supplements due to their medicinal properties and economic significance. Specific fungal groups, including predominantly filamentous endophytic fungi from Ascomycete phylum and several Basidiomycetes, produce secondary metabolites (SMs) with bioactive properties that are involved in the antimicrobial and antioxidant activities. These beneficial fungi, while high in protein and important fat contents, are also a great source of several minerals and vitamins, in particular B vitamins that play important roles in carbohydrate and fat metabolism and the maintenance of the nervous system. This review article will summarize and discuss the abilities of fungi to produce antioxidant, anticancer, antiobesity, and antidiabetic molecules while also reviewing the evidence from the last decade on the importance of research in fungi related products with direct and indirect impact on human health.

Olive Oil Lignan (+)-Acetoxypinoresinol Peripheral Motor and Neuronal Protection against the Tremorgenic Mycotoxin Penitrem A Toxicity via STAT1 Pathway

Penitrem A, PA, is an indole diterpene alkaloid produced by several fungal species. PA acts as a selective Ca²⁺-dependent K-channels (Maxi-K, BK) antagonist in brain, causing motor system dysfunctions including tremors and seizures. However, its molecular mechanism at the peripheral nervous system (PNS) is still ambiguous. The Mediterranean diet key ingredient extra-virgin olive oil (EVOO) provides a variety of minor bioactive phenolics. (+)-Pinoresinol (PN) and (+)-1-acetoxypinoresinol (AC) are naturally occurring lignans in EVOO with diverse biological activities. AC exclusively occurs in EVOO, unlike PN, which occurs in several plants. Results suggest that PA neurotoxicity molecular mechanism is mediated, in part, through distortion of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway. PA selectively activated the STAT1 pathway, independently of the interferon-γ (IFN-γ) pathway, in vitro in Schwann cells and in vivo in Swiss albino mice sciatic nerves. Preliminary in vitro screening of an EVOO phenolic compounds library for the ability to reverse PA toxicity on Schwann cells revealed PN and AC as potential hits. In a Swiss albino mouse model, AC significantly minimized the fatality after intraperitoneal administration of PA fatal doses and normalized most biochemical factors by modulating the STAT1 expression. The olive lignan AC is a novel lead that can prevent the neurotoxicity of food-contaminating tremorgenic indole alkaloid mycotoxins.

Penicillium spp. mycotoxins found in food and feed and their health effects

Mycotoxins are toxic secondary metabolites produced by fungi. These compounds have different structures and target different organs, acting at different steps of biological processes inside the cell. Around 32 mycotoxins have been identified in fungal Penicillium spp. isolated from food and feed. Some of these species are important pathogens which contaminate food, such as maize, cereals, soybeans, sorghum, peanuts, among others. These microorganisms can be present in different steps of the food production process, such as plant growth, harvest, drying, elaboration, transport, and packaging. Although some Penicillium spp. are pathogens, some of them are used in elaboration of processed foods, such as cheese and sausages. This review summarises the Penicillium spp. mycotoxin toxicity, focusing mainly on the subgenus Penicillium, frequently found in food and feed. Toxicity is reviewed both in animal models and cultured cells. Finally, some aspects of their regulations are discussed.

Strong variance in the inflammatory and cytotoxic potentials of Penicillium and Aspergillus species from cleaning workers' exposure in nursing homes

Penicillium and Aspergillus are among the dominant genera of fungi in many environments. Exposure to these fungi may cause inflammation-related health effects, however the knowledge about this at species level is limited. The aim of this study was to obtain knowledge about cleaning workers' exposure to fungi and to investigate the total inflammatory potential (TIP) and the cytotoxic potential of fungal species. The fungi were obtained from the personal exposure of cleaning workers' in five nursing homes. In total 271 fungal isolates were identified using MALDI-TOF MS. The TIP and cytotoxic potential were determined for 30 different fungal isolates covering 17 species in an in vitro assay by exposing HL-60 cells to the fungal spores of each isolate. The geometric mean exposure of the cleaning workers was 351 CFU fungi/m³ air. We showed that the TIP and cytotoxicity varied among both species and isolates. At the two lowest doses, there was a positive relationship between spore concentration and TIP. The species with highest TIPs were A. candidus and P. italicum, while the most cytotoxic ones were A. niger and A. fumigatus. There was no obvious relationship between the TIP of an isolate and its cytotoxicity. The results of this study provide a better understanding of the inflammatory potential and cytotoxicity of different environmental fungal species and contribute to the risk evaluation of exposure to different Penicillium and Aspergillus species.

From genomics to metabolomics, moving toward an integrated strategy for the discovery of fungal secondary metabolites

Fungal secondary metabolites are defined by bioactive properties that ensure adaptation of the fungus to its environment. Although some of these natural products are promising sources of new lead compounds especially for the pharmaceutical industry, others pose risks to human and animal health. The identification of secondary metabolites is critical to assessing both the utility and risks of these compounds. Since fungi present biological specificities different from other microorganisms, this review covers the different strategies specifically used in fungal studies to perform this critical identification. Strategies focused on the direct detection of the secondary metabolites are firstly reported. Particularly, advances in high-throughput untargeted metabolomics have led to the generation of large datasets whose exploitation and interpretation generally require bioinformatics tools. Then, the genome-based methods used to study the entire fungal metabolic potential are reported. Transcriptomic and proteomic tools used in the discovery of fungal secondary metabolites are presented as links between genomic methods and metabolomic experiments. Finally, the influence of the culture environment on the synthesis of secondary metabolites by fungi is highlighted as a major factor to consider in research on fungal secondary metabolites. Through this review, we seek to emphasize that the discovery of natural products should integrate all of these valuable tools. Attention is also drawn to emerging technologies that will certainly revolutionize fungal research and to the use of computational tools that are necessary but whose results should be interpreted carefully.

Marine Fungi from the Sponge Grantia compressa: Biodiversity, Chemodiversity, and Biotechnological Potential

The emergence of antibiotic resistance and viruses with high epidemic potential made unexplored marine environments an appealing target source for new metabolites. Marine fungi represent one of the most suitable sources for the discovery of new compounds. Thus, the aim of this work was (i) to isolate and identify fungi associated with the Atlantic sponge Grantia compressa; (ii) to study the fungal metabolites by applying the OSMAC approach (one strain; many compounds); (iii) to test fungal compounds for their antimicrobial activities. Twenty-one fungal strains (17 taxa) were isolated from G. compressa. The OSMAC approach revealed an astonishing metabolic diversity in the marine fungus Eurotium chevalieri MUT 2316, from which 10 compounds were extracted, isolated, and characterized. All metabolites were tested against viruses and bacteria (reference and multidrug-resistant strains). Dihydroauroglaucin completely inhibited the replication of influenza A virus; as for herpes simplex virus 1, total inhibition of replication was observed for both physcion and neoechinulin D. Six out of 10 compounds were active against Gram-positive bacteria with isodihydroauroglaucin being the most promising compound (minimal inhibitory concentration (MIC) 4-64 µg/mL) with bactericidal activity. Overall, G. compressa proved to be an outstanding source of fungal diversity. Marine fungi were capable of producing different metabolites; in particular, the compounds isolated from E. chevalieri showed promising bioactivity against well-known and emerging pathogens.

Fungal secondary metabolism: regulation, function and drug discovery

One of the exciting movements in microbial sciences has been a refocusing and revitalization of efforts to mine the fungal secondary metabolome. The magnitude of biosynthetic gene clusters (BGCs) in a single filamentous fungal genome combined with the historic number of sequenced genomes suggests that the secondary metabolite wealth of filamentous fungi is largely untapped. Mining algorithms and scalable expression platforms have greatly expanded access to the chemical repertoire of fungal-derived secondary metabolites. In this Review, I discuss new insights into the transcriptional and epigenetic regulation of BGCs and the ecological roles of fungal secondary metabolites in warfare, defence and development. I also explore avenues for the identification of new fungal metabolites and the challenges in harvesting fungal-derived secondary metabolites.

Tremorgenic and neurotoxic paspaline-derived indole-diterpenes: biosynthetic diversity, threats and applications

Indole-diterpenes (IDTs) such as the aflatrems, janthitrems, lolitrems, paspalitrems, penitrems, shearinines, sulpinines, and terpendoles are biogenetically related but structurally varied tremorgenic and neurotoxic mycotoxins produced by fungi. All these metabolites derive from the biosynthetic intermediate paspaline, a frequently occurring IDT on its own right. In this comprehensive review, we highlight the similarities and differences of the IDT biosynthetic pathways that lead to the generation of the main paspaline-derived IDT subgroups. We survey the taxonomic distribution and the regulation of IDT production in various fungi and compare the organization of the known IDT biosynthetic gene clusters. A detailed assessment of the highly diverse biological activities of these mycotoxins leads us to emphasize the significant losses that paspaline-derived IDTs cause in agriculture, and compels us to warn about the various hazards they represent towards human and livestock health. Conversely, we also describe the potential utility of these versatile molecules as lead compounds for pharmaceutical drug discovery, and examine the prospects for their industrial scale manufacture in genetically manipulated IDT producers or domesticated host microorganisms in synthetic biological production systems.

Auranthine, a Benzodiazepinone from Penicillium aurantiogriseum: Refined Structure, Absolute Configuration, and Cytotoxicity

The structure of the known Penicillium aurantiogriseum-derived secondary metabolite auranthine was refined using a combination of synthetic, spectroscopic, and X-ray diffractometric approaches. Thus, auranthine was shown to be a fused quinazolino benzodiazepinedione (2) bearing an acyclic aliphatic nitrile moiety, thereby significantly differing from the originally proposed structure 1 published in 1986. Its absolute configuration was confirmed by CD spectroscopy and DFT calculations. The cultivation of P. aurantiogriseum was optimized, allowing high production of auranthine. The cytotoxicity profile of auranthine and its semisynthetic analogues is reported. The refined structure of auranthine provides a valid target for the total synthesis of this underexplored natural product and its derivatives.

Detection of the Cytotoxic Penitrems A-F in Cheese from the European Single Market by HPLC-MS/MS

Penitrems are fungal indole diterpene-derived tremorgenic secondary metabolites, which are mainly produced by Penicillium spp. Several cases of intoxications with penitrems and subsequent occurrences of penitrem A in foodstuff underline the need for reliable quantitation methods for the detection of these mycotoxins in food. In this study, a simple and fast high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method for the quantitative analysis of penitrems A-F in cheese was developed. Therefore, penitrems A-F were isolated from Penicillium crustosum as analytical reference standards. The analysis of 60 cheese samples from the European single market (EU) revealed the occurrence of penitrem A in 10% of the analyzed samples with an average concentration of 28.4 μg/kg and a maximum concentration of 429 μg/kg. In addition to penitrem A, other members of the group of penitrems, namely, penitrems B, C, D, E, and F, were for the first time quantitatively detected in food samples, although in lower concentrations and with lower incidence in comparison to penitrem A. Moreover, we report cytotoxic effects of all penitrems on two cell lines (HepG2 and CCF-STTG1). This clearly underlines their relevance and the importance to analyze food samples in order to get insights into the human exposure toward these mycotoxins.