Effect of citreoviridin, a mycotoxin from Penicillium citreoviride, on kinetic constants of acetylcholinesterase and ATPase in synaptosomes and microsomes from rat brain

Advancing Natural Product Discovery: A Structure-Oriented Fractions Screening Platform for Compound Annotation and Isolation

Natural product discovery is hindered by the lack of tools that integrate untargeted nuclear magnetic resonance and mass spectrometry data on a library scale. This article describes the first application of the innovative NMR/MS-based machine learning tool, the "Structure-Oriented Fractions Screening Platform (SFSP)", enabling functional-group-guided fractionation and accelerating the discovery and characterization of undescribed natural products. The concept was applied to the extract of a marine fungus known to be a prolific producer of diverse natural products. With the assistance of SFSP, we isolated 24 flavipidin derivatives and five phenalenone analogues from Aspergillus sp. GE2-6, revealing 27 undescribed compounds. Compounds 7-22 were proposed as isomeric derivatives featuring a 5/6-ring fusion, formed by the dimerization of flavipidin E (5). Compounds 23 and 24 were envisaged as isomeric derivatives with a 6/5/6-ring fusion, generated through the degradation of two flavipidin E molecules. Furthermore, flavipidin A (1) and asperphenalenone E (28) exhibited potent anti-influenza (PR8) activities, with IC50 values of 21.9 ± 0.2 and 12.9 ± 0.1 μM, respectively. Meanwhile, asperphenalenone (26) and asperphenalenone P (27) treatments exhibited significant inhibition of HIV pseudovirus infection in 293FT cells, boasting IC50 values of 6.1 ± 0.9 and 4.6 ± 1.1 μM, respectively. Overall, SFSP streamlines natural product isolation through NMR and MS data integration, as showcased by the discovery of numerous undescribed flavipidins and phenalenones based on NMR olefinic signals and low-field hydroxy signals.

Anti-Insect Properties of Penicillium Secondary Metabolites

In connection with their widespread occurrence in diverse environments and ecosystems, fungi in the genus Penicillium are commonly found in association with insects. In addition to some cases possibly implying a mutualistic relationship, this symbiotic interaction has mainly been investigated to verify the entomopathogenic potential in light of its possible exploitation in ecofriendly strategies for pest control. This perspective relies on the assumption that entomopathogenicity is often mediated by fungal products and that Penicillium species are renowned producers of bioactive secondary metabolites. Indeed, a remarkable number of new compounds have been identified and characterized from these fungi in past decades, the properties and possible applications of which in insect pest management are reviewed in this paper.

Na,K-ATPase: A murzyme facilitating thermodynamic equilibriums at the membrane-interface

The redox metabolic paradigm of murburn concept advocates that diffusible reactive species (DRS, particularly oxygen-centric radicals) are mainstays of physiology, and not mere pathological manifestations. The murburn purview of cellular function also integrates the essential principles of bioenergetics, thermogenesis, homeostasis, electrophysiology, and coherence. In this context, any enzyme that generates/modulates/utilizes/sustains DRS functionality is called a murzyme. We have demonstrated that several water-soluble (peroxidases, lactate dehydrogenase, hemogoblin, etc.) and membrane-embedded (Complexes I-V in mitochondria, Photosystems I/II in chloroplasts, rhodopsin/transducin in rod cells, etc.) proteins serve as murzymes. The membrane protein of Na,K-ATPase (NKA, also known as sodium-potassium pump) is the focus of this article, owing to its centrality in neuro-cardio-musculo electrophysiology. Herein, via a series of critical queries starting from the geometric/spatio-temporal considerations of diffusion/mass transfer of solutes in cells to an update on structural/distributional features of NKA in diverse cellular systems, and from various mechanistic aspects of ion-transport (thermodynamics, osmoregulation, evolutionary dictates, etc.) to assays/explanations of inhibitory principles like cardiotonic steroids (CTS), we first highlight some unresolved problems in the field. Thereafter, we propose and apply a minimalist murburn model of trans-membrane ion-differentiation by NKA to address the physiological inhibitory effects of trans-dermal peptide, lithium ion, volatile anesthetics, confirmed interfacial DRS + proton modulators like nitrophenolics and unsaturated fatty acid, and the diverse classes of molecules like CTS, arginine, oximes, etc. These explanations find a pan-systemic connectivity with the inhibitions/uncouplings of other membrane proteins in cells.

Integrated 16S rRNA gene sequencing and LC/MS-based metabolomics ascertained synergistic influences of the combination of acupuncture and NaoMaiTong on ischemic stroke

ETHNOPHARMACOLOGICAL RELEVANCE

Acupuncture is an effective therapy for ischemic stroke, which has been widely used in China and gradually accepted in more countries and regions recently. In addition, Chinese medicine also plays an important role in stroke treatment, among which NaoMaiTong (NMT) is an example of an effective herbal formula for the treatment of stroke. A therapeutic strategy that combines acupuncture and medicine was widely used in stroke patients. However, the synergistic influences and mechanisms of combined acupuncture and medicine on ischemic stroke have not yet been entirely elucidated.

AIM OF THIS STUDY

The purpose of this study is to explore whether acupuncture and medicine combination treatments can produce synergism by using NMT, a clinically effective Chinese medicinal formula for the treatment of ischemic stroke for decades and has been demonstrated to be effective against ischemic brain injury, as a probe. Meanwhile, the potential mechanisms were investigated via cecal microbiome and plasma metabolomics to provide more strategies and basis for acupuncture-medicine combination for stroke.

MATERIALS AND METHODS

Adopted middle-cerebral artery occlusion/reperfusion (MCAO/R) rat models, the effect for the stroke of the combination treatment consisting of acupuncture and NMT was evaluated by detecting neurological issues, cerebral infarct dimensions, levels of inflammatory factors (IL-6, IL-1β, TNF-α) and oxidative stress factors (SOD, MDA) and brain-derived neurotrophic factor (BDNF). Subsequently,16S rRNA gene sequencing and LC/MS-based metabolomic analysis were utilized to explore the characteristics of cecal-contents microecology and plasma metabolic profile, respectively. Finally, the correlation between intestinal microecological characteristics and plasma metabolic characteristics was analyzed to explore the potential mechanism of the acupuncture-NMT combination.

RESULTS

The efficacy of acupuncture-NMT therapy was more effective than a single treatment on ischemic stroke, with more effectively reduced infarct sizes, improved neurobehavioral deficits, and alleviated oxidative stress and inflammatory responses. Besides, the combination therapy not only adjusted gut microbiota disturbances by enriching species diversity, reducing the abundance of pathogenic bacteria (such as Escherichia-Shaigella), as well as increasing the abundance of beneficial bacteria (such as Turicibacter, Bifidobacterium), but also improved metabolic disorders by reversing metabolite plasma levels to normality. The results of the correlation analysis demonstrated a significant association between intestinal microbiota and plasma metabolic profile, especially the strong correlation of Turicibacter and isoflavones phyto-estrogens metabolites.

CONCLUSION

The combination of acupuncture and NMT could produce synergism, suggesting acupuncture-medicine combination therapy might be more conducive to the recovery of ischemic stroke. And the potential mechanism was probably related to the mediation of intestinal microecology and plasma metabolism. Turicibacter and isoflavones phyto-estrogens metabolites might be the targets for acupuncture-NMT combination for stroke. Our current findings could provide a potential therapeutic strategy against ischemic stroke.

Whole Genome Analysis Revealed the Genes Responsible for Citreoviridin Biosynthesis in Penicillium citreonigrum

Citreoviridin (CTV) is a mycotoxin that is produced by Aspergillus terreus, Eupenicillium ochrosalmoneum and Penicillium citreonigrum, and CTV has been detected in a wide range of cereal grains throughout the world. Furthermore, it is especially a serious problem in regions where rice is consumed as a staple food. Moreover, CTV is a well-known yellow rice toxin, and outbreaks of beriberi have occurred due to consumption of rice that is contaminated by CTV even in the recent years. Although CTV biosynthetic genes of A. terreus have been described, those of P. citreonigrum remain unclear, which is concerning since P. citreonigrum is the main cause of CTV contamination in rice. In the present study, we determined the draft genome of the P. citreonigrum strain IMI92228 and revealed the presence of all four genes that form a gene cluster and that are homologous to the CTV biosynthesis genes of A. terreus. The expression of these four homologous genes were highly correlated with CTV production, suggesting that they may play an important role in CTV biosynthesis in P. citreonigrum. We concluded that the gene cluster is a CTV biosynthesis cluster of P. citreonigrum. The findings will contribute to the understanding of the biosynthetic pathway of CTV and will ultimately lead to improvements in the CTV management of agricultural products.

Modulation of Calmodulin and Protein Kinase C Activities by Pencillium Mycotoxins

Calmodulin (CaM), a calcium-binding protein, is found in high concentrations in mammalian brain where it plays a pivotal role in a large number of cellular functions. Protein kinase C (PKC), a multifunctional cytosolic enzyme, in the presence of both Ca2+ and phospholipids, transduce extracellular signals into intracellu-lar events. Both CaM and PKC are partially involved in maintaining Ca2+ homeostasis in the cell. Any fluctuations in the intracel-lular Ca2+ can modulate cellular functions and may contribute to neuronal dysfunction. Hence, the present investigation was initiated to study the effects of some selected penicillium (naturally occurring tremorgenic) mycotoxins like secalonic acid, citreoviridin, and verruculogen on CaM activity, active conformation of CaM and PKC activity. Stimulation of CaM-deflcient bovine brain 3′-5′ phosphodieste rase (PDE) indicated CaM activity. The modification of CaM active conformation was studied by the binding of fluorescent probe N-phenyl-1-napthylamine (NPN) to CaM. Alterations in the fluorescence of dansyl-CaM was used to study the effect of these compounds on complex formation between CaM and PDE. Rat brain cytosolic PKC was studied using 32P-ATP as a measure of altered protein phosphorylation. The concentrations of mycotoxins used were in the range of 10 to 50 μM. All three mycotoxins inhibited CaM-stimulated PDE activity in a concentration-dependent manner. Citreoviridin and secalonic acid inhibited NPN fluorescence and Ca2+-dependent complex formation of dansyl-CaM and PDE. The IC50 values for NPN fluorescence of citreoviridin and secalonic acid were 13 μM and 19 μM respectively. However, verruculogen showed little effect on NPN fluorescence and the Ca2+-dependent complex formation of dansyl-CaM and PDE. These mycotoxins also inhibited PKC activity in a concentration-dependent manner with IC50 values of 19.8, 25.7, and 38.4 μM for secalonic acid, citreoviridin, and verruculogen, respectively. The results of our study suggest that these mycotoxins at very low concentrations are interacting with CaM and PKC. Such an effect could lead to impairment of neurotransmission and result in neurotoxicity.

Binding of citreoviridin to human serum albumin: multispectroscopic and molecular docking

Citreoviridin (CIT), a mycotoxin produced by Penicillium citreonigrum, is a common contaminant of wide range of agriproducts and detrimental to human and animal health. In this study, the interaction of CIT with human serum albumin (HSA) is researched by steady-state fluorescence, ultraviolet-visible (UV-Vis) absorption, circular dichroism (CD) methods, and molecular modeling. The association constants, binding site numbers, and corresponding thermodynamic parameters are used to investigate the quenching mechanism. The alternations of HSA secondary structure in the presence of CIT are demonstrated with UV-Vis, synchronous fluorescence, and CD spectra. The molecular modeling results reveal that CIT can bind with hydrophobic pocket of HSA with hydrophobic and hydrogen bond force. Moreover, an apparent distance of 3.25 nm between Trp214 and CIT is obtained via fluorescence resonance energy transfer method.

Artificial antigen synthesis and the development of polyclonal antibody-based immunoassay for citreoviridin determination

Citreoviridin, a mycotoxin produced by Penicillium citreonigrum is a common contaminant of wide range of agri-products and detrimental to human and animal health. Therefore it is important to develop a rapid, sensitive, and specific immunoassay for citreoviridin detection. In this study, polyclonal antibody against citreoviridin was developed. For the preparation of citreoviridin-bovine serum albumin conjugate (CIT-BSA), hydroxyl groups on adjacent carbon atoms were oxidized by sodium periodate, so the product with reactive aldehyde residues was suitable for coupling with amine. Anti-citreoviridin polyclonal antibody was prepared by immunizing mice with CIT-BSA conjugate. The specificity and sensitivity of the polyclonal antibody was determined by indirect competitive ELISA. Results showed that the IC50 value of the polyclonal antibody was 0.56 μg/mL and no cross-reactivity was found between antiserum and other mycotoxins used in the experiment. The citreoviridin recovery rates by this polyclonal antibody were calculated through rice powder spiked by artificial citreoviridin. The recovery rates ranged were found from 70.5 ± 0.08 % to 94.7 ± 0.09% for inter-assay, and from 77.5 ± 0.04% to 95.4 ± 0.18% for intra-assay, which indicated that this polyclonal antibody could detect trace amount of CIT from the tested samples. Consequently, this study provided a specific and sensitive anti-citreoviridin polyclonal antibody, which made the determination of citreoviridin easier, quicker, and more accurate.

Inhibitory action of the defensive discharge of the grasshopper, Poecilocerus pictus, on certain enzymes in the lizard, Calotes nemoricola

Administration of the defensive secretion of the grasshopper, Poecilocerus pictus inhibited acetyl-cholinesterase (AChE) and adenosine triphosphatases (ATPases) in the brain and muscle tissues of the garden lizard, Calotes nemoricola. The inhibition was gradual, continuous and irreversible with lethal doses of the defensive secretion, whereas the inhibition observed with sublethal doses was followed by an increase towards control levels within 24 h after injection. In vitro application of defensive secretion also showed concentration-dependent inhibition in the activity of AChE and ATPases in the tissue homogenates. Inhibition in AChE activity might be a factor for the observed mortality is the defensive fluid-treated lizards. Since the cardenolides are known to inhibit the activity of ATPases, the inhibition in the activity of ATPases observed in the present study suggests the presence of cardenolides in the defensive fluid of P. pictus.