Oxidative DNA damage and disturbance of antioxidant capacity by alternariol in Caco-2 cells

Unraveling Interspecies Differences in the Phase I Hepatic Metabolism of Alternariol and Alternariol Monomethyl Ether: Closing Data Gaps for a Comprehensive Risk Assessment

The Alternaria mycotoxins alternariol (AOH) and alternariol 9-O-monomethyl ether (AME) are pervasive food contaminants known to exert adverse effects in vitro, yet their toxicokinetics remain inadequately understood. Thus, this study endeavors to elucidate the qualitative and quantitative aspects of the phase I metabolism of AOH and AME. To pursue this goal, reduced nicotinamide adenine dinucleotide phosphate (NADPH)-fortified porcine, rat, and human liver microsomes were incubated for 0-10 min with AOH or AME within a concentration range of 1-100 and 1-50 μM, respectively. The decline in the parent toxin concentration was monitored via liquid chromatography coupled to tandem mass spectrometry, whereas coupling to high-resolution mass spectrometry provided insights into the composition of the arising metabolic mixture. The collected quantitative data allowed us to calculate the hepatic intrinsic clearance rates of AOH and AME, marking a notable contribution to the field. Moreover, we unveiled interspecies differences in the pattern and rate of the phase I metabolism of the investigated mycotoxins. The presented findings lay the groundwork for physiologically based toxicokinetic modeling aimed at estimating local concentrations of these mycotoxins in specific organs, enhancing our understanding of their mode of action and adverse health effects.

Alternariol Monomethyl-Ether Induces Toxicity via Cell Death and Oxidative Stress in Swine Intestinal Epithelial Cells

Alternariol monomethyl-ether (AME), together with altenuene and alternariol, belongs to the Alternaria mycotoxins group, which can contaminate different substrates, including cereals. The aim of the present study was to obtain a deeper understanding concerning the effects of AME on pig intestinal health using epithelial intestinal cell lines as the data concerning the possible effects of Alternaria toxins on swine are scarce and insufficient for assessing the risk represented by Alternaria toxins for animal health. Our results have shown a dose-related effect on IPEC-1 cell viability, with an IC50 value of 10.5 μM. Exposure to the toxin induced an increase in total apoptotic cells, suggesting that AME induces programmed cell death through apoptosis based on caspase-3/7 activation in IPEC-1 cells. DNA and protein oxidative damage triggered by AME were associated with an alteration of the antioxidant response, as shown by a decrease in the enzymatic activity of catalase and superoxide dismutase. These effects on the oxidative response can be related to an inhibition of the Akt/Nrf2/HO-1 signaling pathway; however, further studies are needed in order to validate these in vitro data using in vivo trials in swine.

Combined in vitro and in silico mechanistic approach to explore the potential of Alternaria mycotoxins alternariol and altertoxin II to hamper γH2AX formation in DNA damage signaling pathways

Risk assessment of food and environmental contaminants is faced by substantial data gaps and novel strategies are needed to support science-based regulatory actions. The Alternaria mycotoxins alternariol (AOH) and altertoxin II (ATXII) have garnered attention for their possible genotoxic effects. Nevertheless, data currently available are rather scattered, hindering a comprehensive hazard characterization. This study combined in vitro/in silico approaches to elucidate the potential of AOH and ATXII to induce double-strand breaks (DSBs) in HepG2 cells. Furthermore, it examines the impact of co-exposure to AOH and the DSB-inducing drug doxorubicin (Doxo) on γH2AX expression. AOH slightly increased γH2AX expression, whereas ATXII did not elicit this response. Interestingly, AOH suppressed Doxo-induced γH2AX expression, despite evidence of increased DNA damage in the comet assay. Building on these observations, AOH was postulated to inhibit γH2AX-forming kinases. Along this line, in silico analysis supported AOH potential interaction with the ATP-binding sites of these kinases and immunofluorescence experiments showed decreased intracellular phosphorylation events. Similarly, in silico results suggested that ATXII might also interact with these kinases. This study emphasizes the importance of understanding the implications of AOH-induced γH2AX expression inhibition on DNA repair processes and underscores the need for caution when interpreting γH2AX assay results.

Hazard characterization of Alternaria toxins to identify data gaps and improve risk assessment for human health

Fungi of the genus Alternaria are ubiquitous plant pathogens and saprophytes which are able to grow under varying temperature and moisture conditions as well as on a large range of substrates. A spectrum of structurally diverse secondary metabolites with toxic potential has been identified, but occurrence and relative proportion of the different metabolites in complex mixtures depend on strain, substrate, and growth conditions. This review compiles the available knowledge on hazard identification and characterization of Alternaria toxins. Alternariol (AOH), its monomethylether AME and the perylene quinones altertoxin I (ATX-I), ATX-II, ATX-III, alterperylenol (ALP), and stemphyltoxin III (STTX-III) showed in vitro genotoxic and mutagenic properties. Of all identified Alternaria toxins, the epoxide-bearing analogs ATX-II, ATX-III, and STTX-III show the highest cytotoxic, genotoxic, and mutagenic potential in vitro. Under hormone-sensitive conditions, AOH and AME act as moderate xenoestrogens, but in silico modeling predicts further Alternaria toxins as potential estrogenic factors. Recent studies indicate also an immunosuppressive role of AOH and ATX-II; however, no data are available for the majority of Alternaria toxins. Overall, hazard characterization of Alternaria toxins focused, so far, primarily on the commercially available dibenzo-α-pyrones AOH and AME and tenuazonic acid (TeA). Limited data sets are available for altersetin (ALS), altenuene (ALT), and tentoxin (TEN). The occurrence and toxicological relevance of perylene quinone-based Alternaria toxins still remain to be fully elucidated. We identified data gaps on hazard identification and characterization crucial to improve risk assessment of Alternaria mycotoxins for consumers and occupationally exposed workers.

An updated overview of anticancer effects of alternariol and its derivatives: underlying molecular mechanisms

Alternariol is a toxic metabolite of Alternaria fungi and studies have shown multiple potential pharmacological effects. To outline the anticancer effects and mechanisms of alternariol and its derivatives based on database reports, an updated search of PubMed/MedLine, ScienceDirect, Web of Science, and Scopus databases was performed with relevant keywords for published articles. The studies found to suggest that this mycotoxin and/or its derivatives have potential anticancer effects in many pharmacological preclinical test systems. Scientific reports indicate that alternariol and/or its derivatives exhibit anticancer through several pathways, including cytotoxic, reactive oxygen species leading to oxidative stress and mitochondrial dysfunction-linked cytotoxic effect, anti-inflammatory, cell cycle arrest, apoptotic cell death, genotoxic and mutagenic, anti-proliferative, autophagy, and estrogenic and clastogenic mechanisms. In light of these results, alternariol may be one of the hopeful chemotherapeutic agents.

Estrogen Receptor β Participates in Alternariol-Induced Oxidative Stress in Normal Prostate Epithelial Cells

Alternaria toxins are considered as emerging mycotoxins, however their toxicity has not been fully evaluated in humans. Alternariol (AOH), the most prevalent Alternaria mycotoxin, was previously reported to be genotoxic and to affect hormonal balance in cells; however, its direct molecular mechanism is not known. The imbalance in androgen/estrogen ratio as well as chronic inflammation are postulated as factors in prostate diseases. The environmental agents affecting the hormonal balance might participate in prostate carcinogenesis. Thus, this study evaluated the effect of two doses of AOH on prostate epithelial cells. We observed that AOH in a dose of 10 µM induces oxidative stress, DNA damage and cell cycle arrest and that this effect is partially mediated by estrogen receptor β (ERβ) whereas the lower tested dose of AOH (0.1 µM) induces only oxidative stress in cells. The modulation of nuclear erythroid-related factor 2 (Nrf2) was observed in response to the higher dose of AOH. The use of selective estrogen receptor β (ERβ) inhibitor PHTPP revealed that AOH-induced oxidative stress in both tested doses is partially dependent on activation of ERβ, but lack of its activation did not protect cells against AOH-induced ROS production or DNA-damaging effect in case of higher dose of AOH (10 µM). Taken together, this is the first study reporting that AOH might affect basic processes in normal prostate epithelial cells associated with benign and malignant changes in prostate tissue.

Alternariol exerts embryotoxic and immunotoxic effects on mouse blastocysts through ROS-mediated apoptotic processes

Alternariol (AOH), a mycotoxin belonging to the genus Alternaria, has been shown to induce cytotoxicity, including apoptosis and cell cycle arrest, in several mammalian cell types. However, its effects on early-stage embryonic development require further investigation. Here, we have shown that AOH exerts embryotoxic effects on mouse blastocyst-stage embryos and long-term adverse effects on immunity in one-day-old newborn mice of the next generation. Significant apoptosis and decrease in total cell number, predominantly through loss of inner cell mass (ICM), and to a minor extent, trophectoderm (TE) cells, were observed in AOH-treated blastocysts. Moreover, AOH exerted detrimental effects on pre- and post-implantation embryo development potential and induced a decrease in fetal weight in in vitro development and embryo transfer assays. Injection of pregnant mice with AOH (1, 3 and 5 mg/kg body weight/day) for 4 days resulted in apoptosis of blastocyst-stage embryos and injurious effects on embryonic development from the zygote to blastocyst stage or embryo degradation and a further decrease in fetal weight. Furthermore, AOH exerted a long-term impact on the next generation, triggering a significant increase in total oxidative stress content and expression of genes encoding antioxidant proteins. Lower expression of CXCL1, IL-1β and IL-8 related to innate immunity was detected in liver tissue extracts obtained from one-day-old newborns of AOH-injected pregnant mice (5 mg/kg body weight/day) relative to their non-treated counterparts. In addition, ROS served as an upstream regulator of AOH-triggered apoptotic processes and impairment of embryonic development. Our collective results highlight the potential of AOH as an embryotoxic and immunotoxic risk factor during embryo and infant development stages in mice.

Alternaria Mycotoxins: An Overview of Toxicity, Metabolism, and Analysis in Food

The genus Alternaria is widely distributed in the environment. Numerous species of the genus Alternaria can produce a variety of toxic secondary metabolites, called Alternaria mycotoxins. In this review, natural occurrence, toxicity, metabolism, and analytical methods are introduced. The contamination of these toxins in foodstuffs is ubiquitous, and most of these metabolites present genotoxic and cytotoxic effects. Moreover, Alternaria toxins are mainly hydroxylated to catechol metabolites and combined with sulfate and glucuronic acid in in vitro arrays. A more detailed summary of the metabolism of Alternaria toxins is presented in this work. To effectively detect and determine the mycotoxins in food, analytical methods with high sensitivity and good accuracy are also reviewed. This review will guide the formulation of maximum residue limit standards in the future, covering both toxicity and metabolic mechanism of Alternaria toxins.

The Identification of Anthocyanins from Padus racemosa and Its Protective Effects on H2 O2 -Induced INS-1 Cells Damage and STZ-Induced Diabetes Mice

Oxidative damage in cells induced by reactive oxygen species (ROS) is a main factor in diabetes mellitus diseases progression. The composition of anthocyanins from Padus racemosa (APR) and the protective effects of APR on H₂ O₂ -induced rat insulinoma (INS-1) cells damage and streptozocin (STZ)-induced diabetes mice were investigated in this study. The main components of APR were cyanidin-cyanidin glucosyl-rutinoside, cyanidin-cyanidin xylosyl-rutinoside, cyanidin-xylosyl-glucoside and cyanidin-rutinoside, which were determined by liquid chromatography-mass spectrometry (LC/MS). APR could scavenge the 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl radical and superoxide radical in vitro. ROS level was decreased and the cell viability was increased in INS-1 cells after treated with APR. Cell apoptosis induced by H₂ O₂ in INS-1 cells was decreased after incubation with APR. APR could decrease the phosphorylation of p38 and the nuclear translocation of p65, which indicated that APR could inhibit the activation of p38 Mitogen-activated protein kinase (MAPK) and Nuclear factor kappa B (NF-κB) cell signaling pathways. Meanwhile, APR could effectively reduce the blood glucose and blood lipid in STZ-induced diabetic mice. These results suggested that APR might be a potential agent for diabetes mellitus diseases treatment.

Targeted Isolation of Antioxidant Constituents from Plantago asiatica L. and In Vitro Activity Assay

Plantago asiatica L. is widely distributed in Eastern Asia and a commonly used drug in China, Korea, and Japan for diuretic and antiphlogistic purposes. In this experiment, the present study was performed to isolate antioxidant molecules based on the DPPH scavenging activity assay and discover the bioactive compounds which contributed to performing the function of Plantago asiatica L. Each faction was chosen for further isolation guided by DPPH scavenging activity assay. Afterwards, two potential bioactive molecules, aesculetin and apigenin, were isolated for in vitro antioxidant activity in cells. Hydrogen-peroxide-induced oxidative stress led to decreased cell viability, impaired intercellular junction, and damage to the cell membrane and DNA. Furthermore, aesculetin ameliorated decreased cell viability induced by hydrogen peroxide via upregulation of antioxidant related genes, and apigenin also protected against H₂O₂ mainly by improving the glutathione (GSH) antioxidant system, such as increasing the activity of glutathione peroxidase (GPX), glutathione reductase (GR), and the ration of GSH/glutathione disulfide (GSSG). Above all, these findings suggest that aesculetin and apigenin may be bioactive compounds for antioxidant function in Plantago asiatica L.

Neurotoxic Anatoxin-a Can Also Exert Immunotoxicity by the Induction of Apoptosis on Carassius auratus Lymphocytes in vitro When Exposed to Environmentally Relevant Concentrations

Hazardous anatoxin-a (ANTX-a) is produced by freshwater algal blooms worldwide, which greatly increases the risk of consumer exposure. Although ANTX-a shows widespread neurotoxicity in aquatic animals, little is known about its mechanism of action and biotransformation in biological systems, especially in immunobiological models. In this study, transmission electron microscopy results showed that ANTX-a can destroy lymphocytes of Carassius auratus in vitro by inducing cytoplasmic concentration, vacuolation, and swollen mitochondria. DNA fragmentations clearly showed a ladder pattern in agarose gel electrophoresis, which demonstrated that the apoptosis of fish lymphocytes was caused by exposure to ANTX-a. Flow cytometry results showed that the apoptotic percentage of fish lymphocytes exposed to 0.01, 0.1, 1, and 10 mg/L of ANTX-a for 12 h reached 18.89, 22.89, 39.23, and 35.58%, respectively. ANTX-a exposure induced a significant increase in reactive oxygen species (ROS) and malonaldehyde (MDA) in lymphocytes. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), and the glutathione (GSH) content of the 0.01 mg/L ANTX-a-treated group decreased significantly by about 41, 46, 67, and 54% compared with that of the control group (p < 0.01), respectively. Although these observations were dose-dependent, these results suggested that ANTX-a can induce lymphocyte apoptosis via intracellular oxidative stress and destroy the antioxidant system after a short exposure time of only 12 h. Besides neurotoxicity, ANTX-a may also be toxic to the immune system of fish, even when the fish are exposed to environmentally relevant concentrations, which clearly demonstrated that the potential health risks induced by ANTX-a in aquatic organisms requires attention.

Emerging Mycotoxins: Beyond Traditionally Determined Food Contaminants

Modern analytical techniques can determine a multitude of fungal metabolites contaminating food and feed. In addition to known mycotoxins, for which maximum levels in food are enforced, also currently unregulated, so-called "emerging mycotoxins" were shown to occur frequently in agricultural products. The aim of this review is to critically discuss the relevance of selected emerging mycotoxins to food and feed safety. Acute and chronic toxicity as well as occurrence data are presented for enniatins, beauvericin, moniliformin, fusaproliferin, fusaric acid, culmorin, butenolide, sterigmatocystin, emodin, mycophenolic acid, alternariol, alternariol monomethyl ether, and tenuazonic acid. By far not all of the detected compounds are toxicologically relevant at their naturally occurring levels and are therefore of little or no health concern to consumers. Still, gaps in knowledge have been identified for several compounds. These gaps should be closed by the scientific community in the coming years to allow a proper risk assessment.