Mechanism of citrinin-induced dysfunction of mitochondria. II. Effect on respiration, enzyme activities, and membrane potential of liver mitochondria

Sulforaphane alleviates the meiosis defects induced by 3-nitropropionic acid in mouse oocytes

3-Nitropropionic acid (3-NP) is a mycotoxin commonly found in plants and fungi that has been linked to mammalian intoxication. Previously, we found 3-NP treatment exhibited reproductive toxicity by inducing oxidative stress in mouse ovary; however, the toxic effects of 3-NP on mouse oocyte maturation have not been investigated. Sulforaphane (SFN) is a naturally bioactive phytocompound derived from cruciferous vegetables that has been shown to possess cytoprotective properties. The present study was designed to investigate the cytotoxicity of 3-NP during mouse oocyte maturation and the protective effects of SFN on oocytes challenged with 3-NP. The results showed 3-NP had a dose-dependent inhibitory effect on oocyte maturation, and SFN significantly alleviated the defects caused by 3-NP, including failed first polar body extrusion and abnormal spindle assembly. Furthermore, 3-NP caused abnormal mitochondrial distribution in oocytes and disrupted mitochondrial functions, including mitochondrial depolarization, decreased ATP levels, and increased mitochondrial-derived ROS. Finally, 3-NP induced oxidative stress in oocytes, leading to increased apoptosis and autophagy, while SFN supplementation had significant cytoprotective effects on these damages. Collectively, our results provide insight on the mechanism of 3-NP toxicity in mouse oocytes and suggest the application of SFN may be a viable intervention strategy to mitigate 3-NP-induced reproductive toxicity.

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.

Pelargonidin Modulates Keap1/Nrf2 Pathway Gene Expression and Ameliorates Citrinin-Induced Oxidative Stress in HepG2 Cells

Pelargonidin chloride (PC) is one of the major anthocyanin found in berries, radish and other natural foods. Many natural chemopreventive compounds have been shown to be potent inducers of phase II detoxification genes and its up-regulation is important for oxidative stress related disorders. In the present study, we investigated the effect of PC in ameliorating citrinin (CTN) induced cytotoxicity and oxidative stress. The cytotoxicity of CTN was evaluated by treating HepG2 (Human hepatocellular carcinoma) cells with CTN (0–150 μM) in a dose dependent manner for 24 h, and the IC₅₀ was determined to be 96.16 μM. CTN increased lactate dehydrogenase leakage (59%), elevated reactive oxygen species (2.5-fold), depolarized mitochondrial membrane potential as confirmed by JC-1 monomers and arrested cell cycle at G2/M phase. Further, apoptotic and necrotic analysis revealed significant changes followed by DNA damage. To overcome these toxicological effects, PC was pretreated for 2 h followed by CTN exposure for 24 h. Pretreatment with PC resulted in significant increase in cell viability (84.5%), restored membrane integrity, reactive oxygen species level were maintained and cell cycle phases were normal. PC significantly up-regulated the activity of detoxification enzymes: heme oxygenase 1 (HO-1), glutathione transferase, glutathione peroxidase, superoxide dismutase and quinone reductase. Nrf2 translocation into the nucleus was also observed by immunocytochemistry analysis. These data demonstrate the protective effect of PC against CTN-induced oxidative stress in HepG2 cells and up-regulated the activity of detoxification enzyme levels through Keap1/Nrf2 signaling pathway.

Cytoprotective propensity of green tea polyphenols against citrinin-induced skeletal-myotube damage in C2C12 cells

The mycotoxin citrinin, is produced by several species of Penicillium, Aspergillus and Monascus, and is capable of inducing cytotoxicity, oxidative stress and apoptosis. The aim of the present study was to investigate the effect of citrinin in mouse skeletal muscle cells (C2C12) and to overcome the cellular adverse effects by supplementing green tea extract (GTE) rich in polyphenols. C2C12 myoblasts were differentiated to myotubes and were exposed to citrinin in a dose dependent manner (0-100 µM) for 24 h and IC₅₀ value was found to be 100 µM that resulted in decreased cell viability, increased LDH leakage and compromised membrane integrity. Mitochondrial membrane potential loss, increased accumulation of intracellular ROS and sub G1 phase of cell cycle was observed. To ameliorate the cytotoxic effects of CTN, C2C12 cells were pretreated with GTE (20, 40, 80 µg/ml) for 2 h followed by citrinin (100 µM) treatment for 24 h. GTE pretreatment combated citrinin-induced cytotoxicity and oxidative stress. GTE at 40 and 80 µg/ml significantly promoted cell survival and upregulated antioxidant enzyme activities (CAT, SOD, GPx) and endogenous antioxidant GSH, while the gene and protein expression levels were significantly restored through its effective antioxidant mechanism. Present study results suggested the antioxidant properties of GTE as a herbal source in ameliorating the citrinin-induced oxidative stress.

Low doses of the mycotoxin citrinin protect cortical neurons against glutamate-induced excitotoxicity

Citrinin, a natural mycotoxin that is found in fermented foods, is known as a cytotoxin and nephrotoxin. Exposure to high doses of citrinin result in apoptosis; however, the effects of low doses are not fully understood. Glutamate excitotoxicity is responsible for neuronal death in acute neurological disorders including stroke, trauma and other neurodegenerative diseases. Here, we show the neuroprotective effect of low doses of citrinin against glutamate-induced excitotoxicity. We examined the effect of citrinin exposure on glutamate-induced cell death in cultured rat cortical neurons under two conditions: simultaneous treatment with citrinin 0.1 to 1,000 nM and glutamate (30 μM) for 1, 3 hr; the same simultaneous treatment for 3 hr after pretreatment with citrinin for 21 hr. Both the MTT and immunocytochemical assay showed significant neuroprotective effects at several doses and exposure times tested. All concentrations of citrinin tested showed no remarkable cell death following 14-day exposure, and no marked alterations to synapses. These data suggest that low doses of citrinin can be used as a neuroprotective agent against glutamate-induced excitotoxicity without additional harmful cellular alterations.

Regulation of the antioxidant system in cells of the fission yeast Schizosaccharomyces pombe after combined treatment with patulin and citrinin

The effects of combined treatment with patulin (PAT) and citrinin (CTN) on Schizosaccharomyces pombe cells were investigated in acute toxicity tests. In comparison with the controls the exposure of fission yeast cells (10(7) cells ml(-1)) to PAT + CTN (250 μM each) for 1 h at a survival rate of 66.6% significantly elevated the concentration of total reactive oxygen species (ROS) via increased levels of peroxides without affecting the concentrations of superoxides or the hydroxyl radical. This treatment induced a 3.08-fold increase in the specific concentration of glutathione and elevated specific activities of catalase and glutathione S-transferase, while at the same time the activity of glutathione reductase decreased. The pattern of the ROS was the same as that induced by CTN (Máté et al., 2014), while the presence of PAT in the PAT + CTN combination treatment modified the activities of the antioxidant system (Papp et al., 2012) in comparison with the individual PAT or CTN treatment, suggesting toxin-specific regulation of glutathione and the enzymes of the antioxidant system and the possibility that the transcription factor (pap1 and atf1) -regulated processes might be influenced directly by ROS.

Cannabis microbiome sequencing reveals several mycotoxic fungi native to dispensary grade Cannabis flowers

The Center for Disease Control estimates 128,000 people in the U.S. are hospitalized annually due to food borne illnesses. This has created a demand for food safety testing targeting the detection of pathogenic mold and bacteria on agricultural products. This risk extends to medical Cannabis and is of particular concern with inhaled, vaporized and even concentrated Cannabis products . As a result, third party microbial testing has become a regulatory requirement in the medical and recreational Cannabis markets, yet knowledge of the Cannabis microbiome is limited. Here we describe the first next generation sequencing survey of the fungal communities found in dispensary based Cannabis flowers by ITS2 sequencing, and demonstrate the sensitive detection of several toxigenic Penicillium and Aspergillus species, including P. citrinum and P. paxilli, that were not detected by one or more culture-based methods currently in use for safety testing.

Cannabis microbiome sequencing reveals several mycotoxic fungi native to dispensary grade Cannabis flowers

The Center for Disease Control estimates 128,000 people in the U.S. are hospitalized annually due to food borne illnesses. This has created a demand for food safety testing targeting the detection of pathogenic mold and bacteria on agricultural products. This risk extends to medical Cannabis and is of particular concern with inhaled, vaporized and even concentrated Cannabis products . As a result, third party microbial testing has become a regulatory requirement in the medical and recreational Cannabis markets, yet knowledge of the Cannabis microbiome is limited. Here we describe the first next generation sequencing survey of the microbial communities found in dispensary based Cannabis flowers and demonstrate the limitations in the culture-based regulations that are being superimposed from the food industry.

A 90-d toxicity study of monascus-fermented products including high citrinin level

Monascus is one of the traditional fermentation fungi and has been used in many kinds of food for thousands of years. Although Monascus-fermented red mold rice performs cholesterol-lowering effects, blood pressure-lowing effects, and antioxidant effects, another metabolite, nephrotoxic and hepatotoxic citrinin, causes the concerns for safety. Various citrinin concentrations (1, 2, 10, 20, and 200 ppm) in the red mold rice are, respectively, estimated for safe use in animal tests. According to the results of serum biochemistry assays of liver and kidney in each group, citrinin did not reveal any nephrotoxicity and hepatotoxicity. Furthermore, the results of histopathological slices of liver and kidney in each group did not show any significant differences from control histopathological findings. As a result, we presume that citrinin concentrations in Monascus-fermented products within 200 ppm will not affect the functions of liver and kidney or cause any nephrotoxicity and hepatotoxicity. According to safety factor, it is proposed that 2 ppm citrinin in Monascus-fermented products may be a safe concentration.

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.

Mitochondrial bioenergetics after nine-day treatment regimen with benzonidazole in rats

The bioenergetics of cardiac, liver, and kidney mitochondria after 9-day treatment regimen with benzonidazole was studied in rats. The drug was given by oral gavage to adult male Sprague-Dawley rats for 9 consecutive days (100 mg benzonidazole/kg body weight as daily dose). The assayed mitochondrial bioenergetic parameters were the state 4, state 3, respiratory control, efficiency of oxidative phosphorylation, and the activity of the mitochondrial ATP synthase. The results showed that mitochondrial parameters were not altered statistically after in cardiac and kidney mitochondria, but respiratory control in liver mitochondria was statistically increased with benzonidazole treatment. This change was likely due to a slight decrease in state 4 bioenergy metabolism. These results indicate that 9-day benzonidazole treatment regimen had no negative effect on cardiac, liver, and kidney mitochondrial energy metabolism but increased respiratory control in rat liver mitochondria.

Biologically active components and nutraceuticals in the Monascus-fermented rice: a review

Monascus-fermented rice has traditionally been used as a natural food colorant and food preservative of meat and fish for centuries. It has recently become a popular dietary supplement because of many of its bioactive constituents being discovered, including a series of active drug compounds, monacolins, indicated as the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors for reducing serum cholesterol level. The controversy of its safety has been provoked because a mycotoxin, citrinin, is also produced along with the Monascus secondary metabolites by certain strains or under certain cultivation conditions. This review introduces the basic production process and addresses on the compounds with bioactive functions. Current advances in avoiding the harmful ingredient citrinin are also discussed.

Effects of citrinin on iron-redox cycle

The ability of the mycotoxin citrinin to act as an inhibitor of iron-induced lipoperoxidation of biological membranes prompted us to determine whether it could act as an iron chelating agent, interfering with iron redox reactions or acting as a free radical scavenger. The addition of Fe3+ to citrinin rapidly produced a chromogen, indicating the formation of citrinin-Fe3+ complexes. An EPR study confirms that citrinin acts as a ligand of Fe3+, the complexation depending on the [Fe3+]:[citrinin] ratios. Effects of citrinin on the iron redox cycle were evaluated by oxygen consumption or the o-phenanthroline test. No effect on EDTA-Fe2+-->EDTA-Fe3+ oxidation was observed in the presence of citrinin, but the mycotoxin inhibited, in a dose-dependent manner, the oxidation of Fe2+ to Fe3+ by hydrogen peroxide. Reducing agents such as ascorbic acid and DTT reduced the Fe3+-citrinin complex, but DTT did not cause reduction of Fe3+-EDTA, indicating that the redox potentials of Fe3+-citrinin and Fe3+-EDTA are not the same. The Fe2+ formed from the reduction of Fe3+-citrinin by reducing agents was not rapidly reoxidized to Fe3+ by atmospheric oxygen. Citrinin has no radical scavenger ability as demonstrated by the absence of DPPH reduction. However, a reaction between citrinin and hydrogen peroxide was observed by UV spectrum changes of citrinin after incubation with hydrogen peroxide. It was also observed that citrinin did not induce direct or reductive mobilization of iron from ferritin. These results indicate that the protective effect on iron-induced lipid peroxidation by citrinin occurs due to the formation of a redox inactive Fe3+-citrinin complex, as well as from the reaction of citrinin and hydrogen peroxide.

Mutagenicity of commercial Monascus fermentation products and the role of citrinin contamination

Pigments produced as secondary metabolites by various isolates of moulds belonging to the genus Monascus have been used traditionally as colorants in Oriental food. Modern food industry has rediscovered these moulds as promising source for natural colorants. However, recent studies evidence that one of the secondary metabolites produced by Monascus is identical in structure to the mycotoxin citrinin. Thus, a sensitive HPLC method was developed to analyse these food colorants for contamination with citrinin. The mycotoxin could be detected in all the commercial Monascus samples at concentrations varying between 0.2 to 17.1 microg/g. In addition, the mutagenicity of commercial Monascus samples applying Salmonella-microsome assay and Salmonella-hepatocyte-assay was investigated and compared to the results obtained with citrinin. Citrinin and two Monascus extracts induced a positive dose depending mutagenic response in the Salmonella-hepatocyte-assay applying strain TA-98. However, no mutagenicity could be detected in the Salmonella-microsome assay, neither with nor without S9-mix, for citrinin and Monascus extracts, applying TA-98, TA-100, TA-1535, TA-1538 and TA-97. These findings provide further evidence that citrinin requires complex cellular biotransformation to exert mutagenicity.

Mechanism of citrinin-induced dysfunction of mitochondria. VI. Effect on iron-induced lipid peroxidation of rat liver mitochondria and microsomes

The inhibition by citrinin (CTN) of lipid peroxidation of mitochondria, sub-mitochondrial particles (SMP) and microsomes was studied. This effect was reversed by the presence of high concentrations of Fe3+ (0.4 and 0.5 mM), suggesting chelation of the mycotoxin with iron or interference in the reduction of Fe3+.

Mechanism of citrinin-induced dysfunction of mitochondria. V. Effect on the homeostasis of the reactive oxygen species

The effects of citrinin in the maintenance of the homeostasis of the reactive oxygen species in rat liver cells were evaluated. Citrinin (CTN) modifies the antioxidant enzymatic defences of cells through the inhibition of GSSG-reductase and transhydrogenase. No effect was observed on GSH-peroxidase, catalase, glucose 6-phosphate and 6 phosphogluconate dehydrogenases, and superoxide dismutase. The mycotoxin increased the generation of reactive oxygen species, stimulating the production of the superoxide anion in the respiratory chain. The results suggest that oxidative stress is an important mechanism, side by side with other effects previously shown, in the establishment of the cytotoxicity and cellular death provoked by CTN in several tissues.

Citrinin produces acute adverse changes in renal function and ultrastructure in pentobarbital-anesthetized dogs without concomitant reductions in [potassium]plasma

Citrinin's nephrotoxicity was examined in pentobarbital-anesthetized dogs under conditions that minimized or avoided significant changes in a number of its actions that could indirectly and adversely affect renal function and ultrastructure, such as, (i) major acute reductions in blood pressure and renal blood flow and, (ii) emesis and diarrhea that could lead to dehydration and electrolyte imbalances, especially hypokalemia. Slow intravenous injection of 20 mumol citrinin/kg to pentobarbital-anesthetized dogs did not induce any alterations in renal tissue ultrastructure or in any of the 23 whole blood, plasma or renal function parameters that were monitored over a 6-h post-citrinin period. On the other hand, 80 mumol citrinin/kg produced significant increases in the hematocrit and in the renal excretion rates of protein and glucose; modest reductions were noted in CIN, RBF and excretion rate of inorganic phosphorus. In addition, 80 mumol citrinin/kg induced ultrastructural lesions in the cells of the S2 proximal tubular segment, the thick ascending limb, the distal convoluted tubule and the collecting ducts. The glomeruli, S1 and S3 cells of the proximal tubule and the thin descending and ascending limbs of Henle's loop were unaffected by both citrinin doses. The location and nature of the adverse ultrastructural lesions were most likely the result of the direct actions of citrinin (or a citrinin metabolite) since the effects of citrinin that could lead to indirect adverse renal effects were totally avoided or greatly minimized.

Citrinin affects the oxidative metabolism of BHK-21 cells

The effects of citrinin on energy production along the respiratory chain and on glycolytic lactate production were examined in BHK-21 cultured cells. Citrinin inhibited the oxygen consumption rate by about 45 per cent. The respiratory rate of digitonin-treated cells energized with succinate, in the presence of ADP, was reduced by about 39 per cent. The mycotoxin inhibited the glucose utilization of BHK-21 cells by about 86 per cent. Cells treated with citrinin produced a small quantity of pyruvate, but were unable to produce lactate. It is concluded that BHK-21 cells cannot generate lactate when oxidative metabolism is inhibited by citrinin. The perturbations in BHK-21 cells caused by citrinin are due to alterations in mitochondrial function and in the glycolytic anaerobic pathway.

Mechanism of citrinin-induced dysfunction of mitochondria. III. Effects on renal cortical and liver mitochondrial swelling

The effects of the mycotoxin citrinin on renal cortical and liver mitochondrial swelling were studied. Citrinin decreases the rate of swelling induced by the valinomycin-K+ complex, suggesting that the mycotoxin interferes with the mitochondrial membrane fluidity. Citrinin promotes reduction of the amplitude of swelling in the presence of Na+ ions. This alteration reflects interference with complex I of the respiratory chain and ATP synthase complex activity without disarranging the inner mitochondrial membrane, in view of the fact that the shrinkage was not affected. The effect increases with citrinin concentration. Renal tissue is more susceptible than hepatic tissue.

Mechanism of citrinin-induced dysfunction of mitochondria. IV--Effect on Ca2+ transport

The effect of citrinin on Ca2+ transport was studied in isolated kidney cortex and liver mitochondria, and baby hamster kidney cultured cells. The mycotoxin significantly inhibited the activity of 2-oxoglutarate and pyruvate dehydrogenases in both kidney cortex and liver mitochondria. Citrinin promoted a decrease in the velocity and in the total capacity of Ca2+ uptake, in both mitochondria. Apparently, citrinin acts by a mechanism similar to ruthenium red. In intact cultured cells, citrinin also had a preferential effect on mitochondrial Ca2+ fluxes. Citrinin promoted a marked decrease in the Ca2+ level in the mitochondrial matrix, whereas that of the extramitochondiral fraction became less affected. All the observed effects were dependent on the citrinin concentration.