Effects of the mycotoxins citrinin and ochratoxin a on hepatic mixed-function oxidase and adenosinetriphosphatase in neonatal rats

PRESENCE OF CITRININ IN GRAINS AND ITS POSSIBLE HEALTH EFFECTS

Background:

Citrinin is a mycotoxin produced by several species of the genera Aspergillus, Penicillium and Monascus and it occurs mainly in stored grain. Citrinin is generally formed after harvest and occurs mainly in stored grains, it also occurs in other plant products. Often, the co-occurrence with other mycotoxins is observed, especially ochratoxin A, which is usually associated with endemic nephropathy. At the European Union level, systematic monitoring of Citrinin in grains began with the aim of determining its highest permissible amount in food. Thus, far the systematic monitoring of the above mentioned mycotoxin in Croatia is yet to begin.

Materials and Methods:

The main goal of this study was to determine the presence of Citrinin in grains sampled in the area of Međimurje, Osijek-Baranja, Vukovar-Srijem and Brod-Posavina County. For the purpose of identification and quantification of citrinin, high performance liquid chromatograph (HPLC) with fluorescence was used (Calibration curve k > 0.999; Intra assay CV = 2.1%; Inter assay CV = 4.3%; LOQ < 1 μg/kg).

Results:

From the area of Međimurje County, 10 samples of corn and 10 samples of wheat were analyzed. None of the samples contained Citrinin (<1 μg/kg). From the area of Osijek-Baranja and Vukovar-Srijem County, 15 samples from each County were analyzed. The mean value for the samples of Osijek-Baranja County was 19.63 μg/kg (median=15.8 μg/kg), while for Vukovar-Srijem County the mean value of citrinin was 14,6 μg/kg (median=1.23 μg/kg). From 5 analyzed samples from Brod-Posavina County, one of the samples contained citrinin in the amount of 23.8 μg/kg, while the registered amounts in the other samples were <1 μg/kg.

Conclusion:

The results show that grains from several Counties contain certain amounts of Citrinin possibly indicating a significant intake of citrinin in humans. It must be stated that grains and grain-based products are the basis of everyday diet of all age groups, especially small children, where higher intake of citrinin can occur. Consequently, we emphasize the need for systematic analysis of larger amount of samples, from both large grains and small grains, especially in the area of Brod-Posavina County, in order to obtain more realistic notion of citrinin contamination of grains and to asses the health risk in humans.

Hepatotoxic effect of ochratoxin A and citrinin, alone and in combination, and protective effect of vitamin E: In vitro study in HepG2 cell

Ochratoxin A (OTA) and citrinin (CTN) are the most commonly co-occurring mycotoxins in a wide variety of food and feed commodities. The major target organ of these toxins is kidney but liver could also be a target organ. The combined toxicity of these two toxins in kidney cells has been studied but not in liver cell. In this study HepG2 cells were exposed to OTA and CTN, alone and in combination, with a view to compare the molecular and cellular mechanisms underlying OTA, CTN and OTA + CTN hepatotoxicity. OTA and CTN alone as well as in combination affected the viability of HepG2 cells in a dose-dependent manner. OTA + CTN, at a dose of 20% of IC50 of each, produced effect almost similar to that produced by either of the toxins at its IC50 concentration, indicating that the two toxins in combination act synergistically. The cytotoxicity of OTA + CTN on hepatocytes is mediated by increased level of intracellular ROS followed/accompanied by DNA strand breaks and mitochondria-mediated intrinsic apoptosis. Co-treatment of vitamin E (Vit E) with OTA, CTN and OTA + CTN reduced the levels of ROS and the cytotoxicity. But the genotoxic effect of OTA and OTA + CTN was not completely alleviated by Vit E treatment whereas the DNA damage as caused by CTN when treated alone was obviated, indicating that OTA induces DNA damage directly whereas CTN induces ROS-mediated DNA damage and OTA + CTN combination induces DNA damage not exclusively relying on but influenced by ROS generation. Taken together, these findings indicate that OTA and CTN in combination affect hepatocytes at very low concentrations and, thereby, pose a potential threat to public and animal health.

Producers and important dietary sources of ochratoxin A and citrinin

Ochratoxin A (OTA) is a very important mycotoxin, and its research is focused right now on the new findings of OTA, like being a complete carcinogen, information about OTA producers and new exposure sources of OTA. Citrinin (CIT) is another important mycotoxin, too, and its research turns towards nephrotoxicity. Both additive and synergistic effects have been described in combination with OTA. OTA is produced in foodstuffs by Aspergillus Section Circumdati (Aspergillus ochraceus, A. westerdijkiae, A. steynii) and Aspergillus Section Nigri (Aspergillus carbonarius, A. foetidus, A. lacticoffeatus, A. niger, A. sclerotioniger, A. tubingensis), mostly in subtropical and tropical areas. OTA is produced in foodstuffs by Penicillium verrucosum and P. nordicum, notably in temperate and colder zones. CIT is produced in foodstuffs by Monascus species (Monascus purpureus, M. ruber) and Penicillium species (Penicillium citrinum, P. expansum, P. radicicola, P. verrucosum). OTA was frequently found in foodstuffs of both plant origin (e.g., cereal products, coffee, vegetable, liquorice, raisins, wine) and animal origin (e.g., pork/poultry). CIT was also found in foodstuffs of vegetable origin (e.g., cereals, pomaceous fruits, black olive, roasted nuts, spices), food supplements based on rice fermented with red microfungi Monascus purpureus and in foodstuffs of animal origin (e.g., cheese).

Mycotoxin co-contamination of food and feed: meta-analysis of publications describing toxicological interactions

Most fungi are able to produce several mycotoxins simultaneously; moreover food and feed can be contaminated by several fungi species at the same time. Thus, humans and animals are generally not exposed to one mycotoxin but to several toxins at the same time. Most of the studies concerning the toxicological effect of mycotoxins have been carried out taking into account only one mycotoxin. In the present review, we analysed 112 reports where laboratory or farm animals were exposed to a combination of mycotoxins, and we determined for each parameter measured the type of interaction that was observed. Most of the published papers concern interactions with aflatoxins and other mycotoxins, especially fumonisins, ochratoxin A and trichothecenes. A few papers also investigated the interaction between ochratoxin A and citrinin, or between different toxins from Fusarium species. Only experiments with a 2×2 factorial design with individual and combined effects of the mycotoxins were selected. Based on the raw published data, we classified the interactions in four different categories: synergistic, additive, less than additive or antagonistic effects. This review highlights the complexity of mycotoxins interactions which varies according to the animal species, the dose of toxins, the length of exposure, but also the parameters measured.

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.

Production of mycotoxins by Penicillium expansum inoculated into apples

We investigated the production of mycotoxins in apple fruits inoculated with spores of 40 strains of apple blue mold, Penicillium expansum. Patulin and citrinin contents in the extracts from apples stored at 25 degrees C for 12 days after inoculation were determined by high-performance liquid chromatography (HPLC) analysis with UV and fluorescence detection. Patulin and citrinin were produced by 90% (36) and 80% (32) of the 40 strains, indicating that P. expansum is a consistent producer of these mycotoxins. The patulin content in the extracts was substantially higher than the citrinin content. Other mycotoxins whose production in pure culture has been reported were simultaneously detected with high-resolution liquid chromatography-mass spectrometry (LC-MS) analysis with the positive ion mode of electrospray ionization. Along with patulin and citrinin, expansolides A and B were identified based on the HPLC and LC-MS spectral data and detected in 88% (35) of the extracts. The results indicate that P. expansum is a consistent producer of expansolides A and B in rotten areas of apple fruits. The findings raise the possibility that products from decayed apples might contain expansolides A and B in addition to patulin and citrinin.

Ochratoxin A: An overview on toxicity and carcinogenicity in animals and humans

Ochratoxin A (OTA) is a ubiquitous mycotoxin produced by fungi of improperly stored food products. OTA is nephrotoxic and is suspected of being the main etiological agent responsible for human Balkan endemic nephropathy (BEN) and associated urinary tract tumours. Striking similarities between OTA-induced porcine nephropathy in pigs and BEN in humans are observed. International Agency for Research on Cancer (IARC) has classified OTA as a possible human carcinogen (group 2B). Currently, the mode of carcinogenic action by OTA is unknown. OTA is genotoxic following oxidative metabolism. This activity is thought to play a central role in OTA-mediated carcinogenesis and may be divided into direct (covalent DNA adduction) and indirect (oxidative DNA damage) mechanisms of action. Evidence for a direct mode of genotoxicity has been derived from the sensitive 32P-postlabelling assay. OTA facilitates guanine-specific DNA adducts in vitro and in rat and pig kidney orally dosed, one adduct comigrates with a synthetic carbon (C)-bonded C8-dG OTA adduct standard. In this paper, our current understanding of OTA toxicity and carcinogenicity are reviewed. The available evidence suggests that OTA is a genotoxic carcinogen by induction of oxidative DNA lesions coupled with direct DNA adducts via quinone formation. This mechanism of action should be used to establish acceptable intake levels of OTA from human food sources.

Effect of vitamin E and polyphenols on ochratoxin A-induced cytotoxicity in liver (HepG2) cells

It has been shown that oxidative damage contributes to the wide range of toxic effects of the mycotoxin ochratoxin A (OTA). Therefore, we examined the effects of alpha-tocopherol (alpha-TOC) and different polyphenols--catechin (CAT), daidzein (DAI), epicatechin (EC), epigallocatechin gallate (EGCG), genistein (GEN), and quercetin (QUE)--on OTA-induced cytotoxicity in HepG2 liver cells. Incubation of HepG2 cells with increasing concentrations of OTA resulted in a dose- and time-dependent cytotoxicity as measured by the neutral red assay. Half lethal concentrations (LC50) of OTA were 35 and 10 microM after 48 and 72 h incubation, respectively. Incubation of HepG2 cells with alpha-TOC as well as with different polyphenols (exhibiting different antioxidant potency as determined by the FRAP, TEAC and DPPH assays) did not counteract OTA-induced cytotoxicity. These findings indicate that OTA may exert its toxic effects by affecting other hepatic mechanisms than those directly modulated by alpha-TOC and polyphenols.

Combined toxic effects of mycotoxins

It is known for many years that several food items, derived from plants infected by fungi in the field during growing of the plant or during harvest and storage of the food item, can contain concomitantly different mycotoxins. As these combined mycotoxins occur simultaneously in the food item, consumption of the food will lead to a combined intake depending on the absorption rates of the different mycotoxins. Therefore, the question is justified whether such a combined intake of mycotoxins would lead to a possible higher risk for adverse health effects than the intake of one of these mycotoxins alone. It will be dealt with on the basis of some practical cases of such combined intake of mycotoxins of which research data are available. This is the case for citrinin and ochratoxin A, but as the workshop focuses on trichotecenes and so this paper concentrates on these. When the mycotoxins are of similar structure and of the same species, or of the same families, it is likely to expect that the mode of action of the mycotoxins and or the toxicity profiles will be quite similar. This indicates that such related mycotoxins are likely to exert only additive effects, which is important to know. In terms of risk assessment, these mycotoxins could be dealt with by establishing a group daily tolerable intake (TDI) or a provisional tolerable weekly intake (PTWI). In terms of risk assessment those mycotoxins which interact in synergistic manner are of more concern. It is concluded that, at present tools are not fully developed to establish the type of interaction or whether there is any interaction at all.

Balkan endemic nephropathy and associated urinary tract tumours: a review on aetiological causes and the potential role of mycotoxins

A series of publications in the 1950s described a kidney disease in Bulgaria, the former Yugoslavia and Romania that became known as Balkan endemic nephropathy (BEN). The disease was qualified by World Health Organisation (WHO) experts as 'progressive and very gradually developing renal failure with insidious onset.... The last stage shows marked fibrosis...'. BEN is characterized by tubular degeneration, interstitial fibrosis and hyalinization of glomeruli accompanied by enzymuria and impaired renal function without nephrotic syndrome. Later, an association between BEN and tumours of the kidney pelvis and ureter was recognized, so that the problem of BEN became not only nephrological, but also oncological. There may also be an association with increased urinary bladder cancer incidence, although many confounding factors may interfere in the analysis of data for this organ. In view of the very intimate association between BEN and the urinary tract tumours (UTT), the term 'endemic uropathy' has been proposed. Several hypothesis concerning the aetiology of these diseases has been investigated, which include: predisposing genes factors, environmental factors (heavy metals, minerals, bacteria, leptospira, viruses, fungal toxins and, most recently, pliocene lignites). This paper reviews the different hypotheses about the aetiology of endemic uropathy and pays particular attention to the role of fungal toxins.

Ochratoxin A impairs activity of the membrane bound enzymes in rat pancreas

Ochratoxin A is a mycotoxin produced by Aspergillus ochraceus and is a natural contaminant of moldly food. Ochratoxin A has a number of toxic effects, some of which may be related to the changes in the cell membrane. We measured the activities of 5 pancreatic, membrane bound enzymes in female Fisher rats that were given low oral doses of ochratoxin A (120 micrograms/kg body weight per day) during 20-35 days. The amount of toxin corresponds to 1.5 mg/kg in the feed, daily. These doses are in the range of natural contamination found in feed. The enzymes studied were alanine aminopeptidase, alkaline phosphatase, ecto-Ca2+/Mg(2+)-ATPase, gamma-glutamyl transferase and ecto-5'-nucleotidase. Treatment lasting 20 days caused a strong decrease in the activity of alanine aminopeptidase, Ca2+/Mg(2+)-ATPase and alkaline phosphatase to 0.76 +/- 0.04, 0.53 +/- 0.03 and 0.30 +/- 0.02 of the control values, respectively (p < 0.05). No significant changes in the activity of gamma-glutamyl transferase and 5'-nucleotidase were observed. However, activity of alanine aminopeptidase returned to normal values after 35 days of treatment, suggesting an adaptation of the organism, or a substitution of a released enzyme. Activities of alkaline phosphatase and Ca2+/Mg(2+)-ATPase remained significantly reduced to 0.42 +/- 0.03 and 0.52 +/- 0.04, respectively (p < 0.01). We conclude that treatment of rats with low doses of ochratoxin A resulted in reduction of the activities of the membrane bound enzymes, most probably by inducing their release, as a result of the impairment of the functional integrity of cell membranes.

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.

Interaction of citrinin and ochratoxin A

The mycotoxins citrinin and ochratoxin A are produced in common by some molds and have been found together in a number of foods and animal feeds. We used in vitro tests to determine if the same effects are produced by these two mycotoxins when they act both independently and together. Renal cortical cubes prepared from kidneys of young adult Hormel-Hanford miniature swine were cultured in the presence or absence of the toxins for 1 h at 37 degrees C. The concentration of the toxins both singly and in combination ranged from 10(-6) to 10(-3) M. The tissues were incubated, removed, rinsed, and reincubated to measure transport of either tetraethylammonium (TEA) or paraminohippurate (PAH) ions and protein synthesis, using 3H-leucine. The transport data were analyzed by a recently developed logistic function test to ascertain whether the effects were additive, synergistic, or antagonistic. The significance of deviation was tested after a potency multiplier was added to the mixture. Data for three of the five experiments measuring TEA transport indicated a synergistic effect; for the other two, the results were not significantly different from additivity. The same was true for PAH transport. For protein synthesis, one experiment showed synergism; for the other, nonadditivity was not significant. None of the measurements showed antagonism between the two toxins. As with several other systems, tests of biochemical effects showed that administration of citrinin and ochratoxin A together did not elicit either consistent or strong synergistic responses.

Role of ochratoxin in disease causation

Under experimental conditions renal damage has been induced by alimentary exposure to ochratoxin A in all single-stomach animals tested so far, including rodents, dogs, pigs and birds, and even in young ruminants still functioning as single-stomach animals. Most information on ochratoxin-induced nephropathy has been obtained in pigs during experimental studies comprising structural as well as functional changes. The renal damage is characterized morphologically by atrophy of the proximal tubules, interstitial cortical fibrosis and sclerotized glomeruli, and functionally by impairment of tubular function indicated by a decrease in TmPAH/Cin and reduced ability to produce concentrated urine. The renal effect has been observed using exposure levels of ochratoxin A in the range 200 to 4000 micrograms/kg feed. Field cases of ochratoxin-induced nephropathy in pigs have been encountered in many countries, and the disease mycotoxic porcine nephropathy (MPN) is recognized as an endemic disease entity in several northern and central European countries. Epidemics of MPN have been reported, closely related to excessive climatic conditions in periods preceding harvest. Ochratoxin A is a recognized renal carcinogen in the mouse. In female pigs exposed to alimentary ochratoxin A for 2 years, no renal cancer was observed. Ochratoxin A is metabolized and excreted relatively fast in animals, with an RL50 (residue elimination) in the pig of a few days for various tissues. Past exposure data is a requirement in retrospective epidemiological studies, but because of the short RL50 values tissue analysis for ochratoxin A is unlikely to provide that kind of data, in animals or in humans. In order to meet this demand a procedure has been developed, using renal biopsy material for activity analysis of two renal tubular enzymes, phosphoenolpyruvate carboxykinase and gamma-glutamyl transpeptidase. In pigs exposed to ochratoxin A for 1 week a 40% reduction of the enzyme activity was observed. The dose-related activity decrease of the two enzymes was accompanied by a dose-related aggravation of renal impairment, as measured by a reduction of TmPAH/Cin, suggesting that these enzymes are sensitive indicators of ochratoxin A-induced nephropathy.

Effects of ochratoxin A alone and in combination with citrinin on kidney function of single comb White Leghorn pullets

The present study was designed to evaluate the acute effects of ochratoxin A (OA) on pullet renal function, and to determine if the diuretic effects of citrinin are altered by acute ochratoxicosis. Birds were injected intramuscularly with a 1-mg/mL solution of OA at a dose of 5 mg/kg body weight for 2 consecutive days. Control birds received an equal volume injection of the OA carrier vehicle (100% ethanol). On the 3rd day, birds were anesthetized and prepared for renal function studies. Following 30 min of control urine and plasma collection, an intravenous infusion containing 400 ppm citrinin was initiated, and urine and plasma were collected for an additional 70 min. The OA alone caused an increase in manure moisture and increased hematocrits (hemoconcentration), but direct effects on glomerular filtration rate (GFR), urine flow rate/GFR, para-aminohippuric acid clearance (CPAH), free water clearance (FWC), and electrolye excretion (Na, K, Ca, P) were not consistently demonstrated. The OA may cause hemoconcentration by causing a subtle increase in urine flow (diuresis), or by increasing intestinal water loss (diarrhea). Citrinin infusion caused increased urine flow rate, increased urine flow rate/GFR, increased FWC, increased Na excretion, and decreased urine osmolality. Pretreatment with OA attenuated these effects of citrinin, presumably due to renal compensation for the OA-induced hemoconcentration. Citrinin and OA do not appear to have additive diuretic effects during the first 48 h of toxin exposure.