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.     

Preparation of Artificial Antigen and Egg Yolk-derived Immunoglobulin （IgY） of Citrinin for Enzyme-Linked Immunosorbent Assay

Objective To prepare artificial antigens and anti-citrinin egg yolk-derived immunoglobulin （IgY） to build an enzyme-linked immunosorbent assay （ELISA） for citrinin （CTN）. Methods CTN was conjugated with bovine serum albumin （BSA）, ovalbumin （OVA） with formaldehyde condensation method to prepare artificial antigens and identified by ultraviolet （UV） spectrometry and Infrared （IR） spectrometry. Artificial antigens for CTN and anti-CTN IgY were purified with polyethylene glycol two-step precipitation method and identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis （SDS-PAGE）. ELISA with IgY was established. Cross-reactivity of IgY with various structural similarities to CTN and possible co-occurrence with CTN in agricultural commodities were studied. Results UV and IR absorption spectra suggested that CTN was correlated with the carrier protein of BSA or OVA. SDS-PAGE patterns showed that the anti-CTN IgY was almost pure with a molecular weight of approximate 100 KD. The indirect competitive ELISA showed that the detection limit of CTN was 10 ng·mL^-1, with a good linearity ranging 20-640 ng·mL^-1. Conclusion Artificial antigens of CTN can be successfully synthesized. The established ELISA can be used to determine CTN- contaminated samples.     

New citrinin derivatives isolated from Penicillium citrinum

Three new coupling compounds derived from citrinin (9) and 2,3,4-trimethyl-5,7-dihydroxy-2,3-dihydrobenzofuran (8) – penicitrinone A (1), penicitrinol A (2) and penicitrinone B (3) – and a new citrinin derivative – decarboxydihydrocitrinin (4) – were isolated along with 3-methoxy-1-methyl-4(1H)-quinolone (5), quinolactacin A2 (6), dihydrocitrinone (7), 2,3,4-trimethyl-5,7-dihydroxy-2,3-dihydrobenzofuran (8), citrinin (9), quinocitrinin A or B (10), and decarboxydihydrocitrinone (11) from the extract of Penicillium citrinum IFM 53298. The relative structures of compounds 1–4 were confirmed on the basis of spectroscopic investigations and chemical correlations. Citrinin (9) and quinolactacin A2 (6) both showed antifungal activity.     

Renal and hepatic glutathione concentrations in rats after treatment with hexachloro-1,3-butadiene and citrinin

Renal and hepatic glutathione (GSH) concentrations were examined after treatment of male Sprague-Dawley rats with hexachloro-1,3-butadiene (HCBD) or citrinin alone and in combination, and after pretreatment with the GSH depleting agent diethylmaleate (DEM).It was found that both renal and hepatic GSH depletion were greater when either citrinin or HCBD was given following DEM. The effect was particularly striking when the doses used were so low as to be ineffective when given alone. When HCBD and citrinin were given in combination, the effect on GSH was approximately additive.Renal tubular organic ion transport in kidney slices was also compromised significantly when either citrinin or HCBD followed pretreatment with DEM. With HCBD, depression of tetraethylammonium (TEA) transport was seen after DEM; when given alone HCBD had no effect on TEA transport.     

Effects of citrinin on maturation of mouse oocytes, fertilization, and fetal development in vitro and in vivo

The mycotoxin citrinin (CTN), a natural contaminant in foodstuffs and animal feeds, exerts cytotoxic and genotoxic effects on various mammalian cells. An earlier study by our group shows that CTN has cytotoxic effects on mouse embryonic stem cells and blastocysts, and is associated with defects in their subsequent development, both in vitro and in vivo. Here, we further investigate the effects of CTN on oocyte maturation, and subsequent pre- and postimplantation development in vitro and in vivo. CTN induced a significant reduction in the rate of oocyte maturation, fertilization, and in vitro embryo development. Treatment of oocytes with 5 microM CTN during in vitro maturation (IVM) led to increased resorption of postimplantation embryos, and decreased placental and fetal weight. Using an in vivo mouse model, we show that consumption of drinking water containing 5 microM CTN results in decreased oocyte maturation and in vitro fertilization, as well as early embryonic developmental injury. To our knowledge, this is the first study investigating the impact of CTN on maturation of mouse oocytes, fertilization, and sequential embryonic development.     

Effects of fungal metabolites on testosterone secretion in vitro

To study the direct effect of mycotoxins belonging to different chemical classes on testicular function, dispersed interstitial cells from testes of adult gerbils were short-term cultured either in the absence or presence of mycotoxins, and testosterone secretion was measured. When interstitial cells were incubated with T-2 toxin (0.0076–38.3 nM) there was a dose-dependent decrease of testosterone production (r=–0.72, ID₅₀=0.042 nM). Since neither progesteronenor DHEA-stimulated testosterone production was affected by T-2 toxin, the observed inhibition of basal secretion was apparently due to a decrease of pregnenolone production and/or conversion of pregnenolone to progesterone. Much higher concentrations of zearalenone or of ochratoxin A were necessary to induce a similar inhibition of steroidogenesis (369 M and 1838 M, respectively) when compared to T-2 toxin. In contrast, citrinin or cyclopiazonic acid affected testosterone secretion only slightly, values reaching significant levels at doses of 1.74 nM (citrinin) and 149 nM (cyclopiazonic acid). In the presence of kojic acid (2.63–2633 nM) a significant, though not dose-dependent inhibition of testosterone secretion was observed. From these experiments it is concluded that mycotoxins of distinct chemical structure act directly on testicular tissue, presumably by inhibiting early steps of the steroidogenic pathway.     

Disturbed Hsp70 and Hsp27 expression and thiol redox status in porcine kidney PK15 cells provoked by individual and combined ochratoxin A and citrinin treatments

The aim of this study was to explore the oxidative properties of ochratoxin A (OTA) and citrinin (CTN) as a possible underlying mechanism of their individual and/or combined cytotoxicity. Metabolic activity of PK15 porcine kidney cells was significantly reduced with OTA and CTN co-exposures, with synergistic cytotoxic interactions. Single CTN increased both reduced (GSH) and oxidized (GSSG) glutathione after 24 h. However, GSH was significantly lowered with all OTA and CTN combined applications in synergistic manner after 12 and 24 h. GSH/GSSG ratio was reduced in most single and dual treatments, which suggested the presence of oxidative stress. In addition, OTA and CTN exposures significantly decreased concentrations of total thiols, with mycotoxins interactions being synergistic or antagonistic. The expression levels of Hsps were differentially affected by single and dual mycotoxin(s) applications. Single OTA provoked significant down-regulation of Hsp70 and Hsp27 expressions, while CTN stimulated Hsps expressions. Hsps were also up-regulated by dual treatments, and this induction was much stronger then with single CTN. In conclusion, significant alterations in cellular redox status (glutathione, thiols) and protective mechanisms (Hsps) suggest that those disturbances might be involved in OTA and CTN individual and combined mechanisms of cytotoxicity.