The role of mitochondria in sterigmatocystin-induced apoptosis on SH-SY5Y cells.

Mitochondria are cellular organelles involved in many crucial functions, such as generation of energy (ATP) and initiation of apoptosis. The aim of the present study was to evaluate the role of mitochondria in the toxicity induced by sterigmatocystin (STE), a mycotoxin produced by fungi of the genus Aspergillus, on SH-SY5Y cells. Our results showed that STE exposure decreased cell viability in a time- and concentration-dependent manner by MTT assay and caused mitochondrial dysfunction, as highlighted by the increase of STE cytotoxicity in cells forced to rely on mitochondrial oxidative phosphorylation. Furthermore, intracellular ATP depletion and increased mitochondrial reactive oxygen species were also observed. Since mitochondria play a pivotal role in apoptosis, the induction of this process in response to STE exposure was decided to study. Our results showed an increase in apoptotic cell population by flow cytometry, further confirmed by the up-regulation of the expression levels of the pro-apoptotic genes Bax and Casp-3 and the down-regulation of the anti-apoptotic gene Bcl-2 by qPCR technique. Taken together, our results provide novel insights in the signalling pathways of the cell death process induced by STE in SH-SY5Y cells, highlighting the key role played by mitochondria in STE toxicity.

Sterigmatocystin moderately induces oxidative stress in male Wistar rats after short-term oral treatment.

This study aimed to explore involvement of oxidative stress in sterigmatocystin (STC) toxicity in male Wistar rats. Animals were orally treated with a single STC dose (10, 20 and 40 mg/kg b.w.). Short-term treatment resulted in moderate oxidative stress determined by a significant increase of malondialdehyde (MDA; all STC doses) and catalase (CAT; 10 mg/kg b.w.) in plasma, a decrease of glutathione peroxidase (GPx; 20 and 40 mg/kg b.w.) in the liver, and increase of MDA and superoxide dismutase (SOD) in kidneys (all STC doses). Heat shock protein (Hsp27 and Hsp70) expression was determined by Western blotting in rat liver and kidneys. Hsp27 expression was downregulated by STC, particularly in the liver (40 mg/kg b.w.). The lowest STC dose elevated the expression of Hsp70 in both liver and kidneys, while an increase in STC doses restored Hsp70 expression to control. Alterations in expressions of Hsp27 and Hsp70 could be only partially associated with oxidative stress. STC provoked a significant DNA damage in both liver and kidneys (alkaline comet assay), but the liver was more affected by a broader spectrum of DNA lesions. Oxidative DNA damage (hOGG1-modified comet assay) contribute to the overall mechanism of STC-induced DNA damage in both organs, but kidneys in general seem to be more susceptible to oxidative stress upon short-term exposure to sublethal doses of STC.

Individual and combined effects of mycotoxins from typical indoor moulds.

The mycotoxins patulin, gliotoxin and sterigmatocystin can be produced by common indoor moulds and enter the human body via inhalation of mycotoxin containing spores and particulates. There are various studies about the individual effects of these mycotoxins, but a lack of knowledge about their effects in mixtures. The aim of this study was to evaluate combined effects on the singe celled organism Tetrahymena pyriformis. Using the MIXTOX model (EU project NOMIRACLE) synergistic or antagonistic effects with dose level deviation or dose ratio dependent deviation were analyzed. The most toxic compound gliotoxin (EC50 0.37 µM) and patulin (EC50 9.3 µM) as shown by the MIXTOX model acted synergistic, caused by similar mode of actions. Within the combination with sterigmatocystin (maximum inhibition of 45% at 12.5 µM) antagonistic effects were observed with switch to synergism if the toxicity of the mixture is mainly caused by sterigmatocystin. In the end the MIXTOX model was applicable for the prediction of combined effects of toxic compounds.

Cytotoxicity and genotoxicity of versicolorins and 5-methoxysterigmatocystin in A549 cells.

Aspergillus versicolor and A. flavus are primary colonizers in damp dwellings, and they produce sterigmatocystin (ST) and aflatoxin B1 (AFB(1)), respectively. These hepatotoxic and carcinogenic mycotoxins and their precursors and derivates possess a furofuran ring, which has proven responsible for their toxicity. The aim of this study was to investigate the cytotoxicity and genotoxicity of versicolorin A (VER A) and versicolorin B (VER B), as the furofuran precursors of aflatoxins and ST, and of 5-methoxysterigmatocystin (5-MET-ST), a methoxy derivative of ST, in human adenocarcinoma lung cells A549. The IC(50) values of the tested compounds were obtained by the cell proliferation MTT test as follows: 109 ± 3.5 µM (VER A), 172 ± 4 µM (VER B) and 181 ± 2.6 µM (5-MET-ST). The comet assay and micronucleus test were used to assess their genotoxic potential after 24 h of treatment with concentrations corresponding to ½ and » IC(50) in comparison with AFB(1) and ST, applied in concentrations corresponding to ½ IC(50), as previously determined in A549 cells. DNA damage parameters assessed by the comet assay were tail length, tail intensity and tail moment, while the level of DNA damage in the micronucleus test was evaluated by the number of formed micronuclei (MN), nuclear buds (NB) and nucleoplasmic bridges (NPB) in 1,000 binucleated cells. Considering the three comet parameters, all applied toxins exerted significant DNA damage compared to the control, while ST and VER B produced the highest DNA damage. All toxins provoked a statistically significant increase in MN, and a slightly decreased formation of NB and NPB. AFB(1), ST and 20 µM VER A showed a statistically significant increase in all three micronucleus parameters compared to the control, and the highest increase in the number of MN occurred in cells treated with 50 µM VER A. The differences between results obtained by the micronucleus test and comet assay could be explained by the fact that the micronucleus detects irreversible DNA damage, which is usually correlated with the previously determined cytotoxic potential of the AFB(1) precursors.

Long-term administration of the fungus toxin, sterigmatocystin, induces intestinal metaplasia and increases the proliferative activity of PCNA, p53, and MDM2 in the gastric mucosa of aged Mongolian gerbils.

OBJECTIVE: The causal agents of gastric cancer could include fungus toxins. Sterigmatocystin (ST), a fungus toxin, is a risk factor of gastric cancer. We investigated the effects of ST on the stomach tissues of Mongolian gerbils. METHODS: Seventy-five-week-old male Mongolian gerbils received ST ad libitum at a concentration of 0 ppb (non-treated, n = 11), 100 ppb (n = 7), or 1000 ppb (n = 13) dissolved in drinking water for a period of 24 weeks. After administration, we tested the histopathological changes and immunostaining for proliferating cell nuclear antigen (PCNA), p53, and MDM2 expression. RESULTS: We investigated the histopathological changes and determined the incidence of histopathological changes in animals with various gastric diseases after ST administration at a dose of 0 ppb (non-treated control), 100, or 1,000 ppb as follows: firstly, indices for gastritis were 18.2, 100, and 100%, those for erosion events were 9.1, 100, and 92.3%, and those for polyps were 0, 71.4, and 61.5%, respectively. These incidences in the ST-administered groups (100 or 1000 ppb) showed significant increases compared with those in the non-treated control group. And, lastly, indices for intestinal metaplasia were 0, 100, and 15.4%, respectively. Furthermore, immunostaining for PCNA, p53, and MDM2 expression showed significantly greater rates in the ST-administered groups (100 or 1000 ppb) than in the non-treated control group. CONCLUSION: The histopathological and immunohistopathological findings of this study indicate that ST exerts a marked influence on gastric mucus and gland cells, showing dominant gastritis, erosion events, polyps, and intestinal metaplasia in these animals.

Effects of repeated intra-abdominal injections of sterigmatocystin on relative organ weights, concentration of serum and liver constituents, and histopathology of certain organs of the chick.

The objectives of the study were to establish the effects of five successive intra-abdominal injections of sterigmatocystin (STG), administered at 11, 13, 15, 17, and 19 days of age, on the growth pattern of chicks and their organs, and on the concentration of certain blood and liver constituents. The STG, when administered at dosages of .5 and .7 mg per injection, markedly reduced chick growth and affected organ weights. In general, there was an increase in the relative size of the crop, proventriculus, gizzard, large intestine, kidney and pancreas and a decrease in relative size of the bursa of Fabricius. Liver, heart, and spleen size was not affected. Peritonitis was observed in chicks given the high dosage STG. The STG elevated the activity of serum aspartate aminotransferase and the number of circulating granulocytes and depressed concentrations of total serum proteins, albumin, potassium, and the total number of circulating white blood cells and granulocytes. The STG treatment decreased the concentration of dry matter, DNA, RNA, and protein in the liver, affected glycogen concentration differentially, and had no effect on lipid concentration. Liver and kidneys also showed degenerative changes as detected histopathologically. The results of these studies suggest that STG affects several tissues including the digestive system, liver, kidney, pancreas, and the immunological system.