Interaction effects of Fusarium enniatins (A, A1, B and B1) combinations on in vitro cytotoxicity of Caco-2 cells.

Foodstuff is usually contaminated by more than one mycotoxin, however toxicological data are lacking as regards the effects in combinations compared to their individual effect. This study investigated the in vitro effects of enniatins (ENs) A, A1, B and B1, alone and in combinations, on Caco-2 cells viability by MTT assay after 24h of exposure. Cells were treated with concentrations ranging from 0.9 to 15.0µM, individually and in combination of two, three and four mycotoxins. Dose-response curves were generated for each mycotoxin and the isobologram method was used to determine the interactive effects of tested mixtures. Tested ENs produced significant cytotoxic effects both individually and in combination in a dose-dependent manner. IC50 values obtained for all individually tested mycotoxins ranged from 1.3 to >15µM. In ENs combination tests, synergistic effect in Caco-2 viability are observed for EN B+EN A1, EN B1+EN A1 and EN A+EN A1+EN B (CI=0.33-0.52). All other combinations showed additive effect at medium and high affected fraction with exception of lower fraction affected and the EN B+EN B1 mixture that produced antagonistic effect (CI=1.76-10.36). The use of combination index-isobole method could help to better understand the potential interaction between co-occurring mycotoxins and may contribute to their risk assessment.

Reactive oxygen species involvement in apoptosis and mitochondrial damage in Caco-2 cells induced by enniatins A, A1, B and B1.

The cytotoxic effects, the generation of reactive oxygen species (ROS) and lipid peroxidation (LPO) as well as the cell cycle disruption, the induction of apoptosis and changes in mitochondrial membrane potential (ΔΨm) as a function of increasing time have been determined in human colorectal adenocarcinoma (Caco-2) cells after exposure to enniatins (ENs) A, A1, B and B1. IC50 values obtained by the MTT and Neutral Red assay, after 24, 48 and 72 h of exposure ranged from 0.5±0.1 to >15 µM. A significant increase (p≤0.05) in ROS generation and LPO production, as determined by the fluorescent probe H2-DCFDA and TBARS method respectively, was observed for all mycotoxins tested at 3.0 µM concentration. The highest increase in ROS generation (2.6 fold higher than control) and LPO production (111%, as compared to control) was observed with EN A. Cell cycle was significantly arrested at G2/M phase after 24 h of exposure to EN A, A1, B1, whereas after 72 h of exposure an arrest in S phase was observed almost for all mycotoxins tested. Moreover, after 24 and 48 h of exposure, ENs increased the early apoptotic cells, whereas after 72h of exposure necrosis was observed. In addition the loss of ΔΨm was produced on Caco-2 cells after ENs exposure. ENs A, A1, B and B1 cytotoxicity involved early ROS generation that induced LPO oxidative damage, apoptosis and necrosis via the mitochondrial pathway. ENs A, A1 and B1 induced DNA damage. However the same effects cannot be proposed for EN B. Further studies on the toxicological effects induced by ENs A, A1, B and B1 are needed.

Beauvericin-induced cytotoxicity via ROS production and mitochondrial damage in Caco-2 cells.

The cytotoxicity of beauvericin (BEA) on human colon adenocarcinoma (Caco-2) cells was studied as a function of time. Moreover, the oxidative damage and cell death endpoints were monitored after 24, 48 and 72 h. After BEA exposure, the IC50 values ranged from 1.9 ± 0.7 to 20.6 ± 6.9 µM. A decrease in reduced glutathione (GSH; 31%) levels, as well as an increase in oxidized glutathione (GSSG, 20%) was observed. In the presence of BEA, reactive oxygen species (ROS) level was highly increased at an early stage with the highest production of 2.0-fold higher than the control that was observed at 120 min. BEA induced cell death by mitochondria-dependent apoptotic process with loss of the mitochondrial membrane potential (ΔΨm; 9% compared to the control), increase in LPO level (from 120% to 207% compared to the control) and reduced G0/G1 phase, with an arrest in G2/M, in a dose and time-dependent manner. Cell proliferation, apoptosis and ΔΨm determined, were in a dose- time-dependent manner. Moreover, DNA damage was observed after 12.0 µM concentration. This study demonstrated that oxidative stress is one of the mechanism involved in BEA toxicity, moreover apoptosis induction and loss of ΔΨm contribute to its cytotoxicity in Caco-2 cells.

Effect of polyphenols on enniatins-induced cytotoxic effects in mammalian cells.

Enniatins (ENs) are fungal secondary metabolites produced by genus Fusarium. The ENs exert antimicrobial and insecticidal effect, and has also been demonstrated cytotoxic effects on several mammalian cell lines. On the other hands, it has been proved that natural polyphenols have antioxidant effect. In this study, cell effects at low levels of exposure of four ENs (A, A(1), B and B(1)) and five polyphenols (quercetin, quercetin-3-ß-D-glucoside, rutin, myricetin and t-pterostilbene) present in wine; and the cytoprotective effect of these polyphenols exposed simultaneously with ENs in Chinese Hamster Ovary (CHO-K1) cells, were studied. Cell effects were determined by the MTT test after 24 h of exposure. All ENs showed cytotoxic effect. The IC(50) obtained ranged from 4.5 ± 1.2 to 11.0 ± 2.7 µM. The concentration of polyphenols tested ranged from 5 to 50 µM. Polyphenols did not show cytotoxicity and the cytoprotective effect of polyphenols varies depending on the EN tested. The cytoprotective effect of polyphenols in CHO-K1 cells exposed to ENs was as follow: quercetin, from 24 to 84%; quercetin-3-ß-D-glucoside, from 12 to 76%; rutin, from 17 to 83%; myricetin, from 16 to 92% and pterostilbene from 25 to 100%. All polyphenols protected CHO-K1 cells against EN A(1) exposure.

Study of the cytotoxic activity of beauvericin and fusaproliferin and bioavailability in vitro on Caco-2 cells.

Beauvericin (BEA) is a cyclohexadepsipeptide mycotoxin which has insecticidal properties and produces cytotoxic effects in mammalian cells. Fusaproliferin (FUS) is a mycotoxin that has toxic activity against brine shrimp, insect cells, and teratogenic effects on chicken embryos. The aim of this study was to determine the cytotoxicity of BEA and FUS in human epithelial colorectal adenocarcinoma HT-29 and Caco-2 cells, the transepithelial transport and the bioavailability using Caco-2 cells as a simulated in vitro gastrointestinal model of the human intestinal epithelium. The inhibitory concentration (IC(50)) evidenced by BEA in the Caco-2 cells was 24.6 and 12.7 µM at 24 and 48 h exposure, respectively, whereas the IC(50) values evidenced in HT-29 cells were 15.0 and 9.7 µM, respectively. FUS was cytotoxic, but no IC(50) data were observed in the range of concentration tested. BEA bioavailability was variable from 50.1% to 54.3%, whereas FUS presented a bioavailability variable from 80.2% to 83.2%. Results obtained demonstrated a potential risk for human health.