Cytotoxic Effects of Major and Emerging Mycotoxins on HepaRG Cells and Transcriptomic Response after Exposure of Spheroids to Enniatins B and B1.

Mycotoxins, produced by fungi, frequently occur at different stages in the food supply chain between pre- and postharvest. Globally produced cereal crops are known to be highly susceptible to contamination, thus constituting a major public health concern. Among the encountered mycotoxigenic fungi in cereals, Fusarium spp. are the most frequent and produce both regulated (i.e., T-2 toxin, deoxynivalenol -DON-, zearalenone -ZEA-) and emerging (i.e., enniatins -ENNs-, beauvericin -BEA-) mycotoxins. In this study, we investigated the in vitro cytotoxic effects of regulated and emerging fusariotoxins on HepaRG cells in 2D and 3D models using undifferentiated and differentiated cells. We also studied the impact of ENN B1 and ENN B exposure on gene expression of HepaRG spheroids. Gene expression profiling pinpointed the differentially expressed genes (DEGs) and overall similar pathways were involved in responses to mycotoxin exposure. Complement cascades, metabolism, steroid hormones, bile secretion, and cholesterol pathways were all negatively impacted by both ENNs. For cholesterol biosynthesis, 23/27 genes were significantly down-regulated and could be correlated to a 30% reduction in cholesterol levels. Our results show the impact of ENNs on the cholesterol biosynthesis pathway for the first time. This finding suggests a potential negative effect on human health due to the essential role this pathway plays.

Identification and Characterization of a New Type III Polyketide Synthase from a Marine Yeast, Naganishia uzbekistanensis.

A putative Type III Polyketide synthase (PKSIII) encoding gene was identified from a marine yeast, Naganishia uzbekistanensis strain Mo29 (UBOCC-A-208024) (formerly named as Cryptococcus sp.) isolated from deep-sea hydrothermal vents. This gene is part of a distinct phylogenetic branch compared to all known terrestrial fungal sequences. This new gene encodes a C-terminus extension of 74 amino acids compared to other known PKSIII proteins like Neurospora crassa. Full-length and reduced versions of this PKSIII were successfully cloned and overexpressed in a bacterial host, Escherichia coli BL21 (DE3). Both proteins showed the same activity, suggesting that additional amino acid residues at the C-terminus are probably not required for biochemical functions. We demonstrated by LC-ESI-MS/MS that these two recombinant PKSIII proteins could only produce tri- and tetraketide pyrones and alkylresorcinols using only long fatty acid chain from C8 to C16 acyl-CoAs as starter units, in presence of malonyl-CoA. In addition, we showed that some of these molecules exhibit cytotoxic activities against several cancer cell lines.

Antioxidant and selective anticancer activities of two Euphorbia species in human acute myeloid leukemia.

In this study, two Euphorbia species (i.e. terracina and paralias) were investigated for their cytotoxic and antioxidant activities. Cytotoxicity of plant methanol and chloroform fractions was examined towards human acute myeloid leukemia (THP1) and human colon epithelial (Caco2) cancer cell lines, as well as CD 14 and IEC-6 normal cells by targeting various modulators of apoptosis or inflammation. Moreover, secondary metabolite pools (phenolic classes, alkaloids, terpenes, saponins) and antioxidant activities (DPPH, ABTS and O2- scavenging, as well as FRAP tests) were assessed in plant extracts. Both Euphorbia species appeared to be rich in phenolic compounds and terpenoids, Moreover, E. terracina polar and apolar fractions and E. paralias polar fraction were highly active against THP1 cells, with IC50 values of 2.08, 14.43 and 54.58µg/mL, respectively. However, no cytotoxicity was found against normal cells (CD14+ monocytes). The results indicate that the three fractions induce apoptosis in THP1 cell line after 6h of exposure. Furthermore, apoptosis caused by apolar fraction was related to a caspase-dependent process, whereas other death pathways seemed to be involved with the polar fractions. An enhanced production of reactive oxygen species was detected upon cell treatment with plant extracts. Interestingly, they have no effect on cytokine TNF-α secretion in THP1 and normal cells compared to untreated cells, indicating that the three fractions caused no inflammation. Euphorbia terracina and E. paralias polar fractions showed strong antioxidant activity with potent scavenging capacity against DPPH, ABTS and superoxide radicals. Moreover, these fractions displayed a very high ferric reducing power. These findings confirm the strong antioxidant capacity of Euphorbia plants and suggest a targeted anti-cancer effect with a potent anti-proliferative property of E. terracina and E. paralias extracts, which induce programmed cell death in leukemia cell lines but not in normal monocytes cells.

Cytotoxicity and immunotoxicity of cyclopiazonic acid on human cells.

In this study, in vitro cytotoxicity and immunotoxicity of the mycotoxin cyclopiazonic acid (CPA) was evaluated on human cells. To evaluate cytoxicity, several cellular targets were used (CD34+, monocytes, THP-1 and Caco-2). Monocytes were more sensitive to CPA than the THP-1 monocytic cell line after 48h of incubation in the tested conditions. Half maximal inhibitory concentration (IC50) were determined to be 8.5 × 10(-8) and 1.75 × 10(-7)M for monocytes and THP1, respectively, while IC50>1.25 × 10(-7)M was observed for Caco-2 and CD34+ cells. The CPA effect on macrophage differentiation was also examined at non-cytotoxic concentrations. The monocyte differentiation process was markedly disturbed in the presence of CPA. After 6 days of culture, CD71 expression was downregulated, while CD14 and CD11a expressions did not change. Moreover, activated macrophages showed a raised burst activity and TNF-α secretion. Overall, the results indicated that CPA exhibited toxicity on various human cellular models. Moreover, at non-cytotoxic concentrations, CPA disturbed human monocytes differentiation into macrophages. This work contributes to understanding the immunosuppressive properties of this food-related toxin.