Epigenetic properties of fumonisin B₁: Cell cycle arrest and DNA base modification in C6 glioma cells

Fumonisin B₁ produced by the fungus Fusarium moniliforme is a member of a new class of sphinganine analogue mycotoxins that occur widely in the food chain. Epidemiological studies associate FB₁ with human (esophageal cancer in China and South Africa. FB₁ also causes acute pulmonary edema in pigs and equine leucoencephalomalacia. This disease is thought to be a consequence of inhibition by FB₁ of cellular ceramide synthesis in cells. To investigate further on this pathogenesis, the effect of FB₁ was studied on cell viability (3 to 54 μM of FB₁), protein (2.5 to 20 μM of FB₁) and DNA syntheses (2.5 to 50 μM of FB₁), and cellular cycle (3 to 18 μM of FB₁) of rat C6 glioma cells after 24 h incubation. The results of the viability test show that FB₁ induces 10 ± 2% and 47 ± 4% cell death with, respectively, 3 and 54 μM, in C6 cells. This cytotoxicity induced by FB₁ was efficiently prevented when the cells were preincubated 24 h with vitamin E (25 μM). FB₁ displays epigenetic properties since it induced hypermethylation of the DNA (9-18 μM). Inhibition of protein synthesis was observed with FB₁ with an IC₅₀ of 6 μM showing that C6 glioma cells are very sensitive to FB₁; however, the synthesis of DNA was only slightly inhibited, up to 20 μM of FB1. The flow cytometry showed that the number of cells in phase S decreased significantly as compared to the control p = 0.01 from 18.7 ± 2.5% to 8.1 ± 1.1% for 9 μM FB₁. The number of cells in phase G₂/M increased significantly as compared to the control (p ≤ 0.05) from 45.7 ± 0.4% to 54.8 ± 1.1% for 9 μM FB₁, whereas no change occurs in the number of cells in the phase G₀/H₁. These results show that cytotoxic concentrations of FB₁ induce cellular cycle arrest in phase G₂/M in rat C6 glioma cells possibly in relation with genotoxic events. (C) 2000 Academic Press.