Fumonisin B 1 Induces Necrotic Cell Death in BV-2 Cells and Murine Cultured Astrocytes and is Antiproliferative in BV-2 Cells While N2A Cells and Primary Cortical Neurons are Resistant

Abstract

Fumonisin B 1 (FB 1), a mycotoxin produced by Fusarium verticillioides, causes equine leukoencephalomalacia, impairs myelination, and inhibits neuronal growth in vitro. Intact mice do not show brain damage after systemic administration of FB 1. We recently reported that intracerebroventricular administration of FB 1 in mice caused neurodegeneration in the cortex and activation of astrocytes in the hippocampal area; results suggested that the neuronal damage may be secondary to activation of immunocompetent non-neuronal cells. Current study investigated effects of FB 1 upon murine microglial (BV-2) and neuroblastoma (N2A) cell lines, and primary astrocytes and cortical neurons. BV-2 and N2A cultures and cells prepared from neonatal and postnatal brains of BALB/c mice were exposed to various concentrations of FB 1 for 4 (BV-2 and N2A) or 4 and 8 (astrocytes and cortical neurons) days. FB 1 at 25 μM decreased viability in BV-2 cells, whereas at 50 μM caused necrotic but not apoptotic cell death in both BV-2 and primary astrocytes (at day 8 only), assessed by lactic dehydrogenase release, and pripidium iodide and annexin V staining. Thymidine incorporation indicated that 2.5 μM FB 1 decreased proliferation in BV-2 cells. DNA analysis by flow cytometry showed that the inhibition was not caused by cell cycle arrest. The mitochondrial activity decreased dose-dependently in BV-2 cells and was significantly elevated at 25 μM FB 1, but not at 50 μM at days 4 or 8 in astrocytes. In BV-2 cells and primary astrocytes, the expression of TNFα and IL-1β analyzed by real-time polymerase chain reaction was downregulated at 6 or 24 h. In all cell types tested the FB 1 treatment caused accumulation of free sphinganine and decrease in free sphingosine levels at selected time points. Results indicated that primary and established murine brain immunocompetent cells are vulnerable to the FB 1-dependent cytotoxicity in vitro whereas neuronal cells are not. The toxic effects on the neuronal tissue may therefore be secondary to modulation of astrocyte or glial cell function.