Assessment of neurotoxicity of monocrotaline, an alkaloid extracted from Crotalaria retusa in astrocyte/neuron co-culture system

Abstract

Studies have shown cases of poisoning with plants from the genus Crotalaria (Leguminosae) mainly in animals. They induce damages in the central nervous system (CNS), which has been attributed to toxic effects of the pyrrolizidine alkaloid (PA) monocrotaline (MCT). Previously we demonstrated that both MCT and dehydromonocrotaline (DHMC), its main active metabolite, induce changes in the levels and patterns of expression of the main protein from astrocyte cytoskeleton, glial fibrillary acidic protein (GFAP). In this study we investigated the effect of MCT on rat cortical astrocyte/neuron primary co- cultures. Primary cultures were exposed to 10 or 100 mM MCT. The MTT test and the measurement of LDH activity on the culture medium revealed that after 24 h exposure MCT was not cytotoxic to neuron/astrocyte cells. However, the cell viability after 72 h treatment decreased in 10–20%, and the LDH levels in the culture medium increased at a rate of 12% and 23%, in cultures exposed to 10 or 100 mM MCT. Rosenfeld staining showed vacuolization and increase in cell body in astrocytes after MCT exposure. Immunocytochemistry and Western blot analyses revealed changes on pattern of GFAP and bIII-tubulin expression and steady state levels after MCT treatment, with a dose and time dependent intense down regulation and depolarization of neuronal bIII-tubulin. Moreover, treatment with 100 mM MCT for 12 h induced GSH depletion, which was not seen when cytochrome P450 enzyme system was inhibited indicating that it is involved in MCT induced cytotoxicity in CNS cells.