In vitro neurotoxicity of the antitumor agent 9-methoxy-N²-methylellipticinium acetate (MMEA): role of brain cytochrome P-450

Abstract

9-Methoxy-N2-methylellipticinium acetate (MMEA) is representative of a series of quaternized ellipticine derivatives that are selectively cytotoxic to human brain tumor cell lines derived from non-neuronal (glial) cells (Acton et al, 1994). In an attempt to determine whether MMEA may exhibit toxicity to normal brain cells, we have examined the effect of the drug, in vitro, using sagittal slices of rat brain. Incubation of rat brain slices in an artificial cerebrospinal fluid medium containing MMEA resulted in dose-dependent leakage of lactate dehydrogenase (LDH) into the surrounding medium. However, other subcellular marker enzymes such as Na⁺-K⁺ATPase (plasma membrane), cytochrome c oxidase, isocitrate dehydrogenase, NADH- dehydrogenase (mitochondrial), N-acetylglucosaminidase, acid phosphatase (lysosomal), glyceraldehyde-3-phosphate dehydrogenase and enolase (glycolytic enzymes) were unaffected even at the highest tested concentrations of MMEA (10 and 100 µM). Preincubation of slices with reserpine (1 nM) or dopamine or serotonin-specific reuptake inhibitors abolished MMEA-induced toxicity in brain slices. Pretreatment of slices with piperonyl butoxide and metyrapone, inhibitors of cytochrome P-450, also prevented the toxicity of MMEA. Further, brain slices prepared from phenobarbital-treated rats showed enhanced sensitivity to MMEA.