dizocilpine-maleate and diacetyldichlorofluorescein

Nitric oxide (NO) is responsible for cytochrome P450 (CYP450) loss during isolation and cytokine treatment of primary rat hepatocytes. As P450s mediate the metabolism of toxic chemicals, their inhibition could compromise the cells competence to eliminate toxins, a condition potentially relevant in neurological diseases involving constitutive activation of nitric oxide synthase (NOS) and NO over-production. Here, we have investigated the correlation between NO accumulation and CYP1A2 down-regulation during maturation of mouse cerebellar granule cells (CGC). As neurons matured in culture, the inducible levels of CYP1A2 protein and catalytic activity decreased to almost undetectable values. In parallel, a significant increase in NO concentration was observed. Neuronal NOS remained constitutively active during maturation, thus contributing to NO accumulation. The NOS inhibitor l-NAME, restored CYP1A2 catalytic activity up to 9 days in vitro, supporting a role for NO in the inhibition process. Maturation was also followed by increased NMDA receptor activity and intracellular Ca2+ concentration. We suggest that maintained NOS activity during CGC maturation could lead to NO accumulation and to decreased CYP1A2 inducibility. Increased NMDA receptor activity and Ca2+ entry could contribute to this process. Thus, neurodegeneration could diminish the induction of specific P450s and impair the metabolism of foreign and/or endogenous chemicals in the CNS.

Topics: Aging; Aniline Compounds; Animals; Animals, Newborn; Calcimycin; Calcium; Cells, Cultured; Cellular Senescence; Cerebellum; Citrulline; Copper Sulfate; Cytochrome P-450 CYP1A2; Dizocilpine Maleate; DNA-Binding Proteins; Down-Regulation; Enzyme Induction; Enzyme Inhibitors; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Fluoresceins; Ionophores; Mice; Mice, Inbred C57BL; N-Methylaspartate; Neurons; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Repressor Proteins; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors; Tritium; Xanthenes

The neuroprotective efficacy of antioxidant molecules against iodoacetate (IAA) neurotoxicity in rat cerebellar granule cell (CGC) cultures was investigated. Transient exposure to IAA caused a concentration-dependent decrease in cell viability (ED50 = 9.8 microM). Dizocilpine maleate (MK-801), and 1,2,3,4-tetrahydro-6-nitro-2,3-dioxobenzo[f]quinoxaline-7-sulfonamide (NBQX), failed to prevent IAA toxicity. Certain antioxidant molecules were shown to be neuroprotective against IAA when combined with MK-801 but were ineffective when administered alone. (S)-(-)-Trolox, butylated hydroxytoluene (BHT), and U-83836E exhibited EC50 values of 78, 5.9, and 0.25 microM, respectively, in the presence of 10 microM MK-801. IAA also induced an increase in intracellular oxidative stress, which was quenched by the antioxidants (in the presence of MK-801) in cultures loaded with the oxidant sensitive dye 2'7'-dichlorodihydrofluorescein diacetate (DCFH-DA).

Topics: Animals; Antioxidants; Butylated Hydroxytoluene; Cells, Cultured; Cerebellar Cortex; Chromans; Dizocilpine Maleate; Dose-Response Relationship, Drug; Drug Synergism; Fluoresceins; Fluorescent Dyes; Iodoacetates; Neuroprotective Agents; Neurotoxins; Oxidative Stress; Piperazines; Quinoxalines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate