PT  - JOURNAL ARTICLE
AU  - Kitazawa, Masashi
AU  - Wagner, Jarrad R.
AU  - Kirby, Michael L.
AU  - Anantharam, Vellareddy
AU  - Kanthasamy, Anumantha G.
TI  - Oxidative Stress and Mitochondrial-Mediated Apoptosis in Dopaminergic Cells Exposed to Methylcyclopentadienyl Manganese Tricarbonyl
AID  - 10.1124/jpet.302.1.26
DP  - 2002 Jul 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 26--35
VI  - 302
IP  - 1
4099  - http://jpet.aspetjournals.org/content/302/1/26.short
4100  - http://jpet.aspetjournals.org/content/302/1/26.full
SO  - J Pharmacol Exp Ther2002 Jul 01; 302
AB  - Methylcyclopentadienyl manganese tricarbonyl (MMT), an organic manganese-containing gasoline additive, was investigated to determine whether MMT potentially causes dopaminergic neurotoxic effects. MMT is acutely cytotoxic and dopamine-producing cells (PC-12) seemed to be more susceptible to cytotoxic effects than nondopaminergic cells (striatal γ-aminobutyric acidergic and cerebellar granule cells). MMT also potently depleted dopamine apparently by cytoplasmic vesicular release to the cytosol, a neurochemical change resembling other dopaminergic neurotoxicants. Generation of reactive oxygen species (ROS), an early effect in toxicant-induced apoptosis, occurred within 15 min of MMT exposure. MMT caused a loss of mitochondrial transmembrane potential (ΔΨm), a likely source of ROS generation. The ROS signal further activated caspase-3, an important effector caspase, which could be inhibited by antioxidants (Trolox orN-acetyl cysteine). Predepletion of dopamine by using α-methyl-p-tyrosine (tyrosine hydroxylase inhibitor) treatment partially prevented caspase-3 activation, denoting a significant dopamine and/or dopamine by-product contribution to initiation of apoptosis. Genomic DNA fragmentation, a terminal hallmark of apoptosis, was induced concentration dependently by MMT but completely prevented by pretreatment with Trolox, deprenyl (monoamine oxidase-B inhibitor), and α-methyl-p-tyrosine. A final set of critical experiments was performed to verify the pharmacological studies using a stable Bcl-2-overexpressing PC-12 cell line. Bcl-2-overexpressing cells were significantly refractory to MMT-induced ROS generation, caspase-3 activation, and loss of ΔΨm and were completely resistant to MMT-induced DNA fragmentation. Taken together, the results presented herein demonstrate that oxidative stress plays an important role in mitochondrial-mediated apoptotic cell death in cultured dopamine-producing cells after exposure to MMT. The American Society for Pharmacology and Experimental Therapeutics