Differential cell death induced by salsolinol with and without copper: Possible role of reactive oxygen species

Salsolinol (SAL), a novel dopaminergic catechol tetrahydroisoquinoline neur otoxin, has been speculated to contribute to the etiology of Parkinson's di sease and neuropathology of chronic alcoholism. Our previous studies have d emonstrated that SAL induces strand scission in oX174 supercoiled DNA and o xidative base modification in calf thymus DNA in the presence of cupric ion . We now report that treatment of rat pheochromocytoma (PC12) cells with SA L causes reduced viability, which was exacerbated by Cu2+. The copper chela tor bathocuproinedisulfonic acid ameliorated cytotoxicity induced by SAL an d Cu2+. N-Acetyl-L-cysteine and reduced glutathione protected against SAL- plus Cu2+-mediated PC12 cell death. Cells exposed to SAL underwent apoptosi s, as revealed by characteristic morphological and biochemical changes. SAL treatment resulted in increased levels of Bax with a concomitant decrease in expression of Bcl-X-L. Furthermore, SAL rapidly activated c-Jun N-termin al kinase, whereas the activity of extracellular signal-regulated protein k inase remained unchanged. Transfection with Bcl-X-L or Bcl-2 led to protect ion against SAL-mediated PC12 cell death. Although SAL alone could cause ap optotic death in PC12 cells, cells treated with SAL together with Cu2+ beca me necrotic. Cells exposed to both SAL and Cu2+ exhibited higher levels of intracellular reactive oxygen species, malondialdehyde, and 8-oxo-7,8-dihyd ro-2'-deoxyguanosine than did those treated with SAL alone. These results s uggest that copper accelerates redox cycling of SAL, leading to massive pro duction of reactive oxygen species, which can divert the SAL-induced cell d eath to necrosis.