title: Aggravation of L-DOPA-induced neurotoxicity by tetrahydropapaveroline in PC12 cells.
abstract: Tetrahydropapaveroline (THP) is formed in Parkinsonian patients receiving L-DOPA therapy and is detected in the plasma and urine of these patients. In this study, we have investigated the effects of THP on L-DOPA-induced neurotoxicity in cultured rat adrenal pheochromocytoma, PC12 cells. Exposure of PC12 cells up to 10 microM THP or 20 microM L-DOPA after 24 or 48 hr, neither affected the cell viability determined by MTT assay, nor induced apoptosis by flow cytometry and TUNEL staining. However, at concentrations higher than 15 microM, THP showed cytotoxicity through an apoptotic process. In addition, THP at 5-15 microM for both incubation time points significantly enhanced L-DOPA-induced neurotoxicity (L-DOPA concentration, 50 microM). Exposure of PC12 cells to THP, L-DOPA and THP plus L-DOPA for 48 hr resulted in a marked increase in the cell loss and percentage of apoptotic cells compared with exposure for 24hr. The enhancing effects of THP on L-DOPA-induced neurotoxicity were concentration- and treated-time-dependent. THP, L-DOPA and THP plus L-DOPA produced a significant increase in intracellular reactive oxygen species generation and decrease in ATP levels, supporting the involvement of oxidative stress in THP- and L-DOPA-induced apoptosis. The antioxidant N-acetyl-L-cysteine strongly inhibited changes in apoptosis, decreases in cell viability and ROS generation induced by THP associated with L-DOPA. These results suggest that THP aggravates L-DOPA-induced oxidative neurotoxic and apoptotic effects in PC12 cells. Therefore, Parkinsonian patients treated with L-DOPA for long-term need to be monitored for the relationship between plasma concentration of THP and the symptoms of neurotoxicity.
authors.affiliation: College of Pharmacy, and Research Center for Bioresource and Health, Chungbuk National University, San 48, Kaeshin-Dong, Heungduk-Ku, Cheongju 361-763, South Korea.
authors.forename: Jae Joon
authors.initials: JJ
authors.lastname: Lee
authors.forename: Yu Mi
authors.initials: YM
authors.lastname: Kim
authors.forename: Shou Yu
authors.initials: SY
authors.lastname: Yin
authors.forename: Hee Dong
authors.initials: HD
authors.lastname: Park
authors.forename: Min Hee
authors.initials: MH
authors.lastname: Kang
authors.forename: Jin Tae
authors.initials: JT
authors.lastname: Hong
authors.forename: Myung Koo
authors.initials: MK
authors.lastname: Lee
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002470:Cell Survival / Q000187:drug effects; D015259:Dopamine Agents / Q000494:pharmacology; D004347:Drug Interactions; D007980:Levodopa / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D016716:PC12 Cells; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013765:Tetrahydropapaveroline / Q000494:pharmacology*
chemical_list: D015259:Dopamine Agents; D017382:Reactive Oxygen Species; D007980:Levodopa; D013765:Tetrahydropapaveroline; D000255:Adenosine Triphosphate; D000111:Acetylcysteine