title: Effects of harman and norharman on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells.
abstract: The effects of harman and norharman on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Harman and norharman at a concentration of 20 microM and 100 microM showed 49.4% and 49.5% inhibition of dopamine content for 48 h, respectively. The IC50 values of harman and norharman were 21.2 microM and 103.3 microM. Dopamine content, tyrosine hydroxylase (TH) activity and TH mRNA levels were decreased during the first 6 h, maintained for up to 48 h and then gradually recovered at 72 h after exposure to 20 microM harman and 100 microM norharman. Under the same conditions, the intracellular cyclic AMP levels and Ca2+ concentrations were also decreased by harman and norharman. In addition, harman and norharman at concentrations higher than 80 microM and 150 microM caused cytotoxicity at 48 h in PC12 cells. Non-cytotoxic ranges of 10-30 microM harman and 50-150 microM norharman inhibited L-DOPA (20-50 microM)-induced increases in dopamine content at 48 h. Harman at 20-150 microM and norharman at 100-300 microM also enhanced L-DOPA (20-100 microM)-induced cytotoxicity at 48 h with an apoptotic process. These results suggest that harman and norharman inhibit dopamine biosynthesis by reducing TH activity and enhance L-DOPA-induced cytotoxicity in PC12 cells.
authors.affiliation: College of Pharmacy and Research Center for Bioresource and Health, Chungbuk National University, 12, Gaeshin-dong, Heungduk-gu, Cheongju 361-763, Republic of Korea.
authors.forename: Yoo Jung
authors.initials: YJ
authors.lastname: Yang
authors.forename: Jae Joon
authors.initials: JJ
authors.lastname: Lee
authors.forename: Chun Mei
authors.initials: CM
authors.lastname: Jin
authors.forename: Sung Cil
authors.initials: SC
authors.lastname: Lim
authors.forename: Myung Koo
authors.initials: MK
authors.lastname: Lee
mesh_terms: D000818:Animals; D000978:Antiparkinson Agents / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D015152:Blotting, Northern; D002118:Calcium / Q000378:metabolism; D002243:Carbolines; D002470:Cell Survival / Q000187:drug effects; D000242:Cyclic AMP / Q000378:metabolism; D004298:Dopamine / Q000096:biosynthesis*; D005434:Flow Cytometry; D006247:Harmine / Q000031:analogs & derivatives* / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D007980:Levodopa / Q000633:toxicity*; D008564:Membrane Potentials / Q000502:physiology; D051336:Mitochondrial Membranes / Q000502:physiology; D016716:PC12 Cells; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D051381:Rats; D013778:Tetrazolium Salts; D013844:Thiazoles; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism
chemical_list: D000978:Antiparkinson Agents; D002243:Carbolines; D013778:Tetrazolium Salts; D013844:Thiazoles; D007980:Levodopa; D006247:Harmine; D012313:RNA; C005010:harman; C010262:norharman; D000242:Cyclic AMP; D014446:Tyrosine 3-Monooxygenase; D001142:Aromatic-L-Amino-Acid Decarboxylases; C022616:thiazolyl blue; D002118:Calcium; D004298:Dopamine