Biscoclaurine alkaloid cepharanthine protects DNA in TK6 lymphoblastoid cells from constitutive oxidative damage.
Cepharanthine (CEP), a biscoclaurine (bisbenzylisoquinoline) alkaloid isolated from Stephania cepharantha Hayata, is widely used in Japan to treat variety of diseases. Among a plethora of its biological activities CEP was reported to be able to scavenge radicals and prevent lipid peroxidation. We have recently described the phenomenon of constitutive ATM activation (CAA) and histone H2AX phosphorylation (CHP), the events that report DNA damage induced by endogenously generated radicals, the product of oxidative metabolism in otherwise healthy, untreated cells. The aim of the present study was to explore whether CEP can attenuate the level of CAA and CHP, which would indicate on its ability to protect DNA against endogenous oxidants. The data show that indeed the levels of CAA and CHP in human lymphoblastoid TK6 cells were distinctly lowered upon treatment with CEP. Thus, exposure of cells to 8.3 microM CEP for 4 h led to a reduction of the mean level of CAA and CHP by up to 60% and 50%, respectively. At 1.7 microM CEP the reduction of CAA and CHP after 4 h was 35% and 25%, respectively. Cells exposure to CEP led to a decrease in the level of ondogenous oxidants as measured by the ability to oxidate the fluorescent probe 5-(and-6)-carboxy-2',7'-dichloro-dihydro-fluorescein diacetate. No evidence of apoptosis was seen during the first 8 h of treatment with CEP but initiation of apoptosis (caspase-3 activation) was detected in relatively few (< 10%) cells after exposure to 8.3 microM CEP for 24 h. The data strongly suggest that the scavenging properties of CEP provide a protection of DNA from the radicals generated endogenously during oxidative metabolism.
Halicka
Dorota
D
Branch Cancer Reearch Institute and Department of Pathology, New York Medical College, Valhalla, NY 10595, USA.
Ita
Masamichi
M
Tanaka
Toshiki
T
Kurose
Akira
A
Darzynkiewicz
Zbigniew
Z
D017209:Apoptosis / Q000187:drug effects; D064007:Ataxia Telangiectasia Mutated Proteins; D044182:Benzylisoquinolines / Q000494:pharmacology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D004249:DNA Damage / Q000187:drug effects*; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006657:Histones / Q000378:metabolism; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018384:Oxidative Stress / Q000187:drug effects*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D052117:Benzodioxoles
D064007:Ataxia Telangiectasia Mutated Proteins; D044182:Benzylisoquinolines; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D016166:Free Radical Scavengers; D006657:Histones; D017346:Protein Serine-Threonine Kinases; D017382:Reactive Oxygen Species; D025521:Tumor Suppressor Proteins; C468783:H2AX protein, human; C006947:cepharanthine; D052117:Benzodioxoles; C576324:ATM protein, human