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Prostaglandin H synthase (PHS)‐1/2‐dependent oxidative DNA damage and cytotoxicity caused by neurotransmitters, their precursors and metabolites
Author(s) -
Ramkissoon Annmarie,
Wells Peter G.
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a814
Subject(s) - cytotoxicity , chemistry , biochemistry , reactive oxygen species , dna damage , oxidative stress , homovanillic acid , lactate dehydrogenase , arachidonic acid , pharmacology , in vitro , enzyme , dna , biology , serotonin , receptor
PHS‐1 and PHS‐2 are implicated in neurodegeneration, but the mechanism is unclear. Neurotransmitters, their precursors and metabolites may serve as substrates for PHS‐1/2‐dependent bioactivation in the brain to free radicals that generate potentially neurotoxic reactive oxygen species ( ROS ). To assess this hypothesis, ovine PHS‐1 was incubated in vitro with DNA and dopamine ( DA ) or its precursor or metabolites. DA (p<0.05), L‐dihydroxyphenylalanine ( L‐DOPA ) (p<0.05) and dihydroxyphenylacetic acid ( DOPAC ) (p<0.05) were oPHS‐1 substrates, resulting in PHS‐dependent ROS formation that initiated DNA oxidation, quantified as 8‐oxo‐2′‐deoxyguanosine. CHO‐K1 cell lines expressing human PHS‐2 ( hPHS‐2 ) and untransformed CHO‐K1 cells were used to investigate hPHS‐2‐dependent cytotoxicity. PHS activity, quantified by the conversion of arachidonic acid ( AA ) to prostaglandin E2, was up to 40‐fold higher in hPHS‐2 cells compared to untransformed CHO‐K1 cells and activities were reduced by withholding AA (p<0.01). Cytotoxicity, measured by lactate dehydrogenase release, was higher in hPHS‐2 cells treated with DA, L‐DOPA, DOPAC or homovanillic acid versus vehicle control after a 6 hour incubation (p<0.001). AA‐activation increased hPHS‐2 cytotoxicity (p<0.05), while cytotoxicity was lower in untransformed CHO‐K1 cells (p<0.05). These results show that DA, its precursor and metabolites are substrates for PHS‐1/2‐dependent bioactivation, causing ROS‐mediated oxidative DNA damage and cytotoxicity. This mechanism may be involved in neurodegenerative changes associated with aging and drugs like amphetamines, which initiate neurotransmitter release. [Support: CIHR, CIHR/Rx&D HRF]