A mechanism for the inhibition of neural progenitor cell proliferation by cocaine.
BACKGROUND
Prenatal exposure of the developing brain to cocaine causes morphological and behavioral abnormalities. Recent studies indicate that cocaine-induced proliferation inhibition and/or apoptosis in neural progenitor cells may play a pivotal role in causing these abnormalities. To understand the molecular mechanism through which cocaine inhibits cell proliferation in neural progenitors, we sought to identify the molecules that are responsible for mediating the effect of cocaine on cell cycle regulation.


RESULTS
Microarray analysis followed by quantitative real-time reverse transcription PCR was used to screen cocaine-responsive and cell cycle-related genes in a neural progenitor cell line where cocaine exposure caused a robust anti-proliferative effect by interfering with the G1-to-S transition. Cyclin A2, among genes related to the G1-to-S cell cycle transition, was most strongly down-regulated by cocaine. Down-regulation of cyclin A was also found in cocaine-treated human primary neural and A2B5+ progenitor cells, as well as in rat fetal brains exposed to cocaine in utero. Reversing cyclin A down-regulation by gene transfer counteracted the proliferation inhibition caused by cocaine. Further, we found that cocaine-induced accumulation of reactive oxygen species, which involves N-oxidation of cocaine via cytochrome P450, promotes cyclin A down-regulation by causing an endoplasmic reticulum (ER) stress response, as indicated by increased phosphorylation of eIF2alpha and expression of ATF4. In the developing rat brain, the P450 inhibitor cimetidine counteracted cocaine-induced inhibition of neural progenitor cell proliferation as well as down-regulation of cyclin A.


CONCLUSIONS
Our results demonstrate that down-regulation of cyclin A underlies cocaine-induced proliferation inhibition in neural progenitors. The down-regulation of cyclin A is initiated by N-oxidative metabolism of cocaine and consequent ER stress. Inhibition of cocaine N-oxidative metabolism by P450 inhibitors may provide a preventive strategy for counteracting the adverse effects of cocaine on fetal brain development.
Lee
Chun-Ting
CT
Cellular Neurobiology Research Branch, Intramural Research Program, National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services, Baltimore, Maryland, United States of America. clee@mail.nih.gov
Chen
Jia
J
Hayashi
Teruo
T
Tsai
Shang-Yi
SY
Sanchez
Joseph F
JF
Errico
Stacie L
SL
Amable
Rose
R
Su
Tsung-Ping
TP
Lowe
Ross H
RH
Huestis
Marilyn A
MA
Shen
James
J
Becker
Kevin G
KG
Geller
Herbert M
HM
Freed
William J
WJ
D000818:Animals; D002453:Cell Cycle; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival; D002478:Cells, Cultured; D002927:Cimetidine / Q000494:pharmacology; D003042:Cocaine / Q000494:pharmacology*; D019925:Cyclin A / Q000235:genetics / Q000378:metabolism; D056751:Cyclin A2; D015536:Down-Regulation; D005260:Female; D006801:Humans; D009474:Neurons / Q000187:drug effects*; D010766:Phosphorylation; D011247:Pregnancy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013234:Stem Cells / Q000187:drug effects*; D014162:Transfection
C503721:CCNA2 protein, human; D019925:Cyclin A; D056751:Cyclin A2; D002927:Cimetidine; D003042:Cocaine