Differential protection by rat UDP-glucuronosyltransferase 1A7 against Benzo[a]pyrene-3,6-quinone- versus Benzo[a]pyrene-induced cytotoxic effects in human lymphoblastoid cells.
UDP-glucuronosyltransferase 1A7 (UGT1A7) is a polyaromatic hydrocarbon (PAH)-inducible UGT with activity toward various benzo[a]pyrene (B[a]P) metabolites. To investigate the influence of rat UGT1A7 on B[a]P-induced cytotoxicity, human lymphoblastoid L3 cells were transfected with pMF6 (control expression vector), p167Dtk2 (microsomal epoxide hydrolase expression vector), or p167Dtk2-1A7 (epoxide hydrolase/UGT1A7 coexpression vector), and the cell populations were compared for sensitivity to B[a]P-induced effects. B[a]P inhibited cell proliferation and decreased relative cell survival of p167Dtk2 and p167Dtk2-1A7 cells to a similar extent. Metabolism studies using [(3)H]B[a]P revealed increased formation of glucuronide conjugates of B[a]P-4,5-diol, 3-OH-, or 9-OH-B[a]P and an unidentified metabolite by p167Dtk2-1A7 cells, but the presence of unconjugated metabolites suggested that glucuronidation capacity may be limited. No differences between p167Dtk2 and p167Dtk2-1A7 L3 cells were observed in the growth inhibitory effects of 3-OH-B[a]P or B[a]P-7,8-diol, but p167Dtk2-1A7-expressing cells were found to be less sensitive to B[a]P-3,6-quinone-induced effects on cell proliferation and relative cell survival. The effect was also observed in AHH-1 lymphoblastoid cells expressing UGT1A7 without epoxide hydrolase. The UGT1A7-expressing AHH-1 cells were also less sensitive to growth inhibition by B[a]P-1,6-quinone and B[a]P-6,12-quinone. Flow cytometric analysis of vehicle and B[a]P-3, 6-quinone-exposed cell populations showed an association between UGT1A7 expression and resistance to B[a]P-3,6-quinone-induced apoptosis and loss of cell viability. These data suggest that UGT1A7 may be preferentially active toward B[a]P-quinones and that UGT1A7 may represent the PAH-inducible UGT activity previously implicated in protection against toxic redox cycling by B[a]P-3,6-quinone.
Grove
A D
AD
Department of Pharmacology and Toxicology, Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia 23298-0613, USA.
Llewellyn
G C
GC
Kessler
F K
FK
White
K L
KL
Crespi
C L
CL
Ritter
J K
JK
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001564:Benzo(a)pyrene / Q000493:pharmacokinetics / Q000633:toxicity*; D001580:Benzopyrenes / Q000633:toxicity*; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004347:Drug Interactions; D004851:Epoxide Hydrolases / Q000502:physiology; D005434:Flow Cytometry; D005822:Genetic Vectors / Q000502:physiology; D020719:Glucuronides / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000502:physiology*; D004854:Herpesvirus 4, Human / Q000235:genetics; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects*; D051381:Rats; D014162:Transfection
D001580:Benzopyrenes; D020719:Glucuronides; D001564:Benzo(a)pyrene; C018003:benzo(a)pyrene-3,6-quinone; D014453:Glucuronosyltransferase; C107611:UDP-glucuronosyltransferase, UGT1A7; D004851:Epoxide Hydrolases