Induction of cytochrome P-450 1A1 in human hepatoma HepG2 and lung carcinoma NCI-H322 cells by motorcycle exhaust particulate.
The effects of motorcycle exhaust particulate (MEP) on human cytochrome P-450 (P-450)-dependent monooxygenases were determined using human hepatoma cell line HepG2 and lung carcinoma cell line NCI-H322 treated with organic extracts of MEP from a two-stroke engine. Gas chromatography and mass spectrometry analysis of MEP extract revealed the presence of carcinogens benzo[a]pyrene, benz[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[g,h,i]perylene, chrysene, and indeno[1,2,3-c,d]pyrene in the chemical mixture. Treatment with MEP extract produced concentration- and time-dependent increases of monooxygenase activity in HepG2 cells. Treatment of the cells with 100 microg/ ml MEP extract for 24 h markedly increased benzo[a]pyrene hydroxylation, 7-ethoxycoumarin, and 7-ethoxyresorufin O-deethylation activities in microsomes. Immunoblot analysis of microsomal proteins using mouse monoclonal antibody 1-12-3 against P-450 1A1 revealed that MEP extract induced a P-450-immunorelated protein in the hepatoma cells. RNA blot analysis of cellular total RNA using a human P-450 1A1 3'-end cDNA probe showed that MEP extract increased the level of a hybridizable P-450 mRNA. These P-450 1A1 inductive effects of MEP extract were similar to those from treatment with 10 microM benzo[a]pyrene or 3-methylcholanthrene (3-MC) in HepG2 cells. Treatment of lung carcinoma NCI-H322 cells with 100 microg/ml MEP extract, 10 microM benzo[a]pyrene, or 3-MC resulted in induction of monooxygenase activity, protein, and mRNA of P-450 1A1, similar to the induction observed with the hepatoma cells. The present study demonstrates that MEP extract has the ability to induce human hepatic and pulmonary P-450 1A1 in the liver- and lung-derived cell lines, and the induction involves a pretranslational mechanism. Induction of the human hepatic and pulmonary P-450 1A1 in vitro may provide important information in the assessment of MEP metabolism and toxicity in humans.
Ueng
T H
TH
Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Republic of China. thueng@ha.mc.ntu.edu.tw
Hu
S H
SH
Chen
R M
RM
Wang
H W
HW
Kuo
M L
ML
D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000201:enzymology / Q000473:pathology; D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D002273:Carcinogens / Q000032:analysis / Q000633:toxicity*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000473:pathology; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004790:Enzyme Induction / Q000187:drug effects; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D015151:Immunoblotting; D008113:Liver Neoplasms / Q000201:enzymology / Q000473:pathology; D008175:Lung Neoplasms / Q000201:enzymology / Q000473:pathology; D009049:Motorcycles; D012333:RNA, Messenger / Q000187:drug effects / Q000302:isolation & purification; D014407:Tumor Cells, Cultured; D001335:Vehicle Emissions / Q000032:analysis / Q000633:toxicity*
D000393:Air Pollutants; D002273:Carcinogens; D012333:RNA, Messenger; D001335:Vehicle Emissions; D019363:Cytochrome P-450 CYP1A1