Methyl tertiary butyl ether (MTBE) is the most widely used motor vehicle fuel oxygenate since it reduces harmful emissions due to gasoline combustion. However, the significant increase in its use in recent years has raised new questions related to its potential toxicity. In fact, although available data are somehow conflicting, there is evidence that MTBE is a toxic substance that may have harmful effects on both animals and humans and an unresolved problem is the role played by MTBE metabolites, especially tertiary butyl alcohol (TBA), in determining toxic effects due to MTBE exposure. In this study, the toxic effects of MTBE have been analyzed on a normal diploid rat fibroblast cell line (Rat-1) and compared to the effects of TBA. The results obtained suggest that both MTBE and TBA inhibit cell growth in vitro but with different mechanisms in terms of effects on the cell cycle progression and on the modulation of cell cycle regulatory proteins. In fact, MTBE caused an accumulation of cells in the S-phase of the cell cycle, whereas TBA caused an accumulation in the G0/G1-phase with different effects on the expression of cyclin D1, p27Kip1, and p53. Moreover, both MTBE and TBA were also shown to induce DNA damage, as assessed in terms of oxidative DNA damage and nuclear DNA fragmentation, that appeared to be susceptible of repair by the cell DNA-repair machinery. In conclusion, these findings suggest that both MTBE and TBA can exert, by acting through different molecular mechanisms, important biological effects on fibroblasts in vitro. Further studies are warranted to shed light on the mechanisms responsible for the observed effects and on their potential significance for the in-vivo exposure.
Ahmed FE (2001) Toxicology and human health effects following exposure to oxygenated or reformulated gasoline. Toxicol Lett123: 89–113.
2.
Amberg A Rosner E Dekant W (1999) Biotransformation and kinetics of excretion of methyl tert-butyl ether in rats and humans. Toxicol Sci51: 1–8.
3.
Ayotte JD Argue DM McGarry FJ (2005) Methyl tert-butyl ether occurrence and related factors in public and private wells in southeast New Hampshire. Environ Sci Technol39: 9–16.
4.
Belpoggi F Soffritti M Filippini F Maltoni C (1997) Results of long-term experimental studies on the carcinogenicity of methyl tert-butyl ether. Ann N Y Acad Sci837: 77–95.
5.
Belpoggi F Soffritti M Maltoni C (1995) Methyl-tertiary-butyl ether (MTBE)–a gasoline additive- causes testicular and lymphohaematopoietic cancers in rats. Toxicol Ind Health11: 119–149.
6.
Belpoggi F Soffritti M Maltoni C (1998) Pathological characterization of testicular tumours and lymphomas-leukaemias and of their precursors observed in Sprague-Dawley rats exposed to methyl teriaryt-butyl ether (MTBE). Eur J Oncol3: 201–206.
7.
Bernauer U Amberg A Scheutzow D Dekant W (1998) Biotransformation of 12C- and 2-13C-labeled methyl tert-butyl ether and tert-butyl alcohol in rats: identification of metabolites in urine by 13C nuclear magnetic resonance and gas chromagraphy/mass spectrometry. Chem Res Toxicol11: 651–658.
8.
Bird MG Burleigh-Flayer HD Chun JS Douglas JF Kneiss JJ Andrews LS (1997) Oncogenicity studies of inhaled methyl tertiary-butyl ether (MTBE) in CD-1 mice and F-344 rats. J Appl Toxicol17: S45–S55.
9.
Burleigh-Flayer HD Chun JS Kintigh WJ (1992) Methyl tertiary-butyl ether: vapor inhalation oncogenity study in CD-1 mice.Bushy Run Research Center, Export, PA, USA.
10.
Chen CS Hseu YC Liang SH Kuo JY Chen SC (2008) Assessment of genotoxicity of methyl-tert-butyl ether, benzene, toluene, ethylbenzene, and xylene to human lymphocytes using comet assay. J Hazard Mater153: 351–356.
11.
Chun JS Burleigh-Flayer HD Kintigh WJ (1992) Methyl tertiary-butyl ether: Vapor inhalation oncogenity study in Fischer 344 rats.Bushy Run Research Center, Export, PA, USA.
12.
Cirvello JD Radovsky A Heath JE Farnell DR Lindamood C (1995) Toxicity and carcinogenicity of t-butyl alcohol in rats and mice following chronic exposure in drinking water. Toxicol Ind Health11: 151–165.
13.
Cruzan G Borghoff SJ de Peyster A Hard GC McClain M McGregor DB (2007) Methyl-tertiary-butyl ether mode of action for cancer endpoints in rodents. Regul Toxicol Pharmacol47: 156–165.
14.
Dekant W Bernauer U Rosner E Amberg A (2001) Biotransformation of MTBE, ETBE, and TAME after inhalation or ingestion in rats and humans. Res Rep Health Eff Inst102: 29–71.
15.
Department of Energy (2000) MTBE, Oxygenates and Motor Gasoline.Washington, DC, USA: Energy Information Administration.
16.
17.
Elledge SJ Harper JW (1994) Cdk inhibitors: on the threshold of checkpoints and development. Current Opin in Cell Biol6: 847–852.
18.
Environmental protection Agency (EPA) (1993) Assessment of potential health risks of gasoline oxygenated with methyl tertiary-butyl ether (MTBE). US EPA 600/R-93/206, Washington DC, USA.
19.
Environmental protection Agency (EPA) (1997) Drinking water advisory: consumer acceptability advice and health effects analysis on methyl tertiary-butyl ether (MTBE). US EPA 822-F-97-009, Washington, DC, USA.
20.
Environmental protection Agency (EPA) (2000) Part VII 40 CFR Part 755: Methyl tertiary-butyl ether (MTBE); advanced notice of intent to initiate rulemaking under the Toxic Substances Control Act to eliminate or limit the use of MTBE as a fuel additive in gasoline. Fed Regist 65: 16094–16109.
21.
Fiedler N Kelly-McNeil K Mohr S Lehrer P Opiekun RE Lee CW (2000) Controlled human exposure to methyl tertiary-butyl ether in gasoline: symptoms, psychophysiologic and neurobehavioral responses to self-reported sensitive persons. Environ Health Perspect108: 753–763.
22.
Fiedler N Kipen H (2001) Controlled human exposure to volatile organic compounds in sensitive groups. Ann N Y Acad Sci933: 24–37.
23.
Hakansson A Stromberg K Pedersen J Olsson O (2001) Combustion of gasolines in premixed laminar flames European certified and California phase 2 reformulated gasoline. Chemosphere44: 1243–1252.
24.
Hakkola M Haukasalo ML Palkkinen P (1997) Changes in neurophysiological symptoms and moods among tanker drivers exposed to gasoline during a work week. Occup Med47: 344–348.
25.
Hakkola MA Saarinen LH (2000) Customer exposure to gasoline vapors during refueling at service stations. Appl Occup Environ Hyg15: 677–680.
26.
Hong JY Wang YY Bondoc FY Lee M Yang CS Hu WY (1999) Metabolism of Methyl tert-butyl ether and other petrol ethers by human liver microsomes and heterologously expressed human cytochromes P450: identification of CYP2A6 as a major catalyst. Toxicol Appl Pharmacol160: 43–48.
27.
Hong JY Wang YY Mohr SN Bondoc FY Deng C (2001) Human cytochromes P450 isozymes in metabolism and health effects of gasoline ethers. Res Rep Health Eff Inst102: 7–27.
28.
Hong JY Yang CS Lee M Wang YY Huang WQ Tan Y (1997) Role of cytochromes P450 in the metabolism of methyl tert-butyl ether in human livers. Arch Toxicol71: 266–269.
29.
Hunter T Pines J (1994) Cyclins and cancer II: cyclin D and CDK inhibitors come of age. Cell79: 573–582.
30.
Iavicoli I Carelli G Ardito R Cittadini A Sgambato A (2002) Methyl-tertiary-butyl ether (MTBE) inhibits growth and induces cell transformation in rodent fibroblasts. Anticancer Res22: 2173–2177.
31.
Kado NY Kuzmicky PA Loarca-Pina G Moiz Mumtaz M (1998) Genotoxicity testing of methyl tertiary-butyl ether (MTBE) in the Salmonella microsuspension assay and mouse bone marrow micronucleus test. Mutat Res412: 131–138.
32.
Kim D Andersen ME Pleil JD Nylander-French LA Prah D (2007) Refined PBPK model of aggregate exposure to Methyl tertiary-butyl ether. Toxicol Lett169: 222–235.
33.
Kolb A Püttmann W (2006) Comparison of MTBE concentrations in groundwater of urban and nonurban areas in Germany. Water Res40: 3551–3558.
34.
Le Gal A Dreano Y Gervasi PG Berthou F (2001) Human cytochrome P450 2A6 is the major enzyme involved in the metabolism of three alkoxyethers used as oxyfuels. Toxicol Lett124: 47–58.
35.
Lee CW Mohr SN Weisel CP (2001) Toxicokinetics of human exposure to methyl tertiary-butyl ether (MTBE) following short-term controlled exposures. J Expo Anal Environ Epidemiol11: 67–78.
36.
Lee JW Jo WK (2002) Actual commuter exposure to methyl-tertiary butyl ether, benzene and toluene while travelling in Korean urban areas. Sci Total Environ291: 219–228.
37.
Lin CW Chiang SB Lu SJ (2005) Investigation of MTBE and aromatic compound concentrations at a gas service station. Environ Monit Assess105: 327–339.
38.
McGregor DB Cruzan G Callander RD May K Banton M (2005) The mutagenicity testing of tertiary-butyl alcohol, tertiary-butyl acetate, and methyl-tertiary-butyl ether in Salmonella typhimurium. Mutat Res565: 181–189.
39.
McKee RH Vergnes JS Galvin JB Douglas JR Kneiss JJ Andrews LS (1997) Assessment of the in vivo mutagenic potential of methyl tertiary-butyl ether. J Appl Toxicol17: S31–S36.
40.
Mehlman MA (1996) Dangerous and cancer-causing properties of products and chemicals in the oil-refining and petrochemical industry – part XXII: health hazards from exposure to gasoline containing methyl tertiary-butyl ether: study of New Jersey residents. Toxicol Ind Health12: 613–627.
41.
Moolenaar R Hefflin BJ Ashley DL Middough JP Etzel RA (1994) Methyl tertiary-butyl ether in human blood after exposure to oxygenated fuel in Fairbanks, Alaska. Arch Environ Health49: 402–409.
42.
Moran MJ Zogorski JS Squillace PJ (2005) MTBE and gasoline hydrocarbons in ground water of the United States. Ground Water43: 615–627.
43.
Nihlen A Lof A Johanson G (1998a) Experimental exposure to methyl tertiary-butyl ether. I. Toxicokinetics in humans. Toxicol Appl Pharmacol148: 274–280.
44.
Nihlen A Walinder R Lof A Johanson G (1998b) Experimental exposure to methyl tertiary-butyl ether. II. Acute effects in humans. Toxicol Appl Pharmacol148: 281–287.
45.
National Toxicology Program Report on Carcinogens (NTP) (1995) US Department of Health and Human Services Public Health Service. NTP. Research Triangle Park, NC, USA.
46.
Phillips S Palmer RB Brody A (2008) Epidemiology, toxicokinetics, and health effects of methyl tert-butyl ether (MTBE). J Med Toxicol4: 115–126.
47.
Prah J Ashley D Blount B Case M Leavens T Pleil J (2004) Dermal, oral, and inhalation pharmacokinetics of methyl tertiary-butyl ether (MTBE) in human volunteers. Toxicol Sci77: 195–205.
48.
Sgambato A Ardito R Faraglia B Boninsegna A Wolf FI Cittadini A (2001) Resveratrol, a natural phenolic compound, inhibits cell proliferation and prevents oxidative DNA damage. Mutat Res496: 171–180.
49.
Sgambato A Di Salvatore MA De Paola B Rettino A Faraglia B Boninsegna A (2006) Analysis of dystroglycan regulation and functions in mouse mammary epithelial cells and implications for mammary tumorigenesis. J Cell Physiol207: 520–529.
50.
Sgambato A Faraglia B Cittadini A Weinstein IB (2000) Multiple functions of p27Kip1 and its alterations in tumor cells. A review. J Cell Physiol183: 18–27.
51.
Soffritti M Belpoggi F Ceyolani D Guarino M Padovani M Maltoni C (2002) Results of long-term experimental studies on the carcinogenicity of methyl alcohol and ethyl alcohol in rats. Ann N Y Acad Sci982: 46–69.
52.
Vainiotalo S Ruonakangas A (1999) Tank truk driver exposure to vapors from oxygenated or reformulated gasoline during loading and unloading. Am Ind Hyg Assoc J60: 518–525.
53.
Vayghani SA Weisel C (1999) The MTBE air concentrations in the cabin of automobiles while fueling. J Expo Anal Environ Epidemiol9: 261–267.
54.
Wang CH Lin SS Chan HL (2002) Effect of oxygenates on exhaust emissions from two-stroke motorcycles. J Environ Sci Health A37: 1677–1685.
55.
Ward JB; Dalker DH; Hastings DA; Ammenhauser MM; Legator MS; (1995) Assessment of the mutagenicity of methyl tertiary-butyl ether at the HPRT gene in CD-1 mice. Soc Toxicol Abstr 415.
56.
Williams-Hill D Spears CP Prakash S Olah GA Shamma T Moin T (1999) Mutagenicity studies of methyl-tert-butylether using the Ames tester strain TA102. Mutat Res446: 15–21.
57.
Yarborough A Zhang YJ Hsu TM Santella RM (1996) Immunoperoxidase detection of 8-hydroxydeoxyguanosine in aflatoxin B1-treated rat liver and human oral mucosal cells. Cancer Res56: 683–688.
58.
Zannoni GF Faraglia B Tarquini E Camerini A Vrijens K Migaldi M (2006) Expression of the CDK inhibitor p27kip1 and oxidative DNA damage in non-neoplastic and neoplastic vulvar epithelial lesions. Mod Pathol19: 504–513.
59.
Zhou W Yuan D Huang G Zhang H Ye S (2000) Mutagenicity of methyl tertiary butyl ether. J Environ Pathol Toxicol Oncol19: 35–39.
