Exposure to aristolochic acid (AA) causes aristolochic acid nephropathy (AAN) and Balkan endemic nephropathy (BEN). Conflicting results have been found for the role of human sulfotransferase 1A1 (SULT1A1) contributing to the metabolic activation of aristolochic acid I (AAI) in vitro. We evaluated the role of human SULT1A1 in AA bioactivation in vivo after treatment of transgenic mice carrying a functional human SULT1A1-SULT1A2 gene cluster (i.e. hSULT1A1/2 mice) and Sult1a1(-/-) mice with AAI and aristolochic acid II (AAII). Both compounds formed characteristic DNA adducts in the intact mouse and in cytosolic incubations in vitro. However, we did not find differences in AAI-/AAII-DNA adduct levels between hSULT1A1/2 and wild-type (WT) mice in all tissues analysed including kidney and liver despite strong enhancement of sulfotransferase activity in both kidney and liver of hSULT1A1/2 mice relative to WT, kidney and liver being major organs involved in AA metabolism. In contrast, DNA adduct formation was strongly increased in hSULT1A1/2 mice compared to WT after treatment with 3-nitrobenzanthrone (3-NBA), another carcinogenic aromatic nitro compound where human SULT1A1/2 is known to contribute to genotoxicity. We found no differences in AAI-/AAII-DNA adduct formation in Sult1a1(-/-) and WT mice in vivo. Using renal and hepatic cytosolic fractions of hSULT1A1/2, Sult1a1(-/-) and WT mice, we investigated AAI-DNA adduct formation in vitro but failed to find a contribution of human SULT1A1/2 or murine Sult1a1 to AAI bioactivation. Our results indicate that sulfo-conjugation catalysed by human SULT1A1 does not play a role in the activation pathways of AAI and AAII in vivo, but is important in 3-NBA bioactivation.
- Keywords
- 3-Nitrobenzanthrone, Aristolochic acid nephropathy, Balkan endemic nephropathy, Carcinogen metabolism, DNA adducts, Sulfotransferase 1A1,
- MeSH
- DNA Adducts drug effects genetics MeSH
- Arylsulfotransferase genetics MeSH
- Benz(a)Anthracenes toxicity MeSH
- Cytosol drug effects metabolism MeSH
- Liver drug effects metabolism MeSH
- Carcinogens toxicity MeSH
- Aristolochic Acids toxicity MeSH
- Kidney drug effects metabolism MeSH
- Humans MeSH
- Multigene Family MeSH
- Mice, Knockout MeSH
- Mice, Transgenic MeSH
- Mice MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Mice MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Names of Substances
- 3-nitrobenzanthrone MeSH Browser
- DNA Adducts MeSH
- Arylsulfotransferase MeSH
- Benz(a)Anthracenes MeSH
- Carcinogens MeSH
- Aristolochic Acids MeSH
- SULT1A1 protein, human MeSH Browser
- SULT1A2 protein, human MeSH Browser
The tumour suppressor p53 is one of the most important cancer genes. Previous findings have shown that p53 expression can influence DNA adduct formation of the environmental carcinogen benzo[a]pyrene (BaP) in human cells, indicating a role for p53 in the cytochrome P450 (CYP) 1A1-mediated biotransformation of BaP in vitro. We investigated the potential role of p53 in xenobiotic metabolism in vivo by treating Trp53(+/+), Trp53(+/-) and Trp53(-/-) mice with BaP. BaP-DNA adduct levels, as measured by (32)P-postlabelling analysis, were significantly higher in liver and kidney of Trp53(-/-) mice than of Trp53(+/+) mice. Complementarily, significantly higher amounts of BaP metabolites were also formed ex vivo in hepatic microsomes from BaP-pretreated Trp53(-/-) mice. Bypass of the need for metabolic activation by treating mice with BaP-7,8-dihydrodiol-9,10-epoxide resulted in similar adduct levels in liver and kidney in all mouse lines, confirming that the influence of p53 is on the biotransformation of the parent compound. Higher BaP-DNA adduct levels in the livers of Trp53(-/-) mice correlated with higher CYP1A protein levels and increased CYP1A enzyme activity in these animals. Our study demonstrates a role for p53 in the metabolism of BaP in vivo, confirming previous in vitro results on a novel role for p53 in CYP1A1-mediated BaP metabolism. However, our results also suggest that the mechanisms involved in the altered expression and activity of the CYP1A1 enzyme by p53 in vitro and in vivo are different.
- Keywords
- Benzo[a]pyrene, Carcinogen metabolism, Cytochrome P450, DNA adducts, Mouse models, Tumour suppressor p53,
- MeSH
- DNA Adducts metabolism MeSH
- Benzo(a)pyrene metabolism pharmacokinetics MeSH
- Cytochrome P-450 CYP1A1 metabolism MeSH
- Microsomes, Liver drug effects metabolism MeSH
- Carcinogens, Environmental metabolism pharmacokinetics MeSH
- Kidney drug effects metabolism MeSH
- Activation, Metabolic MeSH
- Inactivation, Metabolic MeSH
- Mice, Mutant Strains MeSH
- Mice, Inbred C57BL MeSH
- NAD(P)H Dehydrogenase (Quinone) metabolism MeSH
- Tumor Suppressor Protein p53 genetics metabolism MeSH
- DNA Damage drug effects genetics MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- DNA Adducts MeSH
- benzo(a)pyrene-DNA adduct MeSH Browser
- Benzo(a)pyrene MeSH
- Cytochrome P-450 CYP1A1 MeSH
- Carcinogens, Environmental MeSH
- NAD(P)H Dehydrogenase (Quinone) MeSH
- Tumor Suppressor Protein p53 MeSH
- Nqo1 protein, mouse MeSH Browser
Pulmonary inflammation can contribute to the development of lung cancer in humans. We investigated whether pulmonary inflammation alters the genotoxicity of polycyclic aromatic hydrocarbons (PAHs) in the lungs of mice and what mechanisms are involved. To model nonallergic acute inflammation, mice were exposed intranasally to lipopolysaccharide (LPS; 20 µg/mouse) and then instilled intratracheally with benzo[a]pyrene (BaP; 0.5 mg/mouse). BaP-DNA adduct levels, measured by (32)P-postlabeling analysis, were approximately 3-fold higher in the lungs of LPS/BaP-treated mice than in mice treated with BaP alone. Pulmonary Cyp1a1 enzyme activity was decreased in LPS/BaP-treated mice relative to BaP-treated mice suggesting that pulmonary inflammation impacted on BaP-induced Cyp1a1 activity in the lung. Our results showed that Cyp1a1 appears to be important for BaP detoxification in vivo and that the decrease of pulmonary Cyp1a1 activity in LPS/BaP-treated mice results in a decrease of pulmonary BaP detoxification, thereby enhancing BaP genotoxicity (ie, DNA adduct formation) in the lung. Because less BaP was detoxified by Cyp1a1 in the lungs of LPS/BaP-treated mice, more BaP circulated via the blood to extrapulmonary tissues relative to mice treated with BaP only. Indeed, we observed higher BaP-DNA adduct levels in livers of LPS/BaP-treated mice compared with BaP-treated mice. Our results indicate that pulmonary inflammation could be a critical determinant in the induction of genotoxicity in the lung by PAHs like BaP. Cyp1a1 appears to be involved in both BaP bioactivation and detoxification although the contribution of other enzymes to BaP-DNA adduct formation in lung and liver under inflammatory conditions remains to be explored.
- Keywords
- DNA adducts, benzo[a]pyrene, bronchoalveolar lavage, carcinogen metabolism, cytochrome P450, pulmonary inflammation,
- MeSH
- Benzo(a)pyrene toxicity MeSH
- Cytochrome P-450 CYP1A1 metabolism MeSH
- Respiratory System metabolism pathology MeSH
- Carcinogens toxicity MeSH
- Air Pollutants toxicity MeSH
- Mice, Inbred C57BL MeSH
- Mice MeSH
- Pneumonia enzymology MeSH
- DNA Damage * MeSH
- Animals MeSH
- Check Tag
- Male MeSH
- Mice MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Benzo(a)pyrene MeSH
- CYP1A1 protein, human MeSH Browser
- Cytochrome P-450 CYP1A1 MeSH
- Carcinogens MeSH
- Air Pollutants MeSH
UNLABELLED: This review summarizes the results found in studies investigating the enzymatic activation of two genotoxic nitro-aromatics, an environmental pollutant and carcinogen 3-nitrobenzanthrone (3-NBA) and a natural plant nephrotoxin and carcinogen aristolochic acid I (AAI), to reactive species forming covalent DNA adducts. Experimental and theoretical approaches determined the reasons why human NAD(P)H: quinone oxidoreductase (NQO1) and cytochromes P450 (CYP) 1A1 and 1A2 have the potential to reductively activate both nitro-aromatics. The results also contributed to the elucidation of the molecular mechanisms of these reactions. The contribution of conjugation enzymes such as N,O-acetyltransferases (NATs) and sulfotransferases (SULTs) to the activation of 3-NBA and AAI was also examined. The results indicated differences in the abilities of 3-NBA and AAI metabolites to be further activated by these conjugation enzymes. The formation of DNA adducts generated by both carcinogens during their reductive activation by the NOQ1 and CYP1A1/2 enzymes was investigated with pure enzymes, enzymes present in subcellular cytosolic and microsomal fractions, selective inhibitors, and animal models (including knock-out and humanized animals). For the theoretical approaches, flexible in silico docking methods as well as ab initio calculations were employed. The results summarized in this review demonstrate that a combination of experimental and theoretical approaches is a useful tool to study the enzyme-mediated reaction mechanisms of 3-NBA and AAI reduction.
- MeSH
- Acetyltransferases metabolism MeSH
- DNA Adducts chemistry metabolism MeSH
- Aryl Hydrocarbon Hydroxylases metabolism MeSH
- Benz(a)Anthracenes chemistry metabolism MeSH
- Biocatalysis MeSH
- Enzymes metabolism MeSH
- Aristolochic Acids chemistry metabolism MeSH
- Humans MeSH
- Models, Molecular * MeSH
- NAD(P)H Dehydrogenase (Quinone) metabolism MeSH
- Sulfotransferases metabolism MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Review MeSH
- Names of Substances
- 3-nitrobenzanthrone MeSH Browser
- Acetyltransferases MeSH
- DNA Adducts MeSH
- aristolochic acid I MeSH Browser
- Aryl Hydrocarbon Hydroxylases MeSH
- Benz(a)Anthracenes MeSH
- Enzymes MeSH
- Aristolochic Acids MeSH
- NAD(P)H Dehydrogenase (Quinone) MeSH
- Sulfotransferases MeSH
