Gene polymorphisms and serum levels of mannose-binding lectin in Czech patients with recurrent aphthous stomatitis: A case-control study.

BACKGROUND: Recurrent aphthous stomatitis is one of the most prevalent oral mucosal immunological diseases. A recent case-control study in the Egyptian population suggested that single nucleotide polymorphism Gly54Asp (rs1800450) of the mannose-binding lectin 2 gene might affect the mannose-binding lectin serum level and recurrent aphthous stomatitis development. The aim of this study was to determine the distribution of six functional mannose-binding lectin 2 gene polymorphisms and analyse their role in recurrent aphthous stomatitis susceptibility in the Czech population. METHODS: The study included 227 subjects; 137 healthy people and 90 patients with recurrent aphthous stomatitis. Six mannose-binding lectin 2 gene polymorphisms (rs11003125, rs7096206, rs7095891, rs5030737, rs1800450, rs1800451) were analysed by the SNaPshot assay method, mannose-binding lectin serum levels were determined by enzyme-linked immunosorbent assay (ELISA) method in a subgroup of subjects (N = 87). RESULTS: No significant differences in mean of mannose-binding lectin serum levels between healthy controls and patients with recurrent aphthous stomatitis were observed (383 ng/ml ± 249 standard deviation (SD) vs. 316 ng/ml ± 177 SD in remission phase vs. 343 ng/ml ± 254 SD in active phase; p > 0.05), also the allele and genotype frequencies of the studied mannose-binding lectin 2 polymorphisms did not differ significantly between the two groups (p > 0.05, odds ratio (OR): 0.75-1.23). Moreover, the distribution of mannose-binding lectin 2 haplotypes and haplogenotypes was similar in the healthy subjects and patients with recurrent aphthous stomatitis (p > 0.05, OR: 0.75-1.23). CONCLUSIONS: This study did not confirm the previously reported association of the mannose-binding lectin 2 Gly54Asp gene variant and low mannose-binding lectin serum level as the risk factors for susceptibility to recurrent aphthous stomatitis. In addition, no significant relationships between mannose-binding lectin 2 functional haplotypes or haplogenotypes and recurrent aphthous stomatitis were observed.

Mechanisms of the different DNA adduct forming potentials of the urban air pollutants 2-nitrobenzanthrone and carcinogenic 3-nitrobenzanthrone.

2-Nitrobenzanthrone (2-NBA) has recently been detected in ambient air particulate matter. Its isomer 3-nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen identified in diesel exhaust. We compared the efficiencies of human enzymatic systems [hepatic microsomes and cytosols, NAD(P)H:quinone oxidoreductase 1 (NQO1), xanthine oxidase, NADPH:cytochrome P450 reductase, N,O-acetyltransferases, and sulfotransferases] and human primary hepatocytes to activate 2-NBA and its isomer 3-NBA to species forming DNA adducts. In contrast to 3-NBA, 2-NBA was not metabolized at detectable levels by the tested human enzymatic systems and enzymes expressed in human hepatocytes, and no DNA adducts detectable by (32)P-postlabeling were generated by 2-NBA. Even NQO1, the most efficient human enzyme to bioactive 3-NBA, did not activate 2-NBA. Molecular docking of 2-NBA and 3-NBA to the active site of NQO1 showed similar binding affinities; however, the binding orientation of 2-NBA does not favor the reduction of the nitro group. This was in line with the inhibition of 3-NBA-DNA adduct formation by 2-NBA, indicating that 2-NBA can compete with 3-NBA for binding to NQO1, thereby decreasing the metabolic activation of 3-NBA. In addition, the predicted equilibrium conditions favor a 3 orders of magnitude higher dissociation of N-OH-3-ABA in comparison to N-OH-2-ABA. These findings explain the very different genotoxicity, mutagenicity, and DNA adduct forming potential of the two compounds. Collectively, our results suggest that 2-NBA possesses a relatively lower risk to humans than 3-NBA.

Human cytochromes P450 1A1 and 1A2 participate in detoxication of carcinogenic aristolochic acid.

OBJECTIVES: A carcinogenic and nephrotoxic plant alkaloid, aristolochic acid (AA), causes the development of aristolochic acid nephropathy, which is characterized by chronic renal failure, tubulointerstitial fibrosis and urothelial cancer. AA may also cause a similar type of kidney fibrosis with malignant transformation of the urothelium, the Balkan endemic nephropathy. The aim of the study was to resolve which cytochromes P450 (CYP) detoxicate the major component of AA, aristolochic acid I (AAI), to its O-demethylated metabolite, aristolochic acid Ia (AAIa). METHODS: High performance liquid chromatography (HPLC) was employed for separation and characterization of AAI metabolites generated by CYPs. RESULTS: Human, rat and mouse hepatic CYPs oxidize AAI into its detoxication metabolite AAIa. Most of the detoxication of AAI in human hepatic microsomes is mediated by CYP1A2 and 1A1, while other CYPs play a minor role. CONCLUSIONS: The data are the first report on identification of human CYP enzymes detoxicating AAI.