ABSTRACT
Evidences show that eukaryotic mRNAs can perform protein translation through internal ribosome entry sites (IRES). 5'-Untranslated region of the mRNA encoding apoptotic protease-activating factor 1 (Apaf-1) contains IRES, and, thus, can be translated in a cap-independent manner. Effects of changes in protein translation pattern through rapamycin pretreatment on 4-(methylnitrosamino)-1-(3-pyridyl)-butanone(NNK, tobacco-specific lung carcinogen)-induced apoptosis in human bronchial epithelial cells were examined by caspase assay, FACS analysis, Western blotting, and transient transfection. Results showed that NNK induced apoptosis in concentration- and time-dependent manners. NNK-induced apoptosis occurred initially through cap-independent protein translation, which during later stage was replaced by cap-dependent protein translation. Our data may be applicable as the mechanical basis of lung cancer treatment.
Subject(s)
Apoptosis/drug effects , Bronchi/pathology , Carcinogens/pharmacology , Epithelial Cells/pathology , Nitrosamines/pharmacology , RNA Cap-Binding Proteins/physiology , Antibiotics, Antineoplastic/pharmacology , Apoptotic Protease-Activating Factor 1 , BH3 Interacting Domain Death Agonist Protein , Blotting, Western , Bronchi/metabolism , Carrier Proteins/metabolism , Caspases/metabolism , Cytochromes c/metabolism , Dose-Response Relationship, Drug , Epithelial Cells/metabolism , Eukaryotic Initiation Factor-4E/metabolism , Flow Cytometry , Humans , Protein Biosynthesis , Proteins/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Sirolimus/pharmacology , Time Factors , bcl-2-Associated X ProteinABSTRACT
Potential toxicological interactions of 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and/or dibuthyl phthalate (DBP) on ozone were investigated after 32- and 52-wk exposures using hprt mutation assay. Male and female B6C3F1 mice exposed to ozone (0.5 ppm), NNK (1.0 mg/kg), DBP (5,000 ppm), and two or three combinations of these toxicants 6 h per day for 32- and 52-wk showed increases in the frequencies of TG rlymphocytes compared to the control groups. Additive interactions were noted from two combination groups compared to the ozone alone in both sexes of 32- and 52-wk studies. The most common specific mutation type in the hprt genes of test materials-treated male and female mice was transversion with very few transition. The results indicate that such dominant transversion may be responsible for toxicity and combined exposure to ozone, NNK, and DBP induces additive genotoxicities compared to ozone alone.
Subject(s)
Carcinogens/toxicity , Dibutyl Phthalate/toxicity , Hypoxanthine Phosphoribosyltransferase/genetics , Mutation , Nitrosamines/toxicity , Ozone/toxicity , Animals , DNA Mutational Analysis , Drug Combinations , Female , Male , Mice , Mutagenicity Tests , Mutation/drug effects , Reverse Transcriptase Polymerase Chain Reaction , T-Lymphocytes/drug effects , T-Lymphocytes/enzymologyABSTRACT
Toxic effects of ozone, 4-(N-methyl-N-nitrosamino)-1-(3- pyridyl)-1-butanone (NNK), and/or dibutyl phthalate (DBP) were examined through NF-kappaB, AP-1, Nrf2, and osteopontin (OPN) in lungs and livers of B6C3F1 mice. Electrophoretic mobility shift assay (EMSA) indicated that mice treated with combination of toxicants induced high NF-kappaB activities. Expression levels of p105, p65, and p50 proteins increased in all treated mice, whereas IkB activity was inhibited in NNK-, DBP-, and combination-treated ones. All treated mice except ozone-treated one showed high AP-1 binding activities. Expression levels of c-fos, c-jun, junB, jun D, Nrf2, and OPN proteins increased in all treated mice. Additive interactions were frequently noted from two-toxicant combination mice compared to ozone-treated one. These results indicate treatment of mixture of toxicants increased toxicity through NF-kappaB, AP-1, Nrf2, and OPN. Our data could be applied to the elucidation of mechanism as well as the risk assessment of mixture-induced toxicity.
