Randomized trial of an inhibitor of formation of advanced glycation end products in diabetic nephropathy.

Background/aims: Pimagedine inhibits the formation of advanced glycation end products and slows the progression of diabetic complications in experimental models. This study was undertaken to determine if pimagedine ameliorates nephropathy in type 1 (insulin-dependent) diabetes mellitus.

Methods: This was a randomized, double-masked, placebo-controlled study performed in 690 patients with type 1 diabetes mellitus, nephropathy, and retinopathy.

Therapeutic potential of breakers of advanced glycation end product-protein crosslinks.

Long-lived structural proteins, collagen and elastin, undergo continual non-enzymatic crosslinking during aging and in diabetic individuals. This abnormal protein crosslinking is mediated by advanced glycation end products (AGEs) generated by non-enzymatic glycosylation of proteins by glucose. The AGE-derived protein crosslinking of structural proteins contributes to the complications of long-term diabetes such as nephropathy, retinopathy, and neuropathy.

Therapeutic potential of AGE inhibitors and breakers of AGE protein cross-links.

Glucose and other reducing sugars react non-enzymatically with proteins leading to the formation of advanced glycosylation end products (AGEs) and AGE-derived protein cross-linking. Formation of AGEs is a normal physiological process, which is accelerated under the hyperglycaemic condition in diabetes. Under normal conditions, AGEs build up slowly and accumulate as one ages.

Evidence for an important role of DNA pyridyloxobutylation in rat lung carcinogenesis by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone: effects of dose and phenethyl isothiocyanate.

The tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), selectively induces lung tumors in F344 rats. NNK is metabolically activated to intermediates that methylate and pyridyloxobutylate DNA. To explore the importance of pyridyloxobutyl DNA adducts in NNK-induced rat lung tumorigenesis, the first study in this report examined levels of these adducts in whole lung and pulmonary cells of F344 rats treated with different doses of NNK (0.

The relationship between N-nitrosodimethylamine metabolism and DNA methylation in isolated rat hepatocytes.

The metabolism of N-nitrosodimethylamine (NDMA) and its methylation of DNA were simultaneously determined in hepatocytes isolated from untreated and saline- and pyrazole-treated male Sprague-Dawley rats. Metabolism of NDMA was directly measured by monitoring its disappearance via gas chromatography coupled with a sensitive and specific detector for N-nitrosamines. DNA methylation was determined in the same cells employed in the metabolism studies using a monoclonal antibody-based competitive ELISA procedure specific for O6-methyldeoxyguanosine (6-Me-dG).

The in vitro methylation of DNA by a minor groove binding methyl sulfonate ester.

The preparation of sequence and groove specific DNA methylating agents based on N-methylpyrrolecarboxamide subunits appended with an O-methyl sulfonate ester functionality (MeOSO2(CH2)2-Lex) has previously been described [Zhang, Y., Chen, F.-X.

Inhibition of pkc and pka by chemopreventive organoselenium compounds.

Numerous efficacy studies in rodents revealed that 1,4-phenylenebis(methylene)-selenocyanat (p-XSC) is a more effective chemopreventive organoselenium compound and less toxic than benzyl selenocyanate (BSC) or the inorganic compound Na2SeO3. To explore mechanisms which mediate chemopreventive activities of p-XSC we have tested its effect on protein kinase A and C using in vitro and cell culture systems. While p-XSC did completely inhibit PKC and PKA activity, BSC was less active and Na2SeO3 had no effect.

Identification and quantification of the N-acetylcysteine conjugate of allyl isothiocyanate in human urine after ingestion of mustard.

Allyl isothiocyanate (AITC) is a constituent of cruciferous vegetables. It occurs widely in the human diet as a natural ingredient or food additive. AITC possesses numerous biochemical and physiological activities.

Biomarkers for human uptake and metabolic activation of tobacco-specific nitrosamines.

Tobacco-specific nitrosamines are a group of carcinogens formed from nicotine and related tobacco alkaloids. Two of these compounds, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine, are believed to be involved as causative agents for cancers of the lung, oral cavity, esophagus, and pancreas associated with the use of tobacco products. The goal of the studies described here is to develop biomarkers which will allow us to understand the uptake, metabolic activation, and detoxification of these carcinogens in humans.

Modulation of carcinogen-induced polyoma DNA-replication by organoselenium and organosulfur chemopreventive agents.

Both chemical and physical carcinogens are potent inducers of asynchronous replication of various DNA tumor viruses. Employing H3 cells that carry an integrated copy of polyoma virus we have evaluated potential effects of known chemopreventive agents on carcinogen-induced polyoma DNA replication. The ability of well established organoselenium and organosulfur chemopreventive agents, in laboratory animals, to modulate polyoma DNA replication induced by AMMN or NNKOAc which are direct acting carcinogens derived from the tobacco carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was examined.

Tobacco-specific nitrosamine adducts: studies in laboratory animals and humans.

This paper describes quantitation of human hemoglobin and DNA adducts of the carcinogenic tobacco-specific nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN). NNK and NNN are believed to be involved in cancers of the lung, esophagus, oral cavity, and pancreas in people who use tobacco products. The adduct dosimetry method employs GC-MS for quantitation of 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB) released by mild base hydrolysis of hemoglobin or acid hydrolysis of DNA as a biochemical marker of the pyridyloxobutylation metabolic activation pathway.

Expression pattern of proteins that bind to the ultraviolet-responsive element (TGACAACA) in human keratinocytes.

We previously identified an ultraviolet (UV)-responsive element (URE; TGACAACA) that plays a role in both transcription and replication of polyoma sequences. Mouse polyclonal antibodies were raised against affinity-purified URE-bound proteins to characterize their expression patterns. These antibodies specifically recognized two of four URE-bound proteins, of 40 and 68 kDa.

Development of monoclonal antibodies specific for 1,N2-ethenodeoxyguanosine and N2,3-ethenodeoxyguanosine and their use for quantitation of adducts in G12 cells exposed to chloroacetaldehyde.

Monoclonal antibodies specific for N2,3-ethenodeoxyguanosine (N2,3-epsilon dGuo) and 1,N2-ethenodeoxyguanosine (1,N2-epsilon dGuo) were developed. In a competitive ELISA, 50% inhibition of binding of the N2,3-epsilon dGuo specific antibody (ETH1) was achieved with 18 fmol of N2,3-epsilon dGuo. Fifty per cent inhibition of the 1,N2-epsilon dGuo-specific antibody (ETH2) required 11 pmol 1,N2-epsilon dGuo.

Carcinogen biomarkers related to smoking and upper aerodigestive tract cancer.

Smoking is the major cause of upper aerodigestive tract cancers. Among the many constituents of tobacco smoke, polynuclear aromatic hydrocarbons and tobacco-specific nitrosamines are strongly implicated as causative factors for these cancers. The probability that these compounds will induce cancer in a given individual will depend on that person's ability to metabolically activate or detoxify them.

Analysis of mutagenic activity and ability to induce replication of polyoma DNA sequences by different model metabolites of the carcinogenic tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone.

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) requires metabolic activation to express its carcinogenic activity. This activation leads to the formation of methylating and pyridyloxobutylating agents. To determine the possible biological effects mediated by each of these metabolic pathways we have studied the activities of model compounds that are metabolized to either a methylating or pyridyloxobutylating species.

DNA and hemoglobin adducts as markers of metabolic activation of tobacco-specific carcinogens.

Lung cancer is now the leading cause of excess mortality among smokers in the United States. The ability to identify smokers with the greatest risk of developing lung cancer would be an important step in reducing lung cancer mortality. Tobacco-specific nitrosamines such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone and N'-nitrosonornicotine are important carcinogens in tobacco smoke.

Detection of acrolein and crotonaldehyde DNA adducts in cultured human cells and canine peripheral blood lymphocytes by 32P-postlabeling and nucleotide chromatography.

People are constantly being exposed to toxic and carcinogenic aldehydes. However, little is actually known about the mechanisms underlying the toxic and carcinogenic effects of these aldehydes on human cells. The DNA alkylating activities of two of the more toxic and environmentally prominent alpha,beta-unsaturated aldehydes, acrolein and crotonaldehyde, have been studied utilizing 32P-postlabeling and nucleotide chromatographic techniques.

Mass spectrometric analysis of tobacco-specific nitrosamine-DNA adducts in smokers and nonsmokers.

A gas chromatography, negative ion chemical ionization mass spectrometry (GC-NICI-MS) based assay for tobacco-specific nitrosamine adducts of DNA is described. The assay is based on the observation that acid hydrolysis of DNA from animals treated with tobacco-specific nitrosamines releases 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB). HPB and the internal standard [4,4-D2]HPB are derivatized with pentafluorobenzoyl chloride and the resulting HPB-pentafluorobenzoate is purified by high-performance liquid chromatography prior to GC-NICI-MS analysis.

Formation of cyclic deoxyguanosine adducts in Chinese hamster ovary cells by acrolein and crotonaldehyde.

Acrolein and crotonaldehyde are alpha,beta-unsaturated carbonyl compounds that form 1,N2-propanodeoxyguanosine adducts when reacted with DNA in vitro. These compounds are mutagenic in Salmonella, and crotonaldehyde is tumorigenic in rats. This study used immunoassay and 32P-postlabeling methods to determine if acrolein and crotonaldehyde form these adducts in cultured mammalian cells.

Mass spectrometric analysis of tobacco-specific nitrosamine hemoglobin adducts in snuff dippers, smokers, and nonsmokers.

Hemoglobin adducts of the carcinogenic tobacco-specific nitrosamines 4-(methylnitrosamino)-1(3-pyridyl)-1-butanone and N'-nitrosonornicotine were quantified in blood samples collected from snuff dippers, smokers, and nonsmokers. Mild base treatment of hemoglobin adducted by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone or N'-nitrosonornicotine releases 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB). HPB was enriched by solvent partitioning and derivatized to its pentafluorobenzoate.

Inhibition of repair of O6-methyldeoxyguanosine and enhanced mutagenesis in rat-liver epithelial cells.

The pro-mutagenicity of chemically-induced methylation of DNA at the O6 position of deoxyguanosine was studied in cultured adult rat liver epithelial cells. To modify the level of O6-methyldeoxyguanosine (O6-medGuo) resulting from exposure to an alkylating agent, partial depletion of the O6-alkylguanine-DNA alkyltransferase (AGT) repair system was produced by pretreatment of ARL 18 cells with a non-toxic dose of exogenous O6-methylguanine (O6-meG). Exposure of cells to 0.

Evaluation of 32P-postlabeling analysis of DNA from exfoliated oral mucosa cells as a means of monitoring exposure of the oral cavity to genotoxic agents.

Development of oral cavity cancer in man has been linked to alcohol consumption and use of tobacco products. In order to understand the underlying carcinogenic mechanisms in the oral cavity a method is needed to monitor exposure of this site to various environmental insults. In this pilot study we evaluate the use of the 32P-postlabeling assay to detect adducts in DNA from exfoliated oral mucosa cells.

Application of an immunoassay for cyclic acrolein deoxyguanosine adducts to assess their formation in DNA of Salmonella typhimurium under conditions of mutation induction by acrolein.

Acrolein has been shown to form cyclic deoxyguanosine adducts when it reacts with DNA in vitro. In this study, we have used a recently developed immunoassay for these adducts to study their formation in DNA from Salmonella typhimurium exposed to acrolein. Acrolein--deoxyguanosine adducts were formed in a dose-dependent fashion in Salmonella tester strains TA100 and TA104, reaching levels as high as 5 mumol adduct per mol deoxyguanosine.

Detection of O6-methyldeoxyguanosine in human placental DNA.

A monoclonal antibody specific for O6-methyldeoxyguanosine (O6-MedGuo) was developed. When used in a competitive enzyme-linked immunosorbent assay, 50% inhibition of binding was achieved with 0.51 pmol O6-MedGuo.

Approaches to the development of assays for interaction of tobacco-specific nitrosamines with haemoglobin and DNA.

The tobacco-specific, nicotine-derived nitrosamines 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK) and N'-nitrosonornicotine (NNN) are among the most important carcinogens in tobacco and tobacco smoke. Treatment of Fischer 344 rats with these carcinogens resulted in alkylation of haemoglobin and DNA by the 4-(3-pyridyl)-4-oxobutyl group formed during their metabolism. This alkyl group can be detached from globin or DNA under mild hydrolytic conditions as 4-hydroxy-1-(3-pyridyl)-1-butanone, which appears to be a potentially useful dosimeter for human exposure to, and activation of, tobacco-specific nitrosamines.