-
Toxicology Apr 2014CYP2E1 has been implicated in the bioactivation of many small molecules into reactive metabolites which form adducts with proteins and DNA, and thus a better...
CYP2E1 has been implicated in the bioactivation of many small molecules into reactive metabolites which form adducts with proteins and DNA, and thus a better understanding of the molecular determinants of its selectivity are critical for accurate toxicological predictions. In this study, we determined the potency of inhibition of human CYP2E1 for various 4-carbon alkanes, alkenes and alcohols. In addition, known CYP2E1 substrates and inhibitors including 4-methylpyrazole, aniline, and dimethylnitrosamine were included to determine their relative potencies. Of the 1,3-butadiene-derived metabolites studied, 3,4-epoxy-1-butene was the strongest inhibitor with an IC50 of 110 μM compared to 1700 μM and 6600 μM for 1,2-butenediol and 1,2:3,4-diepoxybutane, respectively. Compared to known inhibitors, inhibitory potency of 3,4-epoxy-1-butene is between 4-methylpyrazole (IC50 = 1.8 μM) and dimethylnitrosamine (IC50 = 230 μM). All three butadiene metabolites inhibit CYP2E1 activity through a simple competitive mechanism. Among the 4-carbon compounds studied, the presence and location of polar groups seems to influence inhibitory potency. To further examine this notion, the investigation was extended to include structurally and chemically similar analogues, including propylene oxide and various butane alcohols. Those results demonstrated preferential recognition of CYP2E1 toward the type and location of polar and hydrophobic structural elements. Taken together, CYP2E1 metabolism may be modified in vivo by exposure to 4-carbon compounds, such as drugs, and nutritional constituents, a finding that highlights the complexity of exposure to mixtures.
Topics: Alkanes; Butadienes; Complex Mixtures; Cytochrome P-450 CYP2E1; Environmental Pollutants; Enzyme Inhibitors; Epoxy Compounds; Hazardous Substances; Humans; Inhibitory Concentration 50; Microsomes, Liver
PubMed: 24561005
DOI: 10.1016/j.tox.2014.02.003 -
European Journal of Pharmaceutical... Jan 2022For nearly three years, the concerns regarding trace levels of N-nitrosamines in pharmaceuticals and the associated cancer risk have significantly expanded and are a...
BACKGROUND
For nearly three years, the concerns regarding trace levels of N-nitrosamines in pharmaceuticals and the associated cancer risk have significantly expanded and are a major issue facing the global pharmaceutical industry. N-nitrosodimethylamine (NDMA) found in formulations of the popular anti-diabetic drug metformin is a prominent example. This has resulted in product recalls raising the profile within the media. Issues of method robustness, sample preparation and several unexpected sources of nitrosamine contamination have been highlighted as false positive risks. It has become apparent that the identification of the root causes of artefactual formation of nitrosamines must be identified to mitigate risk associated with the analysis.
METHODS
A comparison study between four laboratories, across three companies was designed, employing orthogonal mass spectrometric methods for the quantification of NDMA in two metformin immediate release (IR) formulations and one extended release (XR) formulation. These were 2x LC-MS/MS, GC-MS/MS and GC-HRMS.
RESULTS
Good agreement of results was obtained for the IR formulations. However, we measured higher concentrations of NDMA in the XR formulation using GC-MS/MS compared to LC-MS/MS. We could show that this was due to artefactual (in situ) formation of NDMA when samples were extracted with dichloromethane. Removal of dimethylamine (DMA) and nitrite from the extracted sample or the addition of a nitrosation scavenger are shown to be effective remedies. NDMA in situ formation was not observed in 10% MeOH or acetonitrile.
CONCLUSION
Metformin pharmaceuticals contain traces of the API impurity DMA as well as inorganic nitrite from excipients. This can lead to artefactual formation of NDMA and hence false positive results if DCM is used for sample extraction. Similar artefacts are likely also in other pharmaceuticals if these contain the secondary amine precursor of the respective nitrosamine analyte.
Topics: Chromatography, Liquid; Dimethylnitrosamine; Gas Chromatography-Mass Spectrometry; Metformin; Tandem Mass Spectrometry
PubMed: 34597792
DOI: 10.1016/j.ejps.2021.106026 -
Food Chemistry Jun 2022Several epidemiological studies emphasize the consumption of processed meat products as a risk factor of colorectal cancer, linking N-nitrosamines (NAs) formed during...
Several epidemiological studies emphasize the consumption of processed meat products as a risk factor of colorectal cancer, linking N-nitrosamines (NAs) formed during nitrite curing to this cancer risk. The occurrence of volatile N-nitrosamines (VNAs) has over the years been intensively studied while the knowledge on the occurrence and toxicity of non-volatile N-nitrosamines (NVNAs) is still limited. Therefore, this study focuses on quantification of both VNAs and NVNAs in a large selection of processed meat products. For this purpose, a robust, specific and sensitive method allowing analysis of seven VNAs and two NVNAs was optimized and validated using kassler, sausage, and salami. The limit of quantification achieved was 0.1-0.5 ng·g for most of the VNA, and 2.3-4.2 ng·g for the NVNA. In one hundred commercial samples N-nitroso-thiazolidine-4-carboxylic acid (NTCA) was the most frequently detected (97 samples) among all target NAs and it was found at concentrations ranging from 3.1 ng·g to 1660 ng·g. The samples contained relatively low mean levels of the individual VNAs (≤1 ng·g). The levels of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), and N-nitrosopiperidine (NPIP) ranged from non-detectable to 3.8, 10.8 and 2.9 ng·g, respectively. A correlation between the detected residual levels of nitrite and/or nitrate and concentrations of individual NAs could not be demonstrated. Based on principle component analysis (PCA) some correlations between salami, sausage and bacon and NAs could be shown.
Topics: Denmark; Dimethylnitrosamine; Meat; Meat Products; Nitrites; Nitrosamines
PubMed: 35026484
DOI: 10.1016/j.foodchem.2022.132046 -
Toxicology and Applied Pharmacology Sep 2019Dimethylaminoethanol (DMAE) and its salts have been used to treat numerous disorders in humans and hence safety of its use is a concern. DMAE is a close structural...
Dimethylaminoethanol (DMAE) and its salts have been used to treat numerous disorders in humans and hence safety of its use is a concern. DMAE is a close structural analog of choline, an essential nutrient. Exposure to DMAE may affect choline uptake and synthesis. The current investigation characterizes: 1) the absorption, distribution, metabolism, and excretion (ADME) of DMAE in Wistar Han rats and B6C3F1 mice following a single gavage or intravenous (IV) administration of 10, 100 or 500 mg/kg [C]DMAE, and 2) the ADME of [C]choline (160 mg/kg) and the effect on its disposition following pre-treatment with DMAE (100 or 500 mg/kg). In both rats and mice, following gavage administration, DMAE was excreted in urine (16-69%) and as exhaled CO (3-22%). The tissue retention was moderate (21-44%); however, the brain concentrations were low and there was no accumulation. Serum choline levels were not elevated following administration of DMAE. The DMAE metabolites in urine were DMAE N-oxide and N,N-dimethylglycine; the carcinogen, N-N-dimethylnitrosamine, was not detected. The pattern of disposition of [C]choline following gavage administration was similar to that of [C]DMAE. Prior treatment with DMAE had minimal effects on choline disposition. The pattern of disposition of [C]DMAE and [C]choline following IV administration was similar to gavage administration. There were minimal dose-, sex- or species-related effects following gavage or IV administration of [C]DMAE or [C]choline. Data from the current study did not support previous reports that: 1) DMAE alters choline uptake and distribution, or 2) that DMAE is converted into choline in vivo.
Topics: Administration, Intravenous; Administration, Oral; Animals; Choline; Deanol; Dimethylnitrosamine; Female; Male; Mice; Rats; Rats, Wistar; Tissue Distribution
PubMed: 31100288
DOI: 10.1016/j.taap.2019.05.011 -
International Journal of Environmental... Sep 2021Many nitrosamines are potent carcinogens, with more than 30 listed under California's Proposition 65. Recently, nitrosamine contamination of commonly used drugs for...
Many nitrosamines are potent carcinogens, with more than 30 listed under California's Proposition 65. Recently, nitrosamine contamination of commonly used drugs for treatment of hypertension, heartburn, and type 2 diabetes has prompted numerous Food and Drug Administration (FDA) recalls in the US. These contaminants include the carcinogens NDMA (N-nitrosodimethylamine) and NDEA (N-nitrosodiethylamine) and the animal tumorigen NMBA (N-nitroso-N-methyl-4-aminobutyric acid). NMBA and NDEA are metabolically and/or structurally related to NDMA, an N-nitrosomethyl--alkylamine (NMA), and 12 other carcinogenic NMAs. These nitrosamines exhibit common genotoxic and tumorigenic activities, with shared target tumor sites amongst chemicals and within a given laboratory animal species. We use the drug valsartan as a case study to estimate the additional cancer risks associated with NDMA and NDEA contamination, based on nitrosamine levels reported by the US FDA, cancer potencies developed by California's Proposition 65 program and the US Environmental Protection Agency (EPA), and specific exposure scenarios. These estimates suggest that nitrosamine contamination in drugs that are used long-term can increase cancer risks and pose a serious concern to public health.
Topics: Animals; Carcinogens; Diabetes Mellitus, Type 2; Diethylnitrosamine; Dimethylnitrosamine; Neoplasms; Nitrosamines
PubMed: 34574388
DOI: 10.3390/ijerph18189465 -
Phytomedicine : International Journal... Feb 2024Hepatic fibrosis is the pivotal determinant in the progression of chronic liver diseases towards cirrhosis or advanced stages. Studies have shown that Schisantherin A...
BACKGROUND
Hepatic fibrosis is the pivotal determinant in the progression of chronic liver diseases towards cirrhosis or advanced stages. Studies have shown that Schisantherin A (Sin A), the primary active compound from Schizandra chinensis (Turcz.) Baill., exhibits anti-hepatic fibrosis effects. However, the mechanism of Sin A in liver fibrosis remain unclear.
PURPOSE
To examine the effects and underlying mechanism of Sin A on hepatic fibrosis.
STUDY DESIGN AND METHODS
The effects and mechanism of Sin A were investigated using liver fibrosis mouse models induced by carbon tetrachloride (CCl) or dimethylnitrosamine (DMN), as well as HO-induced hepatocyte injury in vitro.
RESULTS
Sin A treatment ameliorated hepatocyte injury, inflammation, hepatic sinusoidal capillarization, and hepatic fibrosis in both CCl-induced and DMN-induced mice. Sin A effectively reversed the reduction of DDAH1 expression, the p-eNOS/eNOS ratio and NO generation and attenuated the elevation of hepatic ADMA level induced by CCl and DMN. Knockdown of DDAH1 in hepatocytes not only triggered hepatocyte damage, but it also counteracted the effect of Sin A on protecting hepatocytes in vitro.
CONCLUSION
Our findings indicate that Sin A ameliorates liver fibrosis by upregulating DDAH1 to protect against hepatocyte injury. These results provide compelling evidence for Sin A treatment in liver fibrosis.
Topics: Mice; Animals; Hydrogen Peroxide; Liver Cirrhosis; Hepatocytes; Liver; Liver Diseases; Carbon Tetrachloride; Dioxoles; Lignans; Cyclooctanes
PubMed: 38185067
DOI: 10.1016/j.phymed.2023.155330 -
FEBS Open Bio Nov 2019RNA-sequencing (RNA-Seq) is a useful method to explore the molecular events in cells and tissues at the transcriptional level. However, comprehensive transcriptome...
RNA-sequencing (RNA-Seq) is a useful method to explore the molecular events in cells and tissues at the transcriptional level. However, comprehensive transcriptome analysis of hepatocarcinogenesis and progression is lacking. In this study, we aimed to characterize a dimethylnitrosamine (DEN) and carbon tetrachloride (CCl ; DEN+CCl )-induced hepatocellular carcinoma (HCC) mouse model by RNA-Seq. In total, 2033 genes were up-regulated and 841 genes were down-regulated after DEN and CCl stimulation. The differentially expressed genes were highly enriched for the Gene Ontology terms oxoacid metabolic process, carboxylic acid metabolic process, and organic acid metabolic process. Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that the top five significantly overrepresented pathways were metabolic pathways, chemical carcinogenesis, steroid hormone biosynthesis, retinol metabolism and metabolism of xenobiotics by cytochrome P450. Moreover, a protein-protein interaction network analysis indicated that Rous sarcoma oncogene (Src) may play a key role in DEN+CCl -induced HCC. These results provide a comprehensive overview of transcriptome events in DEN+CCl -induced HCC.
Topics: Animals; Carcinoma, Hepatocellular; Diethylnitrosamine; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Injections, Intraperitoneal; Liver Neoplasms; Male; Mice; Mice, Inbred C57BL; Sequence Analysis, RNA
PubMed: 31433574
DOI: 10.1002/2211-5463.12724 -
PloS One 2022This study was undertaken to investigate the inhibitory effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on dimethylnitrosamine (DMN)-induced liver...
This study was undertaken to investigate the inhibitory effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on dimethylnitrosamine (DMN)-induced liver fibrosis in rats. Liver fibrosis was induced in Sprague-Dawley rats by injecting DMN intraperitoneally (at 10 mg/kg of body weight) daily for three consecutive days per week for 4 weeks. To investigate the effect of GM-CSF on disease onset, GM-CSF (50 μg/kg of body weight) was co-treated with DMN for 2 consecutive days per week for 4 weeks (4-week groups). To observe the effect of GM-CSF on the progression of liver fibrosis, GM-CSF was post-treated alone at 5-8 weeks after the 4 weeks of DMN injection (8-week groups). We found that DMN administration for 4 weeks produced molecular and pathological manifestations of liver fibrosis, that is, it increased the expressions of collagen type I, alpha-smooth muscle actin (α-SMA), and transforming growth factor-β1 (TGF-β1), and decreased peroxisome proliferator-activated receptor gamma (PPAR-γ) expression. In addition, elevated serum levels of aspartate aminotransferase (AST), total bilirubin level (TBIL), and decreased albumin level (ALB) were observed. In both the 4-week and 8-week groups, GM-CSF clearly improved the pathological liver conditions in the gross and histological observations, and significantly recovered DMN-induced increases in AST and TBIL and decreases in ALB serum levels to normal. GM-CSF also significantly decreased DMN-induced increases in collagen type I, α-SMA, and TGF-β1 and increased DMN-induced decreases in PPAR-γ expression. In the DMN groups, survival decreased continuously for 8 weeks after DMN treatment for the first 4 weeks. GM-CSF showed a survival benefit when co-treated for the first 4 weeks but a marginal effect when post-treated for 5-8 weeks. In conclusion, co-treatment of GM-CSF showed therapeutic effects on DMN-induced liver fibrosis and survival rates in rats, while post-treatment efficiently blocked liver fibrosis.
Topics: Animals; Body Weight; Collagen Type I; Dimethylnitrosamine; Granulocyte-Macrophage Colony-Stimulating Factor; Liver; Liver Cirrhosis; Peroxisome Proliferator-Activated Receptors; Rats; Rats, Sprague-Dawley; Transforming Growth Factor beta1
PubMed: 36054162
DOI: 10.1371/journal.pone.0274126 -
JAMA Jul 2021In 2019, the US Food and Drug Administration (FDA) received a citizen petition indicating that ranitidine contained the probable human carcinogen N-nitrosodimethylamine... (Comparative Study)
Comparative Study Randomized Controlled Trial
IMPORTANCE
In 2019, the US Food and Drug Administration (FDA) received a citizen petition indicating that ranitidine contained the probable human carcinogen N-nitrosodimethylamine (NDMA). In addition, the petitioner proposed that ranitidine could convert to NDMA in humans; however, this was primarily based on a small clinical study that detected an increase in urinary excretion of NDMA after oral ranitidine consumption.
OBJECTIVE
To evaluate the 24-hour urinary excretion of NDMA after oral administration of ranitidine compared with placebo.
DESIGN, SETTING, AND PARTICIPANTS
Randomized, double-blind, placebo-controlled, crossover clinical trial at a clinical pharmacology unit (West Bend, Wisconsin) conducted in 18 healthy participants. The study began in June 2020, and the end of participant follow-up was July 1, 2020.
INTERVENTIONS
Participants were randomized to 1 of 4 treatment sequences and over 4 periods received ranitidine (300 mg) and placebo (randomized order) with a noncured-meats diet and then a cured-meats diet. The cured-meats diet was designed to have higher nitrites, nitrates (nitrate-reducing bacteria can convert nitrates to nitrites), and NDMA.
MAIN OUTCOME AND MEASURE
Twenty-four-hour urinary excretion of NDMA.
RESULTS
Among 18 randomized participants (median age, 33.0 [interquartile range {IQR}, 28.3 to 42.8] years; 9 women [50%]; 7 White [39%], 11 African American [61%]; and 3 Hispanic or Latino ethnicity [17%]), 17 (94%) completed the trial. The median 24-hour NDMA urinary excretion values for ranitidine and placebo were 0.6 ng (IQR, 0 to 29.7) and 10.5 ng (IQR, 0 to 17.8), respectively, with a noncured-meats diet and 11.9 ng (IQR, 5.6 to 48.6) and 23.4 ng (IQR, 8.6 to 36.7), respectively, with a cured-meats diet. There was no statistically significant difference between ranitidine and placebo in 24-hour urinary excretion of NDMA with a noncured-meats diet (median of the paired differences, 0 [IQR, -6.9 to 0] ng; P = .54) or a cured-meats diet (median of the paired differences, -1.1 [IQR, -9.1 to 11.5] ng; P = .71). No drug-related serious adverse events were reported.
CONCLUSIONS AND RELEVANCE
In this trial that included 18 healthy participants, oral ranitidine (300 mg), compared with placebo, did not significantly increase 24-hour urinary excretion of NDMA when participants consumed noncured-meats or cured-meats diets. The findings do not support that ranitidine is converted to NDMA in a general, healthy population.
TRIAL REGISTRATION
ClinicalTrials.gov Identifier: NCT04397445.
Topics: Administration, Oral; Adult; Cross-Over Studies; Dimethylnitrosamine; Double-Blind Method; Female; Histamine H2 Antagonists; Humans; Male; Placebos; Ranitidine
PubMed: 34180947
DOI: 10.1001/jama.2021.9199 -
Asian Pacific Journal of Cancer... 2012The Kashmiri population is culturally distinct with special dietary features owing to the temperate climatic conditions of Kashmir valley. This has habituated the... (Review)
Review
The Kashmiri population is culturally distinct with special dietary features owing to the temperate climatic conditions of Kashmir valley. This has habituated the population to preserve food in smoked, pickled and sundried forms which include considerable amounts of N-nitroso compounds (NOCs). These are known to cause cytotoxicity, DNA damage, mutation, unscheduled DNA synthesis and DNA methylation. All of these changes at molecular level are known to contribute to the pathogenesis of cancer. One of the prominent NOCs found in Kashmiri food is N-Nitrosodimethylamine (NDMA). Here we review the occurrence of NDMA in sundried foods, dried fish, kehwa, traditional pickle, Brassica oleracia and tobbaco. We also discuss its possible role in the high prevalence of gastrointestinal cancers in Kashmir.
Topics: Diet; Dimethylnitrosamine; Food Analysis; Food Preservation; Food Preservatives; Gastrointestinal Neoplasms; Humans; Incidence; India; Risk Factors
PubMed: 22631641
DOI: 10.7314/apjcp.2012.13.3.1077