scholarly journals In vitro versus in vivo metabolic activation of mutagens.

1973 ◽  
Vol 6 ◽  
pp. 71-82 ◽  
Author(s):  
H V Malling ◽  
C N Frantz
Keyword(s):  
Metabolic Activation

scholarly journals Microbial enzymes induce colitis by reactivating triclosan in the mouse gastrointestinal tract

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Jianan Zhang ◽  
Morgan E. Walker ◽  
Katherine Z. Sanidad ◽  
Hongna Zhang ◽  
Yanshan Liang ◽  
...  
Keyword(s):  
Gut Microbiota ◽  
Molecular Mechanisms ◽  
Ex Vivo ◽  
Metabolic Activation ◽  
Consumer Products ◽  
Environmental Chemicals ◽  
Intestinal Microbes ◽  
Targeted Inhibition

AbstractEmerging research supports that triclosan (TCS), an antimicrobial agent found in thousands of consumer products, exacerbates colitis and colitis-associated colorectal tumorigenesis in animal models. While the intestinal toxicities of TCS require the presence of gut microbiota, the molecular mechanisms involved have not been defined. Here we show that intestinal commensal microbes mediate metabolic activation of TCS in the colon and drive its gut toxicology. Using a range of in vitro, ex vivo, and in vivo approaches, we identify specific microbial β-glucuronidase (GUS) enzymes involved and pinpoint molecular motifs required to metabolically activate TCS in the gut. Finally, we show that targeted inhibition of bacterial GUS enzymes abolishes the colitis-promoting effects of TCS, supporting an essential role of specific microbial proteins in TCS toxicity. Together, our results define a mechanism by which intestinal microbes contribute to the metabolic activation and gut toxicity of TCS, and highlight the importance of considering the contributions of the gut microbiota in evaluating the toxic potential of environmental chemicals.

Triazene metabolism. III. In vitro cytotoxicity towards M21 cells and in vivo antitumour activity of the proposed metabolites of the antitumour 1-aryl-3,3-dimethyltriazenes

1984 ◽  
Vol 62 (4) ◽  
pp. 396-402 ◽  
Author(s):  
Douglas J. Kohlsmith ◽  
Keith Vaughan ◽  
Stephen J. Luner
Keyword(s):  
Cell Line ◽  
Chemical Stability ◽  
Active Metabolite ◽  
Melanoma Cell Line ◽  
Antitumour Activity ◽  
Metabolic Activation ◽  
In Vitro Cytotoxicity ◽  
Structural Analogues

In vitro cytotoxicity of a series of antitumour triazenes towards the M21 melanoma cell line has been studied. Dimethyltriazenes are structural analogues of 5-(3,3-dimethyl-1-triazeno-)imidazole-4-carboxamide (Dacarbazine) and are inactive, which is consistent with the requirement for metabolic activation. Monomethyltriazenes and hydroxymethyltriazenes, the proposed metabolites of the dimethyltriazenes, are cytotoxic to the M21 cell line. A new series of 4-hydroxy-1,2,3-benzotriazines has been tested for in vitro cytotoxicity. A series of monoalkyltriazenes (Ar∙N=N∙NHR) has been tested for antitumour activity against the P388 lymphoma in vivo. Only monomethyltriazenes had significant antitumour activity, which supports the hypothesis that the monomethyltriazene is the active metabolite of the antitumour dimethyltriazenes. The activity of monomethyltriazenes in vivo is correlated with the chemical stability and t1/2 measurements in pH 7.5 phosphate buffer.

Genotoxicity Assessment of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)

2005 ◽  
Vol 24 (6) ◽  
pp. 427-434 ◽  
Author(s):  
Gunda Reddy ◽  
Gregory L. Erexson ◽  
Maria A. Cifone ◽  
Michael A. Major ◽  
Glenn J. Leach
Keyword(s):  
Bone Marrow ◽  
World War Ii ◽  
Environmental Protection Agency ◽  
Bone Marrow Cells ◽  
Metabolic Activation ◽  
Maximum Tolerated Dose ◽  
Mouse Bone Marrow ◽  
Mouse Lymphoma

Hexahydro-1,3,5-trinitro-1,3,5-triazine, a polynitramine compound, commonly known as RDX, has been used as an explosive in military munitions formulations since World War II. There is considerable data available regarding the toxicity and carcinogenicity of RDX. It has been classified as a possible carcinogen (U.S. Environmental Protection Agency, Integrated Risk Information System, 2005, www.epa.gov/IRIS/subst/0313.htm ). In order to better understand its gentoxic potential, the authors conducted the in vitro mouse lymphoma forward mutation and the in vivo mouse bone marrow micronucleus assays. Pure RDX (99.99%) at concentrations ranging from 3.93 to 500 μg/ml showed no cytotoxicity and no mutagenicity in forward mutations at the thymidine kinase (TK) locus in L5178Y mouse lymphoma cells, with and without metabolic activation. This finding was also confirmed by repeat assays under identical conditions. In addition, RDX did not induce micronuclei in mouse bone marrow cells when tested to the maximum tolerated dose of 250 mg/kg in male mice. These results show that RDX was not mutagenic in these in vitro and in vivo mammalian systems.

scholarly journals Stimulation of neutrophil oxidative metabolism by the alternate pathway of complement activation: a mechanism for the spontaneous NBT test

Blood ◽  
1975 ◽  
Vol 45 (6) ◽  
pp. 843-849 ◽  
Author(s):  
RG Strauss ◽  
AM Mauer ◽  
T Asbrock ◽  
RE Spitzer ◽  
AE Stitzel
Keyword(s):  
Complement Activation ◽  
Oxidative Metabolism ◽  
Alternative Pathway ◽  
Metabolic Activation ◽  
Biologically Active ◽  
Nitroblue Tetrazolium ◽  
Human Neutrophils ◽  
Alternate Pathway

Abstract The reduction of nitroblue tetrazolium dye by human neutrophils was measured in the presence of serum in which the complement system had been activated through the alternate pathway by interaction with inulin. Neutrophils incubated with serum inulin supernatants reduced the dye and showed a general increase in oxidative metabolism. The oxidation of glucose-1–14-C by supernatant prepared from selectively depleted sera indicated that the neutrophil-stimulating factor(s) was generated through the alternate pathway of complement activation. The possibility that inulun had been ingested as a particle was ruled out by light microscopy and radiolabeling studies. The failure of neutrophils stimulated by the serum-inulun supernatants to migrate after exposure to a chemotactic agent suggested that the site of neutrophil-complement interaction was on the cell membrane. It is concluded from these results that biologically active fragments generated through the alternative pathway of complement activation can stimulate neutrophil metabolism in the absence of phagocytosis. Interaction of such fragments with circulating neutrophils in vivo and the subsequent metabolic activation of these cells is one explanation for the spontaneous reduction of nitroblue tetrazolium dye in vitro by neutrophils from patients with certain infections and inflammatory disorders.

Genotoxicity and Carcinogenicity Studies of Soy Isoflavones

2002 ◽  
Vol 21 (4) ◽  
pp. 277-285 ◽  
Author(s):  
R. R. Misra ◽  
S. D. Hursting ◽  
S. N. Perkins ◽  
N. Sathyamoorthy ◽  
J. C. Mirsalis ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Drug Product ◽  
Present Report ◽  
Phase 1 ◽  
Metabolic Activation ◽  
Soy Isoflavones ◽  
Oral Toxicity ◽  
Polychromatic Erythrocytes

The potential cancer preventive efficacy of soy isoflavones is being investigated in preclinical and phase 1 clinical studies sponsored by the U.S. National Cancer Institute. Although 90-day oral toxicity studies with PTI G-2535 (an investigational soy isoflavone drug product) in rats and dogs, as well as teratology studies, indicated no signs of toxicity, there remains a mechanistic concern associated with the ability of isoflavones (i.e., genistein) to inhibit topoisomerase, possibly leading to DNA strand breaks. The present report describes results from two in vitro genotoxicity studies, one in vivo genotoxicity study, and a single carcinogenicity study conducted in p53 knockout mice. Bacterial mutagenesis experiments using six tester strains without metabolic activation revealed no evidence that PTI G-2535 was mutagenic. In similar experiments with exogenous metabolic activation there were statistically significant increases in revertants, but less than twofold, in a single (Salmonella typhimurium TA100) tester strain. Mouse lymphoma cell mutagenesis experiments conducted with and without metabolic activation revealed statistically significant increases in mutation frequency at PTI G-2535 concentrations ≥ 0.8 and 12 μg/ml, respectively; such increases were dose related and increases in the frequency of both small and large colonies were observed. A statistically significant increase in the frequency of micronucleated polychromatic erythrocytes was also seen 24 hours after treatment in male, but not female, mice who received 500 and 1000 mg/kg body weight PTI G-2535; however, such increases were small, were not dose related, and were not observed 48 hours after treatment. In contrast, dietary genistein had no effect on survival, weight gain, or the incidence or types of tumors that developed in cancer-prone rodents lacking the p53 tumor suppressor gene, p53 knockout mice. The apparent risk/benefit of isoflavone ingestion may ultimately depend on the dose and developmental timing of exposure.

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