1
|
Shao Y, Schiwy A, Glauch L, Henneberger L, König M, Mühlenbrink M, Xiao H, Thalmann B, Schlichting R, Hollert H, Escher BI. Optimization of a pre-metabolization procedure using rat liver S9 and cell-extracted S9 in the Ames fluctuation test. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 749:141468. [PMID: 32827816 DOI: 10.1016/j.scitotenv.2020.141468] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 08/01/2020] [Accepted: 08/02/2020] [Indexed: 06/11/2023]
Abstract
Many environmental pollutants pose a toxicological hazard only after metabolic activation. In vitro bioassays using cell lines or bacteria have often no or reduced metabolic activity, which impedes their use in the risk assessment. To improve the predictive capability of in vitro assays, external metabolization systems like the liver S9 fraction are frequently combined with in vitro toxicity assays. While it is typical for S9 fractions that samples and testing systems are combined in the same exposure system, we propose to separate the metabolism step and toxicity measurement. This allows for a modular combination of metabolic activation by enzymes isolated from rat liver (S9) or a biotechnological alternative (ewoS9R) with in vitro bioassays that lack metabolic capacity. Benzo(a)pyrene and 2-aminoanthracene were used as model compounds to optimize the conditions for the S9 metabolic degradation/activation step. The Ames assay with Salmonella typhimurium strains TA98 and TA100 was applied to validate the set-up of decoupling the S9 activation/metabolism from the bioassay system. S9 protein concentration of 0.25 mgprotein/mL, a supplement of 0.13 mM NADPH and a pre-incubation time of 100 min are recommended for activation of samples prior to dosing them to in vitro bioassays using the regular dosing protocols of the respective bioassay. EwoS9R performed equally well as Moltox S9, which is a step forward in developing true animal-free in vitro bioassays. After pre-incubation with S9 fraction, chemicals induced bacteria revertants in both the TA98 and the TA100 assay as efficiently as the standard Ames assay. The pre-incubation of chemicals with S9 fraction could serve for a wide range of cellular in vitro assays to efficiently combine activation and toxicity measurement, which may greatly facilitate the application of these assays for chemical hazard assessment and monitoring of environmental samples.
Collapse
Affiliation(s)
- Ying Shao
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany; Key Laboratory of the Three Gorges Reservoir Eco-environment, Ministry of Education, Chongqing University, Shazheng street 174, Shapingba, 400044 Chongqing, China.
| | - Andreas Schiwy
- Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany; Department of Evolutionary Ecology and Ecotoxicology, Goethe University, Max-von-Laue-Str. 13, 60438 Frankfurt/Main, Germany
| | - Lisa Glauch
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Luise Henneberger
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Maria König
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Marie Mühlenbrink
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Hongxia Xiao
- Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany
| | - Beat Thalmann
- EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany
| | - Rita Schlichting
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany
| | - Henner Hollert
- Department of Ecosystem Analysis, Institute for Environmental Research, RWTH Aachen University, Worringerweg 1, 52074 Aachen, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany; Department of Evolutionary Ecology and Ecotoxicology, Goethe University, Max-von-Laue-Str. 13, 60438 Frankfurt/Main, Germany
| | - Beate I Escher
- UFZ - Helmholtz Centre for Environmental Research, Department of Cell Toxicology, Permoser Str. 15, 04318 Leipzig, Germany; EWOMIS GmbH, Schießstraße 26c, 63486 Bruchköbel, Germany; Eberhard Karls University of Tübingen, Environmental Toxicology, Centre for Applied Geosciences, 72074 Tubingen, Germany
| |
Collapse
|
2
|
Erbes M, Wessler A, Obst U, Wild A. Detection of primary DNA damage in Chlamydomonas reinhardtii by means of modified microgel electrophoresis. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 1997; 30:448-458. [PMID: 9435886 DOI: 10.1002/(sici)1098-2280(1997)30:4<448::aid-em10>3.0.co;2-d] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The assessment of genotoxic potential in surface water requires test methods, among which are those that detect initial DNA damage in organisms of aquatic biocenosis. The microgel electrophoresis (MGE) "comet assay" was applied to a ubiquitous unicellular green alga (Chlamydomonas reinhardtii) to detect DNA damage caused by genotoxins. For this, the test protocol described by Singh NP et al. [Exp Cell Res 175: 184-191, 1988] was modified. Major modifications were the use of alkaline lysis buffer with ionic detergents and the reduction of preincubation and electrophoresis times. Short-time exposure of Chlamydomonas to the well-known genotoxicants 4-nitroquinoline-1-oxide (4-NQO), N-nitrosodimethylamine, and hydrogen peroxide led to dose-dependent DNA damage. Chlamydomonas responded very sensitively to treatment with increasing doses of 4-NQO. At a concentration of 25 nM, significant DNA damage was observed. At higher 4-NQO doses (> 100 nM), DNA damage was visible as complete DNA fragmentation into fine granules. N-Nitrosodimethylamine caused genotoxic effects at a concentration range from 0.014 to 0.14 mM without producing complete DNA fragmentation at the concentrations tested (highest dose, 140 mM). To evaluate the influence of illumination conditions during exposure, cells were incubated with increasing doses of H2O2 (0.25-1.0 mM) in darkness and in light. Our results indicate that incubation in light enables Chlamydomonas to cope with oxidative stress more efficiently than under dark conditions. To a certain extent, cytotoxic as well as genotoxic effects of H2O2 depend on the illumination condition or repair and anti-oxidative protection mechanisms activated by light, respectively.
Collapse
Affiliation(s)
- M Erbes
- WFM Wasserforschung Mainz GmbH, Mainz, Germany
| | | | | | | |
Collapse
|
3
|
Schoeny R, Cody T, Warshawsky D, Radike M. Metabolism of mutagenic polycyclic aromatic hydrocarbons by photosynthetic algal species. Mutat Res 1988; 197:289-302. [PMID: 3340087 DOI: 10.1016/0027-5107(88)90099-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAH) known to produce carcinogenic and mutagenic effects have been shown to contaminate waters, sediments and soils. While it is accepted that metabolites of these compounds are responsible for most of their biological effects in mammals, their metabolism, and to a large extent their bioactivity, in aquatic plants have not been explored. Cultures of photosynthetic algal species were assayed for their ability to metabolize benzo[a]pyrene (BaP), a carcinogenic PAH under conditions which either permitted (white light) or disallowed (gold light) photooxidation of the compound. Growth of Selenastrum capricornutum, a fresh-water green alga, was completely inhibited when incubated in white light with 160 micrograms BaP/l medium. By contrast concentrations at the upper limit of BaP solubility in aqueous medium had no effect on algal growth when gold light was used. BaP quinones and phenol derivatives were found to inhibit growth of Selenastrum under white light incubation. BaP phototoxicity and metabolism were observed to be species-specific. All 3 tested species of the order Chlorococcales were growth-inhibited by BaP in white light whereas neither the green alga Chlamydomonas reinhardtii nor a blue-green, a yellow-green or an euglenoid alga responded in this fashion. Assays of radiolabeled BaP metabolism in Selenastrum showed that the majority of radioactivity associated with BaP was found in media as opposed to algal cell pellets, that the extent of metabolism was BaP concentration dependent, and that the proportion of various metabolites detected was a function of the light source. After gold light incubation, BaP diols predominated while after white light treatment at equal BaP concentrations, the 3,6-quinone was found in the highest concentration. Extracted material from algal cell pellets and from media was tested for mutagenicity in a forward mutation suspension assay in Salmonella typhimurium using resistance to 8-azaguanine for selection. Direct-acting mutagens were detected in extracted media from incubation of Selenastrum with 400 micrograms BaP/l for 1 day in gold light. Extracts of media from algae incubated in gold light from 1 to 4 days with 1200 micrograms BaP/l were found to have direct-acting mutagens as well as those requiring further metabolism. Media extracts from white light incubations of BaP were mutagenic upon addition of rat liver homogenates. Activity of these materials from white light treatment are largely attributable to unmetabolized BaP.
Collapse
Affiliation(s)
- R Schoeny
- U.S. Environmental Protection Agency, Environmental Criteria and Assessment Office, Cincinnati, OH 45268
| | | | | | | |
Collapse
|