The induction of mutation in yeast by hydrogen peroxide

Safety Assessment of Hydrogen Peroxide as Used in Cosmetics

The Expert Panel for Cosmetic Ingredient Safety (Panel) assessed the safety of Hydrogen Peroxide for use in cosmetics. This ingredient is reported to function in cosmetics as an antimicrobial agent, cosmetic biocide, oral health care agent, and oxidizing agent. The Panel reviewed the data relevant to the safety of this ingredient and concluded that Hydrogen Peroxide is safe in cosmetics in the present practices of use and concentration described in this safety assessment.

Chloride-accelerated Cu-Fenton chemistry for biofilm removal

Biofilms present challenges to numerous industries. Herein, a simple approach was developed based on chloride-accelerated Fenton chemistry, where copper oxide nanoparticles facilitate efficient generation of reactive chlorine species for biofilm removal.

Aging is a deprivation syndrome driven by a germ-soma conflict

Evolution through natural selection can be described as driven by a perpetual conflict of individuals competing for limited resources. Recently, I postulated that the shortage of resources godfathered the evolutionary achievements of the differentiation-apoptosis programming [Rev. Neurosci. 12 (2001) 217]. Unicellular deprivation-induced differentiation into germ cell-like spores can be regarded as the archaic reproduction events which were fueled by the remains of the fratricided cells of the apoptotic fruiting body. Evidence has been accumulated suggesting that conserved through the ages as the evolutionary legacy of the germ-soma conflict, the somatic loss of immortality during the ontogenetic segregation of primordial germ cells recapitulates the archaic fate of the fruiting body. In this heritage, somatic death is a germ cell-triggered event and has been established as evolutionary-fixed default state following asymmetric reproduction in a world of finite resources. Aging, on the other hand, is the stress resistance-dependent phenotype of the somatic resilience that counteracts the germ cell-inflicted death pathway. Thus, aging is a survival response and, in contrast to current beliefs, is antagonistically linked to death that is not imposed by group selection but enforced upon the soma by the selfish genes of the "enemy within". Environmental conditions shape the trade-off solutions as compromise between the conflicting germ-soma interests. Mechanistically, the neuroendocrine system, particularly those components that control energy balance, reproduction and stress responses, orchestrate these events. The reproductive phase is a self-limited process that moulds onset and progress of senescence with germ cell-dependent factors, e.g. gonadal hormones. These degenerate the regulatory pacemakers of the pineal-hypothalamic-pituitary network and its peripheral, e.g. thymic, gonadal and adrenal targets thereby eroding the trophic milieu. The ensuing cellular metabolic stress engenders adaptive adjustments of the glucose-fatty acid cycle, responses that are adequate and thus fitness-boosting under fuel shortage (e.g. during caloric restriction) but become detrimental under fuel abundance. In a Janus-faced capacity, the cellular stress response apparatus expresses both tolerogenic and mutagenic features of the social and asocial deprivation responses [Rev. Neurosci. 12 (2001) 217]. Mediated by the derangement of the energy-Ca(2+)-redox homeostatic triangle, a mosaic of dedifferentiation/apoptosis and mutagenic responses actuates the gradual exhaustion of functional reserves and eventually results in a multitude of aging-related diseases. This scenario reconciles programmed and stochastic features of aging and resolves the major inconsistencies of current theories by linking ultimate and proximate causes of aging. Reproduction, differentiation, apoptosis, stress response and metabolism are merged into a coherent regulatory network that stages aging as a naturally selected, germ cell-triggered and reproductive phase-modulated deprivation response.

Mutagenic activity and specificity of hydrogen peroxide in the ad-3 forward-mutation test in two-component heterokaryons of Neurospora crassa

In the ad-3 forward-mutation test, hydrogen peroxide was at best a weak mutagen in nongrowing conidia from a DNA repair-proficient heterokaryon (H-12, uvs-2+/uvs-2+) but was a moderate mutagen in nongrowing conidia from a DNA-repair-deficient heterokaryon (H-59, uvs-2/uvs-2) over a narrow range of high concentrations. H-59 also was more sensitive than H-12 to the killing activity of hydrogen peroxide at high concentrations. Thus, a DNA-repair pathway, of which the gene product of the uvs-2+ allele is a part, appears to be involved in the repair of hydrogen peroxide-induced DNA lesions at low survival in these strains. There was slightly, but significantly, more killing by hydrogen peroxide of nongrowing conidia from H-12 and H-59 in the presence of O2 than in the absence of O2 (presence of N2). Thus, the killing activity of hydrogen peroxide was enhanced by O2. The Mutational Spectra of hydrogen peroxide-induced ad-3 mutants shows that hydrogen peroxide induced mainly gene/point mutations but also some multilocus deletion mutations in H-12 and H-59. Multiple-locus mutations occurred only in H-59, but the frequency was very low. The frequencies of the 3 kinds of intracistronic complementation pattern among ad-3BR mutants (gene/point mutations) suggest that hydrogen peroxide induced both base-pair substitutions and frameshift mutations in both strains.

Ultrasonic cavitation indirectly induces single strand breaks in DNA of viable cells in vitro by the action of residual hydrogen peroxide

Direct exposure of cells to vigorous ultrasonic cavitation results predominantly in mechanical cell lysis, but latent effects due to production of toxic sonochemicals can also be present. Phosphate buffered saline (PBS) was exposed to 1.61 MHz ultrasonic cavitation at 20 degrees C in a rotating tube exposure system to build up sonochemical products. Single strand DNA breaks (SSBs) were then induced by treating Chinese hamster ovary (CHO) cells with the cavitated PBS for 30 min on ice. The SSBs resided in viable cells, as evidenced by their ability to repair the breaks when warmed. This indirect effect could be explained by the action of cavitation-generated hydrogen peroxide that had built up (e.g., to 16 microM after 30 min exposure) in the PBS. Dissolution of argon gas in the PBS before exposure enhanced the SSB effect and the H2O2 production. Addition of catalase to the cavitated PBS before cell treatment eliminated the H2O2 and the SSB gamma effect. Tests with hydrogen peroxide showed that 16 microM H2O2 treatment for 30 on ice was as effective as 1 Gy dose of 60Co gamma rays in producing single strand breaks. The SSB effect of H2O2 and gamma rays was reduced by addition of the radical scavenger cysteamine to the cells before treatment, but cysteamine did not reduce the SSB effect of direct exposure to ultrasonic cavitation. These results help to clarify the potential for genetic effects from ultrasonic cavitation. These effects help to clarify the potential for genetic effects from ultrasonic cavitation.

Relationship between the induction of mitotic gene conversion and the formation of thymine glycols in yeast S. cerevisiae treated with hydrogen peroxide

The effects of hydrogen peroxide on yeast Saccharomyces cerevisiae were assessed by measuring gene conversion at the trp 5 locus and the amount of thymine glycols in DNA using a monoclonal antibody specific to this base modification. Our results show that: (a) hydrogen peroxide-induced mitotic gene conversion in yeast strain D7M1 was dose-dependent in the low dose range where no toxicity was observed; (b) in the low dose range, the frequency of gene conversion depended on the temperature of the treatment, with more conversion at 25 degrees C than at 15 degrees C; (c) thymine glycols were induced in DNA in a dose-dependent manner following exposure of cells to up to 400 mM hydrogen peroxide; (d) there was little difference in the amount of thymine glycols formed in DNA when treatment occurred at either 25 degrees C or 15 degrees C.

Comparison of the effects of hydrogen peroxide and x-ray irradiation on toxicity, mutation, and DNA damage/repair in mammalian cells (V-79)

Hydrogen peroxide is not detectably mutagenic at the hypoxanthine-guanine phosphoribosyl transfer locus (measured as 6-thioguanine resistance) in V-79 Chinese hamster lung cells, yet is cytotoxic with a Do dose of 240 muM. X-ray, by contrast, is both mutagenic and cytotoxic with a Do dose of 260 rad for cytotoxicity. The number of DNA single-strand breaks induced at equitoxic doses is much greater for hydrogen peroxide than it is for X-ray. Single-strand breaks are repaired with initial t 1/2 values of 5.0 min for X-ray and 6.8 min for hydrogen peroxide; after 12.5 min X-ray repair becomes biphasic, whereas H2O2 repair remains linear. Hydrogen peroxide does not induce either DNA-protein or DNA-DNA crosslinks, although X-ray has been previously shown to induce DNA-protein crosslinks. Hydroxyl radicals scavengers reduce the number of DNA single-strand breaks induced by hydrogen peroxide and X-ray, which implies that hydroxyl radicals may mediate the formation of these breaks. Because of hydroxyl radicals are produced by both agents, yet only X-ray is mutagenic, we conclude that hydroxyl radicals are not necessarily mutagenic in V-79 cells. The implications of these findings for the detection of carcinogens and mutagens is discussed.

The nucleotide-permeable Escherichia coli cell, a sensitive DNA repair indicator for carcinogens, mutagens, and antitumor agents binding covalently to DNA

Ether-permeabilized (nucleotide-permeable) Escherichia coli cells respond to alkylating and arylalkylating carcinogens with DNA excision repair, as assessed by their stimulation of DNA repair synthesis. In the present work, we have investigated whether DNA repair synthesis in ether-treated E. coli cells can serve as a general indicator to monitor the DNA-binding of carcinogens, mutagens and antitumor agents. Therefore, a standard assay was developed and comparative analyses were performed on 11 ultimate carcinogens, 10 proximate carcinogens, 2 tumor promoters, 6 mutagens, and 12 antitumor agents. All ultimate carcinogens (alkylating, acylating, arylalkylating agents) and mutagens (e.g., hydrogeen peroxide, acridine derivatives) caused DNA excision repair in wild type cells as measured by [3H] dTMP incorporation and simultaneously inhibited replicative DNA synthesis to various extents. Control experiments with the mutant cells uvrA and uvrB were performed to determine whether the pyrimidine-dimer-specific UV-endonuclease was involved in the removal of DNA damage. This was found to be true for the ultimate carcinogens (Ac)2 ONFln, mitomycin C, and for very reactive alkylating carcinogens. None of the ultimate carcinogens induced repair polymerization in mutant cells lacking the 5'-3' exonucleolytic activity of DNA polymerase I. Proximate carcinogens, such as Me2NNO, 4-nitroquinoline-1-oxide and aflatoxins, did not induce excision repair in the standard assay, probably because of the inability of E. coli to perform the activation steps necessary for covalent DNA-binding. However, Me2NNO, when pretreated with Udenfriend's hydroxylating mixture, gave rise to a low level of repair polymerization in ether-treated cells. Intercalating mutagens, such as quinacrine and ethidum bromide, inhibited replicative DNA synthesis. However, they were not found to be repair-inducers. THE TUMOR PROMOters TPA and phorbol-12,13-didecanoate did not cause excision repair, even when applied at high concentrations, nor did they inhibit repair synthesis stimulated by MeNOUr or (Ac)2 ONFln. The antitumor agents may be classified into two groups on the basis of the influence they exert on DNA synthesis: members of the first group (involving BCNU and bleomycin) stimulate repair polymerization and, in addition, inhibit DNA replication. These compounds are known to bind covalently to DNA. The second group of drugs (including adriamycin and cis-Pt(II)diammine complexes) inhibits DNA replication without stimulating repair synthesis. The predominant DNA-interaction of these compounds is known to be a non-covalent (i.e., intercalative, electrostatic) binding. Our experiments show that the ether-permeabilized E. coli cell can be successfully used to test ultimate carcinogens, mutagens and antitumor agents for repair-inducing and replication-inhibiting activity. The standard test might be extended to pre- and proximate carcinogens, provided these can be suitably activated.