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PubMed1990

How cells recognize damaged DNA: clues from xeroderma pigmentosum and yeast.

Xeroderma pigmentosum (XP) is characterized by the defective excision repair of DNA damaged by many agents, including ultraviolet radiation (UV) and cisplatin. We have identified a factor in human cells that recognizes multiple forms of DNA damage and is absent in XP complementation group E. Denoted XPE binding factor, it is expressed at five-fold higher levels in tumor cell lines resistant to the antitumor drug cisplatin. Finally, although it does not have photoreactivating activity, XPE binding factor shares multiple binding characteristics with yeast photolyase, suggesting that it is the human homolog of photolyase.

Cells, Cultured↗

PubMed2004

[DNA damages of liver cells and expressions of DNA damage repair genes in rats exposed to vinyl chloride monomer].

OBJECTIVE: To study DNA damages of liver cells in rats exposed to vinyl chloride monomer (VCM), and the expressions of DNA damage repair enzymes including O(6)-methyl guanine-DNA methyl transferase (MGMT), X-ray repair cross-complementing group 1 (XRCC1) and X-ray repair cross-complementing group 3 (XRCC3); and to explore the repair mechanism of DNA damage induced by VCM. METHODS: Rats were exposed to VCM by intraperitoneal injection. DNA damages were detected by single cell gel electrophoresis (comet assay). The expressions of DNA damage repair enzymes were measured by immunohistochemical methods. RESULTS: The percentages of comet cells in low, moderate, and high dose groups (11.75%, 12.38%, and 17.63%, respectively) were greater than that of control (5.67%). The latter two groups were significantly different from that of control (P < 0.05, P < 0.01). The expressions of MGMT and XRCC1 decreased, and XRCC3 increased with the dose of VCM increased. DNA damage was correlated with the expression of XRCC3 (r = 0.438, P = 0.067). CONCLUSION: VCM can cause DNA damage of liver cells with dose-response relationship. DNA damage repair enzymes take part in the repairing of DNA damage induced by VCM.

Animals↗

PubMed2004

A Werner syndrome protein homolog affects C. elegans development, growth rate, life span and sensitivity to DNA damage by acting at a DNA damage checkpoint.

A Werner syndrome protein homolog in C. elegans (WRN-1) was immunolocalized to the nuclei of germ cells, embryonic cells, and many other cells of larval and adult worms. When wrn-1 expression was inhibited by RNA interference (RNAi), a slight reduction in C. elegans life span was observed, with accompanying signs of premature aging, such as earlier accumulation of lipofuscin and tissue deterioration in the head. In addition, various developmental defects, including small, dumpy, ruptured, transparent body, growth arrest and bag of worms, were induced by RNAi. The frequency of these defects was accentuated by gamma-irradiation, implying that they were derived from spontaneous or induced DNA damage. wrn-1(RNAi) worms showed accelerated larval growth irrespective of gamma-irradiation, and pre-meiotic germ cells had an abnormal checkpoint response to DNA replication blockage. These observations suggest that WRN-1 acts as a checkpoint protein for DNA damage and replication blockage. This idea is also supported by an accelerated S phase in wrn-1(RNAi) embryonic cells. wrn-1(RNAi) phenotypes similar to those of Werner syndrome, such as premature aging and short stature, suggest wrn-1-deficient C. elegans as a useful model organism for Werner syndrome.

Aging↗

PubMed1993

Characterization of a DNA-damage-recognition protein from F9 teratocarcinoma cells, which is inducible by retinoic acid and cyclic AMP.

A nuclear protein that recognizes u.v.-damaged DNA was detected in extracts from murine F9 embryonic stem cells using a DNA-binding assay. The nuclear-protein-binding activity was increased in cells after treatment with retinoic acid/dibutyryl cyclic AMP (dbcAMP), with optimum induction at 6 days. In vitro treatment of nuclear extracts with agents that affect protein conformation (such as urea, Nonidet P40 and Ca2+) slightly modulated the damage-recognition activity. Furthermore, treatment of nuclear extracts with phosphatase dramatically inhibited the binding activity. In addition, damaged-DNA recognition of the nuclear extracts was effectively inhibited by damaged double- and single-stranded DNA. The expression of the nuclear protein with similar characteristics was abundant in HeLa cells and was increased in drug- or u.v.-resistant cells. The findings suggest that the recognition of a u.v.-DNA adduct is modulated, at least in part, by an activity that is induced during retinoic acid/dbcAMP-induced differentiation. These results also imply that the identified damage-recognition protein may be important for the sensitivity or resistance of mammalian cells to DNA damage.

Animals↗

PubMed1996

DNA damage and DNA sequence retrieval from ancient tissues.

Gas chromatography/mass spectrometry (GC/MS) was used to determine the amounts of eight oxidative base modifications in DNA extracted from 11 specimens of bones and soft tissues, ranging in age from 40 to >50 000 years. Among the compounds assayed hydantoin derivatives of pyrimidines were quantitatively dominant. From five of the specimens endogenous ancient DNA sequences could be amplified by PCR. The DNA from these specimens contained substantially lower amounts of hydantoins than the six specimens from which no DNA could be amplified. Other types of damage, e.g. oxidation products of purines, did not correlate with the inability to retrieve DNA sequences. Furthermore, all samples with low amounts of damage and from which DNA could be amplified stemmed from regions where low temperatures have prevailed throughout the burial period of the specimens.

Animals↗

PubMed1998

Analysis of DNA damage and repair accompanying differentiation in the intestinal crypt.

The ability to process damaged DNA may vary between cells depending on their differentiated status. However, there is little in vivo data available and it is not intuitively obvious how the activity of specific repair pathways may vary between different subpopulations (e.g. stem cells and proliferative, committed and differentiated cells) of a particular tissue. To obtain such information for the intestinal epithelium, we have developed an assay that detects differences in the way different regions of the crypt (stem, proliferative and maturation zones) respond to DNA damage. The assay is a variant of the 'comet' assay, which detects DNA strand breaks by measuring the proportion of DNA migrating from individual cells, or in this case intact isolated crypts, in an electrophoretic field. The method is quantitative, with the amount of migrating DNA being proportional to the number of strand breaks. Isolated crypts are repair competent and spatial differences are apparent with some agents. The assay has the potential to characterize the repair properties of cells at different stages of differentiation within the crypt, determine the characteristics that might predispose them to damage and may help in understanding the route of stem cell mutation.

Animals↗

PubMed2000

DNA damage in arsenite- and cadmium-treated bovine aortic endothelial cells.

Reactive oxygen species have been shown to be involved in the mutagenicity, clastogenicity, and apoptosis of mammalian cells treated with arsenic or cadmium. As these endpoints require several hours of cellular processing, it is not clear that reactive oxygen species damage DNA directly or interfere with DNA replication and repair. Using single-cell alkaline electrophoresis, we have detected DNA strand breaks (DSBs) in bovine aortic endothelial cells by a 4-h treatment with sodium arsenite (As) and cadmium chloride (Cd) in sublethal concentrations. As-induced DSBs could be decreased by nitric oxide (NO) synthase inhibitors, superoxide scavengers, and peroxynitrite scavengers and could be increased by superoxide generators and NO generators. Treatment with As also increased nitrite production. These results suggest that As-increased NO may react with O2*- to produce peroxynitrite and cause DNA damage. The results showing that Cd increased cellular H2O2 levels and that Cd-induced DSBs could be modulated by various oxidant modulators suggest that Cd may induce DSBs via O2*-, H2O2, and *OH. Nevertheless, the DSBs in both As- and Cd-treated cells seem to come from the excision of oxidized bases such as formamidopyrimidine and 8-oxoguanine, as the Escherichia coli enzyme formamidopyrimidine-DNA glycosylase (Fpg) increased DSBs in cells treated with As, 3-morpholinosydnonimine (a peroxynitrite-generating agent), Cd, or H2O2.

Amitrole↗

PubMed2005

Cooperative control of Crb2 by ATM family and Cdc2 kinases is essential for the DNA damage checkpoint in fission yeast.

The cellular responses to double-stranded breaks (DSBs) typically involve the extensive accumulation of checkpoint proteins in chromatin surrounding the damaged DNA. One well-characterized example involves the checkpoint protein Crb2 in the fission yeast Schizosaccharomyces pombe. The accumulation of Crb2 at DSBs requires the C-terminal phosphorylation of histone H2A (known as gamma-H2A) by ATM family kinases in chromatin surrounding the break. It also requires the constitutive methylation of histone H4 on lysine-20 (K20). Interestingly, neither type of histone modification is essential for the Crb2-dependent checkpoint response. However, H4-K20 methylation is essential in a crb2-T215A strain that lacks a cyclin-dependent kinase phosphorylation site in Crb2. Here we explain this genetic interaction by describing a previously overlooked effect of the crb2-T215A mutation. We show that crb2-T215A cells are able to initiate but not sustain a checkpoint response. We also report that gamma-H2A is essential for the DNA damage checkpoint in crb2-T215A cells. Importantly, we show that inactivation of Cdc2 in gamma-H2A-defective cells impairs Crb2-dependent signaling to the checkpoint kinase Chk1. These findings demonstrate that full Crb2 activity requires phosphorylation of threonine-215 by Cdc2. This regulation of Crb2 is independent of the histone modifications that are required for the hyperaccumulation of Crb2 at DSBs.

Amino Acid Substitution↗

PubMed2002

Copper redox-dependent activation of 2-tert-butyl(1,4)hydroquinone: formation of reactive oxygen species and induction of oxidative DNA damage in isolated DNA and cultured rat hepatocytes.

The biotransformation of butylated hydroxyanisole (BHA), a possible carcinogenic food antioxidant, includes o-demethylation to 2-tert-butyl(1,4)hydroquinone (TBHQ) which can subsequently be oxidized to 2-tert-butyl(1,4)paraquinone (TBQ). In this study, we have examined the capacity of Cu, a nuclei- and DNA-associated transition metal, to mediate the oxidation of TBHQ. In phosphate buffered saline (PBS), autooxidation of TBHQ to TBQ was not detectable, while Cu(II) at micromolar concentrations strongly catalyzed the oxidation of TBHQ to TBQ. Oxidation of TBHQ by Cu(II) was accompanied by the utilization of O(2) and the concomitant generation of H(2)O(2). Using electron spin resonance spectroscopy, it was observed that Cu(II) mediated the one electron oxidation of TBHQ to a semiquinone anion radical. The formation of a semiquinone anion radical, the utilization of O(2) and the generation of H(2)O(2) and TBQ could be completely blocked by bathocuproinedisulfonic acid (BCS) and reduced glutathione (GSH), two Cu(I)-chelators. 4-Pyridyl-1-oxide-N-tert-butylnitrone (POBN)-spin trapping experiments showed that the reaction of TBHQ with Cu(II) resulted in the generation of POBN-CH(3) and POBN-CH(OH)CH(3) adducts in the presence of dimethyl sulfoxide (DMSO) and ethanol, respectively, suggesting the formation of hydroxyl radical or a similar reactive intermediate. The formation of POBN-CH(3) adduct from the TBHQ/Cu(II)+DMSO could be completely inhibited by catalase, GSH or BCS, indicating that the hydroxyl radical or its equivalent is generated from the interaction of H(2)O(2) with Cu(I). Incubation of supercoiled phiX-174 plasmid DNA with the TBHQ/Cu(II) resulted in extensive DNA strand breaks, which could be prevented by catalase or BCS. Incubation of rat hepatocytes with TBHQ in PBS led to increased formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in nuclear DNA. The TBHQ-induced formation of 8-OHdG was markedly reduced in the presence of cell permeable Cu(I)-specific chelator, bathocuproine or neocuproine, suggesting that a Cu(II)/Cu(I) redox mechanism may also be involved in the induction of oxidative DNA damage by TBHQ in hepatocytes. Taken together, the above results conclusively demonstrate that the activation of TBHQ by Cu(II) results in the formation of TBQ, semiquinone anion radical and reactive oxygen species (ROS), and that the ROS formed may participate in oxidative DNA damage in both isolated DNA and intact cells. These reactions may contribute to the carcinogenicity as well as other biochemical activities observed with BHA in animals. To our knowledge this study provides the first evidence that endogenous cellular Cu may be capable of bioactivating TBHQ, leading to oxidative DNA damage in cultured cells.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2001

Conformation and dynamics of normal and damaged DNA.

The genetic information that determines the structure and function of living organisms is encoded in the nucleotide sequence of double-stranded DNA molecules. Despite an apparent structural homogeneity displayed by DNA, subtle local variations in structure and dynamics are functionally significant. Short sequences exhibit specificity for regulatory and catalytic proteins, which mediate fundamental processes necessary to the survival of the cell. However, the molecular basis for specific recognition is still incompletely understood. The "indirect readout" mechanism suggests that the relative propensity of DNA to undergo structural deformations induced by the protein contributes to specific protein-DNA recognition. Although the hypothesis was originally formulated to explain recognition of specific nucleic acid sequences by DNA-binding proteins, it may have particular application to the recognition of DNA damage, because damaged sites in DNA have different equilibrium structure and dynamics from undamaged DNA. In this work, we review the approaches that we took to investigate the questions of sequence- and damage-dependent structure and dynamics of DNA. We describe a statistical thermodynamic model that relates DNA configurational flexibility to sequence-specific protein-DNA binding. The model provides a theoretical basis for interpreting experimental measurements of DNA dynamics. We describe results from MCSCF calculations of the excited states of 2-aminopurine (2AP), which provide the theoretical basis for the intramolecular mechanism of quenching as well as the effect of environment on this process. We then describe our investigations of the effect of stacking, base pairing, and base dynamics on the fluorescence of 2-AP in model systems, which allow us to develop the relationships between steady-state and time-resolved fluorescence parameters on the one hand and local structural and dynamic properties of DNA on the other hand. Finally, we describe the application of the experimental approach to study the conformational heterogeneity of DNA abasic sites, a commonly occurring type of DNA damage. We demonstrate the power of the experimental algorithm to characterize the physical differences between undamaged and damaged DNA, as well as the effects of nucleic acid sequence in both of these contexts. Thus, the work described herein comprises a combination of theoretical and experimental approaches to the problem of sequence- and damage-dependent DNA deformation.

2-Aminopurine↗

PubMed2005

Effects of motexafin gadolinium on DNA damage and X-ray-induced DNA damage repair, as assessed by the Comet assay.

PURPOSE: To investigate the effects of motexafin gadolinium (MGd) on the levels of reactive oxygen species (ROS), glutathione (GSH), and DNA damage in EMT6 mouse mammary carcinoma cells. The ability of MGd to alter radiosensitivity and to inhibit DNA damage repair after X-ray irradiation was also evaluated. METHODS AND MATERIALS: Reactive oxygen species and GSH levels were assessed by 2,7-dichlorofluorescein fluorescence flow cytometry and the Tietze method, respectively. Cellular radiosensitivity was assessed by clonogenic assays. Deoxyribonucleic acid damage and DNA damage repair were assessed in plateau-phase EMT6 cells by the Comet assay and clonogenic assays. RESULTS: Cells treated with 100 mumol/L MGd plus equimolar ascorbic acid (AA) had significantly increased levels of ROS and a 58.9% +/- 3.4% decrease in GSH levels, relative to controls. Motexafin gadolinium plus AA treatment increased the hypoxic, but not the aerobic, radiosensitivity of EMT6 cells. There were increased levels of single-strand breaks in cells treated with 100 mumol/L MGd plus equimolar AA, as evidenced by changes in the alkaline tail moment (MGd + AA, 6 h: 14.7 +/- 1.8; control: 2.8 +/- 0.9). The level of single-strand breaks was dependent on the length of treatment. Motexafin gadolinium plus AA did not increase double-strand breaks. The repair of single-strand breaks at 2 h, but not at 4 h and 6 h, after irradiation was altered significantly in cells treated with MGd plus AA (MGd + AA, 2 h: 15.8 +/- 3.4; control: 5.8 +/- 0.6). Motexafin gadolinium did not alter the repair of double-strand breaks at any time after irradiation with 10 Gy. CONCLUSIONS: Motexafin gadolinium plus AA generated ROS, which in turn altered GSH homeostasis and induced DNA strand breaks. The MGd plus AA-mediated alteration of GSH levels increased the hypoxic, but not aerobic, radiosensitivity of EMT6 cells. Motexafin gadolinium altered the kinetics of single-strand break repair soon after irradiation but did not inhibit potentially lethal damage repair in EMT6 cells.

Animals↗

PubMed2002

DNA damage induced by hypochlorite and hypobromite with reference to inflammation-associated carcinogenesis.

Hypohalites (OCl-, OBr-) are formed at inflammation sites as antimicrobial agents. OCl- is also used for the disinfection of water supplies and the association of drinking chlorinated water with cancer risk is pointed out. In this study, OCl- itself induced 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation, while OBr- damaged DNA only when glutathione (GSH) was added. OCl- caused oxidative DNA damage more efficiently than OBr-/GSH. In experiment with 32P-labeled DNA fragments, OCl- strongly caused piperidine-labile sites at guanine residues than piperidine-inert 8-oxodG, whereas OBr-/GSH caused no piperidine-labile sites. Endogenous OCl- may play a role in genotoxicity close to the site of inflammation.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2004

High levels of oxidative DNA damage in lymphocyte DNA of premenopausal breast cancer patients from Egypt.

Egypt shows a parallel increase in premenopausal breast cancer and environmental pollution. The purpose of this study is to explore a possible relationship between oxidative DNA damage, urinary estrogen metabolites and breast cancer in Egyptian premenopausal women. We conducted a pilot study of Egyptian breast cancer involving 29 cases and 32 controls and analysed lymphocyte DNA levels of 7,8-dihydro-8-oxo-2'-deoxyguanine (8-oxo-dG), a measure of oxidative DNA damage using high performance liquid chromatography with electro-chemical detection (HPLC-ECD) method. We analysed levels of urinary estrogen metabolites, 2-hydroxyestrone (2-OHE) and 16alpha-hydroxyestrone (16alpha-OHE) by an enzyme immuno assay. We also collected residential, occupational, and reproductive histories of all study subjects. We detected, in all subjects, exceptionally high levels of 8-oxo-dG and thus oxidative DNA damage, the levels (mean 8-oxo-dG/10(5) dG+/-SD) were significantly (P<0.01) higher in breast cancer cases (139.4+/-78.4) than in controls (60.9+/-51.5). Urinary 2-OHE and 16alpha-OHE or their ratio was not significantly different between cases and controls. However, 8-oxo-dG levels were positively correlated (P<0.05) with 2-OHE and 16alpha-OHE from cases while controls showed a negative correlation (P<0.05). Urban residence (Odds Ratio [OR] 3.1; Confidence interval [CI], 1.1-9.3), infertility (OR [9.8]; CI [1.1-89.7]), age (OR [2.6]; CI [1.4-4.6]) and 8-oxo-dG (OR 5.8; CI 1.9-17.5) levels were found to be significant predictors of breast cancer. Our finding of exceptionally high levels of 8-oxo-dG, a common result of oxidative DNA damage, warrant future studies on a larger population of premenopausal women in Egypt with consideration of other susceptibility markers and dietary characteristics.

Adult↗

PubMed2004

A fast Monte Carlo algorithm to simulate the spectrum of DNA damages formed by ionizing radiation.

Ionizing radiation produces both singly and multiply damaged DNA sites. Multiply damaged sites (MDS) have been implicated in radiation-induced cell killing and mutagenesis. The spatial distribution of elementary damages (strand breaks and base damages) that constitute MDS is of special interest, since the complexity of MDS has an impact on damage repair. A fast and easy-to-implement algorithm to simulate the local clustering of elementary damages produced by ionizing radiation is proposed. This algorithm captures the major trends in the DNA damage spectrum predicted using detailed track- structure simulations. An attractive feature of the proposed algorithm is that only four adjustable parameters need to be identified to simulate the formation of DNA damage. A convenient recipe to determine the parameters used in the fast Monte Carlo damage simulation algorithm is provided for selected low- and high-LET radiations. The good agreement among the damage yields predicted by the fast and detailed damage formation algorithms suggests that the small-scale spatial distribution of damage sites is determined primarily by independent and purely stochastic events and processes.

Algorithms↗

PubMed1994

Transcriptional and post-transcriptional responses to DNA-damaging agents.

New methods have recently advanced our understanding of cellular responses to agents that damage DNA directly, such as ionizing or ultraviolet irradiation. Although many of the signal transduction pathways have been dissected, information is still pending on the nature of the relevant initial cellular targets of DNA-damaging agents and on how the agents interact with them.

Animals↗

PubMed2003

The ASPP family: deciding between life and death after DNA damage.

It is well established that p53 is a primary target for mutation in human cancer. p53 carries out the important task of ensuring that damaged DNA is not passed on during cell division, a duty that it performs by either inhibiting the cell cycle or inducing apoptosis. However, it is unclear how this decision is made. The recent identification of the ASPP family of proteins, which act to direct the cell away from cell cycle arrest and towards death following p53 upregulation, may explain how this dilemma is resolved. Furthermore, the observation that ASPP2 is in fact the full length form of the previously identified 53BP2/Bbp protein has clarified the ambiguous data that has been generated in relation to this molecule. The further characterisation of these proteins will enable us to gain further insights into the response of the cell to DNA damage and the progression of the cell towards malignancy.

Apoptosis↗

PubMed1991

Platinum-DNA damage in leukocyte DNA of patients receiving carboplatin and cisplatin chemotherapy, measured by atomic absorption spectrometry.

Previous studies have shown that platinum-DNA adduct level in leukocyte DNA (measured by antibody methodology) is directly related to disease response in ovarian cancer and testicular cancer. To determine if this principle could be more broadly applied, platinum-DNA damage was studied in a blinded fashion in leukocyte DNA of 21 cancer patients who received carboplatin (day 1) and cisplatin (day 3) in a phase 1 clinical trial. Fifteen different tumor types were included in this cohort. Using atomic absorption spectrometry with Zeeman background correction, DNA-bound platinum was measured during cycles 1 (C1) and 2 (C2) of therapy for most patients. For each of two cycles of therapy, most patients developed measurable levels of adduct after carboplatin, and in most patients adduct levels increased further after cisplatin, often in a supra-additive fashion. Total mg dose levels varied by less than 2-fold, whereas individual patients differed by as much as 10(3) in their adduct measurements after C1 and after C2, and by 29-fold after the very first carboplatin dose. All patients had refractory disease at the initiation of therapy, and 19 patients were evaluable for disease response. Adduct determinations were made 24 h after the first dose of platinum therapy in 17 of these individuals. Mean adduct levels after the first dose of carboplatin were higher in six responders (50 fmol/micrograms DNA +/- 26) than in 11 non-responders (14 fmol/micrograms DNA +/- 10); Wilcoxon two sample test two-sided P = 0.0071. The six responders were patients with pleural mesothelioma (2), breast cancer, buccal mucosa cancer, esophageal cancer and ovarian cancer. Adduct levels were consistently higher in the group of responders on each day that adduct was measured, with a summary two-sided P value of 0.00011. We conclude that analysis of platinum-DNA adduct formation may help determine whether pharmacogenetics are important in cancer drug resistance; and may help to determine the relationship between DNA damage in the peripheral blood compartment and internal organ response to in vivo exposures to DNA-damaging agents.

Carboplatin↗

PubMed1987

Role of oxidants in DNA damage. Hydroxyl radical mediates the synergistic DNA damaging effects of asbestos and cigarette smoke.

The mechanism by which cigarette smoking and asbestos exposure synergistically increase the incidence of lung cancer is unknown. We hypothesized that cigarette smoke and asbestos might synergistically increase DNA damage. To test this hypothesis we exposed isolated bacteriophage PM2 DNA to cigarette smoke and/or asbestos, and assessed DNA strand breaks as an index of DNA damage. Our results supported our hypothesis. 78 +/- 12% of the DNA exposed to both cigarette smoke and asbestos developed strand breaks, while only 9.8 +/- 7.0 or 4.3 +/- 3.3% of the DNA exposed to cigarette smoke or asbestos, respectively, developed strand breaks under the conditions of the experiment. Our experimental evidence suggested that cigarette smoke and asbestos synergistically increased DNA damage by stimulating .OH formation. First, significant amounts of .OH were detected by electron paramagnetic resonance (EPR) in DNA mixtures containing both cigarette smoke and asbestos, but no .OH was detected in mixtures containing cigarette smoke alone or asbestos alone. Second, the .OH scavengers, dimethylsulfoxide (DMSO), mannitol, or Na benzoate decreased both .OH detection by EPR and strand breaks in DNA mixtures exposed to cigarette smoke and asbestos. Third, the H2O2 scavenger, catalase, and the iron chelators, 1,10-phenanthroline and desferrithiocin, decreased both .OH detection and strand breaks in DNA mixtures exposed to cigarette smoke and asbestos. These latter findings suggest that iron contained in asbestos may catalyze the formation of .OH from H2O2 generated by cigarette smoke. In summary, our study indicates that cigarette smoke and asbestos synergistically increase DNA damage and suggests that this synergism may involve .OH production.

Asbestos↗