Hydroxyl free radical mediated formation of 8-hydroxyguanine in isolated DNA

Floyd, Robert A.; West, Matthew B.; Eneff, K.L.; Hogsett, William E.; Tingey, David T.

doi:10.1016/0003-9861(88)90188-9

Cited by 156 publications

(57 citation statements)

References 10 publications

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“…The colorimetric assay [31] for methane sulfinic acid in biological materials that we used to demonstrate HO generation in fecal materials also produces a similarly shaped absorbance peaks at 420 nm when DMSO is oxidized by known sources of HO radicals. These standard sources of HO include gamma irradiated water [65] Fenton's reaction [65], and UV irradiated hydrogen peroxide [66][67]. Figure 1 shows the visible absorption spectra from a preliminary experiment, in which a 1:100 suspension of rat feces in TRIS Ringer buffer containing 5% (0.7 M) DMSO was incubated for 16 h at 37°C.…”

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confidence: 99%

Free radicals and the etiology of colon cancer

Babbs

1990

Free Radical Biology and Medicine

313

179

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This hypothesis paper reviews diverse evidence suggesting that intracolonic production of oxygen radicals may play a role in carcinogenesis. The hypothesis began to evolve when the author made the chance discovery that 1/10,000 dilutions of feces generated detectable quantities of highly reactive hydroxyl radicals (HO). The rate of HO formation, detected using DMSO as a molecular probe, was quite remarkable, corresponding to that which would be produced by over 10,000 rads of gamma irradiation per day, absorbed in the periphery of the fecal mass adjacent to the mucosa. The relatively high concentrations of iron in feces, together with the ability of bile pigments to act as iron chelators that support Fenton chemistry, may very well permit efficient HO generation from superoxide and hydrogen peroxide produced by bacterial metabolism. Such free radical generation in feces could provide a missing link in our understanding of the etiology of colon cancer: the oxidation of procarcinogens either by fecal HO, or by secondary peroxyl radicals (ROO) to form active carcinogens or mitogenic tumor promotors. Intracolonic free radical formation may explain the high incidence of cancer in the colon and rectum, compared to other regions of the GI tract, as well as the observed correlations of a higher incidence of colon cancer with red meat in the diet, which increases stool iron, and with excessive fat in the diet, which may increase the fecal content of procarcinogens and bile pigments. OVERVIEW OF THE HYPOTHESIS AND RELEVANT CHEMICAL MECHANISMSMy intention in this hypothesis paper is to present a new hypothesis suggesting how oxygen derived free radicals, generated in fecal material next to colonic epithelium, may play a significant role in the etiology of colon cancer. This hypothesis derives from an earlier conjecture by Graf and Eaton [1], coupled with the serendipitous discovery in our laboratory that highly reactive HO radicals can be produced abundantly by suspensions of feces under aerobic conditions. As do many other hypotheses for the pathogenic effects of oxygen centered free radicals in biologic systems [2][3][4][5][6], this one also invokes the superoxide driven Fenton reaction:In feces a ready biologic source of superoxide is the respiratory activity of bacteria [7][8][9][10], notably E. coli [11], perhaps together with spontaneous autoxidation of ferrous iron chelates that have been previously reduced by metabolites of the anerobic subpopulation of fecal flora. Another intriguing source of colonic superoxide is the lipoxygenase activity of normal or sloughed colonic epithelial cells [12]. The necessary iron is provided from the diet, since only a small fraction of dietary iron is absorbed in upper GI tract [13,14]. Hydroxyl (HO) radicals so formed within the colon could easily trigger a variety of carcinogenic mechanisms. For example, they could participate in aromatic hydroxylation reactions [15,16] to form carcinogenic products [17]; they could abstract hydrogen atoms from indoles to form radicals t...

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confidence: 99%

Free radicals and the etiology of colon cancer

Babbs

1990

Free Radical Biology and Medicine

313

179

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“…Ozone-exposed plants in general had nearly two-fold higher levels of 8-OHdG as compared to control plants. In (7,9,10). Hydroxyl free radicals react with DNA to yield numerous products; one is guanine, which becomes hydroxylated at the 8-carbon position (10, 16).…”

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“…The approach depends upon HPLC with electrochemical detection of products formed as a result of their reaction with oxygen free radicals, specifically hydroxyl free radicals. This approach has been used with either an exogenous hydroxyl free radical trap, salicylate (6,8), or an endogenous macromolecule, DNA (7,9,10). Hydroxyl free radicals react with DNA to yield numerous products; one is guanine, which becomes hydroxylated at the 8-carbon position (10,16).…”

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confidence: 99%

“…This approach has been used with either an exogenous hydroxyl free radical trap, salicylate (6,8), or an endogenous macromolecule, DNA (7,9,10). Hydroxyl free radicals react with DNA to yield numerous products; one is guanine, which becomes hydroxylated at the 8-carbon position (10,16). Following hydroxyl free radical reaction with DNA and its digestion to the nucleoside, 8-OHdG2 (7,10,16) can then be directly quantitated by LCED.…”

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confidence: 99%

“…Hydroxyl free radicals react with DNA to yield numerous products; one is guanine, which becomes hydroxylated at the 8-carbon position (10,16). Following hydroxyl free radical reaction with DNA and its digestion to the nucleoside, 8-OHdG2 (7,10,16) can then be directly quantitated by LCED. The detection sensitivity with LCED is 20 fmol (7).…”

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Increased 8-Hydroxyguanine Content of Chloroplast DNA from Ozone-Treated Plants

Floyd¹,

West²,

Hogsett³

et al. 1989

Plant Physiol.

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The mechanism of ozone-mediated plant injury is not known but has been postulated to involve oxygen free radicals. Hydroxyl free radicals react with DNA causing formation of many products, one of which is 8-hydroxyguanine. By using high performance liquid chromatography with electrochemical detection, the 8-hydroxy-2'-deoxyguanosine (8-OHdG) content of a DNA enzymatic digest can be sensitively quantitated. Beans (Phaseolus vulgaris L.) and peas (Pisum sativum L.) were treated with an ozone regime that caused acute injury. Chloroplast DNA was obtained from plants harvested either immediately after ozone treatment or 24 hours later. Ozone-exposed plants in general had nearly two-fold higher levels of 8-OHdG as compared to control plants. In (7,9,10). Hydroxyl free radicals react with DNA to yield numerous products; one is guanine, which becomes hydroxylated at the 8-carbon position (10, 16). Following hydroxyl free radical reaction with DNA and its digestion to the nucleoside, 8-OHdG2 (7, 10, 16) can then be directly quantitated by LCED. The detection sensitivity with LCED is 20 fmol (7). With DNA as an indicator of hydroxyl free radical occurrence and LCED methodology, it was possible to ascertain that oxidative damage to DNA had occurred in a living system subjected to oxidative stress (7). Kasai

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Overexpression of HSP25 reduces the level of TNFα-induced oxidative DNA damage biomarker, 8-hydroxy-2′-deoxyguanosine, in L929 cells

Park¹,

Han²,

Blackburn

1998

J. Cell. Physiol.

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Previously we and others have demonstrated that oxidative stress involving generation of reactive oxygen species (ROS) is responsible for the cytotoxic action of TNF alpha. Protective effect of small heat shock proteins (HSP) against diverse oxidative stress conditions has been suggested. Although overexpression of small HSP was shown to provide an enhanced survival of TNF alpha-sensitive cells when challenged with TNF alpha, neither the nature of TNF alpha-induced cytotoxicity nor the protective mechanism of small HSP has been completely understood. In this study, we have attempted to determine whether TNF alpha induces oxidative DNA damage in TNF alpha-sensitive L929 cells. We chose to measure the level of 8-hydroxy-2'-deoxyguanosine (8 ohdG), which has been increasingly recognized as one of the most sensitive markers of oxidative DNA damage. Our results clearly demonstrated that the level of 8 ohdG increased in L929 cells in a TNF alpha dose-dependent manner. Subsequently, we asked whether small HSP has a protective effect on TNF alpha-induced oxidative DNA damage. To accomplish this goal, we have stably transfected into L929 cells, which are devoid of endogenous small HSP, with the mouse small hsp cDNA (hsp25). We found that TNF alpha-induced 8 ohdG was decreased in cells overexpressing exogenous small HSP25. We also found that the cell-killing activity of TNF alpha was decreased in these cells as measured by clonogenic survival. Taken together, results from the current study show that a cytotoxic mechanism of TNF alpha involves oxidative damage of DNA, and that overexpression of the small HSP25 reduces this oxidative damage. We suggest that the reduction of oxidative DNA damage is an important protective mechanisms of small HSP against TNF alpha.

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Hydroxyl free radical mediated formation of 8-hydroxyguanine in isolated DNA

Cited by 156 publications

References 10 publications

Free radicals and the etiology of colon cancer

Free radicals and the etiology of colon cancer

Increased 8-Hydroxyguanine Content of Chloroplast DNA from Ozone-Treated Plants

Overexpression of HSP25 reduces the level of TNFα-induced oxidative DNA damage biomarker, 8-hydroxy-2′-deoxyguanosine, in L929 cells

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