Rapid and sensitive detection of hydroxyl radicals formed by activated neutrophils in the presence of chelated iron: hydroxylation of deoxyguanosine to 8-hydroxydeoxyguanosine

8-Hydroxyquinolines: a review of their metal chelating properties and medicinal applications

Metal ions play an important role in biological processes and in metal homeostasis. Metal imbalance is the leading cause for many neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis. 8-Hydroxyquinoline (8HQ) is a small planar molecule with a lipophilic effect and a metal chelating ability. As a result, 8HQ and its derivatives hold medicinal properties such as antineurodegenerative, anticancer, antioxidant, antimicrobial, anti-inflammatory, and antidiabetic activities. Herein, diverse bioactivities of 8HQ and newly synthesized 8HQ-based compounds are discussed together with their mechanisms of actions and structure–activity relationships.

Assays for urinary biomarkers of oxidatively damaged nucleic acids

The analysis of oxidized nucleic acid metabolites can be performed by a variety of methodologies: liquid chromatography coupled with electrochemical or mass-spectrometry detection, gas chromatography coupled with mass spectrometry, capillary electrophoresis and ELISA (Enzyme-linked immunosorbent assay). The major analytical challenge is specificity. The best combination of selectivity and speed of analysis can be obtained by liquid chromatography coupled with tandem mass spectrometric detection. This, however, is also the most demanding technique with regard to price, complexity and skills requirement. The available ELISA methods present considerable specificity problems and cannot be recommended at present. The oxidized nucleic acid metabolites in urine are assumed to originate from the DNA and RNA. However, direct evidence is not available. A possible contribution from the nucleotide pools is most probably minimal, if existing. Recent investigation on RNA oxidation has shown conditions where RNA oxidation but not DNA oxidation is prominent, and while investigation on DNA is of huge interest, RNA oxidation may be overlooked. The methods for analyzing oxidized deoxynucleosides can easily be expanded to analyze the oxidized ribonucleosides. The urinary measurement of oxidized nucleic acid metabolites provides a non-invasive measurement of oxidative stress to DNA and RNA.

Biomarkers in the assessment of therapies for familial amyloidotic polyneuropathy

The identification of specific biomarkers provides opportunities to develop early diagnostic parameters, monitor disease progression, and test drug efficiency in clinical trials. We previously demonstrated that in familial amyloidotic polyneuropathy (FAP) related to the abnormal extracellular tissue deposition of mutant transthyretin (TTR), inflammatory and apoptotic pathways are triggered in the presymptomatic stages of the disease, when nonfibrillar TTR deposits are present. In the present work, to better define biomarkers for future assessment of prophylactic and therapeutic drugs in the treatment of FAP, we extended the search for oxidative stress and apoptotic biomarkers to clinical samples and animal models presenting nonfibrillar and fibrillar TTR. We found that lipid peroxidation measured by hydroxynonenal, oxidative DNA damage measured by 8-hydroxy-2'-deoxyguanosine, and cellular redox homeostasis measured by glutaredoxin 1 were consistently increased in biopsy specimens from FAP patients and in tissues from transgenic mouse models presenting nonfibrillar TTR deposition. Death-receptor Fas, caspase-8, and Bax were also found to be increased, indicative of the involvement of death receptors in the observed apoptosis process. Removal of TTR deposition by an immunization protocol resulted in significant decreases of the selected markers we describe, corroborating the relationship between TTR deposition, oxidative stress, and apoptosis. Taken together, our results provide a robust biomarker profile for initial experimental animal studies and clinical trials to assess the application of the selected markers in therapies aimed at removal and/or inhibition of TTR polymerization.

Vitamin E and genome stability

Free radicals and reactive oxygen species (ROS) which are generated continuously cause mutagenic alterations resulting in cancer, aging and abnormalities in the nervous system. Accumulating evidence indicates that Vitamin E, the most potent lipid peroxyl radical scavenger, may reduce free radical induced chromosomal damages through inhibition of free radical formation, and activation of endonuclease that can be triggered by intracellular oxidative stress, and by increasing the rate of removal of damaged DNA. Although some studies suggest a potential usefulness of Vitamin E in the prevention of mutagenic effects caused by genotoxic free radicals, other studies report no effects. Thus the data are not conclusive enough to be used as a basis to change the current recommended dietary allowances (RDA). Future research should address molecular mechanisms underlying the protective effects of Vitamin E and develop appropriate biologically relevant biomarkers of DNA damage to further help in determining the dietary levels of Vitamin E needed to protect the genetic pool from internally and externally induced DNA damages.

Activated leukocytes oxidatively damage DNA, RNA, and the nucleotide pool through halide-dependent formation of hydroxyl radical

A variety of chronic inflammatory conditions are associated with an increased risk for the development of cancer. Because of the numerous links between DNA oxidative damage and carcinogenesis, a potential role for leukocyte-generated oxidants in these processes has been suggested. In the present study, we demonstrate a novel free transition metal ion-independent mechanism for hydroxyl radical ((*)OH)-mediated damage of cellular DNA, RNA, and cytosolic nucleotides by activated neutrophils and eosinophils. The mechanism involves reaction of peroxidase-generated hypohalous acid (HOCl or HOBr) with intracellular superoxide (O(2)(*)(-)) forming (*)OH, a reactive oxidant species implicated in carcinogenesis. Incubation of DNA with either isolated myeloperoxidase (MPO) or eosinophil peroxidase (EPO), plasma levels of halides (Cl(-) and Br(-)), and a cell-free O(2)(*)(-) -generating system resulted in DNA oxidative damage. Formation of 8-hydroxyguanine (8-OHG), a mutagenic base which is a marker for (*)OH-mediated DNA damage, required peroxidase and halides and occurred in the presence of transition metal chelators (DTPA +/- desferrioxamine), and was inhibited by catalase, superoxide dismutase (SOD), and scavengers of hypohalous acids. Similarly, exposure of DNA to either neutrophils or eosinophils activated in media containing metal ion chelators resulted in 8-OHG formation through a pathway that was blocked by peroxidase inhibitors, hypohalous acid scavengers, and catalytically active (but not heat-inactivated) catalase and SOD. Formation of 8-OHG in target cells (HA1 fibroblasts) occurred in all guanyl nucleotide-containing pools examined following exposure to both a low continuous flux of HOCl (at sublethal doses, as assessed by [(14)C]adenine release and clonogenic survival), and hyperoxia (to enhance intracellular O(2)(*)(-) levels). Mitochondrial DNA, poly A RNA, and the cytosolic nucleotide pool were the primary targets for oxidation. Moreover, modest but statistically significant increases in the 8-OHG content of nuclear DNA were also noted. These results suggest that the peroxidase-H(2)O(2)-halide system of leukocytes is a potential mechanism contributing to the well-established link between chronic inflammation, DNA damage, and cancer development.

Urinary 8-hydroxydeoxyguanosine excretion as a non-invasive marker of neutrophil activation in animal models of inflammatory bowel disease

BACKGROUND

Because free radicals contribute to ulcerative colitis and Crohn's disease, assessing oxidative load in vivo could provide a surrogate marker of inflammation and disease status.

METHODS

Electrochemical high-performance liquid chromatography was used to study urinary excretion of 8-hydroxydeoxyguanosine (8-OH-dGUA), formed by reaction of hydroxyl radicals with native DNA, in 2,4,6-trinitrobenzene-sulfonic acid (TNBS) and dextran sulfate (DSS) rat models of bowel inflammation. Bowel myeloperoxidase (MPO) and histopathology were also assessed.

RESULTS

TNBS enema (75 mg/kg in 50% ethanol) and oral DSS (6% via drinking water) both yielded an inflammatory response reflected by increases in bowel MPO that were significantly correlated with tissue injury. In both models urinary 8-OH-dGUA excretion was significantly correlated with bowel MPO activity and epithelial injury and remained at control levels when neutrophils (PMN) were eliminated, whereas epithelial injury and crypt erosion persisted despite neutropenia.

CONCLUSIONS

Urinary 8-OH-dGUA excretion directly reflects PMN activation in vivo, thereby providing a non-invasive surrogate marker for inflammation in these models which is more indicative of PMN activation than either MPO activity, which does not distinguish inactive from active MPO, or epithelial status, which is independent of PMN activation in both models.

Urinary 8-hydroxydeoxyguanosine in infants and children

Several diseases of prematurity are thought to be related to oxidative injury and many of the available markers are unsatisfactory. An assay was developed using HPLC with electrochemical detection for the quantitation of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a proposed indicator for oxygen-derived free radical injury to DNA in preterm infants. A median value of 3.79 micromol/mol creatinine was obtained for normal children (2-15 years old, n=14). Urinary 8-OHdG excretion in neonates ranged from 0-99 micromol/mol creatinine. There were no gestation or birthweight related differences in urinary 8-OHdG, and no correlation with urinary malondialdehyde. Mean 8-OHdG excretion increased with postnatal age (r=0.80, p < 0.0001, n=15), mirroring the growth velocity curve. These changes could also be due to changes in the activity of the enzyme responsible for 8-OHdG excision. Urinary 8-OHdG levels are unlikely to accurately reflect oxygen derived free radical activity given the strength of the relationship with growth.

Apoptosis overview emphasizing the role of oxidative stress, DNA damage and signal-transduction pathways

Apoptosis (programmed cell death) is a central protective response to excess oxidative damage (especially DNA damage), and is also essential to embryogenesis, morphogenesis and normal immune function. An understanding of the cellular events leading to apoptosis is important for the design of new chemotherapeutic agents directed against the types of leukemias and lymphomas that are resistant to currently used chemotherapeutic protocols. We present here a review of the characteristic features of apoptosis, the cell types and situations in which it occurs, the types of oxidative stress that induce apoptosis, the signal-transduction pathways that either induce or prevent apoptosis, the biologic significance of apoptosis, the role of apoptosis in cancer, and an evaluation of the methodologies used to identify apoptotic cells. Two accompanying articles, demonstrating classic apoptosis and non-classic apoptosis in the same Epstein-Barr virus-transformed lymphoid cell line, are used to illustrate the value of employing multiple criteria to determine the type of cell death occurring in a given experimental system. Aspects of apoptosis and programmed cell death that are not covered in this review include histochemistry, details of cell deletion processes in the sculpting of tissues and organs in embryogenesis and morphogenesis, and the specific pathways leading to apoptosis in specific cell types. The readers should refer to the excellent books and reviews on the morphology, biochemistry and molecular biology of apoptosis already published on these topics. Emphasis is placed, in this review, on a proposed common pathway of apoptosis that may be relevant to all cell types.

Hydrogen peroxide release and hydroxyl radical formation in mixtures containing mineral fibres and human neutrophils

The ability of different mineral fibres (rock wool, glass wool, ceramic fibres, chrysotile A, chrysotile B, amosite, crocidolite, antophyllite, erionite, and wollastonite) to stimulate hydrogen peroxide (H2O2) and hydroxyl radical (OH.) formation in mixtures containing human polymorphonuclear leucocytes (PMNLs) was investigated. In the presence of azide, all the fibres caused considerable H2O2 formation, and about twice as much H2O2 was found in mixtures with the natural fibres (asbestos, erionite, and wollastonite) than in mixtures with the manmade fibres (rock wool, glass wool, and ceramic fibres). In the presence of externally added iron, all the fibres were found to generate OH. and the natural fibres caused about three times more OH. formation than the manmade fibres. In the absence of external iron, there was less OH. formation; however, amosite, crocidolite, antophyllite, erionite, and wollastonite still generated considerable amounts of OH., also under circumstances in which only small amounts of OH. were produced in mixtures with the manmade fibres. These findings indicate that natural fibres generate more H2O2 and OH. than manmade fibres when incubated with PMNLs in the presence of external iron. They also suggest that the natural fibres, amosite, crocidolite, antophyllite, erionite, and wollastonite may act catalytically in the dissociation of H2O2 to OH. in the absence of external iron, whereas manmade fibres such as rock wool, glass wool, and ceramic fibres, do not seem to be able to generate OH. in the absence of external iron.