Publications

Vitamin C Protects Against Hypochlorous Acid–Induced Glutathione Depletion and DNA Base and Protein Damage in Human Vascular Smooth Muscle Cells

Hypochlorous acid (HOCl), generated by myeloperoxidase released from activated macrophages, is thought to contribute to vascular dysfunction and oxidation of low density lipoproteins (LDLs) in atherogenesis. We have previously shown that HOCl exposure can cause chlorination and oxidation of isolated DNA and that vitamin C protects human arterial smooth muscle cells against oxidized LDL-mediated damage. We report in the present study that vitamin C attenuates HOCl-induced DNA base and protein damage and depletion of intracellular glutathione (GSH) and ATP in human arterial smooth muscle cells. Cells were pretreated in the absence or presence of 100 micromol/L vitamin C (24 hours) and then exposed to HOCl (0 to 500 micromol/L, 0 to 60 minutes) in the absence of vitamin C. Intracellular GSH and ATP levels were depleted by HOCl treatment, and gas chromatography-mass spectroscopy revealed a concentration- and time-dependent increase in DNA base oxidation and protein damage (measured as 3-chlorotyrosine). Pretreatment of smooth muscle cells with vitamin C significantly reduced the extent of HOCl-induced DNA and protein damage and attenuated decreases in intracellular ATP and GSH. Our findings suggest that physiological levels of vitamin C provide an important antioxidant defense against HOCl-mediated injury in atherosclerosis.

The wanderings of a free radical

In my career I have moved from chemistry to biochemistry to plant science to clinical chemistry and back again (in a partial way) to plants. This review presents a brief history of my research achievements (ascorbate–glutathione cycle, role of iron in oxidative damage and human disease, biomarkers of free radical damage, and studies on atherosclerosis and neurodegeneration) and how they relate to my research activities today. The field of free radicals/other reactive species/antioxidants underpins all of modern Biology. These agents helped to drive human evolution and the basic principles of the field are repeatedly found to be relevant in other research areas. It was an exciting field when I started some 40 years ago, and it still is today, but some major challenges must be faced.

Vitamin C: the key to health or a slow-acting carcinogen?

Different cytotoxic and clastogenic effects of epigallocatechin gallate in various cell-culture media due to variable rates of its oxidation in the culture medium

Positive genotoxicity results are often observed using mammalian cells in culture with agents that are not in vivo genotoxins. We here illustrate one possible explanation: interaction of test chemicals with the cell-culture media used. We find that the toxicity and clastogenicity of epigallocatechin gallate (EGCG) to Chinese Hamster ovary (CHO) cells is affected by the culture medium used and appears largely or entirely due to variable rates of formation of hydrogen peroxide (H2O2) by chemical reactions of EGCG with the culture media. Catalase decreased EGCG toxicity substantially. Of seven different types of commonly used media evaluated, F-10 and F-12 nutrient mixtures were the least prone to produce this artefact. Although it generated H2O2 in the culture media, ascorbate was not toxic to CHO cells because the H2O2 levels achieved were insufficient to kill these cells. Thus, the culture medium, the cell type and the presence or absence of catalase (e.g. its variable amounts in S9 fractions) must be taken into account in in vitro genotoxicity testing.

Evidence for the generation of reactive nitrogen species following high nitrate consumption

SULPHASALAZINE AND OXIDANT SCAVENGING IN ULCERATIVE COLITIS

DNA strand breakage and base modification induced by hydrogen peroxide treatment of human respiratory tract epithelial cells

Treatment of human respiratory tract epithelial cells with H 2 O 2 led to concentration‐dependent DNA strand breakage that was highly‐correlated with multiple chemical modifications of all four DNA bases, suggesting that damage is due to hydroxyl radical, OH . . However, the major base damage occurred to adenine. Hence, conclusions made about the occurrence and the extent of oxidative DNA damage on the basis only of changes in 8‐hydroxyguanine should be approached with caution.

The Biochemistry of Plants: A Comprehensive Treatise

Clofibrate induced oxidative stress in liver “the role of mitochondria”

Of Oxygen, Fuels and Living Matter, Part 2

Oxygen radicals and the nervous system

The brain has a high oxygen consumption and is rich in oxidizable substrates, mainly catecholamines and unsaturated lipids. Much interest has been shown recently in ‘oxygen radicals’ as mediators of the action of certain neurotoxins, in the role of vitamin E in the nervous system and in the possible use of anti-oxidants in treating degenerative diseases of the nervous system and the consequences of ischaemia. The purpose of this brief review is to explain some of the scientific background to these developments.

Are age-related neurodegenerative diseases caused by a lack of the diet-derived compound ergothioneine?

We propose that the diet-derived compound ergothioneine (ET) is an important nutrient in the human body, especially for maintenance of normal brain function, and that low body ET levels predispose humans to significantly increased risks of neurodegenerative (cognitive impairment, dementia, Parkinson's disease) and possibly other age-related diseases (including frailty, cardiovascular disease, and eye disease). Hence, restoring ET levels in the body could assist in mitigating these risks, which are rapidly increasing due to ageing populations globally. Prevention of neurodegeneration is especially important, since by the time dementia is usually diagnosed damage to the brain is extensive and likely irreversible. ET and vitamin E from the diet may act in parallel or even synergistically to protect different parts of the brain; both may be "neuroprotective vitamins". The present article reviews the substantial scientific basis supporting these proposals about the role of ET.

Properties and physiological function of a glutathione reductase purified from spinach leaves by affinity chromatography

No abstract is provided for this article.

Antioxidants in wine

Making Sense of Neurodegeneration: A Unifying Hypothesis

Factors influencing uptake and blood levels of ergothioneine and selenoneine

Establishing Biomarkers of Oxidative Stress: The Measurement of Hydrogen Peroxide in Human Urine

Hydrogen peroxide (H(2)O(2)) can be detected in freshly-voided human urine from healthy subjects and has been proposed as a "biomarker" of oxidative stress. This paper summarizes our studies to examine the extent to which urinary H(2)O(2) measurement fulfils the criteria for the "ideal biomarker". Levels of H(2)O(2), standardised for creatinine, varied widely between subjects. In most subjects, levels also varied considerably when measurements were made at different times and on different days. A reproducible increase in urinary H(2)O(2) was detected in all subjects examined after drinking coffee, a beverage rich in H(2)O(2). By contrast, green tea decreased urinary H(2)O(2) levels. We conclude that the H(2)O(2) in coffee is not excreted into urine. Instead, hydroxyhydroquinone from coffee is absorbed, excreted and oxidises in urine to produce H(2)O(2). No other confounders of urinary H(2)O(2) have been identified to date. Work is underway to compare H(2)O(2) levels with variations in other biomarkers of oxidative damage, to test the possibility that there are daily or other periodic variations in oxidative damage rates.

Reactive Oxygen Species: Radical Factors in the Evolution of Animal Life

Introduction of O 2 to Earth's early biosphere stimulated remarkable evolutionary adaptations, and a wide range of electron acceptors allowed diverse, energy‐yielding metabolic pathways. Enzymatic reduction of O 2 yielded a several‐fold increase in energy production, enabling evolution of multi‐cellular animal life. However, utilization of O 2 also presented major challenges as O 2 and many of its derived reactive oxygen species (ROS) are highly toxic, possibly impeding multicellular evolution after the Great Oxidation Event. Remarkably, ROS, and especially hydrogen peroxide, seem to play a major part in early diversification and further development of cellular respiration and other oxygenic pathways, thus becoming an intricate part of evolution of complex life. Hence, although harnessing of chemical and thermo‐dynamic properties of O 2 for aerobic metabolism is generally considered to be an evolutionary milestone, the ability to use ROS for cell signaling and regulation may have been the first true breakthrough in development of complex life.

DNA damage and cancer: Measurement and mechanism

There is currently great interest in the possible role of reactive nitrogen species and reactive oxygen species in causing DNA damage that leads to cancer. It appears likely that certain reactive oxygen species can act as complete carcinogens. However, the development of human cancer will depend on other factors such as the extent of DNA damage, antioxidant levels and DNA repair systems. The true picture will only be seen if we have reliable and sensitive techniques for the measurement of DNA damage. In this article we outline various methods for measuring DNA damage base, with special emphasis on HPLC and GC-MS based systems.