High Concentrations Of Reactive Oxygen Species Research Articles

Point:Counterpoint: Hypoxic pulmonary vasoconstriction is/is not mediated by increased production of reactive oxygen species

This series of debates was initiated for the Journal of Applied Physiology because we believe an important means of searching for truth is through debate where contradictory viewpoints are put forward. This dialectic process whereby a thesis is advanced, then opposed by an antithesis, with a

NAD(P)H:quinone oxidoreductase 1 expression in multiple sclerosis lesions

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS), marked by infiltration of monocyte-derived macrophages in the brain parenchyma. Macrophages contribute to disease pathology by secretion of inflammatory mediators, such as reactive oxygen species (ROS). ROS are involved in various processes underlying MS pathology, including monocyte migration across the blood-brain barrier, phagocytosis and degradation of myelin, axonal degeneration, and oligodendrocyte damage. High concentrations of ROS cause oxidative stress, which induces transcriptional activation of phase II detoxification enzymes, such as the antioxidant protein NAD(P)H:quinone oxidoreductase 1 (NQO1). Since NQO1 expression may act as an indicator of oxidative stress and knowledge about the cellular distribution pattern of NQO1 in MS brains is lacking, we examined the expression of NQO1 in various well-characterized MS lesions. Here, we show for the first time that NQO1 is highly upregulated in active and chronic active MS lesions, particularly in hypertrophic astrocytes and myelin-laden macrophages. We hypothesize that increased NQO1 expression may reflect an endogenous defense response against ROS-mediated cellular toxicity. Compounds that induce the production of endogenous antioxidant enzymes, such as NQO1, may be potential targets for future treatment strategies in MS.

SK channels are involved in the stimulation of intracellular Ca 2+ signals by reactive oxygen species (ROS) in intact endothelium

Increased production of ROS such as superoxide anions (O2−) is associated with endothelial dysfunction encountered in cardiovascular pathologies. An elevation of intracellular Ca2+ levels ([Ca2+]i) has been reported in cultured endothelium exposed to high concentration of ROS. However, the impact of O2− on [Ca2+]i dynamics remains to be determined in native endothelium. Therefore, the effects of O2− on Ca2+ signals in the endothelium of cut-open mesenteric arteries from mouse were investigated, using fluo-4 and laser scanning confocal microscopy. Endothelial cells in this preparation exhibit a variety of spontaneous Ca2+ signals (waves and oscillations). Catalase (500 U/ml) had little, if any, effect on basal [Ca2+]i or Ca2+ signals. In contrast, exposure to superoxide dismutase (SOD) (100 U/ml) decreased by 50% the frequency of spontaneous activity. Exposure to O2− caused a rise in global Ca2+ levels, along with a 2- to 3-fold increase in amplitude and frequency of Ca2+ waves, sustained for at least 10 min. The stimulatory effects of O2− on Ca2+ signals did not require extracellular Ca2+, but its maintenance did, suggesting a dependence on the Ca2+ electrochemical gradient. Consistently, blocking SK channels with apamin caused a membrane depolarization, and decreased the long term elevation of Ca2+ signaling by O2−. Therefore, basal production of O2−, but not H2O2, stimulates intracellular Ca2+ signaling in intact endothelium. Furthermore, sustained effects of O2− on [Ca2+]i and its dynamics requires extracellular Ca2+ entry, which is modulated by SK channel-regulation of endothelial membrane potential. Supported by NIH (HL63722 & HL44455) and CIHR.

Evaluation of a urinary multi-parameter biomarker set for oxidative stress in children, adolescents and young adults

The involvement of reactive oxygen species (ROS) and oxidative stress in pediatric diseases is an important concern, but oxidative stress status in healthy young subjects and appropriate methods for its measurement remain unclear. This study evaluated a comprehensive set of urinary biomarkers for oxidative stress in healthy children, adolescents and young adults. Results show that urinary excretion of acrolein–lysine, 8-hydroxy-2′-deoxyguanosine (8-OHdG), nitrite/nitrate and pentosidine were highest in the youngest subjects and decreased to constant levels by early adolescence. Urinary acrolein–lysine, 8-OHdG, nitrite/nitrate and pentosidine showed significant inverse correlations with age, but pyrraline did not change significantly with age. No significant differences in biomarkers were apparent between males and females. Younger subjects grow rapidly and sustain immune activation, and are probably exposed to high concentrations of ROS and nitric oxide. Consequently, they are more vulnerable to oxidation of lipids, proteins, DNA and carbohydrates. Normal reported values in this study are a basis for future studies of disease mechanisms involving oxidative stress and for future trials using antioxidant therapies for oxidative stress-related diseases in the pediatric field.

Oxidative stress and ageing: is ageing a cysteine deficiency syndrome?

Reactive oxygen species (ROS) are constantly produced in biological tissues and play a role in various signalling pathways. Abnormally high ROS concentrations cause oxidative stress associated with tissue damage and dysregulation of physiological signals. There is growing evidence that oxidative stress increases with age. It has also been shown that the life span of worms, flies and mice can be significantly increased by mutations which impede the insulin receptor signalling cascade. Molecular studies revealed that the insulin-independent basal activity of the insulin receptor is increased by ROS and downregulated by certain antioxidants. Complementary clinical studies confirmed that supplementation of the glutathione precursor cysteine decreases insulin responsiveness in the fasted state. In several clinical trials, cysteine supplementation improved skeletal muscle functions, decreased the body fat/lean body mass ratio, decreased plasma levels of the inflammatory cytokine tumour necrosis factor alpha (TNF-alpha), improved immune functions, and increased plasma albumin levels. As all these parameters degenerate with age, these findings suggest: (i) that loss of youth, health and quality of life may be partly explained by a deficit in cysteine and (ii) that the dietary consumption of cysteine is generally suboptimal and everybody is likely to have a cysteine deficiency sooner or later.

Antioxidant defense properties of Arctic amphipods: comparison between deep-, sublittoral and surface-water species

The toxic reactive oxygen species (ROS), produced naturally in an oxygenated environment, led to the development of antioxidant defenses by aerobic organisms to prevent tissue damage. Polar marine waters are regarded as a strongly prooxidant ecosystem, due to the high dissolved oxygen level and intense UV radiation during summer, while the deep waters are considered refuges against oxidative stress. In order to further elucidate the prooxidant and antioxidant forces associated with cold-water ecosystems and the implications of UV radiation, we sampled three amphipod species living at three different depths in the same water mass of the Arctic Ocean, characterized by low temperature (ca. 0°C), high oxygen level, and high ROS concentration in the surface water. The three species were the deep-sea amphipod Eurythenes gryllus, the benthic sublittoral amphipod Anonyx nugax and the surface-water species Gammarus wilkitzkii inhabiting the ice pack. The total oxyradical scavenging capacity (TOSC) was measured in the cytosolic fraction of the digestive gland and in the cell-free hemolymph of the three amphipod species. A significantly low TOSC toward peroxyl and peroxynitrite radicals (P 0.05) was noted in G. wilkitzkii. These data suggest that A. nugax is highly susceptible to oxidative stress and that G. wilkitzkii is characterized by a mechanism that prevents the diffusion of exogenous ROS through the gills or allows excretion of internal H2O2 through the gills to the environment.

Mitochondrial dysfunction, apoptotic cell death, and Alzheimer’s disease

Being major sources of reactive oxygen species (ROS), mitochondrial structures are exposed to high concentrations of ROS and might therefore be particularly susceptible to oxidative injury. Mitochondrial damage may play a pivotal role in the cell death decision. Bolstered evidence indicates that mitochondrial abnormalities might be part of the spectrum of chronic oxidative stress occurring in Alzheimer’s disease (AD) finally contributing to synaptic failure and neuronal degeneration. Accumulation and oligomerization of amyloid beta (Aβ) is also thought to play a central role in the pathogenesis of this disease by probably directly leading to mitochondrial dysfunction. Moreover, numerous lines of findings indicate increased susceptibility to apoptotic cell death and increased oxidative damage as common features in neurons from sporadic AD patients but also from familial AD (FAD) cases. Here we provide a summary of recent work demonstrating some key abnormalities that may initiate and promote pathological events in AD. Finally, we emphasize a hypothetical sequence of the pathogenic steps linking sporadic AD, FAD, and Aβ production with mitochondrial dysfunction, caspase pathway, and neuronal loss.

Effects of EGb 761 Ginkgo biloba extract on mitochondrial function and oxidative stress.

As major sources of reactive oxygen species (ROS), mitochondrial structures are exposed to high concentrations of ROS and may therefore be particularly susceptible to oxidative damage. Mitochondrial damage could play a pivotal role in the cell death decision. A decrease in mitochondrial energy charge and redox state, loss of transmembrane potential (depolarization), mitochondrial respiratory chain impairment, and release of substances such as calcium and cytochrome c all contribute to apoptosis. These mitochondrial abnormalities may constitute a part of the spectrum of chronic oxidative stress in Alzheimer's disease. Accumulation of amyloid beta (Abeta) in form of senile plaques is also thought to play a central role in the pathogenesis of Alzheimer's disease mediated by oxidative stress. In addition, increasing evidence shows that Abeta generates free radicals in vitro, which mediate the toxicity of this peptide. In our study, PC12 cells were used to examine the protective features of EGb 761(definition see editorial) on mitochondria stressed with hydrogen peroxide and antimycin, an inhibitor of complex III. In addition, we investigated the efficacy of EGb 761 in Abeta-induced MTT reduction in PC12 cells. Moreover, we examined the effects of EGb 761 on ROS levels and ROS-induced apoptosis in lymphocytes from aged mice after in vivo administration. Here, we will report that EGb 761 was able to protect mitochondria from the attack of hydrogen peroxide, antimycin and Abeta. Furthermore, EGb 761 reduced ROS levels and ROS-induced apoptosis in lymphocytes from aged mice treated orally with EGb 761 for 2 weeks. Our data further emphasize neuroprotective properties of EGb 761, such as protection against Abeta-toxicity, and antiapoptotic properties, which are probably due to its preventive effects on mitochondria.

Dose effect of oxidative stress on signal transduction in aging

Reactive oxygen species (ROS) during normal metabolism signal cells to stimulate proliferation or to cause cellular damages, depending on a specific concentration. Energy restriction (ER) increases life span in animals, which can explain an effective modulator for reducing oxidative stress. Oxidative stress can result from a decrease in the protection against ROS. The deleterious effects of oxidative stress generally occur after exposure to a relatively high concentration of ROS. Alternatively, it has been suggested that a low concentration of ROS can exert important physiological roles in cellular signaling and proliferation. Signal pathways are crucial for cell survival or death. It is generally acceptable that aged cells have less response to stresses such as ROS than young cells. Oxidative stresses induce JNK and p38 kinase pathways regulated by redox regulatory proteins: thioredoxin and glutathione s-transferase, respectively. Antioxidants such as selenium block apoptosis induced by ROS through blocking apoptotic signal ASK1 and stimulating survival signal Akt activity. Old hepatocytes are more susceptible to ROS-induced apoptosis than young hepatocytes, which is associated with low expression of ERK and Akt kinases. Pharmacological inhibition of ERK and Akt activation in the young cells markedly increase their sensitivity to H 2O 2, and ER, by preventing loss of ERK and Akt activities, enhances survival of old hepatocytes to a level similar to those of young cells. Expressions of signal pathways such as survival and apoptotic signals can regulate cells’ fate and aging process. Further studies on the interaction of signal pathways may change the scientific direction of the study of aging.

The thioredoxin system of Plasmodium falciparum and other parasites.

Antioxidant defence plays a crucial role in rapidly growing and multiplying organisms, including parasites and tumor cells. Apart from reactive oxygen species (ROS) produced in endogenous reactions, parasites are usually exposed to high ROS concentrations imposed by the host immune system. The glutathione and thioredoxin systems represent the two major antioxidant defence lines in most eukaryotes and prokaryotes. Trypanosomatids, however, are characterized by their unique trypanothione system. These systems are NADPH-dependent and based on the catalytic activity of the flavoenzymes glutathione reductase, trypanothione reductase and thioredoxin reductase (TrxR), respectively. TrxR reduces the 12-kDa protein thioredoxin (Trx), which in turn provides elcctrons to ribonucleotide reductase, thioredoxin peroxidases (TPxs), certain transcription factors and other target molecules. Comparing the thioredoxin systems of different parasites and their respective host cells enhances our understanding of parasite biology and evolution, of parasite-host interactions and mechanisms of drug resistance. It furthermore opens avenues for the development of novel antiparasitic compounds. Here we review the current knowledge on the Trx systems of eukaryotic parasites, finally focusing on the malarial parasite Plasmodium falciparum.

A newly adapted pulsed-field gel electrophoresis technique allows to detect distinct types of DNA damage at low frequencies in human dermal fibroblasts upon exposure to non-toxic H2O2 concentrations

Reactive oxygen species (ROS) comprise several oxygen containing compounds, among them hydrogen peroxide (H2O2), which are generated by internal and external sources and play pleiotropic roles in physiological and pathological states. Skin cells as well as cells from other tissues have developed antioxidant defense mechanisms to protect themselves from high concentrations of ROS. Although biological and pathological roles of ROS have previously been elucidated, so far only limited knowledge exists regarding ROS-mediated generation of DNA breaks and base lesions occurring at low frequency in intact skin cells. This study was therefore designed to probe a newly adapted pulsed-field gel electrophoresis technique for the adequate measurement of high molecular weight DNA fragments as well as to investigate the protective role of the antioxidant enzyme catalase against H2O2-mediated damage in human dermal fibroblasts. We stably transfected and overexpressed the full-length catalase cDNA in the human dermal fibroblast cell line 1306 in culture and found that these cells are significantly more protected from cytotoxicity, overall DNA strand breaks, and 8-oxodeoxyguanine base lesions resulting from H2O2-triggered oxidative stress compared to vector-transfected 1306 cells or secondary dermal fibroblasts. This work has outlined the importance of catalase in the protection from H2O2-mediated cytotoxicity and DNA damage which — if unbalanced — even when occurring at low frequency are known to lead to genomic instability, a hallmark in carcinogenesis and premature aging.