SEARCH · PubMed Health

Results for “ROS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources

PubMed1992

Phosphatidic acid and polyphosphoinositide metabolism in rod outer segments. Differential role of soluble and peripheral proteins.

The phosphorylation of endogenous diacylglycerol (DAG) and phosphoinositides by [tau-32P]ATP was studied in bovine rod outer segments (ROS) selectively depleted of soluble or peripheral and soluble proteins by treatment with moderate (100 mM) or low (5 mM) ionic strength medium, respectively. DAG kinase activity was similar in bleached and non-bleached ROS extracted with 100 mM medium, and amounted to 70% of that observed in the corresponding non-extracted ROS. Phosphatidic acid (PtdH) labelling in ROS extracted in the dark with low ionic strength medium was markedly lower than in those extracted in light. Thus, even when a major proportion of DAG kinase was associated to the membrane, a soluble form also occurred. Most of the membrane-bound fraction behaved as a peripherally associated protein, its binding to the membrane being modified by light. Ir ROS extracted at moderate ionic strength the labelling of inositides was similar to that in non-extracted ROS. A marked enhancement in polyphosphoinositide labelling was observed in ROS extracted in the dark with low ionic strength. Alkaline treatment of ROS also produced inhibition of polyphosphoinositide phosphorylation. A peripheral form of a type C phospholipase, or a peripheral protein-mediated activation of a particulate form thereof, is suggested. Labelled polyphosphoinositides were more actively hydrolyzed in the light and in the dark plus GTP tau S than in the dark-incubated membranes. The results of phosphorylation experiments in membranes where differential extraction of the alpha subunit of transducin was carried out suggest that alpha and beta tau subunits may play opposite modulating roles in PtdH and polyphosphoinositide metabolism.

Animals↗

PubMed1990

Unique molecular species composition of glycerolipids of frog rod outer segments.

The composition and metabolism of molecular species of glycerolipids, including phosphatidic acid (PA), phosphatidylinositol (PI) and diacylglycerol (DG), were studied in four frog retinal fractions prepared by discontinuous sucrose gradient centrifugation. Six glycerolipid classes were isolated from the lipid extracts of each fraction and converted to their corresponding 1,2-diacylglycerol acetates by acetolysis for quantitation of their molecular species by HPLC. Rod outer segments (ROS) showed a distinctive molecular species composition in all glycerolipid classes except phosphatidylcholine (PC). The relative amounts of dipolyunsaturated species in ROS were higher in phosphatidylethanolamine (PE), phosphatidylserine (PS), and PA, compared to the other retinal fractions. PI and DG of ROS had a similar molecular species composition and contained only small amounts of dipolyunsaturated species. A unique feature of the molecular species of ROS PI and DG was that they had high amounts of species containing docosahexaenoic acid (22: 6 omega 3), while PI and DG from the other retinal membranes consisted mostly of species containing arachidonic acid (20: 4 omega 6). Following in vitro incubation of frog retinas with [2-3H] glycerol, the mass and radioactivity distributions among molecular species were determined following HPLC fractionation. The unique species composition of PS in ROS is determined mainly by selective translocation from the inner segments to ROS, since the dpm %, representative of newly synthesized species composition of the same glycerolipid classes in the other membrane fractions. This suggests that the distinctive species composition of PE and PA in ROS is determined not by selective translocation from the inner segments, but by remodeling processes taking place in the ROS.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1996

Why are mitochondria involved in apoptosis? Permeability transition pores and apoptosis as selective mechanisms to eliminate superoxide-producing mitochondria and cell.

Petit and co-authors have recently summarized results of their studies on the involvement of mitochondria in apoptosis [Petit et al. (1996) FEBS Lett. 396, 7-13]. The mechanism consists in the release to the cytosol of a protein (presumably a protease) that is normally sequestered in the intermembrane space of mitochondria. This protein, when added to isolated nuclei, caused typical apoptotic changes. Its release from mitochondria was shown to occur as a result of disruption of the outer mitochondrial membrane due to swelling of mitochondria caused by opening of so-called permeability transition pores in their inner membranes. Increase in the level of products of the one-electron reduction of O2 (reactive oxygen species, ROS) is known to induce the mitochondrial pores. The hypothesis described here assumes that pore formation and apoptosis are involved in the organization of a defense system preventing ROS formation. It is proposed that ROS-induced pore opening lowers ROS production due to (a) maximal stimulation of mitochondrial O2 consumption and, hence, intracellular [O2] lowering and (b) complete dissipation of mitochondrial membrane potentials and, as a consequence, maximal oxidation of such respiratory chain carriers as CoQ.- which serve as one-electron O2 reductants. ROS decrease allows pore closure. If, nevertheless, ROS are still accumulating in a mitochondrion, long-lived pores cause degradation of the organelle which cannot import and synthesize proteins due to the absence of the membrane potential. In this way, ROS-producing mitochondria can be eliminated (mitochondrial selection). Another result of the long-lived pores is mitochondrial swelling. This disrupts the outer mitochondrial membrane and releases the apoptosis-inducing protein. Apoptosis eliminates ROS-producing cells (cell selection).

Animals↗

PubMed1995

Evaluation of oxidative stress in patients with hyperlipidemia.

An antioxidant defense system consisting of enzymes and non-enzymatic compounds prevents oxidative damage of lipoproteins in the plasma. When the activity of this system decreases or the reactive oxygen species (ROS) production increases, an oxidative stress may occur. Since fatty acids and triglyceride-rich emulsions can stimulate leukocytes to produce ROS, it is conceivable that raised plasma triglyceride-rich lipoproteins such as very low density lipoprotein (VLDL) may overload the antioxidant system. To test this hypothesis, we selected 14 patients with combined hyperlipidemia (HLP), in whom low density lipoprotein (LDL) and VLDL levels are elevated, as well as 18 hypercholesterolemic patients (HCH) with increased LDL levels and 19 controls (NL) to examine the trend for an imbalance between the production of oxidative species and the antioxidant defense system as challenged by increased plasma lipids. With this goal, plasma lipoprotein lipid fractions were determined and correlated with the release of ROS by leukocytes monitored by luminol-enhanced chemiluminescence. Plasma beta-carotene, alpha-tocopherol, lycopene and the lipoprotein lipid hydroperoxides were determined by high pressure liquid chromatography with electrochemical detection. HLP had lower plasma superoxide dismutase (SOD) activity (0.04 and 0.11 U/mg protein; P < 0.05) as well as lower concentrations of lycopene (0.1 and 0.2 nmol/mg cholesterol; P < 0.05) and beta-carotene (0.8 and 2.7 nmol/mg cholesterol; P < 0.05) in the plasma, as compared with NL. Moreover, HLP showed the highest ROS production by resting mononuclear leukocytes (MN) among the three study groups. When the results of the subjects of the three groups were taken together, the plasma triglyceride concentration was positively correlated to ROS release by resting polymorphonuclear leukocytes (PMN, r = 0.38, P = 0.04) and MN (r = 0.56, P < 0.005). Moreover, ROS release by resting MN was positively correlated with VLDL (r = 0.47, P = 0.02) and LDL (r = 0.57, P = 0.01) triglycerides. There was also a positive correlation between ROS release by stimulated PMN and VLDL (r = 0.44, P = 0.03) as well as LDL (r = 0.53, P = 0.01) triglycerides. High density lipoprotein (HDL) cholesterol showed a negative correlation with ROS release by resting MN (r = -0.48, P = 0.02) and resting PMN (r = -0.49, P = 0.01). VLDL susceptibility to copper (II) oxidation was not different among the three groups. Regarding LDL, there was an increased oxidizability in HLP group.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1991

Modification of cardiac ionic currents by photosensitizer-generated reactive oxygen.

The effects of reactive oxygen species (ROS) generated by light and the photosensitizer Rose Bengal on ionic currents in single frog atrial cells were investigated. The excitatory inward sodium and calcium currents were both suppressed by ROS as was the outward, delayed rectifier potassium current. The inactivation kinetics of the sodium current were slowed markedly whereas the kinetics of calcium current inactivation were much less affected and potassium current activation was not changed. The sodium current-voltage relationship was shifted in the depolarizing direction by ROS whereas the voltage-dependencies of both the calcium and potassium currents were not affected. In addition to suppressing the time- and voltage-dependent sodium, calcium, and potassium currents, ROS enhanced a time-independent current which was outwardly directed at positive membrane potentials. However, the induction of this time-independent current required longer ROS exposure than was required to significantly suppress the other currents. The rapid onset of ROS-induced suppression of calcium and potassium currents followed by a later enhancement of a time-independent current can explain ROS-induced changes in action potential duration. Brief ROS exposure increased action potential duration whereas longer exposure reduced action potential duration.

Action Potentials↗

PubMed2005

In vitro maturation and fertilization of porcine oocytes after a 48 h culture in roscovitine, an inhibitor of p34cdc2/cyclin B kinase.

Maintaining oocytes at the germinal vesicle (GV) stage in vitro may permit enhanced acquisition of the developmental competence. The objective of the current study was to evaluate the nuclear and cytoplasmic maturation in vitro of porcine oocytes after pretreatment with S-roscovitine (ROS). Cumulus oocyte complexes (COC) were treated with 50 microM ROS for 48 h and then matured for various lengths of time in a conventional step-wise in vitro maturation (IVM) system by using dibutyryl cyclic AMP. The COC that were matured in the same system for 44 h without pretreatment with ROS were used as the control group. At various periods after the start of IVM, oocytes were assessed for the meiotic stages and subjected to in vitro fertilization (IVF) with fresh spermatozoa. The ROS treatment inhibited GV breakdown of 94.4% oocytes, with the majority arrested at the GV-I stage (67.4%). Maximum maturation rate to the metaphase-II stage after ROS treatment was achieved by 44 h of IVM (92.1%) and no differences were observed with control oocytes (95.0%). Penetration rate was correlated to the maturation rate. The duration of IVM had no effects on polyspermy and male pronuclear (MPN) formation rates at 8 h post insemination (hpi), whereas both rates increased at 22 hpi. Direct comparison with controls assessed at 22 hpi confirmed a lesser MPN formation in ROS-treated oocytes (73.7% compared with 53.6%). Glutathione (GSH) concentrations were less in oocytes treated with ROS than in control oocytes (5 compared with 7.7 pmol/oocyte) as well as blastocyst rate (22.0% compared with 38.1%, respectively). These results demonstrate that cytoplasmic maturation in porcine oocytes pretreated with ROS for 48 h did not equal that of control oocytes in the current IVM system.

Animals↗

PubMed2005

The effect of camphorquinone (CQ) and CQ-related photosensitizers on the generation of reactive oxygen species and the production of oxidative DNA damage.

Recent evidence suggests that following visible-light (VL) irradiation, CQ and the CQ-related photosensitizers benzil (BZ), benzophenone (BP), and 9-fluorenone (9-F) generate initiating radicals that may indiscriminately react with molecular oxygen forming reactive oxygen species (ROS). The purpose of this investigation was to determine whether VL-irradiated CQ, BZ, BP, and 9-F cause DNA damage due to the generation of ROS in vitro. ROS formation by CQ and CQ-related photosensitizers+/-dimethyl-p-toluidine (DMT) was investigated in a cell-free system with VL irradiation. DNA damage was determined using PhiX-174 RF I supercoiled double-stranded plasmid DNA and ROS quantified with 4-((9-acridinecarbonyl)amino)-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO-9-AC), a fluorogenic ROS-sensitive probe. VL-irradiated CQ, BZ, BP, and 9-F (+/-DMT) produced significant DNA damage at 0.1, 0.5, and 1.0 mM and in a concentration-dependent manner (p<0.05). TEMPO-9-AC revealed that all investigated VL-irradiated photosensitizers produced significant amounts of ROS with BZ in the presence of DMT generating the most ROS after 30, 60, and 90 min. VL-irradiated CQ, BZ, BP, and 9-F +/-DMT continued to generate significant amounts of ROS 90 min after VL irradiation. As a result, future investigations should evaluate the effect of VL-irradiated photosensitizers in cells and possible protective effects provided by antioxidants.

Benzophenones↗

PubMed2006

Redox signaling in hypertension.

Diseases such as hypertension, atherosclerosis and diabetes are associated with vascular functional and structural changes including endothelial dysfunction, altered contractility and vascular remodeling. Cellular events underlying these processes involve changes in vascular smooth muscle cell (VSMC) growth, apoptosis/anoikis, cell migration, inflammation, and fibrosis. Many stimuli influence cellular changes, including mechanical forces, such as shear stress, and vasoactive agents, of which angiotensin II (Ang II) appears to be amongst the most important. Ang II mediates many of its pleiotropic vascular effects through NAD(P)H oxidase-derived reactive oxygen species (ROS). Mechanical forces, comprising both unidirectional laminar and oscillatory shear, are increasingly being recognized as important inducers of vascular NO and ROS generation. In general, laminar flow is associated with upregulation of eNOS and NO production and increased expression of antioxidants glutathione peroxidase and superoxide dismutase, thereby promoting a healthy vascular wall and protecting against oxidative vascular injury. On the other hand, oscillatory shear is linked to increased ROS production with consequent oxidative damage, as occurs in hypertension. ROS function as important intracellular and intercellular second messengers to modulate many downstream signaling molecules, such as protein tyrosine phosphatases, protein tyrosine kinases, transcription factors, mitogen-activated protein kinases, and ion channels. Induction of these signaling cascades leads to VSMC growth and migration, expression of pro-inflammatory mediators, and modification of extracellular matrix. In addition, ROS increase intracellular free Ca(2+) concentration, a major determinant of vascular reactivity. ROS influence signaling molecules by altering the intracellular redox state and by oxidative modification of proteins. In physiological conditions, low concentrations of intracellular ROS play an important role in normal redox signaling involved in maintaining vascular function and integrity. Under pathological conditions ROS contribute to vascular dysfunction and remodeling through oxidative damage. The present review describes some of the redox-sensitive signaling pathways that are involved in the functional and structural vascular changes associated with hypertension.

Animals↗

PubMed2006

Bax affects production of reactive oxygen by the mitochondria of non-apoptotic neurons.

Depriving sympathetic neurons in cell culture of nerve growth factor (NGF) causes their apoptotic death. Bax-induced release of cytochrome c from mitochondria and the subsequent activation of cytosolic caspases are central to this death. A Bax-dependent increase of mitochondrial-derived reactive oxygen species (ROS) that is an important component of the apoptotic cascade in these cells begins soon after NGF withdrawal. Here we report that Bax can also influence mitochondrial production of ROS in non-apoptotic sympathetic neurons. We determined ROS levels by using confocal microscopy to monitor changes in the fluorescence intensity of a redox-sensitive dye loaded into single cells. ROS levels were similar in NGF-replete bax wild-type neurons and neurons from which bax had been deleted. To enhance any effects that Bax might have on ROS levels in NGF-replete cells we exposed cultures to the ATP synthase inhibitor, oligomycin. This treatment hyperpolarizes mitochondrial membrane potential (DeltaPsi(m)), an event that can favor increased ROS production. NGF-replete neurons from mice in which bax had been deleted had much higher levels of mitochondrial-derived ROS when treated with oligomycin than did bax wild-type cells. Oligomycin treatment also caused greater hyperpolarization of DeltaPsi(m) in bax-deleted cells than in wild-type cells. These findings indicate that Bax can affect mitochondrial ROS production in non-apoptotic neurons and may do so by altering DeltaPsi(m).

Animals↗

PubMed2004

Novel association between sperm reactive oxygen species production, sperm morphological defects, and the sperm deformity index.

OBJECTIVE: To examine the relationship between sperm reactive oxygen species (ROS) production and sperm morphology in a group of infertile men and healthy fertile donors. DESIGN: A prospective clinical study. SETTING: Male infertility clinic, Glickman Urological Institute, The Cleveland Clinic Foundation, Cleveland, Ohio, and the Reproductive Medicine Unit, Liverpool Women's Hospital, United Kingdom PATIENT(S): Thirty-nine infertile men and 13 healthy fertile donors (control). INTERVENTION(S): Standard semen analysis, seminal leukocyte concentration, assessment of sperm morphology, and measurement of sperm ROS production. MAIN OUTCOME MEASURE(S): Levels of sperm ROS production, percentages of different sperm morphological abnormalities, and the sperm deformity index (SDI) scores. RESULT(S): A significant negative correlation was observed between sperm ROS production and the proportion of sperm with normal morphology and borderline morphology. Reactive oxygen species production was positively correlated with the proportion of sperm with amorphous heads, damaged acrosomes, midpiece defects, cytoplasmic droplets, tail defects, and SDI scores. Logistic regression analysis identified a two-variable model including SDI and percentage sperm motility, which correctly identified 84% of individuals with high seminal ROS and 85% of individuals with low seminal ROS. The model had an overall accuracy of 85%. CONCLUSION(S): The standard semen analysis to assess sperm motility, sperm morphology, and the SDI scores is a useful tool in identifying infertile men with high seminal ROS in infertility clinics where facilities for measuring levels of seminal ROS are not available.

Female↗

PubMed2003

Proliferation and wound healing of vascular cells trigger the generation of extracellular reactive oxygen species and LDL oxidation.

Cell proliferation of vascular cells is a key feature in vascular biology, wound healing, and pathophysiological processes such as atherosclerosis and restenosis. In atherosclerotic intima, cell proliferation colocalizes with oxidized LDL that indicate a local oxidative stress. This study aims to investigate whether cell proliferation is causally related with extracellular ROS generation and subsequent LDL oxidation. Sparse proliferating endothelial and smooth muscle cells generate higher levels of extracellular ROS (O2*- and H2O2) and LDL oxidation than confluent contact-inhibited cells. During wound healing of confluent cell layer, cell proliferation associated with healing also induced enhanced extracellular ROS generation and LDL oxidation. Proliferation-associated extracellular ROS generation is mediated through mitogenic signaling pathways, involving ERK1/2 and PKC, but is independent of de novo DNA synthesis, gene expression and protein synthesis. Data obtained with inhibitors of oxidases suggest that proliferation-associated extracellular ROS are not generated by a single ROS-generating system and are not essential for cell proliferation. In conclusion, our data show that proliferating vascular cells (in sparse culture or during wound healing) generate high levels of extracellular ROS and LDL oxidation through regulation of ROS-generating systems by mitogenic signaling. This constitutes a link between proliferative events and oxidative stress/LDL oxidation in atherosclerotic lesions and restenosis.

Animals↗

PubMed2004

alpha-keto-beta-methyl-n-valeric acid diminishes reactive oxygen species and alters endoplasmic reticulum Ca(2+) stores.

Mitochondrial dysfunction and oxidative stress occur in neurodegenerative diseases. Other results show that bombesin-releasable calcium stores (BRCS) from the endoplasmic reticulum (ER) are exaggerated in fibroblasts from patients with Alzheimer's disease (AD) compared with controls and in fibroblasts from a young control treated with H(2)O(2). We hypothesize that alterations in oxidative stress underlie the exaggeration in BRCS in AD, and that appropriate antioxidants may be useful in treating this abnormality. Two indicators of different oxidant species were used to determine the effects of select oxidants on cellular oxidation status: carboxydichlorofluorescein (c-DCF) to detect reactive oxygen species (ROS), and 4-amino-5-methylamino-2',7'-difluorofluorescein (DAF) to detect nitric oxide (NO(.-)). Various conditions that induce ROS, including H(2)O(2), oxygen/glucose deprivation, and 3-morpholinosyndnonimine (SIN-1), were used to test the ability of alpha-keto-ss-methyl-n-valeric acid (KMV) to scavenge ROS. KMV diminished c-DCF-detectable ROS that were induced by H(2)O(2), oxygen/glucose deprivation, or SIN-1 in PC12 cells, primary neuronal cultures, or fibroblasts. Furthermore, KMV reduced the H(2)O(2)-induced increase in BRCS and diminished the elevation in BRCS in cells from AD patients to control levels. On the other hand, DAF-detectable NO(.-) induced by SIN-1 was not scavenged by KMV and did not exaggerate BRCS. The results indicate that KMV is an effective antioxidant of c-DCF-detectable ROS. The effects of KMV are not cell type specific, but are ROS specific. The same H(2)O(2)-induced ROS that reacts with KMV may also underlie the changes in BRCS related to AD. Thus, KMV ameliorates the effects of ROS on calcium homeostasis related to oxidative stress and to AD.

Alzheimer Disease↗

PubMed2005

Bile acid modulates transepithelial permeability via the generation of reactive oxygen species in the Caco-2 cell line.

The barrier functions in epithelial and endothelial cells seem to be very important for maintaining normal biological homeostasis. However, it is unclear whether or how bile acids affect the epithelial barrier. We examined the bile acid-induced disruption of the epithelial barrier. We measured the transepithelial electrical resistance (TEER) of Caco-2 cells as a marker of disruption of the epithelial barrier. Reactive oxygen species (ROS) generation was also measured. Cholic acid (CA) decreased the TEER and increased intracellular ROS generation. PLA2 (phospholipase A2), COX (cyclooxygenase), PKC (protein kinase), ERK 1/2 (extracellular signal-regulated kinase 1/2), PI 3 K (phosphatidylinositol 3-kinase), p38 MAPK (p38 mitogen-activated protein kinase), MLCK (myosin light-chain kinase), NADH dehydrogenase, and XO (xanthine oxidase) inhibitors or ROS scavengers prevented the CA-induced TEER decrease. PLA2, COX, PKC, NADH dehydrogenase, and XO inhibitors prevented the CA-induced ROS generation but not ERK 1/2, PI 3 K, p38 MAPK, and MLCK inhibitors. If the cells were treated with ROS generators such as superoxide dismutase, the TEER decreased. ERK 1/2, PI 3 K, p38 MAPK, and MLCK inhibitors prevent these ROS generators from inducing the TEER decrease. These results suggest that ROS play an important role. In addition, PLA2, COX, PKC, NADH dehydrogenase, and XO are located upstream of the ROS generation, but ERK 1/2, PI 3 K, p38 MAPK, and MLCK are downstream during the signaling of CA-induced TEER alterations.

Bile Acids and Salts↗

PubMed2005

A possible cooperation of SOD1 and cytochrome c in mitochondria-dependent apoptosis.

A small amount of reactive oxygen species (ROS) is generated through aerobic respiration even under physiological conditions. Because ROS are known to have various deteriorating actions, the way cells could evade the effects of ROS in and around mitochondria would determine the fate of cells. We previously reported that Cu,Zn-superoxide dismutase (SOD1), a cytosolic enzyme, is also localized in mitochondria in various types of cells. Therefore, we undertook this study to elucidate the physiological significance of SOD1 localization in and around mitochondria. We analyzed the effects of various reagents that could modulate mitochondrial respiration, ROS metabolism, and subcellular localization of SOD1 and cytochrome c. Using rat liver mitochondria, we have shown that Ca2+, Fe2+, or long-chain fatty acids increased the mitochondrial generation of ROS and that the resulting ROS oxidized the critical thiol groups in adenine nucleotide translocase (ANT). The oxidation of ANT induced mitochondrial swelling followed by the release of SOD1 and cytochrome c. Although inhibitors of electron transport, such as rotenone, antimycin A, and KCN, also increased ROS generation, they failed to (i) oxidize the critical thiol groups in ANT, (ii) induce swelling, and (iii) release SOD1 and cytochrome c. These results suggest that the oxidation of ANT thiols and the opening of the membrane permeability transition pores induce the release of both SOD1 and cytochrome c. We demonstrated that the loss of SOD1 increases the susceptibility of mitochondria to oxidative stresses and that the simultaneous release of SOD1 enhances the vicious cycle of apoptotic reactions triggered by the released cytochrome c. Therefore, SOD1 must have important roles in protecting mitochondria from ROS-induced injury. Our data also suggest that SOD1 release parallels cytochrome c release under all conditions. We propose that intramembranously localized SOD1 is a third reagent (along with AIF) that will regulate apoptosis.

Animals↗

PubMed2006

Reactive oxygen species attenuate nitric-oxide-mediated hypoxia-inducible factor-1alpha stabilization.

Tissue hypoxia/ischemia are major pathophysiological determinants. Conditions of decreased oxygen availability provoke accumulation and activation of hypoxia-inducible factor-1 (HIF-1). Recent reports demonstrate a crucial role of HIF-1 for inflammatory events. Regulation of hypoxic responses by the inflammatory mediators nitric oxide (NO) and reactive oxygen species (ROS) is believed to be of pathophysiolgical relevance. It is reported that hypoxic stabilization of HIF-1alpha can be antagonized by NO due to its ability to attenuate mitochondrial electron transport. Likely, the formation of ROS could contribute to this effect. As conflicting results emerged from several studies showing either decreased or increased ROS production during hypoxia, we used experiments mimicking hypoxic intracellular ROS changes by using the redox cycling agent 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), which generates superoxide inside cells. Treatment of A549, HEK293, HepG2, and COS cells with DMNQ resulted in a concentration-dependent raise in ROS which correlated with HIF-1alpha accumulation. By using a HIF-1alpha-von Hippel-Lindau tumor suppressor protein binding assay, we show that ROS produced by DMNQ impaired prolyl hydroxylase activity. When HIF-1alpha is stabilized by NO, low concentrations of DMNQ (<1 microM) revealed no effect, intermediate concentrations of 1 to 40 microM DMNQ attenuated HIF-1alpha accumulation and higher concentrations of DMNQ promoted HIF-1alpha stability. Attenuation of NO-induced HIF-1alpha stability regulation by ROS was mediated by an active proteasomal degradation pathway. In conclusion, we propose that scavenging of NO by ROS and vice versa attenuate HIF-1alpha accumulation in a concentration-dependent manner. This is important to fully elucidate HIF-1alpha regulation under inflammatory conditions.

Acetylcysteine↗

PubMed2004

Molecular events associated with reactive oxygen species and cell cycle progression in mammalian cells.

Cell cycle progression is regulated by a wide variety of external factors, amongst them are growth factors and extracellular matrix factors. During the last decades evidence has been obtained that reactive oxygen species (ROS) may also play an important role in cell cycle progression. ROS may be generated by external and internal factors. In this overview we describe briefly the generation of ROS and their effects on processes that have been demonstrated to play an essential role in cell cycle progression, including such systems as signal transduction cascades, protein ubiquitination and degradation, and the cytoskeleton. These different effects of ROS influence cell cycle progression dependent upon the amount and duration of ROS exposure. Activation of growth factor stimulated signaling cascades by low levels of ROS result in increased cell cycle progression, or, in case of prolonged exposure, to a differentiation like growth arrest. From many studies it seems clear that the cyclin kinase inhibitor protein p21 plays a prominent role, leading to cell cycle arrest at higher but not directly lethal levels of ROS. Dependent upon the nature of p21 induction, the cell cycle arrest may be transient, coupled to repair processes, or permanent. At high concentrations of ROS all of the above processes are activated, in combination with enhanced damage to the building blocks of the cell, leading to apoptosis or even necrosis.

Animals↗

PubMed2004

Synchronized generation of reactive oxygen species with the cell cycle.

A possible appearance of reactive oxygen species (ROS) with the normal cell cycle was studied to find how ROS are generated in cells in relation to the cell cycle. The production of ROS in relation to the cell cycle was examined by determining the changes in intracellular ROS concentrations at different phases of the cell cycle by culturing BALB 3T3 cells in the presence and absence of aphidicolin. The amounts of intracellular ROS and the cell population at specific phases (S and G2/M) were determined as the fluorescence of dichlorodihydrofluorescein and propidium iodide taken up simultaneously by the cells, respectively, by flow cytometry. Although intracellular ROS remained at the control levels when the cell growth was arrested with aphidicolin at the G1 phase, they increased when the arrest was released to result in the increase of the cell population at the S phase. Furthermore, ROS was shown to disturb/stop the cell cycle by means of the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The cell cycle was regulated through oxidative stress by exposure to hydrogen peroxide and glutathione ethyl ester. The cell cycle was prevented more sensitively in metallothionein-null cells than in the wild type cells. Based on the present observations, we proposed for the first time that ROS are generated synchronously with the normal cell cycle, and that they have to be controlled at certain level for normal progress of the cell cycle.

Animals↗

PubMed2006

Reactive oxygen species modulate the differentiation of neurons in clonal cortical cultures.

Reactive oxygen species (ROS) are important regulators of intracellular signaling. We examined the expression of ROS during rat brain development and explored their role in differentiation using cortical cultures. High levels of ROS were found in newborn neurons. Neurons produced ROS, not connected with cell death, throughout embryogenesis and postnatal stages. By P20, ROS-producing cells were found only in neurogenic regions. Cells with low levels of ROS, isolated from E15 brains by FACS, differentiated into neurons, oligodendrocytes, and astrocytes in clonal cultures. Neurons produced high ROS early in culture and later differentiated into two types: large pyramidal-like neurons that fired no or only a single action potential and smaller neurons that expressed nuclear calretinin and fired repeated action potentials. Antioxidant treatment did not alter neuron number but increased the ratio of small to large neurons. These findings suggest that modulation of ROS levels influences multiple aspects of neuronal differentiation.

Analysis of Variance↗