PubMed Health⌕ Search

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 37 records · Page 2Linked to original sources
PubMed2016

Malonate as a ROS product is associated with pyruvate carboxylase activity in acute myeloid leukaemia cells.

BACKGROUND: The role of anaplerotic nutrient entry into the Krebs cycle via pyruvate carboxylase has been the subject of increased scrutiny and in particular whether this is dysregulated in cancer. Here, we use a tracer-based NMR analysis involving high-resolution (1)H-(13)C-HSQC spectra to assess site-specific label incorporation into a range of metabolite pools, including malate, aspartate and glutamate in the acute myeloid leukaemia cell line K562. We also determine how this is affected following treatment with the redeployed drug combination of the lipid-regulating drug bezafibrate and medroxyprogesterone (BaP). RESULTS: Using the tracer-based approach, we assessed the contribution of pyruvate carboxylase (PC) vs. pyruvate dehydrogenase (PDH) activity in the derivation of Krebs cycle intermediates. Our data show that PC activity is indeed high in K562 cells. We also demonstrate a branched entry to the Krebs cycle of K562 cells with one branch running counterclockwise using PC-derived oxaloacetate and the other clockwise from the PDH activity. Finally, we show that the PC activity of K562 cells exclusively fuels the ROS-induced decarboxylation of oxaloacetate to malonate in response to BaP treatment; resulting in further Krebs cycle disruption via depletion of oxaloacetate and malonate-mediated inhibition of succinate dehydrogenase (SDH) resulting in a twofold reduction of fumarate. CONCLUSIONS: This study extends the interest in the PC activity in solid cancers to include leukaemias and further demonstrates the value of tracer-based NMR approaches in generating a more accurate picture of the flow of carbons and metabolites within the increasingly inappropriately named Krebs cycle. Moreover, our studies indicate that the PC activity in cancer cells can be exploited as an Achilles heel by using treatments, such as BaP, that elevate ROS production.

AML↗
PubMed1991

Vitamin D receptor phosphorylation in transfected ROS 17/2.8 cells is localized to the N-terminal region of the hormone-binding domain.

The human 1,25-dihydroxyvitamin D3 receptor (hVDR) has been recently shown to be phosphorylated in vitro by casein kinase-II. Most of the residues phosphorylated by this enzyme were shown to reside between Asn160 and Asp232, a region near the N-terminal boundary of the hormone-binding domain. We report here that the hVDR is also phosphorylated in vivo after transfection into ROS 17/2.8 cells. In addition to testing full-length hVDR, we analyzed several internally deleted hVDR mutants. The expression and phosphorylation of full-length and mutated hVDRs were monitored in transfected cells by metabolic labeling with either [35S]methionine or [32P]orthophosphate, followed by immunopurification using monoclonal anti-VDR antibody linked to agarose beads. Transfected hVDR is distinguishable from the endogenous rat VDR when the immunoprecipitated proteins are resolved on sodium dodecyl sulfate-polyacrylamide gels. Significant phosphorylation of transfected full-length hVDR was observed in ROS 17/2.8 cells, and it was less dependent on the presence of 1,25-dihydroxyvitamin D3 than that of the endogenous rat receptor. Most importantly, the region of in vivo phosphorylation, as defined by internal deletion mutants, resides between Met197 and Val234. Therefore, we have localized the major site of phosphorylation of hVDR to residues in the N-terminal region of the hormone-binding domain. The boundaries of this region fall within the amino acid segment defined for phosphorylation of hVDR by casein kinase-II in vitro, suggesting that VDR is an in vivo substrate for casein kinase-II or a related protein kinase.

Amino Acid Sequence↗
PubMed2026

Strigolactones constrain rice drought acclimation by suppressing ROS scavenging through the D53-OsWRKY31-ZFP36 module.

Strigolactones (SLs) are a class of plant hormones essential for tiller development and yield under diverse environmental conditions. Drought is a major limiting factor for rice yields. Although SLs contribute to drought resistance, mechanisms and practical applications of SL pathway in drought acclimation of rice remain poorly understood. Our study shows that short-term dehydration represses SL biosynthesis in rice roots. Genetic assays indicate that disruption of SL biosynthesis or signaling elevates rice drought resistance, whereas SL signaling activation or supplementation with the SL analog GR244DO impairs drought resistance. SLs negatively regulate drought acclimation by promoting degradation of the repressor protein DWARF53 (D53). D53 interacts with the transcription factor OsWRKY31 via its N-terminal domain and suppresses the protein level of OsWRKY31, which binds to and represses transcription of the ZFP36 promoter. ZFP36 encodes a zinc-finger transcription factor that promotes H2O2 scavenging to sustain reactive oxygen species (ROS) homeostasis during drought stress. Notably, the drought-resistant upland rice variety IRAT109 exhibits lower SL levels in root exudates than the lowland rice variety Nipponbare (NP). Genome editing of key components in SL pathway enhances drought resistance in NP, Huazhan (HZ), and IRAT109. The agronomic potential of tuning SL biosynthesis is further supported by the elite D17/HTD1 allele, which weakens SL biosynthesis and improves drought resistance and grain yield in Nekken 2 (NK2) under field conditions. These findings uncover a key mechanism underlying SL-repressed drought acclimation in rice and provide an effective strategy to improve drought resistance in diverse rice varieties amid ongoing climate change.

D53↗
PubMed2026

CaCl2 Priming Boosts Salinity-Alkalinity Tolerance in Germinating Soybean by Reducing DNA Oxidative Damage and Enhancing Ca2+ -ROS Signaling Crosstalk.

Soybean (Glycine max) seed germination is highly sensitive to saline-alkaline stress. Seed priming represents an effective strategy to mitigate its detrimental effects. However, the optimal priming conditions (agent, concentration, duration) and the underlying molecular mechanisms remain poorly understood. This study investigated the effects of priming with distilled water (Control), calcium chloride (CaCl2), melatonin (MT), and proline (Pro) under saline-alkaline stress on soybean seed germination and the molecular basis of enhanced tolerance. Evaluation of ten germination-related parameters revealed that priming with 100 mM CaCl2 for 12 h significantly enhanced the germination rate. Physiological analyses demonstrated that CaCl2 priming effectively reduced reactive oxygen species (ROS) accumulation by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), while decreasing malondialdehyde (MDA) content. Furthermore, CaCl2 priming activated the Ca2+ signaling pathway by increasing radicle Ca2+ content and upregulating the expression levels of Ca2+ signaling-related genes (e.g., GmCAM7, GmCNGC2, GmCNGC19, GmMPK2, and GmMKK2). Additionally, CaCl2 priming significantly enhanced DNA damage repair capacity of soybean cultivars with differing saline-alkaline tolerance. This was manifested by reduced DNA oxidative damage and decreased random amplified polymorphic DNA (RAPD) polymorphism, thereby enhancing genomic stability and alleviating cell cycle arrest. These findings deepen our understanding of the complex regulatory role of calcium signaling in plant abiotic stress responses and provide important novel theoretical insights for improving crop resilience.

Glycine max↗
PubMed1991

1,25-dihydroxyvitamin D reduces parathyroid hormone receptor number in ROS 17/2.8 cells and prevents the glucocorticoid-induced increase in these receptors: relationship to adenylate cyclase activation.

We have previously shown that 1,25-dihydroxyvitamin D [1,25-(OH)2D3] and glucocorticoid modulate adenylate cyclase activation by PTH in osteoblast-like cells. Here we examine whether steroid effects on PTH receptor density explain the modulation of PTH action. Receptor assays were performed on late logarithmicphase monolayers of ROS 17/2.8 cells using human PTH-like peptide (hPLP) as radioligand. Kd and receptor density were computed from competition of tracer amounts of [125I-Tyr36] hPLP-(1-36) with unlabeled hPLP-(1-36) (0.1-30 nM). Steroid treatment had little or no effect on affinity for ligand. Pretreating cells with 10 nM 1,25-(OH)2D3 for 48 h decreased PTH receptor number to 17% of control values. Treating cells with 10 nM of the glucocorticoid triamcinolone acetonide (TRM) increased receptor number 10-fold, but simultaneous treatment with 1,25-(OH)2D3 (10 nM) completely prevented this receptor increase. Steroid effects required 13-18 h of treatment. Dose-response relationships for steroid modulation, determined from binding at 0.17 nM radioligand, indicated an EC50 of 0.3 nM for glucocorticoid augmentation of PTH receptor number and 0.02 nM for 1,25-(OH)2D3 reduction of receptor number in the presence of absence of the maximum TRM effect. The initial rate of cAMP production by receptor-saturating concentrations of PTH was 11,500 molecules per receptor per minute in untreated cells, comparable to reported turnover numbers for mammalian adenylate cyclase. Control experiments were validated measuring cAMP in intact cells as an indicator of adenylate cyclase activity. Cyclic AMP production was reduced 63% by 1,25-(OH)2D3 (10 nM) treatment. Glucocorticoid (10 nM) enhanced cAMP production twofold but reduced cAMP generation per receptor by 80%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1992

Photosensitivity of 8BrcGMP-induced conductance in ROS-excised patches.

Inside-out patches from ROS plasma membranes contain the basic enzymes of the phototransduction cascade. Similar to a native photoreceptor cell, such patches are capable of responding to light, the effect of which suppresses the cGMP-activated current. Photoresponses are observed only in the presence of GTP, whereas ATP essentially accelerates the current recovery to a dark level. Photoresponses are also observed in the presence of 8BrcGMP. Phosphodiesterase (PDE) hydrolyzes 8BrcGMP two orders of magnitude slower than cGMP, so the light inhibition of the 8BrcGMP-induced current cannot be accounted for by PDE activation. It seems that activity of cGMP-gated channels depends not only on cGMP concentration, but is additionally controlled by some other regulatory mechanisms.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Lead perturbs epidermal growth factor (EGF) modulation of intracellular calcium metabolism and collagen synthesis in clonal rat osteoblastic (ROS 17/2.8) cells.

EGF, a single-chain polypeptide growth factor important for many cellular functions including glycolysis and protein phosphorylation, is known to modulate calcium metabolism in several cell systems. EGF causes an increase in Ca2+ influx and accumulation of inositol triphosphate and probably exhibits many, if not all, of its effects via the calcium messenger system. Lead is known to interact with and perturb normal calcium signaling pathways; therefore, the purpose of this work was to determine if lead perturbs EGF modulation of calcium metabolism in ROS 17/2.8 cells and if lead impairs collagen synthesis, which is controlled by EGF. To characterize 45Ca kinetics, cells were labelled with 45Ca (1.87 mM Ca) for 20 hr in the presence of 5 microM Pb, 50 ng/ml EGF, or 5 microM Pb and 50 ng/ml EGF. Kinetic parameters were determined from 45Ca efflux curves. Three kinetic compartments described the intracellular metabolism of 45Ca; 5 microM Pb significantly altered the effect of EGF on intracellular calcium metabolism. Calcium distribution was shifted from the fast-exchanging, quantitatively small calcium pools S1 and S2 to the slow-exchanging, quantitatively large S3. There was also a 50% increase in total cell calcium in cells treated with 5 microM Pb and 50 ng/ml EGF over calcium in cells treated with 50 ng/ml EGF alone. Because EGF and phorbol 12-myristate 13-acetate (PMA) have similar effects on protein kinase C (PKC) and collagen metabolism, the transient effects of EGF and PMA on 45Ca and 210Pb were also characterized. EGF caused a rapid transient increase in efflux of both isotopes, which was further increased by the addition of PMA. In contrast, PMA pretreatment, which depletes PKC, significantly attenuated the latter effect of EGF, suggesting that downregulation by PKC of EGF-induced increases in 45Ca and 210Pb efflux. Moreover, collagen synthesis was decreased by lead, EGF, and PMA in a similar manner, further suggesting PKC as the common modulator of these effects. These data show that Pb impairs the normal modulation of intracellular calcium homeostasis and collagen synthesis by EGF. Furthermore, these results provide additional support to the postulate that an early and discrete effect of lead involves perturbation of the calcium messenger system at one or several loci.

Animals↗
PubMed1992

The role of iron in an acute model of skin inflammation induced by reactive oxygen species (ROS).

The effect of iron was studied in rats in a ROS-initiated model of acute skin inflammation. Iron dextran was administered i.v. 24 h before the induction of the inflammatory response by intradermal injection of glucose oxidase attached to polyethylene glycol (GOD-PEG). Iron exacerbated the response at 24 and 48 h (P greater than 0.001). Histologically, a similar picture was seen to that without iron except for an increase in tissue oedema and matrix destruction including the skin glands. Associated with iron loading was an increase in Perls stainable iron in the skin (P greater than 0.025) and liver (P greater than 0.001). However, skin inflammation without iron loading also increased skin iron levels (P greater than 0.025). Total serum iron was decreased in iron-loaded and GOD-PEG animals (P greater than 0.01) and the unbound iron binding capacity (UIBC) increased (P greater than 0.01).

Animals↗
PubMed1992

Dose-dependent effects of aluminum on osteocalcin synthesis in osteoblast-like ROS 17/2 cells in culture.

This in vitro study evaluates the effect of aluminum (Al3+) on osteocalcin, a small protein that is produced by the osteoblast. After stimulation with various doses of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3; 10(-11) to 10(-9) M], osteocalcin was consistently lower in the culture medium of ROS 17/2 osteoblastic cells conditioned with 5 microM Al(3+)-saturated transferrin (AlTR) than in apotransferrin (ApoTR)-treated controls. In a second experiment, cultures were conditioned with various doses of AlTR or ApoTR (1.6-8.0 microM) and stimulated with 10(-9) M 1,25(OH)2D3. High doses of AlTR (4.8-8.0 microM) resulted in lower medium and unchanged intracellular content of osteocalcin than treatment with equal amounts of ApoTR. However, in the same experiment, lower doses of AlTR or ApoTR (1.6 and 3.2 microM) yielded different results, i.e., increased medium and intracellular contents of osteocalcin in the Al(3+)-treated cells. Expression of osteocalcin mRNA was not altered in cultures conditioned with low (1.6 microM) or high (8.0 microM) concentrations of AlTR or ApoTR. Similarly, no effect of Al3+ was observed on total protein content, the rate of total protein synthesis, and the degradation of secreted osteocalcin in cultures conditioned with various doses of AlTR or ApoTR. These findings suggest that AlTR affects osteocalcin synthesis in a specific manner, without concomitant effects on the rate of total protein synthesis or on the rate of degradation of osteocalcin. This effect is dose dependent, i.e., low doses of AlTR stimulate and high doses suppress osteocalcin synthesis and/or secretion, and it appears to be posttranscriptional, since the expression of osteocalcin mRNA is not affected.

Aluminum↗
PubMed1992

Evidence that estrogens modulate activity and increase the number of 1,25-dihydroxyvitamin D receptors in osteoblast-like cells (ROS 17/2.8).

A detailed understanding of the mechanism of action of estrogen on bones is still lacking. The present study was designed to examine possible modulation by 17 beta-estradiol (E2) on the effects of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and on vitamin D receptors (VDR) in the ROS 17/2.8 osteoblast-like cell line. Cells were grown in phenol-red free medium supplemented with charcoal-stripped fetal calf serum (FCS). Total cellular VDR were measured in cell homogenates after extraction with a KCl hypertonic buffer. VDR-binding capacity doubled in the presence of 10 nM E2 (16.2 +/- 2.3 vs. 7.0 +/- 1.3 fmol/mg protein, respectively; P less than 0.01), while the Kd for 1,25-(OH)2D3 did not change (approximately 0.1 nM). Tamoxifen alone had no effect on VDR, while it completely abolished the E2-induced increase in VDR, indicating that the effect was specific for E2 and estrogen receptor mediated. 1,25-(OH)2D3 inhibited cell proliferation, determined by [3H] thymidine incorporation to DNA, in a dose-dependent fashion between 0.01-100 nM. The inhibitory effect of 1,25-(OH)2D3 on cell proliferation was significantly augmented in the presence of E2 (10 nM). 1,25-(OH)2D3 increased osteocalcin secretion to the medium by the cells in a dose-dependent fashion between 0.01-100 nM. In the presence of E2 (10 nM), maximal osteocalcin secretion in response to 1,25-(OH)2D3 was 3.5-fold higher than that in response to 1,25-(OH)2D3 alone. These results indicate that E2 modulates 1,25-(OH)2D3 activity in osteoblast-like cells, and that this effect can be attributed to an increase in VDR.

Animals↗
PubMed1992

Estrogens modulate the responsiveness of osteoblast-like cells (ROS 17/2.8) stably transfected with estrogen receptor.

Recent studies have demonstrated the presence of estrogen receptor (ER) in both normal human osteoblast-like and osteoblast-like osteosarcoma cells. The number of ER in cultured osteoblastic cells is very low (200-500 sites/cell). This has complicated characterization of the biological role of estrogens in bone cells. To study the responsiveness of bone cells to estrogens, we established osteoblast-like cell lines expressing higher ER levels. ROS 17/2.8, an osteoblastic cell line, was stably transfected with the cDNA encoding for the mouse ER. After a selection period, positive clones were isolated and evaluated for the presence of ER by both Northern blot analysis and ligand binding assays. Using these techniques, we detected a significant increase in the level of both ER transcript and binding compared to that in wild-type cells. The levels of expressed ER protein were similar to those reported in normal human osteoblast-like cells in primary culture (approximately 2000 sites/cell). To test whether the exogenously inserted ER was responsive, both wild-type and ER stably transfected cells were transiently transfected with a reporter construct containing an estrogen-responsive element linked to a truncated thymidine kinase promoter and a chloramphenicol acetyltransferase (CAT) reporter gene. Exposure of the cells to increased concentrations of estradiol induced a slight increase in CAT activity in wild-type cells (approximately 1.5-fold) at maximal stimulation; however, it provoked a clear concentration-dependent increase in CAT activity in the ER stably transfected cells, with a maximal stimulation of approximately 10-fold. This event was receptor mediated, since ICI 164,384, an ER antagonist, blocked the enhancement of estradiol-induced CAT activity, and it was specific, since other steroid hormones did not stimulate CAT activity. Finally, we evaluated the ability of ER to modulate an endogenous estrogen-responsive gene by measuring the activity of the enzyme alkaline phosphatase. In addition, diethylstilbestrol, a synthetic estrogen agonist, increased the activity of both the CAT reporter gene and the endogenous alkaline phosphatase enzyme. In summary, we have established osteoblast-like cells expressing high levels of an exogenously inserted ER, which has characteristics similar to those of the endogenous ER in terms of its Kd. Finally, the exogenous ER regulates both exogenously inserted construct (VITERECAT) and endogenous properties of the cells (enzymatic activity and proliferation).

Alkaline Phosphatase↗
PubMed1992

The selective protection afforded by ebselen against lipid peroxidation in an ROS-dependent model of inflammation.

The effects of an experimental model of hydrogen-peroxide-induced foot pad oedema on indices of oxidative damage to biomolecules have been investigated. We have demonstrated increased levels of fluorescent protein and lipid peroxides occurring in plasma at 24 and 48 h post-injection. In addition, a decrease in the degree of galactosylation of IgG was observed which kinetically related the degree of inflammation and to the increase in protein autofluorescence (a specific index of oxidative damage). The effects of ebselen, a novel organoselenium compound which protects against oxidative tissue injury in a glutathione-peroxidase-like manner, have also been examined in this model. Pretreatment of animals with a dose of 50 mg/kg ebselen afforded significant and selective protection against lipid peroxidation only. This effect may contribute to the anti-inflammatory effect of this agent in hydroperoxide-linked tissue damage.

Animals↗
PubMed1992

Characterization and application of an in vitro detection system for studying the binding and phagocytosis of rod outer segments by retinal pigment epithelial cells.

Direct and indirect radioactivity and fluorescent assays have been developed to study the interaction of rod outer segments (ROS) with retinal pigment epithelial (RPE) cells. In the direct assays ROS labelled with 125I or fluorescein isothiocyanate (FITC) have been used to measure total phagocytosis, i.e. surface binding and ingestion. In the indirect assays RPE cells were first treated with unlabelled ROS or biotinylated ROS and subsequently probed with [125I]Rho 4D2 antirhodopsin antibody or [125I]streptavidin for radioactivity measurements or with the Rho 4D2 antibody and FITC-goat anti-mouse Ig or FITC-streptavidin for fluorescent counting. In these indirect methods the number of surface bound ROS were distinguished from the number of ingested ROS by comparative labelling of non-permeabilized and permeabilized ROS-treated RPE cells. Using these assays, we have studied the binding and ingestion of bovine ROS with cultured bovine RPE cells. As in the case of newborn cultured rat RPE cells [Hall and Abrams (1987) Exp. Eye Res. 45, 907-22], binding and ingestion of bovine ROS by bovine RPE cells was saturable with respect to ROS concentration and time. At 37 degrees C ROS binding reached a saturating concentration at 1 x 10(7) ROS per well; the number of bovine ROS ingested by bovine RPE cells, however, was less than the number of rat ROS ingested by rat RPE cells. When 1 x 10(7) ROS per well was used, maximal surface binding of bovine ROS to bovine RPE cells was obtained after 2-3 hr, whereas after an initial delay, ingestion rapidly increased to a maximum at 1-2 hr.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Protein phosphorylation in retinal pigment epithelium of Long-Evans and Royal College of Surgeons rats.

Cultures of retinal pigment epithelium (RPE) from normal Long-Evans (LE) and dystrophic Royal College of Surgeons (RCS) rats were incubated with 32P-orthophosphate and then phagocytically challenged with isolated rod outer segments (ROS) or polystyrene latex spheres (PSL). The 32P incorporation into individual proteins was quantified by image analysis of two-dimensional gel autoradiograms, and changes in phosphorylation were identified by comparison with unchallenged control cultures. Phosphorylation changes that were similar in response to either ROS or PSL were classified as nonspecific and omitted from further analysis; those associated solely with ROS exposure were classified as ROS specific and compared between the two strains. None of the 30 ROS-specific changes in protein phosphorylation identified in normal LE RPE were the same as in RCS RPE. However, unique ROS-specific changes in phosphorylation were observed in 13 RCS RPE proteins. Three RCS proteins showed ROS-specific decreases; ten showed ROS-specific increases. Six of these ten RCS proteins with increased phosphorylation showed ROS-specific decreases in LE RPE. No other correspondence in ROS-specific changes was found among the remaining LE or RCS RPE proteins, but several RCS proteins were phosphorylated at abnormal levels under control conditions. Even though ROS-induced changes in phosphorylation were aberrant in RCS RPE, their presence indicated that a ROS-specific transmembrane signal was generated after interaction with ROS. The abnormal increases and decreases observed in ROS-specific phosphorylation in the RCS suggested that the defect in ROS phagocytosis was associated with the misregulation or malfunction of both protein kinases and phosphatases.

Animals↗
PubMed2026

Angiotensin signaling is essential for stress erythropoiesis but causes retention of dysfunctional mitochondria in RBCs.

We previously reported that excessive angiotensin-II→AT receptor-1 (AT→ATR1) signaling results in sickle cell anemia-associated (SCA-associated) nephropathy. Herein, we showed that hyperangiotensinemia in SCA results from high erythroid cell-generated reactive oxygen species (ROS), which oxidized angiotensinogen (ATGN) and favored its rapid conversion to AT. Increased AT→ATR1 signaling in SCA erythroid cells generated ROS and created a positive feedback loop of ROS→oxidized ATGN→AT→ATR1→ROS, perpetuating the hyperangiotensinemia. ATR1 blocker, losartan, reduced erythrocyte ROS, oxidized ATGN, and AT levels. The ROS→AT→ATR1→ROS loop was driven by sickle erythropoiesis, as it was reproduced when WT mice were transplanted with SCA hematopoiesis. Using SCA and WT mice with germline- and erythroid-specific ATR1 deficiency, we found that stress erythropoiesis, but not steady-state erythropoiesis, was critically dependent on erythroid AT→ATR1 signaling, which acted in harmony with increased erythropoietin signaling. Furthermore, instead of the canonical AT→ATR1→NADPH-oxidase→ROS signaling in steady-state erythropoiesis, AT→ATR1 signaling in stress erythroid cells increased mitochondrial mass and dysfunctional mitochondria, which thereby increased ROS. SCA mice with erythroid-specific ATR1 deficiency had decreased RBC accumulation of dysfunctional mitochondria and decreased ROS, which reduced SCA-associated nephropathy. Overall, we demonstrate that AT→ATR1 signaling was essential for stress erythropoiesis but led to increased dysfunctional mitochondria retention in mature RBCs, which generated ROS and perpetuated hyperangiotensinemia, resulting in end-organ damage.

Animals↗
PubMed1992

Production of reactive oxygen by mitochondria from normoxic and hypoxic rat heart tissue.

Reactive oxygen species (ROS), which may be involved in ischemic or reperfusion heart injury, can be produced by mitochondria. Previous work indicated that coupled mitochondria from ischemic heart tissue incubated in calcium-free medium produced less ROS than normal. The effects of calcium, which may be elevated in hypoxic or ischemic tissue, were not examined. The relative production of ROS by mitochondria from normoxic or hypoxic rat heart tissue was estimated by measuring the oxidation of dichlorofluorescin to the fluorescent compound, dichlorofluorescein. ROS were detectable during succinate-stimulated State 4 respiration. In the absence of calcium, mitochondria from hypoxic (60 min) heart tissue produced less ROS than mitochondria from normoxic heart tissue. In the presence of 0.1, 1 or 10 microM calcium, ROS produced by hypoxic mitochondria were increased to normoxic levels. While function was depressed in mitochondria from hypoxic tissue, the presence of 0.1 and 1 microM calcium had no further effect. Respiration was uncoupled in the presence of 10 microM calcium in mitochondria from both normoxic and hypoxic heart tissue. ROS production was increased in mitochondria from hypoxic tissue with both increasing concentrations of calcium and increasing duration of exposure. ROS production in mitochondria from normoxic heart tissue was only stimulated after 200 or more seconds of exposure to 1 or 10 microM calcium. Production of ROS in mitochondria from hypoxic tissue in the presence of 1 microM calcium was inhibited by rotenone (80%), ruthenium red (69%), and a combination of these agents (96%). In contrast, ruthenium red had no effect on ROS production by mitochondria from normoxic heart tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Reactive oxygen species and human spermatozoa. II. Depletion of adenosine triphosphate plays an important role in the inhibition of sperm motility.

Under moderate conditions, reactive oxygen species (ROS) have been shown to inhibit sperm motility after several hours of incubation. The rapid decrease in flagellar beat frequency observed within the first hour of contact between ROS and spermatozoa was associated with a rapid loss of intracellular adenosine triphosphate (ATP). Motility of intact spermatozoa ceased when their ATP concentration was reduced by 85 +/- 5%. Axonemal damage was confirmed when ROS-treated spermatozoa could not reactivate motility after demembranation in a medium containing magnesium adenosine triphosphate (Mg.ATP). However, in conditions allowing rephosphorylation of the axonemes (addition of cyclic adenosine monophosphate, or cAMP, and protein kinase or sperm extracts to the demembranation medium), the motility could reactivate. Three lines of evidence suggested that ATP depletion induced by ROS treatment was responsible for the effects observed in spermatozoa. First, the rapid decrease in intracellular ATP observed after ROS treatment was closely followed by a decrease in beat frequency, loss of intact sperm motility, and axonemal damage due to insufficient phosphorylation. Second, incubation of spermatozoa with the combination pyruvate-lactate allowed maintenance of sperm ATP at a normal level and prevented the effects of ROS; furthermore, spermatozoa immobilized after ROS treatment, then supplemented with pyruvate-lactate, were able to reinitiate motility in parallel with an increase in their ATP level. Third, treatment of spermatozoa with rotenone, an ATP depleting agent, produced effects similar to ROS treatment and could also be reversed by the addition of pyruvate-lactate. These data are consistent with the conclusion that ROS treatment produced axonemal damage mostly as a result of ATP depletion.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗