Metabolism of extracellular adenine nucleotides by human endothelial cells exposed to reactive oxygen metabolites

1993 ◽  
Vol 264 (2) ◽  
pp. C282-C286 ◽  
Author(s):  
T. K. Aalto ◽  
K. O. Raivio
Keyword(s):  
Hydrogen Peroxide ◽  
Endothelial Cells ◽  
Xanthine Oxidase ◽  
Adenine Nucleotides ◽  
Ischemia Reperfusion ◽  
Reactive Oxygen ◽  
Extracellular Nucleotides ◽  
Reactive Oxygen Metabolites ◽  
Human Pathology ◽  
Oxygen Metabolites

Endothelial cells have ectonucleotidases that rapidly catabolize extracellular nucleotides. Our aim was to study whether the metabolism of extracellular nucleotides and adenosine are influenced by exposure of endothelial cells to reactive oxygen metabolites at concentrations relevant to human pathology. Human umbilical vein endothelial cells were incubated with hypoxanthine (100 microM) and xanthine oxidase (80 mU/ml), to generate superoxide, or with hydrogen peroxide (100 microM). The cells were then washed, and the metabolism of radioactive substrates was followed. After exposure to hypoxanthine-xanthine oxidase the half time of disappearance of [14C]ATP (5 microM) was prolonged from 9.9 +/- 5 to 28.3 +/- 15.6 min and that of [14C]AMP from 9.5 +/- 2.5 to 25.0 +/- 9.9 min. The conversion of extra- into intracellular nucleotides via adenosine was also decreased (mean for [14C]ATP 0.25 vs. 0.90 and for [14C]AMP, 0.075 vs. 0.75 nmol/10(6) cells in 30 min compared with parallel controls, respectively). Hydrogen peroxide or trypsin had no significant effect on the metabolism of extracellular adenine nucleotides and neither did a short (up to 15 min) exposure to the superoxide-generating system. The conversion of [14C]adenosine into intracellular nucleotides and hypoxanthine was not influenced by either hypoxanthine-xanthine oxidase or by hydrogen peroxide. We conclude that superoxide radicals inhibit the catabolism of extracellular adenine nucleotides by the ectonucleotidases of endothelial cells and may thus modify the pathophysiology of ischemia-reperfusion injury.

scholarly journals Xanthine oxidase and neutrophil infiltration in intestinal ischemia

1986 ◽  
Vol 251 (4) ◽  
pp. G567-G574 ◽  
Author(s):  
M. B. Grisham ◽  
L. A. Hernandez ◽  
D. N. Granger
Keyword(s):  
Superoxide Dismutase ◽  
Xanthine Oxidase ◽  
Reduced Glutathione ◽  
Ischemia Reperfusion ◽  
Reactive Oxygen ◽  
Neutrophil Infiltration ◽  
Mucosal Injury ◽  
Ischemia And Reperfusion ◽  
Reactive Oxygen Metabolites ◽  
Oxygen Metabolites

A growing body of experimental data indicates that reactive oxygen metabolites such as superoxide, hydrogen peroxide, and hydroxyl radical may mediate the mucosal injury produced by reperfusion of ischemic intestine. Xanthine oxidase has been proposed as the primary source of these reduced O2 species because pretreatment with xanthine oxidase inhibitors such as allopurinol or pterin aldehyde prevent postischemic mucosal injury. Another potential source of oxygen radicals is the inflammatory neutrophil. To ascertain whether neutrophils could play a role in the pathogenesis of ischemia-reperfusion injury in the small bowel we examined the effect of ischemia and reperfusion on neutrophil infiltration and tissue levels of reduced glutathione, superoxide dismutase, and catalase. Our studies demonstrate that reperfusion of ischemic intestines results in a dramatic increase (1,800%) in neutrophil infiltration and a concurrent loss of reduced glutathione and superoxide dismutase of 60 and 30%, respectively. Catalase activity was unaffected by ischemia-reperfusion. Pretreatment with allopurinol or administration of superoxide dismutase prevented the influx of neutrophils and retarded the drop in reduced glutathione levels. These results suggest a relationship among xanthine oxidase-generated oxy radicals, neutrophil extravasation, and mucosal damage. We propose that ischemia and reperfusion results in xanthine oxidase-generated, superoxide-dependent accumulation of inflammatory neutrophils in the mucosa where neutrophil-derived reactive oxygen metabolites mediate and/or exacerbate intestinal injury.

The role of reactive oxygen metabolites in lymphocyte-mediated cytolysis

1987 ◽  
Vol 87 (3) ◽  
pp. 473-481
Author(s):  
C.J. Bishop ◽  
C.M. Rzepczyk ◽  
D. Stenzel ◽  
K. Anderson
Keyword(s):  
Hydrogen Peroxide ◽  
Cell Death ◽  
Xanthine Oxidase ◽  
Natural Killer ◽  
Reactive Oxygen ◽  
Tumour Cells ◽  
Reactive Oxygen Metabolites ◽  
Oxygen Metabolites

To examine the possible role of reactive oxygen metabolites in lymphocyte-mediated cytolysis, the morphology of cell death following the exposure of cells to reactive oxygen metabolites in vitro was compared with the morphology of cell-mediated killing in vitro of tumour cells by natural killer (NK) cells. Ultrastructural examination of human tumour cells that were dying following incubation for 60 min with the oxygen metabolite generating systems, xanthine-xanthine oxidase or t-butylhydroperoxide, showed that cell death in both instances was exclusively by necrosis. It was unclear which oxygen metabolites were involved in killing. Cell death was not decreased by the addition of superoxide dismutase, a scavenger of the superoxide anion, to the xanthine-xanthine oxidase mixture. Although the cells were not killed by incubation with 1 mM-hydrogen peroxide, the addition of catalase, a scavenger of hydrogen peroxide, to the xanthine-xanthine oxidase mixture significantly reduced cell death. The addition of scavengers for the hydroxyl radical to either the xanthine-xanthine oxidase mixture or t-butylhydroperoxide gave inconsistent protection. In contrast, tumour cell killing mediated by natural killer cells was by apoptosis, a morphologically distinct mode of cell death with a different basic mechanism, indicating that reactive oxygen metabolites are not directly involved in lymphocyte-mediated cytolysis.

Generation of reactive oxygen metabolites by phagocytosing endothelial cells

1988 ◽  
Vol 72 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Peter Görög ◽  
Jeremy D. Pearson ◽  
Vijay V. Kakkar
Keyword(s):  
Endothelial Cells ◽  
Reactive Oxygen ◽  
Reactive Oxygen Metabolites ◽  
Oxygen Metabolites

Gentamicin enhanced production of hydrogen peroxide by renal cortical mitochondria

1987 ◽  
Vol 253 (4) ◽  
pp. C495-C499 ◽  
Author(s):  
P. D. Walker ◽  
S. V. Shah
Keyword(s):  
Hydrogen Peroxide ◽  
Mitochondrial Respiration ◽  
Critical Role ◽  
Reactive Oxygen ◽  
Reactive Oxygen Metabolites ◽  
Enhanced Production ◽  
Production Of Hydrogen ◽  
Hydrogen Peroxide Generation ◽  
Dose Dependent ◽  
Oxygen Metabolites

Agents that affect mitochondrial respiration have been shown to enhance the generation of reactive oxygen metabolites. On the basis of the well-demonstrated ability of gentamicin to alter mitochondrial respiration (stimulation of state 4 and inhibition of state 3), it was postulated that gentamicin may enhance the generation of reactive oxygen metabolites by renal cortical mitochondria. The aim of this study was to examine the effect of gentamicin on the production of hydrogen peroxide (measured as the decrease in scopoletin fluorescence) in rat renal cortical mitochondria. The hydrogen peroxide generation by mitochondria was enhanced from 0.17 +/- 0.02 nmol . mg-1 . min-1 (n = 14) in the absence of gentamicin to 6.21 +/- 0.67 nmol . mg-1 . min-1 (n = 14) in the presence of 4 mM gentamicin. This response was dose dependent with a significant increase observed at even the lowest concentration of gentamicin tested, 0.01 mM. Production of hydrogen peroxide was not increased when gentamicin was added to incubation media in which mitochondria or substrate was omitted or heat-inactivated mitochondria were used. The gentamicin-induced change in fluorescence was completely inhibited by catalase (but not by heat-inactivated catalase), indicating that the decrease in fluorescence was due to hydrogen peroxide. Thus this study demonstrates that gentamicin enhances the production of hydrogen peroxide by mitochondria. Because of their well-documented cytotoxicity, reactive oxygen metabolites may play a critical role in gentamicin nephrotoxicity.

Microvascular ischemia-reperfusion injury in striated muscle: significance of "no reflow"

1992 ◽  
Vol 263 (6) ◽  
pp. H1892-H1900 ◽  
Author(s):  
M. D. Menger ◽  
D. Steiner ◽  
K. Messmer
Keyword(s):  
Shear Rate ◽  
Striated Muscle ◽  
Ischemia Reperfusion ◽  
Reactive Oxygen ◽  
Capillary Density ◽  
Wall Shear Rate ◽  
Reactive Oxygen Metabolites ◽  
Capillary Perfusion ◽  
No Reflow ◽  
Oxygen Metabolites

“No reflow” has been implicated as prominent phenomenon in microvascular injury associated with ischemia-reperfusion (I/R). The objectives of this study were 1) to elucidate the significance of no reflow in microvascular I/R injury of striated muscle and 2) to determine whether reactive oxygen metabolites play a role in the development of postischemic no reflow. By use of the hamster dorsal skinfold preparation and intravital microscopy, microvascular perfusion of capillaries and postcapillary venules of striated muscle was quantitatively assessed before and 30 min, 2 h, and 24 h after 4 h of tourniquet-induced ischemia. I/R was characterized by a significant reduction (P < 0.01) in functional capillary density to 35% of baseline values during initial reperfusion, with incomplete recovery after 24 h (n = 9). In addition, capillary perfusion was found to be extremely heterogeneous, and wall shear rate in postcapillary venules was significantly decreased (P < 0.01). Treatment with either superoxide dismutase (SOD; n = 9) or allopurinol (n = 9) resulted in maintenance of capillary density of 60% of baseline (P < 0.05). Furthermore, I/R-induced capillary perfusion inhomogeneities and decrease of wall shear rate in venules were attenuated significantly (P < 0.01) by SOD and allopurinol. Thus part of capillary perfusion disturbances during I/R in striated muscle may be caused by increased postcapillary vascular resistance, probably mediated by reactive oxygen metabolites. However, the fact that in SOD- and allopurinol-treated animals 40% of the capillaries were still found to be nonperfused indicates that mechanisms other than oxygen radicals play an important role in the development of postischemic no reflow.

Microvascular ischemia-reperfusion injury in striated muscle: significance of "reflow paradox"

1992 ◽  
Vol 263 (6) ◽  
pp. H1901-H1906 ◽  
Author(s):  
M. D. Menger ◽  
S. Pelikan ◽  
D. Steiner ◽  
K. Messmer
Keyword(s):  
Striated Muscle ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Reactive Oxygen ◽  
Microvascular Permeability ◽  
Leukocyte Rolling ◽  
Reactive Oxygen Metabolites ◽  
Oxygen Metabolites ◽  
Reflow Paradox

Ischemia-reperfusion (I/R)-induced microvascular injury is characterized by capillary “no-reflow” and reflow-associated events, termed “reflow paradox,” including leukocyte-endothelium interaction and increase in microvascular permeability. The major objectives of this study were 1) to elucidate the significance of reflow paradox after 4 h of tourniquet-induced ischemia in striated muscle and 2) to determine the role of reactive oxygen metabolites in the pathogenesis of reflow paradox-dependent microcirculatory alterations. By use of in vivo fluorescence microscopy in a striated muscle preparation of hamsters, leukocyte-endothelium interaction in postcapillary venules and macromolecular extravasation from capillaries and venules were quantified before ischemia and after 30 min, 2 h, and 24 h of reperfusion. I/R elicited marked enhancement (P < 0.01) of leukocyte rolling during initial reperfusion and a 20-fold increase of leukocyte adherence (P < 0.01) lasting for the entire postischemic reperfusion period (n = 7). These phenomena were accompanied by significant leakage (P< 0.01) of macromolecules from capillaries and in particular from postcapillary venules (n = 9). Both superoxide dismutase (SOD, 20 mg/kg body wt, n = 7) and allopurinol (50 mg/kg body wt, n = 7) were effective in attenuating I/R-induced leukocyte rolling and adherence. In addition, microvascular leakage was significantly reduced by allopurinol (n = 9) and completely abolished by SOD (n = 9) (P < 0.01). These results support the concept that reactive oxygen metabolites contribute to I/R-induced reflow paradox, resulting in leukocyte accumulation, adherence, and increase in microvascular permeability.

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