Antitumoral properties of aged human monocytes

It is known that older people are more sensitive to cancer and infectious agents and need more time to recover from such disorders. Can this difference in sensitivity to cancer and infections between elderly and younger people be a result of a difference in their immune systems and, more specifically, in the way monocytes react to infectious agents and cancer cells? To determine what happens after cells have aged, human monocytes were purified from young donors (approximately 25 years of age) and from older donors (65 years of age or older) and tested for their ability to respond to the polyclonal activator LPS. Our results showed that monocytes from aged donors (aged monocytes), when compared with monocytes from younger donors (young monocytes) did lose part of their cytotoxicity against tumor cells (A375 human melanoma cells and L929 murine fibroblast cells). In addition, aged monocytes displayed a sharp decrease in IL-1 secretion, but did display the intracellular 31 kDa IL-1 precursor. Moreover, aged monocytes displayed a decrease in the production of reactive oxygen intermediates such as NO2 and H2O2. Finally, aged monocytes stimulated by LPS displayed an increase in intracellular cyclic AMP and have lost their protein kinase C translocation from the cytosol to the plasma membranes. These results suggest that age affects the immunologic and antitumoral properties of human monocytes.

[Reactive oxygen species in the pathogenesis of gastrointestinal tumors. A follow-up study]

Development and growth of gastrointestinal tumors seems to correlate closely with the formation of reactive oxygen intermediates (ROI). It is known, that oxygen-free-radicals are able to induce a precancerous stage and tumor growth by damaging DNA or changing the protein and lipid structure. To investigate, whether the cellular formation of oxygen-free radicals plays a role in the pathogenesis of colorectal carcinoma, we performed the study presented here. 40 patients with colorectal carcinoma were studied over a period of 6 months (before operation, 10 days after operation, 3 months later, 6 months later). Oxygen-free radicals were determined by chemiluminescence response in the whole blood, in granulocytes and in monocuclear blood cells (MBC). At the same time the trace elements selenium, Copper and Zinc, known to play an important role as antioxidants, were measured.

RESULTS

We observed, that the ability of granulocytes for phagocytosis was depleted. However, this effect could be reversed as demonstrated in in vitro stimulation assays. After 6 months the phagocytosis by granulocytes achieved again normal values. Simultaneously a dramatic increase in superoxide-anions generated by mononuclear blood cells was seen. This increase was still obvious after 6 month. Independent of the tumor state selenium deficiency was found in all patients. Since no substitution of selenium was performed after operation, this deficiency was not normalised.

CONCLUSION

The ability for phagocytosis and therefore the immune response is reduced in a reversible manner. In addition reactive superoxide-anions, that are able to induce tumors, are formed. This risk is increased in the absence of selenium. Thus, clinical follow-up studies are needed to determine subclinical tumor relapses and to investigate the role of oxidative stress by chemi-luminescence. As consequence of this study selenium substitution seems to be indicated.

[The role of oxygen radicals in acute pancreatitis. Clinical and experimental results of therapy with free radical scavengers]

Numerous studies support the theory that oxygen free radicals (OR) are involved in the development of tissue damage in all forms of experimental acute pancreatitis. OR are generated in an early phase of the disease before tissue damage is detectable by histology. The pathomechanism that leads to this oxidative stress is not fully understood. The efficacy of scavenger treatment was clearly proven in most models of experimental acute pancreatitis. In first clinical trials applying antioxidant treatment with selenium show favorable results in reducing the lipidperoxidation and improving the antioxidant status. However these preliminary results but must be supported in a larger series of patients to allow proper evaluation of patient outcome.

[The value of selenotherapy in patients with mucoviscidosis]

In cystic fibrosis (CF) patients the antioxidative-oxidative balance is chronically disturbed. Free radicals were generated by bronchial-pulmonal infection and additional exist a deficiency of antioxidative substances by enteral malabsorption especially vitamin E and selenium. Because selenium is an essential content of glutathione peroxidase, which is acting in cytosol and cell membranes, for the present we tested a selenium therapy (peroral sodium selenite 155 micrograms (Se/m2 BSA/d i. e. 4 micrograms Se/kg/d; 4 fold of recommended supply) in 32 CF patients. After three months of this therapy we have seen positive metabolic (normalized content of plasma-selenium, -glutathione peroxidase), endocrine (enhanced efficacy of thyroid hormones, mild increased IgF-I reduced LDL-chol) and clinical consequences (enhanced left ventricular cardiac output), but in three patients side effects (anorexia, nausea, mild hair loss) were observed. Longtime sodium selenite therapy only with 60 micrograms Se/m2 BSA/d over 1 year, stabilized the favourable influences without side effects. For CF patients therefore we recommend a sodium selenite substitution therapy, the best in combination with vitamin E.

[Selenium and antioxidant status in various diseases]

All healthy mammalian organisms are characterized by an equilibrium between the occurrence of highly reactive oxygen species and their destruction by anti-oxidants. Numerous diseases go hand in hand with a disturbance of the homoeostatis. In order to avoid or minimize the destructive effect of the oxidant stress on biological structures, therapies utilizing drugs with anti-oxidant effects are increasingly being applied. Preconditions for these therapies are a characterisation and a follow-up of the anti-oxidant status in the diseased organism. In the course of the present study selenium, glutathione peroxidase and malondialdehyde were determined in patients with various clinical pictures (terminal renal insufficiency, septic shock, high-risk gravidieties, arterioscleroisis, pulmonary carcinoma, acute myocardial infarction, test patients taking the contraceptive pill). Patients with terminal renal insufficiency and those suffering from septic shock syndromes clearly show a selenium decrease in serum and whole blood as well as a drop in the GSH-Px-activity, and increased malondialdehyde concentrations in the serum. Both are a reflection of an increased lipid peroxidation. First results of a selenium therapy are available for patients with therminal renal insufficiency and post-traumatically induced renal failure. The interpretation of the findings in the categories "high-risk gravidity" and "women on the contraceptive pill", which show a normal GSH-Px-activity and significantly increased malondialdehyde concentrations, seems problematic. The organism counteracts an increased lipid peroxidation with a normal plasma-GSH-Px-activity, clearly a sign of a still normal anti-oxidant potential.

Modulation of cyclophosphamide-induced early lung injury by curcumin, an anti-inflammatory antioxidant

Cyclophosphamide causes lung injury in rats through its ability to generate free radicals with subsequent endothelial and epithelial cell damage. In order to observe the protective effects of a potent anti-inflammatory antioxidant, curcumin (diferuloyl methane) on cyclophosphamide-induced early lung injury, healthy, pathogen free male Wistar rats were exposed to 20 mg/100 g body weight of cyclophosphamide, intraperitoneally as a single injection. Prior to cyclophosphamide intoxication oral administration of curcumin was performed daily for 7 days. At various time intervals (2, 3, 5 and 7 days post insult) serum and lung samples were analyzed for angiotensin converting enzyme, lipid peroxidation, reduced glutathione and ascorbic acid. Bronchoalveolar lavage fluid was analyzed for biochemical constituents. The lavage cells were examined for lipid peroxidation and glutathione content. Excised lungs were analyzed for antioxidant enzyme levels. Biochemical analyses revealed time course increases in lavage fluid total protein, albumin, angiotensin converting enzyme (ACE), lactate dehydrogenase, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, acid phosphatase, lipid peroxide levels and decreased levels of glutathione (GSH) and ascorbic acid 2, 3, 5 and 7 days after cyclophosphamide intoxication. Increased levels of lipid peroxidation and decreased levels of glutathione and ascorbic acid were seen in serum, lung tissue and lavage cells of cyclophosphamide groups. Serum angiotensin converting enzyme activity increased which coincided with the decrease in lung tissue levels. Activities of antioxidant enzymes were reduced with time in the lungs of cyclophosphamide groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in the prooxidant and antioxidant status of human leukemic T-lymphocyte MOLT4 cells treated with potassium chromate

The involvement of reactive oxygen species in chromate-induced genotoxicity has been postulated. Because intracellular antioxidants help in eliminating the reactive species of oxygen, we have investigated both the prooxidant and antioxidant status of human leukemic T-lymphocyte MOLT4 cells exposed to nontoxic levels of chromium(VI) in culture. The cells treated with 0-->200 microM potassium chromate in a salts/glucose medium for 2 h were found to contain significantly lower levels of both small molecular weight and macromolecular antioxidants. In particular, the levels of glutathione and ascorbate were found to decrease with increased doses of chromate exposure in a dose-dependent manner. As little as 10 microM chromate was found to decrease these small molecular weight antioxidants significantly (p < 0.01). The macromolecular antioxidants, such as glutathione peroxidase, catalase, glutathione reductase, glucose-6-phosphate dehydrogenase and superoxide dismutase were also significantly (p < 0.01) decreased by exposing the cells to as little as 10 microM chromate. Concomitantly, there was a dose-dependent increase in intracellular H2O2 accumulation in cells exposed to chromium(VI). These results indicate that chromate-induced genotoxicity may be due, at least in part, to decreased levels of intracellular antioxidants in conjunction with an increased production of the reactive oxygen species.

Reactive oxygen species produced by liver mitochondria of rats in sepsis

Reactive oxygen species (ROS) can be generated in experimental shock states through several different mechanisms. We measured ROS production in metabolically active liver mitochondria from rats rendered septic by cecal ligation and puncture. By polarography, the State 4 and State 3 respiration rates of liver mitochondria isolated from septic animals were no different from control organelles. During oxidation of succinate, however, nonenzymatic hydroxylation of salicylic acid to 2,3-dihydroxybenzoic acid by mitochondria from septic rats was increased, indicating generation of hydroxyl radical (OH.). Inhibition of electron transport at Complex I with rotenone had no effect on this pattern of OH. production, but rotenone and cyanide abolished the differences in OH. formation between control and septic liver mitochondria. Measurements of H2O2 release suggested that septic mitochondria will increase rates of H2O2 production in the presence of succinate. Additional investigations revealed no difference in the release of iron between septic and control mitochondria. When referenced to respiration rate, both OH. and H2O2 production were greater in septic liver mitochondria. The reproducible effect of sepsis on generation of reactive oxygen species by liver mitochondria utilizing FAD-linked but not NAD-linked substrates suggests that enhanced mitochondrial oxidative stress in sepsis is related to alterations in the activity of Complex II of the electron transport chain.

Regional selectivity in ethanol-induced pro-oxidant events within the brain

Several biochemical parameters that reflect the presence of excess levels of reactive oxygen species were modulated in the brains of rats exposed acutely or subchronically to ethanol. These parameters included depression of cytosolic glutathione (GSH) concentration and of glutamine synthetase levels. However, using these indices, there was a significant difference in susceptibility to ethanol in different brain regions. After dietary exposure to ethanol for 12 days, these indices were selectively depressed in the striatum but not in the cerebral cortex or cerebellum. Eighteen hours after a single acute dose of ethanol (4.5 g/kg body wt), the striatum was also the only one of these areas in which proteolytic activity was elevated by ethanol treatment. Two injections of acetaldehyde (300 mg/kg), given 18 and 2 hr prior to tissue preparation, caused a specific reduction of glutamine synthetase in the striatum and a decrease of GSH levels in both striatum and cerebellum. Taken together, the results suggest a distinctive vulnerability of the striatum to ethanol-promoted oxidative events. Rather than ethanol exerting effects directly, the metabolite acetaldehyde may be the primary agent responsible for these changes.

Effects of zinc on production of active oxygen species by rat neutrophils

The effects of zinc on the production of active oxygen species were investigated in rat neutrophils by chemiluminescence and spectrophotometric assays. The luminol-dependent chemiluminescence in unstimulated neutrophils showed a single peak. Zinc at concentrations lower than 0.1 mM augmented the intensity of chemiluminescence and showed a bimodal pattern, the first peak of which was inhibited by superoxide dismutase and catalase, while the second peak disappeared in the presence of catalase, but was unaffected by superoxide dismutase. At the same concentrations of zinc, O2- and H2O2 production increased, but secretion and activity of myeloperoxidase were not affected. Zinc at 0.1 mM enhanced the second peak of luminol-dependent chemiluminescence, and concomitantly O2- and H2O2 production of neutrophils stimulated with formyl-methionyl-leucyl-phenylalanine. Homogenized neutrophils showed a bimodal pattern on induction by zinc, the second peak of which was inhibited slightly by catalase and completely by sodium azide, but was not inhibited by superoxide dismutase. Zinc-induced O2- production was inhibited by pertussis toxin, but was not significantly inhibited by a protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), or a calmodulin antagonist, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7). These results suggest that zinc can augment luminol-dependent chemiluminescence by increasing O2- production through the classical signal transduction pathway, and by increasing H2O2 not via O2-.

Oxyradical generation after resuscitation of hemorrhagic shock with blood or stroma-free hemoglobin solution

Hypovolemic states are characterized by inadequate tissue perfusion; when this state is reversed, the reintroduction of oxygen is accompanied by the excess generation of oxyradicals and these, in turn, may cause "reperfusion injury" in susceptible tissues. When hemoglobin solution is used to resuscitate the hypovolemic state, the generation of oxyradicals may be enhanced by catalytic means. The generation of oxyradicals was estimated in dogs subjected to the acute removal of 35 ml/Kg blood, and resuscitated 45 mins thereafter with an equal volume of either autologous blood (Group I, n = 6) or 6% stromafree hemoglobin solution (S.F.H.S.) (Group II, n = 6). Hepatic and pancreatic enzymes were measured in blood drawn at intervals. The hypovolemic state was characterized by profound hypotension which was reversed by resuscitation. Oxyradical generation in arterial blood samples, drawn at various times, was estimated by the generation of oxidation products (2,3- and 2,5-dihydroxybenzoic acid) of exogenously administered sodium salicylate, determined by HPLC in plasma samples extracted with diethyl ether. Salicylate oxidation products rose significantly above the baseline value in Group I dogs, whereas they rose 5-6-fold higher than the baseline values in those of Group II. The actual values attained and the increments were significantly (p < .05) greater in Group II than in Group I. In the group resuscitated with S.F.H.S., catalytically active iron concentration in plasma also rose 10-12-fold higher and was associated with spuriously elevated levels of gamma-glutamyl transferase due to interference with the assay. These findings are consistent with the hypothesis that blood-resuscitation of hypovolemic shock is accompanied by oxyradical generation of a modest degree; in contrast, S.F.H.S.-resuscitation introduces catalytically active iron and is accompanied by oxyradical generation of a significantly greater degree.

Adhesion to fibronectin augments eosinophil radical oxygen products

Fibronectin, an extracellular matrix component, is a ligand for very late activation antigen (VLA)-4, which is one of the beta 1-integrin family of molecules expressed by eosinophils. This study examined the effect of adherence to fibronectin on radical oxygen products from eosinophils. Adhesion of eosinophils to fibronectin resulted in enhancement of eosinophil production of radical oxygen species, as determined by luminol-dependent chemiluminescence of eosinophils stimulated with calcium ionophore. It was concluded that eosinophil adhesion to extracellular matrix via adhesion molecules may be important in the pathogenesis of allergic inflammation through eosinophil activation.

D-penicillamine inhibits the action of reactive oxygen species in the pig pulmonary circulation

Oxygen radicals produced by the hypoxanthine-xanthine oxidase (Hyp-XO) system potently constrict the pulmonary circulation of pigs. D-penicillamine (DPA) is thought to be a free radical scavenger. In the present work we have studied if DPA may influence the vasoactive action of Hyp-XO in pig lungs. Further, we have measured how this drug influences the output of cyclooxygenase and lipoxygenase products from the left atrium in pigs infused with XO into the pulmonary circulation. Twelve young pigs were divided into two groups. Group 1, the XO group, was infused 1 U/kg XO into right atrium. Group 2, the DPA group, was pretreated with DPA, 100 mg/kg intravenously before XO infusion as in group 1. Pulmonary artery pressure, left atrial pressure, pulmonary artery blood flow and systemic blood flow and pressure were recorded continuously. Plasma tromboxane B2 and prostaglandin (6-keto-PGF1 alpha) were determined with a radioimmunoassay method. Cysteinyl containing leukotrienes LTC4, LTD4, and LTE4, were measured together by RIA analyses of plasma samples, using a monoclonal antibody. There was a significant parallel decrease in paO2 and saO2 during the 130 minutes duration of the experiments in both groups without differences between the groups. Pulmonary vascular pressure and resistance increased sharply with a peak found after 25 minutes in the XO group. DPA attenuated the hemodynamic response. DPA inhibited the XO induced pulmonary blood pressure changes with 80% and inhibited the increase in pulmonary vascular resistance 68%. Plasma TXB2 increased two folds in the XO group reaching a maximum after 40 minutes, this effect was completely inhibited by DPA (92% inhibition). DPA also inhibited the XO induced increase in 6-keto-PGF1 alpha, however, not as efficient as with TXB2 (40% inhibition). Plasma cysteinyl leukotrienes increased after XO infusion reaching a peak at 20 minutes. DPA completely abolished this effect (100% inhibition). The study demonstrates that DPA attenuates or even abolishes the hemodynamic effects of XO on the pulmonary circulation in pigs. It seems that DPA inhibits the production of both lipoxygenase and cyclooxygenase products per se, and it is tempting to speculate that the observed DPA effect is caused by its action as an oxygen radical scavenger. It is further speculated that the vasoconstricting effect of XO is due to the fact that oxygen radicals may inactivate nitric oxide (NO), and that DPA stabilizes NO so it more efficiently possess its vasorelaxant activity. We conclude that DPA is an extremely potent inhibitor of XO induced pulmonary vascular effects. The mechanism of action is not fully understood, although its action as an oxygen radical scavenger may explain part of it.

Reactive oxygen species, lipid peroxidation and enzymatic defence systems in human spermatozoa

The reactive oxygen species, hydrogen peroxide (H2O2) and superoxide anion (O2o-), were generated with a xanthine-xanthine oxidase system and their effect on human sperm function was studied. The action of reactive oxygen species on selected human spermatozoa resulted in a decreased capacity for ionophore-induced acrosome reaction, a decrease in sperm motility, an increase in the concentration of lipid hydroperoxides and a loss of membrane polyunsaturated fatty acids. H2O2 was the key intermediate of the deleterious effects exerted by the xanthine and xanthine oxidase. Among these parameters, the acrosome reaction appeared most susceptible to the reactive oxygen species generated by the xanthine-xanthine oxidase system, and was decreased without sperm motility being affected. Treatment with H2O2 was shown to inactivate several enzymatic activities involved in the antioxidant defence of spermatozoa: glutathione peroxidase, superoxide dismutase and glucose-6-phosphate dehydrogenase. H2O2 and O2o- were shown to be involved in the lipid alterations triggered by the xanthine-xanthine oxidase system. Singlet oxygen is proposed to intervene in the lipoperoxidation process. The inefficacy of mannitol in protecting spermatozoa suggests that hydroxyl radicals were not produced in the extracellular medium.

The role of free radicals in toxicity and disease

Free radicals are defined as atoms or molecules that contain one or more unpaired electrons. The toxicity of many xenobiotics is associated with the metabolic activation of foreign compounds to form free radicals or with the production of reactive oxygen species as superoxide anion, hydroxyl radicals or hydrogen peroxide which are responsible for the tissue damaging effects as lipid peroxidation, and DNA and protein damage. Oxidative stress associated with production of reactive oxygen species is believed to be involved not only in the toxicity of xenobiotics but also in the pathophysiology of aging, and various age-related diseases, including cataracts, atherosclerosis, neoplastic diseases, diabetes, diabetic retinopathy, chronic inflammatory diseases of the gastrointestinal tract, aging of skin, diseases associated with cartilage, Alzheimer's disease, and other neurologic disorders. The cellular sources of free radicals and reactive oxygen species, the biological targets of free radicals, and clinical conditions which are associated with free radical production and tissue damage are reviewed. In addition, potential therapeutic approaches to the prevention of free radical damage are considered. Free radical-induced injury can explain many clinical conditions.

Immunological functions of aged human monocytes

Aging is associated with an increased occurrence of infection and cancer, and, as people age, they begin to exhibit age-related immune deficiencies, collectively termed immunosenescence. To determine the effects of age on human monocytes, 'aged monocytes' (isolated from individuals > or = 65 years of age) were compared with 'young monocytes' (isolated from individuals approximately 25 years of age) for their ability to be activated by lipopolysaccharide. Our results show that aged monocytes display a decrease in their cytotoxicity against tumor cells in vitro, a decrease in interleukin (IL1) secretion (although no decrease in IL1 precursor production was observed), a decrease in reactive oxygen and nitrogen intermediate (ROI/RNI) release, an increase in intracellular levels of cyclic adenosine monophosphate and a loss of protein kinase translocation. Therefore, aged monocytes present distinct characteristics of immunosenescence.

2-Hydroxyadenine (isoguanine) as oxidative DNA damage: its formation and mutation inducibility

In our experiments we found that hydroxylation occurs at the C-2 position of adenine by oxygen radical treatment (Fe(2+)-EDTA) of dA, dATP, and single- and double-stranded DNA. This oxidatively damaged base, 2-hydroxyadenine (also known as isoguanine), was produced more efficiently in monomers than in polynucleotides. 2-Hydroxydeoxyadenosine triphosphate was incorporated opposite T and C in a DNA template by DNA polymerase alpha and only opposite T by the Klenow fragment. The Klenow fragment, DNA polymerases alpha and beta incorporated dTMP and other nucleotides opposite 2-OH-Ade in DNA templates in vitro in a sequence-dependent manner. These results suggest that the formation of 2-OH-Ade in DNA will induce mutations in cells.

The role of xanthine oxidase in ischemia/reperfusion damage of rat liver

Oxygen radicals have been proposed to be involved in the induction of liver cell damage during reperfusion after ischemia. The role of xanthine oxidase in this process and the potential of the antioxidant system have been studied in a model of in vivo ischemia of rat liver followed by 1 h reperfusion by the use of enzyme histochemistry. Based on decreased lactate dehydrogenase activity in certain areas of liver parenchyma, cell damage could already be detected at 1 h reperfusion after ischemia. Incubations performed on serial sections showed that the same areas contained decreased activities of xanthine oxidoreductase, xanthine oxidase, catalase and glucose-6-phosphate dehydrogenase. Some individual cells in the undamaged liver parenchyma expressed a very high glucose-6-phosphate dehydrogenase, which suggests that these cells have a good defence against oxidative stress. It is concluded that oxygen radicals derived from xanthine oxidase do not play a decisive role in the induction of cell damage immediately at reperfusion after ischemia. However, it cannot be excluded that xanthine oxidase present in the blood stream can give rise to the development of additional damage later on.

Active-oxygen scavenging activity of plant extracts

To find antioxidative compounds present in plants, 65 types of plant extract were tested using the neotetrazolium method for evidence of superoxide anion-scavenging effects and 7 plant extracts were selected for further investigation. The activity of active-oxygen scavengers such as superoxide anion radicals, hydroxyl radicals, singlet oxygens and lipid peroxides in the 7 plant extracts (Aeseclus hippocastanum L., Hamamelis virginiana L. Polygonum cuspidatum Sieb., Quercus robur L., Rosemarinous officinalis L., Salvia officinalis L. and Sanguisorba officinalis L.) was examined in detail by both ESR spin-trapping and malondialdehyde generation. Furthermore, the active-oxygen scavenging activity of these plant extracts was evaluated using a murine dermal fibroblast culture system. Both Aeseclus hippocastanum L. and Hamamelis virginia L. were found to have strong active-oxygen scavenging activity of and protective activity against cell damage induced by active oxygen. Both Aeseclus hippocastanum L. and Hamamelis virginiana L. are proposed as potent plant extracts with potential application as anti-aging or anti-wrinkle material for the skin.

Selenium, oxygen-derived free radicals, and ischemia-reperfusion injury. An experimental study in the rat

Circulatory shock and its treatment have been compared to a whole-body ischemia and reperfusion with activation of oxygen-derived free radicals. A pilot study had suggested a selenium redistribution in this context. To verify this hypothesis, an experimental study was designed. Temporary occlusion of the superior mesenteric artery was performed in 18 male adult Wistar rats using clamping for 0, 10, and 20 min. Hemodynamic and biochemical data were assessed before clamping and 20 min after release of the mesenteric blood flow. After release, mean arterial pressure decreased, plasma lactate increased, and erythrocyte glutathione peroxidase decreased. Plasma and erythrocyte selenium did not change; however, a slight decrease in plasma selenium was observed when related to hematocrit (to take into account the fluid balance). Erythrocyte-reduced glutathione did not change. In contrast, liver and kidney selenium increased, whereas reduced glutathione decreased in kidney, but not in liver after 20 min of clamping as compared to the sham-operated group. These results suggest that, after temporary intestinal ischemia, the changes in selenium and reduced glutathione observed in blood and tissues, like liver or kidney, could be related to a redistribution pattern in selenium metabolism during shock injury.

Increased eosinophil oxidative metabolism by treatment with soluble intercellular adhesion molecule-1

Adhesion molecules may play an important role not only in adherence of inflammatory cells (particularly eosinophils) to an inflamed focus but also in activation of these cells. It is therefore of interest to evaluate eosinophil activation via intercellular adhesion molecule-1 (ICAM-1) and the beta 2-integrin family, namely CR3 (Mac-1), lymphocyte function-associated antigen (LFA)-1 alpha and LFA-1 beta, which are ligands for ICAM-1. Reactive oxygen species generated by eosinophils have also been considered capable of causing airway injury at the inflamed focus. This study examined the effect of recombinant soluble ICAM-1 and its ligands on eosinophil-induced radical oxygen products in terms of luminol-dependent chemiluminescence. Recombinant soluble ICAM-1 augmented eosinophil oxidative metabolism. It was concluded that signaling via adhesion molecules might play an important role in the pathogenesis of allergic inflammation through activation of eosinophils, e.g. an increase in oxidative metabolism.

[Relationship between tumour necrosis factor and anemia of malaria]

In this paper, the relation between the level of the reactive oxygen species (ROS) and relevant free radicals in the blood plasma of the BALB/c mice infected with Plasmodium berghei ANKA strain and their erythrocytic deformability (ED), and the relation between the ED and the Hb indices of these mice were studied by chemiluminescence (CL), induced CL (ICL) and laser diffraction method. The results indicated that the ED decreased with the increase of the level of ROS and free radicals in blood plasma when the anemia is developing. The use of antioxidants may restrain the course and raise the Hb index. The authors deem that the excess TNF produced in the later stage of malaria may induce the release of excess ROS and free radicals from phagocytes, which may cause damage on the deformability of erythrocytes and a drop in ED, resulting in the anemia of malaria.

Neutrophil-macrophage interaction: a paradigm for chronic inflammation

Autoimmune diseases, such as rheumatoid arthritis and inflammatory bowel disease are characterized by chronic inflammatory responses resulting in tissue damage. These diseases have a number of common denominators including: abnormal cytokine expression, aberrant antigen-antibody complexes, T cell anomalies, and increased numbers of neutrophils and macrophages. We propose that the interaction between neutrophils and macrophages induces a state of chronic inflammation which contributes to the disease state. One of the central players in this scenario is myeloperoxidase (MyPo). This enzyme functions in the 'cytotoxic triad' and is involved in cell killing. Studies done by the present investigators have known that MyPo, which is released from neutrophils, induces macrophages to secrete interleukin-1, interferon alpha beta and tumor necrosis factor alpha. Furthermore, our studies have suggested a major immunoregulatory role of this enzyme. We propose that the release of MyPo from neutrophils and subsequent binding to macrophages initiates a cascade of events which enhance the production of reactive oxygen intermediates and cytokine expression resulting in the chronic inflammatory state associated with autoimmune diseases.

Possible role of oxidative damage in metal-induced carcinogenesis

This review presents and evaluates evidence relevant to the mechanisms of metal carcinogenicity with special emphasis on the emerging hypothesis of the oxidative nature of metals' effect on DNA. The carcinogenic transition metals are capable of in vivo binding with the cell nucleus and causing promutagenic damage that includes DNA base modifications, inter- and intramolecular crosslinking of DNA and proteins, DNA strand breaks, rearrangements, and depurination. The chemistry of that damage and the resulting mutations observed in vitro and in metal-induced tumors are both characteristic for oxidative attack on DNA. The underlying mechanism involves various kinds of active oxygen and other radical species arising from metal-catalyzed redox reactions of O2, H2O2, lipid peroxides, and others, with certain amino acids, peptides, and proteins. Other metal-mediated pathogenic effects, such as enhancement of lipid peroxidation, stimulation of inflammation, inhibition of cellular antioxidant defenses, and inhibition of DNA repair, may also contribute to that mechanism. Thus far, published data revealing the oxidative character of metal-induced promutagenic DNA alterations are particularly strong for two of the most powerful human metal carcinogens, chromium and nickel. However, without excluding contribution of other effects, the promotion of oxidative damage tends to take the leading role in explaining mechanisms of carcinogenicity and acute toxicity of certain other metals as well.

Clinical and enzymatic investigation of induction of oxygen free radicals by ischemia and reperfusion in human hepatocellular carcinoma and adjacent liver

Serum concentration of thiobarbituric acid (TBA) reactants in the hepatic vein were measured before and after transient dearterialization of the liver in five human subjects bearing unresectable hepatocellular carcinoma (HCC). During 1 hour of the occlusion of the hepatic artery, change in TBA reactants level was slight. However, the mean value of TBA reactants in 1 hour after the reflow increased to 1.50 +/- 0.11 nmol/ml (mean +/- S.E.) and was significantly higher (p < 0.05) than those before hepatic dearterialization (1.28 +/- 0.11 nmol/ml) and just before the release of occlusion (1.32 +/- 0.09 nmol/ml). Further, two endogeneous scavenger enzymes, superoxide dismutase (SOD) and catalase (CAT), and one of the major sources of oxygen free radicals, xanthine oxidase (XOD) were measured in human untreated HCC and the corresponding adjacent liver tissue. The results demonstrated an increase in SOD in 81.8% (9/11) of HCC, and a decrease in CAT in 72.7% (8/11) of HCC when compared with the corresponding adjacent liver tissue. The mean value of SOD in HCC was significantly higher (66.8 +/- 6.5 vs 52.8 +/- 3.8 U/mg protein; p < 0.05), and that of CAT was significantly lower (22.6 +/- 2.4 vs 36.0 +/- 6.1 U/mg protein; p < 0.05) than those in liver tissue. All of nine HCC samples had a significantly lower activity of XOD (6.4 +/- 1.9 vs 20.3 +/- 3.4 pmol/minute/mg protein; p < 0.01) than the corresponding liver tissue. There was no obvious relation between the content of SOD and CAT in HCC, or in liver tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Neutrophil chemotaxis, phagocytosis, and generation of reaction oxygen species show a hierarchy of responsiveness to increasing concentrations of N-formyl-Met-Leu-Phe

We assessed the effect of varying concentrations of N-formyl-methionyl-leucyl-phenylalanine (fMLP) on neutrophil chemotaxis, phagocytosis, and reactive oxygen species generation. Boyden chamber chemotaxis was first elicited at an fMLP concentration of 10(-11) M, reached a peak at 10(-10) M, and declined at higher concentrations. Phagocytosis was first activated at 10(-10) M, reached its highest level at 10(-9) M, and declined at higher concentrations. O2-, H2O2 and OH. generation were elicited to a significant degree only at a fMLP concentration of 10(-8) M, or higher, reaching a peak at 10(-6) M. Thus, a distinct hierarchy was observed in the order of activation of these three neutrophil functions to varying concentrations of a soluble agonist. A teleologic model of neutrophil function that accounts for these observations is proposed.

Microvascular function in the peripheral vascular bed during ischaemia and oxygen-free perfusion

OBJECTIVES

To determine the influence of acute ischaemia and absence of leukocytes on the microvascular function and capillary permeability in skeletal muscle.

DESIGN

Prospective, open study.

SETTING

University Department of Vascular Surgery and Institute of Medical Physiology.

MATERIALS AND METHODS

Ten isolated cat gastrocnemius muscles were perfused with oxygen-free Ringer-albumin solution through the femoral artery. At 5 microliters bolus with 14.8 MBq 51Cr-EDTA was injected through a side branch into the femoral artery, and the response function was detected over the muscle by a scintillation detector connected to a spectrometer and a computer. The perfusion coefficient was measured directly at the venous outlet. The response function was analysed in accordance with non-compartmental black box kinetic principles to give perfusion rate, capillary extraction fraction and capillary diffusional permeability-surface area product (PdS). In separate experiments the molecular size and the free diffusion coefficient of 51Cr-EDTA in water at 37 degrees C were determined by a modified true transient diffusion method.

MAIN RESULTS

During perfusion the PdS-product increased as a function of flow rate, f, in accordance with the linear regression line PdS = 1.78 + 0.15 f between 5 to 60 ml/100 g/min. This permeative conductance was identical to that found previously in a similar experimental set up with oxygenated whole blood perfusion. During oxygen free perfusion the perfusion rate was a linear function of arterial perfusion pressure, and autoregulation of blood flow did not occur in response to variations of arterial perfusion pressures. The free diffusion coefficient in water at 37 degrees C for 51Cr-EDTA was 7.4 x 10(-6) cm2/s (n = 36), which corresponds to a Stokes-Einstein molecular radius, rSE, of 0.439 nm.

CONCLUSIONS

In spite of complete anoxia and absence of normal microcirculatory flow regulating mechanisms there is no sign of changes in capillary diffusional permeability for smaller hydrophilic molecules and functional membrane damage is not elicited in the absence of oxygen under these conditions.

[Oxygen reactive species in spermatozoa]

The free radicals of oxygen are chemical species of this element formed through enzymatics and non enzymatics reactions and they have been involved in many pathologic and physiologic processes. The most reactive chemical species of oxygen are the hydrogen peroxide and the free radicals frecuradils superoxide anion, hydroxil and free radical, this one being the most reactive. The mammalian spermatozoa, including the human, produce free radicals of oxygen and hydrogen peroxide; although this cell normally has enzymatic mechanics to protect itself from the possible damage of this toxic agents. In spite of, the spermatozoa is susceptible to "oxitative stress", and maybe it is due to the high concentrations of insaturated fatty acids. This fact may be important in the pathology of certain types of masculine infertility like oligozoospermia, because it displays a discontrol production of oxygen reactive species in the spermatozoa.

Role of reactive O2 in phagocyte-induced hypermetabolism and pulmonary injury

Activated phagocytes possess an enormous capacity for O2 consumption via NADPH oxidase. NADPH oxidase partially reduces O2, forming superoxide (O2-). Host enzymes rapidly complete O2- reduction to H2O, leaving little trace of its prior existence. Our objectives were to estimate the magnitude of whole body phagocyte respiration and determine the contribution of NADPH-derived O2- to the ensuing phagocyte-induced pulmonary injury. These objectives were accomplished using specific inhibitors of NADPH oxidase, diphenyl iodonium (DPI) and di-2-thienyl iodonium (DTI). Guinea pigs received intravenous injections of DPI (3.5 mg/kg), DTI (7.5 mg/kg), or vehicle followed by phorbol myristate acetate (PMA). Phagocyte activation by PMA immediately increased whole body respiration from 13.6 to 16.1 ml O2.kg-1.min-1 (P < 0.05). DPI and DTI completely blocked the increase in respiration induced by PMA injection (P < 0.05). Baseline respiration was unchanged by the NADPH oxidase inhibitor alone. Likewise, there was no effect on the respiration of isolated heart and kidney mitochondria from animals receiving the inhibitor with or without PMA. DPI attenuated the pulmonary injury induced by PMA. DPI attenuated the pulmonary injury induced by PMA. The ratio of lung water weight to dry weight was lower (6.4 +/- 0.3 vs. 8.3 +/- 0.6) and arterial PO2 was higher (86 +/- 9 vs. 56 +/- 6 Torr) in animals receiving DPI plus PMA than in those receiving PMA alone. In conclusion, phagocyte activation in vivo increased total body respiration by approximately 18%. The burst in respiration is attributed to the phagocyte respiratory burst in which NADPH oxidase partially O2 to O2-.(ABSTRACT TRUNCATED AT 250 WORDS)

Contrasting influence of peplomycin and azelastine hydrochloride (Azeptin) on reactive oxygen generation in polymorphonuclear leukocytes, cytokine generation in lymphocytes, and collagen synthesis in fibroblasts

The influence of peplomycin (PLM) and azelastine hydrochloride (Azeptin) on reactive oxygen (RO) and cytokine generation was examined in human peripheral blood mononuclear leukocytes, polymorphonuclear leukocytes (PMN), and rabbit alveolar macrophages (RAM). In addition, the influence of these drugs on DNA and collagen synthesis was investigated in human gingival and rabbit pulmonary fibroblasts. In vitro, PLM increased the FMLP- and PMA-induced chemiluminescence and superoxide (O2-) generation in human PMN and RAM in a dose-dependent manner. In contrast to PLM, Azeptin dose-dependently suppressed RO generation. Such contrasting actions of PLM and Azeptin were also observed in RAM and PMN obtained from rabbits treated with PLM or Azeptin. Even when human PMN were preincubated with 10-100 micrograms/ml of PLM, the increase in RO generation was negligible in the presence of 10(-5) M Azeptin in the culture medium. No increases in RO generation were observed in RAM or PMN obtained from rabbits that had received PLM (0.1 mg/kg per day) and Azeptin (0.04 mg/kg per day) concomitantly. PLM suppressed superoxide dismutase activity in RAM and human PMN, while Azeptin did not affect this activity. In vitro, PLM up-regulated the release of interleukin-1 beta, interleukin-6, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor both from human cells and from RAM and pulmonary fibroblasts. In the generation of these cytokines, Azeptin abrogated the up-regulatory action of PLM. PLM and Azeptin also had contrasting actions in [3H]thymidine and [3H]proline incorporation in human and rabbit fibroblasts. Furthermore, protein tyrosine phosphorylation, in particular that of a 115-kDa protein in human PMN, was suppressed by Azeptin and enhanced by PLM. These results seem to indicate that up-regulated RO and collagen generation are the causative factors of PLM-induced pulmonary fibrosis and that Azeptin may suppress the adverse effect.

[Oxygen radicals and nitrogen monoxide in sepsis]

Accumulation and stimulation of PMN-leukocytes, enhanced prostaglandin metabolism and tissue hypoxia lead to high concentrations of oxygen radicals and their metabolites in septic shock. Synchroneously, excessive high concentrations of nitric oxide are found, most likely due to the stimulation of its inducible synthetase. Oxygen radicals seem to be attributable for the irreversible tissue damage leading to multiple organ failure in sepsis. High concentrations of nitric oxide induce the typical macro- and microcirculatory derangements normally seen in sepsis. Both mediators are present in the early phase of sepsis and seem to influence the course of disease. Therapeutic interventions such as scavenger therapy or inhibition of the inducible NO-synthetase are promising. The results of the first clinical therapeutic studies, however, were not always conclusive. It is still unclear which scavenger and which inhibitor should be given when and in which dosage in order to improve the outcome of sepsis and septic shock. Furthermore, it remains unclear to which extend oxygen radicals and nitric oxide react with each other, thus possibly potentiating their effects. The open questions still warrant further research and may lead to new therapeutic options improving the morbidity and mortality of this severe disease.

Studies on the effect of sulfite on benzo[a]pyrene-7,8-dihydrodiol activation to reactive intermediates in human polymorphonuclear leukocytes

Sodium sulfite, a hydrolysis product of the environmental pollutant sulfur dioxide increased the activation of (-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BP-7,8-diol) to the (+)-anti-enantiomer of trans-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) in phorbol myristate acetate (PMA)-stimulated human polymorphonuclear leukocytes (PMNs). This effect was potentiated in the presence of DMSO. No significant effect of sulfite on BP-7,8-diol activation was observed in resting leukocytes. As revealed by the 32P-postlabelling technique the dominant adduct in both intracellular DNA and to DNA added to the leukocytes was (+)-anti-BPDE bound to the exocyclic nitrogen of deoxyguanosine. The mechanism underlying the stimulatory effect of sulfite on diol epoxide production and increased DNA-binding probably involves one-electron oxidation of sulfite to a sulfur trioxide radical anion and subsequent reaction with molecular oxygen to form the corresponding peroxyl radical. This step obviously requires PMA-initiated oxidative burst and thus, production of superoxide radical anions (O2-.).

Quartz inactivates alpha 1-antiproteinase: possible role in mineral dust-induced emphysema

Occupational exposure to some types of mineral particles has been shown to be associated with the development of emphysema, but the mechanism of this process is unknown. Because many mineral particles are known to catalyze the formation of active oxygen species in aqueous solution, we hypothesized that mineral particles could oxidatively inactive antiproteinases, leading to an imbalance between protease and antiprotease activities, events similar to those believed to occur with cigarette smoke. To test this hypothesis, human alpha 1-antiproteinase (alpha 1-AP) was incubated with suspensions of freshly ground or aged quartz, and antiproteolytic activity was determined by using porcine pancreatic elastase. Increasing concentrations of quartz were associated with increasing losses of antiproteolytic activity; this effect could be prevented by catalase. Freshly ground quartz was more active than aged quartz. Western blot analysis for alpha 1-AP showed abnormal banding, suggesting that porcine pancreatic elastase-alpha 1-AP complex formation was impaired by silica exposure. Chemical assay of aqueous quartz suspensions demonstrated production of hydrogen peroxide; incubation of alpha 1-AP with hydrogen peroxide caused a dose-dependent loss of antiproteolytic activity, and this also could be prevented by catalase. We conclude that, at least in vitro, quartz can inactivate alpha 1-AP through a hydrogen peroxide-mediated mechanism and that oxidative loss of antiproteinase activity could play a role in mineral dust-induced emphysema.

Activation of Kupffer cells and neutrophils for reactive oxygen formation is responsible for endotoxin-enhanced liver injury after hepatic ischemia

The potential role of reactive oxygen species generated by Kupffer cells and neutrophils was investigated in a model of endotoxin-enhanced liver injury after hepatic ischemia. Male Fischer rats were subjected to 20 min ischemia and reperfusion of up to 24 h; .5 mg/kg Salmonella enteritidis endotoxin was injected at 30 min of reperfusion. The animals developed severe liver injury resulting in 50% hepatocellular necrosis at 24 h. Isolated Kupffer cells and neutrophils from the postischemic liver generated 10-fold more superoxide than cells from control livers. Treatment with gadolinium chloride (GdCl3) selectively reduced the capacity of Kupffer cells to generate superoxide by 65% and attenuated liver injury by 73% at 4 h and 58-69% at 24 h. Monoclonal antibodies against neutrophil adhesion molecules (CD11/CD18) had no effect on the early injury but reduced hepatocellular necrosis by 90-95% at 24 h. The antioxidant Trolox and the iron-chelator deferoxamine attenuated liver injury by 71 and 80%, respectively. It is concluded that Kupffer cells are mainly responsible for the initial injury, and neutrophils are the dominant cytotoxic cell type during the later phase. Reactive oxygen generated by both cell types is critical for this pathogenesis.

Control of inflammatory processes by cell-impermeable inhibitors of phospholipase A2

Cell-impermeable inhibitors of phospholipase A2 were prepared by linking inhibiting molecules to macromolecular carriers which prevent the inhibitor's internalization. These preparations inhibit the release of oxygen reactive species from neutrophils and cell death induced by inflammatory agents, as well as bleomycin-induced lung injury.

Iron depletion in the remnant kidney

Urinary and proximal tubular iron are increased after subtotal nephrectomy, and iron depletion has been shown to be beneficial in proteinuric models of chronic renal disease in rats. In this study, iron depletion by low iron pair-fed diet and periodic phlebotomy was induced for 6 months in rats with partial (5/6) nephrectomy, resulting in a reduction in hematocrit and serum iron in all iron-deficiency subgroups. Tubular iron, assessed by energy dispersive analysis and electron microscopy, was reduced in quantity but not number of iron-containing lysosomes only within 1 subgroup of severe iron deficiency (p < 0.05). There was no improvement in serial isotopic glomerular filtration rate measurements, urinary protein and transferrin excretion, tubular damage scores, serum creatinine, or measures of reactive oxygen species (ROS) generation. In a subgroup of rats with no supplementation of sulfhydryl amino acids (cysteine and methionine) which can act as ROS scavengers, iron deficiency increased urinary protein excretion (213.3 +/- 23.0 mg/24 h, mean +/- SEM, vs. 87.4 +/- 16.1, p < 0.001), urinary transferrin excretion (p < 0.05), kidney weight (p < 0.05) and tissue malondialdehyde, a lipid peroxidation product (0.78 +/- 0.16 nmol/mg protein vs. 0.57 +/- 0.19, p < 0.05), consistent with increased ROS generation. Hence, no beneficial effect of iron-deficiency was demonstrated by any measure of structure of function in the remnant kidney, and it may enhance damage if sulfhydryl repletion is not provided.

A method of human semen centrifugation to minimize the iatrogenic sperm injuries caused by reactive oxygen species

Current techniques of sperm preparation for in vitro fertilization or intrauterine insemination require centrifugation of human semen to separate spermatozoa from the seminal plasma. Centrifugation increases reactive oxygen species (ROS) formation in semen. Moreover, high levels of ROS are associated with sperm membrane injury through spontaneous lipid peroxidation, which may alter sperm function. We investigated the relationship between centrifugation variables (time and g-force) and ROS production to establish an optimal centrifugation protocol for sperm preparation techniques. Semen from 38 men (24 patients and 14 normal volunteers) was evaluated for the formation of ROS before centrifugation and after centrifugation at 200 g for 2 or 10 min and after 500 g for 2 or 10 min. The absence of white blood cells in semen which can also produce ROS was determined with the myeloperoxidase technique (Endtz test). All specimens were negative (< 1 x 10(6)/ml) by the Endtz test. The formation of ROS was measured by chemiluminescence. ROS formation was regarded as high (positive) when the chemiluminescence response was at least 10 x 10(4) counted photons/min (cpm). The sperm concentration in each sample was adjusted to 15-20 x 10(6) cells/ml before analysis. Eight specimens (7 patients and 1 donor) exhibited high levels of ROS before centrifugation. All 8 showed further, significant increases in ROS formation regardless of g-force or time. The increase in ROS was significantly less when semen was centrifuged for 2 as compared to 10 min (p < 0.001). Six specimens previously ROS-negative became ROS-positive after centrifugation for 10 min at 200 and 500g. We conclude that the time of centrifugation is more important than g-force for inducing ROS formation in semen. Based on these results, we recommend a shorter centrifugation period in the preparation of sperm for assisted reproductive techniques.

Reduction of reoxygenation injury and nitric oxide production in the cyanotic immature heart by controlling pO2

Reintroduction of high levels of molecular oxygen after a hypoxic period is followed by a burst of nitric oxide (NO), peroxynitrite, and oxygen free radicals, which are highly cytotoxic. This study tests the hypotheses that a) controlled reoxygenation of cyanotic immature hearts when starting cardiopulmonary bypass (CPB) with high pO2 pressure of oxygen produces a reoxygenation injury, and b) this oxygen-related damage is avoidable by controlling the circumstances of the reoxygenation period (controlled reoxygenation). Of 40 immature piglets (2-3 weeks), 5 normoxic instrumented piglets served as control, and 6 underwent 1 h of CPB including 30 min of aortic clamping with blood cardioplegic (BCP) arrest without preceding hypoxia (BCP control). Twenty-nine others were made hypoxic (arterial pO2 20-30 mmHg) for up to 2 h by lowering the forced inspiratory oxygen (FiO2) on a ventilator. They were then reoxygenated on CPB as follows, 1) abrupt reoxygenation at pO2 400 mmHg in 5, (Reox), 2) gradual increase in pO2 from 30 to 400 mmHg in 5 (Graded Reox), both without BCP arrest, 3) starting CPB at different pO2 levels (hyperoxic, normoxic or hypoxic) for 5 min, followed by BCP arrest (Reox+BCP: pO2 > 400, 100 or 20-30 mmHg), in 19 others. Reoxygenation on CPB at pO2 more than 400 mmHg depressed contractility (endsystolic elastance [Ees] to 25 +/- 5% of control; P < 0.05), accompanied by reduced antioxidant reserve capacity [AORC] (P < 0.05 vs control), which was only slightly improved by Graded Reox (Ees 34 +/- 4%, P < 0.05 vs control).(ABSTRACT TRUNCATED AT 250 WORDS)

Renal cortical mitochondria are the source of oxygen free radicals enhanced by gentamicin

Rat renal cortical mitochondria were isolated from Wistar male rats weighing 80 to 120 g to investigate whether the source of oxygen free radicals was renal cortical mitochondria enhanced by gentamicin. In renal cortical mitochondria with or without the addition of gentamicin, DMSO, DFO, CAT, SOD, and MT1 were added separately, then incubated at 37 degrees C for 90 min. Superoxide anions and hydroxyl radicals were then determined. The results showed that superoxide anions and hydroxyl radicals generated in mitochondria were enhanced by the addition of in vitro gentamicin (12.4 mg/mL) when compared to those without the addition of gentamicin. Dimethylsulfoxide (DMSO), catalase (CAT), and deferoxamine (DFO) significantly inhibited hydroxyl radicals enhanced by gentamicin, but superoxide dismutase (SOD) and metallothionein-1 (MT1) did not. SOD significantly inhibited the production of superoxide anions. Our data indicated that renal cortical mitochondria are the source of oxygen free radicals and that production is enhanced by gentamicin. This provides more insight on the pathogenetic role of hydroxyl radicals and superoxide anions in gentamicin-induced nephrotoxicity in vitro.

Post-implantation mouse embryos have the capability to generate and release reactive oxygen species

The capability of the mouse embryo to generate reactive oxygen species (ROS) was examined. Post-implantation embryos were carefully harvested on Day 8 of pregnancy and the production of ROS was quantified using luminol-sensitized chemiluminescence. The embryos were stimulated with either phorbol myristate acetate (PMA) or all-trans-retinal (retinal) and the reaction kinetics were followed over 10 min. ROS secretion was directly proportional to the number of embryos and was suppressed 56% by superoxide dismutase (SOD), 25% by mannitol and as little as 16% by catalase. Embryos deprived of trophoblast showed no light emission suggesting that the source of ROS generation is the trophoblast. Dihydronicotinamide adenine dinucleotide (NADH)-dependent oxidase activity in the plasma membrane of the trophoblast surface was demonstrated by cytochemical methods. The release of ROS into the extracellular medium during the phagocytic process has been related to the cytolytic effect exhibited by these molecules and, perhaps by this means, the trophoblast can play an active role in the phagocytosis of maternal cells during the process of embryo implantation.