Oxidative damage to lysozyme by the hydroxyl radical: comparative effects of scavengers

Discovering the Radiation Biomarkers in the Plasma of Total-Body Irradiated Leukemia Patients

The increased risk of acute large-scale radiological exposure for the world's population underlines the need for optimal radiation biomarkers. Ionizing radiation triggers a complex response by the genome, proteome, and metabolome, all of which have been reported as suitable indicators of radiation-induced damage in vivo. This study analyzed peripheral blood samples from total-body irradiation (TBI) leukemia patients through mass spectrometry (MS) to identify and quantify differentially regulated proteins in plasma before and after irradiation. In brief, samples were taken from 16 leukemic patients prior to and 24 h after TBI (2 × 2.0 Gy), processed with Tandem Mass Tag isobaric labelling kit (TMTpro-16-plex), and analyzed by MS. In parallel, label-free relative quantification was performed with a RP-nanoLC-ESI-MS/MS system in a Q-Exactive mass spectrometer. Protein identification was done in Proteome Discoverer v.2.2 platform (Thermo). Data is available via ProteomeXchange with identifier PXD043516. Using two different methods, we acquired two datasets of up-regulated (ratio ≥ 1.2) or down-regulated (ratio ≤ 0.83) plasmatic proteins 24 h after irradiation, identifying 356 and 346 proteins in the TMT-16plex and 285 and 308 label-free analyses, respectively (P ≤ 0.05). Combining the two datasets yielded 15 candidates with significant relation to gamma-radiation exposure. The majority of these proteins were associated with the inflammatory response and lipid metabolism. Subsequently, from these, five proteins showed the strongest potential as radiation biomarkers in humans (C-reactive protein, Alpha amylase 1A, Mannose-binding protein C, Phospholipid transfer protein, and Complement C5). These candidate biomarkers might have implications for practical biological dosimetry.

Influence of Ionizing Radiation on Spontaneously Formed Aggregates in Proteins or Enzymes Solutions

We have shown that many proteins and enzymes (ovalbumin, β-lactoglobulin, lysozyme, insulin, histone, papain) undergo concentration-dependent reversible aggregation as a result of the interaction of the studied biomolecules. Moreover, irradiation of those protein or enzyme solutions under oxidative stress conditions results in the formation of stable soluble protein aggregates. We assume that protein dimers are mainly formed. A pulse radiolysis study has been made to investigate the early stages of protein oxidation by N3• or ^•OH radicals. Reactions of the N3• radical with the studied proteins lead to the generation of aggregates stabilized by covalent bonds between tyrosine residues. The high reactivity of the ^•OH with amino acids contained within proteins is responsible for the formation of various covalent bonds (including C-C or C-O-C) between adjacent protein molecules. In the analysis of the formation of protein aggregates, intramolecular electron transfer from the tyrosine moiety to Trp^• radical should be taken into account. Steady-state spectroscopic measurements with a detection of emission and absorbance, together with measurements of the dynamic scattering of laser light, made it possible to characterize the obtained aggregates. The identification of protein nanostructures generated by ionizing radiation using spectroscopic methods is difficult due to the spontaneous formation of protein aggregates before irradiation. The commonly used fluorescence detection of dityrosyl cross-linking (DT) as a marker of protein modification under the influence of ionizing radiation requires modification in the case of the tested objects. A precise photochemical lifetime measurement of the excited states of radiation-generated aggregates is useful in characterizing their structure. Resonance light scattering (RLS) has proven to be an extremely sensitive and useful technique to detect protein aggregates.

Implications of differential peroxyl radical-induced inactivation of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase for the pentose phosphate pathway

Escherichia coli glucose-6-phosphate dehydrogenase (G6PDH) and 6-phosphogluconate dehydrogenase (6PGDH) are key enzymes of the pentose phosphate pathway, responsible for the NADPH production in cells. We investigated modification of both enzymes mediated by peroxyl radicals (ROO^·) to determine their respective susceptibilities to and mechanisms of oxidation. G6PDH and 6PGDH were incubated with AAPH (2,2'-azobis(2-methylpropionamidine)dihydrochloride), which was employed as ROO^· source. The enzymatic activities of both enzymes were determined by NADPH release, with oxidative modifications examined by electrophoresis and liquid chromatography (LC) with fluorescence and mass (MS) detection. The activity of G6PDH decreased up to 62.0 ± 15.0% after 180 min incubation with 100 mM AAPH, whilst almost total inactivation of 6PGDH was determined under the same conditions. Although both proteins contain abundant Tyr (particularly 6PGDH), these residues were minimally affected by ROO^·, with Trp and Met being major targets. LC-MS and in silico analysis showed that the modification sites of G6PDH are distant to the active site, consistent with a dispersed distribution of modifications, and inactivation resulting from oxidation of multiple Trp and Met residues. In contrast, the sites of oxidation detected on 6PGDH are located close to its catalytic site indicating a more localized oxidation, and a consequent high susceptibility to ROO^·-mediated inactivation.

Denaturation of Lysozyme with Visible-light-responsive Photocatalysts of Ground Rhodium-doped and Ground Rhodium-antimony-co-doped Strontium Titanate

Protein denaturants play an important role in medical and biological research, and development of new denaturants is widely explored to study aging and various diseases. In this research, we treated lysozyme, a model protein, with photocatalysts of ground Rh-doped SrTiO₃ (g-STO:Rh) and ground Rh-Sb-co-doped SrTiO₃ (g-STO:Rh/Sb) under visible light irradiation to explore the potential of those photocatalysts as denaturants. SDS-PAGE showed that photocatalysis with g-STO:Rh induced the fragmentation of lysozyme into unidentifiable decomposition products. BCA and Bradford protein assays indicated that the peptide bonds and basic, aromatic and N-terminal amino acid residues in lysozyme were denaturated by g-STO:Rh photocatalysis. The denaturation of those amino acids, as quantified by the decreased solubility of lysozyme, was estimated to be more severe by Bradford protein assay than by BCA protein assay. Circular dichroism (CD) spectra of lysozyme revealed that the secondary structure was denatured by g-STO:Rh photocatalysis, indicating that g-STO:Rh photocatalysis is especially effective against the amino acid residues that form the secondary structure via hydrogen bonds. Furthermore, the lytic activity of lysozyme was reduced by g-STO:Rh photocatalysis, owing to denaturation of the enzyme. The visible-light-responsive photocatalyst of g-STO:Rh/Sb accelerates the oxidation reaction and has stronger oxidizing power than g-STO:Rh. Lysozyme was denatured more quickly by g-STO:Rh/Sb photocatalysis than by g-STO:Rh according to analysis by SDS-PAGE, CD spectroscopy, BCA and Bradford protein assays, and lytic activity. These results suggest that higher photocatalytic activity induces more significant denaturation of lysozyme, implying that the main factor of photocatalytic denaturation of lysozyme is oxidation. It should be noted that, as far as we know, this is the first report for denaturation of protein using visible-light-responsive photocatalyst.

Neutrophil-derived Oxidants and Proteinases as Immunomodulatory Mediators in Inflammation

Neutrophils generate potent microbicidal molecules via the oxygen-dependent pathway, leading to the generation of reactive oxygen intermediates (ROI), and via the non-oxygen dependent pathway, consisting in the release of serine proteinases and metalloproteinases stored in granules. Over the past years, the concept has emerged that both ROI and proteinases can be viewed as mediators able to modulate neutrophil responses as well as the whole inflammatory process. This is well illustrated by the oxidative regulation of proteinase activity showing that oxidants and proteinases acts is concert to optimize the microbicidal activity and to damage host tissues. ROI and proteinases can modify the activity of several proteins involved in the control of inflammatory process. Among them, tumour necrosis factor-α and interleukin-8, are elective targets for such a modulation. Moreover, ROI and proteinases are also able to modulate the adhesion process of neutrophils to endothelial cells, which is a critical step in the inflammatory process.

Beneficial Effect of Pentoxifylline on Cisplatin-Induced Acute Renal Failure in Rabbits

Pentoxifylline (PTX) has been reported to inhibit TNF-alpha production and prevent several types of acute renal failure. This study was undertaken to determine the effect of PTX on the cisplatin-induced acute renal failure in rabbits. Rabbits received a single injection of cisplatin (5 mg/kg, i.p.) with or without PTX pretreatment (30 mg/kg, i.v.). Alterations in renal function, apoptotic cell death, and TNF-alpha mRNA expression were measured at 24 or 48 h after cisplatin injection. Cisplatin caused an increase in BUN and serum creatinine levels, a reduction in GFR, and an increase in fractional Na+ excretion. Such changes were significantly attenuated by PTX pretreatment (30 mg/kg, i.p.) 30 min before and 24 h after cisplatin injection. Morphological evaluation showed that cisplatin injection induced diffuse proximal tubular necrosis and the effect was reduced by PTX pretreatment. Cisplatin induced apoptotic cell death in renal cortex and the effect was significantly prevented by PTX. Treatment of opossum kidney cells with cisplatin resulted in cell death, which was significantly prevented by PTX. The increase in lipid peroxidation and the decrease in renal blood flow induced by cisplatin were not affected by PTX. The expression of TNF-alpha mRNA was increased after cisplatin injection and the effect was inhibited by PTX pretreatment. These results suggest that cisplatin-induced acute renal failure in rabbits is associated with an induction of TNF-alpha-mediated apoptosis, and that PTX may exert a protective effect against cisplatin nephrotoxicity by inhibiting TNF-alpha production.

Pentoxifylline response in alloxan-induced diabetic rats

CONCLUSION

This study in rats shows that pentoxifylline may reverse detrimental effects of diabetes mellitus (DM) on the auditory system.

OBJECTIVE

To investigate whether delayed auditory brainstem responses (ABRs) induced by DM improve following pentoxifylline treatment in rats.

MATERIALS AND METHODS

Baseline ABRs were recorded in 25 ears of 13 normal-hearing rats. DM was induced by a single injection of alloxan (75 mg/kg of body weight) in all rats. Following a 1-month diabetic period, ABRs were recorded in six diabetic rats. Then, pentoxifylline treatment was administered for 6 weeks (20 mg/kg in drinking water), and final ABR testing was performed. Absolute latencies of waves I, III and V, and inter-peak latency differences (IPL) of I-V were measured in each stage of the experiment. These parameters were compared to each other in a pair-wise manner.

RESULTS

All wave latencies and IPL I-V were prolonged following induction of DM. Delay in waves III and V, and IPL I-V was significant (p<0.05). Pentoxifylline improved all of the wave latencies and IPL I-V, but significant improvement was observed in waves III and V (p<0.05). There was no significant difference between baseline measurements and measurements following pentoxifylline treatment.

Effects of post-translational modifications on prion protein aggregation and the propagation of scrapie-like characteristics in vitro

Prion diseases, or transmissible spongiform encephalopathies (TSEs) are typically characterised by CNS accumulation of PrP(Sc), an aberrant conformer of a normal cellular protein PrP(C). It is thought PrP(Sc) is itself infectious and the causative agent of such diseases. To date, no chemical modifications of PrP(Sc), or a sub-population thereof, have been reported. In this study we have investigated whether chemical modification of amino acids within PrP might cause this protein to exhibit aberrant properties and whether these properties can be propagated onto unmodified prion protein. Of particular interest were post-translational modifications resulting from physiological conditions shown to be associated with TSE disease. Here we report that in vitro exposure of recombinant PrP to conditions that imitate the end effects of oxidative/nitrative stress in TSE-infected mouse brains cause the protein to adopt many of the physical characteristics of PrP(Sc). Most interestingly, these properties could be propagated onto unmodified PrP protein when the modified protein was used as a template. These data suggest that post-translational modifications of PrP might contribute to the initiation and/or propagation of prion protein-associated plaques in vivo during prion disease, thereby high-lighting novel biochemical pathways as possible therapeutic targets for these conditions.

Glycoprotein isolated from Gardenia jasminoides Ellis has a scavenging activity against oxygen radicals and inhibits the oxygen radical-induced protein kinase C alpha and nuclear factor-kappa B in NIH/3T3 cells

This study was earned out to investigate the antioxidative and anti-apoptotic effects of glycoprotein isolated from Gardenia jasminoides Ellis fruit (GJE glycoprotein), which has been used to heal hepatic and inflammatory diseases in folk medicine. GJE glycoprotein showed a single band with a molecular weight of 27kDa on the 15% sodium dodecyl sulfate polyacrylamide gel. It consists of a carbohydrate component (57.65%) and a protein component (42.35%). GJE glycoprotein has dose-dependent scavenging activities for DPPH, lipid peroxyl, superoxide anion and hydroxyl radicals in cell-free systems. We also evaluated the protective and anti-apoptotic activities of GJE glycoprotein on the glucose/glucose oxidase (G/GO)-induced or hypoxanthine/xanthine oxidase (HX/XO)-induced cytotoxicity and apoptosis systems in NIH/3T3 cells, using 3-(4,5-diinettiylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide (MTT), DNA fragmentation and H33342/ethidium bromide staining assays, respectively. Results in this experiment showed that GJE glycoprotein has dose-dependent blocking activities against G/GO- or HX/XO-induced cytotoxicity and apoptosis. In addition, we investigated whether GJE glycoprotein blocks the activation of redox-sensitive signal mediators, protein kinase C alpha (PKCα) and nuclear factor-kappa B (NF-κB) in G/GO or HX/XO-induced apoptotic NIH/3T3 cells, using a Western blot analysis and an electrophoretic mobility shift assay (EMSA). We found that 100μg/ml GJE glycoprotein has an inhibitory effect on PKCα translocation and the DNA binding activity of (NF-κB). Here, we speculate that GJE glycoprotein is a natural antioxidant and one of the modulators of apoptotic signal pathways in NIH/3T3 cells.

Nitric oxide inhibits prooxidant actions of uric acid during copper-mediated LDL oxidation

Interactions between uric acid and physiologically relevant fluxes of nitric oxide ((?)NO) during copper-mediated low-density lipoprotein (LDL) oxidation were evaluated. In the absence of (?)NO, a dual pro- and antioxidant action of uric acid was evident: low concentrations of uric acid enhanced lipid oxidation and alpha-tocopherol consumption, while its protective role was observed at higher concentrations. The prooxidant effects of uric acid were mostly related to its copper-reducing ability to form Cu(+), an initiator of lipid oxidation processes. While the prooxidant action of uric acid was completely inhibited by (?)NO, the antioxidant action of (?)NO was slightly counterbalanced by uric acid. Enhancement of alpha-tocopherol consumption by uric acid was inhibited in the presence of (?)NO while additive antioxidant effects between (?)NO and uric acid were observed in conditions where uric acid spared alpha-tocopherol. Altogether, these results suggest that in the artery wall, the (?)NO/uric acid pair may exert antioxidant actions on LDL, even if increased amounts of redox active copper were available at conditions favoring prooxidant activities of uric acid.

"In vitro" effect of cumene hydroperoxide on hepatic elongation factor-2 and its protection by melatonin

We have examined by immunoblotting the effect of three oxidant compounds on the level of hepatic elongation factor-2 (eEF-2). Rat liver homogenates were exposed to cumene hydroperoxide (CH), 2-2'-azobis (2-aminopropane) dihydrochloride (AAPH) and H(2)O(2). Only CH treatment produced the disappearance of eEF-2, probably due to a phenomena of peptide bond cleavage. The direct implication of free radical species in this process is evident because of the fact that the inclusion of a free radical scavenger such as melatonin prevented the eEF-2 depletion. The results also suggest that the disappearance of eEF-2 induced by CH can be linked to a lipid peroxidant process, which could account for the decline of protein synthesis in aging and other circumstances where lipid peroxidation is high.

Effect of pentoxifylline on ischemic acute renal failure in rabbits

Previous studies have demonstrated that levels of tumor necrosis factor-alpha (TNF-alpha) or its mRNA expression are increased in acute renal failure of various types including ischemia/reperfusion injury. This study was undertaken to determine whether pentoxifylline (PTX), an inhibitor of TNF-alpha production, provides a protective effect against ischemic acute renal failure in rabbits. Renal ischemia was induced by clamping bilateral renal arteries for 60 min. Animals were pretreated with PTX (30 mg/kg, i.v.) 10 min before release of clamp. At 24 h of reperfusion of blood after ischemia, changes in renal function, renal blood flow, and the expression of TNF-alpha mRNA were evaluated. Ischemia/reperfusion caused a marked reduction in GFR, which was accompanied by an increase of serum creatinine levels. Such changes were significantly attenuated by PTX pretreatment. PTX ameliorated the impairment of renal tubular function, but it had no effect on the reduction of renal blood flow induced by ischemia/reperfusion. The protective effect of PTX on functional changes was supported by morphological studies. The impairment of glucose and phosphate reabsorption in postischemic kidneys was associated with a depression in the expression of Na+-glucose and Na+-Pi transporters. The expression of TNF-alpha mRNA was increased after reperfusion, which was inhibited by PTX pretreatment. The PTX pretreatment in vitro prevented the release of lactate dehydrogenase induced by an oxidant t-butylhydroperoxide in rabbit renal cortical slices, but it did not produce any effect on the oxidant-induced lipid peroxidation, suggesting that PTX protection is not resulted from its antioxidant action. These results suggest that PTX may exert a protective effect against ischemic acute renal failure by inhibiting the production of TNF-alpha in rabbits.

Extracts of Ginkgo biloba and Panax ginseng protect brain proteins from free radical induced oxidative damage in vitro

Oxidative damage to normal human brain tissue was induced following exposure to hydroxyl (OH.) or superoxide (O2-.) free radical species generated by CO60 irradiation in vitro. Both enzymic and cytoskeletal proteins showed substantial (dose dependent) oxidative damage following exposure to OH. or O2-., as quantified by SDS-polyacrylamide gel electrophoretic analysis. Extracts of Ginkgo biloba or Panax ginseng showed a remarkable capacity to protect brain tissue proteins from oxidative damage in vitro, even at extreme (2000 kRads) dosage levels of OH. or O2-.. We suggest, therefore, that the beneficial effect of these plant extracts in preventing brain tissue damage in vivo (e.g. following ischemia-reperfusion) may result from their action in protecting brain proteins from oxidative damage, in addition to their previously reported capacity to reduce free radical induced lipid peroxidation.

Comparative antioxidant potential of anaesthetics and perioperative drugs in vitro

We have investigated the comparative antioxidant capacity of a range of anaesthetics (inhaled and intravenous) and perioperative neurosurgical drugs (at clinically relevant concentrations) using different radical species and assay methods in vitro. The highest levels of antioxidant activity against the ABTS(.+) radical were obtained with propofol (100 mmol/LTE) and dopamine (1080 mmol/LTE), respectively. However, only dopamine (12 mmol/l) showed antioxidant activity in protecting proteins in normal brain tissue from oxidative damage (assessed via SDS-PAGE analysis) induced by OH(.) or O(2)(-.) generated radiolytically in vitro. Neither dopamine nor propofol showed antioxidant activity against O(2)(-.) generated chemically via reaction between xanthine and xanthine oxidase in vitro. From these data, together with data on the relative antioxidant properties of anaesthetics/drugs obtained by other research groups which we have reviewed, we conclude that the apparent antioxidant activity of a given compound may depend entirely on the free radical species and/or the method of generation or assay employed. Finally, we suggest that on the basis of data obtained showing protection of brain proteins from oxidative damage induced by OH(.), or O(2)(-.) in vitro, further investigation into the in vivo antioxidant therapeutic potential of dopamine (or its analogues) on neurosurgical patients may be warranted.

Oxidative dimerization of proteins: role of tyrosine accessibility

PURPOSE

To investigate the importance of two possible mechanisms of tyrosine oxidation on the yield of protein dimerization. The model chosen is hen and turkey egg-white lysozymes, which differ by seven amino acids, among which one tyrosine is in the 3 position.

MATERIALS AND METHODS

Aqueous solutions of proteins were oxidized by OH(*) or N(*)(3) free radicals produced by gamma or pulse irradiation in an atmosphere of N(2)O. Protein dimers were quantified by SDS-PAGE and reverse-phase HPLC. Dityrosines were identified by absorption and fluorescence.

RESULTS

Using N(*)(3) free radicals, the initial yields of dimerization are equal to (8.6 +/- 0.7) x 10(-9) mol J(-1) for both proteins. Using OH(*) free radicals, they become equal to (1.23 +/- 0.1) x 10(-8) and (4.42 +/- 0.1) x 10(-8) mol J(-1) for hen and turkey egg-white lysozymes, respectively (gamma radiolysis). DISCUSSION. N(*)(3) radicals react primarily with tryptophan residues only. Tyrosine gets oxidized by intramolecular long-range electron migration, whereas OH(*) may react directly with tyrosines. We propose a low participation of Tyr3 in turkey protein in the intramolecular process, because Tyr3 is far from all tryptophans. On the other hand, Tyr3 is very accessible to solvent and in a flexible area; thus collisions with OH(*) could easily be followed by intermolecular dimerization.

Pentoxifylline decreases neutrophil respiratory bursts in patients with stable angina

We estimated the effect of pentoxifylline (PTX) on the respiratory burst (examined by chemiluminescence method) of unprimed and primed neutrophils with tumor necrosis factor-alpha (TNF-alpha) in patients with stable angina pectoris. Chemiluminescence of non-stimulated as well as formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol myristate acetate (PMA) stimulated neutrophils was measured. We studied 45 patients with stable angina subjected to percutaneous transluminal coronary angioplasty (PTCA) procedure, who were randomly divided into two groups. The study group consisted of 24 patients who were administered pentoxifylline orally, and the control group consisted of 21 patients without pentoxifylline administration. Blood samples for examination were collected from the coronary sinus and peripheral vein just before the PTCA procedure. Pentoxifylline decreased the respiratory burst of non-stimulated and fMLP-stimulated neutrophils without affecting the chemiluminescence of PMA stimulated neutrophils. Moreover, pentoxifylline diminished the chemiluminescence non-stimulated and stimulated by fMLP but not by PMA of TNF-alpha primed neutrophils. We presume that administration of PTX in stable angina patients may have a beneficial effect.

Oxidative modification of high-density lipoprotein 3 induced by human polymorphonuclear neutrophils. Protective effect of pentoxifylline

The function of high-density lipoproteins (HDLs) in reverse cholesterol transport is impaired if HDLs are subjected to oxidative stress. Polymorphonuclear neutrophils (PMNs), which have been detected in the earliest stages of atherosclerotic lesions, are one of the most likely sources of the reactive oxygen species that cause such stress. In this study, we investigated the effect of a PMN oxidative burst on HDL3. We also studied the impact on these events of pentoxifylline, a drug that regulates granulocyte function. HDL3 (370 nmol.mL-1 cholesterol-HDL) was incubated with PMNs (2 x 106. mL-1) in NaCl/Pi in the presence or absence of an iron chelate complex (10 microm Fe-nitrilotriacetic acid) at 37 degreesC for 60 min or 24 h. Phorbol myristate acetate (PMA) or formyl-methionylleucyphenylalanine (fMetLeuPhe) was used to stimulate PMNs. In iron-free NaCl/Pi medium, PMA-stimulated PMNs had a 40% lower HDL3 alpha-tocopherol content, whatever the incubation time. In NaCl/Pi medium containing iron, there was 80% less HDL3 alpha-tocopherol at 60 min, and HDL3 alpha-tocopherol had almost disappeared after 24 h. In this latter condition, the amount of thiobarbituric acid-reactive substances was significantly higher than the respective control HDL3 (P < 0.05) and oxidation of HDL3 by PMA-stimulated PMNs was associated with cross-linking of apoprotein AI, which was detected by SDS/PAGE. Similar results were obtained with fMetLeuPhe-stimulated PMN except that HDL3 alpha-tocopherol was consumed much more slowly during the first 60 min. Pretreatment of PMNs with various concentrations of pentoxifylline (0.001-20 mm) led to the concentration-dependent inhibition of oxidative modification of HDL3 induced by stimulated PMNs. The addition of 20 mm pentoxifylline in the most extreme oxidative stress conditions resulted in 70% of HDL3 alpha-tocopherol being maintained, with no formation of thiobarbituric acid-reactive substances and a lower level of apoprotein AI cross-linking. Thus HDL3 is susceptible to oxidative modifications induced by stimulated PMNs, in the presence of an exogenous source of iron. Pentoxifylline inhibited the oxidative modification of HDL3 by PMNs.

Effect of active oxygen radicals on protein and carbohydrate moieties of recombinant human erythropoietin

Our previous study showed that active oxygen radicals generated from a Fenton system and a xanthine plus xanthine oxidase system caused serious loss of in vivo bioactivity of recombinant human erythropoietin (EPO), a highly glycosylated protein. In the present study, we characterized the oxidative modifications to the protein and carbohydrate moiety of EPO, which lead to a reduction of its bioactivity. In vitro bioactivity was reduced when EPO was treated with oxygen radicals generated from a Fenton system in the presence of 0.016 mM H2O2, and the reduction was directly proportional to the loss of in vivo bioactivity. SDS-PAGE analysis showed that dimer formation and degradation was observed under more severe conditions (Fenton reaction with 0.16 mM H2O2). The tryptophan destruction was detected at 0.016 mM H2O2 and well correlated with the loss of in vitro bioactivity, whereas loss of other amino acids were occurred under more severe conditions. Treatment with the Fenton system did not result in any specific damage on the carbohydrate moiety of EPO, except a reduction of sialic acid content under severe condition. These results suggest that active oxygen radicals mainly react with the protein moiety rather than the carbohydrate moiety of EPO. Destruction of tryptophan residues is the most sensitive marker of oxidative damage to EPO, suggesting the importance of tryptophan in the active EPO structure. Deglycosylation of EPO caused an increased of susceptibility to oxygen radicals compared to intact EPO. The role of oligosaccharides in EPO may be to protect the protein structure from active oxygen radicals.

Pentoxifylline inhibits tumor necrosis factor alpha-induced priming of human neutrophils

The study was designed to study the effect of pentoxifylline PTX on the chemiluminescence responses of neutrophils and on tumor necrosis factor-alpha (TNF-alpha)-induced priming of neutrophils. The results demonstrate that TNF-alpha stimulated the respiratory burst by neutrophils and primed them for enhanced response to fMLP but not to PMA. The effect of TNF-alpha on the oxygen metabolism of neutrophils was inhibited when cells were treated with PTX. This reaction was dose-dependent. Additionally, the inhibiting influence of PTX on the chemiluminescence response of neutrophils was observed.

Cloning of rat grp75, an hsp70-family member, and its expression in normal and ischemic brain

Following metabolic stress a variety of gene products are induced in cells in the brain, some of which may protect the tissue from subsequent stresses. The heat shock proteins (hsps), in particular hsp70, have been widely studied in this context, but evidence for the involvement of known hsps in protection of the CNS is inconclusive. We have therefore undertaken the search for other stress-induced proteins which may mitigate ischemic injury. Beginning with degenerate RT-PCR, we have isolated a rat-brain cDNA encoding a protein highly similar to human grp75, a mitochondrial member of the hsp70-family of stress proteins. It is also highly similar to two non-mitochondrial proteins; mortalin, a senescence-related gene product, and pbp74, a protein implicated in B-cell peptide processing. Sequence structure and phylogenetic analyses predict mitochondrial localization and induction by a calcium ionophore and glucose deprivation in PC12 cells support its identification as rat grp75. In situ analysis of normal brain reveals an unusual distribution, with very high expression in neurons of the basal forebrain, reticular and subthalamic nuclei, globus pallidus, amygdala and elsewhere. grp75-mRNA is upregulated following focal brain ischemia in a distinctive fashion. When the degree of injury is small, induction occurs in the area of injury, similar to the pattern observed for hsp70. However, when the injury is extensive, hsr is upregulated in neurons outside the ischemic area. The induction of grp75 may represent a sensitive marker of metabolically compromised tissue.