[Ferritin, oxidative stress and coronary atherosclerosis]. / Feritin, oxidacní stres a koronární ateroskleróza.

BACKGROUND AND AIM: In the recent years several studies showed the association between body iron stores, represented by serum ferritin, and atherosclerosis. It was proposed that iron bound to ferritin catalyzes the formation of highly reactive forms of oxygen free radicals which subsequently cause the oxidative modification of atherogenic lipoproteins. Aim of our study was to compare serum ferritin concentrations and certain markers of oxidative stress in patients with and without coronarographically assessed coronary vascular disease. METHODS AND RESULTS: Measurements were performed in 216 subjects at the age of 35-60 years. The patient group included 76 patients with coronarographically assessed coronary vascular disease (CVD) (mean age 51.16 +/- 5.713 years) and 140 healthy controls (mean age 50.21 +/- 5.331 years). The plasma concentration of ferritin was higher in patients (169.04 +/- 63.899 micrograms/l) than controls (87.70 +/- 41.394 micrograms/l), p < 0.001. The group of patients revealed significantly lower plasma concentrations of anti-oxLDL antibodies, nitrites/nitrates, tocopherol and high density lipoprotein cholesterol (HDL-cholesterol) than controls; on the contrary patients had significantly higher concentrations of hemoglobin, thrombocytes and triacylglycerols. In the whole cohort of investigated subjects, ferritin correlated positively with retinol, body mass index (BMI), total-cholesterol, triacylglycerols, low density lipoprotein cholesterol (LDL-cholesterol), blood glucose, creatinine, uric acid, alaninaminotransferase (ALT), aspartateaminotransferase (AST), hematocrite, erythrocytes, with occurrence of CVD and with sex. Inverse correlation was observed between ferritin and HDL-cholesterol. CONCLUSIONS: Our observations are consistent with the hypothesis that high stored iron levels, measured by serum ferritin concentrations, may contribute to the oxidative stress and thus elevate the risk for development of CVD.

UV Rays, the prooxidant/antioxidant imbalance in the cornea and oxidative eye damage.

In this minireview, the factors involved in the development of corneal injury due to an increased amount of UVB rays are summarized. Experimental studies have shown that an increased number of UVB rays leads to a profound decrease in corneal antioxidants (high molecular weight, antioxidant enzymes as well as low molecular weight, mainly ascorbic acid) so that a prooxidant/antioxidant imbalance appears. The decrease of corneal antioxidant protective mechanisms results in oxidative injury of the cornea and causes damage of the inner parts of the eye by UVB rays and by reactive oxygen species generated by them.

Oxidative stress in the brain tissue of laboratory mice with acute post insulin hypoglycemia.

Malondialdehyde (MDA), Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and selenium-dependent glutathione peroxidase (GSPHx) are currently considered to be basic markers of oxidative stress. MDA is one of the end-products of the peroxidation of membrane lipids, whereas enzymes Cu,Zn-SOD and GSHPx belong to the natural antioxidants. The role of oxygen free radicals in the pathogenesis of many diseases is well documented. The aim of this study was to ascertain the influence of insulin-induced acute hypoglycemia on oxidative stress in the brain tissue. Hypoglycemia was induced in ICR mice by intraperitoneal administration of insulin at a dose 24 IU/kg. There was a correlation between the severity of hypoglycemia and the levels of MDA, Cu,Zn-SOD and GSHPx. The results showed that in severe hypoglycemia (serum glucose concentration below 1.0 mmol/l) the lipoperoxidation in brain tissue expressed as the level of MDA was higher in comparison with normoglycemic controls (glycemia around 3.7 mmol/l) as well as in comparison with the levels of MDA during moderate hypoglycemia (glycemia ranging between 1-2 mmol/l). This indicates the enhancement of lipoperoxidation in the brain tissue during severe hypoglycemia. However, both enzymes - Cu,Zn-SOD or GSHPx - did not show a similar tendency.

Reactive oxygen species (ROS)-generating oxidases in the normal rabbit cornea and their involvement in the corneal damage evoked by UVB rays.

The corneas of albino rabbits were irradiated (5 min exposure once a day) with UVB rays (312 nm) for 4 days (shorter procedure) or 8 days (longer procedure). The eyes were examined microbiologically and only the corneas of sterile eyes or eyes with non-pathogenic microbes were employed. Histochemically, the activities of reactive oxygen species (ROS)-generating oxidases (xanthine oxidase, D-amino acid oxidase and alpha-hydroxy acid oxidase) were examined in cryostat sections of the whole corneas. Biochemically, the activity of xanthine oxidoreductase/xanthine oxidase was investigated in the scraped corneal epithelium. UVB rays significantly changed enzyme activities in the corneas. In comparison to the normal cornea, where of ROS-generating oxidases only xanthine oxidase showed significant activity in the corneal epithelium and endothelium, D-amino acid oxidase was very low and alpha-hydroxy acid oxidase could not be detected at all, in the cornea repeatedly irradiated with UVB rays, increased activities of xanthine oxidase and D-amino acid oxidase were observed in all corneal layers. Only after the longer procedure the xanthine oxidase and D-amino acid oxidase activities were decreased in the thinned epithelium in parallel with its morphological disturbances. Further results show that the xanthine oxidase/xanthine oxidoreductase ratio increased in the epithelium together with the repeated irradiation with UVB rays. This might suggest that xanthine dehydrogenase is converted to xanthine oxidase. However, in comparison to the normal corneal epithelium, the total amount of xanthine oxidoredutase was decreased in the irradiated epithelium. It is presumed that xanthine oxidoreductase might be released extracellularly (into tears) or the enzyme molecules were denatured due to UVB rays (particulary after the longer procedure). Comparative histochemical and biochemical findings suggest that reactive oxygen species-generating oxidases (xanthine oxidase, D-amino acid oxidase) contribute to the corneal damage evoked by UVB rays.

Oxidative stress, metabolism of ethanol and alcohol-related diseases.

Alcohol-induced oxidative stress is linked to the metabolism of ethanol. Three metabolic pathways of ethanol have been described in the human body so far. They involve the following enzymes: alcohol dehydrogenase, microsomal ethanol oxidation system (MEOS) and catalase. Each of these pathways could produce free radicals which affect the antioxidant system. Ethanol per se, hyperlactacidemia and elevated NADH increase xanthine oxidase activity, which results in the production of superoxide. Lipid peroxidation and superoxide production correlate with the amount of cytochrome P450 2E1. MEOS aggravates the oxidative stress directly as well as indirectly by impairing the defense systems. Hydroxyethyl radicals are probably involved in the alkylation of hepatic proteins. Nitric oxide (NO) is one of the key factors contributing to the vessel wall homeostasis, an important mediator of the vascular tone and neuronal transduction, and has cytotoxic effects. Stable metabolites--nitrites and nitrates--were increased in alcoholics (34.3 +/- 2.6 vs. 22.7 +/- 1.2 micromol/l, p < 0.001). High NO concentration could be discussed for its excitotoxicity and may be linked to cytotoxicity in neurons, glia and myelin. Formation of NO has been linked to an increased preference for and tolerance to alcohol in recent studies. Increased NO biosynthesis also via inducible NO synthase (NOS, chronic stimulation) may contribute to platelet and endothelial dysfunctions. Comparison of chronically ethanol-fed rats and controls demonstrates that exposure to ethanol causes a decrease in NADPH diaphorase activity (neuronal NOS) in neurons and fibers of the cerebellar cortex and superior colliculus (stratum griseum superficiale and intermedium) in rats. These changes in the highly organized structure contribute to the motor disturbances, which are associated with alcohol abuse. Antiphospholipid antibodies (APA) in alcoholic patients seem to reflect membrane lesions, impairment of immunological reactivity, liver disease progression, and they correlate significantly with the disease severity. The low-density lipoprotein (LDL) oxidation is supposed to be one of the most important pathogenic mechanisms of atherogenesis, and antibodies against oxidized LDL (oxLDL) are some kind of epiphenomenon of this process. We studied IgG oxLDL and four APA (anticardiolipin, antiphosphatidylserine, antiphosphatidylethanolamine and antiphosphatidylcholine antibodies). The IgG oxLDL (406.4 +/- 52.5 vs. 499.9 +/- 52.5 mU/ml) was not affected in alcoholic patients, but oxLDL was higher (71.6 +/- 4.1 vs. 44.2 +/- 2.7 micromol/l, p < 0.001). The prevalence of studied APA in alcoholics with mildly affected liver function was higher than in controls, but not significantly. On the contrary, changes of autoantibodies to IgG oxLDL revealed a wide range of IgG oxLDL titers in a healthy population. These parameters do not appear to be very promising for the evaluation of the risk of atherosclerosis. Free radicals increase the oxidative modification of LDL. This is one of the most important mechanisms, which increases cardiovascular risk in chronic alcoholic patients. Important enzymatic antioxidant systems - superoxide dismutase and glutathione peroxidase - are decreased in alcoholics. We did not find any changes of serum retinol and tocopherol concentrations in alcoholics, and blood and plasma selenium and copper levels were unchanged as well. Only the zinc concentration was decreased in plasma. It could be related to the impairment of the immune system in alcoholics. Measurement of these parameters in blood compartments does not seem to indicate a possible organ, e.g. liver deficiency.

Changes of superoxide dismutase, catalase and glutathione peroxidase in the corneal epithelium after UVB rays. Histochemical and biochemical study.

In this study, the effects of UVA and UVB rays on antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase) were examined in the corneal epithelium. The corneas of albino rabbits were irradiated with a UV lamp generating UVA (365 nm wavelength) or UVB rays (312 nm wavelength), 1 x daily for 5 min, from a distance of 0.03 m, over 4 days (shorter procedure) or 8 days (longer procedure). In contrast to UVA rays, which did not evoke significant disturbances, UVB rays changed the activities of antioxidant enzymes. The longer repeated irradiation with UVB rays was performed, the deeper the observed decrease in antioxidant enzymes. The shorter procedure evoked a more profound decrease of glutathione peroxidase and catalase (the enzymes cleaving hydrogen peroxide) than of superoxide dismutase, an enzyme scavenging superoxide radical and producing hydrogen peroxide during the dismutation reaction of a superoxide free radical. This may contribute to an insufficient hydrogen peroxide cleavage at the corneal surface and danger to the cornea from oxidative damage. After the longer procedure (UVB rays), the activities of all antioxidant enzymes were very low or completely absent. In conclusion, repeated irradiation of the cornea with UVB rays evokes a deficiency in antioxidant enzymes in the corneal epithelium, which very probably contributes to the damage of the cornea (and possibly also deeper parts of the eye) from UVB rays and the reactive oxygen products generated by them.

[Effect of losartan and enalapril on urinary excretion of 8-isoprostane in experimental nephrotic syndrome]. / Vliv losartanu a enalaprilu na mocovou exkreci 8-izoprostanu u experimentálního nefrotického syndromu.

BACKGROUND: Increased permeability of glomerular capillary wall in adriamycin nephropathy may be mediated by increased generation of free radicals and possibly also by the non-enzymatic production of isoprostanes induced by oxidative stress. ACE inhibitors may reduce proteinuria, possibly due to the decrease of intraglomerular pressure and increased permselectivity of the glomerular capillary wall. These effects may be partly mediated by the inhibition of the degradation of kinins. It is not clear if newly available angiotensin II antagonists have the same antiproteinuric and renoprotective effects. METHODS AND RESULTS: We compared the effect of an ACE inhibitor (enalapril, 0.4 mg/kg bw i.p. daily for 3 weeks) and angiotensin II antagonist (losartan, 2 mg/kg bw in the same way) on experimental nephrotic syndrome induced in rats by the administration of adriamycin (5 mg/kg bw i.v. in a single dose). To elucidate the potential differences between these two drugs we also measured total malondialdehyde in blood and urinary excretion some eicosanoids and their metabolites (TxB2, 6-keto-PGF1alfa, bicyclo-PGE2 and 8-isoprostane). Proteinuria increased in adriamycin treated rats after 3 weeks from 0.18 +/- 0.01 to 0.44 +/- 0.14 g/mmol creat, p < 0.01. This increase was not prevented by losartan (increase from 0.18 +/- 0.12 to 0.50 +/- 0.11 g/mmol creat, p < 0.05), but tended to be partly blunted by enalapril (increase from 0.20 +/- 0.10 to only 0.32 +/- 0.08 g/mmol creat, p < 0.05). Similarly there was no increase of serum cholesterol, only in enalapril treated rats. On the other hand, both losartan (1.27 +/- 0.13 vs. 1.91 +/- 0.30 mumol/l, p < 0.05) and enalapril (0.93 +/- 0.06 mumol/l, p < 0.001) prevented adriamycin induced increase of total MDA in serum, but urinary excretion of 8-isoprostane was increased in nephrotic rats treated by losartan compared to controls. Enalapril induced increase of urinary excretion of bicyclo-PGE2 (4.32 +/- 0.62 vs. 1.66 +/- 0.81 ng/mmol creat, p < 0.001) was possibly mediated by kinins. There was no significant difference in the urinary excretion of other eicosanoids between different groups, but proteinuria correlated positively with urinary excretion of 8-isoprostane (p < 0.01). Proteinuric rats had also significantly higher urinary excretion of 8-isoprostane than non-proteinuric rats (44.8 +/- 7.1 vs. 26.7 +/- 3.4 ng/mmol. creat, p < 0.05). CONCLUSIONS: Our data suggest that proteinuria in adriamycin nephropathy may mainly depend on free radical generation and the formation of 8-isoprostane. Haemodynamic parameters (glomerular pressure) do not seem to be so important. The mild antiproteinuric effect of enalapril may suggest a contributory role of the inhibition of kinin degradation in this model of nephrotic syndrome.

ICRF-187 (dexrazoxan) protects from adriamycin-induced nephrotic syndrome in rats.

BACKGROUND: Reactive oxygen species produced during metabolism of adriamycin are purported to play an important role in the pathogenesis of experimental adriamycin nephropathy in rats. ICRF-187 (dexrazoxan, Cardioxan), an iron chelator, has been shown to inhibit adriamycin-induced formation of hydroxyl radical and to decrease adriamycin cardiotoxicity in oncological patients. The aim of our study was to assess the putative protective role of ICRF-187 in adriamycin nephropathy by evaluating the possible participation of free radicals in its pathogenesis. METHODS: We examined five experimental groups. Group A, received a single dose of adriamycin (5 mg/kg bw i.v.), group CA was given a single dose of ICRF-187 (100 mg/kg bw i.v.) before adriamycin administration, group CCA received a single dose of ICRF-187 (100 mg/kg bw i.v.) before adriamycin administration followed by three weekly intraperitoneal injections (100 mg/kg bw) ICRF-187. Group CC received one dose of ICRF-187 (100 mg/kg bw i.v.) followed by three weekly intraperitoneal injections of ICRF-187, and group N served as control receiving saline. Common biochemical parameters, malondialdehyde (MDA) and antioxidant enzymes (glutathione peroxidase--GPx and superoxide dismutase--SOD) in blood and kidney homogenates were measure and histology of the kidney was studied after the rats were sacrificed. RESULTS: Full-blown nephrotic syndrome developed after 3 weeks only in A rats. Nephrotic syndrome was completely prevented in all ICRF-187 treated rats (CA, CCA). Proteinuria was significantly increased in A rats (108.2 + 48.4 mg/l of glomerular filtrate) compared with CA (12.4 + 6.8 mg/l, P < 0.0001) and with N (6.1 + 3.5 mg/l, P < 0.0001). Total MDA in erythrocytes was significantly increased only in A rats (1.7 + 0.3 micromol/l) and was completely normalized by ICRF-187 in CA (1.1 + 0.2 micromol/l, P < 0.001). Total TBARS and MDA in kidney homogenates were significantly elevated in groups with repeated administration of ICRF-187 (CC and CCA rats) compared to N, CA, A groups. Activity of GPx and SOD in kidney homogenate and in erythrocytes was not significantly increased by ICRF-187 in adriamycin treated rats. Histologic changes in A rats resembled minimal change nephropathy with fusion of foot processes and hyaline casts in tubules. There was only minimal mesangial proliferation and perivascular mast cell infiltrates in all groups of ICRF-187-treated rats. CONCLUSIONS: We conclude that ICRF-187, probably by chelation iron, completely protected rats from adriamycin-induced nephrotic syndrome. It supports the role of iron-mediated reactive oxygen species in the development of this type of glomerular injury. However, repeated administration of ICRF-187 alone is able to increase parameters of oxidative stress in the kidney.

The effect of silibinin on experimental cyclosporine nephrotoxicity.

The immunosuppressive drug cyclosporine A (CsA), is metabolized by cytochrome P-450 IIIA. It causes acute reversible as well as chronic largely irreversible nephrotoxic effects. This effect is bases on vasoconstriction of the afferent and efferent glomerular arterioles which leads to a reduction in glomerular plasma flow and glomerular filtration rate. The mechanisms of the vasoconstriction are unclear with a number of different pathways under discussion. Silibinin is the main constituent of silymarin. Silibinin inhibits lipid peroxidation on hepatic microsomes and mitochondria of rats and is also able to reduce the activity of various monooxygenases. Cyclosporin-induced lipid peroxidation and affected cytochrome P-450 may even contribute to cyclosporine nephrotoxicity. We examined the possibility that silibinin had a protective effect as a result of its radical scavenging properties. Silibinin, 5 mg/kg BW i.p., was administered 30 min before cyclosporine application at dose of 30 mg/kg BW daily i.p. The biochemical parameters, total malondialdehyde (MDA) in whole blood and kidney homogenates and specific content of cytochrome P-450 in microsomal liver suspension were estimated. Three groups were studied: controls (con), cyclosporine alone (CsA), and cyclosporine plus silibinin (CsA + Sili). Creatinine was significantly increased after 2 weeks in both cyclosporine treated groups compared to controls (CsA 60.2 +/- 10.6 versus 45.8 +/- 10.4 mumol/L, p < 0.05; and CsA + Sili 72.0 +/- 8.3 versus 45.8 +/- 10.4 mumol/L, p < 0.001) and glomerular filtration rate (GFR) was significantly decreased (p < 0.0001) in the same groups. Total MDA was elevated only in CsA rats (2.26 +/- 0.35 mumol/L, p < 0.05) in comparison with controls (1.60 +/- 0.44 mumol/L, p < 0.05) and with rats treated by CsA + Sili (1.65 +/- 0.27 mumol/L, p < 0.05). The specific content of cytochrome P-450 in microsomal liver suspension was increased in group CsA + Sili (1.179 +/- 0.115 nmol/mg prot) compared to control group (0.775 +/- 0.086 nmol/mg prot., p < 0.05) and also CsA group (0.806 +/- 0.098 nmol/mg prot., p < 0.05). In conclusion, silibinin decreased cyclosporine-induced lipid peroxidation without a protective effect on GFR. These data indicate that this pathway is not be important in cyclosporine-induced nephrotoxicity. Administration of both drugs (CsA + sili) increased the specific content of cytochrome P-450 in liver microsomes. This suggests that the effect of silibinin on cyclosporine biotransformation in the liver is via cytochrome P-450.

The effect of quinolinate on rat brain lipid peroxidation is dependent on iron.

Quinolinate, an endogenous excitotoxic metabolite of tryptophan with affinity to the N-methyl-D-aspartate type of glutamate receptor, is known as a stimulator of lipid peroxidation in vitro [Neurochem. Res. (1991) 16, 1139-1143]. To analyse the mechanism of this quinolinate toxicity we used the thiobarbituric acid test to measure malondialdehyde in homogenates of rat cerebral hemispheres incubated in air at 37 degrees C for 30 min in the presence of 0.015-15.0 mM quinolinate, endogenous iron or 0.5-2.0 microM FeSO4 and with or without 250 microM ascorbate. Quinolinate in the concentrations of 0.15-2.5 mM stimulated lipid peroxidation in the homogenates in the presence of 0.5-2.0 microM Fe2+. However, quinolinate concentrations higher than 3.0 mM inhibited the lipid peroxidation at all the tested concentrations of iron. In the presence of a potent iron chelator (10 microM deferoxamine) quinolinate completely failed to induce lipid peroxidation in rat brain homogenates. Spectral analysis revealed that quinolinate is able to form a complex with Fe2+. The results suggest that quinolinate does not have a direct peroxidative effect, but that it modulates lipid peroxidation via its interaction with iron.

The influence of cyclosporin on lipid peroxidation and superoxide dismutase in adriamycin nephropathy in rats.

Cyclosporin A (CsA) was shown to reduce proteinuria in nephrotic syndrome, but its potential to increase lipid peroxidation may play a role in cyclosporin nephrotoxicity. The influence of cyclosporin treatment on the lipid peroxidation (assessed as malondialdehyde (MDA) in plasma and kidney homogenates using HPLC and reaction with thiobarbituric acid) and the activity of superoxide dismutase (SOD) in erythrocytes was studied in rats with nephrotic syndrome induced by single intravenous injection of adriamycin. Rats with nephrotic syndrome treated from the beginning with cyclosporin had lower proteinuria than untreated nephrotic rats. Free MDA in blood and kidney homogenates was significantly elevated in untreated nephrotic rats in comparison with controls. Activity of SOD in erythrocytes was significantly elevated in nephrotic rats treated with cyclosporin (113.40 +/- 34.31 mU/10(6) erythrocytes) in comparison with the control group (55.63 +/- 9.90 mU/10(6) erythrocytes, p < 0.001), rats treated with cyclosporin (65.7 +/- 17.49 mU/10(6) erythrocytes, p < 0.01) and untreated nephrotic rats (65.07 +/- 17.49 mU/10(6) erythrocytes, p < 0.001). In conclusion, cyclosporin reduced proteinuria in rats with mild adriamycin nephropathy (similar to human minimal change disease). Cyclosporin also partially counteracted adriamycin-induced lipid peroxidation probably due to the stimulation of antioxidant enzyme SOD. The possible contribution of decreased lipid peroxidation to the antiproteinuric effect of cyclosporin deserves further study.

Activity of the antioxidant enzymes superoxide dismutase and glutathione peroxidase in fetal erythrocytes.

It is generally accepted that the balance between the formation and inactivation of reactive oxygen species may be abolished within the perinatal period, as a consequence of rapid changes in tissue oxygen concentration and the development of antioxidant defence enzyme activities. We studied the ontogeny of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) in fetal blood samples. The activity of SOD in fetal erythrocytes taken in the 17th gestational week was the same as that in erythrocytes of healthy blood donors. On the other hand, GPx activity was significantly lower between the 17th and 25th gestational week and at the time of delivery, compared with the healthy adult control. Our results suggest that the supposed underdevelopment of the antioxidant system in the lungs or in the other organs of premature infants cannot be monitored by SOD and GPx activities in erythrocytes, because these reach adult levels before the 17th week for SOD and from the 26th to the 35th gestational week for GPx, with lower levels from the 17th to the 25th week and at term.

Lipid peroxidation and antioxidant enzymes in CAPD patients.

The mechanisms of free-radical injury include reactions with proteins, nucleic acids, and polysaccharides; and covalent binding to membrane components and initiation of lipid peroxidation. Cells have developed antioxidant defense to prevent free-radical injury including superoxide dismutase (SOD) and glutathione peroxidase (GPx). Significantly higher concentrations of total malondialdehyde (MDA) in plasma (1.22 +/- 0.42 vs. 0.64 +/- 0.22 micromol/L, p < 0.0001) as well as erythrocytes (2.56 +/- 1.28 vs. 1.03 +/- 0.44 micromol/L, p < 0.0001) of the CAPD patients were found when compared to the control group. The free MDA in plasma and the erythrocytes do not differ significantly in continuous ambulatory peritoneal dialysis (CAPD) patients and the control group. A significantly lower activity of GPx in erythrocytes of CAPD patients (17.85 +/- 2.63 U/g Hb vs. 23.26 +/- 3.61 U/g Hb, p < 0.0001) was found when compared to the control group, but the SOD activity in erythrocytes is not different (2272.36 +/- 579.92 U/g Hb vs. 2347.13 +/- 502.51 U/g Hg, NS). Our results show an increase of total MDA in erythrocytes and plasma. MDA is the product of lipid peroxidation with decreasing activity of GPx, which is capable of detoxifying peroxides. The activity of SOD did not change in CAPD patients. These results propose a possible role of free radicals with reduced antioxidant activity of GPx in CAPD patients and indicate that they could play some role in other pathological conditions such as atherogenesis and hemolysis.

Antioxidant enzymes and lipid peroxidation in patients with multiple myeloma.

Reactive oxygen species and other free radicals are known to be the mediators of phenotypic and genotypic changes that lead from mutation to neoplasia. The imbalance in tumor cell antioxidant defense mechanism can influence also the sensitivity to cytoreductive therapy. In erythrocytes it can result to hemolysis which is one of the pathogenetic mechanisms of anemia in cancer patients. Parameters of lipid peroxidation (malondialdehyde-MDA) and antioxidant enzymes here represented by superoxide dismutase (SOD) and glutathione peroxidase (GPx) in multiple myeloma (MM) have been investigated. Nine patients of various clinical stages and activities of the disease were studied. Significantly higher concentrations of total MDA in plasma (1.20 +/- 0.24 mumol/l vs. 0.64 +/- 0.22 mumol/l, p < 0.0001) as well as in erythrocytes (2.72 +/- 0.81 mumol/l vs. 1.03 +/- 0.44 mumol/l, p < 0.0001) were found comparing to the control group. The levels of free MDA in plasma (0.31 +/- 0.09 mumol/l vs. 0.49 +/- 0.17 mumol/l, p < 0.05) and in erythrocytes (0.29 +/- 0.20 mumol/l vs. 0.59 +/- 0.22 mumol/l, p < 0.001) were decreased in myeloma patients. Significantly lower activities of GPx (19.17 +/- 4.07 U/g Hb vs. 23.26 +/- 3.61 U/g Hb, p < 0.05) and SOD (1882.46 +/- 181.73 U/g Hb vs. 2347.13 +/- 502.51 U/g Hb, p < 0.05) in erythrocytes were found. We did not observe evident relationship between the concentration of MDA or the activities of SOD and GPx and either the stage of the disease, or the level and the type of paraprotein. These results propose possible role of free radicals with reduced antioxidant activities of SOD and GPx in multiple myeloma.

[Lipid peroxidation and activity of antioxidative enzymes in patients with multiple myeloma]. / Lipoperoxidace a aktivita antioxidacních enzymu u pacientu s mnohocetným myelomem.

BACKGROUNDS: Reactive oxygen species and other free radicals are known to be the mediators of phenotypic and genotypic changes that lead from mutation to neoplasia. The imbalance in tumor cell antioxidant defense mechanism can influence also the sensitivity to cytoreductive therapy. In erythrocytes it can results to hemolysis which is one of pathogenetic mechanisms of anemia in cancer patients. METHODS AND RESULTS: We investigated the parameters of lipid peroxidation (malondialdehyde-MDA) and antioxidant enzymes here represented by superoxide dismutase (SOD) and glutathione peroxidase (GPx) in multiple myeloma. Nine patients of various clinical stage and activity of disease were studied. A significant higher concentration of total MDA in plasma (1.20 +/- 0.24 mumol/l v.s. 0.64 +/- 0.22 mumol/l, p < 0.0001) as well as in erythrocytes (2.72 +/- 0.81 mumol/l v.s. 1.03 +/- 0.44 mumol/l, p < 0.0001) was found comparing to the control group. The levels of free MDA in plasma (0.31 +/- 0.09 mumol/l v.s. 0.49 +/- 0.17 mumol/l, p < 0.05) and in erythrocytes (0.29 +/- 0.20 mumol/l v.s. 0.59 +/- 0.22 mumol/l, p < 0.001) were decreased in myeloma patients. A significantly lower activity of GPx (19.17 +/- 4.07 U/g v.s. 23.26 +/- 3.61 U/g Hb, p < 0.05) and SOD (1882.46 +/- 181.73 U/g v.s. 2347.13 +/- 502.51 U/g Hb, p < 0.05) in erythrocytes were found. CONCLUSIONS: We didn't observe evident relationship between the concentration of MDA or activities of SOD and GPx and either the stage of disease or level and type of paraprotein. We can conclude, that higher concentration of total MDA as a parameter of lipid peroxidation, is significantly increased in patients with multiple myeloma. It could be consequence of impaired antioxidant defence. These results propose possible role of free radicals with reduced antioxidant activity of SOD and GPx in multiple myeloma. As we can consider the role of free radicals in pathogenesis of malignant proliferation, prognostic value and the change during the course of therapy should by studied.

Antioxidant enzymes--superoxide dismutase and glutathione peroxidase--in haemodialyzed patients.

The biological effect of oxygen-reactive species controlled by antioxidant mechanisms are exerted on the basis of antioxidant enzymes and substrates. In this study, the activities of antioxidant enzymes-superoxide dismutase (SOD) and glutathione peroxidase (GPx)-were determined in the erythrocytes of patients on regular haemodialysis treatment. The SOD activity was significantly lower (1,810.38 +/- 609.85 vs. 2,347.13 +/- 502.51 U/g haemoglobin, p < 0.05, or 70.71 +/- 11.50 vs. 100.13 +/- 24.28 mU/10(6) erythrocytes, p < 0.0001), as was the GPx activity (18.80 +/- 4.22 vs. 23.26 +/- 3.61 U/g haemoglobin, p < 0.01), when compared with the control group. A positive correlation between GPx activity and number of haemodialysis sessions was found (p = 0.0038), but no correlation between SOD activity and number of HD sessions. An inpaired antioxidant enzyme defence system, here represented by SOD and GPx levels, can potentiate injury caused by free radicals in haemodialysis patients.

Activity of the antioxidant enzyme, glutathione peroxidase, on autosomal dominant polycystic kidney disease patients.

Reactive oxygen species are generated physiologically in cells with a significant increase in certain pathological conditions, such as inflammation, cancer, aging, degenerative disease. If endogenous antioxidant systems, in our study represented by glutathione peroxidase, are exceeded by this oxidant flux, tissue injury may occur. Activity of glutathione peroxidase (GPx) was determined using Beutler's modified spectrophotometric assay in erythrocytes from autosomal dominant polycystic kidney disease patients. Activity of glutathione peroxidase was significantly (at p < 0.0001) lower there (17.75 +/- 3.69 U/g haemoglobin) compared to the control group (23.26 +/- .61 U/g Hb). Lower antioxidant enzyme defence system of ADPKD patients, here represented by GPx, can potentiate injury caused by free radicals and possibly play a role in the progression of autosomal dominant polycystic kidney disease.

Lipid peroxidation and superoxide dismutase activity in umbilical and maternal blood.

Oxygenation of both mother and child tissues oscillate frequently during labour. We tested the lipid peroxidation caused by reactive oxygen species which are produced in consequence of tissue reoxygenation and the inactivation of these species by the maternal and newborn superoxide dismutase. Total malondialdehyde in concentrations (mean +/- SE) of 1.04 +/- 0.17, 1.57 +/- 0.22, 1.33 +/- 0.14 and 1.36 +/- 0.21 mumol/L was found in maternal plasma and red blood cells and newborn plasma and red blood cells, respectively, after uncomplicated deliveries and 4.93 +/- 1.34, 7.12 +/- 1.37, 4.77 +/- 1.29 and 7.37 +/- 1.51 mumol/L, respectively, after deliveries with clinical signs of foetal hypoxia. In newborns, erythrocyte superoxide dismutase activity reached only 82% of the maternal level (p < 0.05). The results indicate that the maternal and foetal antioxidant defence systems can be overloaded during deliveries with abnormal oxygenation, where increased lipid peroxidation occurred.

Xanthine oxidoreductase. Biochemical, biological and pathogenic functions.

Primary biochemical role of xanthine oxidoreductase (XOR, EC 1.1.1.204 and EC 1.1.3.22.) is the hydroxylation of hypoxathine and xanthine to form uric acid. This enzyme may produce very reactive oxygen forms which can be pathogenic. Although it is one of the longest known and most continuously studied enzymes, its biological function remains unclear. The review of these aspects is discussed in relation to the authors' experimental results.