Medical faculties educational network: multidimensional quality assessment

Today, World Wide Web technology provides many opportunities in the disclosure of electronic learning and teaching content. The MEFANET project (MEdical FAculties NETwork) has initiated international, effective and open cooperation among all Czech and Slovak medical faculties in the medical education fields. This paper introduces the original MEFANET educational web portal platform. Its main aim is to present the unique collaborative environment, which combines the sharing of electronic educational resources with the use tools for their quality evaluation. It is in fact a complex e-publishing system, which consists of ten standalone portal instances and one central gateway. The fundamental principles of the developed system and used technologies are reported here, as well as procedures of a new multidimensional quality assessment.

Oxidative stress and inflammation in pregnancy

Pregnancy is a period when increased oxidative stress can be expected. We have focused especially on oxidative stress and inflammation in the period of pregnancy, when prenatal screening is usually performed. We determined advanced oxidation protein products (AOPPs), C-reactive protein (CRP) and anticardiolipin antibodies (ACA) IgG and IgM levels in the serum of 86 pregnant women in the 1st trimester and 102 pregnant women in the 2nd trimester. AOPP levels in the maternal serum of pregnant women were significantly higher in the 1st and 2nd trimesters than they were in that of non-pregnant women (p<0.0001, p<0.001, respectively). Maternal serum CRP levels, too, were increased compared with those in non-pregnant women (1st and 2nd trimester versus non-pregnant women p<0.05, p<0.005, respectively). Just as with AOPPs and CRP, the ACA IgG levels in pregnant women were significantly higher in both trimesters than they were in non-pregnant women (1st and 2nd trimesters versus non-pregnant women p<0.05, p<0.001, respectively). Maternal serum CRP levels correlated positively with AOPPs in the 2nd trimester (r = 0.504, p<0.05). The increased levels of AOPPs, CRP and ACA IgG in the 1st and 2nd trimesters may reflect a maternal response to inflammatory and oxidative stress in pregnant women.

Differences in activities of antioxidant superoxide dismutase, glutathione peroxidase and prooxidant xanthine oxidoreductase/xanthine oxidase in the normal corneal epithelium of various mammals

Under normal conditions, antioxidants at the corneal surface are balanced with the production of reactive oxygen species without any toxic effects. Danger from oxidative stress appears when natural antioxidants are overwhelmed leading to antioxidant/prooxidant imbalance. The aim of the present study was to examine the activities of enzymes contributing to the antioxidant/prooxidant balance in normal corneal epithelium of various mammals. The enzyme activities of antioxidant superoxide dismutase and glutathione peroxidase, as well as prooxidant xanthine oxidoreductase/xanthine oxidase were examined using biochemical methods. Results show that superoxide dismutase activity is high in rabbits and guinea pigs, whereas in pigs the activity is low and in cows it is nearly absent. In contrast, glutathione peroxidase activity is high in cows, pigs and rabbits, whereas in guinea pigs the activity is low. As far as prooxidant enzymes are concerned, elevated xanthine oxidoreductase/xanthine oxidase activities were found in rabbits, lower activities in guinea pigs, very low activity in cows and no activity in pigs. In conclusion, the above results demonstrate inter-species variations in activities of enzymes participating in antioxidant/prooxidant balance in the corneal epithelium. It is suggested that the levels of antioxidant and prooxidant enzymes studied in the corneal epithelium might be associated with the diurnal or nocturnal activity of animals. UV rays decompose hydrogen peroxide to damaging hydroxyl radicals and perhaps for this reason large animals with diurnal activity (cow, pig) require more effective peroxide removal (high glutathione peroxidase activity) together with the suppression of peroxide production (low superoxide dismutase activity, low xanthine oxidoreductase activity).

[Advanced glycation and oxidation products in patients with atherosclerosis]

BACKGROUND

Oxidative stress can potentiate atherogenesis via modification of biological structures and formation of new compounds, e.g. advanced glycation end products (AGEs) and advanced oxidation protein products (AOPP). The aim of the study was to determine AGEs and AOPP in patients with atherosclerosis, effect of statin therapy and relationship to parameters of lipid metabolism.

METHODS AND RESULTS

AGEs (carboxymethyllysine - ELISA and fluorescent AGEs - spectrofluorimetry) and AOPP (spectrophotometry) were assessed in 42 patients with atherosclerosis and 21 healthy controls. AGEs are significantly elevated in patients with atherosclerosis in comparison with healthy subjects (carboxymethyllysine 9.02+/-1.66 microg/g prot. vs 7.52+/-1.18 microg/g prot., p<0.001, fluorescent AGEs 4.39 x 103+/-1.15 x 103 AU/g prot. vs 3.78 x 103+/-0.52 x 103 AU/g prot., p<0.001). Mean AOPP concentrations are also slightly higher, but this elevation is not quite significant (95.0+/-42.9 micromol/l vs 79.7+/-28.2 micromol/l, p=0.096). AGEs and AOPP correlate significantly with each other and with selected lipids. Patients with atherosclerosis treated with statins have slightly lower CML, AGEs and AOPP (it did not reach the statistical significance).

CONCLUSIONS

Advanced glycoxidation products are elevated in patients with atherosclerosis and are related to parameters of lipid metabolism. Glycoxidation might be possibly therapeutically influenced by statins; however, further clinical studies are required to confirm this hypothesis.

Apocynin inhibits NADPH oxidase in phagocytes but stimulates ROS production in non-phagocytic cells

Apocynin is a naturally occurring methoxy-substituted catechol, experimentally used as an inhibitor of NADPH oxidase. Since it acts as a potent inhibitor in studies with neutrophils and macrophages, no inhibitory effect can often be found in non-phagocyte cells. In our experiments, apocynin even stimulated reactive oxygen species (ROS) production by vascular fibroblasts. Even when added to macrophages, apocynin initially caused an increase in ROS production. The inhibition of ROS formation followed, suggesting that in the presence of leukocyte myeloperoxidase and hydrogen peroxide, apocynin is converted to another compound. Apocynin pre-activated with H2O2 and horseradish peroxidase (HRP) inhibited ROS production immediately. In non-phagocytes, apocynin stimulated ROS production and no inhibition was observed even after 60 min. Apocynin treated with H2O2 and HRP, however, decreased ROS production in the same manner as in macrophages. The stimulatory effect on ROS production can be abolished by tiron and superoxide dismutase (SOD), suggesting that superoxide was the produced species. The effect of apocynin was inhibited by diphenylene iodinium (DPI), a non-scavenging NADPH oxidase inhibitor. It can be summarized that apocynin stimulates cell superoxide production. In the presence of peroxidase and hydrogen peroxide, however, it is converted into another compound that acts as an inhibitor of superoxide production. It strongly suggests that under conditions in vivo, apocynin can have opposite effects on phagocytes and non-phagocyte cells. It acts as an inhibitor of phagocyte NADPH oxidase but also as a ROS production stimulator in non-phagocyte cells.

Age-related changes in superoxide dismutase, glutathione peroxidase, catalase and xanthine oxidoreductase/xanthine oxidase activities in the rabbit cornea

The activities of superoxide dismutase, glutathione peroxidase (GPX) and catalase--the enzymatic scavengers of reactive oxygen species and the activities of xanthine oxidoreductase and xanthine oxidase, an enzyme known to generate reactive oxygen species, were studied in the corneas of normal rabbit eyes of various ages (1 month--young eyes; 4-9.5 months--young adult eyes; 2.0-2.75 years--middle aged eyes; 3.0-5.0 years--aged eyes). The activities of GPX, superoxide dismutase, xanthine oxidoreductase and xanthine oxidase were investigated biochemically in the scraped corneal epithelium. Catalase activity was detected histochemically in the corneal epithelium and endothelium. The results show that young corneas revealed lower activities of all the antioxidant enzymes investigated than did young adult corneas, in which enzymatic activities reached their maximum. In middle-aged corneas, GPX and catalase activities remained approximately at the same levels as seen in young adult corneas, whereas superoxide dismutase activity was decreased. In aged corneas, the activities of all antioxidant enzymes were dramatically decreased or even lost (catalase activity in the corneal endothelium). In contrast, xanthine oxidoreductase activity only slightly decreased with age and the xanthine oxidase proportion of total xanthine oxidoreductase remained unchanged. GPX, superoxide dismutase and catalase are important antioxidant enzymes protecting the cornea against the oxidative damage. Because the activities of these enzymes are lower in young animals and greatly reduced in aged animals, it is suggested that young and particularly aged corneas might be more susceptible to oxidative stress than are young adult corneas. This presumption is supported by the fact that the activities of prooxidant enzymes (xanthine oxidoreductase/xanthine oxidase) are only slightly decreased in aged corneas as compared to young adult corneas so that some imbalance between antioxidant and prooxidant enzymes exists already in the normal aged corneas.

[Ferritin, oxidative stress and coronary atherosclerosis]

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.

Advanced Glycation End Products in Clinical Nephrology

As a result of oxidative and carbonyl stress, advanced glycation end products (AGEs) are involved in the pathogenesis of severe and frequent diseases and their fatal vascular/cardiovascular complications, i.e. diabetes mellitus and its complications (nephropathy, angiopathy, neuropathy and retinopathy, renal failure and uremic and dialysis-associated complications), atherosclerosis and dialysis-related amyloidosis, neurodegenerative diseases, and rheumatoid arthritis. They are formed via non-enzymatic glycation which is specifically enhanced through the presence of oxidative and carbonyl stress, and their ability to form glycoxidation products in peptide and protein structures finally modulating or inducing biological reactivity. Food can be another source of AGEs; however, high serum AGEs in hemodialysis patients might reflect nutritional status better. Several methods of renal replacement therapy have been studied in connection with the AGE removal, but unfortunately the possibilities are still unsatisfactory even if high flux dialysis, hemofiltration, or hemodiafiltration give better results than conventional low flux dialysis. AGEs are currently being studied in the patients on peritoneal dialysis as their precursors can be formed in the dialysis fluid. AGEs can cause damage to the peritoneum and so a loss of ultrafiltration capacity. Many compounds give promising results in AGE inhibition (inhibition of formation of AGEs, inhibition of their action or degradation of AGEs), are tested for these properties, and eventually undergo clinical studies (e.g. aminoguanidine, OPB-9195, pyridoxamine, antioxidants, N-phenacylthiazolium bromide, antihypertensive drugs, angiotensin-converting enzyme inhibitors and angiotensin II receptor-1 antagonists).

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, inflammation and autoimmune reaction in type 1 and type 2 diabetes mellitus

Diabetes mellitus (DM) is associated with oxidative stress, elevation of inflammatory markers and other mechanisms, which may contribute to accelerated atherosclerosis. The aim of the study was to determine prominent factors of these pathogenic processes in patients with DM, to examine their relationship in serum, and to find out the differences between DM1 and DM2. Advanced oxidation protein products (AOPP), C-reactive protein (CRP), pregnancy-associated plasma protein-A (PAPP-A), anticardiolipin antibodies (ACA) and anti-beta2-glycoprotein-1 antibodies (anti-beta2-GPI) were determined in 27 patients with DM1, 27 patients with DM2 and 23 healthy subjects. AOPP, CRP and anti-beta2-GPI were significantly elevated in DM2 in comparison with healthy subjects (p<0.01, p<0.0001, p<0.0001, respectively). In DM1, anti-beta2-GPI were elevated (p<0.0001) as well, but there was no increase of either AOPP or CRP. There was no difference in PAPP-A levels in DM1 or DM2 and healthy subjects. In DM 1, AOPP correlate significantly with anti-beta2-GPI (r = 0.68, p<0.05). In DM2, there is a significant correlation between anti-beta2-GPI and PAPP-A (r=0.45, p<0.05). Oxidative stress and inflammation are more expressed in DM2 and they are partly related. In DM1, oxidative stress seems to be in closer link to autoimmune reaction than to inflammation.

Hyperlipoproteinemia impairs endothelium-dependent vasodilation

Atherogenic lipoproteins can cause endothelial dysfunction in the initial stage of atherogenesis. In our study we examined 134 patients with defined hyperlipoproteinemia (non-HDL cholesterol>4.1 mmol/l or triglycerides>2.5 mmol/l or taking any of lipid lowering drugs)--94 men and 40 women. The subgroup of controls of comparable age contained 54 normolipidemic individuals--30 men and 24 women. Patients with hyperlipoproteinemia revealed significantly lower ability of endothelium-dependent flow-mediated vasodilation (EDV) measured on brachial artery (4.13+/-3.07 vs. 5.41+/-3.82 %; p=0.032) and higher carotid intima media thickness than normolipidemic controls (0.68+/-0.22 vs. 0.58+/-0.15 mm; p=0.005). In regression analysis, EDV correlated significantly with plasma concentrations of oxLDL (p<0.05) HDL-cholesterol (p<0.05), Apo A1 (p<0.05), ATI (p<0.01) and non-HDL cholesterol (p<0.05). Patients with hyperlipoproteinemia showed higher plasma levels of oxLDL (65.77+/-9.54 vs. 56.49+/-7.80 U/l; p=0.015), malondialdehyde (0.89+/-0.09 vs. 0.73+/-0.08 micromol/l; p=0.010) and nitrites/nitrates (20.42+/-4.88 vs. 16.37+/-4.44 micromol/l; p=0.018) indicating possible higher long-term oxidative stress in these patients.

Markers of inflammation in preeclampsia

Advanced oxidation protein products (AOPP) represent terminal products of proteins exposure to free radicals. The aim of this study was to estimate the serum AOPP levels in preeclamptic patients together with ultrasensitive C-reactive protein and anticardiolipin antibodies (ACA) IgG and IgM. 21 women in the third trimester of pregnancy were included in the study--10 women with preeclampsia and 11 women with normal outcome of pregnancy. AOPP levels in preeclampsia were higher than those in normal pregnant women in the third trimester, but not statistically significantly. The comparison with AOPP levels in non-pregnant women has shown a significant increase (P<0.0001). CRP in preeclampsia was significantly increased in comparison with third trimester levels in normal pregnancy (P<0.001) as well as with non-pregnant women (P<0.0001). In preeclampsia, the ACA IgG levels were even significantly lower than in normal pregnant women in the same gestation age, but significantly higher than in non-pregnant women (P<0.001). No difference was found in ACA IgM in preeclampsia and normal third trimester pregnancy and non-pregnant women. A statistically significant negative correlation was found between AOPP and ACA IgG (r= - 0.708, P<0.05). The results indicate enhanced oxidative and inflammatory reaction of maternal organism to pregnancy, which is more pronounced in preeclampsia than in uncomplicated pregnancy.

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.

[Determination of advanced glycation end products]

Advanced glycation end products--AGEs take part in the pathogenesis of many diseases and their complications--e.g. diabetes mellitus, chronic renal failure, atherosclerosis, Alzheimer's disease. Their determination could be of importance for follow up of progression of these diseases. Determination of AGEs is very difficult due to the heterogeneity of this group of substances, lack of standards, long analytical procedures and necessity of equipment. There are several methods for determination of advanced glycation end products: immunochemical method--ELISA (enzyme linked immunosorbent assay) with the use of either polyclonal or monoclonal antibodies, fluorimetry using the characteristic fluorescence spectrum of AGEs, HPLC--high performance liquid chromatography, and MS--mass spectrometry. Mass spectrometry is the best and most precise method. When coupled with other methods, mass spectrometry is a unique research method, which can be used mainly for characterization of new AGEs. HPLC is very precise as well, but its drawback is time-consuming sample preparation. Fluorimetry and ELISA could be in the future used for the special diagnostic of complications of chronic diseases.

Antibodies against oxidized low density lipoproteins in pregnant women

Oxidized low density lipoproteins (oxLDL) formed in vivo induce a humoral immune response. Oxidative modification of LDL renders it immunogenic and a heterogeneous population of specific anti-oxLDL antibodies is produced. These antibodies could represent a biological marker of oxidative stress and serve as markers of atherosclerosis. Autoantibodies against oxLDL (oLAb) have been detected in human subjects practically of every age. oLAb also appear in the blood of pregnant women. Some studies have shown that the levels of antibodies to oxLDL were elevated in women with established preeclampsia. The present study was aimed to estimate the oLAb IgG levels in the first and second trimester of pregnancy. Furthermore, we estimated the correlation between maternal serum (MS) levels of oLAb and alpha-1-fetoprotein (MS AFP), human chorionic gonadotrophin (MS HCG) and trophoblast-specific-beta-1-glycoprotein (MS SP1), because these proteins are determined as a part of prenatal biochemical screening for fetal congenital abnormalities. Our study deals with the oLAb changes in women with pregnancy-induced hypertension. We also investigated the correlation between oLAb IgG and anticardiolipin antibodies IgG (ACA) in the serum of pregnant women. We examined 40 pregnant women attending Institute for Mother and Child Care for their antenatal care as outpatients. Routine blood samplings between the 9-13th week of pregnancy and 16-18th week of pregnancy were performed as a part of biochemical prenatal screening for fetal congenital abnormalities (Group 1). Their mean age was 27 +/- 4.1 years. Furthermore, we examined 26 women in the second or third trimester with pregnancy-induced hypertension (Group 2). Group 2 was compared with 49 pregnant women in the second or third trimester who were normotensive (Group 3). We used commercial standardized ELISA kits for determination of oLAb IgG, ACA IgG, MS AFP and MS HCG, MS SP1 was analyzed by single radial immunodiffusion. We did not find any differences in the levels of oLAb IgG in the first and second trimester in the women of Group 1. The correlation between oLAb and ACA IgG was not statistically significant (Spearman coefficient r=0.22, p=0.1). The correlation between oLAb IgG with MS AFP, MS HCG and MS SP1 was not statistically significant. Weak negative correlation for AFP and HCG was suggested both in the first and in the second trimester. The levels of oLAb IgG in the group of women with pregnancy-induced hypertension were significantly lower than in the group of normotensive women (348 +/- 388 U/ml v.s. 579 +/- 400 mU/ml, p<0.01). We can conclude that the levels of oLAb do not differ in the first and second trimester of gravidity. However, we cannot exclude the possible influence of an inverse relationship between oLAb IgG titers and the synthesis of fetoplacental antigens. This finding is important especially in the context of the results of prenatal biochemical screening. Pregnancy-induced hypertension is associated with lower levels of oLAb. Weak cross-reactivity between oLAb and anticardiolipin antibodies may exist but there is a possibility that there are two different populations of antibodies reacting with various antigens.

[Levels of advanced oxidation protein products (AOPP) in the first trimester of pregnancy]

Advanced oxidation protein products (AOPP) may be sensitive biomarkers for protein damage mediated by reactive oxygen species. AOPP were measured in the serum of 41 pregnant women in the 8th-12th week of pregnancy. Parameters of prenatal screening in the first trimester (pregnancy-associated plasma protein A--PAPP-A and free beta human chorionic gonadotrophin--free beta HCG) and anticardiolipin antibodies (ACA) IgG and IgM were determined as well. A group of healthy blood donors--women and men was used for comparison. AOPP were determined spectrophotometrically according to Witko-Sarsat [24] (absorbance at 340 nm) and were expressed in chloramine units (mumol/l). Other analytes were determined by immunoanalytic methods. AOPP levels in pregnant women in the first trimester are significantly higher in comparison with blood donors--women (89.46 +/- 33.38 mumol/l vs 57.34 +/- 16.31 mumol/l, p < 0.0001) but there is no statistically significant difference between pregnant women and blood donors--men (89.46 +/- 33.38 mumol/l vs 78.60 +/- 44.01 mumol/l). AOPP level does not correlate either with the age of pregnant women or with the parameters of prenatal screening and ACA IgG and IgM. Higher levels of AOPP in the serum of pregnant women in comparison with women--blood donors may reflect an increase of oxidative stress in pregnancy.

[Advanced oxidation protein products in pregnancy]

OBJECTIVE

Pregnancy and mainly its complications are associated with increased oxidative stress. Advanced oxidation protein products (AOPP) can serve as one of its markers.

SETTING

First Institute of Medical Chemistry and Biochemistry and Institute for Clinical Biochemistry, First Medical Faculty, Charles University; Institute for Care of Mother and Child, Prague.

METHODS

Together with parameters of prenatal screening, AOPP were measured in the serum of 23 pregnant women in the 2nd trimester of pregnancy. A group of healthy blood donors--women and men was used for comparison. AOPP were determined spectrophotometrically according to Witko-Sarsat (absorbance at 340 nm) and are expressed in chloramin units (mumol/l).

RESULTS

Serum AOPP concentrations in pregnant women are significantly higher in comparison with blood donors--women (85.90 +/- 18.70 mumol/l vs 57.34 +/- 16.31 mumol/l, P < 0.0001) but there is no statistically significant difference between pregnant women and blood donors--men (85.90 +/- 18.70 mumol/l vs 78.60 +/- 44.01 mumol/l). AOPP level does not correlate either with the age of pregnant women or with the parameters of prenatal screening (human chorionic gonadotrophin--HCG, alpha-1-fetoprotein--AFP and trophoblast-specific--beta-1-glycoproteion--SP1).

CONCLUSION

AOPP as a marker of oxidative stress is increased in the serum of pregnant women in comparison with women--blood donors but is similar as in men--blood donors which supports the hypothesis of hormonal influence. Nevertheless, AOPP do not correlate with the parameters of prenatal screening (HCG, AFP and SP1).

[Effect of fibrates on VLDL and LDL lipoprotein composition and parameters of their oxidation in hypertriglyceridemia]

BACKGROUND

Meta-analyses of epidemiological studies proved that hypertriacylglycerolemia (HTAG) is an independent CHD risk factor. The VLDL lipoproteins, which are the main TAG carrier, are precursors of atherogenic LDL and their increased concentration is related to the decrease of antiatherogenic HDL, increased ratio of small, dense LDL and represents one of the causes of the endothelial dysfunction. According to some authors, HTAG is one of the factors of the oxidation stress.

MATERIAL AND METHODS

45 patients of the studied group received 200 mg of micronized fenofibrate per day for six weeks. Before the beginning and after the end of treatment, following examinations were carried out: concentration of plasma lipids, lipoproteins, and apolipoproteins, composition of fatty acids (FA) in main lipid plasma classes and LDL (phosphatidylcholine--PC, TAG, cholesteryl esters--CE) and lipoperoxidation in VLDL and LDL, isolated by preparative ultracentrifugation.

RESULTS AND CONCLUSIONS

In plasma, the treatment of HTAG led to a significant decrease of TC, TAG and apo-B concentration and to the increase of cholesterol concentration in HDL and in both HDL2 and HDL3 subfractions. In isolated LDL particles we observed a decrease of the TAG portion (by 25%) together with significant lag phase prolongation (by 33%, P < 0.05) and peak time retardation (by 24%, P < 0.05). In VLDL particles the concentration of cholesterol became smaller (by 28%), TAG (by 26%), phospholipids (by 28%) (in all groups P < 0.005) and the lag phase became significantly longer (by 16%, P < 0.01). Treatment with fenofibrate significantly reduced the linoleic acid (18:2n-6) in PC and TAG plasma, CE and TG LDL, in a higher ratio of palmitoleic acid (16:1n-7) in CE LDL, oleic (18:1n-9) in PC LDL, in significant concentration of total monoenic FA in PC and CE LDL and to a significant increase of the concentration of myristic acid (14:0) in CE and myristic and stearic acids (18:0) in TAG LDL. From our results it is possible to conclude that the six-week long treatment of HTAG with micronized phenofibrate led to significant modification of LDL and VLDL composition accompanied by their lower lipoperoxidation indexes. These favourable changes in oxidability were accompanied with changes in the composition of FA in CE, TAG and PC plasma as well as LDL.

[Carbonyl stress and chronic renal failure]

Pathogenesis of many diseases and their complications is linked to oxidative stress. In the last two years, the attention has been paid also to carbonyl stress which is alosely related to oxidative stress. Carbonyl stress is characterized as an increase of reactive carbonyl compounds caused by their increased formation and/or decreased breakdown and excretion. Reactive carbonyl compounds can be formed from carbohydrates, lipids and amino acids both by oxidative and non-oxidative pathways, can be detoxified by several enzymes and excreated by kidneys depending on their function. Carbonyl compounds can form advanced glycation end-products (AGEs) and advanced lipoperoxidation end-products (ALEs), which are known to take part in the pathogenesis mainly of diabetic and uremic complications.

Influence of losartan and enalapril on urinary excretion of 8-isoprostane in experimental nephrotic syndrome

BACKGROUND

The increased permeability of the glomerular capillary wall in adriamycin nephropathy may be mediated by increased generation of free radicals, possibly also by the non-enzymatic production of isoprostanes induced by oxidative stress. ACE inhibitors and angiotensin II antagonists may reduce proteinuria, perhaps by decreasing intraglomerular pressure and increasing the selective permeabiity of the glomerular capillary wall.

MATERIAL/METHODS

We compared the effect of an ACE inhibitor, enalapril, and an angiotensin II antagonist, losartan, on total malodialdehyde in blood and the urinary excretion of certain eicosanoids and their metabolites (TxB(2), 6-keto-PGF(1alpha), bicyclo-PGE(2) and 8-isoprostane) in experimental adriamycin-induced nephrotic syndrome in rats.

RESULTS

Increased proteinuria in adriamycin-treated rats was not prevented by losartan, but tended to be partly mitigated by enalapril. However, both losartan and enalapril prevented the 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. The enalapril-induced increase in urinary excretion of bicyclo-PGE(2) was possibly mediated by kinins. Proteinuria positively correlated with urinary excretion of 8-isoprostane, and proteinuric rats also had a significantly higher urinary excretion of 8-isoprostane than non-proteinuric rats.

CONCLUSIONS

Proteinuria in the acute phase of adriamycine nephropathy may be dependent on free radical generation and the formation of 8-isoprostane. The mild antiproteinuric effect of enalapril, but not losartan, may suggest the contributory role of the inhibition of kinin degradation in the antiproteinuric action of enalapril in this model of nephrotic syndrome.

Quinolinic acid-iron(ii) complexes: slow autoxidation, but enhanced hydroxyl radical production in the Fenton reaction

Quinolinate (pyridine-2,3-dicarboxylic acid, Quin) is a neurotoxic tryptophan metabolite produced mainly by immune-activated macrophages. It is implicated in the pathogenesis of several brain disorders including HIV-associated dementia. Previous evidence suggests that Quin may exert its neurotoxic effects not only as an agonist on the NMDA subtype of glutamate receptor, but also by a receptor-independent mechanism. In this study we address ability of ferrous quinolinate chelates to generate reactive oxygen species. Autoxidation of Quin-Fe(II) complexes, followed in Hepes buffer at pH 7.4 using ferrozine as the Fe(II) detector, was found to be markedly slower in comparison with iron unchelated or complexed to citrate or ADP. The rate of Quin-Fe(II) autoxidation depends on pH (squared hydroxide anion concentration), is catalyzed by inorganic phosphate, and in both Hepes and phosphate buffers inversely depends on Quin concentration. These observations can be explained in terms of anion catalysis of hexaaquairon(II) autoxidation, acting mainly on the unchelated or partially chelated pool of iron. In order to follow hydroxyl radical generation in the Fenton chemistry, electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was employed. In the mixture consisting of 100 mM DMPO, 0.1 mM Fe(II), and 8.8 mM hydrogen peroxide in phosphate buffer pH 7.4, 0.5 mM Quin approximately doubled the yield of DMPO-OH adduct, and higher Quin concentration increased the spin adduct signal even more. When DMPO-OH was pre-formed using Ti3+ /hydrogen peroxide followed by peroxide removal with catalase, only addition of Quin-Fe(II), but not Fe(II), Fe(III), or Quin-Fe(III), significantly promoted decomposition of pre-formed DMPO-OH. Furthermore, reaction of Quin-Fe(II) with hydrogen peroxide leads to initial iron oxidation followed by appearance of iron redox cycling, detected as slow accumulation of ferrous ferrozine complex. This phenomenon cannot be abolished by subsequent addition of catalase. Thus, we propose that redox cycling of iron by a Quin derivative, formed by initial attack of hydroxyl radicals on Quin, rather than effects of iron complexes on DMPO-OH stability or redox cycling by hydrogen peroxide, is responsible for enhanced DMPO-OH signal in the presence of Quin. The present observations suggest that Quin-Fe(II) complexes display significant pro-oxidant characteristics that could have implications for Quin neurotoxicity.

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.

[Insulinemia, fatty acids in plasma lipids and lipoproteins and oxidation of VLDL and LDL in hyperlipidemia]

Both insulin resistance and hyperlipidaemia are connected with an increased oxidative stress, playing a significant role in the development of atherosclerosis. A significant event in the process being the oxidative modification of the lipoproteins, especially LDL. Aim of the study was to analyse relationships between the fatty acid composition of the plasma cholesteryl esters (CE), triglycerides (TG) and phosphatidylcholine (PC) and of the separated LDL, insulinaemia and oxidability of both VLDL and LDL particles. We have observed the group of 75 patients with hyperlipidaemia (52 men and 23 women), which was divided in the two subgroups after the basal insulinaemia (more resp. less than 13 mU/l). Fasting hyperinsulinaemia of the probands with normal glucose tolerance served as a marker of an insulin resistance. Patients with both hyperlipidaemia and basal hyperinsulinaemia were characterized by a significantly higher concentration of TG, apolipoprotein B in LDL, and lower concentration of cholesterol in HDL, especially in HDL3. We have observed only marginally significant elevation of concentration of the dihomo-gammalinolenic acid (DGLA) in plasma PC and also higher concentrations of alpha-linolenic and lower of arachidonic acid (AA) and in LDL-CE in the hyperinsulinaemic group. We have also found significantly positive correlations between the stearic acid in plasma PC, alpha-linolenic acid in plasma TG on one hand and the basal insulinaemia on the other hand. Significant positive correlation was also found between the ratio docosahexaenoic/docosapentaenic acid and insulinaemia in 120 min of oral glucose tolerance test. Significant negative correlation was observed between the ratio AA/DGLA and basal insulinaemia. Analysing the lipoperoxidation of VLDL and LDL using the method of conjugated diene kinetics we have found statistically non-significant decrease of lag phase duration of LDL and VLDL (their oxidability).

[Effect of fat distribution on lipoprotein composition and parameters of lipoperoxidation]

Fat distribution, not overweight and obesity per se, are supposed to be associated with hemodynamic, hemostatic and other metabolic disturbances (insulin resistance, hyperuricemia and dyslipidemia). Moreover, obesity increases the total risk of cardiovascular disease. Oxidative modification of lipoproteins, especially of LDL, is supposed to play a key role in the initiation and progression of atherosclerosis. Therefore we analysed VLDL a LDL composition and Cu(2+)-catalyzed conjugated diene formation in both lipoprotein fractions in patients with intraabdominal fat accumulation and in control group. Patients (33, 12 M/21 F) with intraabdominal fat accumulation (WHCR 1.00 for men, 0.85 for women) revealed, in comparison with control group (72, 47 M/25 F), after adjustment for the same age, increased plasma total cholesterol, apolipoprotein B, non-esterified fatty acid concentrations, and systolic blood pressure as well. In the group of patients increased levels of cholesterol, triglycerides, phospholipids, proteins and apolipoprotein B (only in the fraction of VLDL) were found in the both VLDL and LDL fractions. In this group of patients increased concentrations of conjugated dienes in VLDL and decreased length of lag phase of VLDL were found. Parameters of conjugated diene formation of LDL (basal absorbance, length of lag phase, propagation phase) did not differ significantly from controls. Concomitantly, persons with intraabdominal fat distribution showed decreased titres of antibodies against oxidative modified LDL. The results indicated that the patients with intraabdominal fat accumulation revealed not only adverse composition of VLDL and LDL particles, but also increased VLDL oxidation and oxidability.

[New markers of advanced damage caused by oxidative and carbonyl stress]

Oxidative stress, which is characterized as dysbalance between free radicals and antioxidants in favour of radicals, participates in the pathogenesis of many diseases and their complications. Carbonyl stress is closely related to oxidative stress and is described as increase of reactive carbonyl compounds caused by their increased formation or decreased degradation and clearance. Both oxidative and carbonyl stresses cause damage to proteins--they lead to formation of advanced oxidation protein products--AOPP, advanced glycation end-products--AGEs and advanced lipoperoxidation end-products--ALEs. These compounds have several biological effects--e.g. stimulation of secretion of cytokines, adhesive molecules and growth factors and take part in the development of complications of diabetes mellitus and chronic renal failure.

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.

[Fatty acid composition and parameters of VLDL and LDL in persons with dyslipidemia]

BACKGROUND

Oxidatively modified LDL play an important role in the pathogenesis of endothelial dysfunction, initiation and development of atherosclerosis and stability of the atheromatous plaque. The increased oxidative stress is apparent from a number of deviations, which are part of the insulin resistance syndrome (hypertension, hypoalphacholesterolaemia, diabetes and hyperlipoproteinaemia). The objective of the work was to examine the degree of oxidation and oxidability of LDL and VDL in subjects with dyslipidaemia.

METHODS AND RESULTS

In 40 subjects with dyslipidaemia, defined as a triglyceride concentration above 2.30 mmol/l and a drop of HDL cholesterol below 0.90 mmol/l, the authors assessed the fatty acid profile in plasma lipid classes and LDL by capillary gas chromatography. Lipoperoxidation in VLDL and LDL was examined by the method of kinetics of conjugated dienes according to Esterbauser. The results were compared with a group of healthy controls. The group of dyslipidaemic subjects had higher concentrations of NEFA, IRI, blood sugar and uric acid. In these subjects the concentration of conjugated dienes in VLDL was significantly higher and the lag stage in VLDL and LDL was reduced. Both groups differed as to the composition of VLDD and LDL. The group of dyslipidaemic subjects had a higher concentration of cholesterol, phospholipids, triglycerides and apolipoprotein B. A constant finding in the fatty acid profile of all lipid classes was a raised concentration of palmitoleic acid and reduced linoleic acid concentration.

CONCLUSIONS

Dyslipidaemic subjects have, as compared with a control group, higher NEFA, IRI and uric acid concentrations. Furthermore they differed not only by the composition of VLDL and LDL but also by a higher degree of VLDL oxidation and reduced resistance to lipoperoxidation of VLDL and LDL particles. A consistent finding in the fatty acid profile was an increased level of palmitoleic acid in all plasma lipid classes and LDL and a drop of linoleic acid in phosphatidylcholine LDL and plasma cholesterolesters.

Effect of the carbon source on assessment of degrading bacteria with the spread-plating technique during in situ bioremediation

Spread-plating belongs to traditional microbiological methods employed for quantification of subsurface microflora during bioremediation projects in the Czechia. Concentration of degrading organisms is estimated from the number of colonies grown on agar plates supplied with contaminant as the sole carbon source. The data obtained during in situ bioremediation of the Dacice site contaminated by cutting oil suggests that changes in the composition of the carbon source in the subsurface may cause a discrepancy between laboratory data and situation in subsurface.

[Effect of losartan and enalapril on urinary excretion of 8-isoprostane in experimental nephrotic syndrome]

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.

[Plasma leptin levels in patients with kidney diseases of various etiologies]

BACKGROUND

Leptin is a new hormone influencing food intake, energy expenditure and body weight. This protein is produced by adipocytes, exerts its effects on brain, endocrine pancreas and other organs by activating transmembrane receptors and is cleared from plasma mainly by the kidneys. The aim of our study was to compare plasma concentrations of leptin in our nephrological out-patients and controls.

METHODS AND RESULTS

We examined 36 diabetic patients with various stages of nephropathy, 12 males with nephrotic syndrome due to membranous nephropathy, 15 dialysis patients and 11 controls. Leptin was assessed in plasma by ELISA. There was a significant difference between plasma levels of leptin in males and females (7.7 +/- 11.4 vs 17.6 +/- 17.3, p < 0.001) and in dialysis and non-dialysis patients (19.6 +/- 16.5 vs 10.7 +/- 14.5, p < 0.05). There was also a difference between dialysed and non-dialysed men (15.1 +/- 16.2 vs 5.9 +/- 9.2, p < 0.05). We found no difference between men with and without nephrotic syndrome and between BMI or age. There was a positive correlation of leptin with diabetic and non-diabetic women. There was positive correlation of P-leptin with serum creatinine in non-dialysed women (r = 0.68, p < 0.001) and a negative correlation with S-albumin in nephrotic men (r = -0.65, p < 0.05).

CONCLUSIONS

Women have higher plasma leptin concentrations than men and dialysis patients have higher concentrations than non-dialysed patients. Apart from the positive correlation with S-creatinine in non-dialysed women. There was positive correlation with S-albumin in nephrotic men there were no correlations with renal function, BMI, age, S-cholesterol, S-triglycerides and S-albumin.

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 influence of chronic moderate ethanol administration on NADPH-diaphorase (nitric oxide synthase) activity in rat brain

Nitric oxide synthase (NOS), the enzyme with reduced nicotinamide-adenine dinucleotide phosphate (NADPH)-diaphorase activity, generates nitric oxide (NO) which is an important bioregulatory molecule in the nervous, immune, and cardiovascular systems. NOS is linked to non-adrenergic non-cholinergic (NANC) neuronal pathways and modulation of the N-methyl-D-aspartate receptors, yet its modification by ethanol has been little explored. A possible modification by chronic ethanol administration of activity and/or localization of NADPH-diaphorase (NO-synthase) in rat brain may thus provide the pathogenic basis of alcohol-induced brain injury. When female Wistar rats were treated chronically with ethanol for 50 days, the NADPH-diaphorase staining of granular neurons and neurons located in the molecular layer of the cerebral cortex was significantly reduced. Chronic ethanol consumption led to a significant reduction in NADPH-diaphorase staining in the superficial layers of the superior colliculus. The number of NADPH-diaphorase-positive neurons was significantly reduced (P < 0.001) in the stratum zonale and stratum griseum superficiale (by 42.3-65.6% of control values). This could alter synaptic processes in the highly organized structures involved in oculomotor and somatic motor coordination and thus contribute to the motor disturbances which are associated with alcohol abuse.

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.

The influence of pefloxacine on experimental adriamycin-induced nephrotic syndrome in rats

Initial reports on antiproteinuric effect of pefloxacine in small groups of patients with minimal-change nephropathy (MCN) and focal and segmental glomerulosclerosis (FSGS) have not been confirmed in other papers. To assess its antiproteinuric effect in experimental animals we administered pefloxacine to rats with adriamycin nephropathy showing morphological changes resembling human minimal-change disease or focal segmental glomerulosclerosis, and clinically with full-blown nephrotic syndrome. Pefloxacine treatment was at least partially effective in preventing further increase of proteinuria in rats with adriamycin nephropathy. The mechanism of this effect remains unclear and deserves further studies concentrating on the glomerular cytokine network and glomerular production of reactive oxygen species.

[Lipid peroxidation and activity of antioxidative enzymes in patients with multiple myeloma]

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.

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--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.

[The role of oxygen radicals in the pathogenesis of glomerulonephritis]

In the pathogenesis of glomerulonephritis, acute renal failure, pyelonephritis and other diseases of the kidneys oxygen radicals are involved. Some types of glomerulonephritis are characterized by infiltration of the glomeruli by neutrophils and monocytes which can form oxygen radicals (superoxide, hydrogen peroxide). The increased amount of cAMP in glomeruli can be due to oxygen radicals. Cyclic nucleotides modulate the inflammatory or immune response in glomerular disease and play a part in the action of local mediators of the inflammation. Oxygen radicals act as second messenger for the activation of cytokines via NF-kappaB transcription factor, they stimulate the formation of TNF-alpha, IL-1, IL-6 and influence the expression of monocyte-specific cytokines (CSF-1 and MCP-1). Radicals formed by the system myeloperoxidase--hydrogen peroxide--halogen derivatives activate proteolytic enzymes (proteinases) which break down collagen and other components of the extracellular matrix present in the basal membrane of glomeruli and in the mesangium. Oxygen radicals and proteinases can cause and amplify glomerular damage. Glucocorticoid administration leads to an increased activity of endogenous antioxidant enzymes in the glomerulus and reduced the of lipid peroxidation.

[The effect of pefloxacin on nephrotic syndrome in experimental adriamycin nephropathy]

BACKGROUND

Antiproteinuric effect of pefloxacine was demonstrated in a small group of patients with minimal change nephropathy (MCN) and focal and segmental glomerulosclerosis (FSGS). This finding was not, however, confirmed by other papers. Adriamycine nephropathy is an experimental model of nephrotic syndrome with morphological changes resembling MCN and/or FSGS in patients.

METHODS AND RESULTS

Nephrotic syndrome was induced in rats by the i.v. administration of adriamycine. One part of nephrotic animals was treated from the beginning of the 4th week by daily intraperitoneal application of pefloxacine. Administration of adriamycine led in experimental animals after 3 weeks to the development of full-blown nephrotic syndrome with further progression of proteinuria in the next 3 weeks (from 1.4 +/- 1.25 to 2.23 +/- 1.89 g of protein/mmol of urinary creatinine, p < 0.05). Proteinuria did not change in nephrotic rats treated by pefloxacine (from 1.04 +/- 0.97 to 1.26 +/- 1.11 g of protein/mmol of urinary creatinine, p = n.s.). The difference in proteinuria between both groups was also significant (0.83 +/- 0.73 vs. 0.23 +/- 0.67 g of protein/mmol of urinary creatinine, p < 0.05).

CONCLUSIONS

Pefloxacine was antiproteinuric in experimental adriamycine nephropathy. The mechanism of this effect remains unclear and deserves further studies concentrating on glomerular cytokine network and glomerular production of reactive oxygen species.

[Free radicals in the pathogenesis of selected diseases]

Free radicals are chemical substances which contain one or more unpaired electrons, which is the cause of their high reactivity with a series of biologically important substances such as fatty acids, DNA, RNA, amino acids. The source of radicals are immunological reactions and reactions in the endoplasmatic reticulum during detoxication of xenobiotics. Free radicals can act on the organism by a number of reactions, the most frequent on being lipid peroxidation when important toxic products are formed such as 4-hydroxy 2,3 trans-nonenal (4-HNE) and malondialdehyde. Direct assessment of free radicals due to their short life span is difficult in clinical practice. The majority of measurements is based on the assessment of substances which are formed by the reaction of free radicals in the organism. The most frequent method is assessment by means of thiobarbituric acid. Oxidative stress (the reaction produced by the action of free radicals) of tissues and cells is caused by the increased formation of free radicals and/or reduced capacity of antioxidant systems. Free radicals are involved in the process of ageing, cancerogenesis, inflammatory and degenerative diseases, atherogenesis, and play a part in the ischaemic and toxic damage of the organism. During evolution antioxidant defence mechanisms developed which under physiological conditions are sufficient to inactivate free radicals. Antioxidant systems can be divided into two groups--antioxidant enzymes (superoxide dismutase, glutathione peroxidase, catalase etc) and antioxidant substrates (tocopherols, carotenoids, ascorbic acid, glutathione, transferrin, ceruloplasmin etc).

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.

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.

The influence of chronic ethanol administration on adriamycin-induced nephrotic syndrome in rats

Alcoholic liver disease may be frequently complicated by mesangial proliferation with the deposition of IgA in glomeruli and glomerulosclerosis, but these glomerular lesions are usually mild and without greater impact on renal function. To evaluate the putative role of ethanol in glomerular pathology we studied the influence of chronic ethanol administration on the development of experimental adriamycin nephropathy in rats. Nephrotic syndrome was induced by a single i.v. dose of adriamycin (5 mg/kg body wt) both in rats given ethanol at a dose of 4 g/day for 3 months and control rats given standard chow. Further controls on both diets without adriamycin administration were also studied. Blood and urine were examined before and 3 and 6 weeks after adriamycin administration. All rats were killed and examined histologically 6 weeks after adriamycin administration. Ethanol fed nephrotic rats were more catabolic than control nephrotic rats (with higher free fatty acids, lower glycaemia, higher urea with similar creatinine) and had lower proteinuria (0.55 +/- 0.34 versus 5.79 +/- 3.15 g of protein/nmol of creatinine, P < 0.05), higher albuminaemia (5.41 +/- 2.62 versus 1.92 +/- 1.94 g/l, P < 0.01), lower plasma cholesterol (6.54 +/- 2.6 versus 10.57 +/- 2.92 mmol/l, P < 0.01) and triglycerides. The development of nephrotic syndrome and renal morphological changes after adriamycin administration in rats seemed to be ameliorated, or at least delayed by chronic ethanol feeding with much milder and focal glomerulosclerosis as compared with more severe and diffuse glomerulosclerosis in control nephrotic animals. The mechanism of this effect of chronic ethanol feeding remains to be elucidated.(ABSTRACT TRUNCATED AT 250 WORDS)

[The effect of chronic administration of ethanol on experimental adriamycin nephropathy]

BACKGROUND

Alcoholic liver disease may be in humans frequently complicated by mesangial proliferation and sclerosis. The influence of chronic ethanol administration on experimental nephrotic syndrome has not been, however, studied yet.

METHODS AND RESULTS

Experimental nephrotic syndrome was induced in rats by the i.v. administration of adriamycin in ethanol fed rats and in rats given common laboratory chow. Chronic administration of ethanol was in nephrotic rats accompanied by the exaggerated lipolysis (free fatty acids were in control nephrotic rats lower than in nephrotic ethylic rats 6 weeks after adriamycin administration: 914.8 + 96.8 mumol/l vs. 1186.3 + 178.7 mumol/l, p < 0.01) and increased proteocatabolism; the development of nephrotic syndrome was ameliorated, or at least delayed, however, in ethylic rats (control nephrotic rats had higher proteinuria than nephrotic ethylic rats 3 weeks after adriamycin administration: 5.79 + 3.15 vs. 0.55 + 0.34 g protein/mmol creatinine, p < 0.01). In autopsy, diffuse global glomerulosclerosis was found in control nephrotic rats with only mild focal and segmental changes in nephrotic ethylic rats.

CONCLUSIONS

Chronic ethanol administration ameliorated and/or delays the development of nephrotic syndrome in adriamycin nephropathy in rats. Mechanism of this effect of chronic ethanol feeding remains to be elucidated. Metabolic, immunosuppressive and renal haemodynamic effects of ethanol should be taken into consideration.