Erythrocyte superoxide dismutase and redox enzymes in trisomy 21

Pre- and post-natal melatonin administration partially regulates brain oxidative stress but does not improve cognitive or histological alterations in the Ts65Dn mouse model of Down syndrome

Melatonin administered during adulthood induces beneficial effects on cognition and neuroprotection in the Ts65Dn (TS) mouse model of Down syndrome. Here, we investigated the effects of pre- and post-natal melatonin treatment on behavioral and cognitive abnormalities and on several neuromorphological alterations (hypocellularity, neurogenesis impairment and increased oxidative stress) that appear during the early developmental stages in TS mice. Pregnant TS females were orally treated with melatonin or vehicle from the time of conception until the weaning of the offspring, and the pups continued to receive the treatment from weaning until the age of 5 months. Melatonin administered during the pre- and post-natal periods did not improve the cognitive impairment of TS mice as measured by the Morris Water maze or fear conditioning tests. Histological alterations, such as decreased proliferation (Ki67+ cells) and hippocampal hypocellularity (DAPI+ cells), which are typical in TS mice, were not prevented by melatonin. However, melatonin partially regulated brain oxidative stress by modulating the activity of the primary antioxidant enzymes (superoxide dismutase in the cortex and catalase in the cortex and hippocampus) and slightly decreasing the levels of lipid peroxidation in the hippocampus of TS mice. These results show the inability of melatonin to prevent cognitive impairment in TS mice when it is administered at pre- and post-natal stages. Additionally, our findings suggest that to induce pro-cognitive effects in TS mice during the early stages of development, in addition to attenuating oxidative stress, therapies should aim to improve other altered processes, such as hippocampal neurogenesis and/or hypocellularity.

Oral Candidal and Streptococcal carriage in Down syndrome patients

AIM

We aimed to evaluate the prevalence of Candida and Streptococci species in the oral cavity of Down syndrome patients.

MATERIALS AND METHODS

50 children/adolescents with Down syndrome with a karyotype of 47 XX, 21+ (female) and 47 XY, 21+ (male), and 50 normal children/adolescents were included in our study. Oral swab/saliva was used to culture and identify Candida and Streptococci species based on gram and periodic acid schiff staining.

RESULTS

Of the 50 study group samples, which were cultured, 37 (74%) showed growth of Candida colonies, whereas in the 50 control samples only 18 (36%) were positive for Candida growth. In 4 Sabouraud's dextrose agar culture slopes of the study group, more than one morphological type of colonies were observed. 23 out of 50 samples in our study group had Streptococcus viridans colonies. In the 23 samples positive for Streptococci 16 had many streptococcal colonies, and 7 had few streptococcal colonies in the primary culture. 32 out of 50 samples from the control group had S. viridans colonies. In these 32 samples positive for Streptococci, 29 had predominantly streptococcal colonies while 3 had few streptococcal colonies in the primary culture.

CONCLUSION

The oral cavity is an environment heavily colonized by microorganisms, however, the Down syndrome patients run a greater risk of having opportunistic infections especially from Candida species. Hence to improve the quality of life of an individual with Down syndrome, it is necessary to diagnose and treat these infections by more frequent oral microbial assessment.

Down's syndrome: increased enzymatic antioxidative defense is accompanied by decreased superoxide anion generation in blood

Whole blood leukocytes of DS patients were found to produce less superoxide radical anion than in healthy controls, especially without stimulation with zymosan. This decreased superoxide generation may contribute to the immune system deficiency reported for DS.

Oxidative stress in phagocytes--"the enemy within"

Phagocytes represent a powerful defense system against invading microorganisms that threaten the life or functional integrity of the host. The capacity to generate and release substantial amounts of reactive oxygen species is a unique property of activated polymorphonuclear and mononuclear phagocytes. The crucial role of these molecules in killing microorganisms and their consecutive contribution to tissue damage during injury and inflammation is widely known. Although much research has been done to explore the molecular events involved in the interaction of oxygen intermediates with microbes or host tissue, surprisingly little attention has been paid to the effect of reactive metabolites on the phagocyte itself. This fact is especially surprising, since it is apparent that the activated phagocyte is directly exposed to its own toxic metabolites. The potential damage occurring during excessive radical formation might notably alter the vital functions of these primarily immunocompetent cells. Moreover, the critical role of oxygen radicals in apoptosis of leukocytes has been recently revealed. Apoptosis is now supposed to represent a key mechanism in neutrophil deactivation and resolution of inflammation. Therefore, this review will focus on the delicate balance between released oxidants and antioxidative protection within the phagocytes themselves. General and phagocyte-specific antioxidative mechanisms, which have co-evolved with the radical generating machinery of phagocytes, are discussed, since the outcome of local inflammation can directly depend on this antioxidative capacity and might range from adequate elimination of the pathogen with minimal acute tissue damage to progression towards a systemic inflammatory response syndrome.

Antioxidant enzymes and fatty acid status in erythrocytes of Down syndrome patients

The excess of genetic information in patients with Down syndrome (DS) produces an increase in the catalytic activity of superoxide dismutase (SOD1), an antioxidant enzyme coded on chromosome 21. It has been suggested that an increase in oxidative stress in DS patients may cause adverse effects in the cell membranes through the oxidation of polyunsaturated fatty acids (PUFAs). The aim of this study was to evaluate the cellular antioxidant system by determining the catalytic activity of the SOD1, glutathione peroxidase (GPx), catalase (CAT), and glutathione reductase (GR) enzymes and the concentrations of α-tocopherol in red blood cells (RBCs) in a group of 72 DS patients. The profile of fatty acids in the phospholipids of RBC membranes was also evaluated. The activity of the erythrocyte antioxidant enzymes is significantly higher in the DS group than in the control group (SOD1, 635 ± 70 U/g Hb vs 476 ± 67 U/g Hb; CAT, 1843 ± 250 U/g Hb vs 1482 ± 250 U/g Hb; GPx, 23.2 ± 5.3 U/g Hb vs 21.5 ± 3.6 U/g Hb; and GR, 9.32 ± 1.4 U/g Hb vs 6.9 ± 1.3 U/g Hb, respectively). No differences were observed in RBC α-tocopherol concentrations between the two groups studied. Long-chain n6 PUFA (C20:3n6, C20:4n6) concentrations were increased in DS patients, suggesting enhanced Δ-6-desaturase activity. The long-chain n3 PUFA (docosahexenoic acid) does not appear to be affected by increased oxidative stress, probably because of the existence of compensatory antioxidant mechanisms.

Erythrocyte-mediated scavenging of reactive oxygen metabolites generated by human polymorphonuclear leukocytes during phagocytosis: comparison between normal and Down's syndrome blood cells

The phagocytosis of complement-opsonized yeast particles by polymorphonuclear leukocytes from normal and Down's syndrome subjects was compared in the absence and presence of erythrocytes. Granulocytes from children with Down's syndrome showed a large increase of metabolic activity, as measured with chemiluminescence. This was not associated with autooxidative damage in the presence of erythrocytes. The results indicate that erythrocytes could exert an antioxidant effect on the granulocyte cell surface. This was reflected in an enhanced ingestion, which was more pronounced in the presence of Down erythrocytes with a higher superoxide dismutase and glutathione peroxidase content, than normal cells. Our conclusion is that the increase of reactive oxygen metabolites scavengers in Down's syndrome blood cells is of benefit for the homeostasis between generated reactive oxygen metabolites and their propagation.

Catalase and glutathione peroxidase activity in cells with trisomy 21

CuZnSOD is produced in overdose in cells with trisomy 21. This has been considered to be a cause of increased oxidative stress. In the present work we have studied the catalase and glutathione peroxidase activity in fibroblasts from 6, and blood cells from 30, subjects affected by Down syndrome. In the fibroblasts, catalase and glutathione peroxidase activities did not differ significantly from control cells. In platelets, lymphocytes, polymorphs and erythrocytes, no significant increase of catalase activity was found while glutathione peroxidase activity appeared significantly increased in platelets, polymorphs and erythrocytes but not in lymphocytes. These data seem to indicate that the increase of CuZnSOD in trisomy 21 cells does not affect the production of catalase. An increase, instead, of glutathione peroxidase has been detected in all blood cells, except in lymphocytes; this is a sign of a greater need for protection against the risk of lipoperoxidation. The fact that the enhancement of glutathione peroxidase activity could be assessed only in some types of cells examined suggests that the observed increase in those cells is probably a result of an additive effect of the overproduction of CuZnSOD due to gene dosage and the ordinarily higher content of oxygen radicals and peroxides.

Selenium: clinical significance and analytical concepts

Selenium is an essential trace element in humans and animals. Its only established function in humans is the antioxidant activity of glutathione peroxidase, a selenoenzyme. Severe prolonged deficiency may cause a fatal cardiomyopathy. Iatrogenic causes of selenium deficiency include parenteral and enteral nutrition. Low plasma selenium is also found in malabsorption, cystic fibrosis, rheumatoid arthritis, neoplasia, and other varied clinical disorders. Death has resulted from a single massive ingestion of selenium, while chronic excessive intake causes skin, nail, and hair pathology. Extreme geographical variation in population blood and urine selenium levels and a marked age-specific variation in population reference intervals are important factors in understanding selenium nutrition. Nutritional requirements, biological availability, and metabolism are discussed in relation to geographical, age, and method variability. Sampling, processing procedures, and methods for selenium quantitation are reviewed. Selenium content in different biological matrices and reference values for pediatric, adult, and obstetric populations are provided.

Aspects of the structure, function, and applications of superoxide dismutase

The current status of superoxide dismutase (SOD) is that it is an enzyme with diverse ramifications. This review attempts an understanding of SOD as a structural, functional, and biological entity. Accordingly, the review is in three parts. The first part discusses SOD in terms of protein structure, proceeding from primary to secondary and three-dimensional structure for the three forms of SOD: copper/zinc SOD, manganese SOD, and iron SOD. This is the order of structural knowledge of the enzyme. Iron SOD is an enzyme of prokaryotes and some higher plants. Manganese SOD is an enzyme of prokaryotes and eukaryotes. Copper/zinc SOD is an enzyme of eukaryotes and certain prokaryotes. The evolutionary relationships of the three forms of SOD, the status of the copper/zinc SOD gene in prokaryotes, and the cloning and sequencing of SOD genes are discussed. The second part of the review deals with the catalytic mechanism of SOD in the three forms of the enzyme. Structural and mechanistic conclusions from various spectroscopic studies are critically considered. A detailed picture is given of the active site of copper/zinc SOD. The third part is a review of SOD in the general context of oxygen toxicity. After consideration of the question of superoxide toxicity and superoxide pathology, several areas in which SOD has been investigated or used as a tool in a biochemical, pharmacological, or clinical context are discussed, including population genetics; trisomy 21; development and senescence; the nutritional copper, zinc, and manganese status; hemolysis and anemia; oxygen toxicity in the lung and nervous system; inflammation, autoimmune disease and chromosome breakage, ischemia and degenerative changes; radiation damage; and malignancy. A comprehensive picture is given of measurements of SOD activity in disease states, and the question of superoxide-related disease is considered at several points.

Two-dimensional gel analysis of proteins from human trisomy 21 fetal liver tissue after DEAE-Sepharose chromatography

Isoelectrofocusing two-dimensional polyacrylamide gel electrophoresis (IEF-2D-PAGE) offers the opportunity to detect typical alterations in the protein pattern from directly prepared liver tissue of fetuses with trisomy 21 and normal controls. The fractionation of the cell lysate by differential centrifugation into various subcellular components (nuclei, membranes, polyribosomes, cytoplasmic proteins) and fractionation of the proteins through DEAE-Sepharose chromatography allows detection of protein differences. In the 19th week of pregnancy it is possible to establish only three differences in the protein patterns between liver tissue from trisomy 21-fetuses and normal controls. All three proteins are synthesized in euploid controls at a higher level than in trisomy 21-liver tissue and are supposed to be consequences of primary gene dosage effects. The molecular mass of the individual proteins ranges from 14 kdaltons to 31 kdaltons. The data reported here raise the question whether some of the differences found by others represent different gene expression of cells under tissue culture conditions and/or of cells derived from different tissues, or developmental stages.

Is the mental deterioration in Down's syndrome linked to impaired terminal degradation of neurofilaments?

Early detection of foetuses carrying the chromosomal anomaly typical of Down's syndrome provides an efficient means to solve both the social and medical problems inherent in this common form of mental deficiency likely to occur in offsprings to aged mothers. The routine use of this screening procedure, however, is limited to the Western culture. We hope that the present hypothesis suggesting an important role of neurofilament dysfunction in Down's syndrome will stimulate therapeutic approaches aimed at preventing the expression of mental stigmata in children unhappily born with this chromosomal anomaly.

Low superoxide levels in blood phagocytic cells in Down's syndrome

Superoxide anion was measured in polymorphonuclear neutrophils (PMNs) from 10 patients with Down's syndrome (DS) and 10 healthy controls after stimulation with phorobol-myristate-acetate (PMA). The superoxide (O2-) levels were lower in PMNs from nine of 10 DS patients, than in simultaneously tested control cells (p less than 0.01). The findings may in part explain the increased susceptibility of DS patients to infections with certain microorganisms, e.g. S. aureus and C. albicans.

Immunoreactive copper-zinc superoxide-dismutase (SOD-1) in mosaic trisomy 21 and normal subjects

Copper-zinc superoxide-dismutase (SOD-1) (E.C. 1.15.11) levels were measured in 9 children with mosaic trisomy 21 as identified by R, H, G-banding technics. Radioimmunoassay of erythrocytes and fibroblasts did not demonstrate any significant correlation between levels of SOD-1 and percentage of trisomic 21 cells in the two target cell populations studied.