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

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.

Impaired neutrophil functions in the pathogenesis of an outbreak of recurrent furunculosis caused by methicillin-resistant Staphylococcus aureus among mentally retarded adults

Staphylococcus aureus is an important cause of skin infections. We recently described an outbreak of recurrent furunculosis involving methicillin-resistant S. aureus among mentally retarded adults. We sought to determine the role of impaired neutrophil functions in its pathogenesis. Blood neutrophil functions were determined during both the outbreak (1997) and a disease-free period (2000). Chemotaxis was measured by migration toward formyl-methionyl-leucyl-phenylalanine (FMLP), specifically and randomly; phagocytosis of opsonized zymosan (OZ) was assessed by microscopy; superoxide production was determined by cytochrome c reduction in unstimulated neutrophils and after stimulation with 50 ng/ml phorbol myristate acetate, 1 mg/ml OZ or 5 x 10(-7)M FMLP. Functions were compared between recurrent furunculosis (n=10) and non-recurrent furunculosis patients (n=13). During 2000, functions were normal among the 23 subjects, except for specific/nonspecific chemotaxis (mean 68%+/-26 and 69%+/-28). During infection, recurrent furunculosis patients had a significantly increased basal superoxide production as compared to disease-free period (10.5+/-4.7 vs. 4.9+/-1.9 nmol O(-)(2)/10(6) cells/min, p=0.003). During the disease-free period, recurrent furunculosis patients had lower basal superoxide production (4.9+/-1.9 vs. 7.7+/-3.5, p=0.067) and impaired specific chemotaxis (57%+/-28 vs. 76%+/-21, p<0.05) as compared to non-recurrent furunculosis patients. Only specific chemotaxis was an independent risk factor for recurrent furunculosis. Mentally retarded adults have impaired chemotaxis, with recurrent furunculosis cases having an even greater impairment. Abnormal specific chemotaxis is an independent risk factor for recurrent furunculosis. Impaired neutrophil functions thus have a role in the pathogenesis of outbreaks of recurrent furunculosis.

Complementary and alternative therapies for Down syndrome

In their role as committed advocates, parents of children with Down syndrome have always sought alternative therapies, mainly to enhance cognitive function but also to improve their appearance. Nutritional supplements have been the most frequent type of complementary and alternative therapy used. Cell therapy, plastic surgery, hormonal therapy, and a host of other therapies such as massage therapy have been used. There is a lack of well-designed scientific studies on the use of alternative therapies in individuals with Down syndrome. Antioxidants hold theoretical promise for treatment of the cognitive, immune, malignancy, and premature aging problems associated with Down syndrome. Medications for treatment of Alzheimer's disease may also result in benefit for the population of individuals with Down syndrome.

Evaluation of Surgical and Non-Surgical Periodontal Therapies, and Immunological Status, of Young Down's Syndrome Patients

BACKGROUND

Individuals with Down's syndrome (DS) differ in their oral condition compared with the healthy population. Periodontal disease in persons with DS under the age of 30 years is very high. Immune deficiencies are also present. For dental practitioners it is difficult to decide on a particular course of treatment. In this study, patients with DS were selected in order to 1) evaluate the effectiveness of surgical and non-surgical periodontal therapies and 2) assess their immunological status.

METHODS

The population consisted of 14 DS patients (14 to 30 years old). Surgical and non-surgical periodontal therapies were compared in a split-mouth design. Clinical measurements of plaque index (PI), gingival index (GI), probing depth (PD), and clinical attachment levels (CAL) were taken at baseline, posttreatment, 6 months, and 1 year. Immunomodulatory activity of neutrophils was analyzed in vitro by chemotaxis (Boyden migration chamber), phagocytic activity, and production of super-oxide anion (NBT reduction) tests and compared between DS patients and healthy controls.

RESULTS

Both surgical and non-surgical therapies showed a significant improvement in all the clinical parameters compared to baseline. There were no differences between surgical and nonsurgical therapy in PI or GI. There was a significant PD reduction with the non-surgical therapy at 1 to 3 mm PD. However in PD >3 mm the surgical therapy, although not statistically significant, showed better results. Neutrophil chemotaxis, phagocytic activity, and production of super-oxide anion were significantly decreased in the DS patients.

CONCLUSIONS

After a year, both surgical and non-surgical therapies have similar periodontal clinical improvement in DS patients. There is partial impairment of immunological functions in DS individuals which does not seem to affect the clinical response to therapy.

Derangement of non-specific immunity in Down syndrome subjects: low leukocyte chemiluminescence activity after phagocytic activation

Metabolic activation of peripheral blood leukocytes (chemiluminescence) from 27 children with Down syndrome (DS) and 23 age and sex-matched control children after phagocytic stimulation by opsonized zymosan particles was investigated through a chemiluminescence assay. Using autologous plasma or serum as opsonizing media, phagocytic activity of circulating leukocytes was significantly decreased in DS subjects. A further decrease of phagocytic activity was found in neutrophils from DS children, when normal heterologous plasma or sera were used. On the other hand, sera or plasma from DS subjects significantly increased phagocytic activation of leukocytes from normal donors. In DS subjects opsonizing agents such as serum immunoglobulins and complement fractions were in the normal ranges of concentration. Thus, the impaired chemiluminescence of neutrophils was mainly due to a metabolic impairment at the cellular level. A decreased production of radicals derived from the oxygen metabolism in neutrophils may be an important step of immune derangement leading to the increased incidence of infectious diseases frequently associated with DS.

Immunology of Down syndrome: a review

Subjects with Down syndrome (DS) have a high mortality due to infections and a high risk of developing malignancies. These observations, together with the demonstration of a frequent occurrence of HBsAg carrier state and of autoantibodies, have prompted investigations of the immune function in DS. Thymic morphological and functional abnormalities have been demonstrated. Peripheral blood mononuclear cells of DS subjects have been shown to include a high number of T lymphocytes with low avidity for sheep erythrocytes and a very high percentage of cells with an NK phenotype. However, NK activity is low in DS. Production of some important cytokines, such as IL-2, is depressed, thus contributing to T-cell derangement. Abnormalities of the B-cell compartment were also demonstrated, with a tendency towards high IgG and low IgM serum levels. Controversial results have been obtained with regard to antigen-specific antibody response. Also phagocytes of DS subjects display some characteristic functional impairments, with low chemotactic ability and reduced production of oxygen radicals. Despite the clearly established and rather detailed evidence of immune derangements, therapeutic trials have been anecdotal and resulted in marginal effects. HBV vaccination is highly advisable in DS because of the high risk of becoming chronic HBV carriers once infected.

Enhanced levels of prostaglandin E2, leukotriene B4, and matrix metalloproteinase-9 in gingival crevicular fluid from patients with Down syndrome

The aim was to study the levels of prostaglandin E2 (PGE2), leukotriene B4 (LTB4), and matrix metalloproteinase-9 (MMP-9) in gingival crevicular fluid (GCF) from Down syndrome patients exhibiting gingival inflammation. The levels of PGE2, LTB4, and MMP-9 were determined in GCF from 18 Down syndrome patients and from 14 controls matched with respect to age and degree of gingival inflammation. Probing depth (PD) and gingival inflammation, assessed by bleeding on probing (BOP), were determined around all teeth. In each patient, GCF was collected from 6 sites (16m, 26m, 36m, 46m, 41m, 11d) using periopaper, and the volume was determined using Peritron 8000. The PGE2 and LTB4 levels were determined using RIA kits and MMP-9 level using ELISA kits. The degree of gingival inflammation, expressed as mean value of BOP (%) as well as the volume of GCF, was similar between Down syndrome patients and controls. The mean levels of PGE2, LTB4, and MMP-9 were significantly (P<0.05) higher in GCF from Down syndrome patients compared to controls. When comparing the two groups, the correlation coefficients for LTB4 to BOP and PD, respectively, as well as for MMP-9 to BOP significantly differed between Down syndrome and controls (P<0.05). The study supports the concept of an altered host response in periodontal tissue in Down syndrome subjects.

Partial impairment of immune functions in peripheral blood leukocytes from aged men with Down's syndrome

Down's syndrome (DS) has been considered a model of accelerated aging and of Alzheimer's disease. We investigated immunologic functions using peripheral blood leukocytes in order to correlate the production of cytokines and development of neuropathological changes of Alzheimer type in aged persons with DS. Cytokine production (IL-1beta, IL-2, IL-6, IL-8, and TNF-alpha), phytohemagglutinin (PHA)-stimulated proliferation of nonadherent monocytes, and superoxide anion production from polymorphonuclear leukocytes were measured. PHA-stimulated proliferation in aged individuals (>30 years old) with DS was significantly lower than that of age- and sex-matched controls (DS vs control, 55,707+/-5810 vs 88,310+/-6994 cpm, P < 0.001). PHA-stimulated IL-2 production was also significantly decreased in aged individuals with DS (DS vs control, 7.1+/-2.1 vs 10.7+/-1.3 ng/ml). Interestingly, the decrease of proliferation and IL-2 production in aged males with DS is significantly greater than in aged women with DS. PHA-stimulated proliferation and IL-2 production of nonadherent monocytes in females was not significantly reduced. IL-1beta production by LPS-activated adherent monocytes was significantly decreased in older adults with DS compared with non-DS controls. Other immune parameters measured in DS were not significantly different from that of age-matched controls. We conclude that there is partial impairment of T lymphocytes in aged persons with DS that is significantly greater in males than in females.

Oral carriage of Candida species in children and adolescents with Down's syndrome

Oral carriage of Candida albicans was studied in 55 children and adolescents with Down's syndrome (DS), aged between 7 months and 20 years 6 months, and compared with an age- and sex-matched control group of subjects. Twenty-two of the DS subjects were diagnosed as having congenital cardiovascular malformations. Compared to controls, the DS subjects were more prone to infections. The number of subjects colonized with C. albicans in the oral cavity was significantly higher in the DS group (69%) than in the control group (35%). Colonization with C. albicans and simultaneous erythematous or white pseudomembranous lesions of the oral mucosa were diagnosed in 22 (40%) of the DS groups and in only one of the control group. In both the DS and the healthy control subjects the frequency of colonization with C. albicans was positively correlated to age. The DS subjects were significantly more densely colonized by C. albicans than the controls. Abnormalities of the immune response in DS children may contribute to the increased oral carriage of C. albicans.

Nonspecific immunity in Down syndrome: a study of chemotaxis, phagocytosis, oxidative metabolism, and cell surface marker expression of polymorphonuclear cells

We have investigated several aspects of nonspecific immunity in Down syndrome (DS), utilizing peripheral polymorphonuclear leukocytes (PMNL), obtained from 12 children aged 8-16, diagnosed as trisomy 21, and their healthy matched controls. We used the under agarose method for chemotaxis assays, and flow cytometry for the determination of phagocytosis of monodispersed fluorescent beads, metabolic burst activity, and neutrophil surface marker expression on these cells. Our results indicate that a chemotactic defect exists in PMNL of DS children. However, no statistically significant differences were found between PMNL from DS children and those from controls in phagocytosis, oxidative burst, and expression of the markers CD11a, CD11b, CD16, and CD 18. Furthermore, no overexpression of CD11a and CD18 was present as a consequence of gene overdosage in PMNL from DS children. On the other hand, 3 different neutrophil subpopulations could be observed according to the CD16 staining pattern in DS children and controls; this might be a consequence of genetic variation or may represent different states of activation of these cells. Other factors such as T-cell involvement, and the role of cytokines, cyclic nucleotides, and zinc serum levels in DS patients should be further investigated in order to define the causes of the immunological derangement present in this condition.

Abnormal serum IgG subclass pattern in children with Down's syndrome

Susceptibility to infections is a well known feature of Down's syndrome. The possible relation between this predisposition and the serum concentrations of the IgG subclasses was studied in 38 children with Down's syndrome aged 1-12 years. An age matched group of 50 healthy children served as controls. The serum concentrations of IgG1 and IgG3 were significantly raised among children with Down's syndrome in all three age groups studied (that is 1-2.5, 4-8, and 9-12 years). The serum concentrations of IgG2 were normal in the first two groups but significantly reduced in the third age group. In contrast, the concentrations of IgG4 among children with Down's syndrome were significantly reduced in all three age groups. Moreover, among the children with Down's syndrome aged 4-12 years 68% (15/22) had IgG4 concentrations below 2 SDs of the geometrical mean of the controls. The results may partially explain the proneness of children with Down's syndrome to infections with encapsulated bacteria. Although the underlying cause of these abnormalities is unknown, IgG subclass determination seems relevant in the clinical evaluation of children with Down's syndrome.

Immunodeficiency and plasma zinc levels in children with Down's syndrome: a long-term follow-up of oral zinc supplementation

To evaluate the possible effect of zinc treatment on immune disorders in children with Down's syndrome (DS), 38 noninstitutionalized DS children were investigated. Twenty-four patients (63.2%) had plasmatic zinc levels lower than 0.70 microgram/dl ("hypozinkemic," LZn) and 14 patients (36.8%) had levels higher than 0.75 microgram/dl ("normozinkemic," NZn). No correlation was found between the zinc deficiency and recurrence and/or intensity of infections. The absolute numbers of peripheral lymphocytes, the percentages of B lymphocytes, total T cells, and serum IgG, IgA, and IgM levels did not differ between the DS children and the controls. Eight (21%) patients had CD4+ T cell counts below the lowest value for the controls. Seventeen (44%) DS patients had increased levels of CD8+ T cells. The mean percentage of Leu 7+ cells in DS subjects (22.8 +/- 12.9%) was significantly higher than that in controls (15.8 +/- 4.8%) (P less than 0.01). Notably, Ig levels and numbers of lymphocytes in each subset did not show any significant difference in NZn and LZn trisomic subjects. On the contrary the peripheral blood mononuclear cells (PBMCs) from LZn DS children showed a significantly lower proliferative response to phytohemagglutinin (PHA) (S.I. = 23.4 +/- 22.4) than that of PBMCs from NZn DS children (S.I. = 46.1 +/- 21.5, P less than 0.01). A significant increase in DNA synthesis was obtained after oral administration of zinc sulfate (20 mg/kg/day, for 2 months). The lymphocyte response to PHA appeared to be normal in all patients up to 6 months after the end of the zinc treatment and it became low in half of the patients 22 months after therapy.

Enhanced production of superoxide anion by microglia from trisomy 16 mice

Disruption of normal oxygen radical metabolism in the CNS may contribute to the neuropathological changes associated with Down syndrome (trisomy 21) and its mouse counterpart, the trisomy 16 (Ts16) mouse. One potent source of oxyradicals is the CNS-specific macrophage, the microglial cell. We prepared primary glial cultures from the cerebral cortices of Ts16 and normal littermate mice taken at day 15 of gestation. Microglia were isolated from confluent cultures after 14 days in vitro and assayed for superoxide anion production using a cytochrome C reduction assay. Stimulation by either opsonized zymosan (OPZ) or phorbol myristate acetate (PMA), produced significantly higher levels (2.8-20 fold) of superoxide per mg protein in Ts16 microglial cultures. Resting, i.e. unstimulated secretion, was not significantly different from littermate controls. Astrocyte enriched cultures, stimulated by OPZ, exhibited low levels of superoxide production which was higher in Ts16 mice than normal littermates. Microglial enriched cultures from rat neonatal cerebral cortices were exposed for 24 h to medium from the Ts16 glial cultures. Superoxide production in the Ts16 media treated rat microglia was significantly higher than in those treated with littermate conditioned media.

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.

Increased glutathione peroxidase activity in erythrocytes in patients with Alzheimer's disease/senile dementia of Alzheimer's type

Glutathione peroxidase (GSH-Px) activity in erythrocytes was studied in 9 patients with Alzheimer's disease/senile dementia of Alzheimer's type (AD/SDAT) of ages 34-64 years and compared with that in 16 healthy controls of ages 21-66 years. The median GSH-Px activity in erythrocytes from AD/SDAT patients was 408, mu kat/1 (range 338-500 mu kat/1) and that from healthy controls 348, mu kat/1 (range 258-439 mu kat). This difference was significant (p less than 0.005) Wilcoxon rank test. Since there are great clinical and pathological similarities between AD/SDAT and the dementia of Down's syndrome (DS) patients and since both these groups of patients have increased activity of the selenium-dependent enzyme GSH-Px, it is suggested that there could be a similar metabolic background of the dementia. Many findings in the oxidative metabolism of DS suggest increased oxidative damage with an elevation of the turnover of superoxides to peroxides within cells and with a secondary biochemical modification such as increase in tissual GSH-Px activity. A similar mechanism with elevated peroxidation within cells might be responsible for the present finding of increased GSH-Px activity in erythrocytes and for the development of dementia in AD/SDAT.

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.