Showing papers by "Lothar Rink published in 2010"

The Essential Toxin: Impact of Zinc on Human Health

Abstract: Compared to several other metal ions with similar chemical properties, zinc is relatively harmless. Only exposure to high doses has toxic effects, making acute zinc intoxication a rare event. In addition to acute intoxication, long-term, high-dose zinc supplementation interferes with the uptake of copper. Hence, many of its toxic effects are in fact due to copper deficiency. While systemic homeostasis and efficient regulatory mechanisms on the cellular level generally prevent the uptake of cytotoxic doses of exogenous zinc, endogenous zinc plays a significant role in cytotoxic events in single cells. Here, zinc influences apoptosis by acting on several molecular regulators of programmed cell death, including caspases and proteins from the Bcl and Bax families. One organ where zinc is prominently involved in cell death is the brain, and cytotoxicity in consequence of ischemia or trauma involves the accumulation of free zinc. Rather than being a toxic metal ion, zinc is an essential trace element. Whereas intoxication by excessive exposure is rare, zinc deficiency is widespread and has a detrimental impact on growth, neuronal development, and immunity, and in severe cases its consequences are lethal. Zinc deficiency caused by malnutrition and foods with low bioavailability, aging, certain diseases, or deregulated homeostasis is a far more common risk to human health than intoxication.

Zinc signals promote IL‐2‐dependent proliferation of T cells

Abstract: Zinc signals, i.e. a change of the intracellular concentration of free zinc ions in response to receptor stimulation, are involved in signal transduction in several immune cells. Here, the role of zinc signals in T-cell activation by IL-2 was investigated in the murine cytotoxic T-cell line CTLL-2 and in primary human T cells. Measurements with the fluorescent dyes FluoZin-3 and Zinquin showed that zinc is released from lysosomes into the cytosol in response to stimulation of the IL-2-receptor. Activation of the ERK-pathway was blocked by chelation of free zinc with N,N,N′,N′-tetrakis-2(pyridyl-methyl)ethylenediamine, whereas zinc was not required for STAT5 phosphorylation. In addition, the key signaling molecules MEK and ERK were activated in response to elevated free intracellular zinc, induced by incubation with zinc and the ionophore pyrithione. Downstream of ERK activation, ERK-specific gene expression of c-fos and IL-2-induced proliferation was found to depend on zinc. Further experiments indicated that inhibition of MEK and ERK-dephosphorylating protein phosphatases is the molecular mechanism for the influence of zinc on this pathway. In conclusion, an increase of cytoplasmic free zinc is required for IL-2-induced ERK signaling and proliferation of T cells.

Immunosenescence of polymorphonuclear neutrophils.

Abstract: All immune cells are affected by aging, contributing to the high susceptibility to infections and increased mortality observed in the elderly. The effect of aging on cells of the adaptive immune system is well documented. In contrast, knowledge concerning age-related defects of polymorphonuclear neutrophils (PMN) is limited. During the past decade, it has become evident that in addition to their traditional role as phagocytes, neutrophils are able to secrete a wide array of immunomodulating molecules. Their importance is underlined by the finding that genetic defects that lead to neutropenia increase susceptibility to infections. Whereas there is consistence about the constant circulating number of PMN throughout aging, the abilities of tissue infiltration, phagocytosis, and oxidative burst of PMN from aged donors are discussed controversially. Furthermore, there are numerous discrepancies between in vivo and in vitro results, as well as between results for murine and human PMN. Most of the reported functional changes can be explained by defective signaling pathways, but further research is required to get a detailed insight into the underlying molecular mechanisms. This could form the basis for drug development in order to prevent or treat age-related diseases, and thus to unburden the public health systems.

Cellular zinc homeostasis is a regulator in monocyte differentiation of HL-60 cells by 1α,25-dihydroxyvitamin D3

Abstract: It was reported previously that zinc-deficient mice show impaired lymphopoiesis. At the same time, monocyte numbers in these animals are increased, indicating a negative impact of zinc on monocyte development. Here, we investigate the role of zinc homeostasis in the differentiation of myeloid precursors into monocytes. Reduced gene expression of several zinc transporters, predominantly from the Zip family, was observed during 1 alpha, 25-dihydroxyvitamin D(3) (1,25D(3))-induced differentiation of HL-60 cells. This was accompanied by a reduction of intracellular-free zinc, measured by FluoZin-3. Amplifying this reduction with the zinc chelator TPEN or zinc-depleted cell-culture medium enhanced 1,25D(3)-induced expression of monocytic surface markers CD11b and CD14 on HL-60, THP-1, and NB4 cells. In contrast, differentiation of NB4 cells to granulocytes was not zinc-sensitive, pointing toward a specific effect of zinc on monocyte differentiation. Further, monocyte functions, such as TNF-alpha secretion, phagocytosis, and oxidative burst, were also augmented by differentiation in the presence of TPEN. The second messenger cAMP promotes monocyte differentiation. We could show that zinc inhibits the cAMP-synthesizing enzyme adenylate cyclase, and chelation of zinc by TPEN increases cAMP generation after stimulation with the adenylate cyclase activator forskolin. Based on our in vitro results and the in vivo observations from the literature, we suggest a model in which the intracellular-free zinc concentration limits AC activity, and the decrease of zinc after 1,25D(3) treatment promotes differentiation by relieving AC inhibition. Thus, cellular zinc homeostasis acts as an endogenous modulator of monocyte differentiation.

Superantigen Genes Are More Important than the emm Type for the Invasiveness of Group A Streptococcus Infection

Abstract: Background In this study, we examined the role of superantigen genes and emm genotypes of clinical Streptococcus pyogenes isolates collected in Germany between 1997 and 2003. Methods Multiplex polymerase chain reaction for all 11 currently known superantigen genes and sequencing for emm types were used. Results Using a 2-step explorative data analysis procedure, we found that after combined analysis of superantigen genes and emm types, only the superantigen genes spea1-spea3, spem, and spea4 have a predictive value for invasiveness, with odds ratios of 7.992, 3.209, and 2.323, respectively. The predictive value for invasiveness of emm1 was lost after combined analysis because of the association between emm type and the highly predictive superantigen genes. On the other hand, presence of the superantigen gene ssa and of emm77 are predictors of noninvasiveness, with odds ratios of 0.370 and 0.271, respectively. Conclusions These results indicate that the presence of superantigen genes is more important for the invasiveness of group A Streptococcus infection than emm type and may be the connection between the high-risk HLA type of the host and the pathogen. Furthermore, we found a very clear correlation between the presence of the genes spea1-spea3 and the presence of the gene emm1, which indicates that the relationship between emm1 and invasiveness is based on the superantigen gene profile. Our data suggest that the superantigen gene profile is of high importance for the clinical outcome of group A Streptococcus infections.

Changes in chromatin structure and methylation of the human interleukin-1β gene during monopoiesis

Abstract: Interleukin-1β (IL-1β) induces the expression of a variety of proteins responsible for acute inflammation and chronic inflammatory diseases. However, the molecular regulation of IL-1β expression in myeloid differentiation has not been elucidated. In this study the chromatin structure of the IL-1β promoter and the impact of methylation on IL-1β expression in monocytic development were examined. The results revealed that the IL-1β promoter was inaccessible in undifferentiated promyeloid HL-60 cells but highly accessible in differentiated monocytic cells which additionally acquired the ability to produce IL-1β. Accessibilities of differentiated cells were comparable to those of primary monocytes. Lipopolysaccharide (LPS) stimulation did not affect promoter accessibility in promyeloid and monocytic HL-60 cells, demonstrating that the chromatin remodelling of the IL-1β promoter depends on differentiation and not on the transcriptional status of the cell. Demethylation via 5-aza-2′-deoxycytodine led to the induction of IL-1β expression in undifferentiated and differentiated cells, which could be increased after LPS stimulation. Our data indicate that the IL-1β promoter is reorganized into an open poised conformation during monopoiesis being a privilege of mature monocytes but not of the entire myeloid lineage. As a second mechanism, IL-1β expression is regulated by methylation acting independently of the developmental stage of myeloid cells.

IFN-gamma reduction by tricyclic antidepressants.

Abstract: Objective:A growing body of data indicates that an activation of proinflammatory cytokines such as interferon-gamma (IFN-γ) is involved in the pathophysiology of depression and that the suppression...

Assessment of gene-nutrient interactions on inflammatory status of the elderly with the use of a zinc diet score--ZINCAGE study.

Abstract: Although zinc plays an important role in health status of the elderly, their dietary habits in relation to zinc intake are not well documented. The main objective of the current study was the assessment of dietary zinc intake in European old populations and the investigation of its impact on plasma zinc and inflammatory cytokines concentrations, in relation to genetic markers. Within the ZINCAGE study, 819 healthy old Europeans (>or=60 years old) were recruited. Plasma zinc, interleukin-6 (IL-6) and interleukin-8 (IL-8) were measured. Genotype data were obtained for the -174G/C polymorphism in the IL-6 gene. Dietary data were collected with a food frequency questionnaire and were used to calculate a zinc diet score. Zinc score was validated using additional dietary data (24-h recalls), in a subsample of 105 subjects. Zinc score was different among most of the European centres (P<.001), while an age-dependent decline was documented (P=4.4x10(-12)). Plasma zinc concentrations were significantly correlated with the zinc score (standardized beta=0.144, P=8.8x10(-5)). The minor allele frequency for the -174G/C polymorphism was f(C) 0.31. There was a significant interaction of zinc diet score and GG (-174G/C) genotype on higher plasma IL-6 levels (beta+/-S.E.=0.014+/-0.0, P=.008). The main finding of our study was the detection of gene-nutrient and biochemical-nutrient interactions in a multiethnic cohort based on a common dietary assessment tool.

Cadmium ions promote monocytic differentiation of human leukemia HL-60 cells treated with 1α,25-dihydroxyvitamin D3

Abstract: Cadmium exposure has multiple effects on the immune system. These can be stimulating, leading to improved clearance of infections, or inhibiting, increasing susceptibility toward infectious agents. One in vivo observation in cadmium-exposed individuals is increased monocyte numbers. Therefore, the objective of this study is to investigate the impact of cadmium on monocyte differentiation in the HL-60 model cell line. Administered alone, cadmium had no effect. However, cadmium amplified the expression of monocyte surface markers CD11b and CD14 when differentiation was induced by 1α,25-dihydroxyvitamin D3 (VD3). Furthermore, differentiation with VD3 in the presence of cadmium augmented key monocyte functions: the capacities to perform phagocytosis and generate an oxidative burst. One important signaling pathway required for monocyte differentiation involves extracellular signal-regulated kinase (ERK)1/2. Notably, cadmium induced ERK1/2 phosphorylation in HL-60 cells. Furthermore, U0126, which inhibits ERK1/2 phosphorylation by upstream MAPK/ERK kinases (MEK)1/2, reduced VD3-mediated differentiation and abrogated the effects of cadmium. In conclusion, cadmium can augment monocytic differentiation by activating ERK1/2 signaling, leading to increased generation of functional monocytes. These increased monocyte numbers could contribute to the impact of cadmium on the immune system owing to their role in the production of pro-inflammatory cytokines and activation of T-cells by antigen presentation.

UK Food Standards Agency Workshop Report: Diet and Immune Function

Abstract: The UK Food Standards Agency convened a workshop on 13 May 2009 to discuss recently completed research on diet and immune function. The objective of the workshop was to review this research and to establish priorities for future research. Several of the trials presented at the workshop showed some effect of nutritional interventions (e.g. vitamin D, Zn, Se) on immune parameters. One trial found that increased fruit and vegetable intake may improve the antibody response to pneumococcal vaccination in older people. The workshop highlighted the need to further clarify the potential public health relevance of observed nutrition-related changes in immune function, e.g. susceptibility to infections and infectious morbidity.

Das essenzielle Spurenelement Zink. Ein Metall in Biologie und Medizin

Abstract: Der menschliche Korper enthalt 2–3 Gramm des essenziellen Spurenelements Zink. Sowohl die Aufnahme als auch die Ausscheidung von Zink unterliegen einer genauen Kontrolle. Wenn dieses Gleichgewicht gestort ist, kommt es zu einer Beeintrachtigung zahlreicher biologischer Vorgange: Zink ist unter anderem wichtig fur die Entwicklung und Funktion des zentralen Nervensystems, die Infektabwehr des Immunsystems und die Produktion und Funktion von Insulin. In der Zelle gibt es uber 300 zinkhaltige Enzyme, viele weitere Zinkproteine sowie freies Zink, das eine Rolle bei der Weiterleitung von Signalen innerhalb der Zelle spielt. The essential trace element zinc The human body contains 2–3 grams of the essential trace element zinc, and uptake as well as excretion underlies a tight control. If this balance is disturbed, a number of biological processes are affected: among other tasks, zinc is important for the development and function of the central nervous system, the immune defense, and the production and function of insulin. This is based on over 300 different zinc-containing enzymes, several other zinc proteins, and a role of zinc in intracellular signal transduction.