Zinc, T-cell pathways, aging: role of metallothioneins

Zinc and aging: a narrative review of the effects on hematopoiesis and its link with diseases

There has been a global increase in the older population in recent decades and, as age advances, complex metabolic and epigenetic changes occur in the organism, and these may trigger some health complications commonly found among this population. Additionally, several changes occur in older people that can reduce the dietary intake or the process of nutrient absorption. In this way, tissues with high nutrient requirements are more affected. Hematopoiesis is the process of formation, development, and maturation of blood cells and is a process with a high turnover. This high demand makes the integrity of the hematopoietic process susceptible to various factors that impair physiological function, such as aging and micronutrient bioavailability. Among these micronutrients, Zinc is considered an important micronutrient, playing diverse roles across various tissues and cell types. Some of the alterations in hematopoiesis that appear as a consequence of aging and due to insufficient micronutrient intake are well described in the literature; however, not much is known about how zinc deficiency contributes towards the development of diseases seen in aging. Considering the importance of zinc to act on several biological processes, this narrative review discusses several studies related to the physiological requirements, deficiency, or excess of zinc, including studies in experimental models and humans, and aimed to shed light on the relationship between zinc and the regulation of hematopoietic tissue, exploring possible links between this mineral with common disorders that appear during aging.

The Role of Zinc in Cardiovascular Disease

Zinc is an essential trace element due to its role as a key part of human enzymatic activity. As a cofactor in metalloenzymes and metalloproteins, zinc participates in diverse biological functions, including gene transcription, translation, and replication, phagocytosis, and immunoglobulin and cytokine production. In this review, we will focus on the role of zinc in the cardiovascular system, including heart failure, vascular calcification, and myocardial infarction. We will further highlight the role of zinc in cardiovascular pathology in individuals with chronic kidney disease, and type II diabetes mellitus, groups uniquely at risk for cardiovascular morbidity and mortality.

The Correlation Between Whole Blood Copper (Cu), Zinc (Zn) Levels and Cu/Zn Ratio and Sepsis-Induced Left Ventricular Systolic Dysfunction (SILVSD) in Patients with Septic Shock: A Single-Center Prospective Observational Study

Purpose

This study aimed to explore relationships between whole blood copper (Cu), zinc (Zn) and Cu/Zn ratio and cardiac dysfunction in patients with septic shock.

Subjects and Methods

Between April 2018 and March 2020, septic shock patients with sepsis-induced left ventricular systolic dysfunction (SILVSD, left ventricular ejection fraction, LVEF<50%) and with no sepsis-induced myocardial dysfunction (non-SIMD, septic shock alone and LVEF>50%) and controls were prospectively enrolled. Whole blood Cu and Zn levels were measured using flame atomic absorption spectrophotometry.

Results

Eighty-six patients with septic shock including both 41 SILVSD and 45 non-SIMD and 25 controls were studied. Whole blood Cu levels and Cu/Zn ratio were significantly higher and Zn levels were lower in SILVSD compared with non-SIMD and controls (Cu, p=0.009, <0.001; Zn, p=0.029, <0.001; Cu/Zn ratio, p=0.003, <0.001). Both increased whole blood Cu and Cu/Zn ratio and reduced Zn were associated with lower LVEF (all p<0.001) and higher amino-terminal pro-B-type natriuretic peptide (NT-proBNP) (Cu, p=0.002; Zn, p<0.001; Cu/Zn ratio, p<0.001) and had predictive values for SILVSD (Cu, AUC=0.666, p=0.005; Zn, AUC=0.625, p=0.039; Cu/Zn ratio, AUC=0.674, p=0.029). Whole blood Cu levels and Cu/Zn ratio were increased but Zn levels were reduced in non-survivors compared with survivors (Cu, p<0.001; Zn, p<0.001; Cu/Zn ratio, p<0.001). Whole blood Cu and Zn displayed the value of predicting 28-day mortality (Cu, AUC = 0.802, p<0.001; Zn, AUC=0.869, p<0.001; Cu/Zn ratio, AUC=0.902, p<0.001).

Conclusion

Findings of the study suggest that whole blood Cu levels and Cu/Zn ratio are increased in SILVSD patients and positively correlated with cardiac dysfunction, while whole blood Zn levels are reduced and negatively associated with cardiac dysfunction. Moreover, both whole blood Cu, Zn and Cu/Zn ratio might distinguish between SILVSD and non-SIMD in septic shock patients and predict 28-day mortality.

Trial Registration

Registered at http://www.chictr.org.cn/ChiCTR1800015709.

The adaptive immune role of metallothioneins in the pathogenesis of diabetic cardiomyopathy: good or bad

Diabetes is a metabolic disorder characterized by hyperglycemia, resulting in low-grade systemic inflammation. Diabetic cardiomyopathy (DCM) is a common complication among diabetic patients, and the mechanism underlying its induction of cardiac remodeling and dysfunction remains unclear. Numerous experimental and clinical studies have suggested that adaptive immunity, especially T lymphocyte-mediated immunity, plays a potentially important role in the pathogenesis of diabetes and DCM. Metallothioneins (MTs), cysteine-rich, metal-binding proteins, have antioxidant properties. Some potential mechanisms underlying the cardioprotective effects of MTs include the role of MTs in calcium regulation, zinc homeostasis, insulin sensitization, and antioxidant activity. Moreover, metal homeostasis, especially MT-regulated zinc homeostasis, is essential for immune function. This review discusses aberrant immune regulation in diabetic heart disease with respect to endothelial insulin resistance and the effects of hyperglycemia and hyperlipidemia on tissues and the different effects of intracellular and extracellular MTs on adaptive immunity. This review shows that intracellular MTs are involved in naïve T-cell activation and reduce regulatory T-cell (Treg) polarization, whereas extracellular MTs promote proliferation and survival in naïve T cells and Treg polarization but inhibit their activation, thus revealing potential therapeutic strategies targeting the regulation of immune cell function by MTs.

Role of Zinc and Selenium in Oxidative Stress and Immunosenescence: Implications for Healthy Aging and Longevity

Aging is a complex process that includes gradual and spontaneous biochemical and physiological changes which contributes to a decline in performance and increased susceptibility to diseases. Zn and Se are essential trace elements that play a pivotal role in immune functions and antioxidant defense and, consequently, are claimed to play also a role in successful aging trajectories. Consistently with their nature of essential trace elements, a plethora of data obtained “in vitro” and “in vivo” (in humans and animal models) support the relevance of Zn and Se for both the innate and adoptive immune response. Moreover, Zn and Se are strictly involved in the synthesis and regulation of activity of proteins and enzymes, e.g., metallothioneins (MT) and glutathione peroxidase (GPX), that are necessary for our endogenous antioxidant response. This is clearly important to protect our cells from oxidative damage and to slow the decline of our immune system with aging. Age-related changes affecting tissue levels of Zn and Se may indicate that the risk of Zn and Se deficiency increases with aging. However, it is still unclear which of these changes can be the consequence of a “real deficiency” and which can be part of our physiological compensatory response to the accumulating damage occurring in aging. Furthermore, the upregulation of antioxidant proteins (Zn and Se dependent) may be a manifestation of self-induced oxidative stress. By the way, Zn and Se dependent proteins are modulated not only by nutritional status, but also by well-known hallmarks of aging that play antagonistic functions, such as the deregulated nutrient sensing pathways and cellular senescence. Thus, it is not an easy task to conduct Zn or Se supplementation in elderly and it is emerging consistent that these kind of supplementation requires an individualized approach. Anyway, there is consistent support that supplementation with Zn using doses around 10 mg/day is generally safe in elderly and may even improve part of immune performances in those subjects with a baseline deficiency. Regarding Se supplementation, it may induce both beneficial and detrimental effects on cellular immunity depending on the form of Se, supplemental dose, and delivery matrix. The nutritional association of supplements based on “Zn plus Se” is hypothesized to provide additional benefits, but this will likely need a more complex individualized approach. The improvement of our knowledge around screening and detection of Zn and Se deficiency in aging could lead to substantial benefits in terms of efficacy of nutritional supplements aimed at ameliorate performance and health in aging.

Zinc Metabolism and Metallothioneins

Among the trace elements, zinc is one of the most used elements in biological systems. Zinc is found in the structure of more than 2700 enzymes, including hydrolases, transferases, oxyreductases, ligases, isomerases, and lyases. Not surprisingly, it is present in almost all body cells. Preserving the stability and integrity of biological membranes and ion channels, zinc is also an intracellular regulator and provides structural support to proteins during molecular interactions. It acts as a structural element in nucleic acids or other gene-regulating proteins. Metallothioneins, the low molecular weight protein family rich in cysteine groups, are involved significantly in numerous physiological and pathological processes including particularly oxidative stress. A critical role of metallothioneins (MT) is to bind zinc with high affinity and to serve as an intracellular zinc reservoir. By releasing free intracellular zinc when needed, MTs mediate the unique physiological roles of zinc. MT expression is induced by zinc elevation, and thus, zinc homeostasis is maintained. That MT mediates the effects of zinc, besides having strong radical scavenging effects, points to the critical part it plays in oxidative stress. The present review aims to give information on metallothioneins, which have critical importance in the metabolism and molecular pathways of zinc.

The Relationship between Serum Zinc Level and Heart Failure: A Meta-Analysis

Zinc is essential for the maintenance of normal cellular structure and functions. Zinc dyshomeostasis can lead to many diseases, such as cardiovascular disease. However, there are conflicting reports on the relationship between serum zinc levels and heart failure (HF). The purpose of the present study is to explore the relationship between serum zinc levels and HF by using a meta-analysis approach. PubMed, Web of Science, and OVID databases were searched for reports on the association between serum zinc levels and HF until June 2016. 12 reports with 1453 subjects from 27 case-control studies were chosen for the meta-analysis. Overall, the pooled analysis indicated that patients with HF had lower zinc levels than the control subjects. Further subgroup analysis stratified by different geographic locations also showed that HF patients had lower zinc levels than the control subjects. In addition, subgroup analysis stratified by HF subgroups found that patients with idiopathic dilated cardiomyopathy (IDCM) had lower zinc levels than the control subjects, except for patients with ischemic cardiomyopathy (ICM). In conclusion, the results of the meta-analysis indicate that there is a significant association between low serum zinc levels and HF.

Nanosize of zinc oxide and the effects on zinc digestibility, growth performances, immune response and serum parameters of weanling piglets

The aim of this study was to investigate the effect of dietary supplementation of nanosize zinc on zinc digestibility, growth performances, immune response and serum parameters of weanling piglets. Ninety-six LYD weanling piglets were assigned to control, zinc oxide (ZnO), organic-Zn (Zn-methionine) and nanosize ZnO (nano-Zn) groups with four replicates. The zinc was at the 120 mg/kg level in the treatment group's diet, while the control group's was 80 mg/kg Zn. The experiment results indicated that the nano-Zn and organic-Zn groups had significantly higher Zn digestibility compared to the ZnO and control groups. For the immune response traits, the IgG level and goat red blood cells (GRBC) antibody titer were nano-Zn and organic-Zn>ZnO>control; in the phytohemagglutinin (PHA) challenge test result, nano-Zn>organic-Zn>ZnO>control; in regard to the γ-globulin level, nano-Zn and organic-Zn>ZnO and control, with significant difference between groups. In the serum parameters aspect, serum Zn concentration in nano-Zn and organic-Zn groups were higher than in the ZnO and control groups, serum growth hormone concentration was increased in the nano-Zn group than in the other groups. In conclusion, nanosize zinc oxide for dietary supplementation can increase zinc digestibility, serum growth hormone levels and carbonic anhydrase activity and enhance the immune response of weanling piglets.

Dysregulation of hepatic zinc transporters in a mouse model of alcoholic liver disease

Zinc deficiency is a consistent phenomenon observed in patients with alcoholic liver disease, but the mechanisms have not been well defined. The objective of this study was to determine if alcohol alters hepatic zinc transporters in association with reduction of hepatic zinc levels and if oxidative stress mediates the alterations of zinc transporters. C57BL/6 mice were pair-fed with the Lieber-DeCarli control or ethanol diets for 2, 4, or 8 wk. Chronic alcohol exposure reduced hepatic zinc levels, but increased plasma and urine zinc levels, at all time points. Hepatic zinc finger proteins, peroxisome proliferator-activated receptor-α (PPAR-α) and hepatocyte nuclear factor 4α (HNF-4α), were downregulated in ethanol-fed mice. Four hepatic zinc transporter proteins showed significant alterations in ethanol-fed mice compared with the controls. ZIP5 and ZIP14 proteins were downregulated, while ZIP7 and ZnT7 proteins were upregulated, by ethanol exposure at all time points. Immunohistochemical staining demonstrated that chronic ethanol exposure upregulated cytochrome P-450 2E1 and caused 4-hydroxynonenal accumulation in the liver. For the in vitro study, murine FL-83B hepatocytes were treated with 5 μM 4-hydroxynonenal or 100 μM hydrogen peroxide for 72 h. The results from in vitro studies demonstrated that 4-hydroxynonenal treatment altered ZIP5 and ZIP7 protein abundance, and hydrogen peroxide treatment changed ZIP7, ZIP14, and ZnT7 protein abundance. These results suggest that chronic ethanol exposure alters hepatic zinc transporters via oxidative stress, which might account for ethanol-induced hepatic zinc deficiency.

Clinical and echocardiographic correlates of serum copper and zinc in acute and chronic heart failure

AIM

Emerging evidence suggests a pathophysiological role of micronutrient dyshomeostasis in heart failure, including promotion of adverse remodeling and clinical deterioration. We sought to evaluate serum copper (Cu) and zinc (Zn) levels in acute (AHF) and chronic (CHF) heart failure.

METHODS

We studied 125 patients, 71 % male, aged 69 ± 11 years, 37 % with preserved left ventricular ejection fraction (LVEF ≥40 %) (HFPEF), including 81 with AHF and 44 with CHF; 21 healthy volunteers served as controls. Serum Cu and Zn levels were determined using air-acetylene flame atomic absorption spectrophotometry.

RESULTS

Serum Cu levels were significantly higher in AHF (p = 0.006) and CHF (p = 0.002) patients compared to controls after adjusting for age, gender and comorbidities, whereas they did not differ between AHF and CHF (p = 0.840). Additionally, serum Cu in patients with LVEF <40 % was significantly higher compared to both controls (p < 0.001) and HFPEF patients (p = 0.003). Serum Zn was significantly lower in AHF (p < 0.001) and CHF (p = 0.039) compared to control after adjusting for the above-mentioned variables. Moreover, serum Zn was significantly lower in AHF than in CHF (p = 0.015). In multiple linear regression, LVEF (p = 0.033) and E/e ratio (p = 0.006) were independent predictors of serum Cu in total heart failure population, while NYHA class (p < 0.001) and E/e ratio (p = 0.007) were independent predictors of serum Zn.

CONCLUSION

Serum Cu was increased both in AHF and CHF and correlated with LV systolic and diastolic function. Serum Zn, in contrast, was decreased both in AHF and CHF and independently predicted by clinical status and LV diastolic function.

Zinc: dietary intake and impact of supplementation on immune function in elderly

The diet in the elderly does not provide a sufficient level of nutrients needed to maintain an adequate healthy status leading to micronutrient deficiencies and impaired immune response with subsequent development of degenerative diseases. Nutrient "zinc" is a relevant micronutrient involved in maintaining a good integrity of many body homeostatic mechanisms, including immune efficiency, owing to its requirement for the biological activity of many enzymes, proteins and for cellular proliferation and genomic stability. Old people aged 60-65 years and older have zinc intakes below 50% of the recommended daily allowance on a given day. Many causes can be involved: among them, altered intestinal absorption, inadequate mastication, psychosocial factors, drugs interactions, altered subcellular processes (zinc transporters (Zip and ZnT family), metallothioneins, divalent metal transporter-1). Zinc supplementation may remodel the immune alterations in elderly leading to healthy ageing. Several zinc trials have been carried out with contradictory data, perhaps due to incorrect choice of an effective zinc supplementation in old subjects showing subsequent zinc toxic effects on immunity. Old subjects with specific IL-6 polymorphism (GG allele carriers; named C-) are more prone for zinc supplementation than the entire old population, in whom correct dietary habits with foods containing zinc (Mediterranean diet) may be sufficient in restoring zinc deficiency and impaired immune response. We summarise the main causes of low zinc dietary intake in elderly reporting an update on the impact of zinc supplementation upon the immune response also on the basis of individual IL-6 polymorphism.

Zinc and cancer: implications for LIV-1 in breast cancer

Zinc is a trace mineral which is vital for the functioning of numerous cellular processes, is critical for growth, and may play an important role in cancer etiology and outcome. The intracellular levels of this mineral are regulated through the coordinated expression of zinc transporters, which modulate both zinc influx as well as efflux. LIV-1 (ZIP6) was first described in 1988 as an estrogen regulated gene with later work suggesting a role for this transporter in cancer growth and metastasis. Despite evidence of its potential utility as a target gene for cancer prognosis and treatment, LIV-1 has received relatively little attention, with only three prior reviews being published on this topic. Herein, the physiological effects of zinc are reviewed in light of this mineral’s role in cancer growth with specific attention being given to LIV-1 and the potential importance of this transporter to breast cancer etiology.

Micronutrient (Zn, Cu, Fe)-gene interactions in ageing and inflammatory age-related diseases: implications for treatments

In ageing, alterations in inflammatory/immune response and antioxidant capacity lead to increased susceptibility to diseases and loss of mobility and agility. Various essential micronutrients in the diet are involved in age-altered biological functions. Micronutrients (zinc, copper, iron) play a pivotal role either in maintaining and reinforcing the immune and antioxidant performances or in affecting the complex network of genes (nutrigenomic approach) involved in encoding proteins for a correct inflammatory/immune response. By the other side, the genetic inter-individual variability may affect the absorption and uptake of the micronutrients (nutrigenetic approach) with subsequent altered effects on inflammatory/immune response and antioxidant activity. Therefore, the individual micronutrient-gene interactions are fundamental to achieve healthy ageing. In this review, we report and discuss the role of micronutrients (Zn, Cu, Fe)-gene interactions in relation to the inflammatory status and the possibility of a supplement in the event of a micronutrient deficiency or chelation in presence of micronutrient overload in relation to specific polymorphisms of inflammatory proteins or proteins related of the delivery of the micronutriemts to various organs and tissues. In this last context, we report the protein-metal speciation analysis in order to have, coupled with micronutrient-gene interactions, a more complete picture of the individual need in micronutrient supplementation or chelation to achieve healthy ageing and longevity.

Metalloproteases/anti-metalloproteases imbalance in chronic obstructive pulmonary disease: genetic factors and treatment implications

PURPOSE OF REVIEW

The aim is to describe the involvement of matrix metalloprotease (MMP), A Disintegrin And Metalloproteases (ADAM), tissue inhibitors of MMP (TIMP) polymorphisms and the role of α-2 Macroglobulin (α-2M) in chronic obstructive pulmonary disease (COPD) development and progression, with a focus on interventions with synthetic MMP inhibitors alone or associated with current drugs used in COPD therapy in order to restore MMPs/TIMPs imbalance.

RECENT FINDINGS

COPD is one of the major causes of death in the elderly. It is characterized by progressive development of airflow limitation manifested by decreased forced expiratory volume in one second (FEV1) and reduction in the percentage of FEV1/forced vital capacity. The major pathogenic role is played by metalloproteases (MMPs, ADAMs)/anti-metalloproteases (TIMPs, α-2M) imbalance, which is responsible for MMP overproduction not sufficiently counteracted by TIMPs or α-2M. As a consequence, the lung extracellular matrix is destroyed with obstruction of small airways and appearance of emphysema.

SUMMARY

The disease is mainly caused by exposure to cigarette smoke or noxious gases and air pollutants, but also genetic factors are involved. Among them, polymorphisms of MMPs (MMP1, MMP2, MMP9, MMP12), ADAMs (ADAM33) and TIMPs (TIMP1, TIMP2) are relevant, in which the inflammation and the smoking habit play key roles especially in unfavorable allele carriers. The association between these polymorphisms and the current drugs paves the way for personalized therapy with a great impact at clinical level.

Zinc, metallothioneins and immunosenescence: effect of zinc supply as nutrigenomic approach

Ageing is an inevitable biological process associated with gradual and spontaneous biochemical and physiological changes and increased susceptibility to diseases. Nutritional factor, zinc, known to be involved in improving immunity, may remodel some of the age-associated changes, leading to a healthy ageing. "In Vitro" studies involving human lymphocytes exposed to endotoxins, and "in vivo" studies comparing old and young mice fed with low dietary zinc suggest that zinc is important for both innate and adaptive immune efficiency, and more optimal inflammatory/immune response. The intracellular zinc homeostasis is mainly regulated by Metallothioneins (MT), via ion release through the reduction of thiol groups in MT molecule. These processes are crucial because mediating the zinc signalling within the immune cells assigning to zinc a role of "second messenger". Zinc homeostasis is altered in ageing partly due to higher expression levels of MT, leading to an increased sequestration of zinc, resulting in less availability of free intracellular zinc. Improvement of immune functions and stress response systems occurs in elderly after physiological zinc supplementation. The main reason behind these effects seems to be related to a like "hormetic" response induced by zinc. However, the choice of old subjects for zinc supplementation has to be performed in relationship to the specific genetic background of MT and pro-inflammatory cytokine (IL-6) because the latter is involved both in MT gene expression and in intracellular zinc homeostasis. Old subjects carrying GG genotypes (termed C- carriers) in IL-6--174G/C locus display increased IL-6 production, low intracellular zinc ion availability, impaired innate immune response and enhanced MT. By contrast, old subjects carrying GC and CC genotypes (termed C+ carriers) in the same IL-6--174 locus displayed satisfactory intracellular zinc and innate immune response. Moreover, male carriers of C+ allele are more prone to reach centenarian age than C- ones. Therefore, old C- subjects are likely to benefit more from zinc supplementation restoring NK cell cytotoxicity and improving the zinc status. Plasma zinc deficiency and the altered immune response is more evident when the genetic variations of IL-6 polymorphism are associated with the genetic variations of MT1A in position +647, suggesting that the genetic variations of IL-6 and MT1A are very useful tools for the identification of old people who effectively need zinc supplementation.

Increased metallothionein gene expression, zinc, and zinc-dependent resistance to apoptosis in circulating monocytes during HIV viremia

Circulating monocytes exhibit an apoptotic resistance phenotype during HIV viremia in association with increased MT expression. MTs are known to play an important role in zinc metabolism and immune function. We now show, in a cross-sectional study using peripheral monocytes, that expression of MT1 isoforms E, G, H, and X is increased significantly in circulating monocyte cells from HIV+ subjects during chronic viremic episodes as compared with uninfected subjects. This increase in expression is also observed during acute viremia following interruption of suppressive ART. Circulating monocytes from HIV+ donors were also found to have elevated zinc importer gene Zip8 expression in conjunction with elevated intracellular zinc levels in contrast to CD4(+)T-lymphocytes. In vitro HIV-1 infection studies with elutriated MDM confirm a direct relation between HIV-1 infection and increased MDM MT1 (isoform G) gene expression and increased intracellular zinc levels. A direct link between elevated zinc levels and apoptosis resistance was established using a cell-permeable zinc chelator TPEN, which reversed apoptosis resistance effectively in monocytes from HIV-infected to levels comparable with uninfected controls. Taken together, increases in MT gene expression and intracellular zinc levels may contribute directly to maintenance of an immune-activated monocyte by mediating an increased resistance to apoptosis during active HIV-1 viremia.

Infection, immunity and the neuroendocrine response

The Central Nervous (CNS) and Immune Systems (IS) are the two major adaptive systems which respond rapidly to numerous challenges that are able to compromise health. The defensive response strictly linking innate to acquired immunity, works continuously to limit pathogen invasion and damage. The efficiency of the innate response is crucial for survival and for an optimum priming of acquired immunity. During infection, the immune response is modulated by an integrated neuro-immune network which potentiates innate immunity, controls potential harmful effects and also addresses metabolic and nutritional modifications supporting immune function. In the last decade much knowledge has been gained on the molecular signals that orchestrate this integrated adaptive response, with focus on the systemic mediators which have a crucial role in driving and controlling an efficient protective response. These mediators are also able to signal alterations and control pathway dysfunctions which may be involved in the persistence and/or overexpression of inflammation that may lead to tissue damage and to a negative metabolic impact, causing retarded growth. This review aims to describe some important signalling pathways which drive bidirectional communication between the Immune and Nervous Systems during infection. Particular emphasis is placed on pro-inflammatory cytokines, immunomodulator hormones such as Glucocorticoids (GCs), Growth hormone (GH), Insulin-like Growth Factor-1 (IGF-1), and Leptin, as well as nutritional factors such as Zinc (Zn). Finally, the review includes up-to-date information on this neuroimmune cross-talk in domestic animals. Data in domestic animal species are still limited, but there are several exciting areas of research, like the potential interaction pathways between mediators (i.e. cytokine-HPA regulation, IL-6-GCS-Zn, cytokines-GH/IGF-1, IL-6-GH-Leptin and thymus activity) that are or could be promising topics of future research in veterinary medicine.

NK and NKT cells in aging and longevity: role of zinc and metallothioneins

INTRODUCTION

During aging, dysregulated immune functions occur contributing to increased susceptibility to morbidity and mortality. However, these dysregulations are normally counterbalanced by continuous adaptation of the body to the deteriorative changes occurring over time. These adaptive changes well occur in healthy centenarians.

DISCUSSION

Both innate (natural) and adaptive (acquired) immune responses decline with advancing age. Natural killer (NK) and natural killer T (NKT) cell cytotoxicity, representing one of best models of innate immune response, decreases in aging as well as interferon-gamma (IFN-gamma) production by both activated types of cells. Both NK and NKT cell cytotoxicity and IFN-gamma production increase in very old age with respect to normal aging, especially by NKT cells bearing TCRgammadelta. The role played by zinc and metallothioneins (MT) is crucial because this affects NK and NKT cell development, maturation, and functions. In particular, some MT polymorphisms are involved in maintaining innate immune response and intracellular zinc ion availability in aging with thus a role of MT genetic background to escape some age-related diseases with subsequent healthy aging and longevity.

Does promoter methylation of the SLC30A5 (ZnT5) zinc transporter gene contribute to the ageing-related decline in zinc status?

A decline in Zn status with ageing may contribute to the development of frailty, including impaired immune function, and increased incidence of age-related degenerative diseases. This decline may be a result of reduced dietary Zn intake and/or impaired Zn absorption in the gut. The Zn transporter ZnT5 may play a key role in the absorption of dietary Zn. The corresponding gene (SLC30A5) has a CpG island in its promoter region, so could be regulated by epigenetic mechanisms. It is hypothesised that methylation of the SLC30A5 promoter region is increased with age and that a resulting reduction in ZnT5 expression contributes to the decline in Zn status observed with ageing. This hypothesis has been addressed through (1) studies of effects of SLC30A5 promoter methylation on gene expression in vitro and (2) in vivo measurements of the DNA methylation status of this gene domain. It has been established in vitro that methylation of the human SLC30A5 promoter region results in reduced expression of an associated reporter gene. Second, this gene region shows variable levels of methylation in vivo. Correlation between the level of methylation at this locus and age would support the hypothesis that age-related hypermethylation of this region has the potential to modulate dietary Zn absorption. This premise is being investigated by analysis of additional samples from a human adult cohort to test the hypothesis that methylation of the SLC30A5 promoter region contributes to the age-related decline in Zn status.

Topographic trace-elemental analysis in the brain of Wistar rats by X-ray microfluorescence with synchrotron radiation

Knowledge about the spatial distribution and the local concentration of trace elements in tissues is of great importance, since trace elements are involved in many biological functions of living organisms. However, there are few methods available to measure the spatial (two (three)-dimensional) elemental distribution in animal brain. X-ray microfluorescence with synchrotron radiation is a multielemental mapping technique, which was used in this work to determine the topographic of iron, zinc and copper in coronal sections of female Wistar rats of different ages. Young (14 days old) and middle-aged (20 months old) rats (n = 8) were analyzed. The measurements were carried out at the XRF beam line at the Synchrotron Light National Laboratory (Campinas, Brazil). Two-dimensional scanning was performed in order to study the tendency of elemental concentration variation. The acquisition time for each pixel was 10 s/step and the step size was 300 microm/step in both directions. It was observed that the iron distribution was more conspicuous in the cortical area, thalamus and bellow the thalamus. On the other hand, the zinc distribution was more pronounced in the hippocampus. The iron, copper and zinc levels increased with advancing age. Therefore, this study reinforces the idea that these elements are involved in the chemical mechanisms of the brain that induce some neurological diseases, since they are also present in high levels in specific areas of the brain, such as the hippocampus and the substantia nigra of patients with these disorders.

Aging and the immune system

Aging is associated with many physiological changes in a variety of organ systems. Nevertheless, considerable interest has centred on the possibility that age-related immunological changes may play a key "master" role in regulating many, if not all, subsequent events. A growing body of data, some of it highlighted in this review, supports the notion that host resistance in general is changed in both a qualitative and quantitative manner with age, though the biochemical mechanism(s) underlying such changes are not unique to the immune system per se. Moreover, interventions designed to explore treatments which may reverse some or all of those age-related changes have pointed out a fundamentally important role for nutrition, and the way(s) in which this impacts on host resistance mechanism(s), as having a hitherto unappreciated importance in immunosenescence in general.

Role of Zinc and Selenium in Oxidative Stress and Immunosenescence: Implications for Healthy Ageing and Longevity

Ageing is an inevitable biological process with gradual and spontaneous biochemical and physiological changes and increased susceptibility to diseases. Some nutritional factors (zinc and selenium) may remodel these changes leading to a possible escaping of diseases with subsequent healthy ageing, because they are especially involved in improving immune functions as well as antioxidant defense. Experiments performed “in vitro” (human lymphocytes exposed to endotoxins) and “in vivo” (old mice or young mice fed with low zinc dietary intake) show that zinc is important for immune response both innate and adoptive. Selenium provokes zinc release by Metallothioneins (MT), via reduction of glutathione peroxidase. This fact is crucial in ageing because high MT may be unable to release zinc with subsequent low intracellular free zinc ion availability for immune response. Taking into account the existence of zinc transporters (ZnT and ZIP family) for cellular zinc efflux and influx, respectively, the association between ZnT and MT is important in maintaining satisfactory intracellular zinc homeostasis in ageing. Improved immune performance occur in elderly after physiological zinc supplementation, which also induces prolonged survival in old, nude and neonatal thymectomized mice. The association “zinc plus selenium” improves humoral immunity in old subjects after influenza vaccination. Therefore, zinc and selenium are relevant for immunosenescence in order to achieve healthy ageing and longevity.

Zinc-gene interaction related to inflammatory/immune response in ageing

The pivotal role played by zinc-gene interaction in affecting some relevant cytokines (IL-6 and TNF-alpha) and heat shock proteins (HSP70-2) in ageing, successful ageing (nonagenarians) and the most common age-related diseases, such as atherosclerosis and infections, is now recognized. The polymorphisms of genes codifying proteins related to the inflammation are predictive on one hand in longevity, on the other hand they are associated with atherosclerosis or severe infections. Since the health life-span has a strong genetic component, which in turn also affected by nutritional factors like zinc, the association of these polymorphisms with innate immune response, zinc ion bioavailability and Metallothioneins (MT) homeostasis is an useful tool to unravel the role played by zinc-gene interactions in longevity, especially due to the inability of MT in zinc release in ageing and chronic inflammation. In ageing, this last fact leads to depressed innate immune response for host defence. In contrast, in very old age the inflammation is lower with subsequent more zinc ion bioavailability, less MT gene expression and satisfactory innate immunity. Therefore, the zinc-gene (IL-6, TNF-alpha, Hsp70-2) interactions, via MT homeostasis, are crucial to achieve successful ageing.

Zinc-bound metallothioneins and immune plasticity: lessons from very old mice and humans

The capacity of the remodelling immune responses during stress (named immune plasticity) is fundamental to reach successful ageing. We herein report two pivotal experimental models in order to demonstrate the relevance of the immune plasticity in ageing and successful ageing. These two experimental models will be compared with the capacity in remodelling the immune response in human centenarians. With regard to experimental models, one model is represented by the circadian rhythms of immune responses, the other one is the immune responses during partial hepatectomy/liver regeneration (pHx). The latter is suggestive because it mimics the immunosenescence and chronic inflammation 48 h after partial hepatectomy in the young through the continuous production of IL-6, which is the main cause of immune plasticity lack in ageing. The constant production of IL-6 leads to abnormal increments of zinc-bound Metallothionein (MT), which is in turn unable in zinc release in ageing. As a consequence, low zinc ion bioavailability appears for thymic and extrathymic immune efficiency, in particular of liver NKT cells bearing TCR γδ. The remodelling during the circadian cycle and during pHx of zinc-bound MT confers the immune plasticity of liver NKT γδ cells and NK cells in young and very old mice, not in old mice. With regard to human centenarians and their capacity in remodelling the immune response with respect to elderly, these exceptional individuals display low zinc-bound MT associated with: a) satisfactory intracellular zinc ion availability, b) more capacity in zinc release by MT, c) less inflammation due to low gene expression of IL-6 receptor (gp130), d) increased levels of IFN-gamma and number of NKT cell bearing TCR γδ. Moreover, some polymorphisms for MT tested in PBMCs from human donors are related to successful ageing. In conclusion, zinc-bound MT homeostasis is fundamental to confer the immune plasticity that is a condition "sine qua non" to achieve healthy ageing and longevity.

Inflammation, genes and zinc in ageing and age-related diseases

Lifelong antigenic burden determines a condition of chronic inflammation, with increased lymphocyte activation and pro-inflammatory cytokine production. A large number of studies have documented changes in Zn metabolism in experimental animal models of acute and chronic inflammation and in human chronic inflammatory diseases. In particular, modification of zinc plasma concentration as well as intracellular disturbance of antioxidant intracellular pathways have been found associated to age-related inflammatory diseases, like atherosclerosis. Zinc deficiency is extremely diffused in aged people that are educated to avoid meat and other high Zn-content foods due to fear of cholesterol. Rather, they increase consumption of refined wheat products that lack of Zn, magnesium and other critical nutrients in consequence of refining process. On the other hand, plasma concentration of metallic ions like Zn is influenced by pro-inflammatory cytokines production. A major target of Zn may be NF-kB, a transcription factor critical for the expression of many pro-inflammatory cytokines whose production is finely regulated by extra- and intracellular activating and inhibiting factors interacting with regulatory elements on cytokine genes. Moreover, this factor is regulated by the expression of specific cellular genes involved in inflammation. So it is not surprising that Zn deficiency is constantly observed in aged patients affected by infectious diseases. On the other hand, cytokine genes are highly polymorphic and some of these polymorphisms have been found associated to age-related diseases as atherosclerosis. Therefore, Zn deficiency in individuals genetically predisposed to a dis-regulation of inflammation response, may play a crucial role, in causing adverse events and in reducing the probability of a successful aging.

Immunological biomarkers of ageing in man: changes in both innate and adaptive immunity are associated with health and longevity

Scientific and clinical advances in the last century have led to increased numbers of individuals living to older ages. Thus a major concern is how to live these years with a high quality of life. The ageing immune system is less well able to cope with infectious diseases than the youthful immune system probably as a consequence of altered immune response to pathogens. Thus, both innate and adaptive immune responses show age-related changes that could be decisive for healthy ageing and survival. Longitudinal studies in healthy elderly have allowed the definition of the ''immune risk phenotype" (IRP) a predictor of mortality in elderly individuals that is based on several parameters of the adaptive immune response. Here, we hypothesize that failures in innate immunity observed in frail elderly are related to those alterations described in adaptive immunity defined as the IRP. It will be important to include assays of NK cell markers and functions in future longitudinal studies in order to investigate this point in detail as well as to consider the trace element zinc as an essential co-factor for optimal NK cell activity.

Psychosocial and biochemical interactions in aging: preliminary results from an Italian old sample of "Zincage" project

The study of the interactions among biological factors and psychosocial conditions is a very innovative field, because data are lacking in the scientific literature. Among biological aspects, zinc is an essential element in the elderly, especially in relation to one of the proteins, such as albumin, involved in zinc transport into the cells. In this study, the aim is the assessment of the interrelationship between albumin value (used as an index of the body zinc status) and some psychosocial dimensions in elderly Italian sample recruited for ZINCAGE project, supported by the European Commission in the "Sixth Framework Programme". Some tests and questionnaires were administered to older people included in the trial: the "life-style questionnaire"; the mini mental state examination (MMSE); the geriatric depression scale (GDS-15 items). On the basis of the Senieur Protocol for gerontological studies, a sample of 291 Italian healthy old subjects has been recruited in Central Italy and divided into 3 age groups: (a) 125 subjects aged from 65 to 74 years, (b) 89 subjects aged from 75 to 84 years, (c) 77 subjects aged >or=85 years (classified like successful old people). No cognitive impairment assessed by MMSE was observed in 67.5% of the sample; 64.0% had GDS score less than 5, indicating no depression, whereas the prevalence of biological albumin deficiency (<3.5 g/dl) found in Italian old people was 21.0%. Sixty one percent of subjects with albumin deficiency displayed higher values of GDS (>or=5). These preliminary results showed an interrelationship among serum albumin value and psychosocial aspects in Italian old population, suggesting that low albumin values may be involved in impaired psychological dimensions.

Zinc improves the development of human CD34+ cell progenitors towards Natural Killer cells and induces the expression of GATA-3 transcription factor

The Natural Killer cell maturation from CD34(+) hematopoietic cell precursors is a complex process that requires the synergistic effect of different cytokines and growth factors. Although there have been a number of important advances in our understanding of the Natural Killer differentiation, the developmental step leading to mature Natural Killer cells is still poorly defined. We evaluated the effect of two zinc concentrations (10 and 20microM) on the kinetic of development of CD34(+) cell progenitors towards Natural Killer cells. CD34(+) cells were purified from peripheral blood and cultured in medium supplemented with interleukin-15, interleukin-7, Flt 3 ligand, and stem cell factor. CD34(+) cells underwent proliferation and progressively lost CD34 antigen and acquired a CD56(+) phenotype. These CD56(+) cells exerted cytotoxic activity and expressed the CD94 inhibitory receptor. The supplementation with zinc greatly increased both the number of cells in culture and the absolute number of CD56(+) cells. Zinc induced higher levels of cytotoxic activity and a higher number of perforin-producing and of CD94-bearing CD56(+) cells in comparison with zinc unsupplemented cultures in early stages of Natural Killer cell development. The zinc-induced changes in CD34-derived CD56(+) cells were associated with an increased expression of GATA-3, a zinc-finger transcription factor providing for maturation and activity of T and Natural Killer cells. The increase was related to a higher CD56(+) cell number (10microM zinc), or to an increased GATA-3 mRNA transcription in CD56(+) cells (20microM zinc). Our data demonstrate that zinc influences the proliferation and differentiation of CD34(+) progenitors.

Dietary supplementation with antioxidants improves functions and decreases oxidative stress of leukocytes from prematurely aging mice

OBJECTIVES

Aging is accompanied by chronic inflammation and oxidative stress, which lead to a marked impairment of immune function and therefore increased mortality. This study assessed the effect of dietary supplementation, for 15 wk, with 5% and 20% (w/w) of biscuits enriched with nutritional doses of vitamins C and E, zinc, selenium, and beta-carotenes on function and oxidative stress parameters of peritoneal leukocytes from middle-aged, prematurely aging mice (PAM) and non-prematurely aging mice (NPAM).

METHODS

After supplementation we measured leukocyte functions (adherence, chemotaxis, phagocytosis, intracellular reactive oxygen species levels, lymphoproliferation, natural killer activity, and interleukin-2 release), antioxidant defenses (superoxide dismutase, glutathione peroxidase, and reduced glutathione), oxidant compounds (extracellular O(2)(-), glutathione disulfide, glutathione disulfide/reduced glutathione ratio, tumor necrosis factor-alpha, nitric oxide, and prostaglandin E(2)), and lipid and DNA oxidative damage, measured by malondialdehyde and 8-oxo,7,8-dihydro-2'-deoxyguanosine levels, respectively.

RESULTS

In general, leukocyte functions were improved and redox homeostasis was restored after intake of antioxidants. In consequence, malondialdehyde and 8-oxo,7,8-dihydro-2'-deoxyguanosine in PAM and NPAM were strikingly decreased after 5% and 20% supplementation (malondialdehyde, P < 0.001 in PAM; P < 0.01 in NPAM after both treatments; 8-oxo,7,8-dihydro-2'-deoxyguanosine, P < 0.01 after 5% supplementation and P < 0.001 after 20% supplementation in PAM and NPAM). Moreover, the effect of the antioxidants was stronger in PAM than in NPAM, and 20% supplementation was more effective than 5%.

CONCLUSION

Our data suggest that improvement of leukocyte function and restoration of redox balance after consumption of adequate levels of antioxidants from adulthood may be useful to attain healthy aging, especially in animals with premature aging.

Synthesis, structural characterization and influence on the phagocytic activity of human neutrophils of thiazoline and thiazine derivative ligands and their zinc(II) complexes

The zinc(II) complexes dichloro[2-(3,4-dichlorophenyl)imino-kappaN-(2-thiazolin-kappaN-2-yl)thiazolidine]zinc(II) (1) and dichloro[2-(3,4-dichlorophenyl)imino-kappaN-(4H-5,6-dihydro-1,3-thiazin-kappaN-2-yl)tetrahydrothiazine]zinc(II) (2) have been isolated and characterized in the solid state by X-ray diffraction, elemental analysis and IR spectra. In both complexes, the environment around the zinc(II) ion may be described as a distorted tetrahedral geometry, with the metallic atom coordinated to two chlorine atoms [Zn-Cl(1)=2.218(1)A; Zn-Cl(2)=2.221(1)A], one imino nitrogen [Zn-N(3)=2.042(2)A] and one thiazoline nitrogen [Zn-N(1)=2.022(2)A] in complex 1 and to two chlorine atoms [Zn-Cl(1)=2.216(1)A; Zn-Cl(2)=2.192(1)A], one imino nitrogen [Zn-N(3)=2.045(2)A] and one thiazine nitrogen [Zn-N(1)=2.039(2)A] in complex 2. In addition, we also report in this study the crystal structure of the 2-(3,4-dichlorophenyl)imino-N-(2-thiazolin-2-yl)thiazolidine (TdTn) ligand as well as the synthesis and characterization by X-ray diffraction, (1)H and (13)C NMR spectra, elemental analysis, IR and electronic spectra of the 2-(3,4-dichlorophenyl)imino-N-(4H-5,6-dihydro-1,3-thiazin-2-yl)tetrahydrothiazine (TzTz) ligand. Besides, we study the phagocytic function in humans neutrophils treated with each complex and ligand aforementioned.

Zinc-binding proteins (metallothionein and alpha-2 macroglobulin) and immunosenescence

Zinc is a relevant trace element for the efficiency of the entire immune system. The binding of zinc with some proteins, such as metallothioneins (MT) and alpha-2 macroglobulin (alpha-2M) is crucial for the immune efficiency during ageing and in age-related diseases, because these proteins may be involved in antagonistic pleiotropic effects. Indeed, the presence of chronic inflammation during ageing, generally, induces overexpression of these proteins that, due to their original biological function in fighting stressor agents, continuously sequester intracellular zinc. As a consequence, a low zinc ion availability may appear in aged organisms leading to impairments of the immune response at thymic and extrathymic levels with the risk of the appearance of age-related diseases. Therefore, MT and alpha-2M turn from protective in "young-adult age" to harmful agents in "ageing" following the basic assumption of an evolutionary theory of ageing, named the "antagonistic pleiotropy", which suggests that a trade off between early beneficial effects and late negative outcomes can occur at a genetic and molecular level. On the other hand, some polymorphisms of MT (MT2A) and alpha-2M have been associated with atherosclerosis or Alzheimer disease, respectively. Physiological zinc supplementation in elderly restores the thymic endocrine activity and innate immune response (NK cell cytotoxicity) and increases the survival rate in old mice. Therefore, zinc supplementation is useful to achieve health longevity because these zinc-binding proteins may regain their original protective task against oxidative damage with, thus, a beneficial impact on immune response.

Polymorphisms in MT1a gene coding region are associated with longevity in Italian Central female population

Metallothioneins (MTs) play a pivotal role in zinc-related cell homeostasis because of their high affinity for zinc, which is in turn fundamental for immune response and antioxidant activity. MTs regulate zinc homeostasis by binding zinc and releasing zinc at the occurrence for immune response. The zinc release by MT is very limited in chronic inflammation and ageing. Some polymorphisms of MTs gene, in particular MT1a sub-isoform, may affect this release that is a problem still unresolved in ageing. The screening in the present paper of two polymorphisms in MT1a gene has revealed for the first time that the polymorphism corresponding to a A/C (Asp/Thr) transition at 647 nt position in the Mt1a coding region is the more involved in the longevity, at least in old women, rather than the other corresponding to A/G (Lys/Arg) transition at 1,245 nt position. Concomitantly, for the +647 MT1a polymorphism, old and very old female with Asp/Asp genotype (called C-carriers) display higher zinc release by MT (detected by Zinpyr-1 fluorescent probe in presence of NO donor), low MT levels and reduced IL-6 plasma concentrations, suggesting its involvement in longevity and in lower inflammatory status. This fact is confirmed by the analysis of haplotypes in which the allele Asp is more involved in longevity. Therefore the +647 MT1a polymorphism more affects MTs induction and zinc release, which are indispensable to undertake the inflammatory status under control and subsequently to reach healthy longevity.

Plasticity of neuroendocrine-thymus interactions during ontogeny and ageing: role of zinc and arginine

Thymic re-growth and reactivation of thymic functions may be achieved in old animals by different endocrinological or nutritional manipulations such as, (a) treatment with melatonin, (b) implantation of a growth hormone (GH) secreting tumour cell line (GH3 cells) or treatment with exogenous GH, (c) castration or treatment with exogenous luteinizing hormone-releasing hormone (LHRH), (d) treatment with exogenous thyroxin or triiodothyronine, and (e) nutritional interventions such as arginine or zinc supplementation. These data strongly suggest that thymic involution is a phenomenon secondary to age-related alterations in neuroendocrine-thymus interactions and that it is the disruption of these interactions in old age that is responsible for age-associated immune-neuroendocrine dysfunctions. The targets involved in hormones-induced thymic reconstitution may directly or indirectly involve hormone receptors, cytokines, arginine, and a trace element such as zinc, which is pivotal for the efficiency of neuroendocrine-immune network during the whole life of an organism. The effect of GH, thyroid hormones, and LHRH may be due to specific hormone receptors on thymocytes and on thymic epithelial cells (TECs), which synthesize thymic peptides. Melatonin may also act through specific receptors on T-cells. In this context, the role of zinc, which turnover is reduced in old age, is pivotal because of its involvement through zinc fingers in the gene expression of hormone receptors. In addition, the effects of zinc are multifaceted: from the reactivation of zinc-dependent enzymes, to cell proliferation and apoptosis, to cytokines expression and to the reactivation of thymulin, which is a zinc-dependent thymic hormone required for intrathymic T-cell differentiation and maturation as well as for the homing of stem cells into the thymus. Zinc is also required for arginine action, via NO pathway. The role of zinc is therefore crucial in neuroendocrine-thymus interactions. According to data in animals and humans, the above reported endocrinological manipulations (GH, thyroid hormones, and melatonin) or arginine treatment may also act via zinc pool in restoring thymic activity in ageing allowing improvements on peripheral immune efficiency.

Nutrient-gene interaction in ageing and successful ageing. A single nutrient (zinc) and some target genes related to inflammatory/immune response

In this paper, we reviewed data regarding to the pivotal role played by the zinc-gene interaction in affecting some relevant cytokines (IL-6 and TNF-alpha) and heat shock proteins (Hsp70-2) in ageing, successful ageing (nonagenarians) and in some age-related diseases (atherosclerosis and infections). The polymorphisms of the genes codifying these proteins are predictive on one hand in longevity, such as IL-6 -174G/C locus, on the other hand 1267 Hsp70-2A/B or TNF-alpha -308G/A polymorphisms are associated to worsening atherosclerosis or severe infections, respectively, rather than longevity. Taking into account that longevity has a strong genetic component but, at the same time, is affected by life style and environmental factors, the analysis of these polymorphisms in association to some immune parameters (NK cell cytotoxicity) and nutritional factors (zinc) is a useful tool to unravel the role played by these genetic factors in longevity and in the appearance of age-related diseases. Indeed, these polymorphisms are associated with chronic inflammation, low zinc ion bioavailability, depressed innate immune response and high gene expression of metallothioneins, which have a limited zinc release for an optimal innate immune response in ageing. Therefore, the nutrient (zinc)-gene (IL-6, TNF-alpha and Hsp70-2) interaction is pivotal to keep under control the inflammatory/immune response with subsequent longevity, indicating these genes as "robust" for "healthy ageing".

Oxidative stress in leukocytes from young prematurely aging mice is reversed by supplementation with biscuits rich in antioxidants

Aging is associated with a progressive dysregulation of immune responses as a result of increased oxidative stress. Therefore, we have assessed the oxidative stress status of peritoneal leukocytes from young prematurely aging mice (PAM) as compared with non-prematurely aging mice (NPAM), as well as the effects on this oxidative stress of a dietary supplementation with biscuits rich in antioxidants (vitamin C, vitamin E, beta-carotenes, zinc and selenium). We found that, in the peritoneal leukocytes, the levels of several parameters of oxidation such as extracellular superoxide anion (O(2)(-)), Prostaglandin E(2) (PGE(2)), nitric oxide, oxidized glutathione (GSSG) and lipid peroxidation (malondialdehyde, MDA) were higher in PAM as compared with NPAM, whereas the antioxidant defences such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) activities, as well as reduced glutathione (GSH) levels, were decreased. Consequently, young PAM showed an oxidative stress in their leukocytes, which is characteristic of mice of an older chronological age. Antioxidant diet supplementation was able to restore redox homeostasis, increasing the antioxidant and decreasing the oxidant levels. Accordingly, supplementation with adequate levels of antioxidants, from an early age, could be useful to preserve health, especially in prematurely aging populations.

The -308G/A polymorphism of TNF-alpha influences immunological parameters in old subjects affected by infectious diseases

Abnormal increments of pro-inflammatory cytokines (IL-6 and TNF-alpha) characterize the outbreak of infectious diseases, which are the major cause of death in the elderly. A counterbalance to the inflammation is exerted by IL-10 with an inhibitory role on TNF-alpha production. As is well known, some cytokine gene polymorphisms influence the cytokine production, playing a role as susceptibility or resistance factors against immune-mediated and infectious disease. Genetic variations in the -308A/G locus for TNF-alpha seems to affect the clinical outcome of some infectious diseases. In fact, the -308A allele is associated with severe septic shock and death. On this basis, we have screened healthy old subjects, nonagenarians and old patients affected by the acute phase of chronic obstructive bronchitis and bronchopneumonia of bacteria origin for the -308G/A locus (PCR-RFLP). Subjects are grouped in A+ (AG, AA genotypes) and A- (GG genotype) and data on IL-6, TNF-alpha, IL-10, NK cell cytotoxicity, zinc and metallothioneins (MTs) gene expression (RT-PCR) were stratified according to different TNF-alpha genotypes. The frequency of the A allele was increased in infected patients in comparison with healthy old controls. No differences existed between A+ and A- young adult, old and nonagenarian controls in tested parameters. Conversely, A+-infected patients displayed elevated IL-6, TNF-alpha and MTmRNA, low IL-10 coupled with impaired NK cell cytotoxicity and lower zinc ion than A- patients. However, the data reported are gender independent. Therefore, the -308A polymorphism at the locus of TNF-alpha may be one of the susceptibility factor for infectious diseases in old persons, particularly considering its association to the increased release of pro-inflammatory cytokines and to the reduction of zinc release and MTs synthesis involved in the control of the inflammatory response. These data strongly suggest that the genetic screening of the -308G/A polymorphism may be a valid tool for identification of subjects needing a more appropriate therapy when affected by acute and/or recurrent infectious diseases.

Brain, aging and neurodegeneration: role of zinc ion availability

Actual fields of research in neurobiology are not only aimed at understanding the different aspects of brain aging but also at developing strategies useful to preserve brain compensatory capacity and to prevent the onset of neurodegenerative diseases. Consistent with this trend much attention has been addressed to zinc metabolism. In fact, zinc acts as a neuromodulator at excitatory synapses and has a considerable role in the stress response and in the functionality of zinc-dependent enzymes contributing to maintaining brain compensatory capacity. In particular, the mechanisms that modulate the free zinc pool are pivotal for safeguarding brain health and performance. Alterations in zinc homeostasis have been reported in Parkinson's and Alzheimer's disease as well as in transient forebrain ischemia, seizures and traumatic brain injury, but little is known regarding aged brain. There is much evidence that that age-related changes, frequently associated to a decline in brain functions and impaired cognitive performances, could be related to dysfunctions affecting the intracellular zinc ion availability. A general agreement emerges from studies of humans' and rodents' old brains about an increased expression of metallothionein (MT) isoforms I and II, but dyshomogenous results are reported for MT-III, and it is still uncertain whether these proteins maintain in aging the protective role, as it occurs in adult/young age. At the same time, there is considerable evidence that amyloid-beta deposition in Alzheimer's disease is induced by zinc, but the pathological significance and the causes of this phenomenon are still an open question. The scientific debate on the role of zinc and of some zinc-binding proteins in aging and neurodegenerative disorders, as well as on the beneficial effect of zinc supplementation in aged brain and neurodegeneration, is extensively discussed in this review.

Characterization of the hsp70 response in lymphoblasts from aged and centenarian subjects and differential effects of in vitro zinc supplementation

Human centenarians attract increasing interest as they hold some still undefined molecular mechanisms resulting in the achievement of exceptional old age. Recent data suggest the ability of centenarians to efficiently counter the increased cellular stress normally associated with ageing. The ubiquitous heat shock (HS) protein HSP70, expressed under the control of the heat shock transcription factor 1 (HSF-1), is recognized as one of the main chaperones associated with cell protection against stresses. In fact, HSP70 protein induction by heat, a classic well characterized cellular stress, was recently reported to be reduced in cells of most aged humans but not in centenarians. In order to investigate the molecular basis of this feature, we analyzed in vitro the time course expression of the hsp70 gene and the activation of HSF-1 in heat treated Epstein Barr virus transformed B-lymphocytes of centenarians. Our study demonstrates that lymphoblasts from centenarians maintain the transcriptional response of hsp70 gene to heat stress similar to young subjects. Such normal induction of hsp70 is associated to higher binding activity of HSF-1 that compensates an age-dependent delay in HSF-1 phosphorylation. Moreover, in vitro zinc supplementation had an age-dependent effect on hsp70 expression, indicating a role for this nutritionally important molecule and suggesting its involvement in cellular stress responses.