Zinc and immunoresistance to infection in aging: new biological tools

Dietary Zn deficiency, the current situation and potential solutions

Zinc (Zn) deficiency is a worldwide problem, and this review presents an overview of the magnitude of Zn deficiency with a particular emphasis on present global challenges, current recommendations for Zn intake, and factors that affect dietary requirements. The challenges of monitoring Zn status are clarified together with the discussion of relevant Zn bioaccessibility and bioavailability issues. Modern lifestyle factors that may exacerbate Zn deficiency and new strategies of reducing its effects are presented. Biofortification, as a potentially useful strategy for improving Zn status in sensitive populations, is discussed. The review proposes potential actions that could deliver promising results both in terms of monitoring dietary and physiological Zn status as well as in alleviating dietary Zn deficiency in affected populations.

Multifunctional Metallothioneins as a Target for Neuroprotection in Parkinson's Disease

Parkinson's disease (PD) is characterized by motor symptoms based on a loss of nigrostriatal dopaminergic neurons and by non-motor symptoms which precede motor symptoms. Neurodegeneration accompanied by an accumulation of α-synuclein is thought to propagate from the enteric nervous system to the central nervous system. The pathogenesis in sporadic PD remains unknown. However, many reports indicate various etiological factors, such as oxidative stress, inflammation, α-synuclein toxicity and mitochondrial impairment, drive neurodegeneration. Exposure to heavy metals contributes to these etiopathogenesis and increases the risk of developing PD. Metallothioneins (MTs) are cysteine-rich metal-binding proteins; MTs chelate metals and inhibit metal-induced oxidative stress, inflammation and mitochondrial dysfunction. In addition, MTs possess antioxidative properties by scavenging free radicals and exert anti-inflammatory effects by suppression of microglial activation. Furthermore, MTs recently received attention as a potential target for attenuating metal-induced α-synuclein aggregation. In this article, we summarize MTs expression in the central and enteric nervous system, and review protective functions of MTs against etiopathogenesis in PD. We also discuss neuroprotective strategies for the prevention of central dopaminergic and enteric neurodegeneration by targeting MTs. This review highlights multifunctional MTs as a target for the development of disease-modifying drugs for PD.

Impact of Maternal and Offspring Dietary Zn Supplementation on Growth Performance and Antioxidant and Immune Function of Offspring Broilers

The current study investigated the effects of the maternal Zn source in conjunction with their offspring’s dietary Zn supplementation on the growth performance, antioxidant status, Zn concentration, and immune function of the offspring. It also explored whether there is an interaction between maternal Zn and their offspring’s dietary Zn. One-day-old Lingnan Yellow-feathered broilers (n = 800) were completely randomized (n = 4) between two maternal dietary supplemental Zn sources [maternal Zn−Gly (oZn) vs. maternal ZnSO4 (iZn)] × two offspring dietary supplemental Zn doses [Zn-unsupplemented control diet (CON), the control diet + 80 mg of Zn/kg of diet as ZnSO4]. oZn increased progeny ADG and decreased offspring mortality across all periods, especially during the late periods (p < 0.05). The offspring diet supplemented with Zn significantly improved ADG and decreased offspring mortality over the whole period compared with the CON group (p < 0.05). There were significant interactions between the maternal Zn source and offspring dietary Zn with regards to progeny mortality during the late phase and across all phases as a whole (p < 0.05). Compared with the iZn group, the oZn treatment significantly increased progeny liver and serum Zn concentrations; antioxidant capacity in the liver, muscle, and serum; and the IgM concentration in serum; while also decreasing progeny serum IL-1 and TNF-α cytokine secretions (p < 0.05). Similar results were observed when the offspring diet was supplemented with Zn compared with the CON group; moreover, adding Zn to the offspring diet alleviated progeny stress by decreasing corticosterone levels in the serum when compared to the CON group (p < 0.05). In conclusion, maternal Zn−Gly supplementation increased progeny performance and decreased progeny mortality and stress by increasing progeny Zn concentration, antioxidant capacity, and immune function compared with the same Zn levels from ZnSO4. Simultaneously, Zn supplementation in the progeny’s diet is necessary for the growth of broilers.

Relationship of serum copper and zinc with kidney function and urinary albumin to creatinine ratio: Cross-sectional data from the NHANES 2011-2016

BACKGROUND & OBJECTIVE

Chronic kidney disease (CKD) is a common condition in worldwide with underlying causes. The role of trace elements such as copper and zinc in CKD is uncertain. We aimed to examine the relationship of serum copper and zinc with kidney function status and explore its possible effect modifiers in the general population.

METHODS

Data from 5353 National Health and Nutrition Examination Survey (NHANES) participants from 2011 to 2016 were analyzed for the role of trace elements in the age range 18 to 80 years. The kidney outcomes were reduced estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 and increased urinary albumin-to-creatinine ratio (ACR) ≥ 30 mg/g.

RESULTS

Findings showed a significant positive association between serum copper and urinary ACR (OR = 1.04, 95% CI = 1.00-1.07). Serum copper levels of 18.0 μmol/L (median) or higher (reference level <18.0 μmol/L) were significantly associated with increased urinary ACR (OR = 1.67, 95% CI = 1.21-2.31) after adjusting for confounding factors. In contrast, there was a significant inverse association between serum zinc and reduced eGFR (OR = 0.89,95% CI = 0.81-0.99). Where serum zinc level was greater than 12.3 μmol/L (median), the prevalence of reduced eGFR was lower (OR = 0.65, 95% CI = 0.16-0.60). In addition, a stratified analysis based on various risk factors found that in those individuals with serum albumin greater than 43 g/L or systolic blood pressure greater than 120 mmHg, positive correlations between serum copper and risk of increased urinary ACR was more significant.

CONCLUSIONS

Our findings suggest that the reference levels of serum copper and zinc levels in healthy individuals may be different from current understanding. If further studies substantiate the same, the results will be a useful guide for designing future clinical trials and nutritional guidelines.

The ion channel TRPM7 regulates zinc-depletion-induced MDMX degradation

Zinc deficiency has been linked to human diseases, including cancer. MDMX, a crucial zinc-containing negative regulator of p53, has been found to be amplified or overexpressed in various cancers and implicated in the cancer initiation and progression. We report here that zinc depletion by the ion chelator TPEN or Chelex resin results in MDMX protein degradation in a ubiquitination-independent and 20S proteasome-dependent manner. Restoration of zinc led to recovery of cellular levels of MDMX. Further, TPEN treatment inhibits growth of the MCF-7 breast cancer cell line, which is partially rescued by overexpression of MDMX. Moreover, in a mass-spectrometry-based proteomics analysis, we identified TRPM7, a zinc-permeable ion channel, as a novel MDMX-interacting protein. TRPM7 stabilizes and induces the appearance of faster migrating species of MDMX on SDS-PAGE. Depletion of TRPM7 attenuates, while TRPM7 overexpression facilitates, the recovery of MDMX levels upon adding back zinc to TPEN-treated cells. Importantly, we found that TRPM7 inhibition, like TPEN treatment, decreases breast cancer cell MCF-7 proliferation and migration. The inhibitory effect on cell migration upon TRPM7 inhibition is also partially rescued by overexpression of MDMX. Together, our data indicate that TRPM7 regulates cellular levels of MDMX in part by modulating the intracellular Zn²⁺ concentration to promote tumorigenesis.

Theoretical study of spodium bonding in the active site of three Zn-proteins and several model systems

In this manuscript, three examples retrieved from the PDB are selected to demonstrate the existence and relevance of spodium bonding (SpB) in biological systems. SpB is defined as an attractive noncovalent interaction between elements of group 12 of the periodic table acting as a Lewis acid and any atom or group of atoms acting as an electron donor. The utilization of this term (SpB) is convenient to differentiate classical coordination bonds from noncovalent interactions. In the latter, the distance between the electron rich and the spodium atoms is longer than the sum of the covalent radii but shorter than the sum of the van der Waals radii. In most Zn-dependent metalloenzymes, the spodium atom is bonded to three imidazole moieties belonging to the side chains of histidine amino-acids. Herein, in addition to the investigation of the SpB in the active site of three exemplifying enzymes, theoretical models where the Zn(ii) atom is bonded either to three imidazole or triazole ligands are used in order to investigate the strength of the SpB and its competition with hydrogen bonding. A series of Lewis bases and anions have been used as SpB acceptors combined with six SpB donors (receptors) of general formula [ZnY3X]+ (Y = imidazole and triazole and X = Cl, N3 and SCH3). In addition to the investigation of the energetic and geometric features of the complexes, the SpB interactions have been further characterized using the natural bond orbital (NBO) method, quantum theory of "atoms-in-molecules" and the noncovalent interaction plot (NCI plot).

Highly Photoluminescent Nitrogen- and Zinc-Doped Carbon Dots for Efficient Delivery of CRISPR/Cas9 and mRNA

Safe and efficient delivery of CRISPR/Cas9 systems is still a challenge. Here we report the development of fluorescent nitrogen- and zinc-doped carbon dots (N-Zn-doped CDs) using one-step microwave-aided pyrolysis based on citric acid, branched PEI_25k, and different zinc salts. These versatile nanovectors with a quantum yield of around 60% could not only transfect large CRISPR plasmids (∼9 kb) with higher efficiency (80%) compared to PEI_25k and lipofectamine 2000 (Lipo 2K), but they also delivered mRNA into HEK 293T cells with the efficiency 20 times greater than and equal to that of PEI_25k and Lipo 2K, respectively. Unlike PEI_25k, N-Zn-doped CDs exhibited good transfection efficiency even at low plasmid doses and in the presence of 10% fetal bovine serum (FBS). Moreover, these nanovectors demonstrated excellent efficiency in GFP gene disruption by transferring plasmid encoding Cas9 and sgRNA targeting GFP as well as Cas9/sgRNA ribonucleoproteins into HEK 293T-GFP cells. Hence, N-Zn-doped CDs with remarkable photoluminescence properties and high transfection efficiency in the delivery of both CRISPR complexes and mRNA provide a promising platform for developing safe, efficient, and traceable delivery systems for biological research.

Assessment of Concentrations of Heavy Metals in Postmyocardial Infarction Patients and Patients Free from Cardiovascular Event

Cardiovascular diseases (CVDs) constitute the first cause of death among the population of developing and developed countries. Atherosclerosis, which is a disorder with multifactorial etiopathogenesis, underlies most CVDs. The available literature includes ample research studies on the influence of classic cardiovascular (CV) risk factors. However, environmental exposure to heavy metals, among other substances, is still an unappreciated risk factor of CVDs. This study aimed to assess the concentration of some heavy metals (copper (Cu), zinc (Zn), manganese (Mn), cobalt (Co), and iron (Fe)) in the blood serum of postmyocardial infarction (post-MI) patients and patients free from myocardial infarction (MI) as well as estimate the relationship between the occurrence of MI and increased concentration of heavy metals. The concentration of heavy metals (Cu, Zn, Mn, Co, and Fe) was assessed using the inductively coupled plasma mass spectrometry technique in a group of 146 respondents divided into two groups: post-MI group (study group (SG), n = 74) and group without cardiovascular event (CVE) having a low CV risk (control group (CG), n = 72). The concentration of the analyzed heavy metals was higher in SG. All the heavy metals showed a significant diagnostic value (p < 0.001). The highest value of area under the curve (AUC) was observed for manganese (Mn) (0.955; 95% confidence interval (CI) = 0.922–0.988), while the lowest value was found for zinc (Zn) (0.691; 95% CI = 0.599–0.782). In one-dimensional models, high concentrations of each of the analyzed heavy metals significantly increased the chances of having MI from 7-fold (Cu) to 128-fold (Mn). All the models containing a particular metal showed a significant and high discrimination value for MI occurrence (AUC 0.72–0.92). Higher concentrations of Cu, Zn, Mn, Co, and Fe were found to considerably increase the chances of having MI. Considering the increasingly higher environmental exposure to heavy metals in recent times, their concentrations can be distinguished as a potential risk factor of CVDs.

Recent aspects of the effects of zinc on human health

Zinc (Zn) is one of the most important essential nutrients of great public health significance. It is involved in numerous biological functions and it is considered as a multipurpose trace element, due to its capacity to bind to more than 300 enzymes and more than 2000 transcriptional factors. Its role in biochemical pathways and cellular functions, such as the response to oxidative stress, homeostasis, immune responses, DNA replication, DNA damage repair, cell cycle progression, apoptosis and aging is significant. Zn is required for the synthesis of protein and collagen, thus contributing to wound healing and a healthy skin. Metallothioneins are metal-binding proteins and they are potent scavengers of heavy metals, including Zn, and protect the organism against stress. Zn deficiency is observed almost in 17% of the global population and affects many organ systems, leading to dysfunction of both humoral and cell-mediated immunity, thus increasing the susceptibility to infection. This review gives a thorough insight into the most recent evidence on the association between Zn biochemistry and human pathologies, epigenetic processes, gut microbial composition, drug targets and nanomedicine.

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.

Induction of Metallothionein in Rat Liver by Zinc Exposure: A Dose and Time Dependent Study

Metallothioneins (MTs) are low molecular weight ubiquitous metalloproteins with high cysteine (thiol) content. The intracellular concentration of zinc (Zn) is tightly regulated and MT plays a crucial role in it. The present study investigates the relationship between the Zn status (as a function of Zn concentration and time) in the rat liver and the occurrence of hepatic MT. For dose dependent study, four experimental groups, one control and three receiving different levels of metal supplementation, were chosen [Group 1 control and Group 2, Group 3, Group 4 receiving subcutaneous dose of 10, 50 and 100 mg of Zn/kg body weight (in the form of ZnSO₄·7H₂O), respectively]. For the time dependent expression of MT, again four experimental groups, i.e. Group 5 control and Group 6, Group 7, Group 8 receiving 50 mg of Zn/kg body weight (in the form of ZnSO₄·7H₂O) subcutaneously and sacrificed at different time intervals after last injection i.e. 6, 18, 48 h, respectively were chosen. Isolation of MT was done by using combination of gel filtration and ion exchange chromatography while characterization of MT fraction was carried in the wavelength range 200-400 nm. Expression of MT was studied by using Western blot analysis. The results revealed that the MT expression increases with increasing the dose of Zn administered and maximum at 18 h after last Zn injection. Accumulation of MT with increase dose would help in maintaining the intracellular Zn concentration by its sequestration which further reduces the possibility of undesirable binding of Zn to other proteins significantly and maintains Zn homeostasis. The maximum expression of MT at 18 h is indicative of its half life.

Hemocyte-mediated phagocytosis differs between honey bee (Apis mellifera) worker castes

Honey bees as other insects rely on the innate immune system for protection against diseases. The innate immune system includes the circulating hemocytes (immune cells) that clear pathogens from hemolymph (blood) by phagocytosis, nodulation or encapsulation. Honey bee hemocyte numbers have been linked to hemolymph levels of vitellogenin. Vitellogenin is a multifunctional protein with immune-supportive functions identified in a range of species, including the honey bee. Hemocyte numbers can increase via mitosis, and this recruitment process can be important for immune system function and maintenance. Here, we tested if hemocyte mediated phagocytosis differs among the physiologically different honey bee worker castes (nurses, foragers and winter bees), and study possible interactions with vitellogenin and hemocyte recruitment. To this end, we adapted phagocytosis assays, which—together with confocal microscopy and flow cytometry—allow qualitative and quantitative assessment of hemocyte performance. We found that nurses are more efficient in phagocytic uptake than both foragers and winter bees. We detected vitellogenin within the hemocytes, and found that winter bees have the highest numbers of vitellogenin-positive hemocytes. Connections between phagocytosis, hemocyte-vitellogenin and mitosis were worker caste dependent. Our results demonstrate that the phagocytic performance of immune cells differs significantly between honey bee worker castes, and support increased immune competence in nurses as compared to forager bees. Our data, moreover, provides support for roles of vitellogenin in hemocyte activity.

ICP-MS/MS-Based Ionomics: A Validated Methodology to Investigate the Biological Variability of the Human Ionome

We here describe the development, validation and application of a quantitative methodology for the simultaneous determination of 29 elements in human serum using state-of-the-art inductively coupled plasma triple quadrupole mass spectrometry (ICP-MS/MS). This new methodology offers high-throughput elemental profiling using simple dilution of minimal quantity of serum samples. We report the outcomes of the validation procedure including limits of detection/quantification, linearity of calibration curves, precision, recovery and measurement uncertainty. ICP-MS/MS-based ionomics was used to analyze human serum of 120 older adults. Following a metabolomic data mining approach, the generated ionome profiles were subjected to principal component analysis revealing gender and age-specific differences. The ionome of female individuals was marked by higher levels of calcium, phosphorus, copper and copper to zinc ratio, while iron concentration was lower with respect to male subjects. Age was associated with lower concentrations of zinc. These findings were complemented with additional readouts to interpret micronutrient status including ceruloplasmin, ferritin and inorganic phosphate. Our data supports a gender-specific compartmentalization of the ionome that may reflect different bone remodelling in female individuals. Our ICP-MS/MS methodology enriches the panel of validated "Omics" approaches to study molecular relationships between the exposome and the ionome in relation with nutrition and health.

Oxidative stress-induced increase of intracellular zinc in astrocytes decreases their functional expression of P2X7 receptors and engulfing activity

Exposure of astrocytes to oxidative stress induces an increase of intracellular labile zinc and a decrease of functional expression of P2X7 receptorviaits translocation from the plasma membrane to the cytosol by altering the expression profile of P2X7 receptor and its splice variants, leading to a decrease of their engulfing activity.

Serotonin 1A Receptors on Astrocytes as a Potential Target for the Treatment of Parkinson's Disease

Astrocytes are the most abundant neuron-supporting glial cells in the central nervous system. The neuroprotective role of astrocytes has been demonstrated in various neurological disorders such as amyotrophic lateral sclerosis, spinal cord injury, stroke and Parkinson’s disease (PD). Astrocyte dysfunction or loss-of-astrocytes increases the susceptibility of neurons to cell death, while astrocyte transplantation in animal studies has therapeutic advantage. We reported recently that stimulation of serotonin 1A (5-HT_1A) receptors on astrocytes promoted astrocyte proliferation and upregulated antioxidative molecules to act as a neuroprotectant in parkinsonian mice. PD is a progressive neurodegenerative disease with motor symptoms such as tremor, bradykinesia, rigidity and postural instability, that are based on selective loss of nigrostriatal dopaminergic neurons, and with non-motor symptoms such as orthostatic hypotension and constipation based on peripheral neurodegeneration. Although dopaminergic therapy for managing the motor disability associated with PD is being assessed at present, the main challenge remains the development of neuroprotective or disease-modifying treatments. Therefore, it is desirable to find treatments that can reduce the progression of dopaminergic cell death. In this article, we summarize first the neuroprotective properties of astrocytes targeting certain molecules related to PD. Next, we review neuroprotective effects induced by stimulation of 5-HT_1A receptors on astrocytes. The review discusses new promising therapeutic strategies based on neuroprotection against oxidative stress and prevention of dopaminergic neurodegeneration.

Effects of Dietary Zinc Pectin Oligosaccharides Chelate Supplementation on Growth Performance, Nutrient Digestibility and Tissue Zinc Concentrations of Broilers

The experiment was conducted to investigate the effects of zinc pectin oligosaccharides (Zn-POS) chelate on growth performance, nutrient digestibility, and tissue zinc concentrations of Arbor Acre broilers aged from 1 to 42 days. A total of 576 1-day-old broilers were randomly assigned into 4 groups with 9 replicates per group and 16 chicks per replicate. Chicks were fed either a basal diet (control) or basal diet supplemented with Zn-POS at 300 (Zn-POS-300), 600 (Zn-POS-600), or 900 mg/kg (Zn-POS-900), respectively, for 42 days. A 3-day metabolism trial was conducted during the last week of the experiment feeding. The average daily gain and the average daily feed intake of Zn-POS-600 were significantly higher (P < 0.05) than those of either the control, Zn-POS-300, or Zn-POS-900. Zn-POS-600 had the highest apparent digestibility of dry matter, crude protein, and metabolic energy among all groups. The control group had the lowest apparent digestibility of dry matter (P < 0.05), whereas the apparent digestibility of dry matter in Zn-POS-600 was higher (P < 0.05) than that of Zn-POS-300. The apparent digestibility of crude protein in Zn-POS-600 or Zn-POS-900 was higher (P < 0.05) compared to Zn-POS-300 or the control. The apparent digestibility of metabolic energy in Zn-POS-600 or Zn-POS-900 was higher (P < 0.05) than that of Zn-POS-300. Zn-POS-600 had the highest liver zinc concentrations (P < 0.05), while Zn-POS-900 had the highest pancreatic zinc concentrations (P < 0.05). Our data suggest that the supplementation of 600 mg/kg Zn-POS is optimal in improving the average daily gain and the average daily feed intake, utilization of dietary dry matter and crude protein, and increasing tissue zinc concentrations in liver and pancreas of broilers.

Biodegradable Metals for Cardiovascular Stents: from Clinical Concerns to Recent Zn-Alloys

Metallic stents are used to promote revascularization and maintain patency of plaqued or damaged arteries following balloon angioplasty. To mitigate the long-term side effects associated with corrosion-resistant stents (i.e., chronic inflammation and late stage thrombosis), a new generation of so-called "bioabsorbable" stents is currently being developed. The bioabsorbable coronary stents will corrode and be absorbed by the artery after completing their task as vascular scaffolding. Research spanning the last two decades has focused on biodegradable polymeric, iron-based, and magnesium-based stent materials. The inherent mechanical and surface properties of metals make them more attractive stent material candidates than their polymeric counterparts. A third class of metallic bioabsorbable materials that are based on zinc has been introduced in the last few years. This new zinc-based class of materials demonstrates the potential for an absorbable metallic stent with the mechanical and biodegradation characteristics required for optimal stent performance. This review compares bioabsorbable materials and summarizes progress towards bioabsorbable stents. It emphasizes the current understanding of physiological and biological benefits of zinc and its biocompatibility. Finally, the review provides an outlook on challenges in designing zinc-based stents of optimal mechanical properties and biodegradation rate.

Zinc inhibits aflatoxin B1-induced cytotoxicity and genotoxicity in human hepatocytes (HepG2 cells)

Aflatoxin B1 (AFB1) has strong carcinogenicity. Consumption of AFB1-contaminated agricultural products and the occurrence of hepatocellular carcinoma have received widespread attention. The aim of this paper was to investigate whether zinc supplementation could inhibit AFB1-induced cytotoxicity and genotoxicity in HepG2 cells and the mechanism of this inhibition. Our data suggest that zinc sources can relieve a certain degree of AFB1-induced cytotoxicity and genotoxicity by protecting against apoptotic body formation and DNA strand breaks, affecting S phase cell cycle arrest, reducing 8-OHdG formation, inhibiting global DNA hypomethylation and regulating gene expression in antioxidation, zinc-association and apoptosis processes. Consequently, zinc stabilizes the integrity of DNA and improves cell survival. These data provides new insights into the protective role of zinc in alleviating AFB1-induced cytotoxicity and mediating epigenetic changes in hepatocytes, demonstrating that zinc sources have detoxification properties in mycotoxin-induced toxicity.

Heavy Metals and Human Health: Mechanistic Insight into Toxicity and Counter Defense System of Antioxidants

Heavy metals, which have widespread environmental distribution and originate from natural and anthropogenic sources, are common environmental pollutants. In recent decades, their contamination has increased dramatically because of continuous discharge in sewage and untreated industrial effluents. Because they are non-degradable, they persist in the environment; accordingly, they have received a great deal of attention owing to their potential health and environmental risks. Although the toxic effects of metals depend on the forms and routes of exposure, interruptions of intracellular homeostasis include damage to lipids, proteins, enzymes and DNA via the production of free radicals. Following exposure to heavy metals, their metabolism and subsequent excretion from the body depends on the presence of antioxidants (glutathione, α-tocopherol, ascorbate, etc.) associated with the quenching of free radicals by suspending the activity of enzymes (catalase, peroxidase, and superoxide dismutase). Therefore, this review was written to provide a deep understanding of the mechanisms involved in eliciting their toxicity in order to highlight the necessity for development of strategies to decrease exposure to these metals, as well as to identify substances that contribute significantly to overcome their hazardous effects within the body of living organisms.

The role of intracellular zinc release in aging, oxidative stress, and Alzheimer's disease

Brain aging is marked by structural, chemical, and genetic changes leading to cognitive decline and impaired neural functioning. Further, aging itself is also a risk factor for a number of neurodegenerative disorders, most notably Alzheimer’s disease (AD). Many of the pathological changes associated with aging and aging-related disorders have been attributed in part to increased and unregulated production of reactive oxygen species (ROS) in the brain. ROS are produced as a physiological byproduct of various cellular processes, and are normally detoxified by enzymes and antioxidants to help maintain neuronal homeostasis. However, cellular injury can cause excessive ROS production, triggering a state of oxidative stress that can lead to neuronal cell death. ROS and intracellular zinc are intimately related, as ROS production can lead to oxidation of proteins that normally bind the metal, thereby causing the liberation of zinc in cytoplasmic compartments. Similarly, not only can zinc impair mitochondrial function, leading to excess ROS production, but it can also activate a variety of extra-mitochondrial ROS-generating signaling cascades. As such, numerous accounts of oxidative neuronal injury by ROS-producing sources appear to also require zinc. We suggest that zinc deregulation is a common, perhaps ubiquitous component of injurious oxidative processes in neurons. This review summarizes current findings on zinc dyshomeostasis-driven signaling cascades in oxidative stress and age-related neurodegeneration, with a focus on AD, in order to highlight the critical role of the intracellular liberation of the metal during oxidative neuronal injury.

A potent combination microbicide that targets SHIV-RT, HSV-2 and HPV

Prevalent infection with human herpes simplex 2 (HSV-2) or human papillomavirus (HPV) is associated with increased human immunodeficiency virus (HIV) acquisition. Microbicides that target HIV as well as these sexually transmitted infections (STIs) may more effectively limit HIV incidence. Previously, we showed that a microbicide gel (MZC) containing MIV-150, zinc acetate (ZA) and carrageenan (CG) protected macaques against simian-human immunodeficiency virus (SHIV-RT) infection and that a ZC gel protected mice against HSV-2 infection. Here we evaluated a modified MZC gel (containing different buffers, co-solvents, and preservatives suitable for clinical testing) against both vaginal and rectal challenge of animals with SHIV-RT, HSV-2 or HPV. MZC was stable and safe in vitro (cell viability and monolayer integrity) and in vivo (histology). MZC protected macaques against vaginal (p<0.0001) SHIV-RT infection when applied up to 8 hours (h) prior to challenge. When used close to the time of challenge, MZC prevented rectal SHIV-RT infection of macaques similar to the CG control. MZC significantly reduced vaginal (p<0.0001) and anorectal (p = 0.0187) infection of mice when 10(6) pfu HSV-2 were applied immediately after vaginal challenge and also when 5×10(3) pfu were applied between 8 h before and 4 h after vaginal challenge (p<0.0248). Protection of mice against 8×10(6) HPV16 pseudovirus particles (HPV16 PsV) was significant for MZC applied up to 24 h before and 2 h after vaginal challenge (p<0.0001) and also if applied 2 h before or after anorectal challenge (p<0.0006). MZC provides a durable window of protection against vaginal infection with these three viruses and, against HSV-2 and HPV making it an excellent candidate microbicide for clinical use.

Micronutrient-gene interactions related to inflammatory/immune response and antioxidant activity in ageing and inflammation. A systematic review

Recent longitudinal studies in dietary daily intake in human centenarians have shown that a satisfactory content of some micronutrients within the cells maintain several immune functions, a low grade of inflammation and preserve antioxidant activity. Micronutrients (zinc, copper, selenium) play a pivotal role in maintaining and reinforcing the performances of the immune and antioxidant systems as well as in affecting the complex network of the genes (nutrigenomic) with anti- and pro-inflammatory tasks. Genes of pro- and anti-inflammatory cytokines and some key regulators of trace elements homeostasis, such as Metallothioneins (MT), are involved in the susceptibility to major geriatric disease/disorders. Moreover, the genetic inter-individual variability may affect the nutrients' absorption (nutrigenetic) with altered effects on inflammatory/immune response and antioxidant activity. The interaction between genetic factors and micronutrients (nutrigenomic and nutrigenetic approaches) may influence ageing and longevity because the micronutrients may become also toxic. This review reports the micronutrient-gene interactions in ageing and their impact on the healthy state with a focus on the method of protein-metal speciation analysis. The association between micronutrient-gene interactions and the protein-metal speciation analysis can give a complete picture for a personalized nutrient supplementation or chelation in order to reach healthy ageing and longevity.

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.

Functional role of intracellular labile zinc in pulmonary endothelium

After iron, zinc is the most abundant essential trace metal. Intracellular zinc ([Zn]_i) is maintained across a wide range of cells and species in a tight quota (100 to 500 μM) by a dynamic process of transport, intracellular vesicular storage, and binding to a large number of proteins (estimated at 3-10% of human proteome). As such, zinc is an integral component of numerous metalloenzymes, structural proteins, and transcription factors. It is generally assumed that a vanishingly small component of [Zn]_i, referred to as free or labile zinc, and operationally defined as the pool sensitive to chelation (by agents such as N, N, N’, N’-tetrakis [2-pyridylmethyl] ethylenediamine [TPEN]) and capable of detection by a variety of chemical and genetic sensors, participates in signal transduction pathways. Zinc deficiencies, per se, can arise from acquired (malnutrition, alcoholism) or genetic (mutations in molecules affecting zinc homeostasis, the informative and first example being acrodermatitis enteropathica) factors or as a component of various diseases (e.g., sickle cell disease, cystic fibrosis, sepsis). Hypozincemia has profound effects on developing humans, and all facets of physiological function (neuronal, endocrine, immunological) are affected, although considerably less is known regarding cardiovascular pathophysiology. In this review, we provide an update on current knowledge of molecular and cellular aspects of zinc homeostasis and then focus on implications of zinc signaling in pulmonary endothelium as it relates to programmed cell death, altered contractility, and septic and aseptic injury to this segment of the lung.

The effects of new Alibernet red wine extract on nitric oxide and reactive oxygen species production in spontaneously hypertensive rats

We aimed to perform a chemical analysis of both Alibernet red wine and an alcohol-free Alibernet red wine extract (AWE) and to investigate the effects of AWE on nitric oxide and reactive oxygen species production as well as blood pressure development in normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHRs). Total antioxidant capacity together with total phenolic and selected mineral content was measured in wine and AWE. Young 6-week-old male WKY and SHR were treated with AWE (24,2 mg/kg/day) for 3 weeks. Total NOS and SOD activities, eNOS and SOD1 protein expressions, and superoxide production were determined in the tissues. Both antioxidant capacity and phenolic content were significantly higher in AWE compared to wine. The AWE increased NOS activity in the left ventricle, aorta, and kidney of SHR, while it did not change NOS activity in WKY rats. Similarly, increased SOD activity in the plasma and left ventricle was observed in SHR only. There were no changes in eNOS and SOD1 expressions. In conclusion, phenolics and minerals included in AWE may contribute directly to increased NOS and SOD activities of SHR. Nevertheless, 3 weeks of AWE treatment failed to affect blood pressure of SHR.

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.

Interferon-alpha-2a and zinc combination therapy in children with chronic hepatitis B infection

Zinc has been reported to enhance the response to interferon (IFN) or PEG-IFN plus ribavirin therapy, improve liver function, and ameliorate hematologic side effects in patients with chronic hepatitis C. However, the role of zinc supplementation during IFN therapy in chronic hepatitis B infection (CHB) remains unclear. We therefore aimed to report the results of zinc and IFN-alpha-2a therapy in children with CHB. Twenty-two naive, HBeAg-positive children (mean age 10.4 ± 4.4 years) received IFN-α2a (9 MU/m(2) sc) for 6 months plus peroral zinc (7.5 mg/day for <10 years and 10 mg/day for >10 years) for 12 months. Serum zinc, alanine aminotransferase (ALT), complete blood count, hepatitis B virus DNA (HBV DNA), and serological markers were measured. Histological (HR) and sustained response (SR) were evaluated at 6 months after completion of therapy. Normalization of ALT, HBeAg seroconversion, and HBV DNA < 10,000 copies/ml were considered as SR. HR was defined as decrease in Knodell histological activity index (HAI) score by at least 2 points compared to baseline. End of therapy ALT level and log HBV DNA were significantly lower than pretherapy levels (p = 0.001 and p = 0.001, respectively), while zinc level was not different. Portal inflammation score significantly decreased after therapy (p = 0.043), however, total HAI and other HAI components were not different. SR and HR were 25% and 52.9%. In conclusion as a first study investigating the effect of zinc and IFN combination therapy in children with CHB, SR and HR rates were not better than previously reported monotherapy or combination therapies.

Zinc and human health: an update

The importance of micronutrients in health and nutrition is undisputable, and among them, zinc is an essential element whose significance to health is increasingly appreciated and whose deficiency may play an important role in the appearance of diseases. Zinc is one of the most important trace elements in the organism, with three major biological roles, as catalyst, structural, and regulatory ion. Zinc-binding motifs are found in many proteins encoded by the human genome physiologically, and free zinc is mainly regulated at the single-cell level. Zinc has critical effect in homeostasis, in immune function, in oxidative stress, in apoptosis, and in aging, and significant disorders of great public health interest are associated with zinc deficiency. In many chronic diseases, including atherosclerosis, several malignancies, neurological disorders, autoimmune diseases, aging, age-related degenerative diseases, and Wilson's disease, the concurrent zinc deficiency may complicate the clinical features, affect adversely immunological status, increase oxidative stress, and lead to the generation of inflammatory cytokines. In these diseases, oxidative stress and chronic inflammation may play important causative roles. It is therefore important that status of zinc is assessed in any case and zinc deficiency is corrected, since the unique properties of zinc may have significant therapeutic benefits in these diseases. In the present paper, we review the zinc as a multipurpose trace element, its biological role in homeostasis, proliferation and apoptosis and its role in immunity and in chronic diseases, such as cancer, diabetes, depression, Wilson's disease, Alzheimer's disease, and other age-related diseases.

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.

Zinc, metallothioneins and immunosenescence

Ageing is an inevitable biological process with gradual and spontaneous biochemical and physiological changes and increased susceptibility to diseases. The nutritional factor, zinc, may remodel these changes with subsequent healthy ageing, because zinc improves the inflammatory/immune response as shown by in vitro and in vivo studies. The intracellular zinc homeostasis is regulated by buffering metallothioneins (MT) and zinc transporters (ZnT and ZIP families) that mediate the intracellular zinc signalling assigning to zinc a role of ‘second messenger’. In ageing, the intracellular zinc homeostasis is altered, because high MT are unable to release zinc and some zinc transporters deputed to zinc influx (ZIP family) are defective leading to low intracellular zinc content for the immune efficiency. Physiological zinc supplementation in the elderly improves these functions. However, the choice of old subjects for zinc supplementation has to be performed in relation to the specific genetic background of MT and IL-6, because the latter is involved both in MTmRNA and in intracellular zinc homeostasis. Old subjects carrying GG genotypes (C–carriers) in the IL-6–174G/C locus display high IL-6, low intracellular zinc content, impaired innate immunity and enhanced MT. Old subjects carrying GC and CC genotypes (C+carriers) display satisfactory intracellular zinc content, adequate innate immunity and are more prone to reach longevity. Zinc supplementation in old C–carriers restores natural killer cell cytotoxicity and zinc status. The genetic variations of the IL-6−174G/C locus when associated with those of the MT1A+647A/C locus are useful tools for the choice of old people for zinc supplementation.

Effects of zinc glycine chelate on growth, hematological, and immunological characteristics in broilers

Three hundred sixty healthy Ross x Ross 1-day-old broilers were used to study the effects of zinc glycine chelate (Zn-Gly) on growth performance, hematological, and immunological characteristics. All broilers were randomly assigned into six treatments. Diets were as follows: (1) control (containing 29.3 mg Zn kg(-1) basic diet [0-3 weeks] and 27.8 mg Zn kg(-1) [4-6 weeks]); (2) basic diet plus 30 mg Zn kg(-1) from Zn-Gly; (3) basic diet plus 60 mg Zn kg(-1) from Zn-Gly; (4) basic diet plus 90 mg Zn kg(-1) from Zn-Gly; (5) basic diet plus 120 mg Zn kg(-1) from Zn-Gly; (6) positive control, basic diet plus 120 mg Zn kg(-1) from zinc sulfate (ZnSO(4)). After the 21- and 42-day feeding trials, the results showed that both of Zn-Gly and ZnSO(4) could improve the growth performance of broilers, with the greatest average daily feed intake observed in the broilers fed 90 mg Zn kg(-1) from Zn-Gly, but the greatest average daily gain observed with 120 mg Zn kg(-1) from Zn-Gly (0-3 weeks) and 90 mg Zn kg(-1) from Zn-Gly (4-6 weeks). Adding additional Zn-Gly improved the levels of immunoglobulins (IgA, IgM, and IgG) and the contents of total protein and Ca in serum and increased the immune organs index especially with 90 mg Zn kg(-1) as Zn-Gly. However, there were no significant differences in responses to complements (C3 and C4) and albumin in serum among the treatments.

Zinc: the brain's dark horse

Zinc is a life-sustaining trace element, serving structural, catalytic, and regulatory roles in cellular biology. It is required for normal mammalian brain development and physiology, such that deficiency or excess of zinc has been shown to contribute to alterations in behavior, abnormal central nervous system development, and neurological disease. In this light, it is not surprising that zinc ions have now been shown to play a role in the neuromodulation of synaptic transmission as well as in cortical plasticity. Zinc is stored in specific synaptic vesicles by a class of glutamatergic or "gluzinergic" neurons and is released in an activity-dependent manner. Because gluzinergic neurons are found almost exclusively in the cerebral cortex and limbic structures, zinc may be critical for normal cognitive and emotional functioning. Conversely, direct evidence shows that zinc might be a relatively potent neurotoxin. Neuronal injury secondary to in vivo zinc mobilization and release occurs in several neurological disorders such as Alzheimer's disease and amyotrophic lateral sclerosis, in addition to epilepsy and ischemia. Thus, zinc homeostasis is integral to normal central nervous system functioning, and in fact its role may be underappreciated. This article provides an overview of zinc neurobiology and reviews the experimental evidence that implicates zinc signals in the pathophysiology of neuropsychiatric diseases. A greater understanding of zinc's role in the central nervous system may therefore allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

Deficiência de zinco em crianças e adolescentes com doenças hepáticas crônicas

OBJETIVO: Revisar as principais pesquisas referentes ao zinco e ao estado desse mineral em crianças e adolescentes com doenças hepáticas crônicas. FONTES DE DADOS: As palavras-chave "zinco", "hepatopatias", "criança" e "adolescente" foram inseridas nas bases de dados PubMed, SciELO e Web of Science. O critério de seleção compreendeu os artigos de origem nacional e internacional, preferindo-se aqueles publicados de 1998 a 2008, além de estudos mais antigos considerados clássicos. SÍNTESE DOS DADOS: O zinco é um mineral essencial para a saúde das crianças devido às suas inúmeras funções no organismo, dentre elas a atuação no sistema imune, o favorecimento do crescimento estatural e do desenvolvimento sexual e cognitivo. As crianças hepatopatas parecem estar mais suscetíveis à deficiência de zinco do que as saudáveis pelo fato de a doença no fígado alterar o metabolismo desse mineral, principalmente a sua distribuição aos tecidos e sua excreção. O nível de zinco no plasma parece ser baixo nesses pacientes, mas esse biomarcador não reflete o real estado de zinco no organismo e, além disso, a excreção urinária de zinco parece estar aumentada. CONCLUSÕES: É necessário um número maior de estudos sobre o estado de zinco em crianças e adolescentes com doenças hepáticas crônicas.

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.

l-Arginine normalizes NOS activity and zinc-MT homeostasis in the kidney of mice chronically exposed to inorganic mercury

Inorganic mercury (HgCl2) exposure provokes damage in many organs, especially kidney. Inducible nitric oxide synthase (iNOS) expression, total NOS activity and the profiles of zinc (Zn), copper (Cu) and Hg as well as their distribution when bound to specific intracellular proteins, including metallothioneins (MT), were studied during HgCl2 exposure and after l-arginine treatment in C57BL/6 mouse kidney. HgCl2 exposure modulates differently iNOS expression and NOS activity, increasing iNOS expression but, conversely, decreasing total NOS activity in the mouse kidney. Moreover, during Hg exposure an increased MT production occurs. The kidney damage leads to a loss of urinary proteins, increased plasma creatinine and high Zn mobilization with consequent increased urinary Zn excretion. l-arginine treatment recovers NOS activity and induces a normalization of MT induction, plasma creatinine values and urinary proteins excretion, suggesting that l-arginine may limit kidney damages by Hg exposure.

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.

Pro-inflammatory genetic background and zinc status in old atherosclerotic subjects

Inflammation and genetics are prominent mechanisms in the pathogenesis of atherosclerosis (AT) and its complications. In this review we discuss the possible impact on AT development of several genetic determinants involved in inflammation, oxidative stress and cytoprotection (IL-6, TNF-alpha, IL-10, CD14, TLR4, MT, HSP70). Genetic polymorphisms of these genes may affect a differential inflammatory response predisposing to AT. However, allelic polymorphisms of genes which increase the risk of AT frequently occur in the general population but, only adequate gene-environment-polymorphism interactions promote the onset of the disease. Zinc deficiency has been suggested as an environmental risk factor for AT. With advancing age, the incidence of zinc deficiency increases for several reasons. Among them, dietary intake, malabsorption and genetic background of inflammatory markers may be involved. A crucial contribution may also be played by increased oxidative stress which may lead to the appearance of dysfunctional proteins, including metallothioneins (MT) that are in turn involved in zinc homeostasis. The detection of candidate genes related to inflammation and promoting AT and their reciprocal influence/interaction with zinc status might allow earlier appropriate dietary interventions in genetically susceptible subjects.

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.