Zinc decreases C-reactive protein, lipid peroxidation, and inflammatory cytokines in elderly subjects: a potential implication of zinc as an atheroprotective agent.

BACKGROUND: Chronic inflammation and oxidative stress are common risk factors for atherosclerosis. Zinc is an essential micronutrient that can function as an antiinflammatory and antioxidative agent, and as such, it may have atheroprotective properties. OBJECTIVE: We hypothesized that zinc down-regulates the production of atherosclerosis-related cytokines/molecules in humans. DESIGN: To examine these effects, we conducted a randomized, double-blinded, placebo trial of zinc supplementation in elderly subjects. We recruited 40 healthy elderly subjects (aged 56-83 y) and randomly assigned them to 2 groups. One group was given an oral dose of 45 mg zinc/d as a gluconate for 6 mo. The other group was given a placebo. Cell culture models were conducted to study the mechanism of zinc as an atheroprotective agent. RESULTS: After 6 mo of supplementation, the intake of zinc, compared with intake of placebo, increased the concentrations of plasma zinc and decreased the concentrations of plasma high-sensitivity C-reactive protein (hsCRP), interleukin (IL)-6, macrophage chemoattractant protein 1 (MCP-1), vascular cell adhesion molecule 1 (VCAM-1), secretory phospholipase A2, and malondialdehyde and hydroxyalkenals (MDA+HAE) in elderly subjects. Regression analysis showed that changes in concentrations of plasma zinc were inversely associated with changes in concentrations of plasma hsCRP, MCP-1, VCAM-1, and MDA+HAE after 6 mo of supplementation. In cell culture studies, we showed that zinc decreased the generation of tumor necrosis factor-alpha, IL-1beta, VCAM-1, and MDA+HAE and the activation of nuclear transcription factor kappaB and increased antiinflammatory proteins A20 and peroxisome proliferator-activated receptor-alpha in human monocytic leukemia THP-1 cells and human aortic endothelial cells compared with zinc-deficient cells. CONCLUSION: These findings suggest that zinc may have a protective effect in atherosclerosis because of its antiinflammatory and antioxidant functions.

Dietary zinc and prostate cancer in the TRAMP mouse model.

Circumstantial evidence indicates that zinc may have an important role in the prostate. Total zinc levels in the prostate are 10 times higher than in other soft tissues. Zinc concentrations in prostate epithethial cancer cells are decreased significantly. Zinc supplementation for prevention and treatment of prostate cancer in humans has yielded controversial results. No studies have been reported in animal models to show the effect of zinc supplementation on prevention of prostate cancer, thus far. In this study, we have examined the effect of zinc supplementation on development of prostate cancer in a TRAMP mouse model. Results from our study indicate that dietary zinc plays an important role in prostate carcinogenesis. Tumor weights were significantly higher when the dietary zinc intake was either deficient or high in comparison to normal zinc intake level, suggesting that an optimal dietary zinc intake may play a protective role against prostate cancer. Further, our studies also showed decreased insulin-like growth factor (IGF)-1 and IGF-1/IGF binding protein-3 ratio in normal zinc-supplemented animals, suggesting that zinc may modulate IGF-1 metabolism in relation to carcinogenesis. We conclude that optimal prostate zinc concentration has a protective role against cancer.

Zinc in cancer prevention.

Essentiality of zinc for humans was discovered 45 yr ago. Deficiency of zinc is prevalent world wide in developing countries and may affect nearly 2 billion subjects. The major manifestations of zinc deficiency include growth retardation, hypogonadism in males, cell-mediated immune dysfunctions, and cognitive impairment. Zinc not only improves cell mediated immune functions but also functions as an antioxidant and anti-inflammatory agent. Oxidative stress and chronic inflammation have been implicated in development of many cancers. In patients with head and neck cancer, we have shown that nearly 65% of these patients were zinc deficient based on their cellular zinc concentrations. Natural killer (NK) cell activity and IL-2 generation were also affected adversely. Th2 cytokines were not affected. In our patients, zinc status was a better indicator of tumor burden and stage of disease in comparison to the overall nutritional status. Zinc status also correlated with number of hospital admissions and incidences of infections. NF-kappa B is constitutively activated in many cancer cells, and this results in activation of antiapoptotic genes, VEGF, cyclin DI, EGFR, MMP-9 and inflammatory cytokines. Zinc inhibits NF-kappa B via induction of A-20. Thus, zinc supplementation should have beneficial effects on cancer by decreasing angiogenesis and induction of inflammatory cytokines while increasing apoptosis in cancer cells. Based on the above, we recommend further studies and propose that zinc should be utilized in the management and chemoprevention of cancer.

Zinc supplementation decreases oxidative stress, incidence of infection, and generation of inflammatory cytokines in sickle cell disease patients.

Zinc deficiency is common in adult sickle-cell disease (SCD) patients. We previously demonstrated that zinc supplementation to adult SCD patients decreased the incidences of infections and hospital admissions. We hypothesize that zinc supplementation improves T-helper cell function and decreases vascular endothelial cell activation, oxidative stress, and nuclear factor-kappa B (NF-kappaB)-DNA binding in mononuclear cells (MNCs) in SCD patients. To test this hypothesis, 36 SCD patients were recruited and randomly divided into 2 groups. One group (n = 18) received 25-mg zinc orally thrice a day for 3 months. The other group (n = 18) received placebo. The results indicate that the zinc-supplemented group had decreased incidence of infections compared with the placebo group. After zinc supplementation, red blood cell, hemoglobin (Hb), hematocrit, (Hct), plasma zinc, and antioxidant power increased; plasma nitrite and nitrate (NOx), lipid peroxidation products, DNA oxidation products, and soluble vascular cell adhesion molecule-1 decreased in the zinc-supplemented group, compared with the placebo group. Zinc-supplemented patients exhibited significant decreases in lipopolysaccharide-induced tumor necrosis factor-alpha (TNF-alpha) and IL-1beta mRNAs, and TNF-induced nuclear factor of kappaB-DNA binding in MNCs, compared with the placebo group. Ex vivo addition of zinc to MNCs isolated from the placebo subjects decreased TNF-alpha and IL-1beta mRNAs. Zinc supplementation also increased relative levels of IL-2 and IL-2Ralpha mRNAs in phytohemagglutinin-p-stimulated MNCs. These results suggest that zinc supplementation may be beneficial to SCD patients.

Zinc supplementation decreases incidence of infections in the elderly: effect of zinc on generation of cytokines and oxidative stress.

BACKGROUND: Zinc deficiency, cell-mediated immune dysfunction, susceptibility to infections, and increased oxidative stress have been observed in elderly subjects (ie, those >55 y old). Zinc is an effective antiinflammatory and antioxidant agent. OBJECTIVES: The primary objective was to determine the effect of zinc on the incidence of total infections in healthy elderly subjects. The secondary objective was to determine the effect of zinc on cytokines and oxidative stress markers. DESIGN: A randomized, double-blind, placebo-controlled trial of zinc supplementation was conducted in elderly subjects. Fifty healthy subjects of both sexes aged 55-87 y and inclusive of all ethnic groups were recruited for this study from a senior center. The zinc-supplemented group received zinc gluconate (45 mg elemental Zn/d) orally for 12 mo. Incidence of infections during the supplementation period was documented. The generation of inflammatory cytokines, T helper 1 and T helper 2 cytokines, and oxidative stress markers and the plasma concentrations of zinc were measured at baseline and after supplementation. RESULTS: Compared with a group of younger adults, at baseline the older subjects had significantly lower plasma zinc, higher ex vivo generation of inflammatory cytokines and interleukin 10, and higher plasma oxidative stress markers and endothelial cell adhesion molecules. The incidence of infections and ex vivo generation of tumor necrosis factor alpha and plasma oxidative stress markers were significantly lower in the zinc-supplemented than in the placebo group. Plasma zinc and phytohemagglutin-induced interleukin 2 mRNA in isolated mononuclear cells were significantly higher in the zinc-supplemented than in the placebo group. CONCLUSIONS: After zinc supplementation, the incidence of infections was significantly lower, plasma zinc was significantly higher, and generation of tumor necrosis factor alpha and oxidative stress markers was significantly lower in the zinc-supplemented than in the placebo group.

Correction of interleukin-2 gene expression by in vitro zinc addition to mononuclear cells from zinc-deficient human subjects: a specific test for zinc deficiency in humans.

A nutritional deficiency of zinc in humans is widespread in the developing world, and a conditioned zinc deficiency is observed in many diseased states, the elderly population, and pregnant women of both developed and developing nations. It was recently reported that zinc is required for Nuclear Factor-kappaB (NF-kappaB) activation and gene expressions of both interleukin-2 (IL-2) and interleukin-2 receptor alpha (IL-2Ralpha) and beta in HUT-78, a Th0 human malignant lymphoblastoid cell line. In this study, it has been reported for the first time that zinc is also required for gene expression of IL-2 and IL-2Ralpha in primary cells. Isolated peripheral blood mononuclear cells (MNCs) from zinc-deficient elderly subjects was used for this study. NF-kappaB activation was shown to have decreased in the MNCs from zinc-deficient subjects, which was corrected by in vivo zinc supplementation. It was further shown that either in vivo zinc supplementation or the addition of zinc in vitro to MNCs from zinc-deficient subjects results in correction of the gene expression of IL-2 and IL-2Ralpha. Therefore, it was proposed that in vitro addition of zinc to MNCs for correction of gene expression of IL-2 in humans may be used as a specific test for zinc deficiency. Although currently no known specific laboratory test exists for the diagnosis of zinc deficiency in humans, the use of correction of IL-2 messenger RNA (mRNA) with in vitro zinc addition to MNCs from zinc-deficient subjects may be very useful.

Toxic effect of zinc on NF-kappaB, IL-2, IL-2 receptor alpha, and TNF-alpha in HUT-78 (Th(0)) cells.

Zinc deficiency decreased cellular immune response. Zinc supplementation reverses this response. High concentration of zinc intake is reported to alter immune response. We hypothesize that higher concentration of zinc adversely affects T-cell immune response. In this study, we examined whether higher concentration of zinc affects expression of IL-2, IL-2Ralpha, and TNF-alpha, and NF-kappaB activation in HUT-78 (Th(0)) cells. The results show that HUT-78 cells incubated in 15, 50, and 100 microM zinc medium had significantly higher intracellular zinc contents and faster growth after 4 days of incubation, compared to the cells incubated in 1 microM zinc medium. After PMA/PHA stimulation, 1 microM zinc showed significant decreases in NF-kappaB activation, and in the levels of IL-2, IL-2Ralpha, and TNF-alpha production and mRNAs compared to 15 microM zinc. The cells incubated in higher concentrations of zinc (50 and 100 microM zinc) showed mild to moderate decreases in the levels of IL-2, IL-2Ralpha, and TNF-alpha production and mRNAs, and in NF-kappaB activation compared to those incubated in 15 microM zinc medium. These data indicate that not only low level of zinc, but also high levels of zinc decrease Th1 function.

Antioxidant effect of zinc in humans.

Oxidative stress is known to be an important contributing factor in many chronic diseases. We tested the hypothesis that in healthy normal volunteers zinc acts as an effective anti-inflammatory and antioxidant agent. Ten normal volunteers were administered daily oral zinc supplementation (45 mg zinc as gluconate) and 10 volunteers received placebo for 8 weeks. Plasma zinc, MDA, HAE, and 8-OHdG levels; LPS-induced TNF-alpha and IL-1beta mRNA; and ex vivo TNF-alpha-induced NF-kappaB activity in mononuclear cells (MNC) were determined before and after supplementation. In subjects receiving zinc, plasma levels of lipid peroxidation products and DNA adducts were decreased, whereas no change was observed in the placebo group. LPS-stimulated MNC isolated from zinc-supplemented subjects showed reduced mRNA for TNF-alpha and IL-1beta compared to placebo. Ex vivo, zinc protected MNC from TNF-alpha-induced NF-kappaB activation. In parallel studies using HL-60, a promyelocytic cell line, we observed that zinc enhances the upregulation of mRNA and DNA-specific binding for A20, a transactivating factor which inhibits the activation of NF-kappaB. Our results suggest that zinc supplementation may lead to downregulation of the inflammatory cytokines through upregulation of the negative feedback loop A20 to inhibit induced NF-kappaB activation. Zinc administration to human subjects with conditions associated with increased oxidative stress should be explored.

Differential expression of hZnT-4 in human prostate tissues.

BACKGROUND: Altered zinc levels in prostate benign prostatic hyperplasia (BPH) and carcinoma is well documented. It is not known whether loss of zinc, necessary to restrain aggressive growth, results from loss of a single specific or multiple zinc transporters. METHODS: Human prostate tissues from patients who underwent radical prostatectomy were screened by RT-PCR analysis for five zinc transporters. Relative cDNA expression was determined in normal, BPH, and tumor specimens and four prostate epithelial cell lines. RESULTS: Surgical specimens were obtained from patients with assigned Gleason scores ranging from 5 to 9. Relative expression of hZIP-1 and hZnT-1 were prominent in most samples with relatively lesser degree of expression of hZIP-2 and no detectable expression of hZnT-3. Expression of hZnT-4 was decreased in BPH and tumor samples compared to normal tissue. CONCLUSIONS: These data suggest that zinc homeostasis in normal prostate tissues results from an interplay of multiple transporters and decreased hZnT-4 expression is associated with prostate tissue abnormalities independent of total cellular zinc content.

Zinc enhances the expression of interleukin-2 and interleukin-2 receptors in HUT-78 cells by way of NF-kappaB activation.

Production of interleukin (IL)-2 is decreased in zinc-deficient human beings, and zinc is essential to IL-2-mediated T-cell activation. We used a human Th(0) malignant lymphoblastoid cell line, HUT-78, to study the effect of zinc on IL-2 production in PHA/PMA activated T-cells. In zinc-deficient cells, the gene expression of IL-2 was decreased by 50% compared with that in zinc-sufficient cells. The effect of zinc was specific and at the transcriptional level. We also showed a significant effect of zinc on the gene expression of IL-2 receptors alpha and beta. Binding of NF-kappaB (a zinc-dependent transcription factor) to DNA was decreased in zinc-deficient cells. Using transfection of expression vectors of anti-sense NF-kappaB p105 (precursor of NF-kappaB p50) in cells, we showed that a decrease in gene expression of IL-2 and IL-2 Ralpha may be partly due to decreased activation of NF-kappaB in zinc-deficient cells. Our studies demonstrate, for the first time, the role of zinc in gene expression of IL-2 and its receptors in HUT-78 cells. We also document that the binding of NF-kappaB to DNA was adversely affected, thereby decreasing the gene expression of IL-2 and IL-2 Ralpha in zinc-deficient HUT-78 cells.