Zinc Action in Vascular Calcification

Although zinc's involvement in bone calcification is well-established, its role in vascular calcification, characterized by abnormal calcium and phosphorus deposition in soft tissues and a key aspect of various vascular diseases, including atherosclerosis, remains unclear. This review focuses on zinc's action in vascular smooth muscle cell (VSMC) calcification, including the vascular calcification mechanism. Accumulated research has indicated that zinc deficiency induces calcification in VSMCs and the aorta, primarily through apoptosis accompanied by a downregulation of smooth muscle cell markers. Moreover, zinc deficiency-induced vascular calcification operates independently of the action of alkaline phosphatase (ALP) activity, typically associated with osteogenic processes, but is partly regulated via inorganic phosphate transporter-1 (Pit-1). To date, research has shown that zinc regulates vascular calcification through a mechanism distinct from that of osteogenic calcification, providing insight into its dual effects on physiological and pathological calcification and thereby explaining the "zinc paradox," wherein zinc simultaneously increases osteoblastic calcification and decreases VSMC calcification.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

Exogeneous metal ions as therapeutic agents in cardiovascular disease and their delivery strategies

Metal ions participate in many metabolic processes in the human body, and their homeostasis is crucial for life. In cardiovascular diseases (CVDs), the equilibriums of metal ions are frequently interrupted, which are related to a variety of disturbances of physiological processes leading to abnormal cardiac functions. Exogenous supplement of metal ions has the potential to work as therapeutic strategies for the treatment of CVDs. Compared with other therapeutic drugs, metal ions possess broad availability, good stability and safety and diverse drug delivery strategies. The delivery strategies of metal ions are important to exert their therapeutic effects and reduce the potential toxic side effects for cardiovascular applications, which are also receiving increasing attention. Controllable local delivery strategies for metal ions based on various biomaterials are constantly being designed. In this review, we comprehensively summarized the positive roles of metal ions in the treatment of CVDs from three aspects: protecting cells from oxidative stress, inducing angiogenesis, and adjusting the functions of ion channels. In addition, we introduced the transferability of metal ions in vascular reconstruction and cardiac tissue repair, as well as the currently available engineered strategies for the precise delivery of metal ions, such as integrated with nanoparticles, hydrogels and scaffolds.

Dietary Zinc Is Associated with Cardiac Function in the Older Adult Population

The elderly is a group at particularly high cardiovascular risk. The coexistence of chronic diseases and use of multiple medications creates the need to look for non-pharmacological agents to improve cardiovascular health in that population. In view of reports on the potential role of zinc in enhancing pathways of myocardial tissue repair, the aim of this study was to evaluate the association between dietary zinc intake and cardiac structure and function in individuals of advanced age. The study group included 251 community-dwelling patients, with a median age of 80 years. Dieta 6.0 software was used for calculation of zinc consumption. Percentage of Recommended Dietary Allowance (RDA) for zinc correlated with left ventricular ejection fraction (LVEF) (r = 0.196, p < 0.05), left ventricular mass index (r = -0.137, p < 0.05) and tricuspid annular plane systolic excursion (TAPSE) (r = 0.153, p < 0.05), while zinc density did so with E/E' ratio (r = -0.127, p < 0.05). In a multiple stepwise regression analysis, the best determinants of LVEF were %RDA for zinc (p = 0.014; β = 0.143), presence of coronary artery disease (p < 0.001; β = -0.39) and age (p = 0.036; β = -0.12). Furthermore, %RDA for zinc (p = 0.009; β = 0.16), female sex (p = 0.005; β = -0.171), beta-blocker use (p = 0.024; β = -0.136), body mass index (p = 0.008; β = 0.16) and heart rate (p = 0.0006; β = -0.209) had an independent effect on TAPSE. In conclusion, in individuals of very advanced age, lower zinc intake is associated with poorer cardiac function. Therefore, increasing the recommended zinc intake in this group deserves consideration.

Marginal Zinc Deficiency in Mice Increased the Number of Abnormal Sperm and Altered the Expression Level of Spermatogenesis-Related Genes

Marginal zinc deficiency is more common than severe zinc deficiency, and the effect of marginal zinc deficiency on male reproduction is unknown. This study investigated the effect of marginal zinc deficiency on spermatogenesis and its mechanism. Male ICR mice were fed normal zinc (30 mg/kg) and marginal zinc deficiency (10 mg/kg) diets for 35 days. Zinc-dependent proteins and enzymes were measured as biomarkers of zinc levels in the body. Metallothionein and Cu-Zn SOD levels in the control group were higher than those in the marginal zinc deficiency group. Hematoxylin and eosin staining showed that the marginal zinc deficiency diet caused histopathological changes in the testis and destruction of the sperm head under scanning electron microscopy. Sperm parameters and sex hormone levels were also affected by marginal zinc deficiency. In addition, marginal zinc deficiency led to alter expression level of several important spermatogenesis-related genes in the epididymis and testes. These results indicate that although zinc intake in marginal zinc deficiency is close to the recommended reference value, low zinc intake interferes with the expression of genes related to spermatogenesis and may lead to sperm abnormalities in mice.

No Association of Hair Zinc Concentration with Coronary Artery Disease Severity and No Relation with Acute Coronary Syndromes

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Although zinc (Zn) was reported to have antioxidant, anti-inflammatory and protective properties in CVDs, its association with coronary artery disease (CAD) is still unclear. As methods commonly used to assess Zn levels in blood and urine do not show the full picture of the microelement supply, in this study, the nutritional status of Zn in patients with angiographically confirmed CAD was assessed using inductively coupled plasma optical emission spectrometry. We found no association between Zn and the severity of CAD evaluated with the Coronary Artery Surgery Study Score (p = 0.67). There were no statistically significant differences in Zn levels between patients with acute coronary syndrome and those with stable CAD (p = 0.937). A statically significant negative correlation was observed between Zn content and serum triglyceride concentration (p < 0.05). Patients with type 2 diabetes mellitus were found to have a significantly lower hair Zn content compared to non-diabetic individuals (p < 0.01). The role of Zn in the pathogenesis of CAD and its complications need further well-designed research as the moderation and supplementation of Zn dietary intake could be a simple intervention to reduce the CVDs risk.

The Role of Zinc Homeostasis in the Prevention of Diabetes Mellitus and Cardiovascular Diseases

Zinc is an essential micronutrient for human health and is involved in various biological functions, such as growth, metabolism, and immune function. In recent years, research on intracellular zinc dynamics has progressed, and it has become clear that zinc transporters strictly control intracellular zinc localization, zinc regulates the functions of various proteins and signal transduction pathways as a second messenger similar to calcium ions, and intracellular zinc dyshomeostasis is associated with impaired insulin synthesis, secretion, sensitivity, lipid metabolism, and vascular function. Numerous animal and human studies have shown that zinc deficiency may be associated with the risk factors for diabetes and cardiovascular diseases (CVDs) and zinc administration might be beneficial for the prevention and treatment of these diseases. Therefore, an understanding of zinc biology may help the establishment of novel strategies for the prevention and treatment of diabetes and CVDs. This review will summarize the current knowledge on the role of zinc homeostasis in the pathogenesis of diabetes and atherosclerosis and will discuss the potential of zinc in the prevention of these diseases.

Association of dietary zinc intake with coronary artery calcium progression: the Multi-Ethnic Study of Atherosclerosis (MESA)

PURPOSE

Zinc is considered protective against atherosclerosis; however, the association between dietary zinc intake and cardiovascular disease remains debated. We investigated whether dietary zinc intake was associated with coronary artery calcium (CAC) progression in the Multi-Ethnic Study of Atherosclerosis (MESA).

METHODS

This analysis included 5186 participants aged 61.9 ± 10.2 years (48.8% men; 41.3% white, 25.0% black, 21.6% Hispanic, and 12.1% Chinese American) from the MESA. Dietary zinc intake was assessed by a self-administered, 120-item food frequency questionnaire at baseline (2000-2002). Baseline and follow-up CAC were measured by computed tomography. CAC progression was defined as CAC > 0 at follow-up for participants with CAC = 0 at baseline; and an annualized change of 10 or percent change of ≥ 10% for those with 0 < CAC < 100 or CAC ≥ 100 at baseline, respectively.

RESULTS

Dietary zinc intake was 8.4 ± 4.5 mg/day and 2537 (48.9%) of the included participants had CAC at baseline. Over a median follow-up of 3.4 years (25th-75th percentiles = 2.0-9.1 years), 2704 (52.1%) participants had CAC progression. In the fully adjusted model, higher dietary zinc was associated with a lower risk of CAC progression in both men (hazard ratio [HR] 0.697, 95% confidence interval [CI] 0.553-0.878; p = 0.002) and women (HR 0.675; 95% CI 0.496-0.919; p = 0.012, both comparing extreme groups). Furthermore, such an inverse association was attributable to dietary zinc intake from non-red meat (p < 0.05), rather than red meat sources (p > 0.05).

CONCLUSIONS

In this multiethnic population free of clinically apparent cardiovascular disease, higher dietary zinc intake from non-red meat sources was independently associated with a lower risk of CAC progression.

CLINICAL TRIAL REGISTRATION NUMBER

The MESA trial was registered at clinicaltrials.gov as NCT00005487.

Zinc ameliorates human aortic valve calcification through GPR39 mediated ERK1/2 signalling pathway

AIMS

Calcific aortic valve disease (CAVD) is the most common heart valve disease in the Western world. It has been reported that zinc is accumulated in calcified human aortic valves. However, whether zinc directly regulates CAVD is yet to be elucidated. The present study sought to determine the potential role of zinc in the pathogenesis of CAVD.

METHODS AND RESULTS

Using a combination of a human valve interstitial cell (hVIC) calcification model, human aortic valve tissues, and blood samples, we report that 20 μM zinc supplementation attenuates hVIC in vitro calcification, and that this is mediated through inhibition of apoptosis and osteogenic differentiation via the zinc-sensing receptor GPR39-dependent ERK1/2 signalling pathway. Furthermore, we report that GPR39 protein expression is dramatically reduced in calcified human aortic valves, and there is a significant reduction in zinc serum levels in patients with CAVD. Moreover, we reveal that 20 μM zinc treatment prevents the reduction of GPR39 observed in calcified hVICs. We also show that the zinc transporter ZIP13 and ZIP14 are significantly increased in hVICs in response to zinc treatment. Knockdown of ZIP13 or ZIP14 significantly inhibited hVIC in vitro calcification and osteogenic differentiation.

CONCLUSIONS

Together, these findings suggest that zinc is a novel inhibitor of CAVD, and report that zinc transporter ZIP13 and ZIP14 are important regulators of hVIC in vitro calcification and osteogenic differentiation. Zinc supplementation may offer a potential therapeutic strategy for CAVD.

Total antioxidant status reduction conditioned by a serum selenium concentration decrease as a mechanism of the ultrasonographically measured brachial artery dilatation impairment in patients with arterial hypertension

The objective of the study was to determine the relationship between serum concentrations of selenium (SeS) and zinc (ZnS), total antioxidant status (TAS) and endothelial function assessed by ultrasonographic method of dilatation of the brachial artery in 141 hypertensive patients. Patients with SeS < median were characterized by a statistically significantly lower flow-mediated dilation (FMD) than patients with SeS ≥ median. Patients with TAS < median were characterized by a significantly lower FMD than patients with TAS ≥ median. Older age, higher BMI, male gender, higher blood total cholesterol, ischemic heart disease, smoking and lower SeS constitute independent predictors of inferior endothelial function, expressed in lower FMD values. Smoking is an independent predictor of lower TAS, and the use of β-blockers and higher serum selenium levels are independent predictors of higher TAS. In summary, a decrease in TAS should be considered as a mechanism of inferior endothelial function in hypertensive patients conditioned by a decrease in SeS.

Acute dietary zinc deficiency in rats exacerbates myocardial ischaemia–reperfusion injury through depletion of glutathione

Zn plays an important role in maintaining the anti-oxidant status within the heart and helps to counter the acute redox stress that occurs during myocardial ischaemia and reperfusion. Individuals with low Zn levels are at greater risk of developing an acute myocardial infarction; however, the impact of this on the extent of myocardial injury is unknown. The present study aimed to compare the effects of dietary Zn depletion with in vitro removal of Zn (N,N,N′,N′-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine (TPEN)) on the outcome of acute myocardial infarction and vascular function. Male Sprague–Dawley rats were fed either a Zn-adequate (35 mg Zn/kg diet) or Zn-deficient (&lt;1 mg Zn/kg diet) diet for 2 weeks before heart isolation. Perfused hearts were subjected to a 30 min ischaemia/2 h reperfusion (I/R) protocol, during which time ventricular arrhythmias were recorded and after which infarct size was measured, along with markers of anti-oxidant status. In separate experiments, hearts were challenged with the Zn chelator TPEN (10 µm) before ischaemia onset. Both dietary and TPEN-induced Zn depletion significantly extended infarct size; dietary Zn depletion was associated with reduced total cardiac glutathione (GSH) levels, while TPEN decreased cardiac superoxide dismutase 1 levels. TPEN, but not dietary Zn depletion, also suppressed ventricular arrhythmias and depressed vascular responses to nitric oxide. These findings demonstrate that both modes of Zn depletion worsen the outcome from I/R but through different mechanisms. Dietary Zn deficiency, resulting in reduced cardiac GSH, is the most appropriate model for determining the role of endogenous Zn in I/R injury.

Roles for endothelial zinc homeostasis in vascular physiology and coronary artery disease

The discovery of the roles of nitric oxide (NO) in cardiovascular signaling has led to a revolution in the understanding of cardiovascular disease. A new perspective to this story involving zinc (Zn) is emerging. Zn and its associated Zn transporter proteins are important for the integrity and functions of both the large conduit vessels and the microvascular resistance vessels. The Zn and NO pathways are tightly coordinated. Zn ions are required for the dimerization of endothelial nitric oxide synthase and subsequent generation of NO while generation of NO leads to a rapid mobilization of endothelial Zn stores. Labile Zn may mediate important downstream actions of NO including vascular cytoprotection and vasodilation. Several vascular disease risk factors (including aging, smoking and diabetes) interfere with Zn homeostatic mechanisms and both hypozincaemia and Zn transporter protein abnormalities are linked to atherosclerosis and microvascular disease. Some vegetarian diets and long-term use of certain anti-hypertensives may also impact on Zn status. The available evidence supports the existence of a Zn regulatory pathway in the vascular wall that is coupled to the generation and actions of NO and which is compromised in Zn deficiency with consequent implications for the pathogenesis and therapy of vascular disease.

Zinc deficiency and cellular oxidative stress: prognostic implications in cardiovascular diseases

Zinc is an essential nutrient for human health and has anti-oxidative stress and anti-inflammatory functions. The association between zinc deficiency and the development of cardiovascular diseases (CVDs) has been supported by numerous studies. Supplementing zinc can reduce the risk of atherosclerosis and protect against myocardial infarction and ischemia/reperfusion injury. In this review we summarize the evidence in the literature, to consolidate the current knowledge on the dysregulation of zinc homeostasis in CVDs, and to explore the significant roles of the zinc homeostasis-regulatory proteins in cardiac physiology and pathophysiology. Moreover, this review also deliberates on the potential diagnostic and prognostic implications of zinc/zinc homeostasis-associated molecules (ZIP, ZnT, and MTs) in CVDs.

Sphingosylphosphorylcholine inhibits macrophage adhesion to vascular smooth muscle cells

Inflammation in de-endothelialised arteries contributes to the development of cardiovascular diseases. The process that initiates this inflammatory response is the adhesion of monocytes/macrophages to exposed vascular smooth muscle cells, typically stimulated by cytokines such as tumour necrosis factor-α (TNF). The aim of this study was to determine the effect of the sphingolipid sphingosylphosphorylcholine (SPC) on the interaction of monocytes/macrophages with vascular smooth muscle cells. Rat aortic smooth muscle cells and rat bone marrow-derived macrophages were co-cultured using an in vitro assay following incubation with sphingolipids to assess inter-cellular adhesion. We reveal that SPC inhibits the TNF-induced adhesion of macrophages to smooth muscle cells. This anti-adhesive effect was the result of SPC-induced changes to the smooth muscle cells (but not the macrophages) and was mediated, at least partly, via the sphingosine 1-phosphate receptor subtype 2. Lipid raft domains were also required. Although SPC did not alter expression or membrane distribution of the adhesion proteins intercellular adhesion molecule-1 and vascular cellular adhesion protein-1 in smooth muscle cells, SPC preincubation inhibited the TNF-induced increase in inducible nitric oxide synthase (NOS2) resulting in a subsequent decrease in nitric oxide production. Inhibiting NOS2 activation in smooth muscle cells led to a decrease in the adhesion of macrophages to smooth muscle cells. This study has therefore delineated a novel pathway which can inhibit the interaction between macrophages and vascular smooth muscle cells via SPC-induced repression of NOS2 expression. This mechanism could represent a potential drug target in vascular disease.

tert-Butylhydroquinone mobilizes intracellular-bound zinc to stabilize Nrf2 through inhibiting phosphatase activity

The nuclear factor erythroid 2-related factor 2 (Nrf2) is required to combat increases in oxidative stress. The chemical compound tert-butylhydroquinone (tBHQ) can downregulate Kelch-like ECH-associated protein 1 (Keap1), a repressor of Nrf2, thus maintaining the stability of Nrf2. tBHQ can also increase intracellular “free” zinc in human bronchial epithelial (16HBE) cells. We aim to investigate whether the intracellular free zinc change plays a role in Nrf2 activation. tBHQ exposure dose-dependently increases intracellular free zinc concentrations within 30 min in 16HBE cells by mobilizing intracellular zinc pools. Active Nrf2 and the antioxidant enzyme heme oxygenase-1 (HO-1) increase at 3 h after tBHQ treatment. Chelating intracellular free zinc with tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN) during tBHQ exposure partially abrogates the tBHQ-induced activation of Nrf2 and HO-1 expression, while Keap1 is further decreased. These results indicate that tBHQ-induced stability of Nrf2 is associated with the intracellular free zinc level. Because the activated Nrf2 is phosphorylated, the serine/threonine protein phosphatase activity, which is known to be inhibited by zinc, is assayed. The results showed that tBHQ treatment can suppress cellular protein phosphatase-2A (PP2A) and protein phosphatase-2C (PP2C) activity, which can be abrogated by adding TPEN. This finding is verified in a cell-free protein extract experiment by supplying zinc or by chelating zinc with TPEN. These results provide a novel mechanistic insight into Nrf2 activation in antioxidant enzyme induction involving zinc signaling. The increase of intracellular free zinc may be one mechanism for Nrf2 activation. The inhibition of PP2A and PP2C activity may be involved in Nrf2 phosphorylation modulation.

Zinc Restored the Decreased Vascular Smooth Muscle Cell Viability under Atherosclerotic Calcification Conditions

Zinc is considered to be involved in maintaining healthy vascular condition. Atherosclerotic calcification of vascular smooth muscle cells (VSMCs) occurs via the mechanism of cell death; therefore, cell viability is a critical factor for preventing VSMC calcification. In this study, we tested whether zinc affected VSMC viability under both normal physiological non-calcifying (0 mM P) and atherosclerotic calcifying conditions (3 and 5 mM P), since VSMC physiological characters change during the VSMC calcification process. The study results showed that an optimal zinc level (15 μM) restored the decreased VSMC viability which was induced under low zinc levels (0 and 1 μM) and calcifying conditions (3 and 5 mM P) at 9 and 15 days culture. This zinc-protecting effect for VSMC viability is more prominent under atherosclerotic calcifying condition (3 and 5 mM P) than normal condition (0 mM P). Also, the increased VSMC viability was consistent with the decreased Ca and P accumulation in VSMC cell layers. The results suggested that zinc could be an effective biomineral for preventing VSMC calcification under atherosclerotic calcifying conditions.

Zinc and its role in immunity and inflammation

Zinc (Zn) nutritional importance has been known for a long time, but in the last decades its importance in immune modulation has arisen. This review aims at describing the mechanisms involved in the regulation of Zn homeostasis and their effects on the immune response focusing on those which are implicated in the physiopathology of rheumatoid arthritis. Zn functions as a modulator of the immune response through its availability, which is tightly regulated by several transporters and regulators. When this mechanism is disturbed, Zn availability is reduced, altering survival, proliferation and differentiation of the cells of different organs and systems and, in particular, cells of the immune system. Zn deficiency affects cells involved in both innate and adaptive immunity at the survival, proliferation and maturation levels. These cells include monocytes, polymorphonuclear-, natural killer-, T-, and B-cells. T cell functions and the balance between the different T helper cell subsets are particularly susceptible to changes in Zn status. While acute Zn deficiency causes a decrease in innate and adaptive immunity, chronic deficiency increases inflammation. During chronic deficiency, the production of pro-inflammatory cytokines increases, influencing the outcome of a large number of inflammatory diseases, including rheumatoid arthritis.

Zinc proteome interaction network as a model to identify nutrient-affected pathways in human pathologies

Zinc is an essential micronutrient playing fundamental roles in cellular metabolism. It acts mostly through binding a wide range of proteins, thus affecting a broad spectrum of biological processes, which include cell division, growth and differentiation. Full annotation of zinc-binding proteins showed them to represent about 10 % of the human proteome, with over 300 enzymes containing zinc ions within their catalytic domains. Also, hundreds of key regulatory proteins, including transcription factors, require zinc for their activity. In this study, the whole set of zinc-binding proteins together with their direct interactors was listed and defined as the zinc proteome (ZNP). We interrogated pathway analysis tools to identify the cellular processes that are predicted to be affected by zinc availability. Network and functional enrichment analyses highlighted biological processes potentially affected by deregulated zinc homeostasis. This computational approach was also tested on a real case study: The possible involvement of ZNP network proteins in Crohn's disease pathogenesis was assessed on genes transcriptionally regulated in the intestine of patients affected by this condition. The analysis produced a network of pathways likely to be influenced by zinc and associated with Crohn's disease. These results highlight a central role for zinc in the tissue remodeling process which occurs upon gut inflammation, pointing at novel disease pathways whose effect could be worsened by zinc dyshomeostasis and impaired zinc fluxes in specific damaged areas. Overall, our computational approach could provide novel insights into pathological conditions and could therefore be used to drive mechanistic research in under-investigated fields of research. An interactive version of the determined ZNP network is available at URL http://93.63.165.11/ZNnetwork/ .

Phosphate-induced rat vascular smooth muscle cell calcification and the implication of zinc deficiency in a7r5 cell viability

The calcification of vascular smooth muscle cells (VSMCs) is considered one of the major contributors for vascular disease. Phosphate is known as the inducer for VSMC calcification. In this study, we assessed whether phosphate affected cell viability and fetuin-A, a calcification inhibitor protein, both which are related to VSMC calcification. Also, VSMC viability by zinc level was assessed. The results showed that phosphate increased Ca and P deposition in VSMCs (A7r5 cell line, rat aorta origin). This phosphate-induced Ca and P deposition was consistent with the decreased A7r5 cell viability (P<0.05), which implies phosphate-induced calcification in A7r5 cells might be due to the decreased VSMC cell viability. As phosphate increased, the protein expression of fetuin-A protein was up-regulated. A7r5 cell viability decreased as the addition of cellular zinc level was decreased (P<0.05). The results suggested that zinc deficiency causes the decreased cell viability and it would be the future study to clarify how zinc does act for VSMC cell viability. The results suggest that the decreased VSMC viability by high P or low Zn in VSMCs may be the risk factor for vascular disease.