alpha-Lipoic acid and N-acetyl cysteine prevent zinc deficiency-induced activation of NF-kappaB and AP-1 transcription factors in human neuroblastoma IMR-32 cells

Association between serum copper, zinc, and selenium concentrations and depressive symptoms in the US adult population, NHANES (2011-2016)

BACKGROUND

Evidence suggests that alterations in serum trace element concentrations are closely associated with mental illness. However, ​studies on the relationship between serum copper, zinc, and selenium concentrations and depressive symptoms are limited and with controversial results. We aimed to investigate the association between serum concentrations of these trace elements and depressive symptoms in US adults.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) (2011-2016) were used in this cross-sectional study. The Patient Health Questionnaire-9 Items (PHQ-9) was employed to assess depressive symptoms. Multiple logistic regression was performed to determine the relationship between the serum concentrations of copper, zinc, and selenium and depressive symptoms.

RESULTS

A total of 4552 adults were included. Subjects with depressive symptoms had higher serum copper concentrations (123.88 ± 1.87) than those without depressive symptoms (116.99 ± 0.86) (p < 0.001). In Model 2, weighted logistic regression analysis showed that the second (Q2) quartile of zinc concentrations (odds ratio [OR] = 1.534, 95% confident interval [CI]: 1.018 to 2.313) were significantly associated with an increased risk of depressive symptoms. Subgroup analysis revealed that the third (Q3) and fourth (Q4) quartiles of copper concentrations (Q3: OR = 2.699, 95% CI: 1.285 to 5.667; Q4: OR = 2.490, 95% CI: 1.026 to 6.046) were also positively associated with depressive symptoms in obese individuals after controlling for all confounders. However, no significant relationship between serum selenium concentrations and depressive symptoms was observed.

CONCLUSIONS

Obese US adults with high serum copper concentrations, as well as US adults in general with low serum zinc concentrations, were susceptible to depressive symptoms. Nevertheless, the causal mechanisms underlying these relationships need to be further explored.

Zinc trafficking to apo-Zn-proteins 2. Cellular interplay of proteome, metallothionein, and glutathione

A recent study investigated the impact of glutathione (GSH) on the transfer of zinc (Zn) from proteome to apo-carbonic anhydrase. Here, we probed the requirement of glutathione for zinc trafficking in LLC-PK1 pig kidney epithelial cells. Depletion of GSH by at least 95% left cells viable and able to divide and synthesize Zn-proteins at the control rate over a 48-h period. Loss of GSH stimulated the accumulation of 2.5x the normal concentration of cellular Zn. According to gel filtration chromatography, differential centrifugal filtration, and spectrofluorimetry with TSQ, the extra Zn was distributed between the proteome and metallothionein (MT). To test the functionality of proteome and/or MT as sources of Zn for the constitution of Zn-proteins, GSH-deficient cells were incubated with CaEDTA to isolate them from their normal source of nutrient Zn. Control cells plus CaEDTA stopped dividing; GSH-depleted cells plus CaEDTA continued to divide at ∼40% the rate of GSH deficient cells. Evidently, proteome and/or MT served as a functional source of Zn for generating Zn-proteins. In vitro insertion of Zn bound to proteome into apo-carbonic anhydrase occurred faster at larger concentrations of Zn bound to proteome. These results support the hypothesis that enhanced transport of Zn into cells drives the conversion of apo-Zn-proteins to Zn-proteins by mass action. Similar results were also obtained with human Jurkat T lymphocyte epithelial cells. This study reveals a powerful new model for studying the chemistry of Zn trafficking, including transport processes, involvement of intermediate binding sites, and constitution of Zn-proteins.

The role of inflammation in cadmium nephrotoxicity: NF-κB comes into view

Kidney diseases are major health problem and understanding the underlined mechanisms that lead to kidney diseases are critical research points with a marked potential impact on health. Cadmium (Cd) is a heavy metal that occurs naturally and can be found in contaminated food. Kidneys are the most susceptible organ to heavy metal intoxication as it is the main route of waste excretion. The harmful effects of Cd were previously well proved. Cd induces inflammatory responses, oxidative injury, mitochondrial dysfunction and disturbs Ca²⁺ homeostasis. The nuclear factor-kappa B (NF-κB) is a cellular transcription factor that regulates inflammation and controls the expression of many inflammatory cytokines. Therefore, great therapeutic benefits can be attained from NF-κB inhibition. In this review we focused on certain compounds including cytochalasin D, mangiferin, N-acetylcysteine, pyrrolidine dithiocarbamate, roflumilast, rosmarinic acid, sildenafil, sinapic acid, telmisartan and wogonin and certain plants as Astragalus Polysaccharide, Ginkgo Biloba and Thymus serrulatus that potently inhibit NF-κB and effectively counteracted Cd-associated renal intoxication. In conclusion, the proposed NF-κB involvement in Cd-renal intoxication clarified the underlined inflammation associated with Cd-nephropathy and the beneficial effects of NF-κB inhibitors that make them the potential to substantially optimize treatment protocols for Cd-renal intoxication.

Gestational zinc deficiency impairs brain astrogliogenesis in rats through multistep alterations of the JAK/STAT3 signaling pathway

We previously showed that zinc (Zn) deficiency affects the STAT3 signaling pathway in part through redox-regulated mechanisms. Given that STAT3 is central to the process of astrogliogenesis, this study investigated the consequences of maternal marginal Zn deficiency on the developmental timing and key mechanisms of STAT3 activation, and its consequences on astrogliogenesis in the offspring. This work characterized the temporal profile of cortical STAT3 activation from the mid embryonic stage up to young adulthood in the offspring from dams fed a marginal Zn deficient diet (MZD) throughout gestation and until postnatal day (P) 2. All rats were fed a Zn sufficient diet (control) from P2 until P56. Maternal zinc deficiency disrupted cortical STAT3 activation at E19 and P2. This was accompanied by altered activation of JAK2 kinase due to changes in PTP1B phosphatase activity. The underlying mechanisms mediating the adverse impact of a decreased Zn availability on STAT3 activation in the offspring brain include: (i) impaired PTP1B degradation via the ubiquitin/proteasome pathway; (ii) tubulin oxidation, associated decreased interactions with STAT3 and consequent impaired nuclear translocation; and (iii) decreased nuclear STAT3 acetylation. Zn deficiency-associated decreased STAT3 activation adversely impacted astrogliogenesis, leading to a lower astrocyte number in the early postnatal and adult brain cortex. Thus, a decreased availability of Zn during early development can have a major and irreversible adverse effect on astrogliogenesis, in part via multistep alterations in the STAT3 pathway.

A matter of concern - Trace element dyshomeostasis and genomic stability in neurons

Neurons are post-mitotic cells in the brain and their integrity is of central importance to avoid neurodegeneration. Yet, the inability of self-replenishment of post-mitotic cells results in the need to withstand challenges from numerous stressors during life. Neurons are exposed to oxidative stress due to high oxygen consumption during metabolic activity in the brain. Accordingly, DNA damage can occur and accumulate, resulting in genome instability. In this context, imbalances in brain trace element homeostasis are a matter of concern, especially regarding iron, copper, manganese, zinc, and selenium. Although trace elements are essential for brain physiology, excess and deficient conditions are considered to impair neuronal maintenance. Besides increasing oxidative stress, DNA damage response and repair of oxidative DNA damage are affected by trace elements. Hence, a balanced trace element homeostasis is of particular importance to safeguard neuronal genome integrity and prevent neuronal loss. This review summarises the current state of knowledge on the impact of deficient, as well as excessive iron, copper, manganese, zinc, and selenium levels on neuronal genome stability.

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Post-mitotic neurons show an increased vulnerability to oxidative stress.

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Trace element dyshomeostasis impairs neuronal genome maintenance, affecting DNA damage response as well as DNA repair.

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The review summarises the effects of excessive and deficient trace element levels neuronal genome stability maintenance.

Therapeutic Effects of the Combination of Alpha-Lipoic Acid (ALA) and Coenzyme Q10 (CoQ10) on Cisplatin-Induced Nephrotoxicity

Background

Nephrotoxicity of cisplatin has been recognized since its introduction more than 25 years ago. However, despite intense efforts to develop less toxic and equally effective alternatives, cisplatin continues to be widely prescribed. Aim and Objectives. The study is aimed at assessing the possible prophylactic effect of coenzyme Q10 (CoQ10) and alpha-lipoic acid (ALA) (separately or in combination) on experimentally cisplatin-induced nephrotoxicity. Subjects and Methods. An experimental study was performed on adult male albino rats (n = 40), weighing 200–250 g. Rats were randomly divided into 5 groups: group I (normal saline control), group II (cisplatin control), group III (CoQ10 and cisplatin), group IV (ALA and cisplatin), and group V (CoQ10, ALA, and cisplatin). CoQ10 and/or ALA were given as pretreatment for 9 days, followed by cisplatin injection in the 10th day of the study, followed by a short posttreatment course for 3 days. Renal functions, tissue antioxidant activity, and inflammatory markers (tumor necrosis factor, TNF) were estimated along with histopathological study.

Results

Renal function tests and urinary proteins were significantly higher within group II compared with other groups (P value <0.001). Creatinine clearance was significantly higher with combination therapy (group V compared to other groups). Both TNF and malondialdehyde (MDA) were significantly higher within group II whereas GSH content, catalase, and superoxide dismutase (SOD) were significantly lower in group II. MDA level was significantly lower when combination therapy was used. Marked renal damage was histologically detected in the cisplatin group, whereas the least renal damage was noticed in the combination group.

Conclusion

The study confirmed the role of antioxidants in preventing nephrotoxicity caused by cisplatin; the prophylactic effect of combined therapy with CoQ10 and ALA is superior to that of monotherapy.

Zinc prevents mitochondrial superoxide generation by inducing mitophagy in the setting of hypoxia/reoxygenation in cardiac cells

Zinc plays a role in autophagy and protects cardiac cells from ischemia/reperfusion injury. This study aimed to test if zinc can induce mitophagy leading to attenuation of mitochondrial superoxide generation in the setting of hypoxia/reoxygenation (H/R) in cardiac cells. H9c2 cells were subjected to 4 h hypoxia followed by 2 h reoxygenation. Under normoxic conditions, treatments of cells with ZnCl₂ increased both the LC3-II/LC3-I ratio and GFP-LC3 puncta, implying that zinc induces autophagy. Further experiments showed that endogenous zinc is required for the autophagy induced by starvation and rapamycin. Zinc down-regulated TOM20, TIM23, and COX4 both in normoxic cells and the cells subjected to H/R, indicating that zinc can trigger mitophagy. Zinc increased ERK activity and Beclin1 expression, and zinc-induced mitophagy was inhibited by PD98059 and Beclin1 siRNA during reoxygenation. Zinc-induced Beclin1 expression was reversed by PD98059, implying that zinc promotes Beclin1 expression via ERK. In addition, zinc failed to induce mitophagy in cells transfected with PINK1 siRNA and stabilized PINK1 in mitochondria. Moreover, zinc-induced PINK1 stabilization was inhibited by PD98059. Finally, zinc prevented mitochondrial superoxide generation and dissipation of mitochondrial membrane potential (ΔΨ_m) at reoxygenation, which was blocked by both the Beclin1 and PINK1 siRNAs, suggesting that zinc prevents mitochondrial oxidative stress through mitophagy. In summary, zinc induces mitophagy through PINK1 and Beclin1 via ERK leading to the prevention of mitochondrial superoxide generation in the setting of H/R. Clearance of damaged mitochondria may account for the cardioprotective effect of zinc on H/R injury.

Zinc deficiency affects the STAT1/3 signaling pathways in part through redox-mediated mechanisms

Zinc deficiency affects the development of the central nervous system (CNS) through mechanisms only partially understood. We previously showed that zinc deficiency causes CNS oxidative stress, damaging microtubules and impairing protein nuclear shuttling. STAT1 and STAT3 transcription factors, which require nuclear import for their functions, play major roles in CNS development. Thus, we investigated whether zinc deficiency disrupts STAT1 and STAT3 signaling pathways in the developing fetal CNS, characterizing the involvement of oxidative stress and the cytoskeleton in the adverse effects. Maternal (gestation day 0–19) marginal zinc deficiency (MZD) reduced STAT1 and STAT3 tyrosine phosphorylation and their nuclear translocation in the embryonic day 19 (E19) rat brain. Similar effects were observed in zinc depleted IMR-32 neuroblastoma cells, with an associated decrease in STAT1- and STAT3-dependent gene transactivation. Zinc deficiency caused oxidative stress (increased 4-hydroxynonenal-protein adducts) in E19 brain and IMR-32 cells, which was prevented in cells by supplementation with 0.5 mM α-lipoic acid (LA). In zinc depleted IMR-32 cells, the low tyrosine phosphorylation of STAT1, but not that of STAT3, recovered upon incubation with LA. STAT1 and STAT3 nuclear transports were also restored by LA. Accordingly, chemical disruption of the cytoskeleton partially reduced STAT1 and STAT3 nuclear levels. In summary, the redox-dependent tyrosine phosphorylation, and oxidant-mediated disruption of the cytoskeleton are involved in the deleterious effects of zinc deficit on STAT1 and STAT3 activation and nuclear translocation. Therefore, disruption of the STAT1 and STAT3 signaling pathways may in part explain the deleterious effects of maternal MZD on fetal brain development.

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Zinc deficits impair STAT1/STAT3 signaling in fetal brain and neuroblastoma cells.

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Zinc deficiency inhibits STAT1 and STAT3 tyrosine phosphorylation and nuclear translocation.

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Zinc deficiency causes oxidative stress (high HNE-protein adducts) in fetal brain and cells.

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Lipoic acid reverts zinc deficiency-associated decreased STAT1/STAT3 nuclear shuttling.

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Zinc deficiency-associated oxidative stress impairs STAT1/STAT3 modulation.

Nutritional marginal zinc deficiency disrupts placental 11β-hydroxysteroid dehydrogenase type 2 modulation

This paper investigated if marginal zinc nutrition during gestation could affect fetal exposure to glucocorticoids as a consequence of a deregulation of placental 11βHSD2 expression. Placenta 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) plays a central role as a barrier protecting the fetus from the deleterious effects of excess maternal glucocorticoids. Rats were fed control (25 μg zinc per g diet) or marginal (10 μg zinc per g diet, MZD) zinc diets from day 0 through day 19 (GD19) of gestation. At GD19, corticosterone concentration in plasma, placenta, and amniotic fluid was similar in both groups. However, protein and mRNA levels of placenta 11βHSD2 were significantly higher (25% and 58%, respectively) in MZD dams than in controls. The main signaling cascades modulating 11βHSD2 expression were assessed. In MZD placentas the activation of ERK1/2 and of the downstream transcription factor Egr-1 was low, while p38 phosphorylation and SP-1-DNA binding were low compared to the controls. These results point to a central role of ERK1/Egr-1 in the regulation of 11βHSD2 expression under the conditions of limited zinc availability. In summary, results show that an increase in placenta 11βHSD2 expression occurs as a consequence of gestational marginal zinc nutrition. This seems to be due to a low tissue zinc-associated deregulation of ERK1/2 rather than to exposure to high maternal glucocorticoid exposure. The deleterious effects on brain development caused by diet-induced marginal zinc deficiency in rats do not seem to be due to fetal exposure to excess glucocorticoids.

Zinc-induced metallothionein overexpression prevents doxorubicin toxicity in cardiomyocytes by regulating the peroxiredoxins

1. Cardiotoxicity is an important factor that limits the clinical use of doxorubicin (Dox). Metallothionein (MT) can antagonize the Dox-induced cardiotoxicity. Using a proteomics approach we have detected that major peroxiredoxins (Prxs) may be involved in this process. In the present study, we further investigate the mechanisms of the MT effects against Dox-induced cytotoxicity and the interactions between MT and Prxs. 2. We have established a primary cardiomyocyte culture system from MT-I/II null (MT(-/-)) and corresponding wild type (MT(+/+)) neonatal mice, and pretreated the MT(+/+) cardiomyocytes with ZnCl2 to establish the MT overexpression cardiomyocyte model. 3. Based on the results, in MT(+/+) cardiomyocytes, ZnCl2 pretreatment significantly increased the cardiomyocytes MT levels and inhibited the cardiotoxicity of Dox; it can resist LDH leakage, cardiomyocyte apoptosis, DNA damage, ROS accumulation and inhibit the decrease in activity of antioxidant enzymes induced by Dox. Moreover, ZnCl2 enhanced the expression of Prx-2, -3, -5 and -6, it can inhibit the expression of Prxs decrease in MT(+/+) cardiomyocytes induced by Dox, but had no effect in MT(-/-) cardiomyocytes. 4. Therefore, the present study suggests that ZnCl2 can protect the cardiomyocytes from the Dox-induced oxidative injury and can inhibit the changes in Prxs expression through induced MT overexpression.

Impact of Procyanidins from Different Berries on Caspase 8 Activation in Colon Cancer

Scope. The aim of this work is to identify which proapoptotic pathway is induced in human colon cancer cell lines, in contact with proanthocyanidins extracted from various berries. Methods and Results. Proanthocyanidins (Pcys) extracted from 11 berry species are monitored for proapoptotic activities on two related human colon cancer cell lines: SW480-TRAIL-sensitive and SW620-TRAIL-resistant. Apoptosis induction is monitored by cell surface phosphatidylserine (PS) detection. Lowbush blueberry extract triggers the strongest activity. When tested on the human monocytic cell line THP-1, blueberry Pcys are less effective for PS externalisation and DNA fragmentation is absent, highlighting a specificity of apoptosis induction in gut cells. In Pcys-treated gut cell lines, caspase 8 (apoptosis extrinsic pathway) but not caspase 9 (apoptosis intrinsic pathway) is activated after 3 hours through P38 phosphorylation (90 min), emphasizing the potency of lowbush blueberry Pcys to eradicate gut TRAIL-resistant cancer cells. Conclusion. We highlight here that berries Pcys, especially lowbush blueberry Pcys, are of putative interest for nutritional chemoprevention of colorectal cancer in view of their apoptosis induction in a human colorectal cancer cell lines.

Influence of intracellular zinc on cultures of rat cardiac neural crest cells

BACKGROUND

Developmental zinc (Zn) deficiency increases the incidence of heart anomalies in rat fetuses, in regions and structures derived from the outflow tract. Given that the development of the outflow tract requires the presence of cardiac neural crest cells (cNCC), we speculated that Zn deficiency selectively kills cNCC and could lead to heart malformations.

METHODS

Cardiac NCC were isolated from E10.5 rat embryos and cultured in control media (CTRL), media containing 3 μM of the cell permeable metal chelator N, N, N', N'-tetrakis (2-pyridylmethyl) ethylene diamine (TPEN), or in TPEN-treated media supplemented with 3 μM Zn (TPEN + Zn). Cardiac NCC were collected after 6, 8, and 24 h of treatment to assess cell viability, proliferation, and apoptosis.

RESULTS

The addition of TPEN to the culture media reduced free intracellular Zn pools and cell viability as assessed by low ATP production, compared to cells grown in control or Zn-supplemented media. There was an accumulation of reactive oxygen species, a release of mitochondrial cytochrome c into the cytoplasm, and an increased cellular expression of active caspase-3 in TPEN-treated cNCC compared to cNCC cultured in CTRL or TPEN + Zn media.

CONCLUSION

Zn deficiency can result in oxidative stress in cNCC, and subsequent decreases in their population and metabolic activity. These data support the concept that Zn deficiency associated developmental heart defects may arise in part as a consequence of altered cNCC metabolism.

Decreased zinc availability affects glutathione metabolism in neuronal cells and in the developing brain

A deficit in zinc (Zn) availability can increase cell oxidant production, affect the antioxidant defense system, and trigger oxidant-sensitive signals in neuronal cells. This work tested the hypothesis that a decreased Zn availability can affect glutathione (GSH) metabolism in the developing rat brain and in neuronal cells in culture, as well as the capacity of human neuroblastoma IMR-32 cells to upregulate GSH when challenged with dopamine (DA). GSH levels were low in the brain of gestation day 19 (GD19) fetuses from dams fed marginal Zn diets throughout gestation and in Zn-deficient IMR-32 cells. γ-Glutamylcysteine synthetase (GCL), the first enzyme in the GSH synthetic pathway, was altered by Zn deficiency (ZD). The protein and mRNA levels of the GCL modifier (GCLM) and catalytic (GCLC) subunits were lower in the Zn-deficient GD19 fetal brain and in IMR-32 cells compared with controls. The nuclear translocation of transcription factor nuclear factor (erythroid-derived 2)-like 2, which controls GCL transcription, was impaired by ZD. Posttranslationally, the caspase-3-dependent GCLC cleavage was high in Zn-deficient IMR-32 cells. Cells challenged with DA showed an increase in GCLM and GCLC protein and mRNA levels and a consequent increase in GSH concentration. Although Zn-deficient cells partially upregulated GCL subunits after exposure to DA, GSH content remained low. In summary, results show that a low Zn availability affects the GSH synthetic pathway in neuronal cells and fetal brain both at transcriptional and posttranslational levels. This can in part underlie the GSH depletion associated with ZD and the high sensitivity of Zn-deficient neurons to pro-oxidative stressors.

Zinc and the modulation of redox homeostasis

Zinc, a redox-inactive metal, has been long viewed as a component of the antioxidant network, and growing evidence points to its involvement in redox-regulated signaling. These actions are exerted through several mechanisms based on the unique chemical and functional properties of zinc. Overall, zinc contributes to maintaining the cell redox balance through various mechanisms including: (i) the regulation of oxidant production and metal-induced oxidative damage; (ii) the dynamic association of zinc with sulfur in protein cysteine clusters, from which the metal can be released by nitric oxide, peroxides, oxidized glutathione, and other thiol oxidant species; (iii) zinc-mediated induction of the zinc-binding protein metallothionein, which releases the metal under oxidative conditions and acts per se as a scavenging oxidant; (iv) the involvement of zinc in the regulation of glutathione metabolism and of the overall protein thiol redox status; and (v) a direct or indirect regulation of redox signaling. Findings of oxidative stress, altered redox signaling, and associated cell/tissue dysfunction in cell and animal models of zinc deficiency highlight the relevant role of zinc in the preservation of cell redox homeostasis. However, although the participation of zinc in antioxidant protection, redox sensing, and redox-regulated signaling is accepted, the molecules, targets, and mechanisms involved are still partially known and the subject of active research.

Zinc deficiency induces production of the proinflammatory cytokines IL-1β and TNFα in promyeloid cells via epigenetic and redox-dependent mechanisms

The deprivation of zinc, caused by malnutrition or as a consequence of aging or disease, strongly affects immune cell functions, causing higher frequency of infections. Among other effects, an increased production of reactive oxygen species (ROS) and proinflammatory cytokines has been observed in zinc-deficient patients, but the underlying mechanisms were unknown. The aim of the current study was to define mechanisms explaining the increase in proinflammatory cytokine production during zinc deficiency, focusing on the role of epigenetic and redox-mediated mechanisms. Interleukin (IL)-1β and tumor necrosis factor (TNF)α production was increased in HL-60 cells under zinc deficiency. Analyses of the chromatin structure demonstrated that the elevated cytokine production was due to increased accessibilities of IL-1β and TNFα promoters in zinc-deficient cells. Moreover, the level of nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase-produced ROS was elevated under zinc deficiency, subsequently leading to p38 mitogen-activated protein kinase (MAPK) phosphorylation. The increased activation of p38 MAPK appeared to be necessary for posttranscriptional processes in IL-1β and TNFα synthesis. These data demonstrate that IL-1β and TNFα expression under zinc deficiency is regulated via epigenetic and redox-mediated mechanisms. Assuming an important role of zinc in proinflammatory cytokine regulation, this should encourage research in the use of zinc supplementation for treatment of inflammatory diseases.

Zinc and the ERK kinases in the developing brain

This article reviews evidence in support of the hypothesis that impaired activation of the extracellular signal-regulated kinases (ERK1/2) contributes to the disruptions in neurodevelopment associated with zinc deficiency. These kinases are implicated in major events of brain development, including proliferation of progenitor cells, neuronal migration, differentiation, and apoptotic cell death. In humans, mutations in ERK1/2 genes have been associated with neuro-cardio-facial-cutaneous syndromes. ERK1/2 deficits in mice have revealed impaired neurogenesis, altered cellularity, and behavioral abnormalities. Zinc is an important modulator of ERK1/2 signaling. Conditions of both zinc deficiency and excess affect ERK1/2 phosphorylation in fetal and adult brains. Hypophosphorylation of ERK1/2, associated with decreased zinc availability in cell cultures, is accompanied by decreased proliferation and an arrest of the cell cycle at the G0/G1 phase. Zinc and ERK1/2 have both been shown to modulate neural progenitor cell proliferation and cell death in the brain. Furthermore, behavioral deficits resulting from developmental zinc deficiency are similar to those observed in mice with decreased ERK1/2 signaling. For example, impaired performance on behavioral tests of learning and memory; such as the Morris water maze, fear conditioning, and the radial arm maze; has been reported in both animals exposed to developmental zinc deficiency and transgenic mice with decreased ERK signaling. Future study should clarify the mechanisms through which a dysregulation of ERK1/2 may contribute to altered brain development associated with dietary zinc deficiency and with conditions that limit zinc availability.

R-α-lipoic acid does not reverse hepatic inflammation of aging, but lowers lipid anabolism, while accentuating circadian rhythm transcript profiles

To determine the effects of age and lipoic acid supplementation on hepatic gene expression, we fed young (3 mo) and old (24 mo) male Fischer 344 rats a diet with or without 0.2% (wt/wt) R-α-lipoic acid (LA) for 2 wk. Total RNA isolated from liver tissue was analyzed by Affymetrix microarray to examine changes in transcriptional profiles. Results showed elevated proinflammatory gene expression in the aging liver and evidence for increased immune cell activation and tissue remodeling, together representing 45% of the age-related transcriptome changes. In addition, age-related increases in transcripts of genes related to fatty acid, triglyceride, and cholesterol synthesis, including acetyl-CoA carboxylase-β (Acacb) and fatty acid synthase (Fasn), were observed. Supplementation of old animals with LA did not reverse the necroinflammatory phenotype but, intriguingly, altered the expression of genes governing circadian rhythm. Most notably, Arntl, Npas2, and Per changed in a coordinated manner with respect to rhythmic transcription. LA further caused a decrease in transcripts of several bile acid and lipid synthesis genes, including Acacb and Fasn, which are regulated by first-order clock transcription factors. Similar effects of LA supplementation on bile acid and lipid synthesis genes were observed in young animals. Transcript changes of lipid metabolism genes were corroborated by a decrease in FASN and ACC protein levels. We conclude that advanced age is associated with a necroinflammatory phenotype and increased lipid synthesis, while chronic LA supplementation influences hepatic genes associated with lipid and energy metabolism and circadian rhythm, regardless of age.

A deficit in zinc availability can cause alterations in tubulin thiol redox status in cultured neurons and in the developing fetal rat brain

Zinc (Zn) deficiency during early development can result in multiple brain abnormalities and altered neuronal functions. In rats, a gestational deficit of Zn can affect the fetal brain cytoskeleton and signaling cascades involved in cellular processes that are central to brain development. In this paper, we tested the hypothesis that oxidative stress is involved in Zn deficiency-induced altered tubulin dynamics and the associated dysregulation of transcription factor NF-κB. For this purpose, we used two cell culture models (rat cortical neurons, human IMR-32 neuroblastoma cells) and an animal model of Zn deficiency. A low rate of in vitro tubulin polymerization, an increase in tubulin oligomers, and a higher protein cysteine oxidation were observed in the Zn-deficient neuronal cells and in gestation day 19 fetal brains obtained from dams fed marginal-Zn diets throughout pregnancy. These alterations could be prevented by treating the Zn-deficient cells with the reducing agent tris(2-carboxyethyl)phosphine or by the presence of N-acetylcysteine (NAC) and α-lipoic acid (LA). Consistent with the above, Zn deficiency-induced tubulin-mediated alterations in transcription factor NF-κB nuclear translocation were prevented by treating IMR-32 cells with LA and NAC. Binding of the NF-κB protein p50, dynein, and karyopherin α (components of the NF-κB transport complex) to β-tubulin as well as the expression of NF-κB-dependent genes (Bcl-2, cyclin D1, and c-myc) was also restored by the addition of LA and NAC to Zn-deficient cells. In conclusion, a deficit in Zn viability could affect early brain development through: (1) an induction of oxidative stress, (2) tubulin oxidation, (3) altered tubulin dynamics, and (4) deregulation of signals (e.g., NF-κB) involved in critical developmental events.

Aldosterone induces oxidative stress, oxidative DNA damage and NF-κB-activation in kidney tubule cells

An increase of the mineralocorticoid aldosterone is induced by a stimulated renin-angiotensin system in a subgroup of hypertensive patients. Epidemiological studies find higher cancer mortality in hypertensive patients and an increased risk to develop kidney cancer. This work investigated the involvement of oxidants in the genotoxicity of aldosterone and on a potential activation of transcription factor nuclear factor-κB (NF-κB) in kidney tubule cells. Aldosterone, at concentrations as low as 1 nM caused a significant increase of DNA damage, as assessed by comet assay and micronucleus frequency test. Aldosterone also led to a dose-dependent activation of NF-κB. Time courses of DNA damage and NF-κB-activation showed that these effects already occurred after 5 and 3 min of aldosterone exposure, respectively, suggesting non-genomic events of the hormone. Antioxidants prevented aldosterone-induced DNA damage and NF-κB-activation, indicating the involvement of oxidants. In fact, aldosterone caused an increase in intracellular oxidant levels, and in particular of superoxide anions. As a consequence, increased levels of the oxidized DNA modification 7,8-dihydro-8-oxo-guanine were observed in aldosterone-treated kidney cells. Aldosterone-induced DNA damage and NF-κB-activation was dependent on the involvement of the mineralocorticoid receptor. The induction of oxidant-mediated genotoxic effects, and of a long-term activation of the potentially oncogenic cell signal NF-κB by aldosterone could contribute to the increased kidney cancer incidence in hypertensive patients.

Iron overload triggers redox-sensitive signals in human IMR-32 neuroblastoma cells

Excessive neuronal iron has been proposed to contribute to the pathology of several neurodegenerative diseases including Alzheimer's and Parkinson's diseases. This work characterized human neuroblastoma IMR-32 cells exposure to ferric ammonium citrate (FAC) as a model of neuronal iron overload and neurodegeneration. The consequences of FAC treatment on neuronal oxidative stress and on the modulation of the oxidant-sensitive transcription factors AP-1 and NF-κB were investigated. Incubation with FAC (150μM) resulted in a time (3-72h)-dependent increase in cellular iron content, and was associated with cell oxidant increase. FAC caused a time-dependent (3-48h) increase in nuclear AP-1- and NF-κB-DNA binding. This was associated with the upstream activation of the mitogen activated kinases ERK1/2, p38 and JNK and of IκBα phosphorylation and degradation. After 72h incubation with FAC, cell viability was 40% lower than in controls. Iron overload caused apoptotic cell death. After 48-72h of incubation with FAC, caspase 3 activity was increased, and chromatin condensation and nuclear fragmentation were observed. In summary, the exposure of IMR-32 cells to FAC is associated with increased oxidant cell levels, activation of redox-sensitive signals, and apoptosis.

Low extracellular zinc increases neuronal oxidant production through nadph oxidase and nitric oxide synthase activation

A decrease in zinc (Zn) levels increases the production of cell oxidants, affects the oxidant defense system and triggers oxidant sensitive signals in neuronal cells. However, the underlying mechanisms are still unclear. This work tested the hypothesis that the increase in neuronal oxidants that occurs when cellular Zn decreases is mediated by the activation of the NMDA receptor. Differentiated PC12 cells were cultured in control, Zn-deficient or Zn-repleted media. The incubation in Zn deficient media led to a rapid increase in cellular calcium levels, which was prevented by a NMDA receptor antagonist (MK-801). Cellular calcium accumulation was associated with NADPH oxidase and nitric oxide synthase (NOS) activation, an increase in cell oxidant levels, and an associated activation of a redox-sensitive signal (AP-1). In cells incubated in the Zn deficient medium, NADPH oxidase activation was prevented by MK-801 and by a protein kinase C inhibitor. The rise in cell oxidants was prevented by inhibitors of NADPH oxidase, of the NOS and by MK-801. A similar pattern of inhibitor action was observed for zinc deficiency-induced AP-1 activation. Results demonstrate that a decrease in extracellular Zn leads to an increase in neuronal oxidants through the activation of the NMDAR that leads to calcium influx and to a calcium-mediated activation of protein kinase C/NADPH oxidase and NOS. Changes in extracellular Zn concentrations can be sensed by neurons, which using reactive oxygen and nitrogen species as second messengers, can regulate signaling involved in neuronal development and function.

The role of zinc in the modulation of neuronal proliferation and apoptosis

Although a requirement of zinc (Zn) for normal brain development is well documented, the extent to which Zn can modulate neuronal proliferation and apoptosis is not clear. Thus, we investigated the role of Zn in the regulation of these two critical events. A low Zn availability leads to decreased cell viability in human neuroblastoma IMR-32 cells and primary cultures of rat cortical neurons. This occurs in part as a consequence of decreased cell proliferation and increased apoptotic cell death. In IMR-32 cells, Zn deficiency led to the inhibition of cell proliferation through the arrest of the cell cycle at the G₀/G₁ phase. Zn deficiency induced apoptosis in both proliferating and quiescent neuronal cells via the intrinsic apoptotic pathway. Reductions in cellular Zn triggered a translocation of the pro-apoptotic protein Bad to the mitochondria, cytochrome c release, and caspase-3 activation. Apoptosis is the resultant of the inhibition of the prosurvival extracellular-signal-regulated kinase, the inhibition of nuclear factor-kappa B, and associated decreased expression of antiapoptotic proteins, and to a direct activation of caspase-3. A deficit of Zn during critical developmental periods can have persistent effects on brain function secondary to a deregulation of neuronal proliferation and apoptosis.

Zinc deficiency and neurodevelopment: the case of neurons

Zinc is essential for normal brain development. Gestational severe zinc deficiency can lead to overt fetal brain malformations. Although not teratogenic, suboptimal zinc nutrition during gestation can have long-term effects on the offspring's nervous system. This article will review current knowledge on the role of zinc in modulating neurogenesis and neuronal apoptosis as well as the proposed underlying mechanisms. A decrease in neuronal zinc causes cell cycle arrest, which in part involves a deregulation of select signals (ERK1/2, p53, and NF-kappaB). Zinc deficiency also induces apoptotic neuronal death through the intrinsic (mitochondrial) pathway, which can be triggered by the activation of the zinc-regulated enzyme caspase-3, and as a consequence of abnormal regulation of prosurvival signals (ERK1/2 and NF-kappaB). Alterations in the finely tuned processes of neurogenesis, neuronal migration, differentiation, and apoptosis, which involve the developmental shaping of the nervous system, could have a long-term impact on brain health. Zinc deficiency during gestation, even at the marginal levels observed in human populations, could increase the risk for behavioral/neurological disorders in infancy, adolescence, and adulthood.

Gestational zinc deficiency affects the regulation of transcription factors AP-1, NF-κB and NFAT in fetal brain

Transcription factors AP-1, nuclear factor κB (NF-κB) and NFAT are central to brain development by regulating the expression of genes that modulate cell proliferation, differentiation, apoptosis and synaptic plasticity. This work investigated the consequences of feeding zinc-deficient and marginal zinc diets to rat dams during gestation on the modulation of AP-1, NF-κB and NFAT in fetal brain. Sprague-Dawley rats were fed from gestation day (GD) 0 a control diet ad libitum (25 μg zinc/g diet, C), a zinc-deficient diet ad libitum (0.5 μg zinc/g diet, ZD), the control diet in the amounts eaten by the ZD rats (restrict fed, RF) or a diet containing a marginal zinc concentration ad libitum (10 μg zinc/g diet, MZD) until GD 19. AP-1-DNA binding was higher (50-190%) in nuclear fraction isolated from ZD, RF and MZD fetal brains compared to controls. In MZD fetal brain, high levels of activation of the upstream mitogen-activated protein kinases JNK and p38 and low levels of ERK phosphorylation were observed. Total levels of NF-κB and NFAT activation were higher or similar in the ZD and MZD groups than in controls, respectively. However, NF-κB- and NFAT-DNA binding in nuclear fractions was markedly lower in ZD and MZD fetal brain than in controls (50-80%). The latter could be related to zinc deficiency-associated alterations of the cytoskeleton, which is required for NF-κB and NFAT nuclear transport. In summary, suboptimal zinc nutrition during gestation could cause long-term effects on brain function, partially through a deregulation of transcription factors AP-1, NF-κB and NFAT.

Antioxidants modulate the IL-6 induced inhibition of negative acute-phase protein secretion in HepG2 cells

Despite increasing evidence on the potential of dietary antioxidants in modulating the etiology of certain chronic diseases such as cancer and cardiovascular diseases, little is known about their beneficial role in acute-phase responses and inflammatory diseases. From this viewpoint the aim of this study was to investigate the effect of selected dietary antioxidants in modulating the secretion of negative acute-phase proteins caused by interleukin-6 (IL-6) in HepG2 cells. Cells were first stimulated with a fixed dose of IL-6 for 24 h then incubated for a further 8 h with varying concentrations of eight antioxidants, alpha-lipoic acid (LA), (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), alpha-tocopherol (TOC), ascorbic acid (AA) and N-acetylcysteine (NAC). The culture supernatants were assayed for transthyretin (TTR) and retinol binding protein (RBP) using ELISA. The data revealed that IL-6 significantly reduced TTR and RBP secretion compared with the basal production. All tested antioxidants attenuate the reduction in TTR and RPB levels. The strongest effects were achieved with the highest concentration of each antioxidant. The order of effect were LA > EGCG > ECG > TOC > EGC > EC > NAC > AA. In conclusion, these results provide evidence that the dietary antioxidants can play a fundamental role in inflammatory processes.

Oxidative stress as a component of chromium-induced cytotoxicity in rat calvarial osteoblasts

It has been documented that medical prosthetic alloys release metal ions into surrounding tissues and cause cytotoxicity, but the mechanisms remain undefined. In that regard the cellular oxidative stress may be a common pathway in cellular responses to metal ions. The objective of this study was to approach the hypothesis that oxidative stress mediates chromium-induced cytotoxicity in rat calvarial osteoblasts. Osteoblasts were exposed to different concentrations of Cr6+ or Cr3+ (5-20 microM) in the presence or absence of the antioxidant N-acetyl-cysteine (NAC; 1-5 mM). Cellular viability, differentiation, and intracellular ultrastructural alterations were evaluated by MTT assay, alkaline phosphatase (ALP) activity assay, and transmission electron microscopy. Cellular oxidative stress was evaluated by intracellular reactive oxygen species (ROS) production. ROS production was monitored by the oxidation-sensitive fluorescent probe 2'7'-dichlorofluorescin diacetate (DCFH-DA). A time- and concentration- dependent increased cytotoxicity, time-dependent increased intracellular ROS production were indicated on exposure to Cr6+. Pretreatment of osteoblasts with 1-5 mM NAC afforded dose-dependent cytoprotective effects against Cr6+-induced cytotoxicity in osteoblasts. NAC decreased the level of intracellular ROS induced by Cr6+, too. While Cr3+ and NAC did not have any significant effects on osteoblasts (5-20 microM). These results suggest that oxidative stress is involved in Cr6+-induced cytotoxicity in osteoblasts, and NAC can provide protection for osteoblasts against Cr6+-induced oxidative stress. Cr3+ (5-20 microM) have no significant cytotoxicity in osteoblasts based on the results of this study.

Microtubules are required for NF-kappaB nuclear translocation in neuroblastoma IMR-32 cells: modulation by zinc

The relevance of a functional cytoskeleton for Nuclear Factor-kappaB (NF-kappaB) nuclear translocation was investigated in neuronal cells, using conditions that led to a disruption of the cytoskeleton [inhibition of tubulin (vinblastine, colchicine), or actin (cytochalasin D) polymerization and zinc deficiency]. We present evidence that an impairment in tubulin polymerization can inhibit the formation of the complex tubulin-dynein-karyopherin alpha-p50 that is required for neuronal retrograde and nuclear NF-kappaB transport. Cells treated with vinblastine, colchicine or cytochalasin D, and zinc deficient cells, all showed a low nuclear NF-kappaB binding activity, and low nuclear concentrations of RelA and p50. The altered nuclear translocation was reflected by a decreased transactivation of NF-kappaB-driven genes. The immunocytochemical characterization of cellular RelA showed that cytoskeleton disruption can lead to an altered distribution of RelA resulting in the formation of peripheral accumuli. These results support the concept that cytoskeleton integrity is necessary for the transport and translocation of NF-kappaB required for synapse to nuclei communication. We suggest that during development, as well as in the adult brain, conditions such as zinc deficiency, that affect the normal structure and function of the cytoskeleton can affect neuronal proliferation, differentiation, and survival by altering NF-kappaB nuclear translocation and subsequent impairment of NF-kappaB-dependent gene regulation.

Zinc deficiency increases the susceptibility of human neuroblastoma cells to lead-induced activator protein-1 activation

Lead (Pb2+) is a major environmental pollutant that has severe adverse effects on the nervous system. Similar human populations are at risk of suffering both Pb2+ toxicity and zinc (Zn) deficiency. Thus, in the present study we investigated whether Zn deficiency can increase the susceptibility of human neuroblastoma IMR-32 cells to Pb2+-induced oxidative stress which could trigger the activation of the mitogen-activated protein kinases (MAPKs) c-Jun-N-terminal kinase (JNK) and p38 and subsequently activate transcription factor activator protein-1 (AP-1). After 24 h of incubation, 5-50 microM Pb2+ caused a decrease in cell viability that was markedly higher in the Zn-deficient cells compared to controls. Pb caused a time (2-24 h) and dose (5-50 microM)-dependent increase of cell oxidants, with a significantly higher effect in the Zn-deficient cells. Pb2+ treatment triggered the activation of JNK and p38, measured as the phosphorylation of JNK and p38, only in cells incubated in the Zn-deficient media. The exposure to Pb2+ (2-24 h) led to a higher AP-1 DNA-binding activity and AP-1-dependent gene transactivation, only in the Zn-deficient cells. Results show that Zn deficiency can increase the cytotoxicity of Pb2+ and the susceptibility of neurons to Pb2+-induced oxidative stress, leading to JNK and p38 phosphorylation and, subsequently, AP-1 activation.

Zinc and the cytoskeleton in the neuronal modulation of transcription factor NFAT

Transcription factor NFAT is crucial in the development of the nervous system due to its role in neuronal plasticity and survival. In this study we characterized the role of zinc and the cytoskeleton in the modulation of NFAT in neuronal cells. The incubation of cells in zinc deficient media led to NFAT activation that was inhibited by the calcium chelator BAPTA and the antioxidants (+/-)-alpha-lipoic acid and N-acetyl cysteine, suggesting the involvement of calcium and oxidants in the initial steps of NFAT activation associated with zinc deficiency. At a second step of regulation, a decrease in cellular zinc led to an impaired transport of the active NFAT from the cytosol into the nucleus due to alterations in tubulin polymerization secondary to a decrease in neuronal zinc. Furthermore, disruption of the cytoskeleton structure by cold and chemical agents (colchicine (Col), vinblastine (VB), cytochalasin D (Cyt)) also inhibited NFAT transport into the nucleus. The altered nuclear transport caused a decrease in NFAT-dependent gene expression. This study demonstrates for the first time that zinc can modulate transcription factor NFAT in neuronal cells, and that microtubules are involved in NFAT nuclear translocation, crucial event in the regulation of NFAT transcriptional activity.