Changes in hepatic gene expression in response to hepatoprotective levels of zinc

Bombesin protects myocardium against ischemia/reperfusion injury via activation of the Keap1-Nrf2-HO-1 signaling pathway

AIMS

It has been reported that some peptides released by the gastro-intestinal tract play important roles in the prevention of myocardial ischemia/reperfusion injury (MIRI). Bombesin (BN) is a biologically active peptide released by non-adrenergic non-cholinergic nerves on the gastric antrum mucosa controlled by the vagus nerve. However, there is a lack of reports on the impact of BN on MIRI. This study aimed to explore the influence of BN on MIRI and its underlying mechanism.

MATERIALS AND METHODS

MIRI was induced by either 30min of global ischemia in Langendorff perfused rat hearts, or by ligation of the descending coronary artery for 30min in anesthetized Spraque-Dawley rats, and both were followed by 120min reperfusion. Infarct size and left ventricular function were assessed, and lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) levels were measured spectrophotometrically, while cardiomyocyte apoptosis was detected by TUNEL assay. The content of BN in plasma was measured with enzyme-linked immunosorbent assays (ELISA). The expression of caspase 3, Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) were quantified.

KEY FINDINGS

BN and vagus nerve stimulation improved cardiac contractile function and reduced myocardial infarct size, attenuated oxidative stress damage and myocardial cell apoptosis, increased the expression of Keap1, Nrf2, and HO-1. and these effects were blocked by using a BN receptor antagonist.

SIGNIFICANCE

BN provides protection against MIRI, and its underlying mechanism is through activation of the Keap1/Nrf2/HO-1 pathway. This research provides more reliable evidence for the "gut-heart axis dialogue" and explores potential therapeutic approaches for MIRI.

Transcriptional Regulation and Protein Localization of Zip10, Zip13 and Zip14 Transporters of Freshwater Teleost Yellow Catfish Pelteobagrus fulvidraco Following Zn Exposure in a Heterologous HEK293T Model

Zip family proteins are involved in the control of zinc (Zn) ion homeostasis. The present study cloned the promoters and investigated the transcription responses and protein subcellular localizations of three LIV-1 subfamily members (zip10, zip13, and zip14) from common freshwater teleost yellow catfish, Pelteobagrus fulvidraco, using in vitro cultured HEK293T model cells. The 2278 bp, 1917 bp, and 1989 bp sequences of zip10, zip13, and zip14 promoters, respectively, were subcloned into pGL3-Basic plasmid for promoter activity analysis. The pcDNA3.1 plasmid coding EGFP tagged pfZip10, pfZip13, and pfZip14 were generated for subsequent confocal microscope analysis. Several potential transcription factors’ binding sites were predicted within the promoters. In vitro promoter analysis in the HEK293T cells showed that high Zn administration significantly reduced the transcriptional activities of the zip10, zip13, and zip14 promoters. The −2017 bp/−2004 bp MRE in the zip10 promoter, the −360 bp/−345 bp MRE in the zip13 promoter, and the −1457 bp/−1442 bp MRE in the zip14 promoter were functional loci that were involved in the regulation of the three zips. The −606 bp/−594 bp KLF4 binding site in the zip13 promoter was a functional locus responsible for zinc-responsive regulation of zip13. The −1383 bp/−1375 bp STAT3 binding site in the zip14 promoter was a functional locus responsible for zinc-responsive regulation of zip14. Moreover, confocal microscope analysis indicated that zinc incubation significantly reduced the fluorescence intensity of pfZip10-EGFP and pfZip14-EGFP but had no significant influence on pfZip13-EGFP fluorescence intensity. Further investigation found that pfZip10 localizes on cell membranes, pfZip14 colocalized with both cell membranes and lysosome, and pfZip13 colocalized with intracellular ER and Golgi. Our research illustrated the transcription regulation of zip10, zip13, and zip14 from P. fulvidraco under zinc administration, which provided a reference value for the mechanisms involved in Zip-family-mediated control of zinc homeostasis in vertebrates.

Transcriptional responses of four slc30a/znt family members and their roles in Zn homeostatic modulation in yellow catfish Pelteobagrus fulvidraco

The study characterized their regulatory functions of four znt members (znt1, znt2, znt6 and znt8) in Zn homeostasis in vertebrates. We found that the -1281/-1296 bp locus on the znt1 promoter, the -1/-16 bp locus on the znt2 promoter, the -825/-839 bp locus on the znt6 promoter, the -165/-180 bp locus and the -274/-292 bp STAT3 locus on the znt8 promoter were functional MTF-1 binding sites and had metal responsive element (MRE). Zn incubation increased activities of four znt promoters, which was mediated by MRE sites on znt1, znt2, znt6 and znt8 promoters and by STAT3 binding site on znt8 promoter. Moreover, Zn activated the transcription of these znts genes through MTF-1-MRE-dependent pathway. Zn incubation up-regulated the mRNA and total protein expression of ZnT1, ZnT2 and ZnT8 at both 24 h and 48 h. Overall, for the first time, this study offered novel insights for regulatory mechanism of Zn homeostasis in vertebrates.

Testosterone propionate activated the Nrf2-ARE pathway in ageing rats and ameliorated the age-related changes in liver

The present study aimed to evaluate the protective efficacy of testosterone propionate (TP) on age-related liver changes via activation of the nuclear factor erythroid 2-related factor 2-antioxidant response element (Nrf2-ARE) pathway in aged rats. Aged rats received subcutaneous injections of TP (2 mg/kg/d, 84 days). Oxidative stress parameters and the expression levels of signal transducer and activator of transcription 5b (STAT5b), Kelch-like ECH associating protein-1 (Keap1), Nrf2, haem oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase-1 (NQO1) in liver tissues were examined to check whether the Nrf2-ARE pathway was involved in the age-related changes in liver. Our results showed that TP supplementation alleviated liver morphology, liver function and liver fibrosis; improved oxidative stress parameters; and increased the expression of STAT5b, Nrf2, HO-1 and NQO-1 and decreased the expression of Keap1 in the liver tissues of aged rats. These results suggested that TP increased the expression of STAT5b, and then activated the Nrf2-ARE pathway and promoted antioxidant mechanisms in aged rats. These findings may provide new therapeutic uses for TP in patients with age-related liver changes.

Effects of Copper and Zinc Supplementation on Weight Gain and Hematological Parameters in Pre-weaning Calves

Cow-calf operations may be affected by trace mineral deficiencies, particularly copper (Cu) and zinc (Zn) deficiency, which may decrease the calf daily weight gain and alter hematological parameters. We evaluated the effect of Cu and Zn supplementation on pre-weaning calves (n = 40; 92 ± 6 kg initial body weight) from the Salado River basin, Buenos Aires, Argentina. Calves were divided into four groups (n = 10 each) and subcutaneously administered 0.3 mg/kg Cu (Cu group), 1 mg/kg Zn (Zn group), Cu and Zn together (Cu + Zn group), and sterile saline solution (control group) every 40 days for 120 days. Plasma Cu and Zn concentrations, hematological parameters, and weight were recorded every 40 days. A completely randomized 2 × 2 factorial treatment design was used and data were analyzed with a mixed model for repeated measures over time. Cu and Zn were detected in plasma after the second sampling. Cu × Zn interaction was significant (p = 0.09), being Cu concentration higher in the Cu + Zn than in the Cu group. Differences in weight gain (Zn × time interaction; p < 0.01) were observed in the Zn but not in the Cu group (p > 0.1). On the other hand, none of the treatments altered any of the hematological parameters assessed (p > 0.1). Our results show the risk of lower weight gain due to Zn deficiency in pre-weaning calves raised in the Salado River basin.

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

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

β1-Integrin Deletion From the Lens Activates Cellular Stress Responses Leading to Apoptosis and Fibrosis

Purpose

Previous research showed that the absence of β1-integrin from the mouse lens after embryonic day (E) 13.5 (β1MLR10) leads to the perinatal apoptosis of lens epithelial cells (LECs) resulting in severe microphthalmia. This study focuses on elucidating the molecular connections between β1-integrin deletion and this phenotype.

Methods

RNA sequencing was performed to identify differentially regulated genes (DRGs) in β1MLR10 lenses at E15.5. By using bioinformatics analysis and literature searching, Egr1 (early growth response 1) was selected for further study. The activation status of certain signaling pathways (focal adhesion kinase [FAK]/Erk, TGF-β, and Akt signaling) was studied via Western blot and immunohistochemistry. Mice lacking both β1-integrin and Egr1 genes from the lenses were created (β1MLR10/Egr1-/-) to study their relationship.

Results

RNA sequencing identified 120 DRGs that include candidates involved in the cellular stress response, fibrosis, and/or apoptosis. Egr1 was investigated in detail, as it mediates cellular stress responses in various cell types, and is recognized as an upstream regulator of numerous other β1MLR10 lens DRGs. In β1MLR10 mice, Egr1 levels are elevated shortly after β1-integrin loss from the lens. Further, pErk1/2 and pAkt are elevated in β1MLR10 LECs, thus providing the potential signaling mechanism that causes Egr1 upregulation in the mutant. Indeed, deletion of Egr1 from β1MLR10 lenses partially rescues the microphthalmia phenotype.

Conclusions

β1-integrin regulates the appropriate levels of Erk1/2 and Akt phosphorylation in LECs, whereas its deficiency results in the overexpression of Egr1, culminating in reduced cell survival. These findings provide insight into the molecular mechanism underlying the microphthalmia observed in β1MLR10 mice.

Protection from Oxidative Stress in Immunocytes of the Colonial Ascidian Botryllus schlosseri: Transcript Characterization and Expression Studies

Botryllus schlosseri is a cosmopolitan colonial ascidian that undergoes cyclical generation changes, or take-overs, during which adult zooids are resorbed and replaced by their buds. At take-over, adult tissues undergo diffuse apoptosis and effete cells are massively ingested by circulating phagocytes, with a consequent increase in oxygen consumption and in production of reactive oxygen species (ROS). The latter are responsible for the death of phagocytes involved in the clearance of apoptotic cells and corpses by phagocytosis-induced apoptosis. However, the majority of phagocytes and hemocytes do not die, even if they experience oxidative stress. This fact suggests the presence of detoxification mechanisms assuring their protection. To test this assumption, we searched for transcripts of genes involved in detoxification in the transcriptome of B. schlosseri. We identified and characterized transcripts for Cu/Zn superoxide dismutase (SOD), γ-glutamyl-cysteine ligase modulatory subunit (GCLM), glutathione synthase (GS), and two glutathione peroxidases (i.e., GPx3 and GPx5), all involved in protection from ROS. We also carried out a phylogenetic analysis of the putative amino acid sequences, confirming their similarity to their vertebrate counterparts, and studied the location of their mRNAs by in situ hybridization on hemocyte monolayers. We also analyzed gene transcription during the colonial blastogenetic cycle, which is the interval of time between one take-over and the next, by qRT-PCR. In addition, we investigated the effects of cadmium (Cd), an inducer of oxidative stress, on gene transcription. Our results indicated that i) antioxidant gene expression is modulated in the course of the blastogenetic cycle and upon exposure to Cd, and ii) hemocytes synthesize both enzymatic and nonenzymatic antioxidants, in line with the idea that they represent a major detoxification system for ascidians.

Metallothionein does not sequester arsenic(III) ions in condition of acute arsenic toxicity

The major cause of toxicity of trivalent arsenicals is due to their interaction with the sulfhydryl groups in proteins. Because of its high content, Metallothionein (MT) provides one of the most favorable conditions for the binding of As(III) ions to it. MT has long been anticipated for providing resistance in case of arsenic (As) toxicity with similar mechanism as in case of cadmium toxicity. The present study investigates whether the sequestration of As ions by MT is one of the mechanisms in providing protection against acute arsenic toxicity. A rat model study on the metal stoichiometric analysis of MT1 isoform isolated from the liver of arsenic treated, untreated and zinc treated animals has been carried out using the combination of particle induced X-ray emission (PIXE) and electrospray ionisation mass spectrometry (ESI-MS). The results revealed the absence of arsenic bound MT1 in the samples isolated from arsenic treated animals. Although, both Cu and Zn ions were present in MT1 samples isolated from all the treatment groups. Moreover, only partially metallated MT1 with varying number of Zn ions were observed in all the groups. These results suggest that the role of MT during acute arsenic toxicity is different from its already established role in case of cadmium toxicity.

Mechanistic studies of the toxicity of zinc gluconate in the olfactory neuronal cell line Odora

Zinc is both an essential and potentially toxic metal. It is widely believed that oral zinc supplementation can reduce the effects of the common cold; however, there is strong clinical evidence that intranasal (IN) zinc gluconate (ZG) gel treatment for this purpose causes anosmia, or the loss of the sense of smell, in humans. Using the rat olfactory neuron cell line, Odora, we investigated the molecular mechanism by which zinc exposure exerts its toxic effects on olfactory neurons. Following treatment of Odora cells with 100 and 200μM ZG for 0-24h, RNA-seq and in silico analyses revealed up-regulation of pathways associated with zinc metal response, oxidative stress, and ATP production. We observed that Odora cells recovered from zinc-induced oxidative stress, but ATP depletion persisted with longer exposure to ZG. ZG exposure increased levels of NLRP3 and IL-1β protein levels in a time-dependent manner, suggesting that zinc exposure may cause an inflammasome-mediated cell death, pyroptosis, in olfactory neurons.

Chlorogenic acid prevents acetaminophen-induced liver injury: the involvement of CYP450 metabolic enzymes and some antioxidant signals

Chlorogenic acid (CGA), a polyphenolic compound, is abundant in fruits, dietary vegetables, and some medicinal herbs. This study investigated the prevention of CGA against acetaminophen (AP)-induced hepatotoxicity and its engaged mechanisms. CGA reversed the decreased cell viability induced by AP in L-02 cells in vitro. In addition, CGA reduced the AP-induced increased serum levels of alanine/aspartate aminotransferase (ALT/AST) in vivo. The effect of CGA on cytochrome P450 (CYP) enzymatic (CYP2E1, CYP1A2, and CYP3A4) activities showed that CGA caused very little inhibition on CYP2E1 and CYP1A2 enzymatic activities, but not CYP3A4. The measurement of liver malondialdehyde (MDA), reactive oxygen species (ROS), and glutathione (GSH) levels showed that CGA prevented AP-induced liver oxidative stress injury. Further, CGA increased the AP-induced decreased mRNA expression of peroxiredoxin (Prx) 1, 2, 3, 5, 6, epoxide hydrolase (Ephx) 2, and polymerase (RNA) II (DNA directed) polypeptide K (Polr2k), and nuclear factor erythroid-2-related factor 2 (Nrf2). In summary, CGA ameliorates the AP-induced liver injury probably by slightly inhibiting CYP2E1 and CYP1A2 enzymatic properties. In addition, cellular important antioxidant signals such as Prx1, 2, 3, 5, 6, Ephx2, Polr2k, and Nrf2 also contributed to the protection of CGA against AP-induced oxidative stress injury.

Effect of Total Flavone of Haw Leaves on Nuclear Factor Erythroid-2 Related Factor and Other Related Factors in Nonalcoholic Steatohepatitis Rats

OBJECTIVE

To investigate the effect of total flavone of haw leaves (TFHL) on the expression of nuclear factor erythroid-2 related factor (Nrf2) and other related factors in nonalcoholic steatohepatitis (NASH) rats induced by high-fat diet and then to further discuss the mechanism of TFHL's prevention against NASH.

METHODS

High-fat diet was fed to 40 rats to establish the NASH model. Then model rats were intragastrically administrated with 40, 80, 160 mg/(kg•day) TFHL, respectively. The pathological changes of liver tissues in NASH rats were detected by oil red O and hematoxylin-eosin (HE) stainings. The expression of Nrf2 in rat liver was examined through immunohistochemistry. The level of 8-iso-prostaglandin F2α in serum was detected through enzyme linked immunosorbent assay (ELISA). The mRNA and protein levels of Nrf2 and other related factors in liver tissue were measured by real-time reverse transcriptionpolymerase chain reaction and western blot.

RESULTS

Lipid deposition, hepatic steatosis, focal necrosis in lobular inflammation and ballooning degeneration were emerged in livers of NASH rats. The 8-iso-prostaglandin F2α in the serum of NASH rats increased significantly compared with the control group (P<0.05). The mRNA of Nrf2, hemeoxyenase1 (HO-1) and the mRNA and protein levels of quinine oxidoreductase (NQO1) in NASH rats liver tissue showed a striking increase, while the mRNA levels of Keap1, r-glutamylcysteine synthethase (rGCS) and glutathione S-transferase (GST) were significantly decreased compared with the control group (P<0.05). After TFHL treatment, 8-iso-prostaglandin F2α level in serum significantly decreased, and Nrf2 mRNA and protein levels in hepatocytes nucleus enhanced compared with the model group (P<0.05 or 0.01). Meanwhile the Keap1 mRNA, the mRNA and protein levels of HO-1, NQO1 antibody, rGCS antibody, GST increased after TFHL treatment (P<0.05 or 0.01).

CONCLUSIONS

Nrf2 and other related factors were involved in development of NASH, and they also served as an important part in its occurrence. By regulating expression of Nrf2 and other related factors, TFHL may play a role in antioxidative stress and prevention of NASH.

Protective Effects of Zinc Against Acute Arsenic Toxicity by Regulating Antioxidant Defense System and Cumulative Metallothionein Expression

Arsenic (As), a toxic metalloid, is one of the major global concerns. The toxicity resulting from As exposure is linked to the generation of reactive oxygen intermediates during their redox cycling and metabolic activation processes that cause lipid peroxidation (LPO). Zinc (Zn), a redox-inactive metal, helps to maintain cellular functions because of its prominent role in antioxidant network through multiple mechanisms. The present study, therefore, explores the effectiveness of administered Zn to combat against acute As toxicity by analysis of antioxidant defense status, alkaline phosphatase (ALP) activity, histological profile, MT expression, and elemental status in rat liver. To achieve this goal, four experimental groups, one control and three receiving different metal supplementations, were chosen (group 1, control; group 2, Zn supplemented; group 3, As substituted; group 4, Zn + As supplemented). The levels of reduced glutathione (GSH) and activities of glutathione reductase (GR) and ALP were lowered, whereas LPO levels and activity of superoxide dismutase (SOD) were elevated with no significant change in catalase (CAT) activity. Histopathological changes were also observed in the As substituted group in comparison to the control. Particle-induced X-ray emission (PIXE) analysis showed decrease in Fe and S concentration in rat liver after As intoxication, whereas As was below detection limit, i.e., <1 ppm. Zn administration almost restored the antioxidants, ALP activity, histopathological changes, and elemental status. A cumulative increase in MT expression was found with the combined treatment of Zn and As. Also, Zn alone caused no significant change in the antioxidant defense system. It can be concluded that restoration of antioxidant activity and increased MT expression are the two independent protective mechanisms of Zn to reduce acute As toxicity.

Association of serum zinc levels with liver function and survival in patients awaiting liver transplantation

PURPOSE

Zinc is an important trace element with catalytic and defensive functions. We assessed the impact of zinc deficiency in patients with end-stage liver disease awaiting liver transplantation.

METHODS

Serum zinc levels were measured at the time of evaluation for liver transplantation (n = 368). Patients were dichotomized in two groups based on low and normal zinc serum levels.

RESULTS

Serum zinc levels are tightly associated with liver function as patients with low zinc levels (n = 226) had a higher Model for End-Stage Liver Disease (MELD) score (15.0 [5.0-40.0]) than patients with normal zinc (n = 142) levels (9.0 [6.0-34.0]; p < 0.00). Multivariate analysis demonstrated that serum zinc levels function as an independent predictor of hepatic decompensation (hydropic decompensation: odds ratio [OR] 0.82; 95% confidence interval [CI] 0.70-0.96; p = 0.015; hepatic encephalopathy: OR 0.80; 95% CI 0.71-0.90; p = 0.000; spontaneous bacterial peritonitis: OR 0.85; 95% CI 0.72-1.00; p = 0.047; hepatorenal syndrome: OR 0.83; 95% CI 0.72-0.95; p = 0.011). Actuarial survival free of liver transplantation was reduced for low-zinc patients (26.7 ± 4.0 months; 95% CI 18.8-34.6) compared to patients with normal zinc levels (30.9 ± 3.0 months; 95% CI 24.9-36.9; p = 0.008). Reduction of zinc levels for patients on the transplantation list resulted in a 28.3-fold increased risk of death/liver transplantation (95% CI 3.2-244.8, p < 0.001).

CONCLUSIONS

Serum zinc levels are associated with reduced survival in end-stage liver disease patients. Whether or not zinc supplementation might be beneficial for patients on a liver transplantation list requires further study.

Dietary regulation of Keap1/Nrf2/ARE pathway: focus on plant-derived compounds and trace minerals

It has become increasingly evident that chronic inflammation underpins the development of many chronic diseases including cancer, cardiovascular disease and type 2 diabetes. Oxidative stress is inherently a biochemical dysregulation of the redox status of the intracellular environment, which under homeostatic conditions is a reducing environment, whereas inflammation is the biological response to oxidative stress in that the cell initiates the production of proteins, enzymes, and other compounds to restore homeostasis. At the center of the day-to-day biological response to oxidative stress is the Keap1/Nrf2/ARE pathway, which regulates the transcription of many antioxidant genes that preserve cellular homeostasis and detoxification genes that process and eliminate carcinogens and toxins before they can cause damage. The Keap1/Nrf2/ARE pathway plays a major role in health resilience and can be made more robust and responsive by certain dietary factors. Transient activation of Nrf2 by dietary electrophilic phytochemicals can upregulate antioxidant and chemopreventive enzymes in the absence of actual oxidative stress inducers. Priming the Keap1/Nrf2/ARE pathway by upregulating these enzymes prior to oxidative stress or xenobiotic encounter increases cellular fitness to respond more robustly to oxidative assaults without activating more intense inflammatory NFκB-mediated responses.

Survival study of metallothionein-1 transgenic mice and respective controls (C57BL/6J): influence of a zinc-enriched environment

The role of metallothioneins (MTs) in aging is not completely understood. Several studies have shown evidence that these proteins could represent a defense system against oxidative damage, but survival studies on mice overexpressing MTs are poor. Here we describe a survival study performed on old MT-1-overexpressing mice (MT-TG) and their respective controls (C57BL/6J) fed a standard or zinc (Zn)-supplemented diet. MT-TG mice had significantly increased survival compared with control. Zn supplementation affects the survival curves of MT-TG and C57BL/6J mice differently. This study poses the basis for intervention based on gene therapy with MTs to enhance the health span of laboratory mice.

In vitro transdifferentiation of HepG2 cells to pancreatic-like cells by CCl₄, D-galactosamine, and ZnCl₂

OBJECTIVE

The objective of the study was to induce transdifferentiation of human hepatoma HepG2 cells into pancreatic-like cells without direct genetic intervention.

METHODS

HepG2 cells were transfected with plasmids for the hepatocyte marker protein green fluorescent protein (albumin-GFP) and the pancreatic cell marker Discosoma spp red fluorescent protein (elastase-DsRed) to create FAE-HepG2 cells. Fluorescent marker expression was used to monitor in vitro transdifferentiation stimulated 100 mM CCl₄, 2 mM D-galactosamine, or 200 μM ZnCl₂. Concentrations were selected for optimal cell survival rate. Transdifferentiation was also characterized by immunohistochemical detection of amylase, glucagon, and insulin and by polymerase change reaction analysis of amylase and insulin mRNA production.

RESULTS

Control cells expressed albumin-GFP but no elastase-DsRed. By 30 days of culture, all 3 agents induced expression of pancreatic-like cell marker elastase-DsRed. ZnCl₂ was the most effective as most cells expressed elastase-DsRed in the absence of simultaneous expression of albumin-GFP. For CCl₄ and D-galactosamine, elastase-DsRed was expressed in the same cells as albumin-GFP. Cells treated by each agent also expressed amylase, insulin, and glucagon proteins and mRNAs.

CONCLUSIONS

Without direct genetic intervention, select low small molecules can induce in vitro transformation of hepatoma cells into pancreatic-like cells.

Zinc chloride for odontogenesis of dental pulp stem cells via metallothionein up-regulation

INTRODUCTION

Previous studies have shown that zinc chloride (ZnCl(2)) can induce metallthionein (MT) in the liver and kidney to protect tissues against toxicants and shows a better corneal wound healing than conventional drugs do. We hypothesized that ZnCl(2) can promote odontogenesis of dental pulp stem cells (DPSCs) via MT. The purpose of this study was to investigate the effects of ZnCl(2) on human DPSCs and the expression of MT.

METHODS

DPSCs were isolated by flow cytometry with selective surface marker CD146 and STRO-1. After they grew into confluence, DPSCs were induced into odontoblasts with or without ZnCl(2) supplemented in the culture medium for 21 days. The effect of ZnCl(2) on DPSCs differentiation was examined followed by alkaline phosphatase staining/activity and quantitative real-time polymerase chain reaction analysis.

RESULTS

By treating DPSCs with ZnCl(2), the duration of mineralization was shortened and expressions of differentiation markers into odontoblasts were more significant than those without ZnCl(2) stimulation. Besides, the MT gene expression was increased with the increasing expressions of odontoblasts' markers after treated with ZnCl(2).

CONCLUSION

This was the first report that ZnCl(2) could promote odontoblastic differentiation of DPSCs through the up-regulation of gene MT.

Rapid changes in heat-shock cognate 70 levels, heat-shock cognate phosphorylation state, heat-shock transcription factor, and metal transcription factor activity levels in response to heavy metal exposure during sea urchin embryonic development

The aim of the present study was to analyze and compare the effects of several metals on the embryos of the sea urchin Paracentrotus lividus, a key species within the Mediterranean Sea ecosystem. Embryos were continuously exposed from fertilization to the following metals: 0.6 mg/l copper, 3 mg/l lead, and 6 mg/l nickel. The embryos were then monitored for metal responses at the gastrula stage, which occurred 24 h after exposure. A biochemical multi-experimental approach was taken and involved the investigation of the levels of HSC70 expression and the involvement of heat shock factor (HSF) and/or metal transcription factor (MTF) in the response. Immunoblotting assays and electrophoretic mobility shift assays (EMSA) were used to detect stress protein levels and to study the interaction between DNA and specific transcription factors, respectively. In the 1 h during exposure to heavy metals, changes in HSC70 levels and HSC70 a phosphorylation state were observed. Rapid changes in HSF and MTF DNA-binding activity also occurred during the early stages of heavy metal exposure. In contrast, few developmental abnormalities were observed at the gastrula stage but more abnormalities were observed 48 h after metal exposure. These data demonstrate that changes in HSC70 levels and phosphorylation state as well as in HSF and MTF binding activities may be used to rapidly detect responses to heavy metal exposure. Detection of biochemical and molecular changes in response to metal exposure before manifestation of morpho-pathological effects are important for the prediction of morbidity, and these markers will be useful for determining the response to exposure as part of a toxicological exposure-response experiment and for determining responses for an impact assessment.

Metallothionein and the biology of aging

Metallothionein (MT) is a low molecular weight protein with anti-apoptotic properties that has been demonstrated to scavenge free radicals in vitro. MT has not been extensively investigated within the context of aging biology. The purpose of this review, therefore, is to discuss findings on MT that are relevant to basic aging mechanisms and to draw attention to the possible role of MT in pro-longevity interventions. MT is one of just a handful of proteins that, when overexpressed, has been demonstrated to increase mouse lifespan. MT also protects against development of obesity in mice provided a high fat diet as well as diet-induced oxidative stress damage. Abundance of MT is responsive to caloric restriction (CR) and inhibition of the insulin/insulin-like signaling (IIS) pathway, and elevated MT gene expression has been observed in tissues from fasted and CR-fed mice, long-lived dwarf mice, worms maintained under CR conditions, and long-lived daf-2 mutant worms. The dysregulation of MT in these systems is likely to have tissue-specific effects on aging outcomes. Further investigation will therefore be needed to understand how MT contributes to the response of invertebrates and mice to CR and the endocrine mutations studied by aging researchers.

Melatonin prevents the decreased activity of antioxidant enzymes and activates nuclear erythroid 2-related factor 2 signaling in an animal model of fulminant hepatic failure of viral origin

This work was undertaken to investigate whether treatment with melatonin prevents oxidative stress and changes in the expression and activity of factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant enzymes in an animal model of fulminant hepatic failure of viral origin. Rabbits were experimentally infected with 2 x 10(4) hemagglutination units of a rabbit hemorrhagic disease virus (RHDV) isolate and received melatonin at two concentrations of 10 mg/kg and 20 mg/kg at 0, 12 and 24 hr postinfection. Blood transaminases, blood lactate dehydrogenase, liver concentration of thiobarbituric reactive acid substances and the liver oxidized to reduced glutathione ratio significantly increased at 36 hr postinfection in infected animals. Significant decreases were found in the mRNA levels and in the liver activities of Mn-superoxide dismutase, glutathione peroxidase and glutathione-S-transferase in infected rabbits. These effects were prevented by melatonin administration in a concentration-dependent manner. Melatonin treatment was not accompanied by changes in protein levels of Kelch-like ECH-associating protein 1 (Keap1) but resulted in an increased protein expression of Nrf2 in the cytoplasm and the nucleus, which was confirmed by the results of Nrf2 immunostaining. Nuclear extracts from livers of melatonin-treated rats displayed an enhanced antioxidant responsive element (ARE)-binding activity of Nrf2. Our results suggest a potential hepatoprotective role of melatonin in fulminant hepatic failure, partially mediated through the abrogation of oxidative stress and the prevention of the decreased activity of antioxidant enzymes via the Nrf2 pathways.

Mechanism of protection by metallothionein against acetaminophen hepatotoxicity

Acetaminophen (APAP) overdose is the most frequent cause of drug-induced liver failure in the US. Metallothionein (MT) expression attenuates APAP-induced liver injury. However, the mechanism of this protection remains incompletely understood. To address this issue, C57BL/6 mice were treated with 100 micromol/kg ZnCl2 for 3 days to induce MT. Twenty-four hours after the last dose of zinc, the animals received 300 mg/kg APAP. Liver injury (plasma ALT activities, area of necrosis), DNA fragmentation, peroxynitrite formation (nitrotyrosine staining), MT expression, hepatic glutathione (GSH), and glutathione disulfide (GSSG) levels were determined after 6 h. APAP alone caused severe liver injury with oxidant stress (increased GSSG levels), peroxynitrite formation, and DNA fragmentation, all of which were attenuated by zinc-induced MT expression. In contrast, MT knockout mice were not protected by zinc. Hydrogen peroxide-induced cell injury in primary hepatocytes was dependent only on the intracellular GSH levels but not on MT expression. Thus, the protective effect of MT in vivo was not due to the direct scavenging of reactive oxygen species. Zinc treatment had no effect on the early GSH depletion kinetics after APAP administration, which is an indicator of the metabolic activation of APAP to its reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI). However, MT was able to effectively trap NAPQI by covalent binding. We conclude that MT scavenges some of the excess NAPQI after GSH depletion and prevents covalent binding to cellular proteins, which is the trigger for the propagation of the cell injury mechanisms through mitochondrial dysfunction and nuclear DNA damage.