Cadmium induces alpha(1)collagen (I) and metallothionein II gene and alters the antioxidant system in rat hepatic stellate cells

Metal- and Organ-Specific Response to Heavy Metal-Induced Stress Mediated by Antioxidant Enzymes' Activities, Polyamines, and Plant Hormones Levels in Populus deltoides

Besides anthropogenic factors, climate change causes altered precipitation patterns that indirectly affect the increase of heavy metals in soils due to hydrological effects and enhanced leaching (i.e., Cd and Ni), especially in the vicinity of mines and smelters. Phytoextraction is a well-known, powerful "green" technique for environmental clean-up that uses plants to extract, sequester, and/or detoxify heavy metals, and it makes significant contributions to the removal of persistent inorganic pollutants from soils. Poplar species, due to their growth features, high transpiration rate, large biomass, and feasible reproduction represent great candidates for phytoextraction technology. However, the consequences of concomitant oxidative stress upon plant metabolism and the mechanism of the poplar's tolerance to heavy metal-induced stress are still not completely understood. In this study, cuttings of poplar species (Populus deltoides W. Bartram ex Marshall) were separately exposed to two heavy metals (Cd²⁺ and Ni²⁺) that were triple the maximum allowed amount (MAA) (according to national legislation). The aim of the study was to estimate the effects of heavy metals on: (I) the accumulation of free and conjugated polyamines, (II) plant hormones (including abscisic acid-ABA and indole-3-acetic acid-IAA), and (III) the activities of different antioxidant enzymes at root and leaf levels. By using the selected ion monitoring (SIM) mode of gas chromatography with mass spectrometry (GC/MS) coupled with the isotopically labeled technique, amounts of ABA and IAA were quantified, while polyamine amounts were determined by using high-performance liquid chromatography (HPLC) with fluorometric detection after derivatization. The results showed that P. deltoides responded to elevated concentrations of heavy metals in soils by exhibiting metal- and organ-specific tolerance. Knowledge about tolerance mechanisms is of great importance for the development of phytoremediation technology and afforestation programs for polluted soils.

The Impact of a Polyphenol-Rich Extract from the Berries of Aronia melanocarpa L. on Collagen Metabolism in the Liver: A Study in an In Vivo Model of Human Environmental Exposure to Cadmium

This study examined whether a polyphenol-rich extract from the berries of Aronia melanocarpa L. (AE; chokeberries) may protect from the impact of cadmium (Cd) on the metabolism of collagen in the liver. The study was conducted in an experimental model (rats that were fed a diet containing 1 or 5 mg Cd/kg for 3-24 months) of human exposure to this xenobiotic during a lifetime. The concentration of total collagen and the expression of collagen types I and III at the mRNA and protein levels, as well as the concentrations of matrix metalloproteinases (MMP-1 and MMP-2) and their tissue inhibitors (TIMP-1 and TIMP-2), were assayed. The administration of Cd and/or AE had only a slight and temporary impact on the concentration of total collagen in the liver. The supplementation with AE significantly prevented Cd-mediated changes in the expression of collagen types I and III at the mRNA and protein levels and their ratio (collagen III/collagen I), as well as a rise in the concentrations of MMPs and TIMPs in this organ. The results allow the conclusion that the intake of chokeberry products in the case of Cd intoxication may be effective in prevention from this xenobiotic-induced disturbance in collagen homeostasis in the liver.

Glutathione Might Attenuate Cadmium-Induced Liver Oxidative Stress and Hepatic Stellate Cell Activation

The liver is a major organ involved in cadmium (Cd)-induced oxidative damage. Following liver injury, hepatic stellate cells (HSCs) are activated to participate in the wound healing process, but also facilitate liver fibrosis. Previous studies have observed fibrogenic effects of Cd on liver. However, the oxidative stress mechanisms of Cd-induced HSC activation as well as whether administration of glutathione (GSH) alleviates this activation, remain unclear. In this study, 24 rats were divided randomly into four experimental groups: control, GSH-treated, Cd-treated, and Cd + GSH-treated. After 4 weeks, the liver injury index, HSC-specific activation markers, oxidative stress-related antioxidants, and enzyme activities and signals were measured. Cd uptake and the generation of reactive oxygen species (ROS) in hepatocytes were detected by mass cytometry and fluorescence microscopy, respectively. Levels of aspartate aminotransferase, xanthine oxidase, γ-glutamyl transpeptidase, and α-smooth muscle actin (αSMA) were significantly increased in Cd-treated rats. Activated HSCs positive for αSMA expression and excess collagen deposition were detected in the Cd-treated group. In contrast, activities of the antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase were reduced. Supplementation with GSH reversed some of the Cd-induced effects and increased the protein level of phosphorylated (p)-P65 while decreasing p-JNK. Pretreatment with GSH lowered Cd uptake and ROS generation in hepatocytes in vitro. These results indicate that administration of GSH was effective in attenuating Cd-induced oxidative stress via decreasing Cd uptake, restoring the activities of oxidative enzymes, activating NF-κB, inhibiting the JNK signaling pathway, and preventing excessive ROS generation and HSC activation.

P311 modulates hepatic stellate cells migration

BACKGROUND & AIMS

Liver fibrosis is induced by the accumulation of extracellular matrix, deposited mainly by activated hepatic stellate cells (HSCs). One key characteristic of stellate cell activation is the directional migration to the site of injury during the wound-healing process. P311 is a protein that has been shown to play a role in migration and we aimed to study a possible role for this protein during stellate cell migration.

METHODS

Mouse stellate cells were isolated and cultured in vitro to investigate P311 protein and gene expression during HSC activation by immunocytochemistry and RT-qPCR respectively. Expression of P311 during in vivo activation was evaluated in CCl4 and bile duct ligation-induced liver fibrosis. Production of reactive oxygen species was determined using the fluorescent probe DCFH-DA. By siRNA-mediated knockdown of P311, we investigated a possible effect on proliferation by incorporation of EdU and on migration by Boyden chamber assays.

RESULTS

P311 gene expression was increased during both in vitro and in vivo activation of HSCs. siRNA-mediated knockdown led to a decrease in reactive oxygen production and cell proliferation. Migration induced by different chemokines, such as PDGF-bb and MCP-1 was inhibited by knockdown of P311.

CONCLUSIONS

P311 is central to reactive oxygen species-mediated HSC migration induced by different chemokines.

The liver in itai-itai disease (chronic cadmium poisoning): pathological features and metallothionein expression

Cadmium (Cd) is a highly hepatotoxic heavy metal, which is widely dispersed in the environment. Acute Cd hepatotoxicity has been well studied in experimental animals; however, effects of prolonged exposure to Cd doses on the liver remain unclear. In the present study, to evaluate chronic Cd hepatotoxicity, we examined specimens from cases of itai-itai disease, the most severe form of chronic Cd poisoning. We compared 89 cases of itai-itai disease with 27 control cases to assess Cd concentration in organs. We also examined 80 cases of itai-itai disease and 70 control cases for histopathological evaluation. In addition, we performed immunohistochemistry for metallothionein, which binds and detoxifies Cd. Hepatic Cd concentration was higher than Cd concentration in all other organs measured in the itai-itai disease group, whereas it was second highest following renal concentration in the control group. In the liver in the itai-itai disease group, fibrosis was observed at a significantly higher rate than that in the control group. Metallothionein expression was significantly higher in the itai-itai disease group than that in the control group. Prolonged exposure to low doses of Cd leads to high hepatic accumulation, which can then cause fibrosis; however, it also causes high expression of metallothionein, which is thought to reduce Cd hepatotoxicity.

Early defense responses in the freshwater bivalve Corbicula fluminea exposed to copper and cadmium: Transcriptional and histochemical studies

The aim of the present study was to measure the early effects of copper (10 and 50 μg L(-1)), cadmium (2, 10, and 50 μg L(-1)) and mixtures of these metals in the freshwater bivalve Corbicula fluminea exposed for 12 h in laboratory. Transcription levels of superoxide dismutase (SOD), catalase (CAT), selenium-dependent glutathione peroxidase (Se-GPx), pi-class glutathione S-transferase (pi-GST), metallothionein (MT) in digestive gland and gills, and response of lysosomal system and neutral lipids in digestive gland were determined after the exposure period. Results showed that lysosomal system, neutral lipids content, and mRNA levels were modified, suggesting their early response against oxidative stress and their important role in cell integrity. The integrated biomarker response was calculated and showed that the effects of the combinations of Cu and Cd on the biomarker responses are additive. MT and pi-GST mRNA expression correspond to the largest ranges of response. As efficient biomarkers should have an early warning capacity, SOD, CAT, Se-GPx, pi-GST, MT transcripts levels, lysosomal system, and neutral lipids could be used as biomarkers of metal contamination in the aquatic environment.

Gene expression profiling of oxidative stress response of C. elegans aging defective AMPK mutants using massively parallel transcriptome sequencing

BACKGROUND

A strong association between stress resistance and longevity in multicellular organisms has been established as many mutations that extend lifespan also show increased resistance to stress. AAK-2, the C. elegans homolog of an alpha subunit of AMP-activated protein kinase (AMPK) is an intracellular fuel sensor that regulates cellular energy homeostasis and functions in stress resistance and lifespan extension.

FINDINGS

Here, we investigated global transcriptional responses of aak-2 mutants to oxidative stress and in turn identified potential downstream targets of AAK-2 involved in stress resistance in C. elegans. We employed massively parallel Illumina sequencing technology and performed comprehensive comparative transcriptome analysis. Specifically, we compared the transcriptomes of aak-2 and wild type animals under normal conditions and conditions of induced oxidative stress. This research has presented a snapshot of genome-wide transcriptional activities that take place in C. elegans in response to oxidative stress both in the presence and absence of AAK-2.

CONCLUSIONS

The analysis presented in this study has enabled us to identify potential genes involved in stress resistance that may be either directly or indirectly under the control of AAK-2. Furthermore, we have extended our current knowledge of general defense responses of C. elegans against oxidative stress supporting the function for AAK-2 in inhibition of biosynthetic processes, especially lipid synthesis, under oxidative stress and transcriptional regulation of genes involved in reproductive processes.

Melatonin administration ameliorates cadmium-induced oxidative stress and morphological changes in the liver of rat

The oxidative status and the morphological changes of liver of rats exposed to cadmium (5 mg Cd/kg body weight subcutaneously) for 22 days and the protective role of melatonin (10mg/kg b.w.) against the toxicity of cadmium was studied. The concentration of malondialdehyde (MDA), as an indicator of lipid peroxidation, activity of the antioxidant enzyme superoxide dismutase (SOD) as well as the concentration of glutathione (GSH) was measured in the liver. The morphological changes were investigated using both light and electron microscopes. The exposure to Cd led to an increase of MDA levels and a decrease of both the activity of SOD and GSH concentration in the liver. In contrast, melatonin administration restored the previous changes to nearly the normal levels. Morphologically, Cd led to different histopathological changes such as loss of normal architecture of the parenchymatous tissue, cytoplasmic vacuolization, cellular degeneration and necrosis, congested blood vessels, destructed cristae mitochondria, fat globules, severe glycogen depletion, lipofuscin pigments, and collagenous fibers formation. Again, melatonin administration counteracts all changes and the tissue appears more or less normal. The rate of recovery was faster when melatonin was administered for treatment after the exposure to cadmium than if the animals left without any treatment. The results suggest that melatonin may be useful as an antioxidant in combating free radical-induced oxidative stress and tissue injury that is a result of cadmium toxicity.

Characterization of an immortalized hepatic stellate cell line established from metallothionein-null mice

Hepatic stellate (HS) cells were isolated from the livers of metallothionein (MT)-null and control mice and used to establish IMS/MT(-) and IMS/N cell lines, respectively, using SV40 virus transformation. Cellular morphology, incorporation of vitamin A and expression of alpha-SMA, desmin and SV40 T-antigen were used to confirm that both cell lines were immortal HS cells. The growth rates of both cell lines were similar and there was little difference between cell line sensitivity to zinc. MT-null IMS/MT(-) cells were more sensitive to cadmium and mercury, although both cell lines accumulated almost equal amounts of cadmium during a 24-hr culture period. As HS cells play an important role in hepatic fibrosis and are activated by heavy metals such as cadmium or reactive oxygen, the MT-null HS cell line derived in this study should be a useful experimental model for examination of the role of MT in HS cell activation.

Lung carcinogenesis: pivotal role of metals in tobacco smoke

Although significant progress has been made in unraveling the molecular mechanisms responsible for tobacco smoke toxicity and carcinogenicity, only limited information is available concerning the mechanisms by which tar particles and the gaseous phase constituents of tobacco smoke participate and contribute to carcinogenic processes in lung cancer. The present review critically evaluates how metals contained in the tar particles and the gaseous phase of tobacco smoke play a leading role in the carcinogenic process, taking into consideration the physiology and pathophysiology of the bronchial epithelium. Overwhelmingly, the published data indicate that the bronchopulmonary epithelial cells may represent the first and most critical line of defense against cigarette smoke.

Establishment and identification of a novel immortalized rat hepatic stellate cell line HSC-PQ

AIM: To establish and identify a novel immortalized rat hepatic stellate cell (HSC) line.

METHODS: Primary HSCs were isolated from the liver of adult male Sprague-Dawley rats by a combination of pronase-collagenase perfusion and density gradient centrifugation. Then a new HSC line, being HSC-PQ, was established, cultured, and passaged by way of cellular clone. Furthermore, cellular dynamics, light microscopy, transmission electron microscopy, and immunocytochemistry were employed to investigate characteristics of the HSC line.

RESULTS: About 2×10⁷ HSCs could be harvested from a Sprague-Dawley rat with the live rate over 95% and purity over 90%. Afterwards, HSC-PQ line was obtained on the basis of total activation of primary HSCs. The phenotype of HSC-PQ cells resembled that of fibroblasts. Firstly, the existence of a-SMA as well as desmin in these cells exhibited their HSC-derived-myofibroblast identity clearly. Secondly, both the doubling time of about 75 hours, and the stable expression of extracellular matrixs including collagen type I, collagen type III, fibronectin, laminin, etc. showed the fibroblast-like-characteristics of HSC-PQ line. But collagen IV could not be detected in cytoplasm. In addition, maintaining over one year, 32 passages of the cell line might demonstrate its immortalisation.

CONCLUSION: We have established a new immortalized rat HSC line (HSC-PQ), which shares most of the characteristics with primary activated rat HSCs.

Acute cadmium exposure enhances AP-1 DNA binding and induces cytokines expression and heat shock protein 70 in HepG2 cells

Cadmium (Cd) has been regarded as one of the inflammation-related xenobiotics. Cd has been extensively studied in many cellular systems, but a lot of parameters have been evaluated in different experimental conditions. This study was undertaken to examine the effects of low cadmium concentrations in HepG2 cells in the oxidative stress produced, the IL-1beta, tumor necrosis factor (TNF-alpha), IL-6, and IL-8 expression, production of heat shock protein 70 (Hsp70) and the activation of nuclear factors activation protein-1 (AP-1) and NF-kappaB under the same experimental conditions. Also, the participation of TNF-alpha and oxidative stress in AP-1 activation was evaluated. Lipid peroxidation damage increased 1.5 times after the first hour of Cd treatment and increased 1.9 times after 2h. Similar values were maintained until 6h. Reduced glutathione (GSH) diminished 65% after 6h CdCl(2) treatment. N-acetylcysteine (NAC) pre-treatment increased 332% GSH in Cd-treated cells. RNA was isolated from HepG2 cells after 0.5, 1, 3, or 6h incubation with 1, 5, or 10 microM CdCl(2). TNF-alpha and IL-1beta presented a maximum response after 1h treatment, while IL-6 and IL-8 maximum response was after 3h treatment. The Hsp70, determined by Western blot, was constitutively produced, and it increased after 3h Cd treatment. NF-kappaB activation, determined by EMSA, was not increased as a result of Cd treatment. DNA binding of AP-1 was detected and increased, with time up to 4h with an increment of 24 times control value with 5 microM CdCl(2). The HepG2 cells were pretreated with anti-TNF-alpha antibody or 1mM N-acetylcysteine 1h before Cd treatment. Anti-TNF-alpha treatment reduced 67% AP-1 activation, while NAC 47.5%. These data indicate that, Cd-induced TNF-alpha and IL-1beta, that probably, activate AP-1 transcription factor and IL-6 and IL-8 were induced. Anti-TNF-alpha and NAC partially inhibited AP-1 activation. All imply that, a number of factors participate in AP-1 cadmium-induced activation. The Hsp70 is produced by the HepG2 cells after cadmium treatment, and probably has a role in the non-participation of NF-kappaB in the cellular response.

Molecular and cellular mechanisms of cadmium carcinogenesis

Cadmium is a heavy metal, which is widely used in industry, affecting human health through occupational and environmental exposure. In mammals, it exerts multiple toxic effects and has been classified as a human carcinogen by the International Agency for Research on Cancer. Cadmium affects cell proliferation, differentiation, apoptosis and other cellular activities. Cd2+ does not catalyze Fenton-type reactions because it does not accept or donate electrons under physiological conditions, and it is only weakly genotoxic. Hence, indirect mechanisms are implicated in the carcinogenicity of cadmium. In this review multiple mechanisms are discussed, such as modulation of gene expression and signal transduction, interference with enzymes of the cellular antioxidant system and generation of reactive oxygen species (ROS), inhibition of DNA repair and DNA methylation, role in apoptosis and disruption of E-cadherin-mediated cell-cell adhesion. Cadmium affects both gene transcription and translation. The major mechanisms of gene induction by cadmium known so far are modulation of cellular signal transduction pathways by enhancement of protein phosphorylation and activation of transcription and translation factors. Cadmium interferes with antioxidant defense mechanisms and stimulates the production of reactive oxygen species, which may act as signaling molecules in the induction of gene expression and apoptosis. The inhibition of DNA repair processes by cadmium represents a mechanism by which cadmium enhances the genotoxicity of other agents and may contribute to the tumor initiation by this metal. The disruption of E-cadherin-mediated cell-cell adhesion by cadmium probably further stimulates the development of tumors. It becomes clear that there exist multiple mechanisms which contribute to the carcinogenicity of cadmium, although the relative weights of these contributions are difficult to estimate.