Modulation of the stress response during apoptosis and necrosis induction in cadmium-treated U-937 human promonocytic cells

Dermatotoxicity of oral cadmium is strain-dependent and related to differences in skin stress response and inflammatory/immune activity

Adverse effects of non-occupational exposure to cadmium (Cd) are increasingly acknowledged. Since our previous study has showed that orally acquired Cd affects skin, the contribution of genetic background to dermatotoxicity of oral cadmium was examined in two rat strains, Albino Oxford (AO) and Dark Agouti (DA), which differed in response to chemicals. While similar accumulation of Cd in the skin of both strains was noted, the skin response to the metal differed. DA rat individuals mounted antioxidant enzyme defense in the skin already at lower Cd dose, in contrast to AO rats which reacted to higher metal dose solely (and less pronounced), implying higher susceptibility of DA strain to Cd dermatotoxicity. Epidermal cells from both strains developed stress response, but higher intensity of antioxidant response in AO rats implied this strain`s better ability to defend against Cd insult. Cd induced epidermal cells' proinflammatory cytokine response only in DA rats. Increased IL-10 seems responsible for the lack of response in AO rats. Differences in the pattern of skin/epidermal cell responsiveness to cadmium give a new insight into repercussion of genetic variability to dermatotoxicity of orally acquired cadmium, bearing relevance for variations in the link between dietary cadmium and inflammation-based skin pathologies.

Cadmium triggers mitochondrial oxidative stress in human peripheral blood lymphocytes and monocytes: Analysis using in vitro and system toxicology approaches

Cadmium (Cd) is a well-known heavy metal that causes environmental pollution and human health problems. Several studies attempted to assess Cd toxicity in vitro and in vivo. However, the systemic profile of cadmium toxicity has not been studied well. In the present study, we assessed the toxicity of Cd on human peripheral blood lymphocytes and monocytes and gene expression, using a system toxicological approach. Cd effect on cell viability and morphology were analyzed by MTT assay and AO/EB staining respectively. Mitochondrial membrane potential depletion and reactive oxygen singlet generation were assessed by flow cytometry. Effects of Cd treatment on gene expression were also studied. Significant reduction in cell viability and disintegration of nuclear morphology were observed in Cd-treated cells. Cd exposure enhanced the loss of mitochondrial membrane potential through oxidative stress. Dose-dependent upregulation of GSTM3 and downregulation of GSR gene expression were observed. TNF gene expression decreased as the level of Cd exposure increased. We analyzed the toxicological effects of Cd on more than 45 proteins for biological target identification. These system toxicological studies suggested that Cd induced toxicity through various biological processes such as oxidative stress, oxidation-reduction, and ROS and hydrogen peroxide generation. Additionally, Cd affects the cellular component network and modulates the expression level of oxidative stress-related genes.

Cadmium-Mediated Activation of the HSP90/HSF1 Pathway Regulated by Reactive Persulfides/Polysulfides

Cadmium is an environmental electrophile that modifies reactive thiols in proteins, indicating that this heavy metal may modulate redox-signal transduction pathways. The current consensus is that reactive persulfides and polysulfides produced by cystathionine γ-lyase (CSE) and cystathionine β-synthase are highly nucleophilic and thus cadmium may be captured by these reactive sulfur species. It has previously been found that electrophile-mediated covalent modifications of the heat shock protein (HSP) are involved in the activation of heat shock factor 1 (HSF1) pathway. The effects of cadmium on the activation of HSP/HSF1 pathway were investigated in this study. Exposure of bovine aortic endothelial cells to cadmium resulted in modification of HSP90 and HSF1 activation, thereby up-regulating the downstream protein HSP70. The siRNA-mediated knockdown of HSF1 enhanced the cytotoxicity induced by cadmium, suggesting that the HSP90/HSF1 pathway contributes to protection against cadmium toxicity. The knockdown of CSE and/or cystathionine β-synthase decreased the levels of reactive sulfur species in the cells and increased the degree of HSP70 induction and cytotoxicity caused by exposure to cadmium. Overexpression of CSE diminished cadmium-mediated up-regulation of HSP70 and cytotoxicity. These results suggest that cadmium activates HSF1 by modifying HSP90 and that reactive sulfur species regulate the redox signal transduction pathway presumably via capture of cadmium, resulting in protection against cadmium toxicity under toxic conditions.

Characterization of cadmium chloride-induced BiP accumulation in Xenopus laevis A6 kidney epithelial cells

Endoplasmic reticulum (ER) stress can result in the accumulation of unfolded/misfolded protein in the ER lumen, which can trigger the unfolded protein response (UPR) resulting in the activation of various genes including immunoglobulin-binding protein (BiP; also known as glucose-regulated protein 78 or HSPA5). BiP, an ER heat shock protein 70 (HSP70) family member, binds to unfolded protein, inhibits their aggregation and re-folds them in an ATP-dependent manner. While cadmium, an environmental contaminant, was shown to induce the accumulation of HSP70 in vertebrate cells, less information is available regarding the effect of this metal on BiP accumulation or function. In this study, cadmium chloride treatment of Xenopus laevis A6 kidney epithelial cells induced a dose- and time-dependent increase in BiP, HSP70 and heme oxygenase-1 (HO-1) accumulation. Exposure of cells to a relatively low cadmium concentration at a mild heat shock temperature of 30°C greatly enhanced BiP and HSP70 accumulation compared to cadmium at 22°C. Treatment of cells with the glutathione synthesis inhibitor, buthionine sulfoximine, enhanced cadmium-induced BiP and HSP70 accumulation. Immunocytochemistry revealed that cadmium-induced BiP accumulation occurred in a punctate pattern in the perinuclear region. In some cells treated with cadmium chloride or the proteasomal inhibitor, MG132, large BiP complexes were observed that co-localized with aggregated protein or aggresome-like structures. These BiP/aggresome-like structures were also observed in cells treated simultaneously with cadmium at 30°C or in the presence of buthionine sulfoximine. In amphibians, the association of BiP with unfolded protein and its possible role in aggresome function may be vital in the maintenance of cellular proteostasis.

The Effects of Cadmium at Low Environmental Concentrations on THP-1 Macrophage Apoptosis

Cadmium at environmental concentrations is a risk factor for many diseases, including cardiovascular and neurodegenerative diseases, in which macrophages play an important role. The aim of this study was to evaluate the effects of cadmium at low environmental (nanomolar) concentrations on apoptotic processes in THP-1(acute monocytic leukemia cells line)-derived macrophages, with special focus on mitochondrial events involved. Macrophages were incubated with various cadmium chloride (CdCl₂) solutions for 48 h at final concentrations of 5 nM, 20 nM, 200 nM and 2 µM CdCl₂. Cell viability was measured using flow cytometry. Flow cytometric measurement (annexin V/FITC (annexin V/fluorescein isothiocyanate) and PI (propidium iodide) double staining) was used to quantify the extent of apoptosis. Fluorescence and confocal microscopy were used for imaging of apoptosis process. Changes in mitochondrial membrane potential were monitored using cytofluorimetry after cell staining with JC-1(5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazol-carbocyane iodide) probe. Mitochondrial ROS (reactive oxygen species) levels were measured cytofluorimetrically after incubation of cells with mitochondrial superoxide indicator (MitoSOX) red fluorescent marker. The mRNA expression of Bcl-2 and Bax was analysed with qRT-PCR. Our study demonstrates that cadmium, even at low environmental concentrations, exerts mitochondrial toxicity in THP-1 macrophages. Forty-eight-hour exposure to very low concentrations reduces cell viability and results in cell death by apoptosis and necrosis. The decrease in mitochondrial membrane potential, increased ROS production, increased Bax and decreased Bcl-2 mRNA expression are mitochondrial events involved in cadmium-induced apoptosis.

Neuroprotective effect of quercetin in ectoenzymes and acetylcholinesterase activities in cerebral cortex synaptosomes of cadmium-exposed rats

This study investigated the effect of quercetin on nucleoside triphosphate diphosphohydrolase (NTP-Dase), 50-nucleotidase, adenosine deaminase (ADA), and acetylcholinesterase (AChE) activities in synaptosomes from cerebral cortex of adult rats exposed to cadmium (Cd). Rats were exposed to Cd (2.5 mg/Kg) and quercetin (5, 25 or 50 mg/Kg) by gavage for 45 days. Rats were randomly divided into eight groups (n = 8-10): saline/ethanol, saline/Querc 5 mg/kg, saline/Querc 25 mg/kg, saline/Querc 50 mg/kg, Cd/ethanol, Cd/Querc 5 mg/kg, Cd/Querc 25 mg/kg, and Cd/Querc 50 mg/kg. Results demonstrated that AChE activity increased in the Cd/ethanol group when compared to saline/ethanol group. Treatment with quercetin prevented the increase in AChE activity when compared to Cd/ethanol group. Quercetin treatment prevented the cadmium-induced increase in NTPDase, 5-nucleotidase, and ADA activities in Cd/ethanol group when compared to saline/ethanol group. Our data showed that quercetin have a protector effect against Cd intoxication. This way, is a promising candidate among the flavonoids to be investigated as a therapeutic agent to attenuate neurological disorders associated with Cd intoxication.

Role of calcium channels in heavy metal toxicity

The role of voltage-dependent Ca channels (VDCC) in the membrane permeation of two toxic metals, lead (Pb) and cadmium (Cd), was studied in mammalian cells. Both metals interact with Ca-binding sites, but, while Cd influx appears to occur mainly through the same pathways as Ca, Pb is also rapidly taken up by different passive transport systems. Furthermore, I compared the effect of Cd in two Chinese hamster ovary (CHO) cell lines, a wild-type and a modified cell line, which were permanently transfected with an L-type VDCC. When cultures were subjected to a brief (30–60 min) exposure to 50–100 μM Cd, apoptotic features, metal accumulation, and death were comparable in both cell lines although, in transfected cells, the effect of Cd treatment was partially prevented by nimodipine (VDCC antagonist) and enhanced by BayK8644 (VDCC agonist). Thus, expression of L-type Ca channels is not sufficient to modify Cd accumulation and sensitivity to a toxicological significant extent and while both Cd and Pb can take advantage of VDCC to permeate the membrane, these transport proteins are not the only, and frequently not the most important, pathways of permeation.

Linkages between the life-history evolution of tropical and temperate birds and the resistance of cultured skin fibroblasts to oxidative and non-oxidative chemical injury

A fundamental challenge facing physiological ecologists is to understand how variation in life history at the whole-organism level might be linked to cellular function. Thus, because tropical birds have higher annual survival and lower rates of metabolism, we hypothesized that cells from tropical species would have greater cellular resistance to chemical injury than cells from temperate species. We cultured dermal fibroblasts from 26 tropical and 26 temperate species of birds and examined cellular resistance to cadmium, H(2)O(2), paraquat, thapsigargin, tunicamycium, methane methylsulfonate (MMS) and UV light. Using ANCOVA, we found that the values for the dose that killed 50% of cells (LD(50)) from tropical birds were significantly higher for H(2)O(2) and MMS. When we tested for significance using a generalized least squares approach accounting for phylogenetic relationships among species to model LD(50), we found that cells from tropical birds had greater tolerance for Cd, H(2)O(2), paraquat, tunicamycin and MMS than cells from temperate birds. In contrast, tropical birds showed either lower or no difference in tolerance to thapsigargin and UV light in comparison with temperate birds. These findings are consistent with the idea that natural selection has uniquely fashioned cells of long-lived tropical bird species to be more resistant to forms of oxidative and non-oxidative stress than cells from shorter-lived temperate species.

The chemopreventive effects of aged garlic extract against cadmium-induced toxicity

Garlic has been reported in many previous studies as a potent chemopreventive agent. The protective effect of garlic has been ascribed to the presence of organosulphur compounds (OSC). In this study, the efficacy of aged garlic extract (AGE) compared to diallyl disulfide (DADS) in protecting against toxicity induced by cadmium (Cd) in 1321N1 and HEK293 cells was investigated. The involvement of the transcription factor Nrf2 in this protection was also examined. The results show that AGE significantly prevented loss of cell viability in Cd-treated 1321N1 and HEK293 cells. In comparison DADS had no significant effect in protecting HEK293 cells but did protect 1321N1 cells. AGE significantly reduced Cd-induced TBARS production and LDH leakage in the two cell lines, and AGE and DADS both increased GSH levels in Cd-treated cell lines. Pre-treatment of cells with AGE or DADS increased expression of the protective enzyme NAD(P)H:quinone oxidoreductase (NQO1), and this was associated with the accumulation of the transcription factor Nrf2. These results show that AGE and DADS have beneficial effects against Cd-induced toxicity, and this protection appears to be mediated via induction of cytoprotective enzymes in an Nrf2-dependent manner. This indicates the potential for using AGE as a chemoprevention strategy for Cd toxicity.

Glycine reduces cadmium-induced alterations in the viability and activation of macrophage U937 cells

This study investigates the effect of glycine on cadmium-induced alterations on the viability and activation of the cell line U-937. In this experiment, U-937 cells were pre-treated with 16 microM cadmium (as cadmium chloride). These cadmium-treated cells were later incubated with or without glycine (1-16 microM). After 72 h, it was revealed that glycine significantly (P<0.05) reduced the tendency of cadmium to reduce the viability of the cells. U-937 cells were also treated with phorbol, 12-myristate, 13-acetate to enhance their transition to the macrophage form. Thereafter, the cells were treated with cadmium with or without glycine (1-16 microM). Twenty-four hours later, the supernatants of each cell culture were assessed for the production of tumour necrosis factor alpha (TNF-alpha), interleukin 6 (IL-6), interleukin 1 (IL-1), nitric oxide (NO), and catalase activity as indices of the activation of macrophages. The results show that glycine significantly (P<0.05) reduced the cadmium-induced production of all the markers of the activation of macrophages in a concentration-dependent manner. The findings support the immense antioxidant role of glycine.

Lipid peroxidation and HSP72/73 expression in rat following cadmium chloride administration: Interactions of magnesium supplementation

OBJECTIVE

to determine whether magnesium (Mg) supplementation could have a protective effect against the cadmium (Cd)-induced oxidative stress in liver, kidneys and testes of adult male rats. Stress was evaluated by measuring lipid peroxidation by thiobarbituric acid reactive substances (TBARS) and the heat shock protein (HSP) 72/73 expression. CdCl2 injections (2.5mg/day/kg body weight) for 10 days resulted in a time dependent increase of Cd accumulation in liver, kidney and testes, the highest levels being found in liver (400 microg/g dried tissue). At the same time, an increase of lipid peroxidation was observed. The effect was maximal at day 1 of Cd treatment in liver and testes, and later (day 5) in kidney. Then, Cd-induced lipid peroxidation decreased, suggesting the activation of antioxidant defense mechanisms. Injections of Mg SO4 (300-600 mg/day/kg body weight) reduced in a dose-dependent manner Cd-induced lipid peroxidation in liver and kidney as well as the accumulation of Cd in liver, kidney and testes. In testes, a protective effect of Mg was found only during the early phase of Cd-poisoning. On days 5 and 10, lipid peroxidation was even increased as compared to controls. In liver and testes only the constitutive HSP73 was detected whereas in kidney both HSP73 and the inducible HSP72 were expressed. HSP72/73 expression was not significantly increased by Cd and HSP73 was even lowered in kidney, probably due to the strong dose used. These results were not modified by Mg injections.

CONCLUSION

Mg supplementation can reduce Cd accumulation in organs and lipid peroxidation related to Cd administration.

Regulation of apoptosis/necrosis execution in cadmium-treated human promonocytic cells under different forms of oxidative stress

Pulse-treatment of U-937 human promonocytic cells with cadmium chloride followed by recovery caused caspase-9/caspase-3-dependent, caspase-8-independent apoptosis. However, pre-incubation with the glutathione (GSH)-suppressing agent DL-buthionine-(S,R)-sulfoximine (cadmium/BSO), or co-treatment with H2O2 (cadmium/H2O2), switched the mode of death to caspase-independent necrosis. The switch from apoptosis to necrosis did not involve gross alterations in Apaf-1 and pro-caspase-9 expression, nor inhibition of cytochrome c release from mitochondria. However, cadmium/H2O2-induced necrosis involved ATP depletion and was prevented by 3-aminobenzamide, while cadmium/BSO-induced necrosis was ATP independent. Pre-incubation with BSO increased the intracellular cadmium accumulation, while co-treatment with H2O2 did not. Both treatments caused intracellular peroxide over-accumulation and disruption of mitochondrial transmembrane potential (delta psi m). However, while post-treatment with N-acetyl-L-cysteine or butylated hydroxyanisole reduced the cadmium/BSO-mediated necrosis and delta psi m disruption, it did not reduce the effects of cadmium/H2O2. Bcl-2 over-expression, which reduced peroxide accumulation without affecting the intracellular GSH content, attenuated necrosis generation by cadmium/H2O2 but not by cadmium/BSO. By contrast, AIF suppression, which reduced peroxide accumulation and increased the GSH content, attenuated the toxicity of both treatments. These results unravel the existence of two different oxidation-mediated necrotic pathways in cadmium-treated cells, one of them resulting from ATP-dependent apoptosis blockade, and the other involving the concurrence of multiple regulatory factors.

Cadmium chloride-induced DNA and lysosomal damage in a hepatoma cell line

Cadmium is a toxic metal and no uniform mechanism of toxicity has so far been proposed. The aim of this study was to investigate the biochemical effects of cadmium chloride in a rat hepatoma cell line (HTC cells) and the cellular events mediating DNA damage. HTC cells were exposed to various concentrations of cadmium chloride for 5 and 8 h and lysosomal damage was assessed with the neutral red assay (NR) and fluorescence microscopy. Mitochondrial integrity was assessed from ATP levels and DNA damage determined with the single cell gel electrophoresis/comet assay. The formation of reactive oxygen species (ROS) was also determined under the same experimental conditions with the dichlorofluorescein assay. Cytotoxicity was assessed with the LDH leakage assay and the levels of glutathione were measured and correlated with the other effects. The results indicate that lysosomal damage occurs at a lower concentration of cadmium chloride (20 microM) than DNA damage (500 microM) in HTC cells. The latter effect was accompanied by an increase of reactive oxygen species without any significant LDH leakage whereas lysosomal damage was significant as determined by the neutral red assay and confirmed with fluorescence microscopy. The effect of CdCl2 on mitochondria and glutathione levels were observed at concentrations or incubation times higher than the ones required to induce lysosomal damage. The data suggest that DNA damage may be due to the formation of reactive oxygen species. It is possible that cadmium induced lysosomal damage is an earlier event than DNA damage and can mediate other cellular events that lead to cell death.

Expression of stress-related genes in a cadmium-resistant A549 human cell line

This study was designed to explain the basis for Cd-acquired tolerance of A549 cells cultured in the presence of Cd. Thirty-day exposure of cultured human pneumocytes (A549 cell line) to 10 microM Cd was previously found to induce an acquired resistance persisting over several weeks of culture. Moreover, these Cd-resistant cells (R-cells) were found to proliferate faster than controls. No difference was found between R-cells and control cells (S-cells) concerning the basal and Cd-induced level of metallothioneins expression. However, after exposure to Cd, cell glutathione levels were unchanged in R-cells while they were either increased (at 10 microM Cd) or decreased (at 25 microM Cd) in S-cells. cDNA array analysis showed that genes encoding for (GPx1) glutathione peroxidase, glutathione reductase, catalase, and superoxide dismutase were similarly expressed in R- and S-cells, whereas the gene of (GPx2) glutathione peroxidase was overexpressed in R-cells. Most genes encoding stress proteins were similarly expressed, except for HSP27 and GRP94 genes, which were respectively under- (ratio 0.5 +/- 0.1) and over- (1.8 +/- 0.5) expressed in R-cells. Acute exposure to Cd was found to trigger the upregulation of genes encoding the chaperone proteins HSP90A, HSP27, HSP40, GRP78, HSP72, and HO-1 in S-cells. In R-cells, only HO-1 and HSP72 were overexpressed but at a lower level. This suggests that the Cd-related adverse conditions, leading to protein misfolding, are lowered in R-cells. It is likely that the upregulation of GPx2 in R-cells leads to a higher antioxidant defense in these cells.

Differential signatures of protein expression in marmoset liver and thymus induced by single-dose TCDD treatment

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an ubiquitously distributed environmental pollutant. Health effects have been studied intensively, but low-dose effects are quite complex and not yet fully understood. In many studies, the immune system was identified as the most sensitive target. Here, we demonstrate changes of protein expression in liver and thymus of male marmosets (Callithrix jacchus) which were subjected to a single dose of a subcutaneous injection of 100 ng/kg body weight TCDD. Histopathological examination revealed myocardial fibrosis, but there were no significant findings in pathology and histopathology of liver and thymus. In order to detect more subtle treatment-related changes, we performed a comparative proteomic investigation of liver and thymus using a 2-D gel electrophoresis based proteomics approach. Fluorescence labeling and automated image analysis was used to enhance sensitivity and reproducibility. In both organs, distinct changes of protein expression were detected which were more pronounced in thymus, where the pattern of deregulated proteins could be clearly related to immune responses. In the thymus of treated animals, several toxicologically relevant factors were increased, including chaperones, glycerol-3-phosphate dehydrogenase, and adseverin. Among others, vimentin, Ca-dependent protease and protein disulfide isomerase were downregulated. In the liver, transferrins, lamin A and HSP70 were upregulated, whereas thymidine phosphorylase (synonyms: endothelial cell growth factor, PD-ECGF, gliostatin) was significantly reduced. Comparative analysis of deregulated proteins in both organs revealed a pattern of related functions, which fits well into the existing knowledge of the toxic processes and mechanisms underlying TCDD-mediated toxicity.

Evidence for a role of heat shock factor 1 in inhibition of NF-κB pathway during heat shock response-mediated lung protection

Heat shock transcription factor (HSF)-1 is recognized as a central component of the heat shock response, which protects against various harmful conditions. However, the mechanisms underlying the protection and the role of HSF-1 in these mechanisms have not yet been clearly elucidated. Using HSF-1 knockout mice ( Hsf1−/−), we examined whether heat shock response-mediated lung protection involved an inhibition of the proinflammatory pathway via an interaction between HSF-1 and NF-κB, in response to cadmium insult. The HSF-1-dependent protective effect against intranasal instillation of cadmium (10 and 100 μg/mouse) was demonstrated by the higher protein content (1.2- and 1.4-fold), macrophage (1.6- and 1.9-fold), and neutrophil (2.6- and 1.8-fold) number in bronchoalveolar fluids, higher lung wet-to-dry weight ratio, and more severe lung damage evaluated by histopathology in Hsf1−/−compared with wild-type animals. These responses were associated with higher granulocyte/macrophage colony-stimulating factor (GM-CSF; 1.7-fold) but not TNF-α concentrations in bronchoalveolar fluids of Hsf1−/−mice compared with those of wild-type animals, indicating that HSF-1 behaved as a repressor of specific cytokine production in our model. To further investigate the mechanism of GM-CSF repression, we analyzed the NF-κB activity and IκB stability. The DNA binding NF-κB activity, in particular p50 homodimer activity, was higher in Hsf1−/−mice than in wild-type mice after cadmium exposure. These results provide a first line of evidence that mechanisms of lung protection depending on HSF-1 involve specific cytokine repression via inhibition of NF-κB activation in vivo.

Cytoprotective effects of Glycyrrhizae radix extract and its active component liquiritigenin against cadmium-induced toxicity (effects on bad translocation and cytochrome c-mediated PARP cleavage)

Glycyrrhizae radix has been popularly used as one of the oldest and most frequently employed botanicals in herbal medicine in Asian countries, and currently occupies an important place in food products. Cadmium (Cd) induces both apoptotic and non-apoptotic cell death, in which alterations in cellular sulfhydryls participate. In the present study, we determined the effects of G. radix extract (GRE) and its representative active components on cell death induced by Cd and explored the mechanistic basis of cytoprotective effects of G. radix. Incubation of H4IIE cells with GRE inhibited cell death induced by 10 microM Cd. Also, GRE effectively blocked Cd (1 microM)-induced cell death potentiated by buthionine sulfoximine (BSO) without restoration of cellular GSH. GRE prevented both apoptotic and non-apoptotic cell injury induced by Cd (10 microM) or Cd (0.3-1 microM) + BSO. Inhibition of Cd-induced cell injury by pretreatment of cells with GRE suggested that the cytoprotective effect result from alterations in the levels of the protein(s) responsible for cell viability. GRE inhibited mitochondrial Bad translocation by Cd or CD+BSO, and caused restoration of mitochondrial Bcl(xL) and cytochrome c levels. Cd-induced poly(ADP-ribose)polymerase cleavage in control cells or in cells deprived of sulfhydryls was prevented by GRE treatment. Among the major components present in GRE, liquiritigenin, but not liquiritin, isoliquiritigenin or glycyrrhizin, exerted cytoprotective effect. These results demonstrated that GRE blocked Cd-induced cell death by inhibiting the apoptotic processes involving translocation of Bad into mitochondria, decreases in mitochondrial Bcl(xL) and cytochrome c, and poly(ADP-ribose)polymerase cleavage.

The selection between apoptosis and necrosis is differentially regulated in hydrogen peroxide-treated and glutathione-depleted human promonocytic cells

Treatment with 0.2 mM hydrogen peroxide (H(2)O(2)) or with 0.5 mM cisplatin caused caspase-9 and caspase-3 activation and death by apoptosis in U-937 human promonocytic cells. However, treatment with 2 mM H(2)O(2), or incubation with the glutathione suppressor DL-buthionine-(S,R)-sulfoximine (BSO) prior to treatment with cisplatin, suppressed caspase activation and changed the mode of death to necrosis. Treatment with 2 mM H(2)O(2) caused a great decrease in the intracellular ATP level, which was partially prevented by 3-aminobenzamide (3-ABA). Correspondingly, 3-ABA restored the activation of caspases and the execution of apoptosis. By contrast, BSO plus cisplatin did not decrease the ATP levels, and the generation of necrosis by this treatment was not affected by 3-ABA. On the other hand, while all apoptosis-inducing treatments and treatment with 2 mM H(2)O(2) caused Bax translocation from the cytosol to mitochondria as well as cytochrome c release from mitochondria to the cytosol, treatment with BSO plus cisplatin did not. Treatment with cisplatin alone caused Bid cleavage, while BSO plus cisplatin as well as 0.2 and 2 mM H(2)O(2) did not. Bcl-2 overexpression reduced the generation of necrosis by H(2)O(2), but not by BSO plus cisplatin. These results indicate the existence of different apoptosis/necrosis regulatory mechanisms in promonocytic cells subjected to different forms of oxidative stress.

Cell-metal interaction studied by cytotoxic and FT-IR spectroscopic methods

The main purpose of this work is to investigate the possibility of utilizing both a classical biological method to test cytotoxicity and a physical measurement procedure as the FT-IR spectroscopy to study the interaction between cells lines and heavy metals. Jurkart, a lymphocyte cell line, was treated with cadmium chloride, cadmium oxide and the organic germanium compound named Ge-oxy-132. The utilized value of heavy metal concentration allows us to obtain significant results with both methods and with all metals. In fact by using lower values of concentration any effect is revealed after treatment with germanium. The results of the simultaneous measurements by both experimental procedures are here reported for the first time and show that, while the cytotoxic effects of the two cadmium compounds are confirmed, the organic germanium compound reveals a very different and interesting interaction with Jurkart cells. The behaviour of the Jurkart cells upon the uptake of cadmium or organic germanium is very different: while treatment with CdO and CdCl(2) determines proteins denaturation and lipids oxidation in cells until the death, these processes are not revealed after Ge-oxy-132 treatment.

Calcium-mediated telomerase activity in ovarian epithelial cells

Though the potential of telomerase as an anti-cancer target is evident, information about regulation of telomerase remains fragmentary. In the present study, we examined the role of calcium, an essential cellular signaling molecule, in the regulation of telomerase. We found that calcium induced de novo telomerase activity in telomerase-negative ovarian surface epithelial (OSE) cell lines but not in primary cultures of OSE. In addition, we showed that calcium elevated endogenous telomerase levels in a telomerase-positive ovarian cancer cell line. The use of calcium channel blockers or calcium chelators inhibited this calcium-mediated induction of telomerase activity. Furthermore, cadmium and chromium appeared to cause a moderate induction of telomerase activity while several other metal salts did not. Our data provide the first example of calcium-induced telomerase activity in human cell lines, provide a novel avenue for possible intervention of telomerase, and permit development of therapeutic agents for adjunctive chemotherapy.