Copper related toxic effects on cellular protein metabolism in human astrocytes

Assessment of Density Functional Theory Methods for the Structural Prediction of Transition and Post-Transition Metal-Nucleic Acid Complexes

Understanding the structure of metal-nucleic acid systems is important for many applications such as the design of new pharmaceuticals, metal detection platforms, and nanomaterials. Herein, we explore the ability of 20 density functional theory (DFT) functionals to reproduce the crystal structure geometry of transition and post-transition metal-nucleic acid complexes identified in the Protein Data Bank and Cambridge Structural Database. The environmental extremes of the gas phase and implicit water were considered, and analysis focused on the global and inner coordination geometry, including the coordination distances. Although gas-phase calculations were unable to describe the structure of 12 out of the 53 complexes in our test set regardless of the DFT functional considered, accounting for the broader environment through implicit solvation or constraining the model truncation points to crystallographic coordinates generally afforded agreement with the experimental structure, suggesting that functional performance for these systems is likely due to the models rather than the methods. For the remaining 41 complexes, our results show that the reliability of functionals depends on the metal identity, with the magnitude of error varying across the periodic table. Furthermore, minimal changes in the geometries of these metal-nucleic acid complexes occur upon use of the Stuttgart-Dresden effective core potential and/or inclusion of an implicit water environment. The overall top three performing functionals are ωB97X-V, ωB97X-D3(BJ), and MN15, which reliably describe the structure of a broad range of metal-nucleic acid systems. Other suitable functionals include MN15-L, which is a cheaper alternative to MN15, and PBEh-3c, which is commonly used in QM/MM calculations of biomolecules. In fact, these five methods were the only functionals tested to reproduce the coordination sphere of Cu²⁺-containing complexes. For metal-nucleic acid systems that do not contain Cu²⁺, ωB97X and ωB97X-D are also suitable choices. These top-performing methods can be utilized in future investigations of diverse metal-nucleic acid complexes of relevance to biology and material science.

Selenium homeostasis in human brain cells: Effects of copper (II) and Se species

BACKGROUND

Both essential trace elements selenium (Se) and copper (Cu) play an important role in maintaining brain function. Homeostasis of Cu, which is tightly regulated under physiological conditions, seems to be disturbed in Alzheimer´s (AD) and Parkinson´s disease (PD) patients. Excess Cu promotes the formation of oxidative stress, which is thought to be a major cause for development and progression of neurological diseases (NDs). Most selenoproteins exhibit antioxidative properties and may counteract oxidative stress. However, expression of selenoproteins is altered under conditions of Se deficiency. Serum Se levels are decreased in AD and PD patients suggesting Se as an important factor in the development and progression of NDs. The aim of this study was to elucidate the interactions between Cu and Se in human brain cells particularly with respect to Se homeostasis.

METHODS

Firstly, modulation of Se status by selenite or SeMet were assessed in human astrocytes and human differentiated neurons. Therefore, cellular total Se content, intra- and extracellular selenoprotein P (SELENOP) content, and glutathione peroxidase (GPX) activity were quantified. Secondly, to investigate the impact of Cu on these markers, cells were exposed to copper(II)sulphate (CuSO₄) for 48 h. In addition, putative protective effects of Se on Cu-induced toxicity, as measured by cell viability, DNA damage, and neurodegeneration were investigated.

RESULTS

Modulation of cellular Se status was strongly dependent on Se species. In detail, SeMet increased total cellular Se and SELENOP content, whereas selenite led to increased GPX activity and SELENOP excretion. Cu treatment resulted in 133-fold higher cellular Cu concentration with a concomitant decrease in Se content. Additionally, SELENOP excretion was suppressed in both cell lines, while GPX activity was diminished only in astrocytes. These effects of Cu could be partially prevented by the addition of Se depending on the cell line and Se species used. While Cu-induced oxidative DNA damage could not be prevented by addition of Se regardless of chemical species, SeMet protected against neurite network degeneration triggered by Cu.

CONCLUSION

Cu appears to negatively affect Se status in astrocytes and neurons. Especially with regard to an altered homeostasis of those trace elements during aging, this interaction is of high physiological relevance. Increasing Cu concentrations associated with decreased selenoprotein expression or functionality might be a promoting factor for the development of NDs.

The FDX1 methylation regulatory mechanism in the malignant phenotype of glioma

To explore FDX1 methylation as a regulatory mechanism in the malignant phenotype of glioma, we screened for pathways involved through bioinformatic analysis, then proceeded with RIP and cell models to verify the regulation of RNAs and mitophagy. We chose Clone and Transwell assays to evaluate the malignant phenotype of glioma cells. MMP was detected by flow cytometry and mitochondrial morphology was observed by TEM. We also constructed animal models to study the sensitivity of glioma cells to cuproptosis. We successfully identified the signalling pathway: our cell model showed that C-MYC could upregulate FDX1 through YTHDF1 and inhibit mitophagy in glioma cells. Functional experiments revealed C-MYC could also enhance glioma cell proliferation and invasion via YTHDF1 and FDX1. In vivo experiments showed glioma cells were highly sensitive to cuproptosis. We concluded that C-MYC could upregulate FDX1 by m6A methylation, thus promoting the malignant phenotype in glioma cells.

Astrocyte-Like Cells Transcriptome Changes After Exposure to a Low and Non-cytotoxic MeHg Concentration

The central nervous system is the main target of MeHg toxicity and glial cells are the first line of defense; however, their true role remains unclear. This study aimed to identify the global map of human glial-like (U87) cells transcriptome after exposure to a non-toxic and non-lethal MeHg concentration and to investigate the related molecular changes. U87 cells were exposed upon 0.1, 0.5, and 1 µM MeHg for 4 and 24 h. Although no changes were observed in the percentage of viable cells, the metabolic viability was significantly decreased after exposure to 1 µM MeHg for 24 h; thus, the non-toxic concentration of 0.1 µM MeHg was chosen to perform microarray analysis. Significant changes in U87 cells transcriptome were observed only after 24 h. The expression of 392 genes was down regulated while 431 genes were up-regulated. Gene ontology showed alterations in biological processes (75%), cellular components (21%), and molecular functions (4%). The main pathways showed by KEGG and Reactome were cell cycle regulation and Rho GTPase signaling. The complex mechanism of U87 cells response against MeHg exposure indicates that even a low and non-toxic concentration is able to alter the gene expression profile.

Development and validation of cuproptosis-associated prognostic signatures in WHO 2/3 glioma

WHO 2/3 glioma is a common intracranial tumor that seriously affects the quality of life and survival time of patients. Previous studies have shown that the tricarboxylic acid (TCA) cycle is closely related to the occurrence and development of glioma, while recent studies have shown that cuproptosis, a novel programmed death pathway, is closely related to the inhibition of the TCA cycle. In our study, eight of ten cuproptosis-related genes (CRGs) were found to be differentially expressed between normal and WHO 2/3 glioma tissues. Through the LASSO algorithm, the cuproptosis-associated risk signatures (CARSs) were constructed, which can effectively predict the prognosis of WHO 2/3 glioma patients and are closely related to clinicopathological features. We analyzed the relationship between risk score and immune cell infiltration through Xcell, ssGSEA, TIMER database, and immune checkpoint molecules. In addition, the relationship between risk score and chemotherapeutic drug sensitivity was also investigated. The prognosis-related independent risk factors FDX1 and CDKN2A identified from CARSs are considered potential prognostic biomarkers for WHO 2/3 glioma. The clinical prognosis model based on cuproptosis is expected to provide an effective reference for the diagnosis and treatment of clinical WHO 2/3 glioma patients.

Characterizing effects of excess copper levels in a human astrocytic cell line with focus on oxidative stress markers

BACKGROUND

Being an essential trace element, copper is involved in diverse physiological processes. However, excess levels might lead to adverse effects. Disrupted copper homeostasis, particularly in the brain, has been associated with human diseases including the neurodegenerative disorders Wilson and Alzheimer's disease. In this context, astrocytes play an important role in the regulation of the copper homeostasis in the brain and likely in the prevention against neuronal toxicity, consequently pointing them out as a potential target for the neurotoxicity of copper. Major toxic mechanisms are discussed to be directed against mitochondria probably via oxidative stress. However, the toxic potential and mode of action of copper in astrocytes is poorly understood, so far.

METHODS

In this study, excess copper levels affecting human astrocytic cell model and their involvement in the neurotoxic mode of action of copper, as well as, effects on the homeostasis of other trace elements (Mn, Fe, Ca and Mg) were investigated.

RESULTS

Copper induced substantial cytotoxic effects in the human astrocytic cell line following 48 h incubation (EC₃₀: 250 μM) and affected mitochondrial function, as observed via reduction of mitochondrial membrane potential and increased ROS production, likely originating from mitochondria. Moreover, cellular GSH metabolism was altered as well. Interestingly, not only cellular copper levels were affected, but also the homeostasis of other elements (Ca, Fe and Mn) were disrupted.

CONCLUSION

One potential toxic mode of action of copper seems to be effects on the mitochondria along with induction of oxidative stress in the human astrocytic cell model. Moreover, excess copper levels seem to interact with the homeostasis of other essential elements such as Ca, Fe and Mn. Disrupted element homeostasis might also contribute to the induction of oxidative stress, likely involved in the onset and progression of neurodegenerative disorders. These insights in the toxic mechanisms will help to develop ideas and approaches for therapeutic strategies against copper-mediated diseases.

Genotoxic effect of non-lethal concentrations of minocycline in human glial cell culture

Minocycline has been proposed as a neuroprotective agent with pleiotropic effects on several experimental models of neurodegenerative diseases, including microglial inhibition. However, although most studies have focused on the central actions of minocycline in affecting microglial functions, other central nervous system (CNS) cell types may also be affected by this drug toxicity. Hence, considering that glial cells play a pivotal role on CNS physiology and are the main responsible for neuronal integrity, a comprehensive investigation on the effects of minocycline treatment on human glial cells is mandatory before translational studies to afford neuroprotection in humans. Therefore, we explored the cytotoxic and genotoxic effects of minocycline at different concentrations in glial cells using an in vitro model. To achieve this, U87 glial cell were exposed to 10-50 μg/mL for 24 h. After exposure, cell viability, general metabolic status and genotoxic assays were performed. No changes were observed in cell viability, however, the general metabolic status decreased over 20 μg/mL. In addition, although no chromossome aberrations were observed, evidences of genotoxicity, such as increase on micronucleus, buds and bridges, were observed from 10 μg/mL. These results suggest that minocycline may induce genotoxic effects even at concentrations considered previously safe and should be used with caution in translational studies.

High Sensitivity Detection of Copper Ions in Oysters Based on the Fluorescence Property of Cadmium Selenide Quantum Dots

Cadmium selenide (CdSe) quantum dots (QDs) were synthesized by water phase synthesis method using 3-mercaptopropionic acid (3-MPA) as a stabilizer, and they were applied to the detection of copper ions (Cu2+). The results showed that CdSe QDs have excellent selectivity and sensitivity toward Cu2+. The fluorescence intensity of CdSe QDs decreased with the increase of Cu2+ concentration. The linear range was from 30 nM to 3 μM, and the detection limit was 30 nM. Furthermore, CdSe QDs were used for detecting the concentration of Cu2+ in oysters. The content of Cu2+ was 40.91 mg/kg, which was close to the one measured via flame atomic absorption spectrometry (FAAS), and the relative error was 1.81%. Therefore, CdSe QDs have a wide application prospect in the rapid detection of copper ions in food.

Biochemical CuSO4 Toxicity in Drosophila melanogaster Depends on Sex and Developmental Stage of Exposure

Copper is a transition metal that exists in different chemical forms (e.g., Cu²⁺,Cu⁺, and Cu⁰) and at high concentrations it is toxic. Here, we investigated the Cu²⁺-induced toxicity in Drosophila melanogaster, evaluating the survival, locomotion, and the activity of acetylcholinesterase (AChE) and glutathione S-transferase (GST) enzymes. Flies were exposed to Cu²⁺(0.1-1 mmol CuSO₄/kg of diet or approximately 0.1-1 mM Cu²⁺) and allowed to mate during 24 h. GST and AChE enzymes were evaluated in the larvae and in the head and the body (thorax + abdomen) of the adult male and females flies. The total number of adult females (0.4-1 mM) and males (0.75 and 1 mM) was decreased by CuSO₄. The climbing ability was hampered in flies exposed to 1 mM Cu²⁺. In larvae, Cu²⁺(0.4-1 mM) increased AChE activity (P < 0.002). In males' heads, 0.4 mM Cu²⁺ increased the AChE activity (P < 0.01). In adults' bodies, Cu²⁺inhibited the activity in both sexes, but with greater effectiveness in males (0.1 to 1 mM) than in females (1 mM). Regarding GST activity, 0.1 mM Cu²⁺increased, but 1 mM decrease GST in larvae. In the head of flies, Cu²⁺decreased the GST activity at intermediate (0.4 mM) and increased GST at the highest concentration (1 mM) in males. In the bodies, the effect of Cu²⁺was similar. In conclusion, Cu²⁺exposure in D. melanogaster disrupted locomotion and enzymatic parameters that can be related to changes in AChE and in the detoxifying GST enzyme.

Copper signalling: causes and consequences

Copper-containing enzymes perform fundamental functions by activating dioxygen (O2) and therefore allowing chemical energy-transfer for aerobic metabolism. The copper-dependence of O2 transport, metabolism and production of signalling molecules are supported by molecular systems that regulate and preserve tightly-bound static and weakly-bound dynamic cellular copper pools. Disruption of the reducing intracellular environment, characterized by glutathione shortage and ambient Cu(II) abundance drives oxidative stress and interferes with the bidirectional, copper-dependent communication between neurons and astrocytes, eventually leading to various brain disease forms. A deeper understanding of of the regulatory effects of copper on neuro-glia coupling via polyamine metabolism may reveal novel copper signalling functions and new directions for therapeutic intervention in brain disorders associated with aberrant copper metabolism.

Neuronal, astroglial and locomotor injuries in subchronic copper intoxicated rats are repaired by curcumin: A possible link with Parkinson's disease

We aim herein to assess the neurotoxic effects of subchronic Cu-exposition (0125%) for 6 weeks on dopaminergic and astroglial systems then locomotor activity in rats as well as the probable therapeutic efficiency of curcumin-I (30 mg/kg B.W.). We found that intoxicated rats showed a significant impairment of Tyrosine Hydroxylase (TH) within substantia nigra pars compacta (SNc), ventral tegmental area (VTA) and the striatal outputs together with loss expression of GFAP in these structures. This was linked with an evident decrease in locomotor performance. Co-treatment with curcumin-I inverted these damages and exhibited a significant neuroprotective potential, thus, both TH expression and locomotor performance was reinstated in intoxicated rats. These results prove a profound dopaminergic and astroglial damages following subchronic Cu exposition and new beneficial curative potential of curcumin against subchronic Cu-induced astroglial and dopaminergic neurotoxicity. Consequently, we suggest that Cu neurotoxicity may be strengthened in vivo firstly by attacking and weaking the astroglial system, and curcumin could be prized as a powerful and preventive target for the neurodegenerative diseases related metal element, especially Parkinson's disease.

A bioorthogonal turn-on fluorescent strategy for the detection of lysine acetyltransferase activity

Bioorthogonal labelling was applied to design “turn-on” fluorescent probes for sensitive and selective detection of histone acetyltransferase enzymatic activity in a simple mix-and-read manner.

Chemosensitivity of U251 Cells to the Co-treatment of D-Penicillamine and Copper: Possible Implications on Wilson Disease Patients

D-Penicillamine (PA), a copper chelator, and one of the recommended drugs for treatment of Wilson disease (WD) has been reported to worsen the symptoms of patients with neurologic presentations. However, the cause of this paradoxical response has not been fully elucidated and requires further investigations. Accordingly, we have studied the in vitro effect of Copper (Cu) and/or PA treatment on human glioblastoma U251 cells as an in vitro model of Cu cytotoxicity. Treatment of U251 cells with either Cu or PA exerted no significant effect on their morphology, viability or ROS level. In contrast, co-treatment with Cu-PA caused a decrease in viability, altered glutathione and ceruloplasmin expression coupled with marked increase in ROS; depolarization of mitochondrial membrane potential; and an increase in Sub G0 phase; along with alpha-Fodrin proteolysis. These findings along with the absence of LDH release in these assays, suggest that combined Cu-PA exposure induced apoptosis in U251 cells. In addition, pre-/or co-treatment with antioxidants showed a protective effect, with catalase being more effective than N-acetyl cysteine or trolox in restoring viability and reducing generated ROS levels. By comparison, a similar analysis using other cell lines showed that rat PC12 cells were resistant to Cu and/or PA treatment, while the neuroblastoma cell line SH-SY5Y was sensitive to either compound alone, resulting in decreased viability and increased ROS level. Taken together, this study shows that glioblastoma U251 cells provide a model for Cu-PA cytotoxicity mediated by H₂O₂. We postulate that PA oxidation in presence of Cu yields H₂O₂ which in turn permeates the plasma membrane and induced apoptosis. However, other cell lines exhibited different responses to these treatments, potentially providing a model for cell type- specific cytotoxic responses in the nervous system. The sensitivity of different neural and glial cell types to Cu-PA treatment may therefore underlie the neurologic worsening occurring in some PA-treated WD patients. Our results also raise the possibility that the side effects of PA treatment might be reduced or prevented by administering antioxidants.

The neurotoxicity of iron, copper and cobalt in Parkinson's disease through ROS-mediated mechanisms

Parkinson's disease (PD) is the second most common neurodegenerative disease with gradual loss of dopaminergic neurons. Despite extensive research in the past decades, the etiology of PD remains elusive. Nevertheless, multiple lines of evidence suggest that oxidative stress is one of the common causes in the pathogenesis of PD. It has also been suggested that heavy metal-associated oxidative stress may be implicated in the etiology and pathogenesis of PD. Here we review the roles of redox metals, including iron, copper and cobalt, in PD. Iron is a highly reactive element and deregulation of iron homeostasis is accompanied by concomitant oxidation processes in PD. Copper is a key metal in cell division process, and it has been shown to have an important role in neurodegenerative diseases such as PD. Cobalt induces the generation of reactive oxygen species (ROS) and DNA damage in brain tissues.

A thiol fluorescent probe reveals the intricate modulation of cysteine's reactivity by Cu(II)

In this study, Cu(II)-mediated differential alteration of cysteine (Cys) reactivity is reported by using a Cys-specific fluorescent probe. The probe could react with Cys to give out strong fluorescence. When Cys was preincubated with Cu(II), the fluorescence of the probe was decreased due to the inhibition of Cys's reactivity by Cu(II). Remarkably, experimental results reveal that the probe could detect Cu(II) at subnanomolar concentrations. In contrast, Cu(II) could only partially inhibit the reaction between Cys and Ellman's reagent (DTNB). Furthermore, selectivity experiments show that Cu(II) is a much more potent inhibitor for Cys compared to other metal ions. Cell imaging experiments also confirm the inhibitory effects of Cu(II) on Cys's reactivity in living cells. We envision that the probe could add a useful tool for sensitive and selective detection of Cu(II) for biomedical research.

Toxic effects of copper sulfate on the brains of term Hubbard broiler chicks: a stereological and biochemical study

Copper sulfate can cause different pathologies in different organ systems during development. We determined the effects of toxic levels of copper sulfate on brain development in term Hubbard broiler chicks using stereological and biochemical analyses. Hubbard broiler chicken eggs were divided into three groups: controls with no treatment, sham-treated animals and an experimental group. On day 1, 0.1 ml saline was injected into the air chambers of the sham and experimental groups. The experimental group received also 50 μg copper sulfate. At term (day 21), all chick brains were removed and their volumes were determined using the Cavalieri volume estimation. Parallel biochemical analyses were carried out for glutathione and malondialdehyde levels in the brain tissues as indicators of oxidative damage. With copper treatment, the mean brain volume (8079 μm(3)) was significantly decreased compared to both the control (10075 μm(3)) and sham (9547 μm(3)) groups. Copper treatment (143.8 nmol/g tissue) showed significantly decreased malondialdehyde levels compared to the control (293.6 nmol/g tissue) and sham groups (268.8 nmol/g tissue). Copper treatment (404.5 nmol/g tissue) showed significantly increased malondialdehyde levels compared to the control (158.6 nmol/g tissue) and sham (142.8 nmol/g tissue) groups. The morphological and biochemical parameters we measured demonstrated that in term Hubbard broiler chicks, toxic levels of copper sulfate cause developmental and oxidative brain damage.

Cellular glutathione plays a key role in copper uptake mediated by human copper transporter 1

Copper is an essential micronutrient. Following entry via the human copper transporter 1 (hCTR1), copper is delivered to several copper chaperones, which subsequently transfer the metal to specific targets via protein:protein interactions. It is has been assumed, but not demonstrated, that chaperones acquire copper directly from hCTR1. However, some reports have pointed to an intermediary role for glutathione (GSH), an abundant copper-binding tri-peptide. To address the issue of how transported copper is acquired by the copper chaperones in vivo, we measured the initial rate of (64)Cu uptake in cells in which the cellular levels of copper chaperones or GSH were substantially depleted or elevated. Knockdown or overexpression of copper chaperones ATOX1, CCS, or both had no effect on the initial rate of (64)Cu entry into HEK293 cells having endogenous or overexpressed hCTR1. In contrast, depleting cellular GSH using L-buthionine-sulfoximine (BSO) caused a 50% decrease in the initial rate of (64)Cu entry in HEK293 cells and other cell types. This decrease was reversed by washout of BSO or GSH replenishment with a permeable ester. BSO treatment under our experimental conditions had no significant effects on the viability, ATP levels, or metal content of the cells. Attenuated (64)Cu uptake in BSO was not due to oxidation of the cysteine in the putative metal-binding motif (HCH) at the intracellular hCTR1 COOH terminus, because a mutant lacking this motif was fully active, and (64)Cu uptake was still reduced by BSO treatment. Our data suggest that GSH plays an important role in copper handling at the entry step.

Astrocyte functions in the copper homeostasis of the brain

Copper is an essential element that is required for a variety of important cellular functions. Since not only copper deficiency but also excess of copper can seriously affect cellular functions, the cellular copper metabolism is tightly regulated. In brain, astrocytes appear to play a pivotal role in the copper metabolism. With their strategically important localization between capillary endothelial cells and neuronal structures they are ideally positioned to transport copper from the blood-brain barrier to parenchymal brain cells. Accordingly, astrocytes have the capacity to efficiently take up, store and to export copper. Cultured astrocytes appear to be remarkably resistant against copper-induced toxicity. However, copper exposure can lead to profound alterations in the metabolism of these cells. This article will summarize the current knowledge on the copper metabolism of astrocytes, will describe copper-induced alterations in the glucose and glutathione metabolism of astrocytes and will address the potential role of astrocytes in the copper metabolism of the brain in diseases that have been connected with disturbances in brain copper homeostasis.

The mitochondrial permeability transition, and oxidative and nitrosative stress in the mechanism of copper toxicity in cultured neurons and astrocytes

Copper is an essential element and an integral component of various enzymes. However, excess copper is neurotoxic and has been implicated in the pathogenesis of Wilson's disease, Alzheimer's disease, prion conditions, and other disorders. Although mechanisms of copper neurotoxicity are not fully understood, copper is known to cause oxidative stress and mitochondrial dysfunction. As oxidative stress is an important factor in the induction of the mitochondrial permeability transition (mPT), we determined whether mPT plays a role in copper-induced neural cell injury. Cultured astrocytes and neurons were treated with 20 microM copper and mPT was measured by changes in the cyclosporin A (CsA)-sensitive inner mitochondrial membrane potential (Delta Psi m), employing the potentiometric dye TMRE. In astrocytes, copper caused a 36% decrease in the Delta Psi m at 12 h, which decreased further to 48% by 24 h and remained at that level for at least 72 h. Cobalt quenching of calcein fluorescence as a measure of mPT similarly displayed a 45% decrease at 24 h. Pretreatment with antioxidants significantly blocked the copper-induced mPT by 48-75%. Copper (24 h) also caused a 30% reduction in ATP in astrocytes, which was completely blocked by CsA. Copper caused death (42%) in astrocytes by 48 h, which was reduced by antioxidants (35-60%) and CsA (41%). In contrast to astrocytes, copper did not induce mPT in neurons. Instead, it caused early and extensive death with a concomitant reduction (63%) in ATP by 14 h. Neuronal death was prevented by antioxidants and nitric oxide synthase inhibitors but not by CsA. Copper increased protein tyrosine nitration in both astrocytes and neurons. These studies indicate that mPT, and oxidative and nitrosative stress represent major factors in copper-induced toxicity in astrocytes, whereas oxidative and nitrosative stress appears to play a major role in neuronal injury.

Toxic effects of cobalt in primary cultures of mouse astrocytes

Cobalt is suspected to cause memory deficit in humans and was reported to induce neurotoxicity in animal models. We have studied the effects of cobalt in primary cultures of mouse astrocytes. CoCl(2) (0.2-0.8mM) caused dose-dependent ATP depletion, apoptosis (cell shrinkage, phosphatidylserine externalization and chromatin rearrangements) and secondary necrosis. The mitochondria appeared to be a main target of cobalt toxicity, as shown by the loss of mitochondrial membrane potential (DeltaPsi(m)) and release from the mitochondria of apoptogenic factors, e.g. apoptosis inducing factor (AIF). Pre-treatment with bongkrekic acid reduced ATP depletion, implicating the involvement of the mitochondrial permeability transition (MPT) pore. Cobalt increased the generation of oxygen radicals, but antioxidants did not prevent toxicity. There was also an impaired response to ATP stimulation, evaluated as a lower raise in intracellular calcium. Similarly to hypoxia and dymethyloxallyl glycine (DMOG), cobalt triggered stabilization of the alpha-subunit of hypoxia-inducible factor HIF-1 (HIF-1alpha). This early event was followed by an increased expression of HIF-1 regulated genes, e.g. stress protein HO-1, pro-apoptotic factor Nip3 and iNOS. Although all of the three stimuli activated the HIF-1alpha pathway and decreased ATP levels, the downstream effects were different. DMOG only inhibited cell proliferation, whereas the other two conditions caused cell death by apoptosis and necrosis. This points to cobalt and hypoxia not only inducing HIF-1alpha regulated genes but also affecting similarly other cellular functions, including metabolism.