Recreational MDMA doses do not elicit hepatotoxicity in HepG2 spheroids under normo- and hyperthermia.

MDMA (3,4-methylenedioxymethamphetamine), an entactogen with empathogenic and prosocial effects, is widely used in music festivals and other festive settings. High MDMA doses have been associated with drug-induced liver injury and cases of hyperthermia. Although the latter condition is thought to increase MDMA hepatotoxicity, this correlation remains poorly explored for recreational MDMA doses. On the other hand, the fact that MDMA acts to extinguish fear and to reconsolidate memory could be explored as an adjunct to psychotherapy during treatment of neuropsychiatric disorders such as post-traumatic stress disorder. In this context, assessing MDMA toxicity is relevant, and tridimensional cell culture has emerged as an alternative to animal models in toxicity assessment. Herein, we have used HepG2 spheroids to evaluate MDMA-induced hepatotoxicity at recreational doses, under normo- or hyperthermia. The MTT reduction assay did not evidence significantly reduced cell viability. Moreover, MDMA did not increase reactive oxygen species production, deplete the mitochondrial membrane potential, arrest the cell cycle, or induce apoptotic cell death. These findings support further pre-clinical investigation of MDMA safety from the perspective of both harm reduction and therapy given that non-abusive recreational and therapeutic doses overlap.

Targeting Oxidative Stress with Polyphenols to Fight Liver Diseases.

Reactive oxygen species (ROS) are important second messengers in many metabolic processes and signaling pathways. Disruption of the balance between ROS generation and antioxidant defenses results in the overproduction of ROS and subsequent oxidative damage to biomolecules and cellular components that disturb cellular function. Oxidative stress contributes to the initiation and progression of many liver pathologies such as ischemia-reperfusion injury (LIRI), non-alcoholic fatty liver disease (NAFLD), and hepatocellular carcinoma (HCC). Therefore, controlling ROS production is an attractive therapeutic strategy in relation to their treatment. In recent years, increasing evidence has supported the therapeutic effects of polyphenols on liver injury via the regulation of ROS levels. In the current review, we summarize the effects of polyphenols, such as quercetin, resveratrol, and curcumin, on oxidative damage during conditions that induce liver injury, such as LIRI, NAFLD, and HCC.

Magnetized vermiculite as a tool for the treatment of produced water generated by oil companies: Effects on aquatic organisms before and after treatment.

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT-mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT-mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT-mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT-mag diminished PW toxicity. Therefore, using VMT-mag to treat PW may be the key to reducing the PW effects on aquatic organisms.

Surface facet Fe2O3-based visible light photocatalytic activation of persulfate for the removal of RR120 dye: nonlinear modeling and optimization.

Photocatalytic activation of persulfate (PS) is recently emerged as an energy-efficient and environmentally sustainable approach for pollutants degradation, which enables to leverage the strengths of low-cost solar energy and heterogeneous catalysis. Herein, we investigated the photocatalytic decomposition of reactive red 120 (RR120) dye using PS-activated Fe2O3 nanoparticles and elucidated the effect of their facets, α-Fe2O3 (001), ß-Fe2O3 (100), and γ-Fe2O3 (111). ß-Fe2O3 not only boosted the charge carrier separation but also provided more active sites for PS activation resulting in 6- and 3.5-fold higher photocatalytic activities compared to α-Fe2O3 and γ-Fe2O3, respectively. Response surface methodology and artificial neural network coupled with genetic algorithm models were utilized to optimize and foresee Fe2O3/PS system under visible light. Almost 100% color removal and 82% organic removal were observed under the optimum conditions at 20 mg/L RR120, 22 mg/L ß-Fe2O3, 18 mg/L PS, and pH: 3. Scavenger test indicated that both sulfate and hydroxyl radicals are responsible for the observed RR120 removal. Although cell viability test indicated that cytotoxicity of wastewater is not significantly reduced after treatment. All the results proposed that ß-Fe2O3/PS at relatively low doses has a great potential to decompose and mineralize recalcitrant dyes in wastewater under invisible light.

Exposure to decabromodiphenyl ether (BDE-209) produces mitochondrial dysfunction in rat liver and cell death.

Polybrominated diphenyl ethers (PBDE) are ubiquitous environmental pollutants. Exposure to these chemicals has been associated with developmental neurotoxicity, endocrine dysfunctions, reproductive disorders, and hepatotoxicity. The widespread use of PBDE as flame retardants has culminated in daily exposure of humans and wildlife to these contaminants and resulted in their banned use. Thus assessment of the potential effects of each PBDE congener on living organisms has become cause for concern. The aim of this study was to (1) examine the effects of decabromodiphenyl ether (BDE)-209 on different functions of HepG2 cells and (2) investigate whether this congener is involved in mitochondrial toxicity. The use of multiple methods was employed to (i) study the influence of BDE-209 on mitochondrial permeability transition (MPT) process in mitochondria isolated from rat liver and (ii) determine the consequential cellular damage. Our results showed that BDE-209 induced matrix swelling related to MPT with 10 µM and ATP depletion with 0.1 µM. In addition, 0.5 µM BDE-209 reduced HepG2 cell viability, produced collapse of membrane potential, but increased levels of reactive oxygen species (ROS) after 48 h incubation. After 24 h with 5 µM treatment elevated levels of ROS, DNA fragmentation and cytochrome c release, accompanied by caspase 9 and caspase 3 activation was noted. Taken together, these results suggest that short-duration exposure (24 or 48 h) to 0.5 µM or 5 µM BDE-209 concentrations diminished HepG2 cell viability due to apoptosis associated with mitochondrial dysfunction.

Evaluation of Polybrominated Diphenyl Ether Toxicity on HepG2 Cells - Hexabrominated Congener (BDE-154) Is Less Toxic than Tetrabrominated Congener (BDE-47).

Apoptotic cell death is one of the main consequences of exposure to brominated flame retardants, including polybrominated diphenyl ethers. However, few of these compounds have had their potential toxicity investigated. BDE-154 is one of the most poorly studied polybrominated diphenyl ether (PBDE) congeners, but its level in the environment and in biological fluids is rising. In addition, its chemical structure differs from the other congeners with well-documented toxicity, so BDE-154 may display a distinct toxicity pattern. This study has evaluated how BDE-154 affects the human hepatoblastoma cell line (HepG2) and has looked into the impact of this congener on human health. In addition, this study has related the effects of BDE-154 with the effects of BDE-47 to clarify the mechanism of PBDE toxicity. The HepG2 cell line was exposed to BDEs for 24 and 48 hr and submitted to assays to examine proliferation, viability, mitochondrial membrane potential, reactive oxygen species accumulation, phosphatidylserine exposure, nuclear fragmentation and evaluation of pro-caspase 3, pro-caspase 9, cytochrome c release, and apoptosis inductor factor release by Western blot analysis. BDE-154 induced mitochondrial damage and led to apoptotic death of HepG2 cells, but these effects were less intense than the effects promoted by BDE-47. Unlike other extensively reported congeners, BDE-154 was only toxic at the higher tested concentrations, whereas BDE-47 cytotoxicity was evident even at lower concentrations. Hence, like the toxicity pattern of other classes of substances such as polychlorinated biphenyls, the toxicity pattern of BDEs also depends on their chemical structure and aromatic substituent.

Genistein at maximal physiologic serum levels induces G0/G1 arrest in MCF-7 and HB4a cells, but not apoptosis.

Several studies have demonstrated that a balanced diet can contribute to better human health. For this reason, soy-based food and pure isoflavones (pills) are one of the most consumed. The association of this consumption and lower risks of chronic diseases and cancer is well established for the Asian population and has been attracting the attention of people worldwide, especially women at menopause who seek to alleviate the symptoms associated with the lack of estrogen. Despite positive epidemiological data, concerns still exist because of conflicting results found in scientific literature with relation to the role of isoflavones in breast and hormone-related cancers. The aim of our study was to investigate the cytotoxicity, induction of apoptosis, and changes in apoptosis-related genes of maximal physiological serum levels of the isoflavone genistein (Gen) in MCF-7 tumoral cells and in HB4a non-tumoral cells. In addition, induction of cell cycle arrest was also investigated. Only supraphysiological levels of Gen (50 and 100 µM) were cytotoxic to these cell lines. Concentrations of 10 and 25 µM did not induce apoptosis and significant changes in expression of the studied genes. Positive results were found only in cell cycle analysis: G0/G1 delay of MCF-7 cells in both concentrations of Gen and at 25 µM in HB4a cells. It is the first study investigating effects of Gen in the HB4a cell line. Thus, despite the lack of apoptosis induction (generally found with high concentrations), Gen at physiologically relevant serum levels still exerts chemopreventive effects through the modulation of cell cycle.

Effects on mitochondria of mitochondria-induced nitric oxide release from a ruthenium nitrosyl complex.

The ruthenium nitrosyl complex trans-[Ru(NO)(NH(3))(4)(py)](PF(6))(3) (pyNO), a nitric oxide (NO) donor, was studied in regard to the release of NO and its impact both on isolated mitochondria and HepG2 cells. In isolated mitochondria, NO release from pyNO was concomitant with NAD(P)H oxidation and, in the 25-100 microM range, it resulted in dissipation of mitochondrial membrane potential, inhibition of state 3 respiration, ATP depletion and reactive oxygen species (ROS) generation. In the presence of Ca(2+), mitochondrial permeability transition (MPT), an unspecific membrane permeabilization involved in cell necrosis and some types of apoptosis, was elicited. As demonstrated by externalization of phosphatidylserine and activation of caspase-9 and caspase-3, pyNO (50-100 microM) induced HepG2 cell death, mainly by apoptosis. The combined action of the NO itself, the peroxynitrite yielded by NO in the presence of reactive oxygen species (ROS) and the oxidative stress generated by the NAD(P)H oxidation is proposed to be involved in cell death by pyNO, both via respiratory chain inhibition and ROS levels increase, or even via MPT, if Ca(2+) is present.

Antioxidant activity of flavonoids in isolated mitochondria.

Mitochondria are important intracellular sources and targets of reactive oxygen species (ROS), while flavonoids, a large group of secondary plant metabolites, are important antioxidants. Following our previous study on the energetics of mitochondria exposed to the flavonoids quercetin, taxifolin, catechin and galangin, the present work addressed the antioxidant activity of these compounds (1-50 micromol/L) on Fe(2+)/citrate-mediated membrane lipid peroxidation (LPO) in isolated rat liver mitochondria, running in parallel studies of their antioxidant activity in non-organelle systems. Only quercetin inhibited the respiratory chain of mitochondria and only galangin caused uncoupling. Quercetin and galangin were far more potent than taxifolin and catechin in affording protection against LPO (IC(50) = 1.23 +/- 0.27 and 2.39 +/- 0.79 micromol/L, respectively), although only quercetin was an effective scavenger of both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radicals. These results, together with the previous study, suggest that the 2,3-double bond in conjugation with the 4-oxo function in the flavonoid structure are major determinants of the antioxidant activity of flavonoids in mitochondria, the presence of an o-di-OH structure on the B-ring, as occurs in quercetin, favours this activity via superoxide scavenging, while the absence of this structural feature in galangin, favours it via a decrease in membrane fluidity and/or mitochondrial uncoupling.

Dehydromonocrotaline inhibits mitochondrial complex I. A potential mechanism accounting for hepatotoxicity of monocrotaline.

Monocrotaline is a pyrrolizidine alkaloid present in plants of the Crotalaria species, which causes cytotoxicity and genotoxicity, including hepatotoxicity in animals and humans. It is metabolized by cytochrome P-450 in the liver to the alkylating agent dehydromonocrotaline. We evaluated the effects of monocrotaline and its metabolite on respiration, membrane potential and ATP levels in isolated rat liver mitochondria, and on respiratory chain complex I NADH oxidase activity in submitochondrial particles. Dehydromonocrotaline, but not the parent compound, showed a concentration-dependent inhibition of glutamate/malate-supported state 3 respiration (respiratory chain complex I), but did not affect succinate-supported respiration (complex II). Only dehydromonocrotaline dissipated mitochondrial membrane potential, depleted ATP, and inhibited complex I NADH oxidase activity (IC50=62.06 microM) through a non-competitive type of inhibition (K(I)=8.1 microM). Therefore, dehydromonocrotaline is an inhibitor of the activity of respiratory chain complex I NADH oxidase, an action potentially accounting for the well-documented monocrotaline's hepatotoxicity to animals and humans. The mechanism probably involves change of the complex I conformation resulting from modification of cysteine thiol groups by the metabolite.

4-hydroxy nimesulide effects on mitochondria and HepG2 cells. A comparison with nimesulide.

We previously reported that the nonsteroidal anti-inflammatory drug, nimesulide (N-[4-nitro-2-phenoxyphenyl]-methanesulfonamide), is an uncoupler and oxidizes NAD(P)H in isolated rat liver mitochondria, triggering mitochondrial Ca2+ efflux or, if this effect is inhibited, eliciting mitochondrial permeability transition (Mingatto et al., Br. J. Pharmacol. 131:1154-1160, 2000). We presently demonstrated that nimesulide's hydroxylated metabolite (4-hydroxy nimesulide) lacks the uncoupling property of the parent drug, while keeping its ability to oxidize mitochondrial NADPH. In the presence of 10 microM Ca2+, low (5-50 microM) concentrations of 4-hydroxy nimesulide elicited mitochondrial permeability transition, as assessed by cyclosporin A-sensitive mitochondrial swelling, associated with mitochondrial Ca2+ efflux/membrane potential dissipation (Deltapsi), apparently occurring on account of the oxidation of mitochondrial protein thiols; no involvement of reactive oxygen species was observed. While nimesulide (0.5 or 1 mM, 30 h incubation) did not lead to significant HepG2 cell death, 4-hydroxy nimesulide caused a low extent (approximately 15%) of cell necrosis, partly prevented by cyclosporine A, suggesting the involvement of mitochondrial permeability transition. Both nimesulide and 4-hydroxy nimesulide caused NADPH oxidation and Deltapsi dissipation in HepG2 cells. Because such Deltapsi dissipation induced by the metabolite was almost completely inhibited by cyclosporine A, it probably results from the mitochondrial permeability transition. Therefore, mitochondrial permeability transition, in apparent association with NADPH oxidation, constitutes the most probable cause of HepG2 cell death elicited by 4-hydroxy nimesulide.

Antioxidant activity of isocoumarins isolated from Paepalanthus bromelioides on mitochondria.

The isocoumarins (1-50 microM) paepalantine (9,10-dihydroxy-5,7-dimethoxy-1H-naptho(2,3c)pyran-1-one), 8,8'-paepalantine dimer, and vioxanthin isolated from Paepalanthus bromelioides, were assessed for antioxidant activity using isolated rat liver mitochondria and non-mitochondrial systems, and compared with the flavonoid quercetin. The paepalantine and paepalantine dimers, but not vioxanthin, were effective at scavenging both 1,1-diphenyl-2-picrylhydrazyl (DPPH(*)) and superoxide (O(2)(-)) radicals in non-mitochondrial systems, and protected mitochondria from tert-butylhydroperoxide-induced H(2)O(2) accumulation and Fe(2+)-citrate-mediated mitochondrial membrane lipid peroxidation, with almost the same potency as quercetin. These results point towards paepalantine, followed by paepalantine dimer, as being a powerful agent affording protection, apparently via O(2)(-) scavenging, from oxidative stress conditions imposed on mitochondria, the main intracellular source and target of those reactive oxygen species. This strong antioxidant action of paepalantine was reproduced in HepG2 cells exposed to oxidative stress condition induced by H(2)O(2).

Fe(III) shifts the mitochondria permeability transition-eliciting capacity of mangiferin to protection of organelle.

Mangiferin acts as a strong antioxidant on mitochondria. However, when in the presence of Ca(2+), mangiferin elicits mitochondrial permeability transition (MPT), as evidenced by cyclosporin A-sensitive mitochondrial swelling. We now provide evidence, by means of electrochemical and UV-visible spectroscopical analysis, that Fe(III) coordinates with mangiferin. The resulting mangiferin-Fe(III) complex does not elicit MPT and prevents MPT by scavenging reactive oxygen species. Indeed, the complex protects mitochondrial membrane protein thiols and glutathione from oxidation. Fe(III) also significantly increases the ability of mangiferin to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical, as well as to display antioxidant activity toward antimycin A-induced H(2)O(2) production and t-butyl hydroperoxide-promoted membrane lipid peroxidation in mitochondria. We postulate that coordination with Fe(III) constitutes a potential protective mechanism toward the prooxidant action of mangiferin and other catechol-containing antioxidants regarding MPT induction. Potential therapeutic relevance of this finding for conditions of pathological iron overload is discussed.

Fe(III) shifts the mitochondria permeability transition-eliciting capacity of mangiferin to protection of organelle / s. t

Mangiferin acts as a strong antioxidant on mitochondria. However, when in the presence of Ca(2+), mangiferin elicits mitochondrial permeability transition (MPT), as evidenced by cyclosporin A-sensitive mitochondrial swelling. We now provide evidence, by means of electrochemical and UV-visible spectroscopical analysis, that Fe(III) coordinates with mangiferin. The resulting mangiferin-Fe(III) complex does not elicit MPT and prevents MPT by scavenging reactive oxygen species. Indeed, the complex protects mitochondrial membrane protein thiols and glutathione from oxidation. Fe(III) also significantly increases the ability of mangiferin to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical, as well as to display antioxidant activity toward antimycin A-induced H(2)O(2) production and t-butyl hydroperoxide-promoted membrane lipid peroxidation in mitochondria. We postulate that coordination with Fe(III) constitutes a potential protective mechanism toward the prooxidant action of mangiferin and other catechol-containing antioxidants regarding MPT induction. Potential therapeutic relevance of this finding for conditions of pathological iron overload is discussed(AU)

Effects of isocoumarins isolated from Paepalanthus bromelioides on mitochondria: uncoupling, and induction/inhibition of mitochondrial permeability transition.

Isolated mitochondria may undergo uncoupling, and in presence of Ca(2+) at different conditions, a mitochondrial permeability transition (MPT) linked to protein thiol oxidation, and demonstrated by CsA-sensitive mitochondrial swelling; these processes may cause cell death either by necrosis or by apoptosis. Isocoumarins isolated from the Brazilian plant Paepalanthus bromelioides (Eriocaulaceae) paepalantine (9,10-dihydroxy-5,7-dimethoxy-1H-naptho(2,3c)pyran-1-one), 8,8'-paepalantine dimer, and vioxanthin were assayed at 1-50 microM on isolated rat liver mitochondria, for respiration, MPT, protein thiol oxidation, and interaction with the mitochondrial membrane using 1,6-diphenyl-1,3,5-hexatriene (DPH). The isocoumarins did not significantly affect state 3 respiration of succinate-energized mitochondria; they did however, stimulate 4 respiration, indicating mitochondrial uncoupling. Induction of MPT and protein thiol oxidation were assessed in succinate-energized mitochondria exposed to 10 microM Ca(2+); inhibition of these processes was assessed in non-energized organelles in the presence of 300 microM t-butyl hydroperoxide plus 500 microM Ca(2+). Only paepalantine was an effective MPT/protein thiol oxidation inducer, also releasing cytochrome c from mitochondria; the protein thiol oxidation, unlike mitochondrial swelling, was neither inhibited by CsA nor dependent on the presence of Ca(2+). Vioxanthin was an effective inhibitor of MPT/protein thiol oxidation. All isocoumarins inserted deeply into the mitochondrial membrane, but only paepalantine dimer and vioxantin decreased the membrane's fluidity. A direct reaction with mitochondrial membrane protein thiols, involving an oxidation of these groups, is proposed to account for MPT induction by paepalantine, while a restriction of oxidation of these same thiol groups imposed by the decrease of membrane fluidity, is proposed to account for MPT inhibition by vioxanthin.

Protective effect of topical formulations containing quercetin against UVB-induced oxidative stress in hairless mice.

UV radiation-induced skin damages may result in pre-cancerous and cancerous skin lesions, and acceleration of skin aging. It involves an imbalance of the endogenous antioxidant system that leads to the increase of free radical levels and inflammation. Therefore, antioxidant supplementation might inhibit such imbalance. In this regard, quercetin is a promising drug, this plant derived lipophilic flavonoid presents the higher antioxidant activity among flavonoids and multiple antioxidant mechanisms. Thus, the present study investigated the possible beneficial effects of topical formulations containing quercetin to inhibit UVB irradiation-induced oxidative damages. Quercetin was administered on the dorsal skin of hairless mice using two formulations, formulation 1 (non-ionic emulsion with high lipid content) and formulation 2 (anionic emulsion with low lipid content). The UVB irradiation (0.31-3.69 J/cm(2)) induced a dose-dependent increase in the myeloperoxidase (MPO) activity (4-2708%) and depletion of reduced glutathione (GSH) (22-68%) in the skin of hairless mice after 6h. These results demonstrated that the UVB doses are not excessive, and additionally, they are lower than the doses used in other similar studies. Proteinases secretion/activity, detected by the qualitative sodium dodecyl sulphate polyacrylamide gel electrophoresis substrate-embedded enzymography (zymography), was also enhanced in the same manner as MPO activity using the UVB dose of 1.23J /cm(2). Formulations 1 and 2 inhibited the MPO activity increase (62% and 59%, respectively), GSH depletion (119% and 53%, respectively) and proteinases secretion/activity. To our knowledge, this is the first study to demonstrate the effectiveness of topical formulations containing quercetin to inhibit the UVB irradiation-induced skin damages. Thus, these data suggest the possible usefulness of topical formulations containing quercetin to prevent UVB radiation skin damages.

The interaction of flavonoids with mitochondria: effects on energetic processes.

The study addressed aspects of energetics of isolated rat liver mitochondria exposed to the flavonoids quercetin, taxifolin, catechin and galangin, taking into account influences of the 2,3 double bond/3-OH group and 4-oxo function on the C-ring, and o-di-OH on the B-ring of their structures, as well as mitochondrial mechanisms potentially involved in cell necrosis and apoptosis. The major findings/hypothesis, were: The 2,3 double bond/3-OH group in conjugation with the 4-oxo function on the C-ring in the flavonoid structure seems favour the interaction of these compounds with the mitochondrial membrane, decreasing its fluidity either inhibiting the respiratory chain of mitochondria or causing uncoupling; while the o-di-OH on the B-ring seems favour the respiratory chain inhibition, the absence of this structure seems favour the uncoupling activity. The flavonoids not affecting the respiration of mitochondria, induced MPT. The ability of flavonoids to induce the release of mitochondria-accumulated Ca(2+) correlated well with their ability to affect mitochondrial respiration on the one hand, and their inability to induce MPT, on the other. The flavonoids causing substantial respiratory chain inhibition or mitochondrial uncoupling, quercetin and galangin, respectively, also decreased the mitochondrial ATP levels, thus suggesting an apparent higher potential for necrosis induction in relation to the flavonoids inducing MPT, taxifolin and cathechin, which did not decrease significantly the ATP levels, rather suggesting an apparent higher potential for apoptosis induction.

A proposed sequence of events for cadmium-induced mitochondrial impairment.

Cadmium is a very important environmental toxicant, the cytotoxicity mechanism of which is likely to involve mitochondria as a target. In the present study we addressed the cause/effect relationship between the multiple cadmium-induced responses involving the mitochondrial energetic and oxidative status. Assays were performed with succinate-energized rat liver mitochondria incubated with 5 microM CdCl(2) for 0-25 min, in the absence or presence, respectively, of N-ethylmaleimide (NEM), butylhydroxytoluene (BHT), ruthenium red (RR), and cyclosporine A+ADP. A sequence of events accounting for cadmium-induced mitochondrial impairment is proposed, beginning with an apparent interaction of Cd(2+) with specific protein thiols in the mitochondrial membrane, which stimulates the cation's uptake via the Ca(2+) uniporter, and is followed by the onset of mitochondrial permeability transition (MPT); both effects dissipate the transmembrane electrical potential (Deltapsi), causing uncoupling, followed by an early depression of mitochondrial ATP levels. The respiratory chain subsequently undergoes inhibition, generating reactive oxygen species which together with iron mobilized by the cation, cause late, gradual mitochondrial membrane lipid peroxidation.