Pb(NO3 )2 induces cell apoptosis through triggering of reactive oxygen species accumulation and disruption of mitochondrial function via SIRT3/SOD2 pathways

Lead (Pb) is nonbiodegradable and toxic to the lungs. To investigate the potential mechanisms of Pb-induced reactive oxygen species (ROS) accumulation and cell death in the lungs, human non-small lung carcinoma H460 cells were stimulated with Pb(NO3 )2 in this study. The results showed that Pb(NO3 )2 stimulation increased cell death by inducing cell apoptosis which showed a reduced Bcl-2 expression and an enhanced caspase 3 activation. Pb(NO3 )2 also caused the production of H2 O2 in H460 cells that triggering the buildup of ROS and mitochondrial membrane potential loss. We found that Pb(NO3 )2 modulates oxidoreductive activity through reduced the glutathione-disulfide reductase and glutathione levels in Pb(NO3 )2 -exposed H460 cells. Furthermore, the superoxide dismutase (SOD) upstream molecule sirtuin 3 (SIRT3) was increased with Pb(NO3 )2 dose. Collectively, these results demonstrate that Pb(NO3 )2 promotes lung cell death through SIRT3/SOD-mediated ROS accumulation and mitochondrial dysfunction.

Biosynthesis of Silver Nanoparticles Using Salvia pratensis L. Aerial Part and Root Extracts: Bioactivity, Biocompatibility, and Catalytic Potential

The aim of this research was the synthesis of silver nanoparticles (SPA- and SPR-AgNPs) using the aqueous extracts of the aerial (SPA) and the root (SPR) parts of the plant Salvia pratensis L., their characterization, reaction condition optimization, and evaluation of their biological and catalytic activity. UV-Vis spectroscopy, X-ray powder diffraction (XRPD), scanning electron microscopy with EDS analysis (SEM/EDS), and dynamic light scattering (DLS) analysis were utilized to characterize the nanoparticles, while Fourier transform infrared (FTIR) spectroscopy was used to detect some functional groups of compounds present in the plant extracts and nanoparticles. The phenolic and flavonoid contents, as well as the antioxidant activity of the extracts, were determined spectrophotometrically. The synthesized nanoparticles showed twice-higher activity in neutralizing 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) compared with the respective extracts. SPR-AgNPs exhibited strong antimicrobial activity against almost all of the tested bacteria (<0.0039 mg/mL) and fungal strains, especially against the genus Penicillium (<0.0391 mg/mL). Moreover, they were fully biocompatible on all the tested eukaryotic cells, while the hemolysis of erythrocytes was not observed at the highest tested concentration of 150 µg/mL. The catalytic activity of nanoparticles toward Congo Red and 4-nitrophenol was also demonstrated. The obtained results confirm the possibility of the safe application of the synthesized nanoparticles in medicine and as a catalyst in various processes.

Association between prenatal cadmium exposure and cord blood DNA methylation

Prenatal cadmium exposure is known to affect infant growth and organ development. Nonetheless, the role of DNA methylation in cadmium-related health effects has yet to be determined. To this end, we investigated the relationship between prenatal cadmium exposure and cord blood DNA methylation in Korean infants through an epigenome-wide association study. Cadmium concentrations in maternal blood during early and late pregnancy and in cord blood collected from newborns were measured using atomic adsorption spectrometry and DNA methylation analysis was conducted using HumanMethylationEPIC BeadChip kits. After adjusting for infant sex, maternal pregnancy body mass index, smoking status, and estimated leukocyte composition, we analyzed the association between CpG methylation and cadmium concentration in 364 samples. Among 835,252 CpG sites, maternal blood cadmium concentration in early pregnancy was significantly associated with two differentially methylated CpG sites, cg05537752 and cg24904393, which were annotated ATP9A and no gene, respectively. The study findings indicate that prenatal cadmium exposure is significantly associated with methylation statuses of several CpG sites and regions in Korean infants, especially during early pregnancy.

Thermo resistant antioxidants from photoautotrophic microorganisms: screening and characterization

The demand for natural antioxidants to be used in food industry is increasing, as synthetic antioxidants are toxic and have high production costs. Specifically, food processing and preservation require antioxidants resistant to thermal sterilization processes. In this study, twenty-five strains among microalgae and cyanobacteria were screened as antioxidants producers. The species Enallax sp., Synechococcus bigranulatus and Galdieria sulphuraria showed the highest content of chlorophyll a and total carotenoids. In vitro stability and antioxidant activity of the ethanolic extracts were performed. The results revealed that pigments present in the extracts, obtained from the previously mentioned species, were stable at room temperature and exhibited in vitro free radical scavenging potential with IC₅₀ values of 0.099 ± 0.001, 0.048 ± 0.001 and 0.13 ± 0.02 mg mL^-1, respectively. Biocompatibility assay showed that the extracts were not toxic on immortalized cell lines. The antioxidant activity was also tested on a cell-based model by measuring intracellular ROS levels after sodium arsenite treatment. Noteworthy, extracts were able to exert the same protective effect, before and after the pasteurization process. Results clearly indicate the feasibility of obtaining biologically active and thermostable antioxidants from microalgae. Green solvents can be used to obtain thermo-resistant antioxidants from cyanobacteria and microalgae which can be used in the food industry. Thus, the substitution of synthetic pigments with natural ones is now practicable.

Proteomic analysis of rat kidney under maleic acid treatment by SWATH-MS technology

RATIONALE

Maleic acid is an industrial-grade chemical that is often used in adhesives, stabilizers, and preservatives. It is unknown whether long-term consumption of maleic acid modified starch is harmful to humans. However, many studies have indicated that maleic acid causes renal tubular damage in animal models, even as the associated pathways remain unclear. Sequential window acquisition of all theoretical fragment ion spectra (SWATH) is the most innovative of the label-free quantitative technologies which have better quantification performance. Therefore, SWATH technology was used to investigate the effect of maleic acid on the rat kidney proteome in this study.

METHODS

Sprague-Dawley(SD) rats were treated with 0 mg/kg (control), 6 mg/kg (low-dose), 10 mg/kg (medium-dose), and 60 mg/kg (high-dose) of maleic acid. After kidney protein extraction, 28% SDS-PAGE was used, followed by in-gel digestion and desalting. Next, the samples were analyzed with ultra-performance liquid chromatography (UPLC) coupled with quadrupole time-of-flight mass spectrometry (Q-TOF MS), and data-dependent acquisition (DDA) and SWATH technology were also used. The gene ontology and pathway analysis were accomplished. Ultimately, these protein biomarkers were validated by using scheduled high-resolution multiple reaction monitoring (sMRM^HR ).

RESULTS

Comparisons of the control group with the other three groups revealed that 95, 130, and 103 proteins were expressed at significantly different levels in the control group and in the low-dose, medium-dose, and high-dose groups, respectively. According to the gene ontology analysis, the major processes that these proteins were involved in were metabolic processes, biological regulation, cellular processes, and responses to stimuli; the major functions that these proteins were involved in were binding, hydrolase activity, catalytic activity, and oxidoreductase activity; and the major cellular components hat they were involved in were the cytoplasm, extracellular region, membrane, and mitochondria. According to the KEGG pathway analysis, these proteins were involved in 35 pathways, five of which, the carbohydrate metabolism, folate biosynthesis, renal tubular resorption, amino acid metabolism, and Ras signaling pathways, are discussed in this study. Ultimately, 19 proteins involved in 12 important pathways were validated by sMRM^HR .

CONCLUSIONS

It was demonstrated that maleic acid caused insufficient energy production, which might lead to a decrease in the activity of the sodium-potassium ATP pump and hydrogen ion ATP pump, which could in turn have caused renal tubular resorption and hydrogen ion regulation to be blocked, thus leading to the accumulation of hydrogen ions in the renal tubules, which would then result in renal tubular acidification followed finally by Fanconi syndrome.

A Melanin-Related Phenolic Polymer with Potent Photoprotective and Antioxidant Activities for Dermo-Cosmetic Applications

Eumelanins, the dark variant of skin pigments, are endowed with a remarkable antioxidant activity and well-recognized photoprotective properties that have been ascribed to pigment components derived from the biosynthetic precursor 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Herein, we report the protective effect of a polymer obtained starting from the methyl ester of DHICA (MeDHICA-melanin) against Ultraviolet A (UVA)-induced oxidative stress in immortalized human keratinocytes (HaCaT). MeDHICA-melanin was prepared by aerial oxidation of MeDHICA. At concentrations as low as 10 µg/mL, MeDHICA-melanin prevented reactive oxygen species accumulation and partially reduced glutathione oxidation in UVA-irradiated keratinocytes. Western blot experiments revealed that the polymer is able to induce the translocation of nuclear factor erythroid 2–related factor 2 (Nrf-2) to the nucleus with the activation of the transcription of antioxidant enzymes, such as heme-oxygenase 1. Spectrophotometric and HPLC analysis of cell lysate allowed to conclude that a significant fraction (ca. 7%), consisting mainly of the 4,4′-dimer of MeDHICA (ca. 2 μM), was internalized in the cells. Overall these data point to the potential use of MeDHICA-melanin as an antioxidant for the treatment of skin damage, photoaging and skin cancers.

Cadmium exposure during pregnancy and lactation: materno-fetal and newborn repercussions of Cd(ii), and Cd-metallothionein complexes

Cadmium (Cd) is a non-physiological heavy metal that can be harmful at low concentrations. Increasing anthropogenic activities are incrementing the risk of accumulation of this heavy metal in different organs and tissues of the body. In the case of pregnant women, the threat is more serious due to the implications affecting not only their own health but also fetal development as well. Metallothioneins (MTs), small cysteine-rich proteins, are involved in zinc (Zn) and copper homeostasis in mammals but can, however, also bind with Cd if present. The accumulation of Cd in maternal tissues (e.g. placenta, maternal blood, and mammary glands) induces the synthesis of MTs, preferably MT2, in an attempt to sequester the metal to avoid toxicity. The formed Cd-MT complexes will avoid the Cd transport from the placenta to the fetus and end up accumulating in the maternal kidneys. At the same time, high concentrations of MTs will increase the formation of Zn-MT complexes, therefore decreasing the amount of Zn ions available to be transported to the fetus by means of Zn transporters such as ZnT2, ZIP14 and DMT1. Although MTs cannot transport Cd from the mother to the fetus, the divalent DMT1 transporter is suggested to carry the metal to the fetus. As a consequence, the low levels of Zn(ii) in the fetus, together with the presence of Cd(ii) coming from the mother either via the placenta and cord blood or via breast milk induce changes in the fetal development including fetal growth retardation, and low weight or height of the newborn. Likewise, the concentrations of Cd(ii) in the newborn can cause alterations such as cognitive disabilities. In summary, the presence of Cd(ii) in the maternal tissues will induce MT synthesis in an attempt to detoxify these tissues and reduce the possible toxicity of Cd in fetal and newborn tissues.

A highly efficient and selective antitumor agent based on a glucoconjugated carbene platinum(ii) complex

A Pt(ii) complex with a glucosylated carbene shows very high in vitro cytotoxicity and selectivity toward malignant cells.

The marine Gram-negative bacterium Novosphingobium sp. PP1Y as a potential source of novel metabolites with antioxidant activity

OBJECTIVE

The antioxidant activity and protective effect of a methanolic extract obtained from the marine Gram-negative bacterium Novosphingobium sp. PP1Y, isolated from the surface water of a polluted area in the harbour of Pozzuoli (Naples, Italy), was evaluated.

RESULTS

The extract was tested in vitro on epithelial colorectal adenocarcinoma cells and in vivo on Caenorhabditis elegans. It showed strong protective activity against oxidative stress, in both experimental systems, by preventing ROS accumulation. In the case of the cells, pre-treatment with methanolic extract was also able to maintain unaltered intracellular GSH levels and phosphorylation levels of mitogen-activated protein kinases p38. Instead, in the case of the worms, the extract was able to modulate the expression levels of stress response genes, by activating the transcription factor skn-1.

CONCLUSIONS

From a biotechnological and economical point of view, antioxidants from microorganisms are convenient as they provide a valid alternative to chemical synthesis and respond to the ever-growing market demand for natural antioxidants.

Preparation, structure, cytotoxicity and mechanism of action of ferritin-Pt(II) terpyridine compound nanocomposites

AIM

A Pt(II)-terpyridine compound, bearing two piperidine substituents at positions 2 and 2' of the terpyridine ligand (1), is highly cytotoxic and shows a mechanism of action distinct from cisplatin. 1 has been incorporated within the ferritin nanocage (AFt).

MATERIALS & METHODS

Spectroscopic and crystallographic data of the Pt(II)-AFt nanocomposite have been collected and in vitro anticancer activity has been explored using cancer cells.

RESULTS

Pt(II)-containing fragments bind His49, His114 and His132. Pt(II)-AFt nanocomposite is less cytotoxic than 1, but it is more toxic than cisplatin at high concentrations. The Pt(II)-AFt nanocomposite triggers necrosis in cancer cells, as free 1 does.

CONCLUSION

Pt(II)-AFt nanocomposites are promising vehicles to deliver Pt-based drugs to cancer cells.

Alterations in urinary metabolomic profiles due to lead exposure from a lead-acid battery recycling site

Lead poisoning is considered a public health threat, particularly in developing countries. Health problems from Pb exposure occur in many parts of the world, especially near Pb mines, Pb smelters, and used lead-acid battery (ULAB) recycling plants. In this study, we analyzed the urine metabolome of residents in a village located near a ULAB recycling facility to investigate the biological effects of Pb exposure (ULAB: n = 44, Reference: n = 51). Lasso linear regression models were moderately predictive of blood Pb levels, as evaluated by a training set (R² = 0.813) and against an external test set (R²_EXT = 0.647). In lasso logistic regression models, areas under receiver operating characteristic curves, as measured by 5-fold cross-validation (AUC_CV = 0.871) and against an external test set (AUC_EXT = 0.917), indicated accurate classification of urine samples from the affected village and from a reference site. Ten candidate biomarkers identified at false discovery rates of <0.05 were associated with ATP-binding cassette (ABC) transporters, possibly related to the disruption of small-molecule transport in the kidney; amino acid, porphyrin, and chlorophyll metabolism; and the heme biosynthetic pathway. Collectively, the results suggest that lead Pb is related to the health effects in individuals residing in ULAB site by alteration of these biological pathways.

Ferritin nanocages loaded with gold ions induce oxidative stress and apoptosis in MCF-7 human breast cancer cells

Two anticancer gold(iii) compounds, Au2phen and Auoxo4, were encapsulated within a ferritin nanocage. The gold-compound loaded proteins were characterized by UV-Vis spectroscopy, inductively coupled plasma mass spectrometry and circular dichroism. X-ray crystallography shows that the compounds degrade upon encapsulation and gold(i) ions bind Ft within the cage, close to the side chains of Cys126. The gold-encapsulated nanocarriers are cytotoxic to human cancer cells. Au(i)-loaded Ft, obtained upon the encapsulation of Au2phen within the cage, induces oxidative stress activation, which finally leads to apoptosis in MCF-7 cells.

Epiproteome profiling of cadmium-transformed human bronchial epithelial cells by quantitative histone post-translational modification-enzyme-linked immunosorbent assay

Cadmium (Cd), a carcinogenic toxic metal, is pervasively distributed in the soil, water and air. Chronic exposure to Cd has been correlated to lung disease development including cancers. Although many studies have been conducted to investigate the proteome response of cells challenged with Cd, the epiproteomic responses (i.e., global histone post-translational modifications [PTMs]), particularly in human lung cells, are largely unexplored. Here, we provide an epiproteome profiling of human bronchial epithelial cells (BEAS-2B) chronically treated with cadmium chloride (CdCl₂ ), with the aim of identifying global epiproteomic signatures in response to Cd epigenotoxicity. Total histone proteins from Cd-treated and untreated BEAS-2B cells were isolated and subject to quantitative histone PTM-enzyme-linked immunosorbent assay using 18 histone PTM antibodies. Our results unveiled that chronic Cd treatment led to the marked downregulation of H3K4me2 and H3K36me3 and upregulation of H3K9acS10ph, H4K5ac, H4K8ac and H4K12ac PTM marks. Cd-treated cells exhibit transformed cell properties as evidenced by enhanced cell migration and the ability of anchorage-independent growth on soft agar. Notably, treatment of Cd-transformed cells with C646, a potent histone acetyltransferase inhibitor, suppressed the expression of mesenchymal marker genes and cell migration ability of these cells. Taken together, our studies provide for the first time the global epiproteomic interrogation of chronic Cd-exposed human lung cells. The identified aberrant histone PTM alterations associated with Cd-induced epigenotoxicity likely account for the epithelial-mesenchymal transition and neoplastic survival of these cells.

High resolution UPLC-MS/MS profiling of polyphenolics in the methanol extract of Syzygium samarangense leaves and its hepatoprotective activity in rats with CCl4-induced hepatic damage

Oxidative stress plays a crucial role in the development of several liver diseases. Many natural polyphenols can attenuate oxidative stress and liver injury. In this study, a phytochemical profiling of a methanol extract from leaves of Syzygium samarangense revealed 92 compounds belonging to flavonoids, phenolic acids, condensed tannins, and ellagitannins. The S. samarangense extract exhibited a noticeable antioxidant activity with an EC₅₀ of 5.80 μg/mL measured by DPPH scavenging capacity assay, 2632 Trolox equivalents, 10 mM Fe²⁺ equivalents/mg of samples by TEAC and FRAP assays, respectively. The total phenolic content was 419 mg gallic acid equivalent GAE/g extract. In a cell-based model (HaCaT cells), the extract completely inhibited ROS production induced by UVA, and prevented GSH-depletion and p38 phosphorylation. In addition, the extract exhibited a substantial antioxidant and hepatoprotective activities in CCl₄-treated rats, with an increase in GSH (reduced glutathione) and SOD (superoxide dismutase) activities by 84.75 and 26.27%, respectively, and a decrease of 19.08, 63.05, 52.21, 37.00, 13.26, and 15.15% in MDA, ALT, AST, TB (total bilirubin), TC (total cholesterol), and TG (total glycerides), respectively. These results were confirmed by histopathological analyses. We believe that Syzygium samarangense is a good candidate for further evaluation as an antioxidant and liver protecting drug.

The biological response chain to pollution: a case study from the "Italian Triangle of Death" assessed with the liverwort Lunularia cruciata

The liverwort Lunularia cruciata, known for being a species tolerant to pollution able to colonize urban areas, was collected in the town of Acerra (South Italy) to investigate the biological effects of air pollution in one of the three vertices of the so-called Italian Triangle of Death. The ultrastructural damages observed by transmission electron microscopy in specimens collected in Acerra were compared with samples collected in the city center of Naples and in a small rural site far from sources of air pollution (Riccia, Molise, Southern Italy). The biological response chain to air pollution was investigated considering vitality, photosynthetic efficiency, heat shock protein 70 (Hsp70) induction and gene expression levels, and chlorophyll degradation and related ultrastructural alterations. Particularly, a significant increment in Hsp70 expression and occurrence, and modifications in the chloroplasts' ultrastructure can be strictly related to the environmental pollution conditions in the three sites. The results could be interpreted in relation to the use of these parameters as biomarkers for environmental pollution.

Water pollution causes ultrastructural and functional damages in Pellia neesiana (Gottsche) Limpr

The aim of this work is to evaluate the effects of freshwater pollution in the heavily contaminated Sarno River (Campania, South Italy), using Pellia neesiana (Pelliaceae Metzgeriales) in order to propose this liverwort as a potential bioindicator, able to record the effects of water pollution, particularly the one related to metal (loid) contamination. Samples of P. neesiana in nylon bags were disposed floating for one week on the waters of Sarno River in three sites characterised by an increasing pollution. As control, some specimens were cultured in vitro in Cd- and Pb-added media, at the same pollutants' levels as measured in the most polluted site. P. neesiana cell ultrastructure was modified and severe alterations were observed in chloroplasts from samples exposed in the most polluted site, and Cd- and Pb-cultured samples. Concurrently, a strong increase in the occurrence of Heat shock proteins 70 (HSP70) was detected in gametophytes following the pollution gradient. In conclusion, ultrastructural damages can be directly related to HSP 70 occurrence in liverwort tissues, and proportional to the degree of pollution present in the river; thus our study suggests P. neesiana as an affordable bioindicator of freshwaters pollution.

Identification of novel direct protein-protein interactions by irradiating living cells with femtosecond UV laser pulses

The identification of protein-protein interaction networks in living cells is becoming increasingly fundamental to elucidate main biological processes and to understand disease molecular bases on a system-wide level. We recently described a method (LUCK, Laser UV Cross-linKing) to cross-link interacting protein surfaces in living cells by UV laser irradiation. By using this innovative methodology, that does not require any protein modification or cell engineering, here we demonstrate that, upon UV laser irradiation of HeLa cells, a direct interaction between GAPDH and alpha-enolase was "frozen" by a cross-linking event. We validated the occurrence of this direct interaction by co-immunoprecipitation and Immuno-FRET analyses. This represents a proof of principle of the LUCK capability to reveal direct protein interactions in their physiological environment.

Carotenoids in fresh and processed tomato (Solanum lycopersicum) fruits protect cells from oxidative stress injury

BACKGROUND

Lipophilic antioxidants in tomato (Solanum lycopersicum) fruits exert important functions in reducing the risk of human diseases. Here the effect of thermal processing on the antioxidant activity of lipophilic extracts from the commercial tomato hybrid 'Zebrino' was analysed. Carotenoid content and lipophilic antioxidant activity were determined and the ability of tomato extracts in rescuing cells from oxidative stress was assessed.

RESULTS

Lipophilic antioxidant activity was completely retained after heat treatment and extracts were able to mitigate the detrimental effect induced by oxidative stress on different cell lines. Lycopene alone was able to rescue cells from oxidative stress, even if to a lower extent compared with tomato extracts. These results were probably due to the synergistic effect of tomato compounds in protecting cells from oxidative stress injury.

CONCLUSION

The current study provides valuable insights into the health effect of the dietary carotenoids present in fresh and processed tomato fruits. © 2016 Society of Chemical Industry.

Proteome profiling of cadmium-induced apoptosis by antibody array analyses in human bronchial epithelial cells

Protein array technology is a powerful platform for the simultaneous determination of the expression levels of a number of proteins as well as post-translational modifications such as phosphorylation. Here, we screen and report for the first time, the dominant signaling cascades and apoptotic mediators during the course of cadmium (Cd)-induced cytotoxicity in human bronchial epithelial cells (BEAS-2B) by antibody array analyses. Proteins from control and Cd-treated cells were captured on Proteome Profiler™ Arrays for the parallel determination of the relative levels of protein phosphorylation and proteins associated with apoptosis. Our results indicated that the p38 MAPK- and JNK-related signal transduction pathways were dramatically activated by Cd treatment. Cd potently stimulates the phosphorylations of p38α (MAPK14), JNK1/2 (MAPK8/9), and JUN; while the phosphorylations of Akt1, ERK1/2 (MAPK3/1), GSK3β, and mTOR were suppressed. Moreover, there was an induction of proapoptotic protein BAX, release of cytochrome c (CYCS) from mitochondria, activation of caspase-3/9 (CASP3/9); as well as decreased expression of cell cycle checkpoint proteins (TP53, p21, and p27) and several inhibitors of apoptosis proteins (IAPs) [including cIAP-1/2 (BIRC2/3), XIAP (BIRC4), and survivin (BIRC5)]. Pretreatment of cells with the thiol antioxidant glutathione or p38 MAPK/JNK inhibitors before Cd treatment effectively abrogated ROS activation of p38 MAPK/JNK pathways and apoptosis-related proteins. Taken together, our results demonstrate that Cd causes oxidative stress-induced apoptosis; and the p38 MAPK/JNK and mitochondrial pathways are more importantly participated for signal transduction and the induction of apoptosis in Cd-exposed human lung cells.

Proteomic analysis of secreted proteins by human bronchial epithelial cells in response to cadmium toxicity

For years, many studies have been conducted to investigate the intracellular response of cells challenged with toxic metal(s), yet, the corresponding secretome responses, especially in human lung cells, are largely unexplored. Here, we provide a secretome analysis of human bronchial epithelial cells (BEAS-2B) treated with cadmium chloride (CdCl2 ), with the aim of identifying secreted proteins in response to Cd toxicity. Proteins from control and spent media were separated by two-dimensional electrophoresis and visualized by silver staining. Differentially-secreted proteins were identified by MALDI-TOF-MS analysis and database searching. We characterized, for the first time, the extracellular proteome changes of BEAS-2B dosed with Cd. Our results unveiled that Cd treatment led to the marked upregulation of molecular chaperones, antioxidant enzymes, enzymes associated with glutathione metabolic process, proteins involved in cellular energy metabolism, as well as tumor-suppressors. Pretreatment of cells with the thiol antioxidant glutathione before Cd treatment effectively abrogated the secretion of these proteins and prevented cell death. Taken together, our results demonstrate that Cd causes oxidative stress-induced cytotoxicity; and the differentially-secreted protein signatures could be considered as targets for potential use as extracellular biomarkers upon Cd exposure.