Tri-n-butyltin-induced change in cellular level of glutathione in rat thymocytes: a flow cytometric study

Triphenyltin disrupts intracellular Zn2+ homeostasis in rat thymic lymphocytes

Triphenyltin (TPT), previously used as an agricultural fungicide and industrial antifoulant, is now considered an environmental pollutant. The effect of TPT on human health is concerning due to its presence as a contaminant in seafood. In this study, the changes in intracellular Zn²⁺ concentration ([Zn²⁺]i) and cellular content of nonprotein thiols ([NPT]i) induced by triphenyltin chloride (TPTCH), were measured in rat thymic lymphocytes. This was studied by flow-cytometry using the fluorescent probes FluoZin-3-AM and 5-chloromethylfluorescein diacetate (5-CMF-DA). Incubation with TPTCH, at 0.1 μM or more (up to 3 μM), increased [Zn²⁺]i in a concentration-dependent manner. The TPTCH-induced elevation in [Zn²⁺]i was due to the increase in membrane Zn²⁺ permeability and intracellular Zn²⁺ release. Incubation with TPTCH at 0.3 μM significantly increased [NPT]i levels, whereas the addition of an intracellular Zn²⁺ chelator had no effect on the same. TPT at higher concentrations (1 or 3 μM) reduced [NPT]i. TPT may disturb intracellular Zn²⁺ signaling in lymphocytes that disturbs cellular functions.

Deltamethrin induced an apoptogenic signalling pathway in murine thymocytes : exploring the molecular mechanism

Deltamethrin (DLM) is a well-known pyrethroid insecticide; however, the immunotoxic effects of DLM on the mammalian system and its mechanism is still unclear. This study has been designed to first observe the binding affinity of DLM to immune cell receptors and its effects on the immune system. The docking score revealed that DLM has a strong binding affinity towards the CD4 and CD8 receptors. DLM induces apoptosis in murine thymocytes in a concentration-dependent manner. The ear\ly markers of apoptosis such as enhanced reactive oxygen species (ROS) and caspase-3 activation are evident as early as 1 h by 25 and 50 μM DLM. Glutathione (GSH) depletion has also been observed at 1 h by 50 μM DLM concentration. In cell-cycle studies using flow cytometry, the fraction of hypodiploid cells has gradually increased with all the concentrations of DLM at 18 h. The Annexin V binding assay measures the effect of DLM on apoptotic and necrotic cells. The apoptotic cells raised from 18.6% to 35.21% (10-50 μM DLM) at 18 h. N-acetyl cysteine (NAC) effectively reduced the percentage of apoptotic cells which is increased by DLM. In contrast, buthionine sulfoximine (BSO) caused an elevation in the percentage of apoptotic cells. These results demonstrate that caspase activation, ROS activation and GSH act as critical mediators in a DLM-induced apoptogenic signalling pathway in murine thymocytes. In the presence of caspase inhibitor, the percentage of apoptotic cells is partially decreased. Thus, there may be the possibility of some other caspase-independent pathways in DLM-induced apoptosis.

Early cellular responses against tributyltin chloride exposure in primary cultures derived from various brain regions

Tributyltin (TBT) is a potent biocide and commonly used in various industrial sectors. Humans are mainly exposed through the food chain. We have previously demonstrated tin accumulation in brain following TBT-chloride (TBTC) exposure. In this study, effect of TBTC on dissociated cells from different brain regions was evaluated. Cytotoxicity assay (MTT), mode of cell death (Annexin V/PI assay), oxidative stress parameters (ROS and lipid peroxidation), reducing power of the cell (GSH), mitochondrial membrane potential (MMP) and intracellular Ca(2+) were evaluated to ascertain the effect of TBTC. Expression of glial fibrillary acidic protein (GFAP) was measured to understand the effect on astroglial cells. TBTC as low as 30 nM was found to reduce GSH levels, whereas higher doses of 300 and 3000 nM induced ROS generation and marked loss in cell viability mainly through apoptosis. Striatum showed higher susceptibility than other regions, which may have further implications on various neurological aspects.

Consequences of tributyltin chloride induced stress in Leydig cells: an ex-vivo approach

Tributyltin (TBT), a member of the organotin family, is a known endocrine disruptor. It persists long in the environment and is widely used in various industrial applications. This study was planned to understand its toxic influence on Leydig cells isolated from 28 day old wistar rats. In-vitro exposure to TBT-Chloride (TBTC) (300-3000 nM) reduced cell viability (DNA fragmentation, nuclear condensation and MTT assay) and affected testosterone production. TBTC induced both apoptotic and necrotic cell death (AnnexinV/PI binding assay). Involvement of calcium (Ca(2+)), redox imbalance (ROS, GSH and TBARS) and mitochondria in TBTC toxicity was evaluated by using Ca(2+) inhibitors (BAPTA-AM, EGTA, Ruthenium Red), free radical scavengers (NAC, C-Phycocyanin) and mitochondrial permeability transition pore inhibitor (Cyclosporine A). Protein expression analysis of phosphorylated MAPKinases (ERK1/2, JNK1/2, & p38), steroidogenic proteins (3β-HSD, StAR & TSPO) and apoptotic proteins (Bax, Bcl2) illustrates the cytotoxic and anti-steroidogenic activity of TBTC.

Puerarin protects against lead-induced cytotoxicity in cultured primary rat proximal tubular cells

Puerarin, a potent free radicals scavenger, has been demonstrated to have protective efficacy in oxidative damage induced by nephrotoxins. In the present study, the attenuating effect of puerarin (PU) on lead (Pb)-induced apoptosis and oxidative stress was investigated in cultured primary rat proximal tubular (rPT) cells. Results showed that exposure to 0.5 µM Pb induced a decrease in cell viability accompanied with obvious cellular morphological alterations and caused an increase in apoptotic rate and apoptotic morphological changes. Simultaneously, depletion of mitochondrial membrane potential (ΔΨ) and intracellular glutathione (GSH); elevation of caspase-3 activity, intracellular reactive oxygen species, and malondialdehyde levels; and inhibition of GSH peroxidase (GSH-Px) activity were revealed in the cells exposed to Pb alone. However, simultaneous supplementation with PU (50 and 100 µM) protected rPT cells from Pb-induced cytotoxicity through inhibiting apoptosis, attenuating lipid peroxidation, renewing mitochondrial function, and elevating the intracellular antioxidants (nonenzymatic and enzymic) levels. In conclusion, these findings suggested that PU, as a widely distributed dietary antioxidant, contributes potentially to inhibition of Pb-induced cytotoxicity in rPT cells.

The obesogen tributyltin

The obesogen hypothesis postulates the role of environmental chemical pollutants that disrupt homeostatic controls and adaptive mechanisms to promote adipose-dependent weight gain leading to obesity and metabolic syndrome complications. One of the most direct molecular mechanisms for coupling environmental chemical exposures to perturbed physiology invokes pollutants mimicking endogenous endocrine hormones or bioactive dietary signaling metabolites that serve as nuclear receptor ligands. The organotin pollutant tributyltin can exert toxicity through multiple mechanisms but most recently has been shown to bind, activate, and mediate RXR-PPARγ transcriptional regulation central to lipid metabolism and adipocyte biology. Data in support of long-term obesogenic effects on whole body adipose tissue are also reported. Organotins represent an important model test system for evaluating the impact and epidemiological significance of chemical insults as contributing factors for obesity and human metabolic health.

Tributyltin chloride induced testicular toxicity by JNK and p38 activation, redox imbalance and cell death in sertoli-germ cell co-culture

The widespread use of tributyltin (TBT) as biocides in antifouling paints and agricultural chemicals has led to environmental and marine pollution. Human exposure occurs mainly through TBT contaminated seafood and drinking water. It is a well known endocrine disruptor in mammals, but its molecular mechanism in testicular damage is largely unexplored. This study was therefore, designed to ascertain effects of tributyltin chloride (TBTC) on sertoli-germ cell co-culture in ex-vivo and in the testicular tissue in-vivo conditions. An initial Ca(2+) rise followed by ROS generation and glutathione depletion resulted in oxidative damage and cell death. We observed p38 and JNK phosphorylation, stress proteins (Nrf2, MT and GST) induction and mitochondrial depolarization leading to caspase-3 activation. Prevention of TBTC reduced cell survival and cell death by Ca(2+) inhibitors and free radical scavengers specify definitive role of Ca(2+) and ROS. Sertoli cells were found to be more severely affected which in turn can hamper germ cells functionality. TBTC exposure in-vivo resulted in increased tin content in the testis with enhanced Evans blue leakage into the testicular tissue indicating blood-testis barrier disruption. Tesmin levels were significantly diminished and histopathological studies revealed marked tissue damage. Our data collectively indicates the toxic manifestations of TBTC on the male reproductive system and the mechanisms involved.

Involvement of mitochondria mediated pathways in hepatoprotection conferred by Fumaria parviflora Lam. extract against nimesulide induced apoptosis in vitro

Nimesulide, a popular nonsteroidal anti-inflammatory drug, has been associated with serious hepatotoxicity. Reactive oxygen species (ROS) and mitochondrial perturbations have been implicated in drug induced hepatotoxicity, although their role in the pathway needs exploration. Study was undertaken to elucidate the effect of Fumaria parviflora Lam. (Fp) on nimesulide induced cell death in primary rat hepatocyte cultures. Fp extract treated cells showed increased viability as compared to nimesulide stressed cells as assessed by MTT assay. LDH leakage increased significantly at 500microM nimesulide, and the data suggested that apoptosis was the predominant mechanism responsible for cell death. Nimesulide induced apoptosis was further confirmed by DNA fragmentation and chromatin condensation. Nimesulide exposure increased intracellular ROS, translocation of Bax and Bcl2 followed by mitochondrial depolarization and cytochrome c (Cyt c) release along with caspase-9/-3 activity confirming involvement of mitochondria in nimesulide induced apoptosis. Events like membrane depolarization of mitochondria, expression of Bax, Bcl2, externalization of phosphatidyl serine are substantially reversed by the pre-treatment of Fp extract. Thus, the study indicates that Fp extract modulates critical events regulating pro and anti-apoptotic proteins in mitochondria dependent apoptosis induced by nimesulide.

Immunomodulatory role of piperine in cadmium induced thymic atrophy and splenomegaly in mice

Cadmium being a potent immunotoxicant, affects both humoral and cell mediated immunity. In rodents, it is primarily characterized by marked thymic atrophy and splenomegaly. Cadmium induces apoptosis in mice and suppresses the immune functions. Piperine, major alkaloid of Piper longum Linn. and Piper nigrum Linn. with a long history of medicinal value, has shown anti-apoptotic activity in vitro. Thus, to delineate its role in vivo, piperine (2.5mg/kg/day, oral, 7 days) treated Balb/C mice were administered Cd as CdCl(2) (1.8mg/kg, i.p., once, 4th day). The various biochemical indexes of cell damage such as cytotoxicity (MTT assay), oxidative stress (glutathione, reactive oxygen species), apoptosis (mitochondrial membrane potential, caspase-3 activity, phosphatidylserine externalization, apoptotic DNA, intranucleosomal DNA fragmentation) along with lymphocyte phenotyping, cell proliferative response and cytokine secretion (IL-2 and IFNγ) were assessed in thymic and splenic single cell suspensions. Lowering of body weight gain and cellularity and a loss in cell viability seen in Cd group, were abrogated by piperine treatment. Similarly, oxidative stress and apoptotic markers altered by Cd were also modulated by this alkaloid. In addition, a pronounced inhibition of cell proliferative response, alterations in T- and B-cell phenotypes, cytokine release and morphological changes were restored to normalcy. The present in vivo data corroborating with our previous in vitro findings, provide confirmatory evidence of the immuno-protective efficacy of piperine.

Tri-n-butyltin increases intracellular Zn(2+) concentration by decreasing cellular thiol content in rat thymocytes

Effect of tri-n-butyltin (TBT), an environmental pollutant, on intracellular Zn(2+) concentration was tested in rat thymocytes to reveal one of cytotoxic profiles of TBT at nanomolar concentrations using a flow cytometer and appropriate fluorescent probes. TBT at concentrations of 30 nM or more (up to 300 nM) significantly increased the intensity of FluoZin-3 fluorescence, an indicator for intracellular Zn(2+) concentration, under external Ca(2+)- and Zn(2+)-free condition. Chelating intracellular Zn(2+) completely attenuated the TBT-induced augmentation of FluoZin-3 fluorescence. Result suggests that nanomolar TBT releases Zn(2+) from intracellular store site. Oxidative stress induced by hydrogen peroxide also increased the FluoZin-3 fluorescence intensity. The effects of TBT and hydrogen peroxide on the fluorescence were additive. TBT-induced changes in the fluorescence of FluoZin-3 and 5-chloromethylfluorescein, an indicator for cellular thiol content, were correlated with a coefficient of -0.962. Result suggests that the intracellular Zn(2+) release by TBT is associated with TBT-induced reduction of cellular thiol content. However, chelating intracellular Zn(2+) potentiated the cytotoxicity of TBT. Therefore, the TBT-induced increase in intracellular Zn(2+) concentration may be a type of stress responses to protect the cells.

Oxidative stress and apoptotic changes in primary cultures of rat proximal tubular cells exposed to lead

Lead is a known nephrotoxic element. In this study, primary cultures of rat proximal tubular (rPT) cells were treated with different concentrations of lead acetate (0.25, 0.5 and 1 microM) to investigate its cytotoxic mechanism. A progressive loss in cell viability together with a significant increase in the number of apoptotic and necrotic cells and lactate dehydrogenase release were seen in the experiment. Simultaneously, elevation of reactive oxygen species levels and intracellular [Ca(2+)]i, depletion of mitochondrial membrane potential and intracellular glutathione were revealed during the lead exposure. In addition, apoptotic morphological changes induced by lead exposure in rPT cells were demonstrated by Hoechst 33258 staining. The apoptosis was markedly prevented by N-acetyl-L-cysteine, while the necrosis was not affected. Moreover, catalase and superoxide dismutase activities in the living cells rose significantly. In conclusion, exposure of rPT cells to low-concentration lead led to cell death, mediated by an apoptotic and a necrotic mechanism. The apoptotic death induced by oxidative stress was the chief mechanism. Meanwhile, a group of cells survived lead action, mediated by their ability to activate antioxidant defense systems.

The effect of in vitro exposure to tributyltin on the immune competence of Chinook salmon (Oncorhynchus tshawytscha) leukocytes

We evaluated the direct effects of in vitro exposures to tributyltin (TBT), a widely used biocide, on the cell-mediated immune system of Chinook salmon (Oncorhynchus tshawytscha). Splenic and pronephric leukocytes isolated from juvenile Chinook salmon were exposed to TBT (0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 mg/l) in cell cultures for 24 h. Effects of TBT on cell viability, induction of apoptosis, and mitogenic responses were measured by flow cytometry. Splenic and pronephric leukocytes in the presence of TBT experienced a concentration-dependent decrease in viability in cell cultures. Apoptosis was detected as one of the mechanisms of cell death after TBT exposure. In addition, pronephric lymphocytes exhibited a greater sensitivity to TBT exposure than pronephric granulocytes. The functional ability of splenic B-cells to undergo blastogenesis upon lipopolysaccharide stimulation was also significantly inhibited in the presence of 0.05, 0.07, or 0.10 mg/l of TBT in the cell cultures. Flow cytometric assay using a fluorescent conjugated monoclonal antibody against salmon surface immunoglobulin was employed for the conclusive identification of B-cells in the Chinook salmon leukocytes. Our findings suggest that adverse effects of TBT on the function or development of fish immune systems could lead to an increase in disease susceptibility and its subsequent ecological implications.

Glycyrrhizic acid modulates t-BHP induced apoptosis in primary rat hepatocytes

Glycyrrhizic acid (GA) is the main bioactive ingredient of licorice (Glycyrrhiza glabra). The object of this study was to evaluate the protective effects of GA on tert-butyl hydroperoxide (t-BHP) induced oxidative injury leading to apoptosis in cultured primary rat hepatocytes. Throughout the study silymarin was used as positive control. Molecular mechanisms involved in apoptotic pathways induced in hepatocytes by t-BHP at 250 microM were explored in detail. DNA fragmentation, activation of caspases and cytochrome c release were demonstrated. In addition, changes in the mitochondrial membrane potential and ROS generation were detected confirming involvement of mitochondrial pathway. Pre-treatment with GA (4 microg) protected the hepatocytes against t-BHP induced oxidative injury and the results were comparable to the pre-treatment with positive control, i.e. silymarin. The protective potential against cell death was achieved mainly by preventing intracellular GSH depletion, decrease in ROS formation as well as inhibition of mitochondrial membrane depolarization. GA was found to modulate critical end points of oxidative stress induced apoptosis and could be beneficial against liver diseases where oxidative stress is known to play a crucial role.

Cytoprotective and immunomodulating properties of piperine on murine splenocytes: an in vitro study

Piper longum Linn. and Piper nigrum Linn. are conventionally used as immuno-enhancers in Indian system of traditional medicine. The underlying mechanism remains unknown. The present study was therefore, undertaken to delineate the role of piperine (major alkaloid) in cadmium (Cd) induced immuno-compromised murine splenocytes. The various biological determinants such as oxidative stress markers (reactive oxygen species and GSH), Bcl-2 protein expression, mitochondrial membrane potential, caspase-3 activity, DNA damage, splenic B and T cell population, blastogenesis and cytokines (Interleukin-2 and gamma-Interferon) were measured to ascertain its cell protective potential. Cadmium induces apoptosis at 6 h onwards. The oxidative stress markers markedly alter prior to a decline in mitochondrial membrane potential, caspase-3 activation and DNA degradation The splenic cell population was observed to change only at 18 h and the release of two cytokines was affected at 72 h. Addition of piperine in various concentrations (1, 10 and 50 microg/ml) ameliorated the above events. The highest dose of piperine could completely abrogate the toxic manifestations of cadmium and the splenic cells behaved similar to control cells. The reported free radical scavenging property of piperine and its antioxidant potential could be responsible for the modulation of intracellular oxidative stress signals. These in turn appear to mitigate the apoptotic pathway and other cellular responses altered by cadmium. The findings strongly indicate the anti-oxidative, anti-apoptotic and chemo-protective ability of piperine in blastogenesis, cytokine release and restoration of splenic cell population and is suggestive of its therapeutic usefulness in immuno-compromised situations.

Role of oxidative stress and apoptosis in cadmium induced thymic atrophy and splenomegaly in mice

Cadmium immunotoxicity in rodents is primarily characterized by marked thymic damage and splenomegaly. To understand the toxicity of Cd on lymphoid cells in vivo, a single dose of Cd as CdCl2 (1.8 mg/kg, i.p.) was administered to male BALB/c mice and cytotoxicity (MTT assay), oxidative stress indicators (glutathione, reactive oxygen species) and apoptotic markers (mitochondrial membrane potential, caspase-3 activity, phosphatidylserine externalization, apoptotic DNA, intranucleosomal DNA fragmentation) were assessed in thymic and splenic single cell suspensions, at various time intervals. Lowering of body weight gain and cellularity and a loss in cell viability was seen in the Cd treated mice. The earliest significant increase in ROS at 18 h, followed by mitochondrial membrane depolarization, caspase-3 activation and GSH depletion at 24h in spleen and later at 48 h in thymus, strongly implicate the possible involvement of ROS. A pronounced inhibition of cell proliferative response at 48 h and 72 h may also be linked to Cd induced apoptosis. The morphological alterations including thymic cortical cell depletion and an increase in red pulp with diminished white pulp in spleen were observed at 48 h and beyond. The splenic cells appeared more susceptible than thymus cells to the adverse effects of Cd. The present study, therefore, demonstrates potentiation of oxidative stress followed by mitochondrial-caspase dependent apoptotic pathway. This may, in part, be responsible for causing suppression of cell proliferative response, thymic atrophy and splenomegaly.

Tri-n-butyltin-induced blockade of store-operated calcium influx in rat thymocytes

Tri-n-butyltin (TBT), one of environmental pollutants, disturbs intracellular Ca(2+) homeostasis by increasing intracellular Ca(2+) concentration ([Ca(2+)]i). Effect of TBT on oscillatory change in [Ca(2+)]i (Ca(2+) oscillation) of rat thymocytes was examined using a laser microscope with fluo-3-AM in order to further elucidate the TBT toxicity related to intracellular Ca(2+). The Ca(2+) oscillation was completely attenuated by 300nM TBT. Since store-operated Ca(2+) channels are involved in the generation of Ca(2+) oscillation, the action of TBT on an increase in [Ca(2+)]i by Ca(2+) influx through store-operated Ca(2+) channels was examined. The increase in [Ca(2+)]i by the store-operated Ca(2+) influx was not affected by 3nM TBT. However, TBT at 10nM or more significantly reduced the increase in [Ca(2+)]i. It is likely that TBT attenuates the Ca(2+) oscillation by reducing the Ca(2+) influx through store-operated Ca(2+) channels.

Modulation of cadmium induced alterations in murine thymocytes by piperine: oxidative stress, apoptosis, phenotyping and blastogenesis

Piperine, a main component of Piper longum Linn. and Piper nigrum Linn., is a plant alkaloid with a long history of medicinal use in Indian medicine. It is known to exhibit a variety of biological activities which include anti-pyretic, anti-inflammatory, anti-depressant, hepatoprotective and antitumor. Its immunomodulatory role has so far been limited to humoral response. The influence of piperine on murine thymocytes, immunocompromised by cadmium has been reported by us in this investigation. The various biochemical parameters such as oxidative stress markers (ROS and GSH), Bcl-2 protein expression, mitochondrial membrane potential, caspase-3 activity, DNA damage, blastogenesis and T lymphocyte phenotypes were determined. Cadmium (25 microM) induced apoptosis earliest at 6 h. Alterations in ROS and GSH preceded mitochondrial membrane depolarization and caspase-3 activation followed by apoptosis. The phenotypic changes occurred at 18 h and blastogenesis at 72 h. Various conc. of piperine (1, 10 and 50 microg/ml) when added along with Cd (25 microM) from 1.5 to 72 h, caused a dose and time dependent amelioration in all the cellular events mentioned above. Modulation of oxidative stress has earlier been reported to reduce Cd induced apoptosis in murine lymphocytes. Inhibition of the ROS production and replenishment of GSH by piperine, may in part be responsible for the suppression of downstream cascade of events, i.e. apoptosis, blastogenesis and T lymphocyte phenotyping. The study clearly demonstrated the anti-oxidative, anti-apoptotic, and restorative ability against cell proliferative mitogenic response and phenotypic alterations by piperine, suggesting its therapeutic usefulness in immunocompromised conditions.

Influence of cadmium on murine thymocytes: potentiation of apoptosis and oxidative stress

Cadmium (Cd) is a well-known environmental carcinogen and a potent immunotoxicant. It induces thymocyte apoptosis in vitro. However, the mode of action is unclear. In this study, we examined the effect of Cd (10, 25 and 50microM) on mitochondrial membrane potential and caspase-3 as well as oxidative stress markers in murine thymocytes. The cadmium induced apoptosis occurred in a concentration and time dependent manner. The early markers of apoptosis-loss in mitochondrial membrane potential and caspase-3 activation were evident as early as 1.5h by 50microM Cd. Enhanced reactive oxygen species (ROS) generation and glutathione (GSH) depletion were observed at 60min, prior to the lowering of mitochondrial membrane potential. The Cd induced DNA damage as depicted by internucleosomal fragmentation on agarose and histone associated mono- and oligonucleosomes detection by ELISA, corrobated with the apoptotic DNA (sub-G(1) population) and total apoptotic cells by Annexin V binding assay. The number of cells in sub-G(1) population increased to 66% at 50microM Cd concentration and the distribution of early and late apoptotic cells was 47% and 15%, respectively. Addition of N-acetylcysteine and pyrrolidine dithiocarbamate (thiol antioxidants) to the Cd treated cells, lowered the sub-G(1) population, inhibited the ROS generation and raised the GSH levels. Buthionine sulfoximine (GSH depletor) on the other hand, enhanced both the ROS production and the sub-G(1) fraction. These results clearly demonstrate the apoptogenic potential of Cd in murine thymocytes, following mitochondrial membrane depolarization, caspase activation and ROS and GSH acting as critical mediators.

Oxidative stress and apoptotic changes in murine splenocytes exposed to cadmium

Cadmium being a potent immunotoxicant, affects both humoral and cell mediated immunity. However, its effect on spleen is not clearly understood. Hence, to delineate the action of Cd, mouse splenic lymphocytes were exposed to Cd (10, 25 and 50 microM) for 60 min, 1.5, 3, 6 and 18 h. At 6 h, apoptosis was reflected by DNA fragmentation, increased sub-G1 population (apoptotic DNA) and apoptotic cells (Annexin V binding assay). The early stage markers of apoptosis, i.e. decreased mitochondrial membrane potential and caspase-3 activation were observed as early as 1.5 h by the highest dose of Cd (50 microM). Significant ROS production by 25 and 50 microM Cd at 60 min occurred prior to the lowering of mitochondrial membrane potential, suggesting involvement of ROS in causing mitochondrial membrane damage. N-acetylcysteine and pyrrolidine dithiocarbamate (thiol antioxidants) lowered the sub-G(1) population, inhibited the ROS generation and raised the GSH levels induced by Cd. Buthionine sulfoximine (GSH depletor) on the other hand, enhanced the ROS production as well as the sub-G1 fraction. These results imply that ROS is a critical mediator of Cd-induced apoptosis and that cadmium may compromise splenic immune function by accelerating apoptosis.

Antioxidant responses in Meretrix meretrix exposed to environmentally relevant doses of tributyltin

The effects on reduced glutathione (GSH) levels, glutathione-S-transferases (GST) and glutathione peroxidase (GPx) activities of digestive gland in Meretrix meretrix exposed to tributyltin (TBT) at environmental levels (0.1, 1, 10ng/L as Sn), in experimental condition, were evaluated. The GST activities in 0.1ng/L groups were significantly elevated after exposure for 2 days, and were significantly inhibited after exposure to 10ng/L TBT for 8 and 20 days. The GPx activities were mainly induced by TBT exposure, except the GPx activities in 10ng/L groups were significantly inhibited after exposure for 2 days. The GSH content was significantly decreased with prolonged exposure. The GSH content, GST and GPx activities in all exposure groups, transferred to clean recovery tanks for 20 days, were recovered to the level corresponding to that of the control group. Taken together, our present studies indicate that exposure to TBT may induce strong production of reactive oxygen species in the clams.

Tributyltin-sulfhydryl interaction as a cause of immunotoxicity in phagocytes of tunicates

We reported elsewhere that tributyltin (TBT) has detrimental effects on the immune system of the colonial ascidian Botryllus schlosseri, through interaction with calmodulin and alteration of Ca2+ homeostasis. Here, we studied the capability of TBT to react with intracellular thiols. After exposure to 0.1 microM TBT, a significant decrease in B. schlosseri hemocytes stained for total thiols and reduced glutathione (GSH) was detected. Exogenous sulfhydryl and sulfide compounds can prevent TBT-induced cell morphology alterations and decrease the percentage of tin-containing hemocytes, indicating the scavenging ability of thiol peptides. No effects were observed with disulfides, N-acetylcysteine, or the GSH fragment Cys-Gly. No interactions were observed with TBT and carmustine, whereas TBT and N-ethylmaleimide (NEM) showed a combined antagonistic action, suggesting direct interaction of TBT with thiol-containing compounds. Regulation of Ca2+ efflux from internal stores seems to depend on stimulation of the inositol 1,4,5-trisphosphate (InsP3) receptor by oxidized glutathione (GSSG), which results from interactions of both TBT-GSH and TBT-GSH reductase.

Tri-n-butyltin-induced cytotoxicity on rat thymocytes in presence and absence of serum

Influence of fetal bovine serum (FBS) on cytotoxicity induced by tri-n-butyltin (TBT), an environmental pollutant, on rat thymocytes was examined to reveal how FBS modifies TBT cytotoxicity. As the medium FBS concentration was increased from 0 to 10%, the cytotoxicity of TBT was dose-dependently reduced when the cells were incubated with 1 microM TBT for 3 h. Almost complete inhibitions of TBT-induced changes in cell viability and population of cells with exposed phosphatidylserine (cells undergoing apoptosis) were observed when the FBS concentration was 10%. Thus, the cytotoxicity induced by 3 h incubation with TBT in FBS-free medium may be different from that in medium containing 10% FBS. However, even in presence of 10% FBS, TBT at concentrations ranging from 10 to 300 nM exerted cytotoxic action on rat thymocytes when the cells were incubated with TBT for 24 h. TBT dose-dependently increased the population of shrunken cells, of which more than 30% were stained with propidium. TBT at 30 nM or more significantly increased the population of cells with hypodiploid DNA, indicating TBT-induced apoptotic cell death. Thus, in the presence of 10% FBS, the prolonged incubation (24 h) of rat thymocytes with TBT at nanomolar concentrations induced apoptosis rather than necrosis.

Effects of A23187 and CaCl(2) on tri-n-butyltin-induced cell death in rat thymocytes

As tri-n-butyltin (TBT), one of the environmental pollutants, is accumulated in wild animals, concern regarding the toxicity of TBT in both wildlife and human is increasing. TBT has been reported to increase intracellular Ca(2+) concentration in several types of cells. In order to examine how Ca(2+) is involved in TBT-induced cell death, the effect of TBT on rat thymocytes has been compared with that of A23187, a calcium ionophore, under various concentrations of external Ca(2+) using a flow cytometer and fluorescent probes. Although both TBT and A23187 were toxic to cells under normal Ca(2+) condition, under external Ca(2+)-free condition the cytotoxic action of TBT was potentiated without changing the threshold concentration while that of A23187 was completely abolished. A23187 attenuated the TBT-induced descent in cell viability under normal Ca(2+) concentration despite intracellular Ca(2+) concentration was increased. As external Ca(2+) concentration increased, the TBT-induced increase in number of dead cells gradually decreased whereas the number of cells in an early stage of apoptosis increased. Results suggest that Ca(2+) has contradictory actions on the process of TBT-induced cell death in rat thymocytes.

Cytotoxic effects of triphenylbismuth on rat thymocytes: comparisons with bismuth chloride and triphenyltin chloride

The biomedical and industrial uses of organobismuth compounds have become widespread, although there is limited information concerning their cytotoxicity. Therefore, the actions of triphenylbismuth on rat thymocytes were examined using a flow cytometer with ethidium bromide, annexin V-FITC, fluo-3-AM, and 5-chloromethylfluorescein (5CMF) diacetate. Triphenylbismuth at 3-30 microM increased the population of cells stained with ethidium, indicating a decrease in cell viability. Organobismuth at 30 microM increased the population of cells positive to annexin V, suggesting an increase in the population of apoptotic cells. Triphenylbismuth at 3 microM or more decreased cellular glutathione content (5CMF fluorescence intensity) and increased intracellular Ca(2+) concentration ([Ca(2+)](i), fluo-3 fluorescence intensity) in a dose-dependent manner. Because an increase in [Ca(2+)](i) is linked to cell death or cell injury and a decrease in cellular glutathione content increases cell vulnerability to oxidative stress, the triphenylbismuth-induced changes in cellular parameters may be responsible for triphenylbismuth-induced cytotoxicity. Bismuth chloride at 10-30 microM did not significantly affect cell viability. These results suggest that triphenylbismuth at micromolar concentrations exerts cytotoxic action on rat thymocytes, possibly related to a health hazard. Although the cytotoxicity of triphenylbismuth was less than that of triphenyltin, one of the environmental pollutants, it is necessary to direct our attention to the use and disposal of organobismuth compounds.

Butyltin compounds in Portuguese wines

Butyltin compounds are widespread contaminants that have also been found in some wines. The purpose of the present work was to make a survey of butyltin compounds in Portuguese wines. Forty-three table wines and 14 Port wines were analyzed for butyltin contents by using solid-phase microextraction gas chromatography mass spectrometry (SPME-GC-MS). In 14% of the analyzed wine samples, measurable dibutyltin (DBT) was found at concentrations ranging between 0.05 and 0.15 microg/L as Sn. Monobutyltin (MBT) was also observed (0.05 microg/L as Sn) in just a single wine. A search for the possible sources of DBT residues found in the wines was carried out. Therefore, some plastics and oak wood used in the process of wine-making, which have been directly in contact with the musts or the wines, were studied to check their possible release of butyltins. The eventual presence of DBT was also tested directly along the vinification process, from the must to the finished product. The results suggest that high-density polyethylene containers used in the transfer of wine in an early stage of the vinification process may be the main sources of these contaminants. Therefore, it is recommendable that plastic materials to be used in wineries be previously tested for the release of butyltin compounds.

Tri-n-butyltin delays the cell death induced by hydrogen peroxide in rat thymocytes

Tri-n-butyltin (TBT), one of environmental pollutants accumulated in mollusks, at nanomolar concentrations decreases cellular content of glutathione (GSH), suggesting that TBT increases cell vulnerability to oxidative stress because GSH has a role in catabolizing hydrogen peroxide (H(2)O(2)). In order to examine this possibility, the effect of tri-n-butyltin chloride (TBTCl) on rat thymocytes suffering from oxidative stress induced by H(2)O(2) was examined using a flow cytometer with four fluorescent probes; ethidium bromide, 2',7'-dichlorofluorescin diacetate, 5-chloromethylfluorescein diacetate and annexin-V-FITC. TBTCl at concentrations ranging from 100 nM to 1 μM attenuated H(2)O(2)-induced decrease in cell viability in a dose-dependent manner. It was unlikely that TBTCl reduced H(2)O(2)-induced oxidative stress because TBTCl failed to affect H(2)O(2)-induced oxidation of intracellular molecule (2',7'-dichlorofluorescin) and H(2)O(2)-induced decrease in cellular content of GSH. Results suggest that TBTCl may inhibit the pathway of cell death induced by H(2)O(2) or that TBTCl may induce a protective substance against the oxidative stress produced by H(2)O(2).