Molecular mechanisms of apoptosis induced by cytotoxic chemicals

Latcripin-13 domain induces apoptosis and cell cycle arrest at the G1 phase in human lung carcinoma A549 cells

Latcripin-13 domain, isolated from the transcriptome of Lentinula edodes C91-3, contains a regulator of chromosome condensation (RCC1) domain/β-lactamase-inhibitor protein II (BLIP-II) and a plant homeodomain (PHD). Latcripin-13 domain has been shown to have antitumor effects. However, the underlying molecular pharmacology is largely unknown. We report here that Latcripin-13 domain induced cell cycle arrest in the G1 phase and caused the apoptosis of human lung carcinoma A549 cells via the GSK3β-cyclin D1 and caspase-8/NF-κB signaling pathways. Western blot analysis showed that Latcripin-13 domain decreased cyclin D1 and cyclin-dependent kinase 4 (CDK4), while it increased the ratio of GSK3β/phosphorylated GSK3β. Importantly, Latcripin-13 domain induced nuclear fragmentation and chromatin condensation in the A549 cells. In addition, treatment of the A549 cells with Latcripin-13 domain resulted in the loss of mitochondrial membrane potential, accompanied by an increase in the Bax/Bcl-2 ratio and activation of caspase-3, -8, and -9. Intriguingly, western blot analysis revealed that NF-κB was significantly downregulated by Latcripin-13 domain. These results demonstrated that Latcripin-13 domain induced apoptosis and cell cycle arrest at G1 phase in the A549 cells, providing a mechanism for the antitumor effects of Latcripin-13 domain.

Transient delay of radiation-induced apoptosis by phorbol acetate

The mechanisms of interference of a model tumour promoter 12-O-tetra-decanoylphorbol-13-acetate (TPA) with radiation-induced apoptosis in human peripheral lymphocytes have been investigated. The cells were treated with TPA under various conditions and thereafter exposed to a single lethal dose of gamma radiation. Morphological and biochemical changes characteristic of apoptosis were followed up to 72 h of post-irradiation time. Acute exposure to low concentration of TPA resulted in delay in the onset of radiation-induced apoptosis (determined as morphological changes and rate of mitochondrial demise) by 24-48 h as compared to the irradiated, sham TPA-treated cells. The time course of this delay correlated well with confinement of the p53 protein to the cytoplasm and increase in bcl-2 levels at the nuclear periphery of irradiated cells. Our results indicate that confinement of p53 in the cytoplasm is one of the potential mechanisms by which TPA interferes with the process of radiation-induced apoptosis in human lymphocytes.

Gold nanoparticles from indole-3-carbinol exhibit cytotoxic, genotoxic and antineoplastic effects through the induction of apoptosis

The synthesized gold nanoparticles using indole-3-carbinol (AuNPI3Cs) has been characterized and its antineoplastic activities has been studied here.

The endocrine disruptor cadmium alters human osteoblast-like Saos-2 cells homeostasis in vitro by alteration of Wnt/β-catenin pathway and activation of caspases

PURPOSE

The pollutant Cadmium (Cd) is widespread in the environment and causes alterations of human health by acting as an endocrine disruptor. Bone tissue seems to be a crucial target of Cd contamination. Indeed, we have previously demonstrated that this endocrine disruptor induces osteoblast apoptosis and necrosis. Thus, aim of this study was to further evaluate the effect of Cd on osteoblasts homeostasis, investigating potential modification of the Wnt/β-catenin intracellular pathway, the intracellular process involved in programmed cellular death and the cytoskeletal alterations.

MATERIAL AND METHODS

To this purpose, human osteoblastic Saos-2 cells, a human osteosarcoma osteoblast-like cell line, were cultured and treated with Cd.

RESULTS

Osteoblastic cells were treated for 6 h with 10μM Cd, which induced nuclear translocation of β-catenin and increased expression of Wnt/β-catenin target genes. Longer exposure to the same Cd concentration induced osteoblastic cell apoptosis. To better characterize the intracellular events involved in these Cd-induced alterations, we evaluated the effect of Cd exposure on actin filaments and proteins associated to cytoskeletal actin, characterized by the presence of LIM domains. Long (15, 24 h) exposure of osteoblasts to Cd reduced LIM proteins expression and induced actin filaments destruction and a significant caspase-3 activation after 24 h. In addition, to prove that Cd induces osteoblastic cells apoptosis after long exposure, we performed TUNEL assay which demonstrated increase of cell apoptosis after 24 h.

CONCLUSION

In conclusion, our study shows that osteoblasts exposed to Cd for short intervals of time demonstrated an increase in cell proliferation through a Wnt/β-catenin dependent mechanism, likely as a compensatory mechanism in response to cell injury. Longer exposure to the same Cd concentration induced cells apoptosis through cytoskeleton disruption-mediated mechanisms and caspase activation.

N‑acetyl-S-(p-chlorophenylcarbamoyl)cysteine induces mitochondrial-mediated apoptosis and suppresses migration in melanoma cells

We previously reported that N-acetyl-S-(p-chlorophenylcarbamoyl)cysteine (NACC) induces apoptosis in human melanoma UACC-62 cells. In the present study, the molecular mechanism of NACC‑induced apoptosis in melanoma cells was investigated. Briefly, the apoptosis triggered by NACC was confirmed in UACC‑62 cells for shorter treatment periods. Increased activities of caspase‑3 and caspase‑9 but not caspase‑8 were observed in the cell lysates. Western blotting showed that the pro‑apoptotic protein Bax was upregulated and the anti‑apoptotic protein Mcl‑1 was downregulated and cytochrome c (Cyto c) was released into the cytosol. Flow cytometric analysis demonstrated that NACC induced significant mitochondrial membrane potential disruption. Significant increases in the generation of reactive oxygen species (ROS) and cytosolic calcium elevation were also observed. However, opening of the mitochondrial permeability transition pore which could be involved in Cyto c leakage from mitochondria was found to be unaffected by NACC. Taken together, all the results presented in this study including apoptotic induction, activation of the caspase‑3 and ‑9 cascade, upregulation of Bax, downregulation of Mcl‑1, Cyto c release from the mitochondria, mitochondrial membrane potential depletion, ROS production and cytosolic calcium elevation demonstrated that NACC triggered apoptosis in the UACC‑62 cells via the mitochondrial‑dependent pathway. Melanoma is well‑known as an aggressive and highly metastatic disease. In this study, we also investigated the effects of NACC on the migration of UACC‑62 cells using the xCELLigence system. The results revealed that in vitro NACC is capable of inhibiting the migration of melanoma cells.

Cell-Based Microarrays for In Vitro Toxicology

DNA/RNA and protein microarrays have proven their outstanding bioanalytical performance throughout the past decades, given the unprecedented level of parallelization by which molecular recognition assays can be performed and analyzed. Cell microarrays (CMAs) make use of similar construction principles. They are applied to profile a given cell population with respect to the expression of specific molecular markers and also to measure functional cell responses to drugs and chemicals. This review focuses on the use of cell-based microarrays for assessing the cytotoxicity of drugs, toxins, or chemicals in general. It also summarizes CMA construction principles with respect to the cell types that are used for such microarrays, the readout parameters to assess toxicity, and the various formats that have been established and applied. The review ends with a critical comparison of CMAs and well-established microtiter plate (MTP) approaches.

Volatile organic compounds from fungi isolated after hurricane katrina induce developmental defects and apoptosis in a Drosophila melanogaster model

In previous work, our laboratory developed a Drosophila model for studying the adverse effects of fungal volatile organic compounds (VOCs) emitted by growing cultures of molds. In this report, we have extended these studies and compared the toxic effects of fungal VOCs emitted from living cultures of four molds isolated after Hurricane Katrina from a flooded home in New Orleans. Strains of Aspergillus, Mucor, Penicillium, and Trichoderma were grown with wild-type larvae and the toxic effects of volatile products on the developmental stages of Drosophila larvae were evaluated. Furthermore, heterozygous mutants of Drosophila carrying the apoptotic genes, reaper and dronc, were used to assess the role of apoptosis in fungal VOCs mediated toxicity. Third-instar larvae of Drosophila carrying these apoptotic genes were exposed to fungal VOCs emitted from growing mold cultures for 10 days. The larval strains carrying apoptopic genes survived longer than the control wild type larvae; moreover, of those that survived, heterozygous reaper and dronc strains progressed to pupae and adult phases more rapidly, suggesting that fungal VOCs may induce apoptotic changes in flies. These data lend support to the use of Drosophila as an inexpensive and genetically versatile toxicological model to investigate the mechanistic basis for some of the human illnesses/symptoms associated with exposure to mold-contaminated indoor air, especially after hurricanes.

Aspafilioside B induces G2/M cell cycle arrest and apoptosis by up-regulating H-Ras and N-Ras via ERK and p38 MAPK signaling pathways in human hepatoma HepG2 cells

We recently establish that aspafilioside B, a steroidal saponin extracted from Asparagus filicinus, is an active cytotoxic component. However, its antitumor activity is till unknown. In this study, the anticancer effect of aspafilioside B against HCC cells and the underlying mechanisms were investigated. Our results showed that aspafilioside B inhibited the growth and proliferation of HCC cell lines. Further study revealed that aspafilioside B could significantly induce G2 phase cell cycle arrest and apoptosis, accompanying the accumulation of reactive oxygen species (ROS), but blocking ROS generation with N-acetyl-l-cysteine (NAC) could not prevent G2/M arrest and apoptosis. Additionally, treatment with aspafilioside B induced phosphorylation of extracellular signal-regulated kinase (ERK) and p38 MAP kinase. Moreover, both ERK inhibitor PD98059 and p38 inhibitor SB203580 almost abolished the G2/M phase arrest and apoptosis induced by aspafilioside B, and reversed the expression of cell cycle- and apoptosis-related proteins. We also found that aspafilioside B treatment increased both Ras and Raf activation, and transfection of cells with H-Ras and N-Ras shRNA almost attenuated aspafilioside B-induced G2 phase arrest and apoptosis as well as the ERK and p38 activation. Finally, in vivo, aspafilioside B suppressed tumor growth in mouse xenograft models, and the mechanism was the same as in vitro study. Collectively, these findings indicated that aspafilioside B may up-regulate H-Ras and N-Ras, causing c-Raf phosphorylation, and lead to ERK and p38 activation, which consequently induced the G2 phase arrest and apoptosis. This study provides the evidence that aspafilioside B is a promising therapeutic agent against HCC.

ROS-triggered signaling pathways involved in the cytotoxicity and tumor promotion effects of pentachlorophenol and tetrachlorohydroquinone

Free radical-triggered tissue damage is believed to play an essential role in a variety of human diseases. Pentachlorophenol (PCP) is applied as a pesticide worldwide in both industries and homes. It is used extensively as a biocide and wood preservative. Tetrachlorohydroquinone (TCHQ) was proved as a major toxic metabolite of PCP, contributing the release of free radicals during PCP metabolism. PCP has been proposed as a tumor promoter; however, only limited knowledge is available regarding the mechanisms of tumor promotion induced by PCP and its metabolite, TCHQ. A growing amount of literature suggests that a link between reactive oxygen species (ROS) and tumor promotion could exist. Herein, we summarize the findings regarding the ROS-triggered signaling pathways involved in the cytotoxicity and tumor promotion effects of PCP and TCHQ. Some of the notable findings demonstrated that TCHQ can induce DNA lesions and glutathione depletion in mammalian cells; meanwhile, oxidative stress and apoptosis/necrosis can be found both in vivo and in vitro. Interestingly, PCP and TCHQ were proved as mild tumor promoters in two-stage tumorigenesis models, in which the possible mechanism could be through ROS generation and changed Bcl-2 gene expression. We also found significant effects of antioxidants in attenuating the oxidative stress, cyto- and genotoxicity, and apoptosis/necrosis induced by PCP and/or TCHQ. In addition, mitogen-activated protein kinase (MAPK) activation is involved in PCP/TCHQ-triggered cytotoxicity, as evidenced by the finding that higher doses of TCHQ could lead to necrosis of freshly isolated splenocytes through the production of a large amount of ROS and sustained ERK activation. These results could explain partly the underlying molecular mechanisms contributing to the tumorigenesis induced by PCP. However, the detailed mechanisms of free radicals in triggering PCP/TCHQ-mediated tumor promotion and toxicity are still not completely resolved and need to be investigated further.

Development and application of the adverse outcome pathway framework for understanding and predicting chronic toxicity: II. A focus on growth impairment in fish

Adverse outcome pathways (AOPs) organize knowledge on the progression of toxicity through levels of biological organization. By determining the linkages between toxicity events at different levels, AOPs lay the foundation for mechanism-based alternative testing approaches to hazard assessment. Here, we focus on growth impairment in fish to illustrate the initial stages in the process of AOP development for chronic toxicity outcomes. Growth is an apical endpoint commonly assessed in chronic toxicity tests for which a replacement is desirable. Based on several criteria, we identified reduction in food intake to be a suitable key event for initiation of middle-out AOP development. To start exploring the upstream and downstream links of this key event, we developed three AOP case studies, for pyrethroids, selective serotonin reuptake inhibitors (SSRIs) and cadmium. Our analysis showed that the effect of pyrethroids and SSRIs on food intake is strongly linked to growth impairment, while cadmium causes a reduction in growth due to increased metabolic demands rather than changes in food intake. Locomotion impairment by pyrethroids is strongly linked to their effects on food intake and growth, while for SSRIs their direct influence on appetite may play a more important role. We further discuss which alternative tests could be used to inform on the predictive key events identified in the case studies. In conclusion, our work demonstrates how the AOP concept can be used in practice to assess critically the knowledge available for specific chronic toxicity cases and to identify existing knowledge gaps and potential alternative tests.

Tubeimoside-1 induces glioma apoptosis through regulation of Bax/Bcl-2 and the ROS/Cytochrome C/Caspase-3 pathway

Background

Tubeimoside-1 (TBMS1) is a natural compound isolated from tubeimoside, which has been widely used as a traditional Chinese herbal medicine. The purpose of the present study is to investigate the anti-tumor effect and the underling mechanism of TBMS1 on glioma cancer cells.

Methods

The MTT assay was performed to evaluate the effect of TBMS1 on glioma cell proliferation. The fluorescent microscopy and flow cytometry analysis were performed to evaluate the effect of TBMS1 on glioma cell apoptosis. The Western blot analysis was used to evaluate the protein change.

Results

TBMS1 inhibited glioma cancer cell proliferation in a dose- and time-dependent manner. Fluorescent microscopy and flow cytometry analysis demonstrated that TBMS1 induced glioma cell apoptosis in a concentration-dependent manner. Western blotting showed that TBMS1 induced apoptosis by increasing the expression of Bax and downregulating the level of Bcl-2. Furthermore, we found that TBMS1 induced apoptosis by increasing the concentration of reactive oxygen species through the release of Cytochrome C and activation of Caspase-3.

Conclusion

These findings indicate that TBMS1 may be developed as a possible therapeutic agent for the management of glioma.

The role of mitogen-activated protein kinase in cadmium-induced primary rat cerebral cortical neurons apoptosis via a mitochondrial apoptotic pathway

Cadmium (Cd) is an extremely toxic metal capable of severely damaging several organs, including the brain. Studies have shown that Cd induces neuronal apoptosis partially by activating the mitogen-activated protein kinase (MAPK) pathways. However, the underlying mechanism of MAPK involving the mitochondrial apoptotic pathway in neurons remains unclear. In this study, primary rat cerebral cortical neurons were exposed to Cd, which significantly decreased cell viability and the B-cell lymphoma 2/Bcl-2 associate X protein (Bcl-2/Bax) ratio and increased the percentage of apoptotic cells, release of cytochrome c, cleavages of caspase-3 and poly (ADP-ribose) polymerase (PARP), and nuclear translocation of apoptosis-inducing factor (AIF). In addition, Cd induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and p38 MAPK. Inhibition of ERK and JNK, but not p38 MAPK, partially protected the cells from Cd-induced apoptosis. ERK and JNK inhibition also blocked alteration of the Bcl-2/Bax ratio, release of cytochrome c, cleavages of caspase-3 and PARP, and nuclear translocation of AIF. Taken together, these data suggest that the ERK- and JNK-mediated mitochondrial apoptotic pathways play important roles in Cd-induced neuronal apoptosis.

Oxidative stress associated with neuronal apoptosis in experimental models of epilepsy

Epilepsy is considered one of the most common neurological disorders worldwide. Oxidative stress produced by free radicals may play a role in the initiation and progression of epilepsy; the changes in the mitochondrial and the oxidative stress state can lead mechanism associated with neuronal death pathway. Bioenergetics state failure and impaired mitochondrial function include excessive free radical production with impaired synthesis of antioxidants. This review summarizes evidence that suggest what is the role of oxidative stress on induction of apoptosis in experimental models of epilepsy.

Bisdemethoxycurcumin attenuates gastric adenocarcinoma growth by inducing mitochondrial dysfunction

Bisdemethoxycurcumin (BDMC) is a demethoxy derivative of curcumin. In this study, a human gastric adenocarcinoma xenograft model was generated in vivo using nude mice and BDMC was observed to suppress the growth and activity of tumors, in addition to improving the physical and mental capacity of the mice. An increased number of apoptotic cells, decreased ratio of B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein and increased caspase-3 expression was also observed following treatment with BDMC, indicating that BDMC may promote apoptosis in tumors via mitochondrial modulation. The growth of SGC 7901 gastric cancer cells was inhibited and arrested at G₁ phase. Specific indicators of mitochondrial dysfunction, a reduction in adenosine triphosphate generation, the inner mitochondrial membrane potential, augmentation of reactive oxygen species production and cytochrome c were also detected in the mitochondria following treatment with BDMC. These results indicate that BDMC attenuates gastric adenocarcinoma growth by inducing mitochondrial dysfunction.

N-acetylcysteine attenuates hexavalent chromium-induced hypersensitivity through inhibition of cell death, ROS-related signaling and cytokine expression

Chromium hypersensitivity (chromium-induced allergic contact dermatitis) is an important issue in occupational skin disease. Hexavalent chromium (Cr (VI)) can activate the Akt, Nuclear factor κB (NF-κB), and Mitogen-activated protein kinase (MAPK) pathways and induce cell death, via the effects of reactive oxygen species (ROS). Recently, cell death stimuli have been proposed to regulate the release of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1). However, the exact effects of ROS on the signaling molecules and cytotoxicity involved in Cr(VI)-induced hypersensitivity have not yet been fully demonstrated. N-acetylcysteine (NAC) could increase glutathione levels in the skin and act as an antioxidant. In this study, we investigated the effects of NAC on attenuating the Cr(VI)-triggered ROS signaling in both normal keratinocyte cells (HaCaT cells) and a guinea pig (GP) model. The results showed the induction of apoptosis, autophagy and ROS were observed after different concentrations of Cr(VI) treatment. HaCaT cells pretreated with NAC exhibited a decrease in apoptosis and autophagy, which could affect cell viability. In addition, Cr (VI) activated the Akt, NF-κB and MAPK pathways thereby increasing IL-1α and TNF-α production. However, all of these stimulation phenomena could be inhibited by NAC in both of invitro and invivo studies. These novel findings indicate that NAC may prevent the development of chromium hypersensitivity by inhibiting of ROS-induced cell death and cytokine expression.

Mitochondrial gene expression, antioxidant responses, and histopathology after cadmium exposure

The present study investigates cadmium effects on the transcription of mitochondrial genes of Procambarus clarkii after acute (0.05, 0.5, and 5 mg Cd/L; 4-10 days) and chronic exposures (10 μg Cd/L; 30-60 days). Transcriptional responses of cox1, atp6, and 12S using quantitative real-time RT-PCR were assessed in gills and hepatopancreas. Additionally, the expression levels of genes involved in detoxification and/or oxidative stress responses [mt, sod(Mn)] and enzymatic activities of antioxidants (SOD, CAT, GPX, and GST) were analyzed. The histopathological effects in hepatopancreas of crayfish were evaluated by light microscopy. Relationships between endpoints at different levels of biological organization and Cd bioaccumulation were also examined. Cd induced high levels of bioaccumulation, which was followed by mitochondrial dysfunction and histological alterations in both experiments. Moreover, perturbations in the defence mechanisms against oxidative stress tended to increase with time. Results also showed that molecular responses can vary depending on the intensity and duration of the chemical stress applied to the organisms and that the study of mt gene expression levels seemed to be the best tool to assess Cd intoxication.

Effect of daphnoretin on the proliferation and apoptosis of A549 lung cancer cells in vitro

Daphnoretin is an active constituent of Wikstroemia indica C.A. Mey., which is widely distributed in the northwest and southwest regions of China. Previous studies have shown that daphnoretin has anticancer effects on leukemia, osteosarcoma and uterine cervix cancer cells. However, the effect of daphnoretin on human lung cancer cells has yet to be elucidated. In the present study, daphnoretin was observed to inhibit A549 lung cancer cell proliferation in a concentration- and time-dependent manner. Fluorescent microscopy and flow cytometric analysis showed that daphnoretin induced A549 cell apoptosis in a concentration-dependent manner. Western blot analysis also revealed that daphnoretin induced apoptosis through the regulation of the B-cell lymphoma-2 gene family in A549 cells. These findings indicate that daphnoretin may have potential as a therapeutic agent for the management of lung cancer.

Ascorbic acid protects against anxiogenic-like effect induced by methylmercury in zebrafish: action on the serotonergic system

To evaluate the protector effect of ascorbic acid (AA) against anxiogenic-like effect induced by methylmercury (MeHg) exposure, adult zebrafish were treated with AA (2 mg g(-1), intraperitoneal [i.p.]) before MeHg administration (1.0 μg g(-1), i.p.). Groups were tested for the light/dark preference as a behavioral model of anxiety, and the content of serotonin and its oxidized metabolite tryptamine-4,5-dione (T-4,5-D) in the brain was determined by high-performance liquid chromatography. MeHg has produced a marked anxiogenic profile in both tests, and this effect was accompanied by a decrease in the extracellular levels of serotonin, and an increase in the extracellular levels of T-4,5-D. Added to this, a marked increase in the formation of a marker of oxidative stress accompanied these parameters. Interestingly, the anxiogenic-like effect and biochemical alterations induced by MeHg were blocked by pretreatment with AA. These results for the first time demonstrated the potential protector action of AA in neurobehavioral and neurochemical alterations induced by methylmecury exposure demonstrating that zebrafish model could be used as an important tool for testing substances with neuroprotector actions.

Effects of griseofulvin on apoptosis through caspase-3- and caspase-9-dependent pathways in K562 leukemia cells: An in vitro study

BACKGROUND

Griseofulvin, an oral nontoxic antifungal drug, has been reported to possess anticancer effect in human cancer cells, while the mechanisms are not completely understood.

OBJECTIVE

The aim of this study was to investigate the cytotoxic effect of griseofulvin on K562 cells and to understand its underlying molecular pathways.

METHODS

K562 cells were treated with griseofulvin at different concentrations for 24 hours, and the inhibition effect of griseofulvin on K562 cell proliferation was assessed by tetrazolium salt colorimetric assay. Apoptosis was assessed by examining nuclear morphology and quantifying phosphatidylserine externalization, and alterations in cellular morphology were analyzed by laser scanning confocal microscopy for fluorescent analysis. Flow cytometry was used in the analysis of cell cycle, mitochondrial membrane potential, and caspase pathways.

RESULTS

Griseofulvin could inhibit the growth of K562 cells in a dose-dependent manner with a mean (SD) inhibitory concentration of 50% value of 15.38 (1.35) μg/mL compared with untreated controls. Apoptosis was induced in K562 cells (38.35% [2.73%]; P < 0.01) by griseofulvin with the observation of both an increase in phosphatidylserine level and accumulation of chromatin nucleation in griseofulvintreated cells. In addition, cell-cycle analysis using propidium iodide staining suggested a significant G2/M accumulation (increase from mean 17.64% [4.49%] to 48.29 [1.89%]; P < 0.01) as a result of griseofulvin treatment. Flow cytometry analysis found that griseofulvin treatment was associated with the depolarization of the mitochondrial membrane in K562 cells. Furthermore, increased activities of caspase-3 by 22.15-fold (P < 0.01) and caspase-9 by 16.73-fold (P < 0.01) were observed in K562 cells after griseofulvin treatment compared with the untreated control; a decrease of caspase-8 activity was also observed, but the change was not statistically significant.

CONCLUSIONS

These findings suggest that griseofulvin inhibited growth of K562 cells and induced cell apoptosis through cell-cycle arrest and mitochondrial membrane potential decrease as well as caspase-3 and -9 activation. Further testing is needed to evaluate the potential of griseofulvin as a candidate in the chemotherapy of hematologic malignancies.

The pentachlorophenol metabolite tetrachlorohydroquinone induces massive ROS and prolonged p-ERK expression in splenocytes, leading to inhibition of apoptosis and necrotic cell death

Pentachlorophenol (PCP) has been used extensively as a biocide and a wood preservative and has been reported to be immunosuppressive in rodents and humans. Tetrachlorohydroquinone (TCHQ) is a major metabolite of PCP. TCHQ has been identified as the main cause of PCP-induced genotoxicity due to reactive oxidant stress (ROS). However, the precise mechanisms associated with the immunotoxic effects of PCP and TCHQ remain unclear. The aim of this study was to examine the effects of PCP and TCHQ on the induction of ROS and injury to primary mouse splenocytes. Our results shown that TCHQ was more toxic than PCP and that a high dose of TCHQ led to necrotic cell death of the splenocytes through induction of massive and sudden ROS and prolonged ROS-triggered ERK activation. Inhibition of ROS production by N-acetyl-cysteine (NAC) partially restored the mitochondrial membrane potential, inhibited ERK activity, elevated caspase-3 activity and PARP cleavage, and, eventually, switched the TCHQ-induced necrosis to apoptosis. We suggest that prolonged ERK activation is essential for TCHQ-induced necrosis, and that ROS play a pivotal role in the different TCHQ-induced cell death mechanisms.

Mechanism of cadmium induced apoptosis in human peripheral blood lymphocytes: the role of p53, Fas and Caspase-3

Cadmium (Cd) is a major pollutant of environment. It can be fatal to human. In spite of bulk of research and literatures, the mechanism of a fatality against human is still not understood completely. Toxic and carcinogenic effects of Cd in rodents and humans are well known. However, effects of Cd on induction of apoptosis are still elusive. This study indicates immunosuppression and immunotoxicity due to Cd exposure. Present study was undertaken to determine the mechanism of cell death in vitro in human peripheral blood lymphocytes induced by Cd. Our findings suggest the toxicity due to Cd is attributed to programmed cell death-apoptosis. IC₅₀ was calculated at 21.74 μM. A significant increase of expression of the pro-apoptotic genep53, Fas and Caspase-3 in human lymphocytes was found. Cd induced p53-dependent apoptosis through cooperation between Bak upregulation without changing the Bcl-2 and Bax expression. Data of this study compel to speculate that apoptosis may also be attributed to CD95/Fas complex formation, and p53 direct apoptogenic potential at mitochondria. It was confirmed by the increased expression of Caspase-3. Although, this work does not address all the questions regarding the mechanism of Cd induced apoptosis, but these findings establish an important role of p53 and mitochondrial function during apoptosis in human lymphocyte. Moreover, based upon our findings, the role of Fas in Cd induced apoptosis is also undeniable. Hence further investigations are required to understand the different mechanism involved into apoptosis of lymphocytes due to Cd exposure.

A novel synthetic analog of Militarin, MA-1 induces mitochondrial dependent apoptosis by ROS generation in human lung cancer cells

A synthetic Militarin analog-1[(2R,3R,4R,5R)-1,6-bis(4-(2,4,4-trimethylpentan-2-yl)phenoxy) hexane-2,3,4,5-tetraol] is a novel derivative of constituents from Cordyceps militaris, which has been used to treat a variety of chronic diseases including inflammation, diabetes, hyperglycemia and cancers. Here, we report for the first time the synthesis of Militarin analog-1 (MA-1) and the apoptotic mechanism of MA-1 against human lung cancer cell lines. Treatment with MA-1 significantly inhibited the viability of 3 human lung cancer cell lines. The inhibition of viability and growth in MA-1-treated A549 cells with an IC50 of 5μM were mediated through apoptosis induction, as demonstrated by an increase in DNA fragmentation, sub-G0/G1-DNA fraction, nuclear condensation, and phosphatidylserine exposure. The apoptotic cell death caused mitochondrial membrane permeabilization through regulation of expression of the Bcl-2 family proteins, leading to cytochrome c release in a time-dependent manner. Subsequently, the final stage of apoptosis, activation of caspase-9/-3 and cleavage of poly (ADP ribose) polymerase, was induced. Furthermore, A549 lung cancer cells were more responsive to MA-1 than a bronchial epithelial cell line (BEAS-2B), involving the rapid generation of reactive oxygen species (ROS), c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) activation. The pharmacological inhibition of ROS generation and JNK/p38 MAPK exhibited attenuated DNA fragmentation in MA-1-induced apoptosis. Oral administration of MA-1 also retarded growth of A549 orthotopic xenografts. In conclusion, the present study indicates that the new synthetic derivative MA-1 triggers mitochondrial apoptosis through ROS generation and regulation of MAPKs and may be a potent therapeutic agent against human lung cancer.

Role of Metabolism by Intestinal Bacteria in Arbutin-Induced Suppression of Lymphoproliferative Response in vitro

Role of metabolism by intestinal bacteria in arbutin-induced immunotoxicity was investigated in splenocyte cultures. Following an incubation of arbutin with 5 different intestinal bacteria for 24 hr, its aglycone hydroquinone could be produced and detected in the bacterial culture media with different amounts. Toxic effects of activated arbutin by intestinal bacteria on lymphoproliferative response were tested in splenocyte cultures from normal mice. Lipopolysaccharide and concanavalin A were used as mitogens for B- and T-cells, respectively. When bacteria cultured medium with arbutin was treated into the splenocytes for 3 days, the medium cultured with bacteria producing large amounts of hydroquinone induced suppression of lymphoproliferative responses, indicating that metabolic activation by intestinal bacteria might be required in arbutin-induced toxicity. The results indicated that the present testing system might be applied for determining the possible role of metabolism by intestinal bacteria in certain chemical-induced immunotoxicity in animal cell cultures.

Aroclor 1254 induced oxidative stress and mitochondria mediated apoptosis in adult rat sperm in vitro

Aroclor 1254, a commercial mixture of highly toxic environmental pollutant, is known to cause testicular toxicity. The present study was undertaken to delineate and elucidate the nature and the mechanism of action of Aroclor 1254 on rat sperm in vitro. Sperm of adult rat were incubated with 10(-9)M, 10(-8)M or 10(-7)M of Aroclor 1254 for 3h. Sperm motility was significantly decreased. Moreover, sperm viability, acrosome reaction and mitochondrial membrane potential (Δψm) were significantly decreased in a dose-related pattern. DNA integrity was significantly decreased at 10(-8)M and 10(-7)M of Aroclor 1254, while it did not show any significant change at 10(-9)M. Aroclor 1254 induced downstream events included cytochrome c release and caspase-3 activation, in a dose-related manner. ATP content was decreased while protein carbonyl content was significantly increased in a dose-related manner. The oxidative stress status was also assessed. Hydrogen peroxide (H2O2) production and lipid peroxidation (LPO) were significantly increased in a dose-related pattern. The antioxidant enzymes SOD, CAT and GPx were significantly decreased, while at a concentration of 10(-9)M of Aroclor 1254, GR activity did not show any significant change. The non-enzymatic antioxidant (GSH) was significantly decreased in a dose-dependent manner. In conclusion; our data clearly show that Aroclor 1254 induces toxicity, oxidative stress and culminating in mitochondria mediated apoptosis in rat sperm.

T-2 toxin exposure induces apoptosis in rat ovarian granulosa cells through oxidative stress

OBJECTIVE

To investigate the reproductive toxicity and cytotoxicity of T-2 toxin, which is a mycotoxin, and to explore its potential apoptotic induction mechanism.

METHODS

ovarian granulosa cells of rats were treated with T-2 toxin (1-100nM) for 24h. The cytotoxicity was assessed with MTT bioassay and apoptotic cells were detected by flow cytometry, and further identified by chromatin condensation and nuclear fragmentation with Hoechst 33258 under microscope; reactive oxygen species (ROS) with DCFH-DA was analyzed by fluorometry; total superoxide dismutase (SOD) was determined by NBT staining method. Glutathione peroxidase (GSHPx) activity was detected by UV colorimetric assay. The activity of catalase (CAT) in granulosa cells was measured by the Aebi method, and malondialdehyde (MDA) content was determined by thiobarbituric acid assay.

RESULTS

T-2 toxin dose-dependently inhibited the growth of granulosa cells and resulted in apoptosis in rat granulosa cells. Treatment with T-2 toxin could induce ROS and MDA accumulation in granulosa cells, acompanying with losses of activities of SOD, GSH-Px and CAT, whereas T-2 toxin-induced apoptosis in granulosa cells could be significantly inhibited through the use of antioxidant Trolox.

CONCLUSION

These data suggest that T-2 toxin may induce the apoptosis in rat granulosa cells through oxidative stress.

Delphinidin-3-glucoside protects against oxidized low-density lipoprotein-induced mitochondrial dysfunction in vascular endothelial cells via the sodium-dependent glucose transporter SGLT1

Delphinidin-3-glucoside (Dp) is a member of a family of bioactive compounds known as anthocyanins that occur naturally in pigmented plants and are known to ameliorate oxidative stress. Previous studies have showed that Dp decreased oxidative stress in vascular endothelial cells, however, the underlying mechanisms remain largely unknown. In the present study, we showed that pretreatment with Dp significantly suppressed oxidized low-density lipoprotein (oxLDL)-induced cell proliferation inhibition and apoptosis in primary human umbilical vein endothelial cells (HUVECs). Also, Dp pretreatment attenuated oxLDL-induced mitochondrial dysfunction via decreased reactive oxygen species (ROS) and superoxide anion generation, thereby repressing mitochondrial membrane potential and closing mitochondrial permeability transition pore. Furthermore, in vitro and in vivo data showed that Dp was transported into endothelial cells in a temperature, concentration, and time-dependent manner via the sodium-dependent glucose transporter (SGLT1). Suppression of SGLT1 by its substrate glucose, its inhibitor phlorizin or SGLT1 siRNA blocked Dp transportation. Repression of SGLT1 significantly inhibited Dp function of ameliorating mitochondrial dysfunction induced by pro-apoptotic factors (Apoptosis-inducing factor, Cytochrome c, Caspase-3 and Bax/Bcl-2 ratio). Taken together, our data indicate that Dp protects VECs via the SGLT1-ROS-mitochodria pathway. This new insight may help to elucidate the molecular mechanisms underlying the vascular protection afforded by Dp, and anthocyanins in general, in the context of prevention of endothelial dysfunction and atherosclerosis.

Evodiamine, a plant alkaloid, induces calcium/JNK-mediated autophagy and calcium/mitochondria-mediated apoptosis in human glioblastoma cells

Glioblastomas, the most common primary gliomas, are characterized by increased invasion and difficult therapy. Major clinical medicines for treating gliomas merely extend the survival time for a number of months. Therefore, development of new agents against gliomas is important. Autophagy, a process for degrading damaged organelles and proteins, is an adaptive response to environmental stress. However, the role of autophagy in glioblastoma development still needs to be further investigated. Evodiamine, a major alkaloid isolated from Evodia rutaecarpa Bentham, has various pharmacological activities, such as inhibiting tumor growth and metastatic properties. However, the effects of evodiamine on glioblastomas and their detailed molecular mechanisms and autophagy formation are not well understood. In this study, we observed that evodiamine induced dose- and time-dependent apoptosis in glioma cells. Blockade of calcium channels in endoplasmic reticulum (ER) significantly reduced evodiamine-induced cytosolic calcium elevation, apoptosis, and mitochondrial depolarization, which suggests that evodiamine induces a calcium-mediated intrinsic apoptosis pathway. Interestingly, autophagy was also enhanced by evodiamine, and had reached a plateau by 24h. Pharmacological inhibition of autophagy resulted in increased apoptosis and reduced cell viability. Inhibition of ER calcium channel activation also significantly reduced evodiamine-induced autophagy. Inactivation of c-Jun N-terminal kinases (JNK) suppressed evodiamine-mediated autophagy accompanied by increased apoptosis. Furthermore, evodiamine-mediated JNK activation was abolished by BAPTA-AM, an intracellular calcium scavenger, suggesting that evodiamine mediates autophagy via a calcium-JNK signaling pathway. Collectively, these results suggest that evodiamine induces intracellular calcium/JNK signaling-mediated autophagy and calcium/mitochondria-mediated apoptosis in glioma cells.

Metal Species in Biology: Bottom-Up and Top-Down LC Approaches in Applied Toxicological Research

Since the inception of liquid chromatography (LC) more than 100 years ago this separation technique has been developed into a powerful analytical tool that is frequently applied in life science research. To this end, unique insights into the interaction of metal species (throughout this manuscript “metal species” refers to “toxic metals, metalloid compounds, and metal-based drugs” and “toxic metals” to “toxic metals and metalloid compounds”) with endogenous ligands can be obtained by using LC approaches that involve their hyphenation with inductively coupled plasma-based element specific detectors. This review aims to provide a synopsis of the different LC approaches which may be employed to advance our understanding of these interactions either in a “bottom-up” or a “top-down” manner. In the “bottom-up” LC-configuration, endogenous ligands are introduced into a physiologically relevant mobile phase buffer, and the metal species of interest is injected. Subsequent “interrogation” of the on-column formed complex(es) by employing a suitable separation mechanism (e.g., size exclusion chromatography or reversed-phase LC) while changing the ligand concentration(s), the column temperature or the pH can provide valuable insight into the formation of complexes under near physiological conditions. This approach allows to establish the relative stability and hydrophobicity of metal-ligand complexes as well as the dynamic coordination of a metal species (injected) to two ligands (dissolved in the mobile phase). Conversely, the “top-down” analysis of a biological fluid (e.g., blood plasma) by LC (e.g., using size exclusion chromatography) can be used to determine the size distribution of endogenous metalloproteins which are collectively referred to as the “metalloproteome”. This approach can provide unique insight into the metabolism and the plasma protein binding of metal species, and can simultaneously visualize the dose-dependent perturbation of the metalloproteome by a particular metal species. The concerted application of these LC approaches is destined to provide new insight into biochemical processes which represent an important starting point to advance human health in the 21st century.

Wentilactone B induces G2/M phase arrest and apoptosis via the Ras/Raf/MAPK signaling pathway in human hepatoma SMMC-7721 cells

Hepatocellular carcinoma (HCC) is generally acknowledged as the most common primary malignant tumor, and it is known to be resistant to conventional chemotherapy. Wentilactone B (WB), a tetranorditerpenoid derivative extracted from the marine algae-derived endophytic fungus Aspergillus wentii EN-48, has been shown to trigger apoptosis and inhibit metastasis in HCC cell lines. However, the mechanisms of its antitumor activity remain to be elucidated. We report here that WB could significantly induce cell cycle arrest at G2 phase and mitochondrial-related apoptosis, accompanying the accumulation of reactive oxygen species (ROS). Additionally, treatment with WB induced phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), but not p38 MAP kinase. Among the pathway inhibitors examined, only SP600125 (JNK inhibitor) markedly reversedWB-induced apoptosis, and only U0126 (ERK inhibitor) significantly blocked WB-triggered G2 phase arrest. We also found that WB treatment increased both Ras and Raf activation, and transfection of cells with dominant-negative Ras (RasN17) abolishedWB-induced apoptosis and G2 phase arrest in SMMC-7721 cells. Furthermore, the results of inverse docking (INVDOCK) analysis suggested that WB could bind to Ras-GTP, and the direct binding affinity was also confirmed by surface plasmon resonance (SPR). Finally, in vivo, WB suppressed tumor growth in mouse xenograft models. Taken together, these results indicate that WB induced G2/M phase arrest and apoptosis in human hepatoma SMMC-7721 cells via the Ras/Raf/ERK and Ras/Raf/JNK signaling pathways, and this agent may be a potentially useful compound for developing anticancer agents for HCC.

Sterigmatocystin-induced DNA damage triggers G2 arrest via an ATM/p53-related pathway in human gastric epithelium GES-1 cells in vitro

Sterigmatocystin (ST), which is commonly detected in food and feed commodities, is a mutagenic and carcinogenic mycotoxin that has been recognized as a possible human carcinogen. Our previous study showed that ST can induce G2 phase arrest in GES-1 cells in vitro and that the MAPK and PI3K signaling pathways are involved in the ST-induced G2 arrest. It is now widely accepted that DNA damage plays a critical role in the regulation of cell cycle arrest and apoptosis. In response to DNA damage, a complex signaling network is activated in eukaryotic cells to trigger cell cycle arrest and facilitate DNA repair. To further explore the molecular mechanism through which ST induces G2 arrest, the current study was designed to precisely dissect the role of DNA damage and the DNA damage sensor ataxia telangiectasia-mutated (ATM)/p53-dependent pathway in the ST-induced G2 arrest in GES-1 cells. Using the comet assay, we determined that ST induces DNA damage, as evidenced by the formation of DNA comet tails, in GES-1 cells. We also found that ST induces the activation of ATM and its downstream molecules, Chk2 and p53, in GES-1 cells. The ATM pharmacological inhibitor caffeine was found to effectively inhibit the activation of the ATM-dependent pathways and to rescue the ST-induced G2 arrest in GES-1 cells, which indicating its ATM-dependent characteristic. Moreover, the silencing of the p53 expression with siRNA effectively attenuated the ST-induced G2 arrest in GES-1 cells. We also found that ST induces apoptosis in GES-1 cells. Thus, our results show that the ST-induced DNA damage activates the ATM/53-dependent signaling pathway, which contributes to the induction of G2 arrest in GES-1 cells.

The multiple stressor effect in zebrafish embryos from simultaneous exposure to ionising radiation and cadmium

Living organisms are exposed to a mixture of environmental stressors, and the resultant effects are referred to as multiple stressor effects. In the present work, we studied the multiple stressor effect in embryos of the zebrafish (Danio rerio) from simultaneous exposure to ionising radiation (alpha particles) and cadmium through quantification of apoptotic signals at 24 h postfertilisation (hpf) revealed by vital dye acridine orange staining. For each set of experiments, 32-40 dechorionated embryos were deployed, which were divided into four groups each having 8-10 embryos. The four groups of embryos were referred to as (1) the control group (C), which received no further treatments after dechorionation; (2) the Cd-dosed and irradiated group (CdIr), which was exposed to 100 μM Cd from 5 to 24 hpf, and also received about 4.4 mGy from alpha particles at 5 hpf; (3) the irradiated group (Ir), which received about 4.4 mGy from alpha particles at 5 hpf; and (4) the Cd-dosed group (Cd), which was exposed to 100 μM Cd from 5 to 24 hpf. In general, the CdIr, Ir and Cd groups had more apoptotic signals than the C group. Within the 12 sets of experimental results, two showed significant synergistic effects, one showed a weakly synergistic effect and nine showed additive effects. The multiple stressor effect of 100 μM Cd with ~4.4 mGy alpha-particle radiation resulted in an additive or synergistic effect, but no antagonistic effect. The failure to identify significant synergistic effects for some sets of data, and thus their subsequent classification as additive effects, might be a result of the relatively small magnitude of the synergistic effects. The results showed that the radiation risk could be perturbed by another environmental stressor such as a heavy metal, and as such a realistic human radiation risk assessment should in general take into account the multiple stressor effects.

Radioprotective properties of tocopherol succinate against ionizing radiation in mice

Threats of nuclear and other radiologic exposures have been increasing but no countermeasure for acute radiation syndrome has been approved by regulatory authorities. In prior publications we have demonstrated the efficacy of tocopherol succinate (TS) as a promising radiation countermeasure with the potential to protect against lethal doses of ionizing radiation exposure. The aim of this study was to gain further insight regarding how TS protects mice against a lethal dose of radiation. CD2F1 mice were injected subcutaneously with 400 mg/kg of TS, and 24 h later exposed to (60)Co γ-radiation. Intestinal tissues or spleen/thymus were harvested after irradiation and analyzed for CD68-positive inflammatory cells and apoptotic cells by immunostaining of jejunal cross-sections. Comet assay was used to analyze DNA damage in various tissues. Phospho-histone H3(pH3) and the proliferating cell nuclear antigen (PCNA) were used as mitotic markers for immunostaining jejunal cross-sections. We observed that injecting TS significantly decreased the number of CD68-positive cells, DNA damage and apoptotic cells (BAX, caspase 3 and cleaved poly(ADP-ribose) polymerase-positive cells) as judged by various apoptotic pathway markers. TS treatment also increased proliferating cells in irradiated mice. Results of this study further support our contention that TS protects mice against lethal doses of ionizing radiation by inhibiting radiation-induced apoptosis and DNA damage while enhancing cell proliferation.

Adaptive response to ionising radiation induced by cadmium in zebrafish embryos

An adaptive response is a biological response where the exposure of cells or animals to a low priming exposure induces mechanisms that protect the cells or animals against the detrimental effects of a subsequent larger challenging exposure. In realistic environmental situations, living organisms can be exposed to a mixture of stressors, and the resultant effects due to such exposures are referred to as multiple stressor effects. In the present work we demonstrated, via quantification of apoptosis in the embryos, that embryos of the zebrafish (Danio rerio) subjected to a priming exposure provided by one environmental stressor (cadmium in micromolar concentrations) could undergo an adaptive response against a subsequent challenging exposure provided by another environmental stressor (alpha particles). We concluded that zebrafish embryos treated with 1 to 10 μM Cd at 5 h postfertilisation (hpf) for both 1 and 5 h could undergo an adaptive response against subsequent ~4.4 mGy alpha-particle irradiation at 10 hpf, which could be interpreted as an antagonistic multiple stressor effect between Cd and ionising radiation. The zebrafish has become a popular vertebrate model for studying the in vivo response to ionising radiation. As such, our results suggested that multiple stressor effects should be carefully considered for human radiation risk assessment since the risk may be perturbed by another environmental stressor such as a heavy metal.

Effects of tubeimoside-1 on the proliferation and apoptosis of BGC823 gastric cancer cells in vitro

Natural products isolated from Chinese medicinal herbs are useful sources of new drugs for cancer therapy. Tubeimoside-1 (TBMS1) is a natural compound isolated from the Chinese medicinal herb Bolbostemma paniculatum (Maxim.) Franquet (Cucurbitaceae). Studies have shown that TBMS1 has anticancer effects in various human cancer cell lines. However, the effect of TBMS1 on human gastric cancer cells is unknown. In the present study, it was observed that TBMS1 inhibited BGC823 gastric cancer cell proliferation in a concentration- and time-dependent manner. Fluorescent microscopy and flow cytometric analysis showed that TBMS1 induced BGC823 cell apoptosis in a concentration-dependent manner. Western blot analysis also showed that TBMS1 induced apoptosis by regulation of the Bcl-2 gene family in BGC823 cells. These findings indicate that TBMS1 may be developed as a possible therapeutic agent for the management of gastric cancer.

The biological effects and possible modes of action of nanosilver

Novel physicochemical and biological properties have led to a versatile spectrum of applications for nanosized silver particles. Silver nanoparticles are applied primarily for their antimicrobial effects, and may variety of commercially available products have emerged. To better predict and prevent possible environmental impacts from silver nanoparticles that are derived from increasing production volumes and environmental release, more data on the biological effects are needed on appropriate model organisms. We examined the literature that addressed the adverse effects of silver nanoparticles on different levels of biological integration, including in vitro and in vivo test systems. Results of in vitro studies indicate a dose-dependent programmed cell death included by oxidative stress as main possible pathway of toxicity. Furthermore, silver nanoparticles may affect cellular enzymes by interference with free thiol groups and mimicry of endogenous ions. Similar mechanisms may apply for antibacterial effects produced by nonasilver. These effects are primary from the interference nanosilver has with bacterial cell membranes. Few in vivo studies have been performed to evaluated the toxic mode of action of nanosilver or to provide evidence for oxidative stress as an important mechanism of nanosilver toxicity. Organisms that are most acutely sensitive to nanosilver toxicity are the freshwater filter-freeding organisms. Both in vitro and in vivo studies have demonstrated tha silver ions released from nanoparticle surface contribute to the toxicity, and, indeed, some findings indicated a unique nanoparticles effect. For an adequate evaluation of the environmental impact of nanosilver, greater emphasis should be placed on combining mechanistic investigations that are performed in vitro, with results obtained in in vivo test systems. Future in vivo test system studies should emphasize long-term exposure scenarios. Moreover, the dietary uptake of silver nanoparticles and the potential to bioaccumulate through the food web should be examined in detail.

Mechanism of maprotiline-induced apoptosis: role of [Ca2+](i), ERK, JNK and caspase-3 signaling pathways

Antidepressants are generally used for treatment of various mood and anxiety disorders. Several studies have shown the anti-tumor and cytotoxic activities of some antidepressants, but the underlying mechanisms were unclear. Maprotiline is a tetracyclic antidepressant and possesses a highly selective norepinephrine reuptake ability. We found that maprotiline decreased cell viability in a concentration- and time-dependent manner in Neuro-2a cells. Maprotiline induced apoptosis and increased caspase-3 activation. The activation of caspase-3 by maprotiline appears to depend on the activation of JNK and the inactivation of ERK. Maprotiline also induced [Ca(2+)](i) increases which involved the mobilization of intracellular Ca(2+) stored in the endoplasmic reticulum. Pretreatment with BAPTA/AM, a Ca(2+) chelator, suppressed maprotiline-induced ERK phosphorylation, enhanced caspase-3 activation and increased maprotiline-induced apoptosis. In conclusion, maprotiline induced apoptosis in Neuro-2a cells through activation of JNK-associated caspase-3 pathways. Maprotiline also evoked an anti-apoptotic response that was both Ca(2+)- and ERK-dependent.

Alpha radiation exposure decreases apoptotic cells in zebrafish embryos subsequently exposed to the chemical stressor, Cd

The aim of this study was to demonstrate that zebrafish embryos subjected to a priming exposure provided by one environmental stressor (low-dose alpha particles) can induce an adaptive response against a subsequent challenging exposure provided by another environmental stressor (heavy metal Cd). The effect thus identified would be an antagonistic multiple stressor effect. The effects of alpha particle radiation and/or Cd on whole embryos were studied through quantification of apoptotic signals at 24 h post-fertilization (hpf). Embryos were stained with the vital dye acridine orange, followed by counting the stained cells. For each set of experiments, 30 dechorionated embryos were divided into three groups, each having ten embryos. The three groups of embryos were referred to as (A) the control group, which received no more further treatments after dechorionation, (B) Cd-treated group, which did not receive any priming exposure and would receive a challenging exposure at 10 hpf and (C) (alpha + Cd)-treated group, which would receive both priming and challenging exposures. We defined the normalized net number of apoptotic signals in the (alpha + Cd)-treated group as N (C) * = [(apoptotic signals for (alpha + Cd)-treated group - average apoptotic signals for the corresponding control group)/average apoptotic signals for the corresponding control group] and that in the Cd-treated group as N (B)* = [(apoptotic signals for Cd-treated group - average apoptotic signals for the corresponding control group)/ average apoptotic signals for the corresponding control group]. By using the non-parametric Mann-Whitney U statistic, we were able to show that N (C) * was significantly smaller than N (B) *(p = 0.006). These demonstrated an antagonistic multiple stressor effect between ionizing radiation and Cd through the induction of an adaptive response by the ionizing radiation against subsequent exposures to Cd.

Effects of heavy metals on mitogen-activated protein kinase pathways

The signaling pathways leading to cellular protection or cell death following exposure to heavy metals have not been fully clarified. Mitogen-activated protein kinases (MAPKs), i.e., extracellular signal-regulated protein kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 MAPK transmit extracellular signals into the nucleus, and have been shown to participate in a diverse array of cellular functions such as cell growth, differentiation and apoptosis. Treatment with cadmium, inorganic mercury or tributyltin can activate ERK, JNK and p38 MAPK, and induces the expression of c-fos and c-jun genes prior to the development of apoptosis. However, the members of the MAPK family appear to be differentially activated depending on the heavy metal and the cell type exposed. Consequently, various cellular responses may be caused by the distinct pattern of MAPKs activation. MAPKs may be one of the important cellular signal transduction pathways affected by various environmental pollutants, including heavy metals.

Effects of Spent Pot Liner on mitotic activity and nuclear DNA content in meristematic cells of Allium cepa

Industrial waste usually contains complex mixtures of mutagenic chemicals. Spent Pot Liner (SPL) is a complex solid waste from the aluminum industry, which is composed of organics, fluoride salts, inorganic cyanides, metals, and sodium. Due to the toxicity of these compounds, this study sought to use cytogenetics and flow cytometry to assess the effects of SPL on cell cycle parameters and DNA content in meristematic cells of Allium cepa. Three concentrations of leachates from SPL-soil mixtures were used for the study: 0, 10, and 25%. Roots were collected and analyzed after 4, 8, 12, 24, and 36 h of exposure to the above SPL leachates. The results showed an overall mitodepressive effect accompanied by an increased percentage of condensed nuclei and genomic instability as evidenced by the presence of cellular/chromosomal abnormalities. Terminal deoxynucleotidyl transferase dUTP nick end labeling revealed nuclei with fragmented DNA, a marker of programmed cell death. This study also addressed the question of reversibility of the effects of SPL and found that 36 h of exposure to 25% SPL seemed to be the point at which the effects on the induction of apoptosis became irreversible.

7,3',4'-Trihydroxyisoflavone modulates multidrug resistance transporters and induces apoptosis via production of reactive oxygen species

The development of multidrug resistance (MDR) to conventional chemoradiation therapy usually leads to failure in treating cervical cancer. This study aims to explore the effects and mechanisms of 7,3',4'-trihydroxyisoflavone (7,3',4'-THIF), one of the major metabolites of daidzein, on potentiating cytotoxicity of epirubicin (Epi), an anticancer drug in human cervical cancer HeLa cells. The cytotoxicity of Epi remarkably increased when it was combined with 7,3',4'-THIF. The cotreatment increased the reactive oxygen species (ROS) levels, including hydrogen peroxide and superoxide free radicals. 7,3',4'-THIF was shown to down-regulate the MDR1 promoter region composed of the elements of AP1, GC-box, and Y-box, as demonstrated by a luciferase assay. A negative regulation of hMDR1 gene with multiple transcription factors by this isoflavone may provide a novel molecular mechanism for MDR modulation. The mRNA expressions of MDR1, MDR-associated protein (MRP) 1, and MRP2 for the combined treatment were significantly lower than those of the Epi treatment. This result implies that MDR transporter-mediated Epi resistance is inhibited at various degrees by the addition of 7,3',4'-THIF. This isoflavone significantly enhanced intracellular Epi accumulation in HeLa cells. 7,3',4'-THIF and/or Epi triggered apoptosis through the upregulation of p53, Bax, and caspase-9. Apoptosis induction was also confirmed by the reduced mitochondrial membrane potential, increased sub-G1 and G2/M phases, nuclear DNA fragmentation, and chromatin condensation. Our findings demonstrate for the first time that 7,3',4'-THIF causes cell death in human cervical cancer cells through the ROS-dependent suppression of MDR transporters and p53-mediated activation of the intrinsic mitochondrial pathway of apoptosis. Thus, 7,3',4'-THIF has the potential to enhance the activity of a broad range of cancer chemotherapeutics in the MDR spectrum with the advantage of reducing adverse effects.