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1.
Histone post-translational modification heritably regulates gene expression involved in most cellular biological processes. Experimental studies suggest that alteration of histone modifications affects gene expression by changing chromatin structure, causing various cellular responses to environmental influences. Arsenic (As), a naturally occurring element and environmental pollutant, is an established human carcinogen. Recently, increasing evidence suggests that As-mediated epigenetic mechanisms may be involved in its toxicity and carcinogenicity, but how this occurs is still unclear. Here we present evidence that suggests As-induced global histone H4K16 acetylation (H4K16ac) partly due to the direct physical interaction between As and histone acetyltransferase (HAT) hMOF (human male absent on first) protein, leading to the loss of hMOF HAT activity. Our data show that decreased global H4K16ac and increased deacetyltransferase HDAC4 expression occurred in arsenic trioxide (As2O3)-exposed HeLa or HEK293T cells. However, depletion of HDAC4 did not affect global H4K16ac, and it could not raise H4K16ac in cells exposed to As2O3, suggesting that HDAC4 might not directly be involved in histone H4K16 de-acetylation. Using As-immobilized agarose, we confirmed that As binds directly to hMOF, and that this interaction was competitively inhibited by free As2O3. Also, the direct interaction of As and C2CH zinc finger peptide was verified by MAIDI-TOF mass and UV absorption. In an in vitro HAT assay, As2O3 directly inhibited hMOF activity. hMOF over-expression not only increased resistance to As and caused less toxicity, but also effectively reversed reduced H4K16ac caused by As exposure. These data suggest a theoretical basis for elucidating the mechanism of As toxicity.  相似文献   

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Despite considerable efficacy of arsenic trioxide (As2O3) in acute promyelocytic leukemia (APL) treatment, other non-APL leukemias, such as chronic myeloid leukemia (CML), are less sensitive to As2O3 treatment. However, the underlying mechanism is not well understood. Here we show that relative As2O3-resistant K562 cells have significantly lower ROS levels than As2O3-sensitive NB4 cells. We compared the expression of several antioxidant enzymes in these two cell lines and found that peroxiredoxin 1/2/6 and catalase are expressed at high levels in K562 cells. We further investigated the possible role of peroxirdoxin 1/2/6 and catalase in determining the cellular sensitivity to As2O3. Interestingly, knockdown of peroxiredoxin 1/2/6 did not increase the susceptibility of K562 cells to As2O3. On the contrary, knockdown of catalase markedly enhanced As2O3-induced apoptosis. In addition, we provide evidence that overexpression of BCR/ABL cannot increase the expression of PRDX 1/2/6 and catalase. The current study reveals that the functional role of antioxidant enzymes is cellular context and treatment agents dependent; targeting catalase may represent a novel strategy to improve the efficacy of As2O3 in CML treatment.  相似文献   

4.
The precise mechanisms by which nickel and arsenic compounds exert their carcinogenic properties are not completely understood. In recent years, alterations of epigenetic mechanisms have been implicated in the carcinogenesis of compounds of these two metals. In vitro exposure to certain nickel or arsenic compounds induces changes in both DNA methylation patterns, as well as, in the levels of posttranslational modifications of histone tails. Changes in DNA methylation patterns have been reported in human subjects exposed to arsenic. Here we review our recent reports on the alterations in global levels of posttranslational histone modifications in peripheral blood mononuclear cells (PBMCs) of subjects with occupational exposure to nickel and subjects exposed to arsenic in their drinking water. Occupational exposure to nickel was associated with an increase in H3K4me3 and decrease in H3K9me2. A global increase in H3K9me2 and decrease in H3K9ac was found in subjects exposed to arsenic. Additionally, exposure to arsenic resulted in opposite changes in a number of histone modifications in males when compared with females in the arsenic population. The results of these two studies suggest that exposure to nickel or arsenic compounds, and possibly other carcinogenic metal compounds, can induce changes in global levels of posttranslational histone modifications in peripheral blood mononuclear cells.  相似文献   

5.
In the current study, neuroprotective significance of ellagic acid (EA, a polyohenol) was explored by primarily studying its antioxidant and antiapoptotic potential against arsenic trioxide (As2O3)‐induced toxicity in SH‐SY5Y human neuroblastoma cell lines. The mitigatory effects of EA with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied. Pretreatment of SH‐SY5Y cells with EA (10 and 20 μM) for 60 min followed by exposure to 2 μM As2O3 protected the SH‐SY5Y cells against the harmful effects of the second. Also, EA pre‐treated groups expressed improved viability, repaired DNA, reduced free radical generation, and maintained altered mitochondrial membrane potential than those exposed to As2O3 alone. EA supplementation also inhibited As2O3‐induced cytochrome c expression that is an important hallmark for determining mitochondrial dynamics. Thus, the current investigations are more convinced for EA as a promising candidate in modulating As2O3‐induced mitochondria‐mediated neuronal toxicity under in vitro system.  相似文献   

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Though reactive oxygen species (ROS) has been noticed to be involved in arsenic trioxide (As2O3)-induced apoptosis of tumor cells, its role in apoptosis signaling remained to be elucidated. The objective of this work was to explore the association of the inherent cellular ROS level with the susceptibility of the tumor cells to apoptosis induction by As2O3. Low concentration of As2O3 was administered to cultured leukemic cell lines NB4, U937, HL60 and K562. The difference in apoptotic sensitivity was displayed among four cell types. ROS probes were incubated with the cells in the absence of As2O3, and ROS was thus quantified relatively by flow cytometry. We manifested, in four cell types, the inherently existed difference in whole ROS quantity, and a positive correlation between the inherent ROS level and their apoptotic sensitivity to As2O3. Furthermore, by interference using a ROS producer, we demonstrated that an elevation of ROS level would sensitize the cells to As2O3-induced apoptosis. The results of the present work suggested that the inherent ROS level might be determinative in tumor cells for their apoptotic susceptibility to As2O3.  相似文献   

9.
This study aimed to investigate the effects of arsenic trioxide (As2O3) on the mitochondrial DNA (mtDNA) of acute promyelocytic leukemia (APL) cells. The NB4 cell line was treated with 2.0 μmol/L As2O3 in vitro, and the primary APL cells were treated with 2.0 μmol/L As2O3 in vitro and 0.16 mg kg−1 d−1 As2O3 in vivo. The mitochondrial DNA of all the cells above was amplified by PCR, directly sequenced and analyzed by Sequence Navigatore and Factura software. The apoptosis rates were assayed by flow cytometry. Mitochondrial DNA mutation in the D-loop region was found in NB4 and APL cells before As2O3 use, but the mutation spots were remarkably increased after As2O3 treatment, which was positively correlated to the rates of cellular apoptosis, the correlation coefficient: r NB4-As2O3=0.973818, and r APL-As2O3=0.934703. The mutation types include transition, transversion, codon insertion or deletion, and the mutation spots in all samples were not constant and regular. It is revealed that As2O3 aggravates mtDNA mutation in the D-loop region of acute promyelocytic leukemia cells both in vitro and in vivo. Mitochondrial DNA might be one of the targets of As2O3 in APL treatment.  相似文献   

10.
Although arsenic is an infamous carcinogen, it has been effectively used to treat acute promyelocytic leukemia, and can induce cell cycle arrest or apoptosis in human solid tumors. Previously, we had demonstrated that opposing effects of ERK1/2 and JNK on p21 expression in response to arsenic trioxide (As2O3) are mediated through the Sp1 responsive elements of the p21 promoter in A431 cells. Presently, we demonstrate that Sp1, and c-Jun functionally cooperate to activate p21 promoter expression through Sp1 binding sites (−84/−64) by using DNA affinity binding, chromatin immunoprecipitation, and promoter assays. Surprisingly, As2O3-induced c-Jun(Ser63/73) phosphorylation can recruit TGIF/HDAC1 to the Sp1 binding sites and then suppress p21 promoter activation. We suggest that, after As2O3 treatment, the N-terminal domain of c-Jun phosphorylation by JNK recruits TGIF/HDAC1 to the Sp1 sites and then represses p21 expression. That is, TGIF is involved in As2O3-inhibited p21 expression, and then blocks the cell cycle arrest.  相似文献   

11.
Myoblast proliferation and differentiation are essential for skeletal muscle regeneration. Myoblast proliferation is a critical step in the growth and maintenance of skeletal muscle. The precise action of inorganic arsenic on myoblast growth has not been investigated. Here, we investigated the in vitro effect of inorganic arsenic trioxide (As2O3) on the growth of C2C12 myoblasts. As2O3 decreased myoblast growth at submicromolar concentrations (0.25–1 μM) after 72 h of treatment. Submicromolar concentrations of As2O3 did not induce the myoblast apoptosis. Low-concentration As2O3 (0.5 and 1 μM) significantly suppressed the myoblast cell proliferative activity, which was accompanied by a small proportion of bromodeoxyuridine (BrdU) incorporation and decreased proliferating cell nuclear antigen (PCNA) protein expression. As2O3 (0.5 and 1 μM) increased the intracellular arsenic content but did not affect the reactive oxygen species (ROS) levels in the myoblasts. Cell cycle analysis indicated that low-concentrations of As2O3 inhibited cell proliferation via cell cycle arrest in the G1 and G2/M phases. As2O3 also decreased the protein expressions of cyclin D1, cyclin E, cyclin B1, cyclin-dependent kinase (CDK) 2, and CDK4, but did not affect the protein expressions of p21 and p27. Furthermore, As2O3 inhibited the phosphorylation of Akt. Insulin-like growth factor-1 significantly reversed the inhibitory effect of As2O3 on Akt phosphorylation and cell proliferation in the myoblasts. These results suggest that submicromolar concentrations of As2O3 alter cell cycle progression and reduce myoblast proliferation, at least in part, through a ROS-independent Akt inhibition pathway.  相似文献   

12.
Two myelodysplastic syndrome (MDS) celllines, MUTZ-1 and SKM-1 cells, were used to study the effect of arsenic trioxide (As2O3) on hematological malignant cells. As2O3 induced this two cell lines apoptosis via activation of caspase-3/8 and cleavage of poly (ADP-ribose) polymerase (PARP), a DNA repair enzyme. As2O3 reduced NF-κB activity, which was important for inducing MUTZ-1 and SKM-1 cells apoptosis. As2O3 also inhibited the activities of hTERT in MUTZ-1 and SKM-1 cells. Moreover, the NF-κB inhibitor, pyrrolidine dithiocarbamate (PDTC), had no effect on caspase-8 activation, although PDTC did inhibit MUTZ-1 and SKM-1 cells proliferation. Incubation of MUTZ-1 cells with a caspase-8 inhibitor failed to block As2O3-induced inhibition of NF-κB activity. Our findings suggest that As2O3 may induce apoptosis in MUTZ-1 and SKM-1 cells by two independent pathways: first, by activation of caspase-3/8 and PARP; and second, by inhibition of NF-κB activity, which results in downregulation of hTERT expression. We conclude that hTERT and NF-κB are important molecular targets in As2O3-induced apoptosis.  相似文献   

13.
Although both arsenic trioxide (As2O3) and benzo(a)pyrene (BaP) are well-established human carcinogens, the interaction between As2O3 and BaP is synergistic or antagonistic remains controversial in terms of the existing studies. In addition, the mechanisms responsible for the combined effects are still unclear. In this study, we examined the potential interactive effects between As2O3 (1, 5, and 10 μM) and BaP (5, 10, and 20 μM) in cultured A549 cells by treating with BaP and As2O3 alone or in combination at various concentrations for 24 h. The single and combined effects of As2O3 and BaP on the cytotoxicity, DNA/chromosomal damage, and oxidative stress were examined by using tetrazolium (3-(4,5-dimethyithiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) dye colorimetric assay, colony formation assay, fluorescence probe, chemical colorimetry, comet assay as well as micronucleus test. Our results showed that As2O3 synergistically enhanced the cytotoxicity, genotoxicity, and level of oxidative stress induced by BaP at various tested concentrations. Also, our experimental results showed that intracellular glutathione (GSH) contents were increased by various doses of BaP, but single or cotreatment with As2O3 significantly decreased the GSH level in the cells at all tested concentrations. Taken together, our results suggest that As2O3 may exert its synergistic cyto- and genotoxic effects with BaP mainly via elevated intracellular reactive oxygen species and reduced GSH contents and superoxide dismutase activities, thus promoting high level of oxidative stress, which may be a pivotal mechanism underlying As2O3 cocarcinogenic action.  相似文献   

14.
We have recently shown that arsenic trioxide (As2O3) is a potent inducer of autophagic degradation of the BCR-ABL1 oncoprotein, which is the cause of chronic myeloid leukemia (CML) and Ph+ acute lymphoid leukemia (Ph+ ALL). Our recently published work has shown that pharmacological inhibition of autophagy or molecularly targeting of elements of the autophagic machinery partially reverses the suppressive effects of As2O3 on primitive leukemic precursors from CML patients. Altogether, our studies have provided direct evidence that arsenic-induced, autophagy-mediated, degradation of BCR-ABL1 is an important mechanism for the generation of the effects of As2O3 on BCR-ABL1 transformed leukemic progenitors. These studies raise the potential of future clinical-translational efforts employing combinations of arsenic trioxide with autophagy-modulating agents to promote elimination of early leukemic progenitors and, possibly, leukemia-initiating stem cells.  相似文献   

15.
Arsenic is a metalloid that generates various biological effects on cells and tissues. Depending on the specific tissue exposed and the time and degree of exposure, diverse responses can be observed. In humans, prolonged and/or high dose exposure to arsenic can have a variety of outcomes, including the development of malignancies, severe gastrointestinal toxicities, diabetes, cardiac arrhythmias, and death. On the other hand, one arsenic derivative, arsenic trioxide (As2O3), has important antitumor properties. This agent is a potent inducer of antileukemic responses, and it is now approved by the Food and Drug Administration for the treatment of acute promyelocytic leukemia in humans. The promise and therapeutic potential of arsenic and its various derivatives have been exploited for hundreds of years. Remarkably, research focused on the potential use of arsenic compounds in the treatment of human diseases remains highly promising, and it is an area of active investigation. An emerging approach of interest and therapeutic potential involves efforts to target and block cellular pathways activated in a negative feedback manner during treatment of cells with As2O3. Such an approach may ultimately provide the means to selectively enhance the suppressive effects of this agent on malignant cells and render normally resistant tumors sensitive to its antineoplastic properties.Arsenic forms complexes with other elements, and it exists in inorganic and organic forms (13). The three major inorganic forms of arsenic are arsenic trisulfide (As2S3, yellow arsenic), arsenic disulfide (As2S2, red arsenic), and arsenic trioxide (As2O3, white arsenic) (13). There are two different oxidative states of arsenic that correlate with its cytotoxic potential, As(III) and As(V). Among them, As(III) is the most potent form and primarily accounts for its pro-apoptotic and inhibitory effects on target cells and tissues (3). The various forms of arsenic exist in nature primarily in a complex with pyrite (4, 5), although under certain circumstances, arsenic can dissociate from soil and enter natural waters (6), providing a contamination source for humans or animals who ingest such waters. In fact, most associations between long term exposure to arsenic and development of malignancies or other health disorders result from drinking contaminated water, especially in developing countries. Interestingly, pollution of the air with arsenic can also occur under certain circumstances, such as in the case of emissions from coal burning in China (7), providing an additional source of human exposure.The metabolism of arsenic in humans includes reduction to the trivalent state and oxidative methylation to the pentavalent state (reviewed in Ref. 2). There is also reduction of arsenic acid to the arsenous form and subsequent methylation (2). The generation of inorganic or organic trivalent arsenic forms has important implications with regard to the toxicity of this agent, as such compounds are more toxic to the cells and exhibit more carcinogenic properties (2, 3). Thus, many of the consequences of exposure to arsenic as discussed below are the result of the activities and toxicities of the various metabolic products of arsenic compounds. It should be also noted that arsenic has the ability to bind to reduced thiols, including sulfhydryl groups in some proteins (2). Depending on the cellular context, such protein targeting may explain some of its cellular effects and generation of its toxicities and/or therapeutic effects.  相似文献   

16.
Given that arsenic trioxide (As2O3) has been successfully used as a chemotherapeutic agent for refractory malignant tumors, this study is aimed at investigating the effect of As2O3 on human Adriamycin resistant osteosarcoma cell line Saos-2. The mechanism underlying multi drug resistance (MDR) in osteosarcoma cells and the anti-tumor effect of As2O3 on Adriamycin resistant osteosarcoma cells were analyzed. In our experiment, we first selected Adriamycin resistant osteosarcoma cell line by growing the classic osteosarcoma cell line Saos-2 in the medium with increasing drug concentrations. Then, we compared the IC50s of the osteosarcoma cells treated with different anticancer drugs by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Subsequently, we assessed the expression of classic MDR related molecules, Pgp, multidrug resistance-associated protein (MRP) and glutathione (GSH) activity in the wild type and Adriamycin resistant Saos-2 cells. Furthermore, the apoptosis was assessed by concerning DNA fragment and flow cytometry with Annexin-V staining. To elucidate the underlying mechanism of the apoptosis, related proteins Bcl-2, Bcl-xL, Bax, Bak, cleaved Caspase-3 and cleaved Caspase-9 were analyzed by western blotting. The data showed that the resistance to Adriamycin affected the sensitivity of osteosarcoma cell to other chemotherapeutic agents. The IC50s of Saos-2/ADM cells for methotrexate (1.74-fold), Cisplatin (1.43-fold) and As2O3 (1.21-fold) were increased compared with Saos-2 control cells. The expression of Pgp was upregulated comparing with the control cells. No significant difference was detected about the MRP and the glutathione-S-transferase activity and intracellular GSH concentration among different treated osteosarcoma cells. Apoptosis was observed and proved. The western blotting showed that the expression of Bcl-2 and Bcl-xL was downregulated. Meanwhile, the level of Bax, Bak, cleaved Caspase-3 and cleaved Caspase-9 was upregulated after treated with As2O3. The study suggests that Adriamycin resistant osteosarcoma cells have good response to As2O3-based chemotherapy in vitro, probably via the pathway of inducing apoptosis. And As2O3 might serve as an excellent alternative candidate for adjuvant chemotherapeutic agent on this incurable pediatric sarcoma.  相似文献   

17.
Promyelocytic leukemia protein (PML) is a tumor suppressor acting as the organizer of subnuclear structures called PML nuclear bodies (NBs). Both covalent modification of PML by the small ubiquitin-like modifier (SUMO) and non-covalent binding of SUMO to the PML SUMO binding domain (SBD) are necessary for PML NB formation and maturation. PML sumoylation and proteasome-dependent degradation induced by the E3 ubiquitin ligase, RNF4, are enhanced by the acute promyelocytic leukemia therapeutic agent, arsenic trioxide (As2O3). Here, we established a novel bioluminescence resonance energy transfer (BRET) assay to dissect and monitor PML/SUMO interactions dynamically in living cells upon addition of therapeutic agents. Using this sensitive and quantitative SUMO BRET assay that distinguishes PML sumoylation from SBD-mediated PML/SUMO non-covalent interactions, we probed the respective roles of covalent and non-covalent PML/SUMO interactions in PML degradation and interaction with RNF4. We found that, although dispensable for As2O3-enhanced PML sumoylation and RNF4 interaction, PML SBD core sequence was required for As2O3- and RNF4-induced PML degradation. As confirmed with a phosphomimetic mutant, phosphorylation of a stretch of serine residues, contained within PML SBD was needed for PML interaction with SUMO-modified protein partners and thus for NB maturation. However, mutation of these serine residues did not impair As2O3- and RNF4-induced PML degradation, contrasting with the known role of these phosphoserine residues for casein kinase 2-promoted PML degradation. Altogether, these data suggest a model whereby sumoylation- and SBD-dependent PML oligomerization within NBs is sufficient for RNF4-mediated PML degradation and does not require the phosphorylation-dependent association of PML with other sumoylated partners.Promyelocytic leukemia protein (PML)5 is a tumor suppressor (1) whose gene is translocated in cases of acute promyelocytic leukemia (2). PML functions as the organizer of PML NBs, which are dynamic structures harboring numerous transiently and permanently localized proteins (3). The importance of PML NB structural integrity was first revealed in acute promyelocytic leukemia because, in this malignancy, the abnormal fusion protein PML/RARα leads to NB disruption. Patient treatment with As2O3 induces the reversion of the acute promyelocytic leukemia phenotype as well as PML/RARα degradation and PML NB reformation (4).PML is a target for the post-translational modification by SUMO, an ubiquitin-like protein that is covalently coupled to PML lysine residues 65, 160, and 490 via a process called sumoylation (5, 6). Among the four human SUMO paralogs identified, SUMO1, -2, and -3 were found to be conjugated to target proteins. It involves an enzymatic cascade for the transfer of the mature SUMO and the formation of an isopeptide bond between the COOH-terminal glycine of SUMO and a lysine from the target protein. Sumoylation is a reversible process due to the existence of several deconjugating enzymes.PML NB formation requires both the covalent linkage (sumoylation) (reviewed in Ref. 7) and the non-covalent interactions of SUMO with PML through a SUMO binding domain (SBD also named SIM for SUMO interacting motif) (8). Interestingly, PML SBD contains specific serines, acting as substrates for the caseine kinase-2 (CK2), which are implicated in PML ubiquitination and degradation (9) and which phosphorylation status could regulate the function of the SBD.Because sumoylation of proteins is dynamic and reversible, this post-translational modification is difficult to follow in vivo and its detection mainly relies on the identification of sumoylated protein species by Western blot following cell lysis. Recently, we used bioluminescence resonance energy transfer (BRET) to detect covalent linkage of ubiquitin (ubiquitination) in living mammalian cells and in real time (10). In brief, BRET monitors the interaction between a protein fused to a luciferase and a protein fused to yellow or green fluorescent protein (YFP or GFP), upon addition of a luciferase substrate; it is a proximity-based assay that requires that the donor of energy (luciferase fusion) and the acceptor (YFP or GFP fusions) are within 50 to 100 Å for an efficient energy transfer (1113). However, a demonstration that BRET may provide a method of choice to follow the dynamics of protein sumoylation in living cells is lacking. Here, we developed a sensitive and quantitative SUMO BRET assay for the detection of PML interactions with SUMO in living cells. We proved that BRET can be used to detect both SUMO covalent and non-covalent interactions with PML (model, Fig. 1H). For this purpose, we used the PMLIII isoform in which sumoylation is induced by As2O3 and triggers a proteasome-dependent PML degradation (14); the degradation process involves the ubiquitination of poly-SUMO covalently coupled to PML by the poly-SUMO-specific E3 ubiquitin ligase RNF4 (1517). Altogether, our BRET results indicate that, As2O3 and/or RNF4-induced PML degradation are dependent on the integrity of both PML sumoylation target sites and the PML SBD core sequence but not on the CK2 serine phosphorylation sites within the SBD. However, phosphorylation of these serines is required for most PML SBD-dependent non-covalent interactions. This phospho-regulation of PML SBD (“SBD phospho-switch”) establishes another link between the phosphorylation and SUMO, different from the phospho-sumoyl switch (18).Open in a separate windowFIGURE 1.BRET reveals both covalent and non-covalent PML/SUMO1 interactions as well as As2O3-induced PML sumoylation in living cells. A and B, detection of PML/SUMO1 interactions by BRET1 (A) or BRET2 (B) titration assays using HEK293T cells transfected for expression of increasing amounts of YFP-SUMO1 (BRET1) or GFP-SUMO1 (BRET2) and a fixed amount of Luc fusion. Negative controls: BRET pairs including PMLC57,60A-Luc (a non-sumoylatable mutant with Cys57 and Cys60 mutated to Ala) or YFP-SUMO1G (a SUMO1 that cannot be processed) (dotted line) (A) and Luc fused to a NLS (B). C and D, detection of covalent and non-covalent PML/SUMO1 interactions by BRET1 (C) or BRET2 (D) titration assays in the presence (dotted lines, empty symbols) or absence (solid lines and symbols) of As2O3 in HEK293T cells transfected for expression of PMLWT-Luc or its sumoylation deficient mutant PML3K-Luc in pairs with either YFP-SUMO1 (BRET1) or GFP-SUMO1 (BRET2). Negative control: PMLWT-Luc in pairs with YFP-SUMO1G. E, kinetics of As2O3-induced PMLWT-Luc sumoylation revealed by BRET1 (assay on attached cells) and BRET2 (cells in suspension). F, dose-response curve to As2O3 treatment for PMLWT-Luc or PML3KR-Luc/YFP-SUMO1 BRET1 pairs. Negative control: PMLC57,60A-Luc/YFP-SUMO1. G, comparison of As2O3-induced sumoylation of PMLWT, PML3KR, and its single lysine mutants at an identical YFP acceptor/Luc donor expression ratio as derived from titration curves. As2O3 treatment (C–G): 5 μm, 4 h exposure for BRET1 and Western blot or 10 μm, 70-min exposure for BRET2. H, model for the covalent (sumoylation) and non-covalent interactions between a tested protein fused to Luc and SUMO fused to a fluorescent protein (YFP) that generates a BRET signal. The black arrows indicate the bioluminescent transfer of energy (or BRET) that occurs between Luc and GFP fusion upon exposure to the cell-permeable luciferase substrate.  相似文献   

18.
Objectives: Arsenic trioxide (As2O3) is a potent drug for acute promyelocytic leukaemia, but its clinical trials are allied with some serious adverse events mainly cardiac functional abnormalities. So the objective of our investigation is to identify the cardioprotective action of flaxseed oil (FSO), a natural compound against As2O3 induced cardiotoxicity.

Methods: Male wistar rats were treated with As2O3 (4?mg/kg) to induce cardiotoxicity. FSO (250 and 500?mg/kg) was given in combination with As2O3 for evaluating its cardioprotective efficacy.

Results: Treatment with As2O3 resulted in deposition of arsenic in heart tissue, increased cardiac marker enzymes release, lipid peroxidation (LPO), oxidative insults and pathological damages in the heart. Co-treatment with FSO (500?mg/kg) significantly reduced the arsenic accumulation, cardiac marker enzymes, LPO and cardiac structural alterations. FSO treatment significantly improved cardiac glutathione content, antioxidant enzymes and reduced the pathological damages in cardiac tissue. Gas chromatographic–mass spectrometry analysis revealed that the major fatty acid content in the FSO is alpha-linolenic acid, which has a strong milieu in cardiac health.

Conclusion: The results of the current investigation suggested that FSO is an effective agent in reducing arsenic-induced cardiac toxicity and can be used as an adjunct/dietary supplement for the cancer patients on As2O3 therapy.  相似文献   

19.
Summary While arsenic trioxide (As2O3) is an infamous carcinogen, it is also an effective chemotherapeutic agent for acute promyelocytic leukemia and some solid tumors. In human epidermoid carcinoma A431 cells, we found that As2O3 induced cell death in time- and dose-dependent manners. Similarly, dependent regulation of the p21 WAF1/CIP1 (p21) promoter, mRNA synthesis, and resultant protein expression was also observed. Additionally, transfection of a small interfering RNA of p21 could block the As2O3-induced cell growth arrest. The As2O3-induced p21 activation was attenuated by inhibitors of EGFR and MEK in a dose-dependent manner. Using a reporter assay, we demonstrated the involvement of the EGFR-Ras-Raf-ERK1/2 pathway in the promoter activation. In contrast, JNK inhibitor enhanced the As2O3-induced p21 activation, also in a dose-dependent fashion. Over-expression of a dominant negative JNK plasmid likewise also enhanced this activation. Furthermore, MEK inhibitor attenuated the anti-tumor effect of As2O3. In contrast, in combination with JNK inhibitor and As2O3 enhanced cellular cytotoxicity. Therefore, we conclude that in A431 cells the ERK1/2 and JNK pathways might differentially contribute to As2O3-induced p21 expression and then due to cellular cytotoxicity.  相似文献   

20.
This study attempted to investigate if the tolerance of soil bacterial communities in general, and autotrophic ammonia-oxidizing bacteria (AOB) in particular, evolved as a result of prolonged exposure to metals, and could be used as an indigenous bioindicator for soil metal pollution. A soil contaminated with copper, chromium, and arsenic (CCA) was mixed with an uncontaminated garden soil (GS3) to make five test soils with different metal concentrations. A modified potential ammonium oxidation assay was used to determine the metal tolerance of the AOB community. Tolerance to Cr, Cu, and As was tested at the beginning and after up to 13 months of incubation. Compared with the reference GS3 soil, the five CCA soils showed significantly higher tolerance to Cr no matter which form of Cr (Cr3+, CrO4 2?, or Cr2O7 2?) was tested, and the Cr tolerance correlated with the total soil Cr concentration. However, the tolerance to Cu2+, As3+, and As5+ did not differ significantly between the GS3 soil and the five CCA soils. Community level physiological profiles using Biolog microtiter plates were also used to examine the chromate tolerance of the bacterial communities extracted after six months of exposure. Our results showed that the bacterial community tolerance was altered and increased as the soil Cr concentration was increased, indicating that the culturable microbial community and the AOB community responded in a similar manner.  相似文献   

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