Cytochrome c release and caspase activation in hydrogen peroxide- and tributyltin-induced apoptosis

Tributyltin induces apoptosis in mammalian cells in vivo: a scoping review

The present review aimed to evaluate the apoptotic effect of tributyltin (TBT) exposure on mammalian tissues and cells in vivo. A search was conducted in specialized literature databases including Embase, Medline, Pubmed, Scholar Google, and Scopus for all manuscripts using the following keywords: "tributyltin", "apoptosis", "mammals", "mammalian cells', "eukaryotic cells", 'rodents', "rats", "mice" and "in vivo" for all data published until September 2023. A total of 16 studies were included. The studies have demonstrated that TBT exposure induces apoptosis in cells from various mammalian organs or tissues in vivo. TBT is capable to increase apoptotic cells, to activate proapoptotic proteins such as calpain, caspases, bax and beclin-1 and to inhibit antiapoptotic protein bcl-2. Additionally, TBT alters the ratio of bcl-2/bax which favor apoptosis. Therefore, the activation of enzymes such as calpain induces apoptosis mediated by ERS and caspases through the intrinsic apoptosis pathway. This review has demonstrated that TBT exposure induces apoptosis in mammalian tissues and cells in vivo.

A Mycobacterium tuberculosis Effector Targets Mitochondrion, Controls Energy Metabolism, and Limits Cytochrome c Exit

Host metabolism reprogramming is a key feature of Mycobacterium tuberculosis (Mtb) infection that enables the survival of this pathogen within phagocytic cells and modulates the immune response facilitating the spread of the tuberculosis disease. Here, we demonstrate that a previously uncharacterized secreted protein from Mtb, Rv1813c, manipulates the host metabolism by targeting mitochondria. When expressed in eukaryotic cells, the protein is delivered to the mitochondrial intermembrane space and promotes the enhancement of host ATP production by boosting the oxidative phosphorylation metabolic pathway. Furthermore, the release of cytochrome c from mitochondria, an early apoptotic event in response to short-term oxidative stress, is delayed in Rv1813c-expressing cells. This study reveals a novel class of mitochondria targeting effectors from Mtb that might participate in host cell metabolic reprogramming and apoptosis control during Mtb infections. IMPORTANCE In this article, using a combination of techniques (bioinformatics, structural biology, and cell biology), we identified and characterized a new class of effectors present only in intracellular mycobacteria. These proteins specifically target host cell mitochondria when ectopically expressed in cells. We showed that one member of this family (Rv1813c) affects mitochondria metabolism in a way that might twist the immune response. This effector also inhibits the cytochrome c exit from mitochondria, suggesting that it might alter normal host cell apoptotic capacities, one of the first defenses of immune cells against Mtb infection.

Sex differences in antioxidant defence and the regulation of redox homeostasis in physiology and pathology

Reactive oxygen species (ROS) is a term that defines a group of unstable compounds derived from exogenous sources or endogenous metabolism. Under physiological conditions, low levels of ROS play a key role in the regulation of signal transduction- or transcription-mediated cellular responses. In contrast, excessive and uncontrolled loading of ROS results in a pathological state known as oxidative stress (OS), a leading contributor to aging and a pivotal factor for the onset and progression of many disorders. Evolution has endowed cells with an antioxidant system involved in stabilizing ROS levels to a specific threshold, preserving ROS-induced signalling function and limiting negative side effects. In mammals, a great deal of evidence indicates that females defence against ROS is more proficient than males, determining a longer lifespan and lower incidence of most chronic diseases. In this review, we will summarize the most recent sex-related differences in the regulation of redox homeostasis. We will highlight the peculiar aspects of the antioxidant defence in sex-biased diseases whose onset or progression is driven by OS, and we will discuss the molecular, genetic, and evolutionary determinants of female proficiency to cope with ROS.

Cyclic Imine Pinnatoxin G is Cytotoxic to Cancer Cell Lines via Nicotinic Acetylcholine Receptor-Driven Classical Apoptosis

Pinnatoxin G is a cyclic imine neurotoxin produced by dinoflagellates that has been reported in shellfish. Like other members of the pinnatoxin family, it has been shown to have its effects via antagonism of the nicotinic acetylcholine receptors, with preferential binding to the α7 subunit often upregulated in cancer. Because increased activity of α7 nicotinic acetylcholine receptors contributes to increased growth and resistance to apoptosis, the effect of pinnatoxin G on cancer cell viability was tested. In a panel of six cancer cell lines, all cell types lost viability, but HT29 colon cancer and LN18 and U373 glioma cell lines were more sensitive than MDA-MB-231 breast cancer cells, PC3 prostate cancer cells, and U87 glioma cells, correlating with expression levels of α7, α4, and α9 nicotinic acetylcholine receptors. Some loss of cell viability could be attributed to cell cycle arrest, but significant levels of classical apoptosis were found, characterized by caspase activity, phosphatidylserine exposure, mitochondrial membrane permeability, and fragmented DNA. Intracellular Ca²⁺ levels also dropped immediately upon pinnatoxin G treatment, which may relate to antagonism of nicotinic acetylcholine receptor-mediated Ca²⁺ inflow. In conclusion, pinnatoxin G can decrease cancer cell viability, with both cytostatic and cytotoxic effects.

Cytotoxic Mechanism of Sphaerodactylomelol, an Uncommon Bromoditerpene Isolated from Sphaerococcus coronopifolius

Marine natural products have exhibited uncommon chemical structures with relevant antitumor properties highlighting their potential to inspire the development of new anticancer agents. The goal of this work was to study the antitumor activities of the brominated diterpene sphaerodactylomelol, a rare example of the dactylomelane family. Cytotoxicity (10-100 µM; 24 h) was evaluated on tumor cells (A549, CACO-2, HCT-15, MCF-7, NCI-H226, PC-3, SH-SY5Y, SK-ML-28) and the effects estimated by MTT assay. Hydrogen peroxide (H₂O₂) levels and apoptosis biomarkers (membrane translocation of phosphatidylserine, depolarization of mitochondrial membrane potential, Caspase-9 activity, and DNA condensation and/or fragmentation) were studied in the breast adenocarcinoma cellular model (MCF-7) and its genotoxicity on mouse fibroblasts (L929). Sphaerodactylomelol displayed an IC₅₀ range between 33.04 and 89.41 µM without selective activity for a specific tumor tissue. The cells' viability decrease was accompanied by an increase on H₂O₂ production, a depolarization of mitochondrial membrane potential and an increase of Caspase-9 activity and DNA fragmentation. However, the DNA damage studies in L929 non-malignant cell line suggested that this compound is not genotoxic for normal fibroblasts. Overall, the results suggest that the cytotoxicity of sphaerodactylomelol seems to be mediated by an increase of H₂O₂ levels and downstream apoptosis.

Hydroxy-α-sanshool Possesses Protective Potentials on H2O2-Stimulated PC12 Cells by Suppression of Oxidative Stress-Induced Apoptosis through Regulation of PI3K/Akt Signal Pathway

Zanthoxylum bungeanum pericarp is a commonly used herbal medicine in China with effects of anti-inflammatory and analgesic, improving learning and memory ability, while hydroxy-α-sanshool (HAS) is the most important active ingredient of Z. bungeanum pericarps. The purpose of this study was to investigate the neuroprotective effect of HAS and its related possible mechanisms using a H₂O₂-stimulated PC12 cell model. CCK-8 assay results showed that HAS had a significant protective effect on H₂O₂-stimulated PC12 cells without obvious cytotoxicity on normal PC12 cells. Flow cytometry and fluorescence microscope (DAPI staining and DCFH-DA staining) indicated that HAS could reduce the H₂O₂-induced apoptosis in PC12 cells via reduction of intracellular ROS and increase of mitochondrial membrane potential (MMP). Subsequently, results of malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) determination suggested that HAS could increase the enzyme activities of SOD, CAT, and GSH-Px whereas it could decrease the MDA contents in H₂O₂-stimulated PC12 cells. Furthermore, the western blotting assays showed that HAS could upregulate the expressions of p-PI3k, Akt, p-Akt, and Bcl-2, while it could downregulate the expressions of cleaved caspase-3 and Bax in H₂O₂-stimulated PC12 cells. Collectively, it could be concluded according to our results that HAS possesses protective potentials on H₂O₂-stimulated PC12 cells through suppression of oxidative stress-induced apoptosis via regulation of PI3K/Akt signal pathway.

Cytotoxic and Antitumor Activity of Lactaptin in Combination with Autophagy Inducers and Inhibitors

Autophagy is a degradative process in which cellular organelles and proteins are recycled to restore homeostasis and cellular metabolism. Autophagy can be either a prosurvival or a prodeath process and remains one of the most fundamental processes for cell vitality. Thus autophagy modulation is an important approach for reinforcement anticancer therapeutics. Earlier we have demonstrated that recombinant analog of human milk protein lactaptin (RL2) induced apoptosis of various cultured cancer cells and activated lipidation of microtubule-associated protein 1 light chain 3 (LC3). In this study we investigated whether autophagy inhibitors-chloroquine (CQ), Ku55933 (Ku), and 3-methyladenine (3MA)-or inducer-rapamycin (Rap)-can enhance cytotoxic activity of lactaptin analog in cancer cells and its anticancer activity in the mice model. Western Blot analysis revealed that RL2 induced short-term autophagy in MDA-MB-231 and MCF-7 cells at early stages of incubation and that these data were confirmed by the transmission electron microscopy of autophagosome/autophagolysosome formation. RL2 stimulates reactive oxygen species (ROS) production, autophagosomes accumulation, upregulation of ATG5 with processing of LC3I to LC3II, and downregulation of p62/sequestosome 1 (p62). We have shown that autophagy modulators, CQ, Ku, and Rap, synergistically increased cytotoxicity of RL2, and RL2 with CQ induced autophagic cell death. In addition, CQ, Ku, and Rap in combination with RL2 decreased activity of lysosomal protease Cathepsin D. More importantly, combining RL2 with CQ, we improved antitumor effect in mice. Detected synergistic cytotoxic effects of both types of autophagy regulators, inhibitors, and inducers with RL2 against cancer cells allow us to believe that these combinations can be a basis for the new anticancer approach. Finally, we suppose that CQ and Rap promoting of short-term RL2-induced autophagy interlinks with final autophagic cell death.

RIP1 and RIP3 contribute to Tributyltin-induced toxicity in vitro and in vivo

Tributyltin (TBT), a widely distributed environmental pollutant, is toxic to animals and human beings. Although its toxicity, especially the immunosuppressive effect, has been reported a lot, the underlying molecular mechanisms are still unclear. In this study, we investigated the mechanisms of TBT-induced cytotoxicity both in vitro and in vivo. TBT induced cell death in both J774A.1 macrophages and mouse bone marrow-derived macrophages (BMDMs) as measured by the LDH and Annexin V-FITC/PI dual staining assays. Pretreatment with RIP1 inhibitor Necrostatin-1 (Nec-1) or transfection with Rip1 siRNA significantly suppressed TBT-induced cytotoxicity in J774A.1 macrophages or human embryonic kidney cell line (HEK293 cells). TBT-induced cell death was also markedly inhibited in RIP3^-/- BMDMs. In agreement with in vitro results, TBT-induced in vivo immunotoxic effects including leukocyte depletion and thymus atrophy were significantly attenuated in RIP3^-/- mice or WT mice treated with Nec-1. Notably, the mortality rate induced by TBT was remarkably reduced in RIP3^-/- mice (100% vs. 12.5% lethality) or Nec-1-treated mice (100% vs. 59.2% lethality) respectively. These results reveal a critical role of RIP1 and RIP3 in TBT-induced toxicity both in vitro and in vivo.

Neuronal, astroglial and locomotor injuries in subchronic copper intoxicated rats are repaired by curcumin: A possible link with Parkinson's disease

We aim herein to assess the neurotoxic effects of subchronic Cu-exposition (0125%) for 6 weeks on dopaminergic and astroglial systems then locomotor activity in rats as well as the probable therapeutic efficiency of curcumin-I (30 mg/kg B.W.). We found that intoxicated rats showed a significant impairment of Tyrosine Hydroxylase (TH) within substantia nigra pars compacta (SNc), ventral tegmental area (VTA) and the striatal outputs together with loss expression of GFAP in these structures. This was linked with an evident decrease in locomotor performance. Co-treatment with curcumin-I inverted these damages and exhibited a significant neuroprotective potential, thus, both TH expression and locomotor performance was reinstated in intoxicated rats. These results prove a profound dopaminergic and astroglial damages following subchronic Cu exposition and new beneficial curative potential of curcumin against subchronic Cu-induced astroglial and dopaminergic neurotoxicity. Consequently, we suggest that Cu neurotoxicity may be strengthened in vivo firstly by attacking and weaking the astroglial system, and curcumin could be prized as a powerful and preventive target for the neurodegenerative diseases related metal element, especially Parkinson's disease.

Olfactomedin 4 contributes to hydrogen peroxide-induced NADPH oxidase activation and apoptosis in mouse neutrophils

Neutrophils increase production of reactive oxygen species, including superoxide, hydrogen peroxide (H₂O₂), and hydroxyl radical, to destroy invading microorganisms under pathological conditions. Conversely, oxidative stress conditions, such as the presence of H₂O₂, induce neutrophil apoptosis, which helps to remove neutrophils after inflammation. However, the detailed molecular mechanisms that are involved in the latter process have not been elucidated. In this study, we investigated the potential role of olfactomedin 4 (Olfm4) in H₂O₂-induced superoxide production and apoptosis in mouse neutrophils. We have demonstrated that Olfm4 is not required for maximal-dosage PMA- and Escherichia coli bacteria-induced superoxide production, but Olfm4 contributes to suboptimal-dosage PMA- and H₂O₂-induced superoxide production. Using an NADPH oxidase inhibitor and gp91phox-deficient mouse neutrophils, we found that NAPDH oxidase was required for PMA-stimulated superoxide production and that Olfm4 mediated H₂O₂-induced superoxide production through NADPH oxidase, in mouse neutrophils. We have shown that neutrophils from Olfm4-deficient mice exhibited reduced H₂O₂-induced apoptosis compared with neutrophils from wild-type mice. We also demonstrated that neutrophils from Olfm4-deficient mice exhibited reduced H₂O₂-stimulated mitochondrial damage and membrane permeability, and as well as reduced caspase-3 and caspase-9 activity, compared with neutrophils from wild-type mice. Moreover, the cytoplasmic translocation of the proapoptotic mitochondrial proteins Omi/HtrA2 and Smac/DIABLO in response to H₂O₂ was reduced in neutrophils from Olfm4-deficient mice compared with neutrophils from wild-type mice. Our study demonstrates that Olfm4 contributes to H₂O₂-induced NADPH oxidase activation and apoptosis in mouse neutrophils. Olfactomedin 4 might prove to be a potential target for future studies on inflammatory neutrophil biology and for inflammatory disease treatment.

Oxidative stress-induced chromosome breaks within the ABL gene: a model for chromosome rearrangement in nasopharyngeal carcinoma

Background

The mechanism underlying chromosome rearrangement in nasopharyngeal carcinoma (NPC) remains elusive. It is known that most of the aetiological factors of NPC trigger oxidative stress. Oxidative stress is a potent apoptotic inducer. During apoptosis, chromatin cleavage and DNA fragmentation occur. However, cells may undergo DNA repair and survive apoptosis. Non-homologous end joining (NHEJ) pathway has been known as the primary DNA repair system in human cells. The NHEJ process may repair DNA ends without any homology, although region of microhomology (a few nucleotides) is usually utilised by this DNA repair system. Cells that evade apoptosis via erroneous DNA repair may carry chromosomal aberration. Apoptotic nuclease was found to be associated with nuclear matrix during apoptosis. Matrix association region/scaffold attachment region (MAR/SAR) is the binding site of the chromosomal DNA loop structure to the nuclear matrix. When apoptotic nuclease is associated with nuclear matrix during apoptosis, it potentially cleaves at MAR/SAR. Cells that survive apoptosis via compromised DNA repair may carry chromosome rearrangement contributing to NPC tumourigenesis. The Abelson murine leukaemia (ABL) gene at 9q34 was targeted in this study as 9q34 is a common region of loss in NPC. This study aimed to identify the chromosome breakages and/or rearrangements in the ABL gene in cells undergoing oxidative stress-induced apoptosis.

Results

In the present study, in silico prediction of MAR/SAR was performed in the ABL gene. More than 80% of the predicted MAR/SAR sites are closely associated with previously reported patient breakpoint cluster regions (BCR). By using inverse polymerase chain reaction (IPCR), we demonstrated that hydrogen peroxide (H₂O₂)-induced apoptosis in normal nasopharyngeal epithelial and NPC cells led to chromosomal breakages within the ABL BCR that contains a MAR/SAR. Intriguingly, we detected two translocations in H₂O₂-treated cells. Region of microhomology was found at the translocation junctions. This observation is consistent with the operation of microhomology-mediated NHEJ.

Conclusions

Our findings suggested that oxidative stress-induced apoptosis may participate in chromosome rearrangements of NPC. A revised model for oxidative stress-induced apoptosis mediating chromosome rearrangement in NPC is proposed.

Electronic supplementary material

The online version of this article (10.1186/s40246-018-0160-8) contains supplementary material, which is available to authorized users.

The aminopeptidase inhibitor, z-L-CMK, is toxic and induces cell death in Jurkat T cells through oxidative stress

The leucine aminopeptidase inhibitor, benzyloxycarbonyl-leucine-chloromethylketone (z-L-CMK), was found to be toxic and readily induce cell death in Jurkat T cells. Dose-response studies show that lower concentration of z-L-CMK induced apoptosis in Jurkat T cells whereas higher concentration causes necrosis. In z-L-CMK-induced apoptosis, both the initiator caspases (-8 and -9) and effector caspases (-3 and -6) were processed to their respective subunits. However, the caspases remained intact in z-L-CMK-induced necrosis. The caspase inhibitor, z-VAD-FMK inhibited z-L-CMK-mediated apoptosis and caspase processing but has no effect on z-L-CMK-induced necrosis in Jurkat T cells. The high mobility group protein B1 (HMGB1) protein was found to be released into the culture medium by the necrotic cells and not the apoptotic cells. These results indicate that the necrotic cell death mediated by z-L-CMK at high concentrations is via classical necrosis rather than secondary necrosis. We also demonstrated that cell death mediated by z-L-CMK was associated with oxidative stress via the depletion of intracellular glutathione (GSH) and increase in reactive oxygen species (ROS), which was blocked by N-acetyl cysteine. Taken together, the results demonstrated that z-L-CMK is toxic to Jurkat T cells and induces apoptosis at low concentrations, while at higher concentrations the cells die of necrosis. The toxic side effects in Jurkat T cells mediated by z-L-CMK are associated with oxidative stress via the depletion of GSH and accumulation of ROS.

Epigallocatechin-3-gallate inhibits H2O2-induced apoptosis in Mouse Vascular Smooth Muscle Cells via 67kD Laminin Receptor

Epigallocatechin-3-gallate (EGCG) is one of the major polyphenolic compounds present in green tea extracts and has been used as a potential drug for the treatment of numerous diseases. The present study aimed to elucidate the role and mechanism of EGCG in protecting against H₂O₂-induced apoptosis in mouse vascular smooth muscle cells (VSMCs). VSMCs were pretreated with various concentrations of EGCG for 2 hours prior to treatment with H₂O₂. Treatment with H₂O₂ significantly decreased the cell viability and induced apoptosis of VSMCs, which were attenuated by pretreatment with EGCG. In particular, EGCG pretreatment significantly inhibited the H₂O₂-induced upregulation of cleaved forms of caspase-3, caspase-8, and caspase-9, Bax, CathepsinD, and downregulation of Bcl-2. Moreover, the antioxidation effect of EGCG on VSMCs was determined to be associated with the 67kD laminin receptor (67LR). Our results demonstrated that EGCG improved cell viability and protected VSMCs against oxidative stress through both extrinsic and intrinsic pathways, while 67LR is likely to be an active and key receptor of EGCG. These findings provide a novel molecular mechanism of EGCG in inhibiting H₂O₂-induced apoptosis in VSMCs, as well as its function in preventing the development of atherosclerosis.

Neuroprotective potential of Aloe arborescens against copper induced neurobehavioral features of Parkinson's disease in rat

Copper (Cu) is an important trace element for the organism survival, which ensures the normal functioning of different biosystems. However, excessive levels of this heavy metal are responsible for profound physiological alterations including the central nervous system. Numerous findings sustain the involvement of heavy metals, as an environmental risk factor such as copper (Cu), in the neuropathology of Parkinson's disease (PD) which is a chronic neurodegenerative disorder that principally affects the motor system. The classic and evident symptoms of PD namely rigidity, tardiness of movement, and difficulty with walking, result from progressive dopaminergic neurons death within substantia nigra. Whereas, few pharmacological trials have shown a beneficial role against Cu neurotoxicity, Aloe arborescens is one of the powerful medicinal plants with an array of therapeutic effects. Thus, we aimed through the present study, to evaluate the impact of acute Cu intoxication (10μg/g B.W. i.p) for 3days on the dopaminergic system and locomotor performance, together with the possible restorative effect of oral administration of aqueous extract of Aloe arborescens gel (AEAAG) (200mg/kg B.W.). By means of immunohistochemistry, we noted, in the Cu intoxicated rats, a significant loss of TH (tyrosine hydroxylase) expression within substantia nigra compacta (SNc), ventral tegmental area (VTA) and the subsequent striatal outputs, those alterations were correlated to behavioral abnormalities such as a severe drop of locomotor performance. While AEAAG administration to Cu intoxicated rats showed a noticeable beneficial effect; this potential was featured by a complete recovery of the TH expression and locomotor behavior deficiencies in the intoxicated rats. The present investigation have brought, on the one hand, an experimental evidence of an altered dopaminergic innervations following Cu intoxication and on the other hand, a new pharmacological property of Aloe arborescens that may be used as a neuroprotective plant for neurodegenerative disorders, such as PD, touching the dopaminergic system trigged by heavy metals.

The UCP2-related mitochondrial pathway participates in rhein-induced apoptosis in HK-2 cells

Rhein is one of the main active compounds in total rhubarb anthraquinones (TRAs) that were reported to cause nephrotoxicity. This paper explored the mechanism of how rhein induced apoptosis in human renal proximal tubular epithelial cells (HK-2 cells). In this study, rhein was found to induce apoptosis in HK-2 cells according to the results of annexin V/PI staining assay. The underlying mechanisms were investigated, and the mitochondria-mediated pathway was found to be critical. A series of related biological events were explored, including the disruption of mitochondrial membrane potential (MMP), the decrease of the ATP level, the release of cytochrome c (Cyt-c) from the mitochondrion to the cytosol, and down-regulation of Bcl-2 and up-regulation of Bax. Furthermore, rhein significantly increased the levels of ROS and inhibited the expression of mitochondrial uncoupling protein 2 (UCP2). UCP2 inhibition dramatically boosted oxidative stress and exacerbated rhein-induced apoptosis, whereas co-incubation with an ROS scavenger N-acetylcysteine (NAC) could decrease rhein-induced apoptosis. In conclusion, our results have demonstrated that rhein induced apoptosis in HK-2 cells via the UCP2-related mitochondrial pathway and rhein might be a weak inhibitor of UCP2. Our findings provide new evidence that UCP2 plays an important role in the mitochondrial apoptotic pathway.

Lipidomic profile of GM95 cell death induced by Clostridium perfringens alpha-toxin

Clostridium perfringens alpha-toxin (ATX) is considered as a prototype of cytotoxic bacterial phospholipases C, and is the major virulence factor in C. perfringens-induced gas gangrene. It is known that, depending on the dose, ATX causes membrane disruption and cytolysis or only limited hydrolysis of its substrates. In the latter case, toxin activity leads to the unregulated generation of bioactive lipids that can ultimately induce cell death. We have characterized apoptosis and necrosis in highly ATX-sensitive, ganglioside-deficient cells exposed to different concentrations of ATX and we have studied the lipidomic profile of cells treated with ATX as compared to native cells to detect the main changes in the lipidomic profile and the possible involvement of lipid signals in cell death. ATX causes both apoptosis and necrosis, depending on dose and time. ATX activates cell death, stimulating the release of cytochrome C from mitochondria and the consequent activation of caspases-3. Moreover GM95 cells treated with ATX showed important lipidomic alterations, among them we detected a general decrease in several phospholipid species and important changes in lipids involved in programmed cell death e.g. ceramide. The data suggest two different mechanisms of cell death caused by ATX, one leading to (mainly saturated) glycerophospholipid hydrolysis related to an increase in diacylglycerols and associated to membrane damage and necrosis, and a second mechanism involving chiefly sphingomyelin hydrolysis and generation of proapoptotic lipidic mediators such as ceramide, N-acylethanolamine and saturated non-esterified fatty acids.

Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma

Background

Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease caspase-activated deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC.

Results

In the present study, we showed that hydrogen peroxide (H₂O₂) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of caspases 3/7 was detected in H₂O₂-treated cells. This activity was inhibited by caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H₂O₂-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H₂O₂-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia (MLL) gene in acute lymphoblastic leukemia (ALL) patient.

Conclusions

In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.

LYG-202 exerts antitumor effect on PI3K/Akt signaling pathway in human breast cancer cells

In this study, we aimed to investigate the antitumor effect of LYG-202, a newly synthesized piperazine-substituted derivative of flavonoid on human breast cancer cells and illustrate the potential mechanisms. LYG-202 induced apoptosis in MCF-7, MDA-MB-231 and MDA-MB-435 cells. LYG-202 triggered the activation of mitochondrial apoptotic pathway through multiple steps: increasing Bax/Bcl-2 ratio, decreasing mitochondrial membrane potential (ΔΨ(m)), activating caspase-9 and caspase-3, inducing cleavage of poly(ADP-ribose) polymerase, cytochrome c release and apoptosis-inducing factor translocation. Furthermore, LYG-202 inhibited cell cycle progression at the G1/S transition via targeting Cyclin D, CDK4 and p21(Waf1/Cip1). Additionally, LYG-202 increased the generation of intracellular ROS. N-Acetyl cysteine, an antioxidant, reversed LYG-202-induced apoptosis suggesting that LYG-202 induces apoptosis by accelerating ROS generation. Further, we found that LYG-202 deactivated the PI3K/Akt pathway, activated Bad phosphorylation, increased Cyclin D and Bcl-xL expression, and inhibited NF-κB nuclear translocation. Activation of PI3K/Akt pathway by IGF-1 attenuated LYG-202-induced apoptosis and cell cycle arrest. Our in vivo study showed that LYG-202 exhibited a potential antitumor effect in nude mice inoculated with MCF-7 tumor through similar mechanisms identified in cultured cells. In summary, our results demonstrated that LYG-202 induced apoptosis and cell cycle arrest via targeting PI3K/Akt pathway, indicating that LYG-202 is a potential anticancer agent for breast cancer.

An Early and Robust Activation of Caspases Heads Cells for a Regulated Form of Necrotic-like Cell Death

Apoptosis is triggered by the activation of caspases and characterized by chromatin condensation and nuclear fragmentation (type II nuclear morphology). Necrosis is depicted by a gain in cell volume (oncosis), swelling of organelles, plasma membrane leakage, and subsequent loss of intracellular contents. Although considered as different cell death entities, there is an overlap between apoptosis and necrosis. In this sense, mounting evidence suggests that both processes can be morphological expressions of a common biochemical network known as "apoptosis-necrosis continuum." To gain insight into the events driving the apoptosis-necrosis continuum, apoptotically proficient cells were screened facing several apoptotic inducers for the absence of type II apoptotic nuclear morphologies. Chelerythrine was selected for further studies based on its cytotoxicity and the lack of apoptotic nuclear alterations. Chelerythrine triggered an early plasma membrane leakage without condensed chromatin aggregates. Ultrastructural analysis revealed that chelerythrine-mediated cytotoxicity was compatible with a necrotic-like type of cell death. Biochemically, chelerythrine induced the activation of caspases. Moreover, the inhibition of caspases prevented chelerythrine-triggered necrotic-like cell death. Compared with staurosporine, chelerythrine induced stronger caspase activation detectable at earlier times. After using a battery of chemicals, we found that high concentrations of thiolic antioxidants fully prevented chelerythrine-driven caspase activation and necrotic-like cell death. Lower amounts of thiolic antioxidants partially prevented chelerythrine-mediated cytotoxicity and allowed cells to display type II apoptotic nuclear morphology correlating with a delay in caspase-3 activation. Altogether, these data support that an early and pronounced activation of caspases can drive cells to undergo a form of necrotic-like regulated cell death.

Nuclear and cytoplasmic p53 suppress cell invasion by inhibiting respiratory complex-I activity via Bcl-2 family proteins

Although the p53 tumor suppressor/transcription factor often accumulates in the cytoplasm of healthy cells, limited information is available on the cytoplasmic function of p53. Here, we show that cytoplasmic p53 suppresses cell invasion by reducing mitochondrial reactive oxygen species (ROS) levels. Analysis revealed that this function is mediated by Bcl-2 family proteins: Cytoplasmic p53 binds Bcl-w, liberating Bax, which then binds ND5, a subunit of respiratory complex-I, thereby suppressing complex-I activity and thus ROS production. The G13289A mutation of ND5, identified in cancer patients, prevents Bax/ND5 interactions and promotes ROS production and cell invasion. We also showed that Bcl-XL and Bak can substitute for Bcl-w and Bax, respectively, regulating complex-I activity and supporting the cytoplasmic function of p53; nuclear p53 also suppresses complex-I activity by inducing Bax expression. Studies in animal models support the notion that p53 and Bcl-2 family proteins exhibit these functions in vivo. This study demonstrates a link between p53 and Bcl-2 proteins as regulators of ROS production and cellular invasiveness, and reveals complex-I, especially ND5, as their functional target.

Suppression of Human T Cell Proliferation Mediated by the Cathepsin B Inhibitor, z-FA-FMK Is Due to Oxidative Stress

The cathepsin B inhibitor, benzyloxycarbonyl-phenylalanine-alanine-fluoromethyl ketone (z-FA-FMK) readily inhibits anti-CD3-induced human T cell proliferation, whereas the analogue benzyloxycarbonyl-phenylalanine-alanine-diazomethyl ketone (z-FA-DMK) had no effect. In contrast, benzyloxycarbonyl-phenylalanine-alanine-chloromethyl ketone (z-FA-CMK) was toxic. The inhibition of T cell proliferation mediated by z-FA-FMK requires not only the FMK moiety, but also the benzyloxycarbonyl group at the N-terminal, suggesting some degree of specificity in z-FA-FMK-induced inhibition of primary T cell proliferation. We showed that z-FA-FMK treatment leads to a decrease in intracellular glutathione (GSH) with a concomitant increase in reactive oxygen species (ROS) levels in activated T cells. The inhibition of anti-CD3-induced T cell proliferation mediated by z-FA-FMK was abolished by the presence of low molecular weight thiols such as GSH, N-acetylcysteine (NAC) and L-cysteine, whereas D-cysteine which cannot be metabolised to GSH has no effect. The inhibition of anti-CD3-induced up-regulation of CD25 and CD69 expression mediated by z-FA-FMK was also attenuated in the presence of exogenous GSH. Similar to cell proliferation, GSH, NAC and L-cysteine but not D-cysteine, completely restored the processing of caspase-8 and caspase-3 to their respective subunits in z-FA-FMK-treated activated T cells. Our collective results demonstrated that the inhibition of T cell activation and proliferation mediated by z-FA-FMK is due to oxidative stress via the depletion of GSH.

Beyond TGFβ--novel ways to target airway and parenchymal fibrosis

Within the lungs, fibrosis can affect both the parenchyma and the airways. Fibrosis is a hallmark pathological change in the parenchyma in patients with idiopathic pulmonary fibrosis (IPF), whilst in asthma or chronic obstructive pulmonary disease (COPD) fibrosis is a component of the remodelling of the airways. In the past decade, significant advances have been made in understanding the disease behaviour and pathogenesis of parenchymal and airway fibrosis and as a result a variety of novel therapeutic targets for slowing or preventing progression of these fibrotic changes have been identified. This review highlights a number of these targets and discusses the potential for treating parenchymal or airway fibrosis through these mediators/pathways in the future.

Mechanism of immunotoxicological effects of tributyltin chloride on murine thymocytes

Tributyltin-chloride, a well-known organotin compound, is a widespread environmental toxicant. The immunotoxic effects of tributyltin-chloride on mammalian system and its mechanism is still unclear. This study is designed to explore the mode of action of tributyltin-induced apoptosis and other parallel apoptotic pathways in murine thymocytes. The earliest response in oxidative stress followed by mitochondrial membrane depolarization and caspase-3 activation has been observed. Pre-treatment with N-acetyl cysteine and buthionine sulfoximine effectively inhibited the tributyltin-induced apoptotic DNA and elevated the sub G1 population, respectively. Caspase inhibitors pretreatment prevent tributyltin-induced apoptosis. Western blot and flow cytometry indicate no translocation of apoptosis-inducing factor and endonuclease G in the nuclear fraction from mitochondria. Intracellular Ca(2+) levels are significantly raised by tributyltin chloride. These results clearly demonstrate caspase-dependent apoptotic pathway and support the role of oxidative stress, mitochondrial membrane depolarization, caspase-3 activation, and calcium during tributyltin-chloride (TBTC)-induced thymic apoptosis.

Antioxidant properties and PC12 cell protective effects of a novel curcumin analogue (2E,6E)-2,6-bis(3,5- dimethoxybenzylidene)cyclohexanone (MCH)

The antioxidative properties of a novel curcumin analogue (2E,6E)-2,6-bis(3,5-dimethoxybenzylidene)cyclohexanone (MCH) were assessed by several in vitro models, including superoxide anion, hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and PC12 cell protection from H2O2 damage. MCH displayed superior O2•- quenching abilities compared to curcumin and vitamin C. In vitro stability of MCH was also improved compared with curcumin. Exposure of PC12 cells to 150 µM H2O2 caused a decrease of antioxidant enzyme activities, glutathione (GSH) loss, an increase in malondialdehyde (MDA) level, and leakage of lactate dehydrogenase (LDH), cell apoptosis and reduction in cell viability. Pretreatment of the cells with MCH at 0.63-5.00 µM before H2O2 exposure significantly attenuated those changes in a dose-dependent manner. MCH enhanced cellular expression of transcription factor NF-E2-related factor 2 (Nrf2) at the transcriptional level. Moreover, MCH could mitigate intracellular accumulation of reactive oxygen species (ROS), the loss of mitochondrial membrane potential (MMP), and the increase of cleaved caspase-3 activity induced by H2O2. These results show that MCH protects PC12 cells from H2O2 injury by modulating endogenous antioxidant enzymes, scavenging ROS, activating the Nrf2 cytoprotective pathway and prevention of apoptosis.

Competition through dimerization between antiapoptotic and proapoptotic HS-1-associated protein X-1 (Hax-1)

Studies on Hax-1 have mainly focused on variant (v) 1, demonstrating its antiapoptotic properties. However, HAX1 is heavily spliced, generating structurally distinct isoforms. We sought to characterize the Hax-1 isoforms expressed in rat heart before and after insult. We confirmed the presence of at least four Hax-1 transcripts in healthy rat cardiac muscle. These exhibited differential expression before and after induction of myocardial infarction, with v2 being up-regulated 12-fold at the transcript level and 1.5-fold at the protein level post-insult. Contrary to antiapoptotic rat and human v1, overexpression of rat v2 or human v4 (the human homologue of rat v2) in epithelial cells exacerbated cell death by 30% following H2O2 treatment compared with control vector. Coexpression of rat v1 and v2 or human v1 and v4 neutralized the protective effects of rat and human v1 and the proapoptotic effects of rat v2 and human v4 by modulating cytochrome c release. This is, at least partly, mediated by the ability of Hax-1 proteins to form homotypic and heterotypic dimers with binding affinities ranging from ~3.8 nm for v1 dimers to ~97 nm for v1/v2 dimers. The minimal binding region supporting these interactions lies between amino acids 97-278, which are shared by nearly all Hax-1 proteins, indicating that additional factors regulate the preferential formation of Hax-1 homo- or heterodimers. Our studies are the first to show that Hax-1 is a family of anti- and proapoptotic regulators that may modulate cell survival and death through homo- or heterodimerization.

GS-2, a pyrazolo[1,5-a]indole derivative with inhibitory activity of topoisomerases, exerts its potent cytotoxic activity by ROS generation

Pyrazolo[1,5-a]indole derivatives, a new type of topoisomerase (topo) inhibitor, demonstrate a broad spectrum of antitumor activities. However, the mechanism underlying the induced cytotoxicity remains unclear. In this study, we investigated whether GS-2, one of the derivatives, altered the levels of ROS in breast cancer MDA-231 cells and whether these ROS contributed to the observed antitumoral activity. Our data revealed that GS-2 caused a time- and dose-dependent elevation of intracellular ROS level in MDA-231 cells. GS-2 subsequently elicited notable inhibition on the expression of topos, DNA damage, activation of caspase-3, -9. The loss of mitochondrial membrane potential (MMP) was observed during the induction. The addition of N-acetyl cysteine (NAC, a well-known antioxidant) could effectively attenuate the GS-2-induced ROS enhancement and subsequent apoptosis. NAC attenuated the induced inhibition on expression of topos, indicating that topos might be the target of GS-2-induced ROS. The finding of the induced ROS provides new evidence for the molecular mechanisms of antitumor activity of pyrazolo[1,5-a]indole derivatives.

The effect of bicarbonate on menadione-induced redox cycling and cytotoxicity: potential involvement of the carbonate radical

We have investigated the effect of NaHCO3 on menadione redox cycling and cytotoxicity. A cell-free system utilized menadione and ascorbic acid to catalyze a redox cycle, and we utilized murine hepatoma (Hepa 1c1c7) cells for in vitro experiments. Experiments were performed using low (2 mmol/L) and physiological (25 mmol/L) levels of NaHCO3 in buffer equilibrated to physiological pH. Using oximetry, ascorbic acid oxidation, and ascorbyl radical detection, we found that menadione redox cycling was enhanced by NaHCO3. Furthermore, Hepa 1c1c7 cells treated with menadione demonstrated cytotoxicity that was significantly increased with physiological concentrations of NaHCO3 in the media, compared with low levels of NaHCO3. Interestingly, the inhibition of superoxide dismutase (SOD) with 2 different metal chelators was associated with a protective effect against menadione cytotoxicity. Using isolated protein, we found a significant increase in protein carbonyls with menadione-ascorbate-SOD with physiological NaHCO3 levels; low NaHCO3 or SOD-free reactions produced lower levels of protein carbonyls. In conclusion, these findings suggest that the hydrogen peroxide generated by menadione redox cycling together with NaHCO3-CO2 are potential substrates for SOD peroxidase activity that can lead to carbonate-radical-enhanced cytotoxicity. These findings demonstrate the importance of NaHCO3 in menadione redox cycling and cytotoxicity.

D-penicillamine and other low molecular weight thiols: review of anticancer effects and related mechanisms

Low molecular weight thiols (LMWTs) like N-acetyl cysteine, D-penicillamine, captopril, Disulfiram and Amifostine, etc. have been used as chemo-preventive agents. Recent studies have reported cell growth inhibition and cytotoxicity in several different types of cancer cells following treatment with several LMWTs. Cytotoxic and cytostatic effects of LMWTs may involve interaction of the thiol group with cellular lipids, proteins, intermediates or enzymes. Some of the mechanisms that have been proposed include a p53 mediated apoptosis, thiyl radical induced DNA damage, membrane damage through lipid peroxidation, anti-angiogenic effects induced by inhibition of matrix metalloproteinase enzymes and angiostatin generation. LMWTs are strong chelators of transition metals like copper, nickel, zinc, iron and cobalt and may cause metal co-factor depletion resulting in cytotoxicity. Oxidation of thiol group can also generate cytotoxic reactive oxygen species (ROS).

Toxicity of organotin compounds: shared and unshared biochemical targets and mechanisms in animal cells

Most biochemical effects of organotin compounds leading to toxicity are astonishingly similar in different animal species. In vitro tests, designed to explore organotin action modes at cell level by minimizing interfering factors, point out akin responses to these man-made environmental pollutants from prokaryotes to mammals. On the other hand, a broad susceptibility range to organotin toxicants of animal cells and variegated action mechanisms of these compounds have been reported both in vitro and in vivo studies. Endocrine and lipid homeostasis perturbations span from mollusks to mammals, in which organotins mainly favor fat accumulation. Lipid changes were also found in Bacteria. Organotin are immunotoxic both in invertebrates and humans. Mitochondria and membrane functions seem to be a preferred target of these lipophilic pollutants. The inhibition of key membrane-bound enzyme complexes such as Na,K-and F0F1-ATPases, accompanied by perturbation of hydromineral balance, membrane potential and bioenergetics, has been widely reported. Highly conserved mechanisms could be involved in organotin binding to nuclear receptors, membrane components and intracellular proteins as well as in promoting DNA damage, all widely shared action modes of these toxicants. Accordingly, the different responsiveness/refractoriness to organotins, here overviewed, may mirror the biochemical-physiological selectivity of biomembranes, signalling pathways and intracellular protein components.

Follicular fluid hydrogen peroxide and lipid hydroperoxide in bovine antral follicles of various size, atresia, and dominance status

PURPOSE

To avoid inducing a state of oxidative stress (OS), assisted reproductive technologies (ART) must maintain a balance of reactive oxygen species (ROS) and antioxidants during the in vitro culture of oocytes. However, oocyte requirements and tolerance thresholds for ROS during in vivo development are still unclear. Previous studies have examined ROS levels in follicular fluid (FF) using pooled samples or according to follicle size. This study sought to examine two OS markers, lipid hydroperoxides (LPO) and hydrogen peroxide (H2O2), in FF of individually sampled follicles from bovine ovary pairs according to follicle size, atresia, and dominance status.

METHODS

TUNEL and cleaved Caspase-3 labeling were used to identify apoptotic granulosa cells and determine follicle atresia status. LPO were measured directly for the first time in FF.

RESULTS

Non-atretic follicles and dominant follicles contained more FF H2O2 than atretic follicles and corresponding subordinate follicles, respectively. FF LPO did not vary in relation to atretic status, and no difference existed between dominant and subordinate follicles. However, FF LPO was significantly lower in first subordinate follicles than in the second subordinate follicles from each ovary pair. Neither H2O2 nor LPO levels correlated with follicle size.

CONCLUSIONS

These data provide clear evidence that the events of antral folliculogenesis are relevant to ROS dynamics in vivo. Furthermore, such studies will help to optimize in vitro conditions for oocyte culture protocols, particularly when combined with a comparison of oocyte quality with respect to source follicle characteristics.

Cadmium induces hydrogen peroxide production and initiates hydrogen peroxide-dependent apoptosis in the gill of freshwater crab, Sinopotamon henanense

Cadmium (Cd) is a well-known toxic heavy metal that accumulates in the aquatic environment. Cd has been reported to induce oxidative damage and apoptosis. We investigated the regulation mechanism of hydrogen peroxide (H(2)O(2)) on Cd-induced apoptosis. We show that in the gills of the freshwater crab Sinopotamon henanense Cd induced apoptosis, in a time- and concentration-dependent manner, as confirmed by DNA fragmentation analysis and transmission electron microscopy. Additionally, Cd caused production of H(2)O(2) after 2 h of treatment at 58 mg L(-1) Cd, and significantly increased the caspase-3/8/9 activity in crabs relative to the control group. Pre-treatment with the scavenger for H(2)O(2), dimethylthiourea (DMTU) and antioxidant, N-acetyl cysteine (NAC), effectively inhibited the activities of caspase-3 and caspase-9, eventually blocked Cd-induced DNA fragmentation and the appearance of markers for apoptotic cell death. These results suggest that Cd might induce intracellular H(2)O(2) generation to trigger the crab apoptotic processes by regulating the activities of caspase enzymes.

Tributyltin (TBT) increases TNFα mRNA expression and induces apoptosis in the murine macrophage cell line in vitro

OBJECTIVE

Tributyltin (TBT) compounds have been widely used as antifouling agents for shipbottom paint. The immune system is a target of TBT intoxication. We evaluated the effects of TBT chloride in macrophages, which have critical roles in the immune system, using a murine macrophage lineage cell line, J774.1,in vitro.

METHODS

We examined tumor necrosis factor α (TNFα), interleukin-1β (IL-1β) andc-jun mRNA expression in J774.1 cells. The effects of TBT on the apoptosis of J774.1 cells were examined by determining the percentage of TUNEL-positive cells and caspase-3 activity.

RESULTS

The mean values of the viabilities of J774.1 cells exposed to TBT decreased dose-dependently. The relative mRNA expression of TNFα increased dose-dependently, however, that of IL-1β was not significantly different among the groups. The mean percentage of TUNEL-positive cells increased dose-dependently. Increases in the caspase-3 activities of J774.1 cells were observed in the groups exposed to higher concentrations of TBT. The mean value of relative mRNA expression of c-Jun transcription factor increased dose-dependently.

CONCLUSIONS

The increases in the percentage of TUNEL-positive cells and in caspase-3 activity suggested that exposure to TBT induces apoptosis of J774.1 cells. The increases in the mRNA expression of TNFα andc-jun by TBT may be related to apoptosis in macrophages.

Endurance training stimulates growth and survival pathways and the redox balance in rat pancreatic islets

Endurance training has been shown to increase pancreatic β-cell function and mass. However, whether exercise modulates β-cell growth and survival pathways signaling is not completely understood. This study investigated the effects of exercise on growth and apoptotic markers levels in rat pancreatic islets. Male Wistar rats were randomly assigned to 8-wk endurance training or to a sedentary control group. After that, pancreatic islets were isolated; gene expression and the total content and phosphorylation of several proteins related to growth and apoptotic pathways as well as the main antioxidant enzymes were determined by real-time polymerase chain reaction and Western blot analysis, respectively. Reactive oxygen species (ROS) production was measured by fluorescence. Endurance training increased the time to reach fatigue by 50%. Endurance training resulted in increased protein phosphorylation content of AKT (75%), AKT substrate (AS160; 100%), mTOR (60%), p70s6k (90%), and ERK1/2 (50%), compared with islets from control group. Catalase protein content was 50% higher, whereas ROS production was 49 and 77% lower in islets from trained rats under basal and stimulating glucose conditions, respectively. Bcl-2 mRNA and protein levels increased by 46 and 100%, respectively. Bax and cleaved caspase-3 protein contents were reduced by 25 and 50% in islets from trained rats, respectively. In conclusion, these results demonstrate that endurance training favors the β-cell growth and survival by activating AKT and ERK1/2 pathways, enhancing antioxidant capacity, and reducing ROS production and apoptotic proteins content.

Whole-object fluorescence lifetime setup for efficient non-imaging quantitative intracellular fluorophore measurements

In the present study we introduce a Whole-Object Fluorescence Life Time (wo-FLT) measurement approach for ease and a relatively inexpensive method of tracing alterations in intracellular fluorophore distribution and in the physical-chemical features of the microenvironments hosting the fluorophore. Two common fluorophores, Rhodamine 123 and Acridine Orange, were used to stain U937 cells which were incubated, with and without either Carbonyl cyanide 3-chlorphenylhydrazon or the apoptosis inducer H(2)O(2). The wo-FLT, which is a non-imaging quantitative measurement, was able to detect several fluorescence decay components and corresponding weights in a single cell resolution. Following cell treatment, both decay time and weight were altered. Results suggest that the prominent factor responsible for these alterations and in some cases to a shift in emission spectrum as well, is the intracellular fluorophore local concentration. In this study it was demonstrated that the proposed wo-FLT method is superior to color fluorescence based imaging in cases where the emission spectrum of a fluorophore remains unchanged during the investigated process. The proposed wo-FLT approach may be of particular importance when direct imaging is impossible.

Caspase-10 is the key initiator caspase involved in tributyltin-mediated apoptosis in human immune cells

Tributyltin (TBT) is one of the most toxic compounds produced by man and distributed in the environment. A multitude of toxic activities have been described, for example, immunotoxic, neurotoxic, and endocrine disruptive effects. Moreover, it has been shown for many cell types that they undergo apoptosis after treatment with TBT and the cell death of immune cells could be the molecular background of its immunotoxic effect. As low as 200 nM up to 1 μM of TBT induces all signs of apoptosis in Jurkat T cells within 1 to 24 hrs of treatment. When compared to Fas-ligand control stimulation, the same sequence of events occurs: membrane blebbing, phosphatidylserine externalisation, the activation of the “death-inducing signalling complex,” and the following sequence of cleavage processes. In genetically modified caspase-8-deficient Jurkat cells, the apoptotic effects are only slightly reduced, whereas, in FADD-negative Jurkat cells, the TBT effect is significantly diminished. We could show that caspase-10 is recruited by the TRAIL-R2 receptor and apoptosis is totally prevented when caspase-10 is specifically inhibited in all three cell lines.

Tanshinone IIA Attenuates H₂O₂ -induced injury in human umbilical vein endothelial cells

The injury of endothelial cell is the critical event of vascular disease. In endothelial cell, oxidative stress is regarded as critical to pathogenic factors in endothelial cell injury and apoptosis. Tanshinone IIA is the main effective component of Salvia miltiorrhiza known as "Danshen" in traditional Chinese medicine for treating cardiovascular disorders, but the mechanism by which it exerts the protective effect is not well established. The present study was designed to test the hypothesis that tanshinone IIA can inhibit hydrogen peroxide ( H(2)O(2) )-induced injury and unravel its intracellular mechanism in human umbilical vein endothelial cells (HUVECs). In this study, HUVECs were treated with tanshinone IIA in the presence/absence of H(2)O(2) . The protective effects of tanshinone IIA against H(2)O(2) were evaluated. Our results show that HUVECs incubated with 200 μM H(2)O(2) had significantly decreased the viability of endothelial cells, which was accompanied with apparent cell apoptosis, the activation of caspase-3 and the upregulation of p53 expression, which was known to play a key role in H(2)O(2) -induced cell apoptosis. However, pretreatment with tanshinone IIA (3-10 μM) resulted in a significant resistance to H(2)O(2) -induced apoptosis. In addition, pretreatment with tanshinone IIA decreased the activity of caspase-3 and p53 expression. Tanshinone IIA also induced activating transcription factor (ATF) 3 expression; while knockdown of ATF-3 with ATF-3 siRNAsignificantly reduced tanshinone IIA's protective effect. In conclusion, the present study shows that tanshinone IIA can protect endothelial cells against oxidative injury induced by H(2)O(2) , suggesting that this compound may constitute a promising intervention against cardiovascular disorders and ATF-3 may play an important role in this process.

Induction of apoptosis in mussel Mytilus galloprovincialis gills by model cytotoxic agents

Apoptosis signaling pathway was investigated in the marine mussel Mytilus galloprovincialis exposed to various stressors. Analyses were performed in mussels exposed to two major pollutants of the aquatic environment: tributyltin and the water soluble fraction of diesel oil, for 1 h and animals were then maintained in sea water for a recovery period of 6 and 24 h. Apoptosis was evaluated at several levels of the cell signaling cascade by measuring Bcl-xS expression, caspase-3 activity and DNA damage (Fast micromethod(®) and TUNEL techniques). H(2)O(2) was used as a control of apoptosis induction for validation of the assays. Results showed an induction of Bcl-xS expression, a protein implicated in apoptosis, after 1 h exposure to all concentrations of chemicals. Moreover, in the same manner, apoptotic DNA damage was induced with all chemicals tested. Besides, caspase 3 activity was detected after 1 h exposure to low doses of TBT and diesel oil while the high concentrations induced this protein after 6 h. The achieved data were also correlated with our previous study, demonstrating an induction of the mitogen-activated protein kinase (MAPK) activity in the mussel M. galloprovincialis exposed to the same conditions. In conclusion, this study was one of the first characterizing the MAP kinase cell signaling pathway leading to apoptosis in the mussel M. galloprovincialis exposed to chemicals. It showed for the first time that the Bcl-xS protein was present in these mussels as in other species and played a role in apoptosis mediation. Moreover, the main originality of this work was that it showed that two apoptotic pathways might be present in the mussel: a caspase 3-dependent and a caspase 3-independent pathways.

GL-V9, a newly synthetic flavonoid derivative, induces mitochondrial-mediated apoptosis and G2/M cell cycle arrest in human hepatocellular carcinoma HepG2 cells

We recently established that GL-V9, a newly synthetic flavonoid derivative, is an active cytotoxic component. In this study, we demonstrated that GL-V9 inhibited cells growth via inducing apoptosis and G2/M cell cycle arrest in human hepatocellular carcinoma HepG2 cells. Following the treatment of HepG2 cells with GL-V9, we observed poly (ADP-ribose) polymerase (PARP) cleavage and activation of caspase-3 and caspase-9, while caspase-8 remained unchanged. The expression ratio of Bcl-2/Bax was also decreased in GL-V9-treated cells. Meanwhile, the cell cycle-related proteins, such as cyclin B1, CDK1 and cdc25 were down-regulated in GL-V9-induced G2/M cell cycle arrest. Furthermore, we showed that GL-V9-induced apoptosis in HepG2 cells was achieved through mitochondrial pathway. It also regulated changes of mitochondrial membrane potential and increased the production of intracellular reactive oxygen species. Besides, the growth inhibitory effect of GL-V9 was examined in vivo using murine implanted tumor model. These studies indicate that GL-V9 shows promise as a therapeutic agent against human hepatoma.

Effects of manipulation of the caspase system on myofibrillar protein degradation in vitro

Apoptosis via the intrinsic caspase 9 pathway can be induced by oxidative stressors hydrogen peroxide (H₂O₂) and N-(4 hydroxyphenol) rentinamide (fenretinide), a synthetic retinoid. Accelerated muscle atrophy and proteolysis in muscle-wasting conditions have been linked to oxidative stress and activated protease systems. Therefore, the hypothesis of this study was that proteolysis of myofibrillar proteins could be manipulated through the induction or inhibition of the caspase system. After slaughter, LM and supraspinatus muscles from callipyge (n = 5) and normal (n = 3) lambs were excised, finely diced, and incubated with treatment buffers containing oxidative stressors fenretinide or H₂O₂, recombinant caspase 3, caspase-specific inhibitor N-acetyl-Asp-Glu-Val-Asp-CHO (DEVD), or control solution. Muscle samples were incubated for 1, 2, 7, and 21 d at 4°C. Activation of the initiator caspase, caspase 9, and myofibrillar protein degradation was determined by SDS-PAGE and Western blotting. Results showed that fenretinide, H₂O₂, and recombinant caspase 3 increased (P < 0.05) proteolysis of myofibril proteins, whereas DEVD inhibited degradation (P < 0.05). Proteolysis of myofibrillar proteins increased with incubation time (P < 0.0001), and incubation time × treatment interactions (P < 0.05) indicated that the treatment effects did not all occur at the same rate. This study has shown that manipulation of the caspase system through induction or inhibition of activity can affect degradation of myofibrillar proteins, providing further evidence that the caspase system could be involved in postmortem proteolysis and tenderization. However, these stimulated changes were not sufficient to overcome the lack of proteolysis that is characteristic of muscle from callipyge lambs.