Mitochondria as regulators of apoptosis: doubt no more

Apoptosis signal-regulating kinase (ASK)-1 mediates apoptosis through activation of JNK1 following engagement of membrane immunoglobulin

Engagement of membrane immunoglobulin (mIg) on WEHI-231 mouse B lymphoma cells results in growth arrest at the G1 phase of the cell cycle, followed by a reduction of mitochondrial membrane potential (DeltaPsim) and apoptosis. WEHI-231 cells resemble immature B cells in terms of the cell surface phenotype and sensitivity to mIg engagement. However, the molecular mechanisms underlying mIg-induced loss of DeltaPsim and apoptosis have not yet been established. In this study, we show that apoptosis signal-regulating kinase 1 (ASK1)-c-Jun N-terminal kinase 1 (JNK1) signaling pathway participates in mIg-induced apoptosis through the generation of reactive oxygen species (ROS). Stimulation of WEHI-231 cells with anti-IgM induces phosphorylation and subsequent activation of ASK1, leading to JNK activation. Anti-IgM stimulation immediately (5 min) induces hydrogen peroxide (H2O2) production with a substantial increase during later time points (36-48 h), accompanied by loss of DeltaPsim and an increase in cells with sub-G1 DNA content. The anti-IgM-induced late-phase H2O2 production, loss of DeltaPsim, and increase in the sub-G1 fraction were all reduced substantially in WEHI-231 cells overexpressing a dominant-negative form of ASK1, compared with control vector alone, but enhanced substantially in cells overexpressing a constitutively active form of ASK1. These mIg-mediated events were also partially abrogated by ROS scavenger N-acetyl-L-cysteine (NAC). Taken together, these results suggest that mIg engagement induces H2O2 production leading to activation of ASK1-JNK1 pathway, creating a feedback amplification loop of ROS-ASK/JNK that leads to loss of DeltaPsim and finally apoptosis.

Mitochondria-initiated apoptosis triggered by oxidative injury play a role in total parenteral nutrition-associated liver dysfunction in infant rabbit model

PURPOSE

The aim of the study was to investigate oxidative injury and apoptosis as the mechanisms underlying total parenteral nutrition (TPN)-associated liver dysfunction.

METHODS

Twenty New Zealand rabbits (2 weeks old) were divided into 2 groups as follows: 10 in the control group (maternal feed) and 10 in the TPN group. The rabbits in the TPN group received continuous PN infusion through a silastic catheter inserted in the right jugular vein.

RESULTS

After 10 days of treatment, the serum levels of total bilirubin and bile acid were significantly higher in the TPN group than in the control group (P < .01, respectively). The light microscopic findings in the TPN rabbits included inflammatory cell infiltration and hepatic steatosis. Electron microscopy showed change in the cytosolic vacuoles and rare microvilli in the microbile duct. Moreover, 10 days of treatment resulted in an inhibition of the superoxide dismutase (SOD) activity in hepatocytes, an increase of the malondialdehyde level, a significant increase in cytochrome c release from the mitochondria, a significant increase in caspase 3 activity, and increased apoptosis (P < .01, individually).

CONCLUSIONS

Oxidative damage may be one of the essential mechanisms of TPN-associated liver dysfunction. Moreover, mitochondria-initiated apoptosis triggered by oxidative damage may play an important role in this process.

Bax distribution into mitochondrial detergent-resistant microdomains is related to ceramide and cholesterol content in postischemic hearts

*Diverse changes have been described in mitochondria of apoptotic cells: the phospholipid content is modified, ceramide and GD3 concentrations increase, the cristae structure is modified, and nonresident proteins are recruited into the mitochondrial membranes. In particular, Bax, a Bcl-2 family member protein, moves from the cytosol to the mitochondria, inducing cytochrome c release. Modifications of the content and distribution of specific lipids in the mitochondrial membranes, along with the well-known participation of the mitochondrial permeability transition pore in triggering apoptosis, led us to propose that lipid microdomains in mitochondria could coexist as structural elements with some of the mitochondrial permeability transition pore-forming proteins and with members of the Bcl-2 family. In this work, we demonstrated that Bax was associated preferentially with mitochondrial detergent-resistant membranes (mDRMs) in reperfused rat hearts, a well-known apoptotic model. Bax insertion into mDRMs correlated with cytochrome c release from such mitochondria. Bax location in mDRMs was associated with both the voltage-dependent anion channel and the adenine nucleotide translocator, two mitochondrial permeability transition pore-forming proteins. Interestingly, the voltage-dependent anion channel was more abundant in the mDRM fraction than in the Triton X-100-soluble fraction. Ceramide and cholesterol contents were higher in mDRMs from reperfused hearts. Our results suggest that membrane microenvironments enriched in cholesterol and ceramide in mitochondria favor Bax translocation to this organelle, fostering propagation of the apoptotic cascade.

Loss of mitochondrial membrane potential and caspase activation enhance apoptosis in irradiated K562 cells treated with herbimycin A

PURPOSE

We previously reported that herbimycin A (HMA) alters the mode of cell death of K562 cells induced by radiation and enhanced their radiosensitivity. In the present study, we explored the apoptosis-inducing activity of HMA and the fundamental mechanism via which it regulates radiation-induced cell death.

MATERIALS AND METHODS

Chronic myelogenous leukemia (CML) cell line K562 was used. For X-irradiation and drug treatment, cells were plated at approximately 2x10(5) cells/ml. Exponentially growing cells were treated with 10 Gy of X-ray using a 6-MeV X-ray machine at a dose rate of 200-300 cGy/min. The cells were treated with 0.25 microM HMA immediately after irradiation and HMA remained for the entire culture period. The modes of cell death were discriminated by morphological changes, analysis of cell cycle, analysis of the mitochondrial events, and the expression of apoptosis-related proteins.

RESULTS

Our data demonstrates that radiation induced a significant time-dependent increase of cell death and failed to sustain a prolonged G2 arrest in K562 cells. Radiation-induced cell death caused the accumulation of cyclinB1 and weak nuclear fragmentation, suggesting a mitotic catastrophe. This mitotic catastrophe was dependent upon the mitochondrial permeability transition pore (PTP) opening and was independent of caspase-3. In contrast, K562 cells treated with radiation and HMA had an accelerated cell death and induced a p53-independent apoptosis. This apoptotic pathway was dependent upon an initial hyperpolarization of the mitochondrial inner membrane, following the release of cytochrome c and subsequent caspase-3 activation.

CONCLUSIONS

Two mechanisms of radiation-induced cell death in K562 cells, mitotic catastrophe and apoptosis, are regulated through distinct pathways, mitochondria and caspase-independent and -dependent, respectively. The findings of this study may provide new insights into improving the efficiency of radiotherapy in CML patients.

Role of oxidative stress in alcohol-induced liver injury

Reactive oxygen species (ROS) are highly reactive molecules that are naturally generated in small amounts during the body's metabolic reactions and can react with and damage complex cellular molecules such as lipids, proteins, or DNA. Acute and chronic ethanol treatments increase the production of ROS, lower cellular antioxidant levels, and enhance oxidative stress in many tissues, especially the liver. Ethanol-induced oxidative stress plays a major role in the mechanisms by which ethanol produces liver injury. Many pathways play a key role in how ethanol induces oxidative stress. This review summarizes some of the leading pathways and discusses the evidence for their contribution to alcohol-induced liver injury. Special emphasis is placed on CYP2E1, which is induced by alcohol and is reactive in metabolizing and activating many hepatotoxins, including ethanol, to reactive products, and in generating ROS.

Detection and quantification of the evolution dynamics of apoptosis using the PET voltage sensor 18F-fluorobenzyl triphenyl phosphonium

Apoptosis is a key mechanism in numerous pathologies. However, there are no effective noninvasive means available for an early detection and quantitative assessment of evolution dynamics of the apoptotic process. Here, we have characterized the ability of the novel PET voltage sensor (18)F-fluorobenzyl triphenyl phosphonium ((18)F-FBnTP) to quantify the time-dependent apoptotic action of the taxanes paclitaxel and docetaxel in vitro and in vivo.

METHODS

The duration-dependent treatment effect of paclitaxel on (18)F-FBnTP uptake was assayed in human MDA-MB-231 breast carcinoma cells. The expression of the proapoptotic Bax and antiapoptotic Bcl-2 mitochondrial proteins, release of the apoptogen cytochrome c, and activation of executioner caspase-3 were determined by Western blotting. The fraction of viable cells was determined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. The effect of docetaxel on (18)F-FBnTP and (18)F-FDG uptake in orthotopic prostate tumors in mice was compared.

RESULTS

(18)F-FBnTP cellular uptake in viable cells declined linearly with the increasing duration of paclitaxel treatment, from 3 to 24 h, and plateaued at 48 h. The extent of decrease of (18)F-FBnTP correlated strongly with the Bax-to-Bcl-2 ratio (R(2) = 0.83) and release of cytochrome c (R(2) = 0.92), but preceded in time the caspase-3 cleavage. The P-glycoprotein blocker verapamil did not interfere with (18)F-FBnTP cellular uptake. (18)F-FBnTP prostate tumor contrast was greater than (18)F-FDG prostate tumor contrast. Docetaxel caused a marked decrease (52.4%) of (18)F-FBnTP tumor uptake, within 48 h, whereas (18)F-FDG was much less affected (12%).

CONCLUSION

The voltage sensor (18)F-FBnTP is a viable means for quantification of paclitaxel pharmacodynamics. (18)F-FBnTP permits the detection of paclitaxel apoptotic action in vivo earlier than does (18)F-FDG. (18)F-FBnTP may afford a novel approach for early detection and quantitative assessment of the cumulative-effect kinetics of proapoptotic drugs and conditions using PET.

Protection against kainate neurotoxicity by ginsenosides: attenuation of convulsive behavior, mitochondrial dysfunction, and oxidative stress

We previously demonstrated that kainic acid (KA)-mediated mitochondrial oxidative stress contributed to hippocampal degeneration and that ginsenosides attenuated KA-induced neurotoxicity and neuronal degeneration. Here, we examined whether ginsenosides affected KA-induced mitochondrial dysfunction and oxidative stress in the rat hippocampus. Treatment with ginsenosides attenuated KA-induced convulsive behavior dose-dependently. KA treatment increased lipid peroxidation and protein oxidation and decreased the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio to a greater degree in the mitochondrial fraction than in the hippocampal homogenate. KA treatment resulted in decreased Mn-superoxide dismutase expression and diminished the mitochondrial membrane potential. Furthermore, KA treatment increased intramitochondrial Ca(2+) and promoted ultrastructural degeneration in hippocampal mitochondria. Treatment with ginsenosides dose-dependently attenuated convulsive behavior and the KA-induced mitochondrial effects. Protection appeared to be more evident in mitochondria than in tissue homogenates. Collectively, the results suggest that ginsenosides prevent KA-induced neurotoxicity by attenuating mitochondrial oxidative stress and mitochondrial dysfunction.

Intracellularly expressed granulysin induced apoptosis in hepatoma cells and role of mitochondrial apoptotic pathway

Extracellularly added recombinant granulysin was reported to kill mammalian target cells. The sites of actions and molecular mechanisms of granulysin in target cell killing, however, are presently unclear. In order to provide new insights into its potential mechanism of target cell damage, we here constructed recombinant plasmids carrying 9 kDa granulysin cDNA and examined effects of intracellularly expressed granulysin on the target hepatoma SMMC-7721 cells. The localization of intracellularly expressed granulysin was examined by fluorescence microscopy and confocal microscopy. Effects of granulysin on cell proliferation and apoptosis were measured by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromid) assay, flow cytometry and fluorescence microscopy, respectively. Changes of mitochondrial membrane potential were monitored by fluorescence microscopy. On the other hand, mitochondrial release of cytochrome c and apoptosis-inducing factor (AIF) was evaluated by Western blot and confocal microscopy. Intracellularly expressed granulysin was preferentially localized in cytoplasm, noticeably inhibited cell proliferation and induced cell death accompanied by reduced mitochondrial membrane potential, release of AIF and cytochrome c from mitochondria. Taken together, our findings demonstrate for the first time that localization and effect of intracellularly expressed granulysin on non-native cancer cells and indicate its potential utility in gene therapy for cancer.

Apoptosis and its suppression in hepatocytes culture

In order to achieve the goal of developing extracorporeal liver support devices, it is necessary to optimise bioprocess environment such that viability and function are maximised. Optimising culture medium composition and controlling the constitution of the cellular microenvironment within the bioreactor have for many years been considered vital to achieving these aims. Coupled to this is the need to understand apoptosis, the prime suspect in the demise of animal cultures, including those of hepatocytes. Results presented here show that absent nutrients including glucose and amino acids play a substantial part in the induction of apoptosis. The use of chemical apoptosis inhibitors was utilised to investigate key components of hepatic apoptosis where caspases, predominantly caspase 8, were implicated in staurosporine (STS)-induced HepZ apoptosis. Caspase 9 and 3 activation although recorded was of less significance. Interestingly, these results were not consistent with those of mitochondrial membrane depolarisation where inhibition of caspase activation appeared to drive depolarisation. Inhibition of mitochondrial permeability transition and use of anti-oxidants was unsuccessful in reducing apoptosis, caspase activation and mitochondrial membrane depolarisation. In further studies, the anti-apoptotic gene bcl-2 was over-expressed in HepZ, resulting in a cell line that was more robust and resistant to death induced by glucose and cystine deprivation and treatment with STS. Bcl-2 did not however show significant cytoprotectivity where apoptosis was stimulated by deprivation of glutamine and serum. Overall, results indicated that although apoptosis can be curbed by use of chemical inhibitors and genetic manipulation, their success is dependent on apoptotic stimuli.

Mitochondrial dysfunction and apoptosis of acinar cells in chronic pancreatitis

BACKGROUND

The mechanism of acinar cell death in human chronic pancreatitis (CP) remains largely unexplored. Previous studies have demonstrated the role played by apoptosis and necrosis in experimental pancreatitis; however, their relationship with the progression of CP remains unknown. The present study was carried out to elucidate the role and extent of apoptosis in CP tissues with different histopathological scores and to examine the possible apoptotic pathway involved.

METHODS

Pancreatic tissues (25 CP patients) that had been histopathologically graded (I-III) and ten normal pancreatic tissue samples were evaluated for apoptosis by DNA fragmentation and an in situ TUNEL assay. The expression of various apoptotic and antiapoptotic markers in the tissues were studied by immunohistochemistry and Western blotting. To elucidate the role of the mitochondria in acinar cell death, the mitochondrial membrane potential (DeltaPsim) and ATP levels were determined by flow cytometry and a luminometer.

RESULTS

The presence of DNA fragmentation and apoptotic nuclei in all CP tissues confirmed the presence of apoptosis. The apoptotic index in CP tissue ranged from 0.09% to 0.86% +/- 0.02% and was highest in grade II (0.7 +/- 0.04%) tissues. Differential upregulation of the apoptotic mediators p53, Bax, cytochrome c, and caspase-3 and -9, and downregulation of antiapoptotic Bcl-2, was observed in CP. DeltaPsim on the order of 1.2-to 2.2-fold and ATP depletion in the range of 23%-84% in CP tissues was observed.

CONCLUSIONS

Apoptosis plays an important role both in the initial stages and during the progression of CP, as evident in all tissue grades. Increased DeltaPsim, loss of ATP, and activation of caspases suggests the involvement of intrinsic pathways.

c-Jun NH2-terminal kinase (JNK)-dependent nuclear translocation of apoptosis-inducing factor (AIF) following engagement of membrane immunoglobulin on WEHI-231 B lymphoma cells

WEHI-231 B lymphoma cells have been employed for analysis of antigen-induced B cell unresponsiveness because these cells undergo cell cycle arrest in G1, accompanied by induction of apoptosis. In the present study, we examined the requirement for toxic small molecules apoptosis-inducing factor (AIF) and cytochrome c, and subsequent caspase activation in apoptotic cell death in WEHI-231 and CH31 B lymphoma cells following engagement of membrane immunoglobulin (mIg). Pan-caspase inhibitor BD-fmk blocked mIg-mediated increase in cells with sub-G1 DNA content, whereas it did not affect mIg-mediated loss of mitochondrial membrane potential and phosphatidylserine exposure on B cell membrane. Dominant-negative form of c-Jun NH2-terminal kinase1 (JNK1) blocked the translocation of AIF into the nuclei and cytosol from the mitochondria in the WEHI-231 and CH31 cells following mIg engagement, whereas constitutively active form of JNK1 enhanced it. This AIF translocation was also blocked by Bcl-xL, but not by BD-fmk. Moreover, AIF-deficient clones via small interfering RNA (siRNA)-mediated method showed small increase in loss of mitochondrial membrane potential. After mIg engagement, the AIF-deficient clones displayed an enhanced sensitivity to mIg-mediated apoptosis, concomitant with translocation of a residual AIF into the nuclei, compared with control clone. Our findings are compatible with the notion that AIF has dual role, with a proapoptotic function in the nuclei and a distinct anti-apoptotic function in the mitochondria. These observations would be valuable for analysis of B cell unresponsiveness and hopefully for treatment of diseases involving B cell dysfunction.

Diallyl trisulfide (DATS) effectively attenuated oxidative stress-mediated liver injury and hepatic mitochondrial dysfunction in acute ethanol-exposed mice

The protective effects of diallyl trisulfide (DATS) on acute ethanol-induced liver injury were investigated. Mice were pretreated with DATS (30mg/kgbw) for 7d before being exposed to ethanol (4.8g/kgbw). The biochemical indices (aspartate amino transferase, AST; alanine amino transferase, ALT; triglyceride, TG) were examined to evaluate the protective effects. Mitochondria were isolated for the mitochondrial permeability transition (MPT), membrane potential (DeltaPsi(m)) and adenosine nucleotide pool assay. The lipid peroxidation (malondialdehyde, MDA), non-enzymatic antioxidant (glutathione, GSH) and enzymatic antioxidants (superoxide dismutase, SOD; catalase, CAT; glutathione reductase, GR; glutathione peroxidase, GSH-Px) were measured both in the liver homogenate and isolated mitochondria. Acute ethanol exposure resulted in the significant increase of the ALT, AST and TG levels and hepatic mitochondria dysfunction shown as MPT, and the decreases of DeltaPsi(m), ATP and energy charge (EC). However, DATS pretreatment dramatically attenuated these adverse effects. Beside this, DATS was found to significantly inhibit the increase of the hepatic and mitochondrial MDA levels, which were decreased by 33.3% (P<0.01) and 39.0% (P<0.01), respectively. In addition, DATS pretreatment markedly suppressed the ethanol-induced decrease of the hepatic GSH level and increased the mitochondrial GSH level. Moreover, the activities of the hepatic antioxidant enzymes (SOD, CAT, and GR) and the mitochondrial antioxidant enzymes (SOD, GR, and GSH-Px) were significantly boosted. Thus, we concluded that DATS dramatically attenuated acute ethanol-induced liver injury and mitochondrial dysfunction. The increase of the hepatic and mitochondrial GSH levels and the elevation of the antioxidant enzymes activities should account for the preventive effects.

Blood stage malaria antigens induce different activation-induced cell death programs in splenic CD4+T cells

CD4(+) T cells respond to antigen immunization through a process of activation, clonal expansion to generate activated effector T cells followed by activation-induced clonal deletion of the responding T cells. While loss of responding T cells in post-activation death by apoptosis is a major factor regulating immune homeostasis, the precise pathways involved in downsizing of Plasmodium falciparum antigen-induced T cell expansions are not well characterized. We report in this study that splenic CD4(+) T cells from mice immunized with nonreplicating immunogens like OVA or recombinant blood stage P. falciparum antigens, PfMSP-3 and PfMSP-1(19) or crude parasite antigen (PfAg) undergo sequential T cell activation, proliferation followed by activation-induced cell death (AICD) in a dose- and time-dependent manner after Ag restimulation. While PfMSP-3 and OVA-induced AICD was mediated through a death receptor-dependent apoptotic program, PfMSP-1(19) and PfAg-induced AICD was via a mechanism dependent on the activation of mitochondria apoptosis signalling pathway through Bax activation. These results provide insights into the mechanism through which two blood stage merozoite antigens trigger different apoptotic programs of AICD in splenic CD4(+) T cells.

Induction of apoptosis by DC-81-indole conjugate agent through NF-kappaB and JNK/AP-1 pathway

DC-81, an antitumor antibiotic produced by Streptomyces species, belongs to the pyrrolo[2,1- c][1,4]benzodiazepine (PBD) family, which are potent inhibitors of nucleic acid synthesis. We previously reported an efficient synthesis of PBD hybrids linked with indole carboxylates. Recently, we have also shown that a PBD hybrid (IN6CPBD) agent can activate the apoptotic pathway mediated by mitochondria. In this study, we will examine the transcription factors nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) that functionally regulate cell proliferation, transformation, and apoptosis. To investigate the IN6CPBD-induced alterations in NF-kappaB and AP-1 activity that involve cell cycle regulation, we exposed human melanoma A375 cells to different concentrations of IN6CPBD. Our data revealed that treatment of A375 cells with IN6CPBD resulted in a marked loss of cells from the G2/M phase of the cell cycle and an increase in Ca (2+) and cAMP and promoted phosphorylation of Jun N-terminal kinase (JNK) expression. By using the luciferase reporter assay, the NF-kappaB activities were decreased; however, AP-1 activity was further enhanced after A375 cells were treated with graded concentrations of IN6CPBD. Blockade of NF-kappaB or JNK activity further enhanced caspase-3 substrate PARP cleavage and subsequent apoptotic cell death.

Mitochondrial mechanisms of sepsis-induced organ failure

Sepsis is the leading cause of death in medical intensive care units. Though progress has been made in the early treatment of sepsis associated with hemodynamic collapse (septic shock), little is known about the pathogenesis of delayed organ dysfunction during sepsis. A growing body of data indicates that sepsis is associated with acute changes in cell metabolism, and that mitochondria are particularly susceptible. The severity of mitochondrial pathology varies according to host and pathogen factors, and appears to correlate with loss of organ dysfunction. In this regard, low levels of cell apoptosis and mitochondrial turnover are normally observed in all metabolically active tissues; however, these homeostatic mechanisms are frequently overwhelmed during sepsis and contribute to cell and tissue pathology. Thus, a better understanding of the mechanisms regulating mitochondrial damage and repair during severe sepsis may provide new treatment options and better outcomes for this deadly disease (30-60% mortality). Herein, we present compelling evidence linking mitochondrial apoptosis pathways to sepsis-induced cell and organ failure and discuss the implications in terms of future sepsis research.

Therapeutic potential of AIF-mediated caspase-independent programmed cell death

Resistance to anticancer drugs is often related to deficient cell death execution pathways in cancer cells. Apoptosis, which denotes a form of cell death executed by caspases, was traditionally considered as the only physiological and programmed form of cell death. However, recent evidence indicates that programmed cell death (PCD) can occur in complete absence of caspase activation. Indeed, a large number of caspase-independent models are now defined and a key protein implicated in this type of PCD, apoptosis-inducing factor (AIF), has been identified. AIF is a mitochondrial protein with two faces looking in opposite life/death directions. Recently, the identification of five different isoforms allowed a better characterization of AIFs life/mitochondrial versus death/nuclear functions, as well as definition of its pro-apoptotic region and some of its nuclear partners. Importantly, much work on caspase-independent PCD has revealed that AIF participates in more PCD systems than initially thought. A wider molecular knowledge of AIF, and of the caspase-independent PCDs in which it is involved, are key to provide new insights into the role of PCD. There is no doubt that these insights will lead to the development of more selective and efficient drugs against cancer, degenerative diseases, and other pathological disorders implicating AIF.

Methods to dissect mitochondrial membrane permeabilization in the course of apoptosis

In several paradigms of cell death, mitochondrial membrane permeabilization (MMP) delimits the frontier between life and death. Mitochondria control the intrinsic pathway of apoptosis and participate in the extrinsic pathway. Moreover, they have been implicated in nonapoptotic cell death modalities. Irrespective of its initiation at the inner or the outer mitochondrial membrane (IM and OM, respectively), MMP culminates in the functional (dissipation of the mitochondrial transmembrane potential, shutdown of ATP synthesis, redox imbalance) and structural (reorganization of cristae, release of toxic intermembrane space proteins into the cytosol) collapse of mitochondria. This has a profound impact on cellular metabolism, activates caspase-dependent and -independent executioner mechanisms, and finally results in the demise of the cell. However, the partial and/or temporary permeabilization of one or both mitochondrial membranes is not always a prelude to cell death. This chapter proposes a method and several guidelines to discriminate between IM and OM permeabilization and to identify MMP that does indeed precede cell death. This approach relies on the integration of currently available techniques and may be easily introduced in the laboratory routine for a more precise detection of cell death.

Guggulsterone inhibits adipocyte differentiation and induces apoptosis in 3T3-L1 cells

OBJECTIVE

To determine the effects of guggulsterone (GS), the active substance in guggulipid, on apoptosis, adipogenesis, and lipolysis using 3T3-L1 cells.

METHODS AND PROCEDURES

For apoptosis and lipolysis experiments, mature adipocytes were treated with GS isomers. Viability, apoptosis, and caspase 3/7 activation were quantified using MTS, enzyme-linked immunosorbent assay (ELISA), caspase-Glo 3/7 activity assay, respectively. The expression of cytochrome c was demonstrated by western blot. Lipolysis was quantified by measuring the release of glycerol. For adipogenesis experiments, postconfluent preadipocytes were incubated with GS isomers for up to 6 days during maturation. Adipogenesis was quantified by measuring lipid content using Nile Red dye. Western blot was also used to demonstrate the adipocyte-specific transcription factors peroxisome proliferator-activated receptor gamma2 (PPARgamma2), CCAAT/enhancer binding protein alpha (C/EBPalpha), and C/EBPbeta.

RESULTS

In mature adipocytes cis-GS decreased viability, whereas the trans-GS isomer had little effect. Both isomers caused dose-dependent increases in apoptosis and cis-GS was more effective than trans-GS in inducing apoptosis. cis- and trans-GS also increased caspase-3 activity and release of cytochrome c from mitochondria. In maturing preadipocytes, both isomers were equally effective in reducing lipid content. The adipocyte-specific transcription factors PPARgamma2, C/EBPalpha, and C/EBPbeta were downregulated after treatment with cis-GS during the maturation period. Furthermore, cis-GS increased basal lipolysis of mature adipocytes, but trans-GS had no effect.

DISCUSSION

These results indicate that GS isomers may exert antiobesity effects by inhibiting differentiation of preadipocytes, and by inducing apoptosis and promoting lipolysis of mature adipocytes. The cis-GS isomer was more potent than the trans-GS isomer in inducing apoptosis and lipolysis in mature adipocytes.

Oridonin induces human epidermoid carcinoma A431 cell apoptosis through tyrosine kinase and mitochondrial pathway

Oridonin, a diterpenoid isolated from the plant Rabdosia rubescens, induces human epidermoid carcinoma A431 cell death through apoptosis and tyrosine kinase pathway. To examine the pathway of oridonin-induced A431 cell death, morphologic observation, lactate dehydrogenase activity-based assay, DNA agarose gel electrophoresis and Western blot analysis were carried out. When A431 cells, which overexpress epidermal growth factor receptor (EGFR), were treated with oridonin, caspase-3 was activated followed by the degradation of caspase-3 substrates, inhibitor of caspase-activated DNase (ICAD) and poly(ADP-ribose) polymerase (PARP) in a time-dependent manner. Oridonin promoted the release of cytochrome c and the down-regulation of mitochondrial transmembrane potential (DeltaPsim). Oridonin up-regulated the expression ratio of mitochondrial proteins, Bax/Bcl-2. In addition, the total tyrosine kinase activity of A431 cellular proteins and the expression of EGFR were markedly reduced after oridonin treatment. Taken together, oridonin induced apoptosis in A431 cells via mitochondrial pathway, activation of caspase-3 and inhibition of tyrosine kinase activities.

Kainate-induced mitochondrial oxidative stress contributes to hippocampal degeneration in senescence-accelerated mice

We have demonstrated that kainate (KA) induces a reduction in mitochondrial Mn-superoxide dismutase (Mn-SOD) expression in the rat hippocampus and that KA-induced oxidative damage is more prominent in senile-prone (SAM-P8) than senile-resistant (SAM-R1) mice. To extend this, we examined whether KA seizure sensitivity contributed to mitochondrial degeneration in these mouse strains. KA-induced seizure susceptibility in SAM-P8 mice paralleled prominent increases in lipid peroxidation and protein oxidation and was accompanied by significant impairment in glutathione homeostasis in the hippocampus. These findings were more pronounced in the mitochondrial fraction than in the hippocampal homogenate. Consistently, KA-induced decreases in Mn-SOD protein expression, mitochondrial transmembrane potential, and uncoupling protein (UCP)-2 expression were more prominent in SAM-P8 than SAM-R1 mice. Marked release of cytochrome c from mitochondria into the cytosol and a higher level of caspase-3 cleavage were observed in KA-treated SAM-P8 mice. Additionally, electron microscopic evaluation indicated that KA-induced increases in mitochondrial damage and lipofuscin-like substances were more pronounced in SAM-P8 than SAM-R1 animals. These results suggest that KA-mediated mitochondrial oxidative stress contributed to hippocampal degeneration in the senile-prone mouse.

Mitochondrial-targeted active Akt protects SH-SY5Y neuroblastoma cells from staurosporine-induced apoptotic cell death

Akt is a serine/threonine protein kinase that plays a vital role in promoting cellular survival. Predominantly cytosolic, upon stimulation with growth-factors or stress, active Akt translocates into mitochondria, but the functions of Akt in mitochondria are not yet fully understood. Mitochondria play a central role in apoptotic pathways and given Akt's functions in the cytoplasm, Akt in mitochondria may help preserve mitochondrial integrity during cellular stress. To test if the translocation of Akt into mitochondria is neuroprotective, adenoviral vectors expressing a constitutively active Akt, Ad-HA-Akt (DD), and a constitutively active Akt with a mitochondrial targeting signal, Ad-Mito-HA-Akt (DD), were generated. Human SH-SY5Y neuroblastoma cells expressing the adenoviral constructs were treated with staurosporine to initiate intrinsic apoptotic cell death and several aspects of the mitochondrial apoptotic pathway were evaluated. Expression of active Akt targeted to mitochondria was found to be sufficient to significantly reduce staurosporine-induced activation of caspase-3 and caspase-9, the release of cytochrome c from mitochondria, and Bax oligomerization at mitochondria. These findings demonstrate that intramitochondrial active Akt results in efficient protection against apoptotic signaling.

Rescuing neurons and glia: is inhibition of apoptosis useful?

Traumatic brain injury (TBI) represents a leading cause of death in western countries. Despite all research efforts we still lack any pharmacological agent that could effectively be utilized in the clinical treatment of TBI. Detailed unraveling of the pathobiological processes initiated by/operant in TBI is a prerequisite to the development of rational therapeutic interventions. In this review we provide a summary of those therapeutic interventions purported to inhibit the cell death (CD) cascades ignited in TBI. On noxious stimuli three major forms of CD, apoptosis, autophagia and necrosis may occur. Apoptosis can be induced either via the mitochondrial (intrinsic) or the receptor mediated (extrinsic) pathway; endoplasmic reticular stress is the third trigger of caspase-mediated apoptotic processes. Although, theoretically pan-caspase inhibition could be an efficient tool to limit apoptosis and thereby the extent of TBI, potential cross-talk between various avenues of CD suggests that more upstream events, particularly the preservation of the cellular energy homeostasis (cyclosporine-A, poly ADP ribose polymerase (PARP) inhibition, hypothermia treatment) may represent more efficient therapeutic targets hopefully also translated to the clinical care of the severely head injured.

Interferon-alpha induces transient upregulation of c-FLIP through NF-kappaB activation

Interferon-alpha (IFN-alpha) induces apoptosis in some cell types and promotes cell survival in other cell types, but the molecular mechanisms underlying distinct IFN-alpha-induced cell behaviours remain poorly understood. In the present study, we show that IFN-alpha induced the cellular FLICE (FADD-like interleukin-1 beta-converting enzyme) inhibitory protein (c-FLIP), which serves as a promoter of cell survival in human B lymphoma cells. IFN-alpha induction of transient upregulation of c-FLIP was partially abrogated by the NF-kappaB inhibitor BAY11-7082 (BAY). Pretreatment with BAY sensitized both Daudi and U266 cells to the IFN-alpha-induced loss of mitochondrial membrane potential (DeltaPsi(m)). IFN-alpha phosphorylated the PKC isoform PKCalpha at a threonine residue, and the PKCalpha/betaI inhibitor Go6976 abrogated upregulation of IFN-alpha-induced NF-kappaB activity, leading to sensitization of cells to IFN-alpha-induced apoptosis. To analyze the role of PKCalpha in the IFN-alpha-induced signaling, Daudi cells overexpressing a constitutively active mutant of PKCalpha (caPKCalpha) were used. The caPKCalpha-expressing Daudi cells were partially resistant to the IFN-alpha-induced loss of DeltaPsi(m), concomitant with elevated levels of c-FLIP protein. Together, these results demonstrate that IFN-alpha causes a transient upregulation of c-FLIP expression, at least through PKCalpha-mediated activation of NF-kappaB. The balance between IFN-alpha-induced pro-apoptotic and survival signals determines the cell fate. Thus, therapeutic intervention in this balance may be effective for treatment of patients with IFN-alpha-refractory tumours.

MEK activation suppresses CPT11-induced apoptosis in rat intestinal epithelial cells through a COX-2-dependent mechanism

Resistance to chemotherapeutic agents is one of the distinct features of cancer cells. We evaluate the role of activated MEK-ERK signaling in Camptotecin/irinotecan (CPT-11)-induced cell death using constitutively activated MEK1-transfected normal rat intestinal epithelial cells (IEC-caMEK cells). A CPT-11-induced inhibitory concentration of 50% was determined by WST assay. Apoptosis was evaluated by DNA staining and fragmented DNA analysis. Protein expressions were analyzed by western blotting. We also examined the role of cyclooxygenase-2 in the cell systems. IEC-caMEK cells possessed survival advantages compared to control cells. Apoptosis was remarkably suppressed in IEC-caMEK cells. Western blot analysis revealed increased expression of Bcl-2, Bcl-xL, Mcl-1, and COX-2 and decreased expression of Bak in IEC-caMEK cells. The COX-2 selective inhibitor ameliorated the antiapoptotic nature of IEC-caMEK cells. MEK activation suppressed CPT-11-induced apoptosis in IEC-caMEK cells via a COX-2- dependent mechanism. Therefore, MEK-ERK signaling may contribute to the drug-resistant nature of cancer cells.

Role of cyclophilin D in the resistance of brain mitochondria to the permeability transition

The mitochondrial permeability transition (MPT) is involved in both necrosis and apoptosis. Cyclophilin D (CypD) is an important component of the MPT. Brain mitochondria are more resistant to the MPT when compared to heart or liver mitochondria. We found that this increased resistance correlates with low expression of CypD in brain when compared to heart or liver. In newborn rats, sensitivity of brain mitochondria to the MPT and CypD expression are significantly higher than in mature animals. In an in vitro model of neuronal development, mitochondria in differentiated neuronal-like cells exert a higher calcium threshold toward MPT induction and express significantly less CypD when compared to undifferentiated precursor cells. Gain and loss of function experiments confirm the role of CypD in sensitivity to the MPT. Together our data indicate that the increased calcium threshold of brain mitochondria to the MPT correlates with low expression of CypD in brain; and that neuronal cells lose CypD during differentiation and become less sensitive to the MPT induction. This may be a protection mechanism that raises the threshold of brain tissue against injuries.

Induction of apoptosis by immature fruits of Prunus salicina Lindl. cv. Soldam in MDA-MB-231 human breast cancer cells

The goal of this study was to evaluate the anticancer effect of Prunus salicina Lindl. cv. Soldam at three maturity stages (immature, midmature and mature stages). Previous studies have shown that this fruit (plums) possesses hematopoiesis effects, prevents osteoporosis and has anti-mutagenic effects. An acetone extract of immature P. salicina Lindl. cv. Soldam fruit contained higher levels of total phenolics and condensed tannins than midmature and mature plums. The results showed that an acetone extract of immature plums possesses cytotoxic effects, which are related to the activity of the total polyphenols in the fruits. Apoptosis in MDA-MB-231 cells mediated by the immature plums was associated with an increase in Bax levels and a reduction in Bcl-2 levels and the cleavage of caspase 3, caspase 7, caspase 9 and poly-(ADP-ribose) polymerase. These results indicate that immature fruit of P . salicina Lindl. cv. Soldam can be regarded as a safe and promising new dietary source for decreasing the risk of developing breast cancer.

Characterization of membrane potential-dependent uptake of the novel PET tracer 18F-fluorobenzyl triphenylphosphonium cation

PURPOSE

Mitochondrial dysfunction has been attributed a critical role in the etiology and pathogenesis of numerous diseases, and is manifested by alterations of the organelle's membrane potential (Deltapsi(m)). This suggests that Deltapsi(m) measurement can be highly useful for diagnostic purposes. In the current study, we characterized the capability of the novel PET agent (18)F-fluorobenzyl triphenylphosphonium ((18)F-FBnTP) to assess Deltapsi(m), compared with the well-established voltage sensor (3)H-tetraphenylphosphonium ((3)H-TPP).

METHODS

(18)F-FBnTP and (3)H-TPP uptake under conditions known to alter Deltapsi(m) and plasma membrane potential (Deltapsi(p)) was assayed in the H345 lung carcinoma cell line. (18)F-FBnTP biodistribution was assessed in CD1 mice using dynamic PET and ex vivo gamma well counting.

RESULTS

(18)F-FBnTP and (3)H-TPP demonstrated similar uptake kinetics and plateau concentrations in H345 cells. Stepwise membrane depolarization resulted in a linear decrease in (18)F-FBnTP cellular uptake, with a slope (-0.58+/-0.06) and correlation coefficient (0.94+/-0.07) similar (p>0.17) to those measured for (3)H-TPP (-0.63+/-0.06 and 0.96+/-0.05, respectively). Selective collapse of Deltapsi(m) caused a substantial decrease in cellular uptake for (18)F-FBnTP (81.6+/-8.1%) and (3)H-TPP (85.4+/-6.7%), compared with control. Exposure to the proapoptotic staurosporine, known to collapse Deltapsi(m), resulted in a decrease of 68.7+/-10.1% and 71.5+/-8.4% in (18)F-FBnTP and (3)H-TPP cellular uptake, respectively. (18)F-FBnTP accumulated mainly in kidney, heart and liver.

CONCLUSION

(18)F-FBnTP is a mitochondria-targeting PET radiopharmaceutical responsive to alterations in membrane potential with voltage-dependent performance similar to that of (3)H-TPP. (18)F-FBnTP is a promising new voltage sensor for detection of physiological and pathological processes associated with mitochondrial dysfunction, such as apoptosis, using PET.

Silymarin enhanced cytotoxic effect of anti-Fas agonistic antibody CH11 on A375-S2 cells

Silymarin is a polyphenolic flavonoid from milk thistle (Silybum marianum), which has anti-inflammatory, cytoprotective as well as antioxidant effects. Our previous study demonstrated that silymarin has anti-apoptotic effect against UV irradiation. In this study, we assessed the effect of silymarin on anti-Fas agonistic antibody CH11-treated human malignant melanoma, A375-S2 cells. Pretreatment with silymarin (3 x 10(- 4) mol/L) significantly induced cell apoptosis in CH11-treated A375-S2 cells. Mitochondrial transmembrane potential (DeltaPsi(m)) was also down-regulated by silymarin pretreatment. Caspase-8, -9, -3 and pan-caspase inhibitors partially reversed silymarin-induced apoptosis of CH11-treated cells. The expression of Fas-associated proteins with death domain (FADD), a downstream molecule of the death receptor pathway, was increased by silymarin pretreatment, followed by cleavage of procaspase-8, whose activation induced cell apoptosis. Moreover, cleavage of procaspase-3 and digestion of its substrate, the inhibitor of caspase-activated DNase (ICAD), were also increased by silymarin pretreatment. These results suggested that silymarin could also exaggerate the apoptotic effect of anti-Fas agonistic antibody CH11 on A375-S2 cells.

Relationship between mitochondrial DNA damage and photoreceptor death in developing and adult retina, assessed in normal and degenerative rat strains

In this study, we used Real-Time PCR to study the correlation of mtDNA deletions and photoreceptor death by apoptosis in one normal (SD) and two different degenerative (RCS and P23H) rat strains. Our results show that, in the SD and RCS strains, mtDNA deletion frequency increased and fell during neonatal life, correlating with rates of photoreceptor death during the critical period of photoreceptor development, and into adulthood. Results suggest that mitochondrial damage occurs in close association with photoreceptor death, in the normal (SD) and fast degenerative (RCS) retinas. The lack of a similar association was observed in the slowly degenerative P23H-3 strain.

Effect of sydnone SYD-1, a mesoionic compound, on energy-linked functions of rat liver mitochondria

An important antitumour effect of SYD-1 (3-[4-chloro-3-nitrophenyl]-1,2,3-oxadiazolium-5-olate) has been shown. We now report the effects of this mesoionic compound on mitochondrial metabolism. SYD-1 (1.5 micromol mg(-1) protein) dose-dependently inhibited the respiratory rate by 65% and 40% in state 3 using sodium glutamate and succinate, respectively, as substrates. Phosphorylation efficiency was depressed by SYD-1, as evidenced by stimulation of the state 4 respiratory rate, which was more accentuated with glutamate ( approximately 180%) than with succinate ( approximately 40%), with 1.5 micromol mg(-1) protein of SYD-1. As a consequence of the effects on states 3 and 4, the RCC and ADP/O ratios were lowered by SYD-1 using both substrates, although this effect was stronger with glutamate. The formation of membrane electrical potential was inhibited by approximately 50% (1.5 micromol SYD-1mg(-1) protein). SYD-1 interfered with the permeability of the inner mitochondrial membrane, as demonstrated by assays of mitochondrial swelling in the presence of sodium acetate and valinomycin +K(+). SYD-1 (1.5 micromol mg(-1) protein) inhibited glutamate completely and succinate energized-mitochondrial swelling by 80% in preparations containing sodium acetate. The swelling of de-energized mitochondria induced by K(+) and valinomycin was inhibited by 20% at all concentrations of SYD-1. An analysis of the segments of the respiratory chain suggested that the SYD-1 inhibition site goes beyond the complex I and includes complexes III and IV. Glutamate dehydrogenase was inhibited by 20% with SYD-1 (1.5 micromol mg(-1) protein). The hydrolytic activity of complex F(1)F(o) ATPase in intact mitochondria was greatly increased ( approximately 450%) in the presence of SYD-1. Our results show that SYD-1 depresses the efficiency of electron transport and oxidative phosphorylation, suggesting that these effects may be involved in its antitumoural effect.

The role of calcium, P38 MAPK in dihydroartemisinin-induced apoptosis of lung cancer PC-14 cells

INTRODUCTION

Dihydroartemisinin (DHA), a semi-synthetic derivative of artemisinin isolated from the traditional Chinese herb Artemisia annua, is an effective novel antimalarial drug. Recent studies suggest that it also has anticancer effect.

PURPOSE

The present study was designed to investigate the effects of DHA on cultured human lung cancer cells (PC-14 cells) to better understand its apoptosis and apoptosis-related factors in vitro.

METHODS

The cell viability was measured by MTT assay. The apoptosis induction was examined by DNA ladder and flow cytometry. The intracellular-free calcium concentration in the lung cancer cells were evaluated by laser scanning confocal microscopy with Fura-3/AM as probe. The associated gene expression was examined by Western blot.

RESULTS

After treatment with DHA, a decrease in the viability of PC-14 cells and apoptosis were observed. DHA-induced apoptosis were accompanied by an increase of Ca(2+) and activation of p38. Deleted levels of Ca(2+) by BAPTA-AM 20 microM or inhibition of p38 by its selective inhibitor SB202190 then led to decreased DHA-induced apoptosis.

CONCLUSIONS

These results demonstrated that DHA can induce apoptosis of lung cancer cell line PC-14 cells and calcium and p38 play important roles in the apoptotic signalling pathways.

Mitochondria: a hub of redox activities and cellular distress control

In their reductionist approach in unraveling phenomena inside the cell, scientists in recent times have focused attention to mitochondria. An organelle with peculiar evolutionary history and organization, it is turning out to be an important cell survival switch. Besides controlling bioenergetics of a cell it also has its own genetic machinery which codes 37 genes. It is a major source of generation of reactive oxygen species, acts as a safety device against toxic increases of cytosolic Ca2+ and its membrane permeability transition is a critical control point in cell death. Redox status of mitochondria is important in combating oxidative stress and maintaining membrane permeability. Importance of mitochondria in deciding the response of cell to multiplicity of physiological and genetic stresses, inter-organelle communication, and ultimate cell survival is constantly being unraveled and discussed in this review. Mitochondrial events involved in apoptosis and necrotic cell death, such as activation of Bcl-2 family proteins, formation of permeability transition pore, release of cytochrome c and apoptosis inducing factors, activation of caspase cascade, and ultimate cell death is the focus of attention not only for cell biologists, but also for toxicologists in unraveling stress responses. Mutations caused by ROS to mitochondrial DNA, its inability to repair it completely and creation of a vicious cycle of mutations along with role of Bcl-2 family genes and proteins has been implicated in many diseases where mitochondrial dysfunctions play a key role. New therapeutic approaches toward targeting low molecular weight compounds to mitochondria, including antioxidants is a step toward nipping the stress in the bud.

Transfection of hepatic stimulator substance gene desensitizes hepatoma cells to H2O2-induced cell apoptosis via preservation of mitochondria

Hepatic stimulator substance (HSS) protects liver cells from various toxins. However, the mechanism by which HSS protects hepatocytes remains unclear. In this study, we report that the HSS gene, after transfection into BEL-7402 hepatocma cells, is stably expressed in the mitochondria. Hydrogen peroxide (H(2)O(2))-induced cell apoptosis in the HSS-transfected cells is reduced, as shown by morphologic analysis. In the HSS-transfected cells, disruption of mitochondrial transmembrane potential (MTP) and cytochrome c leakage are reduced. The anti-apoptotic gene Bcl-2 is also highly expressed. In addition, ATP levels in the HSS-transfected cells are maintained. In conclusion, in hepatoma cells, HSS gene expression protects cells against H(2)O(2) injury, and this effect is likely to be associated with preservation of mitochondria.

Cadmium induces apoptosis in human embryonic kidney (HEK) 293 cells by caspase-dependent and -independent pathways acting on mitochondria

Cadmium (Cd) is a well-known toxic compound for the kidney in vivo and in vitro. It has been demonstrated to induce nephrotoxicity via in part by apoptotic cell death, but the precise mechanism is still unclear. Therefore, we have studied the effects of Cd on HEK 293 cells and investigated the mechanisms of Cd-induced apoptosis. Studies of morphology and oligonucleosomal DNA fragmentation demonstrated that 30-60 microM Cd induced apoptosis as early as 6-9h with strong effects on MTT activity, whereas 120 microM Cd revealed mainly necrosis, and the result of flow cytometry confirmed it. A concomitant time-dependent decrease of mitochondrial transmembrane potential (DeltaPsi(m)) and Bcl-2 expression was observed, subsequently, release of cytochrome c (Cyt c) and activation of caspase-3 were detected, suggesting a caspase-dependent pathway. Meanwhile, mitochondrial AIF was released to cytoplasm and nucleus, suggesting a caspase-independent pathway. Furthermore, when cells were transfected with pcDNA3/Bcl-2 before exposed to CdCl(2), alleviated apoptosis was assessed by part of the apoptotic features in this study. Taken together, our results showed that CdCl(2) caused time- and dose-dependent apoptosis or even necrosis in HEK 293 cells depending on the exposure conditions. The apoptotic events may involve mitochondrial disruption including both caspase-dependent and -independent pathways.

Activation of cell signaling pathways is dependant on the biotype of bovine viral diarrhea viruses type 2

Bovine viral diarrhea virus (BVDV), a pestivirus of the Flaviviridae family, is an economically important cattle pathogen with a worldwide distribution. Besides the segregation into two distinct species (BVDV1/BVDV2) two different biotypes, a cytopathic (cp) and a noncytopathic (ncp) biotype, are distinguished based on their behavior in epithelial cell cultures. One of the most serious forms of BVDV infection affecting immunocompetent animals of all ages is severe acute BVD (sa BVD) which is caused by highly virulent ncp BVDV2 strains. Previous studies revealed that these highly virulent ncp viruses cause cell death in a lymphoid cell line (BL3) which is not clearly associated with typical apoptotic changes (e.g. PARP cleavage) observed after infection with cp BVDV. To further characterize the underlying molecular mechanisms, we first analyzed the role of the mitochondria and caspases as key mediators of apoptosis. Compared to infection with cp BVDV2, infection with highly virulent ncp BVDV2 resulted in a delayed and less pronounced disruption of the mitochondrial transmembrane potential (DeltaPsi(m)) and a weaker activation of the caspase cascade. In contrast, infection with low virulence ncp BVDV2 showed no significant differences from the uninfected control cells. Since different pro- and anti-apoptotic cellular signaling pathways may become activated upon virus infection, we compared the effect of different BVDV2 strains on cellular signaling pathways in BL3 cells. Stress-mediated p38 MAPK phosphorylation was detected only in cells infected with cp BVDV2. Interestingly, infection with highly virulent ncp BVDV2 was found to influence the phosphoinositide 3-kinase (PI3K)-Akt pathway. This indicates that BL3 cells respond differently to infection with BVDV depending on virulence and biotype.

Geldanamycin, an inhibitor of Hsp90 increases cytochrome P450 2E1 mediated toxicity in HepG2 cells through sustained activation of the p38MAPK pathway

Cytochrome P450 2E1 (CYP2E1) can mediate reactive oxygen species (ROS) induced cell death through its catalytic processes. Heat shock protein 90 (Hsp90) is an important molecular chaperone which is essential for cellular integrity. We previously showed that inhibition of Hsp90 with Geldanamycin (GA), an inhibitor of Hsp90 increased CYP2E1 mediated toxicity in CYP2E1 over-expressing HepG2 cells (E47 cells) but not in C34-HepG2 cells devoid of CYP2E1 expression. The aim of the present study was to test the hypothesis that the potentiation of CYP2E1 toxicity in E47 cells with GA may involve changes in mitogen activated protein kinase signal transduction pathways. GA was toxic to E47 cells and SB203580, an inhibitor of p38 MAPK prevented this decrease in viability. The protective effects of SB203580 were effective only when SB203580 was added before GA treatment. GA activated p38 MAPK in E47 cells and this activation was an early and a sustained event. GA elevated ROS levels and lipid peroxidation and lowered GSH levels in E47 cells and these changes were blunted or prevented by treatment with SB203580. Apoptosis was increased by GA and prevented by pre-treatment with SB203580. The loss in mitochondrial membrane potential in E47 cells after GA treatment was also decreased significantly with SB203580 treatment. The activity and expression of CYP2E1 and Hsp90 levels were not altered by SB203580. In conclusion, the inhibition of Hsp90 with GA increases the toxicity of CYP2E1 in HepG2 cells through an early and sustained activation of the p38 MAPK pathway.

Steep pulsed electric fields modulate cell apoptosis through the change of intracellular calcium concentration

A steep electric pulsed field with low intensity (150-250V/cm) and relative long time (10 min) was applied to adherent liver cancer cell line SMMC-7721 and the liver cell line HL-7702. Results showed that the electric field with intensity of 200 and 250V/cm could trigger cell apoptosis, whereas the SMMC-7721 cell was more sensitive to the electric stimulation than the HL-7702 cell. Laser Scanning Confocal Microscope (LSCM) was used to measuring the real-time change of cytosolic free Ca(2+) concentration. When cells were exposed electric pulses with 100V/cm intensity for 10 min, there was no significant change of intracellular calcium concentration. With the intensity increased to 200 and 250V/cm, intracellular calcium concentration decreased significantly. Results demonstrated the relationship between the apoptosis and change of intracellular calcium concentration. And the steep electric pulsed field can be used to the cancer therapy.

Different behavior of agmatine in liver mitochondria: inducer of oxidative stress or scavenger of reactive oxygen species?

Agmatine, at concentrations of 10 microM or 100 microM, is able to induce oxidative stress in rat liver mitochondria (RLM), as evidenced by increased oxygen uptake, H(2)O(2) generation, and oxidation of sulfhydryl groups and glutathione. One proposal for the production of H(2)O(2) and, most probably, other reactive oxygen species (ROS), is that they are the reaction products of agmatine oxidation by an unknown mitochondrial amine oxidase. Alternatively, by interacting with an iron-sulfur center of the respiratory chain, agmatine can produce an imino radical and subsequently the superoxide anion and other ROS. The observed oxidative stress causes a drop in ATP synthesis and amplification of the mitochondrial permeability transition (MPT) induced by Ca(2+). Instead, 1 mM agmatine generates larger amounts of H(2)O(2) than the lower concentrations, but does not affect RLM respiration or redox levels of thiols and glutathione. Indeed, it maintains the normal level of ATP synthesis and prevents Ca(2+)-induced MPT in the presence of phosphate. The self-scavenging effect against ROS production by agmatine at higher concentrations is also proposed.

Role of intracellular calcium and phospholipase A2 in arachidonic acid-induced toxicity in liver cells overexpressing CYP2E1

Liver cells (HepG2 and primary hepatocytes) overexpressing CYP2E1 and exposed to arachidonic acid (AA) were previously shown to lose viability together with enhanced lipid peroxidation. These events were blocked in cells pre-incubated with antioxidants (alpha-tocopherol, glutathione ethyl ester), or in HepG2 cells not expressing CYP2E1. The goal of the current study was to evaluate the role of calcium and calcium-activated hydrolases in these CYP2E1-AA interactions. CYP2E1-expressing HepG2 cells treated with AA showed an early increase in cytosolic calcium and partial depletion of ionomycin-sensitive calcium stores. These changes in calcium were blocked by alpha-tocopherol. AA activated phospholipase A2 (PLA2) in CYP2E1-expressing liver cells, and this was inhibited by PLA2 inhibitors or alpha-tocopherol. PLA2 inhibitors prevented the cell death caused by AA, without affecting CYP2E1 activity or lipid peroxidation. AA toxicity and PLA2 activation were inhibited in calcium-depleted cells, but not by removal of extracellular calcium alone. Removal of extracellular calcium inhibited the early increase in cytosolic calcium caused by AA. CYP2E1 overexpressing HepG2 cells exposed to AA showed a decrease in mitochondrial membrane potential, which was prevented by the PLA2 inhibitors. These results suggest that AA-induced toxicity to CYPE1-expressing cells: (i) is associated with release of Ca2+ from intracellular stores that depends mainly on oxidative membrane damage; (ii) is associated with activation of PLA2 that depends on intracellular calcium and lipid peroxidation; (iii) does not depend on increased influx of extracellular calcium, and (iv) depends on the effect of converging events (lipid peroxidation, intracellular calcium, activation of PLA2) on mitochondria to induce bioenergetic failure and necrosis. These interactions may play a role in alcohol liver toxicity, which requires polyunsaturated fatty acids, and involves induction of CYP2E1.

Antisense-mediated melanoma inhibitor of apoptosis protein downregulation sensitizes G361 melanoma cells to cisplatin

Malignant melanoma is an aggressive form of skin cancer that is highly resistant to conventional therapies. The melanoma inhibitor of apoptosis protein is a potent inhibitor of apoptosis and is overexpressed in melanoma cells, but undetectable in most normal tissues including melanocytes. We designed 20-mer phosphorothioate antisense oligonucleotides complementary to five putatively single-stranded sites on the melanoma inhibitor of apoptosis protein mRNA and investigated their ability to sensitize G361 melanoma cells to cisplatin. Inhibition of melanoma inhibitor of apoptosis protein mRNA and protein expression were measured by real-time polymerase chain reaction and immunoblotting. Cell viability and apoptosis were quantitated by colorimetric viability assays and by annexin V staining, respectively. Oligonucleotide M706 was identified as the most efficient antisense sequence which downregulated melanoma inhibitor of apoptosis protein mRNA and protein levels in G361 cells by 68 and 78%, respectively. The specificity of target downregulation was confirmed using scrambled sequence control oligonucleotides that only marginally decreased melanoma inhibitor of apoptosis protein expression. Whereas downregulation of melanoma inhibitor of apoptosis protein moderately inhibited cell growth by 26%, in combination with cisplatin, this resulted in a supra-additive effect with almost 57% reduction in G361 cell viability compared with cisplatin alone (17%) (P<0.05). Cell death was mainly due to apoptosis as demonstrated by a 3- to 4-fold increase in annexin V-positive cells and typical morphological changes compared with controls. In summary, we describe a new antisense oligonucleotide that efficiently downregulates melanoma inhibitor of apoptosis protein expression and sensitizes melanoma cells to cisplatin.

Mitochondrial permeability transition induced by novel pyridothiopyranopyrimidine derivatives: Potential new antimitochondrial antitumour agents

New pyridothiopyranopyrimidine derivatives (PTP1 and PTP2) were synthesised. Evaluation of the antiproliferative activity showed a significant capacity of the two compounds to inhibit cell growth. Investigation of the mechanism of action reveals that PTP1 interferes with the mitochondrial functions by inducing both swelling of the mitochondrial matrix and collapse of the electrical potential. These phenomena are fully prevented by typical inhibitors of the mitochondrial permeability transition, and are accompanied by the release of cytochrome c in the cytosol. The estimation of the redox state of thiol groups and glutathione suggests that the induction of permeability transition mediated by PTP1 is the result of an oxidative stress. The ability of cyclosporin A to prevent the antiproliferative effect of PTP1 indicates the induction of mitochondrial permeability transition as the molecular event responsible for the inhibition of cell growth. PTP1 also induces DNA fragmentation in intact cells. As regards PTP2, the presence of the p-toluensulphonamido group makes the lead chromophore unable to induce any effect on mitochondria.

Involvement of mitochondria and caspase pathways in N-demethyl-clarithromycin-induced apoptosis in human cervical cancer HeLa cell

AIM

To study the mechanisms by which N-demethyl-clarithromycin (NDC) induces human cervical cancer HeLa cell apoptosis in vitro.

METHODS

The viability of N-demethyl-clarithromycin-induced HeLa cells was measured by MTT assay. Apoptotic cells with condensed nuclei were visualized by phase contrast microscopy. Nucleosomal DNA fragmentation was assayed by agarose gel electrophoresis. Measurement of mitochondrial transmembrane potential was analyzed by a FACScan flowcytometer. Caspase-3, poly-(ADP-ribose) polymerase (PARP), caspase-activated DNase (ICAD), Bcl-2, Bax, p53, and SIRT1 protein expression and the release of cytochrome c were detected by Western blot analysis.

RESULTS

N-demethyl-clarithromycin, an anti-inflammatory substance, inhibited HeLa cell growth in a dose- and time-dependent manner. N-demethyl-clarithro-mycin induced HeLa cell death through the apoptotic pathways. The pan-caspase inhibitor (z-VAD-fmk), caspase-3 inhibitor (z-DEVD-fmk) and the caspase-9 inhibitor (z-LEHD-fmk) partially enhanced cell viability induced by N-demethyl-clarithromycin, but the caspase-8 inhibitor (z-IETD-fmk) had almost no effect. Caspase-3 was activated then followed by the degradation of caspase-3 substrates, the inhibitor of ICAD and PARP. Simultaneously, mitochondrial transmembrane potential was markedly reduced and the release of cytochrome c in the cytosol was increased. N-demethyl-clarithromycin upregulated the expression ratio of mitochondrial Bax/Bcl-2, and significantly increased the expression of the p53 protein. It also downregulated anti-apoptotic protein SIRT1 expression.

CONCLUSION

N-demethyl-clarithromycin induced apoptosis in HeLa cells via the mitochondrial pathway.

Induction of apoptosis in rat lymphocytes by starvation

The aim of the present study was to investigate whether fasting for 24 and 48 h induces apoptosis of rat mesenteric lymph node lymphocytes similar to that observed previously in diabetic patients and alloxan-induced diabetic rats. Several features of lymphocyte death were evaluated by flow cytometry. Plasma levels of glucose, NEFAs (non-esterified fatty acids) and ketone bodies (acetoacetate and β-hydroxybutyrate) were determined in rats fasted for 24 and 48 h. Lymphocytes obtained from fasted rats had an increase in DNA fragmentation and phosphatidylserine externalization after 48 h of culture, although there was no loss of membrane integrity in lymphocytes even after 48 h of culture. Cytochrome c release from the mitochondrial intermembrane space into the cytosol was increased significantly in lymphocytes from fasted rats cultured for 24 h, whereas the levels of bcl-2 and bax proteins were not affected. Activities of caspases 3, 6, 8 and 9 were increased significantly in lymphocytes from rats fasted for 24 h, whereas only an increase in caspase 3 and 9 activities were observed in rats fasted for 48 h. In conclusion, fasting for 24 and 48 h caused a significant increase in the proportion of lymphocytes undergoing apoptosis. The occurrence of apoptosis was observed by DNA fragmentation, phosphatidylserine externalization, cytochrome c release from the mitochondria and activation of the caspase cascade. These findings support the hypothesis that conditions that raise plasma fatty acids levels (e.g. diabetes and starvation) may impair immune function by causing lymphocyte death.