A rapid and transient ROS generation by cadmium triggers apoptosis via caspase-dependent pathway in HepG2 cells and this is inhibited through N-acetylcysteine-mediated catalase upregulation

Although reactive oxygen species (ROS) have been implicated in cadmium (Cd)-induced hepatotoxicity, the role of ROS in this pathway remains unclear. Therefore, we attempted to determine the molecular mechanisms relevant to Cd-induced cell death in HepG2 cells. Cd was found to induce apoptosis in the HepG2 cells in a time- and dose-dependent fashion, as confirmed by DNA fragmentation analysis and TUNEL staining. In the early stages, both rapid and transient ROS generation triggered apoptosis via Fas activation and subsequent caspase-8-dependent Bid cleavage, as well as by calpain-mediated mitochondrial Bax cleavage. The timing of Bid activation was coincided with the timing at which the mitochondrial transmembrane potential (MMP) collapsed as well as the cytochrome c (Cyt c) released into the cytosol. Furthermore, mitochondrial permeability transition (MPT) pore inhibitors, such as cyclosporin A (CsA) and bongkrekic acid (BA), did not block Cd-induced ROS generation, MMP collapse and Cyt c release. N-acetylcysteine (NAC) pretreatment resulted in the complete inhibition of the Cd-induced apoptosis via catalase upregulation and subsequent Fas downregulation. NAC treatment also completely blocked the Cd-induced intracellular ROS generation, MMP collapse and Cyt c release, indicating that Cd-induced mitochondrial dysfunction may be regulated indirectly by ROS-mediated signaling pathway. Taken together, a rapid and transient ROS generation by Cd triggers apoptosis via caspase-dependent pathway and subsequent mitochondrial pathway. NAC inhibits Cd-induced apoptosis through the blocking of ROS generation as well as the catalase upregulation.     

Induction of apoptosis in human hepatoblastoma cells by tetrandrine via caspase-dependent Bid cleavage and cytochrome c release

Tetrandrine, a bis-benzylisoquinoline alkaloid from the root of Stephania tetrandra, induces apoptosis in human T-cell lines, lung carcinoma and hepatoblastoma cells. However, the mechanisms by which tetrandrine inhibits tumor cell growth are poorly understood. The purpose of the present study was to investigate the intracellular signaling mechanism of tetrandrine-induced apoptosis in HepG2 cells. The induction of apoptosis was determined by morphological analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Treatment of cells with tetrandrine caused the upregulation of p53, downregulation of Bcl-X(L), cleavage of Bid and Bax, and release of cytochrome c, which were accompanied by activation of caspases 9, 3 and 8. The activation of caspases 9 and 3 preceded that of caspase 8. A broad-spectrum caspase inhibitor and a caspase 8-specific inhibitor completely blocked tetrandrine-induced Bid processing, cytochrome c release, activation of caspase 3, and cell death. These findings and data showing the early release of cytochrome c, cleavage of Bid and downregulation of Bcl-X(L) suggest that the mitochondrial pathway is primarily involved in tetrandrine-induced apoptosis. The activation of caspase 8 after early caspases 9 and 3 activation might act as an amplification loop for activation of upstream signals such as Bid cleavage or cytochrome c release. These data suggest that tetrandrine may constitute a plausible therapeutic for hepatocellular carcinoma.     

Apoptosis induction by the dual-action DNA- and protein-reactive antitumor drug irofulven is largely Bcl-2-independent

The overexpression of Bcl-2 is implicated in the resistance of cancer cells to apoptosis. This study explored the potential of irofulven (hydroxymethylacylfulvene, HMAF, MGI 114, NSC 683863), a novel DNA- and protein-reactive anticancer drug, to overcome the anti-apoptotic properties of Bcl-2 in HeLa cells with controlled Bcl-2 overexpression. Irofulven treatment resulted in rapid (12hr) dissipation of the mitochondrial membrane potential, phosphatidylserine externalization, and apoptotic DNA fragmentation, with progressive changes after 24hr. Bcl-2 overexpression caused marginal or partial inhibition of these effects after treatment times ranging from 12 to 48hr. Both Bcl-2-dependent and -independent responses to irofulven were abrogated by a broad-spectrum caspase inhibitor. Despite the somewhat decreased apoptotic indices, cell growth inhibition by irofulven was unaffected by Bcl-2 status. In comparison, Bcl-2 overexpression drastically reduced apoptotic DNA fragmentation by etoposide, acting via topoisomerase II-mediated DNA damage, but had no effect on apoptotic DNA fragmentation by helenalin A, which reacts with proteins but not DNA. Irofulven retains its pro-apoptotic and growth inhibitory potential in cell lines that have naturally high Bcl-2 expression. Collectively, the results implicate multiple mechanisms of apoptosis induction by irofulven, which may differ in time course and Bcl-2 dependence. It is possible that the sustained ability of irofulven to induce profound apoptosis and to block cell growth despite Bcl-2 overexpression may be related to its dual reactivity with both DNA and proteins.     

Critical role of free cytosolic calcium, but not uncoupling, in mitochondrial permeability transition and cell death induced by diclofenac oxidative metabolites in immortalized human hepatocytes

Diclofenac is a widely used nonsteroidal anti-inflammatory drug that has been associated with rare but serious hepatotoxicity. Experimental evidence indicates that diclofenac targets mitochondria and induces the permeability transition (mPT) which leads to apoptotic cell death in hepatocytes. While the downstream effector mechanisms have been well characterized, the more proximal pathways leading to the mPT are not known. The purpose of this study was to explore the role of free cytosolic calcium (Ca(2+)(c)) in diclofenac-induced cell injury in immortalized human hepatocytes. We show that exposure to diclofenac caused time- and concentration-dependent cell injury, which was prevented by the specific mPT inhibitor cyclosporin A (CsA, 5 microM). At 8 h, diclofenac caused increases in [Ca(2+)](c) (Fluo-4 fluorescence), which was unaffected by CsA. Combined exposure to diclofenac/BAPTA (Ca(2+) chelator) inhibited cell injury, indicating that Ca(2+) plays a critical role in precipitating mPT. Diclofenac decreased the mitochondrial membrane potential, DeltaPsi(m) (JC-1 fluorescence), even in the presence of CsA or BAPTA, indicating that mitochondrial depolarization was not a consequence of the mPT or elevated [Ca(2+)](c). The CYP2C9 inhibitor sulphaphenazole (10 microM) protected from diclofenac-induced cell injury and prevented increases in [Ca(2+)](c), while it had no effect on the dissipation of the DeltaPsi(m). Finally, diclofenac exposure greatly increased the mitochondria-selective superoxide levels secondary to the increases in [Ca(2+)](c). In conclusion, these data demonstrate that diclofenac has direct depolarizing effects on mitochondria which does not lead to cell injury, while CYP2C9-mediated bioactivation causes increases in [Ca(2+)](c), triggering the mPT and precipitating cell death.     

Capsaicin-induced apoptosis is regulated by endoplasmic reticulum stress- and calpain-mediated mitochondrial cell death pathways

Capsaicin, a pungent compound found in hot chili peppers, induces apoptotic cell death in various cell lines, however, the precise apoptosis signaling pathway is unknown. Here, we investigated capsaicin-induced apoptotic signaling in the human breast cell line MCF10A and found that it involves both endoplasmic reticulum (ER) stress and calpain activation. Capsaicin inhibited growth in a dose-dependent manner and induced apoptotic nuclear changes in MCF10A cells. Capsaicin also induced degradation of tumor suppressor p53; this effect was enhanced by the ER stressor tunicamycin. The proteasome inhibitor MG132 completely blocked capsaicin-induced p53 degradation and enhanced apoptotic cell death. Capsaicin treatment triggered ER stress by increasing levels of IRE1, GADD153/Chop, GRP78/Bip, and activated caspase-4. It led to an increase in cytosolic Ca²⁺, calpain activation, loss of the mitochondrial transmembrane potential, release of mitochondrial cytochrome c, and caspase-9 and -7 activation. Furthermore, capsaicin-induced the mitochondrial apoptotic pathway through calpain-mediated Bid translocation to the mitochondria and nuclear translocation of apoptosis-inducing factor (AIF). Capsaicin-induced caspase-9, Bid cleavage, and AIF translocation were blocked by calpeptin, and BAPTA and calpeptin attenuated calpain activation and Bid cleavage. Thus, both ER stress- and mitochondria-mediated death pathways are involved in capsaicin-induced apoptosis.     

Necrotic and apoptotic features of cell death in response to Foscan photosensitization of HT29 monolayer and multicell spheroids

Photodynamic therapy (PDT) is an approved anticancer treatment modality that eliminates unwanted cells by the photochemical generation of reactive oxygen species following absorption of visible light by a photosensitizer, which is selectively taken up by tumor cells. Present study reports the modalities of cell death after photosensitization of human adenocarcinoma HT29 monolayer and spheroid cells with a second generation photosensitizer Foscan. Kinetics of apoptosis and necrosis after Foscan-PDT in monolayer cells determined by flow cytometry using labeling of cleaved poly(ADP-ribose) polymerase (PARP) and staining with propidium iodide (PI) demonstrated that Foscan was not a strong inducer of apoptosis and necrosis was a prevailing mode of cell death. Cytochrome c release (cyt c) and mitochondrial membrane potential (Deltapsim) addressed by flow cytometry technique at different time points post-Foscan-PDT demonstrated that cell photoinactivation was governed by these mitochondrial events. Foscan-loaded HT29 multicell spheroids, subjected to irradiation with different fluence rates and equivalent light doses, displayed much better tumoricidal activity at the lowest fluence rate used. Apoptosis, measured by caspase-3 activation was evidenced only in spheroids irradiated with the lowest fluence rate and moderate fluence inducing 65% of cell death. Application of higher fluence rates for the same level of photocytotoxicity did not result in caspase-3 activation. The observation of the fluence rate-dependent modulation of caspase-3 activity in spheroids offers the possibility of regulating the mechanism of direct cell photodamage and could be of great potential in the clinical context.     

Reactive oxygen species-independent rapid initiation of mitochondrial apoptotic pathway by chelerythrine

Chelerythrine, formerly identified as a protein kinase C inhibitor, has also been shown to inhibit the anti-apoptotic Bcl-2 family proteins. However, recent studies have now demonstrated that chelerythrine can induce the loss of mitochondrial membrane potential (ΔΨ_m), a membrane permeability transition (MPT), and the subsequent activation of the mitochondrial apoptotic pathway, even in the cells deficient in Bax and Bak. This suggests the existence of an alternative Bax/Bak-independent pathway for apoptosis. The generation of reactive oxygen species (ROS) from the mitochondrial electron transport chain (ETC) is also implicated in the cytotoxity elicited by chelerythrine. In our current study, we show that chelerythrine induces the rapid apoptotic death of H9c2 cardiomyocyte-derived cells within 8 min of treatment. The proteolytic activation of caspase9 and caspase3, crucial mediators of the mitochondrial apoptotic pathway, are also observed within 6 min of exposure to this drug. The generation of ROS is detected but at only marginal levels in the treated cells. The inhibition of the mitochondrial ETC by rotenone and malonate had almost no effects on ROS generation but in both cases effectively inhibited both cell death and the caspase activation induced by chelerythrine. Hence, chelerythrine initiates the rapid mitochondrial apoptotic death of H9c2 cardiomyoblastoma cells in a manner that is likely independent of the generation of ROS from mitochondria.     

Mitochondria as an important target in heavy metal toxicity in rat hepatoma AS-30D cells

The mechanisms of toxic effects of divalent cations of three heavy metals Hg, Cd and Cu in rat ascites hepatoma AS-30D cells cultivated in vitro were compared. It was found that the toxicity of these ions, applied in the micromolar range (10-500 microM), decreased from Hg(2+) (most toxic) to Cu(2+) (least toxic). Hg(2+) and Cd(2+) produced a high percentage of cell death by both necrosis and apoptosis, whereas Cu(2+) at concentrations up to 500 microM was weakly effective. Hg(2+) at concentration of 10 microM appeared slightly uncoupling (i.e., stimulated resting state respiration and decreased the mitochondrial transmembrane potential), whereas it exerted a strong inhibitory effect on the respiratory chain and rapid dissipation of the membrane potential at higher concentrations. Cu(2+) had inhibitory effect on cell respiration only at 500 microM concentration and after incubation of 48 h but produced a significant uncoupling effect at lower concentrations. Cu(2+) induced an early and sharp increase of intracellular production of reactive oxygen species (ROS). The action of Hg(2+) and Cd(2+) on ROS generation was biphasic. They stimulated ROS generation within the cells at low concentrations and at short incubation times but decreased ROS generation at higher concentrations and at longer incubation. It is concluded that mitochondria are an important target for toxic effects of Hg(2+), Cd(2+) and Cu(2+) in AS-30D rat hepatoma cells.     

Anti-benzopyrene-7,8-diol-9,10-epoxide induces apoptosis via mitochondrial pathway in human bronchiolar epithelium cells independent of the mitochondria permeability transition pore

Anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) is a ubiquitous environmental pollutant contained in tobacco smoke, automobile exhausts and barbecued foods. The carcinogenicity of BPDE on animals has been well characterized, whereas its apoptotic effect is not well defined. A recent study has shown that BPDE-mediated apoptotic pathway has varying specificity across different cell lines. Squamous cell carcinoma (SCC) arises from bronchiolar epithelium cells, therefore, we set out to investigate the pulmonary toxicity and apoptotic effect of BPDE in human bronchiolar epithelium cells (16HBE). Our results show BPDE induces mitochondrial-mediated apoptosis in a dose-dependent manner in 16HBE cells. The cleavage of caspase-3,-9 and release of Cytochrome c (cyt c) was regulated during apoptotic stimulation. However, the opening of mitochondria permeability transition pore (mPTP) has not been detected. Furthermore, our data also indicate that the formation of reactive oxygen species (ROS), decline of mitochondrial membrane potential (ΔΨ_m), increasing p53 and decreasing c-Myc levels play important roles in response to BPDE toxicity. In conclusion, these results suggest that BPDE-mediated apoptosis occurs via caspase-9 dependent mitochondria pathway associated with ROS formation, loss of ΔΨ_m, up-regulation of p53 and down-regulation of c-Myc, but independent of the opening of mPTP in 16HBE cells.     

Protection by ascorbic acid from denaturation and release of cytochrome c, alteration of mitochondrial membrane potential and activation of multiple caspases induced by H(2)O(2), in human leukemia cells

We investigated peroxide and superoxide accumulation, cytochrome c nature and release from mitochondria, as well as caspase activation during exposure of HL-60 cells to H(2)O(2) and the protective effect of ascorbic acid. Exposure of the cells to 100 microM H(2)O(2) resulted in intracellular accumulation of peroxides, denaturation of cytochrome c that was identified in the mitochondria and cytosol, release of native cytochrome c to the cytosol and fall in mitochondrial membrane potential (DeltaPsi(m)). Loading of cells with ascorbic acid before exposure to H(2)O(2) resulted in a dose-dependent protective effect against: intracellular accumulation of peroxides, DeltaPsi(m) alteration, cytochrome c denaturation and release. The accumulation of peroxides induced processings and activations of procaspase-8, -9 and -3. Double staining with antiserum which recognizes the p18 subunit of cleaved caspase-3 and with Hoechst had shown that a high percentage of cells exposed to 100 microM H(2)O(2) stained positively with the antibody and showed features of apoptosis. Ascorbic acid loading prevented caspase activation induced by H(2)O(2). We conclude that ascorbic acid protects against activation of apoptotic cascades in HL-60 cells exposed to H(2)O(2) and against apoptosis.     

Pyrogallol-induced calf pulmonary arterial endothelial cell death via caspase-dependent apoptosis and GSH depletion

Pyrogallol (PG) as a polyphenol induces apoptosis in cells. Here, we evaluated the effects of PG on the growth and death of endothelial cells (ECs). PG dose-dependently inhibited the growth of calf pulmonary artery endothelial cells (CPAEC) and human umbilical vein endothelial cells (HUVEC). PG also induced apoptosis in both cells accompanied by the loss of mitochondrial membrane potential (ΔΨ_m). CPAEC were more sensitive to PG than HUVEC concerning cell growth and death. Caspase inhibitors (pan-caspase, caspase-3, -8 or -9 inhibitor) did not affect the growth inhibition of CPAEC by PG. However, pan-caspase inhibitor (Z-VAD) significantly reduced apoptosis and the loss of ΔΨ_m in PG-treated CPAEC. PG reduced ROS level and increased GSH depleted cell numbers in CPAEC. While Z-VAD increased ROS levels in PG-treated CPAEC, it decreased GSH depleted cell numbers. In conclusion, PG inhibited the growth of ECs, especially CPAEC via caspase-dependent apoptosis and GSH depletion.     

Carbazolequinone induction of caspase-dependent cell death in Src-overexpressing cells

We previously reported that RSV-transformed quail neuroretina cells (QNR-ts68) were highly resistant to apoptosis provoked by serum withdrawal, and that this property was due to v-Src kinase activity. The present study investigates the cytotoxic effect and the functional mechanism of carbazolequinone-mediated cell death in this system. QNR-ts68 cells were subjected to carbazolequinone treatment and both growth inhibition and cell death induction were examined using formazan assays. Cell death mechanism (both apoptosis and necrosis) was confirmed through phosphatidyl serine exposure and propidium iodide incorporation. Furthermore, the effect of active carbazolequinone was inhibited by a pan caspase inhibitor. Cytofluorimetric and immunofluorescence data demonstrated the activation of caspase-3 and the involvement of mitochondria. Therefore, this study clearly indicates that carbazolequinones could induce cell death in transformed cells displaying high levels of antiapoptotic tyrosine kinase activity. Further investigations would be necessary to elucidate the mechanisms by which these carbazolequinones act as antitumor agents.     

Peripheral benzodiazepine receptor ligands: mitochondrial transmembrane potential depolarization and apoptosis induction in rat C6 glioma cells

The peripheral benzodiazepine receptor (PBR) is a component of a multiprotein complex, located at the contact site between the inner and outer mitochondrial membranes, which constitutes the mitochondrial permeability transition (MPT)-pore. The opening of the MPT-pore, leading to the transmembrane mitochondrial potential (DeltaPsi(m)) dissipation, is a critical event in the mechanism of apoptosis. In the present work, we investigated the ability of the specific PBR ligands, PK 11195 or Ro5-4864, to affect mitochondrial potential and to induce apoptotic cell death in rat C6 glioma cells. Both specific ligands inhibited cell survival in a dose- and time-dependent manner, as assessed by MTS conversion assay, whereas the non-site selective ligand Diazepam or the low-affinity benzodiazepine Clonazepam showed no significant effects. After cell exposure to PK 11195 or Ro5-4864 we evidenced typical alterations of apoptotic cell death such as DNA fragmentation and chromatin condensation assessed by flow cytometric and transmission electron microscopy (TEM) analysis, respectively. Activation of the "effector" caspase-3 confirmed the ability of specific PBR ligands to induce apoptosis. Moreover, PK 11195 and Ro5-4864 induced a decrease of DeltaPsi(m), as evidenced by JC-1 flow cytometry analysis. Our data demonstrate the pro-apoptotic effects of specific PBR ligands on rat C6 glioma cells.     

Two-step formation of 1H NMR visible mobile lipids during apoptosis of paclitaxel-treated K562 cells

Despite increasing evidence on the formation of 1H NMR-detectable mobile lipid (ML) domains in cells induced to programmed cell death by continuous exposure to anticancer drugs, the time course of ML generation during the apoptotic cascade has not yet been fully elucidated. The present study shows that ML formation occurs at two different stages of apoptosis induced in human erythroleukemia K562 cells by a brief (3 hr) exposure to paclitaxel (Taxol), an antitumour drug with a stabilising effect on microtubules, or to paclitaxel plus tyrphostin AG957, a selective inhibitor of the p210(BCR-ABL) tyrosine kinase activity. A first wave of ML generation was in fact detected in paclitaxel-treated cells at the onset of the effector phase (8-24hr after exposure to the drug), plateaued at 24-48 hr and was eventually followed by further ML accumulation during the degradative phase (48-72 hr). Addition of AG957 to paclitaxel shifted to the 3-8 hr interval in both the early ML production and the onset of apoptotic events, such as chromatin condensation, phosphatidylserine externalization, cytochrome c release and caspase-3 activation. A significant loss of mitochondrial membrane potential was almost concomitant with the second wave of ML accumulation, associated in both cell systems with the phase of terminal cell degeneration, likely connected to non-regulated degradation of cell lipid components.     

17Alpha-estradiol arrests cell cycle progression at G2/M and induces apoptotic cell death in human acute leukemia Jurkat T cells

A pharmacological dose (2.5-10 μM) of 17α-estradiol (17α-E₂) exerted a cytotoxic effect on human leukemias Jurkat T and U937 cells, which was not suppressed by the estrogen receptor (ER) antagonist ICI 182,780. Along with cytotoxicity in Jurkat T cells, several apoptotic events including mitochondrial cytochrome c release, activation of caspase-9, -3, and -8, PARP degradation, and DNA fragmentation were induced. The cytotoxicity of 17α-E₂ was not blocked by the anti-Fas neutralizing antibody ZB-4. While undergoing apoptosis, there was a remarkable accumulation of G₂/M cells with the upregulatoin of cdc2 kinase activity, which was reflected in the Thr56 phosphorylation of Bcl-2. Dephosphorylation at Tyr15 and phosphorylation at Thr161 of cdc2, and significant increase in the cyclin B1 level were underlying factors for the cdc2 kinase activation. Whereas the 17α-E₂-induced apoptosis was completely abrogated by overexpression of Bcl-2 or by pretreatment with the pan-caspase inhibitor z-VAD-fmk, the accumulation of G₂/M cells significantly increased. The caspase-8 inhibitor z-IETD-fmk failed to influence 17α-E₂-mediated caspase-9 activation, but it markedly reduced caspase-3 activation and PARP degradation with the suppression of apoptosis, indicating the contribution of caspase-8; not as an upstream event of the mitochondrial cytochrome c release, but to caspase-3 activation. In the presence of hydroxyurea, which blocked the cell cycle progression at the G₁/S boundary, 17α-E₂ failed to induce the G₂/M arrest as well as apoptosis. These results demonstrate that the cytotoxicity of 17α-E₂ toward Jurkat T cells is attributable to apoptosis mainly induced in G₂/M-arrested cells, in an ER-independent manner, via a mitochondria-dependent caspase pathway regulated by Bcl-2.     

Diclofenac induces apoptosis in hepatocytes by alteration of mitochondrial function and generation of ROS

Diclofenac is a non-steroidal anti-inflammatory drug that is widely used clinically but side effects associated with the administration of the drug have been reported. The apoptotic effect of the drug has been evaluated in human and rat hepatocytes. Apoptosis was observed after exposure to sub-cytotoxic concentrations of the drug, without overlapping with cell necrosis. Flow cytometric analysis revealed a time- and dose-dependent increase of apoptotic nuclei with sub-diploid DNA content. Caspase 8 and 9 mediate the cell-receptor and the mitochondria-initiated apoptotic pathways, respectively. Inhibition of both caspases prevented activation of downstream caspases, thus indicating that diclofenac at least activates caspase 3 and both effector caspases 8 and 9. The hierarchy of caspase activation by diclofenac was investigated. Analysis of kinetics revealed a simultaneous activation of these caspases that was maximal after 12 hr of exposure to the drug. Inhibitors of MPT, prevented the downstream activation of the caspase cascade, thus showing that diclofenac opened the mitochondrial pore. On the other hand, antioxidants were able to prevent caspase activation by diclofenac, revealing that oxidative stress at the mitochondrial level is in the root of MPT induction and caspase cascade activation. Caspase activation is not mediated by Bid cleavage, suggesting that the cell-receptor pathway seems not to be involved. However, a dose-dependent release of caspase 8 from the mitochondria was observed, indicating that caspase 8 can be processed independently of cell death receptors. Caspases 8 and 9 are very likely the apical caspases in diclofenac-induced apoptosis. In addition, an early dose-dependent increase of bclX(L) expression parallel to the generation of reactive oxygen species in the mitochondria was found. In conclusion, the mitochondrial pathway is very likely the only pathway involved in diclofenac-induced apoptosis, which was related to CYP-mediated metabolism of diclofenac, with the highest apoptotic effect produced by the metabolite 5OH-diclofenac.     

Calcium ionophoretic and apoptotic effects of ferutinin in the human Jurkat T-cell line

We have investigated the ionophoretic and apoptotic properties of the daucane sesquiterpene ferutinin and three related compounds, ferutidin, 2-alpha-hydroxyferutidin and teferin, all isolated from various species of plants from the genus Ferula. Ferutinin induced a biphasic elevation of intracellular Ca2+ in the leukemia T-cell line, Jurkat. First, a rapid calcium peak was observed and inhibited by BAPTA-AM. This initial calcium mobilization was followed by a sustained elevation, mediated by the entry of extracellular calcium through L-type calcium channels and sensitive to inhibition by EGTA. Moreover, ferutinin-induced apoptosis in Jurkat cells, and this event was preceded, in a cyclosporine-A sensitive manner, by a loss of mitochondrial transmembrane potential (DeltaPsim) and by an increase in intracellular reactive oxygen species. Ferutinin-induced DNA fragmentation was mediated by a caspase-3-dependent pathway, and was initiated independently of any specific phase of the cell cycle. The evaluation of ferutinin analogs in calcium mobilization and apoptosis assays showed strict structure-activity relationships, with p-hydroxylation of the benzoyl moiety being requested for activity.     

Modulation of Bax/Bcl-2 and caspases by probiotics during acetaminophen induced apoptosis in primary hepatocytes

Oxidative stress is an important factor in drug induced hepatotoxicity and antioxidants from natural sources have potential to ameliorate it. The present study was aimed to investigate cyto-protective potential of probiotic Enterococcus lactis IITRHR1 (El_SN) and Lactobacillus acidophilus MTCC447 (La_SN) lysate against acetaminophen (APAP) induced hepatotoxicity. Cultured rat hepatocytes pretreated with El_SN/La_SN showed higher cell viability under APAP stress. Pre-treatment with El_SN, restored glutathione level and reduced ROS generation significantly which are major biomarkers of oxidative stress. It also reduced NO level, MDA formation and enhanced SOD activity. Pre-treatment with probiotic lysates significantly inhibited the translocation of pro-apoptotic protein (Bax), enhanced anti-apoptotic (Bcl-2) protein levels and prevented release of cyt c to cytosol; suggesting involvement of mitochondrial proteins in protection against APAP induced oxidative cellular damage. Loss in mitochondrial membrane potential due to APAP treatment was prevented in the presence of probiotic lysates. Protective action of El_SN/La_SN pretreatment was further supported by prevention of procaspase-3 activation, DNA fragmentation and chromatin condensation, in turn inhibiting APAP induced apoptotic cell death. The results indicate that probiotic preparations modulate crucial end points of oxidative stress induced apoptosis and may be used for management of drug induced liver injury.     

(−)-Anonaine induces apoptosis through Bax- and caspase-dependent pathways in human cervical cancer (HeLa) cells

(-)-Anonaine has been shown to have some anticancer activities, but the mechanisms of (-)-anonaine inducing cell death of human cancer cells is not fully understood. We investigated the mechanisms of apoptosis induced by (-)-anonaine in human HeLa cancer cells. Treatment with (-)-anonaine induces dose-dependent DNA damage that is correlated with increased intracellular nitric oxide, reactive oxygen species, glutathione depletion, disruptive mitochondrial transmembrane potential, activation of caspase 3, 7, 8, and 9, and poly ADP ribose polymerase cleavage. Our data indicate that (-)-anonaine up-regulated the expression of Bax and p53 proteins in HeLa cancer cells. The apoptosis and expression of Bax induced by (-)-anonaine could be inhibited when the HeLa cells were pretreated with Boc-Asp(OMe)-fmk, which is a broad caspases inhibitor. There was no obvious DNA damage in the (-)-anonaine-treated Madin-Darby canine kidney and Vero cell lines. Both Madin-Darby canine kidney and Vero cell lines are kidney epithelial cellular morphology. These results suggest that (-)-anonaine might be considered a potent compound for chemotherapy against cervical cancer or a health food supplement for cancer chemoprevention.