Changes in FADD levels,distribution, and phosphorylation in TNFα-induced apoptosis in hepatocytes is caspase-3, caspase-8 and BID dependent

FADD/MORT1 (The adaptor protein of Fas Associate Death Domain/Mediator of Receptor Induced Toxicity) is essential for signal transduction of death receptor signaling. We have previously shown that FADD is significantly up-regulated in TNFα/ActD induced apoptosis. Over-expression of FADD also induces death of lung cancer cells and primary hepatocytes. We hypothesize that the increase in detectable FADD levels require the proximal steps in apoptotic signaling and speculated that FADD would be redistributed in cells destined to undergo apoptosis. We show that monomeric non-phosphorylated FADD is up-regulated in hepatocytes treated with TNFα/ActD and that it accumulates in the cytoplasm. Nuclear phosphorylated FADD decreases with TNFα/ActD treatment. Dimeric FADD in the cytoplasm remains constant with TNFα/ActD. The change in FADD levels and distribution was dependent on caspase-3, caspase-8 activity and the presence of BID. Thus, changes in FADD levels and distribution are downstream of caspase activation and mitochondria changes that are initiated by the formation of the DISC complex. Changes in FADD levels and distribution may represent a novel feed-forward mechanism to propagate apoptosis signaling in hepatocytes. Xiaoying Zhang and Raghuveer Vallabhaneni contributed equally to the work.     

5-Phenylselenyl- and 5-methylselenyl-methyl-2′-deoxyuridine induce oxidative stress, DNA damage, and caspase-2-dependent apoptosis in cancer cells

In the present study, we investigated the signaling pathways implicated in the induction of apoptosis by two modified nucleosides, 5-phenylselenyl-methyl-2′-deoxyuridine (PhSe-T) and 5-methylselenyl-methyl-2′-deoxyuridine (MeSe-T), using human cancer cell lines. The induction of apoptosis was associated with proteolytic activation of caspase-3 and -9, PARP cleavage, and decreased levels of IAP family members, including c-IAP-1 and c-IAP-2, but had no effect on XIAP and survivin. PhSe-T and MeSe-T also enhanced the activities of caspase-2 and -8, Bid cleavage, and the conformational activation of Bax. Additionally, nucleoside derivative-induced apoptosis was inhibited by the selective inhibitors of caspase-2, -3, -8, and -9 and also by si-RNAs against caspase-2, -3, -8, and -9; however, inhibition of caspase-2 and -3 was more effective at preventing apoptosis than inhibition of caspase-8 and -9. Moreover, the inhibition of caspase-2 activation by the pharmacological inhibitor z-VDVAD-fmk or by the knockdown of protein expression using siRNA suppressed nucleoside derivative-induced caspase-3 activation, but not vice versa. PhSe-T and MeSe-T also induced a Δψ_m loss via a CsA-insensitive mechanism, ROS production, and DNA damage, including strand breaks. Moreover, ROS scavengers such as NAC, tiron, and quercetin inhibited nucleoside derivative-induced ROS generation and apoptosis by blocking the sequential activation of caspase-2 and -3, indicating the role of ROS in caspase-2-mediated apoptosis. Taken together, these results indicate that caspase-2 acts upstream of caspase-3 and that caspase-2 functions in response to DNA damage in both PhSe-T- and MeSe-T-induced apoptosis. Our results also suggest that ROS are critical regulators of the sequential activation of caspase-2 and -3 in nucleoside derivative-treated cancer cells.     

Evidence for a non-antioxidant,dose-dependent role of α -lipoic acid in caspase-3 and ERK2 activation in endothelial cells

Endothelial cell apoptosis contributes to atherosclerosis and may be exacerbated by oxidative stress. Results from clinical trials using antioxidant supplementation are equivocal and could be enhanced by antioxidants with additional non-antioxidant properties such as -lipoic acid and -tocopherol. The aim of this study was to investigate the effects of these antioxidants on cytoprotective pathways and endothelial apoptosis. Endothelial cells were incubated with -lipoic acid and -tocopherol, alone or in combination, prior to incubation with H₂O₂ or staurosporine. -lipoic acid pre-treatment alone increased caspase-3 activity in a dose-dependent manner. Both H₂O₂ and staurosporine increased DNA fragmentation and caspase-3 activity and pre-treatment of cells with -lipoic acid and/or -tocopherol failed to prevent stress-induced apoptosis. Neither antioxidant treatments nor apoptotic inducers alone altered expressions of Bcl-2, Bax, HSP70 or pERK1/2 or pJNK. -lipoic decreased pERK2 in staurosporine-treated cells in a dose-dependent manner. These findings indicate that pre-incubation with -lipoic acid and -tocopherol, alone or in combination, does not protect against oxidative- or non-oxidative-induced apoptosis in endothelial cells. Moreover, we have demonstrated a non-antioxidant, dose-dependent role of -lipoic acid in caspase-3 and ERK2 activation. These data provide an insight and indicate caution in the use of high doses of -lipoic acid as an antioxidant.     

Shenfu injection suppresses apoptosis by regulation of Bcl-2 and caspase-3 during hypoxia/reoxygenation in neonatal rat cardiomyocytes in vitro

Shenfu injection (the major components of which are ginsenosides compound, extract of Panax ginseng shown to have antioxidant properties) is a well-known important Chinese traditional medicine used for the treatment of various diseases especial for cardiac diseases. The precise mechanism of the biological actions of this plant is not fully understood, in order to elucidate the protection of cardiomyocytes. The aim of the present study was to investigate the effect of Shenfu injection on hypoxia/reoxygenation (H/R)-induced apoptosis and the expression of bcl-2 and caspase-3 in cultured neonatal rat cardiomyocytes in vitro. Ventricular myocytes were isolated from neonatal rat hearts and were exposed to 4 h of hypoxia followed by 16 h of reoxygenation. The results indicated that treatment with different doses of Shenfu injection protected cardiacmyocyte cultures from hypoxia/reoxygenation-induced apoptosis. Caspase-3 activation was decreased in hypoxic/reoxygenationed cardiomyocytes co-treated with Shenfu injection when compared to hypoxia/reoxygenation alone treated cultures. Expression of the Bcl-2 proteins was increased in Shenfu injection-treated cardiomyocytes subjected to hypoxia/reoxygenation. In conclusion, ginsenosides compound has obviously protective effects on cardiacmyocytes against apoptosis induced by hypoxia/reoxygenation injury, whose mechanisms probably involve the inhibition of down-regulation of Bcl-2 protein levels and sequential activation of caspase-3.     

Nifedipine prevents etoposide-induced caspase-3 activation, prenyl transferase degradation and loss in cell viability in pancreatic β-cells

Emerging evidence implicates novel roles for post-translational prenylation (i.e., farnesylation and geranylgeranylation) of various signaling proteins in a variety of cellular functions including hormone secretion, survival and apoptosis. In the context of cellular apoptosis, it has been shown previously that caspase-3 activation, a hallmark of mitochondrial dysregulation, promotes hydrolysis of several key cellular proteins. We report herein that exposure of insulin-secreting INS 832/13 cells or normal rat islets to etoposide leads to significant activation of caspase-3 and subsequent degradation of the common α-subunit of farnesyl/geranylgeranyl transferases (FTase/GGTase). Furthermore, the above stated signaling steps were prevented by Z-DEVD-FMK, a known inhibitor of caspase-3. In addition, treatment of cell lysates with recombinant caspase-3 also caused FTase/GGTase α-subunit degradation. Moreover, nifedipine, a calcium channel blocker, markedly attenuated etoposide-induced caspase-3 activation, FTase/GGTase α-subunit degradation in INS 832/13 cells and normal rat islets. Further, nifedipine significantly restored etoposide-induced loss in metabolic cell viability in INS 832/13 cells. Based on these findings, we conclude that etoposide induces loss in cell viability by inducing mitochondrial dysfunction, caspase-3 activation and degradation of FTase/GGTase α-subunit. Potential significance of these findings in the context of protein prenylation and β-cell survival are discussed.     

Bortezomib induces in HepG2 cells IκBα degradation mediated by caspase-8

Abstact The present paper demonstrates that the proteasome inhibitor bortezomib, which behaves as an apoptotic agent in hepatoma HepG2 cells, caused in these cells a decrease in IκBα level and a consequent increase in NF-κB activity. The effect already appeared at 4 h of treatment and preceded the onset of apoptosis which was observed at 24 h. Our results demonstrate that bortezomib-induced IκBα degradation occurred in conjunction with the activation of caspase-8; moreover, the decrease in IκBα level was prevented in a dose-dependent manner by the addition of z-IETD, a specific inhibitor of caspase-8. Bortezomib caused the same effects in non-tumor Chang liver cells, which were not susceptible to the apoptotic effect of the drug. Our results also show that other proteases, such as caspase-3 and calpains, exerted only a limited effect on IκBα degradation. These findings suggest that caspase-8 can be involved in the control of IκBα level. In addition, the activation of caspase-8 can exert, at least in the first phase of treatment with bortezomib, a protective effect in both HepG2 and Chang liver cells, favouring the activation of the survival factor NF-κB     

α-Tocopherol increases caspase-3 up-regulation and apoptosis by β-carotene cleavage products in human neutrophils

It has been found that β-carotene cleavage products (CarCP), besides having mutagenic and toxic effects on mitochondria due to their prooxidative properties, also initiate spontaneous apoptosis of human neutrophils. Therefore, it was expected that antioxidants such as α-tocopherol would inhibit the stimulation of apoptosis and caspase-3 activity by CarCP. However, we found that α-tocopherol increases caspase-3 up-regulation and stimulation of apoptosis of human neutrophils by CarCP. Ascorbic acid does not alter this caspase-3 up-regulating and proapoptotic effect exerted by α-tocopherol. Both α-tocopherol and ascorbic acid, in the absence of CarCP, decrease intracellular caspase-3 activity and spontaneous apoptosis of neutrophils. Uric acid alone or in combination with CarCP does not exert apparent effects on caspase-3 activity and apoptosis. Up-regulating effect of α-tocopherol is not observed in the presence of retinol that markedly stimulates apoptosis by itself, whereas increase of caspase-3 activity is induced by concomitant addition of α-tocopherol and β-ionone, a cyclohexenyl degradation product of β-carotene with shorter aliphatic chain.     

Calcium signaling in pancreatic β-cells in health and in Type 2 diabetes

Changes in cytosolic free Ca²⁺ concentration ([Ca²⁺]_c) play a crucial role in the control of insulin secretion from the electrically excitable pancreatic β-cell. Secretion is controlled by the finely tuned balance between Ca²⁺ influx (mainly through voltage-dependent Ca²⁺ channels, but also through voltage-independent Ca²⁺ channels like store-operated channels) and efflux pathways. Changes in [Ca²⁺]_c directly affect [Ca²⁺] in various organelles including the endoplasmic reticulum (ER), mitochondria, the Golgi apparatus, secretory granules and lysosomes, as imaged using recombinant targeted probes. Because most of these organelles have specific Ca²⁺ influx and efflux pathways, they mutually influence free [Ca²⁺] in the others. In this article, we review the mechanisms of control of [Ca²⁺] in various compartments and particularly the cytosol, the endoplasmic reticulum ([Ca²⁺]_ER), acidic stores and mitochondrial matrix ([Ca²⁺]_mito), focusing chiefly on the most important physiological stimulus of β-cells, glucose. We also briefly review some alterations of β-cell Ca²⁺ homeostasis in Type 2 diabetes.     

A caspase-3 ‘death-switch' in colorectal cancer cells for induced and synchronous tumor apoptosis in vitro and in vivo facilitates the development of minimally invasive cell death biomarkers

Novel anticancer drugs targeting key apoptosis regulators have been developed and are undergoing clinical trials. Pharmacodynamic biomarkers to define the optimum dose of drug that provokes tumor apoptosis are in demand; acquisition of longitudinal tumor biopsies is a significant challenge and minimally invasive biomarkers are required. Considering this, we have developed and validated a preclinical ‘death-switch'' model for the discovery of secreted biomarkers of tumour apoptosis using in vitro proteomics and in vivo evaluation of the novel imaging probe [¹⁸F]ML-10 for non-invasive detection of apoptosis using positron emission tomography (PET). The ‘death-switch'' is a constitutively active mutant caspase-3 that is robustly induced by doxycycline to drive synchronous apoptosis in human colorectal cancer cells in vitro or grown as tumor xenografts. Death-switch induction caused caspase-dependent apoptosis between 3 and 24 hours in vitro and regression of ‘death-switched'' xenografts occurred within 24 h correlating with the percentage of apoptotic cells in tumor and levels of an established cell death biomarker (cleaved cytokeratin-18) in the blood. We sought to define secreted biomarkers of tumor apoptosis from cultured cells using Discovery Isobaric Tag proteomics, which may provide candidates to validate in blood. Early after caspase-3 activation, levels of normally secreted proteins were decreased (e.g. Gelsolin and Midkine) and proteins including CD44 and High Mobility Group protein B1 (HMGB1) that were released into cell culture media in vitro were also identified in the bloodstream of mice bearing death-switched tumors. We also exemplify the utility of the death-switch model for the validation of apoptotic imaging probes using [¹⁸F]ML-10, a PET tracer currently in clinical trials. Results showed increased tracer uptake of [¹⁸F]ML-10 in tumours undergoing apoptosis, compared with matched tumour controls imaged in the same animal. Overall, the death-switch model represents a robust and versatile tool for the discovery and validation of apoptosis biomarkers.     

Menstrual-PGF2α, PGE2 and TXA2 in normal and dysmenorrheic women and their temporal relationship to dysmenorrhea

Although it has been demonstrated that primary dysmenorrhea is associated with elevated levels of PGF_2α in the menstrual fluid, little is actually known of the menstrual-PG profiles of either dysmenorrheic or normal women. In this study, menstrual fluid from normal and dysmenorrheic women was collected from tampons and extracted for PG-like substances. The PGF_2α, PGE₂ and TXA₂ content was analyzed by RIA.This study demonstrates that dysmenorrheics have significantly higher levels/concentrations of menstrual-PGF_2α and PGe₂ than do normal women, and that there is no difference in the menstrual-PGF_2α: PGE₂ ratio between the two groups. Also, there is no significant difference in the amount/concentration of menstrual-thromboxane between dysmenorrheic and normal women. Of the parameters considered, the levels/-concentrations of menstrual-PGF_2α, PGE₂ and TXA₂, dysmenorrheic pain correlates best with the rate of menstrual-PGF_2α release.     

ATM kinase promotes both caspase-8 and caspase-9 activation during TNF-α-induced apoptosis of HeLa cells

In this study, we show that atraxia telangiectasia mutated kinase (ATM) activity is generally upregulated by different apoptotic stimuli, i.e. TNF-α, TRAIL, paclitaxel, or UV. Apoptotic progression is markedly attenuated by siATM-RNA through down regulation of caspase-8 and caspase-9 in parallel with decreases in FLIP-S (short form of cellular FLICE inhibitory protein) protein levels and Bid cleavage. In addition, ATM activity is upregulated through t-Cdc6 while caspase-8 and caspase-9 activities increase. Taken together, we suggest that ATM regulates caspase-8 activation by influencing levels of FLIP-S, ATM kinase activity is upregulated by t-Cdc6, and increased ATM activity plays an essential role in the amplification of apoptosis in TNF-α-stimulated HeLa cells.     

Thymic stromal lymphopoietin is expressed and produced by caspase-1/NF-κB pathway in mast cells

Thymic stromal lymphopoietin (TSLP) plays a pivotal role in allergic diseases such as atopic dermatitis, asthma, and chronic obstructive pulmonary disease. Although there are many reports regarding function and regulatory mechanism of TSLP in dendritic cells and/or T cells, the regulatory mechanism of TSLP in mast cells has not been fully elucidated. Here, we describe how TSLP is expressed and produced by inflammatory stimulus in mast cells. TSLP mRNA was expressed by phorbol myristate acetate (PMA) plus A23187 stimulation in HMC-1 cells and reached its peak 5h after PMA plus A23187 stimulation. The expression of TSLP mRNA was inhibited by nuclear factor (NF)-κB inhibitor. In addition, NF-κB luciferase activity was inhibited by caspase-1 inhibitor, indicating that caspase-1 is an upstream of NF-κB in mast cells. Furthermore, caspase-1 inhibitor decreased the expression of TSLP mRNA induced by PMA plus A23187. Finally, TSLP production was inhibited by both caspase-1 inhibitor and NF-κB inhibitor. These results provide proof of principle that TSLP can be expressed and produced through caspase-1 and NF-κB in mast cells and open new perspectives to pharmacologically manipulate the expression and production of TSLP by molecules acting on the caspase-1 and NF-κB pathway.     

Mdmx and Mdm2: Brothers in Arms?

The p53 tumor suppressor pathway is inactivated in most if not all human tumors. In about 50% of the cases this is accomplished directly by gene mutations. The tumors that retain wild type p53 frequently show defects either in effector target genes, or in the expression of p53 regulatory proteins. The Mdm2 protein is generally considered THE master regulator of the p53 tumor suppressor activity. Recently, however, the Mdm2-related protein Mdmx is taking the stage in the p53-Mdm2-Mdmx play. We summarize here observations unambiguously assigning a critical role for the Mdmx protein in the regulation of p53 function during development and tumor formation.     

Diallyl sulfide induces apoptosis in Colo 320 DM human colon cancer cells: involvement of caspase-3, NF-κB, and ERK-2

Chemoprevention is regarded as one of the most promising and realistic approaches in the prevention of human cancer. Diallyl sulfide (DAS), an organosulfur component of garlic has been known for its chemopreventive activities against various cancers and also in recent years, numerous investigations have shown that sulfur-containing compounds induce apoptosis in multiple cell lines and experimental animals. Thus the present study was focused to elucidate the anticancerous effect and the mode of action of DAS against Colo 320 DM colon cancer cells. DAS induced apoptosis in Colo 320 DM cells was revealed by flow cytometer analysis and phosphatidyl serine exposure. DAS also promoted cell cycle arrest substantially at G2/M phase in Colo 320 DM cells. The production of reactive oxygen intermediates, which were examined by 2,7-dichlorodihydrofluorescein diacetate (H₂DCF-DA), increased with time, after treatment with DAS. The activities of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were decreased upon DAS treatment, which shows the antiproliferative and the cytotoxic effects, respectively. The expression of NF-κB was upregulated in DAS treated cells, compared to normal cells. Further, DAS promoted the expression of caspase-3 and suppression of Extracellular Regulatory Kinase-2 (ERK-2) activity in Colo 320 DM cells that was determined by Western blot analysis. In conclusion, DAS increased the production of ROS, caused cell cycle arrest, decreased cell proliferation and induced apoptosis in Colo 320 DM cells. Thus, this study put forward DAS as a drug that can possibly be used to treat cancers.     

Cyclooxygenases and prostaglandin E2 receptors in growth plate chondrocytes in vitro and in situ – prostaglandin E2 dependent proliferation of growth plate chondrocytes

Prostaglandin E₂ (PGE₂) plays an important role in bone development and metabolism. To interfere therapeutically in the PGE₂ pathway, however, knowledge about the involved enzymes (cyclooxygenases) and receptors (PGE₂ receptors) is essential. We therefore examined the production of PGE₂ in cultured growth plate chondrocytes in vitro and the effects of exogenously added PGE₂ on cell proliferation. Furthermore, we analysed the expression and spatial distribution of cyclooxygenase (COX)-1 and COX-2 and PGE₂ receptor types EP1, EP2, EP3 and EP4 in the growth plate in situ and in vitro. PGE₂ synthesis was determined by mass spectrometry, cell proliferation by DNA [³H]-thymidine incorporation, mRNA expression of cyclooxygenases and EP receptors by RT-PCR on cultured cells and in homogenized growth plates. To determine cellular expression, frozen sections of rat tibial growth plate and primary chondrocyte cultures were stained using immunohistochemistry with polyclonal antibodies directed towards COX-1, COX-2, EP1, EP2, EP3, and EP4. Cultured growth plate chondrocytes transiently secreted PGE₂ into the culture medium. Although both enzymes were expressed in chondrocytes in vitro and in vivo, it appears that mainly COX-2 contributed to PGE₂-dependent proliferation. Exogenously added PGE₂ stimulated DNA synthesis in a dose-dependent fashion and gave a bell-shaped curve with a maximum at 10^-8 M. The EP1/EP3 specific agonist sulprostone and the EP1-selective agonist ONO-D1-004 increased DNA synthesis. The effect of PGE₂ was suppressed by ONO-8711. The expression of EP1, EP2, EP3, and EP4 receptors in situ and in vitro was observed; EP2 was homogenously expressed in all zones of the growth plate in situ, whereas EP1 expression was inhomogenous, with spared cells in the reserve zone. In cultured cells these four receptors were expressed in a subset of cells only. The most intense staining for the EP1 receptor was found in polygonal cells surrounded by matrix. Expression of receptor protein for EP3 and EP4 was observed also in rat growth plates. In cultured chrondrocytes, however, only weak expression of EP3 and EP4 receptor was detected. We suggest that in growth plate chondrocytes, COX-2 is responsible for PGE₂ release, which stimulates cell proliferation via the EP1 receptor.     

Diel variation in lacunal CH4 and CO2 concentration and δ13C in Phragmites australis

We tested the hypothesis that the diurnal patterns of variationin lacunal gas concentrations and isotopic fractionationpreviously reported in a single plant genera (Typha)typified the patterns of all through-flow convective plantsby extending our observations to Phragmites australisCav. In daylight, Phragmites CH₄ transport isdriven by internal pressurization which results in gas flowdown young green culms and its exit from one year old deadbrown culms. Flow rates of 10.4 ± 4.0 mL min^–1 weremeasured in this study. At night, CH₄ is transportedfrom the sediments to the atmosphere via the lacunal plantspaces by molecular diffusion. Within green culms, lacunalCH₄ concentrations varied by a factor of 1000, from 3%(parts by volume) pre-dawn to lows of 25 ppmv during midday.Methane in brown culms varied by a factor of 10 diurnally,from 5% pre-dawn to 0.3% at midday. Lacunal CO₂concentrations varied similarly.Concentrations of both gases varied inversely with lacunalpressure. In green culms, large isotopic fractionations wereobserved in CH₄ and CO₂ in the morning and eveningduring transitions in gas transport mode and were associatedwith slight downward flows counter to the upward diffusionof these gases. Methane ¹³C as depletedas –100 was observed. In daylight, lacunal CH₄ wassimilar to or ¹³C depleted relative to sedimentary andemitted CH₄ isotopic values, but at night lacunalCH₄ was ¹³C enriched relative to sedimentarymethane. Overall, the diurnal variations of CH₄concentration and ¹³C value inPhragmiteswere similar to those observed in Typha andindicate that these patterns should be consistent in otherconvective-flow plants. Furthermore, our results demonstratethat the large isotopic fractionations found in aquaticplants can result solely from isotopic fractionationassociated with gas transport.     

Effect of γ-irradiation on F-2 and T-2 toxin production in corn and rice

Fusarium graminearum andF. tricinctum were grown on moistened corn and rice. After inoculation the substrates were exposed to γ-irradiation and growth rate together with mycotoxin production were measured. A delay in mycelium growth and an increase in F-2 and T-2 toxin production occurred after irradiation with 1 and 3 kGy. The maximum F-2 production was 10.7 mg/kg on rice at 3 kGy, whereas T-2 was 735 μg/kg on rice at 3 kGy. At 9 kGy neither growth nor toxin production could be detected in any inoculated corn and rice substrate.