Regulation of apoptosis by Bcl-2 family proteins

Involvement of mitochondrial pathway in NCTD-induced cytotoxicity in human hepG2 cells

BACKGROUND

Norcantharidin, the demethylated analog of cantharidin derived from a traditional Chinese medicine, Mylabris, has been used in the treatment of anti-cancer effects. However, the detailed mechanisms underlying this process are generally unclear. The aim of this study was to investigate the mechanism of NCTD-induced apoptosis in HepG2 cells.

METHODS

The cytotoxicity was measured by MTT assay for cellular viability and by flow cytometry. The mitochondrial membrane potential and reactive oxygen species production was evaluated by flow cytometry analysis. The role of caspase activities were assayed using caspase apoptosis detection kit . Western blot analysis was used to evaluate the level of Cyto-C, Bcl-2, Bax, Bid, caspase 3, -9, -8 and PARP expression

RESULTS

After treatment with NCTD, a decrease in the viability of HepG2 cells and increase in apoptosis were observed. NCTD-induced apoptosis was accompanied by an increase in ROS production, loss of mitochondrial membrane potential and release of cytochrome c(cyto-c) from the mitochondria to the cytosol and down-regulation of anti-apoptotic protein Bcl-2 levels with concurrent up-regulation in pro-apoptotic protein Bax levels. However, another pro-apoptotic molecule, Bid, showed no change in such same treatment. NCTD-increased activity of caspase 9,caspase 3 and the subsequent cleavage caspase substrate PARP were also observed. The expression levels of pro-caspase-8 were not changed after NCTD treatment.

CONCLUSION

These results indicate that NCTD induced cytotoxicity in HepG2 cells by apoptosis, which is mediated through ROS generation and mitochondrial pathway.

Analysis of apoptosis and Bcl-2 expression in polar forms of leprosy

Apoptosis eliminates pathogen-infected cells. Its modulation can influence the course of infections, permitting the survival of intracellular pathogens. In leprosy, which presents several clinical manifestations related to bacillary burden and host immune status, the mechanisms responsible for the persistence of the bacillus are unknown. Few studies have focused on apoptosis over the disease spectrum and as a defense mechanism against Mycobacterium leprae. We evaluated apoptosis using terminal transferase dUTP nick end labeling and the expression of Bcl-2 by immunohistochemistry in skin lesions from 11 tuberculoid and 15 lepromatous leprosy patients. Each specimen was evaluated by determining the number of positive cells in 10 fields at × 400 magnification. We observed a higher number of apoptotic cells in tuberculoid lesions in comparison with lepromatous leprosy (42.5 cells per 10 fields vs. 11.5 cells per 10 fields, P<0.0001). Expression of Bcl-2, conversely, was larger in lepromatous than in tuberculoid samples (172.0 cells per 10 fields vs. 17.7 cells per 10 fields, P<0.0001). These observations suggest modulation of apoptosis in leprosy, primarily in lepromatous patients, for which the decrease in cell death could support M. leprae survival and contribute to the success of infection. Conversely, in tuberculoid patients, apoptosis could contribute to reducing propagation of the bacillus.

An integrated microfluidic cell array for apoptosis and proliferation analysis induction of breast cancer cells

In vitro sensitivity testing of tumor cells could rationalize and improve the choice of chemotherapy and hormone therapy. In this report, a microfluidic device made from poly(dimethylsiloxane) and glass was developed for an assay of drug induced cytotoxicity. We evaluated the apoptotic and proliferation-inhibitory effects of anticancer drugs mitomycin C (MMC) and tamoxifen (TAM) using MCF-7 breast cancer cells. MMC and TAM both induced apoptosis and inhibited proliferation of MCF-7 cells in a concentration-dependent manner. MMC caused the expression of antiapoptotic protein Bcl-2 a dose-dependent reduction in MCF-7 cells. The expression of Bcl-2 did not change significantly in MCF-7 cells treated by TAM. The results in the microfluidic device were correlated well with the data obtained from the parallel experiments carried out in the conventional culture plates. The developed microfluidic device could be a potential useful tool for high content screening and high throughput screening research.

The cytotoxic mechanism of malondialdehyde and protective effect of carnosine via protein cross-linking/mitochondrial dysfunction/reactive oxygen species/MAPK pathway in neurons

The accumulation of malondialdehyde (MDA), a lipid peroxidation by-product that has been used as an indicator of cellular oxidation status, is significantly increased in many neurological diseases such as brain ischemia/reperfusion, Alzheimer's disease and Parkinson's disease in vivo. In the present study, we found that MDA treatment in vitro reduced cortical neuronal viability in a time- and dose-dependent manner and induced cellular apoptosis as well as necrosis simultaneously. Furthermore, exposure to MDA led to accumulation of intracellular reactive oxygen species, dysfunction of mitochondria (denoted by the loss of mitochondrial transmembrane potential (Δψm)) and activation of JNK and ERK. Carnosine exhibited better protection against MDA-induced cell injury than antioxidant N-acetyl-cysteine (NAC) with its multi-potency, which alleviated MDA-induced protein cross-linking, Δψm decrease, reactive oxygen species burst, JNK and ERK activation. In conclusion, our results suggest that MDA induced cell injury in vitro via protein cross-linking and successive mitochondrial dysfunction, and the activation of reactive oxygen species-dependent MAPK signaling pathway. Carnosine alleviated all these alterations induced by MDA, but NAC merely inhibited Bcl-2 family-related activation of JNK and ERK. These results prompt the possibility that carnosine, but not other conventional antioxidants, can protect neurons against MDA-induced injury through decomposition of protein cross-linking toxicity and may serve as a novel agent in the treatment of neurodegenerative diseases.

Vitamin E transport, membrane incorporation and cell metabolism: Is alpha-tocopherol in lipid rafts an oar in the lifeboat?

Vitamin E is composed of closely related compounds, including tocopherols and tocotrienols. Studies of the last decade provide strong support for a specific role of alpha-tocopherol in cell signalling and the regulation of gene expression. It produces significant effects on inflammation, cell proliferation and apoptosis that are not shared by other vitamin E isomers with similar antioxidant properties. The different behaviours of vitamin E isomers might relate, at least in part, to the specific effects they exert at the plasma membrane. alpha-Tocopherol is not randomly distributed throughout the phospholipid bilayer of biological membranes, and as compared with other isomers, it shows a propensity to associate with lipid rafts. Distinct aspects of vitamin E transport and metabolism is discussed with emphasis on the interaction between alpha-tocopherol and lipid rafts and the consequences of these interactions on cell metabolism.

Carthamus tinctorius L. prevents LPS-induced TNFalpha signaling activation and cell apoptosis through JNK1/2-NFkappaB pathway inhibition in H9c2 cardiomyoblast cells

AIM OF THE STUDY

Severe and potentially fatal hypotension and cardiac contractile dysfunction are common symptoms in patients with sepsis. In our previous study, we found that estradiol and estrogen-receptor alpha have cardio-protective effects in myocardial cells exposed to LPS. Estradiol supplementation has been shown to induce breast and cervical cancers. Flos Carthami, the flower of Carthamus tinctorius L. (Compositae) is an important traditional Chinese medicine used for the treatment of heart disease and inflammation, and therefore might be a potential alternative to Estradiol in the prevention of heart damage. This study investigated the effect of Flos Carthami (FC(EtOH)) ethanolic extract on LPS-induced apoptosis in H9c2 cardiomyoblast cells.

MATERIALS AND METHODS

H9c2 cells induced apoptosis with LPS administration (1 microg/mL). H9c2 cells were divided into five groups: Control, LPS (1 microg/mL), and three FC(EtOH) (31.25, 62.5,and 125 microg/mL). We detected apoptosis using MTT, LDH, TUNEL assay. JC-1 staining and Western blot were used to detect pro-apoptosis proteins, anti-apoptosis proteins, MAPK proteins (JNK, ERK, and P38), and NFkappaB expression.

RESULTS

FC(EtOH) (62.5 microg/mL) inhibited LPS-induced apoptosis by suppressing JNK1/2 activity, which resulted in the reduction of both IkappaB degradation and NFkappaB activation. In addition, FC(EtOH) led to the activation of anti-apoptotic proteins, Bcl-2 and Bcl-xL, the stabilization of the mitochondria membrane and the down-regulation of extrinsic and intrinsic pro-apoptotic proteins, such as TNFalpha, active caspase-8, t-Bid, Bax, active caspases-9, and -3.

CONCLUSIONS

Carthamus tinctorius L. possesses the ability to suppress JNK activity and inhibit LPS-induced TNFalpha activation and apoptosis in H9c2 cardiomyoblast cells. Carthamus tinctorius L could potentially serve as a cardio-protective agent against LPS-induced apoptosis.

A novel polysaccharide, isolated from Angelica sinensis (Oliv.) Diels induces the apoptosis of cervical cancer HeLa cells through an intrinsic apoptotic pathway

A novel polysaccharide isolated from Angelica sinensis, named APS-1d showed cytotoxic activity towards several cancer cell lines in vitro. However, the precise antitumor mechanisms of this compound are unknown. In this study, we investigated the pro-apoptotic effects of APS-1d in human cervical cancer HeLa cells both in vitro and in vivo, and further elucidated the mechanisms of this action. Inhibition of HeLa cell proliferation was determined by MTT assay and the therapeutic efficacy of APS-1d was evaluated by human cancer xenografts in nude mice. Cell apoptosis was examined with flow cytometry and TUNEL assay. The mechanism of action of APS-1d was investigated by Western blot analysis. APS-1d decreased HeLa cell proliferation in a concentration- and time-dependent manner in vitro. In addition, APS-1d significantly inhibited tumor growth in athymic nude mice. Characteristic manifestations of apoptosis including apoptotic morphological features and the sub- G(0)/G(1) peaks were observed when the cells were treated with APS-1d. Further analysis showed that APS-1d-induced apoptosis was associated with the regulation of Bcl-2 family protein expression, a decrease in the mitochondrial membrane potential, and an increase in the cytosolic cytochrome c levels. Sequentially, APS-1d increased the activities of caspase-9, -3, and poly (ADP-ribose) polymerase in a concentration-dependent manner, however, no obvious activation of Bid and caspase-8 was observed. Pretreatment with Z-LEHD-FMK, a specific inhibitor of caspase-9, significantly attenuated APS-1d-induced cell apoptosis, and activation of caspase-3. Taken together, our studies indicate that APS-1d is capable of inhibiting HeLa cell proliferation and inducing apoptosis in these cells which primarily involves the activation of the intrinsic mitochondrial pathway.

An oxidative analogue of gambogic acid-induced apoptosis of human hepatocellular carcinoma cell line HepG2 is involved in its anticancer activity in vitro

The objective of this study was to investigate the apoptosis-inducing effect of an oxidative analogue of gambogic acid (GA) on the human hepatocellular carcinoma cell line HepG2 and explore the related molecular mechanisms. HepG2 cells were treated with the analogue of GA and the growth inhibition was analysed by MTT assay. The morphological changes in cells were observed under an inverted light microscope and a fluorescence microscope. In addition, both the cell-cycle arrest and the apoptosis rate were detected by flow cytometry. Western blot was used to evaluate the alteration of protein expression. The viability of HepG2 cells was markedly inhibited in a concentration-dependent manner and obvious morphological changes were confirmed, including condensed chromatin and reduced volume. Increased percentage of apoptotic cells was displayed and altered expression level of several apoptosis-associated proteins, P53, Bcl-2, Bax and pro-caspase-3, was obtained. The newly synthesized analogue of GA exhibited potential anticancer activity, induced remarkable apoptosis in HepG2 cells, probably through the intrinsic mitochondrial pathway, and promised to be a new candidate for future cancer therapy.

The role of cyclooxygenase-2 in cell proliferation and cell death in human malignancies

It is well admitted that the link between chronic inflammation and cancer involves cytokines and mediators of inflammatory pathways, which act during the different steps of tumorigenesis. The cyclooxygenases (COXs) are a family of enzymes, which catalyze the rate-limiting step of prostaglandin biosynthesis. This family contains three members: ubiquitously expressed COX-1, which is involved in homeostasis; the inducible COX-2 isoform, which is upregulated during both inflammation and cancer; and COX-3, expressed in brain and spinal cord, whose functions remain to be elucidated. COX-2 was described to modulate cell proliferation and apoptosis mainly in solid tumors, that is, colorectal, breast, and prostate cancers, and, more recently, in hematological malignancies. These findings prompt us to analyze here the effects of a combination of COX-2 inhibitors together with different clinically used therapeutic strategies in order to further improve the efficiency of future anticancer treatments. COX-2 modulation is a promising field investigated by many research groups.

Overexpression of hepatocyte nuclear factor-3alpha induces apoptosis through the upregulation and accumulation of cytoplasmic p53 in prostate cancer cells

BACKGROUND

Hepatocyte nuclear factor-3alpha (HNF-3alpha) has been known to act as a repressor in the pathogenesis of many cancers. Herein, we investigated the effect of HNF-3alpha overexpression in prostate cancer cells.

METHODS

HNF-3alpha was overexpressed in prostate cancer cells using an adenovirus recombinant expressing wild-type HNF-3alpha. The apoptosis of prostate cancer cells was determined by TUNEL, FACS, and caspase activity analyses.

RESULTS

Adenovirus-mediated overexpression of HNF-3alpha caused cell death in prostate cancer cells as assessed by changes in cellular and nuclear morphology, TUNEL analysis, and caspase activations. Furthermore, FACS analysis showed an increased sub-G1 phase of cell cycle as well as the G2/M phase with a corresponding decrease in S phases. HNF-3alpha overexpression caused the upregulation of p53 protein and its accumulation, together with HNF-3alpha, in the cytoplasm. It also causes Bax protein to localize to the mitochondria-enriched fraction. These findings suggest that multiple apoptotic pathways seem to be involved in the HNF-3alpha-induced cell death: pathways involving the accumulation of p53 protein in the cytoplasm and subsequent cytochrome c release, and other pathways involving death receptor signaling and caspase-8 activation.

CONCLUSIONS

The results of the current study suggest a novel function of HNF-3alpha as a killer of malignant prostate cancer cells, which reveals HNF-3alpha as a promising therapeutic molecule for prostate cancers.

Mechanisms guiding primordial germ cell migration: strategies from different organisms

The regulated migration of cells is essential for development and tissue homeostasis, and aberrant cell migration can lead to an impaired immune response and the progression of cancer. Primordial germ cells (PGCs), precursors to sperm and eggs, have to migrate across the embryo to reach somatic gonadal precursors, where they carry out their function. Studies of model organisms have revealed that, despite important differences, several features of PGC migration are conserved. PGCs require an intrinsic motility programme and external guidance cues to survive and successfully migrate. Proper guidance involves both attractive and repulsive cues and is mediated by protein and lipid signalling.

Granuloma formation induced by low-dose chronic silica inhalation is associated with an anti-apoptotic response in Lewis rats

Chronic human silicosis results primarily from continued occupational exposure to silica and exhibits a long asymptomatic latency. Similarly, continued exposure of Lewis rats to low doses of silica is known to cause delayed granuloma formation with limited lung inflammation and injury. On the other hand, intratracheal exposure to large doses of silica induces acute silicosis characterized by granuloma-like formations in the lung associated with apoptosis, severe alveolitis, and alveolar lipoproteinosis. To ascertain similarities/differences between acute and chronic silicosis, in this communication, we compared cellular and molecular changes in established rat models of acute and chronic silicosis. In Lewis rats, acute silicosis was induced by intratracheal instillation of 35 mg silica, and chronic silicosis through inhalation of aerosolized silica (6.2 mg/m(3), 5 d/wk for 6 wk). Animals exposed to acute high-dose silica were sacrificed at 14 d after silica instillation while chronically silica-treated animals were sacrificed between 4 d and 28 wk after silica exposure. The lung granulomas formation in acute silicosis was associated with strong inflammation, presence of TUNEL-positive cells, and increases in caspase-3 activity and other molecular markers of apoptosis. On the other hand, lungs from chronically silica-exposed animals exhibited limited inflammation and increased expression of anti-apoptotic markers, including dramatic increases in Bcl-2 and procaspase-3, and lower caspase-3 activity. Moreover, chronic silicotic lungs were TUNEL-negative and overexpressed Bcl-3 and NF-kappaB-p50 but not NF-kappaB-p65 subunits. These results suggest that, unlike acute silicosis, chronic exposures to occupationally relevant doses of silica cause significantly lower lung inflammation and elevated expression of anti-apoptotic rather than proapoptotic markers in the lung that might result from interaction between NF-kappaB-p50 and Bcl-3.

Computer-assisted identification of small-molecule Bcl-2 modulators

Apoptosis, the programmed cell death, is a highly regulated process, necessary for normal development and homeostasis of the functions of organisms. The Bcl-2 inhibitors BH3I-1 and BH3I-2 were used as lead compounds to find possible Bcl-2 or Bcl-X(L) inhibitors by using computer-assisted screening with our in-house database, containing more than four million commercially available molecules. Identified compounds were further investigated regarding their possible application as a drug.

Daunorubicin-loaded magnetic nanoparticles of Fe3O4 overcome multidrug resistance and induce apoptosis of K562-n/VCR cells in vivo

Multidrug resistance (MDR) is a major obstacle to cancer chemotherapy. We evaluated the effect of daunorubicin (DNR)-loaded magnetic nanoparticles of Fe₃O₄ (MNPs-Fe₃O₄) on K562-n/VCR cells in vivo. K562-n and its MDR counterpart K562-n/VCR cell were inoculated into nude mice subcutaneously. The mice were randomly divided into four groups: group A received normal saline, group B received DNR, group C received MNPs-Fe₃O₄, and group D received DNR-loaded MNPs-Fe₃O₄. For K562-n/VCR tumor, the weight was markedly lower in group D than that in groups A, B, and C. The transcriptions of Mdr-1 and Bcl-2 gene were significantly lower in group D than those in groups A, B, and C. The expression of Bcl-2 was lower in group D than those in groups A, B, and C, but there was no difference in the expression of P-glycoprotein. The transcriptions and expressions of Bax and caspase-3 in group D were increased significantly when compared with groups A, B, and C. In conclusion, DNR-loaded MNPs-Fe₃O₄ can overcome MDR in vivo.

Direct effects of fascaplysin on human umbilical vein endothelial cells attributing the anti-angiogenesis activity

Novel anti-angiogenesis activity of fascaplysin via VEGF blockage was recently revealed by our previous study in addition to the reported cyclin-dependent kinase 4 (CDK4) selective inhibition. To uncover more details of this pharmacologically prospective property, this study further investigated whether fascaplysin had direct anti-proliferation effects on human umbilical vein endothelial cells (HUVEC), which might be contributing to anti-angiogenesis. The results showed that G1 cell cycle arrest was induced by 2.6 μM fascaplysin in a time-dependent manner, and exhibited more sensitive than hepatocarcinoma cells BeL-7402 and Hela cells. Approximately 56.09 ± 2.63% of the cells were arrested at the G1 phase after 24h, and 64.94 ± 2.07% after 36 h, comparing to the 22.82 ± 1.2% in methanol treated cells. Apoptosis of HUVEC cells was induced by 1.3 μM fascaplysin and indicated by the sub-G1, Hoechst staining, terminal deoxynucleotidyl transferase dUTP-mediated nicked end labeling (TUNEL) assay, and annexin-V and propidium (PI) label. This apoptosis response was further confirmed by the detection of active caspase-3 and by western blotting using antibodies against Bax, Bcl-2, procaspase-8, and Bid, indicating that apoptosis in HUVEC cells may involve a mitochondria pathway, by the demonstration of an increase in the Bax/Bcl-2 ratio. Together, our results suggest that the anti-angiogenesis activity of fascaplysin is through the direct effects of cell cycle arrest and apoptosis on HUVEC.

The role of integrin alpha(v)beta (8) in neonatal hypoxic-ischemic brain injury

Integrin alpha(v)beta(8) plays an important role in cerebral vascular development. It has been proven that alpha(v)beta(8) is a key factor for transforming growth factor-beta1 (TGF-beta1) activation in epithelial cells. However, it is not clear whether alpha(v)beta(8) can activate TGF-beta1 and play a role in protection during neonatal hypoxic-ischemic brain injury. In this study, we investigated the relationship between alpha(v)beta(8) and TGF-beta1 activation, and thus the effects of TGF-beta1 activation in the protection of neurons after hypoxia-ischemia (HI). Astrocytes and neurons from rat brains were cultured and then subjected to oxygen-glucose deprivation to generate HI model in vitro. beta(8) expression was determined using immunocytochemistry, western blot, and reverse-transcriptase polymerase chain reaction. TGF-beta1 activation was determined by TGF-beta bioassay in a tested cell (astrocyte) and a reporter cell co-culture system. The pro-apoptotic protein, cleaved caspase-3, and the anti-apoptotic protein, Bcl-2 and Bcl-xL, were detected using western blot. Cellular apoptosis was detected with TUNEL. We found that beta(8) expression was stronger in astrocytes than that in neurons under normoxia. HI resulted in a rapid and persistent increase of beta(8) expression in astrocytes, but only in a slight and transient increase in neurons. Astrocytes beta(8) could induce TGF-beta1 leading to upregulation of Bcl-2 and Bcl-xL, and thus attenuated neuronal apoptosis. The present findings suggest that beta(8) protecting the brain against neonatal HI injury through TGF-beta1 signaling pathway, which may have implications for the treatment of HI brain injury.

Protection by tetrahydroxystilbene glucoside against cerebral ischemia: involvement of JNK, SIRT1, and NF-kappaB pathways and inhibition of intracellular ROS/RNS generation

Many natural polyphenolic compounds have been shown to attenuate reactive oxygen/nitrogen species (ROS/RNS) formation and protect against ischemia/reperfusion injury both in vitro and in vivo. 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside (TSG), an active component of the rhizome extract from Polygonum multiflorum, exhibits antioxidative and anti-inflammatory effects. Here, we used an in vitro ischemic model of oxygen-glucose deprivation followed by reperfusion (OGD-R) and an in vivo ischemic model of middle cerebral artery occlusion (MCAO) to investigate the neuroprotective effects of TSG on ischemia/reperfusion brain injury and the related mechanisms. We demonstrated that OGD-R-induced neuronal injury, intracellular ROS generation, and mitochondrial membrane potential dissipation were reversed by TSG. The elevation of H2O2-induced [Ca2+]i was also attenuated by TSG. Inhibition of the c-Jun N-terminal kinase (JNK) and Bcl-2 family-related apoptotic signaling pathway was involved in the neuroprotection afforded by TSG. Meanwhile, TSG inhibited iNOS mRNA expression induced by OGD-R, which may be mediated by the activation of SIRT1 and inhibition of NF-kappaB activation. In vivo studies further demonstrated that TSG significantly reduced the brain infarct volume and the number of positive cells by TUNEL staining in the cerebral cortex compared to the MCAO group. Our study indicates that TSG protects against cerebral ischemia/reperfusion injury through multifunctional cytoprotective pathways.

Extremely low frequency (ELF) magnetic fields and apoptosis: a review

In recent years, there has been increasing evidence that extremely low frequency magnetic fields might be linked to tumours, particularly with childhood leukaemia. In the same period, the role of apoptosis in the tumour process has also gained increasing importance. It is the purpose of this review to describe the apoptotic process, discuss selected papers in which apoptosis is examined in cells exposed to magnetic fields and describe the possible biophysical mechanisms responsible for changes in the apoptotic process in exposed cells. Despite some differences, as a whole, the literature seems to demonstrate that magnetic fields induce changes in apoptosis in cells exposed to different experimental protocols. In addition, the important role of ions, particularly of Ca2+, in the apoptotic process is also discussed, and one possible model for magnetic field action on apoptosis that brings together experimental observations of different nature is suggested and discussed.

Regulation of Bcl-2 phosphorylation in response to oxidative stress in cardiac myocytes

Oxidative stress promotes cardiac myocyte death and has been implicated in the pathogenesis of many cardiovascular diseases. Bcl-2 family proteins are key regulators of the apoptotic response, while their functions can be regulated by post-transcriptional modifications including phosphorylation, dimerization or proteolytic cleavage. This study used adult cardiac myocytes to test the hypothesis that activation of specific kinase signalling pathways by oxidative stress may modulate either the expression or the phosphorylation of Bcl-2, with the resulting effect of a decrease or increase in its anti-apoptotic function. Stimulation of cardiac myocytes with 0.2 mM H(2)O(2), which induces apoptosis, resulted in a marked down-regulation of Bcl-2 protein simultaneously with an increase in its phosphorylation. Inhibition of p38-MAPK resulted in attenuation of Bcl-2 phosphorylation, whereas inhibition of ERK1/2, JNKs or PI-3-K had no effect. These data suggest that activation of p38 MAPK by oxidative stress results in the phosphorylation and degradation of Bcl-2 and the inactivation of its anti-apoptotic activity.

2beta-(Isobutyryloxy)florilenalin, a sesquiterpene lactone isolated from the medicinal plant Centipeda minima, induces apoptosis in human nasopharyngeal carcinoma CNE cells

Centipeda minima is a medicinal plant reputed in China as a remedy for nasopharyngeal carcinoma (NPC). In this study, bioactivity-guided fractionation of the anti-NPC compound(s) from C. minima led to the isolation of 2β-(isobutyryloxy)florilenalin (IF), a sesquiterpene lactone. IF showed significant dose- and time- dependent inhibition on the growth of the human nasopharyngeal carcinoma epithelia cells (CNE). It induced apoptosis in CNE cells, as shown by the accumulation of sub-G1 cell population, DNA fragmentation and nuclear condensation, caspase-3 activation and PARP cleavage. Such induction was associated with the depletion of mitochondrial membrane potential (ΔΨm) and the release of cytochrome c to cytosol to regulate the expression of Bcl-2 family proteins. These activities led to the cleavage of caspases and the trigger of cell death process. Overall, IF in C. minima showed potent antiproliferative effect of C. minima on NPC cells, suggesting that the plant deserves more extensive investigation for its potential medicinal application.

Changes in the balance between proliferation and apoptosis during the progression of malignancy in thyroid tumours

The aim of this study was to gain better insight into molecular changes which reflect disturbances in the balance between proliferation and apoptosis during progression of thyroid malignancy from papillary microcarcinoma (PMC) via clinically manifest papillary carcinoma (PTC) to anaplastic carcinoma (ATC). The apoptosis related molecules (Bcl-2, Bax) and proliferation related marker (PCNA) were analysed immunohistochemically in 120 archival cases comprising PMC (n=34), PTC (n=52) and ATC (n=34). In addition, in situ apoptotic cell death was analysed by the TUNEL method. The average Bcl-2 staining score did not differ between PMC and PTC (p>0.05), but was significantly lower in ATC (p<0.05).The Bax score was higher in PTCs and ATCs than in PMCs (p<0.05). Due to these changes, the Bcl-2/Bax ratio showed a marked decrease from PMC to ATC (p<0.05), while proliferation activity increased significantly from PTC to ATC (p<0.05). Despite high Bax expression, the rate of apoptotic cell death was low in the investigated carcinomas, especially in ATC, i.e. the increase in proliferative activity was not counterbalanced with appropriate cell death. Differences were found in the expression of apoptotic molecules (Bcl-2 and Bax), their ratio (Bcl-2 /Bax) and in the rate of apoptotic cell death and proliferative activity between PMC, PTC and ATC, indicating that disturbances in the balance between apoptosis and proliferation, in favour of the latter, occur gradually during the progression of malignancy in thyroid tumours.

Apoptotic signaling induced by H2O2-mediated oxidative stress in differentiated C2C12 myotubes

AIMS

Apoptotic signaling proteins were evaluated in postmitotic skeletal myotubes to test the hypothesis that oxidative stress induced by H(2)O(2) activates both caspase-dependent and caspase-independent apoptotic proteins in differentiated C2C12 myotubes. We hypothesized that oxidative stress would decrease anti-apoptotic protein levels in C2C12 myotubes.

MAIN METHODS

Apoptotic regulatory factors and apoptosis-associated proteins including Bcl-2, Bax, Apaf-1, XIAP, ARC, cleaved PARP, p53, p21(Cip1/Waf1), c-Myc, HSP70, CuZnSOD, and MnSOD protein content were measured by immunoblots.

KEY FINDINGS

H(2)O(2) induced apoptosis in myotubes as shown by DNA laddering and an elevation of apoptotic DNA fragmentation. Cell death ELISA showed increase in the extent of apoptotic DNA fragmentation following treatment with H(2)O(2). Treatment with 4 mM of H(2)O(2) for 24 or 96 h caused increase in Bax (56%, 227%), cytochrome c (282%, 701%), Smac/DIABLO (155%, 260%), caspase-3 protease activity (51%, 141%), and nuclear and cytosolic p53 (719%, 1581%) levels in the myotubes. As an estimate of the mitochondrial AIF release to the cytosol, AIF protein content measured in the mitochondria-free cytosolic fraction was elevated by 65% after 96 h treatment with 4 mM of H(2)O(2). AIF measured in the nuclear protein fraction increased by 74% and 352% following treatment with 4 mM of H(2)O(2) for 24 and 96 h, respectively. Bcl-2 declined in myotubes by 61% and 69% after 24 or 96 h of treatment in 4 mM H(2)O(2), respectively.

SIGNIFICANCE

These findings indicate that both caspase-dependent and caspase-independent mechanisms are involved in coordinating the activation of apoptosis induced by H(2)O(2) in differentiated myotubes.

Oligonucleotide microarray analysis of genes regulating apoptosis in chronically ischemic and postinfarction myocardium

The pathology of cardiomyocyte death during and after myocardial infarction involves both necrosis and apoptosis. Although both mechanisms lead to cell death, participation of apoptosis in this process carries the potential of developing therapies influencing at least part of the population of dying cells. Therefore the aim of this study was to determine (using oligonucleotide microarrays) expression profiles of apoptosis-regulating genes in postinfarction myocardium, comparing chronically ischemic and healthy heart muscle. Tissue samples were obtained during elective surgery from the right cardiac auricles of three patients. The expression of 141 genes involved in fibrosis was assessed using the Affymetrix HG_U133A microarray. The patients' transcriptomes were compared using hierarchical clusterization. Differentiating genes were determined using regression analysis and Bland-Altman graph analysis. Hierarchical clusterization demonstrated that the profile of gene expression in postinfarction myocardium was different from that in the remaining specimens. Further statistical analysis showed two important differentiating genes: FOXO3A (underexpressed in post-MI sample) and CFLAR (overexpressed in post-MI sample). The expression of apoptosis-regulating genes is significantly different in post-MI myocardium from chronically ischemic and a nonischemic myocardium. Our results suggest that CFLAR is important in the induction of apoptosis in postinfarction cardiac tissue.

E1AF promotes mithramycin A-induced Huh-7 cell apoptosis depending on its DNA-binding domain

Transcription factor E1AF is widely known to play critical roles in tumor metastasis via directly binding to the promoters of genes involved in tumor migration and invasion. Here, we reported for the first time the pro-apoptotic role of E1AF in tumor cells. The expression of E1AF at protein level was obviously increased during Huh-7 and Hep3B cells apoptosis induced by the anticancer agent mithramycin A. E1AF overexpression markedly enhanced mithramycin A-induced Huh-7 cell apoptosis and the expression of pro-apoptotic protein Bax depending on its DNA-binding domain. And, reduction of E1AF inhibited mithramycin A-induced Huh-7 cell apoptosis. Furthermore, reducing the expression of Bax significantly inhibited E1AF-increased Huh-7 cell apoptosis induced by mithramycin A. Taken together, E1AF increases mithramycin A-induced Huh-7 cells apoptosis and Bax expression depending on its DNA-binding domain, indicating that E1AF might contribute to the therapeutic efficiency of mithramycin A for hepatoma.

DAP5 promotes cap-independent translation of Bcl-2 and CDK1 to facilitate cell survival during mitosis

DAP5 is an eIF4G protein previously implicated in mediating cap-independent translation in response to cellular stresses. Here we report that DAP5 is crucial for continuous cell survival in nonstressed cells. The knockdown of endogenous DAP5 induced M phase-specific caspase-dependent apoptosis. Bcl-2 and CDK1 were identified by two independent screens as DAP5 translation targets. Notably, the activity of the Bcl-2 IRES was reduced in DAP5 knockdown cells and a selective shift of Bcl-2 mRNA toward light polysomal fractions was detected. Furthermore, a functional IRES was identified in the 5'UTR of CDK1. At the cellular level, attenuated translation of CDK1 by DAP5 knockdown decreased the phosphorylation of its M phase substrates. Ectopic expression of Bcl-2 or CDK1 proteins partially reduced the extent of caspase activation caused by DAP5 knockdown. Thus, DAP5 is necessary for maintaining cell survival during mitosis by promoting cap-independent translation of at least two prosurvival proteins.

Time Course of Expression of Bcl-2 and Bax in Rabbit Condylar Chondrocytes Following Forward Mandibular Positioning

Objective: To clarify the expression of Bcl-2 and Bax following forward mandibular positioning (FMP) in the condylar chondrocytes of rabbits.

Materials and Methods: Sixty rabbits at 8 weeks of age were randomly allocated to the experimental group (n = 36) and control group (n = 24). Rabbits in the experimental group were induced to FMP by a functional appliance. Six rabbits from the experimental group and four from the control group were sacrificed after 3 days and 1, 2, 4, 8, and 12 weeks, respectively. All the right temporomandibular joints (TMJs) were collected and the expression of Bcl-2 and Bax was evaluated by immunohistochemical staining.

Results: The results showed the expression pattern of Bcl-2 and Bax during 12 weeks after FMP. The expression of Bcl-2 reached the highest level at 1 week, whereas Bax reached its maximal expression after 4 weeks. Subsequently, the expression of Bcl-2 and Bax gradually decreased. The ratio of Bcl-2/Bax began to decrease 3 days after FMP and continued to decline until 12 weeks.

Conclusions: FMP with functional appliances could change the expression of Bcl-2 and Bax, which is related to apoptosis in condylar chondrocytes.

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.

Cyclin-dependent kinase inhibitor roscovitine induces cell cycle arrest and apoptosis in rabbit retinal pigment epithelial cells

AIMS

Cyclin-dependent kinases (CDKs) play essential roles in the intracellular control of the cell cycle. It has been postulated that roscovitine, a potent CDK2, CDK5, and CDC2 inhibitor, might inhibit cellular proliferation by arresting the cell cycle. This in vitro study investigated the antiproliferative and apoptotic effects of roscovitine in cultured rabbit retinal pigment epithelial (RPE) cells.

METHODS

Experiments using rabbit RPE from young pigmented rabbits were carried out using roscovitine dissolved in dimethylsulfoxide at concentrations ranging from 1 to 100 micromol. Cell proliferation was measured by an MTT assay. The cell cycle response of RPE cells to roscovitine was analyzed by flow cytometry of propidium iodide-stained nuclei. Proteins related to DNA damage in the RPE cells were then assayed by Western blot.

RESULTS

Roscovitine inhibited proliferation of RPE cells in a dose-dependent manner. Cell cycle analysis after treatment demonstrated an accumulation of cells arrested in the S- and G2/M phases. Flow cytometry showed that 40 microM of roscovitine increased the cell population in the sub-G1 peak, which is considered a marker of cell death by apoptosis. Western blot analysis revealed Bcl-2 decreased and Bax increased after treatment of RPE cells with roscovitine.

CONCLUSIONS

This study of the response of RPE cells to roscovitine demonstrated a bidirectional relationship between cell cycle control and apoptosis.

Blockade of cholecystokinin-2 receptor and cyclooxygenase-2 synergistically induces cell apoptosis, and inhibits the proliferation of human gastric cancer cells in vitro

Gastrin and cyclooxygenase-2 (COX-2) play important roles in the carcinogenesis and progression of gastric cancer. However, it remains unknown whether the combination of cholecystokinin-2 (CCK-2) receptor antagonist plus COX-2 inhibitor exerts synergistic anti-tumor effects on human gastric cancer. Here, we demonstrated that the combination of AG-041R (a CCK-2 receptor antagonist) plus NS-398 (a selective COX-2 inhibitor) treatment had synergistic effects on proliferation inhibition, apoptosis induction, down-regulation of Bcl-2 and up-regulation of Bax expression in MKN-45 cells. These results indicate that simultaneous targeting of CCK-2 receptor and COX-2 may inhibit gastric cancer development more effectively than targeting either molecule alone.

Anti-proliferative effect of clitocine from the mushroom Leucopaxillus giganteus on human cervical cancer HeLa cells by inducing apoptosis

Clitocine, a natural biologically active substance isolated from the mushroom Leucopaxillus giganteus, possesses several bioactivities including antitumor. Here, for the first time, we studied the molecular mechanism of clitocine-induced apoptosis in human cervical cancer cells (HeLa). Clitocine-induced cell death was characterized with the changes in cell morphology, DNA fragmentation, activation of caspase-3, -8, and -9 (like) activities, poly(ADP-ribose) polymerase (PARP) cleavage, release of cytochrome c (cyt c) into cytosol, and increase of Bax:Bcl-2 ratio. These results indicated that the induction of apoptosis by clitocine involved the multiple pathway including death receptor and mitochondrial pathways, and strongly suggested that the mitochondrial pathways were mediated by down-regulation of Bcl-2 and up-regulation of Bax, release of cytochrome c and subsequent activation of caspase-3 followed by down stream events leading to apoptotic mode of cell death.

Progressive apoptosis resistance prior to senescence and control by the anti-apoptotic protein BCL-xL

Senescent cells are known to be resistant to apoptosis induced by genotoxic stress. Here we examine apoptosis in human diploid fibroblasts that are old but not yet senescent. We found that as cells aged, they became progressively more resistant to UV-induced apoptosis with an eventual apoptosis reduction of 10-20-fold. This behavior tracked a progressive disruption of the normal balance between pro- and anti-apoptotic proteins. In young cells, the level of anti-apoptotic protein BCL-xL quickly fell after UV irradiation while pro-apoptotic protein BAX rose. The increase in BAX tracked the level of P53, a transcriptional regulator of BAX. In older cells, the scenario was quite different. Instead of decreasing, the level of BCL-xL increased dramatically after UV stress so that the ratio of pro-apoptotic BAX to anti-apoptotic BCL-xL remained low. RNAi against BCL-xL restored the UV-sensitivity of old cells, indicating that BCL-xL is itself responsible for the pre-senescence decline in the ability of a genotoxic stress to induce apoptosis.

Mitochondria are involved in stress response of A549 alveolar cells to halothane toxicity

During inhalation anaesthesia lung epithelial cells are directly exposed to halogenated hydrocarbons such as halothane. Information about the effects of volatile anaesthetics on lung cells is rather limited although their noxious effect on the A549 alveolar cells has been shown recently. The present study indicated that halothane decreases cell viability, impairs DNA integrity and provokes stress-induced apoptosis in A549 cells when applied at clinically relevant concentrations. Data obtained clearly demonstrated intensive expression of anti-apoptotic Bcl-2 protein during treatment with all tested concentrations. In post-treatment periods the increased DNA injury was accompanied by reduction of Bcl-2 expression. We concluded that the in vitro effect of halothane on lung cells involved alteration in the expression of proteins of the mitochondrial apoptotic pathway.

Age-dependent upregulation of p53 and cytochrome c release and susceptibility to apoptosis in skeletal muscle fiber of aged rats: role of carnitine and lipoic acid

Mitochondrial dysfunction has been implicated in the regulation of myofiber loss during aging, possibly by apoptotic pathways. However, the mitochondrial-mediated pathway of apoptosis by cytochrome c in skeletal muscle remains ambiguous. To understand this, we have studied the upstream and downstream events of cytochrome c release, and assessed the efficacy of carnitine and lipoic acid cosupplementation. The results show that elevated levels of cytosolic cytochrome c activate apoptosis in aged rats, and was confirmed further by in vitro caspase-3 assay. Interestingly, the exogenous addition of cytochrome c results in a much higher increase of caspase-3 activity in aged treated rats than age-matched control rats, strongly suggesting that cytochrome c is a limiting factor for caspase-3 activation in the cytosol. Carnitine and lipoic acid supplement decreased apoptosis in aged rats by maintaining mitochondrial membrane integrity and thereby preventing further loss of cytochrome c in vivo. Furthermore, the upregulation of p53 observed in aged rats is attributed to the loss of outer mitochondrial membrane integrity and subsequent release of cytochrome c through BH3-only proteins. In conclusion, the p53-dependent activation of the mitochondrial-cytochrome c pathway of apoptosis in the present study suggests the existence of cross talk between mitochondria and nucleus. However, the exact molecular mechanism remains to be explored. Oral supplements of carnitine and lipoic acid play an antiapoptotic role in aged rat skeletal muscle by protecting mitochondrial membrane integrity.

Acidic pre-conditioning suppresses apoptosis and increases expression of Bcl-xL in coronary endothelial cells under simulated ischaemia

Ischaemic pre-conditioning has a powerful protective potential against ischaemia-induced cell death, and acidosis is an important featur of ischaemia and can lead to apoptosis. Here we tested whether pre-conditioning with acidosis, that is, acidic pre-conditioning (APC), may protect coronary endothelial cells (EC) against apoptosis induced by simulated ischaemia. For pre-conditioning, EC were exposed fo 40 min. to acidosis (pH 6.4) followed by a 14-hrs recovery period (pH 7.4) and finally treated for 2 hrs with simulated ischaemia (glucose-free anoxia at pH 6.4). Cells undergoing apoptosis were visualized by chromatin staining or by determination of caspase-3 activit Simulated ischaemia in untreated EC increased caspase-3 activity and the number of apoptotic cell (31.3 ± 1.3%versus 3.9 ± 0.6% in control). APC significantly reduced the rate of apoptosis (14.2 ± 1.3%) and caspase-3 activity. Western blot analysis exploring the under lying mechanism leading to this protection revealed suppression of the endoplasmic reticulum- (reduced cleavage of caspase-12) and mitochondria-mediated (reduced cytochrome C release) pathways of apoptosis. These effects were associated with an over-expression of the anti-apoptotic protein Bcl-xL 14 hrs after APC, whereas no effect on the expression of Bcl-2, Bax, Bak, procaspase-12, reticulum-localized chaperones (GRP78, calreticulin), HSP70, HSP32 and HSP27 could be detected. Knock-down of Bcl-xL by siRNA-treatment prevented the protective effect of APC. In conclusion, short acidic pre-treatment can protect EC against ischaemic apoptosis. The mechanism of this protection consists of suppression of the endoplasmic reticulum- and mitochondria-mediated pathways. Over-expression of the anti apoptotic protein Bcl-xL is responsible for the increased resistance to apoptosis during ischaemic insult.

Bim and Bcl-2 mutually affect the expression of the other in T cells

The life and death of T cells is controlled to a large extent by the relative amounts of Bcl-2-related proteins they contain. The antiapoptotic protein Bcl-2 and the proapoptotic protein Bim are particularly important in this process with the amount of Bcl-2 per cell dropping by about one-half when T cells prepare to die. In this study we show that Bcl-2 and Bim each control the expression of the other. Absence of Bim leads to a drop in the amount of intracellular Bcl-2 protein, while having no effect on the amounts of mRNA for Bcl-2. Conversely, high amounts of Bcl-2 per cell allow high amounts of Bim, although in this case the effect involves increases in Bim mRNA. These mutual effects occur even if Bcl-2 is induced acutely. Thus these two proteins control the expression of the other, at either the protein or mRNA level.

Importance of bicarbonate transport for ischaemia-induced apoptosis of coronary endothelial cells

Bicarbonate transport (BT) has been previously shown to participate in apoptosis induced by various stress factors. However, the precise role of BT in ischaemia-induced apoptosis is still unknown. To investigate this subject, rat coronary endothelial cells (EC) were exposed to simulated ischaemia (glucose free anoxia at Ph 6.4) for 2 hrs and cells undergoing apoptosis were visualized by nuclear staining or by determination of cas-pase- 3 activity. To inhibit BT, EC were either treated with the inhibitor of BT 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS, 300 mumol/l) or exposed to ischaemia in bicarbonate free, 4-(2-hydroxyethyl)-I-piperazi-neethanesulphonic acid (HEPES)-buffered medium. Simulated ischaemia in bicarbonate-buffered medium (Bic) increased caspase-3 activity and the number of apoptotic cell (23.7 + 1.4%versus 5.1 + 1.2% in control). Omission of bicarbonate during ischaemia further significantly increased caspase-3 activity and the number of apoptotic cells (36.7 1.7%). Similar proapoptotic effect was produced by DIDS treatment during ischaemia in Bic, whereas DIDS had no effect when applied in bicarbonate-free, HEPES-buffered medium (Hep). Inhibition of BT was without influence on cytosolic acidification during ischaemia and slightly reduced cytosolic Ca(2+) accumulation. Initial characterization of the underlying mechanism leading to apoptosis induced by BT inhibition revealed activation of the mitochondrial pathway of apoptosis, i.e., increase of cytochrome C release, depolarization of mitochondria and translocation of Bax protein to mitochondria. In contrast, no activation of death receptor-dependent pathway (caspase-8 cleavage) and endoplasmic reticulum- dependent pathway (caspase-12 cleavage) was detected. In conclusion, BT plays an important role in ischaemia-induced apoptosis of coronary EC by suppression of mitochondria-dependent apoptotic pathway.

Induction of apoptosis in rabbit oral mucosa by 1.23% acidulated phosphate fluoride gel

Applying of 1.23% acidulated phosphate fluoride (APF) gel to prevent caries in children has become very popular among dental practitioners. When applied to dental surfaces, however, APF often comes into contact with the oral mucosa. Due to the possibility of local toxic effect, we aimed to investigate the effects of APF on rabbit oral mucosa. Rabbits were sacrificed 1, 5 and 8 days after topical application of 1.23% APF on the oral buccal mucosa for 4 min. The nuclei with DNA strand breaks of the basal epithelial cell layer was estimated using terminal-deoxynucleotidyl-transferase-mediated deoxyuridine-triphospate-biotin nick end labeling (TUNEL). Epithelial cells were analyzed by transmission electron microscopy. The number of basal epithelial cells with DNA strand breaks increased with time in rabbits treated with 1.23% APF. Transmission electron microscopy revealed evidence of apoptosis in the parabasal and basal epithelial cells showed, with loss of cell-to-cell contact, nuclear chromatin condensation and apoptotic bodies. The results demonstrate in vivo that 1.23% APF induced apoptosis in basal epithelial cells of rabbit oral mucosa. It suggests the possible necessity to prevent oral mucosa contact when APF applied on teeth.

Advancing mammalian cell culture engineering using genome-scale technologies

Mammalian cell-derived protein therapeutic production has changed the landscape of human healthcare in the past two decades. The importance of protein therapeutics has motivated the search for more cost-effective and efficient cell lines capable of producing high quality protein products. The factors contributing to optimal producer cell lines are often complex, and not simply conferred by one gene or gene product, which makes an understanding of system-wide properties for better engineering of optimized cell lines essential. Genome-scale technologies (genomics, transcriptomics and proteomics) enable such engineering studies. However, the use of these technologies in cell culture engineering is still in its infancy. Here, we summarize current knowledge of cell properties important for the design of efficient protein-producing mammalian cell lines, and highlight relevant studies to-date that use genome-scale technologies in these cell systems. We also provide a focused review of relevant alternative and emerging technologies, which have seen limited use in cell culture engineering, but hold great potential for significant advancements in protein therapeutic production.

beta4GalT-II increases cisplatin-induced apoptosis in HeLa cells depending on its Golgi localization

beta1,4-Galactosyltransferase II (beta4GalT-II) is one of the enzymes transferring galactose to the terminal N-acetylglucosamine of complex-type N-glycans and its expression is significantly altered during oncogenesis with unknown functions. Here, we reported for the first time the pro-apoptotic role of beta4GalT-II in tumor cells. The level of beta4GalT-II mRNA expression was obviously decreased during HeLa cell apoptosis induced by cisplatin. Interestingly, the ectopic expression of beta4GalT-II in HeLa cells markedly increased apoptosis and cleavage of PARP induced by cisplatin as well as the expression of pro-apoptotic protein Bax. Furthermore, deletion of Golgi localization domain abolished the apoptotic role of beta4GalT-II in HeLa cells. Collectively, these results suggest that beta4GalT-II increases HeLa cell apoptosis induced by cisplatin depending on its Golgi localization, which indicates that beta4GalT-II might contribute to the therapeutic efficiency of cisplatin for cervix cancer.

Conjugated linoleic acid induces apoptosis of murine mammary tumor cells via Bcl-2 loss

Conjugated linoleic acid (CLA) is a powerful anticancer agent in a number of tumor model systems; however, its precise mechanism of action remains elusive. Here, we report that t10,c12 CLA, a component of synthetic CLA supplements, induced apoptosis and G1 arrest of p53 mutant TM4t murine mammary tumor cells. Furthermore, t10,c12-CLA induced a time- and concentration-dependent cleavage of caspases-3 and -9, and release of cytochrome c from mitochondria to cytosol. Levels of Bcl-2 protein were decreased both in total cellular lysates and in mitochondria after t10,c12-CLA treatment; however, there was no significant change in Bax or Bak. Overexpression of Bcl-2 attenuated apoptosis in response to t10,c12-CLA treatment. These results demonstrate that t10,c12-CLA triggers apoptosis of p53 mutant murine mammary tumor cells through the mitochondrial pathway by targeting Bcl-2.