Pore-formation and protein-protein interactions are considered to play critical roles in the regulation of apoptosis by Bcl-2 family proteins. During the initiation of apoptosis, the anti-apoptotic Bcl-2 and the pro-apoptotic Bax form different pores to regulate the permeability of mitochondrial outer membrane, playing their opposite functions. Overexpression of Bcl-2 has been found in various cancer cells, therefore it is gaining widespread interest to discover small molecules to compromise Bcl-2 function for anti-cancer treatment. Since Bax binds to Bcl-2's hydrophobic groove via its BH3 domain (composed of helices 2 and 3), by which their functions are inhibited each other, the H2-H3 peptide that contains the functional BH3 domain of Bax has been considered as a potential Bcl-2 antagonist. We recently reported that Bax peptide H2-H3 promotes cell death by inducing Bax-mediated cytochrome c release and by antagonizing Bcl-2's inhibitory effect on Bax. However, the mechanism of how H2-H3 inhibits the anti-apoptotic activity of Bcl-2 remains poorly understood. To address this question, we reconstituted the Bcl-2 or Bax pore-forming process in vitro. We found that H2-H3 inhibited Bcl-2's pore formation and neutralized Bcl-2's inhibitory effect on Bax pore formation in the membrane, whereas the mutant H2-H3 peptide that does not induce apoptosis in cells was shown to have no effect on Bcl-2's activities. Thus, inhibiting Bcl-2's pore-forming and anti-Bax activities in the membrane is strongly correlated with H2-H3's pro-apoptosis function in cells.
Apoptosis ; physiology ; BH3 Interacting Domain Death Agonist Protein ; chemistry ; Humans ; Membrane Proteins ; chemistry ; metabolism ; Mitochondrial Membrane Transport Proteins ; Mitochondrial Membranes ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; antagonists & inhibitors ; chemistry ; bcl-2 Homologous Antagonist-Killer Protein ; chemistry ; bcl-2-Associated X Protein ; chemistry

Evidences show that eukaryotic mRNAs can perform protein translation through internal ribosome entry sites (IRES). 5'-Untranslated region of the mRNA encoding apoptotic protease-activating factor 1 (Apaf-1) contains IRES, and, thus, can be translated in a cap-independent manner. Effects of changes in protein translation pattern through rapamycin pretreatment on 4-(methylnitrosamino)-1-(3-pyridyl)-butanone(NNK, tobacco-specific lung carcinogen)-induced apoptosis in human bronchial epithelial cells were examined by caspase assay, FACS analysis, Western blotting, and transient transfection. Results showed that NNK induced apoptosis in concentration- and time-dependent manners. NNK-induced apoptosis occurred initially through cap-independent protein translation, which during later stage was replaced by cap-dependent protein translation. Our data may be pplicable as the mechanical basis of lung cancer treatment.
Antibiotics, Antineoplastic/pharmacology ; Apoptosis/*drug effects ; Apoptotic Protease-Activating Factor 1 ; BH3 Interacting Domain Death Agonist Protein ; Blotting, Western ; Bronchi/metabolism/*pathology ; Carcinogens/*pharmacology ; Carrier Proteins/metabolism ; Caspases/metabolism ; Cytochromes c/metabolism ; Dose-Response Relationship, Drug ; Epithelial Cells/metabolism/*pathology ; Eukaryotic Initiation Factor-4E/metabolism ; Flow Cytometry ; Humans ; Nitrosamines/*pharmacology ; Protein Biosynthesis ; Proteins/metabolism ; Proto-Oncogene Proteins c-bcl-2/metabolism ; RNA Cap-Binding Proteins/*physiology ; Sirolimus/pharmacology ; Time Factors ; bcl-2-Associated X Protein

OBJECTIVE: To explore the effects of isobavachalcone (IBC) on cell death of human breast cancer MCF-7 cells and explore the possible mechanism. METHODS: MCF-7 cells were treated with different concentrations of IBC, and the changes in cell proliferation were assessed using MTT assay. Apoptosis of MCF-7 cells following treatment with 10, 20, and 40 μmol/L IBC was analyzed using flow cytometry with annexin V-FITC/PI double staining and fluorescence microscopy, and the expressions of apoptosis- and autophagy-related proteins (Bax, Bcl-2, Akt, p-Akt, p62, and LC3) were detected with Western blotting. Electron microscopy was used to observe the changes in submicrostructure of the cells following treatment with 40 μmol/L IBC. JC-1 assay kit, ATP assay kit, and reactive oxygen species (ROS) kit were used to determine the effect of IBC on mitochondrial function of the cells. RESULTS: MTT assay showed that IBC significantly inhibited the proliferation of MCF-7 cells in a concentration- and time-dependent manner, with IC₅₀ values of 38.46, 31.31, and 28.26 μmol/L at 24, 48, and 72 h, respectively. IBC also concentration-dependently induced apoptosis of MCF-7 cells. IBC-induced cell death was inhibited by z-VAD-fmk, a caspase inhibitor (P < 0.05), but not by the necroptosis inhibitor necrostatin-1 (Nec-1). Western blotting showed that IBC-induced MCF-7 cell apoptosis by increasing Bax expression and down-regulating the expressions of Bcl-2, Akt and p-Akt-473 (all P < 0.05). With the increase of IBC concentration, the expression of autophagy-related protein p62 and the LC3-II/I ratio increased progressively. Electron microscopy revealed the presence of autophagic bodies in IBC-treated MCF-7 cells. IBC treatment also resulted in decreased mitochondrial membrane potential and intracellular ATP level and increased ROS accumulation in MCF-7 cells (P < 0.05). CONCLUSION IBC is capable of inducing both apoptosis and autophagy in MCF-7 cells, suggesting the potential value of IBC as a lead compound in the development of anti-breast cancer agents.
Adenosine Triphosphate ; Cell Death ; Chalcones ; Humans ; MCF-7 Cells ; Neoplasms ; Proto-Oncogene Proteins c-akt ; Proto-Oncogene Proteins c-bcl-2/metabolism* ; Reactive Oxygen Species/metabolism* ; bcl-2-Associated X Protein

OBJECTIVETo investigate the growth inhibition effect, cytotoxicity and apoptotic induction of harringtonine (HT) in human acute promyelocytic leukemia (APL) NB4 cells,and the related mechanism.

METHODSNB4 cells were treated with HT. Total cell numbers were counted by hemocytometer, and cell viabilities were determined by trypan blue exclusion. Apoptotic cells were determined by fluorescence microscopy and FACS after staining with AO and EB or PI, respectively. The cleavage of PARP and the activation of Bax and the expression of anti-apoptotic proteins were determined by Western Blot. siRNA was used to silence the expression of target genes. Primary cells were isolated following Ficoll-Hypaque density gradient centrifugation method.

RESULTSHT inhibited cell growth and induced apoptosis of NB4 cells in a dose- and time-dependent manner. Apoptosis induced by HT was correlated with the down-regulation of Mcl-1 and the cleavage of PARP, while HT did not affect the protein level of Bax and Bak or change the protein level of Bcl-2. The silence of Bcl-XL sensitized HT-induced apoptosis in NB4 cells.Apoptosis induced by HT in primarily cultured APL cells was also correlated with the down-regulation of Mcl-1.

CONCLUSIONHT inhibits cell growth and induces apoptosis in NB4 cells and primarily cultured APL cells, which may be associated with down-regulation of Mcl-1.

Apoptosis ; drug effects ; Cell Line, Tumor ; Harringtonines ; pharmacology ; Humans ; Leukemia, Promyelocytic, Acute ; metabolism ; pathology ; Proteins ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; bcl-2 Homologous Antagonist-Killer Protein ; metabolism ; bcl-2-Associated X Protein ; metabolism

PURPOSE: To investigate the anti-tumor effect of capsaicin on human pharyngeal squamous carcinoma cells (FaDu). MATERIALS AND METHODS: The expression of apoptosis/cell cycle-related proteins (or genes) was examined by reverse transcriptase-polymerase chain reaction, western blotting and ELISA methods, while the apoptotic cell population, cell morphology and DNA fragmentation levels were assessed using flow cytometry, fluorescence microscopy and agarose gel electrophoresis. RESULTS: Capsaicin was found to inhibit the growth and proliferation of FaDu cells in a dose- and time-dependent manner. Apoptotic cell death was confirmed by observing increases in nuclear condensation, nuclear DNA fragmentation and sub-G1 DNA content. The observed increase in cytosolic cytochrome c, activation of caspase 3 and PARP (p85) levels following capsaicin treatment indicated that the apoptotic response was mitochondrial pathway-dependent. Gene/protein expression analysis of Bcl-2, Bad and Bax further revealed decreased anti-apoptotic Bcl-2 protein and increased pro-apoptotic Bad/Bax expression. Furthermore, capsaicin suppressed the cell cycle progression at the G1/S phase in FaDu cells by decreasing the expression of the regulators of cyclin B1 and D1, as well as cyclin-dependent protein kinases cdk-1, cdk-2 and cdk-4. CONCLUSION: Our current data show that capsaicin induces apoptosis in FaDu cells and this response is associated with mitochondrial pathways, possibly by mediating cell cycle arrest at G1/S.
Apoptosis/drug effects ; Blotting, Western ; Capsaicin/*pharmacology ; Carcinoma, Squamous Cell/*metabolism ; Cell Cycle/drug effects ; Cell Line, Tumor ; Cell Proliferation/drug effects ; Enzyme-Linked Immunosorbent Assay ; Flow Cytometry ; Humans ; Microscopy, Fluorescence ; Pharyngeal Neoplasms/*metabolism ; Proto-Oncogene Proteins c-bcl-2/genetics/metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; bcl-2-Associated X Protein/genetics/metabolism ; bcl-Associated Death Protein/genetics/metabolism

To investigate whether the Bcl-2 gene family is involved in modulating mechanism of apoptosis and change of cell cycle protein induced by curcumin in acute myeloid leukemia HL-60 cell line and primary acute myelogenous leukemic cells, the Bcl-2 family member Mcl-1, Bax and Bak and cell cycle proteins including P27kipl, P21wafl, cyclin D3 and pRbp- were selected and their expression detected by SABC immuno-histochemical stain method. The attitude of sub-G1 peak in DNA histogram was determined by FCM. The TUNEL positive cell percentage was identified by terminal deoxynucleotidyl transferase (TdT)-mediated Biotin dUNP end labeling technique. It was found that when HL-60 cells were treated with 25 mumol/L curcumin for 24 h, the expression level of Mcl-1 was down-regulated, but that of Bax and Bak up-regulated time-dependently. There was significant difference in the expression level of Mcl-1, Bax and Bak between the curcumin-treated groups and control group (P < 0.05-0.01). At the same time, curcumin had no effect on progress of cell cycle in primaty acute myelogenous leukemia at newly diagnosis, but could increase the peak of Sub-G1 (P < 0.05), and down-regulate the expression of Mcl-1 and up-regulate the expression of Bax and Bak with the difference being statistically significant. The expression of P27kipl, P21wafl and pRbp- were elevated and that of cyclin D3 decreased in the presence of curcumin. These findings suggested that the Bcl-2 gene family indeed participated in the regulatory process of apoptosis induced by curcumin in HL-60 cells and AML cells. Curcumin can induce apoptosis of primary acute myelogenous leukemic cells and disturb cell cycle progression of HL-60 cells. The mechanism appeared to be mediated by perturbing G0/G1 phases checkpoints which associated with up-regulation of P27kipl, P21wafl and pRbp- expression, and down-regulation of cyclin D3.
Antineoplastic Agents, Phytogenic ; pharmacology ; Apoptosis ; drug effects ; Cell Cycle Proteins ; metabolism ; Curcumin ; pharmacology ; Genes, bcl-2 ; genetics ; HL-60 Cells ; Humans ; Leukemia, Myeloid, Acute ; pathology ; Myeloid Cell Leukemia Sequence 1 Protein ; Neoplasm Proteins ; biosynthesis ; genetics ; Proto-Oncogene Proteins ; biosynthesis ; genetics ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Tumor Cells, Cultured ; bcl-2-Associated X Protein

The purpose of this study was to explore the mechanism underlying the regulation of 2-methoxyestradiol (2-ME)-induced cell apoptosis by mcl-1 and bax gene in myelodysplastic syndrome (MDS). The MUTZ-1 cells were pretreated with 2-ME; then the activity of caspases-3 was determined by fluorescent colorimetry; the mRNA expressions of apoptosis-related genes (mcl-1) and bcl-2-related X protein (bax) were determined by RT-PCR. The results showed that as compared with control, the 2-ME enhanced the activity of caspase-3 in MUTZ-1 cells in a dose-and time-dependent manners (p<0.05); along with increasing of 2-ME concentration, the expression of intracellular mcl-1 mRNA reduced (p<0.05), meanwhile the expression level of mcl-1 mRNA negatively correlated to the activity of caspase-3 at the corresponding time points (r=-0.992, p<0.01), but the expression of bax mRNA did not show significant change (p>0.05). It is concluded that 2-ME can regulate the apoptosis of MDS cells through the pathway of down-regulating the expression of mcl-1 mRNA and activating the caspase-3.
Apoptosis ; Caspase 3 ; metabolism ; Cell Line, Tumor ; Estradiol ; adverse effects ; analogs & derivatives ; Humans ; Myelodysplastic Syndromes ; metabolism ; pathology ; Myeloid Cell Leukemia Sequence 1 Protein ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; bcl-2-Associated X Protein ; metabolism

OBJECTIVETo observe the sensitivity change of SMMC-7721 cells transfected with antisense DNMT1 gene fragment to tumor necrosis factor related apoptosis inducing ligand (TRAIL) and its mechanism.

METHODSCell survival rate was measured by trypan blue, apoptosis rate by TUNEL method and the expression of bcl-2, bax and bad by flow cytometry.

RESULTSCell survival rate of SMMC-7721 cells transfected with antisense DNMT1 gene fragment was markedly lower than that transfected with sense DNMT1 gene fragment or empty vector (P < 0.05 and 0.01), but the apoptosis rate was on the contrary (P < 0.05 or 0.01). The expression of bax and bad (especially the former), but not bcl-2 of SMMC-7721 cells transfected with antisense DNMT1 gene fragment was markedly higher than those of SMMC-7721 cells transfected with sense DNMT1 gene fragment or empty vector.

CONCLUSIONThe sensitivity of SMMC-7721 cells to TRAIL can be enhanced by the transfection of antisense DNMT1 gene fragment, which may be related to the increase of bax and bad expression.

Antisense Elements (Genetics) ; genetics ; Apoptosis ; drug effects ; Apoptosis Regulatory Proteins ; Carrier Proteins ; analysis ; Cell Line, Tumor ; DNA (Cytosine-5-)-Methyltransferase 1 ; DNA (Cytosine-5-)-Methyltransferases ; antagonists & inhibitors ; genetics ; Flow Cytometry ; Humans ; Liver Neoplasms ; metabolism ; pathology ; Membrane Glycoproteins ; pharmacology ; Proto-Oncogene Proteins ; analysis ; Proto-Oncogene Proteins c-bcl-2 ; TNF-Related Apoptosis-Inducing Ligand ; Tumor Necrosis Factor-alpha ; pharmacology ; bcl-2-Associated X Protein ; bcl-Associated Death Protein

OBJECTIVE: To explore the mechanism of acupuncture plus medication on treatment of Alzheimer's disease (AD). METHODS: Sixty adult SD rats were randomly divided into a normal group, a sham operation group, a model group, an electroacupuncture (EA) group, a gastrodin group and an EA+gastrodin group, 10 rats in each one. The rat model of AD was established by intraperitoneal injection of D-galactose and bilateral hippocampal injection of Aβ1-40. Two weeks after modeling, the rats in the EA group and EA+gastrodin group were treated with EA at "Baihui" (GV 20) "Dazhui" (GV 14) and bilateral "Zusanli" (ST 36), 30 min per treatment, once a day for consecutive 4 weeks. The rats in the gastrodin group and EA+gastrodin group were treated with intraperitoneal injection of gastrodin, once a day for consecutive 4 weeks. The rats in the normal group, model group and sham operation group were not treated. The morphology of hippocampal neurons was observed by using HE staining. The expression of Bcl-2 and Bax in the hippocampal CA1 area was detected by using immunohistochemical method. The expression of Bcl-2 and Bax protein in hippocampus was detected by using Western blot. RESULTS: The HE staining results showed the arrangement of neurons in the hippocampal CA1 area was regular in the normal group and the sham operation group, and the cytoplasm and nucleus were clearly visible. The neurons in the model group were severely damaged; the cell arrangement was not close, and the cell morphology was incomplete. Compared with the model group, the cell morphology of each intervention group was significantly improved. The immunohistochemistry results showed that, compared with the normal group and the sham operation group, the expression of Bcl-2 in the hippocampal CA1 region in the model group was decreased (<0.05), but the expression of Bax was enhanced (<0.05); compared with the model group, the expression of Bcl-2 was increased (all <0.05) and the expression of Bax was decreased (all <0.05) in all intervention group; compared with the EA group or the gastrodin group, the expression of Bcl-2 was enhanced (<0.05) and the expression of Bax was decreased (<0.05) in the EA+gastrodin group. The result of Western blot method was consistent with that of immunohistochemistry method. CONCLUSION EA and gastrodin could significantly inhibit the expression of Bax and up-regulate the expression of Bcl-2, and the combination of EA and gastrodin has the most significant effect. This indicates that EA combined with gastrodin has synergistic effect on inhibiting the apoptosis of neurons in hippocampus in AD rats, which may be one of the mechanisms of EA plus medication on AD lesions.
Alzheimer Disease ; Animals ; Electroacupuncture ; Hippocampus ; Proto-Oncogene Proteins c-bcl-2 ; Rats ; Rats, Sprague-Dawley ; bcl-2-Associated X Protein

To explore the effect of connexin 43 (Cx43) silence on the apoptosis in mouse chondrocyte under mechanical stress.
 Methods: Mouse chondrocyte ATDC5 cells were divided into a control group, a mechanical stress group, a Cx43 siRNA transfection group, a scramble siRNA transfection group, a mechanical stress+scramble group, and a mechanical stress+siCx43 group. Flexcell FX-5000 system was used to produce mechanical stress on ATDC5 cells cultured in vitro. The mRNA and protein level of Cx43 was detected by quantitative RT-PCR (RT-qPCR) and Western blot. The cell activity and cell apoptosis was detected by cell counting kit-8 (CCK-8) method and flow cytometry, respectively. Caspase-3 activity was detected by colorimetric assay. The protein expression of Bcl-2, Bax, p-JNK and JNK was detected by Western blot.
 Results: Mechanical stress upregulated the mRNA and protein expression of Cx43 (both P<0.05). Transfection of Cx43 siRNA significantly decreased Cx43 mRNA and protein level (both P<0.05). After stimulation with mechanical stress, chondrocyte viability was significantly decreased, whereas cell apoptosis and caspase-3 activity were increased (both P<0.05). Mechanical stress obviously upregulated Bax protein level, and downregulated Bcl-2 protein expression and Bcl-2/Bax (both P<0.05). Cx43 siRNA transfection significantly increased cell viability, inhibited cell apoptosis and caspase-3 activity (both P<0.05). Cx43 siRNA also inhibited Bax expression, and increased the Bcl-2 protein expression and Bcl-2/Bax (both P<0.05). Furthermore, Cx43 siRNA significantly suppressed the p-JNK expression induced by mechanical stress (P<0.05).
 Conclusion: Cx43 silence inhibits mechanical stress-induced apoptosis in chondrocyte, which might be mediated by JNK signaling pathway.
Animals ; Apoptosis ; Chondrocytes ; Connexin 43 ; Mice ; Proto-Oncogene Proteins c-bcl-2 ; Stress, Mechanical ; bcl-2-Associated X Protein