OBJECTIVE: To explore the mechanism of proteasome inhibitor MG132 in improving osteoporosis. METHODS: Total of 32 female SD rats, weighing 220 to 250 g and 8 weeks old, were selected. They were randomly divided into 4 groups(n=8). Rats of group A and group B were cut off ovaris on both sides to make model of osteoporosis, and then they were given proteasome inhibitors MG132 and dimethyl sufoxide (DMSO) respectively. Group C was a sham group and rats were given MG132. Group D was a normal group and rats were given MG132 too. The rats were killed in batches at 6 and 12 weeks after administration, and the femoral neck tissues were obtained. Relevant data were analyzed, such as pathomorphological observation, micro-CT analysis, detection of 20S proteasome activity in tissues, and expression of Wnt and β-catenin. RESULTS: Morphological observation showed that the trabecular were slightly thinner, reticulated, and occasionally interrupted in group A, while the trabecular were obviously thinner and discontinuous in group B. And the trabecular were intact and arranged reticulated in group C and D. The analysis results of bone mineral density(BMD), bone surface(BS), bone volume/total volume(BV/TV) and trabecular thickness(Tb.Th) showed that group B was worse than other groups in all parameters at different time points(P<0.05), and group A was worse than group C and group D in BS(P<0.05), there was no significant difference in all parameters between group C and group D. RFU value of 20S proteasome in group B was significantly higher than that in other groups(P<0.05). According to the results of Western blot, the gray values of Wnt protein and β-catenin protein in group A were significantly higher than those in other groups (P<0.05). CONCLUSION MG-132, a ubiquitin proteasome inhibitor, can regulate Wnt/β-catenin signaling pathway by inhibiting the degradation of β-catenin protein, and delaying the occurrence and development of osteoporosis.
Animals ; Bone Density ; Female ; Leupeptins ; Osteoporosis/drug therapy* ; Proteasome Inhibitors/pharmacology* ; Rats ; Rats, Sprague-Dawley ; Wnt Signaling Pathway ; beta Catenin/metabolism*

OBJECTIVETo explore whether MG-132 could enhance the anti-tumor activity of obatoclax against esophageal cancer cell line CaES-17.

METHODSMTT assay was used to determine the cytotoxicity of obatoclax and MG-132 in CaES-17 cells. The IC(50) of obatoclax and MG-132 were used to determine the molar ratio (1:2.4) of the two drugs for combined treatment of the cells. The concentrations of obatoclax and MG-132 ranged from 1/8 IC(50) to 4 IC(50) after serial dilution, and their combination index (CI) was calculated using CompuSyn software. The expression of ubiquitin and the cleavage of PARP, caspase-9, phospho-histone H3 and phospho-aurora A/B/C in the exposed cells were examined with Western blotting; the cell apoptosis was measured by flow cytometry with Annexin V staining, and the percentage of cells in each cell cycle phase was also determined by flow cytometry.

RESULTSThe CI of obatoclax and MG-132 was 0.296 for a 50% inhibition of Caes-17 cells and was 0.104 for a 95% inhibition. The cells treated with obatoclax or MG-132 alone showed increased expression of ubiquitin and cleavage of PARP and caspase-9. Compared with the cells treated with obatoclax or MG-132 alone, the cells with a combined treatment exhibited significantly increased expression of ubiquitin, cleavage of PARP and caspase-9, and expression of phospho-Histone H3 (P<0.05). The combined treatment of the cells also resulted in significantly increased expression of phospho-Aurora A/B/C compared with obatoclax treatment alone. The cells with the combined treatment showed significantly higher percentages of apoptotic cells and cells in sub-G(1) and G(2)/M phases compared with the cells treated with either of the drugs (P<0.05).

CONCLUSIONObatoclax combined with MG-132 shows a significant synergistic anti-tumor effect against esophageal cancer CaES-17 cells by inducing apoptosis and cell cycle arrest.

Apoptosis ; Caspase 9 ; metabolism ; Cell Cycle Checkpoints ; Cell Line, Tumor ; drug effects ; Esophageal Neoplasms ; pathology ; Histones ; metabolism ; Humans ; Leupeptins ; pharmacology ; Poly (ADP-Ribose) Polymerase-1 ; Poly(ADP-ribose) Polymerases ; metabolism ; Pyrroles ; pharmacology

Chloroquine ; pharmacology ; Down-Regulation ; Gene Expression ; drug effects ; HEK293 Cells ; Humans ; Leupeptins ; pharmacology ; Membrane Proteins ; antagonists & inhibitors ; genetics ; metabolism ; Microscopy, Fluorescence ; Protein Binding ; Protein Subunits ; genetics ; metabolism ; RNA Interference ; RNA, Small Interfering ; metabolism ; Shab Potassium Channels ; genetics ; metabolism

Hypoxia-inducible factor 1alpha (HIF-1alpha), which transactivates a variety of hypoxia-induced genes, is rapidly degraded under nomoxia through the hydroxylation-ubiquitination-proteasome pathway. In this study, we addressed how HIF-1alpha is stabilized by proteasome inhibitors. The ubiquitin pool was rapidly reduced after proteasome inhibition, followed by the accumulation of non-ubiquitinated HIF-1alpha. The poly-ubiquitination of HIF-1alpha was resumed by restoration of free ubiquitin, which suggests that the HIF-1alpha stabilization under proteasome inhibition is attributed to depletion of the free ubiquitin pool. Ni2+ and Zn2+ also stabilized HIF-1alpha with depletion of the free ubiquitin pool and these effects of metal ions were attenuated by restoration of free ubiquitin. Ni2+ and Zn2+ may disturb the recycling of free ubiquitin, as MG132 does. Based on these results, the state of the ubiquitin pool seems to be another critical factor determining the cellular level of HIF-1alpha.
Cell Hypoxia/physiology ; Cell Line, Tumor ; HCT116 Cells ; HEK293 Cells ; Humans ; Hypoxia-Inducible Factor 1, alpha Subunit/biosynthesis/*metabolism ; Leupeptins/pharmacology ; Nickel/chemistry ; Proteasome Endopeptidase Complex/*metabolism ; Proteasome Inhibitors/*pharmacology ; Ubiquitin/*metabolism ; Ubiquitination/*physiology ; Up-Regulation ; Zinc/chemistry

This study was aimed to elucidate the expression of costimulatory molecule CD80 and CD86 in HL-60 cells induced by proteasome inhibitor MG132 and its effect on allogeneic mixed lymphocyte reaction. Acute myelocytic leukemia cell line HL-60 and chronic myelocytic leukemia cell line K562 were cultured. The viability of the cells was measured by flow cytometry. Proteasome inhibitor MG132 at the concentrations of 2 or 3 µmol/L was used to stimulate the HL-60 cell cultured for 24 h and 48 h respectively, and the Annexin V/7-AAD staining and flow cytomotry were used to detect the apoptosis of the HL-60 cells. HL-60 and K562 cells were treated with 1 µmol/L MG132 for 24 h and 48 h respectively, then CD80 and CD86 antibodies were added, finally the expression of CD80 and CD86 was analysed by flow cytomery. The mRNA expression of CD86 in the HL-60 cells treated with 1 µmol/L MG132 was detected by RT-PCR. HL-60 and K562 cells were treated by 1 µmol/L MG132 and then underwent irradiation of 75 Gy (60)Co to kill the cells with their antigenicity preserved. Peripheral blood mononuclear cells (PBMNCs) of healthy volunteers, as reactive cells, were isolated and inoculated into the (60)Co irradiated HL-60 cells of different concentrations, as stimulating cells, CCK-8 was added and then the A value of absorbance was measured at the wave length of 450 nm in an enzyme labeling instrument. The results showed that the cell viability of the HL-60 cells treated with 1 µmol/L MG132 for 24 h an d 48 h was 92.95% and 85.87% respectively. The apoptotic rates of the HL-60 cells treated with MG132 increased in dose-and time-dependent manner. High-concentration of MG132 directly killed HL-60 cells. Before MG132 treatment K562 cells did not express CD86, but the CD86 expression of the HL-60 cells was up-regulated time-dependently after MG132 treatment (P < 0.01). The mRNA expression of CD86 in the HL-60 treated with MG132 was up-regulated time-dependently (P < 0.01). CCK-8 test showed that the proliferation level of PBMNC gradually increased along with the concentration of HL-60 cells treated with MG132 and reached its peak when the concentration of the HL-60 cells was 1×10(5) (P < 0.01). No remarkable proliferation of PBMNC was observed in the K562 groups no matter if the HL-60 cells had been treated with MG132. It is concluded that the high concentration of MG132 can directly kill HL-60 cells, low-concentration of MG132 can induce the expression of costimulatory molecule CD86 in HL-60 cells, also can improve the proliferation of PBMNC.
Apoptosis ; B7-2 Antigen ; immunology ; Cell Survival ; Flow Cytometry ; HL-60 Cells ; Humans ; K562 Cells ; Leukocytes, Mononuclear ; drug effects ; Leupeptins ; pharmacology ; Lymphocyte Culture Test, Mixed ; Proteasome Inhibitors ; pharmacology ; Reverse Transcriptase Polymerase Chain Reaction ; Up-Regulation

Mcl-1 and Bcl-xL, key anti-apoptotic proteins of the Bcl-2 family, have attracted attention as important molecules in the cell survival and drug resistance. In this study, we investigated whether inhibition of Bcl-xL influences cell growth and apoptosis against simultaneous treatment of resveratrol and clofarabine in the human malignant mesothelioma H-2452 cells. Resveratrol and clofarabine decreased Mcl-1 protein levels but had little effect on Bcl-xL levels. In the presence of two compounds, any detectable change in the Mcl-1 mRNA levels was not observed in RT-PCR analysis, whereas pretreatment with the proteasome inhibitor MG132 led to its accumulation to levels far above basal levels. The knockdown of Bcl-xL inhibited cell proliferation with cell accumulation at G2/M phase and the appearance of sub-G0/G1 peak in DNA flow cytometric assay. The suppression of cell growth was accompanied by an increase in the caspase-3/7 activity with the resultant cleavages of procaspase-3 and its substrate poly (ADP-ribose) polymerase, and increased percentage of apoptotic propensities in annexin V binding assay. Collectively, our data represent that the efficacy of resveratrol and clofarabine for apoptosis induction was substantially enhanced by Bcl-xL-lowering strategy in which the simultaneous targeting of Mcl-1 and Bcl-xL could be a more effective strategy for treating malignant mesothelioma.
Adenine Nucleotides/*pharmacology ; Antimetabolites, Antineoplastic/*pharmacology ; Apoptosis/*drug effects ; Arabinonucleosides/*pharmacology ; Caspase 3/metabolism ; Caspase 7/metabolism ; Cell Line, Tumor ; Cell Proliferation/drug effects ; G2 Phase Cell Cycle Checkpoints/drug effects ; Gene Knockdown Techniques ; Humans ; Leupeptins/pharmacology ; Lung Neoplasms/metabolism/pathology ; M Phase Cell Cycle Checkpoints/drug effects ; Mesothelioma/metabolism/pathology ; Myeloid Cell Leukemia Sequence 1 Protein/antagonists & inhibitors/genetics/metabolism ; RNA Interference ; RNA, Messenger/metabolism ; RNA, Small Interfering/metabolism ; Stilbenes/*pharmacology ; bcl-X Protein/antagonists & inhibitors/*genetics/*metabolism

O6-methylguanine DNA methyltransferase (MGMT) can remove DNA alkylation adducts, thereby repairing damaged DNA and contributing to the drug resistance of gliomas to alkylating agents. In addition, glioma stem-like cells (GSCs) have been demonstrated to be involved in the recurrence and treatment resistance of gliomas. In this study, we aimed to investigate MGMT expression and regulatory mechanisms in GSCs and the association of MGMT with temozolomide (TMZ) sensitivity. GSCs were enriched from one MGMT-positive cell line (SF-767) and 7 MGMT-negative cell lines (U251, SKMG-4, SKMG-1, SF295, U87, MGR1, and MGR2) through serum-free clone culture. GSCs from the U251G, SKMG-4G, SF295G, and SKMG-1G cell lines became MGMT-positive, but those from the U87G, MGR1G, and MGR2G cell lines remained MGMT-negative. However, all the GSCs and their parental glioma cell lines were positive for nuclear factor-κB (NF-κB). In addition, GSCs were more resistant to TMZ than their parental glioma cell lines (P < 0.05). However, there was no significant difference in the 50% inhibition concentration (IC50) of TMZ between MGMT-positive and MGMT-negative GSCs (P > 0.05). When we treated the MGMT-positive GSCs with TMZ plus MG-132 (an NF-κB inhibitor), the antitumor activity was significantly enhanced compared to that of GSCs treated with TMZ alone (P <0.05). Furthermore, we found that MGMT expression decreased through the down-regulation of NF-κB expression by MG-132. Our results show that MG-132 may inhibit NF-κB expression and further decrease MGMT expression, resulting in a synergistic effect on MGMT-positive GSCs. These results indicate that enhanced MGMT expression contributes to TMZ resistance in MGMT-positive GSCs.
Antineoplastic Agents, Alkylating ; pharmacology ; Cell Line, Tumor ; Dacarbazine ; analogs & derivatives ; pharmacology ; Drug Resistance, Neoplasm ; Drug Synergism ; Glioma ; metabolism ; pathology ; Humans ; Leupeptins ; pharmacology ; NF-kappa B ; antagonists & inhibitors ; metabolism ; Neoplastic Stem Cells ; metabolism ; O(6)-Methylguanine-DNA Methyltransferase ; metabolism

The activation of hepatic stellate cells (HSCs) and their transformation to myofibroblasts are the key steps in the pathological progress of liver fibrosis. The transforming growth factor-β (TGFβ)/Smad pathway is involved in the proliferation and collagen synthesis of HSCs. This study aimed to examine the effect of the protease inhibitor MG132 on the signaling pathway of TGFβ/Smad in HSC-T6 cells and seek a novel therapeutic approach for liver fibrosis. The HSC-T6 cells were treated with MG132 at different concentrations (0-10 μmol/L). Cell proliferation was detected by MTT method. The mRNA and protein expression levels of TGFβ1, Smad3 and Smad7 were determined in HSC-T6 cells by real-time PCR and Western blotting, respectively, after treatment with MG132 at different concentrations (1, 2, 3 μmol/L) or RPMI1640 alone (serving as control). The results showed that MG132 could inhibit the proliferation of HSC-T6 cells in a dose-dependent manner, and the IC(50) of MG132 was 6.84 μmol/L. After treatment with MG132 at 1, 2 or 3 μmol/L for 24 h, the mRNA expression levels of TGF-β1 and Smad3 were significantly decreased (P<0.05), but the Smad7 mRNA expression had no significant change (P>0.05). There was also a significant decrease in the protein expression level of TGF-β1 and Smad3 (P<0.05). However, the expression of Smad7 protein was substantially increased when compared with the control group (P<0.05). It was concluded that the inhibition of TGFβ/Smad pathway in HSC-T6 cells by MG132 can reduce the production of profibrosis factors (TGFβ1, Smad3) and promote the expression of anti-fibrosis factor (Smad7), suggesting that MG132 may become a potential therapeutic alternative for liver fibrosis.
Animals ; Cell Line ; Leupeptins ; pharmacology ; Protease Inhibitors ; pharmacology ; Rats ; Signal Transduction ; drug effects ; Smad Proteins ; metabolism ; Transforming Growth Factor beta ; metabolism

The purpose of this study was to elucidate the apoptosis, apoptotic pathway of HL-60 cells induced by proteasome inhibitor MG132 and its effect on allogeneic mixed lymphocyte reaction. Apoptosis of HL-60 cells was detected by flow cytometry, the expression of P21, P27 and P53 proteins in HL-60 cells treated with MG132 was assayed by Western blot. The HL-60 cells were treated with 1 µmol/L MG132 for 48 h, and irradiated by 75 Gy of (60)Co γ-ray, but their antigenicity was preserved. The effect of irradiated HL-60 cells treated with MG132 on proliferation of peripheral blood mononuclear cells (PBMNC) was measured by CCK-8 method. The results showed that the apoptotic rate of MG132-treated HL-60 cells increased in dose-and time-dependent manner. No significant changes in MG132-induced apoptosis were observed after inhibiting caspase-8 and caspase-9 pathway. The expression of P21 and P27 protein increased after treatment of HL-60 cells with MG132. CCK-8 test showed that HL-60 cells induced with low-dose of MG132 displayed the enhancing effect on proliferation of PBMNC. It is concluded that high dose of MG132 can induce the apoptosis of HL-60 cells, and has direct killing effect on HL-60 cells, but this inducing apoptotic effect on HL-60 cells can not be realized through caspase-8 and caspase-9 pathway. The P21 and P27 protein may be involved in MG132 induced HL-60 cell apoptosis. Low dose of MG132 promotes the proliferation of PBMNC in healthy individuals and enhance the immunity of organism.
Apoptosis ; drug effects ; Caspase 8 ; metabolism ; Caspase 9 ; metabolism ; Cyclin-Dependent Kinase Inhibitor p21 ; metabolism ; Cyclin-Dependent Kinase Inhibitor p27 ; metabolism ; HL-60 Cells ; Humans ; Leupeptins ; pharmacology ; Proteasome Inhibitors ; pharmacology

Bone marrow-derived mesenchymal stem cells (MSCs) have emerged as attractive candidates for cellular therapies for heart and other organ-system disorders. However, a major dilemma in stem cell therapy for ischemic heart diseases is the low survival of transplanted cells in the ischemic and peri-infarcted region. In this study, MSCs were treated by hypoxia and serum deprivation (H/SD) to mimic the ischemic microenvironment of infarcted hearts where MSCs were transplanted. The effects of proteasome inhibitor MG-132 on H/SD-induced apoptosis and paracrine effects were investigated. Apoptosis of MSCs was detected by Annexin V-FITC flow cytometric analysis. Transcriptional levels of IL-1β, TNF-α and IL-10 were examined by real-time PCR. The nuclear translocation of NF-κBp65 was assessed by immunocytochemical staining. Translational changes of IL-1β and TNF-α were detected by Western blot. The secretion of IL-10 from MSCs was examined by ELISA assay. The results showed that MG-132 could effectively suppress H/SD-induced MSCs apoptosis. Furthermore, the induced IL-1β and TNF-α transcription was also inhibited by MG-132 treatment, which may be due to the inhibition of NF-κBp65 nuclear translocation by MG-132. Importantly, MG-132 effectively enhanced H/SD-induced transcription and secretion of IL-10, which is an important paracrine factor from MSCs. Our findings suggest that pretreatment of MSCs by MG-132 before cell transplantation may be an effective strategy to improve cell survival and enhance paracrine effects of MSCs.
Animals ; Apoptosis ; drug effects ; Bone Marrow Cells ; cytology ; Cell Hypoxia ; Cell Survival ; drug effects ; Cells, Cultured ; Culture Media, Serum-Free ; Cysteine Proteinase Inhibitors ; pharmacology ; Female ; Interleukin-10 ; secretion ; Leupeptins ; pharmacology ; Male ; Mesenchymal Stromal Cells ; cytology ; Rats ; Rats, Sprague-Dawley