This study was aimed to investigate the effect of proteasome inhibitor MG-132 on apoptosis of L1210 cells and its mechanism. L1210 cells were treated with MG-132 of different concentrations (0, 2.5, 5, 10, 10 micromol/L). Cell viability was tested by MTT assay, apoptosis rate was detected by using flow cytometry, activity of caspase 3 was detected by colorimetry, the expression of NF-kappaB nuclear protein was detected by Western blot. The results showed that the growth inhibition of L1210 cells treated for a same time (24 hours) was enhanced along with increasing of MG-132 concentrations (0, 2.5, 5, 10, 20 micromol/L); the inhibitory rate, apoptosis rate and activity of caspase 3 increased also along with raising of MG-132 concentrations; while the expression of NF-kappaB nuclear protein decreased along with raising of GM-132 concentrations. It is concluded that MG-132 can induce the apoptosis of L1210. The mechanism of apoptosis may be related to the down-regulation of the expression of NF-kappaB and the activation of caspase 3.
Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Cell Line, Tumor ; Enzyme Inhibitors ; pharmacology ; Humans ; Leupeptins ; pharmacology ; NF-kappa B ; metabolism

BACKGROUND: The objective of this study was to evaluate the role of proteases on the degradation of parathyroid hormone (PTH) in blood samples. METHODS: Protease inhibitors with specificity against serine proteases (aprotinin), cysteine proteases (E-64), serine and cysteine proteases (leupeptin), metalloproteases (EDTA), or a protease inhibitor cocktail with a broad spectrum of inhibitory activity were added to blood samples. After storage at room temperature (0-48 hr), PTH levels were measured. RESULTS: PTH levels in samples with the protease inhibitor cocktail did not change significantly after 48 hr of storage at room temperature, but the average PTH levels decreased by 40.7% and 20.1%, in samples stored at room temperature and stored at 4degrees C without protease inhibitors, respectively. PTH levels in samples with leupeptin were stable for up to 24 hr. After 48 hr, the mean PTH levels decreased by 17.1%, 16.0%, 26.2%, and 32.1%, with 500 KIU/mL aprotinin, 100 micro mol/L leupeptin, 10 micro mol/L E-64, and 10 micro mol/L EDTA, respectively, in the samples stored at room temperature. CONCLUSIONS: The decrease in PTH levels in blood samples seemed to be due to the degradation of PTH by proteases. Various proteases, including especially serine proteases, would act together to degrade PTH in blood specimen. The PTH degradation may be inhibited in blood specimen with protease inhibitor cocktail.
Aprotinin/pharmacology ; Blood Specimen Collection ; Edetic Acid/pharmacology ; Female ; Humans ; Leucine/analogs & derivatives/pharmacology ; Leupeptins/pharmacology ; Male ; Parathyroid Hormone/*blood/metabolism ; Protease Inhibitors/*pharmacology ; Time Factors

OBJECTIVETo investigate the reversing effect of NF-kappaB inhibitor MG-132 on chemoresistance of gastric cancer cells to vincristine.

METHODSIn vincristine-resistant human gastric cancer cells (SGC7901/VCR) and the parental sensitive clone (SGC7901), NF-kappaB-DNA binding activity was determined by electrophoreses mobility shift assay (EMSA). The inhibition level of kappaB (IkappaB-alpha) expression was measured by cellular-ELISA. Immunocytochemistry was used to detect the translocation of p65 and chemosensitivity of the cells was determined by MTT assay.

RESULTSCompared with the parental SGC7901 cells, both the baseline and VCR-induced NF-kappaB-DNA binding activities in various concentrations were all higher in the SGC7901/VCR cells. Pretreatment with MG-132, the NF-kappaB inhibitor, for 30 minutes remarkably reduced the NF-kappaB activation, IkappaB-alpha degradation and nuclear translocation of p65. As to the SGC7901/VCR cells and the parental sensitive SGC7901 cells, the IC(50) values for VCR were 40.03 mg/L and 0.26 mg/L, respectively. MG-132 (2.5 micromol/L) significantly enhanced the toxicity of VCR in SGC7901/VCR cells and decreased the resistance index from 154.0 to 16.5. However, MG-132 did not show an obvious effect on the VCR sensitivity in sensitive SGC7901 cells.

CONCLUSIONOur data indicate that inhibition of NF-kappaB activation in gastric cancer cells may reverse the drug resistance to VCR in the cancer cells and increase the efficiency of chemotherapy.

Adenocarcinoma ; pathology ; Antineoplastic Agents, Phytogenic ; pharmacology ; Cell Line, Tumor ; Drug Resistance, Neoplasm ; drug effects ; Humans ; Leupeptins ; pharmacology ; NF-kappa B ; antagonists & inhibitors ; Stomach Neoplasms ; pathology ; Vincristine ; pharmacology

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

OBJECTIVETo observe the protective effect of the proteasome inhibitor MG-132 in rats with severe acute pancreatitis (SAP) and the associated lung injury.

METHODSIn rat models of the SAP established with injection of 5% sodium taurocholate into the biliary-pancreatic duct, the changes of the serum amylase and myeloperoxidase (MPO) activity in the pancreatic and lung tissues were evaluated. The pathological changes of the pancreatic and lung tissues were also observed.

RESULTSMG-132 significantly decreased serum amylase, pancreatic weight/body weight ratio, and pancreatic and pulmonary myeloperoxidase activity (P<0.05). Histopathological examinations revealed milder edema, cellular damage, and inflammation in the pancreatic and lung tissues of rats pretreated with the peptide (P<0.05).

CONCLUSIONMG-132 ameliorates SAP and the associated lung injury in rats.

Acute Disease ; Amylases ; blood ; Animals ; Cysteine Proteinase Inhibitors ; pharmacology ; Leupeptins ; pharmacology ; Lung ; pathology ; Lung Injury ; drug therapy ; Pancreas ; pathology ; Pancreatitis ; drug therapy ; Peroxidase ; blood ; Rats ; Rats, Sprague-Dawley

This study was aimed to investigate the effect of proteasome inhibitor MG-132 at different doses on cultured K562 cell apoptosis. MTT assay was used to observe the activity of K562 cell proliferation inhibition rate after treating for 48 hours at different doses (0, 2, 4, 8, 16, 32 micromol/L). Immunocytochemistry was used to detect the NF-kappaB activity and glucocorticoid receptor (GR) expression. Flow cytometry was used to determine the K562 cell apoptosis. The results indicated that proliferation inhibition rate of K562 cells after treated for 48 hours showed dose-dependent, the inhibitory rates of cell proliferation in test groups were significant higher than that in control group, and the effect in 32 micromol/L test group was the most obvious (45.24 +/- 4.12)% (p < 0.05). The NF-kappaB activity and GR expression after treating for 48 hours showed dose-dependent. Compared with control group, the NF-kappaB activities in test groups were lower (p < 0.05), and the NF-kappaB activity in 32 micromol/L test group was the lowest (63.60 +/- 2.95); the GR expression in test groups was higher (p < 0.05), and the GR expression in 16 micromol/L test group was the highest (75.62 +/- 2.70). The K562 cell apoptosis rate after treating for 48 hours also showed dose-dependent. Compared with control group, the K562 cell apoptosis rates in test groups were higher (p < 0.05), the K562 cell apoptosis rate in 32 micromol/L test group was the highest (21.37 +/- 2.02)%. It is concluded that the MG-132 may induce K562 cell apoptosis and proliferation inhibition through up-regulation of NF-kappaB activity and down-regulation of GR expression both in dose-dependent manner.
Apoptosis ; drug effects ; Cell Proliferation ; drug effects ; Cysteine Proteinase Inhibitors ; pharmacology ; Humans ; K562 Cells ; Leupeptins ; pharmacology ; NF-kappa B ; metabolism ; Receptors, Glucocorticoid ; metabolism

OBJECTIVETo study the protective effect of MG-132 on hippocampus cells apoptosis induced by deltamethrin (DM), one kind of pyrethroid pesticide.

METHODS40 Male wistar rats were randomly divided into four groups: olive oil control, DM treated alone (12.5 mg/kg), MG-132 (0.5 mg/kg) plus DM group, MG-132 treated 2h plus olive oil. After 24h treatment of DM, the hippocampus was taken out to detect the apoptotic cell rate, the level of bcl-2 and Caspase-3 activity.

RESULTSCompared with DM treated alone group (27.29% +/- 2.41%), the apoptotic cell rate in MG-132 + DM group (19.94% +/- 2.07%) was increased (P < 0.05), bcl-2 expression was enhanced [(0.43 +/- 0.06) vs. (2.01 +/- 0.23)] (P < 0.05) and the activity of Caspase-3 was decreased significantly (P < 0.05) in MG-132 treated 2h plus DM group [(4.55 +/- 0.46) vs.(3.73 +/- 0.35)].

CONCLUSIONMG-132 can protect hippocampus cells against apoptosis induced by deltamethrin.

Animals ; Apoptosis ; drug effects ; Hippocampus ; cytology ; drug effects ; Insecticides ; toxicity ; Leupeptins ; pharmacology ; Male ; Neurons ; drug effects ; Nitriles ; toxicity ; Pyrethrins ; toxicity ; Rats ; Rats, Wistar

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*

AIMTo study the effects of protease inhibitors on the large and small intestinal absorption of insulin in rats and to explore the mechanism of various protease inhibitors in different intestinal regions.

METHODSThe intestinal absorption of insulin was evaluated by its hypoglycemic effect and serum insulin level using an in situ loop method with the washing treatment.

RESULTSAdministration of insulin alone did not decrease the glucose level at either intestinal region with or without the washing treatment. With the unwashing treatment, there were no hypoglycemic effects in small intestinal loop when coadministration of insulin with protease inhibitors. With the washing treatment, the biological effects of insulin were amplified a little in small intestinal loop; obvious hypoglycemic effects were found in large intestinal loop with or without the washing treatment. The effectiveness of protease inhibitors was susceptible to their categories, concentrations and activities of proteolytic enzymes in different regions. The efficacy order of various protease inhibitors for enhancing hypoglycemic response of insulin was: leupeptin > sodium glycocholate > bacitracin > bestatin > cystatin; the percutaneous enhancement effects were observed in the presence of either sodium glycocholate or bacitracin.

CONCLUSIONCoadministration of protease inhibitors could increase the insulin efficacy more effectively in the large intestine than in the small intestine.

Animals ; Bacitracin ; pharmacology ; Biological Availability ; Blood Glucose ; metabolism ; Colon ; metabolism ; Glycocholic Acid ; pharmacology ; Insulin ; pharmacokinetics ; Intestinal Absorption ; drug effects ; Intestine, Small ; metabolism ; Leupeptins ; pharmacology ; Male ; Protease Inhibitors ; pharmacology ; Random Allocation ; Rats ; Rats, Wistar

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