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ABSTRACT: Background: Glucagon-like peptide-1 (GLP-1) and its potent analog, exendin-4, are well known to inhibit β-cell apoptosis and promote β-cell proliferation. Meanwhile, cytokines, such as interleukin-1β (IL-1β), stimulate inducible nitric oxide synthase (iNOS) expression and nitric oxide overproduction leading to β-cell damage. However, the protective mechanisms of GLP-1 in β-cells exposed to cytokines have not been fully elucidated. Aims: In this study, the protective effects of exendin-4 on IL-1β-induced apoptosis were investigated in murine MIN6 pancreatic β-cells. The role of nuclear factor-κB (NF-κB) signaling in this process was also explored. Methods: The effects of exendin-4 pre-treatment on IL-1β-induced apoptosis were investigated by Hoechst/PI and Annexin V/PI staining. Levels of iNOS and NF-κB proteins were investigated by Western blotting and cytoplasmic nitrite levels were determined using Griess reagent. Results: IL-1β treatment (range, 5-40 ng/ml) for 24 h was positively correlated with nitrite production (R2 = 0.9668, P<0.01), a significant increase in the percentage of apoptotic cells (P<0.01) and a concomitant dose-dependent increase in cytoplasmic levels of iNOS and NF-κB p65 activation. N-acetyl-L-cysteine (NAC), NG-nitro-L-arginine methyl ester (L-NAME) and pyrrolidine dithiocarbamate (PDTC), partially rescued apoptotic β-cells, suggesting involvement of NF-κB-iNOS-nitrite in this process. Exendin-4 (100 nM) treatment significantly decreased IL-1β-induced apoptosis (P<0.01), downregulated NF-κB activation and subsequently decreased iNOS and nitrite levels in IL-1β-induced β-cells (P<0.001), in a manner similar to L-NAME, PDTC and NAC. Conclusions: These results suggest that exendin-4 protects against IL-1β-induced apoptosis in β-cells via downregulation of the NF-κB-iNOS-nitrite pathway.
Journal of endocrinological investigation 04/2013; · 1.57 Impact Factor
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ABSTRACT: Objectives. This study aimed to explore the effect of exendin-4 on t-BHP-induced apoptosis in pancreatic β cells and the mechanism of action. Methods. Murine MIN6 pancreatic β cells were treated with exendin-4 in the presence or absence of tert-butyl hydroperoxide (t-BHP). Cell survival was assessed by MTT staining. The percentage of apoptotic cells was determined by fluorescence microscopy analysis after Hoechst/PI staining and flow cytometric assay after Annexin V-FITC/PI staining. The activity of caspase-3 was determined using a caspase-3 activity kit. Expression of P-IRE1α, IRE1α, C-Jun N-terminal kinase (JNK), P-JNK, C-JUN, and P-C-JUN was detected by western blotting. Results. Exendin-4 was found to inhibit t-BHP-induced apoptosis in pancreatic β-cells by downregulating caspase-3 activity. Exendin-4 also inhibited the endoplasmic reticulum transmembrane protein IRE1, the apoptosis-related signaling molecule JNK, and c-Jun activation. Conclusions. Our findings suggest that exendin-4 ultimately reduces t-BHP-induced β-cell apoptosis. IRE1-JNK-c-Jun signaling is involved in the exendin-4-mediated modulation of β-cell apoptosis.
International Journal of Endocrinology 01/2012; 2012:549081. · 1.87 Impact Factor
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ABSTRACT: Through a third-butyl hydrogen peroxide (t-BHP) induced apoptosis in pancreatic islet β-cells to study the oxidative damage induced endoplasmic reticulum stress-JNK pathway of apoptosis related molecules in vitro.
Mouse insulinoma(MIN6) cells was administered with t-BHP which were cultured in vitro. Choosing medicine with different concentrations(0-400 μmol/L)and time periods(0-8 h)to establish the cells apoptosis model. The percentage of cell viability was determined through CCK-8 assay. The percentage of apoptosis was determined through flow cytometric assay after Annexin-V-FITC-PI staining. The activity of caspase-3 was measured by the caspase-3 activity assay kit. The expression of Endoplasmic reticulum stress-related molecules and the apoptosis signal pathway IRE1, JNK, P-JNK, Caspase-3 were detected by Western blot.
The percentage of MIN6 cell viability was reducing with the concentration of t-BHP increasing. The Caspase-3 significantly change the activity after exposured of t-BHP in a concentration ≥ 25 μmol/L when the role of ≥1 h, With t-BHP concentration was increased, the role of prolonged, endoplasmic reticulum stress transmembrane protein IRE1α, P-JNK, active caspase-3 expression was significantly increased.
The study demonstrates that the percentage of MIN6 cell viability was reduced in a dose-dependent manner. Continuous exposuring of t-BHP induced oxidative damage in MIN6 cells to endoplasmic reticulum stress and apoptosis. The expression of Endoplasmic reticulum stress and apoptosis pathway-related molecules in cell apoptosis in a dose and time-dependent.
Xi bao yu fen zi mian yi xue za zhi = Chinese journal of cellular and molecular immunology 03/2011; 27(3):249-52, 256.
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ABSTRACT: To explore the effect and mechanism of exendin-4 on dexamethasone-induced apoptosis in pancreatic β-cells.
Murine MIN6 pancreatic β-cells were treated with dexamethasone (100 nmol/l) over 48h following pretreatment with exendin-4 (100 nmol/l). Cell viability was determined using an MTT assay. The percentage of apoptotic cells was determined through fluorescence microscopy analysis after Hochest/PI staining and a flow cytometric assay after Annexin V-FITC/PI staining. Caspase 3 activity was measured using the caspase 3 activity assay kit. Expression of cyt-c, bcl-2, bax, AKT, and phosphorylated AKT was detected by western blot.
Exendin-4 reduced the percentage of cells undergoing apoptosis when β-cells were exposed to dexamethasone. Exendin-4 down-regulated caspase 3 activity, reduced cytochrome c levels in cytoplasm, and increased Bcl-2 protein levels and the Bcl-2 to Bax ratio in dexamethasone-treated β-cells. These exendin-4 effects were blocked in the presence of an inhibitor of the phosphoinositide-3 kinase (PI-3K) pathway or of the protein kinase A (PKA) pathway. Exendin-4 reversed dexamethasone-mediated inhibition of Akt phosphorylation, which was abrogated by the PI-3K and PKA inhibitors.
PI-3K and PKA signaling are involved in the exendin-4-mediated modulation of β-cell apoptosis.
Diabetes research and clinical practice 10/2010; 90(3):297-304. · 2.16 Impact Factor
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ABSTRACT: To investigate the chronic effect of palmitic acid (PA) on apoptosis of pancreatic islet beta-cells and the possible mechanism. MEthods: Insulinoma cell line (MIN6 cells) were used in this study. After being incubated in PA (0.1 - 1.6 mml/L) for 24 and 48 hours, MTT method was used to evaluate the livability. After being incubated for 48 h, Hoechst-PI and Annexin-V-FTTC/PI FACS were used to estimate the apoptosis in each group, Western-blotting assay was used to estimate the protein level of p-Akt, Akt, Bax and Bcl-2.
Chronic PA dose-dependently (1) decreased the availability and increased the apoptosis of MIN6 cells; (2) decreased the phosphorylation of Akt and Bcl-2, but had no significant effects on Akt and Bax.
Chronic PA dose-dependently induced apoptosis of MIN6 cells, and this effect was possibly regulated by Akt/Bcl-2.
Zhongguo ying yong sheng li xue za zhi = Zhongguo yingyong shenglixue zazhi = Chinese journal of applied physiology 11/2009; 25(4):553-6.
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ABSTRACT: This study is to investigate the effect of dexamethasone on cell apoptosis of murine MIN6 pancreatic beta-cells, and to investigate the mechanism of dexamethasone-dependent cell apoptosis. The cell apoptosis model was established by choosing the murine MIN6 pancreatic beta-cells, which was cultured in vitro and induced by dexamethasone. The morphology of the cell apoptosis was observed through fluorescence microscopic analysis after Hochest/PI staining and flow cytometric assay after Annexin-V/PI staining. The expression of caspase-3 was detected with caspase-3 activity assay kit. The expressions of Cyt-c, Bcl-2, Bax, AKT and p-AKT were observed with Western blotting. The results indicated that after exposure to dexamethasone at a concentration ranging from 50-800 nmol x L(-1) for 48 h, the percentage of cell apoptosis was significantly increased with the concentration over 100 nmol x L(-1) of dexamethasone; after exposure to dexamethasone (100 nmol x L(-1)) for 72 h, the activity of caspase-3 increased significantly; after exposure to dexamethasone at a concentration ranging from 50-800 nmol x L(-1) for 48 h, the expression of Cyt-c increased, Bcl-2 and AKT phosphorylation decreased while Bax and T-AKT remained unchanged. It could be concluded that the effect of dexamethasone on murine MIN6 pancreatic beta-cells apoptosis is significant. The mechanism of dexamethasone-dependent cell apoptosis is probably related to down regulation of the Bcl-2 expression and reduction of AKT phosphorylation.
Yao xue xue bao = Acta pharmaceutica Sinica 11/2009; 44(11):1216-20.
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ABSTRACT: To explore the possible mechanism of tert-butyl hydroperoxide (t-BHP)-induced apoptosis in murine MIN6 pancreatic beta-cells.
MIN6 cells were cultured in vitro. Cell damage was evaluated by epifluorescence microscopy after staining with AO-EB. The percentage of cell apoptosis was determined by flow cytometric assay after Annexin- V-PI staining. Nitric oxide levels were measured by Griess assay. Inducible nitric oxide synthase(iNOS) protein and NF-kappaBp65 fragment were detected by Western blot.
Exposure of 25 micromol/L t-BHP to MIN6 cells for 60 min, cell viability was reduced and the percentage of apoptosis was increased significantly. The levels of cytoplasmic iNOS protein and nitrite were elevated. Meanwhile, treatment with t-BHP resulted in nucleus NF-kappaBp65 fragment peaking at 20 min. Both L-NAME and N-Acetyl-l-cysteine (NAC) attenuated the elevated levels of nitrite and percentage of apoptosis due to t-BHP alone.
NF-kappa-iNOS-nitric oxide signalling pathway can mediated t-BHP induced apoptosis in MIN6 cells .
Zhongguo ying yong sheng li xue za zhi = Zhongguo yingyong shenglixue zazhi = Chinese journal of applied physiology 05/2009; 25(2):255-9.
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ABSTRACT: To explore the effect of glucagon-like peptide-1 receptor agonist--Exendin-4 (Ex-4) on murine MIN6 pancreatic beta-cells apoptosis induced by oxidative stress, the morphological changes of cell damage were evaluated by epifluorescence microscopy after staining with AO-EB. The percentage of cell apoptosis was determined by flow cytometric assay after Annexin-V-FITC-PI staining. Nitric oxide level was measured by Griess reagent assay. Inducible nitric oxide synthase (iNOS) protein and NF-kappaBp65 fragment were detected by Western blotting. Ex-4 inhibited the increase of nitrite level and percentage of apoptosis induced by t-BHP in MIN6 cells. Furthermore, Ex-4 partly reduced the expression of iNOS protein and the ratio of NF-kappaBp65 protein in nucleus:cytosol induced by t-BHP. These results suggest that Ex4 protects MIN6 pancreatic kappa-cells from oxidative stress-induced apoptosis via down-regulation of NF-kappaB-iNOS-nitric oxide pathway.
Yao xue xue bao = Acta pharmaceutica Sinica 08/2008; 43(7):690-4.
