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Cholesterol induces pancreatic ? cell apoptosis through oxidative stress pathway.

ABSTRACT: Type 2 diabetes is often associated with high blood cholesterol. Here, we investigated the effect of cholesterol loading on MIN6 cells derived from pancreatic ? cells. Exposure of MIN6 cells to cholesterol-induced apoptosis in time- and dose-dependent manner. Treatment with methyl-?-cyclodextrin that removes cholesterol from plasma membrane prevented the cells from cholesterol-induced apoptosis. Western blot analysis revealed that the levels of phosphorylated-p38 mitogen-activated protein kinase (P-p38 MAPK) and c-Jun N-terminal kinases (P-JNK) were significantly increased after the cholesterol loading, suggesting that the stress-activated protein kinase signaling was stimulated. A specific p38 inhibitor rescued MIN6 cells from cholesterol-induced apoptosis, while JNK inhibitor failed, suggesting the importance of activation of p38 MAPK signaling in response to cholesterol. The expression of Bip and CHOP, the endoplasmic reticulum (ER) stress markers, remained unaffected, indicating that the ER stress may not be involved in the cytotoxicity of cholesterol on the ???6 cells. The intracellular concentration of reactive oxygen species measured by use of 2',7'-dichlorofluorescin diacetate was significantly increased after cholesterol loading, demonstrating the induced apoptosis was mediated through oxidative stress. Addition of reduced form of glutathione in the medium rescued MIN6 cells from apoptosis induced by cholesterol loading. Taken together, these results demonstrate that the free cholesterol loading can induce apoptosis of MIN6 cells mediated by oxidative stress and the activation of p38 MAPK signaling.

SUBMITTER: Lu X

PROVIDER: S-EPMC3156264 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Cholesterol induces pancreatic β cell apoptosis through oxidative stress pathway.

Lu Xiuli X Liu Jianli J Hou Fangfang F Liu Zhenqing Z Cao Xiangyu X Seo Hisao H Gao Bing B

Cell stress & chaperones 20110407 5

Type 2 diabetes is often associated with high blood cholesterol. Here, we investigated the effect of cholesterol loading on MIN6 cells derived from pancreatic β cells. Exposure of MIN6 cells to cholesterol-induced apoptosis in time- and dose-dependent manner. Treatment with methyl-β-cyclodextrin that removes cholesterol from plasma membrane prevented the cells from cholesterol-induced apoptosis. Western blot analysis revealed that the levels of phosphorylated-p38 mitogen-activated protein kinase ...[more]

PMID: 21472505

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Project description:BackgroundCancer-associated fibroblasts (CAFs) are among the most prominent cells during the desmoplastic reaction in pancreatic ductal adenocarcinoma (PDAC). However, CAFs are heterogeneous and the precise origins are not fully elucidated. This study aimed to explore whether monocytes can transdifferentiate into fibroblasts in PDAC and evaluate the clinical significance of this event.MethodsCD14+ monocytes were freshly isolated from human peripheral blood. Immunofluorescence, reverse transcription-quantitative PCR, western blot, flow cytometry and enzyme-linked immunosorbent assay were used to detect the expression of αSMA, fibronectin, and other relevant molecules. In addition, latex beads with a mean particle size of 2.0 µm were used to assess the phagocytic capacity. Moreover, RNA sequencing (RNA-seq) was performed to identify the differences induced by H2 O2 and the underlying mechanisms.ResultsImmunofluorescence identified αSMA and fibroblast-specific protein 1 expression by tumor-associated macrophages in PDAC. The in vitro experiment revealed that oxidative stress (H2 O2 or radiation) induced monocyte-to-myofibroblast transdifferentiation (MMT), as identified by upregulated αSMA expression at both the RNA and protein levels. In addition, compared with freshly isolated monocytes, human monocyte-derived macrophages increased fibronectin expression. RNA-seq analysis identified p53 activation and other signatures accompanying this transdifferentiation; however, the p53 stabilizer nutlin-3 induced αSMA expression through reactive oxygen species generation but not through the p53 transcription/mitochondria-dependent pathway, whereas the p38 inhibitor SB203580 could partially inhibit αSMA expression. Finally, MMT produced a unique subset of CAFs with reduced phagocytic capacity that could promote the proliferation of pancreatic cancer cells.ConclusionsOxidative stress in the tumor microenvironment could induce MMT in PDAC, thus inducing reactive stroma, modulating immunosuppression, and promoting tumor progression. Reducing oxidative stress may be a promising future therapeutic regimen.

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Cholesterol induces pancreatic ? cell apoptosis through oxidative stress pathway.

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Cholesterol induces pancreatic β cell apoptosis through oxidative stress pathway.

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