title: Exendin-4 protects mitochondria from reactive oxygen species induced apoptosis in pancreatic Beta cells.
abstract: OBJECTIVE
  Mitochondrial oxidative stress is the basis for pancreatic β-cell apoptosis and a common pathway for numerous types of damage, including glucotoxicity and lipotoxicity. We cultivated mice pancreatic β-cell tumor Min6 cell lines in vitro and observed pancreatic β-cell apoptosis and changes in mitochondrial function before and after the addition of Exendin-4. Based on these observations, we discuss the protective role of Exendin-4 against mitochondrial oxidative damage and its relationship with Ca(2+)-independent phospholipase A2.
  
  
  METHODS
  We established a pancreatic β-cell oxidative stress damage model using Min6 cell lines cultured in vitro with tert-buty1 hydroperoxide and hydrogen peroxide. We then added Exendin-4 to observe changes in the rate of cell apoptosis (Annexin-V-FITC-PI staining flow cytometry and DNA ladder). We detected the activity of the caspase 3 and 8 apoptotic factors, measured the mitochondrial membrane potential losses and reactive oxygen species production levels, and detected the expression of cytochrome c and Smac/DLAMO in the cytosol and mitochondria, mitochondrial Ca2-independent phospholipase A2 and Ca(2+)-independent phospholipase A2 mRNA.
  
  
  RESULTS
  The time-concentration curve showed that different percentages of apoptosis occurred at different time-concentrations in tert-buty1 hydroperoxide- and hydrogen peroxide-induced Min6 cells. Incubation with 100 µmol/l of Exendin-4 for 48 hours reduced the Min6 cell apoptosis rate (p<0.05). The mitochondrial membrane potential loss and total reactive oxygen species levels decreased (p<0.05), and the release of cytochrome c and Smac/DLAMO from the mitochondria was reduced. The study also showed that Ca(2+)-independent phospholipase A2 activity was positively related to Exendin-4 activity.
  
  
  CONCLUSIONS
  Exendin-4 reduces Min6 cell oxidative damage and the cell apoptosis rate, which may be related to Ca(2)-independent phospholipase A2.
authors.affiliation: Diabetes Center, Second Xiangya Hospital, and Institute of Metabolism and Endocrinology, Key Laboratory of Diabetes Immunology, Ministry of Education, Central South University, Changsha, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.forename: Zhiguang
authors.initials: Z
authors.lastname: Zhou
authors.forename: Gan
authors.initials: G
authors.lastname: Huang
authors.forename: Fang
authors.initials: F
authors.lastname: Hu
authors.forename: Yufei
authors.initials: Y
authors.lastname: Xiang
authors.forename: Lining
authors.initials: L
authors.lastname: He
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D053938:DNA Fragmentation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D000077270:Exenatide; D005227:Fatty Acids / Q000378:metabolism; D005786:Gene Expression Regulation; D054522:Group VI Phospholipases A2 / Q000235:genetics / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D018384:Oxidative Stress; D010455:Peptides / Q000494:pharmacology*; D054510:Phospholipases A2, Cytosolic / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D014688:Venoms / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D005227:Fatty Acids; D007004:Hypoglycemic Agents; D010455:Peptides; D017382:Reactive Oxygen Species; D014688:Venoms; D000077270:Exenatide; D054522:Group VI Phospholipases A2; D054510:Phospholipases A2, Cytosolic; D053148:Caspase 3