Effects Of Glucagon-like Peptide-1 On Endoplasmic Reticulum Stress-Induced Apoptosis Of Pancreatic β Cells

Objective:To explore the potential protection of GLP-1(glucagon-like peptide-1,GLP-1) on thapsigargin (TG)induced pancreaticβcell apoptosis.Methods:The rat pancreaticβcell line- r9 cells in vitro was used to compare the pancreaticβcell apoptosis with the presence of GLP - 1 and GLP - 1 receptor agonists exendin-4 when using 100nM thapsigargin as the exutory to be the reason of Isletβapoptosis. We use the methods of MTT, DNA fragmentation, TUNEL staining and AnnexinⅤ-PI respectively to quantitative analysis. Further, we investigated the effects of GLP-1 and exendin-4 on the release of cytochromec, Caspase3 activation and reactive oxygen species (ROS) generation during ER stress.Results:1. The result of AnnexinⅤ-PI FCM and DNA gel electrophoresis showed that 12 hours after exposure to be the data of 0,10,100,300nM thapsigargin respectively and exposure to be the data of 0,6,9,12,24 hours by 100nM thapsigargin,the apoptotic rates of r9 were gradually increase in dose– and time-dependent manner.2. The results by MTT showed that the GLP - 1 and Exendin - 4 could obviously decrease proliferation of inhibition by TG on r9 cell3. The result of DNA gel electrophoresis reveals fragmenting clearly, scalariform stripe from the DNA of r9 induced by the 100nM thapsigargin which had been impacted by r9 cell. However, the group of given GLP-1 or Exendin-4 reveals lighter color. TUNEL and Hochest33342-PI coloration proves the result further. AnnexinⅤ-PI FCM reveals that the apoptosis rate of TG group is 26.7 percent. Comparing to the TG group, the apoptosis rate of early stage GLP-1and Exendin-4 falls respectively to 19.7 and 19.2 percent. The difference in statistics is notable (p<0.05)4.The Western blot detection result of Cytoplasm albumen shows that there are some, and after given the TG, releasing cytochrome–C apparently increase,while given the GLP-1 or Exendin-4, which will reduce the Cytc in the cytoplasm5.The consequence of releasing Cell mitochondria reactive oxygen displays that we could find a given mass of reactive oxygen ROS, and will grow apparently when given the TG, while it will reduce when given the GLP-1 and Exendin-4.6. The detection result of caspase3 in the cytoplasm display that we could detect a given mass of caspase3 in the cytoplasm. Caspase3 will grow apparently when given the TG, while given the GLP-1 and Exendin-4, it will restrain the activation and release.Conclusions:1. Thapsigargin could inhibited the apoptosis of pancreaticβcells in dose– and time-dependent manner.2. GLP - 1 or Exendin– 4 could inhibited the apoptosis of pancreaticβcells induced by TG3. GLP - 1 and Exendin -4 significantly inhibited TG induced cytochromes c, active oxygen release and apoptosis protease caspase3 activity on r9 cells...