Molecular mechanisms of toxicity and cell damage in clonal human and mouse pancreatic beta cells, alpha cells, and intestinal L cells exposed to diabetic milieu.

Abstract

Novel human pancreatic beta cell line, 1.1B4 was generated only recentlyby electrofusion of human islet cells and immortal PANC-1 cell line. Incontrast, the mouse insulinoma cell line – MIN6, pancreatic alpha cell line –Alpha TC1 clone 9 and GLP-1 secreting enteroendocrine cell line –GLUTag are widely used in diabetes research. While cellular responses ofpancreatic beta cells on exposure to diabetic conditions have been studiedextensively, responses of this novel human insulin secreting cell line andpancreatic alpha and intestinal L cells have not been evaluated previously.In this thesis, mechanisms of toxicity and cell damage in 1.1B4, MIN6,Alpha TC1 clone 9 and GLUTag cells exposed to diabetic milieu wereevaluated. 1.1B4, MIN6 and GLUTag cells suffered cell death on exposureto chemicals, high glucose, palmitate and cytokines while Alpha TC1 clone9 cells were relatively resistant to these agents. 1.1B4 and MIN6 cellsecretory function, insulin content and mRNA expression of genes involvedin stimulus secretion coupling were affected to differing degrees.Expression of antioxidant enzyme genes was upregulated but wasinsufficient to detoxify ROS generated by toxins with the exception ofAlpha TC1 clone 9 cells. Pro-inflammatory cytokines caused nitrosativestress while other toxins caused oxidative stress, which was evident fromthe increase in DNA fragmentation and numbers of apoptotic cells.Mechanisms of toxicity and cell damage in the beta cell lines, 1.1B4 andMIN6, were consistent with previously established results using rodent cellmodels and isolated islets. This is the first study to report cellular responsesof 1.1B4, GLUTag and Alpha TC1 clone 9 cells under diabetic conditions. The results indicate that 1.1B4 cells represent a good model of human isletbeta cells for studying beta cell biology. Further, whereas MIN6 andGLUTag cells are sensitive to cytotoxic damage, Alpha TC1 clone 9 cellsexhibit resistance due to their relatively higher expression of catalase andlower expression of Glut2. Further dissection of molecular pathways couldaid in better understanding of mechanisms involved in diabetes, leading tonew therapeutic approaches.

Date of Award	Sept 2012
Original language	English
Sponsors	Vice Chancellor's Research Scholarship (VCRS)
Supervisor	Peter Flatt (Supervisor), Neville Mc Clenaghan (Supervisor), Peter Flatt (Supervisor) & Neville Mc Clenaghan (Supervisor)