Shotgun proteomics of human pancreatic islets: effect of cytokines exposure

The effect of cytokines on β-cell function and survival was studied in β-cells as INS1-E and a different role was suggested for INF-γ and IL-1 (Rondas et al, J Proteome Res, 2013). In order to investigate the effect of cytokines on human islets, the complete proteome before and after exposure to cytokines was analyzed using label free shot-gun proteomics. Aliquots of 40 µg of human islets protein extracts, with and without cytokines treatment, were loaded onto 12% acrylamide resolving gel. After separation, gel pieces were excised from the gel and the proteins were identified by shot-gun after in-gel trypsin digestion. Around 3000 proteins were identified and out of 245 differentially expressed proteins, 158 resulted increased and 87 reduced after treatment with cytokines. Overall these proteins appertain mainly to metabolism, defense, repair and immunoresponse, protein synthesis and degradation. By IPA analysis the network and the involved canonical pathways were suggested. Moreover, 154 predicted upstream regulators (118 activated and 36 inhibited) were prompted. In addition to known regulator factors such as STAT1, NFKb, IRF1, MAPK1, new ones as HMGB1, GPSA and SIRT1 were found. Finally, the cytokines induced a significant decrease of insulin secretion respect to control, together with an increase of apoptotic beta cells and a reduction of volume density of grain of insulin. Overall our results show how the detrimental effects of cytokines treatment in human pancreatic islets could be associated to proteome changes. Further studies are necessary to clarify the correlation between these deregulation and type 1 diabetes features