2136-P: Effects of Cytokine Exposure on the Proteome of Human Islets as Evaluated by Shotgun and 2DE Analysis

Pro-inflammatory cytokines (CYT) lead to several changes in human islet (HI) protein expression, but few data are available on CYT-induced alterations at the whole proteome level, including post-translational modifications (PTM). We used label-free shotgun analysis (SG) and bi-dimensional gel electrophoresis (2DE) to explore how CYT modify the proteome of isolated HI. For this purpose, HI were isolated from the pancreas of 5 nondiabetic organ donors (age: 74±6 years; gender: 3M/2F; BMI: 27.9±3.6 kg/m²) and then cultured for 48h in the presence of 50 U/ml interleukin (IL)-1β + 1000 U/ml interferon (IFN)-γ. Then, 40 or 250 μg protein extracts were used respectively for SG or 2DE (to assess lysine-acetylation) analysis, with the SG mass spectrometry data acquired by nano-liquid chromatography tandem mass spectrometry. SG identified around 3000 proteins, of which 286 were differentially expressed after CYT exposure. Of these, 176 were upregulated and 110 downregulated. Among the former, we found mediators of inflammation, proteins of the ER and the immunoproteasome system and oxidative stress modulators (e.g., CXCL2, CXCL10, PSMB8, PSMB9, PSMB10, SOD2). Among the downregulated proteins, there were cathepsins, antioxidant molecules and enzymes of glycolysis and Krebs’ cycle (e.g., CTSH (a candidate gene for T1D), PRDX2, MDH). Ingenuity Pathway Analysis indicated that several upstream regulators were predicted to be differentially affected. Of them, 118 were presumably activated, including STAT1 and STAT2, NF-κB, JAK1, IRF1, HMGB1 and 36 inhibited, such as ACKR2, TRIM24, MAPK1, SUMO3. Bi-dimensional gel electrophoresis showed 151 spots that were lysine-acetylated, of which 2 were upregulated (PRDX3 and SOD1) and 4 downregulated (GDH, CTSD, ACAD9 and EIF4A1) by CYT. The present study shows novel proteomic changes, including specific PTM, induced in human islets by cytokine treatment that could play a role in beta cell dysfunction and demise and be the target for specific treatments.