Islet protein expression changes during diabetes development in islet syngrafts in BB-DP rats and during rejection of BB-DP islet allografts

Interleukin 1 beta(IL-1) is cytotoxic to rat pancreatic beta-cells in vitro , and increased expression of IL-1 mRNA is found in the islets of Langerhan s during development of diabetes in BB/Wor/Mol-BB2 (BB-DP) rats and NOD mic e. It has been proposed that IL-l induces a Face between protective and del eterious proteins in the beta-cells during development of diabetes, and tha t heat shock proteins 70 and 90, and manganese superoxide dismutase, all in ducible by IL-l are potentially protective proteins, We have established a database of approximately 2000 neonatal rat-islet proteins by two-dimension al gel (2-D gel) electrophoresis of [S-35]-methionine labelled neonatal Wis tar Furth rat islets, In these IL-l was shown to up- or down-regulate the i slet-expression level of 99, and to induce de novo synthesis of 6 proteins. The identity of most of the IL-l induced proteins is unknown and under stu dy, In this study we wished to investigate if changes in protein expression ind uced in vitro by IL-1 stimulation of islets are also seen in vivo during sp ontaneous development of diabetes in BB-DP rats, and during islet allograft rejection, Two-hundred neonatal BB-DP rat islets were grafted under the ki dney capsule of either 30-day-old BB-DP rats killed at onset of diabetes or of 30-day-old Wistar Kyoto (WK) rats, killed 12 days after grafting. Prote ins in excised islet-grafts and in vitro IL-I exposed isolated neonatal BB- DP rat islets were labelled with [S-35]-methionine, and processed for 2-D g el electrophoresis, Fluorographs of the gels were analysed by computer. A t otal of 1815 proteins were found in 3 of 3 12.5% polyacrylamide gels. Inter leukin-l was found to change expression level of 82 of these proteins (22 u p- and 60 down-regulated) in neonatal BB-DP rat islets in vitro. Of these 8 2 proteins 33 (4 up- and 29 down-regulated) also changed level of expressio n during disease occurrence in syngeneic islet grafts from diabetic BB-DP r ats, and 29 (4 up- and 25 down-regulated) during rejection of BB-DP islets grafted to WK rats. Changes in the expression level of 14 (3 up- and 11 dow n-regulated) of the 82 proteins altered by IL-1 in vitro were only found in syngeneic islet grafts in diabetic BB-DP rats, and changes in the expressi on level of 8 (2 up- and 6 down-regulated) of these 82 proteins expression were only found in BB-DP islet allografts in WK recipients. Identification of these proteins may he important in understanding the mechanisms of islet destruction during development of insulin-dependent diabetes mellitus and during islet allograft rejection.