Tissue inhibitor of metalloproteinase-1 prevents cytokine-mediated dysfunction and cytotoxicity in pancreatic islets and beta-cells

In addition to inhibiting matrix metalloproteinase-2 and matrix metalloprot einase-9 activity, recent studies suggest that tissue inhibitor of metallop roteinase (TIMP)1 may inhibit apoptosis in various cell lines. To address t his question in pancreatic islets and beta -cells, we treated rat pancreati c islets and INS-1 cells with a high-dose combination of the cytokines inte rleukin (IL)-1 beta, tumor necrosis factor-alpha, and interferon-gamma with or without the addition of TIMP-1 and TltMP-2 protein. Using flow cytometr y, we quantitated DNA fragmentation to assess cellular apoptosis and confir med these observations with DNA laddering experiments. Next, we transfected the mouse TIMP-1 gene into INS-1 cells and performed Western immunoblottin g to demonstrate expression of TIMP-1 protein. We treated TIMP-1-expressing INS-1 cells with high-dose cytokines and again used flow cytometry to asse ss DNA fragmentation. We also evaluated the effect of TIMP-1 on IL-1 beta - induced inhibition of glucose-stimulated insulin secretion (GSIS) in freshl y isolated rat pancreatic islets. Finally, we evaluated the effect of TIMP- 1 on inducible nitric oxide synthase (iNOS) gene expression and nuclear fac tor (NF)-kappaB activity in INS-1 cells stimulated with high-dose cytokines . TIMP-1 but not TIMP-2 prevented cytokine-induced apoptosis and cytokine-m ediated inhibition of GSIS in rat islets and beta -cells. TIMP-1 mediated t hese effects by inhibiting cytokine activation of NF-KB, but it did not aff ect nitric oxide production or iNOS gene expression. Therefore, TIMP-1 may be an ideal gene to prevent cytokine-mediated P-cell destruction and dysfun ction in models of type 1 diabetes and islet transplantation rejection.