Extracellular Matrix Protects Pancreatic β-Cells Against Apoptosis

Extracellular Matrix Protects Pancreatic β-Cells Against Apoptosis Role of Short- and Long-Term Signaling Pathways Eva Hammar 1 , Géraldine Parnaud 1 , Domenico Bosco 2 , Nadja Perriraz 1 , Kathrin Maedler 3 , Marc Donath 3 , Dominique G. Rouiller 1 and Philippe A. Halban 1 1 Department of Genetic Medicine and Development, University Medical Center, University Hospital, Geneva, Switzerland 2 Cell Isolation and Transplantation Center, University Hospital, Geneva, Switzerland 3 Division of Endocrinology and Diabetes, University Hospital, Zurich, Switzerland Address correspondence and reprint requests to Eva Hammar, Department of Genetic Medecine and Development, University Medical Center, 9th Floor, Rue Michel Servet 1, 1211 Geneva 4, Switzerland. E-mail: eva.hammar{at}medecine.unige.ch Abstract We have shown previously that culture of β-cells on matrix derived from 804G cells and rich in laminin-5 improves their function. The purpose of this study was to investigate whether this matrix protects β-cells against apoptosis and to elucidate signaling pathways involved. Matrix protected sorted rat β-cells against apoptosis under standard conditions (11.2 mmol/l glucose, 10% serum), after serum deprivation (1% serum), and in response to interleukin-1β (IL-1β; 2 ng/ml), compared with control (poly- l -lysine [pLL]). Caspase-8 activity was reduced in cells cultured on matrix, whereas focal adhesion kinase (FAK), protein kinase B (PKB, or Akt), and extracellular signal–regulated kinase (ERK) phosphorylation was augmented. Treatment (4 h) with an anti-β1 integrin antibody, with the ERK pathway inhibitor PD98059, and/or with the phosphatidylinositol 3-kinase inhibitor LY294002 augmented cell death on 804G matrix but not on pLL. In long-term assays (48 h), PD98059 but not LY294002 drastically augmented cell death on 804G matrix but did so to a lesser extent on pLL. The protein inhibitor of nuclear factor-κB (IκBα) was overexpressed in cells cultured 18 h on matrix with partial blockade by PD98059. In summary, this study provides evidence for activation of signaling pathways and gene expression by extracellular matrix leading to improved β-cell survival. ECM, extracellular matrix ELISA, enzyme-linked immunosorbent assay ERK, extracellular signal–regulated kinase FAK, focal adhesion kinase GAPDH, glyceraldehyde-3-phosphate dehydrogenase HRP, horseradish peroxidase IκBα, inhibitor of nuclear factor κB IL-1β, interleukin-1β MAP, mitogen-activated protein MEK1, MAP kinase/E