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.