111-OR: Pancreatic Elastase Regulates Human Beta-Cell Proliferation via the Focal Adhesion and PAR2 Signaling Pathways

Pancreatic elastase (PE) is a serine protease produced by pancreatic acinar cells. PE is mainly secreted in the intestine during digestion, and is also detectable in stromal pancreatic tissue, including the ECM of islets. Recently, we identified serpinB1 (SB1), a protease inhibitor, as a promoter of human β-cell proliferation by inhibiting PE activity and demonstrated that the PE inhibitor, sivelestat, also induced β-cell regeneration. Here, we report the identification two novel PE inhibitors: telaprevir, an antiviral drug, and tebipenem, an antibiotic. We observed that telaprevir and tebipenem inhibited human PE (hPE) with greater or similar potency than sivelestat respectively (IC50: telaprevir 15.7nM, tebipenem 3.6µM, sivelestat 2.3 µM; n=3). We then tested the effects of the compounds in in vitro cultures of human islets. Telaprevir and tebipenem each increased proliferating human β-cells (∼4-fold and 1.5-fold increase respectively; n=6) compared to vehicle-treated islets. Furthermore, in an independent study, both compounds (at 10µM), stimulated β-cell regeneration in a zebrafish model resulting in ∼1.5-fold increase in insulin+ cells in treated versus non-treated groups. Finally, to identify pathways modulated by PE we treated human islets with the two compounds for 10 or 30 minutes and performed a phosphoprotein microarray assay (Kinexus, CA). We discovered that inhibition of hPE increased phosphorylation levels of PXN-PAK proteins belonging to the focal adhesion pathway. In addition, phosphorylation on the effectors of Protease-activated receptor 2 (PAR2) signaling (i.e., PKC, PYK2 and Src) were increased, resulting in the activation of ERK1/2 proteins and the mitogenic pathway in β-cells. These findings provide new insights regarding the molecular mechanisms underlying regulation of β-cell proliferation processes by PE, leading to identification of potential molecular targets that can be modulated in the long-term goal of treating diabetes.