198-OR: Pancreatic Elastase Regulates Human Beta-Cell Viability by Impairing the PAR2 Pathway

The discovery of SerpinB1 pointed to acinar cell-derived proteases such as pancreatic elastase (PE) being involved in regulating human β-cell viability. Indeed, we observed that expression of a major form of PE, namely CELA3B, was increased in acinar cells from donors with type 2 diabetes (T2D) compared to samples from nondiabetic (ND) donors. Surprisingly, CELA3B protein levels were higher in T2D vs. ND islets, although its gene expression levels were virtually undetectable. We confirmed that increasing doses of exogenous PE is able to decrease viability and function of EndoC-βH3 (βH3) cells in vitro. To evaluate the effects of PE inhibition on β-cell survival, we used telaprevir, an FDA-approved drug, that we identified as a potent PE blocker using a High-Throughput Screening assays with an IC50 of 15.6 nM to inhibit PE activity. Consistent with the effects of SerpinB1 on β-cells, telaprevir also increased human β-cell viability in in vitro and in vivo systems. By performing phospho-antibody microarrays and single-cell RNA-Seq in human islets treated with vehicle or telaprevir, we identified the Protease-Activated Receptor 2 (PAR2) pathway as a candidate pathway linking PE inhibition to β-cell viability. We validated the results by treating EndoC-βH1 (βH1) cells with a PAR2 inactivating peptide (FSLLRY-NH2) in addition to PE +/- telaprevir. We observed that PE impaired the PAR2 cascade, and these effects were reversed by telaprevir in control β-cells, but not in cells treated with the PAR2 inhibitor. Furthermore, telaprevir was able to reverse PE effects and improve viability of control human primary β-cells, but not of those in which the PAR2 pathway was pharmacologically impaired. These data point to novel pathways reflecting acinar-β-cell crosstalk that has therapeutic potential to resolve diabetes in patients.