Characterization of Novel Selective Inhibitors of 12-Lipoxygenase and Assessment of Their Utility in Preserving Human Islet Function
Abstract Number: 1006-P
Authors: DAVID A. TAYLOR-FISHWICK, TED HOLMAN, DAVID MALONEY, NORINE KUHN, SWARUP CHAKRABARTI, JERRY L. NADLER
Institutions: Norfolk, VA, Santa Cruz, CA, Bethesda, MD
Results: The enzyme 12-lipoxygenase (12-LO) and its lipid-derived products, which include 12-HETE, are associated with pancreatic beta cell dysfunction and apoptosis. Significantly, targeted knock-out of 12-LO provided nearly 100% protection from diabetes in NOD mice. Inhibition of 12-LO activity therefore provides an attractive target in developing new therapies for diabetes and its complications.
The 12-LO enzyme is a member of a broader lipoxygenase family. We identified ALOX12 as the major form of 12-LO in human islets. Targeted inhibition of 12-LO requires identification of new selective agents. Using a cell-free screen, novel small molecule weight compounds have been identified with a ≥50 fold selective inhibition of ALOX12. These selective 12-LO-inhibitors (12-LO-Is) show efficacy in whole cell studies. Stimulation of human donor islets with arachidonoc acid or calcium ionophore induced the production of 12-HETE; a measure of 12-LO activity. Production of 12-HETE was reduced (77± 6%, non-diabetic; 73% T2DM) in the presence of 1µM 12-LO-I.
Further, a cocktail of pro-inflammatory cytokines (TNF alpha, INF gamma and IL-1 beta) increased gene expression in human islets that associate with islet dysfunction. The induced gene expression was inhibited by 12-LO-Is. Study of the IL-12-STAT4-IFNγ axis in human islets, revealed the 12-LO-Is reduced pro-inflammatory cytokine stimulated gene induction of IL-12 and IFNγ. Microscopically, cell death induced in human islets by pro-inflammatory cytokines was prevented by the inclusion of 12-LO-Is. These gene changes were not seen with structurally related compounds that were inactive in the cell-free screen. The data represents seven human donors and screening of nineteen separate compounds.
Clear experimental data links a role of 12-LO and the products of its activity in the pathogenesis of beta cell destruction in diabetes. Progression of the identified novel small molecular weight inhibitors 12-LO may significantly aid in strategies to preserve beta cell mass and function.