1488-P: Reduced iPLA2b Expression in T-Lymphocytes Decreases Proinflammatory Eicosanoid Production and Cytokine Secretion Delaying Type 1 Diabetes Development in NOD Mice

Abstract

Type 1 diabetes (T1D) is characterized by the destruction of insulin-producing pancreatic islet β-cells, but the causes of this process remain unclear. We find that Ca2+-independent phospholipase A2β (iPLA2β), which hydrolyzes membrane phospholipids at the sn-2 substituent to yield iPLA2β-derived lipids (iDLs), is induced under a diabetic milieu and mitigation of iPLA2β activity attenuates β-cell death. Several iDLs are pro-inflammatory and have been studied in different diseases but are not understood in diabetes. We investigated the role of immune-cell iDLs by utilizing T-cell adoptive transfer. Isolated CD4+/8+ T-cells from splenocytes prepared from donor female NOD and NOD. iPLA2β+/− (HET) mice, were transferred i.p. to NOD.scid recipient mice. We observed T1D onset for all T-cell recipient groups between 10-12 weeks of age. However, reduction of iPLA2β in CD4/8 T-cells delayed 50% incidence by 10 weeks in NOD4/HET8-recipient mice and HET4/NOD8 T-cell recipients compared to “matched” T-cell recipients. Furthermore, reduced insulitis and increased β-cell preservation was detected in HET4/NOD8-recipients compared to NOD4/8 recipients. The immune cell composition between our genotypes revealed no difference suggesting iDL signaling contributes to the observed incidence. Lipidomic analyses revealed a decrease in pro-inflammatory eicosanoids (PGs, DHETs and HETEs) in nondiabetic recipient mice, compared to diabetic counterparts. In addition, by targeting select eicosanoid signaling (PGE2 and DHET) utilizing chemical inhibitors (i.e., Grapiprant (EP4 receptor antagonist) and EC5026 (soluble epoxide hydrolase inhibitor)), we observed decreased IFN-γ production by Th1 helper cells in HET donors compared to NOD. These findings suggest that iPLA2β in T-cells is a critical contributor to the production of pro-inflammatory iDLs and could be a potential target in reducing T1D development. Disclosure T. White: None. S. Ramanadham: None. T.P. DiLorenzo: None. C.E. Chalfant: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK069455); National Institute of Allergy and Infectious Diseases (R21AI146743, R21AI169214); JDRF (2-SRA-2022-1210-S-B); University of Alabama at Birmingham (5T32GM8111-34)