Selective Reduction of Ca²⁺-Independent Phospholipase A₂β (iPLA₂β)-Derived Lipid Signaling from Macrophages Mitigates Type 1 Diabetes Development

Type 1 diabetes (T1D) is a consequence of autoimmune destruction of β-cells and macrophages (MΦ) have a central role in initiating processes that lead to β-cell demise. We reported that Ca²⁺-independent phospholipase A₂β (iPLA₂β)-derived lipid (iDL) signaling contributes to β-cell death. As MΦ express iPLA₂β, we assessed its role in T1D development. We find that selective reduction of myeloid-iPLA₂β in spontaneously diabetes-prone nonobese diabetic (NOD) mice (a) deceases proinflammatory eicosanoid production by MΦ, (b) favors anti-inflammatory (M2-like) MΦ phenotype, and (c) diminishes activated CD4⁺ and CD8⁺ T-cells phenotype in the pancreatic infiltrate, prior to T1D onset. These outcomes are associated with a significant reduction in T1D. Further, inhibition of select proinflammatory lipid signaling pathways reduces M1-like MΦ polarization and adoptive transfer of M2-like MΦ reduces NOD T1D incidence, suggesting a mechanism by which iDLs impact T1D development. These findings identify MΦ-iPLA₂β as a critical contributor to TID development and potential target to counter T1D onset.