165-OR: Lipid Signaling in Macrophages Contributes to Inflammatory Transcriptome in Immune Cells

Macrophages and T-cells play critical roles in β-cell death leading to T1D. We find that reduction of Ca2+-independent phospholipase A2β in macrophages alone reduces T1D. To explore the potential mechanism, we examined changes in immune-responsive genes by single-cell RNAseq analysis using a false discovery rate (FDR)1e10-8. In the BMDM from NOD.cM ΦiPLA2 β-/-, relative to NOD, we find that genes (Slc25a5, Ephx1, Zcchc14) related to inflammation, immune cell infiltration, T-cell activation, antigen presentation, MΦ proliferation, and mitochondrial metabolism were down-regulated, and those that promote M2M Φ polarization (Ccl6) and MΦ-phagocytosis (Tbc1d10c), and reduce MΦ infiltration (Creb313), CD8 T-cell activation (Ccl4), and mitochondrial production of anti-inflammatory itaconate (Acod1) were up-regulated. Intriguingly, nearly 30 DEGs were noted in islet CD4 and CD8 T-cells from NOD.cM ΦiPLA2 β-/-, relative to NOD. In the CD4 cells, genes (Tnfrs23, Jak2, H2-Aa) related to inflammation, activation of T-cells, and antigen presentation were downregulated, whereas genes related to Treg generation (Gpr83) and negative regulation of Th-cell activation (Cd160) were upregulated. In the CD8 cells, genes associated with enhancing inflammation (Epas1, Gata3), CD8 T-cell activation (Nkg7, Ctla2b), CD4 T-cell activation (Gldc), and (4) negative modulation of Treg cell generation (Ctla2a) were down-regulated, while genes (Gbp2b, Gpr83) associated with Tregs were upregulated. Importantly, the top 7 of 16 shared T-cell pathways were related to inflammation. Similar transcriptome profiles were also evident in NOD.cM ΦiPLA2 β-/- islet B and NK cells, relative to NOD. These findings reveal that lipid signaling from macrophages affects the transcriptome in macrophages, triggering islet immune cell transcriptome favoring an inflammatory phenotype. They further suggest that targeting iPLA2β-derived lipid signaling in macrophages is a means to reduce T1D incidence. Disclosure A. Almutairi: None. R.S. Welner: None. T. White: None. Y. Tusing: None. S. Ramanadham: None. Funding NIH/NIAID 1R21AI169214-01JDRF 2-SRA-2022-1210-S-BJDRF 1-INO-2023-1344-A-NNIH/NIAID 1 R21 AI 146743UAB Department of CDIBUAB Comprehensive Diabetes Center