Islet-Autonomous Inflammatory Signaling Propagates Autoimmunity and Promotes Diabetes in Nonobese Diabetic Mice

Type 1 diabetes (T1D) is an immune-mediated disease that leads to ß cell dysfunction and death. However, the contribution of ß cells in this process remains unclear. To understand how islet-derived pro-inflammatory signaling pathways contribute to diabetes pathogenesis, we generated inducible islet-specific Alox15 knockout mice on the NOD background. We report that islet-specific deletion of Alox15 induced a substantial increase of ß-cell mass and decreased islet insulitis, and ultimately lead to a protection against spontaneous autoimmune diabetes in NOD mice. Single cell RNA-sequencing and mass spectrometry analysis revealed that islet-specific knockout of Alox15 leads to an increase of ß cells expressing Pd-l1 and promotes an anti-inflammatory phenotype in myeloid cells and T cells inside the islets. Furthermore, islet- specific Alox15 deletion enhances the expansion of M2-like macrophages and regulatory T cells in the pancreatic islets and pancreatic lymph nodes. Together, these results lead to the conclusion that proinflammatory signals produced by ß cells allows these cells to express immunoregulators that protects these cells of immune cell attack and promote ß cell survival. Overall design: Mouse islets were isolated from collagenase-perfused pancreata and cultured in RPMI medium as previously describe (Stull et al. 2012). After isolation, islets were handpicked and digested with Accutase (EMD Millipore Corporation) containing 2U/ml of DNAse during 5min at 37C sob agitation (1000rpm). Then cells were washed several times with PBS+2%FBS to eliminate DNAse and then filtered using a cell strainer (40?m). Samples with more than 90% viability were used for scRNAseq.