Type 1 diabetes is an autoimmune disease caused by destruction of pancreatic β-cells. During disease progression, β-cells are exposed to proinflammatory cytokines like interleukin-1β (IL-1β) and interferon-γ (IFN-γ), stimulating them to express inducible nitric oxide synthase (iNOS) and produce micromolar levels of nitric oxide. While some cytokine-mediated changes in islet gene expression are known, we do not have a global view of the genes induced by cytokines nor do we know how non-β-cells respond to cytokines. Following 6-hr treatment with IL-1β and IFN-γ, adult C57BL/6 mouse islets were subjected to single-cell RNA-sequencing using the 10x Genomics Chromium platform. iNOS mRNA (Nos2) was induced in 73% of β-cells in response to both cytokines. Unexpectedly, 72% of Δ-cells and 44% of α-cells expressed Nos2 at levels similar to that found in β-cells. This is surprising since β-cells are thought to be the primary islet source of nitric oxide. Of the 241 genes enriched in Nos2-expressing β-cells, 70% were also enriched in Nos2-expressing Δ- and α-cells, suggesting that these cells initially respond to cytokine exposure by activating similar pathways. Among the enriched genes were those indicative of anti-viral defenses, suggesting induction of protective responses. Nos2 expression was negatively correlated with expression of genes encoding heat shock proteins, such as Hsp70, consistent with previous reports that heat shock inhibits cytokine-induced iNOS expression. Finally, we observed IL-1β-induced repression of β-cell identity genes, including Mafa, Pdx1, Slc2a2, and Ucn3. Repression of these identity genes was negatively correlated with Hsp70 expression, suggesting that cellular stress prevents this dedifferentiation. While these studies are ongoing, they suggest that (1) Δ- and α-cells respond to cytokines by upregulating Nos2 mRNA, (2) cytokines repress β-cell identity genes, and (3) both of these outcomes can be inhibited by induction of cellular stress.
J. Stancill: None. A. Khatun: None. M. Kasmani: None. W. Cui: None. J.A. Corbett: None.