Biology subjects

Orr, K. S.

Publications and source records attributed to Orr, K. S..

3 recordsLinked to original sources

bioRxiv2025

IFN-α Induces Heterogenous ROS Production in Human β-Cells

Type 1 diabetes (T1D) is a multifactorial disease involving genetic and environmental factors, including viral infection. We investigated the impact of interferon alpha (IFN-), a cytokine produced during the immune response to viral infection or the presence of un-edited endogenous double-stranded RNAs, on human {beta}-cell physiology. Intravital microscopy on transplanted human islets using a {beta}-cell-selective reactive oxygen species (ROS) biosensor (RIP1-GRX1-roGFP2), revealed a subset of human {beta}-cells that acutely produce ROS in response to IFN-. Comparison to Integrated Islet Distribution Program (IIDP) phenotypic data revealed that healthier donors had more ROS accumulating cells. In vitro IFN- treatment of human islets similarly elicited a heterogenous increase in superoxide production that originated in the mitochondria. To determine the unique molecular signature predisposing cells to IFN- stimulated ROS production, we flow sorted human islets treated with IFN-. RNA sequencing identified genes involved in inflammatory and immune response in the ROS-producing cells. Comparison with single cell RNA-Seq datasets available through the Human Pancreas Analysis Program (HPAP) showed that genes upregulated in ROS-producing cells are enriched in control {beta}-cells rather than T1D donors. Combined, these data suggest that IFN- stimulates mitochondrial ROS production in healthy human {beta}-cells, potentially predicting a more efficient antiviral response.

cell biology↗

bioRxiv2021

12-Lipoxygenase Governs the Innate Immune Pathogenesis of Islet Inflammation and Autoimmune Diabetes

Macrophages and related myeloid cells are innate immune cells that participate in the early islet inflammation of type 1 diabetes (T1D). The inflammatory signals and antigen presentation by these cells may be inducers of the adaptive immune response that is the hallmark of T1D. The enzyme 12-lipoxygenase (12-LOX) catalyzes the formation of pro-inflammatory eicosanoids from membrane-derived phospholipids, but its role and mechanisms in the pathogenesis of islet inflammation have not been elucidated. Leveraging a model of T1D-like islet inflammation in zebrafish, we show here that macrophages contribute significantly to the loss of {beta}-cells and the subsequent development of hyperglycemia. Depletion or inhibition of 12-LOX in this model resulted in significantly reduced macrophage infiltration into islets with preservation of {beta}-cell mass. In mice, we deleted the gene encoding 12-LOX (Alox15) in the myeloid lineage in the non-obese diabetic (NOD) model of T1D. Myeloid cell-specific Alox15 knockout NOD mice demonstrated reduced insulitis and T-cell responses, preserved {beta} cell mass, and almost complete protection from the development of T1D. A critical effect of 12-LOX depletion appeared secondary to a defect in myeloid cell migration, a function required for immune surveillance and tissue injury responses. This effect on migration appeared to be secondary to the loss of the chemokine receptor CXCR3. Transgenic expression of the gene encoding CXCR3 rescued the migrator defect in zebrafish 12-LOX morphants. Taken together, our results reveal a formative role for innate immune myeloid cells in the early pathogenesis of T1D and identify 12-LOX as a necessary enzyme to promote their pro-diabetogenic phenotype in the context of autoimmunity.

immunology↗

bioRxiv2019

Longitudinal Intravital Imaging of Biosensor-labeled In Situ Islet Beta Cells

Impaired function and apoptosis of insulin-secreting islet {beta}-cells is central to disease progression in both type 1 and type 2 diabetes. Oxidative damage resulting from excess reactive oxygen species (ROS) is a central factor in {beta}-cell dysfunction and death, but the dynamic nature of ROS accumulation and its depletion pose a problem for mechanistic studies in vivo. Biosensors, including the redox-sensitive GFP (roGFPs), coupled with intravital microscopy provide a sensitive and dynamic solution to this problem. Here, we utilize a virally-delivered roGFP2-containing human glutaredoxin-1 (Grx1-roGFP2) to selectively monitor {beta}-cell ROS dynamics in vivo in response to toxic glucose analogs. We paired viral biosensor delivery with implanted abdominal imaging windows over the pancreas, thus allowing longitudinal measurements of {beta}-cell ROS and islet area during and after streptozotocin (STZ) exposure. The studies presented here represent a robust experimental platform that could be readily adapted to various transgenic or physiological mouse models in conjunction with any number of available biosensors, and thus opens a vast realm of potential for discovery in islet biology in vivo.

cell biology↗