Advisory Committee Chair
Laurie F Harrington
Advisory Committee Members
Ronadip R Banerjee
Chad M Petit
Hubert M Tse
Allan J Zajac
Document Type
Dissertation
Date of Award
2022
Degree Name by School
Doctor of Philosophy (PhD) Heersink School of Medicine
Abstract
NADPH oxidase 2 (NOX2)-derived superoxide, a precursor for many reactive oxygen species (ROS), regulates cell signaling, cellular trafficking, melanoma differentiation-associated protein 5 (MDA5) responses, and Type 1 diabetes (T1D). Previously, we demonstrated that NOX2-derived superoxide promotes chemokine synthesis, spontaneous and virus-accelerated T1D, and MDA5 responses to coxsackievirus B3 (CVB3), an associated environmental trigger for T1D. Yet, it remains unknown if ROS is necessary for diabetogenic T cell trafficking into islets or how MDA5 responses affect T1D. First, using non-obese diabetic (NOD) mice that contain an in-frame deletion within the helicase 1 domain of MDA5 (ΔHel1) or lack MDA5 expression (KO), we tested the hypothesis that reduced MDA5 responses impair type 1 interferon (type I IFN) synthesis, immune cell responses, and T1D. NOD and KO mice develop T1D equally, but ΔHel1 mice exhibit delayed spontaneous and CVB3-accelerated T1D. The ΔHel1 mutation significantly reduced pancreatic IFN-α and IFN-β levels compared to NOD following CVB3 infection. CVB3-infected ΔHel1 mice had significantly fewer pancreatic TNF-α+ F4/80+ MΦ compared to NOD and KO. However, CVB3-infected ΔHel1 and KO mice had fewer pancreatic perforin+ CD8+ T cells and IFNγ+ CD4+ T cells compared to NOD. Furthermore, the ΔHel1 mutation caused a reduction in MDA5 ATPase activity compared to WT protein. This suggests that MDA5 ATPase activity promotes MΦ responses iv necessary for T1D, but complete loss of MDA5 expression does not delay T1D. Second, using NOD mice deficient in NOX2-derived superoxide (NOD.Ncf1m1J), we tested the hypothesis that loss of NOX2-derived superoxide delays T1D by reducing autoreactive T cells islet infiltration. Previous studies show that NOD.Ncf1m1J mice have delayed T1D. We now find immunodeficient NOD.Rag.Ncf1m1J islets produce less CCL2 and CCL5 compared to NOD.Rag, and recruit fewer CD4+ T cells and CD8+ T cells. Using tetramer staining we observed a decrease in NOD.Ncf1m1J islet-infiltrating CD4+ T cells specific for insulin (Ins), Ins-chromogranin A hybrid insulin peptide (HIP), and Ins-islet amyloid polypeptide HIP compared to NOD. Our data suggest loss of NOX-derived superoxide impairs autoreactive T cell islet infiltration as a potential mechanism to delay T1D. Overall, ROS and MDA5-dependent responses contribute to immune cell activation and trafficking during T1D development.
Recommended Citation
Blum, Samuel Isaac, "NOX2-Derived Superoxide and MDA5-Dependant Responses Contribute to Autoimmune Diabetes" (2022). All ETDs from UAB. 212.
https://digitalcommons.library.uab.edu/etd-collection/212