Mitochondrial DNA Activates the NLRP3 Inflammasome and Predisposes to Type 1 Diabetes in Murine Model

Abstract

Although a correlation between polymorphisms of NOD-like receptor family-pyrin domain containing 3 (NLRP3) and predisposition to type 1 diabetes (T1D) has been identified, the potential function and activation of the NLRP3 inflammasome in T1D have not been clarified. The present study shows that non-obese diabetic mice exhibited increased NLRP3, and pro-IL-1β gene expression in pancreatic lymph nodes (PLNs). Similar increases in gene expression of NLRP3, apoptosis associated speck like protein (ASC) and pro-IL-1β were induced by multiple low doses of streptozotocin (STZ) in C57BL/6 mice. In addition, diabetic C57BL/6 mice also exhibited increased IL-1β protein expression in the pancreatic tissue at day 7, which remained elevated until day 15. Diabetic mice also showed increased positive caspase-1 macrophages in the PLNs, which were decreased in NLRP3−/− mice, but not in ASC−/− mice, after STZ treatment. NLRP3- and IL-1R-deficient mice, but not ASC-deficient mice, showed reduced incidence of diabetes, less insulitis, lower hyperglycemia, and normal insulin levels compared to wild-type (WT) diabetic mice. Notably, these mice also displayed a decrease in IL-17-producing CD4 and CD8 T cells (Th17 and Tc17) and IFN-γ-producing CD4 and CD8 T cells (Th1 and Tc1) in the PLNs. Following STZ treatment to induce T1D, NLRP3-deficient mice also exhibited an increase in myeloid-derived suppressor cell and mast cell numbers in the PLNs along with a significant increase in IL-6, IL-10, and IL-4 expression in the pancreatic tissue. Interestingly, diabetic mice revealed increased circulating expression of genes related to mitochondrial DNA, such as cytochrome b and cytochrome c, but not NADH dehydrogenase subunit 6 (NADH). Mitochondrial DNA (mDNA) from diabetic mice, but not from non-diabetic mice, induced significant IL-1β production and caspase-1 activation by WT macrophages, which was reduced in NLRP3−/− macrophages. Finally, mDNA administration in vivo increased Th17/Tc17/Th1/Tc1 cells in the PLNs and precipitated T1D onset, which was abolished in NLRP3−/− mice. Overall, our results demonstrate that mDNA-mediated NLRP3 activation triggers caspase-1-dependent IL-1β production and contributes to pathogenic cellular responses during the development of STZ-induced T1D.

Mitochondrial ROS-induced lysosomal dysfunction impairs autophagic flux and contributes to M1 macrophage polarization in a diabetic condition

“…For sustained energy production, M1 macrophages relied on glycolysis whereas M2 cells relied on mitochondrial oxidative phosphorylation (OXPHOS) [24,25]. Studies reported that ROS generation caused by mitochondrial dysfunction promoted NLRP3 inflammasome activation and other inflammatory responses in macrophages [26,27]. Contrarily, M1 macrophages induced by LPS + IFNγ exhibited mitochondrial dysfunction because of defective mitochondrial oxidative respiration.…”

Modulatory Mechanisms of the NLRP3 Inflammasomes in Diabetes

“…In vivo studies demonstrated that mDNA increased the levels of Th17/Tc17/Th1/Tc1 cells in pancreatic lymph nodes, promoting the development of T1DM, whereas this T1DM development was inhibited in NLRP3 −/− mice. In addition, mDNA-mediated activation of the NLRP3 inflammasome triggers caspase-1-dependent production of IL-1β and contributes to pathogenic cell responses in streptozotocin-induced T1DM models [66]. NLRP3 −/− mice NLRP3 Reduced glucose tolerance and insulin sensitivity [70] PBMCs: blood mononuclear cells; GCs: granulocytes.…”

The rOX‐stars of inflammation: links between the inflammasome and mitochondrial meltdown

“…108 In murine models, ccf-mtDNA predisposes mice to type I diabetes. 109 Patients with type II diabetes and coronary heart disease exhibit significantly elevated levels of ccf-mtDNA compared to their healthy counterparts. 110 In chronic obstructive pulmonary disease (COPD), ccf-mtDNA may activate TLR9 to drive inflammation 111 and may potentially provide signal 1 for NLRP3 activation, as NLRP3 contributes to disease pathology.…”