Degraded Mitochondrial DNA is a Newly Identified Subtype of the Damage Associated Molecular Pattern (DAMP) Family and Possible Trigger of Neurodegeneration
Affiliations: [a] Center for Immunology and Microbial Disease, The Albany Medical College, Albany, NY, USA | [b] Center for Neuropharmacology and Neuroscience, The Albany Medical College, Albany, NY, USA | [c] School of Arts and Sciences, Albany College of Pharmacy and Health Sciences, Albany, NY, USA
Correspondence:
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Correspondence to: Dana R. Crawford, Ph.D., Center for Immunology and Microbial Disease MC-151, The Albany Medical College, Albany, New York 12208, USA. Tel.: +1 518 262 6652, E-mail: crawfod@mail.amc.edu.
Abstract: We previously showed a preferential degradation and down-regulation of mitochondrial DNA and RNA in hamster fibroblasts in response to hydrogen peroxide. Subsequent studies by others demonstrated that mitochondrial DNA can stimulate immune cells as a DAMP (damage associated molecular patterns) family member. However, the actual physical structure of this mitochondrial DNA DAMP and its importance in non-immune cell types are poorly understood. Here we report that transfected oxidant-initiated degraded mitochondrial polynucleotides, which we term “DeMPs”, strongly induce the proinflammatory cytokines interleukin 6, monocyte chemotactic protein-1, and tumor necrosis factor α in mouse primary astrocytes. Additionally, proinflammatory IL1β was induced, implicating DeMPs in inflammasome activation. Furthermore, human cerebrospinal fluid (CSF) and plasma were found to contain detectable DeMP signal. Finally, significant degradation of mitochondrial DNA was observed in response to either a bolus or steady state hydrogen peroxide. Combined, these studies demonstrate, all for the first time, that a pathophysiologically relevant form of mitochondrial DNA (degraded) can elicit a proinflammatory cytokine induction; that a brain cell type (astrocytes) elicits a proinflammatory cytokine induction in response to these DeMPs; that this induction includes the inflammasome; that astrocytes are capable of inflammasome activation by DeMPs; that DeMPs are detectable in CSF and plasma; and that hydrogen peroxide can stimulate an early stage cellular degradation of mitochondrial DNA. These results provide new insights and are supportive of our hypothesis that DeMPs are a newly identified trigger of neurodegenerative diseases such as Alzheimer's disease, which are known to be associated with early stage inflammation and oxidation.
