Extracellular mtDNA activates NF-κB via toll-like receptor 9 and induces cell death in cardiomyocytes
- 958 Downloads
Acute myocardial infarction (AMI) causes sterile inflammation, which exacerbates tissue injury. Elevated levels of circulating mitochondrial DNA (mtDNA) have been associated with AMI. We hypothesized that mtDNA triggers an innate immune response via TLR9 and NF-κB activation, causing cardiomyocyte injury. Murine cardiomyocytes express TLR9 mRNA and protein and were able to internalize fluorescently labeled mouse mtDNA. Incubation of human embryonic kidney cells with serum from AMI patients containing naturally elevated levels of mtDNA induced TLR9-dependent NF-κB activity. This effect was mimicked by isolated mtDNA. mtDNA activated NF-κB in reporter mice both in vivo and in isolated cardiomyocytes. Moreover, incubation of isolated cardiomyocytes with mtDNA induced cell death after 4 and 24 h. Laser confocal microscopy showed that incubation of cardiomyocytes with mtDNA accelerated mitochondrial depolarization induced by reactive oxygen species. In contrast to mtDNA, isolated total DNA did not activate NF-κB nor induce cell death. In conclusion, mtDNA can induce TLR9-dependent NF-κB activation in reporter cells and activate NF-κB in cardiomyocytes. In cardiomyocytes, mtDNA causes mitochondrial dysfunction and death. Endogenous mtDNA in the extracellular space is a danger signal with direct detrimental effects on cardiomyocytes.
KeywordsMitochondrial DNA mtDNA Inflammation TLR9 NF-κB Myocardial infarction
Harald Carlsen and Jan Øivind Moskaug, Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, kindly provided NF-κB luciferase reporter mice. The authors acknowledge the expertise of Gerbrand Koster for technical advice (NorMIC imaging cluster, Department of Biosciences, University of Oslo) and technical assistance was expertly performed by Torun Flatebø and Sowmya Sanjeevini.
This work was supported by the Norwegian Health Association, UNIFOR, the Norwegian Research Council, the University of Oslo, and the Novo Nordisk Foundation. Marte Bliksøen was supported by a grant from South-Eastern Regional Health Trust.
Compliance with ethical standards
Conflict of interest
- 4.Bulicheva N, Fidelina O, Mkrtumova N, Neverova M, Bogush A, Bogush M, Roginko O, Veiko N (2008) Effect of cell-free DNA of patients with cardiomyopathy and rDNA on the frequency of contraction of electrically paced neonatal rat ventricular myocytes in culture. Ann N Y Acad Sci 1137:273–277. doi: 10.1196/annals.1448.023 CrossRefPubMedGoogle Scholar
- 19.Knuefermann P, Schwederski M, Velten M, Krings P, Ehrentraut H, Rudiger M, Boehm O, Fink K, Dreiner U, Grohe C, Hoeft A, Baumgarten G, Koch A, Zacharowski K, Meyer R (2008) Bacterial DNA induces myocardial inflammation and reduces cardiomyocyte contractility: role of toll-like receptor 9. Cardiovasc Res 78:26–35. doi: 10.1093/cvr/cvn011 CrossRefPubMedGoogle Scholar
- 21.Lei P, Baysa A, Nebb HI, Valen G, Skomedal T, Osnes JB, Yang Z, Haugen F (2013) Activation of Liver X receptors in the heart leads to accumulation of intracellular lipids and attenuation of ischemia-reperfusion injury. Basic Res Cardiol 108:323. doi: 10.1007/s00395-012-0323-z CrossRefPubMedGoogle Scholar
- 24.Lohner R, Schwederski M, Narath C, Klein J, Duerr GD, Torno A, Knuefermann P, Hoeft A, Baumgarten G, Meyer R, Boehm O (2013) Toll-like receptor 9 promotes cardiac inflammation and heart failure during polymicrobial sepsis. Mediators Inflamm 2013:261049. doi: 10.1155/2013/261049 CrossRefPubMedPubMedCentralGoogle Scholar
- 30.Oka T, Hikoso S, Yamaguchi O, Taneike M, Takeda T, Tamai T, Oyabu J, Murakawa T, Nakayama H, Nishida K, Akira S, Yamamoto A, Komuro I, Otsu K (2012) Mitochondrial DNA that escapes from autophagy causes inflammation and heart failure. Nature 485:251–255. doi: 10.1038/nature10992 CrossRefPubMedPubMedCentralGoogle Scholar
- 32.Riad A, Westermann D, Escher F, Becher PM, Savvatis K, Lettau O, Heimesaat MM, Bereswill S, Volk HD, Schultheiss HP, Tschope C (2010) Myeloid differentiation factor-88 contributes to TLR9-mediated modulation of acute coxsackievirus B3-induced myocarditis in vivo. Am J Physiol Heart Circ Physiol 298:H2024–H2031. doi: 10.1152/ajpheart.01188.2009 CrossRefPubMedGoogle Scholar
- 35.Shintani Y, Kapoor A, Kaneko M, Smolenski RT, D’Acquisto F, Coppen SR, Harada-Shoji N, Lee HJ, Thiemermann C, Takashima S, Yashiro K, Suzuki K (2013) TLR9 mediates cellular protection by modulating energy metabolism in cardiomyocytes and neurons. Proc Natl Acad Sci USA 110:5109–5114. doi: 10.1073/pnas.1219243110 CrossRefPubMedPubMedCentralGoogle Scholar
- 41.Velten M, Duerr GD, Pessies T, Schild J, Lohner R, Mersmann J, Dewald O, Zacharowski K, Klaschik S, Hilbert T, Hoeft A, Baumgarten G, Meyer R, Boehm O, Knuefermann P (2012) Priming with synthetic oligonucleotides attenuates pressure overload-induced inflammation and cardiac hypertrophy in mice. Cardiovasc Res 96:422–432. doi: 10.1093/cvr/cvs280 CrossRefPubMedGoogle Scholar
- 43.Yang XM, Cui L, White J, Kuck J, Ruchko MV, Wilson GL, Alexeyev M, Gillespie MN, Downey JM, Cohen MV (2015) Mitochondrially targeted Endonuclease III has a powerful anti-infarct effect in an in vivo rat model of myocardial ischemia/reperfusion. Basic Res Cardiol 110:3. doi: 10.1007/s00395-014-0459-0 CrossRefPubMedPubMedCentralGoogle Scholar