Toll-like receptor 4 mediates mitochondrial DNA damage and biogenic responses after heat-inactivated E. coli

ABSTRACTAn important site of cellular damage in bacterial sepsis is mitochondrial DNA (mtDNA), which we proposed is caused by reactive oxygen and nitrogen species generated by activation of signaling through specific toll‐like receptors (TLR). In wild‐type (Wt) mice injected with heat‐inactivated E....

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Bibliographic Details
Published in:The FASEB journal 2005-09, Vol.19 (11), p.1531-1533
Main Authors: Suliman, Hagir B, Welty-Wolf, Karen E, Carraway, Martha Sue, Schwartz, David A, Hollingsworth, John W, Piantadosi, Claude A
Format: Article
Language:English
Subjects:
Adaptor Proteins, Signal Transducing - metabolism
Animals
bacterial infection
DNA Damage
DNA, Mitochondrial - analysis
DNA, Mitochondrial - metabolism
endotoxin shock
Escherichia coli
Escherichia coli - pathogenicity
inflammation
Interleukin-1 Receptor-Associated Kinases
Interleukin-6 - genetics
Intracellular Signaling Peptides and Proteins - metabolism
knockout mice
Liver - metabolism
Male
Mice
Mice, Inbred C57BL
Mitochondria - metabolism
mitochondrial biogenesis
Myeloid Differentiation Factor 88
NF-kappa B - metabolism
nitric oxide
Nitric Oxide Synthase Type II - antagonists & inhibitors
Nitric Oxide Synthase Type II - genetics
Oxidative Stress
Protein-Serine-Threonine Kinases - metabolism
Proto-Oncogene Proteins c-akt - metabolism
RNA, Messenger - metabolism
signal transduction
Toll-Like Receptor 2 - analysis
Toll-Like Receptor 2 - physiology
Toll-Like Receptor 4 - analysis
Toll-Like Receptor 4 - physiology
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Summary:ABSTRACTAn important site of cellular damage in bacterial sepsis is mitochondrial DNA (mtDNA), which we proposed is caused by reactive oxygen and nitrogen species generated by activation of signaling through specific toll‐like receptors (TLR). In wild‐type (Wt) mice injected with heat‐inactivated E. coli, hepatic TLR4 and TLR2 proteins were up‐regulated with TLR‐dependent increases in transcript levels for tumor necrosis factor (TNF‐α), interleukin 6, nitric oxide synthase‐II (iNOS), and NADPH oxidase 2 (Nox2). The accompanying stress significantly depleted hepatic mtDNA despite eight‐ and fourfold increases in manganese superoxide dismutase (MnSOD) and mitochondrial transcription factor A (Tfam) expression, respectively. The identical E. coli dose generated significantly less TNF‐α, NO, and Nox2 in TLR4−/− and TLR2/4−/− but not in TLR2−/− mice. TLR4−/− and TLR2/4−/− compared with Wt mice were protected from mtDNA oxidation but showed no Tfam up‐regulation and little copy number restoration. A critical role in the mtDNA damage was determined for TLR4‐mediated iNOS transcription through the MyD88 pathway. In Wt mice, mtDNA depletion was avoided by selective iNOS blockade, and residual mtDNA loss was linked to NF‐κB‐dependent TNF‐α expression. These data disclose the dual role of TLR4 in mtDNA damage and compensatory mitochondrial biogenic responses after innate immune activation.
ISSN:0892-6638
1530-6860
DOI:10.1096/fj.04-3500fje