Endogenously oxidized mitochondrial DNA induces in vivo and in vitro inflammatory responses

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Abstract
We report that mitochondrial DNA (mtDNA) is inflammatogenic in vitro and in vivo as a result of the presence of unmethylated CpG sequences and its oxidative status. Purified human and murine mtDNAs induced arthritis when injected intra-articularly (i.a.) in mice. Importantly, oligodeoxynucleotide that contained a single oxidatively damaged base also induced arthritis when injected i.a. in mice. In contrast, neither human nor murine nuclear DNA induced inflammation. mtDNA-induced arthritis was neither B cell- nor T cell-dependent but was mediated by monocytes/macrophages. mtDNA-induced nuclear factor-κB stimulation resulted in the production of tumor necrosis factor α, a potent, arthritogenic factor. Finally, extracellular mtDNA was detected in the synovial fluids of rheumatoid arthritis patients but not of control subjects. We conclude that endogenous mtDNA displays inflammatogenic properties as a result of its content of unmethylated CpG motifs and oxidatively damaged adducts.
Funding Information
  • Swedish Association against Rheumatism
  • Swedish Inflammation Network
  • Nanna Svartz Foundation
  • King Gustaf V Foundation
  • Swedish Medical Research Council
  • EU Commission Biotechnology Program (BIO4CT97-5130)