Mammalian DNA is an endogenous danger signal that stimulates local synthesis and release of complement factor B.

Abstract

Complement factor B plays a critical role in ischemic tissue injury and autoimmunity. Factor B is dynamically synthesized and released by cells outside of the liver, but the molecules that trigger local factor B synthesis and release during endogenous tissue injury have not been identified. We determined that factor B is upregulated early after cold ischemia-reperfusion in mice, using a heterotopic heart transplant model. These data suggested upregulation of factor B by damage-associated molecular patterns (DAMPs), but multiple common DAMPs did not induce factor B in RAW264.7 mouse macrophages. However, exogenous DNA induced factor B mRNA and protein expression in RAW cells in vitro, as well as in peritoneal and alveolar macrophages in vivo. To determine the cellular mechanisms involved in DNA-induced factor B upregulation we then investigated the role of multiple known DNA receptors or binding partners. We stimulated peritoneal macrophages from wild-type (WT), toll-like receptor 9 (TLR9)-deficient, receptor for advanced glycation end products (RAGE)⁻/⁻ and myeloid differentiation factor 88 (MyD88)⁻/⁻ mice, or mouse macrophages deficient in high-mobility group box proteins (HMGBs), DNA-dependent activator of interferon-regulatory factors (DAI) or absent in melanoma 2 (AIM2), with DNA in the presence or absence of lipofection reagent. Reverse transcription-polymerase chain reaction, Western blotting and immunocytochemical analysis were employed for analysis. Synthesis of factor B was independent of TLR9, RAGE, DAI and AIM2, but was dependent on HMGBs, MyD88, p38 and NF-κB. Our data therefore show that mammalian DNA is an endogenous molecule that stimulates factor B synthesis and release from macrophages via HMGBs, MyD88, p38 and NF-κB signaling. This activation of the immune system likely contributes to damage following sterile injury such as hemorrhagic shock and ischemia-reperfusion.

• Authors: David J Kaczorowski, Melanie J Scott, John P Pibris, Amin Afrazi, Atsunori Nakao, Rebecca D Edmonds, Sodam Kim, Joon H Kwak, Yujian Liu, Jie Fan, Timothy R Billiar
• Journal: Molecular medicine (Cambridge, Mass.) (Mol Med) Vol. 18 Pg. 851-60 (Jul 18 2012) ISSN: 1528-3658 [Electronic] England
• PMID: 22526919 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Aim2 protein, mouse
• DNA-Binding Proteins
• Glycoproteins
• HMGB Proteins
• Myeloid Differentiation Factor 88
• NF-kappa B
• Nuclear Proteins
• RNA-Binding Proteins
• Toll-Like Receptor 9
• Zbp1 protein, mouse
• DNA
• Mitogen-Activated Protein Kinases
• Complement Factor B

Topics

• Animals
• Cell Line
• Complement Factor B (genetics, metabolism)
• DNA (metabolism)
• DNA-Binding Proteins
• Glycoproteins (genetics, metabolism)
• HMGB Proteins (genetics, metabolism)
• Macrophages (immunology, metabolism)
• Male
• Mice
• Mice, Inbred C57BL
• Mice, Knockout
• Mitogen-Activated Protein Kinases (metabolism)
• Myeloid Differentiation Factor 88 (genetics, metabolism)
• Myocardial Reperfusion Injury (genetics, metabolism)
• NF-kappa B (metabolism)
• Nuclear Proteins (genetics, metabolism)
• RNA Interference
• RNA-Binding Proteins
• Toll-Like Receptor 9 (genetics, metabolism)
• Up-Regulation (genetics)