Abstract 12014: Macrophage-Specific DNaseII Deficiency Plays a Critical Role in Vascular Inflammation and Atherosclerosis in Apolipoprotein E-Deficient Mice

Background: Atherosclerosis is a chronic inflammatory disease of the walls of blood vessels. Macrophage activated by endogenous ligands plays an important role in chronic inflammation of blood vessels. Deoxyribonuclease (DNase) II in macrophages digests the endogenous DNA derived from apoptotic cells. Recent studies show that Toll-like receptor 9 (TLR9), one of the major receptors of endogenous DNA, activates macrophages, suggesting that DNA degradation by DNase II may contribute to the pathogenesis of inflammatory disease. We investigated whether DNase II in macrophages contributes to the development of vascular inflammation and atherogenesis using apolipoprotein E-deficient (ApoE-/-) mice.

Methods: Macrophage specific DNase II deleted ApoE-/- (DNase2flox LysMCre ApoE-/-) mice and its control (DNase2flox ApoE-/-) mice were generated. For in vivo TLR9 inhibition, DNase2flox LysMCre ApoE-/- mice received TLR9 antagonist (iODN2088) or genetically lacked TLR9 (DNase2flox LysMCre ApoE-/- TLR9-/-) mice were also evaluated. All mice were fed a western-type diet and received subcutaneous angiotensin II infusion (1000 ng/kg per minute) for 8 weeks. Atherosclerotic lesions were investigated by en face Sudan IV staining and quantitative reverse transcription polymerase chain reaction. In vitro experiments using peritoneal macrophages were performed to confirm the proinflammatory roles of mitochondrial DNA (mtDNA) in the absence of DNase II.

Results: Expression of DNase II and TLR9 increased in the atherosclerotic plaques. Macrophage-specific DNase II deletion significantly atherogenesis in the aortic arch in ApoE-/- mice (P<0.05) and increased RNA expression of inflammatory molecules in the aorta. In vitro experiments demonstrated that mtDNA or TLR9 agonist significantly increased the expression of inflammatory molecules in DNase II deficient peritoneal macrophages. Activation of NF-κB signaling was involved in DNase II deficient vascular inflammation and macrophage activation.

Conclusions: Macrophage-specific DNase II deletion accelerated vascular inflammation and atherogenesis, which are attenuated by genetic deletion or pharmacological blockade of TLR9. DNase II may be a potential therapeutic target for atherosclerosis.