Abstract 1192: Increased ADAM17 Activity is Associated with Atherosclerosis Resistance in LDL-receptor-deficient Mice
Objective: In previous work, we have identified a locus of atherosclerosis susceptibility on mouse chromosome (Chr) 12 by quantitative trait locus (QTL) mapping in an F2-intercross of atherosclerosis susceptible C57BL/6 (B6) and atherosclerosis resistant FVB mice on the LDL-receptor deficient background (Teupser et al, PNAS 2006). The aim of the present study was to identify the causative gene(s) regulating atherosclerosis susceptibility at this locus.
Methods and Results: We used a systematic sequencing approach of candidate genes at the Chr 12 QTL interval and ruled out several of these genes with no sequence differences between the parental B6 and FVB mice. However, a number of sequence variations were identified in the promoters and in the coding regions of the metalloproteinase ADAM17 and the cytosolic receptor AhR. To test for differential gene-regulation by the Chr 12 locus, we performed expression QTL (eQTL) mapping in RNA from livers of the F2. A significant eQTL of ADAM17 expression was detected on proximal Chr 12 (LOD 3.5), co-localizing with the atherosclerosis QTL (LOD 4.2) and the physical position of ADAM17. ADAM17 expression was significantly (39%) elevated in F2-mice carrying the FVB allele at the Chr 12 locus compared to F2-mice carrying the B6 allele. In contrast, mRNA-expression of AhR and AhR-regulated genes (VCAM-1) did not map to the atherosclerosis QTL on Chr 12, and AhR was thus excluded. Differential expression of ADAM17 was confirmed in livers and macrophages of parental B6 and FVB mice and was up-regulated in FVB (57%). To test whether this had functional consequences, we determined ADAM17-mediated shedding of its prototypical substrate TNF-alpha, upon stimulation with the PKC-activator PMA. TNF-alpha shedding was 5-fold elevated in FVB compared to B6 macrophages. In addition, the release of TNF-receptor-I from macrophages of B6 and FVB mice was also elevated (73%) in FVB.
Conclusions: Thus, increased activity of ADAM17 was associated with decreased lesion formation and elevated release of inflammatory mediators and their receptors and may play a complex role in atherogenesis. We conclude that these data provide strong evidence for a role of ADAM17 in modulating atherosclerosis susceptibility.