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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2007;27:571.)
© 2007 American Heart Association, Inc.

Vascular Biology

Genomics of Foam Cells and Nonfoamy Macrophages From Rabbits Identifies Arginase-I as a Differential Regulator of Nitric Oxide Production

Anita C. Thomas; Graciela B. Sala-Newby; Yasmin Ismail; Jason L. Johnson; Gerard Pasterkamp; Andrew C. Newby

From Bristol Heart Institute (A.C.T., G.B.S.-N., Y.I., J.L.J., A.C.N.), University of Bristol, Bristol, UK; University Medical Center Utrecht (G.P.), Experimental Cardiology Laboratory, Utrecht, The Netherlands. Current address for A.C.T.: Centre for Research in Vascular Biology, University of Queensland, Brisbane, Australia.

Correspondence to Graciela B. Sala-Newby, Bristol Heart Institute, University of Bristol, 7^th Floor, Bristol Royal Infirmary, Bristol, BS2 8HW, United Kingdom. E-mail g.newby{at}bristol.ac.uk

Objective— Conversion of macrophages to foam cells is a critical step in the initiation and progression of atherosclerosis. We sought to identify genes differentially regulated in foam cells, since these are likely to include new targets for intervention.

Methods and Results— We used suppression subtraction hybridization to compare foam cells and nonfoamy macrophages isolated from subcutaneous granulomas of rabbits fed a cholesterol-rich or normal chow diet and confirmed upregulation of 3 genes, including matrix metalloproteinase-12 (mRNA 2.0-fold, P<0.005; protein 3.9-fold, P<0.03). Arginase-I mRNA showed the biggest decrease among 11 downregulated genes in foam cells (2.7-fold, P<0.001) and was accompanied by significantly reduced arginase enzymatic activity (60-fold, P<0.01). Arginase-I competes for substrate L-arginine with nitric oxide synthase and consequently nitric oxide production was significantly increased (3-fold, P<0.02) in foam cells compared with nonfoamy macrophages despite no difference in nitric oxide synthase isoenzyme expression. We validated upregulation of matrix metalloproteinase-12 and downregulation of arginase-1 in foam cells of rabbit and human atherosclerotic plaques.

Conclusions— Our study identified several differentially expressed genes in foam cells and nonfoamy macrophages derived from live rabbits. The altered pattern of gene expression in foam cells is likely to influence atherosclerosis formation and stability.

Suppression subtraction hybridization showed upregulation of 3 and downregulation of 11 genes in rabbit foam cells compared with nonfoamy macrophages. FCMs had more MMP-12 but less arginase-I activity, leading to more NO production, which probably influences atherosclerosis.

Key Words: arginase-I • atherosclerosis • foam cells • nitric oxide • suppression subtraction hybridization

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