Abstract 15992: STAMP2 Controls Macrophage Inflammatory Responses by NADPH Regulation
Regulatory mechanisms are important to control systemic metabolic homeostasis and to counteract visceral adipose tissue inflammation to metabolic challenges. The six-transmembrane protein of prostate (STAMP)-2 plays an important role in this context. STAMP2-deficiency recapitulates most features of the metabolic syndrome in mice including a pro-inflammatory phenotype of visceral adipose tissue. STAMP2 is expressed in macrophages, and macrophage inflammation is a hallmark of atherosclerosis. Consequently, we evaluated the role of STAMP2 in this context. STAMP2-deficiency of primary macrophages led to significantly increased expression (n=6-8, p<0,05) and secretion (n=9-12, p<0,05) of Interleukin- (IL)-6, IL-1β, TNF-α, and MCP-1 compared to WT. Furthermore, expression of inducible NO synthase (iNOS) (n=10 for mRNA, n=11 for protein, p<0,05) and NO production (n=11, p<0,05) were enhanced compared to WT. As (i) iNOS is an NADPH-dependent enzyme and (ii) STAMP2 possesses NADPH oxidoreductase activity, we measured NADPH levels in WT and STAMP2-deficient macrophages. We found that NADPH levels were significantly higher in STAMP2-deficient macrophages (n=3, p<0,01). Both pharmacological inhibition with dehydroandrosterone and RNA interference blocked increased inflammation of STAMP2-deficient macrophages (n=3, p<0,05), confirming an important role of NADPH for the observed phenotype. Adding back full-length STAMP2 to STAMP2-deficient macrophages decreased NADPH levels, whereas adding back STAMP2 lacking NADPH oxidoreductase activity did not (n=4-5, p<0,05). These data show that NADPH oxidoreductase activity of STAMP2 is involved in regulation of NADPH levels in macrophages. To assess, whether macrophage STAMP2 deficiency has in vivo relevance, we analyzed atherosclerotic lesion formation in the atherogenic ApoE-/- genetic background. STAMP2-deficiency led to accelerated atherosclerosis both in the en face aorta (n=10-12, p<0,01) and in the aortic root (n=8, p<0,01). Taken together, these data show that STAMP2 has an important role in atherosclerosis and in the control of macrophage inflammation that is partially attributable to control of NADPH levels of cells.
- © 2011 by American Heart Association, Inc.