Pharmacological Suppression of Hepcidin Increases Macrophage Cholesterol Efflux and Reduces Foam Cell Formation and Atherosclerosis

Abstract

Objectives We recently reported that lowering of macrophage free intracellular iron increases expression of cholesterol efflux transporters ABCA1 and ABCG1 by reducing generation of reactive oxygen species. In this study, we explore whether reducing macrophage intracellular iron levels via pharmacologic suppression of hepcidin can increase macrophage-specific expression of cholesterol efflux transporters and reduce atherosclerosis. Methods and Results To suppress hepcidin, increase expression of the iron exporter ferroportin (FPN), and reduce macrophage intracellular iron, we used a small molecule inhibitor of BMP signaling, LDN 193189 (LDN). LDN (10 mg/kg i.p. bid) was administered to mice and its effects on atherosclerosis, intracellular iron, oxidative stress, lipid efflux, and foam cell formation were measured in plaques and peritoneal macrophages. Long-term LDN administration to Apo E (-/-) mice increased ABCA1 immunoreactivity within intraplaque macrophages by 3.7-fold (n=8; p=0.03), reduced oil-red-o positive lipid area by 50% (n=8; p=0.02) and decreased total plaque area by 43% (n=8; p=0.001). LDN suppressed liver hepcidin transcription and increased macrophage FPN, lowering intracellular iron and hydrogen peroxide production. LDN treatment increased macrophage ABCA1 and ABCG1 expression, significantly raised cholesterol efflux to ApoA-1 and decreased foam cell formation. All preceding LDN-induced effects on cholesterol efflux were reversed by exogenous hepcidin administration, suggesting that modulation of intracellular iron levels within macrophages as the mechanism by which LDN triggers these effects. Conclusion These data suggest that pharmacologic manipulation of iron homeostasis may be a promising target to increase macrophage reverse cholesterol transport and limit atherosclerosis.

TGF-β1, but Not Bone Morphogenetic Proteins, Activates Smad1/5 Pathway in Primary Human Macrophages and Induces Expression of Proatherogenic Genes

“…In contrast, genes, activated by Smad1/5-dependent BMP signaling, contribute to plaque instability. Hepcidin (53) alters iron metabolism in macrophages and reduces lipid efflux (54), whereas increased expression of the receptor for plasminogen urokinase activator PLAUR is associated with unstable plaques and plaque rupture (55). We clearly demonstrated in this article that TGF-b alone is sufficient for activation of both Smad2/3-and Smad1/5-dependent signaling in macrophages, whereas macrophages do not respond to BMP.…”

Molecular Biology of Atherosclerosis

“…Recently, the effect of hepcidin reduction by pharmacological means was tested for its affect on atherosclerosis in ApoE-deficient mice (1526). A small molecule inhibitor of SMAD1/5/8 activation (LDN 193189) was used to reduce hepatic expression of hepcidin.…”

Hepcidin levels in chronic hemodialysis patients: a critical evaluation

“…Experimental data suggest that hepcidin may be implicated in the pathogenesis of atherosclerosis though its ability to induce iron accumulation and oxidative stress within macrophages of the arterial walls [37]. Indeed, hepcidin levels have been associated with both reduced cholesterol efflux in macrophages [37], and release of the atherogenic chemokine macrophage chemoattractant protein-1 (MCP-1) [38]. In CHD patients, hepcidin levels have been recently shown to correlate with arterial stiffness [39], as well as to predict cardiovascular events independently of inflammation [40].…”