Absence of heme oxygenase‐1 exacerbates atherosclerotic lesion formation and vascular remodeling

Abstract

To examine the role of heme oxygenase (HO)‐1 in the pathophysiology of vascular diseases, we generated mice deficient in both HO‐1 and apolipoprotein E (HO‐1 −/− apoE −/− ). Despite similar total plasma cholesterol levels in response to hypercholesterolemia, HO‐1 −/− apoE −/− mice, in comparison with HO‐1 +/+ apoE −/− mice, had an accelerated and more advanced atherosclerotic lesion formation. In addition to greater lipid accumulation, these advanced lesions from HO‐1 −/− apoE −/− mice contained macrophages and smooth muscle α‐actin‐positive cells. We further tested the role of HO‐1 on neointimal formation in a mouse model of vein graft stenosis. Autologous vein grafts in HO‐1 −/− mice showed robust neointima consisting of α‐actin‐positive vascular smooth muscle cells (VSMC) 10 days after surgery in comparison to the smaller neointima formed in autologous vein grafts in HO‐1 +/+ mice. However, at 14 days after surgery, the neointima from composite vessels of HO‐1 −/− mice was composed mainly of acellular material, indicative of substantial VSMC death. VSMC isolated from HO‐1 −/− mice were susceptible to oxidant stress, leading to cell death. Our data demonstrate that HO‐1 plays an essential protective role in the pathophysiology of atherosclerosis and vein graft stenosis.