Abstract
Various antioxidants, including polyphenols, prevent the development of atherosclerosis in animal models, contrasting with the failure of antioxidants to provide benefits in patients with established atherosclerosis. We therefore tested in a mouse model the hypothesis that although catechin is atheroprotective in prevention, catechin brings no global vascular protection when initiated after established atherosclerosis, because aging associated with dyslipidemia has induced irreversible dysfunctions. To this end, LDLr(-/-); hApoB(+/+) atherosclerotic (ATX, 9 mo old) and pre-ATX (3 mo old) male mice were treated with catechin (30 mg x kg(-1) x day(-1)) up to 12 mo of age. Vascular function and endothelium/leukocyte interactions were studied at 12 mo old. The renal artery endothelium-dependent dilations were impaired with age whereas adhesion of leukocytes onto the native aortic endothelium was increased (P < 0.05). Aortic oxidative stress [reactive oxygen species (ROS)] increased (P < 0.05) at 3 mo in ATX and at 12 mo in wild-type mice. Aorta mRNA expression of NADPH oxidase increased, whereas that of manganese superoxide dismutase decreased in 12-mo-old ATX mice only. In mice with established ATX, catechin (from 9 to 12 mo) reduced (P < 0.05) by approximately 60% ROS without affecting plaque burden. Notably, catechin worsened endothelial dysfunction and further increased leukocyte adhesion (P < 0.05) in ATX mice. In contrast, the same catechin treatment reversed all age-related dysfunctions in wild-type mice. On the other hand, in pre-ATX mice treated for 9 mo with catechin, plaque burden was reduced by 64% (P < 0.05) and all vascular markers were normalized to the 3-mo-old values. These results demonstrate that an antioxidant treatment is deleterious in mice with established atherosclerosis.