Processes Involved in the Site-Specific Effect of Probucol on Atherosclerosis in Apolipoprotein E Gene Knockout Mice

Abstract

Objective-To elucidate processes by which the antioxidant probucol increases lesion size at the aortic sinus and decreases atherosclerosis at more distal sites in apolipoprotein E-deficient (apoE Ϫ/Ϫ ) mice. Methods and Results-Male apoEϪ/Ϫ mice were fed high-fat chow with 1% (w/w) probucol or without (controls) for 6 months, before aortic sinus, arch, and descending aorta were analyzed separately for lesion size and composition. Compared with control, probucol significantly increased lesion size by 33% at the sinus, but it inhibited atherosclerosis at the descending aorta by 94%. Sites where atherosclerosis was inhibited contained substantially fewer macrophages, less lipids (cholesterol and cholesteryl esters), and endogenous antioxidant (␣-tocopherol), but not oxidized lipids, and the extent to which probucol metabolism occurred was increased. Compared with control, aortic sinus lesions of probucol mice contained a substantially increased content of extracellular matrix, but decreased total cell and macrophage density, comparable levels of lipids and ␣-tocopherol, and decreased concentrations of oxidized lipids (cholesteryl ester hydroperoxides, F 2 -isoprostanes, and 7-ketocholesterol). Conclusions-Probucol affects atherosclerosis in apoEϪ/Ϫ mice independent of the accumulation of arterial lipid oxidation products, thereby dissociating the 2 processes. Rather, probucol exerts antiinflammatory activity by decreasing accumulation of macrophages in lesions, and it promotes a more stable lesion composition at the aortic sinus. Key Words: antioxidants Ⅲ atherosclerosis Ⅲ collagen Ⅲ free radicals Ⅲ inflammation A therosclerosis represents a state of heightened oxidative stress characterized by lipid and protein oxidation in the vascular wall. 1 The oxidative modification hypothesis of atherosclerosis predicts that low-density lipoprotein (LDL) oxidation is an early event in and that oxidized LDL contributes to atherogenesis. 2 Oxidized LDL supports foam cell formation in vitro and other potentially pro-atherogenic activities, the lipid in human lesions is oxidized and contains oxidized LDL, and several different antioxidants inhibit atherosclerosis in animals. 1 In addition to LDL oxidation, other relevant oxidative events include the production of reactive oxygen and nitrogen species by vascular cells, 3 and oxidative modifications contributing to important clinical manifestations of coronary artery disease such as endothelial dysfunction and plaque disruption. 1 However, despite abundant data, fundamental problems remain with implicating oxidative modification as a requisite cause for atherosclerosis. 1 These include the poor performance of antioxidants in limiting atherosclerosis or cardiovascular events from it, 4 and observations in animals that suggest dissociation between atherosclerosis and lipoprotein lipid oxidation. [5][6][7][8][9] To reconcile these discrepancies, the "oxidative response to inflammation" model of atherosclerosis 1 considers inflammation as a primary process of atherosclerosis, an...

Probucol [4,4′-[(1-Methylethylidene)bis(thio)]bis-[2,6-bis(1,1-dimethylethyl)phenol]] Inhibits Compensatory Remodeling and Promotes Lumen Loss Associated with Atherosclerosis in Apolipoprotein E-Deficient Mice

“…The near perfect compensation for plaque growth during the time period examined also adds weight to the suggestion that inward remodeling may be due to healing of plaque rupture, an event that does not occur in the carotid arteries of ApoE Ϫ/Ϫ mice. Previous studies reported probucol to increase lesion size in the aortic root of ApoE Ϫ/Ϫ mice (Zhang et al, 1997;Moghadasian et al, 1999), although subsequent studies showed probucol to decrease disease distal to the aortic root (Witting et al, 2000;Choy et al, 2005). The observed inhibition by probucol of atherosclerosis at the prebifurcational common carotid artery is consistent with these latter studies.…”

“…Although remodeling after angioplasty and remodeling during de novo atherosclerosis are quite different processes, it is possible that key components of both forms of remodeling are shared and may be affected by probucol. For example, collagen deposition (Lafont et al, 1999;Burke et al, 2002) and inflammatory cells (Pasterkamp et al, 1998;Okamoto et al, 2001) play key roles in both forms of remodeling and have been reported previously to be affected by probucol in ApoE Ϫ/Ϫ mice (Zhang et al, 1997;Choy et al, 2005). Similarly, MMPs seem to be important in both forms of remodeling (de Smet et al, 2000;Pasterkamp et al, 2000).…”

“…These include the ability to inhibit the secretion of the proinflammatory cytokine interleukin-1 by macrophages (Ku et al, 1990) and to decrease the expression of monocyte chemotactic protein 1 (Chang et al, 1995;Nakamura et al, 2002) and monocyte infiltration in vivo (Nakamura et al, 2002). Indeed, anti-inflammatory rather than antioxidant activities have been proposed recently to explain probucol's protection against experimental atherosclerotic vascular disease (Choy et al, 2005;Wu et al, 2006). By inhibiting monocyte infiltration and macrophage foam cell accumulation in the vessel wall (Choy et al, 2005), probucol could conceivably decrease arterial matrix metalloproteinase (MMP) activity (Nakamura et al, 2002) and thus affect arterial remodeling Ivan et al, 2002;Kuzuya et al, 2006).…”

“…Indeed, anti-inflammatory rather than antioxidant activities have been proposed recently to explain probucol's protection against experimental atherosclerotic vascular disease (Choy et al, 2005;Wu et al, 2006). By inhibiting monocyte infiltration and macrophage foam cell accumulation in the vessel wall (Choy et al, 2005), probucol could conceivably decrease arterial matrix metalloproteinase (MMP) activity (Nakamura et al, 2002) and thus affect arterial remodeling Ivan et al, 2002;Kuzuya et al, 2006). Arterial remodeling refers to a change in cross-sectional area of the blood vessel (Glagov et al, 1987) (Fig.…”

Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association

“…Because atherosclerosis can develop nonuniformly in different vascular regions, [191][192][193] it can be informative to obtain data in several atherosclerosis-prone regions. If an intervention exhibits similar effects on lesion size in all regions quantified, this offers a straightforward interpretation of its effect on atherogenesis.…”