Haemin‐enhanced expression of haem oxygenase‐1 stabilizes erythrocyte‐induced vulnerable atherosclerotic plaques

Abstract

Background and purpose:Previous studies demonstrated that intraplaque haemorrhage increased the contents of cholesterol and oxidants in atherosclerotic plaques. The present study was aimed to test the hypothesis that enhanced expression of haem oxygenase-1 (HO-1) may stabilize vulnerable plaques. Experimental approach: Intravascular ultrasound (IVUS) was performed to identify three similar abdominal aortic plaques in each of 58 fat-fed New Zealand rabbits after aortic balloon injury. With the guidance of IVUS, 50 mL autologous erythrocytes (RBC) or normal saline (NS) were injected from adventitia into two of the pre-selected plaques, respectively, whereas the third plaque served as a blank control. All rabbits were randomly divided into two groups, receiving intraperitoneal injection of haemin and saline respectively. Key results: Compared with NS or control plaques, RBC plaques had more macrophage infiltration and lipid content, thinner plaque fibrous cap, and higher expression of inflammatory factors and incidence of plaque rupture. RBC plaques in the haemin group had about a 50% lower incidence of plaque rupture than those in the control group. Conclusions and implications:Haem oxygenase-1 may eliminate haem or other oxidants, exert unexpected anti-oxidative and anti-inflammatory effects and serve as a promising approach to the direct inhibition of erythrocyte-induced plaque instability.British Journal of Pharmacology (2010) 160, 1484-1495; doi:10.1111/j.1476-5381.2010.00799.x Keywords: atherosclerosis; erythrocyte; vulnerable plaque; haem oxygenase-1; intraplaque hemorrhage Abbreviations: EEMA, external elastic membrane area; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; HDL, highdensity lipoprotein; HO-1, haem oxygenase-1; IVUS, intravascular ultrasound; LA, lumen area; LDL, lowdensity lipoprotein; MCP-1, monocyte chemoattractant protein-1; MDA, malondialdehyde; MMP, matrix metalloproteinase; NF-kB, nuclear transcription factor kB; NS, normal saline; PB, plaque burden; PBS, phosphate buffered saline; RBC, erythrocyte; SDS-PAGE, sodium dodecyl sulphate-polyacrylamide gel electrophoresis; SOD, superoxide dismutase; TC, total cholesterol; TG, triglycerides; TIMP-1, tissue inhibitor of metalloproteinase 1; VCAM-1, vascular cell adhesion molecule-1 IntroductionPathological studies have demonstrated that vulnerable plaques induced by intraplaque hemorrhage are frequently associated with increased density of microvessels (Burke et al., 1999;Kockx et al., 2003) and presence of erythrocyte membranes within the necrotic core (Kolodgie et al., 2003). The number of vasa vasorum was increased twofold and fourfold in vulnerable and ruptured plaques, respectively, as compared with stable plaques. The cholesterol content of the erythrocyte membrane was also found to contribute to the progression of atherosclerosis (Torkhovskaia et al., 1983;Miwa et al., 2003). Lipid contents derived from erythrocytes were associated with large necrotic cores of atherosclerotic plaques with intraplaque hemorrhage (Kolodgie et al., 200...

Effects of Induction/Inhibition of Endogenous Heme Oxygenase-1 on Lipid Metabolism, Endothelial Function, and Atherosclerosis in Rabbits on a High Fat Diet

“…In these two studies, the authors used Snprotoporphyrin 9, another HO-1 inhibitor, to show the anti-atherosclerosis effects of HO-1. Recently, Lin et al demonstrated that hemin-induced upregulation of HO-1 could stabilize vulnerable plaques (26). Our data are in agreement with these results.…”

Intraplaque haemorrhages as the trigger of plaque vulnerability

“…This experimental model has now been reproduced for exploring the relationship between erythrocyte accumulation and oxidative stress. 52 , 53 The pathogenicity of cholesterol crystals is linked to their ability to rupture biological membranes, 54 to erode the thin cap, 55 and to protrude within the lumen inducing luminal thrombosis 56 and possibly embolism. Lastly, cholesterol crystals within vascular cells at the early stage of atheroma could trigger the inflammatory response.…”

Overexpression of Toll-Like Receptors 2, 3, 4, and 8 Is Correlated to the Vascular Atherosclerotic Process in the Hyperlipidemic Rabbit Model: The Effect of Statin Treatment

“…Appropriate isotype controls (negative control) were performed at the same concentrations as the primary antibodies. Immunohistochemically, (a) detection of neovessels was performed with a monoclonal mouse anti-rabbit CD34 antibody (CBL555, dilution 1:500, Chemicon International, CA, USA); (b) smooth muscle cells (SMC) were detected with a monoclonal mouse anti-rabbit α-actin antibody (HHF, dilution 1:400, Chemicon International, CA, USA); (c) macrophages were stained with a monoclonal mouse anti-rabbit RAM-11 antibody (M063, dilution 1:100, Dako, North America Inc., CA, USA); (d) intraplaque erythrocyte membranes (necrotic core) were visualized against biotin-conjugated Bandeiraea simplicifolia isolectin B4 (IB4) (L2140, dilution 1:200, Sigma Aldrich, MI, USA) [9]. …”