Objective-6-Mercaptopurine (6-MP), the active metabolite of the immunosuppressive prodrug azathioprine, is commonly used in autoimmune diseases and transplant recipients, who are at high risk for... Show moreObjective-6-Mercaptopurine (6-MP), the active metabolite of the immunosuppressive prodrug azathioprine, is commonly used in autoimmune diseases and transplant recipients, who are at high risk for cardiovascular disease. Here, we aimed to gain knowledge on the action of 6-MP in atherosclerosis, with a focus on monocytes and macrophages. Methods and Results-We demonstrate that 6-MP induces apoptosis of THP-1 monocytes, involving decreased expression of the intrinsic antiapoptotic factors B-cell CLL/Lymphoma-2 (Bcl-2) and Bcl2-like 1 (Bcl-xL). In addition, we show that 6-MP decreases expression of the monocyte adhesion molecules platelet endothelial adhesion molecule-1 (PECAM-1) and very late antigen-4 (VLA-4) and inhibits monocyte adhesion. Screening of a panel of cytokines relevant to atherosclerosis revealed that 6-MP robustly inhibits monocyte chemoattractant chemokine-1 (MCP-1) expression in macrophages stimulated with lipopolysaccharide (LPS). Finally, local delivery of 6-MP to the vessel wall, using a drug-eluting cuff, attenuates atherosclerosis in hypercholesterolemic apolipoprotein E*3-Leiden transgenic mice (P<0.05). In line with our in vitro data, this inhibition of atherosclerosis by 6-MP was accompanied with decreased lesion monocyte chemoattractant chemokine-1 levels, enhanced vascular apoptosis, and reduced macrophage content. Conclusion-We report novel, previously unrecognized atheroprotective actions of 6-MP in cultured monocytes/macrophages and in a mouse model of atherosclerosis, providing further insight into the effect of the immunosuppressive drug azathioprine in atherosclerosis. (Arterioscler Thromb Vasc Biol. 2010;30:1591-1597.) Show less
Objective: CCR2, the receptor for monocyte chemoattractant protein 1 (MCP1), is involved in atherosclerosis and abdominal aortic aneurysms (AAAs). Here, we explored the potential beneficial... Show moreObjective: CCR2, the receptor for monocyte chemoattractant protein 1 (MCP1), is involved in atherosclerosis and abdominal aortic aneurysms (AAAs). Here, we explored the potential beneficial blockade of the MCP1/CCR2 pathway. Methods: We applied an AAA model in aging apolipoprotein E deficient mice with pre-existing atherosclerotic lesions. These mice were subjected to two therapeutic strategies. First, a dominant negative form of MCP1 was overexpressed in femoral muscles, resulting in circulating levels of MCP1-7ND (7ND), competing with native MCP1. In the second approach, bone marrow transplantation was performed using bone marrow cells that were infected with a lentiviral construct containing siRNA for CCR2, to specifically inhibit only leukocyte CCR2 expression. Results: Both strategies did not influence lesion size of the advanced atherosclerotic plaques. However, 7ND induced a more fibrous plaque phenotype. Yet, surprisingly a trend in increased number and severity of AAA was observed in the 7ND group. Smooth muscle cells in the aneurysm showed decreased phosphorylated signal transducer and activator of transcription five (STAT5, P < 0.01) in the 7ND group, which is indicative for a decreased proliferative and migratory (wound healing) response. This presumably resulted in the increased AAA development. In contrast, siRNA-induced inhibition of CCR2 in leukocytes led to a significant inhibition in aneurysm formation. In conclusion, systemic inhibition of the MCP1/CCR2 pathway leads to a fibrous plaque phenotype in the advanced atherosclerotic lesions, but to potential adverse effects on AAA formation, implying that for a beneficial overall therapeutic approach, specific inhibitory targeting of leukocyte CCR2 will be essential. (C) 2010 Elsevier Ireland Ltd. All rights reserved. Show less
