Doxazosin Inhibits MCP-1 Directed Migration of Human Monocytes
Monocyte chemotactic protein 1 (MCP-1) - directed transendothelial migration of monocytes plays a key role in the early development of atherosclerosis. Migration requires degradation of extracellular matrices, a process that involves matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP). Recent studies suggest that the alpha1-adrenergic receptor (alpha1-AR) antagonist doxazosin (Dox) might have antiatherosclerotic effects by inhibiting proliferation and migration of vascular cells. The purpose of the present study was to determine the effects of Dox on MCP-1 directed monocyte migration, MMP-9 and TIMP-1 regulation, and to identify signalling pathways mediating these processes. MCP-1 (50ng/ml) stimulated migration of human peripheral blood monocytes (HPBM) by 2.8 +/-0.7 fold and of THP-1 human monocytes by 7 +/- 2.7 - fold (both p<0.05 vs. unstimulated cells). Dox inhibited MCP-1 induced migration in a dose dependent manner, with a maximal reduction at 10μM of 50.8 +/- 1.9% in HPBM and 73.5 +/- 3.2 % in THP-1 cells (both p<0.01 vs. MCP-1 alone). Dox blocked migration even after pretreatment with phenoxybenzamine (PBA), an irreversible alpha1-AR antagonist (THP-1 cells: PBA 1μM + Dox 10μM: 76 +/- 11.6% inhibition, p<0.01 vs. MCP-1 alone), suggesting that the antimigratory activity of Dox is mediated through a novel mechanism unrelated to its blocking the alpha1-AR. Pretreatment of monocytes with SB203580 (10μM), a p38 MAPK inhibitor, also attenuated MCP-1 directed migration ( HPBM: 55.3 +/- 0.3% inhibtion; THP-1 cells: 55.4 +/- 13.9% inhibition, both p< 0.05 vs. MCP-1 alone), indicating that activation of this pathway is required for migration towards MCP-1 by these cells. Dox (10μM) inhibited MMP-9 activity by 62% +/- 3.15% (p<0.05) measured by ELISA, whereas MMP-9 protein levels were not affected. Dox also increased phorbol 12-myristate 13-acetate (PMA) induced TIMP-1 expression, which may account for its inhibition of MMP activity. The present study demonstrates a potential novel antiatherosclerotic action of Dox by blocking MCP-1 directed-monocyte migration, mediated, in part, through an inhibtion of MMP-9 activity and upregulation of TIMP-1 production.