Angiotensin II Induces Migration and Pyk2/Paxillin Phosphorylation of Human Monocytes

Abstract

Angiotensin (Ang) II has been shown to enhance the development of atherosclerotic lesions. Migration of monocytes is an early critical step in the atherosclerotic process. To elucidate mechanisms by which Ang II promotes atherogenesis, we investigated its effects on human monocyte migration. Ang II induced migration of human peripheral blood monocytes (HPBM) and human THP-1 monocytes at concentrations between 0.01 and 1 μmol/L, with a 3.6±0.6-fold induction in HPBM and a 4.8±0.9-fold induction in THP-1 cells at 1 μmol/L Ang II (both P <0.01 versus unstimulated cells). Addition of the Ang II receptor type 1 (AT1-R) antagonist losartan (1 to 100 μmol/L) suppressed Ang II–induced migration of HPBM and THP-1 monocytes in a dose-dependent manner, demonstrating an AT1-R–mediated mechanism. Ang II–directed migration was also blocked by the Src kinase inhibitor PP2 (10 μmol/L), by the extracellular-regulated protein kinase (ERK 1/2) inhibitor PD98059 (30 μmol/L), and by the p38-MAPK inhibitor SB203580 (10 μmol/L), indicating that Src, ERK 1/2, and p38 are all involved in Ang II–induced migration of HPBM and human THP-1 monocytes. The proline-rich tyrosine kinase 2 (Pyk2) and paxillin are 2 cytoskeleton-associated proteins involved in cell movement, phosphorylated by Ang II in other cell types, and abundantly expressed in monocytes. Ang II (1 μmol/L) induced Pyk2 and paxillin phosphorylation in human THP-1 monocytes, peaking after 10 minutes for Pyk2 with a 6.7±0.9-fold induction and after 2 minutes for paxillin with a 3.2±0.4-fold induction. Ang II–induced phosphorylation of both proteins was suppressed by losartan and the Src inhibitor PP2, whereas no effect was observed with PD98059 and SB203580. This study demonstrates a novel proatherogenic action of Ang II on human monocytes by stimulating their migration, through an AT1-R–dependent process, involving signaling through Src, ERK 1/2, and p38. Furthermore, the promigratory actions of Ang II in human monocytes are associated with the phosphorylation of 2 cytoskeleton-associated proteins, Pyk2 and paxillin.