Macrophage migration inhibitory factor führt in humanen Endothelzellen zur Aktivierung der SRC-Kinase, der PI-3-Kinase und des MAP-Kinase Signalwegs

Abstract

Aims: Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine widely expressed in vascular cells. Its proatherogenic role in lesion development has recently been detected in MIF-deficient mice. However, little is known how MIF regulates the contractile machinery of endothelial cells. Methods and results: Human umbilical vein endothelial cells (HUVECs) were stimulated with 40 ng/ml MIF for 30 min. Phosphorylation of mysion light chain (MLC) increased to 187±21 %, (n=5, p<0.05). At the same time cytoskeletal rearrangement and stress fibre formation occurred (immunohistochemical staining). Preincubation with the specific inhibitor of Src-Kinase PP2 (5 µmol/l) reduced MIF-induced MLC-phosphorylation to 81±7 % (n=5, p<0.05). Phosphorylation of Src following stimulation with MIF peaked after 15 minutes and reached 223±87 % (n=8, p<0.05). Also the downstream target of Src, PI-3-Kinase was activated as shown by kinase activity assay. PI-3-Kinase activity increased to 212±44 % compared to control (n=5, p<0.05). Concomitantly Akt phosphorylation increased to 173±12 % (n=4, p<0.05). Finally phosphorylation of ERK1/2 was analysed (209±16 %, n=5, p<0.05), indicating ERK activation after stimulation with MIF. Conclusions: We show here for the first time that MIF activates the contractile machinery of endothelial cells by phosphorylating MLC via Src-Kinase, PI3-Kinase/Akt and ERK1/2.