casein-kinase-ii and Arteriosclerosis

Innate immune system activation is associated with atherosclerotic lesion development. The specific sites of lesion development are believed to be defined by the shear stress of blood flow. Consequently, we investigated the responsiveness of human coronary artery endothelial cells (HCAECs) to Toll-like receptor (TLR) 2 and 4 agonists in an in vitro model of chronic laminar flow. HCAECs under chronic laminar flow were found to be normally responsive to lipopolysaccharide (and tumor necrosis factor) in terms of E-selectin expression but were found to be hyporesponsive to stimulation with the specific TLR2 ligands macrophage activating lipopeptide-2, PAM2-Cys, and Lip19; this was observed to be attributable to downregulation of TLR2 transcription and protein expression. We found that laminar flow induced SP1 serine phosphorylation by protein kinase CK2 and thereby blocked SP1 binding to the TLR2 promoter, which is required for TLR2 expression. This regulatory mechanism also blocked lipopolysaccharide- and tumor necrosis factor-induced TLR2 upregulation in HCAECs and could be important for suppression of other flow-sensitive endothelial proteins. These results extend the role of flow in controlling endothelial responsiveness. Given the current evidence that TLRs are proatherogenic, flow suppression of TLR2 expression may be atheroprotective.

Topics: Arteriosclerosis; Carrier Proteins; Casein Kinase II; Cells, Cultured; Coronary Vessels; DNA-Binding Proteins; Endothelial Cells; Endothelium, Vascular; Gene Expression Regulation; Hemorheology; Humans; Lipopeptides; Lipopolysaccharides; Membrane Glycoproteins; Oligopeptides; Phosphorylation; Protein Processing, Post-Translational; Receptors, Cell Surface; Recombinant Proteins; RNA, Messenger; Sp1 Transcription Factor; Sp3 Transcription Factor; Stress, Mechanical; Toll-Like Receptor 2; Toll-Like Receptors; Transcription Factors; Triazoles; Tumor Necrosis Factor-alpha

Emerging data suggest that urokinase-type plasminogen activator (UPA), beyond its role in pericellular proteolysis, may also act as a mitogen. We investigated the function of endogenous UPA in mediating the mitogenic effects of platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF) on human vascular smooth muscle cells (SMC). Growth-arrested SMC constitutively expressed UPA, but UPA expression and secretion increased several times upon stimulation with either PDGF or bFGF. Inhibition of endogenous UPA with a polyclonal antibody significantly reduced DNA synthesis and proliferation of PDGF or bFGF stimulated SMC, this effect already being evident when the cells entered S-phase. The proliferative activity of endogenous UPA was dependent on a functional catalytic domain as demonstrated by inhibition experiments with a specific monoclonal antibody (394OA) and p-aminobenzamidine, respectively. In contrast, neither plasmin generation nor binding of UPA to its receptor (CD87) were required for UPA-mediated mitogenic effects. The results demonstrate that endogenous UPA is not only overexpressed in SMC upon stimulation with PDGF/bFGF, but also mediates the mitogenic activity of the growth factors in a catalytic-domain-dependent manner. Specific inhibition of this UPA domain may represent an attractive target for pharmacological interventions in atherogenesis and restenosis after angioplasty.

Topics: Arteriosclerosis; Casein Kinase II; Catalytic Domain; Cell Division; Cells, Cultured; DNA; Dose-Response Relationship, Drug; Drug Administration Schedule; Enzyme Inhibitors; Fibrinolysin; Fibroblast Growth Factor 2; Graft Occlusion, Vascular; Humans; Hypertrophy; Muscle, Smooth, Vascular; Platelet-Derived Growth Factor; Protein Serine-Threonine Kinases; Receptors, Cell Surface; Receptors, Urokinase Plasminogen Activator; Up-Regulation; Urokinase-Type Plasminogen Activator