title: Laminar shear stress inhibits CXCR4 expression on endothelial cells: functional consequences for atherogenesis.
abstract: Laminar shear stress (LSS) represents a major athero-protective stimulus. However, the mechanisms for this effect are poorly characterized. As chemokine receptors modulate endothelial cell functions, we hypothesized that at least some LSS effects on endothelial cells (ECs) may be due to LSS-dependent changes in chemokine receptor expression and function. Exposure of Human umbilical vein endothelial cells (HUVECs) to 15 dynes/cm2/sec(-1) LSS strongly inhibited CXC chemokine receptor 4 (CXCR4) expression at the transcriptional level and impaired stromal-derived factor (SDF)-1/CXCL12-driven chemotaxis. On the contrary, low shear stress (SS; 4 dynes/cm2/sec(-1)) only marginally affected CXCR4 expression when compared with static control cells. Differently from CXCR4, the expression of SDF-1 mRNA was not affected by LSS treatment. CXCR4 overexpression induced a dose-dependent endothelial cell apoptosis that was enhanced by SDF-1 treatment and was caspase-dependent. CXCR4 overexpression inhibited the LSS-mediated antiapoptotic effect on ECs and was associated to impairment of LSS-induced ERK1/2 phosphorylation. These findings suggest that LSS-induced CXCR4 down-regulation may contribute to endothelial cell survival. Interestingly, the expression of the proatherogenic chemokines MCP-1 and IL-8 was induced by SDF-1 treatment and by CXCR4 overexpression in HUVECs. Further, the known LSS-induced inhibition of MCP-1 expression was impaired in CXCR4 overexpressing ECs. Finally, CXCR4 was abundantly expressed by human atherosclerotic plaque endothelium that is exposed to low/absent shear stress, while it was poorly expressed by minimally diseased carotid artery endothelium. In conclusion, LSS-dependent CXCR4 down-regulation may contribute to atheroprotection by favoring the integrity of the endothelial barrier and by inhibiting MCP-1 and IL-8 expression.
authors.affiliation: Laboratorio di Patologia Vascolare, Istituto Dermopatico dell'Immacolata-IRCCS, Rome, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Melchionna
authors.forename: Daniele
authors.initials: D
authors.lastname: Porcelli
authors.forename: Antonella
authors.initials: A
authors.lastname: Mangoni
authors.forename: Daniele
authors.initials: D
authors.lastname: Carlini
authors.forename: Giovanna
authors.initials: G
authors.lastname: Liuzzo
authors.forename: Gaia
authors.initials: G
authors.lastname: Spinetti
authors.forename: Annalisa
authors.initials: A
authors.lastname: Antonini
authors.forename: Maurizio C
authors.initials: MC
authors.lastname: Capogrossi
authors.forename: Monica
authors.initials: M
authors.lastname: Napolitano
mesh_terms: D050197:Atherosclerosis / Q000209:etiology*; D002470:Cell Survival; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D002633:Chemotaxis; D042783:Endothelial Cells / Q000737:chemistry / Q000502:physiology*; D015870:Gene Expression / Q000187:drug effects; D018056:Hemorheology; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics; D008833:Microcirculation / Q000166:cytology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D019718:Receptors, CXCR4 / Q000235:genetics* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013312:Stress, Physiological; D014471:Umbilical Veins
chemical_list: C111835:CCL2 protein, human; C515255:CXCL12 protein, human; D018932:Chemokine CCL2; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D016209:Interleukin-8; D012333:RNA, Messenger; D019718:Receptors, CXCR4; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3