title: Activation of p38(MAPK) mediates the angiostatic effect of the chemokine receptor CXCR3-B.
abstract: Chemokines binding the CXCR3 receptor have been shown to inhibit angiogenesis via the CXCR3-B isoform, but the underlying molecular mechanisms are unknown. Aim of this study was to elucidate the effects of CXCR3-B on activation of members of the mitogen-activated protein kinase family, and to explore the relevance of defined signaling pathways to the angiostatic effects of CXCR3-B ligands. Human embryonic kidney (HEK) 293 cells were transfected with expression vectors encoding for CXCR3-A or CXCR3-B. In cells expressing CXCR3-A, CXCL10 (IP-10) at nanomolar concentrations induced activation of ERK, Akt, and Src, as previously described in human vascular pericytes. In HEK-293 cells expressing CXCR3-B, exposure to CXCL10 in the micromolar concentration range led to activation of the p38(MAPK) pathway, as indicated by phosphorylation of p38(MAPK) itself, and of MKK3/6 and MAPKAPK-2, that lie upstream and downstream of p38(MAPK), respectively. Similar results were obtained in cells stimulated with CXCL4 (PF4), a specific ligand of CXCR3-B. In contrast, CXCL4 was unable to activate p38(MAPK) in mock-transfected HEK-293 cells. Only a modest induction of ERK or JNK was observed upon CXCR3-B activation. In human microvascular endothelial cells, which selectively express CXCR3-B, in a cell cycle-dependent fashion, CXCL10 and CXCL4 increased the enzymatic activity of p38(MAPK). Pharmacologic inhibition of p38(MAPK) by SB302580 resulted in a significant increase in DNA synthesis and in reversal of the inhibitory action of CXCL10. In conclusion, the p38(MAPK) pathway is a downstream effector of CXCR3-B implicated in the angiostatic action of this chemokine receptor.
authors.affiliation: Dipartimento di Medicina Interna, University of Florence, Viale Morgagni 85, I-50134 Florence, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Petrai
authors.forename: Krista
authors.initials: K
authors.lastname: Rombouts
authors.forename: Laura
authors.initials: L
authors.lastname: Lasagni
authors.forename: Francesco
authors.initials: F
authors.lastname: Annunziato
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Cosmi
authors.forename: Roberto G
authors.initials: RG
authors.lastname: Romanelli
authors.forename: Costanza
authors.initials: C
authors.lastname: Sagrinati
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mazzinghi
authors.forename: Massimo
authors.initials: M
authors.lastname: Pinzani
authors.forename: Sergio
authors.initials: S
authors.lastname: Romagnani
authors.forename: Paola
authors.initials: P
authors.lastname: Romagnani
authors.forename: Fabio
authors.initials: F
authors.lastname: Marra
mesh_terms: D043165:Angiostatic Proteins / Q000378:metabolism*; D002460:Cell Line; D054357:Chemokine CXCL10 / Q000378:metabolism; D004789:Enzyme Activation; D005786:Gene Expression Regulation; D006801:Humans; D010978:Platelet Factor 4 / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D054367:Receptors, CXCR3 / Q000378:metabolism*; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D043165:Angiostatic Proteins; C114753:CXCL10 protein, human; C515187:CXCR3 protein, human; D054357:Chemokine CXCL10; D020033:Protein Isoforms; D054367:Receptors, CXCR3; D010978:Platelet Factor 4; D048051:p38 Mitogen-Activated Protein Kinases