RESUMO
Endothelial cell receptors for the angiostatic chemokines IFN-gamma-inducible protein of 10 kDa (IP-10) and monokine induced by IFN-gamma (Mig) have not yet been identified, and the mechanisms responsible for the effects of these chemokines on angiogenesis are still unclear. IP-10 and Mig share a common functional receptor on activated T lymphocytes, named CXC chemokine receptor 3 (CXCR3). Using in situ hybridization and immunohistochemistry, we show that CXCR3 is expressed by a small percentage of microvascular endothelial cells in several human normal and pathological tissues. Primary cultures of human microvascular endothelial cells (HMVECs) likewise express CXCR3, although this expression is limited to the S/G2-M phase of their cell cycle. Both IP-10 and Mig, as well as the IFN-gamma-inducible T-cell alpha chemoattractant (I-TAC), which all share high-affinity binding for CXCR3, block HMVEC proliferation in vitro, an effect that can be inhibited by an anti-CXCR3 antibody. These data provide definitive evidence of CXCR3 expression by HMVEC and open new avenues for therapeutic interventions in all conditions in which an angiostatic effect may be beneficial.
Assuntos
Endotélio Vascular/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular , Receptores de Quimiocinas/genética , Receptores de Quimiocinas/metabolismo , Inibidores da Angiogênese/farmacologia , Ciclo Celular , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Quimiocina CXCL10 , Quimiocina CXCL11 , Quimiocina CXCL9 , Quimiocinas CXC/farmacologia , Endotélio Vascular/citologia , Endotélio Vascular/efeitos dos fármacos , Expressão Gênica , Humanos , Neovascularização Fisiológica , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores CXCR3 , Receptores de Quimiocinas/antagonistas & inibidores , Distribuição TecidualRESUMO
L-arginine uptake takes place in human platelets through a saturable high affinity Na(+)-independent process mediated by the y(+) carrier for cationic amino acids. In the present study the effect of thrombin and collagen on L-arginine transport in human platelets was investigated. Thrombin significantly affected L-arginine uptake whereas collagen was uneffective. In particular, thrombin increased Vmax of the uptake by 77%, while it reduced the affinity of the carrier for L-arginine. The effect of thrombin on the transport process did not result in any increase in L-arginine metabolism since no conversion of the amino acid, either to L-citrulline (indicative of the presence of the L-arginine/nitric oxide pathway) or to any other metabolite, could be detected in resting or stimulated platelets.
