Signal transduction pathways in directed migration of human monocytes induced by human growth hormone in vitro

The human growth hormone (GH) was shown to modulate leukocyte functions such as stimulating directed migration of human monocytes in vitro, Dimerisation of OH-receptors leads to the activation of various signalling mechanisms. As transduction of GH signals to monocytes is unknown. we investigated GH signalling mechanisms in monocyte migration using a modified Boyden chamber chemotaxis assay. Inhibition of tyrosyl phosphorylation of OH receptor-associated tyrosine kinase by tyrphostin-23 or staurosporine blocked OH-stimulated monocyte migration down to random levels. Furthermore. pre-incubation with effective concentrations of 4B-phorbol-12-myristate-13-acetate (PMA). staurosporine and bisindolymaleimide I. inhibitors of protein kinase C. significantly decreased OH-induced migration, suggesting that PKC is involved in the signalling cascade. Additionally. phosphatidylinositol 3-kinase and mitogen-activated protein kinase (MAPK) activation seems to be required. This study revealed signalling pathways in monocyte movement toward GH in vitro. (C) 2001 Elsevier Science B.V. All rights reserved.