Transforming growth factor-beta(1) stimulates degranulation and oxidant release by adherent human neutrophils

The signal transduction pathways that are activated by cytokines and growth factors binding to their receptors on human neutrophils (PMN) are poorly understood, When PMN in suspension encounter many of these agonists they are not activated, but rather are primed for subsequent activation, We and others reported that when PMN are plated onto fibrinogen and stimulated with cytokines or with the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP) they respond by releasing hydrogen peroxide (H2O2) and the specific granule component lactoferrin, Transforming growth factor-beta(1) (TGF-beta(1)) is released by many cells including PMN, It has been reported that TGF-beta(1) stimulates chemotaxis but not exocytosis or superoxide production by cells in suspension, We hypothesized that TGF-beta(1) would activate PMN to release H2O2 when they were adherent to fibrinogen, a response mediated by beta(2) integrin receptors, In this study, we determined whether TGF-beta(1) stimulated H2O2 and lactoferrin release by PMN adherent to fibrinogen, TGF-beta(1) stimulated H2O2 and lactoferrin release from adherent PMN in a concentration-dependent manner, with effects seen in the range of 0.1 to 100 pg/mL, Both H2O2 and lactoferrin release were detected by 60 min and continued for at least 180 min, Adhesion and spreading of PMN paralleled H2O2 and lactoferrin release, Ethanol (200 mM) blocked both H2O2 and lactoferrin release, suggesting the involvement of the phospholipase D pathway, In PMN labeled with lyso-[H-3]phosphatidylcholine, we observed that TGF-beta(1) treatment caused an increase in [H-3]phosphatidate. Propranolol (150 mu M), an inhibitor of phosphatidate phosphohydrolase, blocked both H2O2 and lactoferrin release, suggesting that the conversion of phosphatidic acid to diradylglycerol is an important step in PMN activation by TGF-beta 1. Overall, these results are similar to those reported for fMLP activation of adherent PMN and suggest that a common pathway is involved in both chemoattractant and cytokine activation.