ACTIVATION OF NEUTROPHIL RESPIRATORY BURST BY CYTOKINES AND CHEMOATTRACTANTS - REGULATORY ROLE OF EXTRACELLULAR-MATRIX GLYCOPROTEINS

Objective and Design: We investigated the in vitro responsiveness of n eutrophils adherent to fibronectin (FN) and laminin (LM), toward natur al pro-inflammatory and/or phagocyte-activating agents. Materials and Methods: Neutrophils from normal volunteers were layered on polystyren e wells precoated or not with FN and/or LM and tested for their abilit y of responding to eleven pro-inflammatory mediators by evaluation of superoxide anion (O-2(-)) production and adherence. Results, expressed as mean +/- 1 SEM, were evaluated by non-parametric analyses (Mann-Wh itney U-test or Kruskal-Wallis non-parametric ANOVA analysis) Results: Precoating polystyrene wells with LM or FN prevented the plastic-indu ced neutrophil O-2(-) production. Among eleven agents, tumor necrosis factor-alpha (TNF, 3.0 +/- 0.3 nmoles O-2(-)/5 x 10(4) neutrophils/180 min, p < 0.001), granulocyte-macrophage colony stimulating factor (GM -CSF, 2.1 +/- 0.3 nmoles O-2(-)/5 x 10(4) neutrophils/180min, p < 0.05 ) and formyl-peptides (fMLP, 2.5 +/- 0.5 nmoles O-2(-)/5 x 10(4) neutr ophils/180min, p < 0.01) caused massive O-2(-) production by neutrophi ls adherent to FN. None of the mediators was capable of triggering O-2 (-) production by neutrophils adherent to LM. LM, mixed with FN to coa t wells, caused a dose-dependent inhibition of the oxidative burst tri ggered by TNF (IC50 LM: 0.84 +/- 0.03 mu g, mean +/- 1 SEM), GM-CSF (I C50 LM: 0.36 +/- 0.16 mu g, mean +/- 1 SEM) and fMLP (IC50 LM: 0.54 +/ - 0.008 mu g, mean +/- 1 SEM). To the contrary, fMLP (85.5 +/- 27.7%), TNF (163.1 +/- 67.5%), and GM-CSF (121.8 +/- 66.4%) caused a signific ant augmentation of neutrophil adherence to LM, suggesting that LM-med iated inhibition of neutrophil oxidative metabolism does not depend on the concomitant LM-induced inhibition of neutrophil adherence. Finall y, neither solid-phase FN nor LM affected O-2(-) production by neutrop hils in response to immune complexes. Conclusions: Extracellular matri x glycoproteins dictate the response of neutrophils to soluble mediato rs but not to immune complexes. This appears to be a biologically mean ingful mechanism to localise the risk of cellular reactions to mediato rs that are able to diffuse easily from tissue sites of generation and become widely distributed in body fluids during inflammatory diseases .