Priming of human monocyte superoxide production and arachidonic acid metabolism by adherence to collagen- and basement membrane–coated surfaces

Abstract

Monocytes (m phi s) come into intimate contact with basement membranes and extracellular matrix proteins as they extravasate from the blood to the interstitium or to sites of tissue injury. We examined the in vitro effects of m phi adherence to an endothelial cell-derived basement membrane or to purified extracellular matrix proteins on phorbol myristate acetate (PMA)-stimulated superoxide production and prostanoid secretion. Elutriation-purified human peripheral blood m phi s were adhered to tissue culture wells that were precoated with the following purified proteins: bovine serum albumin (BSA), collagen type I (COL I), collagen type IV (COL IV), fibronectin (FN), or laminin (LM). To model the provisional matrix at sites of tissue injury, m phi s were also adhered to wells coated with either denatured collagen type I or gelatin (GEL) or coated with basement membrane (BM) derived from endothelial cell monolayers. The m phi s were adhered to the protein-coated surfaces for 1 h at 37 degrees C in serum-free medium and washed to remove nonadherent cells, and the number of adherent m phi s was measured. Monolayers of m phi s were also incubated for an additional 18 h, at which time both adherence and cell spreading were measured. PMA-stimulated superoxide production by adherent m phi s was determined after 1 and 18 h of adherence to the protein-coated surfaces. PMA-stimulated release of two prostanoids, prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) was measured after 18 h of m phi adherence to the surfaces. Following 18 h of adherence, PMA-stimulated superoxide anion secretion and secretion of PGE2 and TxB2 were augmented of primed by m phi s adherent to COL I, GEL, or BM. In contrast, no such priming effects were observed by m phi s adherent to COL IV, FN, or LM. The results suggest that adherence to basement membranes, collagen type I-containing surfaces in the interstitium, or denatured collagen at sites of tissue injury primes m phi respiratory burst and arachidonate metabolism to inflammatory agonists. Induction of priming events by substrate-specific adherence may be an important factor regulating host defense functions of m phi s in the extracellular matrix.

Extracellular Matrix Modulates Macrophage Functions Characteristic to Atheroma

“…However, we rationalized our approach and chose to study the effects of collagen type I on the basis of its overwhelming presence in the atherosclerotic plaques (Ϸ50% of the total protein content of plaques 3 ) and thus its likelihood of interacting with monocytes infiltrating the vessel wall in vivo. Gudewicz et al 26 suggested previously that a collagen type I substrate increases in vitro monocyte spreading compared with collagen type IV or denatured gelatin. In contrast to their study, in which noted effects on cell shape did not reach statistical significance, probably because of the smaller numbers of monocytes analyzed, collagen type I effects were found to be statistically significant in all our experiments (nϭ6).…”

Human blood monocytes, but not alveolar macrophages, reveal increased CD11b/CD18 expression and adhesion properties upon receptor-dependent activation

“…Adherence is an important immunological step that is not only essential for the migration process but also serves as an important signal for a variety of different functions [8][9][10][11][12][13][14][15]. Adherence events can also prime the cells for augmented activity in the presence of an additional environmental stimuli [28].…”

“…For this purpose, monocytes are equipped with specific cell surface receptors. The receptorligand interaction has far-reaching effects on monocyte differentiation [7], and functions such as phagocytosis [8,9], cytotoxicity [10], arachidonic acid metabolism [11] and gene expression of inflammatory cytokines [12][13][14][15]. Based on these observations, it has been suggested that adherence is an important primary and amplifying signal for the differentiation and activation of monocytes/ macrophages.…”

Collagens in the progression and complications of atherosclerosis

“…49 Collagen stimulation also enhanced phorbol myristate acetate (PMA)-induced superoxide production by macrophages, and primed the secretion of arachidonic acid metabolites such as prostaglandin E2 and thromboxane B2. 51 Finally, type I collagen stimulated MMP-9 expression by PBMCs 49 and MMP-1 expression by alveolar macrophages in vitro. 52 Akin to the differences described above for SMCs, polymeric and monomeric type I collagen elicit different responses in macrophages.…”