12-o-Tetradecanoyl-phorbol-13-acetate-differentiated U937 cells express a macrophage-like profile of neutral proteinases. High levels of secreted collagenase and collagenase inhibitor accompany low levels of intracellular elastase and cathepsin G.

Abstract

Human monocytic tumor cells of the U937 cell line contain substantial quantities of two neutrophil neutral proteinases, elastase and cathepsin G, raising the question of whether their presence reflects an expression of transformation or whether normal monocytes undergo a developmental stage in which they produce certain neutrophil proteinases. To address this issue, we examined U937 cells for production of collagenase, since human alveolar macrophages release fibroblast-like collagenase, an enzyme that is distinct from neutrophil collagenase. Using an immunoassay that utilized antibody to skin fibroblast collagenase, we found that U937 cells secreted barely detectable quantities of enzyme, 10-12 ng/10' cells per 24 h, under basal conditions. Upon incubation with 10 nM 12-o-tetradecanoyl-phorbol-13-acetate (TPA), however, collagenase release increased 200-fold, comparable to the amount secreted by phorbol-stimulated human fibroblasts. Metabolic labeling and immunoprecipitation confirmed the enhanced synthesis of U937 cell collagenase upon TPA exposure. This enzyme activity further resembled fibroblast collagenase and differed from neutrophil collagenase by exhibiting preferential cleavage of monomeric type III collagen relative to type I. As previously observed with human alveolar macrophages, U937 cells also released a protein identical to the collagenase inhibitor produced by human skin fibroblasts, a molecule not associated with neutrophils. Release of this inhibitor increased 10-fold with TPA exposure.In contrast to collagenase and collagense inhibitor, TPAtreated U937 cells contained only 10-15% as much elastase and cathepsin G activities as control cells. Thus, TPA-induced differentiation modified the presence of these enzymes in the direction of their content in normal monocytes. Since the neutral proteinase profile of undifferentiated U937 cells resembles that of neutrophils and changes markedly after cellular differentiation to one that is characteristic of monocytes, these data suggest that neutrophilic proteinases may be produced by normal monocytes during the early stages of their differentiation.

Increased pathology in lungs of mice after infection with an α-crystallin mutant of Mycobacterium tuberculosis: changes in cathepsin proteases and certain cytokines

“…CatG is highly abundant in the azurophilic granules of neutrophils and monocytes (Senior & Campbell, 1984;Senior et al, 1982), and is synthesized during the promyelocytic and promonocytic stages of maturation, respectively (Bainton et al, 1971;van der Meer et al, 1981). In U937 monocytes, treatment with the phorbol ester 12-Otetradecanoylphorbol 13-acetate (TPA) results in transcriptional downregulation of catG (Hanson et al, 1990;Ley et al, 1989;Welgus et al, 1986). Since there is no evidence that catG is expressed by alveolar epithelial pneumocytes, it is possible that the CatG detected in the normal lung is derived from circulating monocytes and/or neutrophils.…”

CCR1-Mediated STAT3 Tyrosine Phosphorylation and CXCL8 Expression in THP-1 Macrophage-like Cells Involve Pertussis Toxin-Insensitive Gα14/16 Signaling and IL-6 Release

“…To further confirm the involvement of IL-6 in CCL15-mediated STAT3 Tyr 705 phosphorylation in macrophages, U-937 macrophage-like cells were treated with IL-6-neutralizing Ab for 30 min before the addition of CCL15. PMAdifferentiated U-937 cells, which endogenously express CCR1 (42) as well as Ga 14 and Ga 16 (23), are another widely used in vitro model of human macrophages (43). As shown in Fig.…”

Urokinase receptor is a multifunctional protein: influence of receptor occupancy on macrophage gene expression.

“…ated with cessation of proliferation and acquisition of a differentiated, macrophage-like phenotype (1)(2)(3). Among the many changes in gene expression that accompany the differentiation of these cells are striking changes in the expression of proteases (4)(5)(6)(7)(8). These changes reflect the complex developmental control of proteases and presumably facilitate the functions of migratory progenitors and tissue macrophages.…”

“…These changes reflect the complex developmental control of proteases and presumably facilitate the functions of migratory progenitors and tissue macrophages. Unstimulated myeloid cells and fresh monocytes contain high levels of the serine proteases cathepsin G and human neutrophil elastase (HNE) (4,9,10). Analogous to neutrophils, these serine proteases are stored in cytoplasmic granules and can be rapidly released in response to extracellular signals.…”