CHARACTERIZATION OF THE RELEASE OF HUMAN MONOCYTE REGULATORS OF FIBROBLAST PROLIFERATION

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  • 1 January 1982
    • journal article
    • research article
    • Vol. 31  (4) , 295-305
Abstract
The mechanism of release of monocyte-derived mediators that stimulate fibroblast proliferation in vitro was examined. Adherence of human monocytes promoted the rapid release of these factors, and treatment of adherent peripheral blood mononuclear cell (APBM) cultures with lipopolysaccharide (LPS) greatly enhanced the level of fibroblast-stimulating activity in the cell-free culture supernatant fluid (SN). Stimulation of phagocytosis or pinocytosis did not alter the release of these mediators from APBM cultures, while trypan blue pretreatment of peripheral blood mononuclear cells (PBM) resulted in a significant reduction in fibroblast stimulation by PBM-SN. Protein synthesis was blocked by pretreatment of monocytes with puromycin and was accompanied by a concomitant reduction in the production of these mediators. Monocyte serine proteases appeared to be essential for mediator synthesis or release, since tosyl-lysine chloromethyl ketone (TLCK) and phenylmethyl sulfonyl fluoride (PMSF) (irreversible inhibitors of serine esterase activity) diminished the release of fibroblast-stimulating factors. Time course data indicate that monocytes rapidly release these products in vitro during the first 24 h of culture with significantly reduced levels being produced from 24-96 h. Adherent human monocytes apparently rapidly release fibroblast-activating mediators in vitro, requiring both protein synthesis and protease activity; LPS, but not phagocytosis, can enhance the release of these products.

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