Matrilysin expression by human mononuclear phagocytes and its regulation by cytokines and hormones

Matrilysin is a recently described metalloproteinase with strong catalytic activity against a variety of extracellular matrix substrates including proteoglycans, elastin, laminin, fibronectin, gelatin, and entactin. Production of this metalloproteinase appears to be limited only to a few normal human cell types including glandular epithelium, mononuclear phagocytes, and renal mesangial cells. Furthermore, matrilysin expression in vivo has been demonstrated only in glandular epithelium, especially the endometrium. In the process of examining various cutaneous and lung inflammatory disorders for matrilysin expression by immunohistochemistry and in situ hybridization, we occasionally found monocytes within blood vessels and newly extravasated tissue-associated macrophages that exhibited matrilysin production. In specimens characterized by severe inflammation and, in particular, cystic fibrosis, this feature was commonly observed. We therefore studied the production of matrilysin by monocyte-derived macrophages in vitro in response to various physiologic signals such as endotoxin, phagocytosable material, cytokines, and hormones. We found that matrilysin expression was stimulated by LPS and opsonized zymosan. Up-regulation of matrilysin by LPS was PGE2-dependent, because indomethacin blocked production, an effect at least partially reversed by the addition of exogenous prostaglandin. LPS stimulated matrilysin production pretranslationally and, furthermore, when cultured cells were subjected to in situ hybridization after LPS exposure, considerable variability in matrilysin mRNA expression was observed on an individual cell basis, with some cells having strong signal and others being completely negative. We also found that matrilysin biosynthesis was inhibited by the lymphokines IL-4, IL-10, and IFN-gamma. Other cytokines such as IL-1, TNF-alpha, and IL-6 failed to modulate the production of matrilysin. Finally, matrilysin biosynthesis was suppressed by glucocorticoids and retinoids. Our studies indicate that matrilysin is produced in vivo by mononuclear phagocytes and is a highly regulated metalloproteinase whose production can be modified by a variety of physiologic and pharmacologic signals.