SYNERGISTIC AND SELECTIVE STIMULATION OF GELATINASE-B PRODUCTION IN MACROPHAGES BY LIPOPOLYSACCHARIDE, TRANS-RETINOIC ACID AND CGP-41251, APROTEIN-KINASE-C REGULATOR

The production of gelatinase B by macrophages is relevant in the immun ological and migratory functions of macrophages. CGP 41251, an inhibit or of protein kinase C (PKC), was found to stimulate the expression of gelatinase B in macrophages, as shown by the study of two different m onocytic/macrophagic cell lines, mouse RAW 264.7 and human THP-1 cells . When human monocytes and rat peritoneal macrophages were treated wit h CGP 41251, insignificant increases of 10 and 25% were obtained. This can possibly be due to the presence of contaminating cells in these t wo enriched populations, since the CGP 41251 treatment of non-macropha gic cell lines inhibited their PMA-induced gelatinase B production. Ta ken together, these results suggest that the stimulatory effect of CGP 41251 is specific to cells of the monocytic lineage. Using RAW 264.7 cells as a model, the effect of CGP 41251 is additive to that obtained using lipopolysaccharide (LPS) and phorbol 12-myristate 13-acetate (P MA), as revealed by gelatin zymography and Northern blot analysis. The stimulatory effect of CGP 41251 on gelatinase B production in RAW 264 .7 was: (a) inhibited by calphostin C (as is the LPS-induced response) , indicating a PKC-dependence; (b) inhibited by dexamethasone (as oppo sed to the LPS-induced response); and (c) enhanced by addition of tran s-retinoic acid (RA). In fact, RA can induce gelatinase B production, either alone or in synergy with LPS and/or CGP 41251, since the combin ation of the three agents gives the highest gelatinase B response, at both the protein and the mRNA levels. This represents an important obs ervation considering that RA is now being tested as an anti-cancer age nt and proposed for prevention studies.