RAT FIBROBLASTS SYNTHESIZE T-KININOGEN IN RESPONSE TO CYCLIC-AMP, PROSTAGLANDIN E(2) AND CYTOKINES

T-Kininogen is a plasma protein characterized as a kinin-precursor, a cysteine protease inhibitor and an acute phase protein in the rat. Rat fibroblasts prepared from meninges or embryos and 3Y1-B clone 1-6 cells, a rat fibroblast cell line, secreted T-kininogen. Incubating these cells with 1 mM Bt(2)cAMP or a combination with 1 mu M dexamethasone resulted in a marked increase in T-kininogen secretion, as well as in the incorporation of radioactive methionine into newly synthesized T-kininogen. Secretion of T kinino en by meningeal fibroblasts was stimulated by forskolin, prostaglandin E(2), bradykinin and cytokines, such as tumor necrosis factor alpha, interleukin-1 alpha (IL-1) and IL-6. Expression of T-kininogen mRNA was demonstrated in meningeal fibroblasts by Northern blot hybridization using T-kininogen cDNA as a probe, and the expression was stimulated by Bt(2)cAMP, prostaglandin E(2), and the cytokines described above. In contrast, expression of T-kininogen mRNA in rat hepatocytes was not altered by Bt(2)cAMP, prostaglandin E(2), tumor necrosis factor and DL-l, whereas it was greatly stimulated by IL-6, suggesting the differential regulation of T-kininogen gene expression in fibroblasts and hepatocytes, These results demonstrated for the first time, that rat fibroblasts express the T-kininogen gene, and that the expression is regulated by inflammatory mediators and cytokines.