BRADYKININ DECREASES T-KININOGEN SYNTHESIS IN A RAT HEPATOMA-CELL LINE - EVIDENCE OF BRADYKININ B-2-TYPE RECEPTORS

Using the rat H4-II-E-C3 hepatoma cell line, we investigated the prese nce of [I-125][Tyr(8)]BK binding sites and the direct modulation of T- kininogen synthesis, an acute phase protein of inflammation, by bradyk inin (BK) analogues. H4-II-E-C3 membrane preparations exhibited [I-125 ][Tyr(8)]BK binding sites with a K-d Of 4 nM and a B-max of 120 fmol/m g of protein. Des-Arg(9)-BK showed no affinity (K-i > 10(-4) M) for th ese sites. The B2 metabolism-resistant and selective agonist [Phe(8) P si(CH2-NH)Arg(9)]BK decreased the T-kininogen concentration in H4-II-E -C3 medium by 23% (p < 0.05). This effect was reversed by coincubation with the B-2 antagonist HOE140. The B-1 agonist Sar[D-Phe(8)]des-Arg( 9)-BK and the B-1 antagonist Lys [Leu(8)]des-Arg(9)-BK did not modify T-kininogen concentrations. The interaction between cytokines and kini ns in the modulation of T-kininogen synthesis was also studied. Preinc ubation of hepatoma cells for 1 h with interleukin-1 alpha (IL-1 alpha ) alone reduced T-kininogen concentrations by 37%, and this effect was blocked by co-addition of HOE140. Preincubation with interleukin-6 (I L-6) increased T-kininogen levels by threefold. Coincubation in the pr esence of the B-2 agonist decreased this augmentation by 24%. The latt er effect was reversed by co-addition of HOE140. None of the cytokines tested induced a response to the B-1 agonist or antagonist under the experimental conditions studied. Overall, these results support the pr esence of a functional B-2 receptor on H4-II-E-C3 cells that modulates T-kininogen synthesis. We suggest that the receptor is involved in vi vo in a retroaction loop between kinins and T-kininogen production dur ing inflammation. We speculate that BK could be a mediator in the modu lation of acute phase protein synthesis by the cytokines IL-1 alpha an d IL-6. Copyright (C) 1996 Elsevier Science Inc.