Effects of dexamethasone and insulin on the acute phase response of Morris hepatoma cells and of rat hepatocytes in culture.

Dexamethasone and insulin stimulate production of several plasma proteins in primary cultures of adult rat hepatocytes but inhibit their production in primary cultures of Morris hepatoma cell line 7777W. The acute phase response elicited in cultured cells by crude cytokines from activated rat peritoneal macrophages is considerably higher in hepatocytes in the presence of hormones, and especially of dexamethasone. In hepatoma cells the hormones enhance the cytokine-induced formation of fibrinogen and cysteine proteinase inhibitor but are without significant effect on suppression of albumin and alpha-fetoprotein synthesis by macrophage supernatants.

The cascade of inflammatory cytokines regulating synthesis of acute phase proteins.

The acute phase cytokines: interleukin 1, tumor necrosis factor alpha (cachectin) and beta (lymphotoxin), hepatocyte stimulating factor and several interferons, all belong to the family of endotoxin-inducible, low molecular weight proteins. Their synthesis in macrophages, fibroblasts, lymphocytes, epithelial and some tumor cells is enhanced by the same cytokines, often in the autocrine manner, and suppressed by dexamethasone. The principal hepatocyte stimulating factor (HSF) regulating synthesis of acute phase proteins is probably identical with IFN-beta 2/BSF-2/IL-6, but other inflammatory cytokines (IL-1, TNF alpha, IFN-gamma) are able to induce distinct sets of acute phase proteins, or to modulate the final response pattern. The effect of hrIFN-gamma on production of acute phase proteins by human hepatoma Hep G2 cells is discussed in detail. It is concluded that the cascades of inflammatory cytokines in different tissues represent amplification and regulatory pathways controlling the development of acute phase response in vivo.

Inhibitory effect of human recombinant interferon gamma on synthesis of acute phase proteins in human hepatoma Hep G2 cells stimulated by leukocyte cytokines, TNF alpha and IFN-beta 2/BSF-2/IL-6.

Supernatants from endotoxin-stimulated human leukemic cells and human recombinant interferon-beta 2 similarly enhance synthesis of alpha 1-antichymotrypsin and haptoglobin but suppress synthesis of albumin in cultured Hep G2 cells. Human recombinant tumor necrosis factor only slightly affects production of alpha 1-antichymotrypsin and albumin in a similar manner as leukocyte cytokines. In distinction, recombinant human interferon-gamma profoundly inhibits synthesis of alpha 1-antichymotrypsin, and especially of haptoglobin, but stimulates production of alpha 2-macroglobulin thus modulating the acute phase response of these cells.

Plasma proteinase inhibitors in Morris hepatoma-bearing rats: changes in the blood level and synthesis in tissue slices.

The antiproteinase activities against trypsin, chymotrypsin, elastase, papain and rat leucocyte proteinases were determined in plasma from control and Morris hepatoma-bearing rats. Bovine trypsin and chymotrypsin were similarly inhibited by the two types of plasma whereas porcine pancreatic elastase, papain and rat leucocyte neutral proteinases were more efficiently inhibited by plasma from tumour-bearing rats. The increased plasma concentrations of some proteinase inhibitors, as determined by rocket immunoelectrophoresis, are suggested to be responsible for the observed differences in inhibition. The highest increases in plasma of tumour-bearing rats were observed for alpha 2-macroglobulin and alpha 1-acute-phase globulin. The synthesis and secretion of six proteinase inhibitors: antithrombin III, alpha 1-proteinase inhibitor, alpha 1-macroglobulin, alpha 2-macroglobulin, alpha 1-acute-phase globulin and haptoglobin, as well as albumin, were measured in tissue slices from rat liver and Morris hepatoma after incubation with [14C]leucine. Local inflammation inflicted upon the tumour-bearing rats increased formation of acute-phase proteins in liver slices but not in hepatoma slices.

Comparison of the acute phase response of cultured Morris hepatoma 7777 cells and of rat hepatocytes.

Isolated Morris hepatoma cells (line 7777) or adult rat hepatocytes were cultured for 3 days and daily production of four plasma proteins was estimated in the cell media by rocket immunoelectrophoresis with monospecific antisera. Addition of cytokines from rat peritoneal macrophages to cultured hepatocytes or hepatoma cells augmented accumulation in the medium of two positive acute phase proteins: fibrinogen (FIB) and cysteine proteinase inhibitor (CPI). At the same time synthesis of alpha-fetoprotein (AFP) was inhibited in hepatoma cells but remained undetectable in hepatocytes. Rat macrophage cytokines typically depressed synthesis of albumin (ALB) in cultured rat hepatocytes but increased production of this protein by hepatoma cells.

Limited effects of recombinant human and murine interleukin 1 and tumour necrosis factor on production of acute phase proteins by cultured rat hepatocytes.

Albumin, fibrinogen, alpha 1-acid glycoprotein and cysteine proteinase inhibitor were determined by electroimmunoassay in the media of primary cultures of rat hepatocytes exposed to dialysed supernatants of rat, mouse and human macrophages or to recombinant human and murine interleukin 1 and tumour necrosis factor. Recombinant cytokines in the range of 1 to 1000 ng/ml caused only reduction of albumin synthesis and slight stimulation of alpha 1 acid glycoprotein production while crude preparations of macrophage cytokines elicited typical acute phase response. The results suggest that interleukin 1 or tumour necrosis factor are not likely the principal mediators responsible for the direct stimulation of normal rat hepatocytes to acute phase protein synthesis.