Affiliations: Dept. of Chem. Immunology, The Weizmann Institute, 76100 Rehovot, Israel | Preclinical Research Dept. Boehringer Mannheim GmbH, D-68305 Mannheim, FRG | Department of Anatomy II, University of Heidelberg, D-69120 Heidelberg, FRG
Abstract: Alterations in the release of acute phase proteins as one of the phenomena of an acute phase response are reportedly initiated by cytokines and glucocorticoids. To determine, whether apolipoproteins are similarly affected, human hepatoma HepG2 cells were exposed for up to 12 days to recombinant interleukin-6 (rhIL-6) either on its own or in combination with dexamethasone. The quantities of the apolipoproteins A-I and B secreted daily were determined, and were compared with those of the known acute phase plasma proteins albumin, fibrinogen, haptoglobin and α2-macroglobulin. The apolipoproteins responded differently to the mediators: while apo B was down-regulated by both mediators, apo A-I was not affected by the cytokine but stimulated by the glucocorticoid. A divergent effect of IL-6 and dexamethasone was also observed for α2-macroglobulin, whereas they interacted synergistically in respect to fibrinogen, haptoglobin and albumin. Apparently, IL-6 and dexamethasone not only operate separately in the regulation of apolipoproteins but also of known acute phase proteins.
Keywords: Apolipoprotein A-I and B, acute phase proteins, interleukin-6, dexamethasone, human hepatoma cells
