N. Gonzalez-ramon et al., Pig MAP/ITIH4 and haptoglobin are interleukin-6-dependent acute-phase plasma proteins in porcine primary cultured hepatocytes, EUR J BIOCH, 267(6), 2000, pp. 1878-1885
The acute-phase expression of pig MAP (major acute-phase protein)/ITIH4 (in
ter-alpha-trypsin inhibitor heavy chain 4) and haptoglobin were analysed in
primary cultures of isolated pig hepatocytes in response to recombinant hu
man (rh) cytokines: tumor necrosis factor-alpha (TNF-alpha), interleukin-1
(IL-1), interleukin-6 (IL-6), as well as to bacterial lipopolysaccharide (L
PS). Analysis of pig MAP/ITIH4 and haptoglobin mRNAs was carried out by RT-
PCR amplification. Secreted proteins from the cytokine-treated hepatocytes
were quantified by immunochemical techniques. Time-course and dose-response
experiments show that pig MAP/ITIH4 and haptoglobin belong to the type II
acute-phase proteins, as they are specifically induced by rhIL-6 and not by
rhTNF-alpha or rhIL-1. Stimulation of cultured pig hepatocytes with rhIL-6
for 48 h at doses of 1000 U.mL(-1) showed a fourfold to fivefold increase
in pig MAP/ITIH4 concentration in the medium, while the concentration of ha
ptoglobin only increased twofold. A similar increase in the concentration o
f pig MAP/ITIH4 was also observed in media of LPS-treated hepatocytes with
the simultaneous generation of IL-6 by the Kupfer cells present in the cult
ures. Albumin secretion decreased after stimulation with doses of 100 or 10
00 U.mL(-1) rhTNF-alpha, rhIL-1 or rhIL-6. Therefore, it can be concluded t
hat pig MAP/ITIH4 behaves as a major acute-phase protein produced by porcin
e hepatocytes under the effect of inflammatory cytokines.