Abstract
Human keratinocytes and activated monocytes produces factors which can stimulate the proliferation of thymocytes. The same activity has also been implicated in regulating the expression of plasma proteins in liver cells during the acute phase reaction. To assess whether factors produced by such cells can directly influence liver cells to change the production of acute phase plasma proteins, we studied in tissue culture the response pattern of hepatic cells from three species: human hepatoma cells ( HepG2 cells), and primary cultures of rat and mouse hepatocytes. Conditioned media from the squamous carcinoma COLO-16 cells, normal epidermal cells, and activated peripheral monocytes were able to stimulate the synthesis of specific acute phase plasma proteins: alpha 1-antichymotrypsin in HepG -2 cells, alpha 1-antichymotrypsin, alpha 1-acid glycoprotein, alpha 1-acute phase protein, and alpha 2-macroglobulin in rat hepatocytes, and alpha 1-acid glycoprotein, haptoglobin, and hemopexin in mouse hepatocytes. Only in rat cells, dexamethasone was found to have further enhancing effect. The increased production of plasma proteins could be explained by an elevated level of functional mRNA. Comparing thymocyte-stimulating activities with the effects on plasma protein production, we found some difference both between the conditioned media of epidermal cells and monocytes, and between the responses of the three hepatic cell systems. Furthermore, gel chromatography of conditioned media resulted in partial separation of activities regulating liver cells and thymocytes. Since there is no strict correlation between thymocyte- and hepatocyte-stimulating activities, the presence of different sets of specific factors is assumed.
Highlights
Human keratinocytes and activated monocytes pro- in manyspecies (I),there arealso species-specificacute phase duces factors which can stimulate the proliferationof reactants
Still open questions are whether the factor(s) promoting the thymocyte growth is alsh directly responsible for modulation of most, if not all, acute phase plasma proteins in liver cells and whether the liver-regulating activity is limited to a species-specific set of acutephaseproteins.Inthisstudy we present evidence that human keratinocytes and monocytes produce factors which modulate the synthesiosf different sets of major acutephaseproteins in human and murine liver cells
Since factors produced by activated monocytes were implicated in mediating the hepatic acute phase response (1271, 23,51), we determined the effectof CM derived from peripheral human monocytes on HepG2 cells
Summary
WistarInstitute, Philadelphia, PA) was maintained in monolayer culture using above culture medium. Epidermal cells and the human skin carcinoma cell line COLO16 (32) were cultured in DMEM containing 5% fetal calf serum without any additional stimulantsM. Conditioned Media-Medium, designated here as CM, was collected after 5-days culture of subconfluent monolayers of COLO-16 cells, or 24-h culture of epidermal cells or monocytes in DMEM containing 2-10% fetal calf serum. HepG2 cells in triplicate culturewells weretreated for 48 h with: culture medium alone (control); CM of COLO-. Twenty-five pl of labeled culture medium from each well was separated by two-dimensional gel electrophoresis (see Fig. l),and the relative radioactivity present in the selected plasma proteins was determined. The values represent means and s.d. of the triplicate cultures
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