Cultured human liver fat-storing cells produce monocyte chemotactic protein-1. Regulation by proinflammatory cytokines.
Monocytes infiltrate the portal space during chronic liver inflammation. Monocyte chemotactic protein-1 (MCP-1) is a cytokine that induces monocyte chemotaxis and activation. We investigated if human liver fat-storing cells (FSC) secrete MCP-1, and the mechanisms that regulate MCP-1 production. Unstimulated FSC secrete MCP-1 as measured by radioimmunoassay as well as a chemotactic assay and express mRNA that encodes for this cytokine. A two- to threefold increase in MCP-1 secretion was observed when FSC were treated with either interleukin-1 alpha (IL-1 alpha) or interferon-gamma (IFN-gamma). Tumor necrosis factor-alpha (TNF alpha) also increased MCP-1 secretion, although to a lesser extent (1.6-fold). Northern blot analysis showed that IL-1 alpha and IFN-gamma strongly increase the levels of mRNA that encodes for MCP-1, whereas TNF alpha appears to be a weaker stimulus. Analysis of FSC-conditioned medium by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting revealed three bands of MCP-1 that most likely represent isoforms of different apparent molecular weights. Pretreatment of FSC with H-7, a protein kinase C inhibitor, blocked cytokine-induced increase in both MCP-1 gene expression and secretion. To determine the potential role of MCP-1 in vivo, we also analyzed normal and pathologic human liver tissue. Northern blot analysis showed that MCP-1 mRNA expression is more abundant in liver tissue obtained from patients with chronic active hepatitis compared with normal liver tissue. These studies indicate that MCP-1 secreted by FSC is stimulated by proinflammatory cytokines and that MCP-1 gene expression is upregulated in chronic inflammatory liver disease. MCP-1 released by FSC may participate in the recruitment and activation of monocytes at sites of liver injury.
Marra
F
F
Department of Medicine, University of Texas Health Science Center at San Antonio 78284-7882.
Valente
A J
AJ
Pinzani
M
M
Abboud
H E
HE
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015152:Blotting, Northern; D002478:Cells, Cultured; D018932:Chemokine CCL2; D002630:Chemotactic Factors / Q000032:analysis / Q000096:biosynthesis*; D046508:Culture Techniques / Q000379:methods; D016207:Cytokines / Q000494:pharmacology*; D004591:Electrophoresis, Polyacrylamide Gel; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007249:Inflammation; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008970:Molecular Weight; D010879:Piperazines / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism*; D011863:Radioimmunoassay; D011994:Recombinant Proteins / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D018932:Chemokine CCL2; D002630:Chemotactic Factors; D016207:Cytokines; D007375:Interleukin-1; D007546:Isoquinolines; D010879:Piperazines; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C