Activation of mitogen-activated protein kinases and IL-6 release in response to lipopolysaccharides in Kupffer cells is modulated by anisoosmolarity.
OBJECTIVE
The influence of anisoosmolarity on the activation of the extracellular signal-regulated kinases-1 and -2 and on interleukin-6 release was studied in lipopolysaccharide-stimulated rat liver macrophages.


METHODS
Experiments were performed with rat liver macrophages. Activation of the extracellular signal-regulated kinases was determined by kinase shift assay and immune complex kinase assay. Interleukin-6 mRNA was measured by Northern blot analysis and interleukin-6 production by enzyme-linked immunosorbent assay.


RESULTS
Lipopolysaccharide-induced activation of the extracellular signal-regulated kinases-1 and -2 was enhanced in hypoosmotic media (205 mosm/l) and diminished by hyperosmotic (405 mosm/l) exposure when compared to normoosmotic (305 mosm/l) conditions. These effects were paralleled by changes in lipopolysaccharide-stimulated interleukin-6 mRNA expression, when determined after 4 h and interleukin-6 release after 18 h. The mitogen-activated protein kinase-kinase inhibitor PD 098059 abolished phosphorylation of the extracellular signal-regulated kinases-1 and -2 in response to lipopolysaccharide, irrespective of the medium osmolarity, and diminished lipopolysaccharide-induced interleukin-6 mRNA expression and interleukin-6 production under normo- and hypoosmotic conditions by about 50%; it also resulted under hyperosmotic conditions in an about 80% inhibition. SB 203580, a specific inhibitor of p38 largely abolished interleukin-6 mRNA expression and interleukin-6 production, irrespective of medium osmolarity, whereas phosphorylation of the extracellular signal-regulated kinases was not affected.


CONCLUSIONS
The data indicate a modulation of lipopolysaccharide-induced interleukin-6 production by ambient osmolarity and an involvement of both p38 and the extracellular signal-regulated kinases-1 and -2 in the stimulation of interleukin-6 production by lipopolysaccharide.
Bode
J G
JG
Medizinische Universitätsklinik, Heinrich-Heine-University, Düsseldorf, Germany.
Peters-Regehr
T
T
Schliess
F
F
Häussinger
D
D
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007093:Imidazoles / Q000494:pharmacology; D015850:Interleukin-6 / Q000096:biosynthesis*; D007700:Kinetics; D007728:Kupffer Cells / Q000187:drug effects* / Q000201:enzymology / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009994:Osmolar Concentration; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases
D004791:Enzyme Inhibitors; D005419:Flavonoids; D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D007093:Imidazoles; D015850:Interleukin-6; D008070:Lipopolysaccharides; D047428:Protein Kinase Inhibitors; D011725:Pyridines; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one