Compatible organic osmolytes and osmotic modulation of inducible nitric oxide synthetase in RAW 264.7 mouse macrophages.
The influence of osmolarity and compatible organic osmolytes on the phosphorylation of the MAP-kinases Erk-1 and Erk-2 and on the expression of taurine transporter (TAUT) and lipopolysaccharide (LPS)-induced nitric oxide synthetase (iNOS) was studied in RAW 264.7 mouse macrophages. Hypoosmolarity (205 mosmol/l) but not hyperosmolarity (405 mosmol/l) or challenge of the cells with betaine or taurine increased phosphorylation of Erk-1 and Erk-2. Hypoosmotic Erk-phosphorylation was blocked by the MEK-inhibitor PD098059 but was resistant to depletion of extracellular calcium and to inhibition of PLC, PKC, erbstatin-sensitive tyrosine kinases and elevation of intracellular cAMP. Hyperosmolarity stimulated Na+-dependent taurine uptake and led to an increase of TAUT mRNA levels, whereas hypoosmotic exposure diminished both and induced a rapid efflux of the osmolyte from taurine-preloaded cells. The hyperosmotic elevation of TAUT mRNA levels was antagonized upon addition of taurine but not of betaine or myo-inositol. Hyperosmolarity increased the LPS-induced iNOS expression at the mRNA and the protein level. This was suppressed by betaine but not by taurine or myo-inositol. The osmotic regulation of taurine transport and iNOS expression appeared independent of the MEK-Erk pathway and the p38MAPK.
Department of Gastroenterology, Hepatology and Infectiology, Heinrich-Heine-University, Düsseldorf, Germany.
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Warskulat
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Schliess
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Häussinger
D000818:Animals; D001622:Betaine / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D007294:Inositol / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008082:Lipotropic Agents / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D026901:Membrane Transport Proteins; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009994:Osmolar Concentration; D010766:Phosphorylation; D013654:Taurine / Q000378:metabolism / Q000494:pharmacology; D000099247:Taurine Transporters
D001622:Betaine; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002352:Carrier Proteins; D007294:Inositol; D008070:Lipopolysaccharides; D008082:Lipotropic Agents; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D013654:Taurine; D000099247:Taurine Transporters; C496317:Nos2 protein, mouse