Tyrosine kinases are involved with the expression of inducible nitric oxide synthase in human articular chondrocytes.
The present study characterizes mechanisms involved with the induction of nitric oxide (NO) production, nitric oxide synthase (NOS) enzymatic activity and mRNA expression in human articular chondrocytes. Activation of chondrocytes with lipopolysaccharide (LPS) or IL-1 resulted in time- and dose-dependent increases in iNOS mRNA followed by increased NOS enzymatic activity and NO release. The protein tyrosine kinase (PTK) inhibitors herbimycin A or genistein reduced IL-1 or LPS-induced NO release and NOS enzymatic activity. This was associated with inhibition of iNOS mRNA expression as determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. In contrast, inhibitors of protein kinase C (PKC) or protein kinase A (PKA) did not affect these responses. These results were confirmed in experiments with second messenger agonists where neither activation of PKC, nor increases in cyclic adenosine monophosphate (cAMP) or increased intracellular calcium levels were associated with the induction of iNOS mRNA or NO release. These results suggest that PKC, PKA and calcium-dependent signals are not required or sufficient for the stimulation of NO production. However, NO production is dependent on tyrosine kinases due to their role in the expression of iNOS mRNA.
Geng
Y
Y
Sam and Rose Stein Institute for Research on Aging, University of California, San Diego, La Jolla 92093-0663, USA.
Maier
R
R
Lotz
M
M
D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002358:Cartilage, Articular / Q000166:cytology / Q000201:enzymology*; D002478:Cells, Cultured; D004790:Enzyme Induction; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D015290:Second Messenger Systems
D007375:Interleukin-1; D008070:Lipopolysaccharides; D015335:Molecular Probes; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D011505:Protein-Tyrosine Kinases