Differential Effect of Transforming Growth Factor β (TGF-β) on the Genes Encoding Hyaluronan Synthases and Utilization of the p38 MAPK Pathway in TGF-β-induced Hyaluronan Synthase 1 Activation

• Published in: The Journal of biological chemistry 2004-03, Vol.279 (10), p.8753-8760
• Main Authors: Stuhlmeier, Karl M., Pollaschek, Christine
• Format: Article
• Language: English
• Subjects: Arthritis, Rheumatoid - metabolism; Cells, Cultured; Enzyme Activation - drug effects; Enzyme Activation - genetics; Fibroblasts - enzymology; Gene Expression Regulation, Enzymologic - drug effects; Glucuronosyltransferase; HAS1 gene; Humans; hyaluronan synthase; Hyaluronan Synthases; MAP Kinase Signaling System - genetics; Mitogen-Activated Protein Kinases - metabolism; p38 Mitogen-Activated Protein Kinases; synoviocytes; Transcriptional Activation; Transferases - genetics; Transferases - metabolism; Transforming Growth Factor beta - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M303945200

Unfettered hyaluronan (HA) production is a hallmark of rheumatoid arthritis. The discovery of three genes encoding hyaluronan synthases (HASs) allows for the investigation of the signaling pathways leading to the activation of these genes. Our objective is to further understanding of the regulation of these genes as well as to find ways to prevent undesired gene activation. Human fibroblast-like synoviocytes were used in these experiments. mRNA levels of HAS were monitored by reverse transcriptase-PCR. A series of specific kinase inhibitors were used to investigate intracellular pathways leading to the up-regulation of HAS1. Our experiments, testing a series of stimuli including tumor necrosis factor α (TNFα), demonstrate that TGF-β is the most potent stimulus for HAS1 transcription. TGF-β activates HAS1 in a dose-dependent manner with a maximum effect at a concentration of 0.5–1 ng/ml. TGF-β-induced HAS1 mRNA can be detected within 60 min and reaches maximal levels at 6 h. Furthermore, TGF-β treatment leads to an increase in synthase activity as determined by HA ELISA and by in vitro HA synthase assays. In contrast to the activatory effect on HAS1, TGF-β dose-dependently suppresses HAS3 mRNA. As to the mode of action of TGF-β-induced HAS1 mRNA activation, our experiments reveal that blocking p38 MAPK inhibited the TGF-β effect by 90%, blocking the MEK pathway led to an inhibition by 40%, and blocking the JNK pathway had no effect. The presented data might contribute to a better understanding of the role of TGF-β and of HA in the pathology of diseases.