Role of NF-kappaB in the antiproliferative effect of endothelin-1 and tumor necrosis factor-alpha in human hepatic stellate cells. Involvement of cyclooxygenase-2.
During chronic liver diseases, hepatic stellate cells (HSC) acquire an activated myofibroblast-like phenotype and proliferate and synthesize fibrosis components. Endothelin-1 (ET-1), which inhibited the growth of human myofibroblastic HSC, increased the formation of two NF-kappaB DNA binding complexes; this effect was also observed with tumor necrosis factor-alpha (TNF-alpha). The complexes ... were identified as the p50/p50 and p50/p65 NF-kappaB dimers. Activation of NF-kappaB was associated with the degradation of the inhibitory protein IkappaB-alpha; no IkappaB-beta was detected. Activation of NF-kappaB and degradation of IkappaB-alpha were prevented by the NF-kappaB inhibitors sodium salicylate and MG-132. In addition to cyclooxygenase-1 (COX-1), COX-2 is also constitutively expressed in human HSC, and the use of dexamethasone and of SC-58125, a selective COX-2 inhibitor, revealed that COX-2 accounts for basal COX activity. Moreover, COX-2 mRNA and protein were up-regulated by ET-1 and TNF-alpha, whereas COX-1 was unaffected. Induction of COX-2 and stimulation of COX activity by ET-1 and TNF-alpha were prevented by sodium salicylate and MG-132, suggesting that activation of NF-kappaB by either factor is needed for stimulation of COX-2. Finally, SC-58125 and dexamethasone reduced the growth inhibitory effect of ET-1 and TNF-alpha, indicating that activation of COX-2 is required for inhibition of HSC proliferation. Taken together, our results suggest that NF-kappaB, by inducing COX-2 expression, may play an important role in the negative regulation of human myofibroblastic HSC proliferation.
Mesh Terms:
Adipocytes, Antineoplastic Agents, Cyclooxygenase 1, Cyclooxygenase 2, Cyclooxygenase 2 Inhibitors, Cyclooxygenase Inhibitors, DNA-Binding Proteins, Dexamethasone, Dimerization, Endothelin-1, Fibroblasts, Humans, I-kappa B Proteins, Isoenzymes, Leupeptins, Liver, Membrane Proteins, NF-kappa B, Prostaglandin-Endoperoxide Synthases, Pyrazoles, Receptor, Endothelin B, Receptors, Endothelin, Sodium Salicylate, Tumor Necrosis Factor-alpha, Up-Regulation, Viper Venoms
Adipocytes, Antineoplastic Agents, Cyclooxygenase 1, Cyclooxygenase 2, Cyclooxygenase 2 Inhibitors, Cyclooxygenase Inhibitors, DNA-Binding Proteins, Dexamethasone, Dimerization, Endothelin-1, Fibroblasts, Humans, I-kappa B Proteins, Isoenzymes, Leupeptins, Liver, Membrane Proteins, NF-kappa B, Prostaglandin-Endoperoxide Synthases, Pyrazoles, Receptor, Endothelin B, Receptors, Endothelin, Sodium Salicylate, Tumor Necrosis Factor-alpha, Up-Regulation, Viper Venoms
J. Biol. Chem.
Date: Sep. 04, 1998
PubMed ID: 9722548
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