Cyclooxygenase-2 up-regulates hepatic somatostatin receptor 2 expression

Sci Rep. 2018 Jul 23;8(1):11033. doi: 10.1038/s41598-018-29349-y.

Abstract

Somatostatin and its analogues, which function by binding to somatostatin receptors (SSTRs) 1-5, play a protective role in liver cirrhosis. Hepatic SSTR-2 expression is up-regulated in subjects with liver cirrhosis. However, little is known about the mechanisms underlying this process. In the present study, we observed the up-regulation of hepatic SSTR-2 expression in thioacetamide (TAA)-induced cirrhotic rats and further showed that cyclooxygenase-2 (COX-2) might play a role in this process via the protein kinase C (PKC)-cAMP response element binding protein (CREB) signaling pathway. In vivo, the up-regulated SSTR-2 in liver cirrhosis was inhibited by the addition of a selective COX-2 inhibitor, such as celecoxib. In vitro, the up-regulation of COX-2 by either transfection with COX-2 plasmids or treatment with TAA increased levels of SSTR-2 and phosphorylated CREB (p-CREB) in the human hepatocyte cell line L02. Furthermore, the increase in SSTR-2 expression was inhibited by the addition of celecoxib and a PKC inhibitor. Moreover, for comparable DNA methylation levels in the region upstream of the hepatic SSTR-2 gene in normal and cirrhotic livers, DNA methylation may not contribute to the up-regulation of SSTR-2 expression in cirrhotic livers. In conclusion, the up-regulation of hepatic SSTR-2 might be induced by COX-2 via the PKC-CREB signaling pathway but is probably not induced by DNA methylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Cyclic AMP Response Element-Binding Protein / metabolism
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism*
  • DNA Methylation / genetics
  • Hepatocytes / metabolism
  • Humans
  • Liver Cirrhosis / chemically induced
  • Male
  • Plasmids / genetics
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Somatostatin / genetics
  • Receptors, Somatostatin / metabolism*
  • Thioacetamide / toxicity

Substances

  • Cyclic AMP Response Element-Binding Protein
  • Receptors, Somatostatin
  • Thioacetamide
  • somatostatin receptor 2
  • Cyclooxygenase 2