Dataset Information

Cyclooxygenase-2 up-regulates hepatic somatostatin receptor 2 expression.

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.

SUBMITTER: Lu YY

PROVIDER: S-EPMC6056476 | biostudies-literature | 2018 Jul

REPOSITORIES: biostudies-literature

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Cyclooxygenase-2 up-regulates hepatic somatostatin receptor 2 expression.

Lu Yao-Yao YY Gao Jin-Hang JH Zhao Chong C Wen Shi-Lei SL Tang Cheng-Wei CW Wang Yu-Fang YF

Scientific reports 20180723 1

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 ...[more]

PMID: 30038293

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Project description:BACKGROUND: Nicotinic acetylcholine (Ach) receptors are ligand-gated pentameric ion channels whose main function is to transmit signals for the neurotransmitter Ach in peripheral and central nervous system. However, the alpha7 nicotinic receptor has been recently found in several non-neuronal cells and described as an important regulator of cellular function. Nicotine and ACh have been recently reported to inhibit tumor necrosis factor-alpha (TNF-alpha) production in human macrophages as well as in mouse microglial cultures. In the present study, we investigated whether the stimulation of alpha7 nicotinic receptor by the specific agonist nicotine could affect the functional state of activated microglia by promoting and/or inhibiting the release of other important pro-inflammatory and lipid mediator such as prostaglandin E2. METHODS: Expression of alpha7 nicotinic receptor in rat microglial cell was examined by RT-PCR, immunofluorescence staining and Western blot. The functional effects of alpha7 receptor activation were analyzed in resting or lipopolysaccharide (LPS) stimulated microglial cells pre-treated with nicotine. Culture media were assayed for the levels of tumor necrosis factor, interleukin-1beta, nitric oxide, interleukin-10 and prostaglandin E2. Total RNA was assayed by RT-PCR for the expression of COX-2 mRNA. RESULTS: Rat microglial cells express alpha7 nicotinic receptor, and its activation by nicotine dose-dependently reduces the LPS-induced release of TNF-alpha, but has little or no effect on nitric oxide, interleukin-10 and interleukin-1beta. By contrast, nicotine enhances the expression of cyclooxygenase-2 and the synthesis of one of its major products, prostaglandin E2. CONCLUSIONS: Since prostaglandin E2 modulates several macrophage and lymphocyte functions, which are instrumental for inflammatory resolution, our study further supports the existence of a brain cholinergic anti-inflammatory pathway mediated by alpha7 nicotinic receptor that could be potentially exploited for novel treatments of several neuropathologies in which local inflammation, sustained by activated microglia, plays a crucial role.

Project description:Osteoarthritis (OA) is a most common form of arthritis worldwide leading to significant disability. MicroRNAs (miRNAs) are non-coding RNAs involved in various aspects of cartilage development, homoeostasis and pathology. Several miRNAs have been identified which have shown to regulate expression of target genes relevant to OA pathogenesis such as matrix metalloproteinase (MMP)-13, cyclooxygenase (COX)-2, etc. Epigallocatechin-3-O-gallate (EGCG), the most abundant and active polyphenol in green tea, has been reported to have anti-arthritic effects, however, the role of EGCG in the regulation of miRNAs has not been investigated in OA. Here, we showed that EGCG inhibits COX-2 mRNA/protein expression or prostaglandin E2 (PGE2 ) production via up-regulating microRNA hsa-miR-199a-3p expression in interleukin (IL)-1β-stimulated human OA chondrocytes. This negative co-regulation of hsa-miR-199a-3p and COX-2 by EGCG was confirmed by transfection of OA chondrocytes with anti-miR-199a-3p. Transfection of OA chondrocytes with anti-miR-199a-3p significantly enhanced COX-2 expression and PGE2 production (P < 0.001), while EGCG treatment significantly inhibited anti-miR-199a-3p transfection-induced COX-2 expression or PGE2 production in a dose-dependent manner. These results were further re-validated by co-treatment of these transfection OA chondrocytes with IL-1β and EGCG. EGCG treatment consistently up-regulated the IL-1β-decreased hsa-miR-199a-3p expression (P < 0.05) and significantly inhibited the IL-1β-induced COX-2 expression/PGE2 production (P < 0.05) in OA chondrocytes transfected with anti-hsa-miR-199a-3p. Taken together, these results clearly indicate that EGCG inhibits COX-2 expression/PGE2 production via up-regulation of hsa-miR-199a-3p expression. These novel pharmacological actions of EGCG on IL-1β-stimulated human OA chondrocytes provide new suggestions that EGCG or EGCG-derived compounds inhibit cartilage breakdown or pain by up-regulating the expression of microRNAs in human chondrocytes.

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Cyclooxygenase-2 up-regulates hepatic somatostatin receptor 2 expression.

Publications

Cyclooxygenase-2 up-regulates hepatic somatostatin receptor 2 expression.

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