Conjugated Bile Acids Activate the Sphingosine–1–Phosphate... : Hepatology (original) (raw)

Hepatobiliary Malignancies

Conjugated Bile Acids Activate the Sphingosine–1–Phosphate Receptor 2 in Primary Rodent Hepatocytes

Studer, Elaine1,†; Zhou, Xiqiao1,6,†; Zhao, Renping1,8,†; Wang, Yun1,8; Takabe, Kazuaki3; Nagahashi, Masayuki3; Pandak, William M.2; Dent, Paul4; Spiegel, Sarah5; Shi, Ruihua6; Xu, Weiren7; Liu, Xuyuan7; Bohdan, Pat1; Zhang, Luyong8; Zhou, Huiping1,2,*; Hylemon, Phillip B.1,2,*,‡

1_Microbiology and Immunology, Biochemistry and Molecular Biology and Virginia Commonwealth University, Richmond, VA_

2_McGuire Veterans Affairs Medical Center, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA_

3_Surgery, Virginia Commonwealth University, Richmond, VA_

4_Neurosurgery, Virginia Commonwealth University, Richmond, VA_

5_Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA_

6_Department of Gastroenterology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, Jiangsu, China_

7_Tianjin Key Laboratory of Molecular Design and Drug Discovery, Tianjin Institute of Pharmaceutical Research, Tianjin China_

8_China Pharmaceutical University, Nanjing, Jiangsu, China_

*Address reprint requests to: Department of Microbiology and Immunology, Medical College of Virginia Campus–VCU, PO Box 908678, Richmond, VA 23298–0678

Email: [email protected]

Received 26 April 2011; Accepted 29 August 2011

Grant sponsor: National Institutes of Health; Grant Number: R01 DK–057543.

Potential conflict of interest: Nothing to report.

†These authors contributed equally to this work.

‡fax: 804–828–0676

Additional Supporting Information may be found in the online version of this article.

Abstract

Bile acids have been shown to be important regulatory molecules for cells in the liver and gastrointestinal tract. They can activate various cell signaling pathways including extracellular regulated kinase (ERK)1/2 and protein kinase B (AKT) as well as the G–protein–coupled receptor (GPCR) membrane–type bile acid receptor (TGR5/M–BAR). Activation of the ERK1/2 and AKT signaling pathways by conjugated bile acids has been reported to be sensitive to pertussis toxin (PTX) and dominant–negative Gαi in primary rodent hepatocytes. However, the GPCRs responsible for activation of these pathways have not been identified. Screening GPCRs in the lipid–activated phylogenetic family (expressed in HEK293 cells) identified sphingosine–1–phosphate receptor 2 (S1P2) as being activated by taurocholate (TCA). TCA, taurodeoxycholic acid (TDCA), tauroursodeoxycholic acid (TUDCA), glycocholic acid (GCA), glycodeoxycholic acid (GDCA), and S1P–induced activation of ERK1/2 and AKT were significantly inhibited by JTE–013, a S1P2 antagonist, in primary rat hepatocytes. JTE–013 significantly inhibited hepatic ERK1/2 and AKT activation as well as short heterodimeric partner (SHP) mRNA induction by TCA in the chronic bile fistula rat. Knockdown of the expression of S1P2 by a recombinant lentivirus encoding S1P2 shRNA markedly inhibited the activation of ERK1/2 and AKT by TCA and S1P in rat primary hepatocytes. Primary hepatocytes prepared from S1P2 knock out (S1P2−/−) mice were significantly blunted in the activation of the ERK1/2 and AKT pathways by TCA. Structural modeling of the S1P receptors indicated that only S1P2 can accommodate TCA binding. In summary, all these data support the hypothesis that conjugated bile acids activate the ERK1/2 and AKT signaling pathways primarily through S1P2 in primary rodent hepatocytes. (Hepatology 2012)