Hepatic cystogenesis in polycystic liver disease is associated with increased levels of cyclic adenosine monophosphate (cAMP) in cholangiocytes lining liver cysts. Takeda G protein receptor 5 (TGR5), a G protein–coupled bile acid receptor, is linked to cAMP and expressed in cholangiocytes. Therefore, we hypothesized that TGR5 might contribute to disease progression. We examined expression of TGR5 and Gα proteins in cultured cholangiocytes and in livers of animal models and humans with polycystic liver disease. In vitro, we assessed cholangiocyte proliferation, cAMP levels, and cyst growth in response to (1) TGR5 agonists (taurolithocholic acid, oleanolic acid [OA], and two synthetic compounds), (2) a novel TGR5 antagonist (m‐tolyl 5‐chloro‐2‐[ethylsulfonyl] pyrimidine‐4‐carboxylate [SBI‐115]), and (3) a combination of SBI‐115 and pasireotide, a somatostatin receptor analogue. In vivo, we examined hepatic cystogenesis in OA‐treated polycystic kidney rats and after genetic elimination of TGR5 in double mutant TGR5−/−;Pkhd1del2/del2 mice. Compared to control, expression of TGR5 and Gαs (but not Gαi and Gαq) proteins was increased 2‐fold to 3‐fold in cystic cholangiocytes in vitro and in vivo. In vitro, TGR5 stimulation enhanced cAMP production, cell proliferation, and cyst growth by ∼40%; these effects were abolished after TGR5 reduction by short hairpin RNA. OA increased cystogenesis in polycystic kidney rats by 35%; in contrast, hepatic cystic areas were decreased by 45% in TGR5‐deficient TGR5−/−;Pkhd1del2/del2 mice. TGR5 expression and its colocalization with Gαs were increased ∼2‐fold upon OA treatment. Levels of cAMP, cell proliferation, and cyst growth in vitro were decreased by ∼30% in cystic cholangiocytes after treatment with SBI‐115 alone and by ∼50% when SBI‐115 was combined with pasireotide. Conclusion: TGR5 contributes to hepatic cystogenesis by increasing cAMP and enhancing cholangiocyte proliferation; our data suggest that a TGR5 antagonist alone or concurrently with somatostatin receptor agonists represents a potential therapeutic approach in polycystic liver disease. (Hepatology 2017;66:1197‐1218).

中文翻译：

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TGR5 通过 cAMP/Gαs 信号传导促进多囊性肝病啮齿动物肝脏囊肿发生

多囊性肝病中的肝囊肿发生与肝囊肿内胆管细胞中环磷酸腺苷 (cAMP) 水平升高有关。武田 G 蛋白受体 5 (TGR5) 是一种 G 蛋白偶联胆汁酸受体，与 cAMP 相连并在胆管细胞中表达。因此，我们假设 TGR5 可能有助于疾病进展。我们检查了 TGR5 和 Gα 蛋白在培养的胆管细胞和动物模型和患有多囊性肝病的人的肝脏中的表达。在体外，我们评估了胆管细胞增殖、cAMP 水平和囊肿生长对 (1) TGR5 激动剂（牛磺石胆酸、齐墩果酸 [OA] 和两种合成化合物）的反应，（2）一种新型 TGR5 拮抗剂（m-tolyl 5 -氯-2-[乙基磺酰基]嘧啶-4-羧酸盐[SBI-115]），和（3）SBI-115和帕瑞肽的组合，生长抑素受体类似物。在体内，我们检查了 OA 治疗的多囊肾大鼠和双突变 TGR5-/-;Pkhd1del2/del2 小鼠中 TGR5 基因消除后的肝脏囊肿发生。与对照相比，TGR5 和 Gαs（但不是 Gαi 和 Gαq）蛋白在体外和体内囊性胆管细胞中的表达增加了 2 到 3 倍。在体外，TGR5 刺激使 cAMP 产生、细胞增殖和囊肿生长增加了约 40%；这些影响在通过短发夹 RNA 减少 TGR5 后被消除。OA 使多囊肾大鼠的膀胱发生增加了 35%；相比之下，TGR5 缺陷型 TGR5-/-;Pkhd1del2/del2 小鼠的肝囊性区域减少了 45%。OA 治疗后，TGR5 表达及其与 Gαs 的共定位增加了约 2 倍。cAMP 水平、细胞增殖、单独使用 SBI-115 处理后，囊性胆管细胞的体外囊肿生长减少了约 30%，而当 SBI-115 与帕瑞肽联合使用时，减少了约 50%。结论：TGR5通过增加cAMP和促进胆管细胞增殖促进肝囊肿形成；我们的数据表明，单独使用 TGR5 拮抗剂或与生长抑素受体激动剂同时使用是一种潜在的多囊肝疾病治疗方法。（肝病学 2017；66：1197-1218）。我们的数据表明，单独使用 TGR5 拮抗剂或与生长抑素受体激动剂同时使用是一种潜在的多囊肝疾病治疗方法。（肝病学 2017；66：1197-1218）。我们的数据表明，单独使用 TGR5 拮抗剂或与生长抑素受体激动剂同时使用是一种潜在的多囊肝治疗方法。（肝病学 2017；66：1197-1218）。