1 Department of Medicine, Division Gastroenterology, Texas A&M Health Science Center, College of Medicine, Temple, TX, USA ; 2 University of Rome Sapienza, Rome, Italy ; 3 Research, Central Texas Veterans Health Care System, TX, USA ; 4 Scott & White Digestive Disease Research Center, Scott & White, TX, USA.
Hepatobiliary Surg Nutr. 2014 Jun;3(3):118-25. doi: 10.3978/j.issn.2304-3881.2014.04.04.
Cholangiocyte proliferation is coordinately regulated by a number of gastrointestinal hormones/peptides, some of which display stimulatory effects and some have inhibitory actions on cholangiocyte proliferation. Enhanced biliary proliferation [for example after bile duct ligation (BDL) and partial hepatectomy] is associated with increased expression of secretin receptor (SR), cystic fibrosis transmembrane conductance regulator (CFTR) and Cl(-)/HCO3 (-) anion exchanger 2 and secretin-stimulated ductal secretion, whereas loss/damage of bile ducts [for example after acute carbon tetrachloride (CCl4) administration] is associated with reduced secretin-stimulated ductal secretory activity. There is growing information regarding the role of gastrointestinal hormones the regulation of biliary growth. For example, while gastrin, somatostatin and serotonin inhibit bile duct hyperplasia of cholestatic rats by downregulation of cAMP signaling, secretin has been shown to stimulate the proliferation of normal mice by activation of cyclic adenosine 3',5'-monophosphate (cAMP)-dependent signaling. However, no information exists regarding the stimulatory effects of secretin on biliary proliferation of normal rats. Thus, we evaluated the in vivo and in vitro effect of secretin on biliary proliferation, the expression of markers key of ductal secretion and secretin-stimulated ductal secretion.
Normal male rats were treated with saline or secretin (2.5 nmoles/kg BW/day by osmotic minipumps for one week). We evaluated: (I) intrahepatic bile duct mass (IBDM) in liver sections and PCNA expression in purified cholangiocytes; (II) SR and CFTR mRNA expression and secretin-stimulated cAMP levels in purified cholangiocytes; and (III) secretin-stimulated bile and bicarbonate secretion in bile fistula rats. In vitro, normal rat intrahepatic cholangiocyte lines (NRIC) were treated with BSA (basal) or secretin (100 nM) for 24 to 72 hours in the absence/presence of a PKA or a MEK inhibitor before evaluating proliferation by MTS assays.
Prolonged administration of secretin to normal rats increased IBDM and PCNA expression in purified cholangiocytes compared to saline-treated normal rats. Also, secretin increased the expression of proteins (SR and CFTR) that are key in the regulating ductal secretion and enhanced secretin-stimulated cAMP levels and bile and bicarbonate secretion. In vitro, secretin increased the proliferation of NRIC, increase that was prevented by PKA and MAPK inhibitors.
We have demonstrated that secretin stimulates both in vivo and in vitro biliary proliferation and secretin-stimulated ductal secretory activity in normal rats. We suggest that the stimulatory effect of secretin on biliary proliferation and secretion may be important for preventing biliary dysfunction during ductopenic disorders.
胆管细胞增殖受到多种胃肠激素/肽的协调调节，其中一些表现出刺激作用，而另一些则对胆管细胞增殖具有抑制作用。增强的胆汁分泌增殖[例如胆管结扎（BDL）和部分肝切除后]与胆囊收缩素受体（SR）、囊性纤维化跨膜电导调节剂（CFTR）和 Cl(-)/HCO3(-)阴离子交换体 2 的表达增加以及胆囊收缩素刺激的胆管分泌有关，而胆管的丧失/损伤[例如急性四氯化碳（CCl4）给药后]与胆囊收缩素刺激的胆管分泌活性降低有关。关于胃肠激素在调节胆汁生长中的作用，有越来越多的信息。例如，虽然胃泌素、生长抑素和 5-羟色胺通过下调 cAMP 信号来抑制胆汁淤积大鼠的胆管增生，但已经表明胆囊收缩素通过激活环腺苷酸 3'，5'-单磷酸（cAMP）依赖性信号来刺激正常小鼠的增殖。然而，关于胆囊收缩素对正常大鼠胆汁分泌增殖的刺激作用，尚无信息。因此，我们评估了胆囊收缩素对正常大鼠胆汁分泌增殖、关键胆管分泌标志物的表达和胆囊收缩素刺激的胆管分泌的体内和体外作用。
正常雄性大鼠用生理盐水或胆囊收缩素（通过渗透微型泵每天 2.5nmoles/kgBW）治疗一周。我们评估了：（I）肝切片中的肝内胆管质量（IBDM）和纯化胆管细胞中的 PCNA 表达；（II）纯化胆管细胞中的 SR 和 CFTR mRNA 表达和胆囊收缩素刺激的 cAMP 水平；和（III）胆汁瘘大鼠中胆囊收缩素刺激的胆汁和碳酸氢盐分泌。在体外，用 BSA（基础）或胆囊收缩素（100nM）处理正常大鼠肝内胆管细胞系（NRIC）24 至 72 小时，然后在存在/不存在 PKA 或 MEK 抑制剂的情况下，通过 MTS 测定评估增殖。
与生理盐水处理的正常大鼠相比，长期给予正常大鼠胆囊收缩素可增加 IBDM 和纯化胆管细胞中的 PCNA 表达。此外，胆囊收缩素增加了调节胆管分泌的关键蛋白（SR 和 CFTR）的表达，并增强了胆囊收缩素刺激的 cAMP 水平和胆汁及碳酸氢盐分泌。在体外，胆囊收缩素增加了 NRIC 的增殖，PKA 和 MAPK 抑制剂可阻止这种增殖增加。
我们已经证明，胆囊收缩素刺激正常大鼠体内和体外的胆汁分泌增殖和胆囊收缩素刺激的胆管分泌活性。我们认为，胆囊收缩素对胆汁分泌增殖的刺激作用可能对预防导管缺失障碍期间的胆汁功能障碍很重要。
