Endogenous gastrin and cholecystokinin do not promote growth of rat liver

Endothelin inhibits cholangiocarcinoma growth by a decrease in the vascular endothelial growth factor expression

BACKGROUND

Endothelins (ET-1, ET-2, ET-3) are peptides with vasoactive properties interacting with ET(A) and ET(B) receptors. ET-1 inhibits secretin-stimulated ductal secretion (hallmark of cholangiocyte growth) of cholestatic rats by interaction with ET receptors.

AIM

The aims of the studies were to evaluate (i) the effect of ET-1 on cholangiocarcinoma growth in Mz-ChA-1 cells and nude mice and (ii) whether ET-1 regulation of cholangiocarcinoma growth is associated with changes in the expression of vascular endothelial growth factor-A (VEGF-A), VEGF-C, VEGF receptor-2 (VEGFR-2) and VEGFR-3.

METHODS

We determined the expression of ET(A) and ET(B) receptors on normal and malignant (Mz-ChA-1) cholangiocytes and human cholangiocarcinoma tissue and the effect of ET-1 on the proliferation and expression of VEGF-A, VEGF-C (regulators of tumour angiogenesis) and its receptors, VEGFR-2 and VEGFR-3, in Mz-ChA-1 cells. In vivo, Mz-ChA-1 cells were injected into the flanks of athymic mice and injections of ET-1 or saline into the tumours were performed daily. The effect of ET-1 on tumour size, cell proliferation, apoptosis, collagen quantity and the expression of VEGF-A and VEGF-C and VEGFR-2 and VEGFR-3 were measured after 73 days.

RESULTS

Higher expression of ET(A) and ET(B) was observed in malignant compared with normal cholangiocytes. ET-1 inhibited proliferation and VEGF-A, VEGF-C, VEGFR-2 and VEGFR-3 expression of Mz-ChA-1 cells. Chronic ET-1 treatment decreased tumour volume, tumour cell proliferation and VEGF-A and VEGF-C expression but increased apoptosis and collagen tissue deposition compared with controls.

CONCLUSIONS

Modulation of VEGF-A and VEGF-C (by ET-1) may be important for managing cholangiocarcinoma growth.

Endothelin inhibits cholangiocarcinoma growth by a decrease in the vascular endothelial growth factor expression

BACKGROUND

Endothelins (ET-1, ET-2, ET-3) are peptides with vasoactive properties interacting with ET(A) and ET(B) receptors. ET-1 inhibits secretin-stimulated ductal secretion (hallmark of cholangiocyte growth) of cholestatic rats by interaction with ET receptors.

AIM

The aims of the studies were to evaluate (i) the effect of ET-1 on cholangiocarcinoma growth in Mz-ChA-1 cells and nude mice and (ii) whether ET-1 regulation of cholangiocarcinoma growth is associated with changes in the expression of vascular endothelial growth factor-A (VEGF-A), VEGF-C, VEGF receptor-2 (VEGFR-2) and VEGFR-3.

METHODS

We determined the expression of ET(A) and ET(B) receptors on normal and malignant (Mz-ChA-1) cholangiocytes and human cholangiocarcinoma tissue and the effect of ET-1 on the proliferation and expression of VEGF-A, VEGF-C (regulators of tumour angiogenesis) and its receptors, VEGFR-2 and VEGFR-3, in Mz-ChA-1 cells. In vivo, Mz-ChA-1 cells were injected into the flanks of athymic mice and injections of ET-1 or saline into the tumours were performed daily. The effect of ET-1 on tumour size, cell proliferation, apoptosis, collagen quantity and the expression of VEGF-A and VEGF-C and VEGFR-2 and VEGFR-3 were measured after 73 days.

RESULTS

Higher expression of ET(A) and ET(B) was observed in malignant compared with normal cholangiocytes. ET-1 inhibited proliferation and VEGF-A, VEGF-C, VEGFR-2 and VEGFR-3 expression of Mz-ChA-1 cells. Chronic ET-1 treatment decreased tumour volume, tumour cell proliferation and VEGF-A and VEGF-C expression but increased apoptosis and collagen tissue deposition compared with controls.

CONCLUSIONS

Modulation of VEGF-A and VEGF-C (by ET-1) may be important for managing cholangiocarcinoma growth.

Gastrin is not required for liver regeneration

BACKGROUND

Although several growth factors are known to be essential for liver regeneration, the role of gastrin remains controversial.

METHODS

Liver regeneration was examined in wild-type (WT) and gastrin-deficient (gastrin KO) mice at days 2 and 10 after partial (40%) hepatectomy by measurement of liver weight. Hepatocyte proliferation and circulating gastrin concentrations were measured at the same time points by immunohistochemistry and radioimmunoassay, respectively.

RESULTS

There was no significant difference in the rate of liver regeneration between gastrin KO and WT mice. Hepatocyte proliferation in both groups was increased at day 2 but had returned to baseline values by day 10. At day 2, hepatocyte proliferation in the gastrin KO mice was significantly higher than in WT animals, whereas at day 10, proliferation was significantly greater in the WT mice. The circulating gastrin concentration in the WT mice was significantly lower at day 10 than in unoperated WT animals.

CONCLUSION

This study suggests that gastrin is not essential for liver regeneration after partial hepatectomy.

Studies on hypertrophic effect of 90% partial pancreatectomy on the stomach in rats

INTRODUCTION

Stomach changes after major pancreatectomy (Px) are unclear. We previously reported that 90% Px increased stomach weight in rats similarly to endogenous hypergastrinemia by lansoprazole, a proton-pump inhibitor.

AIM

To investigate the role of endogenous gastrin in gastric hypertrophy after Px.

METHODOLOGY

In male Wistar rats, we compared the wet weight of the stomach and serum gastrin levels between normal (n = 10) or sham-operated controls (n = 10) and 90% partially pancreatectomized rats (n = 7). Then, using Northern blot analysis, we compared gene expression of gastrin, cholecystokinin-B (CCK-B) receptor, and somatostatin in the stomach among normal controls (n = 7), sham-operated rats (n = 7), and 90% partially pancreatectomized rats (n = 8). The samples were obtained on the third and seventh postoperative days (POD).

RESULTS

Wet weight of the stomach was significantly heavier in the Px rats than in the sham-operated controls (3.90 +/- 0.12 mg/g vs 2.63 +/- 0.07mg/g; p< 0.0001) on the 14th POD. Serum gastrin levels were also higher in the Px rats than in controls (161.4 +/- 13.35 pg/mL vs 110.6 +/- 5.67 pg/mL; p< 0.005) on the 14th POD. Gene expression of gastrin in the stomach on the 7th POD was significantly higher in the Px rats than in the sham-operated rats (p < 0.05), and gene expression of CCK-B receptor clearly increased in the Px rats on the 7th POD, when compared with that of controls (p < 0.05). Gastric somatostatin gene expression in both operated groups increased approximately twice as much as in normal controls after operation (p < 0.005). However, on the 7th POD, it returned to control levels only in Px rats and not in sham-operate rats (p < 0.05).

CONCLUSION

Increased gene expression of gastrin and CCK-B receptor suggests that gastrin may act as a trophic factor on the stomach after partial Px. Moreover, the relative decrease in gastric somatostatin gene expression may also influence gastric hypertrophy after Px.

Involvement of cholecystokinin/gastrin-related peptides and their receptors in clinical gastrointestinal disorders

In this paper the possible roles of cholecystokinin (CCK), gastrin, or gastrin-related peptides and their receptors in human gastrointestinal diseases are reviewed. For CCK/CCK(A) receptors (CCK(A)-R), the evidence for their proposed involvement in diseases caused by impaired CCK release or CCK(A)-R mutations, pancreatic disorders (acute/chronic pancreatitis), gastrointestinal motility disorders (gallbladder disease, irritable bowel syndrome), pancreatic tumor growth and satiety disorders, is briefly reviewed. The evidence that has established the involvement of gastrin/CCK(B)-R in mediating the action of hypergastrinaemic disorders, mediating hypergastrinaemic effects on the gastric mucosa (ECL hyperplasia, carcinoids, parietal cell mass), and acid-peptic diseases, is reviewed. The evidence for their possible involvement in mediating growth of gastric and pancreatic tumours and possible involvement of gastrin-related peptides in colon cancers, is reviewed briefly.

Extragastric effects of gastrin gene knock-out mice

Gastrin is a peptide hormone that regulates both acid secretion and growth of the gastric oxyntic mucosa. Recent studies suggest that gastrin, in both its amidated, and less processed forms (glycine-extended gastrin and progastrin) may also exert biological activity in other organs in the gastrointestinal tract. This article will review the studies performed to date addressing the physiological role of gastrin outside of the gastric mucosa, with particular emphasis on the information gleaned from gastrin-deficient mice. Most of these studies address the potential role for the less processed forms of gastrin in regulating the proliferation of the colonic mucosa and colon cancers. There is also some data to support a potential role for gastrin in the regulation of the pancreas and the kidney, although the effects of gastrin deficiency on the function of these organs in mice have not yet been rigorously studied.

Gastrin as a growth factor in the gastrointestinal tract

The peptide hormone gastrin, released from antral G cells, is known to stimulate the synthesis and release of histamine from ECL cells in the oxyntic mucosa via CCK-2 receptors. The mobilized histamine induces acid secretion by binding to the H(2) receptors located on parietal cells. Recent studies suggest that gastrin, in both its fully amidated and less processed forms (progastrin and glycine-extended gastrin), is also a growth factor for the gastrointestinal tract. In this article, we review the recent evidence (including those from the transgenic and knockout mice) for the trophic targets of both the amidated and less processed forms of gastrin in the gastrointestinal tract, pancreas and liver. It has been established that the major trophic effect of amidated gastrin is for the oxyntic mucosa of stomach, where it causes increased proliferation of gastric stem cells and ECL cells, resulting in increased parietal and ECL cell mass. There is insufficient evidence to support that amidated gastrin is a trophic factor for the rest of gastrointestinal tract, exocrine pancreas and liver. On the other hand, the major trophic target of the less processed gastrin (e.g. glycine-extended gastrin) appears to be the colonic mucosa. There is no evidence to suggest that it is trophic for the stomach. It remains to be examined whether the rest of gastrointestinal tract, pancreas and liver are the trophic targets by glycine-extended gastrin and progastrin.

Gastrin inhibits cholangiocyte growth in bile duct-ligated rats by interaction with cholecystokinin-B/Gastrin receptors via D-myo-inositol 1,4,5-triphosphate-, Ca(2+)-, and protein kinase C alpha-dependent mechanisms

We studied the role of gastrin in regulating cholangiocyte proliferation induced by bile duct ligation (BDL). In purified cholangiocytes, we evaluated (1) for the presence of cholecystokinin-B (CCK-B)/gastrin receptors, (2) the effect of gastrin on D-myo-Inositol 1,4,5-triphosphate (IP(3)) levels, and (3) the effect of gastrin on DNA synthesis and adenosine 3', 5'-monophosphate (cAMP) levels in the absence or presence of CCK-A (L-364,718) and CCK-B/gastrin (L-365,260) receptor inhibitors, 1, 2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetrakis(acetxymethyl ester) (BAPTA/AM; an intracellular Ca(2+) chelator), and 2 protein kinase C (PKC) inhibitors, 1-(5-Isoquinolinylsulfonyl)-2-methylpiperazine (H7) and staurosporin. To evaluate if gastrin effects on cholangiocyte proliferation are mediated by the isoform PKCalpha, we evaluated (1) for the presence of PKCalpha in cholangiocytes and (2) the effect of gastrin on the PKCalpha protein expression in a triton-soluble (containing cytoplasm + membrane) and a triton-insoluble (containing cytoskeleton) fraction. To evaluate the effects of gastrin in vivo, immediately following BDL, gastrin or bovine serum albumin (BSA) was infused by minipumps for 7 days to rats and we measured cholangiocyte growth and cAMP levels. We found CCK-B/gastrin receptors on cholangiocytes. Gastrin increased IP(3) levels. Gastrin inhibited DNA synthesis and cAMP synthesis in cholangiocytes. Gastrin effects on cholangiocyte functions were blocked by L-365,260, BAPTA/AM, H7, and staurosporin but not by L-364,718. Gastrin induced translocation of PKCalpha from cholangiocyte cytoskeleton to membrane. In vivo, gastrin decreased cholangiocyte growth and cAMP synthesis compared with controls. We concluded that gastrin inhibits cholangiocyte growth in BDL rats by interacting with CCK-B/gastrin receptors through a signal transduction pathway involving IP(3), Ca(2+), and PKCalpha.

Expression and processing of gastrin in hepatocellular carcinoma, fibrolamellar carcinoma and cholangiocarcinoma

BACKGROUND/AIMS

Gastrin is a trophic factor within the normal gastrointestinal tract and is also a mitogen for a number of gastrointestinal and non-gastrointestinal tumours. Precursor forms of gastrin including progastrin (proG) and glycine-extended gastrin (G-gly) as well as the fully processed amidated gastrin (G-NH2) are expressed by tumours. There has been little study of the role of gastrin in either normal liver or liver tumours. The aim of this study was to identify the expression of CCK-B/gastrin receptor (CCK-BR), proG, G-gly and G-NH2 in normal liver and liver tumours.

METHODS

Tissue sections from patients with hepatocellular carcinoma, fibrolamellar carcinoma, cholangiocarcinoma as well as normal liver biopsies were assessed for expression of CCK-BR and gastrin isoforms.

RESULTS

Most liver tumours express CCK-BR and are able to process gastrin as far as proG and G-gly, although not as far as the amidated form. There appears to be little expression of the receptor and no expression of precursor forms of gastrin in normal liver.

CONCLUSIONS

Liver tumours express the CCK-BR and precursor forms of gastrin. This expression may be associated with tumour proliferation.

Gastrin inhibits secretin-induced ductal secretion by interaction with specific receptors on rat cholangiocytes

We assessed the effect of gastrin on ductal secretion in normal and bile duct-ligated (BDL) rats. The effect of gastrin on ductal secretion was examined in the presence of proglumide, a specific antagonist for gastrin receptor (GR). We isolated pure cholangiocytes from normal and BDL rats and assessed gastrin effects on secretin receptor (SR) gene expression and intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels. We examined the presence of GR mRNA in cholangiocytes by reverse transcription polymerase chain reaction (RT-PCR). In normal or BDL rats, gastrin produced no changes in spontaneous bile secretion. Simultaneous infusion of gastrin inhibited secretin-induced choleresis and bicarbonate output in BDL rats. In the presence of proglumide gastrin did not inhibit secretin-induced choleresis in BDL rats. Gastrin decreased in cholangiocytes from BDL rats 1) SR gene expression and 2) secretin-induced cAMP levels. With the use of RT-PCR, GR mRNA was detected in cholangiocytes. Similar to what is shown for secretin and somatostatin, we propose that the opposing effects of secretin and gastrin on cholangiocyte secretory activity regulate ductal secretion in rats.

Role of endogenous hypergastrinemia in regenerating endocrine pancreas after partial pancreatectomy

We studied the possible role of endogenous gastrin in the regenerating pancreas. Male Wistar rats underwent sham operation or 90% partial pancreatectomy (Px). Lansoprazole (30 mg/kg body wt), a proton pump inhibitor (PPI), was given p.o. for 3 weeks after surgery. Plasma glucose levels were higher in Px rats than in shams. Lansoprazole lowered plasma glucose levels in the Px rats. In addition, integrated insulin secretion during an oral glucose tolerance test (2 g/kg body wt) was significantly (p < 0.01) higher in lansoprazole-treated Px rats than in control Px rats, while lansoprazole did not affect insulin secretion in shams. Fasting serum gastrin levels were higher (p < 0.01) in lansoprazole-treated animals than in controls both in sham rats and in Px rats. Furthermore, lansoprazole increased the pancreas weight per body weight and elevated the insulin content of the pancreas in Px rats. These results suggest that endogenous hypergastrinemia has a trophic effect on endocrine pancreas during regenerating processes and that administration of PPI may be clinically beneficial to the remnant pancreas after pancreatectomy if the whole stomach is preserved.