Hepatocyte growth factor and fibroblast growth factor 2 are overexpressed after cerulein-induced acute pancreatitis

Recombinant human hepatocyte growth factor provides protective effects in cerulein-induced acute pancreatitis in mice

Acute pancreatitis is a multifactorial disease associated with profound changes of the pancreas induced by release of digestive enzymes that lead to increase in proinflammatory cytokine production, excessive tissue necrosis, edema, and bleeding. Elevated levels of hepatocyte growth factor (HGF) and its receptor c-Met have been observed in different chronic and acute pancreatic diseases including experimental models of acute pancreatitis. In the present study, we investigated the protective effects induced by the recombinant human HGF in a mouse model of cerulein-induced acute pancreatitis. Pancreatitis was induced by 8 hourly administrations of supramaximal cerulein injections (50 µg/kg, ip). HGF treatment (20 µg/kg, iv), significantly attenuated lipase content and amylase activity in serum as well as the degree inflammation and edema overall leading to less severe histologic changes such as necrosis, induced by cerulein. Protective effects of HGF were associated with activation of pro-survival pathways such as Akt, Erk1/2, and Nrf2 and increase in executor survival-related proteins and decrease in pro-apoptotic proteins. In addition, ROS content and lipid peroxidation were diminished, and glutathione synthesis increased in pancreas. Systemic protection was observed by lung histology. In conclusion, our data indicate that HGF exerts an Nrf2 and glutathione-mediated protective effect on acute pancreatitis reflected by a reduction in inflammation, edema, and oxidative stress.

Induction of chronic pancreatitis by pancreatic duct ligation activates BMP2, apelin, and PTHrP expression in mice

Chronic pancreatitis (CP) is a devastating disease with no treatments. Experimental models have been developed to reproduce the parenchyma and inflammatory responses typical of human CP. For the present study, one objective was to assess and compare the effects of pancreatic duct ligation (PDL) to those of repetitive cerulein (Cer)-induced CP in mice on pancreatic production of bone morphogenetic protein-2 (BMP2), apelin, and parathyroid hormone-related protein (PTHrP). A second objective was to determine the extent of cross talk among pancreatic BMP2, apelin, and PTHrP signaling systems. We focused on BMP2, apelin, and PTHrP since these factors regulate the inflammation-fibrosis cascade during pancreatitis. Findings showed that PDL- and Cer-induced CP resulted in significant elevations in expression and peptide/protein levels of pancreatic BMP2, apelin, and PTHrP. In vivo mouse and in vitro pancreatic cell culture experiments demonstrated that BMP2 stimulated pancreatic apelin expression whereas apelin expression was inhibited by PTHrP exposure. Apelin or BMP2 exposure inhibited PTHrP expression, and PTHrP stimulated upregulation of gremlin, an endogenous inhibitor of BMP2 activity. Transforming growth factor-β (TGF-β) stimulated PTHrP expression. Together, findings demonstrated that PDL- and Cer-induced CP resulted in increased production of the pancreatic BMP2, apelin, and PTHrP signaling systems and that significant cross talk occurred among pancreatic BMP2, apelin, and PTHrP. These results together with previous findings imply that these factors interact via a pancreatic network to regulate the inflammation-fibrosis cascade during CP. More importantly, this network communicated with TGF-β, a key effector of pancreatic pathophysiology. This novel network may be amenable to pharmacologic manipulations during CP in humans.

Involvement of inflammatory factors in pancreatic carcinogenesis and preventive effects of anti-inflammatory agents

Chronic inflammation is known to be a risk for many cancers, including pancreatic cancer. Heavy alcohol drinking and cigarette smoking are major causes of pancreatitis, and epidemiological studies have shown that smoking and chronic pancreatitis are risk factors for pancreatic cancer. Meanwhile, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) are elevated in pancreatitis and pancreatic cancer tissues in humans and in animal models. Selective inhibitors of iNOS and COX-2 suppress pancreatic cancer development in a chemical carcinogenesis model of hamsters treated with N-nitrosobis(2-oxopropyl)amine (BOP). In addition, hyperlipidemia, obesity, and type II diabetes are also suggested to be associated with chronic inflammation in the pancreas and involved in pancreatic cancer development. We have shown that a high-fat diet increased pancreatic cancer development in BOP-treated hamsters, along with aggravation of hyperlipidemia, severe fatty infiltration, and increased expression of adipokines and inflammatory factors in the pancreas. Of note, fatty pancreas has been observed in obese and/or diabetic cases in humans. Preventive effects of anti-hyperlipidemic/anti-diabetic agents on pancreatic cancer have also been shown in humans and animals. Taking this evidence into consideration, modulation of inflammatory factors by anti-inflammatory agents will provide useful data for prevention of pancreatic cancer.

Expression of insulin-like growth factor binding protein-4 (IGFBP-4) in acute pancreatitis induced by L-arginine in mice

The mechanisms of injury and regeneration after acute pancreatitis are still incompletely understood. Insulin-like growth factor binding proteins (IGFBPs) have been reported to play roles in various pancreatic diseases, but the involvement of insulin-like growth factor binding protein-4 (IGFBP-4) in acute pancreatitis is unknown. The aim of the study was to examine the expression of IGFBP-4 in mice with acute pancreatitis induced by two doses of L-arginine. IGFBP-4 expression was assayed by microarray test, real-time RT-PCR, Western blotting, ELISA and by an immunohistochemical assay. Microarray test of pancreatic mRNA showed that IGFBP-4 mRNA increased significantly after L-arginine treatment and the increase was confirmed by real-time RT-PCR. Western blotting and ELISA assay showed similar patterns of increase of IGFBP-4 in pancreatic tissues and serum. In the control pancreas, IGFBP-4 was mainly immunolocalized in the pancreatic islets. In the pancreatic tissues of mice with pancreatitis induced by L-arginine, the immunolocalization of IGFBP-4 was detected in both acinar cells and pancreatic islets. In conclusion, our results suggest that IGFBP-4 may play a potential role in pancreatic injury and regeneration in a murine model of acute pancreatitis induced by L-arginine.

Fibroblast growth factor 21 reduces the severity of cerulein-induced pancreatitis in mice

BACKGROUND & AIMS

Fibroblast growth factor 21 (FGF21) acts as a hormonal regulator during fasting and is involved in lipid metabolism. Fgf21 gene expression is regulated by peroxisome proliferator-activated receptor (PPAR)-dependent pathways, which are enhanced during pancreatitis. Therefore, the aim of this study was to investigate FGF21's role in pancreatic injury.

METHODS

Fgf21 expression was quantified during cerulein-induced pancreatitis (CIP) or following mechanical or thapsigargin-induced stress through Northern blot analysis, in situ hybridization, and quantitative reverse transcription polymerase chain reaction. FGF21 protein was quantified by Western blot analysis. Isolated acinar cells or AR42J acinar cells were treated with recombinant FGF21 protein, and extracellular regulated kinase 1/2 activation was examined. The severity of CIP was compared between wild-type mice and mice overexpressing FGF21 (FGF21Tg) or harboring a targeted deletion of Fgf21 (Fgf21(-/-)).

RESULTS

Acinar cell Fgf21 expression markedly increased during CIP and following injury in vitro. Purified FGF21 activated the extracellular regulated kinase 1/2 pathway in pancreatic acinar cells. The severity of CIP is inversely correlated to FGF21 expression because FGF21Tg mice exhibited decreased serum amylase and decreased pancreatic stellate cell activation, whereas Fgf21(-/-) mice had increased serum amylase and tissue damage. The expression of Fgf21 was also inversely correlated to expression of Early growth response 1, a proinflammatory and profibrotic transcription factor.

CONCLUSIONS

These studies suggest a novel function for Fgf21 as an immediate response gene protecting pancreatic acini from overt damage.

Hedgehog signaling is required for effective regeneration of exocrine pancreas

Although both endocrine and the exocrine pancreas display a significant capacity for tissue regeneration and renewal, the existence of progenitor cells in the adult pancreas remains uncertain. Using a model of cerulein-mediated injury and repair, we demonstrate that mature exocrine cells, defined by expression of an Elastase1 promoter, actively contribute to regenerating pancreatic epithelium through formation of metaplastic ductal intermediates. Acinar cell regeneration is associated with activation of Hedgehog (Hh) signaling, as assessed by up-regulated expression of multiple pathway components, as well as activation of a Ptch-lacZ reporter allele. Using both pharmacologic and genetic techniques, we also show that the ability of mature exocrine cells to accomplish pancreatic regeneration is impaired by blockade of Hh signaling. Specifically, attenuated regeneration in the absence of an intact Hh pathway is characterized by persistence of metaplastic epithelium expressing markers of pancreatic progenitor cells, suggesting an inhibition of redifferentiation into mature exocrine cells. Given the known role of Hh signaling in exocrine pancreatic cancer, these findings may provide a mechanistic link between injury-induced activation of pancreatic progenitors and subsequent pancreatic neoplasia.

Acinar plasticity: development of a novel in vitro model to study human acinar-to-duct-to-islet differentiation

OBJECTIVES

The plasticity of pancreatic tissue is demonstrated in many pancreatic diseases. It has previously been shown that pancreatic islet-to-duct transformation and acinoductal metaplasia have been associated with both pancreatic regeneration and adenocarcinoma in various in vivo and in vitro settings. Understanding this inherent morphogenetic plasticity of the adult pancreas could lead to new therapeutic approaches to pancreatic disease.

METHODS

Cadaveric human pancreases (n = 7) were digested, and purified acinar tissue, which was approximately 85% immunoreactive for amylase and approximately 15% immunoreactive for CK-19, was embedded in a type 1 collagen matrix and cultured in a differentiation medium (DM) consisting of Dulbecco modified Eagle/F12 medium supplemented with cholera toxin (100 ng/mL), epidermal growth factor (10 ng/mL), and insulin (24 mU/mL) for 8 days. After this initial period, the resulting tissues were cultured in DM without cholera toxin, supplemented with gastrin (50 nmol/L) and hepatocyte growth factor (HGF; 10 ng/mL), with islet neogenesis-associated protein (INGAP; 167 nmol/L) or with gastrin + HGF + INGAP for 6 days. Tissue samples were then analyzed for amylase, cytokeratin 19, pancreas duodenum homeobox 1, and endocrine hormone immunoreactivity as well as dithizione positivity.

RESULTS

After 8 days of culture, approximately 90% of acini transformed into ductlike structures. This acinoductal transformation was characterized by a complete absence of amylase staining, with virtually all cells CK-19 immunoreactive. Addition of INGAP led to an approximately 18-fold increase in pancreas duodenum homeobox 1 immunoreactivity, although without an observed increase in insulin production as measured by dithizone positivity. However, when acinar-derived ductlike structures were cultured with gastrin + HGF + INGAP, the total incidence of dithizone-positive structures increased approximately 6-fold (10.9 +/- 2.9% vs 1.7 +/- 0.4%, P = 0.037). Treatment with gastrin + HGF alone led to no significant change in any of the measured parameters.

CONCLUSIONS

We have developed a novel in vitro model of adult human acinoductal metaplasia that will aid not only in developing new methods of expanding beta-cell mass but also provide insights into pancreatic carcinogenesis.

Gastrointestinal Hormones Cause Rapid c-Met Receptor Down-regulation by a Novel Mechanism Involving Clathrin-mediated Endocytosis and a Lysosome-dependent Mechanism

The activated c-Met receptor has potent effects on normal tissues and tumors. c-Met levels are regulated by hepatocyte growth factor (HGF); however, it is unknown if they can be regulated by gastrointestinal (GI) hormones. c-Met is found in many GI tissues/tumors that possess GI hormone receptors. We studied the effect of GI hormones on c-Met in rat pancreatic acini, which possess both receptors. CCK-8, carbachol, and bombesin, but not VIP/secretin, decreased c-Met. CCK-8 caused rapid and potent c-Met down-regulation and abolished HGF-induced c-Met and Gab1 tyrosine phosphorylation, while stimulating c-Met serine phosphorylation. The effect of cholecystokinin (CCK) was also seen in intact acini using immunofluorescence, in a biotinylated fraction representing membrane proteins, in single acinar cells, in Panc-1 tumor cells, and in vivo in rats injected with CCK. CCK-8 did not decrease cell viability or overall responsiveness. GF109203X, thapsigargin, or their combination partially reversed the effect of CCK-8. In contrast to HGF-induced c-Met down-regulation, the effect of CCK was decreased by a lysosome inhibitor (concanamycin) but not the proteasome inhibitor lactacystin. Inhibitors of clathrin-mediated endocytosis blocked the effect of CCK. HGF but not CCK-8 caused c-Met ubiquitination. These results show CCK and other GI hormones can cause rapid c-Met down-regulation, which occurs by a novel mechanism. These results could be important for c-Met regulation in normal as well as in neoplastic tissue in the GI tract.

Role of peroxisome proliferator-activated receptor-alpha in acute pancreatitis induced by cerulein

The peroxisome proliferator-activated receptor-alpha (PPAR-alpha) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors related to retinoid, steroid and thyroid hormone receptors. The aim of the present study was to examine the effects of endogenous PPAR-alpha ligand on the development of acute pancreatitis caused by cerulein in mice. Intraperitoneal injection of cerulein into PPAR-alpha wild-type (WT) mice resulted in severe, acute pancreatitis characterized by oedema, neutrophil infiltration and necrosis and by elevated serum levels of amylase and lipase. Infiltration of pancreatic and lung tissue with neutrophils (measured as an increase in myeloperoxidase activity) was associated with enhanced expression of the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and P-selectin. Immunohistochemical examination demonstrated a marked increase in the staining (immunoreactivity) for transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF) in the pancreas of cerulein-treated PPAR-alpha wild-type (WT) mice in comparison to sham-treated mice. Acute pancreatitis in PPAR-alphaWT mice was also associated with a significant mortality (20% survival at 5 days after cerulein administration). In contrast, the degree of pancreatic inflammation and tissue injury (histological score), up-regulation/formation of ICAM-1 and P-selectin, infiltration of neutrophils, and the expression of TGF-beta and VEGF was markedly enhanced in pancreatic tissue obtained from cerulein-treated PPAR-alpha knockout (KO) mice. Thus, endogenous PPAR-alpha ligands reduce the degree of pancreas injury caused by acute pancreatitis induced by cerulein administration.

Effect of early administration of exogenous basic fibroblast growth factor on acute edematous pancreatitis in rats

AIM

To observe the therapeutic effect of early administration of exogenous Basic fibroblast growth factor (bFGF) on acute edematous pancreatitis (AEP) in rats.

METHODS

Thirty male Sprague-Dawley rats were randomly divided into three (n = 10): normal control group (group I), AEP group (group II) and AEP with bFGF treatment group (group III). AEP was induced by subcutaneous injection of cerulein (5.5 microg/kg and 7.5 microg/kg) at 1 h interval into rats of groups II and III. Three hours after induction of AEP, 100 microg/kg bFGF was administrated intraperitoneally for 1 h to group III rats. For test of DNA synthesis in acinar cells, 5-bromo-2'-deoxyuridine (BrdU) labeling solution was intraperitoneally injected into the rats of groups II and III 24 h after bFGF treatment. The changes in serum amylase, lipase, pancreatic tissue wet/dry ratio were detected.

RESULTS

In bFGF treatment group, there was a significant decrease in the volume of serum amylase, lipase and the pancreatic wet/dry weight ratio(1383.0+/-94.6 U/L, 194.0+/-43.6 U/L, 4.32+/-0.32) compared to AEP group (3464+/-223.7 U/L, 456+/-68.7 U/L, 6.89+/-0.47) (P < 0.01), and no significant difference was found between bFGF treatment and control group (1289+/-94.0 U/L, 171+/-23.4 U/L, 4.12+/-0.26, P > 0.05). The inflammatory changes such as interstitial edema, polymorphonuclear neutrophils (PMNs) and vacuolization were significantly ameliorated compared to AEP group (P < 0.01). A small number of BrdU-labeled nuclei were observed in acinar cells of AEP rats (1.8+/-0.3 nuclei/microscopic field, n = 10) while diffuse BrdU-labeled nuclei were found in bFGF-treated rats (18.9+/-1.4 nuclei/microscopic field, n = 10) (P < 0.01). Immunohistochemical study showed increased DNA synthesis in pancreatic acinar cells.

CONCLUSION

Early administration of exogenous bFGF has significant therapeutic effect on cerulein-induced acute edematous pancreatitis in rats. Its mechanism is related to the amelioration of inflammation and facilitation of pancreatic regeneration.

Ischemic preconditioning inhibits development of edematous cerulein-induced pancreatitis: Involvement of cyclooxygenases and heat shock protein 70

AIM: To determine whether ischemic preconditioning (IP) affects the development of edematous cerulein-induced pancreatitis and to assess the role of cyclooxygenase-1 (COX-1), COX-2, and heat shock protein 70 (HSP 70) in this process.

METHODS: In male Wistar rats, IP was performed by clamping of celiac artery (twice for 5 min at 5-min intervals). Thirty minutes after IP or sham operation, acute pancreatitis was induced by cerulein. Activity of COX-1 or COX-2 was inhibited by resveratrol or rofecoxib, respectively (10 mg/kg).

RESULTS: IP significantly reduced pancreatic damage in cerulein-induced pancreatitis as demonstrated by the improvement of pancreas histology, reduction in serum lipase and poly-C ribonuclease activity, and serum concentration of pro-inflammatory interleukin (IL)-1β. Also, IP attenuated the pancreatitis-evoked fall in pancreatic blood flow and pancreatic DNA synthesis. Serum level of anti-inflammatory IL-10 was not affected by IP. Cerulein-induced pancreatitis and IP increased the content of HSP 70 in the pancreas. Maximal increase in HSP 70 was observed when IP was combined with cerulein-induced pancreatitis. Inhibition of COXs, especially COX-2, reduced the protective effect of IP in edematous pancreatitis.

CONCLUSION: Our results indicate that IP reduces pancreatic damage in cerulein-induced pancreatitis and this effect, at least in part, depends on the activity of COXs and pancreatic production of HSP 70.

Growth factors and beta cell replication

Recent studies have demonstrated that human islet allograft transplantation can be a successful therapeutic option in the treatment of patients with Type I diabetes. However, this impressive recent advance is accompanied by a very important constraint. There is a critical paucity of pancreatic islets or pancreatic beta cells for islet transplantation to become a large-scale therapeutic option in patients with diabetes. This has prompted many laboratories around the world to invigorate their efforts in finding ways for increasing the availability of beta cells or beta cell surrogates that potentially could be transplanted into patients with diabetes. The number of studies analyzing the mechanisms that govern beta cell proliferation and growth in physiological and pathological conditions has increased exponentially during the last decade. These studies exploring the role of growth factors, intracellular signaling molecules and cell cycle regulators constitute the substrate for future strategies aimed at expanding human beta cells in vitro and/or in vivo after transplantation. In this review, we describe the current knowledge on the effects of several beta cell growth factors that have been shown to increase beta cell proliferation and expand beta cell mass in vitro and/or in vivo and that they could be potentially deployed in an effort to increase the number of patients transplanted with islets. Furthermore, we also analyze in this review recent studies deciphering the relevance of these specific islet growth factors as physiological and pathophysiological regulators of beta cell proliferation and islet growth.

Fibroblast growth factor-2 stimulates interleukin-6 secretion in human pancreatic periacinar myofibroblasts

OBJECTIVES

Fibroblast growth factor-2 (FGF-2) plays an important role in the pathophysiology of acute and chronic pancreatitis. In the present study, to evaluate the proinflammatory nature of FGF-2, we investigated the effects of FGF-2 on IL-6 secretion in human pancreatic periacinar myofibroblasts.

METHODS

IL-6 supernatant levels were determined by enzyme-linked immunosorbent assays (ELISA). IL-6 mRNA expression were determined by Northern blots and quantitative PCRs. Activated protein (AP)-1 DNA-binding activities were evaluated by electrophoretic gel mobility shift assays (EMSA).

RESULTS

FGF-2 induced IL-6 release in a dose- and time-dependent manner. FGF-2 activity for IL-6 induction was the same as that of IL-17. The combination of FGF-2 and IL-17 exerted additive effects at mRNA and protein levels. FGF-2 induced AP-1 DNA-binding activity, but blockage of AP-1 signaling by adenovirus-mediated transfer of a dominant negative c-Jun gene did not affect FGF-2-induced IL-6 mRNA expression. FGF-2 rapidly induced activation of ERK1/2 and p38 MAP kinases, and specific inhibitors for these enzymes significantly reduced FGF-2-induced IL-6 release.

CONCLUSION

In the pancreas, FGF-2 may not only play a role as a growth factor in tissue injury repair processes but also as an inducer of acute-phase response via stimulation of IL-6 release.

Inhibition of cyclooxygenase-2 reduces the protective effect of hepatocyte growth factor in experimental pancreatitis

Hepatocyte growth factor (HGF) overexpression is observed in experimental and clinical acute pancreatitis. Moreover, previous studies have shown that administration of HGF reduces pancreatic damage in experimental pancreatitis. The aim of our studies was to determine the role of cyclooxygenase-1 and cyclooxygenase-2 in the protective effect of HGF administration against caerulein-induced pancreatitis. Acute pancreatitis was induced in rats by infusion of caerulein. HGF was administered twice at the dose 10 microg/kg s.c. The activity of cyclooxygenase-1 and cyclooxygenase-2 was inhibited by resveratrol and rofecoxib, respectively (10 mg/kg). Immediately after cessation of caerulein or saline infusion, pancreatic blood flow, pancreatic cell proliferation, pancreatic prostaglandin E(2) generation, plasma lipase activity, plasma interleukin-1 beta and interleukin-10 concentration were measured and morphological signs of pancreatitis were examined. Expression of cyclooxygenase-1 and cyclooxygenase-2 mRNA transcripts was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Cyclooxygenase protein production was analyzed by Western blot. Administration of HGF or caerulein alone, or their combination, was without effect on cyclooxygenase-1 mRNA expression in pancreatic tissue. Expression of cyclooxygenase-2 mRNA was increased by HGF and caerulein. The maximal increase in cyclooxygenase-2 mRNA expression was observed when HGF administration was combined with caerulein infusion. A similar effect was observed when we studied the influence of HGF and caerulein on pancreatic cyclooxygenase-2 production, as determined by Western blot. Administration of HGF without induction of acute pancreatitis increased pancreatic prostaglandin E(2) generation and plasma interleukin-10, and this effect was abolished by the cyclooxygenase-2 inhibitor, rofecoxib. Treatment with HGF, during the development of pancreatitis, increased the plasma interleukin-10 concentration and attenuated pancreatic damage, as evidenced by: (a) histological improvement of pancreatic integrity; (b) the partial reversal of the decrease in DNA synthesis and pancreatic blood flow; (c) the reduction in pancreatitis-evoked increase in plasma lipase and interleukin-1 beta. Administration of resveratrol and rofecoxib alone was without effect on the development of pancreatitis. Combination of rofecoxib with HGF reduced the HGF-evoked increase in plasma interleukin-10 concentration and pancreatic prostaglandin E(2) generation, and abolished the protective effect of HGF against pancreatic damage in pancreatitis. Resveratrol did not affect the protective effect of HGF. We conclude that: (1) HGF induces cyclooxygenase-2 but not cyclooxygenase-1 expression; (2) inhibition of cyclooxygenase-2 in HGF-treated rats decreases the release of anti-inflammatory interleukin-10, increases the production of pro-inflammatory interleukin-1 beta and reduces pancreatic blood flow; (3) cyclooxygenase-2 activity is necessary for the protective effect of HGF in acute pancreatitis.

Hepatocyte growth factor gene therapy for islet transplantation

Recent clinical studies have documented that human islet transplantation has the potential to replace pancreatic endocrine function in patients with type 1 diabetes. These studies have also highlighted an enormous shortage of human islets that impedes the use of islet transplantation in clinical practice on a larger scale. To address this problem, one potential approach is to use islet growth factors to increase beta cell replication, to improve beta cell function and to enhance beta cell survival. In that context, transgenic mice overexpressing hepatocyte growth factor (HGF) in the pancreatic beta cell display increased beta cell proliferation, function and survival. More importantly, HGF-overexpressing transgenic mouse islets markedly improve transplant performance in severe combined immunodeficiency (SCID) mice and reduce the number of islets required for successful islet transplantation. Recently, adenoviral-mediated gene transfer of HGF into normal rodent islets has confirmed the beneficial effects of HGF in improving islet transplant outcomes in two marginal mass islet transplant models in rodents: islet transplant under the kidney capsule in SCID mice; and portal islet allograft transplantation in rats treated with the Edmonton immunosuppressive regimen. These studies suggest that ex vivo HGF gene therapy has the potential to reduce the number of human islets required for successful islet transplantation.

Hepatocyte growth factor activates several transduction pathways in rat pancreatic acini

The receptor of hepatocyte growth factor (HGF), c-met induces different physiological responses in several cell types. Little is known about the role of HGF in exocrine pancreas. However, abnormal HGF signaling has been strongly implicated in pancreatic tumorigenesis and association of HGF with pancreatitis has been demonstrated. We have studied the presence of c-met and activation of their intracellular pathways associated in rat pancreatic acini in comparison with cholecystokinin (CCK) and epidermal growth factor (EGF). C-met expression in rat exocrine pancreas was identified by immunohistochemistry and immunoprecipitation followed by Western analysis. Tyrosine phosphorylation of c-met is strongly stimulated as well as kinase pathways leading to ERK1/2 cascade. HGF, but not CCK or EGF, selectively caused a consistent increase in the amount of p85 regulatory subunit of PI3-K present in anti-phosphotyrosine immunoprecipitates. Downstream of PI3-K, HGF increased Ser473 phosphorylation of Akt selectively, as CCK or EGF did not affect it. HGF selectively stimulated tyrosine phosphorylation of phosphatase PTP1D. HGF failed to promote the well-known CCK effects in pancreatic acini such as amylase secretion and intracellular calcium mobilization. Although HGF shares activation of ERK1/2 with CCK, we demonstrate that it promotes the selective activation of intracellular pathways not regulated by CCK or EGF. Our results suggest that HGF is an in vivo stimulus of pancreatic acini and provide novel insight into the transduction pathways and effects of c-met/HGF in normal pancreatic acinar cells.

Role for growth factors and extracellular matrix in controlling differentiation of prospectively isolated hepatic stem cells

In liver development, a number of growth factors (GFs) and components of the extracellular matrix (ECMs) lead to differentiation of liver parenchymal cells. As the liver contains many cell types, specifically investigating their functional effects on hepatic stem cell populations is difficult. Prospective isolation and clonal assays for hepatic stem cells enable the examination of direct effects of GFs and ECMs on this rare cell fraction. Using previously purified cells that fulfill the criteria for hepatic stem cells, we examined how GFs and ECMs regulate differentiation in the developing liver. We show here that hepatocyte growth factor (HGF) induced early transition of albumin (ALB)-negative stem cells to ALB-positive hepatic precursors resembling hepatoblasts and then oncostatin M (OSM) promoted their differentiation to tryptophan-2, 3-dioxygenase (TO)-positive mature hepatocytes. During this transition, ECMs were necessary for the differentiation of stem cells and precursors, but their effects were only supportive. In the first step of stem cell differentiation induced by HGF, the expression of CCAAT/enhancer binding protein (C/EBP), a basic leucine zipper transcription factor, changed dramatically. When C/EBP function was inhibited in stem cells, they stopped differentiating to hepatocyte-lineage cells and proliferated actively. These are the first findings to illustrate the mechanism of hepatic stem cell differentiation in liver development.

Differential distribution of fibroblast growth factor (FGF)-7 and FGF-10 in L-arginine-induced acute pancreatitis

The regenerative process of the pancreas after acute pancreatitis (AP) is characterized by acinar and ductal cell proliferation with synthesis and transient deposition of extracellular matrices. Various growth factors were reported to be highly expressed in AP, but their regulation has not yet been clarified. Fibroblast growth factor (FGF)-7, also known as keratinocyte growth factor (KGF), and FGF-10 are members of the FGF family and show high structural homology and similar biological characteristics. Both are mainly synthesized by mesenchymal cells and stimulate epithelial cells via KGF receptor (KGFR) which is a splice variant of FGFR-2. In the present study, we attempted to immunohistochemically determine the localization of FGF-7 and FGF-10 in pancreatic tissues of an L-arginine-induced rat pancreatitis model. Furthermore, highly specific KGFR antibodies were prepared and used for Western blot analysis and immunohistochemistry. In the normal pancreas, FGF-7 was localized in alpha cells of islets, but FGF-10 was not detected. KGFR was also localized in islet cells, ductal cells, and centroacinar cells in the normal pancreas. In the pancreatic tissues of rats with L-arginine-induced pancreatitis, FGF-7 was localized in alpha cells, whereas FGF-10 was expressed in vascular smooth muscle cells (VSMCs). KGFR was not expressed in centroacinar cells and its level decreased after L-arginine treatment. However, KGFR was detected instead in some acinar cells and VSMCs in addition to islet cells. These findings suggest that FGF-7 and FGF-10 contribute to the regeneration and differentiation of acinar cells and angiogenesis in AP through KGFR.

Connective tissue growth factor is involved in pancreatic repair and tissue remodeling in human and rat acute necrotizing pancreatitis

OBJECTIVE

To analyze the involvement of connective tissue growth factor (CTGF) in the transforming growth factor-beta (TGF-beta) pathway during acute necrotizing pancreatitis (ANP) in humans and rats.

SUMMARY BACKGROUND DATA

Connective tissue growth factor is involved in several fibrotic diseases and has a critical role in fibrogenesis and tissue remodeling after injury.

METHODS

Normal human pancreas tissue samples were obtained through an organ donor program from five individuals without a history of pancreatic disease. Human ANP tissues were obtained from eight persons undergoing surgery for this disease. In rats, ANP was induced by intraductal infusion of taurocholate. The expression of CTGF was studied by Northern blot analysis, in situ hybridization, and immunohistochemistry in both human and rat pancreatic tissue samples.

RESULTS

Northern blot analysis revealed enhanced CTGF mRNA expression in human ANP tissue samples compared with normal controls. In addition, a concomitant increase in TGF-beta1 was present. By in situ hybridization, CTGF mRNA was localized in the remaining acinar and ductal cells and in fibroblasts. In regions of intense damage adjacent to areas of necrosis, CTGF mRNA signals were most intense. Inflammatory cells were devoid of any CTGF mRNA signals. By immunohistochemistry, CTGF protein was localized at high levels in the same cell types as CTGF mRNA. In ANP in rats, concomitantly enhanced mRNA levels of CTGF, TGF-beta1, and collagen type 1 were present, with a biphasic peak pattern on days 2 to 3 and day 7 after induction of ANP.

CONCLUSIONS

These data indicate that CTGF participates in tissue remodeling in ANP. The expression of CTGF predominantly in the remaining acinar and ductal cells indicates that extracellular matrix synthesis after necrosis is at least partly regulated by the remaining pancreatic parenchyma and only to a minor extent by inflammatory cells. Blockage of CTGF, a downstream mediator of TGF-beta in fibrogenesis, might be useful as a target to influence and reduce fibrogenesis in this disorder.

Hepatocyte growth factor attenuates pancreatic damage in caerulein-induced pancreatitis in rats

Hepatocyte growth factor (HGF) overexpression was reported in experimental and clinical acute pancreatitis. These observations prompted us to determine the effect of HGF administration on the development of caerulein-induced pancreatitis in rats. Acute pancreatitis was induced by s.c. infusion of caerulein (10 microg/kg/h) for 5 h. HGF was administrated twice (30 min before caerulein or saline infusion and 3 h later) at the doses: 0.4, 2, 10 or 50 microg/kg s.c. Immediately after cessation of caerulein or saline infusion, the pancreatic blood flow, plasma amylase and lipase activity, plasma cytokines concentration, cell proliferation, and morphological signs of pancreatitis were examined. Caerulein administration induced acute edematous pancreatitis manifested by 41% decrease in DNA synthesis, 53% inhibition of pancreatic blood flow, a significant increase in plasma amylase and lipase activity, plasma interleukin-1beta and interleukin-6 concentration, as well as, the development of the histological signs of pancreatic damage (edema, leukocyte infiltration, and vacuolization). Administration of HGF without induction of pancreatitis increased plasma interleukin-10. Treatment with HGF, during induction of pancreatitis, increased plasma interleukin-10 and attenuated the pancreatic damage, what was manifested by histological improvement of pancreatic integrity, the partial reversion of the drop in DNA synthesis and pancreatic blood flow, and the reduction in pancreatitis evoked increase in plasma amylase, lipase, and interleukin-1beta and interleukin-6 levels. HGF administrated at the dose 2 microg/kg exhibited a similar beneficial effect as administration of HGF at the doses 10 or 50 microg/kg. Treatment with HGF at the dose 0.4 microg/kg was less effective. We conclude that: (1) administration of HGF attenuates pancreatic damage in caerulein-induced pancreatitis; (2) this effect seems to be related to the increase in production of interleukin-10, the reduction in release of interleukin-1beta and interleukin-6, and the improvement of pancreatic blood flow.

Expression of hepatocyte growth factor, keratinocyte growth factor and their receptors in experimental chronic pancreatitis

BACKGROUND

Hepatocyte (HGF) and Keratinocyte growth factors (KGF) are key factors of tissue organization and regeneration. These peptide growth factors and their receptors c-met and keratinocyte growth factor receptor (KGFR) are overexpressed in pancreatic cancer.

AIM

Expression and localization of ligands and receptors were investigated during the development of experimental chronic pancreatitis.

METHODS

Chronic pancreatitis was induced in rats by intravenous injection of dibutyltin dichloride. One to 60 days after treatment, the expression of growth factors and receptors was analysed by competitive polymerase chain reaction, Western blot analysis and immunohistochemistry.

RESULTS

HGF mRNA expression increased (10-fold) until days 7-14 followed by a decrease to control level. Expression of c-met mRNA constantly increased (15-fold). KGF and KGFR mRNA expression were increased after 14-28 days (5-fold) and then returned to control levels. mRNA expression patterns correlated with changes in the protein expression, whereas protein levels of KGF remained unchanged. Ligands were localized in mesenchymal cells and their receptors on epithelial cells.

CONCLUSIONS

The significant increase of HGF and c-met expression suggests an essential role of this growth factor in the morphological changes during the development of chronic pancreatitis. Changes in the expression of KGF and KGFR are less pronounced.

Multipotential nestin-positive stem cells isolated from adult pancreatic islets differentiate ex vivo into pancreatic endocrine, exocrine, and hepatic phenotypes

The endocrine cells of the rat pancreatic islets of Langerhans, including insulin-producing beta-cells, turn over every 40-50 days by processes of apoptosis and the proliferation and differentiation of new islet cells (neogenesis) from progenitor epithelial cells located in the pancreatic ducts. However, the administration to rats of islet trophic factors such as glucose or glucagon-like peptide 1 for 48 h results in a doubling of islet cell mass, suggesting that islet progenitor cells may reside within the islets themselves. Here we show that rat and human pancreatic islets contain a heretofore unrecognized distinct population of cells that express the neural stem cell-specific marker nestin. Nestin-positive cells within pancreatic islets express neither the hormones insulin, glucagon, somatostatin, or pancreatic polypeptide nor the markers of vascular endothelium or neurons, such as collagen IV and galanin. Focal regions of nestin-positive cells are also identified in large, small, and centrolobular ducts of the rat pancreas. Nestin-positive cells in the islets and in pancreatic ducts are distinct from ductal epithelium because they do not express the ductal marker cytokeratin 19 (CK19). After their isolation, these nestin-positive cells have an unusually extended proliferative capacity when cultured in vitro (approximately 8 months), can be cloned repeatedly, and appear to be multipotential. Upon confluence, they are able to differentiate into cells that express liver and exocrine pancreas markers, such as alpha-fetoprotein and pancreatic amylase, and display a ductal/endocrine phenotype with expression of CK19, neural-specific cell adhesion molecule, insulin, glucagon, and the pancreas/duodenum specific homeodomain transcription factor, IDX-1. We propose that these nestin-positive islet-derived progenitor (NIP) cells are a distinct population of cells that reside within pancreatic islets and may participate in the neogenesis of islet endocrine cells. The NIP cells that also reside in the pancreatic ducts may be contributors to the established location of islet progenitor cells. The identification of NIP cells within the pancreatic islets themselves suggest possibilities for treatment of diabetes, whereby NIP cells isolated from pancreas biopsies could be expanded ex vivo and transplanted into the donor/recipient.

C-met protooncogene expression and its regulation by cytokines in the regenerating pancreas and in pancreatic cancer cells

BACKGROUND

Activation of the receptor c-met stimulates motility, mitosis, morphogenesis, processes involved in organ regeneration, or progression of malignancies. In the present study we investigated the expression of c-met protein in the regenerating pancreas and characterized the influence of cytokines on c-met expression.

METHODS

Acute pancreatitis was induced in rats by cerulein injection. Rat acini and rat and human pancreatic cancer cells were stimulated with interleukin-1alpha (IL-1alpha), IL-6, tumor necrosis factor-alpha (TNF-alpha) or transforming growth factor-beta1 (TGF-beta1). C-met expression was analyzed by means of Western blotting and localization in pancreatic tissue by immunohistochemistry.

RESULTS

C-met protein expression was significantly upregulated in the regenerating pancreas and localized in areas of regenerating tissue. Stimulation with cytokines resulted in a two- to threefold increase of c-met expression in vitro.

CONCLUSION

Enhanced c-met expression after acute pancreatitis suggests that HGF/met has an important role in pancreatic regeneration, which is probably mediated by cytokines. This regulatory mechanism is also of importance in pancreatic cancer.

Transforming growth factor-beta-induced upregulation of transforming growth factor-beta receptor expression in pancreatic regeneration

The transforming growth factor-beta (TGFbeta) signaling pathway is one important player in the regulation of extracellular matrix turnover and cell proliferation in epithelial regeneration. We used cerulein-induced pancreatitis in rats as a model to investigate the regulation of TGFbeta receptor type I and type II expression on protein and messenger RNA level during regeneration. In the regenerating pancreas, mRNA levels of TGFbeta receptor I and II were significantly increased with a maximum after 2 days. On protein level, expression of TGFbeta receptor II was significantly increased after three to 3-5 days. This elevated expression could be inhibited by neutralizing the endogenous biological activity of TGFbeta1 with a specific antibody. In cultured pancreatic epithelial cells, TGFbeta1 reduced cell proliferation as measured by [3H]thymidine incorporation. Furthermore the transcript levels of TGFbeta1 as well as mRNA and protein concentrations of type I and type II receptor increased during TGFbeta stimulation in vitro. These results indicate that epithelial pancreatic cells contribute to the enhanced TGFbeta1 synthesis during pancreatic regeneration by an autocrine mechanism. TGFbeta1, furthermore, upregulates the expression of its own receptors during the regenerative process, thereby contributing to the increase of the TGFbeta-induced cellular responses.