Platelet-derived growth factors stimulate proliferation and extracellular matrix synthesis of pancreatic stellate cells: implications in pathogenesis of pancreas fibrosis

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Inhibitory effects of interferons on pancreatic stellate cell activation

AIM: To analyze and to compare the effects of interferon (IFN)-α, IFN-β, and IFN-γ on pancreatic stellate cell (PSC) activation in vitro and to elucidate the molecular basis of IFN action.

METHODS: PSCs were isolated from rat’s pancreatic tissue, cultured and stimulated with recombinant rat IFNs. Cell proliferation and collagen synthesis were assessed by measuring the incorporation of 5-bromo-2’-deoxyuridine (BrdU) into DNA and [³H]-proline into acetic acid-soluble proteins, respectively. Apoptotic cells were determined by FACS analysis (sub-G₁ peak method). Exhibition of the myofibroblastic PSC phenotype was monitored by immunoblot analysis of α-smooth muscle actin (α-SMA) expression. To assess the activation of signal transducer and activator of transcription (STAT), Western blots using phospho-STAT-specific antibodies were performed. In studies on STAT1 function, expression of the protein was inhibited by siRNA.

RESULTS: IFN-β and IFN-γ, but not IFN-α significantly diminished PSC proliferation and collagen synthesis. IFN-γ was the only IFN that clearly inhibited α-SMA expression. Under the experimental conditions used, no enhanced rate of apoptotic cell death was observed in response to any IFN treatment. IFN-β and IFN-γ induced a strong increase of STAT1 and STAT3 tyrosine phosphorylation, while the effect of IFN-α was much weaker. Inhibition of STAT1 expression with siRNA was associated with a significantly reduced growth-inhibitory effect of IFN-γ.

CONCLUSION: IFN-β and particularly IFN-γ display inhibitory effects on PSC activation in vitro and should be tested regarding their in vitro efficiency. Growth inhibition by IFN-γ action requires STAT1.

Chronic pancreatitis of alcoholic and nonalcoholic origin

Fibroinflammatory changes to the pancreatic tissue characterize chronic pancreatitis. This article summarizes the current state of knowledge on the pathology and pathogenesis of chronic pancreatitis associated with alcohol, hereditary factors, metabolic conditions, and anatomical abnormalities. Specifically, the pathogenetic mechanisms that lead to chronic pancreatitis in patients with alcohol abuse will be discussed. In addition, brief descriptions of the features of chronic pancreatitis of nonalcoholic origin and of the pancreatic fibrosis that is not associated with symptoms of chronic pancreatitis will be given.

Fibrogenesis in the pancreas after acinar cell injury

Fibrosis within the pancreas is a key feature of chronic pancreatitis and pancreatic cancer. It has now been well demonstrated that following injury to acinar cells, pancreatic stellate cell activation, migration and proliferation is the key mediator of this process. Many cytokines and growth factors have been studied, particularly TGF-beta, which appears to be the major stimulus to fibrinogenesis. There is current interest in the mechanisms of phenotypic change between the active and quiescent forms, apoptosis and the signalling pathways that may be involved. The pancreatic stellate cell is likely to play an important role in maintaining the normal extracellular matrix; we speculate that the dysregulation of this process is an important factor in chronic pancreatitis.

Inhibition of lymphocyte apoptosis by pancreatic stellate cells: impact of interleukin-15

There is growing evidence that pancreatic stellate cells (PSCs) produce cytokines and take part in the regulation of inflammatory processes in the pancreas. IL-15 inhibits apoptosis of various cell populations. This study was performed to investigate whether PSCs produce IL-15 and thereby can affect lymphocytes. Primary PSCs were isolated from the rat pancreas using density gradient centrifugation. mRNA expression of IL-15 was demonstrated by RT-PCR, and IL-15 protein was analyzed by immunoblotting. Lymphocytes obtained from rat mesenterial lymph nodes were cocultured with in vitro activated PSCs. Apoptosis has been quantified by the binding of annexin V-FITC with a flow cytometer. Proliferation was monitored using [3H]thymidine incorporation. PSCs express two splice variants of IL-15. The protein was detectable only in cell lysates but not in the cell culture supernatant. Cocultivation of lymphocytes with PSCs and IL-15 inhibited spontaneous lymphocyte apoptosis, and this effect was reduced by an anti-IL-15 antibody. Lymphocytes induced vice versa the proliferation and collagen production of PSCs. The inhibition of spontaneous lymphocyte apoptosis in cocultures with PSCs was at least partially mediated by cell-bound IL-15. This effect and the stimulation of PSCs by lymphocytes may lead to a circulus vitiosus, resulting in the persistence of inflammatory processes and the development of fibrosis during chronic pancreatitis.

Immortalization of pancreatic stellate cells as an in vitro model of pancreatic fibrosis: deactivation is induced by matrigel and N-acetylcysteine

Tissue fibrosis is one of the characteristics of chronic pancreatitis and pancreatic adenocarcinoma. Activated pancreatic stellate cells (PSC) play a central role in this process. However, analysis of the molecular mechanisms leading to PSC activation is hampered by the lack of an established human PSC line. To overcome this problem, we immortalized and characterized primary human PSC. The cells were isolated by the outgrowth method and were immortalized by transfection with SV40 large T antigen and human telomerase (hTERT). Primary human PSC served as controls. An immortalized line, RLT-PSC, was analyzed for the expression of stellate cell markers. Moreover, the effects of transforming growth factor beta 1(TGFbeta1) or platelet-derived growth factor stimulation and of cultivation on basement membrane components or N-acetylcysteine (NAC) treatment on gene and protein expression and proliferation were analyzed. Immortal RLT-PSC cells retained the phenotype of activated PSC proven by the expression of alpha-smooth muscle actin (alphaSMA), vimentin, desmin and glial fibrillary acidic protein (GFAP). TGFbeta1 treatment upregulated the expression of alphaSMA, collagen type I (Col I), fibronectin and TGFbeta1. Incubation of RLT-PSC cells and primary human activated PSC on Matrigel plus NAC treatment resulted in a deactivated phenotype as evidenced by a decrease of alphaSMA, connective tissue growth factor and Col I expression and by a decreased proliferation of the cells. Moreover, this treatment restored the ability of the cells to store vitamin A in cytoplasmic vesicles. In conclusion, we have established an immortal pancreatic stellate cell line, without changing the characteristic phenotype. Importantly, we were able to demonstrate that besides soluble factors, the matrix surrounding PSC plays a pivotal role in the maintenance of the activation process of PSC. Cultivation of activated PSC on a reconstituted basement membrane plus treatment with NAC was able to deactivate the cells, thus pointing to the possibility of an antifibrosis therapy in chronic pancreatitis.

[Spectrum of chronic pancreatitis. On the way to etiological classification]

Chronic pancreatitis is a fibroinflammatory disease that is induced by injuries to the interstitial, ductal, and/or acinar cells. The most important causes are alcohol abuse, gene mutations, autoimmune processes, special anatomic changes, and obstructive duct lesions. The morphologic spectrum of the various types of chronic pancreatitis related to the above causes shows features that increasingly allow an etiological distinction and categorization to be made. A catalog of five criteria is presented for distinguishing chronic pancreatitis from ductal adenocarcinoma of the pancreas.

Differential and synergistic effects of platelet-derived growth factor-BB and transforming growth factor-beta1 on activated pancreatic stellate cells

OBJECTIVE

The cytokines platelet-derived growth factor (PDGF) and transforming growth factor (TGF)-beta1 are major factors influencing the transformation from the quiescent to the activated phenotype of pancreatic stellate cells (PSC), a process involved in the pathogenesis of chronic pancreatitis. Albeit much effort has been made to study the effects of PDGF and TGF-beta1 on PSCs, their interaction is still unclear, because these cytokines show both differential and synergistic effects as outlined by this study.

METHODS

Culture-activated PSCs of rats were treated with PDGF-BB and TGF-beta1. Subsequent changes of cell proliferation and migration were determined by cell counting, (+)-bromo-2'-deoxyuridine enzyme-linked immunosarbant assay (ELISA), and migration assay. Gene expression, synthesis of proteins, and activation of kinases were further studied by reverse transcription-polymerase chain reaction, real-time polymerase chain reaction, ELISA, and Western blot.

RESULTS

PDGF-BB increased PSC proliferation and migration, accompanied by elevated expression of matrix metalloproteinases (MMP)-13 and MMP-3. The mRNA amount of procollagen alpha2(I), alpha-smooth muscle actin (alpha-SMA), tissue inhibitor of metalloproteinase (TIMP)-1, and TGF-beta1 was also increased by PDGF-BB. In contrast, PDGF-BB reduced collagen type I in culture medium and synthesis of alpha-SMA. Treatment of PSC with TGF-beta1 decreased proliferation, had no significant effect on migration and MMP expression, but increased expression and synthesis of procollagen alpha2(I) and alpha-SMA. Both cytokines induced phosphorylation of extracellular signal regulated kinase (ERK)-1/2 and p38, but only PDGF-BB activated the protein kinase B signaling pathway.

CONCLUSION

PDGF-BB augments effects of TGF-beta1 on the mRNA level presumably because of up-regulation of TGF-beta1 synthesis and common signaling pathways of the 2 cytokines. However, at the protein level, PDGF-BB impairs typical TGF-beta1 effects such as increased synthesis of collagen (type I) and alpha-SMA. Moreover, PDGF-BB facilitates degradation of extracellular matrix proteins by enhancement of MMP synthesis, but MMP activity was probably limited because of elevated tissue inhibitor of metalloproteinase 1 expression.

Transcriptome analysis of human hepatic and pancreatic stellate cells: organ-specific variations of a common transcriptional phenotype

Pancreatic stellate cells (PSCs) are thought to be the primary source of the extensive fibrotic reaction characteristic of pancreatic cancer and chronic pancreatitis in humans. PSCs share many morphological and functional characteristics with hepatic stellate cells (HSCs), whose central role in liver fibrosis is well established. However, it has remained unclear if hepatic and pancreatic stellate cells are derived from a common cell lineage and if they are completely similar or if they possess organ-specific features. We have analysed the transcriptomes of HSCs, PSCs and skin fibroblasts to assess how the transcriptional phenotype of stellate cells differs from that of a typical fibroblast lineage cell and if there is evidence for a common stellate cell precursor. To this end, we have performed expression profiling of primary cultures of human HSCs, PSCs and skin fibroblasts using 23,000-feature 'whole genome' oligonucleotide micro-arrays. Expression data were verified using real-time PCR. The expression profiles of HSCs and PSCs displayed a great extent of similarity, clearly separating them from the fibroblasts. Predominantly extracellular and cell surface genes, but also signalling molecules, transcription factors and novel neural markers, were concordantly expressed in both stellate cell types. Despite this high degree of similarity, distinct differences in expression patterns were observed between HSCs and PSCs, reflecting organ-specific variations of the common stellate cell-specific phenotype.

Activation of JAK-STAT pathway is required for platelet-derived growth factor-induced proliferation of pancreatic stellate cells

AIM: To clarify the role of Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway in platelet-derived growth factor (PDGF) induced proliferation in activated pancreatic stellate cells (PSCs).

METHODS: PSCs were isolated from rat pancreas tissue, and used in their culture-activated, myofibroblast-like phenotype. STAT-specific binding activity was assessed by electrophoretic mobility shift assay. Activation of Src, JAK2, STAT1, STAT3, and ERK was determined by Western blotting using anti-phosphospecific antibodies. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2’-deoxyuridine.

RESULTS: PDGF-BB induced STAT-specific binding activity, and activation of Src, JAK2, STAT1, STAT3, and ERK. Ethanol and acetaldehyde at clinically relevant concentrations decreased basal activation of JAK2 and STAT3. PDGF-induced activation of STAT1 and STAT3 was inhibited by a Src inhibitor PP1 and a JAK2 inhibitor AG490, whereas PDGF-induced activation of ERK was inhibited by PP1, and not by AG490. PDGF-induced proliferation was inhibited by PP1 and AG490 as well as by STAT3 antisense oligonucleotide.

CONCLUSION: PDGF-BB activated JAK2-STAT pathway via Src-dependent mechanism. Activation of JAK2-STAT3 pathway, in addition to ERK, may play a role in PDGF-induced proliferation of PSCs.

Green tea polyphenol epigallocatechin-3-gallate blocks PDGF-induced proliferation and migration of rat pancreatic stellate cells

AIM: To clarify the effects of epigallocatechin-3-gallate (EGCG) on the platelet-derived growth factor (PDGF)-BB-induced proliferation and migration of pancreatic stellate cells (PSCs).

METHODS: PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2’-deoxyuridine. Cell migration was assessed using modified Boyden chambers. Cyclin D1, p21^Waf1, and p27^Kip1 expression and phosphorylation of PDGF β-receptor, extracellular signal-regulated kinase, and Akt were examined by Western blotting. Activation of phospha-tidylinositol 3-kinase was examined by kinase assay using phosphatidylinositol as a substrate. Cell cycle was assessed by flow cytometry after staining with propidium iodide.

RESULTS: EGCG at non-cytotoxic concentrations inhibited PDGF-induced proliferation and migration. This effect was associated with the inhibition of cell cycle progression beyond the G₁ phase, decreased cyclin D1 and increased p27^Kip1 expression. EGCG inhibited tyrosine phosphorylation of PDGF β-receptor and downstream activation of extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/Akt pathways.

CONCLUSION: EGCG inhibited PDGF-BB-induced proliferation and migration of PSCs through the inhibition of PDGF-mediated signaling pathways.

Therapeutic effects of troglitazone in experimental chronic pancreatitis in mice

Peroxisome proliferator-activated receptor (PPAR)-gamma controls growth, differentiation, and inflammation. PPAR-gamma agonists exert anti-inflammatory effects in vitro and inhibit the activation of pancreas stellate cells, implicated in the formation and progression of fibrosis. We determined the influence of troglitazone, a ligand for PPAR-gamma, on pancreatic damage and fibrosis in experimental chronic pancreatitis. Mice received six hourly intraperitoneal injections with 50 microg/kg of cerulein or saline, three times a week for 6 weeks. One week after the last injection all mice were sacrificed. Untreated mice were compared with mice treated with troglitazone either during weeks 1 to 6 or weeks 4 to 6. All mice that received cerulein injections displayed histopathological signs of chronic pancreatitis at week 7. Troglitazone treatment improved all markers for severity of pancreatitis. Moreover, early and postponed troglitazone treatments were equally effective in diminishing intrapancreatic fibrosis as quantified by Sirius red staining, hydroxyproline content, and laminin staining as well as the increased number of pancreatic stellate cells and pancreas levels of transforming growth factor-beta. Thus, troglitazone attenuated pancreatic damage and inflammation in experimental chronic pancreatitis and remained beneficial in a therapeutic setting when given after initial damage had been established.

Pancreatic carcinoma cells induce fibrosis by stimulating proliferation and matrix synthesis of stellate cells

BACKGROUND & AIMS

Tumor desmoplasia is one of the representative histopathologic findings in ductal pancreatic adenocarcinoma. The aims of this study were to examine the cellular and molecular mechanisms of fibrogenesis associated with pancreatic adenocarcinomas.

METHODS

Immunostainings were performed with human pancreatic adenocarcinomas (n = 27) and tumors induced in nude mice (n = 36) by subcutaneously injecting MiaPaCa2, Panc1, and SW850 with and without pancreatic stellate cells. Matrix-producing cells were isolated from pancreatic adenocarcinomas and compared with pancreatic stellate cells isolated from tissue of chronic pancreatitis. Paracrine stimulation of pancreatic stellate cells by carcinoma cells was studied regarding matrix synthesis (collagen and c-fibronectin on protein and messenger RNA level) and cell proliferation (bromodeoxyuridine incorporation).

RESULTS

High numbers of desmin and alpha-smooth muscle actin-positive cells were detected in 26 of 27 pancreatic adenocarcinomas. Intense fibronectin and collagen stainings were associated with these cells. By using cytofilament stainings, gene expression profiling, and morphological examinations, the matrix-producing cells obtained by the outgrowth method from pancreatic adenocarcinomas were identified as pancreatic stellate cells. Supernatants of MiaPaCa2, Panc1, and SW850 cells stimulated proliferation and collagen type I and c-fibronectin synthesis of cultured pancreatic stellate cells. Preincubation of the carcinoma cell supernatants with neutralizing antibodies against fibroblast growth factor 2, transforming growth factor beta 1, and platelet-derived growth factor significantly reduced the stimulatory effects. Subcutaneous injection of carcinoma cells and pancreatic stellate cells induced fast-growing subcutaneous fibrotic tumors in nude mice. Morphometric analysis of carcinoma cells (cytokeratin stainings) showed a high density of carcinoma cells in these tumors.

CONCLUSIONS

Pancreatic stellate cells strongly support tumor growth in the nude mouse model. The increased deposition of connective tissue in pancreatic carcinoma is the result of a paracrine stimulation of pancreatic stellate cells by carcinoma cells.

Transforming growth factor-beta-1 variants are not associated with chronic nonalcoholic pancreatitis

BACKGROUND

Pancreatic fibrosis is a key pathological feature of chronic pancreatitis. In vivo and in vitro data have demonstrated that pancreatic stellate cells (PSC) play a central role in pancreatic fibrosis. PSC activation and collagen synthesis are highly controlled by transforming growth factor-beta-1 (TGF-beta1). We evaluated whether functionally relevant genetic variants of TGF-beta1 are associated with chronic nonalcoholic pancreatitis.

METHODS

The promotor as well as exon 1 variants of the TGF-beta1 gene (G-800A, Leu10Pro and Arg25Pro) were investigated. Forty-two CP patients with a family history of nonalcoholic chronic pancreatitis (group A) and 88 patients without a family history of nonalcoholic chronic pancreatitis (group B) were studied. One hundred blood donors served as controls (group C).

RESULTS

The allelic frequencies of G-800A, Leu10Pro and Arg25Pro were 12, 38 and 6% in group A; 7, 40 and 6% in group B and 12, 29 and 3% in group C, respectively. The differences were not significant.

CONCLUSION

Functionally relevant genetic variants of the TGF-beta1 gene are not associated with nonalcoholic chronic pancreatitis.

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Galectin-1 is an inductor of pancreatic stellate cell activation

Pancreatic stellate cells (PSCs) play a key role in the development of pancreatic fibrosis, a pathological feature of chronic pancreatitis and pancreatic cancer. Here, we show that activation of rat PSCs in vitro is associated with increased expression of galectin-1 (gal-1) and that gal-1 modulates PSC function. Expression of the lectin was stimulated by fetal calf serum and platelet-derived growth factor. PSCs exposed to exogenous gal-1 proliferated at a higher rate and synthesised more collagen than controls. Gal-1-dependent collagen synthesis was blocked by lactose but not by cellobiose, suggesting that gal-1 acts on PSCs through targeting beta-galactoside-containing glycoconjugates. Analysis of gal-1 signalling in PSCs revealed an activation of the extracellular signal-regulated kinases 1 and 2 and enhanced DNA binding of AP-1 transcription factors. Together, our data implicate gal-1 in PSC activation and suggest further studies to analyse the role of endogenous lectins in the development of pancreatic fibrosis in vivo.

PD98059 inhibited the activation of pancreatic stellate cells mediated by platelet-derived growth factor BB in rats

To determine the biological effects of extracelluar signal regulated kinase (ERK) specific inhibitor PD98059 on pancreatic stellate cells (PSCs) activated by platelet-derived factor-BB (PDGF-BB), cultured rat PSCs were co-incubated at 37 DC for 24 h with 25 ng/ml PDGF-BB and different doses of PD98059 (ranging from 5 ng/ml to 40 ng/ml). Expression of pERK1 protein was detected by Western blot and collagen alpha1 ( I ) mRNA was tested by reverse transcription-polymerase chain reaction (RT-PCR). Our results showed that there were statistical differences in the expression of pERK1 protein in all groups. Expression of pERK1 protein was up-regulated in the group treated by PDGF-BB, and gradually down-regulated in the other groups treated by PD98059 of different doses. An excellent positive correlation was revealed between the inhibitory effect and PD98059 concentrations. It was also observed that the expression of collagen alpha1 ( I ) mRNA had similar response to pERK1. The level of collagen alpha1 ( I ) mRNA was the highest in the PDGF-BB group, and gradually reduced in the other groups treated by PD98059 of different doses. It is concluded that expression of pERK1 protein and collagen alpha1 ( I ) mRNA was up-regulated in rat PSCs activated by PDGF-BB. Meanwhile, PD98059 could inhibit PSCs activation mediated by PDGF. It is suggested that ERK1 protein plays an important role on PSCs activation mediated by PDGF signal pathway.

Combination therapy with an angiotensin-converting enzyme inhibitor and an angiotensin II receptor blocker synergistically suppresses chronic pancreatitis in rats

We recently demonstrated that both lisinopril and candesartan, an angiotensin-converting enzyme inhibitor and angiotensin II type 1 receptor blocker, respectively, attenuate pancreatic inflammation and fibrosis in male Wistar Bonn/Kobori (WBN/Kob) rats. The purpose of the present study was to assess whether combination therapy with low doses of both, ineffective when given alone, might synergistically exert protective effects. Lisinopril, candesartan, or a combination of both in drinking water was administered to 10-week-old male WBN/Kob rats for 10 weeks. Parameters of inflammation and fibrosis, positive immunostaining for alpha-smooth muscle actin, and gene expression of cytokine and growth factors were assessed, as well as circulating renin-angiotensin system components. Dose-dependent effects of combination therapy were also investigated. Only combination therapy attenuated gross alterations in the pancreas, as quantitatively confirmed by increases in pancreatic weights and decreases in myeloperoxidase activity, hydroxyproline content, histologic scores, relative fibrosis area, and relative area of alpha-smooth muscle actin-positive cells. Combination therapy suppressed up-regulation of tumor necrosis factor-alpha, platelet-derived growth factor-receptor beta, and transforming growth factor-beta1 mRNA in the pancreas. Dose dependence of combination therapy was recognized with reference to improvement in these parameters. The conclusions are that combination therapy synergistically alleviated pancreatic inflammation and fibrosis in male WBN/Kob rats. This effect may be related to suppression of tumor necrosis factor-alpha, platelet-derived growth factor-receptor beta, and transforming growth factor-beta1 mRNA. Compared with the either therapy alone, combination therapy with an angiotensin-converting enzyme inhibitor and an angiotensin II type 1 receptor blocker may be more beneficial for treating chronic pancreatitis.

Inhibition of transforming growth factor beta decreases pancreatic fibrosis and protects the pancreas against chronic injury in mice

Transforming growth factor-beta (TGF-beta) is an important cytokine in the fibrogenesis in many organs, including the pancreas. Using an adenoviral vector expressing the entire extracellular domain of type II human TGF-beta receptor (AdTbeta-ExR), we investigated whether inhibition of TGF-beta action is effective against persistent pancreatic fibrosis, and whether it exerts a beneficial effect on the pancreas in the process of chronic injury. To induce chronic pancreatic injury and pancreatic fibrosis, mice were subjected to three episodes of acute pancreatitis induced by six intraperitoneal injections of 50 microg/kg body weight cerulein at hourly intervals, per week for 3 consecutive weeks. Mice were infected once with AdTbeta-ExR, or with a control adenoviral vector expressing bacterial beta-galactosidase (AdLacZ). Pancreatic fibrosis was evaluated by histology and hydroxyproline content. Activation of pancreatic stellate cells (PSCs) was assessed by immunostaining for alpha-smooth muscle actin. Apoptosis and proliferation of acinar cells were assessed by immunostaining of ssDNA and Ki-67, respectively. Three-week cerulein injection induced pancreatic fibrosis and pancreatic atrophy with proliferation of activated PSCs. In AdTbeta-ExR-injected mice, but not AdLacZ-injected mice, pancreatic fibrosis was significantly attenuated. This finding was accompanied by a reduction of activated PSCs. AdTbeta-ExR, but not AdLacZ, significantly increased pancreas weight after chronic pancreatic injury. AdTbeta-ExR did not change the proportion of proliferating acinar cells, whereas it reduced the number of apoptotic acinar cells. Our results demonstrate that inhibition of TGF-beta action not only decreases pancreatic fibrosis but also protects the pancreas against chronic injury by preventing acinar cell apoptosis.

Molecular Mechanisms of Low Intensity Pulsed Ultrasound in Human Skin Fibroblasts

Soluble factors such as polypeptide growth factors, mitogenic lipids, inflammatory cytokines, and hormones are known regulators of cell proliferation. However, the effect of mechanical stimuli on cell proliferation is less well understood. Here we examined the effect of low intensity pulsed ultrasound (US), which is used to promote wound healing, on the proliferation of primary human foreskin fibroblasts and the underlying signaling mechanisms. We show that a single 6-11-min US stimulation increases bromodeoxyuridine incorporation. In addition, an increase in the total cell number is observed after sequential US stimulation. US induced stress fiber and focal adhesion formation via activation of Rho. We further observed that US selectively induced activation of extracellular signal-regulated kinase (ERK) 1/2. Inhibition of Rho-associated coiled-coil-containing protein kinase (ROCK) prevented US-induced ERK1/2 activation, demonstrating that the Rho/ROCK pathway is an upstream regulator of ERK activation in response to US. Consequently, activation of ROCK and MEK-1 was required for US-induced DNA synthesis. Finally, an integrin beta(1) blocking antibody as well as a RGD peptide prevented US-induced DNA synthesis. In addition, US slightly increased phosphorylation of Src at Tyr(416), and Src activity was found to be required for ERK1/2 activation in response to US. In conclusion, our data demonstrate for the first time that US promotes cell proliferation via activation of integrin receptors and a Rho/ROCK/Src/ERK signaling pathway.

Pancreatic cancer stimulates pancreatic stellate cell proliferation and TIMP-1 production through the MAP kinase pathway

Pancreatic adenocarcinoma is characterized by an intense desmoplastic reaction that surrounds the tumor. Pancreatic stellate cells (PSCs) are thought to be responsible for production of this extracellular matrix. When activated, PSCs have a myofibroblast phenotype and produce not only components of the extracellular matrix including collagen, fibronectin, and laminin, but also matrix metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). Since PSCs are found in the stroma surrounding human pancreatic adenocarcinoma, we postulate that pancreatic cancer could impact PSC proliferation and TIMP-1 production. Rat PSCs were isolated and cultured. Isolated PSCs were exposed to PANC-1 conditioned medium (CM) and proliferation, activation of the mitogen-activated protein (MAP) kinase pathway, and TIMP-1 gene induction were determined. Exposure to PANC-1 CM increased PSC DNA synthesis, cell number, and TIMP-1 mRNA (real-time PCR) as well as activating the extracellular-regulated kinase (ERK) 1/2. Inhibition of ERK 1/2 phosphorylation (U0126) prevented the increases in growth and TIMP-1 expression. PANC-1 CM stimulates PSC proliferation and TIMP-1 through the MAP kinase (ERK 1/2) pathway.

The molecular basis of pancreatic fibrosis: common stromal gene expression in chronic pancreatitis and pancreatic adenocarcinoma

OBJECTIVES

Tissue desmoplasia occurs in a number of disease states, but its molecular basis is poorly understood. To determine which genes are overexpressed in cells contained within the desmoplastic stroma of pancreatic adenocarcinoma and chronic pancreatitis, we undertook genetic profiling of microdissected tissue samples of pancreatic adenocarcinoma, chronic pancreatitis, normal pancreas, and pancreatic cancer cell lines. We observed that samples of both pancreatic adenocarcinoma and chronic pancreatitis showed elevated expression of many shared genes compared with the normal pancreas. We hypothesized that these common genes likely important in stromal production and/or function could be identified using a strategy that involved comparisons between pancreatic adenocarcinoma, chronic pancreatitis, normal pancreas, and pancreatic cancer cell lines.

METHODS

We performed oligonucleotide microarray analysis of 6800 different genes expressed in 10 samples of pancreatic adenocarcinoma, 5 samples of normal pancreas, 5 samples of chronic pancreatitis, and 7 pancreatic cancer cell lines. Microarray findings were validated with RT-PCR, and immunohistochemistry was used to verify protein localization to the stromal compartment of both pancreatic cancer and chronic pancreatitis.

RESULTS

We employed a deductive comparison whereby genes expressed in the normal pancreas and pancreatic cancer cell lines were selectively eliminated from those expressed in common by pancreatic adenocarcinoma and chronic pancreatitis. This strategy identified 107 genes predicted to be expressed within cells of the stromal compartment of both pancreatic adenocarcinoma and chronic pancreatitis.

CONCLUSIONS

These genes are likely important factors in epithelial-stromal signaling in pancreatic desmoplasia and may serve as diagnostic or therapeutic targets.

Pathogenesis of chronic pancreatitis: an evidence-based review of past theories and recent developments

In the past several decades, four prominent theories of chronic pancreatitis pathogenesis have emerged: the toxic-metabolic theory, the oxidative stress hypothesis, the stone and duct obstruction theory, and the necrosis-fibrosis hypothesis. Although these traditional theories are formulated based on compelling scientific observations, substantial contradictory data also exist for each. Furthermore, the basic premises of some of these theories are directly contradictory. Because of the recent scientific progress in the underlying genetic, cellular, and molecular pathophysiology, there have been substantial advances in the understanding of chronic pancreatitis pathogenesis. This paper will provide an evidence-based review and critique of the traditional pathogenic theories, followed by a discussion of the new advances in pancreatic fibrogenesis. Moreover, we will discuss plausible pathogenic sequences applied to each of the known etiologies.

Molecular regulation of pancreatic stellate cell function

Until now, no specific therapies are available to inhibit pancreatic fibrosis, a constant pathological feature of chronic pancreatitis and pancreatic cancer. One major reason is the incomplete knowledge of the molecular principles underlying fibrogenesis in the pancreas. In the past few years, evidence has been accumulated that activated pancreatic stellate cells (PSCs) are the predominant source of extracellular matrix (ECM) proteins in the diseased organ. PSCs are vitamin A-storing, fibroblast-like cells with close morphological and biochemical similarities to hepatic stellate cells (also known as Ito-cells). In response to profibrogenic mediators such as various cytokines, PSCs undergo an activation process that involves proliferation, exhibition of a myofibroblastic phenotype and enhanced production of ECM proteins. The intracellular mediators of activation signals, and their antagonists, are only partially known so far. Recent data suggest an important role of enzymes of the mitogen-activated protein kinase family in PSC activation. On the other hand, ligands of the nuclear receptor PPARγ (peroxisome proliferator-activated receptor γ) stimulate maintenance of a quiescent PSC phenotype. In the future, targeting regulators of the PSC activation process might become a promising approach for the treatment of pancreatic fibrosis.

Angiotensin II type 1 receptor interaction is an important regulator for the development of pancreatic fibrosis in mice

The renin-angiotensin system (RAS) plays important roles in various pathophysiological processes. However, the role of the RAS in pancreatic fibrosis has not been established. We investigated the role of angiotensin II (ANG II)-ANG II type 1 (AT(1)) receptor pathway in the development of pancreatic fibrosis with AT(1a) receptor-deficient [AT(1a)(-/-)] mice. To induce pancreatic fibrosis, AT(1a)(-/-) and wild-type (WT) mice were submitted to three episodes of acute pancreatitis induced by six intraperitoneal injections of 50 microg/kg body wt cerulein at hourly intervals, per week, for four consecutive weeks. Pancreatic fibrosis was assessed by histology and hydroxyproline content. Pancreatic stellate cell (PSC) activation and the localization of AT(1) receptors were assessed by Western blot analysis for alpha-smooth muscle actin and immunostaining. Transforming growth factor-beta(1) (TGF-beta(1)) mRNA expression in the pancreas was assessed by RT-PCR. Six intraperitoneal injections of cerulein induced acute pancreatitis in both AT(1a)(-/-) and WT mice. There were no significant differences between two groups with regard to serum amylase and histological changes. Pancreatic fibrosis induced by repeated episodes of acute pancreatitis was significantly attenuated in AT(1a)(-/-) mice compared with that in WT mice. This finding was accompanied by a reduction of activated PSCs. Dual-immunofluorescence staining in WT mice revealed that activated PSCs express AT(1) receptors. The level of TGF-beta(1) mRNA was lower in AT(1a)(-/-) mice than in WT mice. Our results demonstrate that the ANG II-AT(1) receptor pathway is not essential for the local pancreatic injury in acute pancreatitis but plays an important role in the development of pancreatic fibrosis through PSC activation and proliferation.

Generation and characterization of immortalized rat pancreatic stellate cells

Pancreatic stellate cells (PSCs) are involved in, among other things, the pathogenesis of pancreatic fibrosis. Here, we present the generation of immortalized PSCs 7 and 14 days after isolation by retroviral gene transfer of the SV40 large T antigen encoding region. Propagated cell lines [large T immortalized cells (LTC)-7, LTC-14] retained characteristics of primary cells in terms of morphology, responsiveness to mediators regulating cellular functions such as proliferation, and expression profile of a number of investigated genes. Whereas LTC-14 kept the morphological features of the differentiation status of the primary cells they were made of, LTC-7 appeared similar to an earlier stage. Thus the established cell lines represent a versatile tool to investigate various aspects of PSC biology.

Tumour Lines from a Spontaneous Rat Endometrial Stromal Sarcoma, Showing Dendritic Cell-like and Myofibroblastic Cell-like Phenotypes

A transplantable tumour (RY) and cell lines (RY-PB and clone RY-B-E3 isolated from RY-PB) were established from a naturally occurring endometrial stromal sarcoma (ESS) found in a 24-month-old female F344 rat. The primary tumour and RY tumours, which had been serially passaged in syngeneic female rats up to the 10th generation, consisted of spindle or round cells arranged in ill-defined bundles or sheets. Neoplastic cells of the primary and RY tumours, as well as cultured cells of RY-PB and RY-B-E3, showed positive reactions to vimentin, ED1/ED2 (both for rat macrophages/histiocytes), OX6 (for dendritic cells expressing rat MHC class II antigens), and lysosomal enzymes such as acid phosphatase and non-specific esterase, in varying degrees. Ultrastructurally, neoplastic cells characteristically had tubulovesicular system-like structures and variously developed lysosomes in the cytoplasm. Neoplastic cells also exhibited immunoexpression to an alpha-smooth muscle actin (alpha-SMA). The addition of transforming growth factor (TGF)-beta1 to RY-PB and RY-B-E3 cultures increased the number of alpha-SMA-positive cells, whilst the positive cell number was decreased by anti-TGF-beta antibody. The RT-PCR method revealed the expression of TGF-beta1 mRNA in the cultured cells. The present study showed that rat ESS-derived cells exhibited dendritic cell-like and myofibroblastic cell-like phenotypes. The histogenesis of ESSs in human beings and rats remains poorly understood, and these tumour lines may therefore become useful tools for further research.

Fibrosis of the pancreas: the initial tissue damage and the resulting pattern

Fibrosis in the pancreas is caused by such processes as necrosis/apoptosis, inflammation or duct obstruction. The initial event that induces fibrogenesis in the pancreas is an injury that may involve the interstitial mesenchymal cells, the duct cells and/or the acinar cells. Damage to any one of these tissue compartments of the pancreas is associated with cytokine-triggered transformation of resident fibroblasts/pancreatic stellate cells into myofibroblasts and the subsequent production and deposition of extracellular matrix. Depending on the site of injury in the pancreas and the involved tissue compartment, predominantly inter(peri)lobular fibrosis (as in alcoholic chronic pancreatitis), periductal fibrosis (as in hereditary pancreatitis), periductal and interlobular fibrosis (as in autoimmune pancreatitis) or diffuse inter- and intralobular fibrosis (as in obstructive chronic pancreatitis) develops.

Fibrosis of the pancreas: the initial tissue damage and the resulting pattern

Fibrosis in the pancreas is caused by such processes as necrosis/apoptosis, inflammation or duct obstruction. The initial event that induces fibrogenesis in the pancreas is an injury that may involve the interstitial mesenchymal cells, the duct cells and/or the acinar cells. Damage to any one of these tissue compartments of the pancreas is associated with cytokine-triggered transformation of resident fibroblasts/pancreatic stellate cells into myofibroblasts and the subsequent production and deposition of extracellular matrix. Depending on the site of injury in the pancreas and the involved tissue compartment, predominantly inter(peri)lobular fibrosis (as in alcoholic chronic pancreatitis), periductal fibrosis (as in hereditary pancreatitis), periductal and interlobular fibrosis (as in autoimmune pancreatitis) or diffuse inter- and intralobular fibrosis (as in obstructive chronic pancreatitis) develops.

Establishment and characterization of a rat pancreatic stellate cell line by spontaneous immortalization

AIM: Activated pancreatic stellate cells (PSCs) have been implicated in the pathogenesis of pancreatic fibrosis and inflammation. Primary PSCs can be subcultured only several times because of their limited growth potential. A continuous cell line may therefore be valuable in studying molecular mechanisms of these pancreatic disorders. The aim of this study was to establish a cell line of rat PSCs by spontaneous immortalization.

METHODS: PSCs were isolated from the pancreas of male Wistar rats, and conventional subcultivation was performed repeatedly. Telomerase activity was measured using the telomere repeat amplification protocol. Activation of transcription factors was assessed by electrophoretic mobility shift assay. Activation of mitogen-activated protein (MAP) kinases was examined by Western blotting using anti-phosphospecific antibodies. Expression of cytokine-induced neutrophil chemoattractant-1 was determined by enzyme immunoassay.

RESULTS: Conventional subcultivation yielded actively growing cells. One clone was obtained after limiting dilution, and designated as SIPS. This cell line has been passaged repeatedly more than 2 years, and is thus likely immortalized. SIPS cells retained morphological characteristics of primary, culture-activated PSCs. SIPS expressed α-smooth muscle actin, glial acidic fibrillary protein, vimentin, desmin, type I collagen, fibronectin, and prolyl hydroxylases. Telomerase activity and p53 expression were negative. Proliferation of SIPS cells was serum-dependent, and stimulated with platelet-derived growth factor-BB through the activation of extracellular signal-regulated kinase. Interleukin-1β activated nuclear factor-κB, activator protein-1, and MAP kinases. Interleukin-1β induced cytokine-induced neutrophil chemoattractant-1 expression through the activation of nuclear factor-κB and MAP kinases.

CONCLUSION: SIPS cells can be useful for in vitro studies of cell biology and signal transduction of PSCs.

Stellate cell activation in alcoholic pancreatitis

The pathogenesis of pancreatic fibrosis, a characteristic feature of alcohol-induced chronic pancreatitis, has received increasing attention over the past few years, largely due to the identification and characterization of stellate cells in the pancreas. These cells are morphologically similar to hepatic stellate cells, the principal effector cells in liver fibrosis. The role of pancreatic stellate cells (PSCs) in alcoholic pancreatic fibrosis has been studied using 2 approaches: (i) in vivo studies using pancreatic tissue from patients with alcohol-induced chronic pancreatitis and from animal models of experimental pancreatitis and (ii) in vitro studies using cultured PSCs. These studies indicate that PSCs are activated early in the course of pancreatic injury and are the predominant source of collagen in the fibrotic pancreas. Several factors that may be responsible for mediating PSC activation during chronic alcohol exposure have also been identified. From the findings to date, it may be speculated that the pathogenesis of alcoholic pancreatic fibrosis may involve 2 pathways: (i) a necroinflammatory pathway involving cytokine release and PSC activation and (ii) a nonnecroinflammatory pathway involving direct activation of PSCs by ethanol via its metabolism to acetaldehyde and the generation of oxidant stress.

Latency-Associated Peptide Prevents Skin Fibrosis in Murine Sclerodermatous Graft-Versus-Host Disease, a Model for Human Scleroderma

Murine sclerodermatous graft-versus-host disease (Scl GVHD), produced by transplanting B10.D2 bone marrow and spleen cells to lethally irradiated BALB/cJ mice, is a model for human scleroderma. Mice with Scl GVHD have skin thickening, lung fibrosis, cutaneous mononuclear cell infiltration, and upregulation of cutaneous transforming growth factor beta1 (TGF-beta1) and type I collagen mRNAs by day 21 after bone marrow transplantation. Elevated TGF-beta1 appears to be the critical cytokine driving fibrosis in Scl GVHD, which can be prevented with antibodies to TGF-beta administered early in disease. Here we demonstrate that we can also prevent skin thickening in mice with Scl GVHD with a naturally occurring antagonist to TGF-beta1, human latency-associated peptide (LAP). By quantitative real-time PCR analysis and immunostaining, LAP treatment also abrogates the upregulation of cutaneous TGF-beta1 and connective tissue growth factor mRNAs and type I collagen synthesis in Scl GVHD. In contrast to anti-TGF-beta antibodies, LAP at 4 ng total per mouse has no significant suppressive effect on cutaneous influx of T cells and monocytes or immune cell activation. LAP may be a potential new therapy in scleroderma and other TGF-beta-driven fibrosing disease that targets TGF-beta more specifically, without affecting systemic critical roles of TGF-beta on immune cell function.

TGFbeta-induced fibrogenesis of the pancreas

The biological cause of fibrosis is the accumulation of excessive amounts of extracellular matrix (ECM) which leads to tissue dysfunction and organ failure. A strong correlation can be found between pancreatic diseases and fibrotic processes, in particular chronic pancreatitis and pancreatic cancer. There is growing evidence that pancreatic fibrosis represents a dysregulation of the normal repair processes after injury. This concept is based on the findings that fibrosis and tissue repair involve similar biological reactions regulated by the same group of molecules. The best characterized example for these regulatory molecules are the members of the transforming growth factor beta family (TGFbeta). TGFbeta1 represents the prototype of this family of highly similar growth factors, with the unique ability to stimulate the expression and deposition of extracellular matrix and to inhibit its degradation. Growth factor-induced fibrotic events are targeted by a myofibroblast-like cell called pancreatic stellate cell (PSC). These cells show enhanced expression of all-important ECM proteins after TGFbeta stimulation including collagen, fibronectin and proteoglycans. At the same time TGFbeta inhibits the degradation of ECM by blocking the secretion of proteases and stimulating the production of naturally occurring protease inhibitors.

Regulation of pancreatic stellate cell function in vitro: biological and molecular effects of all-trans retinoic acid

Pancreatic stellate cells (PSCs) are essentially involved in the development of pancreatic fibrosis, a constant feature of chronic pancreatitis and pancreatic cancer. Profibrogenic mediators, such as ethanol metabolites and cytokines, induce a PSC activation process that involves proliferation, enhanced production of extracellular matrix proteins and a phenotypic transition towards myofibroblasts which includes a loss of the characteristic retinoid-containing fat droplets. Here, we have analysed how exogenous all-trans retinoic acid (ATRA) affects activation of rat PSCs induced by sustained culture. Bromodeoxyuridine-incorporation assays indicated an ATRA-dependent inhibition of DNA synthesis. In contrast, ATRA did not affect expression of alpha-smooth muscle actin, a protein typical for myofibroblasts. Quantification of [3H]proline incorporation revealed a diminished collagen production in ATRA-treated PSCs. Furthermore, zymography experiments showed that supernatants of ATRA-exposed PSC cultures contained higher levels of matrix metalloproteinase-9 but not of matrix metalloproteinase-2 than untreated controls. At the level of intracellular signalling, ATRA had no effect on extracellular signal-regulated kinase activation after incubation of PSCs with the mitogen platelet-derived growth factor (PDGF). In addition, PDGF-induced DNA binding of activator protein-1 (AP-1) transcription factors was not inhibited by ATRA treatment. Luciferase reporter gene assays, however, revealed an ATRA-dependent transrepression of AP-1 in PDGF-stimulated PSCs. Together, the results indicate that exogenous ATRA displays inhibitory effects on PSC proliferation and collagen synthesis but does not block phenotypic transition towards myofibroblasts. We hypothesise that inhibition of AP-1 signalling may be involved in the mediation of biological effects of ATRA on PSCs.

An evaluation of endogenous pancreatic enzyme levels after human islet isolation

INTRODUCTION

Recent evidence has suggested that inconsistencies in human islet yield and viability after collagenase digestion is attributed to the activation of endogenous enzymes of the cadaveric donor pancreas. A study of the enzyme kinetics of serine proteases throughout human islet isolations showed a significant increase in activity levels throughout the digestion period. Following the digestion, it is important to further inhibit these enzymes by the addition of an inhibitor to the dilution media.

AIM

To report the levels of endogenous pancreatic enzymes remaining after human islet isolation and the effects of three potential enzyme inhibitors on the proteases.

METHODOLOGY

Human albumin, fetal calf serum, and the protease inhibitor aprotinin were incubated with the trypsin, chymotrypsin, elastase, and collagenase and were assayed for activity.

RESULTS

Results at the final stage indicated that chymotrypsin retained 21.0 +/- 7.5% (mean +/- SE; n = 20) of the activity observed at the conclusion of the enzymatic digestion phase of the isolation process, whereas trypsin, elastase, and collagenase retained 3.0 +/- 1.5%, 2.1 +/- 0.6%, and 3.9 +/- 0.9%, respectively. Fetal calf serum and aprotinin showed strong inhibitory effects against bovine pancreatic trypsin; however, they showed a weak inhibitory effect against elastase. Supplementation with aprotinin failed to inhibit human chymotrypsin and elastase. Human albumin showed minimal inhibition and was shown to serve only as a competitive inhibitor. No inhibition to collagenase was observed with human albumin, fetal calf serum, or aprotinin.

CONCLUSIONS

This study clearly demonstrates that low amounts of endogenous pancreatic enzymes remain active throughout the human islet isolation process and that the added inhibitors at the end of the isolation process are not fully effective at inhibiting the enzymes.

Pancreas: healing response in critical illness

OBJECTIVE

The pathophysiology of acute pancreatitis represents a diverse mix of congenital, hereditary, and acquired problems associated with or causing acute pancreatic inflammation. Acute pancreatitis is characterized by acinar cell injury that may involve regional and systemic inflammatory responses. The systemic manifestations of acute pancreatitis are responsible for the majority of pancreatitis-associated morbidity and are due to the actions of specific inflammatory cytokines. This report summarizes this pancreatic injury, the role of cytokines in the pathogenesis of acute pancreatitis, and the pancreatic healing response that follows.

DESIGN

A comprehensive literature review of experimental pancreatitis as well as reports of cytokine involvement and healing response during clinical pancreatitis was performed.

RESULTS

Histamine release, bradykinin generation, and cytokine release play a significant role during acute pancreatic inflammation. Following an experimental insult, there is rapid expression of tumor necrosis factor-alpha, interleukin-6, interleukin-1, and chemokines by pancreatic acinar cells and/or transmigrated leukocytes. Preventing the action of these mediators has a profound beneficial effect in experimental animals. Pancreatic fibrosis is a central histologic response after pancreatitis. Transient collagen deposition with acinar necrosis occurs in acute pancreatitis; in chronic pancreatitis, permanent and disorganized pancreatic fibrosis and parenchymal cell atrophy occur.

CONCLUSIONS

Inflammatory mediators are responsible for the systemic manifestations of acute pancreatitis and the associated distant organ dysfunction. After the acute injury, regeneration or pancreatic repair is characterized by decreased release of proinflammatory mediators and decreased infiltrating inflammatory cells. Differentiation and proliferation of pancreatic myofibroblasts or "stellate" cells may be responsible for increased extracellular matrix production. The predictable nature in which the inflammation and fibrosis are produced may stimulate novel approaches to disease treatment.

Urinary amino-terminal propeptide of type III procollagen (PIIINP) as a marker of interstitial fibrosis in renal transplant recipients

BACKGROUND

Interstitial fibrosis in the protocol biopsy specimens of transplanted kidneys is regarded as the most reliable predictor of future impaired renal function. Type I and III collagens are the main components of renal fibrosis. During the synthesis and deposition of type III collagen, an amino-terminal propeptide (PIIINP) of a molecular weight of 44 kDa is degraded from the collagen and secreted into surroundings. Increased circulating PIIINP has been shown to reflect ongoing fibrotic processes.

METHODS

The extent of interstitial fibrosis in 6-month protocol biopsy specimens was recorded, and the urinary excretion of PIIINP in 24-hr urine specimens was measured in 79 graft patients. We also measured the urinary excretion of transforming growth factor (TGF)-beta 1, alpha(1)-microglobulin (alpha(1)M), and albumin and recorded the changes in creatinine clearance during 0.5 to 6 (mean, 4.3) posttransplant follow-up years.

RESULTS

The urinary excretion of PIIINP was significantly lower in patients with no interstitial fibrosis compared with patients with mild or moderate interstitial fibrosis (P<0.01). The urinary PIIINP-to-creatinine ratio correlated closely with the extent of interstitial fibrosis (r=0.410, P<0.001), with TGF-beta 1-to-creatinine (r=0.585, P<0.001) and alpha(1)M-to-creatinine (r=0.438, P<0.001) but not with the albumin-to-creatinine ratio. There was a close correlation between urinary TGF-beta 1 and alpha(1)M (r=0.508, P<0.001), whereas no correlation was found between urinary and serum PIIINP or between urinary PIIINP-to-creatinine ratio and glomerular filtration rate (GFR). During the follow-up, the GFR decreased in 42% of patients with a PIIINP-to-creatinine ratio over 100 ng/mmol, but only in 8% of patients with a ratio less than 100 ng/mmol (P<0.01).

CONCLUSIONS

These findings show that the urinary PIIINP-to-creatinine ratio reflects the ongoing fibrotic processes in the kidney. Tubular epithelial cell injury may initiate the fibrotic processes, and elevated concentrations of urinary TGF-beta 1 and alpha(1)M may associate with the increased production and deposition of collagen type III in the graft. We conclude that measurements of urinary excretion of PIIINP can be used as an early noninvasive indicator of renal fibrosis after kidney transplantation.

Inhibition of pancreatic stellate cell activation by the hydroxymethylglutaryl coenzyme A reductase inhibitor lovastatin

Pancreatic stellate cells (PSCs) play a key role in pancreatic fibrosis, a constant feature of chronic pancreatitis. PSC activation occurs in response to profibrogenic mediators such as cytokines and involves proliferation, transition towards a myofibroblastic phenotype and enhanced production of extracellular matrix proteins. Previously, we have shown that PSC activation correlates with the activity of the Ras-Raf-ERK (extracellular signal-regulated kinase) signalling cascade [Gut 51 (2002) 579]. Using a rat culture model of PSCs, we have now evaluated the effects of lovastatin, a hydroxymethylglutaryl coenzyme A reductase inhibitor that interferes with protein isoprenylation, on PSC viability and activation as well as on signalling through Ras proteins. Apoptotic cells were detected applying the TUNEL assay. Proliferation of PSCs was quantitated using the bromodeoxyuridine DNA incorporation assay. Expression of alpha-smooth muscle actin (an indicator of the myofibroblastic phenotype), ERK activation and membrane translocation of the Ras superfamily member RhoA were analysed by immunoblotting. Lovastatin inhibited serum- and platelet-derived growth factor-stimulated PSC proliferation in a dose-dependent manner. At drug concentrations above the level required for growth inhibition, a strong increase of apoptotic cells was observed. Furthermore, lovastatin inhibited induction of alpha-smooth muscle actin expression in the course of primary culture. Immunoblot experiments indicated that lovastatin suppressed both Ras-mediated ERK 1/2 activation and platelet-derived growth factor-induced membrane translocation of RhoA. Together, our data suggest that lovastatin, through the interruption of Ras signalling, interferes with PSC activation. The antifibrotic efficiency of statins should be tested in animal models of chronic pancreatitis.

Bezafibrate, a peroxisome proliferator-activated receptor (PPAR)-alpha activator, prevents pancreatic degeneration in obese and diabetic rats

INTRODUCTION

Damage to the exocrine pancreas has been observed in patients and animals with hyperlipidemia and hyperglycemia. Bezafibrate, a peroxisome proliferator-activated receptor (PPAR)-alpha activator, has been shown to improve lipid and glucose metabolism, and to interfere with the inflammatory response.

AIM

To examine the effects of bezafibrate on exocrine pancreas in hyperlipidemic obese and diabetic Otsuka Long-Evans Tokushima Fatty (OLETF) rats that have no cholecystokinin-1 receptor gene expression.

METHODOLOGY

One group of rats (n = 8) received a bezafibrate-rich diet (150 mg/100 g normal chow) from 12 weeks of age until 30 weeks of age, whereas a control group (n = 8) received standard rat chow.

RESULTS

Bezafibrate treatment significantly reduced serum triglyceride, total cholesterol, and free fatty acids levels and significantly increased the pancreatic wet weight (1,145 +/- 54 vs 874 +/- 33 mg/rat, p < 0.01), and protein (169 +/- 7 vs 128 +/- 11 mg/pancreas p < 0.01) and enzyme contents in the pancreas compared with those in untreated control rats. Immunohistochemical studies of the pancreas showed that expression of proinflammatory cytokines such as tumor necrosis factor-alpha, interleukin-1beta and interleukin-6, and alpha-smooth muscle actin in bezafibrate-treated rats was greatly suppressed compared with that in the untreated control rats. The histopathologic changes such as vacuolar degeneration and tubular complexes observed in the control rat pancreas were markedly improved in bezafibrate-treated rats.

CONCLUSIONS

Our results suggest that bezafibrate reduces hyperlipidemia, inhibits pancreatic inflammation, and prevents pancreatic degeneration in obese and diabetic OLETF rats.

Matrix metalloproteinase-1 and cytokines in patients with acute pancreatitis

INTRODUCTION

Hypercytokinemia is known to occur in severe acute pancreatitis, suggesting that the production, deposition, and degradation of the extracellular matrix (ECM) occur actively as a result of the actions of the complicated cytokine network.

AIMS AND METHODOLOGY

To examine the influence of cytokines and growth factors on the ECM in acute pancreatitis from the points of view of the severity of the disease, the complication of multiple organ dysfunction syndrome (MODS), and the prognosis, 25 patients with acute pancreatitis were divided into three groups according to the severity of the condition as assessed by the Ranson score. The serum levels of matrix metalloproteinase (MMP)-1, tissue inhibitor of metalloproteinases (TIMP)-1, the MMP-1.TIMP-1 complex, tumor necrosis factor (TNF)-alpha, and transfer growth factor (TGF)-beta1 were determined by enzyme-linked immunosorbent assay.

RESULTS

Comparison of the three groups divided according to the severity of the disease revealed significant differences in the levels of MMP-1 and TNF-alpha among the three groups, with the levels being higher in patients with more severe disease. The TIMP-1/MMP-1 ratio and the TGF-beta1 levels were found to be significantly lower in patients with more severe disease. Comparison between the group with the complication of MODS and the group without the complication showed that the levels of MMP-1, the MMP-1.TIMP-1 complex, and TNF-alpha were significantly higher in the former group than in the latter group. The TIMP-1/MMP-1 ratio and the TGF-beta1 levels were significantly lower in the group with the complication of MODS than in the group without the complication. Comparison between the nonsurvivor group and the survivor group revealed significantly higher levels of MMP-1, TIMP-1, and TNF-alpha in the nonsurvivors than in the survivors. The TIMP-1/MMP-1 ratio and the TGF-beta1 levels were significantly higher in the survivors than in the nonsurvivors. A significant correlation was observed between MMP-1 levels and TNF-alpha levels. On the other hand, a significant negative correlation was noted between MMP-1 levels and TGF-beta1 levels.

CONCLUSION

The results of our study suggest that the activity of the ECM catabolic enzyme MMP-1 and cytokines are related to the development of acute pancreatitis.

Differential roles of signaling pathways for proliferation and migration of rat pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) have recently been implicated in the pathogenesis of pancreatic fibrosis and inflammation. Accumulation of PSCs is a fundamental feature of pancreatic fibrosis, and platelet-derived growth factor (PDGF)-BB is the most potent mitogen for PSCs. But, the molecular mechanisms responsible for PDGF's actions in PSCs are largely unknown. In hepatic stellate cells, it has been established that activation of both phosphatidylinositol (PI) 3-kinase and extracellular-signal regulated kinase (ERK) pathways is required for PDGF-BB-induced proliferation and migration. The aim of this study was to elucidate the signaling pathways mediating PDGF-BB's actions in PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype. Culture-activated PSCs expressed PDGF alpha- and beta-receptors. PDGF-BB induced autophosphorylation of its receptor, followed by the activation of PI 3-kinase, Akt, and ERK pathways. Activation of PI 3-kinase was not required for PDGF-BB-induced ERK activation. PDGF-BB induced approximately five-fold increase in proliferation and chemotaxis of PSCs. Inhibition of ERK pathway with PD98059 completely blocked proliferation, whereas PD98059 had a modest inhibitory effect on cell migration (approximately 50%). On the other hand, inhibition of PI 3-kinase pathway with wortmannin or LY294002 almost completely inhibited migration, but did not affect proliferation of PSCs. In conclusion, our results suggest that ERK pathway regulates proliferation and migration in response to PDGF-BB, whereas PI 3-kinase mediates cellular migration, but not proliferation of PSCs.

Inhibition of p38 mitogen-activated protein kinase blocks activation of rat pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) have recently been implicated in the pathogenesis of pancreatic fibrosis and inflammation. However, the signal transduction pathways in PSCs remain largely unknown. We examined the role of p38 mitogen-activated protein (MAP) kinase in the activation of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype. Activation of p38 MAP kinase was determined by Western blotting using anti-phosphospecific antibody. The effects of two p38 MAP kinase inhibitors, 4-(4-flurophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)imidazole (SB203580) and 4-(4-flurophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)1H-imidazole (SB202190), on the parameters of PSC activation, including proliferation, expression of alpha-smooth muscle actin, alpha1(I) procollagen, and prolyl 4-hydroxylase (alpha) genes, and monocyte chemoattractant protein-1 production were evaluated. Interleukin-1beta and platelet-derived growth factor-BB activated p38 MAP kinase. Platelet-derived growth factor-induced PSC proliferation was inhibited by SB203580 and SB202190. These reagents decreased alpha-smooth muscle actin protein expression, and alpha1(I) procollagen and prolyl 4-hydroxylase (alpha) mRNA levels. Treatment with these p38 MAP kinase inhibitors also resulted in inhibition of monocyte chemoattractant protein-1 expression. In addition, SB203580 inhibited spontaneous activation of freshly isolated PSCs in culture on plastic. Thus, inhibition of p38 MAP kinase modulated profibrogenic and proinflammatory actions in PSCs, implying a potential application of p38 MAP kinase inhibitors for the treatment of pancreatic fibrosis and inflammation.

Establishment and characterization of a simian virus 40-immortalized rat pancreatic stellate cell line

Activated pancreatic stellate cells (PSCs) have recently been implicated in the pathogenesis of pancreatic fibrosis and inflammation. Primary PSCs can be subcultured only several times because of their limited growth potential. A continuous cell line would be valuable in studying molecular mechanisms of these pancreatic disorders. The aim of this study was to establish an immortalized cell line of rat PSCs. PSCs were isolated from the pancreas of male Wistar rats, and the simian virus 40 T antigen was introduced to PSCs by retrovirus-mediated gene transfer. This procedure yielded an actively growing cell line, designated as SAM-K. This cell line has been passaged repeatedly for almost 2 years, and is thus likely immortalized. SAM-K cells retained morphological characteristics of primary PSCs, and expressed alpha-smooth muscle actin, glial fibrillary acidic protein, type I collagen, fibronectin, and prolyl hydroxylases. The level of p53 expression was very high in SAM-K cells. Proliferation of SAM-K cells was stimulated by serum and platelet-derived growth factor-BB. Interleukin-1beta (IL-1beta) activated nuclear factor-kappaB, activator protein-1, and three classes of mitogen-activated protein (MAP) kinases: extracellular signal-regulated kinase1/2, c-Jun N-terminal kinase, and p38 MAP kinase. IL-1beta induced expression of intercellular adhesion molecule-1 and monocyte chemoattractant protein-1, both of which were abolished in the presence of pyrrolidine dithiocarbamate, a specific inhibitor of nuclear factor-kappaB activation. IL-1beta-induced monocyte chemoattractant protein-1 was partially inhibited by specific inhibitors of MAP kinase kinase (U0126) and of p38 MAP kinase (SB203580) whereas intercellular adhesion molecule-1 expression was not altered by the inhibitors. Thus, SAM-K would be useful for in vitro studies of cell biology and signal transduction of PSCs.

Apoptosis in activated rat pancreatic stellate cells

Proliferation and matrix synthesis by activated pancreatic stellate cells (PSC) participate in the development of chronic pancreatitis. Apoptosis of PSC may terminate this process but has not yet been studied in this particular cell type and was the aim of the present study. PSC were isolated from rat pancreas and characterized for expression of glial fibrillary acidic protein, alpha-smooth muscle actin, CD95, and tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL) receptors. Apoptosis was determined by TdT-UTP nick end-labeling reaction, annexin V binding, and caspase-8 activation. Both CD95L and TRAIL induced apoptosis in PSC. The apoptotic response was minor in PSC cultured for 7 days but increased markedly thereafter. Sensitization of PSC with culture duration was accompanied by increased expression of CD95 and TRAIL receptor 2 and no alterations of Flip expression or protein kinase B phosphorylation but was paralleled by the appearance of a COOH-terminal cleavage product of receptor-interacting protein. PSC apoptosis was also induced by PK-11195, a ligand of the peripheral benzodiazepine receptor. PSC apoptosis may be important in terminating the wound-healing response after pancreas injury and exhibits features distinct from apoptosis induction in hepatic stellate cells.

Pancreatic stellate cell activation and MMP production in experimental pancreatic fibrosis

BACKGROUND

The early events in pancreatic fibrosis are poorly understood. We examined the production of collagen and matrix metalloproteinases as well as the activation of pancreatic stellate cells in a rodent model of pancreatic fibrosis.

MATERIALS AND METHODS

Pancreatitis was induced in rats by hyperstimulation with cerulein (50 microg/kg/day ip) and concurrent pancreatic duct obstruction (SHOP model) for 96 h (n = 48). Sham animals were injected with saline and underwent laparotomy and manipulation of the pancreas with no duct obstruction (n = 28). Rats were sacrificed daily for 18 days. Serial pancreatic sections were stained with H&E [histology], trichrome [collagen], and alpha smooth muscle actin (alpha-SMA) antibodies [activated stellate cells]. Total pancreatic matrix metalloproteinase (MMP)-2 and 9 were determined by gelatin zymography. MMP-1 production was examined using Western blotting.

RESULTS

There were occasional alpha-SMA-positive cells in the pancreatic parenchyma of normal and sham animals. Within 48 h of pancreatitis induction in SHOP animals, histologic evidence of pancreatic inflammation was present, and stellate cells (alpha-SMA-positive cells) appeared surrounding pancreatic acini. The appearance of these cells was followed by collagen deposition in the same area. MMP-1 and 2 proteins increased significantly during pancreatitis while MMP-9 did not. The pancreatic architecture returned to normal by 18 days after the induction of pancreatitis.

CONCLUSION

Acute pancreatic inflammation results in stellate cell activation and collagen deposition in the same area. Collagen is then resorbed at a time when MMP-1 and 2 peak. The fibrosis of acute pancreatic inflammation in this model completely resolves with restoration of normal architecture.

Current insights into the pathogenesis of acute and chronic pancreatitis

For a long time the pathogenesis of pancreatitis has remained enigmatic. Recent developments in cellular and molecular biology, however, have provided a tremendous research impetus and some of its mysteries are finally being disclosed. This review discusses the implications of the discovery of the disease gene in hereditary pancreatitis and outlines recent advances in our understanding of the mechanism and site of trypsinogen activation and the role of immunocytes and cytokines in acute pancreatitis. With respect to chronic pancreatitis, this review focuses on its association with mutations in the cystic fibrosis conductance regulator gene and the mechanisms of pancreatic fibrosis. These advances in our knowledge of the pathogenesis of the disease, together with emerging biotechnological techniques, will boost the development of future therapies aimed at strategically targeting key pathophysiological processes involved in acute and chronic pancreatitis.

Myofibroblasts are responsible for the desmoplastic reaction surrounding human pancreatic carcinomas

BACKGROUND

The cell type responsible for the desmoplastic reaction surrounding human pancreatic carcinoma is unknown. Hepatic stellate cells, which activate to a myofibroblast-like form, are responsible for collagen deposition in cirrhosis and around hepatocellular carcinomas. Recently, pancreatic stellate cells have been described and implicated in the fibrosis of chronic pancreatitis. We sought to determine whether these cells are responsible for the scirrhous reaction surrounding pancreatic adenocarcinomas.

METHODS

Archival formalin-fixed, paraffin-embedded pancreatic tissues from 10 patients undergoing pancreaticoduodenectomy for ductal adenocarcinoma and from 2 patients with pancreatic islet cell tumors were examined immunohistochemically for alpha-smooth muscle actin (alpha-SMA), smooth muscle myosin heavy chain (SMMHC), procollagen I, collagen IV, and endothelial cell markers, von Willebrand factor and cluster of differentiation 31.

RESULTS

In non-neoplastic areas, staining for alpha-SMA and SMMHC was confined to interlobular septal regions. In contrast, the desmoplastic reaction surrounding all 10 pancreatic adenocarcinoma specimens displayed intense interstitial staining for alpha-SMA, SMMHC, and collagen IV but no staining for von Willebrand factor and cluster of differentiation 31. Procollagen I staining localized intracellularly to fibroblast-shaped cells within this alpha-SMA/SMMHC-positive scirrhous region. Islet cell tumors demonstrated an increase in alpha-SMA staining, although this was not as marked as in ductal adenocarcinomas.

CONCLUSIONS

A massive increase in myofibroblast activity, compatible with the activation of stellate cells, is associated with the deposition of collagen types I and IV in the desmoplastic reaction around pancreatic adenocarcinomas.

Identification of mediators stimulating proliferation and matrix synthesis of rat pancreatic stellate cells

The aim of this study was to identify fibrogenic mediators stimulating activation, proliferation, and/or matrix synthesis of rat pancreatic stellate cells (PSC). PSC were isolated from the pancreas of normal Wistar rats and from rats with cerulein pancreatitis. Cell activation was demonstrated by immunofluorescence microscopy of smooth muscle alpha-actin (SMA) and real-time quantitative RT-PCR of SMA, fibronectin, and transforming growth factor (TGF)-beta(1). Proliferation was measured by bromodeoxyuridine incorporation. Matrix synthesis was demonstrated on the protein and mRNA level. Within a few days in primary culture, PSC changed their phenotype from fat-storing to SMA-positive myofibroblast-like cells expressing platelet-derived growth factor (PDGF) alpha- and PDGF beta-receptors. TGF-beta(1) and tumor necrosis factor (TNF)-alpha accelerated the change in the cells' phenotype. Addition of 50 ng/ml PDGF and 5 ng/ml basic fibroblast growth factor (bFGF) to cultured PSC significantly stimulated cell proliferation (4.37 +/- 0.49- and 2.96 +/- 0.39-fold of control). Fibronectin synthesis calculated on the basis of DNA was stimulated by 5 ng/ml bFGF (3.44 +/- 1.13-fold), 5 ng/ml TGF-beta(1) (2.46 +/- 0.89-fold), 20 ng/ml PDGF (2.27 +/- 0.68-fold), and 50 ng/ml TGF-alpha (1.87 +/- 0.19-fold). As shown by RT-PCR, PSC express predominantly the splice variant EIII-A of fibronectin. Immunofluorescence microscopy and Northern blot confirmed that in particular bFGF and TGF-beta(1) stimulated the synthesis of fibronectin and collagens type I and III. In conclusion, our data demonstrate that 1) TGF-beta(1) and TNF-alpha accelerate the change in the cell phenotype, 2) PDGF represents the most effective mitogen, and 3) bFGF, TGF-beta(1), PDGF, and, to a lesser extent, TGF-alpha stimulate extracellular matrix synthesis of cultured rat PSC.

Differential effects of transforming growth factor-beta1, a fibrogenic factor, on macrophage-like cells (HS-P) and myofibroblastic cells (MT-9) in vitro

Transforming growth factor-beta1 (TGF-beta1) produced by infiltrating macrophages plays a role in fibrotic disorders through the induction of myofibroblasts. To explore possible mechanisms by which TGF-beta1 may act in this context, we investigated effects of TGF-beta1 on macrophage-like (HS-P) and myofibroblastic (MT-9) cells, two novel cell lines developed by us. Immunocytochemically, the addition of TGF-beta1 (0, 0.1, 0.5, and 1.0 ng/ml) dose-dependently suppressed the expressions of antigens recognized by macrophage/histiocyte-specific antibodies (ED1 and ED2) in HS-P cells, whereas the addition concomitantly increased the number of anti-alpha-smooth muscle actin antibody-positive myofibroblastic cells, suggesting a possible phenotypical modulation of macrophages into myofibroblasts in the fibrotic lesions. By contrast, MT-9 cells did not show such immunophenotypical changes following TGF-beta1 addition. DNA synthesis, measured by tritiated thymidine-incorporation, was inhibited in a dose-dependent manner in MT-9 cells by TGF-beta1 addition (0, 0.1, 0.2, 0.5, 1.0, 5, and 10 ng/ml), but that in HS-P cells was unchanged. Northern blot analysis revealed that expressions of cell cycle-related early genes, c-jun and c-myc, were increased in HS-P cells after TGF-beta1 (1 ng/ml) addition, with c-jun showing peak expression prior to c-myc. By contrast, the peak expressions of c-jun and c-myc were delayed in TGF-beta1 (1 ng/ml)-added MT-9 cells, and their levels were less in MT-9 cells than in HS-P cells. Furthermore, TGF-beta1 (1 and 10 ng/ml) induced DNA laddering in MT-9 cells, but did not in HS-P cells. Based on these findings, it was speculated that TGF-beta1 could have induced G1 arrest in cell cycle and apoptosis in MT-9 cells. The present study showed that there were significant differences in the effects of TGF-beta1 between macrophage-like HS-P cells and myofibroblastic MT-9 cells, presumably depending on divergent susceptibilities to TGF-beta1 between both cell types. Because such cell types are key cells in the fibrogenesis, HS-P and MT-9 might be useful models for investigating the pathogenesis of fibrosis in vitro.