A c-Jun NH2-Terminal Kinase Inhibitor SP600125 (Anthra[1,9-cd]pyrazole-6 (2H)-one) Blocks Activation of Pancreatic Stellate Cells

Nintedanib Alleviates Chronic Pancreatitis by Inhibiting the Activation of Pancreatic Stellate Cells via the JAK/STAT3 and ERK1/2 Pathways

BACKGROUND

Nintedanib (Ninte) has been approved for the treatment of pulmonary fibrosis, and whether it can ameliorate chronic pancreatitis (CP) is unknown.

AIMS

This study was conducted to investigate the effect and molecular mechanism of Ninte on pancreatic fibrosis and inflammation in vivo and in vitro.

METHODS

The caerulein-induced CP model of murine was applied, and Ninte was orally administered. Pathological changes in pancreas were evaluated using hematoxylin & eosin, Sirius Red, Masson's trichrome, and anti-Ki-67 staining. For in vitro studies, the effects of Ninte on cell viability, apoptosis, and migration of pancreatic stellate cells (PSCs) were determined by CCK-8, flow cytometry, and wound healing assays, respectively. The potential molecular mechanisms of the effects of Ninte on PSCs were analyzed by RNA-Seq and verified at the gene expression and protein activity levels by qRT-PCR and Western Blot.

RESULTS

Ninte significantly alleviated the weight loss in mice with caerulein-induced CP and simultaneously attenuated the pancreatic damage, as evidenced by reduced acinar atrophy, collagen deposition, infiltration of inflammatory cells, and inhibited cell proliferation/regeneration. Besides, Ninte markedly suppressed the transcription of fibrogenic and proinflammatory genes in pancreatic tissues. Further in vitro studies showed that Ninte significantly inhibited the transcription and protein expression of genes corresponding to fibrogenesis and proliferation in PSCs. The results of RNA-Seq analysis and subsequent verification assays indicated that Ninte inhibited the activation and proliferation of PSCs via the JAK/STAT3 and ERK1/2 pathways.

CONCLUSIONS

These findings indicate that Ninte may be a potential anti-inflammatory and anti-fibrotic therapeutic agent for CP.

Pancreatic Stellate Cells and the Targeted Therapeutic Strategies in Chronic Pancreatitis

Chronic pancreatitis (CP) is a disease characterized by inflammatory recurrence that accompanies the development of pancreatic fibrosis. As the mystery of CP pathogenesis is gradually revealed, accumulating evidence suggests that the activation of pancreatic stellate cells (PSCs) and the appearance of a myofibroblast-like phenotype are the key gatekeepers in the development of CP. Targeting PSCs to prevent their activation and conversion to a myofibroblast-like phenotype, as well as increasing antioxidant capacity to counteract ongoing oxidative stress, are effective strategies for preventing or treating CP. Therefore, we reviewed the crosstalk between CP and pancreatic fibrosis, summarized the activation mechanisms of PSCs, and investigated potential CP therapeutic strategies targeting PSCs, including, but not limited to, anti-fibrosis therapy, antioxidant therapy, and gene therapy. Meanwhile, the above therapeutic strategies are selected in order to update the available phytopharmaceuticals as novel complementary or alternative approaches for the prevention and treatment of CP to clarify their potential mechanisms of action and their relevant molecular targets, aiming to provide the most comprehensive therapeutic treatment direction for CP and to bring new hope to CP patients.

Molecular mechanisms of pancreatic myofibroblast activation in chronic pancreatitis and pancreatic ductal adenocarcinoma

Pancreatic fibrosis (PF) is an essential component of the pathobiology of chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC). Activated pancreatic myofibroblasts (PMFs) are crucial for the deposition of the extracellular matrix, and fibrotic reaction in response to sustained signaling. Consequently, understanding of the molecular mechanisms of PMF activation is not only critical for understanding CP and PDAC biology but is also a fertile area of research for the development of novel therapeutic strategies for pancreatic pathologies. This review analyzes the key signaling events that drive PMF activation including, initiating signals from transforming growth factor-β1, platelet derived growth factor, as well as other microenvironmental cues, like hypoxia and extracellular matrix rigidity. Further, we discussed the intracellular signal events contributing to PMF activation, and crosstalk with different components of tumor microenvironment. Additionally, association of epidemiologically established risk factors for CP and PDAC, like alcohol intake, tobacco exposure, and metabolic factors with PMF activation, is discussed to comprehend the role of lifestyle factors on pancreatic pathologies. Overall, this analysis provides insight into the biology of PMF activation and highlights salient features of this process, which offer promising therapeutic targets.

Chaihu Guizhi Ganjiang Decoction Ameliorates Pancreatic Fibrosis via JNK/mTOR Signaling Pathway

Pancreatic fibrosis is a pathological characteristic of chronic pancreatitis (CP) and pancreatic cancer. Chaihu Guizhi Ganjiang Decoction (CGGD) is a traditional Chinese medicine, which is widely used in the clinical treatment of digestive diseases. However, the potential anti-fibrosis mechanism of CGGD in treating CP remains unclear. Here, we conducted a series of experiments to examine the effect of CGGD on the CP rat model and primary isolated pancreatic stellate cells (PSCs). The results revealed that CGGD attenuated pancreatic damage, decreased collagen deposition, and inhibited PSC activation in the pancreas of CP rats. However, compared with the CP group, CGGD had no effect on body weight and serum amylase and lipase. In addition, CGGD suppressed autophagy by downregulating Atg5, Beclin-1, and LC3B and facilitated phosphorylation of mTOR and JNK in pancreatic tissues and PSCs. Moreover, the CGGD-containing serum also decreased LC3B or collagen I expression after rapamycin (mTOR inhibitor) or SP600125 (JNK inhibitor) treatment in PSCs. In conclusion, CGGD attenuated pancreatic fibrosis and PSC activation, possibly by suppressing autophagy of PSCs through the JNK/mTOR signaling pathway.

Isoliquiritigenin ameliorates caerulein-induced chronic pancreatitis by inhibiting the activation of PSCs and pancreatic infiltration of macrophages

Chronic pancreatitis (CP) is characterized by persistent inflammation of the pancreas that results in progressive loss of the endocrine and exocrine compartment owing to atrophy and/or replacement with fibrotic tissue. Currently, the clinical therapeutic scheme of CP is mainly symptomatic treatment including pancreatic enzyme replacement, glycaemic control and nutritional support therapy, lacking of specific therapeutic drugs for prevention and suppression of inflammation and fibrosis aggravating in CP. Here, we investigated the effect of isoliquiritigenin (ILG), a chalcone-type dietary compound derived from licorice, on pancreatic fibrosis and inflammation in a model of caerulein-induced murine CP, and the results indicated that ILG notably alleviated pancreatic fibrosis and infiltration of macrophages. Further in vitro studies in human pancreatic stellate cells (hPSCs) showed that ILG exerted significant inhibition on the proliferation and activation of hPSCs, which may be due to negative regulation of the ERK1/2 and JNK1/2 activities. Moreover, ILG significantly restrained the M1 polarization of macrophages (RAW 264.7) via attenuation of the NF-κB signalling pathway, whereas the M2 polarization was hardly affected. These findings indicated that ILG might be a potential anti-inflammatory and anti-fibrotic therapeutic agent for CP.

Molecular Mechanism of Pancreatic Stellate Cells Activation in Chronic Pancreatitis and Pancreatic Cancer

Activated pancreatic stellate cells (PSCs) are the main effector cells in the process of fibrosis, a major pathological feature in pancreatic diseases that including chronic pancreatitis and pancreatic cancer. During tumorigenesis, quiescent PSCs change into an active myofibroblast-like phenotype which could create a favorable tumor microenvironment and facilitate cancer progression by increasing proliferation, invasiveness and inducing treatment resistance of pancreatic cancer cells. Many cellular signals are revealed contributing to the activation of PSCs, such as transforming growth factor-β, platelet derived growth factor, mitogen-activated protein kinase (MAPK), Smads, nuclear factor-κB (NF-κB) pathways and so on. Therefore, investigating the role of these factors and signaling pathways in PSCs activation will promote the development of PSCs-specific therapeutic strategies that may provide novel options for pancreatic cancer therapy. In this review, we systematically summarize the current knowledge about PSCs activation-associated stimulating factors and signaling pathways and hope to provide new strategies for the treatment of pancreatic diseases.

Respective roles of the mitogen-activated protein kinase (MAPK) family members in pancreatic stellate cell activation induced by transforming growth factor-β1 (TGF-β1)

Activated pancreatic stellate cells (PSCs) play a crucial role in the progression of pancreatic fibrosis. Transforming growth factor-β (TGF-β) is one of the strongest stimulator inducing fibrosis. The mitogen-activated protein kinase (MAPK) proteins (including ERK, JNK and p38 MAPK) are known to contribute to PSC activation and pancreatic fibrosis. Previous studies have identified PSC activation induced by TGF-β1 is related to MAPK pathway, but the respective role of MAPK family members in PSC activation still unclear, and which family member may be the key mediator in mice PSC activation still controversial. In this study, we investigated the influence of different MAPK family member (JNK, ERK, and p38 MAPK) on mice PSC activation using an in vivo and in vitro model. The results showed p-JNK, p-ERK and p-p38 MAPK were all over-expressed in CP group, and p-JNK, p-ERK, and p-p38 MAPK were co-expressed with activated PSC. In vitro, TGF-β1 induced JNK and ERK over-expression in PSCs. In contrast, p38 MAPK expression in PSC showed only a very weak increase. JNK- and ERK-specific inhibitors inhibited FN and α-SMA mRNA expression in PSCs, and a p38 MAPK inhibitor had no effect on PSC activation. These findings indicate that JNK and ERK were directly involved in the PSCs activation induced by TGF-β1 and the development of pancreatic fibrosis. p38 MAPK participate in the progression of CP, but it does not respond to TGF-β1 directly and may not be regarded as the target of TGF-β1 induced PSC activation.

Senescent fibroblast-derived Chemerin promotes squamous cell carcinoma migration

Aging is associated with a rising incidence of cutaneous squamous cell carcinoma (cSCC), an aggressive skin cancer with the potential for local invasion and metastasis. Acquisition of a senescence-associated secretory phenotype (SASP) in dermal fibroblasts has been postulated to promote skin cancer progression in elderly individuals. The underlying molecular mechanisms are largely unexplored. We show that Chemerin, a previously unreported SASP factor released from senescent human dermal fibroblasts, promotes cSCC cell migration, a key feature driving tumor progression. Whereas the Chemerin abundance is downregulated in malignant cSCC cells, increased Chemerin transcripts and protein concentrations are detected in replicative senescent fibroblasts in vitro and in the fibroblast of skin sections from old donors, indicating that a Chemerin gradient is built up in the dermis of elderly. Using Transwell^® migration assays, we show that Chemerin enhances the chemotaxis of different cSCC cell lines. Notably, the Chemerin receptor CCRL2 is remarkably upregulated in cSCC cell lines and human patient biopsies. Silencing Chemerin in senescent fibroblasts or the CCRL2 and GPR1 receptors in the SCL-1 cSCC cell line abrogates the Chemerin-mediated chemotaxis. Chemerin triggers the MAPK cascade via JNK and ERK1 activation, whereby the inhibition impairs the SASP- or Chemerin-mediated cSCC cell migration.

Taken together, we uncover a key role for Chemerin, as a major factor in the secretome of senescent fibroblasts, promoting cSCC cell migration and possibly progression, relaying its signals through CCRL2 and GPR1 receptors with subsequent MAPK activation. These findings might have implications for targeted therapeutic interventions in elderly patients.

Pancreatic stellate cell: Pandora's box for pancreatic disease biology

Pancreatic stellate cells (PSCs) were identified in the early 1980s, but received much attention after 1998 when the methods to isolate and culture them from murine and human sources were developed. PSCs contribute to a small proportion of all pancreatic cells under physiological condition, but are essential for maintaining the normal pancreatic architecture. Quiescent PSCs are characterized by the presence of vitamin A laden lipid droplets. Upon PSC activation, these perinuclear lipid droplets disappear from the cytosol, attain a myofibroblast like phenotype and expresses the activation marker, alpha smooth muscle actin. PSCs maintain their activated phenotype via an autocrine loop involving different cytokines and contribute to progressive fibrosis in chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma (PDAC). Several pathways (e.g., JAK-STAT, Smad, Wnt signaling, Hedgehog etc.), transcription factors and miRNAs have been implicated in the inflammatory and profibrogenic function of PSCs. The role of PSCs goes much beyond fibrosis/desmoplasia in PDAC. It is now shown that PSCs are involved in significant crosstalk between the pancreatic cancer cells and the cancer stroma. These interactions result in tumour progression, metastasis, tumour hypoxia, immune evasion and drug resistance. This is the rationale for therapeutic preclinical and clinical trials that have targeted PSCs and the cancer stroma.

Inflammation and pancreatic cancer: disease promoter and new therapeutic target

Chronic inflammation has a certain impact on the carcinogenesis of the digestive organs. The characteristic tissue structure of pancreatic cancer, desmoplasia, results from inflammatory processes induced by cancer cells and stromal cells. Concerning the progression of pancreatic cancer, recent research has clarified the pivotal role of tumor-stromal interaction, which promotes the development of an invasive phenotype of cancer and provides survival advantages against chemotherapeutic agents or immune surveillance. Tumor stromal cells such as pancreatic stellate cells and immune cells establish a microenvironment that protects cancer cells through complex interactions. The microenvironment of pancreatic cancer acts as a niche for pancreatic cancer stem cells from which therapy-resistance and disease recurrence develop. Inhibition of the stromal functions or restoration of the immune reaction against cancer cells has therapeutic benefits that enhance the efficacy of conventional therapies. Some of the recent advances in this field are now under evaluation in clinical settings, but many problems must be overcome to establish a radical therapy for pancreatic cancer. This review summarizes current knowledge about the tumor-promoting stromal functions, immune system modulation and therapeutic strategies targeting tumor-stromal interactions in pancreatic cancer.

JNK1 stress signaling is hyper-activated in high breast density and the tumor stroma: connecting fibrosis, inflammation, and stemness for cancer prevention

Mammography is an important screening modality for the early detection of DCIS and breast cancer lesions. More specifically, high mammographic density is associated with an increased risk of breast cancer. However, the biological processes underlying this phenomenon remain largely unknown. Here, we re-interrogated genome-wide transcriptional profiling data obtained from low-density (LD) mammary fibroblasts (n = 6 patients) and high-density (HD) mammary fibroblasts (n = 7 patients) derived from a series of 13 female patients. We used these raw data to generate a "breast density" gene signature consisting of>1250 transcripts that were significantly increased in HD fibroblasts, relative to LD fibroblasts. We then focused on the genes that were increased by ≥ 1.5-fold (P<0.05) and performed gene set enrichment analysis (GSEA), using the molecular signatures database (MSigDB). Our results indicate that HD fibroblasts show the upregulation and/or hyper-activation of several key cellular processes, including the stress response, inflammation, stemness, and signal transduction. The transcriptional profiles of HD fibroblasts also showed striking similarities to human tumors, including head and neck, liver, thyroid, lung, and breast cancers. This may reflect functional similarities between cancer-associated fibroblasts (CAFs) and HD fibroblasts. This is consistent with the idea that the presence of HD fibroblasts may be a hallmark of a pre-cancerous phenotype. In these biological processes, GSEA predicts that several key signaling pathways may be involved, including JNK1, iNOS, Rho GTPase(s), FGF-R, EGF-R, and PDGF-R-mediated signal transduction, thereby creating a pro-inflammatory, pro-proliferative, cytokine, and chemokine-rich microenvironment. HD fibroblasts also showed significant overlap with gene profiles derived from smooth muscle cells under stress (JNK1) and activated/infected macrophages (iNOS). Thus, HD fibroblasts may behave like activated myofibroblasts and macrophages, to create and maintain a fibrotic and inflammatory microenvironment. Finally, comparisons between the HD fibroblast gene signature and breast cancer tumor stroma revealed that JNK1 stress signaling is the single most significant biological process that is shared between these 2 data sets (with P values between 5.40E-09 and 1.02E-14), and is specifically associated with tumor recurrence. These results implicate "stromal JNK1 signaling" in the pathogenesis of human breast cancers and the transition to malignancy. Augmented TGF-β signaling also emerged as a common feature linking high breast density with tumor stroma and breast cancer recurrence (P = 5.23E-05). Similarities between the HD fibroblast gene signature, wound healing, and the cancer-associated fibroblast phenotype were also noted. Thus, this unbiased informatics analysis of high breast density provides a novel framework for additional experimental exploration and new hypothesis-driven breast cancer research, with a focus on cancer prevention and personalized medicine.

Therapeutic potential of perineural invasion, hypoxia and desmoplasia in pancreatic cancer

Pancreatic cancer is one of the most fatal human malignancies. Though a relatively rare malignancy, it remains one of the deadliest tumors, with an extremely high mortality rate. The prognosis of patients with pancreatic cancer remains poor; only patients with small tumors and complete resection have a chance of a complete cure. Pancreatic cancer responds poorly to conventional therapies, including chemotherapy and irradiation. Tumor-specific targeted therapy is a relatively recent addition to the arsenal of anti-cancer therapies. It is important to find novel targets to distinguish tumor cells from their normal counterparts in therapeutic approaches. In the past few decades, studies have revealed the molecular mechanisms of pancreatic tumorigenesis, growth, invasion and metastasis. The proteins that participate in the pathophysiological processes of pancreatic cancer might be potential targets for therapy. This review describes the main players in perineural invasion, hypoxia and desmoplasia and the molecular mechanisms of these pathophysiological processes.

A potential role of the JNK pathway in hyperoxia-induced cell death, myofibroblast transdifferentiation and TGF-β1-mediated injury in the developing murine lung

Background

Transforming growth factor-beta 1 (TGF-β1) has been implicated in hyperoxia-induced cell death and impaired alveolarization in the developing lung. In addition, the c-JunNH2-terminal kinase (JNK) pathway has been shown to have a role for TGF-β1-mediated effects. We hypothesized that the JNK pathway is an important regulator of hyperoxia-induced pulmonary responses in the developing murine lung.

Results

We used cultured human lung epithelial cells, fetal rat lung fibroblasts and a neonatal TGF-β1 transgenic mouse model. We demonstrate that hyperoxia inhibits cell proliferation, activates cell death mediators and causes cell death, and promotes myofibroblast transdifferentiation, in a dose-dependent manner. Except for fibroblast proliferation, the effects were mediated via the JNK pathway. In addition, since we observed increased expression of TGF-β1 by epithelial cells on exposure to hyperoxia, we used a TGF-β1 transgenic mouse model to determine the role of JNK activation in TGF-β1 induced effects on lung development and on exposure to hyperoxia. We noted that, in this model, inhibition of JNK signaling significantly improved the spontaneously impaired alveolarization in room air and decreased mortality on exposure to hyperoxia.

Conclusions

When viewed in combination, these studies demonstrate that hyperoxia-induced cell death, myofibroblast transdifferentiation, TGF-β1- and hyperoxia-mediated pulmonary responses are mediated, at least in part, via signaling through the JNK pathway.

Phenotypic changes in mouse pancreatic stellate cell Ca2+ signaling events following activation in culture and in a disease model of pancreatitis

The specific characteristics of intracellular Ca 2+ signaling and the downstream consequences of these events were investigated in mouse pancreatic stellate cells (PSC) in culture and in situ using multiphoton microscopy in pancreatic lobules. PSC undergo a phenotypic transformation from a quiescent state to a myofibroblast-like phenotype in culture. This is believed to parallel the induction of an activated state observed in pancreatic disease such as chronic pancreatitis and pancreatic cancer. By day 7 in culture, the complement of cell surface receptors coupled to intracellular Ca 2+ signaling was shown to be markedly altered. Specifically, protease-activated receptors (PAR) 1 and 2, responsive to thrombin and trypsin, respectively, and platelet-derived growth factor (PDGF) receptors were expressed only in activated PSC (aPSC). PAR-1, ATP, and PDGF receptor activation resulted in prominent nuclear Ca 2+ signals. Nuclear Ca 2+ signals and aPSC proliferation were abolished by expression of parvalbumin targeted to the nucleus. In pancreatic lobules, PSC responded to agonists consistent with the presence of only quiescent PSC. aPSC were observed following induction of experimental pancreatitis. In contrast, in a mouse model of pancreatic disease harboring elevated K-Ras activity in acinar cells, aPSC were present under control conditions and their number greatly increased following induction of pancreatitis. These data are consistent with nuclear Ca 2+ signaling generated by agents such as trypsin and thrombin, likely present in the pancreas in disease states, resulting in proliferation of "primed" aPSC to contribute to the severity of pancreatic disease.

Signal transduction in pancreatic stellate cells

Pancreatic fibrosis is a characteristic feature of chronic pancreatitis and of desmoplastic reaction associated with pancreatic cancer. For over a decade, there has been accumulating evidence that activated pancreatic stellate cells (PSCs) play a pivotal role in the development of pancreatic fibrosis in these pathological settings. In response to pancreatic injury or inflammation, quiescent PSCs undergo morphological and functional changes to become myofibroblast-like cells, which express alpha-smooth muscle actin (alpha-SMA). Activated PSCs actively proliferate, migrate, produce extracellular matrix (ECM) components, such as type I collagen, and express cytokines and chemokines. In addition, PSCs might play roles in local immune functions and angiogenesis in the pancreas. Following the initiation of activation, if the inflammation and injury are sustained or repeated, PSCs activation is perpetuated, leading to the development of pancreatic fibrosis. From this point of view, pancreatic fibrosis can be defined as pathological changes of ECM composition in the pancreas both in quantity and quality, resulting from perpetuated activation of PSCs. Because the activation and cell functions in PSCs are regulated by the dynamic but coordinated activation of intracellular signaling pathways, identification of signaling molecules that play a crucial role in PSCs activation is important for the development of anti-fibrosis therapy. Recent studies have identified key mediators of stimulatory and inhibitory signals. Signaling molecules, such as peroxisome proliferator-activated receptor-gamma (PPAR-gamma), Rho/Rho kinase, nuclear factor-kappaB (NF-kappaB), mitogen-activated protein (MAP) kinases, phosphatidylinositol 3 kinase (PI3K), Sma- and Mad-related proteins, and reactive oxygen species (ROS) might be candidates for the development of anti-fibrosis therapy targeting PSCs.

Heme oxygenase-1 inhibits the proliferation of pancreatic stellate cells by repression of the extracellular signal-regulated kinase1/2 pathway

Activation of pancreatic stellate cells (PSCs) is the key process in the development of pancreatic fibrosis, a common feature of chronic pancreatitis and pancreatic cancer. In recent studies, curcumin has been shown to inhibit PSC proliferation via an extracellular signal-regulated kinase (ERK)1/2-dependent mechanism. In addition, curcumin is a potent inducer of the cytoprotective enzyme heme oxygenase-1 (HO-1) in other cell types. Therefore, the aims of this study were to 1) characterize the effect of curcumin on HO-1 gene expression in PSCs, 2) explore whether HO-1 induction contributes to the inhibitory effect of curcumin on PSC proliferation, and 3) clarify the involvement of the mitogen-activated protein kinase (MAPK) family in this context. Cultured rat PSCs were incubated with curcumin and assessed for HO-1 up-regulation by Northern blot analysis, immunoblotting, and activity assays. The effect of HO-1 on platelet-derived growth factor (PDGF)-induced PSC proliferation and MAPK activation was determined by immunoblotting, cell proliferation assays, and cell count analyses. Curcumin induced HO-1 gene expression in PSCs in a time- and dose-dependent manner and inhibited PDGF-mediated ERK1/2 phosphorylation and PSC proliferation. These effects were blocked by treatment of PSCs with tin protoporphyrin IX, an HO inhibitor, or transfection of HO-1 small interfering RNA. Our data provide evidence that HO-1 induction contributes to the inhibitory effect of curcumin on PSC proliferation. Therefore, therapeutic up-regulation of HO-1 could represent a mode for inhibition of PSC proliferation and thus may provide a novel strategy in the prevention of pancreatic fibrosis.

Pancreatic stellate cells express Toll-like receptors

BACKGROUND

Toll-like receptors (TLRs) are proteins involved in recognition of foreign pathogen-associated molecular patterns (PAMPs) and activation of innate immunity. This study aimed to clarify whether pancreatic stellate cells (PSCs), a major profibrogenic cell type in the pancreas, expressed TLRs and responded to PAMPs.

METHODS

PSCs were isolated from rat pancreas tissue, and expression of TLRs was examined. PSCs were treated with lipoteichoic acid (a ligand for TLR2), polyinosinic-polycytidylic acid (a ligand for TLR3), lipopolysaccharide (a ligand for TLR4), or flagellin (a ligand for TLR5). The effects of the TLR ligands on key cell functions and activation of signaling pathways were examined. The ability of PSCs to perform endocytosis and phagocytosis was also examined.

RESULTS

PSCs expressed TLR2, 3, 4, and 5, as well as the associated molecules CD14 and MD2. All of the TLR ligands activated nuclear factor-kappaB, and three classes of mitogen-activated protein kinases (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase). TLR ligands induced expression of monocyte chemoattractant protein 1, cytokine-induced neutrophil chemoattractant 1 (a rat homolog of interleukin-8), and inducible nitric oxide synthase, but not proliferation or type I collagen production. PSCs could perform fluid-phase and receptor-mediated endocytosis, as well as phagocytosis of Escherichia coli.

CONCLUSIONS

PSCs expressed a variety of TLRs and responded to TLR ligands, leading to the activation of signaling pathways and proinflammatory responses. PSCs could process exogenous antigens by endocytosis and phagocytosis. PSCs might play a role in the immune functions of the pancreas through the recognition of PAMPs.

JNK MAP kinase activation is required for MTOC and granule polarization in NKG2D-mediated NK cell cytotoxicity

Interaction of the activating receptor NKG2D with its ligands is a major stimulatory pathway for cytotoxicity of natural killer (NK) cells. Here, the signaling pathway involved after NKG2D ligation is examined. Either incubation of the NKG2D-bearing human NKL tumor cell line with K562 target cells or cross-linking with NKG2D mAb induced strong activation of the mitogen-activated protein (MAP) kinases. Selective inhibition of JNK MAP kinase with four different means of inhibition greatly reduced NKG2D-mediated cytotoxicity toward target cells and furthermore, blocked the movement of the microtubule organizing center (MTOC), granzyme B (a component of cytotoxic granules), and paxillin (a scaffold protein) to the immune synapse. NKG2D-induced activation of JNK kinase was also blocked by inhibitors of Src protein tyrosine kinases and phospholipase PLCgamma, upstream of JNK. Similarly, a second MAP kinase pathway through ERK was previously shown to be required for NK cell cytotoxicity. Thus, activation of two MAP kinase pathways is required for cytotoxic granule and MTOC polarization and for cytotoxicity of human NK cells when NKG2D is ligated.

Crucial role of fibrogenesis in pancreatic diseases

Chronic pancreatitis and pancreatic cancer are characterised by a progressive fibrosis. Accumulation of extracellular matrix not only accompanies both diseases but is directly involved in their progression, suggesting inhibition of fibrogenesis as a potential therapeutic strategy. Pancreatic stellate cells (PSC) are the main extracellular matrix-producing cell type in the diseased pancreas. In response to pro-fibrogenic mediators including cytokines and ethanol metabolites, PSC undergo phenotypic changes termed activation, resulting in the exhibition of a myofibroblast-like phenotype. In the perpetuation of PSC activation, autocrine loops of mediators such as transforming growth factor beta play an important role. Most recently signal transduction pathways in PSC that are associated with the process of activation were characterised, facilitating identification of potential intracellular targets for an anti-fibrotic therapy. While some putative inhibitors of fibrogenesis have been tested in animal models of pancreatic fibrosis for their in vivo efficiency, clinical studies still remain to be performed.

The integrin-extracellular matrix axis in pancreatic cancer

Pancreatic cancer is the fifth leading cause of adult cancer death in the United States, with 5-year survival rates of only 1% to 4%. Current therapeutic strategies generally result in only a few months of extended life. Recent evidence from several independent laboratories in vitro and in vivo indicate that integrin-mediated cell attachment to the extracellular matrix (ECM), components of which are highly up-regulated in pancreatic cancer, evokes phenotypes and signaling pathways that regulate tumor cell growth and migration. In this review, we will discuss our current understanding of the role of the ECM in directing pancreatic cancer growth, progression, and metastasis. Topics covered include a survey of the existing literature regarding the in vivo and in vitro expression of the ECM and its cell surface receptors, the integrins, in pancreatic cancer; mechanisms involved in the integrin-ECM-mediated malignant phenotype; and future directions for the study of the integrin-ECM axis and its role in pancreatic cancer progression, including potential therapeutic strategies.

The pancreatic stellate cell: a star on the rise in pancreatic diseases

Pancreatic stellate cells (PaSCs) are myofibroblast-like cells found in the areas of the pancreas that have exocrine function. PaSCs are regulated by autocrine and paracrine stimuli and share many features with their hepatic counterparts, studies of which have helped further our understanding of PaSC biology. Activation of PaSCs induces them to proliferate, to migrate to sites of tissue damage, to contract and possibly phagocytose, and to synthesize ECM components to promote tissue repair. Sustained activation of PaSCs has an increasingly appreciated role in the fibrosis that is associated with chronic pancreatitis and with pancreatic cancer. Therefore, understanding the biology of PaSCs offers potential therapeutic targets for the treatment and prevention of these diseases.

Inhibitory effects of interferon-gamma on activation of rat pancreatic stellate cells are mediated by STAT1 and involve down-regulation of CTGF expression

Pancreatic stellate cells (PSCs) are the main source of extracellular matrix proteins in pancreatic fibrosis, a pathological feature of chronic pancreatitis and pancreatic cancer. Interferon-gamma (IFN-gamma) is an antifibrotic cytokine, but how precisely it exerts its effects on PSCs is largely unknown. Here, we have focussed on the role of STAT1 as well as target genes of IFN-gamma signalling. Our data indicate that IFN-gamma regulates the expression of two autocrine mediators of PSC activation, connective tissue growth factor and endothelin-1, in a transforming growth factor-beta1-antagonistic manner. STAT1 overexpression under the control of a tetracycline-dependent promoter revealed a close correlation between STAT1 expression and activation, the biological effects of IFN-gamma (growth inhibition, induction of apoptosis), and target gene expression. Our data further support the hypothesis that IFN-gamma interferes with stellate cell activation in the pancreas and suggest activated STAT1 as an inductor of a quiescent PSC phenotype.

Curcumin blocks activation of pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis and inflammation. Inhibition of activation and cell functions of PSCs is a potential target for the treatment of pancreatic fibrosis and inflammation. The polyphenol compound curcumin is the yellow pigment in curry, and has anti-inflammatory and anti-fibrotic properties. We here evaluated the effects of curcumin on the activation and cell functions of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. The effects of curcumin on proliferation, alpha-smooth muscle actin gene expression, monocyte chemoattractant protein (MCP)-1 production, and collagen expression were examined. The effect of curcumin on the activation of freshly isolated cells in culture was also assessed. Curcumin inhibited platelet-derived growth factor (PDGF)-induced proliferation, alpha-smooth muscle actin gene expression, interleukin-1beta- and tumor necrosis factor (TNF)-alpha-induced MCP-1 production, type I collagen production, and expression of type I and type III collagen genes. Curcumin inhibited PDGF-BB-induced cyclin D1 expression and activation of extracellular signal-regulated kinase (ERK). Curcumin inhibited interleukin-1beta- and TNF-alpha-induced activation of activator protein-1 (AP-1) and mitogen-activated protein (MAP) kinases (ERK, c-Jun N-terminal kinase (JNK), and p38 MAP kinase), but not of nuclear factor-kappaB (NF-kappaB). In addition, curcumin inhibited transformation of freshly isolated cells to myofibroblast-like phenotype. In conclusion, curcumin inhibited key cell functions and activation of PSCs.

Cyclooxygenase-2 is required for activated pancreatic stellate cells to respond to proinflammatory cytokines

Cyclooxygenase-2 (COX-2) mediates various inflammatory responses and is expressed in pancreatic tissue from patients with chronic pancreatitis. To examine the role of COX-2 in chronic pancreatitis, we investigated its participation in regulating functions of pancreatic stellate cells (PSCs), using isolated rat PSCs. COX-2 was expressed in culture-activated PSCs but not in freshly isolated quiescent PSCs. TGF-beta1, IL-1beta, and IL-6 enhanced COX-2 expression in activated PSCs, concomitantly increasing the expression of alpha-smooth muscle actin (alpha-SMA), a parameter of PSC activation. The COX-2 inhibitor NS-398 blocked culture activation of freshly isolated quiescent PSCs. NS-398 also inhibited the enhancement of alpha-SMA expression by TGF-beta1, IL-1beta, and IL-6 in activated PSCs. These data indicate that COX-2 is required for the initiation and promotion of PSC activation. We further investigated the mechanism by which cytokines enhance COX-2 expression in PSCs. Adenovirus-mediated expression of dominant negative Smad2/3 inhibited the increase in expression of COX-2, alpha-SMA, and collagen-1 mediated by TGF-beta1 in activated PSCs. Moreover, dominant negative Smad2/3 expression attenuated the expression of COX-2 and alpha-SMA enhanced by IL-1beta and IL-6. Anti-TGF-beta neutralizing antibody also attenuated the increase in COX-2 and alpha-SMA expression caused by IL-1beta and IL-6. IL-6 as well as IL-1beta enhanced TGF-beta1 secretion from PSCs. These data indicate that Smad2/3-dependent pathway plays a central role in COX-2 induction by TGF-beta1, IL-1beta, and IL-6. Furthermore, IL-1beta and IL-6 promote PSC activation by enhancing COX-2 expression indirectly through Smad2/3-dependent pathway by increasing TGF-beta1 secretion from PSCs.

Hydrogen peroxide activates activator protein-1 and mitogen-activated protein kinases in pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) are implicated in the pathogenesis of pancreatic inflammation and fibrosis, where oxidative stress is thought to play a key role. Reactive oxygen species such as hydrogen peroxide (H(2)O(2)) may act as a second messenger to mediate the actions of growth factors and cytokines. But the role of reactive oxygen species in the activation and regulation of cell functions in PSCs remains largely unknown. We here examined the effects of H(2)O(2) on the activation of signal transduction pathways and cell functions in PSCs. PSCs were isolated from the pancreas of male Wistar rats, and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. Activation of transcription factors was examined by electrophoretic mobility shift assay and luciferase assay. Activation of mitogen-activated protein (MAP) kinases was assessed by Western blotting using anti-phosphospecific antibodies. The effects of H(2)O(2) on proliferation, alpha(1)(I)procollagen gene expression, and monocyte chemoattractant protein-1 production were evaluated. The effect of H(2)O(2) on the transformation of freshly isolated PSCs in culture was also assessed. H(2)O(2) at non-cytotoxic concentrations (up to 100 microM) induced oxidative stress in PSCs. H(2)O(2) activated activator protein-1, but not nuclear factor kappaB. In addition, H(2)O(2) activated three classes of MAP kinases: extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAP kinase. H(2)O(2) induced alpha(1)(I)procollagen gene expression but did not induce proliferation or monocyte chemoattractant protein-1 production. H(2)O(2) did not initiate the transformation of freshly isolated PSCs to myofibroblast-like phenotype. Specific activation of these signal transduction pathways and collagen gene expression by H(2)O(2) may play a role in the pathogenesis of pancreatic fibrosis.

Galectin-1 induces chemokine production and proliferation in pancreatic stellate cells

Galectin-1 is a beta-galactoside-binding lectin. Previous studies have shown that galectin-1 was expressed in fibroblasts of chronic pancreatitis and of desmoplastic reaction associated with pancreatic cancer. These fibroblasts are now recognized as activated pancreatic stellate cells (PSCs). Here, we examined the role of galectin-1 in cell functions of PSCs. PSCs were isolated from rat pancreatic tissue and used in their culture-activated phenotype unless otherwise stated. Expression of galectin-1 was assessed by Western blot analysis, RT-PCR, and immunofluorescent staining. The effects of recombinant galectin-1 on chemokine production and proliferation were evaluated. Activation of transcription factors was assessed by EMSA. Activation of MAPKs was examined by Western blot analysis using anti-phosphospecific antibodies. Galectin-1 was strongly expressed in culture-activated but not freshly isolated PSCs. Recombinant galectin-1 increased proliferation and production of monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1. Galectin-1 activated ERK, JNK, activator protein-1, and NF-kappaB, but not p38 MAPK or Akt. Galectin-1 induced proliferation through ERK and chemokine production mainly through the activation of NF-kappaB and in part by JNK and ERK pathways. These effects of galectin-1 were abolished in the presence of thiodigalactosie, an inhibitor of beta-galactoside binding. In conclusion, our results suggest a role of galectin-1 in chemokine production and proliferation through its beta-galactoside binding activity in activated PSCs.

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.

Endothelin-1 stimulates contraction and migration of rat pancreatic stellate cells

AIM: To examine the ability of ET-1 to affect the cell functions of PSCs and the underlying molecular mechanisms.

METHODS: PSCs were isolated from the pancreas of male Wistar rats after perfusion with collagenase, and cells between passages two and five were used. Expression of ET-1 and ET receptors was assessed by reverse transcription-PCR and immunostaining. Phosphorylation of myosin regulatory light chain (MLC), extracellular-signal regulated kinase (ERK), and Akt was examined by Western blotting. Contraction of PSCs was assessed on hydrated collagen lattices. Cell migration was examined using modified Boyden chambers. Cell proliferation was assessed by measuring the incorporation of 5-bromo-2×deoxyuridine.

RESULTS: Culture-activated PSCs expressed ET_A and ET_B receptors, and ET-1. ET-1 induced phosphorylation of MLC and ERK, but not Akt. ET-1 induced contraction and migration, but did not alter proliferation of PSCs. ET-1-induced contraction was inhibited by an ET_A receptor antagonist BQ-123 and an ET_B receptor antagonist BQ-788, whereas migration was inhibited by BQ-788 but not by BQ-123. A Rho kinase inhibitor Y-27632 abolished both contraction and migration.

CONCLUSION: ET-1 induced contraction and migration of PSCs through ET receptors and activation of Rho-Rho kinase. ET_A and ET_B receptors play different roles in the regulation of these cellular functions in response to ET-1.

Ellagic acid blocks activation of pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic fibrosis and inflammation. Ellagic acid is a plant-derived polyphenol found in fruits and nuts, and has anti-oxidant and anti-inflammatory properties. But, little is known about the effects of ellagic acid on PSCs as well as on the activation of signal transduction pathways. We here evaluated the effects of ellagic acid on the activation and cell functions of PSCs. PSCs were isolated from rat pancreas tissue and used in their culture-activated, myofibroblast-like phenotype unless otherwise stated. Ellagic acid inhibited platelet-derived growth factor (PDGF)-BB-induced proliferation and migration, interleukin (IL)-1beta- and tumor necrosis factor (TNF)-alpha-induced monocyte chemoattractant protein-1 production, and expression of alpha-smooth muscle actin and collagen genes. Ellagic acid inhibited PDGF-BB-induced tyrosine phosphorylation of PDGF beta-receptor and the downstream activation of extracellular signal-regulated kinase and Akt. Ellagic acid inhibited IL-1beta- and TNF-alpha-induced activation of activator protein-1 and mitogen-activated protein kinases (extracellular signal-regulated kinase, c-Jun N-terminal kinase and p38 mitogen-activated protein kinase), but not of nuclear factor-kappaB. In addition, ellagic acid inhibited transformation of freshly isolated cells to an activated, myofibroblast-like phenotype. In conclusion, ellagic acid inhibited key cell functions and activation of PSCs.

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.

Inhibition of tumor growth, angiogenesis, and tumor cell proliferation by a small molecule inhibitor of c-Jun N-terminal kinase

c-Jun N-terminal kinase (JNK) is a member of the mitogen-activated protein kinase family, and its function is critical for signal transduction in tumor and endothelial cells. JNK is a serine/threonine protein kinase that phosphorylates c-Jun, a component of the activator protein-1 transcription factor complex. We hypothesize that inhibiting JNK will lead to the inhibition of tumor growth; therefore, we evaluated the efficacy of the recently described JNK inhibitor SP600125 [anthra[1,9-cd] pyrazol-6 (2H)-one]. SP600125 is an anthrapyrazole that is a reversible, ATP-competitive inhibitor of JNK1/2. SP600125 exhibited broad-based antiproliferative activity in human endothelial and tumor cell lines. SP600125 affects proliferation by arresting cells in the G2/M phase of the cell cycle. SP600125 also acts to inhibit endothelial cell migration. In cell lines, a correlation of cell growth inhibition with reduced JNK activity was observed. The systemic administration of SP600125 resulted in the inhibition of DU145 human prostate carcinoma xenografts and murine Lewis lung carcinoma. SP600125 also enhanced the potency of cyclophosphamide in the inhibition of Lewis lung tumor growth. These data indicate the therapeutic antitumor potential of small molecule inhibitors that act to block the cellular activity of JNK.

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.

Protease-activated receptor-2-mediated proliferation and collagen production of rat pancreatic stellate cells

Activated pancreatic stellate cells (PSCs) play a pivotal role in the pathogenesis of pancreatic inflammation and fibrosis. Trypsin and tryptase, which are agonists for protease-activated receptor-2 (PAR-2), are involved in the pathogenesis of pancreatitis. Here, we examined whether PSCs expressed PAR-2 and its agonists affect the cell functions of PSCs. PSCs were isolated from rat pancreas tissue. Expression of PAR-2 was examined by Western blotting and reverse transcription-polymerase chain reaction. Trypsin, activating peptide (SLIGRL-NH(2), corresponding to the PAR-2 tethered ligand), and tryptase were tested for their ability to affect proliferation, chemokine production, and collagen synthesis in culture-activated PSCs. Activation of mitogen-activated protein (MAP) kinases was assessed by Western blotting using antiphosphospecific antibodies. The effect of PAR-2 agonists on the activation of freshly isolated PSCs in culture was also examined. PAR-2 expression was observed in culture-activated PSCs, whereas it was undetectable in freshly isolated PSCs. PAR-2 agonists activated activator protein-1 and MAP kinases (extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 MAP kinase) but not nuclear factor kappaB. PAR-2 agonists induced proliferation of PSCs through the activation of extracellular signal-regulated kinase. PAR-2 agonists increased collagen synthesis through the activation of c-Jun N-terminal kinase and p38 MAP kinase. PAR-2 agonists did not induce the production of monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1 or initiate the transformation of freshly isolated PSCs in culture. Taken together, our results suggest a role of PAR-2 in the sustenance of pancreatic fibrosis through the increased proliferation and collagen production in PSCs.