The burning question: why is smoking a risk factor for pancreatic cancer?

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease. The prognosis is poor; less than 5% of those diagnosed are still alive five years after diagnosis, and complete remission is still rare. Tobacco smoking is a major risk factor of pancreatic cancer. However, the mechanism(s) through which it causes the disease remains unknown. Accumulating evidence indicates that carcinogenic compounds in cigarette smoke stimulate pancreatic cancer progression through induction of inflammation and fibrosis which act in concert with genetic factors leading to the inhibition of cell death and stimulation of proliferation resulting in the promotion of the PDAC.

Dangerous liaisons: pancreatic stellate cells and pancreatic cancer cells

One of the characteristic features of the majority of pancreatic ductal adenocarcinomas is an abundant desmoplastic/stromal reaction. Until recently, this stroma had received little attention from researchers studying the pathogenesis of pancreatic cancer, with most of the research focus resting on the biology of tumor cells themselves. However, evidence is now accumulating that the stroma plays a critical role in pancreatic cancer progression. The cells responsible for producing the stromal reaction in pancreatic cancer are activated pancreatic stellate cells (PSCs, the key effector cells in pancreatic fibrogenesis). In vitro and in vivo studies have convincingly demonstrated a close bi-directional interaction between PSCs and pancreatic cancer cells, which facilitates local tumor growth as well as distant metastasis. PSCs also interact closely with endothelial cells to stimulate angiogenesis and are possibly involved in the known resistance of pancreatic cancer to chemotherapy and radiation. Most interestingly, it has recently been shown that PSCs from the primary tumor can travel to distant metastatic sites where they likely facilitate the seeding, survival, and proliferation of cancer cells. Thus, it is now recognized that the stroma is an important alternative therapeutic target in this disease and concerted pre-clinical research is underway to develop strategies to modulate/deplete the stromal reaction to inhibit cancer progression. The challenge is to translate these developments into clinically applicable treatments for patients.

Retinoid signaling in pancreatic cancer, injury and regeneration

BACKGROUND

Activation of embryonic signaling pathways quiescent in the adult pancreas is a feature of pancreatic cancer (PC). These discoveries have led to the development of novel inhibitors of pathways such as Notch and Hedgehog signaling that are currently in early phase clinical trials in the treatment of several cancer types. Retinoid signaling is also essential for pancreatic development, and retinoid therapy is used successfully in other malignancies such as leukemia, but little is known concerning retinoid signaling in PC.

METHODOLOGY/PRINCIPAL FINDINGS

We investigated the role of retinoid signaling in vitro and in vivo in normal pancreas, pancreatic injury, regeneration and cancer. Retinoid signaling is active in occasional cells in the adult pancreas but is markedly augmented throughout the parenchyma during injury and regeneration. Both chemically induced and genetically engineered mouse models of PC exhibit a lack of retinoid signaling activity compared to normal pancreas. As a consequence, we investigated Cellular Retinoid Binding Protein 1 (CRBP1), a key regulator of retinoid signaling known to play a role in breast cancer development, as a potential therapeutic target. Loss, or significant downregulation of CRBP1 was present in 70% of human PC, and was evident in the very earliest precursor lesions (PanIN-1A). However, in vitro gain and loss of function studies and CRBP1 knockout mice suggested that loss of CRBP1 expression alone was not sufficient to induce carcinogenesis or to alter PC sensitivity to retinoid based therapies.

CONCLUSIONS/SIGNIFICANCE

In conclusion, retinoid signalling appears to play a role in pancreatic regeneration and carcinogenesis, but unlike breast cancer, it is not mediated directly by CRBP1.

The fibrosis of chronic pancreatitis: new insights into the role of pancreatic stellate cells

SIGNIFICANCE

Prominent fibrosis is a major histological feature of chronic pancreatitis, a progressive necroinflammatory condition of the pancreas, most commonly associated with alcohol abuse. Patients with this disease often develop exocrine and endocrine insufficiency characterized by maldigestion and diabetes. Up until just over a decade ago, there was little understanding of the pathogenesis of pancreatic fibrosis in chronic pancreatitis.

RECENT ADVANCES

In recent times, significant progress has been made in this area, mostly due to the identification, isolation, and characterization of the cells, namely pancreatic stellate cells (PSCs) that are now established as key players in pancreatic fibrogenesis. In health, PSCs maintain normal tissue architecture via regulation of the synthesis and degradation of extracellular matrix (ECM) proteins. During pancreatic injury, PSCs transform into an activated phenotype that secretes excessive amounts of the ECM proteins that comprise fibrous tissue.

CRITICAL ISSUES

This Review summarizes current knowledge and critical aspects of PSC biology which have been increasingly well characterized over the past few years, particularly with respect to the response of PSCs to factors that stimulate or inhibit their activation and the intracellular signaling pathways governing these processes. Based on this knowledge, several therapeutic strategies have been examined in experimental models of pancreatic fibrosis, demonstrating that pancreatic fibrosis is a potentially reversible condition, at least in early stages.

FUTURE DIRECTIONS

These will involve translation of the laboratory findings into effective clinical approaches to prevent/inhibit PSC activation so as to prevent, retard, or reverse the fibrotic process in pancreatitis.

Recruitment and activation of pancreatic stellate cells from the bone marrow in pancreatic cancer: a model of tumor-host interaction

Background and Aims

Chronic pancreatitis and pancreatic cancer are characterised by extensive stellate cell mediated fibrosis, and current therapeutic development includes targeting pancreatic cancer stroma and tumor-host interactions. Recent evidence has suggested that circulating bone marrow derived stem cells (BMDC) contribute to solid organs. We aimed to define the role of circulating haematopoietic cells in the normal and diseased pancreas.

Methods

Whole bone marrow was harvested from male β-actin-EGFP donor mice and transplanted into irradiated female recipient C57/BL6 mice. Chronic pancreatitis was induced with repeat injections of caerulein, while carcinogenesis was induced with an intrapancreatic injection of dimethylbenzanthracene (DMBA). Phenotype of engrafted donor-derived cells within the pancreas was assessed by immunohistochemistry, immunofluorescence and in situ hybridisation.

Results

GFP positive cells were visible in the exocrine pancreatic epithelia from 3 months post transplantation. These exhibited acinar morphology and were positive for amylase and peanut agglutinin. Mice administered caerulein developed chronic pancreatitis while DMBA mice exhibited precursor lesions and pancreatic cancer. No acinar cells were identified to be donor-derived upon cessation of cerulein treatment, however rare occurrences of bone marrow-derived acinar cells were observed during pancreatic regeneration. Increased recruitment of BMDC was observed within the desmoplastic stroma, contributing to the activated pancreatic stellate cell (PaSC) population in both diseases. Expression of stellate cell markers CELSR3, PBX1 and GFAP was observed in BMD cancer-associated PaSCs, however cancer-associated, but not pancreatitis-associated BMD PaSCs, expressed the cancer PaSC specific marker CELSR3.

Conclusions

This study demonstrates that BMDC can incorporate into the pancreas and adopt the differentiated state of the exocrine compartment. BMDC that contribute to the activated PaSC population in chronic pancreatitis and pancreatic cancer have different phenotypes, and may play important roles in these diseases. Further, bone marrow transplantation may provide a useful model for the study of tumor-host interactions in cancer and pancreatitis.

Withdrawal of alcohol promotes regression while continued alcohol intake promotes persistence of LPS-induced pancreatic injury in alcohol-fed rats

BACKGROUND AND AIMS

Administration of repeated lipopolysaccharide (LPS) injections in alcohol-fed rats leads to significant pancreatic injury including fibrosis. However, it remains unknown whether alcoholic (chronic) pancreatitis has the potential to regress when alcohol is withdrawn. The aims of the study were (1) to compare the effect of alcohol withdrawal/continuation on pancreatic acute injury and fibrosis; and (2) to assess the effects of alcohol ± LPS on pancreatic stellate cell (PSC) apoptosis in vivo and in vitro.

METHODS

Rats fed isocaloric Liebere-De-Carli liquid diets ± alcohol for 10 weeks were challenged with LPS (3 mg/kg/week for 3 weeks) and then either switched to control diet or maintained on an alcohol diet for 3 days, 7 days or 3 weeks. Pancreatic sections were assessed for acute tissue injury, fibrosis, PSC apoptosis and activation. Cultured rat PSCs were exposed to 10 mM ethanol 6 1 mg/ml LPS for 48 or 72 h and apoptosis was assessed (Annexin V, caspase-3 and terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL)).

RESULTS

Withdrawal of alcohol led to resolution of pancreatic lesions including fibrosis and to increased PSC apoptosis. Continued alcohol administration perpetuated pancreatic injury and prevented PSC apoptosis. Alcohol and LPS significantly inhibited PSC apoptosis in vitro, and the effect of LPS on PSC apoptosis could be blocked by Toll-like receptor 4 small interfering RNA.

CONCLUSIONS

Induction of PSC apoptosis upon alcohol withdrawal is a key mechanism mediating the resolution of pancreatic fibrosis. Conversely, continued alcohol intake perpetuates pancreatic injury by inhibiting apoptosis and promoting activation of PSCs. Characterisation of the pathways mediating PSC apoptosis has the potential to yield novel therapeutic strategies for chronic pancreatitis.

Mechanisms of alcoholic pancreatitis

Alcoholic pancreatitis is a major complication of alcohol abuse. The risk of developing pancreatitis increases with increasing doses of alcohol, suggesting that alcohol exerts dose-related toxic effects on the pancreas. However, it is also clear that only a minority of alcoholics develop the disease, indicating that an additional trigger may be required to initiate clinically evident pancreatic injury. It is now well established that alcohol is metabolized by the pancreas via both oxidative and non-oxidative metabolites. Alcohol and its metabolites produce changes in the acinar cells, which may promote premature intracellular digestive enzyme activation thereby predisposing the gland to autodigestive injury. Pancreatic stellate cells (PSCs) are activated directly by alcohol and its metabolites and also by cytokines and growth factors released during alcohol-induced pancreatic necroinflammation. Activated PSCs are the key cells responsible for producing the fibrosis of alcoholic chronic pancreatitis. Efforts to identify clinically relevant factors that may explain the susceptibility of some alcoholics to pancreatitis have been underway for several years. An unequivocal, functionally characterized, association is yet to be identified in clinical studies, although in the experimental setting, endotoxin has been shown to trigger overt pancreatic injury and to promote disease progression in alcohol-fed animals. Thus, while the molecular effects of alcohol on the pancreas have been increasingly clarified in recent years, identification of predisposing or triggering factors remains a challenge.

Role of pancreatic stellate cells in pancreatic cancer metastasis

Pancreatic stellate cells (PSCs) produce the stromal reaction in pancreatic cancer (PC), and their interaction with cancer cells facilitates cancer progression. This study investigated the role of human PSCs (hPSCs) in the metastatic process and tumor angiogenesis using both in vivo (orthotopic model) and in vitro (cultured PSC and PC cells) approaches. A sex mismatch study (injection of male hPSCs plus female PC cells into the pancreas of female mice) was conducted to determine whether hPSCs accompany cancer cells to metastatic sites. Metastatic nodules were examined by fluorescent in situ hybridization for the presence of the Y chromosome. Angiogenesis was assessed by i) immunostaining tumors for CD31, an endothelial cell marker; and ii) quantifying human microvascular endothelial cell (HMEC-1) tube formation in vitro on exposure to conditioned media from hPSCs. Transendothelial migration was assessed in vitro by examining the movement of fluorescently labeled hPSCs through an endothelial cell monolayer. Human PSCs i) were found in multiple metastatic sites in each mouse injected with male hPSCs plus female PC cells; ii) increased CD31 expression in primary tumors from mice injected with MiaPaCa-2 and hPSCs and stimulated tube formation by HMEC-1 in vitro; and iii) exhibited transendothelial migration that was stimulated by cancer cells. Human PSCs accompany cancer cells to metastatic sites, stimulate angiogenesis, and are able to intravasate/extravasate to and from blood vessels.

Pancreatic stellate cells produce acetylcholine and may play a role in pancreatic exocrine secretion

The pancreatic secretagogue cholecystokinin (CCK) is widely thought to stimulate enzyme secretion by acinar cells indirectly via activation of the vagus nerve. We postulate an alternative pathway for CCK-induced pancreatic secretion. We hypothesize that neurally related pancreatic stellate cells (PSCs; located in close proximity to the basolateral aspect of acinar cells) play a regulatory role in pancreatic secretion by serving as an intermediate target for CCK and secreting the neurotransmitter acetylcholine (ACh), which, in turn, stimulates acinar enzyme secretion. To determine whether PSCs (i) exhibit CCK-dependent ACh secretion and (ii) influence acinar enzyme secretion, primary cultures of human and rat PSCs were used. Immunoblotting and/or immunofluorescence was used to detect choline acetyltransferase (ACh synthesizing enzyme), vesicular ACh transporter (VAChT), synaptophysin, and CCK receptors 1 and 2. Synaptic-like vesicles in PSCs were identified by EM. ACh secretion by PSCs exposed to 20 pM CCK was measured by LC-MS/MS. Amylase secretion by acini [pretreated with and without the muscarinic receptor antagonist atropine (10 μM) and cocultured with PSCs] was measured by colorimetry. PSCs express ACh synthesizing enzyme, VAChT, synaptophysin, and CCK receptors; exhibit CCK-dependent ACh secretion; and stimulate amylase secretion by acini, which is blocked by atropine. In conclusion, PSCs express the essential elements for ACh synthesis and secretion. CCK stimulates ACh secretion by PSCs, which, in turn, induces amylase secretion by acini. Therefore, PSCs may represent a previously unrecognized intrapancreatic pathway regulating CCK-induced pancreatic exocrine secretion.

Isolation of quiescent human pancreatic stellate cells: a promising in vitro tool for studies of human pancreatic stellate cell biology

BACKGROUND

Pancreatic stellate cells (PSCs) play a critical role in pancreatic fibrosis. To date, human PSC biology has been studied using cancer- or inflammation-associated (pre-activated) PSCs, but an in vitro model of quiescent normal human PSCs (NhPSCs) has been lacking.

AIMS

To (i) isolate and characterize quiescent NhPSCs, and (ii) evaluate the response of culture-activated NhPSCs to cytokines and LPS.

METHODS

Quiescent NhPSCs were isolated from normal pancreatic tissue using density gradient centrifugation. PSC markers, glial fibrillary acidic protein (GFAP), desmin, α-smooth muscle actin (αSMA) and the lipopolysaccharide (LPS) receptors TLR4 and CD14 were identified by immunoblotting and immunocytochemistry. The effect of platelet-derived growth factor (PDGF), transforming growth factor β (TGFβ) and LPS on NhPSC activation was also assessed.

RESULTS

Freshly isolated NhPSCs displayed a polygonal appearance with refringent cytoplasmic lipid droplets. Culture-activated NhPSCs expressed GFAP, desmin, αSMA, TLR4 and CD14, and were responsive to PDGF, TGFβ and LPS.

CONCLUSION

Isolated NhPSCs expressed the same markers as rat PSCs and human cancer-associated PSCs and responded to PDGF and TGFβ similarly to rat PSCs. NhPSC preparations provide a useful in vitro tool to study the biology of PSCs in their physiological, non-activated state. and IAP.

Alcohol, signaling, and ECM turnover

Alcohol is recognized as a direct hepatotoxin, but the precise molecular pathways that are important for the initiation and progression of alcohol-induced tissue injury are not completely understood. The current understanding of alcohol toxicity to organs suggests that alcohol initiates injury by generation of oxidative and nonoxidative ethanol metabolites and via translocation of gut-derived endotoxin. These processes lead to cellular injury and stimulation of the inflammatory responses mediated through a variety of molecules. With continuing alcohol abuse, the injury progresses through impairment of tissue regeneration and extracellular matrix (ECM) turnover, leading to fibrogenesis and cirrhosis. Several cell types are involved in this process, the predominant being stellate cells, macrophages, and parenchymal cells. In response to alcohol, growth factors and cytokines activate many signaling cascades that regulate fibrogenesis. This mini-review brings together research focusing on the underlying mechanisms of alcohol-mediated injury in a number of organs. It highlights the various processes and molecules that are likely involved in inflammation, immune modulation, susceptibility to infection, ECM turnover and fibrogenesis in the liver, pancreas, and lung triggered by alcohol abuse.

New insights into alcoholic pancreatitis and pancreatic cancer

Pancreatitis and pancreatic cancer represent two major diseases of the exocrine pancreas. Pancreatitis exhibits both acute and chronic manifestations. The commonest causes of acute pancreatitis are gallstones and alcohol abuse; the latter is also the predominant cause of chronic pancreatitis. Recent evidence indicates that endotoxinemia, which occurs in alcoholics due to increased gut permeability, may trigger overt necroinflammation of the pancreas in alcoholics and one that may also play a critical role in progression to chronic pancreatitis (acinar atrophy and fibrosis) via activation of pancreatic stellate cells (PSCs). Chronic pancreatitis is a major risk factor for the development of pancreatic cancer, which is the fourth leading cause of cancer-related deaths in humans. Increasing attention has been paid in recent years to the role of the stroma in pancreatic cancer progression. It is now well established that PSCs play a key role in the production of cancer stroma and that they interact closely with cancer cells to create a tumor facilitatory environment that stimulates local tumor growth and distant metastasis. This review summarizes recent advances in our understanding of the pathogenesis of alcoholic pancreatitis and pancreatic cancer, with particular reference to the central role played by PSCs in both diseases. An improved knowledge of PSC biology has the potential to provide an insight into pathways that may be therapeutically targeted to inhibit PSC activation, thereby inhibiting the development of fibrosis in chronic pancreatitis and interrupting stellate cell-cancer cell interactions so as to retard cancer progression.

A fire inside: current concepts in chronic pancreatitis

Chronic pancreatitis is a necroinflammatory process characterized pathologically by acinar atrophy and fibrosis and clinically by abdominal pain, diabetes and maldigestion. In this review we summarize some of the recent advances in the understanding of the pathogenesis of pancreatitis and how they have shaped our current understanding of chronic pancreatitis. We pay particular attention to advances in the genetic basis of idiopathic, hereditary and tropical pancreatitis as well as research into the relationship between alcohol and the pancreas. We have also reviewed current practices with respect to diagnosis and management of chronic pancreatitis.

Pancreatic stellate cells and pancreatic cancer cells: an unholy alliance

Pancreatic cancer--a tumor displaying a particularly abundant stromal reaction--is notorious for its poor prognosis. Recent studies, via newly developed orthotopic models, provide compelling evidence of an important role for pancreatic stellate cells (PSC) in pancreatic cancer progression. Characterization of the mechanisms mediating PSC-cancer interactions will lead to the development of much needed alternative therapeutic approaches to improve disease outcome.

Molecular mechanisms of pancreatitis: current opinion

Pancreatitis (necroinflammation of the pancreas) has both acute and chronic manifestations. Gallstones are the major cause of acute pancreatitis, whereas alcohol is associated with acute as well as chronic forms of the disease. Cases of true idiopathic pancreatitis are steadily diminishing as more genetic causes of the disease are discovered. The pathogenesis of acute pancreatitis has been extensively investigated over the past four decades; the general current consensus is that the injury is initiated within pancreatic acinar cells subsequent to premature intracellular activation of digestive enzymes. Repeated attacks of acute pancreatitis have the potential to evolve into chronic disease characterized by fibrosis and loss of pancreatic function. Our knowledge of the process of scarring has advanced considerably with the isolation and study of pancreatic stellate cells, now established as the key cells in pancreatic fibrogenesis. The present review summarizes recent developments in the field particularly with respect to the progress made in unraveling the molecular mechanisms of acute and chronic pancreatic injury secondary to gallstones, alcohol and genetic factors. It is anticipated that continued research in the area will lead to the identification and characterization of molecular pathways that may be therapeutically targeted to prevent/inhibit the initiation and progression of the disease.

Pancreatic stellate cells: partners in crime with pancreatic cancer cells

Pancreatic stellate cells (PSC) produce the stromal reaction in pancreatic cancer, but their role in cancer progression is not fully elucidated. We examined the influence of PSCs on pancreatic cancer growth using (a) an orthotopic model of pancreatic cancer and (b) cultured human PSCs (hPSC) and human pancreatic cancer cell lines MiaPaCa-2 and Panc-1. Athymic mice received an intrapancreatic injection of saline, hPSCs, MiaPaCa-2 cells, or hPSCs + MiaPaCa-2. After 7 weeks, tumor size, metastases, and tumor histology were assessed. In vitro studies assessed the effect of cancer cell secretions on PSC migration and the effect of hPSC secretions on cancer cell proliferation, apoptosis, and migration. Possible mediators of the effects of hPSC secretions on cancer cell proliferation were examined using neutralizing antibodies. Compared with mice receiving MiaPaCa-2 cells alone, mice injected with hPSCs + MiaPaCa-2 exhibited (a) increased tumor size and regional and distant metastasis, (b) fibrotic bands (desmoplasia) containing activated PSCs within tumors, and (c) increased tumor cell numbers. In vitro studies showed that, in the presence of pancreatic cancer cells, PSC migration was significantly increased. Furthermore, hPSC secretions induced the proliferation and migration, but inhibited the apoptosis, of MiaPaCa-2 and Panc-1 cells. The proliferative effect of hPSC secretions on pancreatic cancer cells was inhibited in the presence of neutralizing antibody to platelet-derived growth factor. Our studies indicate a significant interaction between pancreatic cancer cells and stromal cells (PSCs) and imply that pancreatic cancer cells recruit stromal cells to establish an environment that promotes cancer progression.

Individual susceptibility to alcoholic pancreatitis

The observation that only a minority of heavy drinkers develop pancreatitis has prompted an intensive search for a trigger factor/cofactor/susceptibility factor that may precipitate a clinical attack. Putative susceptibility factors examined so far include diet, smoking, amount and type of alcohol consumed, the pattern of drinking and lipid intolerance. In addition, a range of inherited factors have been assessed including blood group antigens, human leukocyte antigen serotypes, alpha-1-antitrypsin phenotypes and several genotypes. The latter group comprises mutations/polymorphisms in genes related to alcohol-metabolizing enzymes, detoxifying enzymes, pancreatic digestive enzymes, pancreatic enzyme inhibitors, cystic fibrosis and cytokines. Disappointingly, despite this concerted research effort, no clear association has been established between the above factors and alcoholic pancreatitis. Experimentally, the secretagogue cholecystokinin (CCK) has been investigated as a candidate 'trigger' for alcoholic pancreatitis. However, the clinical relevance of CCK as a trigger factor has to be questioned, as it is difficult to envisage a situation in humans where abnormally high levels of CCK would be released into the circulation to trigger pancreatitis in alcoholics. In contrast, bacterial endotoxemia is a candidate cofactor that does have relevance to the clinical situation. Plasma lipopolysaccharide (LPS, an endotoxin) levels are significantly higher in drinkers (either after chronic alcohol intake or a single binge) compared to non-drinkers. We have recently shown that alcohol-fed animals challenged with otherwise innocuous doses of LPS exhibit significant pancreatic injury. Moreover, repeated LPS exposure in alcohol-fed rats leads to progressive injury to the gland characterized by significant pancreatic fibrosis. These studies support the concept that endotoxin may be an important factor in the initiation and progression of alcoholic pancreatitis. Scope remains for further studies examining proteins related to cellular anti-oxidant defenses, minor cystic fibrosis (CF) mutations and trans-heterozygosity involving a combination of mutations of different genes (such as CFTR alterations combined with SPINK1 or PRSS1 variants), as potential triggers of alcoholic pancreatitis.

The role of inflammatory and parenchymal cells in acute pancreatitis

The infiltration of inflammatory cells into the pancreas is an early and central event in acute pancreatitis that promotes local injury and systemic complications of the disease. Recent research has yielded the important finding that resident cells of the pancreas (particularly acinar and pancreatic stellate cells) play a dynamic role in leukocyte attraction via secretion of chemokines and cytokines and expression of adhesion molecules. Significant progress has been made in recent years in our understanding of the role of leukocyte movement (adhesion to the blood vessel wall, transmigration through the blood vessel wall and infiltration into the parenchyma) in the pathophysiology of acute pancreatitis. This review discusses recent studies and describes the current state of knowledge in the field. It is clear that detailed elucidation of the numerous processes in the inflammatory cascade is an essential step towards the development of improved therapeutic strategies in acute pancreatitis. Studies to date suggest that combination therapy targeting different steps of the inflammatory cascade may be the treatment of choice for this disease.

Bacterial endotoxin: a trigger factor for alcoholic pancreatitis? Evidence from a novel, physiologically relevant animal model

BACKGROUND & AIMS

This study examined the possible role of endotoxinemia (from increased gut permeability) as an additional trigger factor for overt pancreatic disease and as a promoter of chronic pancreatic injury in alcoholics by using a rat model of chronic alcohol feeding and in vitro experiments with cultured pancreatic stellate cells (PSCs), the key mediators of pancreatic fibrosis.

METHODS

In the in vivo model, Sprague-Dawley rats fed isocaloric Lieber-DeCarli liquid diets +/- alcohol for 10 weeks were challenged with a single dose or 3 repeated doses of the endotoxin lipopolysaccharide (LPS) and the pancreas was examined. In the in vitro studies, rat PSCs were assessed for activation on exposure to LPS +/- ethanol. The expression of LPS receptors TLR4 and CD14 also was assessed in rat and human PSCs.

RESULTS

In the in vivo model, single or repeated LPS challenge resulted in significantly greater pancreatic injury in alcohol-fed rats compared with rats fed the control diet without alcohol. Notably, repeated LPS injections caused pancreatic fibrosis in alcohol-fed rats, but not in rats fed the control diet. In the in vitro studies, PSCs were activated by LPS. Alcohol + LPS exerted a synergistic effect on PSC activation. Importantly, both rat and human PSCs expressed TLR4 and CD14.

CONCLUSIONS

This study describes, for the first time, a clinically relevant animal model of alcohol-related pancreatic injury and provides strong in vivo and in vitro evidence that suggests that LPS is a trigger factor in the initiation and progression of alcoholic pancreatitis.