Role of alcohol metabolism in alcoholic pancreatitis

Metabolism of ethanol by acinar and other pancreatic cells and the consequent generation of toxic metabolites are postulated to play an important role in the development of alcohol-related acute and chronic pancreatic injury. Studies using cultured pancreatic acinar cells and isolated pancreatic acini have established that (i) the pancreas can metabolize ethanol via the oxidative pathway involving the enzymes alcohol dehydrogenase (ADH) and possibly cytochrome P4502E1 (although the role of the latter remains to be fully delineated) as well as the nonoxidative pathway [involving fatty acid ethyl ester (FAEE) synthases] and (ii) the oxidative pathway (which generates acetaldehyde) is quantitatively greater than the nonoxidative pathway, which yields FAEEs. Most recently, pancreatic stellate cells (PSCs) (implicated in pancreatic fibrogenesis) have been reported to exhibit ADH activity, suggesting that the capacity of the pancreas to metabolize ethanol may reside not only in parenchymal (acinar) cells but also in nonparenchymal cells. Polymorphisms/mutations of ethanol metabolizing enzymes have been examined to determine whether they may confer individual susceptibility to alcoholic pancreatitis. However, no association has been demonstrated between ADH and CYP2E1 polymorphisms and the predisposition to alcoholic pancreatitis. Other candidate factors that remain to be studied include polymorphisms of FAEE synthetic enzymes and proteins relevant to antioxidant pathways in the cell. Injury to the pancreas due to its capacity to metabolize ethanol may be mediated by direct effects of both acetaldehyde and FAEEs and by alterations induced within the cells during ethanol metabolism, such as changes in the intracellular redox state and the generation of oxidant stress.

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.

Targeting the HGF/c-MET pathway: stromal remodelling in pancreatic cancer

Stromal-tumor interactions in pancreatic cancer (PC) impact on treatment outcomes. Pancreatic stellate cells (PSCs) produce the collagenous stroma of PC and interact with cancer cells to facilitate disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells. We studied the effects on PC progression of inhibiting the HGF/c-MET pathway in the presence and absence of a representative chemotherapeutic agent, gemcitabine. Using an orthotopic model of PC we have shown that "triple therapy" (inhibition of both HGF and c-MET combined with gemcitabine) resulted in the greatest reduction in tumor volume compared to each of the treatments alone or in dual combinations. Importantly, metastasis was virtually eliminated in mice receiving triple therapy. Our in vivo findings were supported by in vitro studies showing that the increase in cancer cell proliferation and migration in response to PSC secretions was significantly inhibited by the triple regimen. Our studies suggest that a combined approach, that targets tumor cells by chemotherapy while inhibiting specific pathways that mediate stromal-tumor interactions, may represent a novel therapeutic strategy to improve outcomes in PC.

Targeting the HGF/c-MET pathway in advanced pancreatic cancer: a key element of treatment that limits primary tumour growth and eliminates metastasis

BACKGROUND

Stromal-tumour interactions facilitate pancreatic cancer (PC) progression. The hepatocyte growth factor (HGF)/c-MET pathway is upregulated in PC and mediates the interaction between cancer cells and stromal pancreatic stellate cells (PSCs). This study assessed the effect of HGF/c-MET inhibition plus gemcitabine (G) on the progression of advanced PC.

METHODS

Orthotopic PC was produced by implantation of luciferase-tagged human cancer cells + human PSCs into mouse pancreas. Tumours were allowed to develop without treatment for 4 weeks. Mice were then treated for 6 weeks with one of the following: IgG, G, HGF inhibitor (Hi), c-MET inhibitor (Ci), Hi + Ci, Hi + G, Ci + G, or Hi + Ci + G.

RESULTS

Bioluminescence imaging showed similar tumour sizes in all mice at the initiation of treatments. Triple therapy (Hi + Ci + G): (1) completely eliminated metastasis; (2) significantly reduced tumour size as assessed by bioluminescence and at necropsy; (3) significantly reduced proliferating cancer cell density and stem cell marker DCLK1 expression in tumours. In vitro 3D culture studies supported our in vivo findings.

CONCLUSION

Even at an advanced disease stage, a two-pronged approach, targeting (a) HGF/c-MET with relevant inhibitors and (b) cancer cells with chemotherapy, completely eliminated metastasis and significantly decreased tumour growth, suggesting that this is a promising treatment approach for PC.

Battle-scarred pancreas: role of alcohol and pancreatic stellate cells in pancreatic fibrosis

Pancreatic stellate cells (PSC) are now recognized as the key mediators of pancreatic fibrosis, a characteristic feature of chronic pancreatitis. The role of PSC in alcoholic pancreatic fibrosis has been examined in vivo (using pancreatic tissue from patients with alcohol-induced chronic pancreatitis and from animal models of experimental pancreatitis) and in vitro (using PSC in culture). These studies indicate that PSC are activated early in the course of pancreatic injury and are the predominant source of collagen in the fibrotic pancreas. The factors responsible for mediating PSC activation during chronic alcohol exposure include ethanol, its metabolite acetaldehyde, oxidant stress and cytokines (released during episodes of alcohol-induced pancreatic necroinflammation). Most recently, the intracellular signaling mechanisms regulating ethanol-induced PSC activation have been identified and include the mitogen-activated protein kinase (MAPK) pathway, phosphatidylinositol-3-kinase (PI3K) and protein kinase C (PKC), and the transcription factor activator protein-1 (AP-1).

Ethanol augments PDGF-induced NADPH oxidase activity and proliferation in rat pancreatic stellate cells

BACKGROUND/AIMS

Activated stellate cells are considered the principal mediators of chronic alcoholic pancreatitis/fibrosis. However the mechanisms of alcohol action on pancreatic stellate cells (PaSCs) are poorly understood. The aims of this study were to determine the presence and role of the NADPH oxidase system in mediating alcohol effects on PaSCs with specific emphasis on proliferation.

METHODS

PaSC NADPH oxidase components mRNA and protein were determined by RT-PCR and Western blot. The NADPH oxidase activity was measured by detecting the production of reactive oxygen species using lucigenin-derived chemiluminescence assay. PaSC DNA synthesis, a measure of proliferation, was performed by determining the [3H] thymidine incorporation into DNA.

RESULTS

mRNA for NADPH oxidase components Nox1, gp91(phox), Nox4, p22(phox), p47(phox) and p67(phox) and protein for NADPH oxidase subunits gp91(phox), p22(phox), p47(phox) and p67(phox) are present in PaSCs. Treatment with platelet-derived growth factor (PDGF) significantly increased the NADPH oxidase activity and DNA synthesis in cultured PaSCs. Alcohol treatment markedly augmented both the NADPH oxidase activity and the DNA synthesis caused by PDGF, which was prevented by antioxidant N-acetyl-L-cysteine, ROS scavenger tiron, and the NADPH oxidase inhibitor diphenylene iodium. The effects of PDGF on NADPH oxidase activity and DNA synthesis were prevented in PaSCs isolated from the pancreas of mice with a genetic deficiency of p47(phox).

CONCLUSIONS

Ethanol causes proliferation of stellate cells by augmenting the activation of the cell's NADPH oxidase system stimulated by PDGF. These results provide new insights into the mechanisms of alcohol-induced fibrosing disorders.

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.

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.

Alcohol and cigarette smoke components activate human pancreatic stellate cells: implications for the progression of chronic pancreatitis

BACKGROUND

Chronic pancreatitis, a known complication of alcohol abuse, is characterized histopathologically by prominent fibrosis. Pancreatic stellate cells (PSCs) are responsible for producing this fibrous tissue in chronic pancreatitis and are activated by alcohol. Progression of alcoholic chronic pancreatitis (as assessed by calcification and fibrosis) is thought to be facilitated by concurrent smoking, but the mechanisms are unknown. This study aimed to (a) determine whether human PSCs (hPSCs) and rat PSCs express nicotinic acetylcholine receptors (nAChRs), which are known to bind 2 important components of cigarette smoke, namely nicotine and nicotine-derived nitrosamine ketone (NNK), and (b) examine the effects of cigarette smoke components in the presence and absence of alcohol on PSC activation in vitro.

METHODS

Western blotting was used to detect the presence of nAChRs in primary cultures of PSCs. Clinically relevant concentrations of cigarette smoke components (either cigarette smoke extract [CSE], NNK, or nicotine) ± ethanol (EtOH) were used to treat primary cultures of PSCs, and stellate cell activation was assessed by cell migration, proliferation, collagen production, and apoptosis.

RESULTS

We demonstrate, for the first time, that PSCs express nAChRs (isoforms α3, α7, β, ε) and that the expression of the α7 isoform in hPSCs is induced by CSE + EtOH. We also provide novel findings that PSCs are activated by CSE and NNK (both alone and in combination with EtOH) as evidenced by an increase in cell migration and/or proliferation. Further, we demonstrate that activation of PSCs by CSE + EtOH and NNK + EtOH may be mediated via nAChRs on the cells.

CONCLUSIONS

PSCs are activated by clinically relevant concentrations of cigarette smoke components (CSE and NNK), alone and in combination with EtOH. Thus, in alcoholics who smoke, progression of pancreatic fibrosis may be facilitated by the combined effects of alcohol and cigarette smoke components on hPSC behavior.

Cystic fibrosis genotypes and alcoholic pancreatitis

Pancreatitis and pancreatic insufficiency are associated with both cystic fibrosis and alcoholism. The pathogenesis of alcoholic pancreatitis is unknown, but only a minority of alcoholics develop pancreatitis, and it has been suggested that a genetic predisposition may play a role in this disease. Two observations led to the hypothesis that this genetic predisposition could result from mutations in the cystic fibrosis gene. First, the prevalence of cystic fibrosis mutations in the Caucasian population (approximately 5%) is similar to the prevalence of pancreatitis among heavy drinkers. Second, in both diseases, pancreatic duct damage is a prominent feature and has been postulated to be the initial site of injury. Therefore, the aim of this study was to determine whether an increased frequency of mutations in the cystic fibrosis gene occurs in alcoholic pancreatitis. The 15 most common cystic fibrosis mutations in a Caucasian community were sought in 24 subjects with alcoholic pancreatitis. None were homozygous or heterozygous for these mutations. These findings suggest that cystic fibrosis mutations are not a major genetic factor predisposing to pancreatic injury in alcoholics.

Targeting HGF/c-MET Axis in Pancreatic Cancer

Pancreatic cancer (pancreatic ductal adenocarcinoma (PDAC/PC)) has been an aggressive disease that is associated with early metastases. It is characterized by dense and collagenous desmoplasia/stroma, predominantly produced by pancreatic stellate cells (PSCs). PSCs interact with cancer cells as well as other stromal cells, facilitating disease progression. A candidate growth factor pathway that may mediate this interaction is the hepatocyte growth factor (HGF)/c-MET pathway. HGF is produced by PSCs and its receptor c-MET is expressed on pancreatic cancer cells and endothelial cells. The current review discusses the role of the MET/HGF axis in tumour progression and dissemination of pancreatic cancer. Therapeutic approaches that were developed targeting either the ligand (HGF) or the receptor (c-MET) have not been shown to translate well into clinical settings. We discuss a two-pronged approach of targeting both the components of this pathway to interrupt the stromal-tumour interactions, which may represent a potential therapeutic strategy to improve outcomes in PC.

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.

Non-oxidative metabolism of ethanol by rat pancreatic acini

BACKGROUND

The pathogenesis of alcoholic pancreatitis may involve the metabolism of ethanol (via oxidative and non-oxidative pathways) within the pancreas. The aims of this study were to determine the rate of non-oxidative metabolism in isolated rat pancreatic acini and to compare this to the rate of ethanol oxidation.

METHODS

Pancreatic acini were isolated from male Sprague-Dawley rats and incubated with (14)C-ethanol. Radiolabelled fatty acid ethyl esters (non-oxidative metabolites) were isolated from lipid extracts by thin-layer chromatography. Radiolabelled acetate (oxidative metabolite) was isolated from the incubation medium by ion-exchange chromatography.

RESULTS

Non-oxidative metabolism by isolated pancreatic acini was demonstrated. At 50 and 100 mmol/l ethanol, fatty acid ethyl ester concentrations were 49.6 +/- 13.3 and 199 +/- 93 micromol/l, respectively. These levels have previously been shown to result in tissue injury. Non-oxidative metabolism was increased 9-fold by addition of oleic acid and inhibited by the lipase inhibitor, tetrahydrolipstatin, by 91.05 +/- 1.99%. The rate of oxidative metabolism was 21-fold higher than that of non-oxidative metabolism.

CONCLUSIONS

Intact pancreatic cells metabolize ethanol by the non-oxidative pathway, generating fatty acid ethyl esters at a rate sufficient to cause pancreatic damage. Oxidative metabolism of ethanol occurs at a much higher rate and may also play a role in pancreatitis.

Effects of ethanol and protein deficiency on pancreatic digestive and lysosomal enzymes

The pathogenesis of alcoholic pancreatitis is not fully understood. An increase in pancreatic digestive and lysosomal enzyme synthesis because of ethanol consumption could contribute to the development of pancreatic injury in alcoholics. This study aimed, firstly, to determine the effect of ethanol on the content and messenger RNA levels of pancreatic digestive enzymes and on the messenger RNA level of the lysosomal enzyme cathepsin B, and secondly, to examine the influence of concomitant protein deficiency (a known association of alcoholism and pancreatic injury) on these effects. A rat model of chronic ethanol administration was used in which rats were fed in groups of four, and for four weeks, protein sufficient and protein deficient diets with or without ethanol. Ethanol increased the pancreatic content of lipase but did not influence chymotrypsinogen or trypsinogen values. mRNA levels for lipase, trypsinogen, and chymotrypsinogen were raised in rats fed ethanol. Protein deficiency resulted in reduced tissue levels of lipase, chymotrypsinogen, and amylase but did not influence trypsinogen values. mRNA levels for proteases were increased in protein deficient rats, while those for lipase remained unaltered. Both ethanol and protein deficiency increased mRNA levels for cathepsin B. It is concluded that chronic ethanol consumption, in both protein sufficient and protein deficient states, increases the capacity of the pancreatic acinar cell to synthesise digestive and lysosomal enzymes.

Modern management of pancreatic carcinoma

Pancreatic cancer remains a fearsome disease. New insights into the molecular pathogenesis may influence choice of treatment modalities and provide avenues for novel therapeutic strategies for testing in the clinic. The survival rate of patients with all stages of disease is poor and clinical trials are appropriate alternatives for treatment and should be considered. Surgical resection, when possible, remains the primary treatment modality and can result in long-term cure. Less invasive techniques such as laparoscopy may reduce the rate of unnecessary laparotomies. The role of adjuvant therapy is re-emerging. Patients with unresectable and metastatic disease are incurable and optimal palliation is the goal. These patients may benefit from palliative bypass of biliary or duodenal obstruction if symptomatic. Pain associated with local tumour infiltration may be palliated with radiation, with or without chemotherapy, or with coeliac nerve blocks or local neurosurgical procedures. Chemotherapy with gemcitabine has modest objective response rates but has been shown to improve symptoms.

Chronic ethanol consumption increases the fragility of rat pancreatic zymogen granules

Intracellular activation of pancreatic digestive enzymes by lysosomal hydrolases is thought to be an early event in the pathogenesis of pancreatic injury. As ethanol excess is an important association of pancreatitis, experimental work has been directed towards exploring possible mechanisms whereby ethanol may facilitate contact between inactive digestive enzyme precursors and lysosomal enzymes. The aim of this study was to find out if chronic ethanol administration increases the fragility of rat pancreatic zymogen granules. Sixteen male Sprague-Dawley rats were pair fed ethanol and control liquid diets for four weeks. Zymogen granule fragility was then assessed in pancreatic homogenate by determination of (a) latency and (b) per cent supernatant enzyme after sedimentation of zymogen granules. Amylase was used as a zymogen granule marker enzyme. Latency was significantly reduced in pancreatic homogenates of ethanol fed animals suggesting increased zymogen granule fragility. In support of this finding, there was a trend towards increased supernatant enzyme after ethanol feeding. In conclusion, administration of ethanol increases the fragility of pancreatic zymogen granules in the absence of morphological evidence of pancreatic injury. It is proposed that zymogen granule fragility may play an early part in the pathogenesis of alcoholic pancreatitis by permitting contact between digestive and lysosomal enzymes.

Pancreatic stellate cells: what's new?

PURPOSE OF REVIEW

Pancreatic stellate cells (PSCs) play an integral role in the pathogenesis of pancreatitis and pancreatic cancer. With the developing knowledge of this important cell type, we are at the cusp of developing effective therapies for the above diseases based upon targeting the PSC and modulating its function.

RECENT FINDINGS

The major themes of the recent PSC literature include: PSC interactions with the extracellular matrix and other stromal components; intracellular calcium physiology as drivers of mechanical interactions and necrosis; the relationship between proinflammatory, protumoural, angiogenic, and metabolic pathways in pancreatic necrosis, fibrosis, and carcinogenesis; and targeting of the stroma for antitumoural and antifibrotic effects.

SUMMARY

Traditionally, there have been few treatment options for pancreatitis and pancreatic cancer. The elucidation of the wide-ranging functions of PSCs provide an opportunity for treatments based on stromal reprogramming.

Small extracellular vesicles (exosomes) and their cargo in pancreatic cancer: Key roles in the hallmarks of cancer

Pancreatic cancer (PC) is a devastating disease, offering poor mortality rates for patients. The current challenge being faced is the inability to diagnose patients in a timely manner, where potentially curative resection provides the best chance of survival. Recently, small/nanosized extracellular vesicles (sEVs), including exosomes, have gained significant preclinical and clinical attention due to their emerging roles in cancer progression and diagnosis. Extracellular vesicles (EVs) possess endogenous properties that offer stability and facilitate crossing of biological barriers for delivery of molecular cargo to cells, acting as a form of intercellular communication to regulate function and phenotype of recipient cells. This review provides an overview of the role of EVs, their subtypes and their oncogenic cargo (as characterised by targeted studies as well as agnostic '-omics' analyses) in the pathobiology of pancreatic cancer. The discussion covers the progress of 'omics technology' that has enabled elucidation of the molecular mechanisms that mediate the role of EVs and their cargo in pancreatic cancer progression.

Chronic pancreatitis: complications and management

Chronic pancreatitis is characterized by progressive and irreversible loss of pancreatic exocrine and endocrine function. In the majority of cases, particularly in Western populations, the disease is associated with alcohol abuse. The major complications of chronic pancreatitis include abdominal pain, malabsorption, and diabetes. Of these, pain is the most difficult to treat and is therefore the most frustrating symptom for both the patient and the physician. While analgesics form the cornerstone of pain therapy, a number of other treatment modalities (inhibition of pancreatic secretion, antioxidants, and surgery) have also been described. Unfortunately, the efficacy of these modalities is difficult to assess, principally because of the lack of properly controlled clinical trials. Replacement of pancreatic enzymes (particularly lipase) in the gut is the mainstay of treatment for malabsorption; the recent discovery of a bacterial lipase (with high lipolytic activity and resistance to degradation in gastric and duodenal juice) represents an important advance that may significantly increase the efficacy of enzyme replacement therapy by replacing the easily degradable porcine lipase found in existing enzyme preparations. Diabetes secondary to chronic pancreatitis is difficult to control and its course is often complicated by hypoglycaemic attacks. Therefore, it is essential that caution is exercised when treating this condition with insulin. This paper reviews recent research and prevailing concepts regarding the three major complications of chronic pancreatitis noted above. A comprehensive discussion of current opinion on clinical issues relating to the other known complications of chronic pancreatitis such as pseudocysts, venous thromboses, biliary and duodenal obstruction, biliary cirrhosis, and pancreatic cancer is also presented.

Effects of ethanol, acetaldehyde and cholesteryl esters on pancreatic lysosomes

Recent studies indicate that altered lysosomal function may be involved in the early stages of pancreatic injury. Chronic consumption of ethanol increases rat pancreatic lysosomal fragility. The aim of this study is to determine whether the lysosomal fragility observed after chronic ethanol consumption is mediated by ethanol per se, its oxidative metabolite acetaldehyde or cholesteryl esters (substances which accumulate in the pancreas after ethanol consumption). Pancreatic lysosomes from chow fed rats were incubated for 30 minutes at 37 degrees C with ethanol, acetaldehyde or phosphatidylcholine vesicles containing cholesteryl oleate. Lysosomal stability was then assessed by determination of: (a) Latency--that is, the per cent increase in lysosomal enzyme activity after addition of Triton X-100 and (b) Supernatant activity--that is, the proportion of lysosomal enzyme remaining in the supernatant after resedimentation of lysosomes. Acid phosphatase, N-acetyl glucosaminidase, beta-glucuronidase and cathepsin B were assayed as lysosomal marker enzymes. Lysosomes incubated with homogenising medium alone or equivalent volumes of phosphatidylcholine vesicles without cholesteryl oleate were used as controls. Cholesteryl oleate at concentrations of 15 and 20 mM increased pancreatic lysosomal fragility as shown by decreased latency and increased supernatant enzyme. In contrast, ethanol (150 mM) and acetaldehyde (5 mM) had no effect on lysosomal stability in vitro. These results suggest that increased pancreatic lysosomal fragility observed with ethanol may be mediated by cholesteryl ester accumulation rather than by ethanol or acetaldehyde.

Lipid intolerance does not account for susceptibility to alcoholic and gallstone pancreatitis

BACKGROUND/AIMS

Hypertriglyceridemia is an established cause of pancreatitis and has been suggested as a predisposing factor in alcohol and gallstone-induced pancreatitis. The aims of this study were to determine fasting and postprandial triglyceride levels of alcoholics with pancreatitis, alcoholics without pancreatitis, patients with previous gallstone pancreatitis, patients with choledocholithiasis, and healthy controls.

METHODS

Oral lipid tolerance studies were performed in the above groups.

RESULTS

No relationship was found between alcoholic pancreatitis and hypertriglyceridemia, regardless of whether subjects were studied in the fasting state, after ingestion of fat, or after ingestion of fat with ethanol. Plasma triglyceride levels of alcoholics with pancreatitis remained similar to those of alcoholics without pancreatitis, but levels in both groups varied in relation to recent alcohol intake. Plasma triglyceride levels from both groups of alcoholics were greater than those of nonalcoholic healthy subjects. In addition, the previously reported association between postprandial hypertriglyceridemia and gallstone pancreatitis was not observed.

CONCLUSIONS

Plasma triglyceride levels do not account for individual susceptibility to either alcoholic or gallstone pancreatitis.

Alcoholic pancreatitis and polymorphisms of the variable length polythymidine tract in the cystic fibrosis gene

BACKGROUND

The observation that only a minority of alcoholics develops clinical pancreatic disease has led to a search for a predisposing factor to the disease. One possible predisposing factor is mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene as cystic fibrosis leads to pancreatic injury. We have recently demonstrated that 15 common CFTR mutations are not found in patients with alcoholic pancreatitis. Another common polymorphism of the CFTR gene has recently been implicated in the pathogenesis of idiopathic chronic pancreatitis, the 5T variant of the variable length polythymidine tract in intron 8 (the normal genotypes are 7T and 9T). The 5T variant inhibits transcription of exon 9 resulting in a CFTR protein lacking chloride channel activity. The aim of this study was to determine whether the 5T variant is associated with alcoholic pancreatitis.

METHODS

Fifty-two patients with alcoholic pancreatitis were identified using standardized diagnostic criteria. Fifty alcoholics without pancreatitis were also studied as controls. Genomic DNA was extracted from peripheral blood leukocytes and the polythymidine tract of intron 8 was amplified by nested polymerase chain reaction using established primers. The polymerase chain reaction products were digested with MseI, separated by electrophoresis on 15% polyacrylamide gels and genotypes assigned by comparison with known positive controls.

RESULTS

The 5T allele we found in only two patients with alcoholic pancreatitis (3.9% of th index group; 95% confidence intervals 0-10%) and in seven alco holic controls. Allele frequencies for 5T, 7T, and 9T in patients with alcoholic pancreatitis were 1.9%, 85.6%, and 12.5%, respectively These did not differ from the allele frequencies in alcoholic controls (7%, 79%, and 14% for 5T, 7T, and 9T, respectively).

CONCLUSION

The 5T allele was not associated with alcoholic pancreatitis. Individual susceptibility to this disease remains unexplained.

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.

Metastatic phenotype and immunosuppressive tumour microenvironment in pancreatic ductal adenocarcinoma: Key role of the urokinase plasminogen activator (PLAU)

BACKGROUND

Previous studies have revealed the role of dysregulated urokinase plasminogen activator (encoded by PLAU) expression and activity in several pathways associated with cancer progression. However, systematic investigation into the association of PLAU expression with factors that modulate PDAC (pancreatic ductal adenocarcinoma) progression is lacking, such as those affecting stromal (pancreatic stellate cell, PSC)-cancer cell interactions, tumour immunity, PDAC subtypes and clinical outcomes from potential PLAU inhibition.

METHODS

This study used an integrated bioinformatics approach to identify prognostic markers correlated with PLAU expression using different transcriptomics, proteomics, and clinical data sets. We then determined the association of dysregulated PLAU and correlated signatures with oncogenic pathways, metastatic phenotypes, stroma, immunosuppressive tumour microenvironment (TME) and clinical outcome. Finally, using an in vivo orthotopic model of pancreatic cancer, we confirmed the predicted effect of inhibiting PLAU on tumour growth and metastasis.

RESULTS

Our analyses revealed that PLAU upregulation is not only associated with numerous other prognostic markers but also associated with the activation of various oncogenic signalling pathways, aggressive phenotypes relevant to PDAC growth and metastasis, such as proliferation, epithelial-mesenchymal transition (EMT), stemness, hypoxia, extracellular cell matrix (ECM) degradation, upregulation of stromal signatures, and immune suppression in the tumour microenvironment (TME). Moreover, the upregulation of PLAU was directly connected with signalling pathways known to mediate PSC-cancer cell interactions. Furthermore, PLAU upregulation was associated with the aggressive basal/squamous phenotype of PDAC and significantly reduced overall survival, indicating that this subset of patients may benefit from therapeutic interventions to inhibit PLAU activity. Our studies with a clinically relevant orthotopic pancreatic model showed that even short-term PLAU inhibition is sufficient to significantly halt tumour growth and, importantly, eliminate visible metastasis.

CONCLUSION

Elevated PLAU correlates with increased aggressive phenotypes, stromal score, and immune suppression in PDAC. PLAU upregulation is also closely associated with the basal subtype type of PDAC; patients with this subtype are at high risk of mortality from the disease and may benefit from therapeutic targeting of PLAU.

Breaking the cycle: Targeting of NDRG1 to inhibit bi-directional oncogenic cross-talk between pancreatic cancer and stroma

Pancreatic cancer (PaCa) is characterized by dense stroma that hinders treatment efficacy, with pancreatic stellate cells (PSCs) being a major contributor to this stromal barrier and PaCa progression. Activated PSCs release hepatocyte growth factor (HGF) and insulin-like growth factor (IGF-1) that induce PaCa proliferation, metastasis and resistance to chemotherapy. We demonstrate for the first time that the metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1), is a potent inhibitor of the PaCa-PSC cross-talk, leading to inhibition of HGF and IGF-1 signaling. NDRG1 also potently reduced the key driver of PaCa metastasis, namely GLI1, leading to reduced PSC-mediated cell migration. The novel clinically trialed anticancer agent, di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC), which upregulates NDRG1, potently de-sensitized PaCa cells to ligands secreted by activated PSCs. DpC and NDRG1 also inhibited the PaCa-mediated activation of PSCs via inhibition of sonic hedgehog (SHH) signaling. In vivo, DpC markedly reduced PaCa tumor growth and metastasis more avidly than the standard chemotherapy for this disease, gemcitabine. Uniquely, DpC was selectively cytotoxic against PaCa cells, while "re-programming" PSCs to an inactive state, decreasing collagen deposition and desmoplasia. Thus, targeting NDRG1 can effectively break the oncogenic cycle of PaCa-PSC bi-directional cross-talk to overcome PaCa desmoplasia and improve therapeutic outcomes.