Pancreatic cholesterol esterase, ES-10, and fatty acid ethyl ester synthase III gene expression are increased in the pancreas and liver but not in the brain or heart with long-term ethanol feeding in rats

Long-chain fatty acids - The turning point between 'mild' and 'severe' acute pancreatitis

Acute pancreatitis (AP) is an inflammatory disease characterized by localized pancreatic injury and a systemic inflammatory response. Fatty acids (FAs), produced during the breakdown of triglycerides (TGs) in blood and peripancreatic fat, escalate local pancreatic inflammation to a systemic level by damaging pancreatic acinar cells (PACs) and triggering M1 macrophage polarization. This paper provides a comprehensive analysis of lipases' roles in the onset and progression of AP, as well as the effects of long-chain fatty acids (LCFAs) on the function of pancreatic acinar cells (PACs). Abnormalities in the function of PACs include Ca2+ overload, premature trypsinogen activation, protein kinase C (PKC) expression, endoplasmic reticulum (ER) stress, and mitochondrial and autophagic dysfunction. The study highlights the contribution of long-chain saturated fatty acids (LC-SFAs), especially palmitic acid (PA), to M1 macrophage polarization through the activation of the NLRP3 inflammasome and the NF-κB pathway. Furthermore, we investigated lipid lowering therapy for AP. This review establishes a theoretical foundation for pro-inflammatory mechanisms associated with FAs in AP and facilitating drug development.

Intrauterine growth restriction in piglets modulates postnatal immune function and hepatic transcriptional responses independently of energy intake

Introduction: Insufficient prenatal nutrition can affect fetal development and lead to intrauterine growth restriction (IUGR). The aim of this study was to investigate hepatic transcriptional responses and innate immune function in piglets suffering from IUGR compared to normal-sized piglets at 3 days of age and explore whether the provision of an energy-rich supplement at birth could modulate these parameters. Methods: A total of 68 piglets were included in the study. Peripheral blood mononuclear cells were harvested for LPS stimulation, and organs were harvested post-mortem to quantify relative weights. Liver tissue was utilized for RNA sequencing coupled with gene-set enrichment analysis. Results: IUGR resulted in increased expression of genes such as PDK4 and substantial alterations in transcriptional pathways related to metabolic activity (e.g., citric acid and Krebs cycles), but these changes were equivalent in piglets given an energy-rich supplement or not. Transcriptomic analysis and serum biochemistry suggested altered glucose metabolism and a shift toward oxidation of fatty acids. IUGR piglets also exhibited suppression of genes related to innate immune function (e.g., CXCL12) and pathways related to cell proliferation (e.g., WNT and PDGF signaling). Moreover, they produced less IL-1β in response to LPS stimulation and had lower levels of blood eosinophils than normal-sized piglets. Discussion: Taken together, our results indicate that IUGR results in early-life alterations in metabolism and immunity that may not be easily restored by the provision of exogenous energy supplementation.

Dysregulated pancreatic lipid phenotype, inflammation and cellular injury in a chronic ethanol feeding model of hepatic alcohol dehydrogenase-deficient deer mice

AIMS

Dysregulation of pancreatic fat and lipotoxic inflammation are common clinical findings in alcoholic chronic pancreatitis (ACP). In this study, we investigated a relationship between dysregulated pancreatic lipid metabolism and the development of injury in a chronic ethanol (EtOH) feeding model of hepatic alcohol dehydrogenase 1- deficient (ADH^-) deer mice.

METHODS

ADH^- and hepatic ADH normal (ADH⁺) deer mice were fed a liquid diet containing 3 % EtOH for three months and received a single gavage of binge EtOH with/without fatty acid ethyl esters (FAEEs) one week before the euthanasia. Plasma and pancreatic tissue were analyzed for lipids including FAEEs, inflammatory markers and adipokines using GC-MS, bioassays/kits, and immunostaining, respectively. Pancreatic morphology and proteins involved in lipogenesis were determined by the H & E staining, electron microscopy and Western blot analysis.

KEY FINDINGS

Chronic EtOH feeding in ADH^- vs. ADH⁺ deer mice resulted in a significant increase in the levels of pancreatic lipids including FAEEs, adipokines (leptin and resistin), fat infiltration with inflammatory cells and lipid droplet deposition along with the proteins involved in lipogenesis. These changes were exacerbated by an administration of binge EtOH with/without FAEEs in the pancreas of ADH^- vs. ADH⁺ deer mice fed chronic EtOH suggest a metabolic basis for ACP.

SIGNIFICANCE

These findings suggest that the liver-pancreatic axis plays a crucial role in etiopathogenesis of ACP, as the increased body burden of EtOH due to hepatic ADH deficiency exacerbates pancreatic injury.

Alcoholic liver disease: a new insight into the pathogenesis of liver disease

Excessive alcohol consumption contributes to a broad clinical spectrum of liver diseases, from simple steatosis to end-stage hepatocellular carcinoma. The liver is the primary organ that metabolizes ingested alcohol and is exquisitely sensitive to alcohol intake. Alcohol metabolism is classified into two pathways: oxidative and non-oxidative alcohol metabolism. Both oxidative and non-oxidative alcohol metabolisms and their metabolites have toxic consequences for multiple organs, including the liver, adipose tissue, intestine, and pancreas. Although many studies have focused on the effects of oxidative alcohol metabolites on liver damage, the importance of non-oxidative alcohol metabolites in cellular damage has also been discovered. Furthermore, extrahepatic alcohol effects are crucial for providing additional information necessary for the progression of alcoholic liver disease. Therefore, studying the effects of alcohol-producing metabolites and interorgan crosstalk between the liver and peripheral organs that express ethanol-metabolizing enzymes will facilitate a comprehensive understanding of the pathogenesis of alcoholic liver disease. This review focuses on alcohol-metabolite-associated hepatotoxicity due to oxidative and non-oxidative alcohol metabolites and the role of interorgan crosstalk in alcoholic liver disease pathogenesis.

Exposure to binge ethanol and fatty acid ethyl esters exacerbates chronic ethanol-induced pancreatic injury in hepatic alcohol dehydrogenase-deficient deer mice

Alcoholic chronic pancreatitis (ACP) is a fibroinflammatory disease of the pancreas. However, metabolic basis of ACP is not clearly understood. In this study, we evaluated differential pancreatic injury in hepatic alcohol dehydrogenase-deficient (ADH^-) deer mice fed chronic ethanol (EtOH), chronic plus binge EtOH, and chronic plus binge EtOH and fatty acid ethyl esters (FAEEs, nonoxidative metabolites of EtOH) to understand the metabolic basis of ACP. Hepatic ADH^- and ADH normal (ADH⁺) deer mice were fed Lieber-DeCarli liquid diet containing 3% (wt/vol) EtOH for 3 mo. One week before the euthanization, chronic EtOH-fed mice were further administered with an oral gavage of binge EtOH with/without FAEEs. Blood alcohol concentration (BAC), pancreatic injury, and inflammatory markers were measured. Pancreatic morphology, ultrastructural changes, and endoplasmic reticulum (ER)/oxidative stress were examined using H&E staining, electron microscopy, immunostaining, and/or Western blot, respectively. Overall, BAC was substantially increased in chronic EtOH-fed groups of ADH^- versus ADH⁺ deer mice. A significant change in pancreatic acinar cell morphology, with mild to moderate fibrosis and ultrastructural changes evident by dilatations and disruption of ER cisternae, ER/oxidative stress along with increased levels of inflammatory markers were observed in the pancreas of chronic EtOH-fed groups of ADH^- versus ADH⁺ deer mice. Furthermore, chronic plus binge EtOH and FAEEs exposure elevated BAC, enhanced ER/oxidative stress, and exacerbated chronic EtOH-induced pancreatic injury in ADH^- deer mice suggesting a role of increased body burden of EtOH and its metabolism under reduced hepatic ADH in initiation and progression of ACP.NEW & NOTEWORTHY We established a chronic EtOH feeding model of hepatic alcohol dehydrogenase-deficient (ADH^-) deer mice, which mimics several fibroinflammatory features of human alcoholic chronic pancreatitis (ACP). The fibroinflammatory and morphological features exacerbated by chronic plus binge EtOH and FAEEs exposure provide a strong case for metabolic basis of ACP. Most importantly, several pathological and molecular targets identified in this study provide a much broader understanding of the mechanism and avenues to develop therapeutics for ACP.

Recent Advances in Understanding the Complexity of Alcohol-Induced Pancreatic Dysfunction and Pancreatitis Development

Chronic excessive alcohol use is a well-recognized risk factor for pancreatic dysfunction and pancreatitis development. Evidence from in vivo and in vitro studies indicates that the detrimental effects of alcohol on the pancreas are from the direct toxic effects of metabolites and byproducts of ethanol metabolism such as reactive oxygen species. Pancreatic dysfunction and pancreatitis development are now increasingly thought to be multifactorial conditions, where alcohol, genetics, lifestyle, and infectious agents may determine the initiation and course of the disease. In this review, we first highlight the role of nonoxidative ethanol metabolism in the generation and accumulation of fatty acid ethyl esters (FAEEs) that cause multi-organellar dysfunction in the pancreas which ultimately leads to pancreatitis development. Further, we discuss how alcohol-mediated altered autophagy leads to the development of pancreatitis. We also provide insights into how alcohol interactions with other co-morbidities such as smoking or viral infections may negatively affect exocrine and endocrine pancreatic function. Finally, we present potential strategies to ameliorate organellar dysfunction which could attenuate pancreatic dysfunction and pancreatitis severity.

Pancreatic adenocarcinoma, chronic pancreatitis, and MODY-8 diabetes: is bile salt-dependent lipase (or carboxyl ester lipase) at the crossroads of pancreatic pathologies?

Pancreatic adenocarcinomas and diabetes mellitus are responsible for the deaths of around two million people each year worldwide. Patients with chronic pancreatitis do not die directly of this disease, except where the pathology is hereditary. Much current literature supports the involvement of bile salt-dependent lipase (BSDL), also known as carboxyl ester lipase (CEL), in the pathophysiology of these pancreatic diseases. The purpose of this review is to shed light on connections between chronic pancreatitis, diabetes, and pancreatic adenocarcinomas by gaining an insight into BSDL and its variants. This enzyme is normally secreted by the exocrine pancreas, and is diverted within the intestinal lumen to participate in the hydrolysis of dietary lipids. However, BSDL is also expressed by other cells and tissues, where it participates in lipid homeostasis. Variants of BSDL resulting from germline and/or somatic mutations (nucleotide insertion/deletion or nonallelic homologous recombination) are expressed in the pancreas of patients with pancreatic pathologies such as chronic pancreatitis, MODY-8, and pancreatic adenocarcinomas. We discuss the possible link between the expression of BSDL variants and these dramatic pancreatic pathologies, putting forward the suggestion that BSDL and its variants are implicated in the cell lipid metabolism/reprogramming that leads to the dyslipidemia observed in chronic pancreatitis, MODY-8, and pancreatic adenocarcinomas. We also propose potential strategies for translation to therapeutic applications.

Hepatic alcohol dehydrogenase deficiency induces pancreatic injury in chronic ethanol feeding model of deer mice

The single most common cause of chronic pancreatitis (CP, a serious inflammatory disease) is chronic alcohol abuse, which impairs hepatic alcohol dehydrogenase (ADH, a major ethanol oxidizing enzyme). Previously, we found ~5 fold greater fatty acid ethyl esters (FAEEs), and injury in the pancreas of hepatic ADH deficient (ADH^-) vs. hepatic normal ADH (ADH⁺) deer mice fed 3.5g% ethanol via liquid diet daily for two months. Therefore, progression of ethanol-induced pancreatic injury was determined in ADH^- deer mice fed ethanol for four months to delineate the mechanism and metabolic basis of alcoholic chronic pancreatitis (ACP). In addition to a substantially increased blood alcohol concentration and plasma FAEEs, significant degenerative changes, including atrophy and loss of acinar cells in some areas, ultrastructural changes evident by such features as swelling and disintegration of endoplasmic reticulum (ER) cisternae and ER stress were observed in the pancreas of ethanol-fed ADH^- deer mice vs. ADH⁺ deer mice. These changes are consistent with noted increases in pancreatic injury markers (plasma lipase, pancreatic trypsinogen activation peptide, FAEE synthase and cathepsin B) in ethanol-fed ADH^- deer mice. Most importantly, an increased levels of pancreatic glucose regulated protein (GRP) 78 (a prominent ER stress marker) were found to be closely associated with increased phosphorylated eukaryotic initiation factor (eIF) 2α signaling molecule in PKR-like ER kinase branch of unfolded protein response (UPR) as compared to X box binding protein 1S and activating transcription factor (ATF)6 - 50kDa protein of inositol requiring enzyme 1α and ATF6 branches of UPR, respectively, in ethanol-fed ADH^- vs. ADH⁺ deer mice. These results along with findings on plasma FAEEs, and pancreatic histology and injury markers suggest a metabolic basis of ethanol-induced pancreatic injury, and provide new avenues to understand metabolic basis and molecular mechanism of ACP.

The role of fat and alcohol in acute pancreatitis: A dangerous liaison

Excessive alcohol consumption is a major trigger for severe acute pancreatitis which may lead to multi-organ dysfunction and premature death of the individual. Hyperlipidaemia is a risk factor for both acute and chronic pancreatitis and the role of fatty acids in mediating damage has received increasing attention in recent years. In the pancreas ethanol is metabolised by both oxidative and non-oxidative pathways. The latter, predominant route generates fatty acid ethyl esters (FAEEs) from fatty acid substrates via the action of diverse enzymes called FAEE synthases, including carboxylester lipase an enzyme synthesized and secreted by the acinar cells. Inhibition of the oxidative pathway promotes formation of FAEEs which induce sustained elevations of cytosolic calcium leading to inhibition of mitochondrial function, loss of ATP and necrosis of isolated pancreatic acinar cells. Furthermore, FAEEs undergo hydrolysis in the mitochondria releasing free fatty acids that exert toxic effects. Our recent work has shown that pharmacological inhibition of carboxylester lipase ameliorated detrimental effects of non-oxidative ethanol metabolism in isolated pancreatic acinar cells in vitro and in a new in vivo experimental model of alcoholic acute pancreatitis, revealing a specific enzyme target for ethanol-induced injury. Strategies that prevent FAEE synthesis, protect mitochondria, reduce calcium overload or sustain calcium homeostasis by ATP provision may provide promising therapeutic avenues for the treatment of alcoholic acute pancreatitis.

Fatty acid ethyl ester synthase inhibition ameliorates ethanol-induced Ca2+-dependent mitochondrial dysfunction and acute pancreatitis

OBJECTIVE

Non-oxidative metabolism of ethanol (NOME) produces fatty acid ethyl esters (FAEEs) via carboxylester lipase (CEL) and other enzyme action implicated in mitochondrial injury and acute pancreatitis (AP). This study investigated the relative importance of oxidative and non-oxidative pathways in mitochondrial dysfunction, pancreatic damage and development of alcoholic AP, and whether deleterious effects of NOME are preventable.

DESIGN

Intracellular calcium ([Ca(2+)](C)), NAD(P)H, mitochondrial membrane potential and activation of apoptotic and necrotic cell death pathways were examined in isolated pancreatic acinar cells in response to ethanol and/or palmitoleic acid (POA) in the presence or absence of 4-methylpyrazole (4-MP) to inhibit oxidative metabolism. A novel in vivo model of alcoholic AP induced by intraperitoneal administration of ethanol and POA was developed to assess the effects of manipulating alcohol metabolism.

RESULTS

Inhibition of OME with 4-MP converted predominantly transient [Ca(2+)](C) rises induced by low ethanol/POA combination to sustained elevations, with concurrent mitochondrial depolarisation, fall of NAD(P)H and cellular necrosis in vitro. All effects were prevented by 3-benzyl-6-chloro-2-pyrone (3-BCP), a CEL inhibitor. 3-BCP also significantly inhibited rises of pancreatic FAEE in vivo and ameliorated acute pancreatic damage and inflammation induced by administration of ethanol and POA to mice.

CONCLUSIONS

A combination of low ethanol and fatty acid that did not exert deleterious effects per se became toxic when oxidative metabolism was inhibited. The in vitro and in vivo damage was markedly inhibited by blockade of CEL, indicating the potential for development of specific therapy for treatment of alcoholic AP via inhibition of FAEE generation.

Alcohol oxidizing enzymes and ethanol-induced cytotoxicity in rat pancreatic acinar AR42J cells

Alcoholic chronic pancreatitis (ACP) is a serious inflammatory disease causing significant morbidity and mortality. Due to lack of a suitable animal model, the underlying mechanism of ACP is poorly understood. Chronic alcohol abuse inhibits alcohol dehydrogenase (ADH) and facilitates nonoxidative metabolism of ethanol to fatty acid ethyl esters (FAEEs) in the pancreas frequently damaged during chronic ethanol abuse. Earlier, we reported a concentration-dependent formation of FAEEs and cytotoxicity in ethanol-treated rat pancreatic tumor (AR42J) cells, which express high FAEE synthase activity as compared to ADH and cytochrome P450 2E1. Therefore, the present study was undertaken to investigate the role of various ethanol oxidizing enzymes in ethanol-induced pancreatic acinar cell injury. Confluent AR42J cells were pre-treated with inhibitors of ADH class I and II [4-methylpyrazole (MP)] or class I, II, and III [1,10-phenanthroline (PT)], cytochrome P450 2E1 (trans-1,2-dichloroethylene) or catalase (sodium azide) followed by incubation with 800 mg% ethanol at 37°C for 6 h. Ethanol metabolism, cell viability, cytotoxicity (apoptosis and necrosis), cell proliferation status, and formation of FAEEs in AR42J cells were measured. The cell viability and cell proliferation rate were significantly reduced in cells pretreated with 1,10-PT + ethanol followed by those with 4-MP + ethanol. In situ formation of FAEEs was twofold greater in cells incubated with 1,10-PT + ethanol and ∼1.5-fold in those treated with 4-MP + ethanol vs. respective controls. However, cells treated with inhibitors of cytochrome P450 2E1 or catalase in combination of ethanol showed no significant changes either for FAEE formation, cell death or proliferation rate. Therefore, an impaired ADH class I-III catalyzed oxidation of ethanol appears to be a key contributing factor in ethanol-induced pancreatic injury via formation of nonoxidative metabolites of ethanol.

Synthesis of fatty acid ethyl esters in mammalian tissues after ethanol exposure: a systematic review of the literature

The ability to undergo non-oxidative metabolism from ethanol to fatty acid ethyl esters (FAEEs) varies greatly among tissues and organs. To gain a greater understanding of non-oxidative ethanol metabolism to FAEE, we aimed to collect all published data on FAEE synthesis in mammalian organs and tissues to identify all tissues, organs, and enzymes that are known to, or likely possess FAEE-synthetic activity. A systematic search for relevant papers was performed and two independent reviewers examined potentially relevant abstracts (articles on FAEEs that pertain to ethanol exposure) to determine whether they met the inclusion criteria. Information on FAEE synthesis was retrieved from papers meeting the inclusion/exclusion criteria and summarized by organ/tissue/matrix examined. The systematic search through four databases yielded 78 articles that investigated FAEE synthesis by tissues, tissue fractions and cell lines, and 29 articles that attempted to purify and/or characterize the enzymes involved in FAEE synthesis. Two enzyme activities have been studied: FAEE synthase (FAEES, which conjugates ethanol and free fatty acid) and acyl-CoA: ethanol O-acyltransferase (AEAT, which conjugates ethanol and fatty acyl-CoA). Both activities are expressed by a variety of different enzymes. FAEES activity is the most widely studied and has been purified from several tissues and shown to be associated with several well-known enzymes, while the identity of enzymes possessing AEAT activity remains unknown. The organs and tissues that have been shown to synthesize FAEEs are discussed, with special emphasis on the studies that attempted to elucidate the enzymology of FAEE synthesis in those tissues.

Overexpression of hydroxymethylglutaryl CoA synthase 2 and 2,4-dienoyl-CoA reductase in rat pancreas following chronic alcohol consumption

OBJECTIVES

The mechanism of alcohol-induced pancreatic damage is unclear. The aim of this study was to clarify the effects of chronic alcohol intake on the pancreatic proteome.

METHODS

Rats were fed an alcohol-containing Lieber-DeCarli liquid diet, and the pancreatic proteome was compared with that of pair-fed control rats using agarose 2-dimensional gel electrophoresis followed by liquid chromatography-tandem mass spectrometry.

RESULTS

The expression of 3 proteins was consistently altered in alcohol-fed rats: 1 protein was down-regulated, and 2 proteins were up-regulated. The 2 up-regulated proteins were identified as 2,4-dienoyl-CoA reductase and hydroxymethylglutaryl-CoA synthase (HMGCS2). The combined concentration of malondialdehyde and 4-hydroxyalkenals was significantly greater in alcohol-fed rats. It is noteworthy that the reactivity of anti-4-hydroxy-2-nonenal antibody was significantly higher toward HMGCS2 isolated from alcohol-fed rats. The activity of HMGCS2 was higher in alcohol-fed rats, but the relative increase in enzyme activity in alcohol-fed rats was less than the relative increase in HMGCS2 expression.

CONCLUSIONS

Chronic alcohol consumption results in distinct alterations in the expression of 3 pancreatic proteins. The reactivity of 4-hydroxy-2-nonenal toward one of the up-regulated proteins, HMGCS2, increased markedly following chronic alcohol intake, suggesting that up-regulation of HMGCS2 is connected with alterations of lipid peroxidation induced by alcohol.

Genetics and alcohol: a lethal combination in pancreatic disease?

An association between alcohol consumption and pancreatic diseases has been recognized for decades, but the absolute risk for pancreatic disease for individuals who drink alcohol is low. Other than smoking, few additional environmental factors have been identified, which suggests that genetic risk factors may be important. Studies in our laboratory using the Lieber-DeCarli feeding technique demonstrate that alcohol causes oxidative stress and mitochondrial damage and alters neruohormonal regulation of the pancreas after a threshold dose is exceeded, which makes the pancreas susceptible to withdrawal hypersensitivity and acute pancreatitis. Alcohol also shifts cell death from apoptosis to necrosis and promotes fibrosis through anti-inflammatory immune mechanisms. Others have demonstrated that alcohol lowers the threshold for trypsin activation in acinar cells, which increases sensitivity to triggering pancreatitis. In addition, we used the Lieber-DeCarli diet plus recurrent acute pancreatitis insults to develop the first animal model of chronic pancreatitis that mimics human disease. Finally, our North American Pancreatitis Study 2 (NAPS2), which was built on insights from animal studies, confirmed the threshold effect predicted by Charles Lieber (>5 drinks per day and >35 drinks/week). These studies and others also defined distinctive roles of alcohol and genetics in the etiology and progression of chronic pancreatitis.

Investigating the pathobiology of alcoholic pancreatitis

Alcohol abuse is one of the most common causes of pancreatitis. The risk of developing alcohol-induced pancreatitis is related to the amount and duration of drinking. However, only a small portion of heavy drinkers develop disease, indicating that other factors (genetic, environmental, or dietary) contribute to disease initiation. Epidemiologic studies suggest roles for cigarette smoking and dietary factors in the development of alcoholic pancreatitis. The mechanisms underlying alcoholic pancreatitis are starting to be understood. Studies from animal models reveal that alcohol sensitizes the pancreas to key pathobiologic processes that are involved in pancreatitis. Current studies are focussed on the mechanisms responsible for the sensitizing effect of alcohol; recent findings reveal disordering of key cellular organelles including endoplasmic reticulum, mitochondria, and lysosomes. As our understanding of alcohol's effects continue to advance to the level of molecular mechanisms, insights into potential therapeutic strategies will emerge providing opportunities for clinical benefit.

Pancreatic injury in hepatic alcohol dehydrogenase-deficient deer mice after subchronic exposure to ethanol

Pancreatitis caused by activation of digestive zymogens in the exocrine pancreas is a serious chronic health problem in alcoholic patients. However, mechanism of alcoholic pancreatitis remains obscure due to lack of a suitable animal model. Earlier, we reported pancreatic injury and substantial increases in endogenous formation of fatty acid ethyl esters (FAEEs) in the pancreas of hepatic alcohol dehydrogenase (ADH)-deficient (ADH(-)) deer mice fed 4% ethanol. To understand the mechanism of alcoholic pancreatitis, we evaluated dose-dependent metabolism of ethanol and related pancreatic injury in ADH(-) and hepatic ADH-normal (ADH(+)) deer mice fed 1%, 2% or 3.5% ethanol via Lieber-DeCarli liquid diet daily for 2months. Blood alcohol concentration (BAC) was remarkably increased and the concentration was ∼1.5-fold greater in ADH(-) vs. ADH(+) deer mice fed 3.5% ethanol. At the end of the experiment, remarkable increases in pancreatic FAEEs and significant pancreatic injury indicated by the presence of prominent perinuclear space, pyknotic nuclei, apoptotic bodies and dilation of glandular ER were found only in ADH(-) deer mice fed 3.5% ethanol. This pancreatic injury was further supported by increased plasma lipase and pancreatic cathepsin B (a lysosomal hydrolase capable of activating trypsinogen), trypsinogen activation peptide (by-product of trypsinogen activation process) and glucose-regulated protein 78 (endoplasmic reticulum stress marker). These findings suggest that ADH-deficiency and high alcohol levels in the body are the key factors in ethanol-induced pancreatic injury. Therefore, determining how this early stage of pancreatic injury advances to inflammation stage could be important for understanding the mechanism(s) of alcoholic pancreatitis.

The role of alcohol and smoking in pancreatitis

Chronic alcohol use has been linked to chronic pancreatitis for over a century, but it has not been until the last decade that the role of alcohol in chronic pancreatitis has been elucidated in animals and, only in recent years, in human populations. Although a dose-dependent association between alcohol consumption and chronic pancreatitis may exist, a staistical association has been shown only with the consumption of >or=5 alcoholic drinks per day. Smoking also confers a strong, independent and dose-dependent risk of pancreatitis that may be additive or multiplicative when combined with alcohol. Alcohol increases the risk of acute pancreatitis in several ways and, most importantly, changes the immune response to injury. Genetic factors are also important and further studies are needed to clarify the role of gene-environment interactions in pancreatitis. In humans, aggressive interventional counseling against alcohol use may reduce the frequency of recurrent attacks of disease and smoking cessation may help to slow the progression of acute to chronic pancreatitis.

Pathobiology of alcoholic pancreatitis

This paper provides a summary of the effects of alcohol abuse on the pathobiologic responses that occur during acute and chronic pancreatitis considering both the human disease and animal/tissue models. The effects are multiple and include ones on cell death leading to necrosis; on inflammation resulting in a sensitized response to pancreatic stress; and fibrosis through effects of ethanol on pancreatic stellate cells and the plasminogen system. Although the effects of alcohol are multiple and complex, it is likely that a combination of a few key effects on these pathobiologic responses drive the increased sensitivity of the pancreas to acute pancreatitis with pancreatic stress and the promotion of chronic pancreatitis with pancreatic injury occurring during acute pancreatitis.

Detection of alcohol consumption during pregnancy—Current and future biomarkers

Alcohol, one of the most frequently reported addictions, is a significant public health problem in the USA. Early identification is important and would aid in intervention for the pregnant woman who continues to drink and for the affected infant. To date, there isn't a definitive test which identifies either alcohol abuse during pregnancy or newborns exposed to alcohol prenatally. The existing biomarkers can detect varying degrees of alcohol exposure but further research is needed to improve sensitivity/specificity and to validate these markers.

Ethanol administration to cystic fibrosis knockout mice results in increased fatty acid ethyl ester production

BACKGROUND

Fatty acid ethyl esters (FAEE) are nonoxidative ethanol metabolites shown to produce toxic effects in the liver and pancreas in vivo and in vitro. Because alcohol-induced chronic pancreatitis is associated with mutations in the gene responsible for cystic fibrosis (CFTR), we hypothesized that CFTR dysfunction leads to increased levels of these toxic nonoxidative ethanol metabolites following alcohol administration.

METHODS

Cystic fibrosis (CF) and wild-type (WT) mice were injected intraperitoneally with 1, 2, or 3 g/kg of 50% ethanol. Mice were sacrificed and the liver and pancreas removed for FAEE analysis.

RESULTS

The mean FAEE concentration (pmol/g) detected in the liver of cftr mice following injection with 2 g/kg of ethanol was significantly greater than the amount detected in WT (p < 0.005). A similar trend in FAEE concentration was seen in the pancreas, but the difference was not statistically different. In both the liver and pancreas, analysis of individual FAEE species demonstrated a selective increase in ethyl oleate.

CONCLUSION

These data show an association between CFTR dysfunction and qualitative and quantitative changes in FAEE in liver and pancreas upon ethanol exposure.

Gene-environment factors that contribute to alcoholic pancreatitis in humans

Alcohol-associated acute and chronic pancreatitis occur in a minority of alcohol users, suggesting that most drinkers are protected from pancreatic diseases while a subset is susceptible. Ongoing studies suggest that the pathophysiology is complex and can involve multiple genetic and environmental pathways and stochastic events. Both rat models and human genetic epidemiology studies have been used to understand susceptibility and modifying factors in humans. Rat studies suggest that different types of altered pancreatic physiology occur depending on dose, they occur rapidly and that alcohol changes the immune response to recurrent pancreatic injury. Human studies suggest that PRSS1 and SPINK1 mutation increase the pancreas' susceptibility to alcohol-associated pancreatitis, and that tobacco smoking, and some factors, affect disease progression.

Structure, function and regulation of carboxylesterases

This review covers current developments in molecular-based studies of the structure and function of carboxylesterases. To allay the confusion of the classic classification of carboxylesterase isozymes, we have proposed a novel nomenclature and classification of mammalian carboxylesterases on the basis of molecular properties. In addition, mechanisms of regulation of gene expression of carboxylesterases by xenobiotics and involvement of carboxylesterase in drug metabolism and enzyme induction are also described.

Metabolic basis of ethanol-induced cytotoxicity in recombinant HepG2 cells: role of nonoxidative metabolism

Chronic alcohol abuse, a major health problem, causes liver and pancreatic diseases and is known to impair hepatic alcohol dehydrogenase (ADH). Hepatic ADH-catalyzed oxidation of ethanol is a major pathway for the ethanol disposition in the body. Hepatic microsomal cytochrome P450 (CYP2E1), induced in chronic alcohol abuse, is also reported to oxidize ethanol. However, impaired hepatic ADH activity in a rat model is known to facilitate a nonoxidative metabolism resulting in formation of nonoxidative metabolites of ethanol such as fatty acid ethyl esters (FAEEs) via a nonoxidative pathway catalyzed by FAEE synthase. Therefore, the metabolic basis of ethanol-induced cytotoxicity was determined in HepG2 cells and recombinant HepG2 cells transfected with ADH (VA-13), CYP2E1 (E47) or ADH + CYP2E1 (VL-17A). Western blot analysis shows ADH deficiency in HepG2 and E47 cells, compared to ADH-overexpressed VA-13 and VL-17A cells. Attached HepG2 cells and the recombinant cells were incubated with ethanol, and nonoxidative metabolism of ethanol was determined by measuring the formation of FAEEs. Significantly higher levels of FAEEs were synthesized in HepG2 and E47 cells than in VA-13 and VL-17A cells at all concentrations of ethanol (100-800 mg%) incubated for 6 h (optimal time for the synthesis of FAEEs) in cell culture. These results suggest that ADH-catalyzed oxidative metabolism of ethanol is the major mechanism of its disposition, regardless of CYP2E1 overexpression. On the other hand, diminished ADH activity facilitates nonoxidative metabolism of ethanol to FAEEs as found in E47 cells, regardless of CYP2E1 overexpression. Therefore, CYP2E1-mediated oxidation of ethanol could be a minor mechanism of ethanol disposition. Further studies conducted only in HepG2 and VA-13 cells showed lower ethanol disposition and ATP concentration and higher accumulation of neutral lipids and cytotoxicity (apoptosis) in HepG2 cells than in VA-13 cells. The apoptosis observed in HepG2 vs. VA-13 cells incubated with ethanol appears to be mediated by release of mitochondrial cytochrome c via activation of caspase-9 and caspase-3. These results strongly support our hypothesis that diminished hepatic ADH activity facilitates nonoxidative metabolism of ethanol and the products of ethanol nonoxidative metabolism cause apoptosis in HepG2 cells via intrinsic pathway.

Fatty acid ethyl esters cause pancreatic calcium toxicity via inositol trisphosphate receptors and loss of ATP synthesis

BACKGROUND & AIMS

Fatty acid ethyl esters are ethanol metabolites inducing sustained, toxic elevations of the acinar cytosolic free calcium ion concentration ([Ca(2+)](C)) implicated in pancreatitis. We sought to define the mechanisms of this elevation.

METHODS

Isolated mouse pancreatic acinar cells were loaded with fluorescent dyes for confocal microscopy to measure [Ca(2+)](C) (Fluo 4, Fura Red), endoplasmic reticulum calcium ion concentration ([Ca(2+)](ER), Mg Fluo 4), mitochondrial membrane potential (TMRM), ADP:ATP ratio (Mg Green), and NADH autofluorescence in response to palmitoleic acid ethyl ester and palmitoleic acid (10-100 micromol/L). Whole-cell patch clamp was used to measure the calcium-activated chloride current and apply ethanol metabolites and/or ATP intracellularly.

RESULTS

Intracellular delivery of ester induced oscillatory increases of [Ca(2+)](C) and calcium-activated currents, inhibited acutely by caffeine (20 mmol/L), but not atropine, indicating involvement of inositol trisphosphate receptor channels. The stronger effect of extracellular ester or acid caused depletion of [Ca(2+)](ER), not prevented by caffeine, but associated with depleted ATP, depleted NADH autofluorescence, and depolarized mitochondria, suggesting calcium-ATPase pump failure because of lack of ATP. Intracellular ATP abolished the sustained rise in [Ca(2+)](C), although oscillatory signals persisted that were prevented by caffeine. Inhibition of ester hydrolysis markedly reduced its calcium-releasing effect and consequent toxicity.

CONCLUSIONS

Fatty acid ethyl ester increases [Ca(2+)](C) through inositol trisphosphate receptors and, following hydrolysis, through calcium-ATPase pump failure from impaired mitochondrial ATP production. Lowering cellular fatty acid substrate concentrations may reduce cell injury in pancreatitis.

Animal models and their results in gastrointestinal alcohol research

Alcohol-induced diseases of the gastrointestinal tract play an important role in clinical gastroenterology. However, the precise pathophysiological mechanisms are still largely unknown. Alcohol research depends essentially on animal models due to the fact that controlled experimental studies of ethanol-induced diseases in humans are unethical. Animal models have already been successfully applied to disclose and analyze molecular mechanisms in alcohol-induced diseases, partially by using knockout technology. Because of a lack of transferability of some animal models to the human condition, results have to be interpreted cautiously. For some alcohol-related diseases like chronic alcoholic pancreatitis, the ideal animal model does not yet exist. Here we provide an overview of the most commonly used animal models in gastrointestinal alcohol research. We will also briefly discuss the findings based on animal models as well as the current concepts of pathophysiological mechanisms involved in acute and chronic alcoholic damage of the esophagus, stomach, small and large intestine, pancreas and liver.

Alcoholic pancreatitis

A history of excessive alcohol consumption is found in the majority of patients with chronic pancreatitis, and numerous research efforts revealed insights into the pathogenesis of alcohol-induced pancreatic damage. However, the exact mechanisms underlying the disease are not yet clarified, and the origin of alcoholic chronic pancreatitis continues to be the topic of speculation and investigation. This article provides an overview about the epidemiology of alcoholic chronic pancreatitis, the epidemiologic association of alcohol intake and pancreatitis and the clinical course of the disease. Finally, this article summarizes several hypothetical concepts that try to explain the early and late pathophysiological mechanisms of acute and chronic pancreatitis.

Alcoholic pancreatitis

Without doubt, alcohol consumption is one of the most important considerations in adults with acute or chronic pancreatitis. Understanding chronic pancreatitis as a complex disorder in which complimentary factors are required for recurrent acute and late chronic pancreatitis to develop in subsets of patients is critical for the early diagnosis and management of these individuals. Recent pathophysiological and genetic findings represent the beginning of major diagnostic and treatment breakthroughs that are likely to continue for the foreseeable future. The information provided in this article should provide the physician with a fresh perspective and remind the clinician of the importance of an accurate and complete history, and the need to document the actual alcohol consumption, pattern of drinking, and raise appropriate concerns if signs of alcoholism are detected. If alcohol-associated pancreatitis is detected, then limitation of pancreatic damage, limitation of progression, or preventative intervention should become the major concern.

Theories, mechanisms, and models of alcoholic chronic pancreatitis

Alcoholic chronic pancreatitis is a severe, disabling, chronic inflammatory condition of the pancreas that is seen in fewer than 5% of alcoholics. The severity and unpredictability of this condition has lead to several theories on the mechanism causing chronic pancreatitis based on careful clinical observation. Hypothetical mechanisms were applied to various animal models. Finally, following multiple lines of evidence, there is a convergence of thought and development of some new models that are quite instructive. Taken together, chronic alcohol consumption by rats results in multiple effects on the pancreas that increase the risk of acute pancreatitis, including ongoing acinar cell injury that lowers the threshold for hyperstimulation-induced acute pancreatitis, neurohormonal injury, and adaptation that results in acinar cell hyperstimulation, increased susceptibility to viral mediated acute pancreatitis, and possibly other factors. After acute pancreatitis initiates the inflammatory process, the chronic inflammation and fibrosis of alcoholic chronic pancreatitis are driven by diet, the acinar cell stress response to continued alcohol that may be potentiated by toxic alcohol metabolites, hypoxia, hyperstimulation, and partial duct obstruction; plus the effects of proinflammatory immunocytes and cytokines; and by stellate cell-mediated fibrosis driven by anti-inflammatory cytokines, alcohol, and alcohol metabolites. The factors determining which alcoholic will develop alcoholic chronic pancreatitis likely involve genetic factors, dietary factors, and susceptibility to pancreatic injury through several mechanisms ranging from trauma to gallstones to viruses.

Purification and characterization of rat pancreatic fatty acid ethyl ester synthase and its structural and functional relationship to pancreatic cholesterol esterase

Formation of fatty acid ethyl esters (FAEEs, catalyzed by FAEE synthase) has been implicated in the pathogenesis of chronic pancreatitis. In previous studies, we demonstrated that FAEE synthase, purified from rat liver microsomes, is identical to rat liver carboxylesterase (pI 6.1), and structurally and functionally different than that from pancreas. In this study, we purified and characterized rat pancreatic microsomal FAEE synthase, and determined its relationship with rat pancreatic cholesterol esterase (ChE). Since most of the serine esterases express p-nitrophenyl acetate (PNPA)-hydrolyzing activity as well as synthetic activity to form fatty acid esters or amides with a wide spectrum of alcohols and amines, respectively, we used PNPA-hydrolyzing activity to monitor the purification of FAEE synthase during various chromatographic purification steps. Synthesizing activity towards FAEEs, fatty acid methyl esters, and fatty acid anilides was measured only in the pooled fractions. At each step of purification (ammonium sulfate saturation, Q Sepharose XL, and heparin-agarose column chromatographies, and high performance liquid chromatography (anion exchange and gel filtration)) synthetic as well as hydrolytic activities copurified. Using ethanol, methanol, or aniline as substrates, the ester or anilide synthesizing activity of the purified protein was found to be 8709, 13000, and 2201 nmol/h/mg protein, respectively. The purified protein displayed a single band with an estimated molecular mass of approximately 68 kD upon SDS-PAGE under reduced denaturing conditions, cross-reacted with antisera against rat pancreatic ChE and showed 100% N-terminal sequence homology of the first 15 amino acids to that of rat pancreatic ChE. These results suggest that the purified protein has broad substrate specificity towards the conjugation of endogenous long chain fatty acids with substrates having hydroxyl and amino groups and is identical to ChE.

Nonoxidative ethanol metabolites alter extracellular matrix protein content in rat pancreas

BACKGROUND & AIMS

The mechanisms involved in ethanol-induced pancreas fibrosis are poorly understood. Here we show that fatty acid ethyl esters (FAEEs), nonoxidative ethanol metabolites, increase extracellular matrix (ECM) protein levels in pancreas.

METHODS

Rat pancreatic acini were incubated for 1-4 hours with FAEEs or acetaldehyde. In another set of experiments, rats received an intravenous infusion of FAEEs for 6 hours. Collagens were assessed by a hydroxyproline assay. Laminin and fibronectin were analyzed by Western blotting. Gene expression of ECM proteins was measured by conventional and real-time reverse-transcription polymerase chain reaction (RT-PCR). Matrix metalloproteinase (MMP), plasmin, and urokinase-type plasminogen activator (uPA) activities were determined by zymography and fluorogenic assays.

RESULTS

FAEEs increased collagen, laminin, and fibronectin levels in pancreatic acini without affecting messenger RNA (mRNA) expression for these proteins. Actinomycin D, a transcriptional inhibitor, did not block the increase in ECM proteins induced by FAEEs. FAEEs reduced the activity of the serine protease, plasmin, and that of the uPA. Consistent with these results, the serine protease inhibitor aprotinin reproduced the effects of FAEEs and prevented the further increase in ECM proteins induced by FAEEs. In vivo administration of FAEEs reduced plasmin and uPA activities and increased ECM protein levels in pancreas. Acetaldehyde had minor effects on ECM protein levels and did not affect plasmin activity.

CONCLUSIONS

FAEEs increase ECM protein levels in pancreas. The results suggest that this effect is caused primarily by an inhibition in ECM degradation via serine proteases including the plasminogen system.

Animal models in gastrointestinal alcohol research-a short appraisal of the different models and their results

Alcohol-related diseases of the gastrointestinal tract play an important role in clinical gastroenterology. However, the mechanisms and pathophysiology underlying the effects of ethanol on the organs of the digestive tract are not yet completely understood. Animal models represent an essential tool for investigating alcohol-related diseases because they give researchers the opportunity to use methods that cannot be used in humans, such as knockout technology. However, there is still a need for new animal models resembling the human condition, since for some alcohol-related diseases such as chronic alcoholic pancreatitis, the ideal animal model does not yet exist. In this chapter, we provide an overview of the most commonly used animal models in gastrointestinal alcohol research. We will also briefly discuss the current concepts of the pathophysiological mechanisms involved in acute and chronic alcoholic damage of the oesophagus, stomach, small and large intestine, pancreas and liver.

Animal models in alcoholic pancreatitis--what can we learn?

Although the majority of patients with chronic pancreatitis present a history of excessive alcohol consumption, the pathophysiology underlying chronic alcoholic pancreatitis remains poorly defined. Since experimental animal models represent helpful tools in understanding human disease, numerous laboratory studies have been designed to study the effects of alcohol on the pancreas. In the present article we summarize the existing animal models that have been used to investigate the effects of acute and chronic alcohol application on the development of morphological alterations and pancreatic injury. Despite considerable experimental effort, acute or chronic ethanol feeding alone failed to cause acute or chronic pancreatitis in animals. However, ethanol-feeding and the combination with other procedures has demonstrated several mechanisms that play a role in ethanol-induced pancreatic injury. Among these ethanol-induced alterations and mechanisms are the reduction of pancreatic blood-flow and microcirculation, damaging effects of ethanol metabolites, increased pancreatic acinar cell expression of digestive and lysosomal enzymes, increased glandular enzyme content, additional nutritional factors, pancreatic duct obstruction, and limitations of pancreatic regeneration. Although no satisfactory animal model for alcoholic pancreatitis has been developed, these animal models have provided insights in several factors that predispose the pancreas to development of pancreatic injury and contribute to alcoholic pancreatitis.

Hereditary pancreatitis: a model for inflammatory diseases of the pancreas

Acute and chronic pancreatitis remain among the most recalcitrant of all diseases to investigation and intervention. In the majority of patients, excessive alcohol consumption is associated with development of the disease. Therefore, several theories have been proposed seeking to explain the relationship between alcohol and the development of acute and chronic pancreatitis. However, recent investigations in hereditary pancreatitis provided important insights into chronic pancreatitis pathogenesis and offer an important model for understanding pancreatic inflammation. This article highlights several advances gained from investigating hereditary pancreatitis kindreds, and reviews the TIGAR-O risk/aetiology classification system. Finally, the major independent theories on development of chronic pancreatitis are reviewed with respect to the SAPE hypothesis of chronic pancreatitis pathogenesis.