The effect of chronic alcohol administration on cerulein-induced pancreatitis

How Alcohol Induces Human Acute Alcoholic Pancreatitis-Problem Solved?

It has been a puzzle why only a minority of heavy alcohol drinkers develop acute alcoholic pancreatitis. In this review, the sparse data available from published studies were collected and, based on them, a hypothesis was formed. Long-term high alcohol consumption results in lowered cholecystokinin and cholinergic stimulus of the pancreas, and causes concentration and acidification of pancreatic fluid, predisposing to protein secretion. Early during the withdrawal period when returning to a normal or high-fat nonalcoholic diet, there is a relative hyperstimulation of the pancreas, a well-established mechanism that results in experimental acute pancreatitis. Lower, physiological stimulation is enough to start acute pancreatitis, when the secretions cause temporary obstruction in the duct system; the stimulation against temporary obstruction is also well-known to result in experimental acute pancreatitis. The magnitude of alcohol-induced deficits in acinar cell defense mechanisms then finally determines the onset of pancreatitis.

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.

Ethanol consumption as inductor of pancreatitis

Alcohol abuse is a major cause of pancreatitis, a condition that can manifest as both acute necroinflammation and chronic damage (acinar atrophy and fibrosis). Pancreatic acinar cells can metabolize ethanol via the oxidative pathway, which generates acetaldehyde and involves the enzymes alcohol dehydrogenase and possibly cytochrome P4502E1. Additionally, ethanol can be metabolized via a nonoxidative pathway involving fatty acid ethyl ester synthases. 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. This current work will review some recent advances in the knowledge about ethanol actions on the exocrine pancreas and its relationship to inflammatory disease and cancer.

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.

A rat model reproducing key pathological responses of alcoholic chronic pancreatitis

Although alcohol abuse is the major cause of chronic pancreatitis, the pathogenesis of alcoholic chronic pancreatitis (ACP) remains obscure. A critical obstacle to understanding the mechanism of ACP is lack of animal models. Our objective was to develop one such model. Rats were pair-fed for 8 wk ethanol or control Lieber-DeCarli liquid diet. For the last 2 wk, they received cyclosporin A (CsA; 20 mg/kg once daily) or vehicle. After 1 wk on CsA, one episode of acute pancreatitis was induced by four 20 microg/kg injections of cerulein (Cer); controls received saline. Pancreas was analyzed 1 wk after the acute pancreatitis. CsA or Cer treatments alone did not result in pancreatic injury in either control (C)- or ethanol (E)-fed rats. We found, however, that alcohol dramatically aggravated pathological effect of the combined CsA+Cer treatment on pancreas, resulting in massive loss of acinar cells, persistent inflammatory infiltration, and fibrosis. Macrophages were prominent in the inflammatory infiltrate. Compared with control-fed C+CsA+Cer rats, their ethanol-fed E+CsA+Cer counterparts showed marked increases in pancreatic NF-kappaB activation and cytokine/chemokine mRNA expression, collagen and fibronectin, the expression and activities of matrix metalloproteinase-2 and -9, and activation of pancreatic stellate cells. Thus we have developed a model of alcohol-mediated postacute pancreatitis that reproduces three key responses of human ACP: loss of parenchyma, sustained inflammation, and fibrosis. The results indicate that alcohol impairs recovery from acute pancreatitis, suggesting a mechanism by which alcohol sensitizes pancreas to chronic injury.