Clinical evidence of pathogenesis in chronic pancreatitis

Chronic pancreatitis is a continuing inflammatory disease characterized by irreversible morphological change and, typically, by pain and permanent impairment of function. The pathogenesis of pancreatitis, either acute or chronic, is still controversial. There have been no widely accepted concepts to provide a reasonable explanation linking the known etiological factors and the pathophysiological aspects of the disease. Alcohol is undoubtedly the major etiological factor in most countries, and the relative importance of alcohol as a cause of chronic pancreatitis ranges from 40% to 90% in various countries. As fewer than 10% of alcoholics develop chronic pancreatitis, other nutritional or genetic influences are likely to be involved in the pathogenesis of alcoholic pancreatitis. Accessory pancreas incidentally found in patients with chronic alcoholic pancreatitis does not always have the pathological findings seen in the main pancreas. Integrity of the pancreatic duct seems to be another important factor for chronic alcoholic pancreatitis. Gene mutations of the cystic fibrosis transmembrane conductance regulator (CFTR), cationic trypsinogen, and pancreatic secretory trypsin inhibitor have been investigated in idiopathic chronic pancreatitis. Molecular and cell biology research during the past few years has elucidated pathophysiological factors that are involved in the pathogenesis of chronic pancreatitis, but cannot demonstrate a common pathway between etiological factors and the pathogenesis or development of the disease.     

Genetics of acute and chronic pancreatitis: An update

Progress made in identifying the genetic susceptibility underlying acute and chronic pancreatitis has benefitted the clinicians in understanding the pathogenesis of the disease in a better way. The identification of mutations in cationic trypsinogen gene(PRSS1 gene; functional gain mutations) and serine protease inhibitor kazal type 1(SPINK1 gene; functional loss mutations) and other potential susceptibility factors in genes that play an important role in the pancreatic secretory functions or response to inflammation during pancreatic injury has changed the current concepts and understanding of a complex multifactorial disease like pancreatitis. An indi-vidual's susceptibility to the disease is governed by ge-netic factors in combination with environmental factors. Candidate gene and genetic linkage studies have iden-tified polymorphisms in cationic trypsinogen(PRSS1), SPINK1, cystic fibrosis trans-membrane conductance regulator(CFTR), Chymotrypsinogen C(CTRC), Ca-thepsin B(CTSB) and calcium sensing receptor(CASR). Individuals with polymorphisms in the mentioned genes and other as yet identified genes are at an enhanced risk for the disease. Recently, polymorphisms in genes other than those involved in "intra-pancreatic trypsin regulatory mechanism" namely Claudin-2(CLDN2) andCarboxypeptidase A1(CPA1) gene have also been iden-tified for their association with pancreatitis. With ever growing number of studies trying to identify the genetic susceptibility in the form of single nucleotide polymor-phisms, this review is an attempt to compile the avail-able information on the topic.     

Molecular mechanisms of pancreatitis: current opinion

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

Genetic factors in pancreatitis

A number of genetic mutations have recently been identified that appear to be important in the development of pancreatitis. Point mutations in the cationic trypsinogen gene are capable of initiating pancreatitis. These mutations also provide important insights into the pathophysiology of acute pancreatitis and into potential connections between acute and chronic pancreatitis. Mutations in the genes encoding for the pancreatic secretory trypsin inhibitor and the cystic fibrosis transmembrane conductance regulator more likely work in concert with other genes and environmental factors in affecting disease susceptibility. Although the subject so far has recieved only a limited amount of study, genetic polymorphisms in a wide range of genes relating to pancreatic function and to regulation of inflammation are likely to play major roles in determining each individual’s susceptibility to developing pancreatitis, and its severity if it does develop.     

Chronic pancreatitis and cystic fibrosis

Recent discoveries of trypsinogen and trypsin inhibitor mutations in patients with chronic pancreatitis (CP) support the hypothesis that an inappropriate activation of pancreatic zymogens to active enzymes within the pancreatic parenchyma starts the inflammatory process. Current data suggest that CP may be inherited dominant, recessive, or complex as a result of mutations in the above mentioned or yet unidentified genes. Evaluation of patients with CP should include genetic testing. Cystic fibrosis (CF) is an autosomal recessive inherited disorder caused by mutations in the CF transmembrane conductance regulator (CFTR) gene and is characterised by pancreatic insufficiency and chronic bronchopulmonary infection. The progression and severity of pulmonary disease differs considerably between people with identical CFTR mutations and does not seem to correlate with the type or class of the CFTR mutation. The identification of further disease modifying genetic factors will increase the pathophysiological understanding and may help to identify new therapeutic targets.     

Role of genetic disorders in acute recurrent pancreatitis

There was remarkable progress in the understanding of the role genetic risk factors in chronic pancreatitis. These factors seem to be much more important than thought in the past. The rare autosomal-dominant mutations N29I and R122H of PRSS1 （cationic trypsinogen） as well as the variant N34S of SPINK1 （pancreatic secretory trypsin inhibitor） are associated to a disease onset in childhood or youth. Compared to chronic alcoholic pancreatitis the progression is slow so that for a long time only signs of acute-recurrent pancreatitis are found. Only at later time points （more than 10-15 years） there is evidence for chronic pancreatitis in the majority of patients. Acute recurrent pancreatitis may therefore be regarded as a transition state until definite signs of chronic pancreatitis are detectable.     

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.     

Etiopathogenesis of chronic pancreatitis--present state

Chronic pancreatitis is in advanced European and North American countries the statistically most important source of morbidity and mortality among benign pancreatopathies. It is defined as affection of the pancreas by chronic inflammation whereby the secretory parenchyma is gradually replaced by fibrous tissue. The fibrosis is irreversible and the disease has a progressing trend. In advanced countries the main pathogenetic factor has been for some centuries alcohol consumption. Chronic pancreatitis can be classified with regard to its morphology, etiology or pathogenesis. Most frequently the classification of chronic pancreatitis with regard to morphological changes is used, whereby the latter are based on different pathogenetic mechanisms. The present Marseille-Rome classification is valid from 1988 and divides chronic pancreatitis according to morphological changes into three groups. 1. Chronic calcifying pancreatitis. 2. Obstructive chronic pancreatitis. 3. Primarily inflammatory chronic pancreatitis. In some publications pancreatic fibrosis is listed as a special category. The submitted paper gives an up to date picture of chronic pancreatitis from the aspect of etiopathogenesis, it draws attention to the weak points of the contemporary classification and provides information on the genetic diagnosis of some rare forms of this highly prevalent disease.     

Genetic basis of chronic pancreatitis

BACKGROUND: Pancreatitis has a proven genetic basis in a minority of patients. METHODS: Review of the literature on genetics of pancreatitis. RESULTS: Ever since the discovery that in most patients with hereditary pancreatitis a mutation in the gene encoding for cationic trypsinogen (R122H) was found that results in a gain of trypsin function', many other mutations in the cationic trypsinogen gene, as well as in the gene encoding for pancreatic secretory trypsin inhibitor, have been found in patients with chronic pancreatitis. Furthermore, mutations in other genes, like the mucoviscoidosis-gene encoding for a chloride channel, and in genes encoding for enzymes involved in the metabolism of ethanol, have been linked to chronic pancreatitis. This article reviews the highlights that have been achieved in this field of pancreatic research. CONCLUSIONS: Recent data suggest that genetics may play a role in the pathogenesis of pancreatitis.     

Motion--genetic testing is useful in the diagnosis of nonhereditary pancreatic conditions: arguments for the motion.

Mutations of three major genes are associated with an increased risk of acute and chronic pancreatitis: the cationic trypsinogen (PRSS1) gene, the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and the pancreatic secretory trypsin inhibitor (PSTI) or serine protease inhibitor, Kazal type 1 (SPINK1) gene. Some autosomal dominant forms of hereditary pancreatitis are associated with mutations of the PRSS1 gene, which can be readily identified by genetic testing. Mutations of the CFTR gene can lead either to cystic fibrosis or to idiopathic chronic pancreatitis, and to a variety of cystic fibrosis-associated disorders, including congenital bilateral absence of the vas deferens and sinusitis. These mutations, as with those of the SPINK1 (or PSTI) gene, are prevalent in North America; thus, the presence of such a mutation in an asymptomatic person does not confer a high risk of developing pancreatitis. Combinations of mutations of the PRSS1 and SPINK1 genes lead to more severe disease, as indicated by an earlier onset of symptoms, which suggests that SPINK1 is a disease modifier. The major fear expressed by potential candidates for genetic testing is that the results could lead to insurance discrimination. Studies of the positive predictive value of genetic tests are hampered by recruitment bias and lack of knowledge of family history of pancreatitis. Genetic testing is most useful for persons for whom family members have already been found to exhibit a particular pancreatitis-associated mutation. In the future, increased knowledge of the myriad genetic causes of pancreatitis, as well as advances in the diagnosis and treatment of early chronic pancreatitis, should enhance the utility of genetic testing.     

Germline mutations and gene polymorphism associated with human pancreatitis.

A wide range of mutations and polymorphisms in genes that relate to pancreatic function seem to be involved in the development of pancreatitis. Some of these genetic alterations lead to disease phenotypes with unequivocal mendelian inheritance patterns, whereas others seem to act as modifier genes in conjunction with environ-mental or, as yet unidentified, genetic cofactors. This article reviews germline changes in the genes for trypsin, pancreatic secretory trypsin inhibitor, the cystic fibrosis conductance regulator, lipid metabolism proteins, inflammatory mediators for cytokines, and cathepsin B.     

Pancreatitis--etiology and pathogenesis]

Pancreatic inflammatory disease can be classified as acute pancreatitis (AP) and chronic pancreatitis (CP) primarily by clinical criteria, with an obvious difference by restoration of normal function in the former or by permanent residual damage in the latter. Gallstones and alcohol are the most common causes of AP. Recent investigations have established that AP from all cause may disrupt normal stimulus-secretion coupling function within the acinar cell. This disruption within the acinar cell leads to an event termed 'co-localization' in which the digestive and lysosomal enzymes merge resulting in a premature activation of proteases. The mechanisms of inflammatory cells which adhere to endothelial cell are determined by a variety of mediators of cytokines released at the site of tissue damage. Cytokines hold the key for both local and systemic inflammatory response in AP. Besides, CP is a debilitating disease characterized by progressive and irreversible destruction of pancreatic tissue leading to exocrine and endocrine insufficiencies. Alcohol intake is the most common cause of CP. Mutations in the cationic trypsinogen gene were identified as causative gene for hereditary pancreatitis. The recognition of frequent cystic fibrosis transmembrane conductance regulator (CFTR) mutations and serine protease inhibitor, Kazal type 1 (SPINK1) mutations in idiopathic CP has hightened the awareness of importance of genetic mutations in CP. Pancreatic stellate cells represent the main cellular source of extracellular matrix in CP and play a key role in pancreatic fibrosis.     

Risk factors of chronic pancreatitis

Chronic pancreatitis (CP) still remains a challenging clinical problem with many controversial issues regarding pathogenesis, outcome, and treatment. The disease comprises a spectrum of disorders that culminate as a final step in the destruction of the pancreas. Complex interaction does exist between genetic, environmental and immunologic factors leading to development of the disease. Multiple risk factors interact in a multiple-step model; the pancreatic injury may occur through different mechanisms with transition between an acute pancreatitis condition to recurrent pancreatitis and, finally, to CP. Most patients have multiple risk factors and the overall risk is a product of all risk factors in additive or multiplicative fashion. Susceptibility to develop CP in alcoholics depends on the expression of single gene mutation or is derived from complex genetic polymorphism; in addition, smoking habit can influence the risk of pancreatic calcifications and severity in alcoholic and idiopathic CP. Alteration of the immune response induced by gene mutations and/or environmental factors represents the main determinant of pancreatic fibrosis, the end-stage histologic feature from all CP etiologies.     

Chronic pancreatitis: diagnosis, classification, and new genetic developments

The utilization of recent advances in molecular and genomic technologies and progress in pancreatic imaging techniques provided remarkable insight into genetic, environmental, immunologic, and pathobiological factors leading to chronic pancreatitis. Translation of these advances into clinical practice demands a reassessment of current approaches to diagnosis, classification, and staging. We conclude that an adequate pancreatic biopsy must be the gold standard against which all diagnostic approaches are judged. Although computed tomography remains the initial test of choice for the diagnosis of chronic pancreatitis, the roles of endoscopic retrograde pancreatography, endoscopic ultrasonography, and magnetic resonance imaging are considered. Once chronic pancreatitis is diagnosed, proper classification becomes important. Major predisposing risk factors to chronic pancreatitis may be categorized as either (1) toxic-metabolic, (2) idiopathic, (3) genetic, (4) autoimmune, (5) recurrent and severe acute pancreatitis, or (6) obstructive (TIGAR-O system). After classification, staging of pancreatic function, injury, and fibrosis becomes the next major concern. Further research is needed to determine the clinical and natural history of chronic pancreatitis developing in the context of various risk factors. New methods are needed for early diagnosis of chronic pancreatitis, and new therapies are needed to determine whether interventions will delay or prevent the progression of the irreversible damage characterizing end-stage chronic pancreatitis.     

Pathophysiology of SPINK mutations in pancreatic development and disease.

The endogenous pancreatic trypsin inhibitor, SPINK, is believed to limit enzyme activity in the pancreas and reduce the risk of pancreatitis. Recently, mutations in the SPINK1 gene have been associated with development of both acute and chronic pancreatitis. In most patients with SPINK1 mutations, the genetic variants do not cause the disease independently, but may act in concert with other genetic or environmental factors. Recent studies, using mice in which the trypsin inhibitor gene has been deleted or overexpressed, provide novel insights into the role of SPINK in pancreatic development and pancreatitis.     

Phospholipase A2 in acute pancreatitis: new biochemical and pathological aspects

Phospholipase A2 has been implicated in the pathogenesis and pathophysiology of acute pancreatitis. The initial enthusiasm concerning pancreatic group I phospholipase A2 as an enzyme responsible for pancreatic necrosis and systemic manifestations of acute pancreatitis has gradually waned, as the mechanisms of the pathogenesis and the pathophysiology of acute pancreatitis have been revealed. The overactive systemic inflammatory response associated with the activation of different cascade systems and increased levels of inflammatory mediators as seen in severe acute pancreatitis, closely resembles that associated with other severe inflammatory diseases such as septic shock. The critical role of the non-pancreatic secretory group II phospholipase A2 in the chain of inflammatory mediators has been emphasized recently, as new detection methods for the enzyme have become available.     

Hereditary pancreatitis]

Hereditary pancreatitis (HP) is an autosomal dominant inherited disease characterized by recurrent episodes of pancreatitis often beginning in childhood, a family history of at least 2 other affected members, and the absence of known etiologic factors. The discovery of mutations in cationic trypsinogen gene (PRSS1) in HP not only provided insights into the molecular mechanisms of pancreatitis, but also opened a new era in the field of chronic pancreatitis. The detection of mutations in serine protease inhibitor, Kazal type 1 (SPINK1) and CFTR in patients with hereditary or idiopathic chronic pancreatitis has placed the emphasis on the importance of genetic mutations in pancreatitis. Because the estimated cumulative risk of pancreatic cancer development in hereditary pancreatitis is nearly 40%, screening tests are important in selected cases. There are no specific medical therapies recommended in patients with HP. Registration of patients with Nationwise Registries is essential if management strategies are to be improved and genetic research to be continued.     

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.     

Genetic issues in pediatric pancreatitis

The number of hospitalizations in children with acute and chronic pancreatitis is increasing and accounts for significant morbidity. Acute pancreatitis is a reversible event involving diffuse inflammation of the pancreas with variable involvement of other regional tissues, remote organs, or both, whereas chronic pancreatitis is a process that produces irreversible changes in the pancreatic structure and function. Mutations in the gene encoding cationic trypsinogen have recently been identified to be associated with hereditary pancreatitis. Genetic mutations in the pancreatic secretory trypsin inhibitor and the cystic fibrosis transmembrane conductance regulator have been described to play a role in the development of pancreatitis as well. Mutations in the cytokine target genes relating to regulation of inflammation are likely to be important in determining the severity of pancreatitis. These findings, along with the advances in cell biology, have contributed to a better understanding of the pathophysiology of pancreatic diseases.