Substrate specificity of human chymotrypsin-like protease (CTRL) characterized by phage display-selected small-protein inhibitors.

Chymotrypsin-like protease (CTRL) is one of the four chymotrypsin isoforms expressed in the human exocrine pancreas. Human genetic and experimental evidence indicate that chymotrypsins B1, B2, and C (CTRB1, CTRB2 and CTRC) are important not only for protein digestion but also for protecting the pancreas against pancreatitis by degrading potentially harmful trypsinogen. CTRL has not been reported to play a similar role, possibly due to its low abundance and/or different substrate specificity. To address this problem, we investigated the specificity of the substrate-binding groove of CTRL by evolving the substrate-like canonical loop of the Schistocerca gregaria proteinase inhibitor 2 (SGPI-2), a small-protein reversible chymotrypsin inhibitor to bind CTRL. We found that phage-associated SGPI-2 variants with strong affinity to CTRL were similar to those evolved previously against CTRB1, CTRB2 or bovine chymotrypsin A (bCTRA), indicating comparable substrate specificity. When tested as recombinant proteins, SGPI-2 variants inhibited CTRL with similar or slightly weaker affinity than bCTRA, confirming that CTRL is a typical chymotrypsin. Interestingly, an SGPI-2 variant selected with a Thr29His mutation in its reactive loop was found to inhibit CTRL strongly, but it was digested rapidly by bCTRA. Finally, CTRL was shown to degrade human anionic trypsinogen, however, at a much slower rate than CTRB2, suggesting that CTRL may not have a significant role in the pancreatic defense mechanisms against inappropriate trypsinogen activation and pancreatitis.

Risk of chronic pancreatitis in carriers of the c.180C>T (p.Gly60=) CTRC variant: case-control studies and meta-analysis.

Chymotrypsin C (CTRC) is a digestive serine protease produced by the pancreas that regulates intrapancreatic trypsin activity and provides a defensive mechanism against chronic pancreatitis (CP). CTRC exerts its protective effect by promoting degradation of trypsinogen, the precursor to trypsin. Loss-of-function missense and microdeletion variants of CTRC are found in around 4% of CP cases and increase disease risk by approximately 3-7-fold. In addition, a commonly occurring synonymous CTRC variant c.180C>T (p.Gly60=) was reported to increase CP risk in various cohorts but a global analysis of its impact has been lacking. Here, we analyzed the frequency and effect size of variant c.180C>T in Hungarian and pan-European cohorts, and performed meta-analysis of the new and published genetic association data. When allele frequency was considered, meta-analysis revealed an overall frequency of 14.2% in patients and 8.7% in controls (allelic odds ratio (OR) 2.18, 95% confidence interval (CI) 1.72-2.75). When genotypes were examined, c.180TT homozygosity was observed in 3.9% of CP patients and in 1.2% of controls, and c.180CT heterozygosity was present in 22.9% of CP patients and in 15.5% of controls. Relative to the c.180CC genotype, the genotypic OR values were 5.29 (95% CI 2.63-10.64), and 1.94 (95% CI 1.57-2.38), respectively, indicating stronger CP risk in homozygous carriers. Finally, we obtained preliminary evidence that the variant is associated with reduced CTRC mRNA levels in the pancreas. Taken together, the results indicate that CTRC variant c.180C>T is a clinically relevant risk factor, and should be considered when genetic etiology of CP is investigated.

Bicarbonate defective CFTR variants increase risk for chronic pancreatitis: A meta-analysis.

INTRODUCTION: Cystic fibrosis transmembrane conductance regulator (CFTR) plays a central role in pancreatic ductal fluid secretion by mediating Cl- and HCO3- ion transport across the apical membrane. Severe CFTR mutations that diminish chloride conductance cause cystic fibrosis (CF) if both alleles are affected, whereas heterozygous carrier status increases risk for chronic pancreatitis (CP). It has been proposed that a subset of CFTR variants characterized by a selective bicarbonate conductance defect (CFTRBD) may be associated with CP but not CF. However, a rigorous genetic analysis of the presumed association has been lacking. AIMS: To investigate the role of heterozygous CFTRBD variants in CP by meta-analysis of published case-control studies. MATERIALS AND METHODS: A systematic search was conducted in the MEDLINE, Embase, Scopus, and CENTRAL databases for published studies that reported the CFTRBD variants p.R74Q, p.R75Q, p.R117H, p.R170H, p.L967S, p.L997F, p.D1152H, p.S1235R, and p.D1270N in CP patients and controls. RESULTS: Twenty-two studies were eligible for quantitative synthesis. Combined analysis of the 9 CFTRBD variants indicated enrichment in CP patients versus controls (OR = 2.31, 95% CI = 1.17-4.56). Individual analysis of CFTRBD variants revealed no association of p.R75Q with CP (OR = 1.12, 95% CI = 0.89-1.40), whereas variants p.R117H and p.L967S were significantly overrepresented in cases relative to controls (OR = 3.16, 95% CI = 1.94-5.14, and OR = 3.88, 95% CI = 1.32-11.47, respectively). The remaining 6 low-frequency variants gave inconclusive results when analyzed individually, however, their pooled analysis indicated association with CP (OR = 2.08, 95% CI = 1.38-3.13). CONCLUSION: Heterozygous CFTRBD variants, with the exception of p.R75Q, increase CP risk about 2-4-fold.

Arg236 in human chymotrypsin B2 (CTRB2) is a key determinant of high enzyme activity, trypsinogen degradation capacity, and protection against pancreatitis.

Pancreatic chymotrypsins (CTRs) are digestive proteases that in humans include CTRB1, CTRB2, CTRC, and CTRL. The highly similar CTRB1 and CTRB2 are the products of gene duplication. A common inversion at the CTRB1-CTRB2 locus reverses the expression ratio of these isoforms in favor of CTRB2. Carriers of the inversion allele are protected against the inflammatory disorder pancreatitis presumably via their increased capacity for CTRB2-mediated degradation of harmful trypsinogen. To reveal the protective molecular determinants of CTRB2, we compared enzymatic properties of CTRB1, CTRB2, and bovine CTRA (bCTRA). By evolving substrate-like Schistocerca gregaria proteinase inhibitor 2 (SGPI-2) inhibitory loop variants against the chymotrypsins, we found that the substrate binding groove of the three enzymes had overlapping specificities. Based on the selected sequences, we produced eight SGPI-2 variants. Remarkably, CTRB2 and bCTRA bound these inhibitors with significantly higher affinity than CTRB1. Moreover, digestion of peptide substrates, beta casein, and human anionic trypsinogen unequivocally confirmed that CTRB2 is a generally better enzyme than CTRB1 while the potency of bCTRA lies between those of the human isoforms. Unexpectedly, mutation D236R alone converted CTRB1 to a CTRB2-like high activity protease. Modeling indicated that in CTRB1 Met210 partially obstructed the substrate binding groove, which was relieved by the D236R mutation. Taken together, we identify CTRB2 Arg236 as a key positive determinant, while CTRB1 Asp236 as a negative determinant for chymotrypsin activity. These findings strongly support the concept that in carriers of the CTRB1-CTRB2 inversion allele, the superior trypsinogen degradation capacity of CTRB2 protects against pancreatitis.

Loss-of-function variant in chymotrypsin like elastase 3B (CELA3B) is associated with non-alcoholic chronic pancreatitis.

BACKGROUND: Genetic alterations in digestive enzymes have been associated with chronic pancreatitis (CP). Recently, chymotrypsin like elastase 3B (CELA3B) emerged as a novel risk gene. Thus, we evaluated CELA3B in two European cohorts with CP. METHODS: We analyzed all 8 CELA3B exons in 550 German non-alcoholic CP (NACP) patients and in 241 German controls by targeted DNA sequencing. In addition, we analyzed exons 6 and 7 by Sanger sequencing and the c.129+1G>A variant by melting curve analysis in 1078 further German controls. As replication cohort, we investigated up to 243 non-German European NACP patients and up to 1665 controls originating from Poland, Hungary, and Sweden. We assessed the cellular secretion and the elastase activity of recombinant CELA3B variants. RESULTS: In the German discovery cohort, we detected a splice-site variant in intron 2, c.129+1G>A, in 9/550 (1.64%) CP patients and in 5/1319 (0.38%) controls (P=0.007, OR=4.4, 95% CI=1.5-13.0). In the European replication cohort, this variant was also enriched in patients (9/178 [5.06%]) versus controls (13/1247 [1.04%]) (P=0.001, OR=5.1, 95% CI=2.1-12.0). We did not find the two previously reported codon 90 variants, p.R90C and p.R90L. CONCLUSIONS: Our data indicate that CELA3B is a susceptibility gene for CP. In contrast to previous reports suggesting that increased CELA3B activity is associated with CP risk, the splice-site variant identified here is predicted to cause diminished CELA3B expression. How reduced CELA3B function predisposes to pancreatitis remains to be elucidated.

Variants in the pancreatic CUB and zona pellucida-like domains 1 (CUZD1) gene in early-onset chronic pancreatitis - A possible new susceptibility gene.

OBJECTIVE: Non-alcoholic chronic pancreatitis (NACP) frequently develops in the setting of genetic susceptibility associated with alterations in genes that are highly expressed in the pancreas. However, the genetic basis of NACP remains unresolved in a significant number of patients warranting a search for further risk genes. DESIGN: We analyzed CUZD1, which encodes the CUB and zona pellucida-like domains 1 protein that is found in high levels in pancreatic acinar cells. We sequenced the coding region in 1163 European patients and 2018 European controls. In addition, we analyzed 297 patients and 1070 controls from Japan. We analyzed secretion of wild-type and mutant CUZD1 from transfected cells using Western blotting. RESULTS: In the European cohort, we detected 30 non-synonymous variants. Using different prediction tools (SIFT, CADD, PROVEAN, PredictSNP) or the combination of these tools, we found accumulation of predicted deleterious variants in patients (p-value range 0.002-0.013; OR range 3.1-5.2). No association was found in the Japanese cohort, in which 13 non-synonymous variants were detected. Functional studies revealed >50% reduced secretion of 7 variants, however, these variants were not significantly enriched in European CP patients. CONCLUSION: Our data indicate that CUZD1 might be a novel susceptibility gene for NACP. How these variants predispose to pancreatitis remains to be elucidated.

Risk of chronic pancreatitis in carriers of loss-of-function CTRC variants: A meta-analysis.

The digestive protease chymotrypsin C (CTRC) protects the pancreas against pancreatitis by degrading potentially harmful trypsinogen. Loss-of-function genetic variants in CTRC increase risk for chronic pancreatitis (CP) with variable effect size, as judged by the reported odds ratio (OR) values. Here, we performed a meta-analysis of published studies on four variants that alter the CTRC amino-acid sequence, are clinically relatively common (global carrier frequency in CP >1%), reproducibly showed association with CP and their loss of function phenotype was verified experimentally. We found strong enrichment of CTRC variants p.A73T, p.V235I, p.K247_R254del, and p.R245W in CP cases versus controls, yielding OR values of 6.5 (95% confidence interval (CI) 2.4-17.8), 4.5 (CI 2.2-9.1), 5.4 (CI 2.6-11.0), and 2.6 (CI 1.6-4.2), respectively. Subgroup analysis demonstrated disease association of variants p.K247_R254del and p.R245W in alcoholic CP with similar effect sizes as seen in the overall CP group. Homozygosity or compound heterozygosity were rare and seemed to be associated with higher risk. We also identified a so far unreported linkage disequilibrium between variant p.K247_R254del and the common c.180C>T (p.G60 =) haplotype. Taken together, the results indicate that heterozygous loss-of-function CTRC variants increase the risk for CP approximately 3-7-fold. This meta-analysis confirms the clinical significance of CTRC variants and provides further justification for the genetic screening of CP patients.

Common calcium-sensing receptor (CASR) gene variants do not modify risk for chronic pancreatitis in a Hungarian cohort.

The calcium-sensing receptor (CASR) is expressed in the pancreas where it might regulate calcium concentrations in pancreatic secretions. Two independent studies reported conflicting results claiming that commonly occurring missense variants of the CASR gene are risk factors for chronic pancreatitis (CP). Here, we attempted to replicate the association between CASR variants and CP. We analyzed 337 patients and 840 controls from the Hungarian National Pancreas Registry either by direct sequencing of exon 7 and the flanking noncoding regions or by TaqMan SNP genotyping assays. We identified two common missense variants, c.2956G>T (p.A986S), and c.2968A>G (p.R990G), three low-frequency variants, c.3031C>G (p.Q1011E), c.2610G>A (p.E870=) and c.∗60T>A, and 8 rare variants including the novel variant c.1895G>A (p.G632D). When allelic or genotype distributions were considered, none of the CASR variants associated with CP. Subgroup analysis of nonalcoholic versus alcoholic patients revealed no disease association either. Our results demonstrate that common CASR variants do not modify the risk for CP and should not be considered as genetic risk factors in the clinical setting.

Oral Proton Pump Inhibitors May Be as Effective as Intravenous in Peptic Ulcer Bleeding: A Systematic Review and Meta-analysis.

INTRODUCTION: Current guidelines recommend intravenous (IV) proton pump inhibitor (PPI) therapy in peptic ulcer bleeding (PUB). We aimed to compare the efficacy of oral and IV administration of PPIs in PUB. METHODS: We performed a systematic search in 4 databases for randomized controlled trials, which compared the outcomes of oral PPI therapy with IV PPI therapy for PUB. The primary outcomes were 30-day recurrent bleeding and 30-day mortality. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for dichotomous outcomes, while weighted mean differences (WMDs) with CI were calculated for continuous outcomes in meta-analysis. The protocol was registered a priori onto PROSPERO (CRD42020155852). RESULTS: A total of 14 randomized controlled trials reported 1,951 peptic ulcer patients, 977 and 974 of which were in the control and intervention groups, respectively. There were no statistically significant differences between oral and IV administration regarding 30-day rebleeding rate (OR = 0.96, CI: 0.65-1.44); 30-day mortality (OR = 0.70, CI: 0.35-1.40); length of hospital stay (WMD = -0.25, CI: -0.93 to -0.42); transfusion requirements (WMD = -0.09, CI: -0.07 to 0.24); need for surgery (OR = 0.91, CI: 0.40-2.07); further endoscopic therapy (OR = 1.04, CI: 0.56-1.93); and need for re-endoscopy (OR = 0.81, CI: 0.52-1.28). Heterogeneity was negligible in all analysis, except for the analysis on the length of hospitalization (I2 = 82.3%, P = 0.001). DISCUSSION: Recent evidence suggests that the oral administration of PPI is not inferior to the IV PPI treatment in PUB after endoscopic management, but further studies are warranted.

Inflammatory Bowel Diseases Elevate the Risk of Developing Acute Pancreatitis: A Meta-analysis.

OBJECTIVES: Increasing data suggest that acute pancreatitis (AP) occurs more frequently among patients with inflammatory bowel diseases (IBDs) than in the non-IBD population; however, currently no comprehensive meta-analysis is available. METHODS: Systematic literature search was conducted in 4 major databases. We included observational studies sampling from the general population. Basic study characteristics and crude incidences of AP were extracted. Pooled odds ratios (ORs) with 95% confidence interval (CIs) were calculated using the random-effects model. Subgroups were set up by Crohn disease and ulcerative colitis. Heterogeneity was tested with I statistics. RESULTS: Eight studies were eligible for the analysis. The odds of AP were 3 times higher in IBD (OR, 3.11; 95% CI, 2.93-3.30; I, 0.0%), significantly higher in Crohn disease than in ulcerative colitis (P < 0.001; OR, 4.12 vs OR, 2.61; I, 0.0%). The pooled annual incidence of AP in IBD was 210/100,000 person-years (95% CI, 84-392/100,000 person-years; I, 98.66%). CONCLUSIONS: We confirmed that IBD elevates the risk of AP and of 100,000 IBD patients 210 AP cases are to be expected annually. Therefore, it is important to include pancreatic enzyme level measurements and radiological investigations in the workup of IBD patients with acute abdominal pain.

Personalised health education against health damage of COVID-19 epidemic in the elderly Hungarian population (PROACTIVE-19): protocol of an adaptive randomised controlled clinical trial.

BACKGROUND: Early reports indicate that COVID-19 may require intensive care unit (ICU) admission in 5-26% and overall mortality can rise to 11% of the recognised cases, particularly affecting the elderly. There is a lack of evidence-based targeted pharmacological therapy for its prevention and treatment. We aim to compare the effects of a World Health Organization recommendation-based education and a personalised complex preventive lifestyle intervention package (based on the same WHO recommendation) on the outcomes of the COVID-19. METHODS: PROACTIVE-19 is a pragmatic, randomised controlled clinical trial with adaptive "sample size re-estimation" design. Hungarian population over the age of 60 years without confirmed COVID-19 will be approached to participate in a telephone health assessment and lifestyle counselling voluntarily. Volunteers will be randomised into two groups: (A) general health education and (B) personalised health education. Participants will go through questioning and recommendation in 5 fields: (1) mental health, (2) smoking habits, (3) physical activity, (4) dietary habits, and (5) alcohol consumption. Both groups A and B will receive the same line of questioning to assess habits concerning these topics. Assessment will be done weekly during the first month, every second week in the second month, then monthly. The composite primary endpoint will include the rate of ICU admission, hospital admission (longer than 48 h), and mortality in COVID-19-positive cases. The estimated sample size is 3788 subjects per study arm. The planned duration of the follow-up is a minimum of 1 year. DISCUSSION: These interventions may boost the body's cardiovascular and pulmonary reserve capacities, leading to improved resistance against the damage caused by COVID-19. Consequently, lifestyle changes can reduce the incidence of life-threatening conditions and attenuate the detrimental effects of the pandemic seriously affecting the older population. TRIAL REGISTRATION: The study has been approved by the Scientific and Research Ethics Committee of the Hungarian Medical Research Council (IV/2428- 2 /2020/EKU) and has been registered at clinicaltrials.gov ( NCT04321928 ) on 25 March 2020.

Chronic pancreatitis with polycystic kidney disease: A rare coincidence? / Pancreatitis crónica con enfermedad renal poliquística: ¿una rara coincidencia?

INTRODUCTION: In children, chronic pancreatitis (CP) is usually associated with anatomical anomalies of the pancreas and biliary tract or is genetically determined. Autosomal dominant polycystic kidney disease (ADPKD) may present with extrarenal cyst formation, sometimes involving the pancreas. Large enough, these cysts may cause pancreatitis in ADPKD patients. Case presentation: Herein, we present a case of a 12-year-old Caucasian girl with recurrent pancreatitis with no identifiable traumatic, metabolic, infectious, drug, or immunologic causes. Structural anomalies of the pancreas, including cysts, were ruled out by imaging. However, bilateral cystic kidneys were found as an incidental finding. Her family history was negative for pancreatitis, but positive for polycystic kidney disease. Molecular analysis of ADPKD-causing mutations revealed a novel c.9659C>A (p.Ser3220*) mutation in the PKD1 gene confirming the clinical suspicion of ADPKD. Although CP may rarely occur as an extrarenal manifestation of ADPKD with pancreatic cysts, it is unusual in their absence. Thus, molecular analysis of pancreatitis susceptibility genes was performed and a homozygous pathologic c.180C>T (p.G60=) variant of the CTRC gene, known to increase the risk of CP, was confirmed. CONCLUSION: This is the first reported case of a pediatric patient with coincidence of genetically determined CP and ADPKD. Occurrence of pancreatitis in children with ADPKD without pancreatic cysts warrants further investigation of CP causing mutations

INTRODUCCIÓN: En niños, la pancreatitis crónica (CP, por sus siglas en inglés) generalmente se asocia con anomalías anatómicas del páncreas y el tracto biliar, o está genéticamente determinada. La enfermedad renal poliquística autosómica dominante (ADPKD, por sus siglas en inglés) puede presentarse con la formación de quistes extrarrenales, que a veces afecta al páncreas. Suficientemente grandes, estos quistes pueden causar pancreatitis en pacientes con ADPKD. Presentación del caso: Presentamos el caso de una niña caucásica de 12 años con pancreatitis recurrente sin causas identificables traumáticas, metabólicas, infecciosas, farmacológicas o inmunológicas. Las anomalías estructurales del páncreas, incluidos los quistes, se descartaron mediante imágenes. Sin embargo, los riñones quísticos bilaterales se encontraron como un hallazgo accidental. Su historia familiar fue negativa para la pancreatitis, pero positiva para la enfermedad renal poliquística. El análisis molecular de las mutaciones causantes de ADPKD reveló una nueva mutación c.9659C>A (p.Ser3220*) en el gen PKD1 que confirma la sospecha clínica de ADPKD. Aunque la CP rara vez ocurre como una manifestación extrarrenal de ADPKD con quistes pancreáticos es inusual. Por lo tanto, se realizó el análisis molecular de los genes de susceptibilidad a pancreatitis y se confirmó una variante homocigótica patológica c.180C>T (p.G60=) del gen CTRC, que se sabe que aumenta el riesgo de CP. CONCLUSIÓN: Este es el primer caso reportado de un paciente pediátrico con coincidencia de CP y ADPKD genéticamente determinados. La aparición de pancreatitis en niños con ADPKD sin quistes pancreáticos justifica una mayor investigación de CP que causan mutaciones

Chronic pancreatitis with polycystic kidney disease: A rare coincidence?

INTRODUCTION: In children, chronic pancreatitis (CP) is usually associated with anatomical anomalies of the pancreas and biliary tract or is genetically determined. Autosomal dominant polycystic kidney disease (ADPKD) may present with extrarenal cyst formation, sometimes involving the pancreas. Large enough, these cysts may cause pancreatitis in ADPKD patients. CASE PRESENTATION: Herein, we present a case of a 12-year-old Caucasian girl with recurrent pancreatitis with no identifiable traumatic, metabolic, infectious, drug, or immunologic causes. Structural anomalies of the pancreas, including cysts, were ruled out by imaging. However, bilateral cystic kidneys were found as an incidental finding. Her family history was negative for pancreatitis, but positive for polycystic kidney disease. Molecular analysis of ADPKD-causing mutations revealed a novel c.9659C>A (p.Ser3220*) mutation in the PKD1 gene confirming the clinical suspicion of ADPKD. Although CP may rarely occur as an extrarenal manifestation of ADPKD with pancreatic cysts, it is unusual in their absence. Thus, molecular analysis of pancreatitis susceptibility genes was performed and a homozygous pathologic c.180C>T (p.G60=) variant of the CTRC gene, known to increase the risk of CP, was confirmed. CONCLUSION: This is the first reported case of a pediatric patient with coincidence of genetically determined CP and ADPKD. Occurrence of pancreatitis in children with ADPKD without pancreatic cysts warrants further investigation of CP causing mutations.

Observational longitudinal multicentre investigation of acute pancreatitis (GOULASH PLUS): follow-up of the GOULASH study, protocol.

BACKGROUND: Acute pancreatitis (AP) is an inflammatory condition that can lead to late consequences. Recurrent AP (RAP) develops in 20% of patients and chronic pancreatitis (CP) occurs in 7%-12.8%. However, we do not have sufficient information to establish an evidence-based statement to define early CP, or how to prevent its development. AIM: The aim of this study was to understand the influencing factors and to determine which parameters should be measured or used as a biomarker to detect the early phase of CP. METHODS/DESIGN: This is an observational prospective follow-up study of the GOULASH-trial (ISRTCN 63827758) in which (1) all severity of pancreatitis are included; (2) patients receive only therapeutic modalities which are accepted by the evidence based medicine (EBM) guideline; (3) whole blood, serum and plasma samples are stored in our biobank; and (4) large amount of variables are collected and kept in our electronic database including anamnestic data, physical examination, laboratory parameters, imaging, therapy and complications. Therefore, this fully characterised patient cohort are well suitable for this longitudinal follow-up study. Patients' selection: patients enrolled in the GOULASH study will be offered to join to the longitudinal study. The follow-up will be at 1, 2, 3, 4, 5 and 6 years after the episode of AP. Anamnestic data will be collected by questionnaires: (1) diet history questionnaire, (2) 36-Item Short-Form Health Survey, (3) physical activity questionnaire and (4) stress questionnaire. Genetic tests will be performed for the genes associated with CP. The exocrine and endocrine pancreatic, liver and kidney functions will be determined by laboratory tests, stool sample analyses and imaging. Cost-effectiveness will be analysed to examine the relationship between events of interest and health-related quality of life or to explore subgroup differences. CONCLUSION: This study will provide information about the risk and influencing factors leading to CP and identify the most useful measurable parameters. TRIAL REGISTRATION NUMBER: ISRCTN63396106.

Natural single-nucleotide deletion in chymotrypsinogen C gene increases severity of secretagogue-induced pancreatitis in C57BL/6 mice.

Genetic susceptibility to chronic pancreatitis in humans is frequently associated with mutations that increase activation of the digestive protease trypsin. Intrapancreatic trypsin activation is an early event in experimental acute pancreatitis in rodents, suggesting that trypsin is a key driver of pathology. In contrast to trypsin, the pancreatic protease chymotrypsin serves a protective function by mitigating trypsin activation through degradation. In humans, loss-of-function mutations in chymotrypsin C (CTRC) are common risk factors for chronic pancreatitis; however, the pathogenic effect of CTRC deficiency has not been corroborated in animal models yet. Here we report that C57BL/6 mice that are widely used for genetic manipulations do not express functional CTRC due to a single-nucleotide deletion in exon 2 of the Ctrc gene. We restored a functional Ctrc locus in C57BL/6N mice and demonstrated that in the novel Ctrc+ strain the severity of cerulein-induced experimental acute and chronic pancreatitis was significantly ameliorated. Improved disease parameters were associated with reduced intrapancreatic trypsin activation suggesting a causal link between CTRC-mediated trypsinogen degradation and protection against pancreatitis. Taken together with prior human genetic and biochemical studies, the observations provide conclusive evidence for the protective role of CTRC against pancreatitis.

Genetics, Cell Biology, and Pathophysiology of Pancreatitis.

Since the discovery of the first trypsinogen mutation in families with hereditary pancreatitis, pancreatic genetics has made rapid progress. The identification of mutations in genes involved in the digestive protease-antiprotease pathway has lent additional support to the notion that pancreatitis is a disease of autodigestion. Clinical and experimental observations have provided compelling evidence that premature intrapancreatic activation of digestive proteases is critical in pancreatitis onset. However, disease course and severity are mostly governed by inflammatory cells that drive local and systemic immune responses. In this article, we review the genetics, cell biology, and immunology of pancreatitis with a focus on protease activation pathways and other early events.

Human CPA1 mutation causes digestive enzyme misfolding and chronic pancreatitis in mice.

OBJECTIVE: Chronic pancreatitis is a progressive, relapsing inflammatory disorder of the pancreas, which often develops in the background of genetic susceptibility. Recently, loss-of-function mutations in CPA1, which encodes the digestive enzyme carboxypeptidase A1, were described in sporadic early onset cases and in hereditary pancreatitis. Mutation-induced misfolding of CPA1 and associated endoplasmic reticulum (ER) stress was suggested as potential disease mechanism; however, in vivo evidence has been lacking. The objective of the present study was to create a mouse model that recapitulates features of CPA1-associated chronic pancreatitis. DESIGN: We knocked-in the most frequently occurring p.N256K human CPA1 mutation to the mouse Cpa1 locus. Mutant mice were characterised with respect to pancreas pathology and ER stress and compared with C57BL/6N and CPA1 null control mice. RESULTS: In the CPA1 N256K mutant mice, we observed hallmarks of chronic pancreatitis that included progressive acinar cell atrophy, inflammatory cell infiltration, fibrosis and acinar-ductal metaplasia. In contrast, similarly to the C57BL/6N mice, the CPA1 null control strain exhibited no signs of pancreatic disease. Mutation p.N256K induced misfolding of mouse CPA1 and resulted in elevated expression of ER stress markers Hspa5 (BiP) and Ddit3 (CHOP) both in cell culture and mutant mice. CONCLUSION: The results offer categorical evidence that CPA1 mutations elicit enzyme misfolding and cause chronic pancreatitis via an ER stress-related mechanism.