Chymotrypsin C mutations in chronic pancreatitis

Secretagogue-induced pancreatitis in mice devoid of chymotrypsin

The serine protease chymotrypsin protects the pancreas against pancreatitis by degrading trypsinogen, the precursor to the digestive protease trypsin. Taking advantage of previously generated mouse models with either the Ctrb1 gene (encoding chymotrypsin B1) or the Ctrl gene (encoding chymotrypsin-like protease) disrupted, here we generated the novel Ctrb1-del × Ctrl-KO strain in the C57BL/6N genetic background, which harbors a naturally inactivated Ctrc gene (encoding chymotrypsin C). The newly created mice are devoid of chymotrypsin, yet the animals develop normally, breed well, and show no spontaneous phenotype, indicating that chymotrypsin is dispensable under laboratory conditions. When given cerulein, the Ctrb1-del × Ctrl-KO strain exhibited markedly increased intrapancreatic trypsin activation and more severe acute pancreatitis, relative to wild-type C57BL/6N mice. After the acute episode, Ctrb1-del × Ctrl-KO mice spontaneously progressed to chronic pancreatitis, whereas C57BL/6N mice recovered rapidly. The cerulein-induced pancreas pathology in Ctrb1-del × Ctrl-KO mice was highly similar to that previously observed in Ctrb1-del mice; however, trypsin activation was more robust and pancreatitis severity was increased. Taken together, the results confirm and extend prior observations demonstrating that chymotrypsin safeguards the pancreas against pancreatitis by limiting pathologic trypsin activity. In mice, the CTRB1 isoform, which constitutes about 90% of the total chymotrypsin content, is responsible primarily for the anti-trypsin defenses and protection against pancreatitis; however, the minor isoform CTRL also contributes to an appreciable extent.NEW & NOTEWORTHY Chymotrypsins defend the pancreas against the inflammatory disorder pancreatitis by degrading harmful trypsinogen. This study demonstrates that mice devoid of pancreatic chymotrypsins are phenotypically normal but become sensitized to secretagogue hyperstimulation and exhibit increased intrapancreatic trypsin activation, more severe acute pancreatitis, and rapid progression to chronic pancreatitis. The observations confirm and extend the essential role of chymotrypsins in pancreas health.

Pancreatic Diseases: Genetics and Modeling Using Human Pluripotent Stem Cells

Pancreas serves endocrine and exocrine functions in the body; thus, their pathology can cause a broad range of irreparable consequences. Endocrine functions include the production of hormones such as insulin and glucagon, while exocrine functions involve the secretion of digestive enzymes. Disruption of these functions can lead to conditions like diabetes mellitus and exocrine pancreatic insufficiency. Also, the symptoms and causality of pancreatic cancer very greatly depends on their origin: pancreatic ductal adenocarcinoma is one of the most fatal cancer; however, most of tumor derived from endocrine part of pancreas are benign. Pancreatitis, an inflammation of the pancreatic tissues, is caused by excessive alcohol consumption, the bile duct obstruction by gallstones, and the premature activation of digestive enzymes in the pancreas. Hereditary pancreatic diseases, such as maturity-onset diabetes of the young and hereditary pancreatitis, can be a candidate for disease modeling using human pluripotent stem cells (hPSCs), due to their strong genetic influence. hPSC-derived pancreatic differentiation has been established for cell replacement therapy for diabetic patients and is robustly used for disease modeling. The disease modeling platform that allows interactions between immune cells and pancreatic cells is necessary to perform in-depth investigation of disease pathogenesis.

Novel chymotrypsin C (CTRC) variants from real-world genetic testing of pediatric chronic pancreatitis cases

BACKGROUND

Chymotrypsin C (CTRC) protects the pancreas against unwanted intrapancreatic trypsin activity through degradation of trypsinogen. Loss-of-function CTRC variants increase the risk for chronic pancreatitis (CP). The aim of the present study was to characterize novel CTRC variants found during genetic testing of CP cases at a pediatric pancreatitis center.

METHODS

We used next-generation sequencing to screen patients. We analyzed the functional effects of CTRC variants in HEK 293T cells and using purified enzymes.

RESULTS

In 5 separate cases, we detected 5 novel heterozygous CTRC variants: c.407C>T (p.Thr136Ile), c.550G>A (p.Ala184Thr), c.627Cdup (p.Ser210Leufs∗?, where the naming indicates a frame shift with no stop codon), c.628T>C (p.Ser210Pro), and c.779A>G (p.Asp260Gly). Functional studies revealed that with the exception of p.Ser210Leufs∗?, the CTRC variants were secreted normally from transfected cells. Enzyme activity of purified variants p.Thr136Ile, p.Ala184Thr, and p.Asp260Gly was similar to that of wild-type CTRC, whereas variant p.Ser210Pro was inactive. The frame-shift variant p.Ser210Leufs∗? was not secreted but accumulated intracellularly, and induced endoplasmic reticulum stress, as judged by elevated mRNA levels of HSPA5 and DDIT3, and increased mRNA splicing of XBP1.

CONCLUSIONS

CTRC variants p.Ser210Pro and p.Ser210Leufs∗? abolish CTRC function and should be classified as pathogenic. Mechanistically, variant p.Ser210Pro directly affects the amino acid at the bottom of the substrate-binding pocket while the frame-shift variant promotes misfolding and thereby blocks enzyme secretion. Importantly, 3 of the 5 novel CTRC variants proved to be benign, indicating that functional analysis is indispensable for reliable determination of pathogenicity and the correct interpretation of genetic test results.

A De Novo CaSR Missense Variant in Combination with Two Inherited Missense Variants in CFTR and SPINK1 Detected in a Patient with Chronic Pancreatitis

Chronic pancreatitis is often secondary to alcohol abuse, but pancreatitis with no other aetiology is frequently associated with variants in genes encoding proteins related to zymogen granule activation. Our goal was to identify genomic variants in a patient by analyzing an extended panel of genes associated with the intra-pancreatic activation of the trypsin pathway. A 23-year-old woman was addressed at our institution because of chronic pancreatitis of unknown aetiology presenting recurrent episodes since she was the age of four. Next Generation Sequencing was performed to analyze a panel of nine genes associated with pancreatitis (CaSR, CFTR, CPA1, CTRC, CTSB, KRT8, PRSS1, PRSS2, and SPINK1). Three missense variants were found: p.Leu997Phe, maternally inherited, in the CFTR gene; p.Ile73Phe, paternally inherited, in the SPINK1 gene; and p.Phe790Ser, a de novo variant, in the CaSR gene. They were classified, respectively as probably benign, a Variant of Uncertain Significance, and the last one, which has never been described in the literature, as likely being pathogenic following American College of Medical Genetics and Genomics standard guidelines. Extensive intra-pancreatic activation of trypsin pathway gene sequencing detected rare variants that were not found with other gene screening and showed that variants in different genes may interact in contributing to the onset of the pancreatitis phenotype.

Molecular docking studies of isolated marine natural products against α-chymotrypsin

The α-chymotrypsin is widely present in the digestive system of prokaryotes and eukaryotes that helps in the digestion by the hydrolysis of the peptide bond. It is serine protease enzyme (E.C. 3.4.21.1) and involves in many biological processes as well as in pancreatic disorders. In the previous study, marine red alga namely Jolyna laminariodes was used for the isolation of succinylanthranilic acid ester (2). Further, analogues were synthesised from anthranilic acid by using succinic anhydride, maleic anhydride and glutaric anhydride into corresponding dicarboxylic acids and further into acid ester including succinylanthranilic acid (1), succinylanthranilic acid ester (2), maleinylanthranilic acid (3), maleinylanthranilic acid ester (4), glutarnylanthranilic acid (5) and glutarnylanthranilic acid ester (6). For all natural products analogues percent inhibition against α-chymotrypsin have been calculated. In this study, molecular docking is used to estimate the binding energy of natural product analogues against α-chymotrypsin enzyme. The docking energies are in good agreement with experimental findings.

Genetics and Genomics of Chronic Pancreatitis with a Focus on Disease Biology and Molecular Pathogenesis

Chronic pancreatitis is a long-term fibroinflammatory condition of the pancreas with varying incidences across countries. The recent increase in its occurrence implies the involvement of genetic, hereditary, and unconventional risk factors. However, there is a lack of updated literature on recent advances in genetic polymorphisms of chronic pancreatitis. Therefore, this review aims to present recent findings on the genetic implications of chronic pancreatitis based on individual gene mechanisms and to discuss epigenetics and epistasis involved in the disease. Four mechanisms have been implicated in the pathogenesis of chronic pancreatitis, including premature activation of proteases, endoplasmic reticulum stress, ductal pathway dysfunction, and inflammatory pathway dysfunction. These mechanisms involve genes such as PRSS1, PRSS2, SPINK, CEL, PNLIP, PNLIPRP2, CFTR, CaSR, CLDN2, Alpha 1 antitrypsin, and GGT1 . Studying genetic polymorphisms on the basis of altered genes and their products may aid clinicians in identifying predispositions in patients with and without common risk factors. Further research may also identify associations between genetic predispositions and disease staging or prognosis, leading to personalized treatment protocols and precision medicine.

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.

Rational Design of Esterase-Insensitive Fluorogenic Probes for In Vivo Imaging

Small-molecule fluorogenic probes are indispensable tools for performing research in biomedical fields and chemical biology. Although numerous cleavable fluorogenic probes have been developed to investigate various bioanalytes, few of them meet the baseline requirements for in vivo biosensing for disease diagnosis due to their insufficient specificity resulted from the remarkable esterase interferences. To address this critical issue, we developed a general approach called fragment-based fluorogenic probe discovery (FBFPD) to design esterase-insensitive probes for in vitro and in vivo applications. With the designed esterase-insensitive fluorogenic probe, we successfully achieved light-up in vivo imaging and quantitative analysis of cysteine. This strategy was further extended to design highly specific fluorogenic probes for other representative targets, sulfites, and chymotrypsin. The present study expands the bioanalytical toolboxes available and offers a promising platform to develop esterase-insensitive cleavable fluorogenic probes for in vivo biosensing and bioimaging for the early diagnosis of diseases.

Proteome-Wide Mendelian Randomization Identifies Causal Links Between Blood Proteins and Acute Pancreatitis

BACKGROUND & AIMS

Acute pancreatitis (AP) is a complex disease and the leading cause of gastrointestinal disease-related hospital admissions. Few therapeutic options exist for AP prevention. Blood proteins with causal evidence may represent promising drug targets, but few have been causally linked with AP. Our objective was to identify blood proteins linked with AP by combining genome-wide association meta-analysis and proteome-wide Mendelian randomization (MR) studies.

METHODS

We performed a genome-wide association meta-analysis totalling 10,630 patients with AP and 844,679 controls and a series of inverse-variance weighted MR analyses using cis-acting variants on 4719 blood proteins from the deCODE study (n = 35,559) and 4979 blood proteins from the Fenland study (n = 10,708).

RESULTS

The meta-analysis identified genome-wide significant variants (P <5 × 10^-8) at 5 loci (ABCG5/8, TWIST2, SPINK1, PRSS2 and MORC4). The proteome-wide MR analyses identified 68 unique blood proteins that may causally be associated with AP, including 29 proteins validated in both data sets. Functional annotation of these proteins confirmed expression of many proteins in metabolic tissues responsible for digestion and energy metabolism, such as the esophagus, adipose tissue, and liver as well as acinar cells of the pancreas. Genetic colocalization and investigations into the druggable genome also identified potential drug targets for AP.

CONCLUSIONS

This large genome-wide association study meta-analysis for AP identified new variants linked with AP as well as several blood proteins that may be causally associated with AP. This study provides new information on the genetic architecture of this disease and identified pathways related to AP, which may be further explored as possible therapeutic targets for AP.

Genotype-Phenotype Correlations in Asian Indian Children and Adolescents with Primary Hyperparathyroidism

Childhood and adolescent primary hyperparathyroidism (PHPT) is a very rare disease. Data on its molecular genetics are scarce. We performed a retrospective analysis (January 2000-January 2021) to determine the deleterious germline variants and genotype-phenotype correlations in children and adolescents < 20 years diagnosed with PHPT from a single referral center. Clinical features, biochemistry, imaging, management, and genetics (clinical exome analyzed for 11 PHPT and 7 pancreatitis-associated genes, MLPA for CDC73) were recorded. Thirty-six patients (20 males; median age 17 years) were classified into those with familial and/or syndromic (F/S) or apparently sporadic (AS) presentation. Sixteen (44.4%) harbored pathogenic/likely pathogenic germline variants in PHPT-associated genes. The genetic yield in F/S group was 90% (MEN1:8/10; CDC73:1/10), and AS group was 26.9% (CDC73:4/26; CASR:3/26). F/S group had frequent asymptomatic presentation (60% vs none; P < 0.001), lower serum PTH (237.5 vs 1369.1 pg/mL; P = 0.001), and maximum parathyroid dimension (0.9 vs 2.2 cm; P = 0.01) than AS group. Among the AS group, renal involvement was higher in those with molecular diagnoses (71.4% vs 10.5%; P = 0.01). All those with novel CASR variants (including one homozygous) had hypercalciuria and histology-proven parathyroid adenoma/carcinoma. A missense CTRC VUS occurred in one patient with chronic pancreatitis. In summary, Asian Indian children and adolescents with PHPT have high genetic yield, even with apparently sporadic presentation. The phenotypic spectrum of CASR variants is expanded to include childhood/adolescent PHPT with hypercalciuria and single gland neoplasia. The proposed roles for renal involvement to predict molecular diagnosis among those with apparently sporadic presentation require further elucidation.

Cigarette smoke toxin hydroquinone and misfolding pancreatic lipase variant cooperatively promote endoplasmic reticulum stress and cell death

Mutation-induced protein misfolding of pancreatic secretory enzymes and consequent endoplasmic reticulum stress can cause chronic pancreatitis. A recent study revealed that cigarette smoke also increases the risk of the disease through endoplasmic reticulum stress. Here, we investigated the cumulative cellular effect of the G233E misfolding human pancreatic lipase variant and hydroquinone; a main toxic constituent of cigarette smoke, using mammalian cell lines. We found that hydroquinone reduces cell viability on a dose-dependent manner through programmed cell death, and diminishes lipase secretion without affecting its expression. Interestingly, hydroquinone decreased the viability more markedly in cells expressing the G233E lipase variant, than in cells producing wild-type lipase. The more substantial viability loss was due to increased endoplasmic reticulum stress, as demonstrated by elevated levels of X-box binding protein 1 mRNA splicing and immunoglobulin binding protein, NAD(P)H:quinone oxidoreductase 1 and C/EBP homologous protein expression. Unresolved endoplasmic reticulum stress, and especially up-regulation of the pro-apoptotic transcription factor C/EBP homologous protein were likely responsible for the increased cell death. Our observations demonstrated that the combination of hydroquinone and misfolding pancreatic lipase variant promote increased levels of endoplasmic reticulum stress and cell death, which may predispose to chronic pancreatitis.

Macrocyclic Cavitand β-Cyclodextrin Inhibits the Alcohol-induced Trypsin Aggregation

Trypsin, the most abundant pancreatic protein, aids in protein digestion by hydrolysis and exhibits aggregation propensity in presence of alcohol which can further lead to pancreatitis and eventually pancreatic cancer. Herein, by several experimental and theoretical approaches, we unearth the inhibition of alcohol-induced aggregation of Trypsin by macrocyclic cavitand, β-cyclodextrin (β-CD). β-CD interacts with the native protein and shows inhibitory effect in a dose dependent manner. Moreover, the secondary structures and morphologies of Trypsin in presence of β-CD also clearly emphasize the inhibition of fibril formation. From Fluorescence Correlation Spectroscopy, we observed an enhancement in diffusion time of Nile Red with ~ 2.5 times increase in hydrodynamic radius, substantiating the presence of fibrillar structure. Trypsin also shows reduction in its functional activity due to alcohol-induced aggregation. Our simulation data reports the probable residues responsible for fibril formation which was validated by molecular docking studies.

Development of the human pancreas and its exocrine function

The pancreas has both endocrine and exocrine function and plays an important role in digestion and glucose control. Understanding the development of the pancreas, grossly and microscopically, and the genetic factors regulating it provides further insight into clinical problems that arise when these processes fail. Animal models of development are known to have inherent issues when understanding human development. Therefore, in this review, we focus on human studies that have reported gross and microscopic development including acinar-, ductal-, and endocrine cells and the neural network. We review the genes and transcription factors involved in organ formation using data from animal models to bridge current understanding where necessary. We describe the development of exocrine function in the fetus and postnatally. A deeper review of the genes involved in pancreatic formation allows us to describe the development of the different groups (proteases, lipids, and amylase) of enzymes during fetal life and postnatally and describe the genetic defects. We discuss the constellation of gross anatomical, as well as microscopic defects that with genetic mutations lead to pancreatic insufficiency and disease states.

The unfolded protein response: An emerging therapeutic target for pancreatitis and pancreatic ductal adenocarcinoma

Pancreatitis is a debilitating disease involving inflammation and fibrosis of the exocrine pancreas. Recurrent or chronic forms of pancreatitis are a significant risk factor for pancreatic ductal adenocarcinoma. While genetic factors have been identified for both pathologies, environmental stresses play a large role in their etiology. All cells have adapted mechanisms to handle acute environmental stress that alters energy demands. A common pathway involved in the stress response involves endoplasmic reticulum stress and the unfolded protein response (UPR). While rapidly activated by many external stressors, in the pancreas the UPR plays a fundamental biological role, likely due to the high protein demands in acinar cells. Despite this, increased UPR activity is observed in response to acute injury or following exposure to risk factors associated with pancreatitis and pancreatic cancer. Studies in animal and cell cultures models show the importance of affecting the UPR in the context of both diseases, and inhibitors have been developed for several specific mediators of the UPR. Given the importance of the UPR to normal acinar cell function, efforts to affect the UPR in the context of disease must be able to specifically target pathology vs. physiology. In this review, we highlight the importance of the UPR to normal and pathological conditions of the exocrine pancreas. We discuss recent studies suggesting the UPR may be involved in the initiation and progression of pancreatitis and PDAC, as well as contributing to chemoresistance that occurs in pancreatic cancer. Finally, we discuss the potential of targeting the UPR for treatment.

CHRONIC PANCREATIC DISEASE IN THE LESSER KUDU (TRAGELAPHUS IMBERBIS): A REPORT OF 16 CASES IN THE UNITED STATES

A review of archival cases at Northwest ZooPath from 1995-2018 identified 16/96 (17%; eight females, eight males) lesser kudus (Tragelaphus imberbis) with chronic pancreatic disease (CPD) from three institutions, all of which originated from an initial founder stock of 12 animals. Ages at time of death or euthanasia ranged from 2 to 132 mo (average age = 69 mo). All cases had varying degrees of pancreatic acinar cell depletion, ductular hyperplasia, and fibrosis. Serum fructosamine, glucose, insulin, and insulin to glucose ratio collected close to time of death from 13 affected animals were not significantly different from controls (n = 19). Of these analytes, receiver operating characteristic analysis identified fructosamine as the best-performing analyte with an area under the curve 0.671 (95% confidence interval = 0.480-0.828; sensitivity = 58.3%, specificity = 84.2%; cutoff point >352 µmol/L) in the diagnosis of CPD. With a 15% prevalence, there was a positive predictive value of 41% and a negative predictive value of 92%, indicating that the probability of false positives is high, but of false negatives is low. An etiologic agent was not identified by histology (n = 16), transmission electron microscopy (n = 1), or enterovirus PCR (n = 2). Serum zinc and hepatic heavy metal analyses were judged to be within normal limits. Chronic pancreatic disease is considered an important cause of morbidity and mortality in the lesser kudu; serum chemistry analysis warrants further investigation in its use for diagnosis. The etiopathogenesis is not understood, but the absence of obvious causes, the occurrence also in very young animals, and the inbred lineage of lesser kudus in the United States suggest a genetic basis for this disease.

Trypsinogen and chymotrypsinogen: potent anti-tumor agents

Introduction: Trypsinogen and chymotrypsinogen have been used clinically in tissue repair due to their ability to resolve inflammatory symptoms. Recently, novel evidence has supported the anti-tumourigenic potential of a mixture of trypsinogen and chymotrypsinogen.Areas covered: First, we analyze the structure of these proteases and the effects of pancreatic proteinases on tissue repair, inflammation and the immune system. Second, we summarize studies that provided evidence of the effects of pancreatic (pro)enzymes on tumor cells both in vitro and in vivo and some successful clinical applications of pancreatic (pro)enzymes. Finally, we study pancreatic (pro)enzymes potential molecular targets, such as the proteinase-activated receptors (PARs).Expert opinion: This novel therapy has been shown to have effective antitumor effects. Treatment with these (pro) enzymes sensitizes Cancer Stem Cells (CSCs) which may allow chemotherapy and radiotherapy to be more effective, which could positively affect the recovery of cancer patients.

Interpreting Sequence Variation in PDAC-Predisposing Genes Using a Multi-Tier Annotation Approach Performed at the Gene, Patient, and Cohort Level

We investigated germline variation in pancreatic ductal adenocarcinoma (PDAC) predisposition genes in 535 patients, using a custom-built panel and a new complementary bioinformatic approach. Our panel assessed genes belonging to DNA repair, cell cycle checkpoints, migration, and preneoplastic pancreatic conditions. Our bioinformatics approach integrated annotations of variants by using data derived from both germline and somatic references. This integrated approach with expanded evidence enabled us to consider patterns even among private mutations, supporting a functional role for certain alleles, which we believe enhances individualized medicine beyond classic gene-centric approaches. Concurrent evaluation of three levels of evidence, at the gene, sample, and cohort level, has not been previously done. Overall, we identified in PDAC patient germline samples, 12% with mutations previously observed in pancreatic cancers, 23% with mutations previously discovered by sequencing other human tumors, and 46% with mutations with germline associations to cancer. Non-polymorphic protein-coding pathogenic variants were found in 18.4% of patient samples. Moreover, among patients with metastatic PDAC, 16% carried at least one pathogenic variant, and this subgroup was found to have an improved overall survival (22.0 months versus 9.8; p=0.008) despite a higher pre-treatment CA19-9 level (p=0.02). Genetic alterations in DNA damage repair genes were associated with longer overall survival among patients who underwent resection surgery (92 months vs. 46; p=0.06). ATM alterations were associated with more frequent metastatic stage (p = 0.04) while patients with BRCA1 or BRCA2 alterations had improved overall survival (79 months vs. 39; p=0.05). We found that mutations in genes associated with chronic pancreatitis were more common in non-white patients (p<0.001) and associated with longer overall survival (52 months vs. 26; p=0.004), indicating the need for greater study of the relationship among these factors. More than 90% of patients were found to have variants of uncertain significance, which is higher than previously reported. Furthermore, we generated 3D models for selected mutant proteins, which suggested distinct mechanisms underlying their dysfunction, likely caused by genetic alterations. Notably, this type of information is not predictable from sequence alone, underscoring the value of structural bioinformatics to improve genomic interpretation. In conclusion, the variation in PDAC predisposition genes appears to be more extensive than anticipated. This information adds to the growing body of literature on the genomic landscape of PDAC and brings us closer to a more widespread use of precision medicine for this challenging disease.

Serpina3n is closely associated with fibrotic procession and knockdown ameliorates bleomycin-induced pulmonary fibrosis

OBJECTIVE

Pulmonary fibrosis is a fatal interstitial lung disease that is characterized by excessive accumulation of extracellular matrix (ECM) and remodeling of lung. The precise mechanisms underlying pulmonary fibrosis still remain unclear. In the current study, we aimed to investigate the alteration and function of serine (or cysteine) peptidase inhibitor, clade A, member 3 N (Serpina3n) in pulmonary fibrotic models and explore the potential mechanisms.

METHODS

We induced pulmonary fibrosis in mice by silica and bleomycin respectively and determined Serpina3n in lung tissues, and then verified the expression of Serpina3n and its correlation with pulmonary fibrosis at seven time points in a bleomycin longstanding model. Moreover, adeno-associated virus type 9 (AAV9)-mediated Serpina3n knockdown was used to treat pulmonary fibrosis in the bleomycin model, whose possible mechanisms would be preliminarily explored by detecting chymotrypsin C as an example.

RESULTS

Serpina3n was up-regulated significantly in lungs of both models at mRNA and protein levels relative to control. Notably, the expression of Serpina3n peaked during the 3rd week and then decreased until nearly normal levels during the 10th week, which was closely related to fibrotic procession in bleomycin-treated mice. AAV-mediated Serpina3n knockdown in the lung tissues alleviated bleomycin-induced fibrotic symptoms at various levels and disinhibit chymotrypsin C.

CONCLUSIONS

Our study revealed that Serpina3n is a critical regulator in pulmonary fibrosis and suggested Serpina3n inhibition as a potential therapeutic strategy in chronic pulmonary injuries.

Sulfidation of Ag and ZnO Nanomaterials Significantly Affects Protein Corona Composition: Implications for Human Exposure to Environmentally Aged Nanomaterials

The physicochemical properties of engineered nanomaterials can change drastically during aging in the environment. Understanding how these changes influence protein corona formation on nanomaterials is critical for accurately predicting the human exposure risks of aged nanomaterials. Here, we show that sulfidation, a prevalently occurring environmental aging process, of Ag and ZnO nanomaterials significantly affected the protein compositions of the hard corona formed in human saliva, sweat, and bronchoalveolar lavage fluid, corresponding to three most common exposure pathways, that is, ingestion, dermal contact, and inhalation. In particular, a diverse variety of proteins selectively associated with either sulfidized or pristine nanomaterials. Random forest classification of the proteomic data revealed that this selective protein adsorption process was mainly dictated by electrostatic interaction, hydrophobic interaction, and steric hindrance between proteins and nanomaterials, which were susceptible to the changes in surface charge, hydrophobicity, and aggregation status of nanomaterials induced by sulfidation. Furthermore, even for the proteins that do not exhibit distinct adsorption selectivity between sulfidized and pristine nanomaterials, sulfidation altered the extents of impact of nanomaterials on the conformation and likely functions of the adsorbed proteins. These findings unearth a previously neglected mechanism via which environmental sulfidation process mediates the biological effects of soft-metal-containing nanomaterials.

Risk Factors for Rapid Progression From Acute Recurrent to Chronic Pancreatitis in Children: Report From INSPPIRE

OBJECTIVE

The aim of the study was to determine the rate of progression from acute recurrent pancreatitis (ARP) to chronic pancreatitis (CP) in children and assess risk factors.

STUDY DESIGN

Data were collected from the INternational Study group of Pediatric Pancreatitis: In search for a cuRE (INSPPIRE) cohort. Kaplan-Meier curves were constructed to calculate duration of progression from initial attack of acute pancreatitis (AP) to CP. Log-rank test was used to compare survival (nonprogression) probability distribution between groups. Cox proportional hazard regression models were fitted to obtain hazard ratio (with 95% confidence interval [CI]) of progression for each risk variable.

RESULTS

Of 442 children, 251 had ARP and 191 had CP. The median time of progression from initial attack of AP to CP was 3.79 years. The progression was faster in those ages 6 years or older at the first episode of AP compared to those younger than 6 years (median time to CP: 2.91 vs 4.92 years; P = 0.01). Children with pathogenic PRSS1 variants progressed more rapidly to CP compared to children without PRSS1 variants (median time to CP: 2.52 vs 4.48 years; P = 0.003). Within 6 years after the initial AP attack, cumulative proportion with exocrine pancreatic insufficiency was 18.0% (95% CI: 12.4%, 25.6%); diabetes mellitus was 7.7% (95% CI: 4.2%, 14.1%).

CONCLUSIONS

Children with ARP rapidly progress to CP, exocrine pancreatic insufficiency, and diabetes. The progression to CP is faster in children who were 6 years or older at the first episode of AP or with pathogenic PRSS1 variants. The factors that affect the aggressive disease course in childhood warrant further investigation.

Serine protease inhibitors and activators from Dalbergia tonkinensis species

The vulnerable plant Dalbergia tonkinensis Prain is a rare species in Vietnam. In the course of our studies on biologically active plants, we performed serine protease enzyme screenings. The results suggest that at concentrations of 25-250 ng/mL, methanol extracts of leaf and root, root ethanol extract and its dichloromethane fraction, and heartwood water decoction extract can serve as useful sources to stimulate trypsin enzyme activity. In addition, water decoction extracts of leaf and stem bark may explain unknown ethno-pharmacology due to the high inhibitory effects in enzyme assays using trypsin, chymotrypsin, and elastase. Among 23 isolated compounds and two semi-synthetic derivatives tested, quercetin (17) inhibits the activities of trypsin and chymotrypsin with IC₅₀ 9.7 µM. Flavonoids categorized as flavanone, isoflavanone, flavone, isoflavone, pretocarpan, aurone, and neoflavanone demonstrated variable activities. Several substitutions are closely correlated with protease actions, including hydroxylation at C-3 and C-3' in flavone and C-5 and C-3' in isoflavone, hydroxylation at C-3, C-5 and C-3', carboxylation at C-6 and C-8, and 7-substitution in flavanone; 7-substitution and methoxylation at C-3' in isoflavanone; and lactone ring opening in neoflavanone. In the assessment of casein cleavage, at a dose of 25 ng/mL, leaf water decoction extract demonstrates an inhibitory effect on casein cleavage by trypsin, whereas ethanol and methanol extracts of the root caused activation.

Early Intra-Acinar Events in Pathogenesis of Pancreatitis

Premature activation of digestive enzymes in the pancreas has been linked to development of pancreatitis for more than a century. Recent development of novel models to study the role of pathologic enzyme activation has led to advances in our understanding of the mechanisms of pancreatic injury. Colocalization of zymogen and lysosomal fraction occurs early after pancreatitis-causing stimulus. Cathepsin B activates trypsinogen in these colocalized organelles. Active trypsin increases permeability of these organelles resulting in leakage of cathepsin B into the cytosol leading to acinar cell death. Although trypsin-mediated cell death leads to pancreatic injury in early stages of pancreatitis, multiple parallel mechanisms, including activation of inflammatory cascades, endoplasmic reticulum stress, autophagy, and mitochondrial dysfunction in the acinar cells are now recognized to be important in driving the profound systemic inflammatory response and extensive pancreatic injury seen in acute pancreatitis. Chymotrypsin, another acinar protease, has recently been shown be play critical role in clearance of pathologically activated trypsin protecting against pancreatic injury. Mutations in trypsin and other genes thought to be associated with pathologic enzyme activation (such as serine protease inhibitor 1) have been found in familial forms of pancreatitis. Sustained intra-acinar activation of nuclear factor κB pathway seems to be key pathogenic mechanism in chronic pancreatitis. Better understanding of these mechanisms will hopefully allow us to improve treatment strategies in acute and chronic pancreatitis.

Idiopathic recurrent acute pancreatitis

Idiopathic recurrent acute pancreatitis is clinically challenging and has substantial socioeconomic consequences. Investigations are expensive and often reveal little about the cause of the disease. Little is known about the interaction between genetic, environmental, anatomical, and other factors that contribute to the disease. Data on the efficacy, safety, and long-term outcomes of endoscopic therapies are scarce. The effect of idiopathic recurrent pancreatitis on quality of life is often underestimated. A more thorough examination of the causes of the disease and the roles of other associated risk factors is needed, as are well designed clinical studies with robust and objectively measurable outcomes. Ideally, evaluation of the causes of disease and therapy should be done only in specialised centres, should follow a protocol, and all outcomes should be formally assessed.

Diabetes of the exocrine pancreas

Diabetes of the exocrine pancreas (DEP) is a form of diabetes that occurs due to pancreatic disease. It is far more common than has been previously considered, with a recent study showing 1.8% of adults with new-onset diabetes should have been classified as DEP. The majority is misdiagnosed as type 2 diabetes mellitus (T2DM). Patients with DEP exhibit varying degrees of exocrine and endocrine dysfunction. Damage to the islet of Langerhans effects the secretion of hormones from the β, α, and pancreatic polypeptide cells; the combination of low insulin, glucagon, and pancreatic polypeptide contributes to rapid fluctuations in glucose levels. This form of "brittle diabetes" may result in the poorer glycemic control observed in patients with DEP, when compared with those with T2DM. Diabetes of the exocrine pancreas has a different natural history to other forms of diabetes; patients are more likely to require early insulin initiation compared with those with T2DM. Therefore, individuals with DEP should be advised about the symptoms of decompensated hyperglycemia, although they are less likely to develop ketoacidosis. Clinicians should screen for DEP in patients with acute or chronic pancreatitis, following pancreatic resection, or with co-existing cystic fibrosis or hemochromatosis. Incident diabetes may herald the onset of pancreatic ductal carcinoma in a small subset of patients. Once identified, patients with DEP can benefit from specific lifestyle advice, pancreatic enzyme replacement therapy, metformin treatment, appropriate insulin dosing, and monitoring. Further research is needed to establish the ideal treatment regimens to provide optimal clinical outcomes for this unique form of diabetes.

A non-peptide NIR fluorescent probe for detection of chymotrypsin and its imaging application

A novel non-peptide NIR fluorescent probe for the detection of chymotrypsin and its imaging application.

Genetic predisposition in pancreatitis

PURPOSE OF REVIEW

Genetic mutations are the primary cause for acute recurrent (ARP) and chronic pancreatitis in children. Further, our medical approach for many diseases is changing from a one-drug therapy to more individualized therapeutic strategies. In respect to the therapeutic management of ARP/chronic pancreatitis, this entails an understanding of the individual, mainly genetic, risk factors that led to pancreatitis disease.

RECENT FINDINGS

New pancreatitis-associated genes are continuously emerging from increasingly large genetic cohort studies. Furthermore, newer research findings demonstrate that multiple genetic and nongenetic factors are required to increase the individual risk for developing ARP/chronic pancreatitis. Last, there is new exciting development towards targeted pancreatitis therapy in the future.

SUMMARY

This review introduces the current concept of ARP/chronic pancreatitis as a complex disease caused by multiple genetic and nongenetic factors. This warrants careful evaluation of these patients and ideally consultation of a pancreas expert to help understand individual genetic risk profiles and to provide more effective patient consultation.

Genetic Risk in Chronic Pancreatitis: The Trypsin-Dependent Pathway

Genetic investigations have provided unique insight into the mechanism of chronic pancreatitis in humans and firmly established that uncontrolled trypsin activity is a central pathogenic factor. Mutations in the PRSS1, SPINK1, and CTRC genes promote increased activation of trypsinogen to trypsin by stimulation of autoactivation or by impairing protective trypsinogen degradation and/or trypsin inhibition. Here we review key genetic and biochemical features of the trypsin-dependent pathological pathway in chronic pancreatitis.

What's unique about acute pancreatitis in children: risk factors, diagnosis and management

Pancreatitis in children is an appreciable problem that has become increasingly prevalent. This Review covers the principles related to the definitions, epidemiology, risk factors, diagnosis and management of acute pancreatitis in children and identifies features that are unique among children. Additionally, knowledge gaps related to management principles are identified.

The Etiology and Clinical Course of Chronic Pancreatitis in Children With Early Onset of the Disease

OBJECTIVES

The etiological factors of chronic pancreatitis (CP) in children differ from those in adults. To date, no study has assessed the clinical course of CP in young children. The aim of our study was to evaluate the etiology and the clinical presentation of the disease in children with disease onset before 5 years of age in comparison to later-onset of CP.

METHODS

A total of 276 children with CP, hospitalized from 1988 to 2015, were enrolled in the study. Data on presentation, diagnostic findings, and treatment were reviewed. Two hundred sixty patients were screened for the most frequent mutations in major pancreatitis-associated genes, such as cationic trypsinogen/serine protease gene (PRSS1), serine protease inhibitor, Kazal type 1 gene (SPINK1), and cystic fibrosis transmembrane conductance regulator gene (CFTR).

RESULTS

The disease onset before the age of 5 years occurred in 51 patients (group 1), the later onset in 225 patients (group 2). We found no significant discrepancies in distribution of the etiological factors between groups. The youngest patients (group 1) had more pancreatitis episodes (median 5.0 vs 3.00; P < 0.05) and underwent surgeries more frequently (25.5% vs 8.9%; P < 0.05). It could be associated with significantly longer follow-up in early onset group (median 6 vs 4 years; P < 0.05). There were no differences in nutritional status or exocrine and endocrine pancreatic function.

CONCLUSIONS

Early- and later-onset pancreatitis have similar etiological factors with predominance of gene mutations. The most frequent mutation found was p.Asn34Ser (N34S) in SPINK1 gene. The clinical presentation differed in number of pancreatitis episodes and frequency of surgeries.

Frequency of Tabagism and N34S and P55S Mutations of Serine Peptidase Inhibitor, Kazal Type 1 (SPINK1) and R254W Mutation of Chymotrypsin C (CTRC) in Patients With Chronic Pancreatitis and Controls

OBJECTIVE

This study aimed to investigate the association between chronic pancreatitis and smoking or genetic mutations.

METHODS

The study sample comprised 148 patients with chronic pancreatitis, 110 chronic alcoholic subjects without pancreatic disease, and 297 volunteer blood donors.

RESULTS

Of the patients with chronic pancreatitis, 74% had alcoholic etiology and 26% had idiopathic pancreatitis. The frequency of smoking was 91.4% in patients with alcoholic pancreatitis, higher than 73.3% in alcoholic subjects without pancreatitis (P < 0.01). The difference in smoking frequency was not significant between the patients with idiopathic pancreatitis and blood donors. The N34S mutation of serine peptidase inhibitor, Kazal type 1 (SPINK1) was found in 2.7% of patients with chronic alcoholic pancreatitis, in 5.3% of patients with idiopathic pancreatitis, and in 0.4% of blood donors (P = 0.02). The P55S mutation of SPINK1 was found in 2.7% of patients with alcoholic pancreatitis and in 0.7% of blood donors (P = 0.12). The R254W mutation of chymotrypsin C was found in 0.9% of patients with alcoholic pancreatitis, in 0.9% of chronic alcoholic subjects without pancreatitis, and in 0.4% of blood donors (P = 0.75). In all cases, the mutations were heterozygous.

CONCLUSIONS

Smoking and the N34S mutation of SPINK1 were positively correlated with chronic pancreatitis.

Caldecrin: A pancreas-derived hypocalcemic factor, regulates osteoclast formation and function

Caldecrin was originally isolated from the pancreas as a factor that reduced serum calcium levels. This secreted serine protease has chymotrypsin-like activity and is also known as chymotrypsin C; it belongs to the elastase family. Although intravenous administration of caldecrin decreases the serum calcium concentration even when its protease activity is blocked, this effect does require cleavage of caldecrin’s pro-peptide by trypsin, converting it to the mature enzyme. Ectopic intramuscular expression of caldecrin prevented bone resorption in ovariectomized mice. Caldecrin inhibited parathyroid hormone-stimulated calcium release from fetal mouse long bone organ cultures. Furthermore, caldecrin suppressed the formation of osteoclasts from bone marrow cells by inhibiting the receptor activator of nuclear factor-κ B ligand (RANKL)-stimulated phospholipase Cγ-calcium oscillation-calcineurin-nuclear factor of activated T-cells, cytoplasmic 1 pathway. Caldecrin also suppressed the bone resorption activity of mature osteoclasts by preventing RANKL-stimulated Src activation, calcium entry, and actin ring formation. In vivo and in vitro studies have indicated that caldecrin is a unique multifunctional protease with anti-osteoclastogenic activities that are distinct from its protease activity. Caldecrin might be a potential therapeutic target for the treatment of osteolytic diseases such as osteoporosis and osteoarthritis. This mini-review describes caldecrin’s historical background and its mechanisms of action.

Gene conversion between cationic trypsinogen (PRSS1) and the pseudogene trypsinogen 6 (PRSS3P2) in patients with chronic pancreatitis

Mutations of the human cationic trypsinogen gene (PRSS1) are frequently found in association with hereditary pancreatitis. The most frequent variants p.N29I and p.R122H are recognized as disease-causing mutations. Three pseudogene paralogs in the human trypsinogen family, including trypsinogen 6 (PRSS3P2), carry sequence variations in exon 3 that mimic the p.R122H mutation. In routine genetic testing of patients with chronic pancreatitis, we identified in two unrelated individuals similar gene conversion events of 24-71 nucleotides length between exon 3 of the PRSS1 (acceptor) and PRSS3P2 (donor) genes. The converted allele resulted in three nonsynonymous alterations c.343T>A (p.S115T), c.347G>C (p.R116P), and c.365_366delinsAT (p.R122H). Functional analysis of the conversion triple mutant revealed markedly increased autoactivation resulting in high and sustained trypsin activity in the presence of chymotrypsin C. This activation phenotype was identical to that of the p.R122H mutant. In addition, cellular secretion of the triple mutant from transfected HEK 293T cells was increased about twofold and this effect was attributable to mutation p.R116P. Our observations confirm and extend the notion that recombination events between members of the trypsinogen family can generate high-risk PRSS1 alleles. The pathogenic phenotype of the novel conversion is explained by a unique combination of increased trypsinogen activation and secretion.

Genetic mutations in SPINK1, CFTR, CTRC genes in acute pancreatitis

Background

Explanation of the ultimate causes of acute and chronic pancreatitis is challenging. Hence, it is necessary to seek various etiological factors, including genetic mutations that may be of importance in triggering recurrence and progression of acute to chronic pancreatitis. The aim of this study was to determine the frequency of genetic mutations in patients with acute pancreatitis and to investigate their relationship with the etiology and clinical course.

Methods

The study included 221 patients treated for acute pancreatitis and 345 healthy subjects as a control group. Peripheral blood samples were collected from each study participant and genomic DNA was isolated. Genotyping of common mutations in the SPINK1 (p.N34S and p.P55S) and CTRC (p.I259V, p.V235I, p.K247_R254del, p.E225A) genes was performed using the high-resolution melting method. Mutations in the CFTR p.F508del (delF508_CTT) were genotyped using allele-specific amplification polymerase chain reaction. All detected mutations were confirmed with direct capillary DNA sequencing.

Results

Mutations in SPINK 1, CFTR and CTRC were detected in 6.3 %, 2.3 % and 1.8 % of patients with acute pancreatitis versus 3.2 %, 3.8 % and 1.2 % of volunteers in the control group. No relationship was found between the detected mutations and severity of acute pancreatitis: mild acute pancreatitis, mutation of CFTR in 4 (2.8 %) and CTRC in 2 (1.4 %) patients; severe acute pancreatitis, mutation of CFTR and CTRC in 1 (2.6 %) case each. The SPINK1 mutation was significantly more frequent in 8 (10.4 %) severe cases than in 6 (4.2 %) mild cases (P < 0.05), and was observed in 5/70 (7.1 %) patients with alcohol-related AP, 5/81 (6.2 %) with biliary AP, and 4/63 (6.3 %) in those without any established cause of the disease.

Conclusions

Mutation p.N34S in SPINK1 may predispose patients to acute pancreatitis, especially in those abusing alcohol, and may promote a more severe course of the disease.

Relationship between CFTR and CTRC variants and the clinical phenotype in late-onset cystic fibrosis disease with chronic pancreatitis

Cystic fibrosis (CF), the most common autosomal recessive disease in whites, is caused by mutations in the CF transmembrane conductance regulator (CFTR). So far, >1900 mutations have been described, most of which are nonsense, missense, and frameshift, and can lead to severe phenotypes, reducing the level of function of the CFTR protein. Synonymous variations are usually considered silent without pathogenic effects. However, synonymous mutations exhibiting exon skipping as a consequence of aberrant splicing of pre-mRNA differ. Herein, we describe the effect of the aberrant splicing of the c.273G>C (G91G) synonymous variation found in a 9-year-old white (ΔF508) patient affected by CF and pancreatitis associated with a variant in chymotrypsin C (CTRC). Magnetic resonance imaging showed an atrophic pancreatic gland with substitution of the pancreatic parenchyma with three cysts. Genetic examination revealed compound heterozygosity for the c.1521_1523delCTT (ΔF508) pathogenic variant and the c.273G>C (G91G) variant in CFTR. Sweat test results confirmed the diagnosis of CF. We have thus identified a synonymous variation (G91G) causing the skipping of exon 3 in a CF patient carrying the ΔF508 mutation. However, the clinical phenotype with pancreatic symptoms encouraged us to investigate a panel of pancreas-related genes, which resulted in finding a known sequence variation inside CTRC. We further discuss the role of these variants and their possible interactions in determining the current phenotype.

Framework for interpretation of trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis

Early intracellular premature trypsinogen activation was interpreted as the key initiator of pancreatitis. When the balance in the homeostasis of trypsin and antitrypsin system is disequilibrated, elevated aggressive enzymes directly attack the pancreatic tissue, which leads to pancreatic destruction and inflammation. However, trypsin alone is not enough to cause complications in pancreatitis, which may play a crucial role in modulating signaling events in the initial phase of the disease. NFκB activation is the major inflammatory pathway involved in the occurrence and development of pancreatitis and it can be induced by intrapancreatic activation of trypsinogen. Synthesis of trypsinogen occurs in endoplasmic reticulum (ER), and ER stress is an important early acinar cell event. Components of ER stress response are known to be able to trigger cell death as well as NFκB signaling cascade. The strongest evidence supporting the trypsin-centered theory is that gene mutations, which lead to the generation of more trypsin, or reduce the activity of trypsin inhibitors or trypsin degradation, are associated with pancreatitis. Thus, trypsin-antitrypsin imbalance may be the first step leading to pancreatic autodigestion and inducing other pathways. Continued experimental studies are necessary to determine the specific relationships between trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis. In this article, we review the latest advances that contributed to the understanding of the basic mechanisms behind the occurrence and development of pancreatitis with a focus on the interpretation of trypsin-antitrypsin imbalance and their relationships with other inflammation pathways. We additionally highlight genetic predispositions to pancreatitis and possible mechanisms associated with them.

Genetic and phenotypic heterogeneity in tropical calcific pancreatitis

Tropical calcific pancreatitis (TCP) is a form of chronic non-alcoholic pancreatitis initially reported in the developing parts of the tropical world. The clinical phenotype of TCP has undergone marked changes since its first description in 1968. The disease is now seen in relatively older people with less severe symptoms. In addition, there are varying reports on the proportion of cases presenting with imaging abnormalities like calcification, ductal dilation, and glandular atrophy. Significant progress has also been made in understanding the etiopathology of TCP. The role of malnutrition and cassava toxicity in its pathogenesis is disproven and few studies have focused on the role of micronutrient deficiency and oxidative stress in the etiopathogenesis of TCP. Emerging evidence support an important role for genetic risk factors in TCP. Several studies have shown that, rather than mutations in trypsinogens, variants in serine protease inhibitor kazal type 1, cathepsin B, chymotrypsin C, cystic fibrosis transmembrane regulator, and carboxypeptidase A1, predict risk of TCP. These studies also provided evidence of mutational heterogeneity between TCP and chronic pancreatitis in Western populations. The current review summarizes recent advances that have implications in the understanding of the pathophysiology and thus, heterogeneity in genotype-phenotype correlations in TCP.

CFTR, SPINK1, PRSS1, and CTRC mutations are not associated with pancreatic cancer in German patients

OBJECTIVE

Mutations in the cationic trypsinogen (PRSS1), cystic fibrosis transmembrane conductance regulator (CFTR), serine protease inhibitor Kazal type 1 (SPINK1), and chymotrypsin C (CTRC) genes are associated with an elevated risk for chronic pancreatitis, which is a known risk factor for pancreatic cancer (PC). Therefore, we analyzed whether PRSS1, CFTR, SPINK1, and/or CTRC mutations are associated with pancreatic adenocarcinoma.

METHODS

The study cohort was composed of 121 PC patients, of whom 74 were classified as having chronic pancreatitis, 102 patients with idiopathic chronic pancreatitis, and 130 as healthy controls. Mutation analyses for the CFTR, SPINK1, PRSS1, and CTRC genes were performed for the presence of the most common mutations.

RESULTS

The frequency of CFTR mutations in patients with PC was not significantly different in comparison with healthy controls and controls with pancreatitis. The SPINK1 mutation frequency was significantly decreased in patients with PC in comparison with patients with idiopathic pancreatitis but varied not significantly in comparison with healthy controls. None of the selected 121 PC samples showed a pancreatitis-predisposing mutation in the PRSS1 or CTRC gene.

CONCLUSIONS

Mutations in the genes CFTR, SPINK1, PRSS1, and CTRC do not seem to significantly increase the risk for pancreatic adenocarcinoma.

Kallikrein-related peptidase-4 (KLK4): role in enamel formation and revelations from ablated mice

Enamel development occurs in stages. During the secretory stage, a soft protein rich enamel layer is produced that expands to reach its final thickness. During the maturation stage, proteins are removed and the enamel matures into the hardest substance in the body. KLK4 is expressed during the transition from secretory to the maturation stage and its expression continues throughout maturation. KLK4 is a glycosylated chymotrypsin-like serine protease that cleaves enamel matrix proteins prior to their export out of the hardening enamel layer. Mutations in KLK4 can cause autosomal recessive, non-syndromic enamel malformations in humans and mice. Klk4 ablated mice initially have normal-looking teeth with enamel of full thickness. However, the enamel is soft and protein-rich. Three findings are notable from Klk4 ablated mice: first, enamel rods fall from the interrod enamel leaving behind empty holes where the enamel fractures near the underlying dentin surface. Second, the ~10,000 crystallites that normally fuse to form a solid enamel rod fail to grow together in the ablated mice and can fall out of the rods. Third, and most striking, the crystallites grow substantially in width and thickness (a- and b-axis) in the ablated mice until they almost interlock. The crystallites grow in defined enamel rods, but interlocking is prevented presumably because too much protein remains. Conventional thought holds that enamel proteins bind specifically to the sides of enamel crystals to inhibit growth in width and thickness so that the thin, ribbon-like enamel crystallites grow predominantly in length. Results from Klk4 ablated mice demonstrate that this convention requires updating. An alternative mechanism is proposed whereby enamel proteins serve to form a mold or support structure that shapes and orients the mineral ribbons as they grow in length. The remnants of this support structure must be removed by KLK4 so that the crystallites can interlock to form fully hardened enamel.

Association of CTRC and SPINK1 gene variants with recurrent hospitalizations for pancreatitis or acute abdominal pain in lipoprotein lipase deficiency

Background: There are important inter-individual variations in the incidence and severity of acute pancreatitis in patients with severe hypertriglyceridemia. Several genes involved in triglyceride-rich lipoprotein metabolism or serine proteases pathways are known to influence the risk of pancreatitis.

Aim: To evaluate the association between genes regulating serine proteases, chymotrypsin C (CTRC) and serine peptidase inhibitor kazal type1 (SPINK1), and recurrence of hospitalizations for acute pancreatitis or severe abdominal pain in patients with Lipoprotein Lipase Deficiency (LPLD), a rare and extreme monogenic model of severe hypertriglyceridemia and pancreatitis.

Method: The CTRC and SPINK1 genes promoter and coding regions sequencing has been performed in a sample of 38 LPLD adults (22 men and 16 women) and 100 controls (53 men and 47 women). Estimation of the association of CTRC and SPINK1 gene variants or combinations of variants with history of hospitalizations for pancreatitis or acute abdominal pain in LPLD was investigated using non-parametric analyses with correction for multiple testing and logistic regression models controlling for age, gender, family history, and life habits.

Results: Gene sequencing followed by genotype-stratified analyses of the CTRC and SPINK1 genes in LPLD and controls revealed a positive association between recurrence of hospitalizations and the rs545634 (CTRC)—rs11319 (SPINK1) combination [OR = 41.4 (CI: 2.0–848.0); p = 0.016]. In all models, a positive family history of pancreatitis was a significant predictor of recurrent hospitalizations independently of the contribution of SPINK1 or CTRC (p < 0.001).

Conclusion: These results suggest that a positive family history of pancreatitis and genetic markers in the serine protease pathways could be associated with a risk of recurrent hospitalization for acute pancreatitis in severe hypertriglyceridemia due to LPLD.

Comprehensive functional analysis of chymotrypsin C (CTRC) variants reveals distinct loss-of-function mechanisms associated with pancreatitis risk

OBJECTIVE

The digestive enzyme chymotrypsin C (CTRC) protects against pancreatitis by promoting degradation of trypsinogen, thereby curtailing potentially harmful trypsinogen activation. Loss-of-function variants in CTRC increase the risk for chronic pancreatitis. The aim of the present study was to perform comprehensive functional analysis of all missense CTRC variants identified to date.

DESIGN

We investigated secretion, activity and degradation of 27 published and five novel CTRC mutants. We also assessed the effect of five mutants on endoplasmic reticulum (ER) stress.

RESULTS

None of the mutants exhibited a gain of function, such as increased secretion or activity. By contrast, 11 mutants showed marked loss of function, three mutants had moderate functional defects, whereas 18 mutants were functionally similar to wild-type CTRC. The functional deficiencies observed were diminished secretion, impaired catalytic activity and degradation by trypsin. Mutants with a secretion defect caused ER stress that was proportional to the loss in secretion. ER stress was not associated with loss-of-function phenotypes related to catalytic defect or proteolytic instability.

CONCLUSIONS

Pathogenic CTRC variants cause loss of function by three distinct but mutually non-exclusive mechanisms that affect secretion, activity and proteolytic stability. ER stress may be induced by a subset of CTRC mutants, but does not represent a common pathological mechanism of CTRC variants. This phenotypic dataset should aid in the classification of the clinical relevance of CTRC variants identified in patients with chronic pancreatitis.

Comprehensive screening for PRSS1, SPINK1, CFTR, CTRC and CLDN2 gene mutations in Chinese paediatric patients with idiopathic chronic pancreatitis: a cohort study

OBJECTIVE

Genetic alterations may contribute to chronic pancreatitis (CP) in Chinese young patients. This study was designed to investigate mutations of cationic trypsinogen (PRSS1), pancreatic secretory trypsin inhibitor or serine protease inhibitor Kazal type 1 (SPINK1), cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsin C (CTRC) and CLDN2 genes and the copy number variations (CNVs) of PRSS1 and asses associations with the development of idiopathic CP (ICP) in Chinese children.

DESIGN

Retrospective.

SETTING

A single center.

PARTICIPANTS

75 ICP Chinese children (40 boys and 35 girls).

PRIMARY AND SECONDARY OUTCOME MEASURES

Mutations of PRSS1, SPINK1, CFTR, CTRC and CLDN2 genes and CNVs.

RESULTS

7 patients had heterozygous mutations in PRSS1, that is, N29I (n=1), R122H or R122C (n=6). The CNVs of PRSS1 in five patients had abnormal copies (1 copy (n=4), five copies (n=1)). 43 patients had IVS3+2T>C (rs148954387) (10 homozygous and 33 heterozygous) in SPINK1. None of the PRSS1 mutation patients carried a SPINK1 mutation. Frequency of PRSS1 and SPINK1 mutations was 9.3% and 57.3%, respectively, with an overall frequency of 66.6% (50/75). In addition, one patient had a novel deletion of CFTR (GCTTCCTA from c.500 to c.508 leading to the shortened polypeptide molecule via a stop codon). Another patient had a novel missense in CLDN2 exon 2 (c.592A>C mutation). Clinically, patients with SPINK1 mutations had a higher rate of pancreatic duct stones, pancreatic pseudocyst and pancreatic calcification than those without SPINK1 mutations (p<0.05).

CONCLUSIONS

SPINK1 mutations were more commonly associated with Chinese children with ICP. SPINK1 IVS3+2T>C mutation may play an important role in the pathogenesis of Chinese paediatric ICP. However, further study is needed to confirm and to investigate the role of these genes in the development of Chinese ICP.