Cathepsin L inactivates human trypsinogen, whereas cathepsin L-deletion reduces the severity of pancreatitis in mice

Involvement of heparanase in the pathogenesis of acute pancreatitis: Implication of novel therapeutic approaches

Acute pancreatitis (AP) is a common gastrointestinal disease with high morbidity and mortality rate. Unfortunately, neither the etiology nor the pathophysiology of AP are fully understood and causal treatment options are not available. Recently we demonstrated that heparanase (Hpa) is adversely involved in the pathogenesis of AP and inhibition of this enzyme ameliorates the manifestation of the disease. Moreover, a pioneer study demonstrated that Aspirin has partial inhibitory effect on Hpa. Another compound, which possesses a mild pancreato-protective effect against AP, is Trehalose, a common disaccharide. We hypothesized that combination of Aspirin, Trehalose, PG545 (Pixatimod) and SST0001 (Roneparstat), specific inhibitors of Hpa, may exert pancreato-protective effect better than each drug alone. Thus, the current study examines the pancreato-protective effects of Aspirin, Trehalose, PG545 and SST0001 in experimental model of AP induced by cerulein in wild-type (WT) and Hpa over-expressing (Hpa-Tg) mice. Cerulein-induced AP in WT mice was associated with significant rises in the serum levels of lipase (X4) and amylase (X3) with enhancement of pancreatic edema index, inflammatory response, and autophagy. Responses to cerulein were all more profound in Hpa-Tg mice versus WT mice, evident by X7 and X5 folds increase in lipase and amylase levels, respectively. Treatment with Aspirin or Trehalose alone and even more so in combination with PG545 or SST0001 were highly effective, restoring the serum level of lipase back to the basal level. Importantly, a novel newly synthesized compound termed Aspirlose effectively ameliorated the pathogenesis of AP as a single agent. Collectively, the results strongly indicate that targeting Hpa by using anti-Hpa drug combinations constitute a novel therapy for this common orphan disease.

Deletion of the WD40 domain of ATG16L1 exacerbates acute pancreatitis, abolishes LAP-like non-canonical autophagy and slows trypsin degradation

The WD40 domain (WDD) of ATG16L1 plays a pivotal role in non-canonical autophagy. This study examined the role of recently identified LAP-like non-canonical autophagy (LNCA) in acute pancreatitis. LNCA involves rapid single-membrane LC3 conjugation to endocytic vacuoles in pancreatic acinar cells. The rationale for this study was the previously observed presence of trypsin in the organelles undergoing LNCA; aberrant trypsin formation is an important factor in pancreatitis development. Here we report that the deletion of WDD (attained in ATG16L1[E230] mice) eliminated LNCA, aggravated caerulein-induced acute pancreatitis and suppressed the fast trypsin degradation observed in both a rapid caerulein-induced disease model and in caerulein-treated isolated pancreatic acinar cells. These experiments indicate that LNCA is a WDD-dependent mechanism and suggest that it plays not an activating but a protective role in acute pancreatitis. Furthermore, palmitoleic acid, another inducer of experimental acute pancreatitis, strongly inhibited LNCA, suggesting a novel mechanism of pancreatic lipotoxicity.Abbreviation: AMY: amylase; AP: acute pancreatitis; CASM: conjugation of Atg8 to single membranes; CCK: cholecystokinin; FAEE model: fatty acid and ethanol model; IL6: interleukin 6; LA: linoleic acid; LAP: LC3-associated phagocytosis; LMPO: lung myeloperoxidase; LNCA: LAP-like non-canonical autophagy; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MPO: myeloperoxidase; PMPO: pancreatic myeloperoxidase; POA: palmitoleic acid; WDD: WD40 domain; WT: wild type.

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.

Initiation of acute pancreatitis in mice is independent of fusion between lysosomes and zymogen granules

The co-localization of the lysosomal protease cathepsin B (CTSB) and the digestive zymogen trypsinogen is a prerequisite for the initiation of acute pancreatitis. However, the exact molecular mechanisms of co-localization are not fully understood. In this study, we investigated the role of lysosomes in the onset of acute pancreatitis by using two different experimental approaches. Using an acinar cell-specific genetic deletion of the ras-related protein Rab7, important for intracellular vesicle trafficking and fusion, we analyzed the subcellular distribution of lysosomal enzymes and the severity of pancreatitis in vivo and ex vivo. Lysosomal permeabilization was performed by the lysosomotropic agent Glycyl-L-phenylalanine 2-naphthylamide (GPN). Acinar cell-specific deletion of Rab7 increased endogenous CTSB activity and despite the lack of re-distribution of CTSB from lysosomes to the secretory vesicles, the activation of CTSB localized in the zymogen compartment still took place leading to trypsinogen activation and pancreatic injury. Disease severity was comparable to controls during the early phase but more severe at later time points. Similarly, GPN did not prevent CTSB activation inside the secretory compartment upon caerulein stimulation, while lysosomal CTSB shifted to the cytosol. Intracellular trypsinogen activation was maintained leading to acute pancreatitis similar to controls. Our results indicate that initiation of acute pancreatitis seems to be independent of the presence of lysosomes and that fusion of lysosomes and zymogen granules is dispensable for the disease onset. Intact lysosomes rather appear to have protective effects at later disease stages.

Elevated Circulating Procathepsin L as a Potential Biomarker of Inflamm-aging

Inflamm-aging is a condition of low-grade and chronic systemic inflammation characterized by a systemic increase in multiple inflammatory biomarkers such as tumor necrosis factor (TNF), interleukin 6 (IL-6), C-reactive protein (CRP), and CXCL9 (MIG) in experimental and clinical settings. However, despite the recent identification of extracellular procathepsin L (pCTS-L) as a novel mediator of inflammatory diseases such as sepsis, its possible role in inflamm-aging was previously not investigated. In the present study, we compared blood levels of pCTS-L and other 62 cytokines and chemokines between young and aged Balb/C mice by Western blotting and Cytokine Antibody Arrays. In light of the surprising finding of a marked increase in blood pCTS-L levels in aged mice, we propose that blood pCTS-L levels may serve as another biomarker of inflamm-aging. Given the capacity of pCTS-L in inducing various cytokines (e.g., TNF and IL-6), it will be important to test the hypothetic role of pCTS-L in inflamm-aging under experimental and clinical conditions.

Compensational role between cathepsins

Cathepsins, a family of lysosomal peptidases, play a crucial role in maintaining cellular homeostasis by regulating protein turnover and degradation as well as many specific regulatory actions that are important for proper cell function and human health. Alterations in the activity and expression of cathepsins have been observed in many diseases such as cancer, inflammation, neurodegenerative disorders, bone remodelling-related conditions and others. These changes are not exclusively harmful, but rather appear to be a compensatory response on the lack of one cathepsin in order to maintain tissue integrity. The upregulation of specific cathepsins in response to the inhibition or dysfunction of other cathepsins suggests a fine-tuned system of proteolytic balance and understanding the compensatory role of cathepsins may improve therapeutic potential of cathepsin's inhibitors. Selectively targeting one cathepsin or modulating their activity could offer new treatment strategies for a number of diseases. This review emphasises the need for comprehensive research into cathepsin biology in the context of disease. The identification of the specific cathepsins involved in compensatory responses, the elucidation of the underlying molecular mechanisms and the development of targeted interventions could lead to innovative therapeutic approaches.

Therapeutic potential of procathepsin L-inhibiting and progesterone-entrapping dimethyl-β-cyclodextrin nanoparticles in treating experimental sepsis

The pathogenic mechanisms of bacterial infections and resultant sepsis are partly attributed to dysregulated inflammatory responses sustained by some late-acting mediators including the procathepsin-L (pCTS-L). It was entirely unknown whether any compounds of the U.S. Drug Collection could suppress pCTS-L-induced inflammation, and pharmacologically be exploited into possible therapies. Here, we demonstrated that a macrophage cell-based screening of a U.S. Drug Collection of 1360 compounds resulted in the identification of progesterone (PRO) as an inhibitor of pCTS-L-mediated production of several chemokines [e.g., Epithelial Neutrophil-Activating Peptide (ENA-78), Monocyte Chemoattractant Protein-1 (MCP-1) or MCP-3] and cytokines [e.g., Interleukin-10 (IL-10) or Tumor Necrosis Factor (TNF)] in primary human peripheral blood mononuclear cells (PBMCs). In vivo, these PRO-entrapping 2,6-dimethal-β-cyclodextrin (DM-β-CD) nanoparticles (containing 1.35 mg/kg PRO and 14.65 mg/kg DM-β-CD) significantly increased animal survival in both male (from 30% to 70%, n = 20, P = 0.041) and female (from 50% to 80%, n = 30, P = 0.026) mice even when they were initially administered at 24 h post the onset of sepsis. This protective effect was associated with a reduction of sepsis-triggered accumulation of three surrogate biomarkers [e.g., Granulocyte Colony Stimulating Factor (G-CSF) by 40%; Macrophage Inflammatory Protein-2 (MIP-2) by 45%; and Soluble Tumor Necrosis Factor Receptor I (sTNFRI) by 80%]. Surface Plasmon Resonance (SPR) analysis revealed a strong interaction between PRO and pCTS-L (KD = 78.2 ± 33.7 nM), which was paralleled with a positive correlation between serum PRO concentration and serum pCTS-L level (ρ = 0.56, P = 0.0009) or disease severity (Sequential Organ Failure Assessment, SOFA; ρ = 0.64, P = 0.0001) score in septic patients. Our observations support a promising opportunity to explore DM-β-CD nanoparticles entrapping lipophilic drugs as possible therapies for clinical sepsis.

Immune response mechanisms in acute and chronic pancreatitis: strategies for therapeutic intervention

Acute pancreatitis (AP) is one of the most common inflammatory diseases of the gastrointestinal tract and a steady rising diagnosis for inpatient hospitalization. About one in four patients, who experience an episode of AP, will develop chronic pancreatitis (CP) over time. While the initiating causes of pancreatitis can be complex, they consistently elicit an immune response that significantly determines the severity and course of the disease. Overall, AP is associated with a significant mortality rate of 1-5%, which is caused by either an excessive pro-inflammation, or a strong compensatory inhibition of bacterial defense mechanisms which lead to a severe necrotizing form of pancreatitis. At the time-point of hospitalization the already initiated immune response is the only promising common therapeutic target to treat or prevent a severe disease course. However, the complexity of the immune response requires fine-balanced therapeutic intervention which in addition is limited by the fact that a significant proportion of patients is in danger of development or progress to recurrent and chronic disease. Based on the recent literature we survey the disease-relevant immune mechanisms and evaluate appropriate and promising therapeutic targets for the treatment of acute and chronic pancreatitis.

A two-decade journey in identifying high mobility group box 1 (HMGB1) and procathepsin L (pCTS-L) as potential therapeutic targets for sepsis

INTRODUCTION

Microbial infections and resultant sepsis are leading causes of death in hospitals, representing approximately 20% of total deaths worldwide. Despite the difficulties in translating experimental insights into effective therapies for often heterogenous patient populations, an improved understanding of the pathogenic mechanisms underlying experimental sepsis is still urgently needed. Sepsis is partly attributable to dysregulated innate immune responses manifested by hyperinflammation and immunosuppression at different stages of microbial infections.

AREAS COVERED

Here we review our recent progress in searching for late-acting mediators of experimental sepsis and propose high mobility group box 1 (HMGB1) and procathepsin-L (pCTS-L) as potential therapeutic targets for improving outcomes of lethal sepsis and other infectious diseases.

EXPERT OPINION

It will be important to evaluate the efficacy of HMGB1- or pCTS-L-targeting agents for the clinical management of human sepsis and other infectious diseases in future studies.

Development of Procathepsin L (pCTS-L)-Inhibiting Lanosterol-Carrying Liposome Nanoparticles to Treat Lethal Sepsis

The pathogenesis of microbial infections and sepsis is partly attributable to dysregulated innate immune responses propagated by late-acting proinflammatory mediators such as procathepsin L (pCTS-L). It was previously not known whether any natural product could inhibit pCTS-L-mediated inflammation or could be strategically developed into a potential sepsis therapy. Here, we report that systemic screening of a NatProduct Collection of 800 natural products led to the identification of a lipophilic sterol, lanosterol (LAN), as a selective inhibitor of pCTS-L-induced production of cytokines [e.g., Tumor Necrosis Factor (TNF) and Interleukin-6 (IL-6)] and chemokines [e.g., Monocyte Chemoattractant Protein-1 (MCP-1) and Epithelial Neutrophil-Activating Peptide (ENA-78)] in innate immune cells. To improve its bioavailability, we generated LAN-carrying liposome nanoparticles and found that these LAN-containing liposomes (LAN-L) similarly inhibited pCTS-L-induced production of several chemokines [e.g., MCP-1, Regulated upon Activation, Normal T Cell Expressed and Presumably Secreted (RANTES) and Macrophage Inflammatory Protein-2 (MIP-2)] in human blood mononuclear cells (PBMCs). In vivo, these LAN-carrying liposomes effectively rescued mice from lethal sepsis even when the first dose was given at 24 h post the onset of this disease. This protection was associated with a significant attenuation of sepsis-induced tissue injury and systemic accumulation of serval surrogate biomarkers [e.g., IL-6, Keratinocyte-derived Chemokine (KC), and Soluble Tumor Necrosis Factor Receptor I (sTNFRI)]. These findings support an exciting possibility to develop liposome nanoparticles carrying anti-inflammatory sterols as potential therapies for human sepsis and other inflammatory diseases.

Effects of Dietary Alpha-Lipoic Acid on Growth Performance, Serum Biochemical Indexes, Liver Antioxidant Capacity and Transcriptome of Juvenile Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂)

We aimed to investigate the effects of dietary alpha-lipoic acid (α-LA) on the growth performance, serum biochemical indexes, liver morphology, antioxidant capacity, and transcriptome of juvenile hybrid groupers (Epinephelus fuscoguttatus♀ × Epinephelus polyphekadion♂). Four experimental diets supplemented with 0 (SL0), 0.4 (L1), 0.6 (L2), and 1.2 (L3) g/kg α-LA were formulated and fed to three replicates of juvenile hybrid grouper (24.06 ± 0.15 g) for 56 d. The results indicated that dietary 0.4 and 0.6 g/kg α-LA significantly decreased the weight gain rate in juvenile hybrid groupers. Compared with SL0, the content of total protein in the serum of L1, L2, and L3 increased significantly, and alanine aminotransferase decreased significantly. The content of albumin in the serum of L3 increased significantly, and triglyceride, total cholesterol, and aspartate aminotransferase decreased significantly. In addition, the hepatocyte morphology in L1, L2, and L3 all showed varying degrees of improvement, and the activities of glutathione peroxidase and superoxide dismutase in the liver of L2 and L3 were significantly increased. A total of 42 differentially expressed genes were screened in the transcriptome data. KEGG showed that a total of 12 pathways were significantly enriched, including the pathway related to immune function and glucose homeostasis. The expression of genes (ifnk, prl4a1, prl3b1, and ctsl) related to immune were significantly up-regulated, and the expressions of gapdh and eno1 genes related to glucose homeostasis were significantly down-regulated and up-regulated, respectively. In summary, dietary supplementation of 0.4 and 0.6 g/kg α-LA inhibited the growth performance of juvenile hybrid groupers. A total of 1.2 g/kg α-LA could reduce the blood lipid level, improve hepatocyte damage, and increase the hepatic antioxidant enzyme activity. Dietary α-LA significantly affected the pathway related to immune function and glucose homeostasis.

Identification of procathepsin L (pCTS-L)-neutralizing monoclonal antibodies to treat potentially lethal sepsis

Antibody-based strategies have been attempted to antagonize early cytokines of sepsis, but not yet been tried to target inducible late-acting mediators. Here, we report that the expression and secretion of procathepsin-L (pCTS-L) was induced by serum amyloid A (SAA) in innate immune cells, contributing to its late and systemic accumulation in experimental and clinical sepsis. Recombinant pCTS-L induced interleukin-6 (IL-6), IL-8, GRO-α/KC, GRO-β/MIP-2, and MCP-1 release in innate immune cells and moderately correlated with blood concentrations of these cytokines/chemokines in clinical sepsis. Mechanistically, pCTS-L interacted with Toll-like receptor 4 (TLR4) and the receptor for advanced glycation end products (RAGE) to induce cytokines/chemokines. Pharmacological suppression of pCTS-L with neutralizing polyclonal and monoclonal antibodies attenuated pCTS-L-mediated inflammation by impairing its interaction with TLR4 and RAGE receptors, and consequently rescued animals from lethal sepsis. Our findings have suggested a possibility of developing antibody strategies to prevent dysregulated immune responses mediated by late-acting cytokines.

Cysteine cathepsins: A long and winding road towards clinics

Biomedical research often focuses on properties that differentiate between diseased and healthy tissue; one of the current focuses is elevated expression and altered localisation of proteases. Among these proteases, dysregulation of cysteine cathepsins can frequently be observed in inflammation-associated diseases, which tips the functional balance from normal physiological to pathological manifestations. Their overexpression and secretion regularly exhibit a strong correlation with the development and progression of such diseases, making them attractive pharmacological targets. But beyond their mostly detrimental role in inflammation-associated diseases, cysteine cathepsins are physiologically highly important enzymes involved in various biological processes crucial for maintaining homeostasis and responding to different stimuli. Consequently, several challenges have emerged during the efforts made to translate basic research data into clinical applications. In this review, we present both physiological and pathological roles of cysteine cathepsins and discuss the clinical potential of cysteine cathepsin-targeting strategies for disease management and diagnosis.

Systemic Bile Acids Affect the Severity of Acute Pancreatitis in Mice Depending on Their Hydrophobicity and the Disease Pathogenesis

Acute pancreatitis (AP) is a major, globally increasing gastrointestinal disease and a biliary origin is the most common cause. However, the effects of bile acids (BAs), given systemically, on the pancreas and on disease severity remains elusive. In this study, we have investigated the roles of different circulating BAs in animal models for AP to elucidate their impact on disease severity and the underlying pathomechanisms. BAs were incubated on isolated acini and AP was induced through repetitive injections of caerulein or L-arginine; pancreatic duct ligation (PDL); or combined biliopancreatic duct ligation (BPDL). Disease severity was assessed using biochemical and histological parameters. Serum cholecystokinin (CCK) concentrations were determined via enzyme immunoassay. The binding of the CCK1 receptor was measured using fluorescence-labeled CCK. In isolated acini, hydrophobic BAs mitigated the damaging effects of CCK. The same BAs further enhanced pancreatitis in L-arginine- and PDL-based pancreatitis, whereas they ameliorated pancreatic damage in the caerulein and BPDL models. Mechanistically, the binding affinity of the CCK1 receptor was significantly reduced by hydrophobic BAs. The hydrophobicity of BAs and the involvement of CCK seem to be relevant in the course of AP. Systemic BAs may affect the severity of AP by interfering with the CCK1 receptor.

Double deficiency of cathepsin B and L in the mouse pancreas alters trypsin activity without affecting acute pancreatitis severity

BACKGROUND

Premature intracellular trypsinogen activation has long been considered a key initiator of acute pancreatitis (AP). Cathepsin B (CTSB) activates trypsinogen, while cathepsin L (CTSL) inactivates trypsin(ogen), and both proteins play a role in the onset of AP.

METHODS

AP was induced by 7 hourly intraperitoneal injections of cerulein (50 μg/kg) in wild-type and pancreas-specific conditional Ctsb knockout (Ctsb^Δpan), Ctsl knockout (Ctsl^Δpan), and Ctsb;Ctsl double-knockout (Ctsb^Δpan;Ctsl^Δpan) mice. Pancreatic samples were collected and analyzed by histology, immunohistochemistry, real-time PCR, and immunoblots. Trypsin activity was measured in pancreatic homogenates. Peripheral blood was collected, and serum amylase activity was measured.

RESULTS

Double deletion of Ctsb and Cstl did not affect pancreatic development or mouse growth. After 7 times cerulein injections, double Ctsb and Ctsl deficiency in mouse pancreases increased trypsin activity to the same extent as that in Ctsl-deficient mice, while Ctsb deficiency decreased trypsin activity but did not affect the severity of AP. Ctsb^Δpan;Ctsl^Δpan mice had comparable serum amylase activity and histopathological changes and displayed similar levels of proinflammatory cytokines, apoptosis, and autophagy activity compared with wild-type, Ctsb^Δpan, and Ctsl^Δpan mice.

CONCLUSION

Double deletion of Ctsb and Ctsl in the mouse pancreas altered intrapancreatic trypsin activity but did not affect disease severity and inflammatory response after cerulein-induced AP.

The Pancreas and Known Factors of Acute Pancreatitis

Pancreatitis is regarded by clinicians as one of the most complicated and clinically challenging of all disorders affecting the abdomen. It is classified on the basis of clinical, morphological, and histological criteria. Causes of acute pancreatitis can easily be identified in 75–85% of patients. The main causes of acute, recurrent acute, and chronic pancreatitis are gallstone migration and alcohol abuse. Other causes are uncommon, controversial, or unexplained. For instance, cofactors of all forms of pancreatitis are pancreas divisum and hypertriglyceridemia. Another factor that should be considered is a complication of endoscopic retrograde cholangiopancreatography: post-endoscopic retrograde cholangiopancreatography acute pancreatitis. The aim of this study is to present the known risk factors for acute pancreatitis, beginning with an account of the morphology, physiology, and development of the pancreas.

Autophagy, Acute Pancreatitis and the Metamorphoses of a Trypsinogen-Activating Organelle

Recent studies have highlighted the importance of autophagy and particularly non-canonical autophagy in the development and progression of acute pancreatitis (a frequent disease with considerable morbidity and significant mortality). An important early event in the development of acute pancreatitis is the intrapancreatic activation of trypsinogen, (i.e., formation of trypsin) leading to the autodigestion of the organ. Another prominent phenomenon associated with the initiation of this disease is vacuolisation and specifically the formation of giant endocytic vacuoles in pancreatic acinar cells. These organelles develop in acinar cells exposed to several inducers of acute pancreatitis (including taurolithocholic acid and high concentrations of secretagogues cholecystokinin and acetylcholine). Notably, early trypsinogen activation occurs in the endocytic vacuoles. These trypsinogen-activating organelles undergo activation, long-distance trafficking, and non-canonical autophagy. In this review, we will discuss the role of autophagy in acute pancreatitis and particularly focus on the recently discovered LAP-like non-canonical autophagy (LNCA) of endocytic vacuoles.

Bibliometric Analysis of Cathepsin B Research From 2011 to 2021

Cathepsin B (CTSB) is a lysosomal protease implicated in the progression of various diseases. A large number of CTSB-related studies have been conducted to date. However, there is no comprehensive bibliometric analysis on this subject. In our study, we performed quantitative analysis of CTSB-related publications retrieved from the Science Citation Index Expanded (SCIE) of the Web of Science Core Collection (reference period: 2011–2021). A total of 3,062 original articles and reviews were retrieved. The largest number of publications were from USA (n = 847, 27.66%). The research output of each country showed positive correlation with gross domestic product (GDP) (r = 0.9745, P < 0.0001). Active collaborations between countries/regions were also observed. Reinheckel T and Sloane BF were perhaps the most impactful researchers in the research landscape of CTSB. Plos ONE was the most prevalent (119/3,062, 3.89%) and cited journal (3,021 citations). Comprehensive analysis of the top citations, co-citations, and keywords was performed to acquire the theoretical basis and hotspots of CTSB-related research. The main topics included CTSB-related cancers and inflammatory diseases, CTSB-associated cell death pattern, and the applications of CTSB. These results provide comprehensive insights into the current status of global CTSB-related research especially in pancreas, which is worthy of continued follow-up by practitioners and clinicians in this field.

Hereditary Pancreatitis-25 Years of an Evolving Paradigm: Frank Brooks Memorial Lecture 2021

ABSTRACT

The identification of the genetic basis of hereditary pancreatitis in 1996 confirmed the critical role of trypsinogen in this disease and opened a new avenue of research on pancreatitis-associated genetic risk factors and their mechanism of action. Through the following 25 years, the ensuing discoveries fundamentally changed our understanding of pancreatitis pathogenesis, clarified the role of trypsinogen autoactivation in disease onset and progression, and set the stage for future therapeutic interventions. This Frank Brooks Memorial Lecture was delivered on November 4, 2021, at the 52nd Annual Meeting of the American Pancreatic Association, held in Miami Beach, Florida.

Excess fatty acids induce pancreatic acinar cell pyroptosis through macrophage M1 polarization

Free fatty acid derived from hyperlipidemia contributes to the development of inflammation in the pancreas. Here we explore the molecular mechanisms of fatty acid-induced pancreatitis through cellular experiments and the construction of a mouse model of hyperlipidemic pancreatitis. We found that palmitic acid stimulation leads to M1 polarization of macrophage, which secretes cathepsin S via exosomes to pancreatic acinar cells and leads to activation of the caspase1-mediated classical pyrolysis pathway, resulting in inflammation and pancreatic tissue damage. In vivo experiments have also demonstrated that the high levels of fatty acids induced by hyperlipidaemia exacerbate the development of pancreatitis, and that cathepsin S inhibitors significantly alleviate hyperlipidemic pancreatitis. Therefore, cathepsin S may be a new target for the clinical treatment of hyperlipidemic pancreatitis.

Alcohol Aggravates Acute Pancreatitis by Impairing Autophagic Flux Through Activation of AMPK Signaling Pathway

OBJECTIVE

Alcohol consumption is always the main cause of acute pancreatitis (AP). It has been reported that alcohol exerts direct damage to the pancreas. However, the specific role of alcohol during AP needs to be investigated. This study aims to examine the effects of alcohol in cerulein-induced AP and the role of the AMPK pathway.

METHODS

Human subjects from operations, cerulein-induced AP rat, and cerulein-stimulated AR42J cell line were enrolled in this study. Electron microscopy was employed for observation of cell morphology, immunohistochemistry for identification of cells, ELISA for detection of inflammation factors, Annexin V/PI double staining for evaluation of cell apoptosis, immunofluorescence for assessment of autophagic flux, oil red O staining for examination of lipid droplet accumulation, and Western blot for measurement of expressions of proteins related to autophagy, apoptosis, and AMPK signal pathway. PI3K inhibitor 3-MA and AMPK inhibitor BML-275 were utilized for investigation of the relationship between impaired autophagic flux and the AMPK pathway by inhibiting or stimulating the formation of autophagosome.

RESULTS

Alcohol consumption caused lipid droplet accumulation in the pancreas, and it also activated AMPK signaling pathway, thus aggravating the autophagic flux during AP. Alcohol up-regulated the expressions of anti-apoptotic proteins during the induction of AP to inhibit cell apoptosis and enhance cell necrosis. Inhibition of autophagosome formation by AMPK inhibitor BML-275 ameliorated the decreased cell viability caused by alcohol and cerulein in vitro.

CONCLUSION

Alcohol aggravates AP progression by impairing autophagic flux and enhancing cell autophagy through the AMPK signaling pathway.

Inherited pancreatic exocrine insufficiency and pancreatitis: When children transition to adult care

Hereditary pancreatitis (HP) encompasses two distinct disease groups: the first manifests as congenital exocrine pancreatic insufficiency (EPI), and the second includes hereditary forms of pancreatitis. EPI represents the ultimate expression of gland function loss. Cystic fibrosis is by far the most frequent aetiology of early-onset EPI; genetics and a growing understanding of the disease mechanisms have paved the way for innovative and personalized treatment approaches. Efforts are ongoing to further decipher the pathophysiology and explore new therapies for other causes of EPI. HP occurs in patients carrying mutations in genes encoding digestive proteases or proteins playing an important role in proper pancreatic function and homeostasis. Improved sequencing techniques have led to the discovery of several causal and disease promoting genes. Most forms of HP have a paediatric onset but complications usually manifest during adulthood. Surveillance in experienced centres is mandatory to diagnose and address these complications in a timely manner.

Clickable, selective, and cell-permeable activity-based probe of human cathepsin B - Minimalistic approach for enhanced selectivity

Human cathepsin B is a cysteine-dependent protease whose roles in both normal and diseased cellular states remain yet to be fully delineated. This is primarily due to overlapping substrate specificities and lack of unambiguously annotated physiological functions. In this work, a selective, cell-permeable, clickable and tagless small molecule cathepsin B probe, KDA-1, is developed and kinetically characterized. KDA-1 selectively targets active site Cys25 residue of cathepsin B for labeling and can detect active cellular cathepsin B in proteomes derived from live human MDA-MB-231 breast cancer cells and HEK293 cells. It is anticipated that KDA-1 probe will find suitable applications in functional proteomics involving human cathepsin B enzyme.

MicroRNAs as biomarkers and perspectives in the therapy of pancreatic cancer

Pancreatic cancer is considered as one of the most aggressive tumor types, representing over 45,750 mortality cases annually in the USA solely. The aggressive nature and late identification of pancreatic cancer, combined with the restrictions of existing chemotherapeutics, present the mandatory need for the advancement of novel treatment systems. Ongoing reports have shown an important role of microRNAs (miRNAs) in the initiation, migration, and metastasis of malignancies. Besides, abnormal transcriptional levels of miRNAs have regularly been related with etiopathogenesis of pancreatic malignancy, underlining the conceivable utilization of miRNAs in the management of pancreatic disease patients. In this review article, we give a concise outline of molecular pathways involved in etiopathogenesis of pancreatic cancer patients as well as miRNA implications in pancreatic cancer patients. Ensuing sections describe the involvement of miRNAs in the diagnosis, prognosis, and therapy of pancreatic cancer patients. The involvement of miRNAs in the chemoresistance of pancreatic cancers was also discussed. End area portrays the substance of survey with future headings.

The Gut Microbiome in Patients With Chronic Pancreatitis Is Characterized by Significant Dysbiosis and Overgrowth by Opportunistic Pathogens

Exocrine pancreatic function is a critical host factor in determining the intestinal microbiota composition. Diseases affecting the exocrine pancreas could therefore influence the gut microbiome. We investigated the changes in gut microbiota of patients with chronic pancreatitis (CP).

Immunoproteasome impairment via β5i/LMP7-deletion leads to sustained pancreatic injury from experimental pancreatitis

Uncovering potential new targets involved in pancreatitis may permit the development of new therapies and improvement of patient's outcome. Acute pancreatitis is a primarily sterile disease characterized by a severe systemic inflammatory response associated with extensive necrosis and a mortality rate of up to 24%. Considering that one of the reported disease mechanisms comprises the endoplasmic reticulum (ER) stress response and that the immunoproteasome is a key regulator to prevent proteotoxic stress in an inflammatory context, we investigated its role in acute pancreatitis. In this study, we demonstrate that immunoproteasome deficiency by deletion of the β5i/LMP7-subunit leads to persistent pancreatic damage. Interestingly, immunoproteasome-deficient mice unveil increased activity of pancreatic enzymes in the acute disease phase as well as higher secretion of Interleukin-6 and transcript expression of the Interleukin IL-1β, IFN-β cytokines and the CXCL-10 chemokine. Cell death was increased in immunoproteasome-deficient mice, which appears to be due to the increased accumulation of ubiquitin-protein conjugates and prolonged unfolded protein response. Accordingly, our findings suggest that the immunoproteasome plays a protective role in acute pancreatitis via its role in the clearance of damaged proteins and the balance of ER stress responses in pancreatic acini and in macrophages cytokine production.

Role of lysosomes in physiological activities, diseases, and therapy

Long known as digestive organelles, lysosomes have now emerged as multifaceted centers responsible for degradation, nutrient sensing, and immunity. Growing evidence also implicates role of lysosome-related mechanisms in pathologic process. In this review, we discuss physiological function of lysosomes and, more importantly, how the homeostasis of lysosomes is disrupted in several diseases, including atherosclerosis, neurodegenerative diseases, autoimmune disorders, pancreatitis, lysosomal storage disorders, and malignant tumors. In atherosclerosis and Gaucher disease, dysfunction of lysosomes changes cytokine secretion from macrophages, partially through inflammasome activation. In neurodegenerative diseases, defect autophagy facilitates accumulation of toxic protein and dysfunctional organelles leading to neuron death. Lysosomal dysfunction has been demonstrated in pathology of pancreatitis. Abnormal autophagy activation or inhibition has been revealed in autoimmune disorders. In tumor microenvironment, malignant phenotypes, including tumorigenesis, growth regulation, invasion, drug resistance, and radiotherapy resistance, of tumor cells and behaviors of tumor-associated macrophages, fibroblasts, dendritic cells, and T cells are also mediated by lysosomes. Based on these findings, a series of therapeutic methods targeting lysosomal proteins and processes have been developed from bench to bedside. In a word, present researches corroborate lysosomes to be pivotal organelles for understanding pathology of atherosclerosis, neurodegenerative diseases, autoimmune disorders, pancreatitis, and lysosomal storage disorders, and malignant tumors and developing novel therapeutic strategies.

Cathepsin B and D deficiency in the mouse pancreas induces impaired autophagy and chronic pancreatitis

The major lysosomal proteases, Cathepsin B (CTSB), Cathepsin D (CTSD) and Cathepsin L (CTSL), are implicated in autophagic activity. To investigate the role of each cathepsin in the exocrine pancreas, we generated mice in which the pancreas was specifically deficient in Ctsb, Ctsd and Ctsl. Each of these gene knockout (KO) and Ctsb;Ctsl and Ctsd;Ctsl double-knockout (DKO) mice were almost normal. However, we found cytoplasmic degeneration in the pancreatic acinar cells of Ctsb;Ctsd DKO mice, similar to autophagy related 5 (Atg5) KO mice. LC3 and p62 (autophagy markers) showed remarkable accumulation and the numbers of autophagosomes and autolysosomes were increased in the pancreatic acinar cells of Ctsb;Ctsd DKO mice. Moreover, these Ctsb;Ctsd DKO mice also developed chronic pancreatitis (CP). Thus, we conclude that both Ctsb and Ctsd deficiency caused impaired autophagy in the pancreatic acinar cells, and induced CP in mice.

Pancreatitis severity in mice with impaired CFTR function but pancreatic sufficiency is mediated via ductal and inflammatory cells-Not acinar cells

Mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR) are an established risk factor for cystic fibrosis (CF) and chronic pancreatitis. Whereas patients with CF usually develop complete exocrine pancreatic insufficiency, pancreatitis patients with CFTR mutations have mostly preserved exocrine pancreatic function. We therefore used a strain of transgenic mice with significant residual CFTR function (CFTR^tm1HGU ) to induce pancreatitis experimentally by serial caerulein injections. Protease activation and necrosis were investigated in isolated acini, disease severity over 24h, pancreatic function by MRI, isolated duct stimulation and faecal chymotrypsin, and leucocyte function by ex vivo lipopolysaccharide (LPS) stimulation. Pancreatic and lung injury were more severe in CFTR^tm1HGU but intrapancreatic trypsin and serum enzyme activities higher than in wild-type controls only at 8h, a time interval previously attributed to leucocyte infiltration. CCK-induced trypsin activation and necrosis in acini from CFTR^tm1HGU did not differ from controls. Fluid and bicarbonate secretion were greatly impaired, whereas faecal chymotrypsin remained unchanged. LPS stimulation of splenocytes from CFTR^tm1HGU resulted in increased INF-γ and IL-6, but decreased IL-10 secretion. CFTR mutations that preserve residual pancreatic function significantly increase the severity of experimental pancreatitis-mostly via impairing duct cell function and a shift towards a pro-inflammatory phenotype, not by rendering acinar cells more susceptible to pathological stimuli.

Role of Bile Acids and Bile Salts in Acute Pancreatitis: From the Experimental to Clinical Studies

ABSTRACT

Acute pancreatitis (AP) is one of the most common gastroenterological disorders leading to hospitalization. It has long been debated whether biliary AP, about 30% to 50% of all cases, is induced by bile acids (BAs) when they reach the pancreas via reflux or via the systemic blood circulation.Besides their classical function in digestion, BAs have become an attractive research target because of their recently discovered property as signaling molecules. The underlying mechanisms of BAs have been investigated in various studies. Bile acids are internalized into acinar cells through specific G-protein-coupled BA receptor 1 and various transporters. They can further act via different receptors: the farnesoid X, ryanodine, and inositol triphosphate receptor. Bile acids induce a sustained Ca2+ influx from the endoplasmic reticulum and release of Ca2+ from acidic stores into the cytosol of acinar cells. The overload of intracellular Ca2+ results in mitochondrial depolarization and subsequent acinar cell necrosis. In addition, BAs have a biphasic effect on pancreatic ductal cells. A more detailed characterization of the mechanisms through which BAs contribute to the disease pathogenesis and severity will greatly improve our understanding of the underlying pathophysiology and may allow for the development of therapeutic and preventive strategies for gallstone-inducedAP.

Activation of α7nACh receptor protects against acute pancreatitis through enhancing TFEB-regulated autophagy

Acute pancreatitis (AP) is associated with impaired acinar cell autophagic flux, intracellular zymogen activation, cell necrosis and inflammation. Activation of the cholinergic system of vagus nerve has been shown to attenuate AP, but the effect of organ-intrinsic cholinergic system on pancreatitis remains unknown. In this study, we aim to examine the effect of α7 nicotinic acetylcholine receptor (α7nAChR) stimulation within the pancreas during AP. In vivo, AP was induced by caerulein plus LPS or ethanol plus palmitoleic acid in mice. In vitro, pancreatic acini were isolated and subjected to cholecystokinin (CCK) stimulation. Mice or acini were pre-treated with PNU-282987 (selective α7nAChR agonist) or methyllycaconitine citrate salt (selective α7nAChR antagonist). Pancreatitis severity, acinar cell injury, autophagic flux, and transcription factor EB (TFEB) pathway were analyzed. Both caerulein plus LPS in vivo and CCK in vitro led to an up-regulation of α7nAChR, indicating activation of pancreas-intrinsic α7nAChR signaling during AP. PNU-282987 decreased acinar cell injury, trypsinogen activation and pancreatitis severity. Conversely, methyllycaconitine citrate salt increased acinar cell injury and aggravated AP. Moreover, activation of α7nAChR by PNU-282987 promoted autophagic flux as indicated by reduced p62, increased LysoTracker staining and decreased number of autolysosomes with undegraded contents. Furthermore, PNU-282987 treatment significantly increased TFEB activity in pancreatic acinar cells. α7nAChR activation also attenuated pancreatic inflammation and NF-κB activation. Our results showed that activation of α7nAChR protected against experimental pancreatitis through enhancing TFEB-mediated acinar cell autophagy, suggesting that activation of pancreas-intrinsic α7nAChR may serve as an endogenous protective mechanism during AP.

New horizons in pancreatic genetics

PURPOSE OF REVIEW

Pancreatitis remains an intractable disease because no causative treatment is yet available. Recent studies have uncovered some of its underlying pathophysiology, a requirement for identifying potential treatment targets. These advancements were achieved by human genetic studies and by introducing genetic mechanisms into experimental pancreatitis models.

RECENT FINDINGS

Cationic trypsin mutations are the most prominent genetic risk factor for pancreatitis. Investigators have now introduced genetically modified trypsin variants into transgenic animals. In this manner they characterized the role of cellular defense mechanisms, for example degradation of active trypsin by chymotrypsin-C, but also found that increased autoactivation or decreased degradation, not only boost disease severity but also drive progression to chonic pancreatitis. Other studies found that harmful trypsin effects are not restricted to acinar cells, that other digestive enzymes, notably pancreatic elastase, can also induce cellular injury and that endoplasmic-reticulum-stress is an important mechanism when mutations induce protein misfolding.

SUMMARY

Identifying genetic subsceptibility factors for a disease never completely uncovers its underlying pathogenesis or potential treatment targets. This requires studying the mechanisms suggested by genetic findings in experimentel disease models. Pancreatitis is a field, in which much progress has now been achieved by adopting this approach.

Preclinical insights into the gut-skeletal muscle axis in chronic gastrointestinal diseases

Muscle wasting represents a constant pathological feature of common chronic gastrointestinal diseases, including liver cirrhosis (LC), inflammatory bowel diseases (IBD), chronic pancreatitis (CP) and pancreatic cancer (PC), and is associated with increased morbidity and mortality. Recent clinical and experimental studies point to the existence of a gut‐skeletal muscle axis that is constituted by specific gut‐derived mediators which activate pro‐ and anti‐sarcopenic signalling pathways in skeletal muscle cells. A pathophysiological link between both organs is also provided by low‐grade systemic inflammation. Animal models of LC, IBD, CP and PC represent an important resource for mechanistic and preclinical studies on disease‐associated muscle wasting. They are also required to test and validate specific anti‐sarcopenic therapies prior to clinical application. In this article, we review frequently used rodent models of muscle wasting in the context of chronic gastrointestinal diseases, survey their specific advantages and limitations and discuss possibilities for further research activities in the field. We conclude that animal models of LC‐, IBD‐ and PC‐associated sarcopenia are an essential supplement to clinical studies because they may provide additional mechanistic insights and help to identify molecular targets for therapeutic interventions in humans.

BRD4 Inhibition Protects Against Acute Pancreatitis Through Restoring Impaired Autophagic Flux

Impaired autophagy has been shown to play a critical role in experimental and human acute pancreatitis (AP). However, the mechanism for transcriptional regulation of autophagy remains largely unknown. In this study, we aim to explore the role of BRD4 (bromodomain-containing protein 4), a transcriptional repressor of autophagy, during AP. Changes in pancreatic BRD4 expression and the effect of BRD4 inhibition were measured in mice with AP (induced by caerulein and ethanol and palmitoleic acid) and in isolated pancreatic acinar cells stimulated with cholecystokinin (CCK). Pancreatitis severity was evaluated by serum amylase and pancreatic histopathology. The autophagic flux, the fusion of autophagosome and lysosome, and lysosomal degradation were evaluated. Sirtuin 1 (SIRT1) expression and the effect of SIRT1 inhibition were assessed. We found that pancreatic BRD4 expression was upregulated during various models of AP. BRD4 inhibition reduced CCK-stimulated pancreatic acinar cell injury and pro-inflammatory expression in vitro and protected against two models of experimental AP. Mechanistically, BRD4 inhibition restored impaired autophagic flux via promoting autophagosome-lysosome fusion and lysosomal degradation. BRD4 inhibition also upregulated SIRT1 and inhibition of SIRT1 reversed the effects of BRD4 inhibition on autophagic flux. Our data suggest that BRD4 is a potential therapeutic target for treating AP.

Early trypsin activation develops independently of autophagy in caerulein-induced pancreatitis in mice

Premature intrapancreatic trypsinogen activation is widely regarded as an initiating event for acute pancreatitis. Previous studies have alternatively implicated secretory vesicles, endosomes, lysosomes, or autophagosomes/autophagolysosomes as the primary site of trypsinogen activation, from which a cell-damaging proteolytic cascade originates. To identify the subcellular compartment of initial trypsinogen activation we performed a time-resolution analysis of the first 12 h of caerulein-induced pancreatitis in transgenic light chain 3 (LC3)-GFP autophagy reporter mice. Intrapancreatic trypsin activity increased within 60 min and serum amylase within 2 h, but fluorescent autophagosome formation only by 4 h of pancreatitis in parallel with a shift from cytosolic LC3-I to membranous LC3-II on Western blots. At 60 min, activated trypsin in heavier subcellular fractions was co-distributed with cathepsin B, but not with the autophagy markers LC3 or autophagy protein 16 (ATG16). Supramaximal caerulein stimulation of primary pancreatic acini derived from LC3-GFP mice revealed that trypsinogen activation is independent of autophagolysosome formation already during the first 15 min of exposure to caerulein. Co-localization studies (with GFP-LC3 autophagosomes versus Ile-Pro-Arg-AMC trypsin activity and immunogold-labelling of lysosomal-associated membrane protein 2 [LAMP-2] versus trypsinogen activation peptide [TAP]) indicated active trypsin in autophagolysosomes only at the later timepoints. In conclusion, during the initiating phase of caerulein-induced pancreatitis, premature protease activation develops independently of autophagolysosome formation and in vesicles arising from the secretory pathway. However, autophagy is likely to regulate overall intracellular trypsin activity during the later stages of this disease.

Mutation That Promotes Activation of Trypsinogen Increases Severity of Secretagogue-Induced Pancreatitis in Mice

BACKGROUND & AIMS

Mutations in the human serine protease 1 gene (PRSS1), which encodes cationic trypsinogen, can accelerate its autoactivation and cause hereditary or sporadic chronic pancreatitis. Disruption of the locus that encodes cationic trypsinogen in mice (T7) causes loss of expression of the protein, but only partially decreases the severity of secretagogue-induced acute pancreatitis and has no effect on chronic pancreatitis. We investigated whether trypsinogen becomes pathogenic only when its activation is promoted by mutation.

METHODS

We generated mice with knock-in of the p.K24R mutation (called T7K24R mice), which is analogous to human PRSS1 mutation p.K23R. We gave T7K24R and C57BL/6N (control) mice repeated injections of cerulein to induce pancreatitis. Plasma amylase activity, pancreatic edema, and myeloperoxidase content in pancreas and lungs were quantified. We expressed mutant and full-length forms of PRSS1 in Escherichia coli and compared their autoactivation.

RESULTS

The p.K24R mutation increased autoactivation of T7 5-fold. T7K24R mice developed no spontaneous pancreatitis. T7K24R mice given cerulein injections had increased pancreatic activation of trypsinogen and more edema, infiltration of lung and pancreas by inflammatory cells, and plasma amylase activity compared with control mice given cerulein injections. Injection of cerulein for 2 days induced progressive pancreatitis in T7K24R mice, but not in control mice, with typical features of chronic pancreatitis.

CONCLUSIONS

Introduction of a mutation into mice that is analogous to the p.K23R mutation in PRSS1 increases pancreatic activation of trypsinogen during secretagogue-induced pancreatitis. Higher pancreatic activity of trypsin increases the severity of pancreatitis, even though loss of trypsin activity does not prevent pancreatitis in mice.

Measuring digestive protease activation in the mouse pancreas

Intrapancreatic activation of digestive proteases, trypsin and chymotrypsin in particular, is a hallmark of pancreatitis. In experimental rodent models, protease activation is routinely measured from pancreatic homogenates using fluorogenic peptide substrates. Here we investigated the optimal conditions for the determination of intrapancreatic trypsin and chymotrypsin activation elicited by a single intraperitoneal injection of cerulein in C57BL/6N mice. We found that these protease assays were significantly improved by using lower amounts of pancreatic homogenate and exclusion of bovine serum albumin from the assay buffer. Furthermore, pancreatic homogenates had to be freshly prepared and assayed; as freezing and thawing stimulated protease activation. Finally, replacement of the widely used Boc-Gln-Ala-Arg-AMC trypsin substrate with Z-Gly-Pro-Arg-AMC reduced the background activity in saline-treated control mice and thereby increased the extent of cerulein-induced trypsin activation. Using the optimized protocol, we reproducibly measured 20-fold and 200-fold increases in the intrapancreatic trypsin and chymotrypsin activity, respectively, in mice given cerulein.

Immunoreactivity of cytotoxic T-lymphocyte antigen 2 alpha in mouse pancreatic islet cells

Cells of the pancreatic islets produce several molecules including insulin (beta cells), glucagon (alpha cells), somatostatin (delta cells), pancreatic polypeptide (PP cells), ghrelin (epsilon cells), serotonin (enterochromaffin cells), gastrin (G cells) and small granules of unknown content secreted by the P/D1 cells. Secretion mechanism of some of these molecules is still poorly understood. However, Cathepsin L is shown to regulate insulin exocytosis in beta cells and activate the trypsinogen produced by the pancreatic serous acini cells into trypsin. The structure of the propeptide region of Cathepsin L is homologous to Cytotoxic T-lymphocyte antigen-2 alpha (CTLA-2 alpha) which is also shown to exhibit selective inhibitory activities against Cathepsin L. It was thought that if CTLA-2 alpha was expressed in the pancreas; then, it would be an important regulator of protease activation and insulin secretion. The purpose of this study was, therefore, to examine by immunohistochemistry the cellular localization and distribution pattern of CTLA-2 alpha in the pancreas. Results showed that strong immunoreactivity was specifically detected in the pancreatic islets (endocrine pancreas) but not in the exocrine pancreas and pancreatic stroma. Immunostaining was further performed to investigate more on localization of Cathepsin L in the pancreas. Strong immunoreactivity for Cathepsin L was detected in the pancreatic islets, serous cells and the pancreas duct system. These findings suggest that CTLA-2 alpha may be involved in the proteolytic processing and secretion of insulin through regulation of Cathepsin L and that the regulated inhibition of Cathepsin L may have therapeutic potential for type 1 diabetes.

A Review of Small Molecule Inhibitors and Functional Probes of Human Cathepsin L

Human cathepsin L belongs to the cathepsin family of proteolytic enzymes with primarily an endopeptidase activity. Although its primary functions were originally thought to be only of a housekeeping enzyme that degraded intracellular and endocytosed proteins in lysosome, numerous recent studies suggest that it plays many critical and specific roles in diverse cellular settings. Not surprisingly, the dysregulated function of cathepsin L has manifested itself in several human diseases, making it an attractive target for drug development. Unfortunately, several redundant and isoform-specific functions have recently emerged, adding complexities to the drug discovery process. To address this, a series of chemical biology tools have been developed that helped define cathepsin L biology with exquisite precision in specific cellular contexts. This review elaborates on the recently developed small molecule inhibitors and probes of human cathepsin L, outlining their mechanisms of action, and describing their potential utilities in dissecting unknown function.

The Regulatory Effect of the Kinase Inhibitor PD98059 on Autophagic Flux During Trypsinogen Activation in Pancreatic Acinar Cells

OBJECTIVES

To study the role of kinase inhibitor PD98059 on autophagy flow in the process of trypsinogen activation in pancreatic acinar cell and its related mechanism.

METHODS

In the present study, bioinformatics analysis was used to predict kinases and their most relevant inhibitor (PD98059) which participates in autophagy of acute pancreatitis (AP). The rat pancreatic acini AR42J cells were divided into 4 groups: control group, sodium taurocholate hydrate (TLC) group, PD98059 group, and TLC + PD group. Twenty-seven Sprague-Dawley rats were divided into 3 groups (n = 9), including control group, severe AP (SAP) group, and SAP + PD group. We detected trypsinogen activation, autophagic activation, lysosome pH, and cathepsin-L activity in vivo and in vitro.

RESULTS

Results revealed trypsinogen activation was significantly inhibited in mitogen-activated protein kinase 1, JAK2, LYN, and their common inhibitor was PD98059. The trypsinogen activation, Beclin1, and light chain 3 II expressions were reduced, whereas the expressions of lysosomal-associated membrane protein 2, cathepsin L1, and cathepsin-L activity is upregulated after the PD98059 pretreatment, both in vivo and in vitro.

CONCLUSIONS

Lysosomal dysfunction blocked autophagy flux, accompanied by increasing pancreatic acinar cell autophagy in the process of trypsinogen activation. PD98059 inhibited AP occurrence and pancreatic injury via improving the blocked autophagic pathway and reducing trypsinogen activation.

Absence of the neutrophil serine protease cathepsin G decreases neutrophil granulocyte infiltration but does not change the severity of acute pancreatitis

Acute pancreatitis is characterized by an early intracellular protease activation and invasion of leukocytes into the pancreas. Cathepsins constitute a large group of lysosomal enzymes, that have been shown to modulate trypsinogen activation and neutrophil infiltration. Cathepsin G (CTSG) is a neutrophil serine protease of the chymotrypsin C family known to degrade extracellular matrix components and to have regulatory functions in inflammatory disorders. The aim of this study was to investigate the role of CTSG in pancreatitis. Isolated acinar cells were exposed to recombinant CTSG and supramaximal cholezystokinin stimulation. In CTSG^-/- mice and corresponding controls acute experimental pancreatitis was induced by serial caerulein injections. Severity was assessed by histology, serum enzyme levels and zymogen activation. Neutrophil infiltration was quantified by chloro-acetate ersterase staining and myeloperoxidase measurement. CTSG was expessed in inflammatory cells but not in pancreatic acinar cells. CTSG had no effect on intra-acinar-cell trypsinogen activation. In CTSG^-/- mice a transient decrease of neutrophil infiltration into the pancreas and lungs was found during acute pancreatitis while the disease severity remained largely unchanged. CTSG is involved in pancreatic neutrophil infiltration during pancreatitis, albeit to a lesser degree than the related neutrophil (PMN) elastase. Its absence therefore leaves pancreatitis severity essentially unaffected.

Functional analysis and gene expression profiling of extracellular cathepsin Z in red sea bream, Pagrus major

Cathepsin Z (CTSZ) is a lysosomal cysteine protease that is known to be involved in the maintenance of homeostasis and the biological mechanisms of immune cells. In this study, we have confirmed the tissue specific expression of the cathepsin Z (PmCTSZ) gene in Pagrus major, and confirmed its biological function after producing recombinant protein using Escherichia coli (E. coli). Multiple sequence alignment analysis revealed that the active site of the cysteine proteases and three N-glycosylation sites of the deduced protein sequence were highly conserved among all of the organisms. Phylogenetic analysis revealed that PmCTSZ was included in the clusters of CTSZ and the cysteine proteases of other bony fish and is most closely related to Japanese flounder CTSZ. PmCTSZ was distributed in all of the tissues from healthy red sea bream that were used in the experiment and was most abundantly found in the spleen and gill. Analysis of mRNA expression after bacterial (Edwardsiella piscicida: E. piscicida and Streptococcus iniae: S. iniae) or viral (red seabream iridovirus: RSIV) challenge showed significant gene expression regulation in immune-related tissues, but they maintained relatively normal levels of expression. We produced recombinant PmCTSZ (rPmCTSZ) using an E. coli expression system and confirmed the biological function of extracellular rPmCTSZ in vitro. We found that bacterial proliferation was significantly inhibited by rPmCTSZ, and the leukocytes of red sea bream also induced apoptosis and viability reduction.

MicroRNAs in acute pancreatitis: From pathogenesis to novel diagnosis and therapy

Acute pancreatitis (AP) is an inflammatory disorder initiated by activation of pancreatic zymogens, leading to pancreatic injury and systemic inflammatory response. MicroRNAs (miRNAs) have emerged as important regulators of gene expression and key players in human physiological and pathological processes. Discoveries over the past decade have confirmed that altered expression of miRNAs is implicated in the pathogenesis of AP. Indeed, a number of miRNAs have been found to be dysregulated in various cell types involved in AP such as acinar cells, macrophages, and lymphocytes. These aberrant miRNAs can regulate acinar cell necrosis and apoptosis, local and systemic inflammatory response, thereby contributing to the initiation and progression of AP. Moreover, patients with AP possess unique miRNA signatures when compared with healthy individuals or those with other diseases. In view of their stability and easy detection, therefore, miRNAs have the potential to act as biomarkers for the diagnosis and assessment of patients with AP. In this review, we provide an overview of the novel cellular and molecular mechanisms underlying the roles of miRNAs during the disease processes of AP, as well as the potential diagnosis and therapeutic biomarkers of miRNAs in patients with AP.

New insights into acute pancreatitis

The incidence of acute pancreatitis continues to increase worldwide, and it is one of the most common gastrointestinal causes for hospital admission in the USA. In the past decade, substantial advancements have been made in our understanding of the pathophysiological mechanisms of acute pancreatitis. Studies have elucidated mechanisms of calcium-mediated acinar cell injury and death and the importance of store-operated calcium entry channels and mitochondrial permeability transition pores. The cytoprotective role of the unfolded protein response and autophagy in preventing sustained endoplasmic reticulum stress, apoptosis and necrosis has also been characterized, as has the central role of unsaturated fatty acids in causing pancreatic organ failure. Characterization of these pathways has led to the identification of potential molecular targets for future therapeutic trials. At the patient level, two classification systems have been developed to classify the severity of acute pancreatitis into prognostically meaningful groups, and several landmark clinical trials have informed management strategies in areas of nutritional support and interventions for infected pancreatic necrosis that have resulted in important changes to acute pancreatitis management paradigms. In this Review, we provide a summary of recent advances in acute pancreatitis with a special emphasis on pathophysiological mechanisms and clinical management of the disorder.