Overexpression of Smad6 exacerbates pancreatic fibrosis in murine caerulein-induced chronic pancreatic injuries

Trypsin in pancreatitis: The culprit, a mediator, or epiphenomenon?

Pancreatitis is a common, life-threatening inflammatory disease of the exocrine pancreas. Its pathogenesis remains obscure, and no specific or effective treatment is available. Gallstones and alcohol excess are major etiologies of pancreatitis; in a small portion of patients the disease is hereditary. Pancreatitis is believed to be initiated by injured acinar cells (the main exocrine pancreas cell type), leading to parenchymal necrosis and local and systemic inflammation. The primary function of these cells is to produce, store, and secrete a variety of enzymes that break down all categories of nutrients. Most digestive enzymes, including all proteases, are secreted by acinar cells as inactive proforms (zymogens) and in physiological conditions are only activated when reaching the intestine. The generation of trypsin from inactive trypsinogen in the intestine plays a critical role in physiological activation of other zymogens. It was proposed that pancreatitis results from proteolytic autodigestion of the gland, mediated by premature/inappropriate trypsinogen activation within acinar cells. The intra-acinar trypsinogen activation is observed in experimental models of acute and chronic pancreatitis, and in human disease. On the basis of these observations, it has been considered the central pathogenic mechanism of pancreatitis - a concept with a century-old history. This review summarizes the data on trypsinogen activation in experimental and genetic rodent models of pancreatitis, particularly the more recent genetically engineered mouse models that mimic mutations associated with hereditary pancreatitis; analyzes the mechanisms mediating trypsinogen activation and protecting the pancreas against its' damaging effects; discusses the gaps in our knowledge, potential therapeutic approaches, and directions for future research. We conclude that trypsin is not the culprit in the disease pathogenesis but, at most, a mediator of some pancreatitis responses. Therefore, the search for effective therapies should focus on approaches to prevent or normalize other intra-acinar pathologic processes, such as defective autophagy leading to parenchymal cell death and unrelenting inflammation.

Prognostic biomarkers of pancreatic cancer identified based on a competing endogenous RNA regulatory network

BACKGROUND

Pancreatic cancer is an insidious and heterogeneous malignancy with poor prognosis that is often locally unresectable. Therefore, determining the underlying mechanisms and effective prognostic indicators of pancreatic cancer may help optimize clinical management. This study was conducted to develop a prognostic model for pancreatic cancer based on a competing endogenous RNA (ceRNA) network.

METHODS

We obtained transcriptomic data and corresponding clinicopathological information of pancreatic cancer samples from The Cancer Genome Atlas (TCGA) database (training set). Based on the ceRNA interaction network, we screened candidate genes to build prediction models. Univariate Cox regression analysis was performed to screen for genes associated with prognosis, and least absolute shrinkage and selection operator (LASSO) regression analysis was conducted to construct a predictive model. A receiver operating characteristic (ROC) curve was drawn, and the C-index was calculated to evaluate the accuracy of the prediction model. Furthermore, we downloaded transcriptomic data and related clinical information of pancreatic cancer samples from the Gene Expression Omnibus database (validation set) to evaluate the robustness of our prediction model.

RESULTS

Eight genes (ANLN, FHDC1, LY6D, SMAD6, ACKR4, RAB27B, AUNIP, and GPRIN3) were used to construct the prediction model, which was confirmed as an independent predictor for evaluating the prognosis of patients with pancreatic cancer through univariate and multivariate Cox regression analysis. By plotting the decision curve, we found that the risk score model is an independent predictor has the greatest impact on survival compared to pathological stage and targeted molecular therapy.

CONCLUSIONS

An eight-gene prediction model was constructed for effectively and independently predicting the prognosis of patients with pancreatic cancer. These eight genes identified show potential as diagnostic and therapeutic targets.

Legumain promotes fibrogenesis in chronic pancreatitis via activation of transforming growth factor β1

Chronic pancreatitis (CP) is a major risk factor for pancreatic cancer; however, little is known about the pathogenic mechanisms underlying the development of CP. Legumain (Lgmn) has been linked to some chronic inflammatory diseases. The present study investigated the role of legumain in pancreatic fibrogenesis. We induced CP in wild type C57BL6 (WT), Lgmn-deficient (Lgmn^-/-), Lgmn^flox/flox and Lgmn^flox/flox × LysM^Cre mice by intraperitoneal injection of caerulein for 4 weeks. Pancreata were collected and analyzed by quantitative reverse transcription polymerase chain reaction, Western blotting, and histology. Pancreatic stellate cells and macrophages were isolated and studied using immunofluorescence, gelatin zymography, and enzyme-linked immunosorbent assay. The effects of inhibition of legumain were investigated in vivo by administration of the specific legumain inhibitor, RR-11a. Legumain was found to be upregulated in the serum and pancreatic tissues of mice with caerulein-induced CP. Mice with global and macrophage-specific legumain deficiency exhibited significantly reduced development of pancreatic fibrosis compared with control mice, based on pancreas size, histology, and expression of fibrosis-associated genes. Our results indicate that legumain promotes activation of pancreatic stellate cells and increases synthesis of extracellular matrix proteins via activation of matrix metalloproteinase-2(MMP-2), which hydrolyzes the transforming growth factor-β1 (TGF-β1) precursor to form active TGF-β1. Administration of RR-11a markedly attenuated pancreatic fibrosis in mice with CP. Deficiency or inhibition of legumain significantly reduces the severity of pancreatic fibrosis by suppressing activation of the TGF-β1 precursor. Our results highlight the potential of legumain as a novel therapeutic target for CP. KEY MESSAGES: • Legumain expression was markedly upregulated in CP mice. • Deletion of legumain attenuated pancreatic fibrosis in CP mice. • Legumain promotes fibrosis via MMP-2 activation, which hydrolyzed the TGF-β1 precursor to the active form. • Legumain is a potential therapeutic target for the management of CP.

Transforming growth factor-β in pancreatic diseases: Mechanisms and therapeutic potential

Pancreatic diseases, such as acute pancreatitis, chronic pancreatitis, and pancreatic cancer, are common gastrointestinal diseases resulting in the development of local and systemic complications with a high risk of death. Numerous studies have examined pancreatic diseases over the past few decades; however, the pathogenesis remains unclear, and there is a lack of effective treatment options. Recently, emerging evidence has suggested that transforming growth factor beta (TGF-β) exerts controversial functions in apoptosis, inflammatory responses, and carcinogenesis, indicating its complex role in the pathogenesis of pancreas-associated disease. Therefore, a further understanding of relevant TGF-β signalling will provide new ideas and potential therapeutic targets for preventing disease progression. This is the first systematic review of recent data from animal and human clinical studies focusing on TGF-β signalling in pancreas damage and diseases. This information may aid in the development of therapeutic agents for regulating TGF-β in this pathology to prevent or treat pancreatic diseases.

P2X7R Blockade Prevents NLRP3 Inflammasome Activation and Pancreatic Fibrosis in a Mouse Model of Chronic Pancreatitis

OBJECTIVES

The aim of this study was to investigate the role of P2X7R (purinergic 2X7 receptor) and NLRP3 (NACHT, LRR, and PYD domains-containing protein 3) inflammasome activation in the process of pancreatic fibrosis in a mouse model of chronic pancreatitis (CP).

METHODS

Chronic pancreatitis was induced by repeated intraperitoneal injections of 50 μg/kg cerulein for 6 weeks in mice. P2X7R antagonist oxidized ATP (OxATP) or brilliant blue G (BBG) was administered after the last cerulein injection for 2 weeks. Pancreatic chronic inflammation and fibrosis were evaluated by histological score, Sirius red staining, and alpha-smooth muscle actin immunohistochemical staining. We further determined pancreatic P2X7R, NLRP3, and caspase-1 expressions in gene and protein levels and the pancreatic concentrations of caspase-1, interleukin 1β (IL-1β), and IL-18.

RESULTS

The pancreatic P2X7R, NLRP3, and caspase-1 expressions in gene and protein levels and the pancreatic concentrations of caspase-1, IL-1β, and IL-18 were all reduced significantly in both the OxATP and BBG groups (P < 0.05). The pancreatic chronic inflammation and the fibrosis indices were all remarkably attenuated (P < 0.05).

CONCLUSIONS

P2X7R antagonist OxATP and BBG significantly decreased pancreatic chronic inflammation and fibrosis in a mouse CP model and suggested that blockade of P2X7R-NLRP3 inflammasome signaling pathway may represent a novel therapeutic strategy for CP and its fibrotic process.

Modified Xiaochaihu Decoction () prevents the progression of chronic pancreatitis in rats possibly by inhibiting transforming growth factor-β1/Sma- and mad-related proteins signaling pathway

OBJECTIVE

To investigate the effect of modified Xiaochaihu Decoction (, MXD) on transforming growth factor-β1/Sma- and Mad-related proteins (TGF-β1/Smads) signaling pathway in rats with chronic pancreatitis (CP) induced by dibutyltin dichloride.

METHODS

Thirty healthy male Wistar rats were randomly divided into the normal control group, CP group and CP+MXD-treated group. CP was induced by injection of dibutyltin dichloride (DBTC, 7 mg/kg of body weight) into the right caudal vein, and the control rats were treated with vehicle. MXD was given daily by gavage at a dose of 10 g/kg of body weight, starting from the day after CP induction. After 28-day treatment, the n-benzoyl-tyrosyl para-aminobenzoic acid (NBT-PABA) test was carried out to evaluate exocrine pancreatic function. Then, rats were sacrificed, and pancreatic tissues were harvested for histological evaluation. In addition, the mRNA expression of TGF-β1, TGF-β1 type II receptor (TGFβRII), Smad3 and Smad7 was determined in pancreatic tissues by using real-time polymerase chain reaction.

RESULTS

Treatment of CP with MXD improved the PABA recovery, decreased the histological lesion, and reduced the mRNA expression of TGF-β1, TGFβRII and Smad3 (P<0.05). However, MXD had no effect on Smad7 mRNA level.

CONCLUSIONS

MXD could protect the pancreas against chronic injury and improve pancreatic exocrine function in DBTC induced rat CP model. Its mechanism may involve inhibition of the TGF-β1/Smads signaling pathway.

Alcohol exacerbates LPS-induced fibrosis in subclinical acute pancreatitis

The role of pancreatic acinar cells in initiating fibrogenic responses during the early stages of alcoholic acute pancreatitis has not been evaluated. We investigated the ability of injured acinar cells to generate pancreatic fibrosis in acute pancreatitis. Rats were fed either an ethanol-containing or control diet over 14 weeks and euthanized 3 or 24 hours after a single lipopolysaccharide injection. Profibrotic transforming growth factor-β of acinar cells and pancreatic fibrosis were assessed by immunofluorescence, histological characteristics, and electron microscopy. Human pancreatic tissues were also evaluated. Periacinar cell fibrosis and collagen were exacerbated 24 hours after endotoxemia in alcohol-fed rats. Alcohol exposure exacerbated acinar cell-specific production of transforming growth factor β in response to lipopolysaccharide in vivo and in acinar cell-like AR42J cells in vitro. Although a morphological examination showed no visible signs of necrosis, early pancreatic fibrosis can be initiated by little or no pancreatic necrosis. Transforming growth factor β was also significantly increased in human acinar cells from patients with acute/recurrent pancreatitis compared with chronic pancreatitis tissue. Alcohol exacerbates lipopolysaccharide-induced pancreatic fibrosis during the early onset of mild, subclinical, acute pancreatitis. We suggest that multiple, subclinical, acute pancreatitis episodes can accumulate in fibrosis during the development of chronic pancreatitis, even if there is no history of acute pancreatitis.

Transient receptor potential ankyrin 1 mediates chronic pancreatitis pain in mice

Chronic pancreatitis (CP) is a devastating disease characterized by persistent and uncontrolled abdominal pain. Our lack of understanding is partially due to the lack of experimental models that mimic the human disease and also to the lack of validated behavioral measures of visceral pain. The ligand-gated cation channel transient receptor potential ankyrin 1 (TRPA1) mediates inflammation and pain in early experimental pancreatitis. It is unknown if TRPA1 causes fibrosis and sustained pancreatic pain. We induced CP by injecting the chemical agent trinitrobenzene sulfonic acid (TNBS), which causes severe acute pancreatitis, into the pancreatic duct of C57BL/6 trpa1(+/+) and trpa1(-/-) mice. Chronic inflammatory changes and pain behaviors were assessed after 2-3 wk. TNBS injection caused marked pancreatic fibrosis with increased collagen-staining intensity, atrophy, fatty replacement, monocyte infiltration, and pancreatic stellate cell activation, and these changes were reflected by increased histological damage scores. TNBS-injected animals showed mechanical hypersensitivity during von Frey filament probing of the abdomen, decreased daily voluntary wheel-running activity, and increased immobility scores during open-field testing. Pancreatic TNBS also reduced the threshold to hindpaw withdrawal to von Frey filament probing, suggesting central sensitization. Inflammatory changes and pain indexes were significantly reduced in trpa1(-/-) mice. In conclusion, we have characterized in mice a model of CP that resembles the human condition, with marked histological changes and behavioral measures of pain. We have demonstrated, using novel and objective pain measurements, that TRPA1 mediates inflammation and visceral hypersensitivity in CP and could be a therapeutic target for the treatment of sustained inflammatory abdominal pain.

Animal models for investigating chronic pancreatitis

Chronic pancreatitis is defined as a continuous or recurrent inflammatory disease of the pancreas characterized by progressive and irreversible morphological changes. It typically causes pain and permanent impairment of pancreatic function. In chronic pancreatitis areas of focal necrosis are followed by perilobular and intralobular fibrosis of the parenchyma, by stone formation in the pancreatic duct, calcifications in the parenchyma as well as the formation of pseudocysts. Late in the course of the disease a progressive loss of endocrine and exocrine function occurs. Despite advances in understanding the pathogenesis no causal treatment for chronic pancreatitis is presently available. Thus, there is a need for well characterized animal models for further investigations that allow translation to the human situation. This review summarizes existing experimental models and distinguishes them according to the type of pathological stimulus used for induction of pancreatitis. There is a special focus on pancreatic duct ligation, repetitive overstimulation with caerulein and chronic alcohol feeding. Secondly, attention is drawn to genetic models that have recently been generated and which mimic features of chronic pancreatitis in man. Each technique will be supplemented with data on the pathophysiological background of the model and their limitations will be discussed.