Autophagy regulation by the nuclear factor κB signal axis in acute pancreatitis

Integration of scRNA-Seq and Bulk RNA-Seq Reveals Molecular Characterization of the Immune Microenvironment in Acute Pancreatitis

Acute pancreatitis (AP) is an acute inflammatory disease of the exocrine pancreas. The pathogenesis of AP is still unclear, and there is currently no specific treatment. A variety of immune cells infiltrate in AP, which may play an important role in the progression of the disease. In this study, for the first time, scRNA-Seq and Bulk RNA-Seq data were used to show the characteristics of immune cell infiltration in AP, and to explore the specific molecular markers of different cell types. The present study also investigated cell-to-cell communication networks using the CellChat package, and AP-specific gene signatures (Clic1, Sat1, Serpina3n, Atf3, Lcn2, Osmr, Ccl9, Hspb1, Anxa2, Krt8, Cd44, Cd9, Hsp90aa1, Tmsb10, Hmox1, Fxyd5, Plin2, Pnp) were identified through integrative analysis of multiple sequencing datasets. We also defined disease-specific associated genes in different cell types, revealing dynamic changes through cell trajectory and pseudo-time analysis using the Monocle2 package. The results showed that macrophages were significantly increased in acute pancreatitis, and the number of interactions and interaction weight/strength of the macrophages in AP were significantly higher than those in the controls. The activities of various signaling pathways were abnormally regulated such as apoptosis, oxidative stress, lysosome, autophagy, ferroptosis, and inflammatory responses signaling pathways. In conclusion, this study comprehensively depicted the immune microenvironment of AP, explored the interaction network between different cell types, and defined AP-specific gene signatures, providing many new directions for basic research in AP.

Bidirectional Effects of Pyrrolidine Dithiocarbamate on Severe Acute Pancreatitis in a Rat Model

Introduction

The mechanism by which intestinal mucosal barrier is damaged in severe acute pancreatitis (SAP)-associated impairment is not fully understood.

Methods

We established an l-arginine-induced SAP rat model, pretreated with or without pyrrolidine dithiocarbamate (PDTC). Hematoxylin and eosin staining was performed to evaluate the pathological alterations. Western blotting was conducted to detect the expression of autophagy-related proteins. Oxidative stress was assessed by the levels of malondialdehyde and superoxide dismutase.

Results

We found significant injury of the intestinal mucosal barrier in SAP rats, with overexpression of Beclin-1, LC3, and p65. Pyrrolidine dithiocarbamate showed a bidirectional effect in protecting SAP rats. A high dose of PDTC aggravated disease in rats, while a low or medium dose of PDTC pretreatment, was able to alleviate tissue damage. Pyrrolidine dithiocarbamate changed the expression of Beclin-1, LC3, and p65 in the intestines. The fatty acid-binding protein level was increased in SAP rats with high-dose PDTC or without PDTC pretreatment and was reduced in SAP rats with low- or medium-dose PDTC exposure.

Conclusions

Autophagy is involved in the impairment of intestinal mucosal barrier during SAP. A suitable dose of PDTC (1 or 10 mg/kg) may decrease the severity of SAP by inhibiting autophagy in intestinal mucosal cells.

Guts and Gall: Bile Acids in Regulation of Intestinal Epithelial Function in Health and Disease

Epithelial cells line the entire surface of the gastrointestinal tract and its accessory organs where they primarily function in transporting digestive enzymes, nutrients, electrolytes, and fluid to and from the luminal contents. At the same time, epithelial cells are responsible for forming a physical and biochemical barrier that prevents the entry into the body of harmful agents, such as bacteria and their toxins. Dysregulation of epithelial transport and barrier function is associated with the pathogenesis of a number of conditions throughout the intestine, such as inflammatory bowel disease, chronic diarrhea, pancreatitis, reflux esophagitis, and cancer. Driven by discovery of specific receptors on intestinal epithelial cells, new insights into mechanisms that control their synthesis and enterohepatic circulation, and a growing appreciation of their roles as bioactive bacterial metabolites, bile acids are currently receiving a great deal of interest as critical regulators of epithelial function in health and disease. This review aims to summarize recent advances in this field and to highlight how bile acids are now emerging as exciting new targets for disease intervention.

Regulation of Autophagy Affects the Prognosis of Mice with Severe Acute Pancreatitis

BACKGROUND

Acute pancreatitis (AP) is a common inflammatory disease that may develop to severe AP (SAP), resulting in life-threatening complications. Impaired autophagic flux is a characteristic of early AP, and its accumulation could activate oxidative stress and nuclear factor κB (NF-κB) pathways, which aggravate the disease process.

AIM

To explore the therapeutic effects of regulating autophagy after the onset of AP.

METHODS

In this study, intraperitoneal injections of 3-methyladenine (3-MA) and rapamycin (RAPA) in the L-arginine or cerulein plus lipopolysaccharide (LPS) Balb/C mouse model. At 24 h after the last injection, pulmonary, intestinal, renal and pancreatic tissues were analyzed.

RESULTS

We found that 3-MA ameliorated systemic organ injury in two SAP models. 3-MA treatment impaired autophagic flux and alleviated inflammatory activation by modulating the NF-κB signaling pathway and the caspase-1-IL-1β pathway, thus decreasing the injuries to the organs and the levels of inflammatory cytokines.

CONCLUSION

Our study found that the regulation of autophagy could alter the progression of AP induced by L-arginine or cerulein plus LPS in mice.

SOCE induced calcium overload regulates autophagy in acute pancreatitis via calcineurin activation

Acute pancreatitis (AP) is an acute inflammatory process of the pancreas that is characterized by inflammation, edema, vacuolization and necrosis, which has significant morbidity and lethality. The pathogenesis of AP has not been established completely. An early and critical feature of AP is the aberrant signaling of Calcium (Ca2+) within the pancreatic acinar cell, termed Ca2+ overload. Store-operated Ca2+ (SOC) channels are the principal Ca2+ influx channels that contribute to Ca2+ overload in pancreatic acinar cells. Store-operated Ca2+ entry (SOCE) has been proved to be a key pathogenic step in AP development that leads to trypsin activation, inflammation and vacuolization. However, the molecular mechanisms are still poorly understood. By establishing Ca2+ overload model and mouse AP model using caerulein, we found that caerulein triggered SOCE via inducing interaction between STIM1 and Orai1, which activated calcineurin (CaN); CaN activated the nuclear factor of activated T cells (NFAT) and transcription factor EB (TFEB), thus promoting the transcriptional activation of multiple chemokines genes and autophagy-associated genes respectively. To the best of our knowledge, this is the first evidence showing that SOCE activates TFEB via CaN activation, which may have noticeable longer-term effects on autophagy and vacuolization in AP development. Our findings reveal the role for SOCE/CaN in AP development and provide potential targets for AP treatment.

miR-352 participates in the regulation of trypsinogen activation in pancreatic acinar cells by influencing the function of autophagic lysosomes

This study was performed to screen miRNAs and mRNAs that are differentially expressed during trypsinogen activation in acute pancreatitis and to verify their role in the process of trypsinogen activation. The function enrichment analysis showed that the functions of miR-352 and its regulatory targets lysosome-associated membrane protein 2 (LAMP2) and cathepsin L1 (CTSL1) were lysosome related. The results of the verification experiment showed that in the TLC-S-treated AR42J (pancreatic cell line) cells, miR-352 expression increased, expression levels of LAMP2 and CTSL1 were significantly reduced, trypsinogen activation was increased, and the autophagy pathway was blocked. In the miR-352 mimic-transfected cells, miR-352 expression increased, expression levels of LAMP2 and CTSL1 were significantly reduced, trypsinogen activation was increased, intracellular lysosomal pH increased, cathepsins L activity decreased and the amount of autophagolysosomes increased. In the miR-352 inhibitor-transfected cells, miR-352 expression was reduced, expression levels of LAMP2 and CTSL1 were significantly increased, trypsinogen activation was decreased, intracellular lysosomal pH decreased, cathepsins L activity increased and the amount of autophagolysosomes decreased. In the process of taurolithocholic acid 3-sulfate (TLC-S) induced trypsinogen activation, overexpression of miR-352 could down-regulate LAMP2 and CTSL1, resulting in the dysfunction of autophagic lysosome. Thus, the autophagy pathway was blocked, and trypsinogen activation was enhanced.

Acanthopanax versus 3-Methyladenine Ameliorates Sodium Taurocholate-Induced Severe Acute Pancreatitis by Inhibiting the Autophagic Pathway in Rats

Objectives. To observe the therapeutic effects of Acanthopanax and 3-methyladenine against severe acute pancreatitis (SAP). Methods. Sodium taurocholate-induced SAP rats were equally randomized into a SAP group, an Acanthopanax group, and a 3-methyladenine group. Serum amylase levels were determined by ELISA; protein and mRNA expression levels of nucleus nuclear factor kappa B (NF-κB) p65, light chain 3II (LC3-II), and Beclin-1 and mRNA expression levels of Class III phosphatidylinositol 3-kinase (PI3K-III) in pancreas tissue were detected by Western blot and quantitative real-time PCR, respectively; mortality and pathological change of the pancreas were observed at 3, 12, and 24 h after operation. Results. There was no significant difference in mortality between SAP group and both treatment groups (P > 0.05). Serum amylase levels, protein, and mRNA expression levels of nucleus NF-κB p65, LC3-II, and Beclin-1 protein, mRNA expression levels of PI3K-III, and pathological score of the pancreas in both treatment groups were significantly lower than those in SAP group at 12 and 24 h after operation (P < 0.05 or 0.01). The number of autophagosomes and autophagolysosomes of pancreatic acinar cells in both treatment groups was smaller than that in SAP group at 12 and 24 h. Conclusions. Acanthopanax and 3-methyladenine had similar therapeutic effects against SAP in rats. The mechanism may be through inhibiting abnormal autophagy activation of pancreatic acinar cells.

Expression pattern of HMGB1 and its association with autophagy in acute necrotizing pancreatitis

High-motility group box protein 1 (HMGB1) has an important role in autophagy; however, its exact role in acute necrotizing pancreatitis (ANP) remains unknown. The present study aimed to investigate the expression pattern of HMGB1 in ANP, and to determine its association with autophagy. Sprague Dawley rats (weight, 350±30 g, n=48) were randomly divided into control (n=12) and experimental (n=36) groups. Experimental rats were retrogradely injected with 5% sodium taurocholate into the biliopancreatic duct to induce ANP. Control rats received an equal amount of saline. Serum amylase levels were used to determine whether the model had been successfully generated. Autophagosomes in pancreatic acinar cells were observed under electron microscopy. The expression levels of HMGB1 and Beclin 1 were detected in pancreatic tissues by western blotting, quantitative polymerase chain reaction and immunohistochemistry. HMGB1 levels were also determined in the serum and in isolated nuclei. The results demonstrated that autophagy was detected at 3 h post-ANP induction; however, HMGB1 expression remained unaltered during the early stage (0–6 h; P>0.05). HMGB1 expression was significantly increased at 12 h, and was still increasing at 24 h (P<0.05). Notably, HMGB1 was increased in the nuclei compared with in the cytoplasm at 3–6 h. Furthermore, serum HMGB1 levels began to increase at 3 h, and reached the highest levels at 24 h in the ANP group. In conclusion, in an ANP model, HMGB1 was initially increased in the nuclei to initiate autophagy. Subsequently, it moved into the cytoplasm, where it interacted with Beclin 1 to enhance autophagy, and HMGB1 was released into the blood, leading to the deterioration of ANP.

Regulation of autophagy by the nuclear factor κB signaling pathway in the hippocampus of rats with sepsis

BACKGROUND

Sepsis with brain dysfunction has contributed to an increase risk of morbidity and mortality. In its pathophysiology, both autophagy and nuclear factor κB (NF-κB) have been suggested to play important roles. Based on the fact that crosstalk between autophagy and NF-κB, two stress-response signaling pathways, has been detected in other pathophysiological processes, this study was undertaken to explore the process of autophagy in the hippocampus of septic rats and the role NF-κB plays in the regulation of autophagy during the process.

METHODS

Cecal ligation and puncture (CLP) or a sham operation was conducted on male Wistar rats. Pyrrolidine dithiocarbamate (PDTC), an inhibitor of the NF-κB signaling pathway, or a vehicle control, was used to treat with the rats 2 h before the CLP operation. Hematoxylin-eosin staining and biological signal recording was used to measure the morphological and physiological signs of hippocampal dysfunction. An electron microscope was used to observe autophagosome formation and lysosome activation in the hippocampus after CLP. Western blotting and immune histochemistry were used to detect the hippocampus levels of NF-κB and essential proteins involved in formation of the autophagosome (microtubule-associated protein light chain 3 (LC3), Beclin1, Lamp-1, and Rab7).

RESULTS

Compared with sham-operated rats, the CLP rats showed decreasing mean arterial pressure (MAP), increasing heart rate (HR), and pathological histological changes. CLP rats exhibited not only increased vacuolization through electron micrographs but also increased LC3-II, decreased Beclin1, LAMP-1, and Rab7 through the immunofluorescence and Western blot. However, PDTC + CLP rats revealed that inhibition of the NF-κB signal axis by PDTC increased the levels of LC3-II, Beclin1, LAMP-1, and Rab7 and improved physiological function including blood pressure and heart rate.

CONCLUSIONS

The autophagy process during the hippocampus of CLP rats might be blocked by the activation of NF-κB signaling pathway. Inhibition of NF-κB signaling pathway could enhance the completion of autophagy with a neuroprotective function in septic brains.

Database screening of herbal monomers regulating autophagy by constructing a "disease-gene-drug" network

Background

Studies suggest an important role of autophagy as a target for cancer therapy. We constructed a "disease-gene-drug" network using the modular approach of bioinformatics and screened herbal monomers demonstrating functions related to autophagy regulation.

Methods

Based on the microarray results of the gene expression omnibus (GEO) database (GSE2435 and GSE31040, starvation-induced autophagy model), we used the human protein reference database (HPRD) to obtain the protein-protein interaction (PPI) network. In addition, we used the CFinder software to identify several functional modules, performed gene ontology-biological process (GO-BP) functional enrichment analysis using the DAVID software, constructed a herbal monomer-module gene regulatory network using literature search and the Cytoscape software, and then analyzed the relationships between autophagy, genes, and herbal monomers.

Results

We screened 544 differentially expressed genes related to autophagy, 375 pairs of differentially expressed genes, and 7 gene modules, wherein the functions of module 3 (composed of 7 genes) were enriched in "cell death". Using the constructed herbal monomer-module gene regulatory network, we found that 30 herbal monomers can simultaneously regulate these 7 genes, indicating a potential regulatory role in autophagy.

Conclusions

Database screening using the disease-gene-drug network can provide new strategies and ideas for the application of herbal medicines in cancer therapy.

Antioxidative phytoceuticals to ameliorate pancreatitis in animal models: An answer from nature

Despite enthusiastic efforts directed at elucidating critical underlying mechanisms towards the identification of novel therapeutic targets for severe acute pancreatitis (SAP), the disease remains without a specific therapy to be executed within the first hours to days after onset of symptoms. Although earlier management for SAP should aim to either treat organ failure or reduce infectious complications, the current standard of care for the general management of AP in the first hours to days after onset of symptoms include intravenous fluid replacement, nutritional changes, and the use of analgesics with a close monitoring of vital signs. Furthermore, repeated evaluation of severity is very important, as the condition is particularly unstable in the early stages. In cases where biliary pancreatitis is accompanied by acute cholangitis or in cases where biliary stasis is suspected, an early endoscopic retrograde cholangiopancreatography is recommended. However, practice guidelines regarding the treatment of pancreatitis are suboptimal. In chronic pancreatitis, conservative management strategies include lifestyle modifications and dietary changes followed by analgesics and pancreatic enzyme supplementation. Recently, attention has been focused on phytoceuticals or antioxidants as agents that could surpass the limitations associated with currently available therapies. Because oxidative stress has been shown to play an important role in the pathogenesis of pancreatitis, antioxidants alone or combined with conventional therapy may improve oxidative-stress-induced organ damage. Interest in phytoceuticals stems from their potential use as simple, accurate tools for pancreatitis prognostication that could replace older and more tedious methods. Therefore, the use of antioxidative nutrition or phytoceuticals may represent a new direction for clinical research in pancreatitis. In this review article, recent advances in the understanding of the pathogenesis of pancreatitis are discussed and the paradigm shift underway to develop phytoceuticals and antioxidants to treat it is introduced. Despite the promise of studies evaluating the effects of antioxidants/phytoceuticals in pancreatitis, translation to the clinic has thus far been disappointing. However, it is expected that continued research will provide solid evidence to justify the use of antioxidative phytoceuticals in the treatment of pancreatitis.

Immune-modulating therapy in acute pancreatitis: Fact or fiction

Acute pancreatitis (AP) is one of the most common diseases of the gastrointestinal tract, bearing significant morbidity and mortality worldwide. Current treatment of AP remains unspecific and supportive and is mainly targeted to aggressively prevent systemic complications and organ failure by intensive care. As acute pancreatitis shares an indistinguishable profile of inflammation with sepsis, therapeutic approaches have turned towards modulating the systemic inflammatory response. Targets, among others, have included pro- and anti-inflammatory modulators, cytokines, chemokines, immune cells, adhesive molecules and platelets. Even though, initial results in experimental models have been encouraging, clinical implementation of immune-regulating therapies in acute pancreatitis has had a slow progress. Main reasons include difficulty in clinical translation of experimental data, poor understanding of inflammatory response time-course, flaws in experimental designs, need for multimodal approaches and commercial drawbacks. Whether immune-modulation in acute pancreatitis remains a fact or just fiction remains to be seen in the future.

Autophagy in pancreatic acinar cells and pathogenesis of acute pancreatitis

Acute pancreatitis is an inflammatory disorder of the pancreas, and its pathogenesis remains poorly understood. Autodigestion of the pancreas by its own prematurely activated digestive proteases is a critical event in the onset of acute pancreatitis. Mitochondrial permeability transition results in mitochondrial depolarization and loss of ATP production, which has been found to induce autophagy in several cell types, e.g. cardiomyocytes and hepatocytes and is of vital importance for the fate of cells. Elucidating the relationship between mitochondrial permeability transition and autophagy within pancreatic acinar cells may enlighten the pathogenesis of acute pancreatitis and help provide potential therapeutic targets for this disease.