Cerulein hyperstimulation decreases AMP-activated protein kinase levels at the site of maximal zymogen activation

Dysregulated pancreatic lipid phenotype, inflammation and cellular injury in a chronic ethanol feeding model of hepatic alcohol dehydrogenase-deficient deer mice

AIMS

Dysregulation of pancreatic fat and lipotoxic inflammation are common clinical findings in alcoholic chronic pancreatitis (ACP). In this study, we investigated a relationship between dysregulated pancreatic lipid metabolism and the development of injury in a chronic ethanol (EtOH) feeding model of hepatic alcohol dehydrogenase 1- deficient (ADH^-) deer mice.

METHODS

ADH^- and hepatic ADH normal (ADH⁺) deer mice were fed a liquid diet containing 3 % EtOH for three months and received a single gavage of binge EtOH with/without fatty acid ethyl esters (FAEEs) one week before the euthanasia. Plasma and pancreatic tissue were analyzed for lipids including FAEEs, inflammatory markers and adipokines using GC-MS, bioassays/kits, and immunostaining, respectively. Pancreatic morphology and proteins involved in lipogenesis were determined by the H & E staining, electron microscopy and Western blot analysis.

KEY FINDINGS

Chronic EtOH feeding in ADH^- vs. ADH⁺ deer mice resulted in a significant increase in the levels of pancreatic lipids including FAEEs, adipokines (leptin and resistin), fat infiltration with inflammatory cells and lipid droplet deposition along with the proteins involved in lipogenesis. These changes were exacerbated by an administration of binge EtOH with/without FAEEs in the pancreas of ADH^- vs. ADH⁺ deer mice fed chronic EtOH suggest a metabolic basis for ACP.

SIGNIFICANCE

These findings suggest that the liver-pancreatic axis plays a crucial role in etiopathogenesis of ACP, as the increased body burden of EtOH due to hepatic ADH deficiency exacerbates pancreatic injury.

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.

Activation of AMP-activated protein kinase attenuates ethanol-induced ER/oxidative stress and lipid phenotype in human pancreatic acinar cells

Primary toxicity targets of alcohol and its metabolites in the pancreas are cellular energetics and endoplasmic reticulum (ER). Therefore, the role of AMP-Activated Protein Kinase (AMPKα) in amelioration of ethanol (EtOH)-induced pancreatic acinar cell injury including ER/oxidative stress, inflammatory responses, the formation of fatty acid ethyl esters (FAEEs) and mitochondrial bioenergetics were determined in human pancreatic acinar cells (hPACs) and AR42J cells incubated with/without AMPKα activator [5-aminoimidazole-4-carboxamide ribonucleotide (AICAR)]. EtOH treated hPACs showed concentration and time-dependent increases for FAEEs and inactivation of AMPKα, along with the upregulation of ACC1 and FAS (key lipogenic proteins) and downregulation of CPT1A (involved β-oxidation of fatty acids). These cells also showed significant ER stress as evidenced by the increased expression for GRP78, IRE1α, and PERK/CHOP arm of unfolded protein response promoting apoptosis and activating p-JNK1/2 and p-ERK1/2 with increased secretion of cytokines. AR42J cells treated with EtOH showed increased oxidative stress, impaired mitochondrial biogenesis, and decreased ATP production rate. However, AMPKα activation by AICAR attenuated EtOH-induced ER/oxidative stress, lipogenesis, and inflammatory responses as well as the formation of FAEEs and restored mitochondrial function in hPACs as well as AR42J cells. Therefore, it is likely that EtOH-induced inactivation of AMPKα plays a crucial role in acinar cell injury leading to pancreatitis. Findings from this study also suggest that EtOH-induced inactivation of AMPKα is closely related to ER/oxidative stress and synthesis of FAEEs, as activation of AMPKα by AICAR attenuates formation of FAEEs, ER/oxidative stress and lipogenesis, and improves inflammatory responses and mitochondrial bioenergetics.

Docosahexaenoic acid inhibits zymogen activation by suppressing vacuolar ATPase activation in cerulein-stimulated pancreatic acinar cells

BACKGROUND

The premature activation of digestive enzyme zymogens within pancreatic acinar cells is an important early feature of acute pancreatitis. Supraphysiological concentrations of cholecystokinin (CCK) cause intrapancreatic zymogen activation and acute pancreatitis. Stimulation of vacuolar ATPase (vATPase) activity is required for zymogen activation in pancreatic acinar cells. Parkin, a multiprotein E3 ubiquitin ligase complex, promotes vATPase ubiquitination and degradation, which inhibits vATPase activity. Docosahexaenoic acid (DHA), an omega-3 fatty acid, exerts anti-inflammatory effects. It is reported to bind to G-protein coupled receptor 120 (GPR120) and GPR40. DHA induces the degradation of certain proteins by activating ubiquitin-proteasome system in various cells. This study aimed to investigate whether DHA induces Parkin and inhibits vATPase activity, resulting in zymogen inactivation in pancreatic acinar AR42J cells stimulated with cerulein, a CCK analog.

RESULTS

Cerulein induced the translocation of the cytosolic V1 domain (E subunit) of vATPase to the membrane, which indicated vATPase activation, and zymogen activation in AR42J cells. DHA suppressed the association of the vATPase with membranes, and zymogen activation (increased trypsin activity and amylase release) induced by cerulein. Pretreatment with a GPR120 antagonist AH-7614, a GPR40 antagonist DC260126, or an ubiquitination inhibitor PYR-41 reduced the effect of DHA on cerulein-induced zymogen activation. Treatment with PYR-41 reversed the DHA-induced decrease in vATPase activation in cerulein-treated cells. Furthermore, DHA increased the level of Parkin in membranes of cerulein-treated cells.

CONCLUSIONS

DHA upregulates Parkin which inhibits vATPase-mediated zymogen activation, via GPR120 and GPR40, in cerulein-stimulated pancreatic acinar cells.

Simvastatin induces autophagic flux to restore cerulein-impaired phagosome-lysosome fusion in acute pancreatitis

BACKGROUND

During pancreatitis, autophagy is activated, but lysosomal degradation of dysfunctional organelles including mitochondria is impaired, resulting in acinar cell death. Retrospective cohort analyses demonstrated an association between simvastatin use and decreased acute pancreatitis incidence.

METHODS

We examined whether simvastatin can protect cell death induced by cerulein and the mechanisms involved during acute pancreatitis. Mice were pretreated with DMSO or simvastatin (20 mg/kg) for 24 h followed by 7 hourly cerulein injections and sacrificed 1 h after last injection to harvest blood and tissue for analysis.

RESULTS

Pancreatic histopathology revealed that simvastatin reduced necrotic cell death, inflammatory cell infiltration and edema. We found that cerulein triggered mitophagy with autophagosome formation in acinar cells. However, autophagosome-lysosome fusion was impaired due to altered levels of LAMP-1, AMPK and ULK-1, resulting in autophagosome accumulation (incomplete autophagy). Simvastatin abrogated these effects by upregulating LAMP-1 and activating AMPK which phosphorylated ULK-1, resulting in increased formation of functional autolysosomes. In contrast, autophagosomes accumulated in control group during pancreatitis. The effects of simvastatin to promote autophagic flux were inhibited by chloroquine. Mitochondria from simvastatin-treated mice were resistant to calcium overload compared to control, suggesting that simvastatin induced mitochondrial quality control to eliminate susceptible mitochondria. Clinical specimens showed a significant increase in cell-free mtDNA in plasma during pancreatitis compared to normal controls. Furthermore, genetic deletion of parkin abrogated the benefits of simvastatin.

CONCLUSION

Our findings reveal the novel role of simvastatin in enhancing autophagic flux to prevent pancreatic cell injury and pancreatitis.

Autophagy, Inflammation, and Immune Dysfunction in the Pathogenesis of Pancreatitis

Pancreatitis is a common disorder with significant morbidity and mortality, yet little is known about its pathogenesis, and there is no specific or effective treatment. Its development involves dysregulated autophagy and unresolved inflammation, demonstrated by studies in genetic and experimental mouse models. Disease severity depends on whether the inflammatory response resolves or amplifies, leading to multi-organ failure. Dysregulated autophagy might promote the inflammatory response in the pancreas. We discuss the roles of autophagy and inflammation in pancreatitis, mechanisms of deregulation, and connections among disordered pathways. We identify gaps in our knowledge and delineate perspective directions for research. Elucidation of pathogenic mechanisms could lead to new targets for treating or reducing the severity of pancreatitis.

Human Pancreatic Acinar Cells: Proteomic Characterization, Physiologic Responses, and Organellar Disorders in ex Vivo Pancreatitis

Knowledge of the molecular mechanisms of acute pancreatitis is largely based on studies using rodents. To assess similar mechanisms in humans, we performed ex vivo pancreatitis studies in human acini isolated from cadaveric pancreata from organ donors. Because data on these human acinar preparations are sparse, we assessed their functional integrity and cellular and organellar morphology using light, fluorescence, and electron microscopy; and their proteome by liquid chromatography-tandem mass spectrometry. Acinar cell responses to the muscarinic agonist carbachol (CCh) and the bile acid taurolithocholic acid 3-sulfate were also analyzed. Proteomic analysis of acini from donors of diverse ethnicity showed similar profiles of digestive enzymes and proteins involved in translation, secretion, and endolysosomal function. Human acini preferentially expressed the muscarinic acetylcholine receptor M3 and maintained physiological responses to CCh for at least 20 hours. As in rodent acini, human acini exposed to toxic concentrations of CCh and taurolithocholic acid 3-sulfate responded with trypsinogen activation, decreased cell viability, organelle damage manifest by mitochondrial depolarization, disordered autophagy, and pathological endoplasmic reticulum stress. Human acini also secreted inflammatory mediators elevated in acute pancreatitis patients, including IL-6, tumor necrosis factor-α, IL-1β, chemokine (C-C motif) ligands 2 and 3, macrophage inhibitory factor, and chemokines mediating neutrophil and monocyte infiltration. In conclusion, human cadaveric pancreatic acini maintain physiological functions and have similar pathological responses and organellar disorders with pancreatitis-causing treatments as observed in rodent acini.

Protective effect of bacillopeptidase CFR5 from Bacillus subtilis CFR5 on cerulein-induced pancreatitis

Bacillopeptidase is a serine peptidase, known for its fibrinolytic activity. However, a very little information is known about its in vivo inflammatory and/or anti-inflammatory properties. Thus, to understand whether bacillopeptidase incorporation can regulate pancreatitis or not, the cerulein-induced pancreatitis model was used, and the role of bacillopeptidase on pancreatitis was studied. In this study, 46 kDa protein was purified from Bacillus subtilis and identified as bacillopeptidase CFR5 (BPC) through MS/MS analysis. The nutritional prophylactic group was orally fed with two doses of BPC (100 μg/Kg/BW of rat) 6 h before cerulein administration and analyzed for its effect on intestine and pancreas inflammation, cytokines, and pancreatitis marker gene expression. BPC administration significantly reduced the severity of pancreatitis by decreasing serum amylase, lipase, pancreatic edema and myeloperoxidase activity. The pretreatment with BPC suppressed the pancreatic pro-inflammatory and inflammatory cytokines production including IL-6, IL-1β, TNF-α, IL-2, IL-4, IL-5, IL-10, and IL-13 in both pancreas and serum samples. Moreover, BPC supplementation restored pancreatitis mediated disruption of intestinal barrier integrity by upregulating tight junction proteins (ZO-1, occludin), antimicrobial peptides (DEFB1, CRAMP), MUC-2, TFF3 expression and by enhancing SCFA's production. Pretreatment with BPC suppressed the intestinal inflammation with reduced cytokines production in the colon and ileal region of cerulein-induced pancreatitis. Thus, BPC based pretreatment protocol is a novel intervention to prevent acute pancreatitis.

Hydrogen sulphide exacerbates acute pancreatitis by over-activating autophagy via AMPK/mTOR pathway

Previously, we have shown that hydrogen sulphide (H₂ S) might be pro-inflammatory during acute pancreatitis (AP) through inhibiting apoptosis and subsequently favouring a predominance of necrosis over apoptosis. In this study, we sought to investigate the detrimental effects of H₂ S during AP specifically with regard to its regulation on the impaired autophagy. The incubated levels of H₂ S were artificially intervened by an administration of sodium hydrosulphide (NaHS) or DL-propargylglycine (PAG) after AP induction. Accumulation of autophagic vacuoles and pre-mature activation of trypsinogen within acini, which indicate the impairment of autophagy during AP, were both exacerbated by treatment with NaHS but attenuated by treatment with PAG. The regulation that H₂ S exerted on the impaired autophagy during AP was further attributed to over-activation of autophagy rather than hampered autophagosome-lysosome fusion. To elucidate the molecular mechanism that underlies H₂ S-mediated over-activation of autophagy during AP, we evaluated phosphorylations of AMP-activated protein kinase (AMPK), AKT and mammalian target of rapamycin (mTOR). Furthermore, Compound C (CC) was introduced to determine the involvement of mTOR signalling by evaluating phosphorylations of downstream effecters including p70 S6 kinase (P70S6k) and UNC-51-Like kinase 1 (ULK1). Our findings suggested that H₂ S exacerbated taurocholate-induced AP by over-activating autophagy via activation of AMPK and subsequently, inhibition of mTOR. Thus, an active suppression of H₂ S to restore over-activated autophagy might be a promising therapeutic approach against AP-related injuries.

Chronic Nicotine Exposure In Vivo and In Vitro Inhibits Vitamin B1 (Thiamin) Uptake by Pancreatic Acinar Cells

Thiamin (vitamin B1), a member of the water-soluble family of vitamins, is essential for normal cellular functions; its deficiency results in oxidative stress and mitochondrial dysfunction. Pancreatic acinar cells (PAC) obtain thiamin from the circulation using a specific carrier-mediated process mediated by both thiamin transporters -1 and -2 (THTR-1 and THTR-2; encoded by the SLC19A2 and SLC19A3 genes, respectively). The aim of the current study was to examine the effect of chronic exposure of mouse PAC in vivo and human PAC in vitro to nicotine (a major component of cigarette smoke that has been implicated in pancreatic diseases) on thiamin uptake and to delineate the mechanism involved. The results showed that chronic exposure of mice to nicotine significantly inhibits thiamin uptake in murine PAC, and that this inhibition is associated with a marked decrease in expression of THTR-1 and THTR-2 at the protein, mRNA and hnRNAs level. Furthermore, expression of the important thiamin-metabolizing enzyme, thiamin pyrophosphokinase (TPKase), was significantly reduced in PAC of mice exposed to nicotine. Similarly, chronic exposure of cultured human PAC to nicotine (0.5 μM, 48 h) significantly inhibited thiamin uptake, which was also associated with a decrease in expression of THTR-1 and THTR-2 proteins and mRNAs. This study demonstrates that chronic exposure of PAC to nicotine impairs the physiology and the molecular biology of the thiamin uptake process. Furthermore, the study suggests that the effect is, in part, mediated through transcriptional mechanism(s) affecting the SLC19A2 and SLC19A3 genes.

Pathologic cellular events in smoking-related pancreatitis

Pancreatitis, a debilitating inflammatory disorder, results from pancreatic injury. Alcohol abuse is the foremost cause, although cigarette smoking has recently surfaced as a distinct risk factor. The mechanisms by which cigarette smoke and its toxins initiate pathological cellular events leading to pancreatitis, have not been clearly defined. Although cigarette smoke is composed of more than 4000 compounds, it is mainly nicotine and the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), which have been extensively studied with respect to pancreatic diseases. This review summarizes these research findings and highlights cellular pathways which may be of relevance in initiation and progression of smoking-related pancreatitis.

Inflammasomes in pancreatic physiology and disease

In this review we summarize the role of inflammasomes in pancreatic physiology and disease with a focus on acute pancreatitis where much recent progress has been made. New findings have identified inducers of and cell specificity of inflammasome component expression in the pancreas, the contribution of inflammasome-regulated effectors to pancreatitis, and metabolic regulation of inflammasome activation, which are strong determinants of injury in pancreatitis. New areas of pancreatic biology will be highlighted in the context of our evolving understanding of gut microbiome- and injury-induced inflammasome priming, pyroptosis, and innate immune-mediated regulation of cell metabolism.

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.

Risk factors for pancreatic cancer: underlying mechanisms and potential targets

PURPOSE OF THE REVIEW

Pancreatic cancer is extremely aggressive, forming highly chemo-resistant tumors, and has one of the worst prognoses. The evolution of this cancer is multi-factorial. Repeated acute pancreatic injury and inflammation are important contributing factors in the development of pancreatic cancer. This article attempts to understand the common pathways linking pancreatitis to pancreatic cancer.

RECENT FINDINGS

Intracellular activation of both pancreatic enzymes and the transcription factor NF-κB are important mechanisms that induce acute pancreatitis (AP). Recurrent pancreatic injury due to genetic susceptibility, environmental factors such as smoking, alcohol intake, and conditions such as obesity lead to increases in oxidative stress, impaired autophagy and constitutive activation of inflammatory pathways. These processes can stimulate pancreatic stellate cells, thereby increasing fibrosis and encouraging chronic disease development. Activation of oncogenic Kras mutations through inflammation, coupled with altered levels of tumor suppressor proteins (p53 and p16) can ultimately lead to development of pancreatic cancer.

SUMMARY

Although our understanding of pancreatitis and pancreatic cancer has tremendously increased over many years, much remains to be elucidated in terms of common pathways linking these conditions.

Beneficial effect of the bioflavonoid quercetin on cholecystokinin-induced mitochondrial dysfunction in isolated rat pancreatic acinar cells

The pathogenesis of acute pancreatitis (AP) is still poorly understood. Thus, a reliable pharmacological therapy is currently lacking. In recent years, an impairment of the energy metabolism of pancreatic acinar cells, caused by Ca(2+)-mediated depolarization of the inner mitochondrial membrane and a decreased ATP supply, has been implicated as an important pathological event. In this study, we investigated whether quercetin exerts protection against mitochondrial dysfunction. Following treatment with or without quercetin, rat pancreatic acinar cells were stimulated with supramaximal cholecystokinin-8 (CCK). CCK caused a decrease in the mitochondrial membrane potential (MMP) and ATP concentration, whereas the mitochondrial dehydrogenase activity was significantly increased. Quercetin treatment before CCK application exerted no protection on MMP but increased ATP to a normal level, leading to a continuous decrease in the dehydrogenase activity. The protective effect of quercetin on mitochondrial function was accompanied by a reduction in CCK-induced changes to the cell membrane. Concerning the molecular mechanism underlying the protective effect of quercetin, an increased AMP/ATP ratio suggests that the AMP-activated protein kinase system may be activated. In addition, quercetin strongly inhibited CCK-induced trypsin activity. The results indicate that the use of quercetin may be a therapeutic strategy for reducing the severity of AP.